ePrints@IIScePrints@IISc Home | About | Browse | Latest Additions | Advanced Search | Contact | Help

Nuclearity dependent solvent contribution to the catechol oxidase activity of novel copper(II) complexes derived from Mannich-base ligand platforms: synthesis, crystal structure and mechanism

Sanyal, Ria and Ketkov, Sergey and Purkait, Suranjana and Mautner, Franz A and Zhigulin, Grigory and Das, Debasis (2017) Nuclearity dependent solvent contribution to the catechol oxidase activity of novel copper(II) complexes derived from Mannich-base ligand platforms: synthesis, crystal structure and mechanism. In: NEW JOURNAL OF CHEMISTRY, 41 (16). pp. 8586-8597.

[img] PDF
New_Jou_Che_41-16_8586_2017.pdf - Published Version
Restricted to Registered users only

Download (4MB) | Request a copy
Official URL: http://doi.org/10.1039/c7nj00425g

Abstract

A set of tetra-and dinuclear copper(II) complexes, Cu-4(L-1)(mu-O)(OAc)(4)] (1), Cu-2(L-2)(2)](ClO4)(2) (2), Cu-2(L-2)(2)(OAc)(2)] (3), Cu-2(L-2)(2)(Br)(2)] (4) and Cu-2(L-2)(2)(Cl)(2)] (5), were synthesized from two Mannich-base ligands HL1 and HL2, where HL1 = 2,6-bisbis(2-methoxyethyl)aminomethyl]-4-methylphenol and HL2 = 2-bis(2-methoxyethyl)aminomethyl]-4-methylphenol. The catalytic efficiency of the complexes for catecholase activity was systematically evaluated by spectrophotometry using 3,5-di-tert-butylcatechol (3,5-DTBC) and tetrachlorocatechol (TCC) in pure dry acetonitrile (MeCN) and water-MeCN solvent mixtures (10%, 25%, 40% and 50% water). In spite of remarkable rate enhancements by the tetranuclear species in MeCN (k(cat) = 0.0218 s(-1)), complex 1 follows a reverse trend in the solvent dependent kinetic study compared to complexes 2-5 with a minimum at 25% water (k(cat) = 0.0118 s(-1)) under similar experimental conditions. Theoretical modeling involving the reactions of complexes 1, 3 and 5 provides the counterintuitive rationalization of the apparently dramatic behaviour of these novel catechol models on addition of water to the MeCN solution. More importantly, it vindicates the combination of the contradictory parameters like alcoholysis and hydrolysis as the governing factors for k(cat) extrema in catalytic pathways. Thus, the reactivity and mechanism of Mannich-base metallocatalysts across water-induced oxidation of catechols is predictable through their nuclearity.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Depositing User: Id for Latest eprints
Date Deposited: 01 Sep 2017 06:40
Last Modified: 01 Sep 2017 06:40
URI: http://eprints.iisc.ac.in/id/eprint/57693

Actions (login required)

View Item View Item