We studied new perovskite material lead (II) thiocyanate [Pb(SCN)2] in ambient air with humidity above 90%. We prepared perovskite film by use of two-step method combination of spin-coating and dip-coating technique. The Pb(SCN)2 film was first spin-coated either on bare glass or TiO2 coated glass and then followed by dipping it into methylammonium iodide (MAI) solution. The UV-Vis spectrum of Pb(SCN)2 film shows absorption at wavelength shorter than 400 nm. Meanwhile, perovskite MAPb(SCN)xI3-x film absorps light ranging from 300 nm to 760 nm, which shows that the perovskite film can absorp more light to be converted into free charge carrier for generating electricity in solar cells. The XRD patterns shows that perovskite peaks are clearly observed which confirms that perovskite is already well formed. We also observe no significant changes in XRD pattern of perovskite films after stored for five days at ambient air with humidity exceed 90%. This result shows that perovskite MAPb(SCN)XI3-X film is environmentally stable, therefore high stability perovskite solar cells is expected to be produced in ambient air with high humidity. This is in accordance with the SEM images of surface morphology that shows no "pin-hole".

Raman images of carriers (positive polarons) at the channel of an ionic liquid-gated transistor (ILGT) fabricated with regioregular poly(3-hexylthiophene) (P3HT) have been measured with excitation at 785 nm. The observed spectra indicate that carriers generated are positive polarons. The intensities of the 1415 cm−1 band attributed to polarons in the P3HT channel were plotted as Raman images
they showed the carrier density distribution. When the source–drain voltage VD is lower than the source–gate voltage VG (linear region), the carrier density was uniform. When VD is nearly equal to VG (saturation region), a negative carrier density gradient from the source electrode towards the drain electrode was observed. This carrier density distribution is associated with the observed current–voltage characteristics, which is not consistent with the “pinch-off” theory of inorganic semiconductor transistors.

Voltage-induced infrared spectra of annealed spin-cast thin films of ferroelectric poly(vinylidene fluoride-cotrifluoroethylene) (P(VDF-TrFE)) (molar ratio, 3:1) were measured in a stepwise cyclic external electric field. Most of the observed infrared bands originated from the beta ferroelectric crystalline phase. The voltage-induced spectral changes were decomposed into zeroth- (original), first-, and second-derivative spectra, and were attributed to the rotational motions of the polymer chains and the vibrational Stark effect. The values of the original spectral absorbance change ratios, Delta A/A, for the 849-cm(-1) band (CF2 symmetric stretching, a(1)) and the 884-cm(-1) band (CH2 rocking, b(2)) of the film exhibited double minimum and maximum peak hysteresis loops, respectively. The intensity of each band increased or decreased suddenly near a coercive field of +/- 0.6 MV/cm. These sudden intensity changes were attributed to the rotational inversion of the polymer chains that are associated with ferroelectricity.

Regeneration heat in strippers of CCS system is affected by operating temperature and concentration of amine solutions and accurate measurement, modelling and prediction of it are necessary to design the strippers with selecting new or blend amine solutions. This paper reports the heat of dissociation of CO2-loaded 30wt% monoethanolamine (MEA) solution quantified experimentally by a small-scale apparatus circulating the solution through absorber and stripper. This method can quantify total regeneration heat as well as breakdown of regeneration heat consisted of the heat of CO2 dissociation, the sensible heat of solution and the latent heat of condensed water simultaneously. The heat of CO2 dissociation agreed well with the heat of CO2 absorption at 120 degrees C in literatures. Aspen Plus offers an example file of rate-based CCS system using MEA, and the process flow diagram (PFD) was developed to simulate the apparatus by using it. The developed PFD with the original electrolyte NRTL model underestimated heat duty of the stripper. We modified temperature dependency of the specific heat capacity of protonated MEA. The modified model could predict accurately the heat of CO2 dissociation as well as mole fraction of chemical species, while effect of solution concentration on the heat of CO2 absorption was still not sufficiently simulated.

We have studied the formation rates of HCO3 -/CO3 2-, amine/protonated amine, carbamate/protonated carbamate, and carbonate/protonated carbonate in the course of CO2 absorption at room temperature, and composition changes and CO2 release upon heating at 93 °C for 30 min for aqueous solutions of 9 kinds of alkanolpiperidines using 13C-NMR spectroscopy. The pKa values of these alkanolpiperidines were measured. The initial CO2 capture rates of alkanolpiperidines do not depend on their pKa values, which is quite different from general trends of aqueous amine absorbents. The CO2 release amount of each alkanolpiperidine increased with decreasing pKa, as a general trend. The CO2 release amounts of 1-HE-PD, 2-HM-1-M-PD, 3-HM-1-M-PD, and 4-HM-1-M-PD increased with increasing concentrations.

Reactions between acetylenes and a stable digermyne bearing 4-t-Bu-2,6-[CH(SiMe3)(2)](2)-C6H2 (Tbb) groups afforded the corresponding stable 1,2-digermabenzenes together with the respective 1,4-digermabarrelenes. The properties of the obtained products and the reaction mechanism are discussed on the basis of experimental and theoretical results. Especially, the aromaticity of the newly obtained 1,2-digermabenzene has been discussed on the detailed calculations, revealing its aromatic character to some degree.

We observed the Raman spectra of carriers, positive polarons and bipolarons, generated in a poly(2,5-bis (3-tetradecylthiophen-2-ypthieno[3,2-13]thiophene) (PBTIT-C14) film by FeCl3 vapor doping. Electrical conductivity and Raman measurements indicate that the dominant carriers in the conducting state were bipolarons. We identified positive polarons and bipolarons generated in an ionic-liquid-gated transistor (ILGT) fabricated with PBTIT-C14 as an active semiconductor and an ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [BMIM[TFSI] as a gate dielectric using Raman spectroscopy. The relationship between the source-drain current (ID) at a constant source-drain voltage (VD) and the gate voltage (VG) was measured. ID increased above -V-G = 1.1 V and showed a maximum at -V-G = 2.0 V. Positive polarons were formed at the initial stage of electrochemical doping (-V-G = 0.8 V). As ID increased, positive bipolarons were formed. Above V-G = -2.0 V, bipolarons were dominant. The charge density (n), the doping level (x), and the mobility of the bipolarons were calculated from the electrochemical measurements. The highest mobility (mu,) of bipolarons was 0.72 cm(2) V-1 s(-1) at x=110 mol%/repeating unit (-V-G = 2.0 V), whereas the highest mu of polarons was 4.6 x 10(-4) cm(2) V-1 s(-1) at x = 10 mol%. (C) 2016 Elsevier B.V. All rights reserved.

We measured 785 nm excited Raman and infrared spectra of pentacene-d(14). The observed spectra were assigned on the basis of the Raman and infrared spectra calculated by the density functional theory (DFT) method at the B3LYP/6-311 + G** level. We measured 785 nm excited Raman spectrum of a pentacne-d(14): C-60 bulk heterojunction film. The spectrum was assigned on the basis of the wavenumber shifts upon deuteration of pentacene. The assignments of the 1462 and 493 cm(-1) A(g) bands of C-60 were confirmed. The 511, 453, and 256 cm(-1) bands, which were observed only in pentacene:C-60 bulk heterojunction films, did not show large deuteration shifts. This result indicates that the 511, 453, and 256 cm(-1) bands are attributed to activation of the silent modes of C-60 due to symmetry lowering. (C) 2016 Elsevier B.V. All rights reserved.

We studied the intensity changes of the infrared bands of a ferroelectric melt-quenched, cold-drawn film of nylon-12 as a function of an external cyclic stepwise electric field with the polarization perpendicular to the draw direction. The infrared bands assigned to the NH stretching and amide I modes exhibited butterfly-shaped hysteresis loops characteristic of ferroelectric materials, whereas the intensity changes of the infrared bands assigned to the CH2 antisymmetric and symmetric stretching modes were small and showed no butterfly-shaped hysteresis loops. These results indicate that only the amide groups were inverted under the external electric field. We proposed a molecular mechanism explaining the ferroelectric properties of nylon-12: the amide groups in the antiparallel beta-sheet structure are inverted by the external electric field to form new hydrogen bonds, generating two stable states in a nearly double minimum potential. (C) 2016 Elsevier B.V. All rights reserved.

Using Raman spectroscopy, we observed carriers, polarons and bipolarons formed in an ionic-liquid-gated P3HT electrochemical transistor with an ionic liquid [BMIM][TFSI] as a gate dielectric. The relationships between the source-drain current (I-D), the gate voltage (V-G) at a constant source-drain voltage (V-D), and injected charges at each V-G were investigated. An increase in I-D is attributed to the formation of positive polarons, whereas a decrease in I-D corresponded to positive bipolarons. Thus, positive polarons are efficient carriers in P3HT electrochemical transistors. Charge densities, doping levels, electrical conductivities, and mobilities of tiolarons in P3HT were calculated from the electrochemical measurements. Only positive polarons exist below the dopant level x = 27 mol%, whereas at higher doping levels, polarons and bipolarons coexist. The mobility of polarons was dependent on the doping level. The highest mobility was 031 cm(2) V-1 s(-1) at x = 15 mol%. (C) 2015 Elsevier B.V. All rights reserved.

We measured the Raman spectra of indium-tin oxide (ITO)/poly(3-hexylthiophene) (P3HT)/metal oxide (MoO3, V2O(5), or WO3) samples as an anode buffer layer. The difference Raman spectrum between ITO/P3HT/MoO3 and ITO/P3HT was similar to that of positive polarons generated by FeCl3 doping, which indicated that positive polarons were formed upon MoO3 deposition. MoO3 functioned as an oxidizing dopant. Positive polarons were also formed upon V2O(5) and WO3 deposition. The polaron electronic energy levels formed near the Fermi level of an ITO, Ag, or Au electrode are associated with an improvement of charge transport through the interface. (C) 2015 Elsevier B.V. All rights reserved.

The heavy B-doping of an intrinsic Si(1 0 0) wafer has been performed by irradiating a B-doped Si nanoparticle film on the surface of the Si(1 0 0) substrate with energy densities of 8.0 and 16.0 J/cm(2) by 532-nm laser light. The thicknesses of the heavily doped surface layers were investigated using Raman spectroscopy. The observed 488.0-nm-excited Raman bands were decomposed into two bands: a Fano-type band due to the heavily doped Si surface layer and a Voigt band due to the lightly doped, intrinsic Si region. The analysis of the Fano-type band indicated that the carrier concentration of the heavily doped region was larger than approximately 10(19) cm(-3). Based on the two-state model, the thicknesses of the heavily doped surface layers were 480 and 630 nm for the samples prepared with energy densities of 8.0 and 16.0 J/cm(2), respectively. These values were consistent with those obtained by secondary ion mass spectroscopy (SIMS). (C) 2015 Elsevier Ltd. All rights reserved.

The changes in intensity of the infrared bands of a ferroelectric melt-quenched, cold-drawn film of nylon-11 were measured as a function of a cyclic external electric field of 1.4 MV/cm. The infrared bands assigned to the NH stretching, amide I, NH-vicinal, and CO-vicinal CH2 scissoring modes showed butterfly-shaped hysteresis loops that are characteristic of ferroelectrics; however, the intensity changes of the infrared bands assigned to the CH2 antisymmetric and symmetric stretching modes are small and showed no butterfly-shaped hysteresis loops. These results indicate that the amide groups are inverted, while the methylene groups are not inverted under the external electric field. We propose a new molecular mechanism that explains the ferroelectric properties of nylon-11. Only the amide groups in the antiparallel beta-sheet structure are inverted by the external electric field to form new hydrogen bonds; these two states form a nearly double-minimum potential.

We measured the 785-nm excited Raman spectrum of a pentacene:C-60 blend film. The 1462-, 492-, and 268-cm(-1) bands of C-60 showed broadening in bandwidth and downward shifts in peak wavenumbers, whereas such broadening and downward shifts were not observed for pentacene. These results indicate that there are pentacene crystallites among the amorphous C-60. The intensity ratio of the 1598-cm(-1) (B-3g) and the 1534-cm(-1) (A(g)) bands indicates that pentacene molecules have standing orientations. The appearance of a 514-cm (1) band (Flu) and the splitting of the H-g bands of C-60 indicate symmetry lowering induced by the interaction between pentacene and C-60 molecules. (C) 2015 Elsevier B.V. All rights reserved.

The vibrational Stark effect (VSE) spectra of the CN stretching band of 9-cyanoanthracene dispersed in a poly(methyl methacrylate) (PMMA) film were measured under electric fields of 1.27-1.82 MV/cm at 77K using the difference FT-IR method and a cell with a BaF2/Al/9-cyanoanthracene (10 mol%):PMMA/Al structure. The changes in the electric dipole moment between the ground and the first excited states of the CN stretching mode were 0.0299 +/- 0.0003 D/f, where f is a local field correction factor. This novel polymer matrix method will be useful for measuring the VSE of low molecular weight compounds. (C) 2015 Elsevier B.V. All rights reserved.

The Raman spectra of films prepared from 8, 19, and 30 nm nanoparticles of silicon doped with phosphorous were measured with excitation at 514.5 nm. The observed spectra were analyzed by decomposing the observed Raman bands into three symmetric Voigt function bands, which were assigned to the Si Si stretching modes of crystalline, boundary, and amorphous-like components. The fractions of crystalline, boundary, and amorphous-like regions were estimated from the obtained components. The obtained fractions can be explained as a sphere-like nanoparticle consisting of a crystalline core surrounded with boundary and amorphous-like shells, which is consistent with the transmission electron microscope images showing a sphere-like shape. The observed spectral shape of the 8 nm nanoparticle film showed significant changes upon light irradiation with a power density of 5.5 kW cm(-2), i.e., the amorphous-like region converted to a crystalline one. The temperature of the film under laser irradiation was estimated to be lower than 1041 degrees C from the anti-Stokes to the Stokes Raman bands due to the Si Si stretching mode. The observed partial crystallization is probably induced by heating associated with light irradiation.

