The layered structures of graphite and related nanographene molecules play key roles in their physical and electronic functions. However, the stacking modes of negatively curved nanographenes remains unclear, owing to the lack of suitable nanographene molecules. Herein we report the synthesis and one-dimensional supramolecular self-assembly of negatively curved nanographenes without any assembly-assisting substituents. This curved nanographene self-assembles in various organic solvents and acts as an efficient gelator. The formation of nanofibers was confirmed by microscopic measurements, and an unprecedented double-helix assembly by continuous π-π stacking was uncovered by three-dimensional electron crystallography. This work not only reports the discovery of an all-sp<sup>2</sup>-carbon supramolecular π-organogelator with negative curvature, but also demonstrates the power of three-dimensional electron crystallography for the structural determination of submicrometer-sized molecular alignment.

Hexa-peri-hexabenzocoronene (HBC) is known to be a poorly soluble polycyclic aromatic hydrocarbon for which direct functionalization methods have been very limited. Herein, the synthesis of hexaborylated HBC from unsubstituted HBC is described. Iridium-catalyzed six-fold C-H borylation of HBC was successfully achieved by screening solvents. The crystal structure of hexaborylated HBC was confirmed via X-ray crystallography. Optoelectronic properties of the thus-obtained hexaborylated HBC were analyzed with the support of density functional theory calculations. The spectra revealed a bathochromic shift of absorption bands compared with unsubstituted HBC under the effect of the sigma-donation of boryl groups.

The regioselective ten-fold borylation of warped nanographene (WNG: C80H30) was achieved by modifying the reaction conditions of a previously reported Ir-catalyzed C-H borylation, affording decaborylated WNG in high yield (75%) from pristine WNG. The solid-state structure of decaborylated WNG was confirmed by X-ray crystallography. Corresponding decaarylated WNGs containing electron-withdrawing and -donating groups were synthesized from decaborylated WNG using Suzuki-Miyaura cross-coupling reactions to afford the red-emissive warped nanographene derivative.

This account focuses on the synthesis and structures of symmetric multiple carbohelicenes; i.e., fully fused polycyclic aromatic hydrocarbons containing two or more symmetric helicene moieties. Synergies of the multiplexed helicene structures within a -system generate a number of local minima and transition states between each state. Based on recent studies on multiple helicenes, a systematic molecular design for further multiplexed symmetric helicenes is proposed in the last section of this article.

1015 0103 8441

第60077681601号

本研究者は前年度までの研究において、コラニュレンを基盤とする新奇湾曲炭素分子の合成と物性評価を行い、三次元に広がる湾曲炭素分子の開拓的研究を行ってきた。これらの成果をもとに、今年度はさらに新奇湾曲炭化水素の合成と性質解明を行った。
受け入れ研究室ですでに報告されている、「ワープドナノグラフェン（以下WNG）」の合成経路解析をしていく中で、7員環を3つ含むWNG合成中間体が湾曲しているにも関わらず、結晶中で大きなπ-π相互作用をもつことが明らかとなった。そこで、新たにWNG合成中間体からビフェニル基を除いた構造の湾曲π共役骨格である欠損型WNGを合成した。欠損型WNGは有機溶媒に溶解させた後、過飽和状態にさせることでゲル化することが明らかとなった。TEM観察によりファイバーの形成が確認された。この世界初となる無置換PAHの超分子ゲル化剤に関して、学会発表を8件行った。
巨大湾曲炭素分子へのヘテロ原子の導入による電気的・光学的性質の変化を明らかにするために、WNGと5重ヘリセンのチオフェン縮合類似体の合成を行った。さらに、単結晶X線構造解析および理論化学計算をもちいた構造的特徴の解明を行った。このチオフェン縮合類似体については論文としてChemical Scienceに発表した。
巨大湾曲炭化水素として複数7員環を含む3回回転対象性のプロペラ分子の合成と構造的特徴の解明を行い、論文1件(Organic Letters)、学会発表1件を行った。
また昨年度報告した5重ヘリセンに関連して、近年の対象性多重カルボヘリセン研究を総説としてSynlettで発表した。