含酯基和酰胺基支链的苯并菲液晶电荷传输性质的量子化学研究

根据Marcus半经典模型，计算了支链中含酰胺基和含酯基的苯并菲盘状液晶化合物C18H6(OC2H5)3(OCH2CONHCH3)3和C18H6(OC2H5)3(OCH2COOCH3)3的电荷转移反应的速率常数。这两种化合物的支链都可以对称性分布，也可以非对称性分布。计算表明，支链排列的对称性对电荷转移矩阵元和电荷传输速率常数的影响很大，非对称性分子的正电荷传输速率常数和负电荷传输速率常数均大于对称性分子。所以，取代基非对称性排列对增加电荷传输速率常数有利。其原因是支链非对称排列的分子的质量中心与几何中心不重合，当液晶分子绕质量中心旋转的同时形成了分子间的相对平移，从而增大了电荷转移矩阵元。本文为设计、改善液晶分子的电荷传输性能提供了一条新的思路。

A Quantum-Chemical Study on Charge Transport Properties of Triphenylene Discotic Crystals Substituted with Ester or Amide Functional Groups

The relative charge transfer rate of symmetrical and asymmetrical triphenylene discotic liquid crystals with two different kinds of peripheral chains, C18H6(OC2H5)3(OCH2CONHCH3)3 and C18H6(OC2H5)3(OCH2COOCH3)3 were estimated on the basis of semiclassical Marcus theory. The results showed that the asymmetrical compounds have bigger charge transfer integrals and higher charge transfer rate. The reason is that the mass center does not coincide with the geommetrical center for asymmetrcal compounts. While one asymmetrical molecule rotating about an axis that goes through the molecular mass center, the geommetrical centers of two asymmetrical molecules will have relative displacement. The relative displacement can probably lead to higher orbital splittings, so lead to higher charge transfer rate. We predict a significant increase in the charge transfer rate when going from symmetrical triphenylene to asymmetrical one.