We have used infrared spectroscopy to study electric-field induced motions of polymer chains in a ferroelectric uniaxially drawn film of poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)] (molar ratio, 1:0.18) consisting mainly of the polar crystalline beta phase. We analyzed the observed spectra under the C-2v symmetry of an infinite poly(vinylidene fluoride) (PVDF) chain. The changes in intensity of the a(1) bands (2979, 1432, 1280, and 842 cm(-1)), b(1) bands (1073 cm(-1)), and b(2) bands (3017, 1168, and 880 cm(-1)) showed butterfly-shaped hysteresis loops characteristic of ferroelectricity when the electric field was varied from 1.4 to 1.4 MV/cm. The changes in intensity of the a(1) and b(2) bands with transition dipole moments perpendicular to the polymer chain were large, whereas those of the b(1) bands with transition dipole moments parallel to the polymer chain were small. The changes in intensity of the a(1) and b(2) bands were mainly attributed to the inversion of the polymer chain around the polymer axis. On the other hand, the changes in intensity of the b(1) band were attributed to the motion of a polar crystallite. (C) 2015 Elsevier B.V. All rights reserved.

Electric-field-induced infrared spectra of a poly(methyl methacrylate) (PMMA) thin film have been collected in the temperature range between 77 and 297 K by the difference FT-IR method using a cell with a BaF2/Al/PMMA (500 nm)/Al layered structure. The observed temperature dependence suggests that the electric-field-induced spectra collected below 150 K are due to the vibrational Stark effect (VSE), whereas those collected above 150 K are caused by the VSE, electric-field-induced molecular orientation changes, etc. The dependence of the VSE spectrum on the electric field was also measured between 2.0 and 2.8 MV/cm at 77K. The slightly asymmetric infrared band with a peak at 1732 cm(-1) and its VSE spectrum were fitted with two bands with peaks at 1741 and 1731 cm-1. The 1731-cm(-1) band was assigned to C=O stretching vibration. The values of the changes in the electric dipole moment Delta mu and polarizability Delta alpha between the ground and the first excited vibrational states of the C=O stretching mode were determined to be 0.0633 Df(-1) and -3.3 angstrom(3)f(-2), respectively, where f is a local field correction factor. (C) 2015 Elsevier B.V. All rights reserved.

We studied the carriers generated in regioregular poly(3-hexylthiophene) (P3HT) upon FeCl3 vapor and solution doping using visible/near-infrared (VIS/NIR) absorption, infrared (IR), and Raman spectroscopy. Upon doping with an FeCl3 solution in air, the main carriers that were generated were positive polarons. Upon doping with FeCl3 vapor, positive polarons also formed initially, but at higher doping levels, positive bipolarons formed with the concomitant disappearance of the positive polarons. The Raman and IR spectra of the positive bipolarons and the positive polarons were obtained. Raman spectroscopy is very useful for characterizing positive polarons and bipolarons. The Raman results indicated that the positive bipolarons were converted to polarons upon heating to 85 degrees C, indicating that the positive bipolarons formed a metastable state. The temporal changes in the electrical conductivity of a P3HT film upon doping with FeCl3 vapor were measured. The conductivity reached a maximum and then decreased by 2 orders of magnitude. This result suggests that the mobility of the polarons is approximately 100 times as high as that of the bipolarons.

Low-density polyethylene, either cross-linked or not, was oxidized and its absorption spectra were measured in the terahertz (THz) range and infrared range. The absorption was increased by the oxidation in the whole THz range. In accord with this, infrared absorption due to carbonyl groups appears. Although these results indicate that the increase in absorption is induced by oxidation, its attribution to resonance or relaxation is unclear. To clarify this point, the vibrational frequencies of three-dimensional polyethylene models with and without carbonyl groups were quantum chemically calculated. As a result, it was clarified that optically inactive skeletal vibrations in polyethylene become active upon oxidation. Furthermore, several absorption peaks due to vibrational resonances are induced by oxidation at wavenumbers from 20 to 100 cm(-1). If these absorption peaks are broadened and are superimposed on each other, the absorption spectrum observed experimentally can be reproduced. Therefore, the absorption is ascribable to resonance. (C) 2014 The Japan Society of Applied Physics

We have successfully synthesized 3,4,5-substituted 1,4-dihydropyridines (1,4-DHPs) from amine hydrochloride salts, aldehydes, and acetals in good yields without the addition of a catalyst. The synthesized 1,4-DHPs exhibit various wavelengths of fluorescence, which could be tuned by changing the substituents at the 3- and 5-positions of the 1,4-DHPs.

Raman analyses were performed on thin films prepared from B-doped Si nanoparticles with an average diameter of 15 nm using the spin-coating method. The resulting spectrum exhibited a broad band with a peak near 520 cm(-1). The band was decomposed into three bands corresponding to the crystalline, grain boundary (GB), and amorphous regions by the least-squares band-fitting method based on the three Voigt bands. The fractions of the crystalline, GB, and amorphous regions were 37%, 35%, and 28%, respectively. A spherical particle exhibited an ordered crystalline core surrounded by a disordered shell in a transmission electron microscope (TEM) image. The crystalline fraction of the 15-nm B-doped Si nanoparticle film was much lower than that of the 19-nm P-doped Si nanoparticle film. This result suggested that the B-doping mechanism was different from that of P-doping. The temperature of the sample was estimated from the ratio of the peak intensities of anti-Stokes to Stokes Raman bands (I-AS/I-S) observed near 520 cm(-1). The temperature of the B-doped Si nanoparticle film upon irradiation at a power density of 4.6 kW/cm(2) was 298 degrees C, whereas the temperature of the P-doped Si nanoparticle film was 92 degrees C. The B-doped Si nanoparticle films were capable of producing light-induced heat. (C) 2014 Elsevier B.V. All rights reserved.

Control of the crystallinity parameter and phase segregation of poly(3-hexylthiophene-2,5-diyl) (P3HT) and the soluble fullerene derivative [6,6]-phenyl C-61-butyric acid methyl ester (PCBM) is a critical issue for polymer/ fullerene-type organic photovoltaic cell applications. In this paper, P3HT thin films and P3HT: PCBM blend thin films were fabricated using the electrospray deposition method. The Raman spectral features of the samples were estimated using a two-peak fitting with a mixture of Gaussian and Lorentzian functions to determine their crystallinity parameters. Then, the relationship between the film morphology and crystallinity parameter was investigated. Homogenous P3HT thin films with high crystallinity parameters were obtained under dry/wet conditions, and a similar trend was found for P3HT: PCBM blend films. (C) 2013 Elsevier B. V. All rights reserved.

We have studied the formation rates of chemical species such as CO32-/HCO3-, amine/protonated amine, and carbonate/protonated carbonate in the course of CO2 absorption at room temperature and concentration changes after CO2 release upon heating at 93 degrees C for 30 min for aqueous solutions of 12 kinds of tertiary alkanolamines using C-13-NMR spectroscopy. A positive linear correlation was found between the CO2 capture rates of alkanolamines having a normal hydroxyalkyl group and their pKa values. The CO2 capture rates of alkanolamines having a branched hydroxyalkyl group were lower than those in this relationship. The CO2 release amount of each tertiary amine increased with decreasing pKa, as a general trend. N-ethyldiethanolamine (EDEA) showed the largest CO2 release amount and a moderately high rate of CO2 absorption. (C) 2013 The Authors. Published by Elsevier Ltd.

Oxidative degradation produces carboxylic acids which are one of the undesirable degradation products and may have a negative impact on the CO2 separation energy of post combustion capture system. 30wt% MEA solutions mixed with carboxylic acids were regarded as a simulated solution for degraded MEA and effect of the additives on heat of CO2 absorption, equilibrium CO2 loading and CO2 absorption rate were experimentally evaluated by using a differential reaction calorimetry (DRC) apparatus, a pressurized vessel to obtain vapor liquid equilibrium (VLE) data and a gas-liquid contactor, respectively. At the range of CO2 loading from 0.0 to 0.3 mol-CO2/mol-amine, the heat of CO2 absorption of the simulated solution increased by around 10% compared to the normal MEA solution. Moreover, the changing-point of the heat of CO2 absorption of the simulated solution moved to a leaner CO2 loading compared to the normal solution. Result of a C-13-NMR analysis also indicated the change in reaction mechanism. At the absorber condition, the equilibrium CO2 loading of the simulated solution decreased by 20% in comparison with the normal solution, where it decreased by 10 /0 at the stripper condition and therefore the cyclic CO2 loading also decreased. Both CO2 absorption rates decreased linearly but in different gradients with increasing CO2 loading. Higher pH in the simulated solution kept higher CO2 absorption rate, which is consistent with the result of pH measurement. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creati vecornmons.orgll censes/hy-nc-nd/3.0/)

We have studied the concentration changes of chemical species such as CO32-/HCO3-, amine/protonated species, carbonate/protonated species, carbamates/protonated species, etc. in the course of CO2 absorption and those after CO2 release upon heating at 93 degrees C for 30 min for aqueous blends of piperazine (PZ) and each of 11 tertiary alkanolamines using C-13-NMR spectroscopy. The initial rates of CO2 capture of the blends ranged between 0.125 and 0.167 mol/L min, which were contributed by the rapid formation of PZ monocarbamate. A positive linear correlation was found between the CO2 release amounts of the blends upon heating and the pKa values of the tertiary alkanolamines. The CO2 content captured as PZ mono-and bis-carbamates decreased upon heating in the pKa range smaller than 9.34, whereas it increased upon heating in the pKa range higher than 9.55. A tertiary alkanolamine having the pKa smaller than 9.34 is promising as a blend amine with PZ. (C) 2013 The Authors. Published by Elsevier Ltd.

We have estimated the temperature of a buried copper phthalocyanine (CuPc) layer in an organic light-emitting diode with the glass/indium-tinoxide (ITO)/CuPc/N,N0-di-1-naphthaleyl-N,N0-diphenyl-1,10-biphenyl-4,40-diamine (NPD)/tris(8-quinolinolato)aluminum(III) (Alq3)/LiF-Al structure from the full width at half-maximum (FWHM) of a Raman band at around 1528 cm-1. The FWHMs of the band were measured at temperatures in the range from 25 to 200 C. A linear equation was obtained from the observed data by the least-squares method. We estimated the temperature of the CuPc layer in an operating organic light-emitting diode at current densities from 100 to 1000 mA/cm2 using this relationship. The highest temperature was 148 4 -C at a current density of 1000 mA/cm2. © 2013 The Japan Society of Applied Physics.

Pi in the sky: 1,2-bis(ferrocenyl)distibene and 1,2-bis(ferrocenyl) dibismuthene derivatives, where two bulky ferrocenyl units are bridged by a Sb=Sb and Bi=Bi π spacer, have been synthesized as a new family of novel d-π conjugated systems. Their molecular structures, spectroscopic behavior, and electrochemical properties reveal the Sb=Sb and Bi=Bi units to be effective π-electron spacers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vapor liquid equilibrium (VLE) experiments using pressurized vessel operated at wide range of temperatures from 40 degrees C to 120 degrees C were conducted with four binary solutions of Piperazine (PZ) and alkanolamines, which are 2-Isopropylaminoethanol (IPAE), Monoethanolamine (MEA), Diethanolamine (DEA) and Methyldiethanolamine (MDEA). Effective CO2 loadings of some PZ based binary solutions, which meant the difference between the CO2 loadings at the consistent absorber and stripper conditions, increased in comparison with the PZ only solution and especially, PZ/MDEA showed the largest effective CO2 loading. CO2 loadings at the stripper condition did not depend on additive amount of MDEA to PZ and was the same CO2 loading as PZ only solution, while those increased with increase in MDEA concentration at the absorber condition. According to the reaction products analysis for PZ/MDEA samples operated at different temperature by using C-13-NMR spectroscopy, the bicarbonate in the solution decreased significantly with increase in temperature, but the PZ carbamate dissociated CO2 much less than the carbamate even at 120 degrees C. (C) 2013 The Authors. Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and/or peer-review under responsibility of GHGT

Chemical reactions associated with the absorption of CO2 into aqueous solutions of blends of piperazine (PZ) with N-methyldiethanolamine (MDEA), etc. were studied by C-13-NMR spectroscopy. The coexistence of PZ and MDEA enhanced the initial apparent rate of HCO3-/CO32- formation. This result can be explained by considering that PZ monocarbamate rapidly formed works as an organocatalyst in the formation reaction of HCO3-. Concentration changes of chemical species in CO2-absorbed aqueous amine solutions upon heating (80 degrees C, 30 min) were studied by C-13-NMR spectroscopy. Carbon dioxide regeneration originates mainly from HCO3-/CO32-, and not from carbamate and carbonate.(C) 2013 The Authors. Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and/or peer-review under responsibility of GHGT

We have studied the templating effect of bis(1,2,5-thiadiazolo)-p-quinobis(1,3-dithiole) (BTQBT) on structure and performance of organic solar cells having the multilayer of ITO/BTQBT/metal-free phthalocyanine (H2Pc)/C-60/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/Al. Orientation of H2Pc molecules has been studied by infrared reflection-absorption spectroscopy. The angle between the molecular plane and the substrate surface was 82 degrees for an ITO/H2Pc sample, whereas 32 degrees for an ITO/BTQBT/H2Pc sample. The angle depends on the materials below the H2Pc layer. The short-circuit current was increased from 3.97 to 5.45 mA/cm(2) by the insertion of the BTQBT layer. This result probably originates from the change in orientation of H2Pc molecules. The power conversion efficiency of the solar cell with the ITO/BTQBT/H2Pc/C-60/BCP/Al structure was 1.4 %, whereas that of a cell without the BTQBT layer was 1.1 %. The efficiency was also enhanced by the insertion of the BTQBT layer.

