Theoretical studies on vibrational spectra of mixed cyanide–halide complexes of gold (III)

Abstract

The vibrational spectra of Au(CN) 4 − and its mixed cyanide–halide complexes, trans-Au(CN) 2X 2 −, cis-Au(CN) 2X 2 − and Au(CN) 3X − (X=F, Cl, Br and I), have been systematically investigated by ab initio RHF and density functional B3LYP methods with LanL2DZ and SDD basis sets. The calculated vibrational frequencies of complexes Au(CN) 4 − and trans-Au(CN) 2X 2 − are evaluated via comparison with the experimental values. In the infrared frequency region, the C–N stretching vibrational frequencies calculated at B3LYP level with two basis sets are in good agreement with the observed values with deviations, 3–7 cm −1 for Au(CN) 4 − and −3 to 16 cm −1 for trans-Au(CN) 2X 2 −. However, in the far-infrared region, the RHF/SDD method achieved the best results with deviations, −4 to 2 cm −1 for B 3u ν 13 Au–X stretching vibrational frequencies in trans-Au(CN) 2X 2 −; 14–37 cm −1 and 1–8 cm −1 for Au–C stretching vibrational frequencies in the complexes of Au(CN) 4 − and trans-Au(CN) 2X 2 −, respectively. The vibrational frequencies for cis-Au(CN) 2X 2 − and Au(CN) 3X − complexes that have not been experimentally reported were predicted.