New Y-shaped structures of tetra-gold cation clusters stabilised by absorption of oxygen molecules

Abstract

Theoretically calculated research studies of oxygen absorption on gold cluster surface were used to simulate chemical reactions on the surfaces of gold nanoparticles. Low-energy conformational structures of tetra-nuclear gold cluster complexes with multiple oxygen molecule ligands, Au4(O2) n + (n = 1∼4), were theoretically investigated by the DFT calculations with long-range-corrected hybridisation functional CAM-B3LYP. In addition to known low-energy structures with tetragonal four-gold core, new low-energy isomers with Y-shaped four-gold core were revealed to be stable. The rationality of new structures was confirmed by the agreement of calculated infrared vibrational spectra with experimental results. The findings of new structures successfully interpreted the features of the vibrational spectra of this series of clusters. Highlights: New low-energy complex structures, containing a Y-shaped four-gold core, are stabilised by absorption of oxygen molecules and possess large first dissociation energy of oxygen molecule. The O–O stretching fundamental frequency of the Au–O–O–Au tetragon in the complexes with the Y-shaped four-gold core is found to be the origin of experimental vibrational absorption at about 1250 cm−1. Sum frequency of the stretching vibrations of the Au–O bond and the O–O bond is responsible for absorption observed at 1470 cm−1. A new activation mode of oxygen molecule is found in the Au–O–O–Au tetragon of new Y-core complexes, where the O-O bond length is ca. 1.30 angstrom (normally, ca. 1.20 angstrom).