Energetically favorable anti-electrostatic hydrogen bonded cationic clusters in Ni(II) 3,5-dimethylpyrazole complexes: Anticancer evaluation and theoretical studies

Two new Ni(II) coordination complexes of pyrazole and acetato ligands, involving nitrate and chloride counter anions, viz. [Ni(Hdmpz)(2)(CH3COO)(H2O)(3)]NO3 center dot 2H(2)O (1) and [Ni(Hdmpz)(2)(CH3COO)(H2O)(3)]Cl (2) (where Hdmpz = 3,5-dimethylpyrazole), have been synthesized in purely aqueous medium at room temperature. The complexes have been characterized by elemental analysis, FT-IR, electronic spectroscopy, PXRD, TGA and single crystal X-ray diffraction. The H-bonds established between the isostructural cationic [Ni(Hdmpz)(2)(CH3COO)(H2O)(3)](+) moieties of both complexes can be classified as anti-electrostatic H-bonds (AEHBs) and these have been studied using DFT calculations. Remarkably, in one case these AEHBs exhibit favorable interaction energies, thus indicating that the attractive nature of the H-bonds is able to compensate the pure electrostatic repulsion. The analyses of the cell viability results for the DL cell line show a significant concentration dependent decrease by compounds 1 and 2 with a negligible cytotoxic effect observed against normal cells (PBMC) in comparison to the cancer cells (DL). The cytotoxic activity of these compounds in DL cells occurs via apoptosis. Molecular docking and SAR analysis reveal that the compounds possess high binding affinities against most common cancer target proteins. (C) 2019 Elsevier Ltd. All rights reserved.