Histamine derived dimer of µ-Chlorido-µ-Phenoxido Dicopper(II) complex as a potential enzyme mimic with catecholase activity

• Published in: Polyhedron 2022-04, Vol.216, p.115700, Article 115700
• Main Authors: Salunke, Priyanka S., Puranik, Aditya A., Kulkarni, Neelima D.
• Format: Article
• Language: English
• Subjects: Binuclear copper complex; Catecholase activity; Kinetic studies; Magnetic properties; Type 3 copper proteins; X-ray crystallography
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2022.115700

The exchange coupled site behaves as a good structural and functional model for type 3 active site in copper oxidases and is both efficient and selective catalyst for oxidation of diphenols. [Display omitted] A new copper(II) complex, [Cu2(L1)(µ-Cl)2]2 (C1), of the binucleating 2,6-bis((2-(4′-imidazolyl)ethyl)aminomethylidene)-4-methylphenol (HL1) with N4O binding sites, has been synthesized to investigate as potential structural and functional model for catecholase activity of the dicopper(II) site. It has been characterized by spectroscopic techniques and X-ray crystallography. The complex C1 exists as chlorido bridged dimer of binuclear copper(II) units, each possessing one end-off compartmental ligand (L1) with endogenous µ-phenoxido and exogenous µ-chlorido groups leading to intermetallic distance Cu1···Cu2 of 3.129 Å and Cu1-O1(phenoxo)-Cu2 angle of 107.67(10)o. Each copper(II) center has distorted octahedral geometry with bridging by chlorides in the tetranuclear dimer. The crystal system is monoclinc with space group P21/c. Magnetic measurements reveal that C1 is strongly antiferromagnetically coupled with J = − 115.663 ± 0.82547 cm−1. The catecholase activity of the complex has been evaluated by oxidation of 3,5-di(tert-butyl)catechol and 4-methyl catechol to the corresponding quinones under aerobic conditions. A kinetic treatment on the basis of the Michaelis-Menten model has been applied for the kinetic study. The complex is found to be selective for the substrates with higher Vmax = 8.2726x10−8 M s−1 and Km = 0.0107 M for 3,5-DTBC at 30 °C as compared to Vmax = 5.0371x10−8 M s−1 and Km = 0.027 M for 4-methyl catechol at 50 °C while it is found to be practically inactive for dopamine, 2,3-dihydroxy naphthalene and pyrocatechol oxidation.