Theoretical studies on metal-metal interaction and spectroscopic properties of a series of hetero-binuclear d(8)-d(10) complexes containing iridium(i) and gold(i)

The ground and triplet excited state geometries, metal-metal (Ir-Au) attractive interaction, electronic structures, absorptions, and phosphorescence of three d(8)-d(10) Ir(i)-Au(i) complexes Ir(CO)ClAu(mu-dpm)(2)](-) (1), Ir(CNCH(3))(2)Au(mu-dpm)(2)](2-) (2), and Ir(CNCH(3))(3)Au(mu-dpm)(2)](2-) (3) dpm = bis(diphosphino)methane] were investigated theoretically. Their ground and triplet excited states geometries were fully optimized at the MP2 and UMP2 (6-31G for H/C/N/O atoms, LANL2DZ for Ir/Au/P/Cl) levels, respectively, and the calculated geometries are well consistent with the X-ray results. The calculated results indicated that a weak Ir-Au interaction exists in the ground state of , moreover the interaction of and is strengthened by excitation, on contrast, the Ir-Au attractive interaction of in the excited state becomes little lower than that in the ground state. By adding one more CNMe group on complex , the bond type of HOMO can be changed from sigma*d(z(2))(Ir/Au)] to sigmad(z(2))(Ir/Au)]. Under the TD-DFT level with PCM model, the absorptions and phosphorescence of were calculated based on the optimized ground and excited states geometries, respectively. The lowest-lying absorptions of 1 and 2 are all attributed to sigma*d(z(2))] --> sigmap(z)] and that of 3 is assigned to sigmad(z(2))] --> pip(z)] with MC/MMLCT transition characters. The phosphorescence of 1, 2 and 3 and are assigned to sigmap(z)] --> sigma*d], sigmap(z)] --> sigma*d], and pip(z)] --> sigmad] transitions, respectively. The calculated results also indicated that with the increase of the Ir-Au bond distance both in the ground and the excited state, the absorptions and the emissions are red-shifted correspondingly.