电负性
极化率
分子内力
接受者
化学
密度泛函理论
计算化学
共轭体系
分子
物理
凝聚态物理
有机化学
聚合物
作者
Jin Yong Lee,Kwang S. Kim,Byung Jin Mhin
摘要
We have derived a simple expression to evaluate the amount of intramolecular charge transfer (ICT) of π-conjugate push–pull systems from the properties of electronegativity (χ) and polarizability (α) of the corresponding push and pull systems. This simple model is verified from ab initio calculations of disubstituted benzenes, stilbenes, and butadienes (push–pull systems) and their monosubstituted (push or pull) systems with various donors and acceptors. The bond length alternation (BLA) is often used as a good structural parameter to describe the amount of ICT; however, it is not a complete parameter because the amounts of ICT for the same sets of donor/acceptor pairs are different for different bridge systems. Here, we report a parameter composed of polarizability and electronegativity to give a consistent amount of ICT for different bridge systems. In particular, when a highly electropositive donor is used, the polarizability of an acceptor is the most determining factor for ICT. On the basis of this model, we find a very strong acceptor with large polarization effect, CH=C5H4, which gives a large nonlinear optical (NLO) response when a highly electropositive donor is used. The model would be a very useful utility to design various types of new functional molecular systems involving ICT optimization.
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