The ground-state structures of heterobimetallic d10-d8 complexes, [MM′(CN)2(PH2CH2PH2)2]+ (M = AuI, M′ = PtII (1), PdII (2), NiII (3); M′ = PtII, M = AgI (4), CuI (5)), were optimized using Density Functional Theory (DFT) and ab initio (MP2) method. It was shown that the M–M′ distances calculated with the BH&H functional are closest to the corresponding experimental values. The attempts of methods and substituents effects on the Au-Pt complex confirm the present calculations reasonable. The CIS calculations revealed that 1 features two excited states with the combined characters of MC (Metal-centered) and ICT (Intramolecular Charge Transfer). They give rise to the phosphorescent emissions at 399 and 234 nm, respectively, along with the promotion of electrons into bonding orbitals that results in the decrease of the Au–Pt distances in going from the ground state to the excited states. Optimizations on the lower-energy MC/ICT excited states of [AuIPtII(CN)2(PH2CH2PH2)2]+•X (1•X) (X = Cl–, Br–, I–, ClO–, HCN and MeCN) indicated that the environment effect (counterion and solvent) results in a red shift of emission wavelength. Among these, we predicted the emission of 1•ClO at 473 nm, agreeing with 451 nm of [AuPt(CN)2(PCy2CH2PCy2)2]•ClO4 in the solid state in the experiment.

Key words: Heterobimetallic d10-d8 complex, Excited state, Environmental effect, DFT and Ab initio method