Exploring the hydrogen-bonding interactions in the piperazinylethanol substituted homoleptic zinc(II)-dithiocarbamate and its diimine 2,2′-bipyridyl and 1,10-phenanthroline adducts, and their DNA binding studies

Abstract

Keeping in view the significance of H-bonding hydroxyethyl substituent in the supramolecular organization of the compounds of general formula Zn(S2CNR1R2)2, herein we report synthesis and characterization (1H/13C NMR, FTIR, UV–Vis spectroscopy, CV, elemental analysis and single crystal XRD) of piperazinylethanol substituted complex [Zn{S2CN(CH2)4N(C2H4OH)}2]2 (1) and its 2,2′-bipyridyl (2) and 1,10-phenanthroline (3) adducts. Inferred from XRD data, these compounds show a variety of coordination geometries, i.e., Zn1-center (τ = 0.668) in (1) is more inclined towards trigonal-bipyramidal environment than the Zn2-center (τ = 0.567), whereas (2) and (3) exhibit distorted octa- and tetra-hedral geometries, respectively. Unlike the others, complex (2) co-crystallized with an uncoordinated 2,2′-bipyridyl ligand showing more stable trans-conformation of the N-atoms. Supramolecular data reveal pivotal role of the H-bonding interactions in the crystal packing, especially in (1) where (hydroxyethyl)OH···OH(hydroxyethyl) interaction sustains 3-D network. The interaction propagates in infinite open chain fashion and the network secures undulating topology. Adducts (2) and (3) also feature undulating topologies, however, OH···N H-bonding interaction plays the role to sustain 2- and 1-D networks, respectively. Other secondary bonding interactions, like CH···S, CH···π(aromatic), CH···O and π···π stacking etc. contribute to transform these 1- and 2-D architectures into 3-D aggregates. Compared to closely related systems, these compounds show enhanced H-bonding potential with less hydroxyethyl substituents per molecule, possibly due to the presence of sterically flexible piperazine ring. Further, their DNA-binding capability was assessed through multiple techniques (like UV–vis spectroscopy, CV and viscometry), which revealed promising DNA binding potential for these compounds.