As part of an investigation on singlet diradicaloid and tetraradicaloid compounds, a mesityl derivative of tetracyclopentatetraphenylene (TCPTP) consisting of a cyclic array of four benzene ring conjoined by five-membered rings was synthesized recently in Tobe Lab. On the basis of X-ray structure analysis and temperature-dependent 1H NMR, the molecular structure was considered to adopt a low-symmetric D2h structure. However, it is assumed that in crystals which was obtained by recrystallization from CCl4, two molecule is packed in a space group with four-fold symmetry, suggesting that it has high-symmetry D4h structure due to the packing force exerted by substituents and solvent molecules. In my presentation, I will explain aromaticity and anti-aromaticity briefly and show some examples of molecules that interconvert between high/low symmetric structures relevant to anti-aromaticity. Finally I will introduce preceding work on the molecular structure of the TCPTP derivative which was synthesized in Tobe Lab. and my research project.
当研究室では一重項ジラジカルやテトララジカル性を示す化合物に関する研究の一環として最近、5員環と6員環を交互に環状に縮環させたテトラシクロペンタテトラフェニレン(TCPTP)のメシチル誘導体が合成された。メシチル誘導体はX線結晶解析と温度可変1H NMRの結果、その構造は低対称のD2h構造であると考えられる。しかし、四塩化炭素から再結晶した結晶では4回対称の空間群を持つことが推定され、置換基により高対称のD4h構造をとる可能性が考えられる。 本発表では芳香族性と反芳香族について簡単に説明し、反芳香族性に関係して対称性が異なる構造間で相互変換を起こすような分子の例を紹介する。続いて、当研究室で合成されたTCPTP誘導体の物性を説明し、最後に私の研究テーマを紹介する。