Mixed ligand complexes of CuII with pyridoxal thiosemicarbazone and dipeptides: Synthesis, characterization, DNA binding, cleavage, antibacterial and docking studies

Department of Chemistry, Jawaharlal Nehru Technological University Hyderabad, Hyderabad-500 085, India
E-mail: vrr9@yahoo.com
Department of Chemistry, St. Francis College for Women, Hyderabad-500 016, India
Department of Chemistry, Nizam College, Osmania University, Hyderabad-500 001, India
Manuscript received online 28 November 2018, accepted 07 December 2018

Mixed ligand complexes of Cu^II of the type, [CuAL] where, A = pyridoxal thiosemicarbazone (PLTSC) and L = dipeptide viz.
glycyl-glycine (gly-gly), glycyl-L-leucine (gly-leu), glycyl-L-tyrosine (gly-tyr) and glycyl-L-valine (gly-val), have been synthesized.
They were characterized by elemental analyses, LC-MS, FTIR, UV-Vis and ESR studies, thermal analysis, molar conductance
and magnetic susceptibility measurements. The ligand, A is coordinated through O,N,S donor atoms while, L is coordinated
through the O,N,N donor atoms. However, in the complexes [Cu(PLTSC)(gly-leu)(H₂O)] and [Cu(PLTSC)(gly-tyr)(H₂O)], the
PLTSC is coordinated only through O,N donor atoms. The interaction of the complexes with calf thymus DNA (CT-DNA) was
investigated by UV-Vis absorption and fluorescence emission spectroscopy and also by viscosity measurements, which suggested
intercalative mode of binding between the complexes and CT-DNA. The mode of DNA binding was further analyzed
by docking studies, which supports intercalative binding. The complexes demonstrate excellent nuclease activity on super coiled
plasmid pBR322 DNA in the studies by agarose gel electrophoresis. The metal complexes also exhibit moderate inhibition
activity against Gram-positive bacteria.