1,2-Bis(ferrocenyl)dipnictenes bearing a Pn=Pn π-spacer (Pn: P (1), Sb (2), and Bi (3)) between two ferrocenyl units have been synthesized as stable compounds. Not only their molecular structures and fundamental properties but also their redox behavior have been systematically disclosed. Interestingly, in the reduction region, the dipnictenes showed two pseudo-reversible one-electron redox couples at low temperature, suggesting possible generation of the corresponding radical anion and dianion species. On the other hand, they showed three-step one-electron oxidation processes in the oxidation region. The first two oxidation steps would correspond to those of the two ferrocenyl moieties, while the third step would be that of the Pn=Pn π-spacer moiety, respectively. Thus, these 1,2-bis(ferrocenyl)dipnictenes with a Pn=Pn π-spacer should be stable multiredox systems reflecting unique properties of a double bond between heavier 15 group elements. As a result, all Pn=Pn units (Pn: P, Sb, and Bi) were found to work as a more effective π-spacer than those of 2nd row elements such as C=C and N=N. © 2013 The Chemical Society of Japan.

Electrical insulation properties of low density polyethylene (LDPE) are still unclear, especially when it is degraded. In this regard, ultraviolet (UV) photons were irradiated to LDPE sheets at room temperature and 85 degrees C and their absorption spectra were measured at frequencies from 0.5 to 3.0 THz and from 18 to 105 THz. A very broad absorption band with its peak at around 1.6 THz appears by the UV irradiation. In accord with this appearance, the infrared absorption peak due to a carbonyl structure increases. Quantum chemical calculations were carried out using 3-dimensional models with and without carbonyl groups. As a result, the model with carbonyl groups was found to have optically active modes at about 1.7 THz. From these results, the increase in absorption at 1.6 THz is assumed to be induced by oxidation.

Characterizations of CO2 absorbents containing various amine species were carried out with their simple aqueous solutions and binary mixed solutions. Absorption and desorption process were demonstrated under the temperature of 50 degrees C and 80 degrees C, respectively. All absorbents were characterized using two indexes; absorption rate and release ratio. The results show typical primary amines have high absorption rate and low release ratio, while tertiary amines has low absorption rate and high release ratio. The characteristics of mixed absorbents changed continuously by changing compositions of mixed amine species. The result of quantitative analysis show negative relationship between bicarbonate formation and release ratio, indicating bicarbonate formation does not affect directly to release ratio of the CO2 absorbent. (C) 2013 The Authors. Published by Elsevier Ltd.

We present a 532-nm excited Raman imaging study of pentacene thin films (thickness, 2, 5, 10, 20, 50, 100, and 150?nm) prepared on an SiO2 surface. The structure of the pentacene films has been investigated by images and histograms of the ratio (R) of intensity of the 1596-cm-1 band (b3g) to that of the 1533-cm-1 band (ag), which can be used as a marker of solid-state phases: 1.54-nm and 1.44-nm phases. The Raman images showed that island-like 1.44-nm phase domains are grown on the 1.54-nm phase layer from 50?nm, and all the surface of the 1.54-nm phase layer is covered with the 1.44-nm phase layer from 100?nm. The structural disorders have been discussed on the basis of the full width at half maximum of a band in the histogram of the R values for each film. Copyright (c) 2012 John Wiley & Sons, Ltd.

We present Raman imaging and photoexcitation infrared studies of organic semiconductor films, which are used in organic light-emitting diodes, thin-film transistors, and photovoltaic solar cells. Raman images of the ratio (R) of intensity of the 1596-cm(-1) band (b(3g)) to that of the 1533-cm(-1) band (a(g)) were used for characterizing the 1.55-nm and the 1.44-nm phases in pentacene thin films. The Raman spectrum of N,N'-di-1-naphthaleyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPD) film formed on a MoO3-deposited indium-tin-oxide (ITO)/glass substrate indicated that the cation of NPD is formed upon oxidation by MoO3. The Raman image of the sample showed the heterogeneous distribution of the cation of NPD. Photoinduced infrared absorption from a film of regioregular poly(3-octylthiophene) (P3OT) and [6,6]-phenyl-C-61-butyric acid methyl ether (PCBM) blend was measured by difference infrared spectroscopy. The temperature dependence of photoinduced infrared absorption due to positive polarons showed the existence of two kinds of carrier traps. (C) 2011 Elsevier B.V. All rights reserved.

The stable 1,2-dibromodialumane(4) Bbp(Br)Al-Al(Br)Bbp (1; Bbp = 2,6-bis[bis(trimethylsily)methyl]phenyl) was synthesized by the reduction of the corresponding dibromoalumane etherate BbpAlBr(2)center dot OEt2 (2). The structure and properties of 1 have been elucidated on the basis of the analyses of spectroscopic and crystallographic data and are supported by DFT calculations.

The synthesis and structural analysis of the 1,2-bis(ferrocenyl)digermene (E)-Tip(Fc)Ge=Ge(Fc)Tip (Tip = 2,4,6-triisopropylphenyl, Fc = ferrocenyl), a stable crystalline compound, is reported. In this digermene, two ferrocenyl d electron systems are bridged by a Ge=Ge π spacer. As is evident from X-ray crystallographic, spectroscopic, and electrochemical analysis, this 1,2-bis(ferrocenyl)digermene shows effective d-π interaction and the Ge=Ge π bond is stable in the solid state. The Ge=Ge double bond is cleaved at elevated temperatures in the presence of butadiene, with concomitant loss of the π conjugation in the molecule. © 2012 American Chemical Society.

We present the electrical properties of an organic memory device based on an organic field-effect transistor using a thin film of nylon 11 as a gate dielectric. The transfer characteristics of the memory device showed large hysteresis. A large shift of 37 V in the transfer characteristics was obtained by the application of a writing bias to the gate dielectric. The drain current ratio of the on-state to off-state was ca. 100. The on-state of the memory device showed a clear memory characteristic. (C) 2012 The Japan Society of Applied Physics

Kinetically stabilized 1,2-dihydrodisilenes were successfully synthesized and isolated by the introduction of sterically protecting bulky aryl groups. These 1,2-dihydrodisilenes exhibit distinct Si=Si double-bond character in both solution and the solid state. The Si H bonds in these 1,2-dihydrodisilenes exhibit higher s character than those of typical sigma(4),lambda(4)-hydrosilanes. Moderate heating of these 1,2-dihydrodisilenes in solution resulted in their isomerization to the corresponding trihydrodisilanes, with an intramolecular hydrogen migration as the rate-determining step.

Solid-state structures of thin blend films of perylene and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) formed on the Au surface have been studied by a combination of infrared reflection-absorption spectroscopy and the RATIO method of Debe. In the blend films, PTCDA molecules take the face-on orientation in the whole range of PTCDA contents from 7.5 to 88 mol%. On the other hand, the molecular orientation of perylene molecules changes from edge-on toward random as the PTCDA content increases. (C) 2012 Elsevier B. V. All rights reserved.

The synthesis and characterization of a stable 1,2-bis(ferrocenyl)diphosphene, wherein a P=P pi-bond connects two ferrocenyl units will be reported. This represents an unprecedented example for a d-pi electron system containing a heavier pnictogen pi-spacer group. Stabilization of the highly reactive P=P pi-bond was achieved by steric protection using two bulky ferrocenyl moieties.

Simple bottom-up fabrication processes for molecular self-assembly have been developed for the construction of higher-order structures using organic materials, and have contributed to maximization of the potential of organic materials in chemical and bioengineering. However, their application to organic thin-film devices such as organic light-emitting diodes have not been widely considered because simple fabrication of a solid film containing an internal self-assembly structure has been regarded as difficult. Here it is shown that the intermolecular C-H···N hydrogen bonds can be simply formed even in vacuum-deposited organic films having flat interfaces. By designing the molecules containing pyridine rings properly for the intermolecular interaction, one can control the molecular stacking induced by the intermolecular hydrogen bonds. It is also demonstrated that the molecular stacking contributes to the high carrier mobility of the film. These findings provide new guidelines to improve the performance of organic optoelectronic devices and open up the possibilities for further development of organic devices with higher-order structures. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The first stable anthryldiphosphenes, 1 and 2, were synthesized by utilizing kinetic stabilization of 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) and 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt) groups, and were characterized by spectroscopic and X-ray crystallographic analyses. The UV-visible spectroscopic data suggested the electronic communication between the anthryl moiety and the P=P unit. It was found that TbtP=P(9-Anth) (1a: 9-Anth = 9-anthryl) showed weak fluorescence in hexane solution. Furthermore, the reactivities of anthryldiphosphene 1 with a chromium complex, chalcogenation reagents, a diene, and electron-deficient olefins have been revealed.

The one-pot synthesis of 2-arylquinoline with arylamines, arylaldehyde, and 1,1-diethoxyethane were studied using a catalytic amount ytterbium triflate. Various 2-arylquinolines showed fluorescence properties and the fluorescence was quenched by introducing the nitro group into aryl moiety of 2-arylquinolines.

We have observed the Raman spectrum of an operating phosphorescent organic light-emitting diode fabricated with bis(2-(2'-benzothienyl)-pyridinato-N, C(3')) iridium( acetylacetonate) (Btp(2)Ir(acac)) as a phosphorescent emitter with excitation at 532 nm. All of the observed bands have been attributed to Btp(2)Ir( acac) because of the resonance Raman effect. We have determined the temperature of the emitting layer containing Btp(2)Ir( acac) from the ratio of the anti-Stokes to Stokes Raman bands of the 283-cm (1) vibrational mode attributed to Btp(2)Ir( acac). The temperature of the emitting layer is estimated to be 89 +/- 8 degrees C at a current density of 400 A/m(2). (C) 2010 Elsevier B.V. All rights reserved.

Stable 1,2-bis(metallocenyl)disilenes were synthesized for the first time and were characterized by spectroscopic and X-ray crystallographic analyses. On the basis of cyclic voltammograms, (E)-1,2-bis(ferrocenyl)-1,2-bis(2,4,6- triisopropylphenyl)disilene (1a) was found to be a stable five-electron redox system with four steps, while (E)-1,2-bis(ruthenocenyl)-1,2-bis(2,4,6- triisopropylphenyl)disilene (1b) showed four-step redox couples with four electrons. The UV-vis spectra and theoretical calculations for these disilenes suggested that they should be novel d-π conjugated systems containing a disilene unit. In addition, chalcogenation reactions of 1a resulted in the formation of new heterocyclic compounds bearing ferrocenyl units. For example, the first stable 1,2,3,4-dithiadisiletane derivative was obtained by the sulfurization reaction of 1a. © 2009 The Chemical Society of Japan.

Synthesis and isolation of the stable diaryldibromodisilene, Bbt (Br)Si =(Br)Bbt, has been accomplished for the first time. The dibromodisilene underewent substitution reactions with organometallic reagents on the low-coordinated silicon atom to afford the corresponding substituted disilenes. Futhermore, the reaction of 1 with t-BuLi afforded the corresponding 1,2-diaryldisilyne, BbtSi SiBbt, the characters of which were revealed by spectroscopic and crystallographic analyses.

A new type of disilene substituted by ferrocenyl groups, 1,2-bis(ferrocenyl)disilene, was synthesized as a good candidate for a novel d-pi electron system, and the unique properties of the Si=Si pi bond of this new disilene were revealed. On the basis of the results of the electrochemical analyses, 1,2-TiP(2)-1,2-Fc(2)-disilene (Tip = 2,4,6-triisopropylphenyl, Fc = ferrocenyl) was found to be a stable five-electron redox system with four steps.

We have measured the temperatures of the organic layers in operating organic light-emitting diodes (OLEDs) by Raman spectroscopy. The wavenumbers of the Raman bands due to N,N'-di-naphthaleyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPD) and copper phthalocyanine (CuPc) have been measured as a function of temperature in the range of 25-191 degrees C. The observed positions of strong bands around 1607 cm(-1) (NPD) and 1531 cm(-1) (CuPc) shifted downward linearly with increasing temperature in the ranges lower than 92 and 191 degrees C, respectively. We have determined the temperatures of the NPD and CuPc layers in an operating OLED from the wavenumber-temperature relations of these bands. [DOT: 10.1143/JJAP.47.3537]

We have measured the Stokes and anti-Stokes Raman scattering from organic light-emitting diodes based on copper phthalocyanine (CuPc), N,N'-di-1-naphthalenyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (alpha-NPD), and tris(8-quinolinolate) aluminum(III) (Alq(3)) with excitation at 633 nm. All of the observed bands have been attributed to CuPc because of the resonance Raman effect. The temperature of the CuPc layer has been obtained by taking the intensity ratio of anti-Stokes to Stokes Raman scattering of the 483 cm(-1) vibration. The temperature of the CuPc layer in the device operated at 400 mA was 140 degrees C.

We have observed Stokes and anti-Stokes Raman scattering from an operating double-layer polymer light-emitting diode fabricated with poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate) (PEDOT-PSS) as a hole-injection layer (50 nm thickness) and a polyfluorene-based polymer blend as a light-emitting layer (90 nm thickness) with excitation at 633 nm. The temperature of the PEDOT-PSS layer was estimated to be 74 +/- 6 degrees C at a current of 150 mA/cm(2) (1000 cd/m(2)), whereas that of the glass surface measured by a thermocouple was 41 degrees C. (C) 2008 Elsevier B.V. All rights reserved.

The stable lithium diphosphene anion radical, [Li(dme)(3)](+)[TbtPPTbt](.-) (dme: 1,2-dimethoxyethane, Tbt: 2,4,6- tris[bis(trimethyl-silyl) methyl]phenyl), was readily synthesized by the one-electron reduction of the corresponding neutral diphosphene (TbtP=PTbt). The molecular structure of the diphosphene anion radical was discussed in detail on the basis of its ESR, UV-Vis and Raman spectra, and theoretical calculations. The diphosphene anion radical was found to undergo ready chalcogenation reactions using elemental sulfur and selenium to afford the corresponding thiadiphosphirane and selenadiphosphirane, respectively. (C) 2007 Elsevier B. V. All rights reserved.

