Molecular structures of trans-[(trpy)(pic)RuCl] and cis-[(trpy)(pic)RuCl] were optimized at the level of B3LYP/LANL2DZ, and their absorption spectra in acetonitrile were investigated by using time-dependent density functional method. Calculation results indicate that both of the two isomers have broad and relative strong absorption bands in visible region. Calculated positions of absorption peaks in the visible region for the cis- and trans- isomers are at 510.2 and 383.2, 522.5 and 398.4 nm respectively, the positions and relative strength are in good agreeement with experimental results, and the lowest-energy absorption bands of the two isomers display MLCT/ILCT/LLCT character. It can be predicted that after adjoining polar groups such as —COOH etc on ligand trpy, the two isomers may be used as sensitizers in solar cells.

Key words: trans-[(trpy)(pic)RuCl], cis-[(trpy)(pic)RuCl], B3LYP/LANL2DZ, time-dependent density functional method (TD-DFT), absorption spectra