Synthesis, characterization and biological studies of S-4-methylbenzyl-β-N-(2-furylmethylene)dithiocarbazate (S4MFuH) its Zn2+, Cu2+, Cd2+ and Ni2+ complexes

•A new bidentate dithiocarbazate Schiff base and its metal complexes are reported.•The complexes have been characterized by physical and spectroscopic techniques.•The U-shaped dithiocarbazate and its Zn(II) and Cd(II) have been structurally confirmed.•Only the Cu(II) complex shows moderate activity against MCF-7 breast cancer cells.•DNA binding studies prove that the Cu(II) complex had the strongest binding affinity.

S-4-methylbenzyl-β-N-(2-furylmethylene)dithiocarbazate (S4MFuH, 1) derived from the condensation reaction of furaldehyde (Fu) with S-4-methylbenzyldithiocarbazate (S4MBDTC) has been complexed with transition metal acetates to give Zn(S4MFu)2 (2), Cd(S4MFu)2 (3), Cu(S4MFu)2 (4) and Ni(S4MFu)2 (5). It is evident from the shift in ν(CN) and ν(NN) in the IR spectra of the complexes that deprotonated 1 acts as a bidentate ligand coordinating through the azomethine nitrogen and thiolato sulfur atoms. This was confirmed by single crystal X-ray diffractometry. The U-shaped dithiocarbazate 1 exists in the E configuration with the thione bond anti to the azo bond. A change in conformation is noted in the transition metal complexes resulting from deprotonation and NS-chelation. 2 and 3 display a distorted tetrahedral geometry with the major cause of the distortion being two close intramolecular M…O interactions. Binding interaction studies with calf thymus DNA demonstrated that 4 also had the strongest DNA binding affinity (Kb = 2.85 × 104 M−1) among all compounds prepared in this work. The Cu(II) complex, 4, was also moderately active against estrogen receptor-positive breast cancer cells, MCF-7 (IC50 = 3.02 μM) while the remainder were inactive against MCF-7 and all showed no activity towards receptor negative breast cancer cells, MDA-MB-231.

Graphical abstractA new bidentate dithiocarbazate Schiff base derived from furaldehyde and its metal complexes have been synthesized and characterized by various spectroscopic and physicochemical analysis. Some of the metal complexes have been characterized by single crystal X-ray diffraction analysis. The Cu(II)–Schiff base complex showed moderate activity against MCF-7 breast cancer cells and has the strongest DNA binding affinity.Figure optionsDownload full-size imageDownload as PowerPoint slide