New palladium(II) hydrazone complexes: Synthesis, structure and biological evaluation

Two new palladium(II) complexes of 4-hydoxy-benzoic acid (5-bromo-2-hydroxy-benzylidene)-hydrazide (H2L) (1) with triphenylphosphine and triphenylarsine as coligand have been synthesized and characterized by the aid of various spectral techniques. The structure of the ligand and complexes was confirmed by single crystal X-ray diffraction studies. The hydrazone ligand acts as a tridendate ligand with ONO as the donor sites and is preferably found in the enol form in all the complexes. The structural analysis of 2 and 3 confirms the square planar geometry of the two complexes. The DNA binding of these complexes and ligand calf thymus DNA (CT-DNA) was investigated by using various methods, which revealed that the compounds interacted with CT-DNA through intercalation. Binding properties of the free ligand and its complexes with bovine serum albumin (BSA) protein have been investigated using UV-visible and fluorescence spectroscopic methods which indicated the stronger binding nature of the palladium complexes to BSA than the free hydrazone ligand. In addition, concentration dependent free radical scavenging potential of all the synthesized compounds (1-3) was also carried out under in vitro conditions. Further, the in vitro cytotoxicity of the compounds was examined on a HeLa and MCF-7 cell lines, which revealed that complex 2 exhibited a superior cytotoxicity than complex 3 and ligand 1.