取代基对联萘桥联手性双卟啉分子二阶非线性光学性质的影响

The effect of substituents on the second-order nonlinear optical properties of binaphthyl bridged chiral bis-porphyrins

在6-31G(d,p)水平上用B3LYP(DFT)方法对联萘桥联推拉双卟啉Ⅱ_c系列分子进行几何构型优化。用ZINDO/SOS方法计算了这些分子的一阶超极化率。计算结果表明:采用具有较大一阶超极化率的卟啉单体构建的手性双卟啉分子,其一阶超极化率有显著提高。此外,推拉基团的排列方式不同会导致基态偶极矩以及一阶超极化率存在明显差别。一阶超极化率随着基态偶极距μ_0增大而增强。双卟啉系列分子一阶超极化率提高主要起源于激子跃迁态偶极耦合作用的增强。跃迁通道分析表明:偶极耦合增强不仅与B带激子跃迁态有关,还与CT态密切相关。

The geometries of a series of binaphthyl bridged chiral push-pull bis-porphyrins were optimized using B3LYP method at 6-31G（d,p） basis set level. First hyperpolarizabilities of these porphyrins were calculated using the ZINDO/SOS method.Calculation results showed that the first hyperpolarizabilities of chiral bis-porphyrin increased significantly when using substituted porphyrin monomer with larger non-linear optical response.Further more,the ground-state dipole moment and the first hyperpolarizability of bis-porphyrin depend on the spacial arrangement of substituents.The second-order nonlinear optical response increases with the increasing of the molecular ground-state dipole moment.The increase in first hyperpolarizabilities of bis-porphyrins is mainly resulted from the enhancement of the exciton coupling interaction.Transition channels analysis showed that dipole coupling enhancement not only related to the B bands exciton interation but also related to the CT state.