影响超极化度的分子结构因素

The Dependence of Hyperpolarizabilities on the Structures of Molecules

利用MNDO哈密顿中PM-3方法计算了三个系列D-A化合物的偶极矩(μ),极化系数(α),一阶(β)和二阶(σ)超极化系数。计算结果与实验值相符。计算显示β和ν与推、拉电子基团强弱有关,利用电荷转移可以提高β和ν值。计算结果证明杂原子对超极化度的影响是显著的。通过对双取代-二苯基多烯的β和ν计算,证实在共轭键上引入C=C双键是提高β和ν的有效方法。双键数对ν的影响可以表示成:ν=(n)=ν(0)+70n+9.4n^2。

The dipole moments (μ), polarizabilities (α) , hyperpolarizabilities (β), and second-order hyperpolarizabilities(ν) of three series of donor-accept molecules have been calculated by a finite-field method with the PM-3 parametrization of the MNDO Hamil-tonian. These results are quite satisfactory by comparing with experimental values. The calculations generally reproduced the dependence of β and ν on the strength of donors and acceptors and the enhancement of β , ν by charge transfer. The βand ν for the Disub-stituted-Diphenyl polyenes were calculated. The results confirm the efficiency of enhancing β and ν by insertion of C = C double bonds into a chain. The dependence of ν on the number of C = C double bonds can be expressed: ν(n) = ν(0)+70n+9. 4n2.