Chiral metal–dithiocarbamate complexes with pendant phenolic groups: synthesis, crystallographic, photophysical and in silico study†

Abstract

We report a novel series of chiral monometallic dithiocarbamate complexes with pendant phenolic groups, formulated as [M{κ₂S^S-S₂CN(CH₂PhOH)(CH(S-CH₃))(NaPh)}₂] (M = Ni(II) S,S-1, Cu(II) S,S-2, Zn(II) S,S-3) and [M{κ₂S^S-S₂CN(CH₂PhOH)(CH(R-CH₃))(NaPh)}₂] (M = Ni(II) R,R-4, Cu(II) R,R-5, Zn(II) R,R-6). These compounds were synthesized through a process involving chiral amino precursors S-HL¹, R-HL², CS₂ and the corresponding metal acetates. All the compounds have been characterized by microanalysis and standard spectroscopic methods such as ¹H and ¹³C{¹H}NMR, IR, UV-visible absorption and EPR spectroscopy. The spectral data suggest a square planar coordination geometry around the nickel(II) and copper(II) centers and a tetrahedral coordination geometry around zinc(II), which is corroborated by density functional theory calculations. The unprecedented molecular structures of imine precursors S-I, R-I and Ni(II)-dithiocarbamate complex S,S-1 were elucidated by single crystal X-ray diffraction (SCXRD), and their crystal packing patterns were studied. Evidently, the change in chirality could not induce changes in the donor–acceptor sites of S-I and R-I, and their molecules are primarily stabilized by O–H⋯N and C–H⋯π interactions, forming a 2D sheet-like structure in the ab-plane. Notably, the chiral S,S-1 complex crystallized in a monomeric achiral space group (triclinic, P1) in which two dithiocarbamate ligands are bonded to the nickel(II) ion in a S^S chelating mode forming a square planar geometry around the metal center. The photophysical properties of all the compounds have been investigated using UV-visible absorption, emission, and thermogravimetric analyses. Compounds exhibited intense blue photoluminescence with maximum emissions in the 330–336 nm region upon excitation in the UV region. A molecular docking study was performed to validate the potentials of these compounds in protein–ligand interactions against B-DNA Dodecamer (PDB Id: 1BNA) and cyclins (PDB Id: 1w98), which are indeed essential proteins of the cell cycle, and their proper functioning is necessary for the human health.