<i>Ab initio</i> molecular‐orbital study of the binding of Zn^II with SH₂ and SH⁻

Abstract

Abstract This paper reports an ab initio molecular‐orbital ( MO ) study of binding of SH 2 and SH − with Zn II . The mechanism of binding of Zn II with these ligands is investigated using a detailed analysis of the energy decomposition and of the electronic distribution. The dependence of the results on the choice of the basis set for sulfur (in particular the effect of incorporation of diffuses p and d orbitals) on the geometry of ligand binding, the binding energy, and the proton affinity of SH − are investigated. Comparison made with the corresponding results concerning the binding of OH 2 , OH − , and NH 3 shows that sulfur binding is less favorable although more covalent. Both sulfur ligands show a marked preference for angular conformations for binding with the metal ion. The effect of Zn II binding on the ease of deprotonation of H 2 S is quite similar to the corresponding effect found earlier for H 2 O.