New series of MII-dithiocarbamate complexes (M = CuII, NiII and ZnII) holding pendant N,O-Schiff base moieties: Synthesis, characterization, photophysical, crystallographic, anti-microbial and DFT study

Abstract

Multi-functional ligand precursors 2-[2-(1-piperazinyl)ethyliminomethyl] phenol (L1), 1-[2-(1-piperazinyl)ethyliminomethyl]naphthlene-2-ol (L2) and 6-methoxy-2-[2-(1-piperazinyl)ethyliminomethyl]phenol (L3) were selected to derive a new series of binuclear and mononuclear MII-dithiocarbamate complexes of the type [Cu{κ2S,S-S2C-piperazine-C2H4N=C(H)(R)}2]2 (R = -Ph(OH) 1, -Naph(OH) 2, -Ph(OH)(OCH3) 3 and [M{κ2S,S-S2C-piperazine-C2H4N = C(H)(R)}2] (R = -Ph(OH), M = NiII4, ZnII5; R = -Naph(OH), M = NiII6, ZnII7; R =- Ph(OH)(OCH3), M = NiII8, ZnII9). All the compounds have been characterized by microanalysis and standard spectroscopic methods such as 1H and 13C NMR, IR and UV–visible absorption spectroscopy. The molecular structures for L1 and its CuII-/NiII-dithiocarbamate complexes 1 and 4 were elucidated by single crystal X-ray diffraction (SCXRD) and their crystal packing patterns were studied. Interestingly, molecules of L1 forms 3D multiple open tubular supramolecular assembly by involving H bonding and other NH…OC, CHbenzene…O and CHpiperazine…O weak intermolecular forces. Notably, ZnII-dithiocarabamate complexes give maximum emission in visible nm region (ca 444–489) upon excitation of ultraviolet radiation with concomitant Stock shift ca < 200 nm. Thermogravimetric study was performed on 1–9 to investigate their thermal stability and degradation patterns. All the compounds have been screened for their potential in vitro antimicrobial activity against by using S. aureus, E. coli and C. albicans by Broth dilution method. The density functional theory calculations have been carried out to reinforce the experimental outcomes.