The MP2 and unrestricted MP2 methods were performed to fully optimize the structures of [Au-2(S2CS)(2)](2-) (1) in the ground and lowest-energy triplet excited states, respectively. It was shown that upon excitation the An An distance shortens about 0.156 (A) over circle with respect to the 2.814 (A) over circle one in the ground state. In the calculations, vibrational frequencies at the MP2 level and solution absorption spectra at the TD-DFT level agree with experimental observations. The comparison among 1, [Au-2(S2CC(CN)(2))(2)](2-) (2) and [Au-2(S2CH2)(2)](2-) (3) in ground- and excited-state properties was discussed in detail. (c) 2005 Elsevier B.V. All rights reserved.