Density Functional Theory Studies of Aun+(CH3OH)m (n=3, 5, m=1-5) Complexes

The structural, energetic, and electronic properties of gold ions adsorbed methanol, Au-3(+)-(CH3OH)(m)(m = 1-3) and Au-5(+)-(CH3OH)(m) (m = 1 -5), have been investigated using density functional theory (DFT) within a generalized gradient approximation (GGA). The geometric parameters, vibrational frequencies, adsorption energies, and Mulliken charges are used to analyze the interactions between Au-3,5(+) clusters and methanol molecules. The present calculations show that more than one methanol molecule can be adsorbed onto small clusters of gold ions and that this adsorption is different from that of single-molecule absorption. The red shift of the C-O stretching frequency decreases as the number of methanol molecules, m, increases or as gold cluster size increases. The positive charge on Au-3,5(+) and coordination number of the adsorption sites on the gold cluster are the dominant factors responsible for the strength of the interactions. We obtained C-O stretching frequencies in Au-1,2(+)-(CH3OH) complexes that are below 931 cm(-1), which provides theoretical evidence for the experimental observation by Dietrich et al. [J. Chem. Phys. 2000, 112, 752].