Abstract: MP2 and CIS methods were used to optimize the ground- and excited-state structures of (IrR(CO)(PH3)2(mnt) complexes, (mnt=maleonitriedithiolat e; R= H(1), Me(2), and Br(3)). The absorption and emission spectra were calculated using TD-DFT method with the PCM solvent model at the B3LYP level. The calculated results indicated that the lowest-energy absorption of 1-3 at 430, 435 and 439 nm were all assigned as the admixture of the ILCT/LLCT/MLCT transitions. The emissions are red-shifted to 760, 770 and 800 nm, the origin of which is similar to those of lowest-energy absorptions. The structure and spectroscopic properties of 2 and 1 are close to each other, but the introduction of Br in 3 changes the geometry of ground-state and excited-state and frontier orbitals, which affects the emission spectra and transition characters.

Key words: Ir complexes, excited state, solvent effect, TD-DFT