Structure and Bonding in MPb5− (M = Cu, Ag, and Au): A Combined Investigation by Theoretical Calculations and Photoelectron Imaging Spectroscopy

Bimetallic clusters of mpb5- (m = cu, ag, and au) have been studied using density functional theory and photoelectron imaging spectroscopy. these anionic clusters and their neutrals were determined to be a pb-5 trigonal bipyramid with the coinage metal atom on its triangular facet. this structure of each mpb5- or mpb5 was found to be more than 0.5 ev lower than other structural candidates and that of each mpb5- has a homo-lumo gap of larger than 1.2 ev. the chemical bonding between m and pb-5 in mpb5- was dominantly attributed to the interaction between the outer s orbital of m and the lowest unoccupied molecular orbital (lumo) of pb-5. the inner d orbitals of m and the occupied orbitals of pb-5 unit only make a little contribution. the different bonding behaviors of cu, ag, and au, which are noticeable in many other species, have little effect on the pb-5 counterpart in mpb5-, indicating pb-5 unit acts partially like a large artificial atom. additionally, photoelectron spectra of mpb5- (m = cu, ag, and au) provide good experimental data to evaluate different theoretical approaches dealing with relativistic effects in clusters containing heavy atoms.