Abstract: Geometry optimizations and frequency calculations of three (C^N)PtIIQtype complexes in the ground state were performed at the level of B3LYP/LANL2DZ, and their absorption properties in dichloromethane (CH2Cl2) media were calculated by using time-dependent density functional theory (TD-DFT) associated with the polarized continuum model (PCM). The optimized structures and calculated absorption spectra were in reasonable agreement with experimental data. All the complexes had relative strong absorption and broad absorption bands in visible region. The lowest-energy absorption bands of (C^N)PtIIQ type complexes exhibited ILCT (intra-ligand charge transfer) mixed with partially MLCT (metal-to-ligand charge transfer) characteristic, and showed different transition mechanisms compared with those of PtIIQ2 type complexes, whose lowest energy absorption bands were usually dominated by ILCT transitions.

Key words: (C^N)PtIIQ type complex, Density functional theory, Polarized continuummodel, Absorption spectrum, Energy gap