Catecholase activity of Mannich-based dinuclear CuII complexes with theoretical modeling: new insight into the solvent role in the catalytic cycle. (31st May 2016)

• Record Type: Journal Article
• Authors: Sanyal, Ria; Kundu, Priyanka; Rychagova, Elena; Zhigulin, Grigory; Ketkov, Sergey; Ghosh, Bipinbihari; Chattopadhyay, Shyamal Kumar; Zangrando, Ennio; Das, Debasis
• Is Part Of: New journal of chemistry. Volume 40:Number 8(2016:Aug.)
• Page Start: 6623
• Page End: 6635
• Publication Date: 2016-05-31
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c6nj00105j
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Catecholase activity has been explored by combined experimental and theoretical approaches using di-copper(ii ) complexes of Mannich-base ligands. Abstract : Four new dinuclear Cu II complexes were synthesised from two Mannich-base ligands namely 2, 6-bis[bis(2-methoxyethyl)aminomethyl]-4-chlorophenol (HL1 ) and 2-[bis(2-methoxyethyl)aminomethyl]-4-chlorophenol (HL2 ): [Cu2 (L1)(OH)](ClO4 )2 ·CH3 OH (1 ), [Cu2 (L2)2 ](ClO4 )2 ·H2 O (2 ), [Cu2 (L2)2 (NO3 )2 ] (3 ) and [Cu2 (L2)2 (OAc)2 ]·H2 O (4 ) and well characterised. X-ray diffraction analysis of the complexes reveals a Cu⋯Cu distance of 2.9183(13), 2.9604(6), 3.0278(4) and 3.0569(11) Å, respectively. In1 the metal coordination geometry is intermediate between trigonal bipyramidal (TBP) and square pyramidal (SP) ( τ = 0.488), in2 the geometry is TBP (0.828 and 0.639) and in3 and4 is SP ( τ = 0.188 and 0.083, respectively). Spectrophotometric investigations to evaluate the catecholase activity of complexes against 3, 5-di- tert -butylcatechol (3, 5-DTBC) and tetrachlorocatechol (TCC) in three different solvents (acetonitrile, methanol and DMSO) under completely aerobic conditions reveal that complexes1–4 are able to oxidise 3, 5-DTBC in all the solvents, while TCC can be oxidised only in acetonitrile ( k cat = 0.0002–0.02 s −1 ). Intensive DFT calculations prove an ionic pathway for1–3 while a unique neutral catalytic cycle for4 .