Chemical and photophysical properties of AuI, AuII, AuIII, and AuI-dimer complexes

Various Au-I, Au-II, Au-III, and Au-I-dimer complexes were probed using density-functional theory (DFT), specifically the B3PW91 hybrid functional, and relativistic effective core potentials. The research aimed to investigate the photophysical properties of gold complexes, and inspect the factors that influence the geometry and bonding properties of gold compounds. The results illustrate that the geometry of Au-I complexes (ground-state singlet) is very sensitive to the electronic nature of the ligands: sigma-donors give a two-coordinate, linear shape; however, pi-acceptors yield a three-coordinate, trigonal planar geometry. Doublet (AuL3)-L-II complexes distort to a T-shape coordination geometry, and are thus ground state models of the corresponding (AuL3)-L-I triplet excitons. The disproportionation of (AuL3)-L-II to (AuL3)-L-I and (AuL3)-L-III complexes is endothermic for all ligands investigated, suggesting that these complexes, neglected by experimentalists, are interesting subjects for study and may display unique photochemical properties. For dimeric Au-I complexes, the optimized triplet exciton shows a Jahn-Teller distortion around only one of the gold centers. Furthermore, the Au-Au distance is reduced in the dimer excited state versus the ground state, which should yield interesting Stokes' shifts. (C) 2004 Elsevier B.V. All rights reserved.