Computational modelling of gold complexes using density functional theory

Abstract

This study demonstrates the computation of the structures and properties of different gold complexes with significant relativistic effects including gold chloro–hydroxy species, gold thiosulphate and thiourea, using density functional theory (DFT). Simulations using the COSMO (COnductor-like Screening Model) description of solvation for systems with different complexants can effectively represent the surrounding media and produce results comparable with the limited available experimental data. In gold chloride systems, the stability constant for each gold(III) chloro–hydroxy species was calculated using the DFT methodology for the first time, showing excellent correlation with experimental results. The best results were obtained based on the addition of solvation energy values from COSMO media for complex species, and from experiments for small species, to the total energy calculated in the gas phase. The gold(I) thiourea cation in aqueous form was also modelled using DFT and COSMO for the first time, and the stability constant for gold thiourea complexation also showed good agreement with experimental data. The molecular structure of gold(I) thiosulphate was optimised using DFT, yielding good correlation with previous computational data as well as experimental results, although with the need identified for further analysis of some geometrical parameters. The results presented here confirm the ability of the DFT method and the COSMO model to compute the structures and properties of different aqueous gold complexes, and the results can be used further to study their stability and potential interactions with other species.