Electronic Alteration on Oligothiophenes by o‑Carborane: Electron Acceptor Character of o‑Carborane in Oligothiophene Frameworks with Dicyano-Vinyl End-On Group

We
studied electronic change in oligothiophenes by employing o-carborane into a molecular array in which one or both
end(s) were substituted by electron-withdrawing dicyano-vinyl group(s).
Depending on mono- or bis-substitution at the o-carborane,
a series of linear A1-D-A2 (1a–1c) or V-shaped A1-D-A2-D-A1 (2a–2c) oligothiophene chain structures
of variable length were prepared; A1, D, and A2, represent dicyano-vinyl, oligothiophenyl, and o-carboranyl groups, respectively. Among this series, 2a shows strong electron-acceptor capability of o-carborane
comparable to that of the dicyano-vinyl substituent, which can be
elaborated by a conformational effect driven by cage σ*−π*
interaction. As a result, electronic communications between o-carborane and dicyano-vinyl groups are successfully achieved
in 2a.

本研究通过将o-碳硼烷引入分子阵列，并以此阵列的一端或两端进行电子吸引的二氰乙烯基取代，探讨了寡噻吩中的电子变化。根据o-碳硼烷的单取代或双取代，成功制备了一系列可变长度的线性A1-D-A2（1a-1c）或V型A1-D-A2-D-A1（2a-2c）寡噻吩链结构；其中，A1、D和A2分别代表二氰乙烯基、寡噻吩基和o-碳硼基团。在此系列中，2a展现出与二氰乙烯基取代基相当强的电子受体能力，这种能力可通过由笼状结构的σ*−π*相互作用驱动的构象效应进行阐述。因此，在2a中成功实现了o-碳硼烷与二氰乙烯基团之间的电子通讯。