The first stable neutral stannaaromatic compound, 2-stannanaphthalene 1a, was synthesized by taking advantage of an extremely bulky and efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). The molecular structure and aromaticity of 1a were discussed on the basis of X-ray crystallographic analysis, NMR, UV-vis, and Raman spectroscopy, cyclic voltammetry, and theoretical calculations. 2-Germanaphthalene 2a, which has a framework similar to that of 1a, was synthesized for comparison, and systematic elucidation was made for the properties of 2-metallanaphthalene systems containing a heavier group 14 element (Si, Ge, or Sn).

The first stable neutral stannaaromatic compound, 2-stannanaphthalene 1a, was synthesized by taking advantage of an extremely bulky and efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). The molecular structure and aromaticity of 1a were discussed on the basis of X-ray crystallographic analysis, NMR, UV-vis, and Raman spectroscopy, cyclic voltammetry, and theoretical calculations. 2-Germanaphthalene 2a, which has a framework similar to that of 1a, was synthesized for comparison, and systematic elucidation was made for the properties of 2-metallanaphthalene systems containing a heavier group 14 element (Si, Ge, or Sn). © 2008 The Royal Society of Chemistry.

Molecular orientation in pentacene films and thin-film transistors has been studied by micro-Raman spectroscopy. We have found that the relative intensity of the 1596-cm(-1) band (B-3g) is sensitive to the molecular orientation. The standing orientation was observed for the films formed on the bare and hexamethyldisilazane (HMDS)-modified SiO2 surfaces and the Au surfaces modified with self-assembled monolayers (SAMs), whereas the lying orientation for the films on the bare Au surface. We have explicitly demonstrated the differences of the molecular orientation in the films on SiO2 dielectric layers and Au electrodes in the devices by mapping measurements.

Kinetically stabilized 1,1'-bis[(E)-diphosphenyl]ferrocenes were synthesized by taking advantage of extremely bulky substituents, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (denoted as Tbt) and 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (denoted as Bbt) groups, and characterized by the spectroscopic and X-ray crystallographic analyses. The electronic structures of the 1,1'-bis[(E)-diphosphenyl]ferrocenes were determined by analyzing electronic spectra, the transitions of which were reasonably assigned based on theoretical calculations. In the cyclic voltammograms, there were two well-defined reversible one-electron reduction couples corresponding to the intramolecular two diphosphene units. Furthermore, the 1,1'-bis[(E)-diphosphenyl]ferrocene was found to undergo ligand-exchange reactions with group 6 metal carbonyl complexes along with the E-to-Z isomerization of the diphosphene moieties, leading to the formation of the corresponding 1,1'-bis[(Z)-diphosphenyllferrocene group 6 metal tetracarbonyl complexes, [M(CO)(4))(Z,Z)-(BbtP=PC5H4)(2)Fe)] (M = Cr, Mo, and W). The molecular structures of these complexes were determined by spectroscopic analyses (H-1, C-13, and (PNMR)-P-31 spectra, and UV-vis spectra), and that of the tungsten complex was determined by X-ray crystallographic analysis. Several types of d -> pi*(P=P) electron transitions due to the iron and group 6 metals were detected by using UV-vis spectroscopy, and these results were supported by theoretical calculations.

Blue polydiacetylene films were prepared from the Langmuir-Schaefer (LS) and Langmuir-Blodgett (LB) films of the cadmium salt of 10,12-pentacosadiynoic acid, CH3(CH2)(11)-C C-C C-(CH2)(8)COOH, and the C C stretching modes of the Raman spectra of the LS and LB films were observed at 2068 and 2079 cm(-1), respectively. These wavenumbers appeared to be sensitive to the packing of polymer chains. Most of the progression bands observed in the range of 1332-1182 cm(-1) have been assigned to the CH2 wagging modes of the all-trans structure of the (CH2)(11)CH3 group. (C) 2007 Elsevier B.V. All rights reserved.

Reaction of 9-bromo-9,10-dihydro-9-silaphenanthrene (6) with lithium diisopropylamide (LDA) in THF at room temperature afforded kinetically stabilized 9-silaphenanthrene 1a bearing an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). 9-Silaphenanthrene 1a was isolated as pale yellow crystals, and the structure of 1a was completely determined by spectroscopic and X-ray crystallographic analyses. The H-1 and C-13 NMR chemical shifts corresponding to the 9-silaphenanthrene ring of 1a were observed in a typical aromatic region, while the central silicon atom showed the characteristic signal at 86.9 ppm in the Si-29 NMR in C6D6. The 9-silaphenanthrene ring of 1a showed completely planar geometry, indicating that 9-silaphenanthrene has a delocalized 14 pi-electron system as an aromatic compound. In spite of its high thermal stability, 1a still has high reactivity at the 9,10-position toward small reagents such as H2O.

Air-stable n-channel field-effect transistors based on thin films of the compound, N,N′-bis(4-trifluoromethylbenzyl)perylene-3,4,9,10-tetracarboxylic diimide (PTCDI-TFB), were fabricated, and the effects of surface treatment and substrate temperature at the film deposition on the electron mobility of the transistors were studied. The maximum mobility, 4.1 × 10-2cm2V-1s-1in the saturation region (1.7 × 10-2cm2V-1s-1in the linear region), was obtained in air for the film deposited at 95 °C on the SiO2surface modified with hexamethyldisilazane. The high electron affinity of PTCDI-TFB estimated at 4.8 eV by photoelectron yield spectroscopy and UV-Vis absorption spectroscopy, which is ascribable to the trifluoromethylbenzyl groups, is likely to result in the observed stable transistor operation in air. © 2007 Elsevier B.V. All rights reserved.

The organic field-effect transistors based on N,N'-dioctyl-3,4,9,10- perylene tetracarboxylic diimide have been fabricated on the pristine SiO2/Si substrate whose surfaces are modified with hexamethyldisilazane (HMDS) and octadecyltriethoxysilane (OTES). The surface modifications have enhanced the electron mobility and on/off ratio, and decreased the threshold voltage. The atomic force microscopy and infrared spectroscopy studies have revealed no differences in the morphology and molecular orientation of the thin films on the pristine and the HMDS-treated substrates.

We have fabricated organic field-effect transistors (OFETs) based on three derivatives of perylene tetracarboxylic diimide (PTCDI). The electron mobility more than 8 x 10(-2) cm(2)V(-1)s-(1) has been obtained in both vacuum and air for N,N'-bis(4-fluorobenzyl) perylene-3,4,9,10-tetracarboxylic diimide. The study of the film structures suggests that the flat-layer structures near the SiO2 surfaces induce the high electron mobilities.

The first stable 9-anthryldiphosphene, TbtP=P(9-Anth) (1: Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, 9-Anth = 9-anthryl), was synthesized and its properties were revealed by spectroscopic and X-ray crystallographic analyses. The weak fluorescence of I was observed in hexane solution.

Voltage-induced infrared absorption spectra from the top- and bottom-contact field-effect transistors fabricated with n-Si, SiO2, and poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) as a gate electrode, an insulator, and a semiconductor, respectively, have been measured in a transmission-absorption configuration by the FT-IR difference-spectrum method. The observed voltage-induced infrared bands have been attributed to positive carriers (polarons) injected into the MEH-PPV layer by the application of minus gate bias. The cross section of the doping-induced 1510-cm(-1) band has been obtained to be 7.7x10(-17) cm(2) for the MEH-PPV films doped electrochemically with ClO4-. The observed intensities of the voltage-induced 1510-cm(-1) band have been converted to carrier sheet densities by this cross section. The carrier sheet density induced by field effect shows a saturation effect as the gate voltage increases for the top- and bottom-contact devices. The number of carriers injected in the top-contact device is larger than that in the bottom-contact device. (C) 2006 Elsevier B.V. All rights reserved.

The redox behavior of kinetically stabilized dipnictenes, BbtE=EBbt [E = P, Sb, Bi; Bbt = 2,6-bis[ bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl], was systematically disclosed using cyclic voltammetry and theoretical calculations. It was found that they showed reversible one-electron redox couples in the reduction region. The anion radical species of the Bbt-substituted diphosphene and distibene were successfully synthesized by the reduction of the corresponding neutral dipnictenes (BbtP=PBbt and BbtSb= SbBbt). Their structures were reasonably characterized by ESR, UV-vis, and Raman spectroscopy, and the distibene anion radical was structurally characterized by X-ray crystallographic analysis.

The infrared Stark spectrum of a thin film of poly(gamma-benzyl-L-glutamate) (PBLG) has been measured in a field-effect transistor (FET) configuration, instead of the standard Stark cell with semitransparent metal electrodes. In the FET-type cell the PBLG film is sandwiched with an interdigital gold film and a SiO2/n-Si substrate; the gold and n-Si have been used as electrodes. The obtained Stark spectrum is in good agreement with that in the literature. Each of the observed Stark bands, which are assigned to the NH str, the C=O str of the ester group, and the amide I, has been decomposed into the zeroth-, first-, and second-derivative components by the least-squares method. The effective electric field in the PBLG film has been estimated from the obtained second-derivative component for each vibrational mode on the basis of the reported difference electric dipole moment, following excitation to a vibrationally excited state. The effective electric field is 0.42 times as large as that of the corresponding capacitor with a plate electrode instead of the interdigital one. The FET-type cell can be used for the measurements of infrared Stark spectra on the basis of the obtained effective electric field. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

The first stable 9-germaanthracene and 9-germaphenanthrene were successfully synthesized by taking advantage of kinetic stabilization utilizing effective steric protection groups, Tbt and Bbt groups (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Bbt = 2,6-bis[bis(trimethylsilyl)methylJ4-[tris(trimethylsilyl)methyl]phenyl). The similarities and differences of the structures and properties between the two isomers of germaaromatics are discussed. © 2006 American Chemical Society.

Photophysical and photochemical processes of 9-methyl- and 9-phenyl-9,10-dihydro-9-silaphenanthrene derivatives have been studied at room temperature and 77 K in comparison with the carbon analogue, 9,10-dihydrophenanthrene. These 9,10-dihydro-9-silaphenanthrene derivatives show smaller fluorescence quantum yield and remarkably larger Stokes shifts than those of the carbon analogue. In contrast, their phosphorescence quantum yields are two times larger than those of the carbon analogue, although the absolute value is not so large (∼0.1). Reaction products and intermediates produced by the 266 nm light photolysis have been studied, and it has been confirmed that 9-methyl- and 9-phenyl-9-silaphenanthrenes have been photochemically formed in methylcyclohexane at 77 K, in addition to the formation of radical cations of 9,10-dihydro-9-silaphenanthrene derivatives and the carbon-centered radical: 9-hydro-9-silaphenanthrenyl radical. © 2006 American Chemical Society.

Experimental Raman and infrared spectra of poly(p-phenylenevinylene) have been analyzed on the basis of the normal coordinate calculations based on the density functional theory method at the B3LYP/cc-pVDZ level for a model oligomer. Vibrational modes corresponding to optically active modes of an infinite polymer chain have been selected from the calculated results. On the basis of these normal vibrations, the observed vibrational spectra of poly( p-phenylenevinylene) have been explained successfully. The angles between the calculated transition dipole moment vectors and the polymer axis for some infrared bands agree with those derived from observed infrared dichroic spectrum. (c) 2005 Elsevier B.V. All rights reserved.

The organic field-effect transistors based on polydiacetylene as an active semiconductor have been made. The hole mobility and the on/off ratio have been determined to be 1.3 x 10(-3) cm(2)/V s and 1.0 x 10(4), respectively, for the transistor based on the blue phase of polydiacetylene prepared from 10, 12-pentacosadiynoic acid. The gate-voltage-induced infrared absorption spectrum has been attributed to the positive carriers injected by field effect. The spectrum shows a remarkable electron-molecular vibration coupling between vibration levels and an electronic transition.

The reduction of an overcrowded (E)-1,2-dibromodigermene, Bbt(Br)Ge=Ge(Br)Bbt (2) [Bbt = 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl], with KC8 afforded a stable digermyne, BbtGe GeBbt (1). The Ge Ge triple-bond characters of 1 were revealed by the X-ray crystallographic analysis and spectroscopic studies (UV/vis and Raman spectra) together with theoretical calculations. The Ge Ge bond lengths of the two nonidentical molecules of 1 observed in the unit cell were shorter than that of the previously reported digermyne, Ar'Ge GeAr' (Ar' = 2,6-Dip(2)C(6)H(3), Dip = 2,6-diisopropylphenyl).

The field-effect transistor fabricated with N,N′-bis(3-methylphenyl)- N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD) on a silicon substrate has shown a p-channel organic field-effect transistor (OFET) operating in the accumulation mode. The hole mobility in the TPD layer has been obtained to be 7.2 × 10 -4 cm 2 V -1 s -1 . Gate-voltage-induced infrared absorption from the OFET has been measured in the transmission-absorption configuration by the FT-IR difference-spectrum method. The observed spectra depend on the gate voltage applied. The vibrational Stark effect and the bands originating from the carriers injected into the TPD layer have been observed.

We here report our theoretical as well as experimental studies on the stacking manner of peptide nanorings (PNRs) in peptide nanotubes (PNTs). We focus on the molecular vibrations of N-H and C=O stretching modes and discuss this subject via their infrared (IR) spectroscopy, because PNTs are formed by the inter-ring H bonds between the adjacent PNRs via -N-H(...)O=C-. Symmetry analysis based on group theory reveals that parallel stacking causes two IR active modes in these molecular vibrations while three modes are active in the antiparallel stacking. This difference in the number of IR active modes is determined only by the stacking manner and not by the number of amino acid residues composing the PNRs. By using two typical PNRs Of cyclo[-((L)-Gln-D-Ala)(3)] and cyclo[-((L)-Gln-(D)-Ala)(4)], we further studied the favorable stacking manners of PNRs via IR observation. Our IR experiments as well as the ab initio energetics show that the former PNRs create a PNT by stacking themselves in parallel while the latter PNRs do so by stacking themselves in an antiparallel manner.

