Density Functional Theory Study on Second-order Nonlinear Optical Properties of C∧N∧NPt(II) and N∧C∧NPt(II) Complexes

Density functional theory (DFT) with the BHandHLYP functional was employed to investigate the polarizability and second-order nonlinear optical (NLO) coefficients of C boolean AND N boolean AND N ligands, C boolean AND N boolean AND NPt(II) (C boolean AND N boolean AND N = 6-phenyl-2,2'-bipyridines) and N boolean AND C boolean AND NPt(II) (N boolean AND C boolean AND N = 1,3-di(2-pyridyl)-benzene) complexes. The calculations indicate that the second-order NLO coefficients of complexes are enhanced significantly and the beta value of complex 2b is about 11 times as large as that of ligand Lb. In addition, the second-order NLO coefficients of complexes are also enhanced by increasing the conjugation of ancillary ligands and the electron-withdrawing ability of substituents. The electronic spectra of complexes were analyzed by the time-dependent density function theory (TD-BHandHLYP) method. The results show that the experimental absorption spectra are well reproduced by the theoretical data. The maximum absorptions of C boolean AND N boolean AND NPt(II) and N boolean AND C boolean AND NPt(II) complexes are assigned to different kinds of electronic transitions. And the substituents have larger effects on the maximum absorptions of N boolean AND C boolean AND NPt(II) complexes, while less effects on that of C boolean AND N boolean AND NPt(II) complexes.