Electrocatalytic property, anticancer activity, and density functional theory calculation of [NiCl(P^N^P)]Cl.EtOH

Abstract

This study describes the electrocatalytic, anticancer, and density functional theory (DFT) studies of a nickel complex, [NiCl(P^N^P)]Cl.EtOH, based on a neutral P^N^P‐type pincer ligand (P^N^P = bis[(2‐diphenylphosphino)ethyl]amine). The ligand was synthesized without time‐consuming and costly amine protection. It was characterized by 1H NMR, 31P NMR, Fourier transform infrared (FT‐IR), UV–vis, and single‐crystal X‐ray diffraction. The complex was isolated as a solvated chloride salt and characterized by FT‐IR, UV–visible, 1H NMR, 13C NMR, and 31P NMR spectroscopies as well as single‐crystal X‐ray diffraction and CHN analysis. The ligand and complex crystallized in a monoclinic P21/c space group. The molecular structure of the complex contains a four‐coordinated distorted nickel ion with square‐planar geometry. The electrocatalytic hydrogen ion reduction was studied for the nickel complex in an acidic non‐aqueous medium. Cyclic voltammetry studies showed that this complex is an efficient electrocatalyst for hydrogen evolution at the potential of the Ni(II/I) couple. As a potential anticancer agent, the biological activities of the Ni complex were tested against two human cancer cell lines (MCF7 and HT29). The IC50 results demonstrated that the nickel complex has better cytotoxic activity than cis‐platin against the human breast cancer cell (MCF7) line. DFT calculations were performed to study the kinetics and thermodynamics of the pincer ligand's synthetic procedure and its Ni complex. Time‐dependent DFT calculations were performed to calculate the pincer ligand's UV–vis spectra and the complex, which was in agreement with the experimental data. To assign the calculated UV spectra, molecular orbital calculations were performed. Finally, a modified mechanism was proposed for the electrocatalytic hydrogen ion reduction by [Ni(P^N^P)Cl]Cl.EtOH. The theoretical calculations showed that the cycle is thermodynamically favorable.

Dithiolato-Bridged Nickel(II) Salicylcysteamine Complexes as Robust Proton Reduction Electrocatalysts: Cyclic Voltammetry and Computational Studies

“…The [NiFe] hydrogenase is able to catalyze the reversible reduction of protons into H 2 at high conversion rates (10 3 s –1 ) close to the thermodynamic equilibrium. , The structure of its active site has been characterized, and the nickel center is believed to play a crucial and active role in the redox and protonation processes. , It is thus not surprising that many nickel complexes have been prepared and tested as proton reduction catalysts. − While not all nickel complexes are promising, one of the best synthetic catalysts reported so far is a nickel phosphine complex containing a pendant amine, which catalyzes H 2 production with high turnover frequencies (105 s –1 ) in the presence of water in acetonitrile …”