含有咪唑生色团系列树型有机分子二阶非线性光学性质的密度泛函理论研究

Density Functional Theory of Second-order Nonlinear Optical Properties of a Series of Organic Dendrimer Molecules with an Imidazole Chromophore

应用密度泛函理论(DFT)B3LYP/6-31G*方法研究了含有咪唑生色团的系列树型有机分子的结构和非线性光学(NLO)性质.结果表明,该系列分子具有A-π-D-π-A(A:受体,D:给体)结构,分子基态的偶极矩、极化率和二阶NLO系数(β)均随共轭链的增长及吸电子基的增强而增大;同时,此类分子前线分子轨道能级差值越小,其二阶NLO系数总有效值(βtot)越大.吸收光谱结果表明,此系列树型分子在低能区域247.79～419.87 nm内都有一个最强吸收,并且均对应最高占据轨道与最低空轨道之间的跃迁.

Density functional theory（DFT） B3LYP/6-31G＊ method was employed to optimize the structures of a series of organic dendrimer molecules containing an imidazole chromophore and second-order nonlinear optical properties.Results show that the molecules possess A-π-D-π-A（A： acceptor,D： donor） structures,and the dipole moment of the ground state,the polarizability,and the second-order nonlinear optical（NLO） coefficient（β） of the molecules increase with the increase of the length of conjugate bridge of the branched chain and the conjugation effect of the chromophore.The molecule with smaller energy gap of the frontier molecular orbital shows larger values of the second-order NLO coefficient βtot.The calculated electronic absorption spectra of the organic dendrimer molecules exhibit the most intensive excitations in the low-lying region 247.79—419.87 nm,which are arisen from the charge transfers from HOMO to LUMO.