The work in this paper presents syntheses, characterization, crystal structures, catecholase activity, electrospray ionization mass spectroscopy (ESI-MS positive), and magnetic properties of seven triple bridged μ-phenoxo-bis(μ-carboxylate) dicopper(II) complexes [CuII 2L(μ-HCOO)2](ClO4)·CH3OH (1), [CuII 2L(μ-CH3COO)2](ClO 4) (2), [CuII 2L(μ-CCl3COO) 2(H2O)](ClO4) (3), [CuII 2L(μ-CH3CH2COO)2](ClO 4) (4), [CuII 2L(μ-CH3CH 2CH2COO)2](ClO4) (5), [Cu II 2L(μ-PhCOO)2](ClO4) ·CH3CN (6) and [CuII 2L(μ-o-ClPhCOO) 2](ClO4) (7), one double bridged μ-phenoxo-μ 1,1-azide system [CuII 2L(μ1,1- N3)(N3)2] (8) and one double bridged μ-phenoxo-μ-methoxide system [CuII 2L(μ-OCH 3)(NCO)2] (9), derived from a new dinucleating ligand HL, which is the 1:2 condensation product of 2,6-diformyl-4-ethylphenol and 3-dimethylaminopropylamine. The variable-temperature (300-2 K) magnetic studies reveal moderate or strong antiferromagnetic interaction in 1-9 with J values of -81.5, -64.8, -136.5, -66.9, -61.4, -49.1, -61.5, -186.3 and &gt;-350 cm- 1 for 1-9, respectively. The seven μ-phenoxo-bis(μ-carboxylate) dicopper(II) complexes 1-7 show catecholase activity with turnover (K cat) numbers lying in the range 18.8-89.1 h-1. The positive ions observed in the ESI-MS spectra of 1-8 are heterobridged dinuclear species having oxidized CuIICuII or reduced Cu ICuI or mixed-valence CuIICuI metal centers having double/triple bridging moieties. A complex-substrate aggregate [CuII 2L(μ-3,5-DTBC2-)]+ has been identified in the ESI-MS positive spectrum of the mixture of complex 4 and 3,5-DTBCH2. © 2012 Elsevier Ltd. All rights reserved.

SASANKA MOHANTA

Chemistry

S SARKAR

S MAJUMDER

S SASMAL

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Polyhedron

A dinuclear Cu(II) species [Cu2L2(H2O)2(N3)](NO3)2 (L = 2,6-bis(N-ethylpyrrolidine-iminomethyl)-4- methyl-phenolato) where two Cu centers are bridged by phenoxido and l1,1-azido bridges with Cu&ndash;Cu separation of 3 &Aring; have been synthesized with the view to explore the role of azido bridge on catecholase activity and electrochemical property and the roles of both the bridging groups on magnetic coupling of two copper centers. The complex exhibits excellent catecholase activity in acetonitrile as well as in DMSO medium not only by oxidizing 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very thorny to oxidize, under aerobic conditions and becomes the first example of its own kind. CV study reveals three quasi-reversible reductive couples which are tentatively assigned as Cu2 II to CuIICuI and CuI CuI reduction followed by reduction of CuI CuI complex to Cu0 Cu0 species. Variable tem- perature magnetic study suggests the presence of an antiferromagnetic spin&ndash;exchange interaction between Cu(II) ions in the dimer via double bridge where the antiferromagnetic contribution of phenox- ido bridge predominates over the ferromagnetic interaction of azido bridge.

Inorganica Chimica Acta

Azido bridge mediated catecholase activity, electrochemistry and magnetic behavior of a dinuclear copper(II) complex of a phenol based “end-off” compartmental ligand

Abstract A dinuclear Cu(II) species [Cu2L2(H2O)2(N3)](NO3)2 (L = 2,6-bis(N-ethylpyrrolidine-iminomethyl)-4-methyl-phenolato) where two Cu centers are bridged by phenoxido and μ1,1-azido bridges with Cu-Cu separation of ∼3 Å have been synthesized with the view to explore the role of azido bridge on catecholase activity and electrochemical property and the roles of both the bridging groups on magnetic coupling of two copper centers. The complex exhibits excellent catecholase activity in acetonitrile as well as in DMSO medium not only by oxidizing 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very thorny to oxidize, under aerobic conditions and becomes the first example of its own kind. CV study reveals three quasi-reversible reductive couples which are tentatively assigned as Cu2II to CuIICuI and CuICuI reduction followed by reduction of CuICuI complex to Cu0Cu0 species. Variable temperature magnetic study suggests the presence of an antiferromagnetic spin-exchange interaction between Cu(II) ions in the dimer via double bridge where the antiferromagnetic contribution of phenoxido bridge predominates over the ferromagnetic interaction of azido bridge. © 2015 Elsevier B.V.

Azido bridge mediated catecholase activity, electrochemistry and magnetic behavior of a dinuclear copper(II) complex of a phenol based "end-off" compartmental ligand

