Synthesis,crystal structures and characterization of late first row transition metal complexes derived from thiosemicarbazone hub: DNA binding/cleavage studies

Air‐ and moisture‐stable coordination compounds of late first row transition metals, i.e. Co(III), Ni(II), Cu(II) and Zn(II), derived from the ligand (E)‐4‐(4‐chlorophenyl)‐1‐(1‐hydroxypropan‐2‐ylidene)thiosemicarbazide were prepared and successfully characterized using various spectro‐analytical techniques. The molecular structures of the ligand LH and complexes C1 and C2 were determined using single‐crystal X‐ray diffraction. The complexes C1 and C2 are stabilized by weak intermolecular CH???π stacking interactions: C1 between phenyl rings (C2–H21???C2) with a contact distance of 2.855 Å and C2 between phenyl ring and thione sulfur (C13???S1) with a contact distance of 3.366(6) Å. Complex C3 is found to be electrochemically active in the working potential range, showing a quasi‐reversible redox process. The interactions of all the compounds with calf thymus DNA were comprehensively investigated using electronic absorption spectroscopy, viscosity and thermal denaturation studies. Cleavage studies of Escherichia coli DNA were monitored using agarose gel electrophoresis. The results show that LH and complex C4 bind to calf thymus DNA through partial intercalation, while remaining complexes bind electrostatically. Further, C1, C2 and C4 complexes show better cleavage potential towards E. coli DNA. Copyright © 2015 John Wiley & Sons, Ltd.