The micro-Raman spectra of a double-layer light-emitting diode fabricated with poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate) (PEDOT-PSS) as a hole-injection layer and poly(2,7-(9,9-dioctylfluorene)-alt-benzothiadiazole) (F8BT) blended with poly(9,9-dioctylfluorene) (PF8) as an emissive layer have been measured with excitation at 633 nm. After the operation of the device, the intensities of the bands due to PEDOT have increased. These increases in Raman intensity have been attributed to the reduction (dedoping) of PEDOT chains during operation on the basis of the results of electrochemical oxidation and reduction of a PEDOT-PSS film. The reduction of PEDOT chains is most likely one of the intrinsic factors of the degradation of polymer light-emitting diodes. (c) 2005 Published by Elsevier B.V.

A novel point-arc microwave plasma chemical vapor deposition (CVD) apparatus was employed to grow single-walled carbon nanotubes (SWNTs) on Si substrates coated with a sandwich-like nano-layer structure of 0.7 nm Al2O3 (top)/0.5 nm Fe/ 5-70nm Al2O3 by conventional high frequency sputtering. The growth of extremely dense and vertically aligned SWNTs with an almost constant growth rate of 270 mu m/h within 40 min at a temperature as low as 600 degrees C was demonstrated for the first time. The volume density of the as-grown SWNT films is as higher as 66 kg/m(3).

Raman marker bands characteristic of solid-state structure have been found for N, N'-di-1-naphthaleyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine(NPD), which is used as a hole-transport material in organic light-emitting diodes. The widths of the marker bands observed for an amorphous state at 1607, 1290, and 1192 cm(-1) are broader than those for the crystalline state observed at 1609, 1288, and 1198 cm(-1). These Raman bands are found to be useful for detecting the crystallization, which may cause degradation of organic light emitting diodes, of amorphous NPD films. (c) 2005 Elsevier B.V. All rights reserved.

The structures, vibrational frequencies, and infrared and Raman intensities of p-terphenyl have been calculated by the density functional theory method at the B3LYP/6-311 + G** level. On the basis of the results, the infrared and Raman spectra of p-terphenyl in solution and in the melt have been analyzed. The observed spectra have been attributed to two stable rotational isomers around the inter-ring, CC bonds: a helical conformer (D, symmetry) and an alternately twisted conformer (C-2h symmetry). These two isomers coexist in solution and in the melt. The 518-cm(-1) infrared band and the 375-cm(-1) Raman band of the helical conformer are correlated with the 483-cm(-1) infrared band and the 329-cm(-1) Raman band of the twisted conformer, respectively. All of these bands have been assigned to the mixtures of out-of-plane boat deformations and in-plane rotational displacements. The frequencies of these modes are sensitive to the conformation of p-terphenyl. (C) 2004 Elsevier B.V. All rights reserved.

Field-effect mobilities and on/off current ratios have been determined for the organic field-effect transistors (OFETs) based on three kinds of poly(p-phenylenevinylene) derivatives. The best transistor performance has been obtained for poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEHPPV). The hole mobility and the on/off ratio obtained for the MEH-PPV OFET are 3.6 x 10(-4) cm(2)/Vs and 1.5 x 10(6), respectively. These OFETs operate stably in the atmosphere as well as in vacuum.

The Ta2O5 film prepared on silicon by RF sputtering has been used as a gate insulator for the top-contact field-effect transistors fabricated with poly(2-methoxy-5-(2'-ethylhexyloxy)1,4-phenylenevinylene) (MEH-PPV) or pentacene. Good transistor characteristics have been obtained with saturation at low drive voltages (about -3 V) and with hole mobilities of 5.2 x 10(-4) cm(2)/VS (MEH-PPV) and 0.8 cm(2)/VS (pentacene).

Charge-induced infrared absorption spectra from the metal-insulator-semiconductor diodes fabricated with aluminum oxide, poly(p-xylylene), and SiO2 as gate dielectric and regioregular poly(3-octylthiophene) as organic semiconductor have been measured in situ with reflection or transmission configurations by the FT-IR difference-spectrum method. The observed bands have been attributed to the carriers injected into the polymer layers under the application of minus gate bias. The wavenumber of the band around 1300 cm(-1) depends on the gate voltage, indicating that the structure of the carriers depends on the carrier concentration. There exist upper limits in the concentrations of the injected carriers. In situ infrared absorption measurements provide the information about the injected carriers, which affect the properties and the functions of polymer field-effect devices.

Peptide nanotubes of cyclo[-(D-Ala-L-Glu)(4)], cyclo[-(D-Ala-L-Gln)(3)], cyclo[-(D-CyS-L-Gln)(3)], and cyclo[-(L-Gln)(5)] have been synthesized and their morphologies have been studied by scanning probe microscopy. The atomic force microscopy displayed several interesting self-assembling forms of these peptide nanotubes. The three D,L-peptides showed not only the straight tubular forms but also the self-assembled bundles. The number and size of observed nanotubes and their bundles were different among those three and also among employed solvents and substrates. On the contrary, the homo-L-peptide of cyclo[-(L-Gln)(5)] provided meandering nanotubes. which were caused by the symmetry lowering due to the odd number of amino acids. The meandering characteristics also resulted peculiar super-ring forms of the homo-L-peptide nanotubes. Additionally, the scanning tunneling microscopy was performed and high-resolution images of D,L-peptide nanotubes as well as their bundles were obtained.

Infrared absorption induced by field effect from a metal-insulator-semiconductor diode with an Au/aluminum oxide/regioregular poly(3-hexylthiophene) structure has been obtained by using a combination of infrared reflection-absorption spectroscopy and the FT-IR difference-spectrum method. The observed bands have been attributed to carriers (positive polarons) injected into the polymer layer and accumulated near the surface of the layer.

The absorption spectra of a poly(p-phenylene) film doped with FeCl3 in the range from visible to infrared have been measured. The observation of two intra-gap electronic absorptions indicates the formation of positive polarons upon FeCl3 doping. The observed doping-induced infrared spectrum is in good agreement with that calculated by the density functional theory method at the BLYP/6-31G* level for the radical cation of p-sexiphenyl. Although the infrared bands predicted by the effective conjugation coordinate theory have strong intensities, the infrared bands not predicted by this theory have considerable intensities.

Field-induced infrared absorption spectra from the metal-insulator-semiconductor diodes fabricated with regioregular poly(3-hexylthiophene) or poly(3-octylthiophene) have been obtained by using a combination of infrared reflection-absorption spectroscopy and the FT-IR difference-spectrum method. The obtained spectra have been attributed to positive polarons generated at the interface with the insulator (aluminum oxide) layer in the range of minus gate voltage.

We observed Raman spectra of Silk I and Silk II powders of (Ala-Gly)15, which is a model peptide of crystalline region of Bombyx mori silk fibroin. Additionally Raman spectra of Ac-(Gly-Ala)4-NHMe and Ac-(Gly-Ala)3-NHMe with Silk I and Silk II forms were calculated according to the repeated β-turn type II structural model and β-sheet model, respectively. The ab initio molecular orbital calculation was used for the theoretical calculation. The calculated results could reproduce the spectra. Especially, in silk I form, observation of splitting of amide I and III bands was in agreement with the predicted bands according to the repeated β-turn type II structural model.

The difference of Raman spectra between lightly and heavily Na-doped traps-polyacetylene (trans-PA) was observed with the 1320 nm laser line, and these were discussed on the basis of the Raman spectra of the negatively charged anions Ph(CH)(n)Ph- [DPn-, n = 3, 5, 7, 9, and 13] and the radical-anion species Ph(CH)(n)Ph.- [DPn.-, n = 4, 6, 8, and 10] and 19,19',20,20'-tetranor-beta,beta'-carotene [TNBC.-, n = 22] of the model compounds, which correspond respectively to negatively charged soliton and negative polarons in traps-PA. The observed wavenumbers of the nu(1) and nu(4) bands (C=C and C-C stretches) of lightly doped traps-PA are lower than those of the corresponding bands of pristine traps-PA, whereas the contrary is the case for heavily doped traps-PA. Raman spectra of the negatively charged soliton models (DPn-) and the negative polaron models (DPn.- and TNBC.-) were very similar to their spectrum patterns as a whole, but their wavenumbers and relative intensities are mutually different to some extent. In particular, the Raman wavenumbers of heavily doped traps-PA are very similar with those of the polaron models. The dispersion of the C=C stretching band (nu(1)) in doped PA with the various wavelengths of excitation laser line were explained as the presence of charged domains having various lengths of electron localization.

The FT-infrared (IR) and Raman spectra of the radical anion of α,ω-diphenyl-1,3,5,7,9-decapentaene (DP10˙-), a polyene molecule with five conjugated CC bonds, were observed in vacuum condition. The IR absorption spectrum for ionic species of polyene molecule was observed for the first time in the experimental method. The CC stretching band of IR absorption has the weak at 1591-1603cm-1, while the Raman band has the two intense peaks at 1533 and 1574cm-1. In IR absorption, the in-plane CH bending has the several strong bands between 1448 and 1551cm-1, whereas the Raman has a strong band used as a marker of negatively charged polyene at 1272cm-1. The origin of IR and Raman spectra of DP10̇-is discussed in terms of a polaron model compound in polyacetylene. © 2002 Elsevier Science B.V. All rights reserved.

Density functional theory with the 6-31G* basis set and the BYLP nonlocal exchange-correlation functional has been used for the normal coordinate calculations of the neutral, radical anion, and dianion species of p-terphenyl to p-sexiphenyl. The bands attributed to negative polarons and negative bipolarons in the reported Raman spectra of Na-doped poly(p-phenylene) have been successfully assigned on the basis of the present calculations. The calculated atomic displacements have indicated that the Raman bands not corresponding to the zone-center modes of neutral poly(p-phenylene) are due to negative polarons and negative bipolarons. The Raman bands characteristic of negative polarons and negative bipolarons have been identified. The frequency of the inter-ring CC stretch is sensitive to the structural changes in going from benzenoid to quinoid structure in negative polarons and negative bipolarons.

The FT-Raman spectra of trans-polyacetylene films doped lightly with iodine were obtained with the 1320-nm laser line. The observed Raman bands are attributed to positively charged domains created by acceptor doping. The observed Raman wavenumbers of the ν2 (CC stretch), ν3 and ν4 bands (mixed of CC stretch and CH in-plan bending) of iodine-doped form are slightly higher than those of the corresponding bands of pristine trans-polyacetylene, whereas the contrary is the case for ν1 band (C=C stretch) of iodine-doped form. In particular, these upshifts of the ν2 and ν3 bands are distinguished from the downshifts of these bands in donor doping. The origin of doping induced Raman bands is discussed in terms of solitons and polarons.

The first stable distibene (RSb=SbR) and dibismuthene (RBi=BiR) were successfully synthesized by taking advantage of steric protection using an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). Since it is quite difficult to investigate the reactivities of the distibene (TbtSb=SbTbt) and dibismuthene (TbtBi= BiTbt) in solution due to their extremely low solubility values, similarly overcrowded distibene and dibismuthene, BbtE=EBbt (E = Sb, Bi), with sufficiently high solubility were also synthesized using another bulky substituent, 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl group (Bbt). The crystallographic analysis and spectroscopic studies of these stable dipnictenes led to the systematic comparison of structural parameters and physical properties for all homonuclear doubly bonded systems between heavier group 15 elements. In addition to these experimentally obtained results, theoretical calculations for these doubly bonded systems also revealed the intrinsic character of dipnictenes.

The infrared spectra of the light-emitting diodes and the metal-insulator-semiconductor devices based on a poly(p-phenylenevinylene) derivative MEH-PPV have been measured in situ with a reflection configuration. The voltage-induced infrared spectra of these devices have been measured by the FT-IR difference-spectrum method. The observed bands have been attributed to the carriers injected into the polymer layers. The observation of positive carriers in the polymer light-emitting diode is probably related to the predominance of injected positive carriers, which is one of the factors in the low efficiency of the polymer light-emitting diode. In situ infrared reflective absorption measurements provide the information about injected carriers, which play a central role in the properties and the functions of polymer electronic devices.

Infrared spectra of the light-emitting diodes fabricated with poly(2-methoxy-5-(2 ' -ethylhexyl oxy)-p-phenylenevinylene) have been measured in situ with an external reflection apparatus on a Fourier-transform infrared spectrophotometer. Voltage-induced infrared absorption spectra have been measured using the difference-spectrum method. The observed bands have been attributed to injected positive carriers (polarons) on the basis of the spectra of the carriers generated by iodine-doping, Na-doping, and photo-irradiation. The observation of positive carriers is probably related to the predominance of injected positive carriers, which reduces the electroluminescence efficiency of the light-emitting diodes.

The structural and vibrational properties of streptocyanine dyes, expressed as [(CH3)(2)N(CH)(x)N(CH3)(2)]+ClO4- (called SCx in this paper) with x 2n + 1 (n = 0-10), are examined by measuring the infrared (IR) and Raman spectra in solution and in the polycrystalline state (for x 1, 3, 7, 9) and by carrying out density functional calculations at the BHandHLYP/6-31G* level. It is shown that the strong IR bands observed and calculated in the 1800-800 cm(-1) region arise from the normal modes containing large contributions from the vibrations along the bond-alternation coordinate of the conjugated chains. As the conjugated chain becomes longer, the strongest IR band shifts toward the lower-wavenumber side, inducing noticeable changes in the spectral pattern, and the total IR intensity increases significantly. The shifts to lower wavenumbers and the changes in the spectral pattern are explained by the decrease in the intrinsic wavenumber of the bond-alternation mode. A two-state model Hamiltonian, which involves electron-vibration interaction of the bond-alternation mode, reasonably explains the IR intensity enhancement. In the Raman spectra of SC7 and SC9, a few strong bands appear in solution which are not seen in the polycrystalline state. These Raman bands are considered to arise from the same vibrational modes as the strong IR bands, as in the case of similar Raman bands observed previously for SC5 in solution. The relative Raman intensities of the bands are, however, larger in the spectra of SC7 and SC9. These results provide strong evidence for the validity of the mechanism proposed previously that the electron-vibration interaction in the conjugated chain and the intermolecular interaction with the perchlorate ions (existing at various positions near the conjugated chain in solution) give rise to the strong Raman intensities of these bands. It is also suggested that the appearance of these bands is a good signature of the large vibrational contributions to the polarizability tensors in this type of conjugated molecules. The diagonal and off-diagonal force constants of the CC stretches in the conjugated chains are analyzed. It is shown that the conjugated chains of streptocyanine dyes are more strongly correlated than those of neutral polyene chains.

