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

2004-04-22T00:00:00Z (GMT) by Qing-Jiang Pan Hong-Xing Zhang
The structures of ground state and lowest energy triplet excited state for [Au<sub>2</sub>(PH<sub>2</sub>CH<sub>2</sub>PH<sub>2</sub>)<sub>2</sub>]<sup>2+</sup> (<b>1</b>), [Au<sub>2</sub>(PH<sub>2</sub>CH<sub>2</sub>PH<sub>2</sub>)(SHCH<sub>2</sub>SH)]<sup>2+</sup> (<b>2</b>) and [Au<sub>2</sub>(SHCH<sub>2</sub>SH)<sub>2</sub>]<sup>2+</sup> (<b>3</b>) as well as their solvated <b>1</b>−<b>3</b>·(MeCN)<sub>2</sub> species are fully optimized by the MP2 and CIS methods, respectively. The <sup>3</sup>[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 <b>2</b>, all the possible geometries, the substituent effect of methyl groups on P and/or S atoms and the comparison with thiolate complex [Au<sub>2</sub>(PH<sub>2</sub>CH<sub>2</sub>PH<sub>2</sub>)(SCH<sub>2</sub>S)] (<b>6</b>) are discussed. The unrestricted MP2 calculations on <b>1</b>−<b>3</b>, head-to-tail [Au<sub>2</sub>(PH<sub>2</sub>CH<sub>2</sub>SH)<sub>2</sub>]<sup>2+</sup> (<b>7</b>) and head-to-head [Au<sub>2</sub>(PH<sub>2</sub>CH<sub>2</sub>SH)<sub>2</sub>]<sup>2+</sup> (<b>8</b>) confirm the CIS results in both optimized geometry and emissive energy related to the <sup>3</sup>[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(Au<sub>2</sub>) = 89−101 cm<sup>-1</sup>) but is strongly strengthened in the excited state (ν(Au<sub>2</sub>) = 144−189 cm<sup>-1</sup>).