The structures of heterobinuclear complex, [(AuPtII)-Pt-I(CN)(2)(PH2CH2PH2)(2)](+) (2), in the ground and lowest-energy triplet excited states were optimized by the MP2 and unrestricted MP2 methods, respectively. The metal-localized transition shortens the Au-Pt distance about 0.321 angstrom in the excited state with respect to 2.912 angstrom one in the ground state. This is further evident in the calculated stretching frequencies and bond orders of Au-Pt. The experimental absorption spectra are well reproduced by the time-dependent density functional theory (TD-DFT) calculations. The present investigation was compared with the previous results of the homobinuclear [Au-2(I)(PH2CH2PH2)(2)](2+) (1) and trans-[Pt-2(II)(CN)(4) (PH2CH2PH2)(2)] (3). (C) 2008 Elsevier B.V. All rights reserved.