Photoinduced infrared absorption spectra of poly(p-phenylene) and poly(2,5-dioctyloxy-p-phenylenevinylene) have been measured by the phase-modulation technique. The modulation-frequency dependencies of the intensity and the phase delay of the photoinduced infrared absorptions have been obtained. The observed modulation-frequency dependencies have been numerically simulated on the basis of a model consisting of a bimolecular recombination of the positive and negative polarons that are formed from a photogenerated polaron pair (interchain charge-transfer exciton). The rate constant of the bimolecular recombination process has been obtained. (C) 2000 Elsevier Science B.V. All rights reserved.

The application of phase-modulation infrared spectroscopy to the photoexcitation dynamics of conjugated polymers is described. The modulation-frequency dependencies of the intensity and phase delay of photoinduced absorption have been observed and simulated numerically on the basis of a model based on second-order kinetics involving a neutralization process between the positive and negative charge carriers (polarons) that are formed from a photogenerated interchain charge-transfer exciton (polaron pair). The rate constant of the bimolecular recombination process has been obtained. This numerical simulation is useful in analyzing the observed responses of a nonlinear system in the phase-modulation measurements. © 1999 Elsevier Science B.V. All rights reserved.

The Raman spectra of trans-polyacetylene films doped heavily with electron donor (Na) and acceptors (iodine, SO3, HClO4 FeCl3) were studied with excitation wavelengths between 488.0 and 1320 nm. The observed Raman bands are attributed to negatively and positively charged domains created by donor- and acceptor-doping, respectively. The observed large wavenumber dispersion of the C=C stretching vibration (v1 band) of charged domains suggests a broad distribution of localization lengths in the charged domains. The charged domains generated by doping are localized over not more than eleven conjugated C=C bonds. The observed wavenumber of the v2 band (CC stretch) of the acceptor-doped forms is higher than that of the corresponding band of pristine trans-poylacetylene, whereas the contrary is the case for the donor-doped forms.

Vibrational analysis is carried out for the organic (cationic) part of a pentamethine streptocyanine dye, [(CH3)(2)N(CH)(5)N(CH3)(2)]+ClO4- (alias SC5), by measuring its infrared and Raman spectra in solution and in the polycrystalline state and by calculating the vibrational force field and the IR and Raman intensities by the ab initio molecular orbital and density functional methods. It is found that a reasonable set of structural parameters and vibrational force field can be obtained for the SC5 organic part at the BHandHLYP/6-31G* level. The observed features of the IR and Raman spectra, including relative intensities, are well reproduced by the calculations at this theoretical level. Two strong IR bands observed in the 1600-1200-cm(-1) region arise from the delocalized b(1) modes along the bond-alternation coordinate of the conjugated chain. The strong IR intensities are explained by large charge fluxes induced by these modes due to the strong electron-vibration interaction. These modes also appear in the Raman spectrum in solution because of the interaction with the perchlorate ion existing at an asymmetric position near the conjugated chain. A delocalized al mode of the conjugated chain gives rise to a strong Raman band. Examination of the LR and Raman intensities and the vibrational force constants clearly shows that the conjugated chain of the SC5 organic part is a strongly correlated system. A detailed analysis of the origin of the IR and Raman intensities shows that the potential energy distribution is not necessarily a good indicator of the origin of intensities.

Density functional theory using the 6-31G* basis set and two non-local exchange-correlation functionals (B-YLP and B3-LYP) has been applied to the calculations of the structures and vibrational spectra of the radical anion and cation, of biphenyl. The B3-LYP dihedral angles between the two phenyl rings are 5.8 degrees and 19.5 degrees for the radical anion and cation, respectively. Upon ionization, structural changes occur in the direction from benzenoid to quinoid. The unsealed vibrational frequencies calculated at the B-YLP/6-31G* level are mostly in agreement with the frequencies in the Raman spectra of the radical anion and cation of the normal and perdeuterated species reported in the literature. The calculations predict that both the radical anion and cation give rise to a very strong infrared band, and that this band arises from a mode in which the benzenoid-to-quinoid deformation occurs out of phase in the two phenyl rings. (C) 1998 Elsevier Science B.V.

Photoinduced infrared absorption spectra have been measured from poly(2,5-thienylenevinylene) by the phase-modulation method with modulation frequencies between 0.8 and 15 kHz. The modulation-frequency dependencies of the intensity and phase delay of the photoinduced infrared absorption have been numerically simulated by the use of a model based on second-order kinetics involving a neutralization recombination process between the positive and negative polarons, This numerical method is useful in analysing the nonlinear response associated with a bimolecular process. (C) 1997 Elsevier Science B.V.

The electronic absorption and Raman spectra of the radical anion and dianion of 19,19′,20,20′-tetranor-β,β-carotene, a polyene molecule with eleven conjugated C=C bonds, have been studied. The radical anion has an intense absorption at 1.46 eV and a weak absorption at 1.00 eV, while the dianion has an intense absorption at 1.59 eV. The C=C stretching (v1) band of the radical anion is 26 cm-1lower, whereas the v1band of the dianion is 15 cm-1higher, than that of the neutral species. This upshift observed for the dianion suggests large structural changes such as inversion of bond alternation. The CH in-plane-bending (v2) bands of the radical anion and the dianion, both observed at 1275 cm-1, are 15 cm-1lower than that of the neutral species and may be used as a marker of negatively charged polyenes. © 1997 Elsevier Science B.V.

Photoinduced infrared absorptions from poly(p-phenylene), poly(p-phenylenelinylene), poly(2,5-dioctyloxy-p-phenylenevinylene) and poly(2,5-thienylenevinylene) have been measured using the FT-IR difference-spectrum method, The observed photoinduced bands are attributable to photo-generated charged species which give rise to giant infrared intensities. The excitation-power dependences of the photoinduced absorption intensities can be explained by means of the bimolecular recombination of the positive and negative polarons that are formed from a polaron pair (interchain charge-transfer exciton) generated by photoirradiation. (C) 1997 Elsevier Science B,V.

Reversible dimerization of the radical cations of a model compound [CH3(C6H4CH=CH)(2)C6H4CH3] of poly-(p-phenylenevinylene) (PPV) in dichloromethane solution has been studied by electronic absorption, electron spin resonance, and resonance Raman spectroscopy. The electronic absorption spectrum of the radical-cation monomer drastically changes upon dimerization; the absorption maxima of the monomer are located at 636 and 1200 nm (15 700 and 8330 cm(-1)) and those of the dimer at 527 and 981 nm (19 000 and 10 200 cm(-1)) The monomer-dimer equilibrium constants (K's) at various temperatures have been determined from the observed temperature dependence of the electronic absorption spectra. From the van't Hoff plot of ln K against 1/T, the heat of dimerization Delta H has been evaluated to be -12.6 kcal mol(-1). Electron spin resonance measurements have shown that the unpaired spins of the radical-cation monomers make a pair in the dimer. Such a radical-cation dimer is a good model of interchain interaction between polarons that are created on neighboring chains of PPV. The resonance Raman spectra of sulfuric-acid-treated PPV have been analyzed on the basis of the spectra of the radical-cation monomer and dimer. Sulfuric-acid-treated PPV is considered to contain positive polarons that interact with other polarons, in addition to positive polarons without such interaction.

The FT-Raman spectra of trans-polyacetylene doped with Na at various concentrations were observed with the 1320-nm laser line. Doping-induced Raman bands for lightly doped trans-polyacetylene were observed for the first time. The observed wavenumbers of the ν1, and ν4bands (C=C and C-C stretches) of lightly doped trans-polyacetylene are lower than those of the corresponding bands of pristine transpolyacetylene, whereas the contrary is the case for heavily doped trans-polyacetylene. The origins of doping-induced Raman bands are discussed in terms of solitons and polarons. © 1997 Elsevier Science S.A.

A high-resolution inelastic neutron scattering (INS) spectrum has been observed for trans-polyacetylene films in the range 8-4000 cm(-1) at 6 K, and compared with the calculated INS spectrum based on the force field obtained in our previous study. The peak positions as well as the overall intensity profile of the observed INS spectrum are well reproduced by the present calculation, in which the effects of the Debye-Waller factors and the phonon wings are taken into account.

The electronic absorption and Raman spectra of as-polymerized BF-4-doped polythiophene have been analyzed on the basis of the spectra of the radical cation and dication of α-sexithiophene, viewed as models of a positive polaron and a positive bipolaron, respectively. The Raman spectra taken with laser lines between 632.8 and 1064 nm have been attributed to positive polarons existing in doped polythiophene. The Raman results confirm that the two-band feature observed in the electronic absorption spectra of doped polythiophene is attributable to polarons.

The magnitude and phase delay of the photoinduced infrared absorption bands of polythiophene have been measured at 78 K with a sinusoidal intensity-modulation of 514.5 nm laser light. All the photoinduced bands show the same response in magnitude and phase delay to the external stimulus. The magnitudes of the photoinduced bands show an approximate f 0.6 dependence on the modulation frequency above 1.25 kHz. The micro- to millisecond photoexcitation dynamics are discussed. © 1996 Elsevier Science B.V. All rights reserved.

Conjugated conducting polymers constitute a subject of research lying at the interface between solid-state physics and molecular science. Electronic absorption and vibrational spectroscopies of doped conjugated polymers, whose ground states are nondegenerate, are reviewed from a viewpoint of molecular spectroscopy. Raman spectroscopy is a powerful tool for studying the structures of polarons and bipolarons, which are associated with electrical, magnetic, and optical properties of the polymers. Electronic absorption and Raman spectra of doped polymers have been analyzed on the basis of those of model compounds. These analyses have led us to the conclusion that polarons are the major species generated by doping in most nondegenerate conjugated polymers such as polythiophene, poly(p-phenylene), and poly(p-phenylenevinylene), in contrast with the previous view that bipolarons are the major species. The theoretical and experimental bases of these two contradictory views are discussed. © 1996 American Chemical Society.

Electronic and vibrational spectra of poly(p-phenylenevinylene) doped with donors or accepters have been studied, together with the spectra obtained for the radical ions and divalent ions of its oligomers. The electronic absorption spectra of doped poly(p-phenylenevinylene) in the region from visible to near-infrared show two bands for the H2SO4-doped species and one very broad band for the Na-doped species. On the basis of the analyses of resonance Raman spectra, the two electronic absorption bands of the H2SO4-doped species are attributed to a polaron-lattice structure, whereas the broad band of the Na-doped species is attributed to overlapping absorptions associated with localized electronic levels of polarons and bipolarons. A Pauli spin susceptibility of the H2SO4-doped species is explained by the polaron-lattice structure.

The density functional theory has been used for calculating the structures and vibrational wavenumbers of the radical anion and cation of biphenyl. The radical anion has a planar structure, while the radical cation is twisted. Upon ionization, structural changes occur in the direction from benzenoid to quinoid. Unsealed wavenumbers calculated at the Becke-Lee-Yang-Parr/6-31G* level are mostly in agreement with observed vibrational wavenumbers in the literature.

The resonance Raman spectra of SO3-doped poly(p-phenylenevinylene) (PPV) with two different electrical conductivities of 1 and 10 S cm(-1) have been observed and analyzed by referring to the data of the radical cations of the model compounds. Both SO3-doped PPV films with electrical conductivities of 1 and 10 S cm(-1) are considered to contain positive polarons having a more or less uniform lengths. The difference in the formation of polarons on the two sides of the doped film, i.e., one shiny side and the other dull side, is observed.

The Raman spectra of a polyacetylene film doped heavily with SO3 have been measured with excitation wavelengths between 488.0 and 1064 nm. Observed Raman bands are attributed to positively charged domains generated by SO3 doping. Doping-induced changes in the Raman spectra are summarized as follows. (1) The nu(1) and nu(3) bands observed in the region of 1575-1485 and 1147-1122 cm(-1) respectively, upshift upon doping. (2) The nu(1) and nu(3) bands become broad upon doping. (3) Small but significant upshifts of the nu(2) band in the region of 1301-1294 cm(-1) are observed upon p-type doping in contrast to downshifts for n-type doping.

Electronic absorptions due to polarons and bipolarons in nondegenerate polymers have been reexamined on the basis of the data of the radical ions (models of polarons) and divalent ions (models of bipolarons) of alpha-oligothiophenes and p-oligophenyls. From the electronic absorption spectra of these model species, it has been concluded that two transitions are strong among the three expected for a polaron, whereas one transition is strong among the two expected for a bipolaron. Two bands observed in the electronic absorption spectra of doped polythiophene, poly(p-phenylene) and poly(-phenylenevinylene), which were previously attributed to bipolarons, have been reassigned to polarons. These assignments are consistent with the results of Raman studies reported recently. The confinement parameters of these polymers have been estimated on the basis of the new assignments.

The near-infrared Raman and electronic absorption spectra of an as-polymerized BF4--doped polythiophene film have been measured and analyzed by referring to the data of the radical cation and dication of alpha-quinquethiophene, which are models of a positive polaron and a positive bipolaron, respectively. Similarities between the Raman spectrum of doped polythiophene and that of the radical cation suggest that the observed Raman bands of the doped polymer arise from positive polarons. It is shown that the two characteristic bands in the electronic absorption spectrum of the doped polymer are assignable to positive polarons.

The Raman spectra of trans-polyacetylene doped with sodium (Na) at the maximal level have been measured with excitation laser lines between 488.0 and 1064 nm. These spectra have been compared with those of model compounds, i.e., the radical anions of alpha, omega-diphenylpolyenes (Ph-(CH=CH)(n)-Ph, n = 3, 4) and alpha, omega-di-2-thienylpolyenes (Th-(CH=CH)(n)-Th, n = 3 and 4). The similarity between the Raman spectra of Na-doped polyacetylene and those of the radical anions indicates that the observed bands of Na-doped polyacetylene arise from charged domains generated by Na-doping. The observed large wavenumber dispersion of the C=C stretching vibration of the charged domains suggests a broad distribution of localization lengths in the charged domains.

