Theoretical study on photophysical properties of Pt(II) triarylborons with a 2,2-bpy core derivatives

The photophysical properties of the linear and v shaped Pt(II) triarylborons with a 2,2'-bpy core derivatives have been investigated by density functional theory (DFT) method. The calculated electronic absorption wavelengths are in agreement with experimental ones, which can be described as a mixed transition of intra-ligand charge transfer (ILCT), ligand to ligand charge-transfer (LLCT), and metal-to-ligand charge transfer (MLCT). It is found that the MLCT transition is mainly responsible for the low-energy absorption band with relative smaller oscillator strength, while the high-energy absorption band mainly derives from ILCT and LLCT transition. Moreover, the electron absorption wavelengths are not only dependent on the position of the Ph-BMes2 but also on the electron-accepting ability of the acceptor groups. The first hyperpolarizability values of the v shaped complexes are larger than that of the linear shape complex, which indicates that larger intramolecular charge transfer for the v shaped complexes will come into being under the external electric field. Moreover, these complexes exhibit two-dimensional second-order nonlinear optical (NLO) character. Thus, the studied complexes have a possibility to be excellent second-order NLO materials. Based on the two-level model, the variation of first hyperpolarizabilities of the studied complexes can be explained by the combined effect of the difference between the ground state and excited state dipole moment, the oscillator strength, and the cube of the transition energy.