Coordination Behavior of Ni2+, Cu2+, and Zn2+ in Tetrahedral 1-Methylimidazole Complexes: A DFT/CSD Study.

Samuel Tetteh

doi:10.1155/2018/3157969

Abstract

The interaction between nickel (Ni2+), copper (Cu2+), and zinc (Zn2+) ions and 1-methylimidazole has been studied by exploring the geometries of eleven crystal structures in the Cambridge Structural Database (CSD). The coordination behavior of the respective ions was further investigated by means of density functional theory (DFT) methods. The gas-phase complexes were fully optimized using B3LYP/GENECP functionals with 6-31G∗ and LANL2DZ basis sets. The Ni2+ and Cu2+ complexes show distorted tetrahedral geometries around the central ions, with Zn2+ being a perfect tetrahedron. Natural bond orbital (NBO) analysis and natural population analysis (NPA) show substantial reduction in the formal charge on the respective ions. The interaction between metal d-orbitals (donor) and ligand orbitals (acceptor) was also explored using second-order perturbation of the Fock matrix. These interactions followed the order Ni2+ > Cu2+ > Zn2+ with Zn2+ having the least interaction with the ligand orbitals. Examination of the frontier orbitals shows the stability of the complexes in the order Ni2+ > Cu2+ < Zn2+ which is consistent with the Irving–Williams series.

Highlights

Metalloproteins play important roles in the structure and physiology of cells. ey account for nearly half of all proteins in nature [1]
Some of their cellular functions include water oxidation, photosynthesis, respiration, molecular oxygen reduction, and zinc fingers [1, 2]. e binding stability of divalent transition metals in metalloproteins has been largely studied in terms of semiempirical and qualitative theories such as the hard and soft acid and base principles of Parr and Pearson and the Irving–Williams series of stability constants [3]
The fundamental role of metal ions in the structure and function of metalloproteins is still a matter of ongoing research [4, 5]. e amino acid histidine is a common ligand in metalloproteins [6]. e imidazole ring of histidine is an important five-membered heterocycle that is widely present in natural products and most synthetic molecules

Summary

Samuel Tetteh

E interaction between nickel (Ni2+), copper (Cu2+), and zinc (Zn2+) ions and 1-methylimidazole has been studied by exploring the geometries of eleven crystal structures in the Cambridge Structural Database (CSD). E coordination behavior of the respective ions was further investigated by means of density functional theory (DFT) methods. E gas-phase complexes were fully optimized using B3LYP/GENECP functionals with 6-31G∗ and LANL2DZ basis sets. E interaction between metal d-orbitals (donor) and ligand orbitals (acceptor) was explored using second-order perturbation of the Fock matrix. Ese interactions followed the order Ni2+ > Cu2+ > Zn2+ with Zn2+ having the least interaction with the ligand orbitals. Examination of the frontier orbitals shows the stability of the complexes in the order Ni2+ > Cu2+ < Zn2+ which is consistent with the Irving–Williams series

Introduction

Methodology

Results and Discussion

Bond Type