Ab Initio Studies on Metal−Metal Interaction and 3[σ*(d)σ(s)] Excited State of the Binuclear Au(I) Complexes Formed by Phosphine and/or Thioether Ligands

Abstract

The structures of ground state and lowest energy triplet excited state for [Au2(PH2CH2PH2)2]2+ (1), [Au2(PH2CH2PH2)(SHCH2SH)]2+ (2) and [Au2(SHCH2SH)2]2+ (3) as well as their solvated 1−3·(MeCN)2 species are fully optimized by the MP2 and CIS methods, respectively. The 3[σ*(d)σ(s)] excited states give the 300−390 emissions in the gas phase, red shifting to 500−730 nm in acetonitrile. The coordination of solvent molecule to the gold atom in the excited states is responsible for such a red shift. For 2, all the possible geometries, the substituent effect of methyl groups on P and/or S atoms and the comparison with thiolate complex [Au2(PH2CH2PH2)(SCH2S)] (6) are discussed. The unrestricted MP2 calculations on 1−3, head-to-tail [Au2(PH2CH2SH)2]2+ (7) and head-to-head [Au2(PH2CH2SH)2]2+ (8) confirm the CIS results in both optimized geometry and emissive energy related to the 3[σ*(d)σ(s)] state. The frequency calculations at the MP2 level indicate that the Au(I)−Au(I) interaction is weak in the ground state (ν(Au2) = 89−101 cm-1) but is strongly strengthened in the excited state (ν(Au2) = 144−189 cm-1).