Hexanuclear Zn(II) and Mononuclear Cu(II) Complexes containing imino phenol ligands: Exploitation of their Catalytic and Biological Perspectives

Abstract

A unique hexanuclear zinc(II) (1) and two mononuclear copper(II) (2 and 3) complexes anchored with imino phenol ligand HL 1 and HL 2 were synthesized with good yield and purity (where HL 1 = 4-tert-butyl-2,6-bis((mesitylimino) methylphenol and HL 2 = 5-tert-butyl-2-hydroxy-3-((mesitylimino)methyl) benzaldehyde). These complexes were characterized by utilizing various spectroscopic protocols like NMR, FTIR, UV as well as ESI-Mass spectrometry, elemental analysis and single crystal X-ray diffraction studies. Their potential to bind calf thymus DNA (CT-DNA) was tested utilizing different techniques such as UV-visible and fluorescence spectroscopy. The experiment implies that they interact with CT-DNA via non-intercalative mode with moderate capabilities (K b~1 0 4 M −1 ). On the other hand, these complexes have high capabilities to quench the fluorescence of bovine serum albumin (BSA) following the static pathway. In addition, they are active catalysts for the oxidation reaction of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) under aerobic condition. From the recorded EPR signals of all complexes, it has been concluded that the oxidation reaction proceeds via ligand oriented radical pathway instead of metal based redox participation. Kinetic studies using 1-3 indicate that it follows Michaelis-Menten type of equation with moderate to high turnover number (k cat ). Apart from these aspects, complexes 1-3 were screened for their cytotoxic behavior towards HeLa cells (human cervical carcinoma) and found quite active with comparable IC 50 values to cisplatin.

A Family of [Zn6] Complexes from the Carboxylate-Bridge-Supported Assembly of [Zn2] Building Units: Synthetic, Structural, Spectroscopic, and Systematic Biological Studies

“…In this context, it is worth mentioning that the use of a carboxylate bridge has proved to be a useful tool for accessing multimetallic complexes in a controlled fashion, thus showing their potential coordination properties for generating different macrocyclic ring systems . Furthermore, it should be pointed out that there are several examples of hexanuclear carboxylate-bridged zinc­(II) complexes, some of which exhibit attractive biological activities. − Recently, our research group has reported several di- and tetranuclear copper­(II), zinc­(II), iron­(III), and cobalt­(II) model complexes of the ligand H 3 cpdp showing interesting biological properties. − Moreover, we have also reported copper­(II)-based hexanuclear and nickel­(II)-based tetranuclear complexes of similar carboxylate-containing ligands with methodical biological studies. , Therefore, in the present contribution, we report the synthetic, structural, spectroscopic, and thermal aspects of three new [Zn 6 ] complexes, as well as their biological properties such as antidiabetic and anticancer activities.…”