The resonance Raman and infrared spectra of sulfuric-acid-treated poly(p-phenylenevinylene) (PPV) have been observed and analyzed on the basis of the resonance Raman spectra of the radical-cation and dication species of the model compounds CH3(C6H4CH=CH)nC6H 4CH3 (PVn, n = 1-3), which correspond, respectively, to positive polarons and bipolarons in PPV. Sulfuric-acid-treated PPV is considered to contain a considerable amount of positive polarons having a more or less uniform length and a relatively small amount of positive bipolarons. Of the two electronic absorption bands at 2.25 and 1.00 eV of sulfuric-acid-treated PPV, the former absorption band is due to the positive polarons, whereas the latter has overlapping components arising from the positive polarons and bipolarons. It is suggested that the high electrical conductivity of sulfuric-acid-treated PPV may be due to formation of a polaron lattice, a regular array of polarons. © 1994 American Chemical Society.

Electronic structures in metallic and insulating phases of the Li, Cu, and Ba complexes of 2,5-R1,R2-DCNQI [R1=R 2=Br (abbreviated as DBr) or R1=R2=CH 3 (abbreviated as DMe)
DCNQI=N,N′-dicyanoquinonediimine
2,5- is usually omitted] have been studied by observing temperature dependencies of their infrared absorption bands between 295 and 23 K. At room temperature, the wave numbers (ṽi) of infrared absorption bands of R 1,R2-DCNQI and its Li and Ba complexes are linearly correlated with the degrees of charge transfer (ρ) (ρ=- 0.5 and -1.0e for the Li and Ba complexes, respectively). The ṽi-ρ relationships indicate that the ρ value for the Cu complexes is -0.67e. This result is consistent with the previously established view that the Cu cations in the Cu complexes at room temperature are in a mixed-valence state of Cu 1.33+. In the infrared spectrum of Cu(DBr-DCNQI)2 at room temperature, no electron-molecular vibration (EMV) coupling bands are observed. Below the metal-insulator (M-I) transition temperature (TMI), EMV bands grow continuously and the ordinary infrared bands observed at room temperature gradually split into three bands with decreasing temperature. Similarly, the infrared bands of Li(DBr-DCNQI)2 split into two bands. These splittings are due to an inhomogeneous charge distribution in the DCNQI columns produced by the freezing of charge-density wave (CDW). The peak-to-peak amplitudes of CDWs in the DCNQI columns estimated by use of the ṽi-ρ relationships are 0.08±0.04 and 0.40±0.04e, respectively, for the Li and Cu complexes of DBr-DCNQI. The state of the frozen CDW is inferred from the number of split bands. Based on the observed continuous change of the infrared spectra of Cu(DBr-DCNQI)2 and the discontinuous changes of other quantities such as x-ray satellite reflections, lattice parameters, and magnetic susceptibilities, the M-I transition in Cu(DBr-DCNQI)2 may be described as follows: (1) above TMI the charges on Cu cations (two Cu1+'s: one Cu 2+) are dynamically averaged to + 1.33e through the Cu⋯N≡C bridge. (2) At TMI the charges abruptly localize in the order of (Cu1+⋯Cu2+⋯Cu 1+⋯)n. At the same time, the CDWs begin to be frozen in the DCNQI columns. (3) As temperature decreases below TMI, the order of the frozen CDW develops gradually. In contrast to these changes in Cu(DBr-DCNQI)2, neither EMV bands nor band splittings are observed in the infrared spectra of Cu(DMe-DCNQI)2 at low temperatures. Instead, almost all bands show negative absorption lobes on their low-wave number sides and become asymmetric. This asymmetrization is due to interactions between the vibrational levels and low-lying continuous electronic levels responsible for a broad band observed in the 1600-800 cm-1 region. © 1994 American Institute of Physics.

The resonant Raman spectra of lightly sodium-doped and heavily potassium-doped poly(p-phenylenevinylene)'s (PPV's) have been studied. These spectra have been analyzed on the basis of the resonant Raman spectra of the radical anions and dianions of three model compounds CH3(C6H4CH=CH)nC6H4CH3 (PVn, n=1-3), which correspond, respectively, to negative polarons and bipolarons in PPV. The lightly sodium-doped PPV film contains a bipolaron which is localized in a region close to PV3, in addition to two kinds of polarons whose lengths are close to PV2 and PV3. The 1064-nm-excited resonant Raman spectrum of potassium-doped PPV is attributed to a bipolaron localized in a region close to PV3. The resonant Raman spectra of potassium-doped PPV excited at 514.5, 632.8 and 752.5 nm are explained by the existence of negative polarons. However, the bands in the 1271 - 1246 cm-1 range, which are observed for sodium-doped PPV and assigned to polarons, are not observed for potassium-doped PPV. The reason for their absence is discussed.

Raman spectra have been measured of heavily Na-doped poly-p-phenylene (PPP) with various laser lines in the 488.0-1064 nm region. They have been compared with those of the radical anions and dianions of p-oligophenyls (p-terphenyl, p-quaterphenyl, p-quinquephenyl and p-sexiphenyl). The Raman spectra of Na-doped PPP excited at 488.0-514.5 nm and 632.8-1064 nm are attributed, respectively, to negative polarons and bipolarons. Electronic absorption spectra of doped PPP are explained by the coexistence of negative polarons and bipolarons on the basis of the Raman results.

The Raman and infrared spectra of 13C‐substituted poly‐p‐phenylene (PPP) and the Raman spectra of Na‐doped PPP excited at 488.0 and 1064 nm were observed and compared with the corresponding spectra for the ordinary (12C) polymer. 13C substitution is shown to be useful for characterizing not only the bands of intact PPP but also those of polarons and bipolarons generated in Na‐doped PPP. The number of Raman bands observed for bioplarons (and also for polarons) is greater than that for intact PPP. This observation is explained as the result of the loss of translational symmetry in the regions of these local excitations. Copyright © 1993 John Wiley & Sons, Ltd.

The 1064 nm excited Raman spectra of p-terphenyl, p-quaterphenyl, p-quinquephenyl and p-sexiphenyl have been observed and compared with the 514.5 nm excited spectra. Dependencies of intensities of some major bands on the chain length and the excitation wavelength are discussed in terms of the preresonant Raman effect. A method for estimating the chain length from relative intensities is proposed. © 1993.

The unique molecular conductors with pπ-d mixing band structures (R1,R2-N,N'-dicyanoquinonediimine)2Cu [(R1,R2-DCNQI)2Cu] (R1,R2=CH3,CH3O,Cl,Br) were examined. General features of the phase diagram of the DCNQI-Cu system were depicted. A region that is related to the existence of anomalously heavy-metal electrons has been found. The T2 dependence of the low-temperature resistivity of the alloyed system (DMe1-xMeBrx-DCNQI)2Cu (where Me=CH3) suggests a large enhancement of the electron mass at the critical situation where the system begins to exhibit a characteristic metal instability. The mixed valency of Cu (Cu+1.3) in (DMe-DCNQI)2Cu was confirmed by ir experiments performed on neutral DMe-DCNQI crystals and (DMe-DCNQI)2M (M=Li, Ba, Cu). The same conclusion was also derived from a low-temperature x-ray-diffraction experiment. The gradual temperature dependences of the ir absorption intensities of totally symmetric modes of (DBr-DCNQI)2Cu observed below the metal-insulator transition temperature (TMI) are in contrast with the discontinuous resistivity and susceptibility changes at TMI. This may be attributable to the existence of two driving forces characterizing the M-I transition. One is the sharp charge ordering in Cu sites and the other is the continuous development of charge-density waves on DCNQI stacks. The arrangement of Cu2+ and Cu+ below TMI was determined by an x-ray crystal-structure analysis of the threefold insulating phase of (MeBr-DCNQI)2Cu at 110 K. The nearest-neighbor Cu2+ ions interact with each other via two DCNQI molecules. A plausible spin structure of the antiferromagnetic ground state was proposed. According to this spin-structure model, the magnetic moments of Cu2+ along the crystallographic c axis will be arranged ferromagnetically. © 1993 The American Physical Society.

Time-resolved polarized infrared spectra have been observed from a ferroelectric liquid crystal (chiral smectic C phase) consisting of a chiral dopant and a nonchiral smectic base during the course of switching between the surface-stabilized states. A primary fast process and the subsequent slow process have been observed for all infrared bands. The chiral dopant and smectic base molecules move simultaneously. The observed time behavior of the infrared bands can be mostly explained by the reorientation of a rigid molecule whose rotational motion around the molecular long axis is almost free. The static intensities and the time behavior of the ester and keto C=O stretching bands do not seem to be consistent with the simple view on the role of these groups. © 1993 Society for Applied Spectroscopy.

The outline of phase-modulation infrared spectroscopy is described. The relationship between the frequency-domain response from phase-modulation experiments and the time-domain response from time-resolved experiments is derived. The microsecond dynamics following photoexcitation in trans-polyacetylene has been studied by phase-modulation infrared spectroscopy. The magnitude and phase (or in-phase and quadrature components) of the photo-induced infrared band at 1367 cm J have been measured at 78 K with modulation frequencies between 600 Hz and 10.5 kHz by using an experimental setup based on a continuousscan Fourier transform infrared spectrophotometer. The magnitude of this band shows an approximate ε-1 dependence for frequencies below 9 kHz and a rapid decrease above 9 kHz. These results are inconsistent with a unimolecular decay, which should show a dependence of the form ε-1. © 1993 Society for Applied Spectroscopy.

An asynchronous pulsed-laser-excited Fourier transform Raman spectrophotometer based on a conventional continuous-scan interferometer has been developed. The additional assembly required for pulsed-laserexcited measurements, which consists of a pulsed Nd:YAG laser, a gate circuit, and a low-pass filter, can be attached to any conventional FTRaman spectrophotometer. The principle of the signal-processing of this method is almost the same as that of the asynchronous time-resolved Fourier transform infrared spectroscopy reported previously. This method does not require the synchronization between the Raman excitation and the sampling of the A/D converter. As an application of this method, it is demonstrated that the use of a pulsed laser and a gate circuit can give a significant increase in signal-to-noise ratios over continuous-wave measurements with the same average laser power. It is also shown that when a constant background (for example, thermal radiation from samples at high temperatures) or a long-lived background is present, the use of pulsed excitation and a gate circuit can effectively reduce the background. Moreover, pulsed excitation can be used for recording timeresolved Raman spectra by using an FT-Raman spectrophotometer. The time resolution is governed only by the width of the probe laser pulse. The potentiality of this method is demonstrated. © 1993 Society for Applied Spectroscopy.

The use of Raman spectroscopy for characterizing self-localized excitations (polarons, bipolarons and solitons) in conducting polymers is described. A methodology for identifying these excitations is proposed. The method includes two important points: (1) Raman measurements with not only visible but also near-infrared laser excitation; (2) spectral analysis based on the Raman spectra of radical ions, divalent ions and ions of oligomers. Applications of this method to Na-doped poly(1,4-phenylenevinylene) and Na-doped trans-polyacetylene are demonstrated.

The infrared and Raman spectra of poly(p-phenylenevinylene) (PPV) and its low molecular weight model compounds CH3(C6H4CH=CH)nC6H 4CH3 (n = 1-3) have been studied, and the following points have been made clear. (1) The vinylene groups in PPV are slightly distorted from a planar trans form, so that the PPV molecule has approximate C2h symmetry. (2) Extensive π-electron conjugation takes place between the phenylene and vinylene groups, and the degree of conjugation increases with increasing chain length. (3) The positions and relative intensities of the infrared and Raman bands of the model compounds change regularly as the chain length increases and rapidly converge on those of PPV, which are considered to be practically identical to those of an infinitely long chain. (4) The positions of the Raman bands of PPV slightly shift with the excitation wavelength. The 363.8-nm-excited Raman spectrum seems to arise from segments whose lengths are of the order of the model compound n = 3, whereas the Raman spectra excited at longer wavelengths correspond to longer segments which are dominant in quantity. © 1992 American Chemical Society.

The resonance Raman spectra of sodium-doped poly(p-phenylenevinylene) (PPV) and the radical anions and dianions of three model compounds CH3(C6H4CH=CH)nC6H 4CH3 (PVn, n = 1-3) have been studied. The Raman spectra of sodium-doped PPV show marked changes with laser wavelengths used for Raman excitation. These spectra have been analyzed on the basis of the resonance Raman spectra of the radical anions and dianions of the model compounds, which correspond, respectively, to negative polarons and bipolarons in PPV. Three kinds of negative polarons whose lengths are close to PV1, PV2, and PV3, and a bipolaron which is localized in a region close to PV3, exist in a sodium-doped PPV film. Upon prolonged heat treatment of the sodium-doped PPV (290°C, 12 h), the shortest polaron corresponding to the radical anion of PV1 disappears, probably because it combines with another polaron to form a bipolaron. These results indicate that resonance Raman spectroscopy is a powerful tool for characterizing polarons and bipolarons in conducting polymers. © 1992 American Chemical Society.

A new method for measuring infrared spectra of a Ti(O-n-Bu)4-AlEt3 catalyst is developed. Upon heat treatment of the catalyst, formation of linear and/or cyclic oxo-complexes of titanium having the Ti-O-Ti linkage is suggested. The existence of oxo-complexes seems to be correlated with high electrical conductivity of resulting polyacetylene upon full iodine-doping. Raman spectra arising from doped domains have been obtained for the first time by Fourier transform Raman spectroscopy with 1064-nm excitation. Even at full iodine-doping, the polymer chain does not have a uniform bond order, and contains doped domains in which bond alternation persists. Small differences are observed between the Raman spectra of conventional and new highly-conducting polyacetylenes.

