Exploring dithiolate-amine binary ligand systems for the supramolecular assemblies of Ni(II) coordination compounds: Crystal structures, theoretical studies, cytotoxicity studies, and molecular docking studies

Abstract

Dithiolate-amine binary ligand systems based two novel supramolecular structures of Ni(II) coordination compounds [Ni(2-ap)2(i-mnt)] (1) and [Ni2(i-mnt)2(tn)2]n (2) [where i-mnt−2: 1,1-dicyanoethylene-2,2-dithiolate, 2-ap: 2-amino pyridine, tn: 1,3-diaminopropane] have been designed, synthesized and characterized by spectroscopic techniques and X-ray crystallography. In complex 1, the N2S2 coordination kernel around Ni+2 attains distorted square planar geometry (Okuniewski parameter τ/4 = 0.17) and its supramolecular array has a dominant influence of N H···N type hydrogen bonds forming significant ring geometry of graph-set-motifR428. The i-mnt−2 adopts a diverse coordination mode in 2 contrary to 1 resulting in a binuclear one-dimensional infinite polymeric chain structure of consecutive NiS4 [square planar, S4 donor set τ/4 = 0] and NiN6 (octahedral) coordination kernels linked by i-mnt−2 that runs along [1 0 0] axis wherein N H···S, N H···N, C H···S type hydrogen bonds are believed to be crystal structure stabilizers. The Hirshfeld surface analyses (HS) at the molecular and atomic levels have been extensively studied to quantify all non-covalent interactions/contacts and the nature of ligand - metal interactions. The prominent N···H/H···N [28.1 % (1), 27.3 % (2A, NiS4), 20 % (2B, NiN6)] and S···H/H···S contacts [10.4 % (1), 32.8 % (2A), 29 % (2B)] presumably play vital role in crystal packing. The non-covalent interactions were further investigated by Molecular Electrostatic Potential (MEP) surface at PBE0-D3/def2-TZVP level and QTAIM optimizations (for 1). The MTT assay study using SW620 metastatic colon cancer cells shows a significant dose-dependent decline in cell proliferation with increasing concentration for 1 but for 2, the reverse trend is followed. A molecular docking study with the APC protein has further investigated the antiproliferative activity of 1 (MTT assay).