Computational Study on the Second-Order Nonlinear Optical Properties of Coumarin Derivatives with N-p-Vinylphenyl Carbazole Chromophores

Abstract

Based on the density functional theory, a computational study was performed to investigate the second-order nonlinear optical properties of ten coumarin derivatives with N-p-vinylphenyl carbazole chromophores. All tested derivatives were divided into two groups, one with different substituent groups on carbazole (named as compounds b1 to b4) and the other with the N-p-vinylphenyl carbazole substituent modified at different positions on coumarin (named as compounds a to f). The geometrical structure of these derivatives were first comprehensively optimized through density functional theory method at B3LYP/6-311G level. Then their static second-order nonlinear optical polarizabilities (b) were calculated at the same level and the molecular electric spectrum of each derivative was obtained via the time dependent density functional theory (TD-DFT). Computational results show that all these derivatives have large b_tot values and excellent transparence. However, as compared to compounds a-f, compounds b1-b4 have longer conjugated bridges and larger b_tot values and show better planarity. It suggests that low transition energy, large Dμ_eg values and large charge transfer range play vital roles in the high second-order nonlinear optical response.