QTAIM topological analyses of zinc(II), cadmium(II), and mercury(II) xanthate complexes

Context

Environmental contamination by heavy metals is increasing due to population growth and industrial activity, which is having a major impact on the environment. Xanthates, which form stable complexes with metals, are used to remove them from aqueous environments. Known for their role in ore flotation, these compounds also have applications in the biological field and thin film production. Due to the versatility of the coordination of xanthates to metal centers, it is essential to understand the nature of the metal–ligand bonds in these systems. Given their coordination versatility, understanding metal–ligand interactions is essential. Therefore, this study investigates the nature of the metal–ligand bonds of compounds containing n-propyl xanthate and water, with Zn²⁺, Cd²⁺, and Hg²⁺ ions. QTAIM analysis revealed that the metal-OH₂ bonds are predominantly electrostatic, while the metal-S bonds are partially covalent, with an increasing trend of covalency along group 12 (Zn²⁺ < Cd²⁺ < Hg²⁺), especially in the neutral and bidentate complexes, corroborating Pearson’s theory.

Methods

QTAIM analysis was carried out on 30 structures of n-propyl xanthate complexes with group 12 metals, which were previously investigated in earlier studies. These compounds had already been analyzed through energy decomposition analysis, providing a basis for comparison with the QTAIM results presented in this work. QTAIM was performed using wfx files generated at the DFT level (M06L/def2-TZVP) and analyzed with Multiwfn. Wavefunction (wfx) files, which contain detailed information on the electronic density distribution essential for accurate topological analysis, were generated and analyzed using Multiwfn to characterize the metal–ligand interactions.

Graphical abstract