1064-nm-excited Fourier transform Raman spectra of bacteriochlorophyll-a (BChl) in various solid films and in chromatophores from a blue-green mutant of Rhodobacter sphaeroides have been obtained. The observed Raman spectra are free from high fluorescence backgrounds and sample degradation. The observed intensities seem to be enhanced because of a pre-resonant effect between the exciting radiation at 1064 nm and the Qy absorption at 770-870 nm of BChl. The spectral features are substantially different from the Soret and Qx resonance Raman spectra extensively investigated so far
several bands in the wavenumber region lower than 1200 cm-1 are particularly enhanced in the Qy pre-resonance Raman spectra. Bands due to both the C2O and C9O stretches appear at 1700-1620 cm-1, providing structural information on these carbonyl groups. In the CC stretching region (1620-1490 cm-1), the correlation between band positions and the co-ordination number of central magnesium, which was previously found in the Soret-excited Raman spectra, is preserved in the Qy, pre-resonance Raman spectra as well. The relative intensities of strong bands in the 1200-1000 cm-1 region appear to be useful for characterizing the BChl state. By using these advantages of the Qy, pre-resonance Raman spectra, molecular interactions and arrangements of BChl in hydrated films and in the B870 light-harvesting complex of R. sphaeroides are discussed. © 1991.

Application of 1064-nm-excited Fourier transform (FT)-Raman spectroscopy to the characterization of conducting polymers is described. 1064-nm-excited FT-Raman spectra with high signal-to-noise ratios are obtained from polyacetylene (PA), poly(1,4-phenylene) (PPP), poly(1,4-phenylene vinylene) (PPV) and poly(2,5-thienylene vinylene) (PTV) in their neutral (insulting) state. The resonant Raman spectra of acceptor- or donor-doped (conducting) PA and PPV are also obtained with 1064-nm excitation. The resonant Raman spectra of Na-doped PA change in two stages with increasing dopant concentration, the first change corresponding to the increase in electrical conductivity and the second to the appearance of a Pauli susceptibility. The 1064-nm-excited FT-Raman spectrum of Na-doped PPV indicates existence of negative bipolarons which are equivalent to divalent anions extending over a few repeating units in the polymer chains.

XPS N1S and valence spectra of various forms of polyaniline were studied and the compositions of four unit structures in some films were determined. A proposed scheme of interconversion of the unit structures by reduction/oxidation and acid/base treatment is useful to understand the interconversion mechanism of polyaniline. Reduced-base-treated polyaniline (1A, white) is taken as a standard material because it consists solely of imino-l,4-phenylene (IP) units (—NHC6H4—). Electrochemical oxidation of 1A in nonaqueous medium converts part (46%) of IP into its radical cation (IP.+) (doped 1A). Acid treatment of 1A changes some IP (28%) to its cation (IP+) (IS). Base treatment of doped 1A converts two IP.+-IP parts into two IP parts and one nitrilo-2,5-cyclohexadiene-l,4-diylidenenitrilo-l,4-phenylene (NP) (—N=C6H4= N—C6H4—) part to give a sample which is practically the same as base-treated polyaniline (2A). Washing of as-polymerized polyaniline changes some IP+to IP and some IP*+to NP (2S(H20)). An earlier conclusion that the radical cation of imino-l,4-phenylene plays an important role in electrical conduction in polyaniline has been supported, and it is pointed out that a highly conducting form of polyaniline exhibits a finite density of state at the Fermi energy. A large change in the valence structure is also observed at 8.7 eV in polyaniline containing IP*+. The advantage of an electrochemical redox process in nonaqueous media over that in aqueous media for practical purposes is explained. © 1989, American Chemical Society. All rights reserved.

In frared spectra of the less stable conformer of isoprene have been observed in low-temperature argon matrices (Figs 1-3). Irradiation of the matrix-isolated isoprene with a low-pressure Hg lamp increases the population of the less stable conformer. Deposition of an isoprene/argon mixture heated through a high temperature nozzle exhibits a similar effect. The less stable conformer has been identified as the gauche form by comparing the observed spectra with the results of normal-coordinate calculations previously reported by Bock et al. Most of the observed bands in the region below 1700 cm-1 have been reasonably assigned to the calculated modes of either the trans or the gauche form (Table 1). © 1989, The Chemical Society of Japan. All rights reserved.

For 3-trans and 3-cis isomers of 1,3,5-hexatriene, structure parameters of not only the stable (trans about the CC single bonds) but also less stable conformers have been optimized by restricted Hartree-Fock calculations at the 6-31G level. The less stable conformers are found to have torsional angles about the CC single bonds in the range between 32° and 48° from the planar s-cis conformation. Force constants in the Cartesian-coordinate space have been calculated and transformed into the group-coordinate force constants, which have then been adjusted to obtain good agreement between the calculated and observed vibrational frequencies. Vibrational assignments for the stable conformers are reexamined in view of the latest experimental data. Infrared bands of less stable conformers previously reported by two of the present authors are reasonably assigned on the basis of the results of normal-coordinate calculations. Characteristics features of some normal modes of individual conformers are discussed in detail. © 1989.

The Raman and infrared spectra of poly(1,4-phenylenevinylene) (PPV) and poly(2,5-thienylenevinylene) (PTV) show that extensive π-electron conjugation take place in both polymers. There are indications that the phenylene ring in PPV is considerably different from a typical p-phenylene ring. The peak wavenumbers and bandwidths of a few Raman bands of PTV depend on the excitation wavelength. This observation is explained as a result of existence of segments with various lengths of π-electron conjugation. No bands in the Raman spectrum of PPV show such behavior.

Raman and optical absorption spectra were studied on electrochemically polymerized polypyrrole in as-polymerized doped (highly conductive), partially undoped and substantially undoped 'neutral' (insulating) states. Vibrational assignments were made on the basis of the data of 2,5-13C-substituted and C-deuterated derivatives. The Raman result of the neutral polymer is consistent with the α,α′-linked all-s-trans coplanar and conjugated structure. In the as-polymerized polymer there exist both radical cation and dication in which the bond orders of C3C4 and interring CC are increased as compared to those in the neutral polymer. The structural distortion in the dication is greater than that in the radical cation. Changes in optical absorption and Raman spectra during reduction (undoping) were explained by the conversions of the dication to the radical cation and the radical cation to the neutral species. © 1988.

Vibrational spectra have been studied on polyaniline in various forms with different electrical properties: two conducting forms, as-polymerized (2S) and doped 1A polyanilines
and three insulating forms, reduced-alkali-treated (1A), acid-treated 1A (IS), and oxygen-treated 1A [1A(O2)] polyanilines. Polyaniline 1A is spectroscopically evidenced to be poly(imino-l,4-phenylene), -(NHC6H4)n-. Polyaniline 1S consists of imino-l,4-phenylene (IP) unit (-NHC6H4-) and its salt unit (-NH2 +A--C6H4-, (A-, anion)). Treatment of 1A with oxygen converts part of consecutive IP units (-NHC6H4NHC6H4-) to nitrilo-2,5-cyclo-hexadiene-l,4-diylidenenitrilo-l,4-phenylene (NP) unit (-N=C6H4=NC6H4-). Semiquinone radical cations of IP units exist only in the conducting forms of polyaniline, 2S and doped 1A, indicating that semiquinone radical cations play an important role in electrical conduction in polyaniline. © 1988, American Chemical Society. All rights reserved.

The density of states has been calculated for the in-plane and out-of-plane vibrations in the infinite trans polyene chains. Comparison of the density of states spectra with the IR and Raman spectra of trans-polyacetylenes, (CH)x, (13CH)x and (CD)x, shows that most of the weak bands as well as the strong bands arise from the trans polyene segments in the polymer films. The IR bands newly assigned to the trans segments include the 740 cm-1 band, which was previously assigned to remnant cis CC bonds. The IR spectra of (13CH)x and (CD)x clearly indicate that the amount of remnant cis bonds in thermally isomerized trans films is much smaller than that proposed previously. The hydrogen-amplitude-weighted density of states calculated for the infinite polyene chain also shows satisfactory agreement with a neutron inelastic scattering spectrum of trans-(CH)x. © 1987.

Infrared and Raman spectra of neutral polythiophene were analyzed on the basis of the data of oligomers (α-bithiophene, α-terthiophene, α-quaterthiophene, and α-sexithiophene) and deuterated and 2,5-13C-substituted polythiophenes. Vibrational assignments were confirmed including those of key bands useful in deriving the degree of polymerization (Ndp), the average number of s-trans conjugated successive rings (Nc), and the amount of distorted part (kink) relative to that of conjugated part (Ak). It is possible to estimate Ndp, Nc, and Ak from the vibrational spectra of a neutral film. Among ten films prepared under different conditions, the one which showed the highest electrical conductivity (2.0×102 Scm-1) on maximum iodine doping exhibited the largest Nc (&gt
6) and the smallest Ak but an intermediate (5th) Ndp (20). The film with the largest Ndp (35) happened to show Nc smaller and Ak larger than those of the above-mentioned film and the conductivity was 5.0×10 Scm-1. Hence, a small number of kinks (i.e., abundance of long conjugated segments) is indispensable for a polymer film to gain high electrical conductivity at the doped state. © 1987.

Raman spectra of polyaniline and its 15N- and 2H-substituted derivatives were studied in as-polymerized (conductive), alkali-treated (insulating) and electrochemically reduced (insulating) states. Emeraldine and N,N′-diphenyl-p-benzoquinone diimine were also studied. The CN stretching and some other vibrations were assigned on the basis of the isotopic shifts of the Raman wavenumbers. The presence of quinone diimine (Q) and p-disubstituted benzene (φ) structures was identified in alkali-treated samples (2A) by the 632.8 and 457.9 nm excited spectra in resonance and preresonance with the 630 and 330 nm absorptions, respectively. Together with the infrared NH stretching bands, these observations give experimental evidence of: (1) the head-to-tail polymerization and (2) the partial structure of 2A, -Q-φ-(NH-φ)x-Q-φ-(NH-φ)y-. The partial structure is the same for samples prepared electrochemically and chemically except that the composition (x, y, etc.) depends on the synthetic conditions in both cases. In the quinone diimine part (Q′) of as-polymerized samples (2S), electrons are more delocalized than in the corresponding part of 2A, since the CN stretching wavenumber is about 137 cm-1 lower than that of 2A. In the course of reduction of 2S, such modified quinone diimine parts are changed into p-disubstituted benzene structure and the fully reduced samples (1S) are mostly composed of p-disubstituted benzene. The presence of the electron-delocalized quinone diimine parts in 2S is closely related to its high electrical conductivity. © 1986.

Polythiophene films synthesized by electrochemical polymerization under various conditions were undoped and redoped maximally with iodine. The electrical conductivity of the redoped films was in the range 2 × 102 - 5.9 S cm-1. Vibrational spectra of the undoped films were analysed on the basis of those of model compounds including 2,2′-bithiophene, 2,2′:5′,2″-terthiophene and 2,2′:5′,2″:5″,2′-quaterthiophene. First, the intensity ratio of the infrared CH out-of-plane bending bands at 697 (2-substituted thiophene) and 787 cm-1 (2,5-substituted thiophene) is a clue to the degree of polymerization. Secondly, the intensity ratio of the infrared double-bond symmetric and antisymmetric stretching bands reflects the distribution in length of the conjugated segment. Finally, the intensities of three Raman bands at 1155, 682 and 652 cm-1 give information about the amount of distorted structure around the inter-ring C-C bonds. From the comparison of the spectroscopic and conductivity data, it is concluded that a high degree of polymerization alone is not adequate for a doped film to have high electrical conductivity but abundance of long conjugated coplanar segments is the requisite condition. © 1986.

Normal coordinate calculations have been performed for the in-plane vibrations of several trans-polyene chains from butadiene to polyacetylene in order to obtain a set of force constants commonly applicable to short and long polyenes. The force field finally obtained consists of short range forces, which are primarily determined by the frequency data on short polyenes, and long range interactions which are important in explaining the data on polyacetylene. The long range interactions between the C=C stretching coordinates as far as the fifth neighbor have significant effects on the dynamical properties of the infinite chain. Frequencies of some Raman active vibrations are greatly lowered by the long range terms to become comparable with the experimental frequencies of polyacetylene. These vibrations shift to higher frequencies steeply as the phase difference between adjacent HC=CH units increases from zero. Such steep dispersion as well as the other features of calculated dispersion curves are fully consistent with the expectation based on the Raman spectra of copoly(acetylene + acetylene-d2). Further support for the dispersion curves is given by a general agreement between the experimental Raman spectra and theoretical spectra calculated for model copolymer chains using an approximate equation of resonance Raman intensity. © 1986 American Institute of Physics.

In order to elucidate the structural details of doped polyacetylene (a highly conducting organic polymer), the optical absorption, Raman, and infrared spectra of not only trans-(CH)xdoped with iodine, AsF5, and SO3but also β-carotene doped with iodine and SO3were studied. The infrared spectra of two kinds of isotopically substituted polyacetylenes (CD)xand (13CH)xdoped with iodine were also observed. Analysis of the experimental results shows that upon doping each of the four vibrational branches (ν1-ν4) in the 1600-900 cm-1region of a polyene chain splits into two groups, namely, the higher frequency group and the lower frequency one. The former group consists of the "gerade" vibrations of polyene parts which are not directly attacked by dopants but are perturbed along the chain, whereas the latter is made up of the "ungerade" vibrations of the positively charged polyene part with the doped site at its center. The Raman bands in the higher-frequency group of ν1(mainly the C = C stretching mode) observed with various laser lines give definite information on the segments of conjugated trans double bonds existing in doped polyacetylene. The Raman spectra are also useful for clarifying the structures of dopants. In the infrared spectra of doped trans-(CO)xand (13CH)xthe bands appearing on doping all showed respective isotope shifts which confirmed the view that these bands are of vibrational origin. In many respects doped β-carotene proved to be a useful model of doped trans-polyacetylene. © 1980 American Institute of Physics.