Synthesis, Characterization, and Biological Studies of Binuclear Copper(II) Complexes of (2E)-2-(2-Hydroxy-3-Methoxybenzylidene)- 4 N -Substituted Hydrazinecarbothioamides

Abstract

Four novel binuclear copper(II) complexes [ 1 – 4 ] of (2E)-2-(2-hydroxy-3-methoxybenzylidene)- 4 N -substituted hydrazinecarbothioamides, (OH)(OCH 3 )C 6 H 4 CH=NNHC(S)NHR, where R = H ( L 1 ), Me ( L 2 ), Et ( L 3 ), or Ph ( L 4 ), have been synthesized and characterized. The FT-IR spectral data suggested the attachment of copper(II) ion to ligand moiety through the azomethine nitrogen, thioketonic sulphur, and phenolic-O. The spectroscopic characterization indicates the dissociation of dimeric complex into mononuclear [Cu(L)Cl] units in polar solvents like DMSO, where L is monoanionic thiosemicarbazone. The DNA binding properties of the complexes with calf thymus (CT) DNA were studied by spectroscopic titration. The complexes show binding affinity to CT DNA with binding constant ( K b ) values in the order of 10 6 M −1 . The ligands and their metal complexes were tested for antibacterial and antifungal activities by agar disc diffusion method. Except for complex 4 , all complexes showed considerable activity almost equal to the activity of ciprofloxacin. These complexes did not show any effect on Gram-negative bacteria, whereas they showed moderate activity for Gram-positive strains.