Snyder Gregory R, Chowdhury Azhad U, Simpson Garth J
Department of Chemistry, Purdue University , West Lafayette Indiana 47907, United States.
J Phys Chem A. 2014 Jun 19;118(24):4301-8. doi: 10.1021/jp5003935. Epub 2014 Jun 9.
A simple model is presented for interpreting the presence of substantial second harmonic generation (SHG) activity from assemblies of centrosymmetric molecular building blocks. Using butadiene as a computationally tractable centrosymmetric model system, time-dependent Hartree-Fock calculations of the nonlinear polarizability of butadiene dimer were well-described through exciton coupling arguments based on the electronic structure of the monomer and the relative orientation between the monomers within the dimer. Experimental studies of the centrosymmetric molecule 2,6-di-tert-butylanthraquinone suggest the formation of a combination of SHG-active and SHG-inactive crystal forms. The structure for the centrosymmetric form is known, serving as a negative control for the model, while the presence of an additional SHG-active metastable form is consistent with predictions of the model for alternative molecular packing configurations.
提出了一个简单模型，用于解释来自中心对称分子构建块组装体的大量二次谐波产生（SHG）活性的存在。使用丁二烯作为计算上易于处理的中心对称模型系统，基于单体的电子结构和二聚体内单体之间的相对取向，通过激子耦合论证很好地描述了丁二烯二聚体非线性极化率的含时Hartree-Fock计算。对中心对称分子2,6-二叔丁基蒽醌的实验研究表明形成了SHG活性和SHG非活性晶体形式的组合。中心对称形式的结构是已知的，作为该模型的阴性对照，而另一种SHG活性亚稳形式的存在与该模型对替代分子堆积构型的预测一致。
