Experimental and in silico DNA binding studies with easily accessible and stable zinc(II) carboxylates

Abstract

Abstract [Zn(OOCCH2C6H4OH)2]n (1) and [(Phen)Zn(OOCCH2C6H4OH)2] (2) were made by the reaction of zinc(II)acetate dihydrate with 4-hydroxyphenylacetic acid in the absence and presence of 1,10-phenenthroline, respectively. The complex 1 crystallizes as coordination polymer formed by the μ−η1,η1 carboxylate bridged tetrahedral zinc centers. The complex 2 comprises a distorted octahedral zinc center coordinated by the two bidentate carboxylates and a bidentate 1,10-phenanthroline. Thermal stabilities of the complexes were studied by TG and DTA techniques at varied heating rates (10\u202f°C/min, 15\u202f°C/min and 20\u202f°C/min). Both complexes follow a two-stage degradation processes with the formation of ZnO as the final residue where complex 2 has higher energetic stability compared with complex 1. The kinetic and thermodynamic parameters were calculated from the TG curves employing the Horowitz-Metzger method. Zinc complexes were examined for their DNA binding abilities by UV–vis spectroscopic analysis and structurally rationalized by the docking studies. The binding constant values (Kb) for DNA-complex interactions were found to be 7.7\u202f×\u202f104\u202fM-1 and 2.94\u202f×\u202f104\u202fM-1 for complexes 1 and 2, respectively. Complex 1 interacted with DNA exclusively by hydrogen bond formation whereas complex 2 developed both hydrogen and arene-cation interactions with the active residues of DNA.