Synthesis, Structure and Catechol Oxidase Activity of Mono Nuclear Cu(II) Complex with Phenol-Based Chelating Agent with N, N, O Donor Sites

Abstract

A square-planar Cu(II) complex [Cu(L)Cl], 1, with sterically constrained tridentate phenol-based ligand (HL= N,N,N′-trimethyl-N′-(2-hydroxy-3,5-di-tert-butylbenzyl)-ethylenediamine) with N, N, O donor sites has been synthesized. The complex is characterized by single crystal X-ray diffraction study as well as other spectroscopic techniques. The reported complex crystallizes in monoclinic space group C2/c with a = 30.248(6), b = 13.750(3) and c = 11.410(2) Å with β = 110.232(2)°. The Cu(II) ion adopts a square planar environment in this complex. Electrochemical study of the complex 1 gives quasi-reversible reductive response at E1/2 ≈ −0.5 V due to the reduction of the Cu(II) center along with a reversible oxidation peak at E1/2 ≈ 0.75 V. The oxidation peak arises due to the ligand-based oxidation of phenolate group to phenoxyl radical in the complex. The Cu(II) complex exhibits catechol oxidase activity in methanol as observed by the UV–vis spectroscopy of the aerial oxidation of 3,5-DTBC to 3,5-DTBQ and the reaction proceeds via the formation of ligand phenoxyl radical. The turnover number for complex 1 is 2560 h−1.

Facile synthesis of novel NNO-tethered copper(ii) complexes: characterization details, theoretical studies, promising enzyme-like activities, and biomolecular interactions

“…The coordination bond distances of all complexes (listed in Table S2†) are comparably similar and in agreement with the published values of other copper complexes. 26,47,59 a ,61 b ,63,64 In particular, the Cu–N1 bond lengths of 1.9483(19), 1.963(4), and 1.952(5) Å, in 1–3 , respectively, are similar within their estimated standard deviations and are not affected by the anion located in trans . The values of bond angles (Table S2†) indicate the deviations from the ideal values of square planar geometry in 1 and 2 , and the pentacoordination environment in 3 .…”

“…23 As soon as the crystal structure of catecholase 24 and phenoxazinone synthase 22a was known, it drew the attention of people worldwide, especially synthetic inorganic and bio-inorganic chemists, to design bio-inspired small molecules that can imitate the structural characteristics of the active site in metalloenzymes. Although catecholase and phenoxazinone synthase contain multi-copper active sites, many monocopper [25][26][27][28][29] and non-copper [30][31][32][33] complexes have already been reported, and their ability to act as functional models of the enzymes has been thoroughly examined. 34,35 Tridentate NNO Schiff base ligands have been extensively used in synthesizing copper complexes because they are biocompatible with low toxicity, are redox active, and, overall, they resemble the active sites in copper proteins.…”

Synthesis of a new benzoate bridged NNO tethered copper(ii) complex: exploration of its bio, catalytic and anticancer activities

“…Tridentate NNO Schiff base ligands have become an incredibly adaptable class of molecules in making copper complexes as they are multifarious, redox active, low toxicity and generally mimic the structure of the active sites in copper proteins. [23][24][25][26][27][28] As a result of their electronic and steric characteristics, the copper centre adopts varied geometries and coordination numbers, producing complexes with intriguing features. These complexes are used in redox activities, O 2 transport, 29 catalysis, [30][31][32] magnetism 33,34 DNA damage, protein binding, anticancer, antioxidative and cytotoxic actions.…”