An &ldquo;end-off&rdquo; pentadentate compartmental ligand HL has been synthesized by Mannich base condensation using p-cresol and 2-benzyl amino ethanol and structurally characterized. A dinuclear copper(II) complex, namely [Cu2(L)(&micro;-OH)(H2O)(ClO4)2], has been prepared by treating HL with Cu(ClO4)2 . 6H2O in methanolic solution with the aim to investigate its catalytic promiscuity. Single crystal structural analysis reveals that Cu-Cu separation is of 2.9 &Aring;. Catecholase activity of the complex has been investigated in anhydrous DMSO as well as in DMSO-water mixture with progressive increasing quantity of water up to a 1:1 volume ratio in order to assess the bio compatibility of the catalyst using 3,5-DTBC as model substrate. In anhydrous DMSO the catalytic activity reaches its peak and decreases with increasing the water concentration, a feature most likely due to insolubility of 3,5-DTBQ, the product formed in the catalysis, in water. The complex also shows excellent phosphatase-like activity by exploiting the Lewis acidity, the necessary requirement for that activity, under different pH. Thorough investigation reveals that no activity is observed at pH 6 but the activity increases with increasing pH and attains maximum at pH 9. Variable temperature magnetic study shows that the two Cu centers are antiferromagnetically coupled at low temperature with J value Page 1 of 29 RSC Advances RSC Advances Accepted Manuscript Published on 03 June 2015. Downloaded by University of Birmingham on 04/06/2015 08:15:19. View Article Online DOI: 10.1039/C5RA05776K 2 2 &ndash;78.63&plusmn;1.30cm&minus;1. In acetonitrile medium the complex shows very exciting behavior. A new transformed ligand is generated that has been assigned as a Schiff-base ligand, 2,6-bis-[(2- hydroxy-ethylimino)-methyl]-4-methylphenol. The genesis of the new ligand is a consequence of dealkylation from HL followed by oxidation. This oxidation is counterbalanced by reduction of Cu(II) to Cu(I) as it is evidenced from isolation of [Cu(MeCN)4](ClO4) from the mixture followed by X-ray structural characterization of the species.

RSC Advances

Solvent dependent ligand transformation in a dinuclear copper(ii) complex of a compartmental Mannich-base ligand: synthesis, characterization, bio-relevant catalytic promiscuity and magnetic study

This paper presents the synthesis, crystal structure, catechol oxidase activity and electrospray ionization mass spectra (ESI-MS positive) of a mixed-valence CoIIICoII compound [CoIIICo IIL(N3)3]· 0.5CH3CN·0. 27H2O (1) derived from the Robson type tetraiminodiphenolate macrocyclic ligand H2L, which is the [2 + 2] condensation product of 2,6-diformyl-4-methylphenol and 2,2-dimethyl-1,3-diaminopropane. Compound 1 crystallizes in the monoclinic P21/n space group. The structure consists of two independent units of diphenoxo-bridged CoIIICo II moieties where the CoIII center is hexacoordinated (distorted octahedral) having O(phenoxo)2N(imine)2N(azide) 2 environment, while CoII center is pentacoordinated (distorted square pyramidal) having O(phenoxo)2N(imine) 2N(azide) environment. Catechol oxidase activity of 1 has been investigated using 3,5-di-tert-butylcatechol (3,5-DTBCH2) as the substrate, revealing that it is an active catalyst with Kcat value 114.24 h-1. Electrospray ionization mass spectra (ESI-MS positive) of 1 and 1 + 3,5-DTBCH2 in acetonitrile have been recorded. No complex⋯substrate aggregate in the spectrum of 1 + 3,5-DTBCH 2 has been identified. However, interestingly, two hydrogen bonded metal complex⋯solvent aggregates [{CoII(LH2)(N 3)}⋯(CH3CN)]+ and [{Co III(LH2)(N3)2}⋯(CH 3CN)]+ have been identified in the spectrum of 1. Catecholase activity has also been studied with pyrocatechol and tetrachlorocatechol (TCCH2) as substrates. While no activity has been found with TCCH2, weak activity has been observed with pyrocatechol. © 2013 Elsevier B.V. All rights reserved.

Crystal structure, catecholase activity and ESI-MS of a mixed valence cobalt(III)-cobalt(II) complex derived from a macrocyclic ligand: Identification/proposition of hydrogen bonded metal complexâ‹¯solvent aggregates in ESI-MS

The work in this report presents the syntheses, characterization, catechol oxidase activity, electrochemistry and electrospray ionization mass spectroscopy (ESI-MS positive) of five mononuclear manganese(III) compounds [Mn IIIL(OAc)(H2O)]·DMF (1), [MnIIIL(Cl) (H2O)]·2H2O (2), [MnIIIL(N 3)(H2O)] (3), [MnIIIL(NCS)(H2O)] (4) and [MnIIIL(NCSe)(H2O)]·MeCN (5), derived from the Schiff base compartmental ligand N,N′-ethylenebis(3- ethoxysalicylaldimine) (H2L). All the five complexes are characterized by elemental analyses, FT-IR, UV-Vis spectra, molar conductance and single crystal X-ray structure determination. The structures of 1-5 show that these are mononuclear compounds in which the manganese(III) center occupies the N(imine)2O(phenoxo)2 compartment. In all structures, a dimer-of-mononuclear species is formed by bifurcated hydrogen bonding involving coordinated water molecule. The five mononuclear manganese(III) complexes 1-5 show catecholase activity with turnover (Kcat) numbers lying in the range 17.0-41.7 h-1 (for 1-5) in DMF and 16.9-137.3 h-1 (for 2-5) in MeCN. ESI-MS positive of 2-5 and their mixtures with 3,5-di-tert-butylcatechol have been recorded, revealing the existence of 3,5-di-tert-butylquinone containing species and a complex-substrate aggregate [MnIIIL(3,5-DTBCH)+H+]+. Cyclic voltammetric and square wave voltammetric studies of the compounds 1-5 reveal that these undergo quasireversible Mn(III)/Mn(II) redox couple with very close E 1/2 values (from -200 to -213 mV). © 2013 Elsevier B.V. All rights reserved.

Syntheses, structures, catecholase activity, spectroscopy and electrochemistry of a series of manganese(III) complexes: Role of auxiliary anionic ligand on catecholase activity

Triple bridged Î¼-phenoxo-bis(Î¼-carboxylate) and double bridged Î¼-phenoxo-Î¼1,1-azide/Î¼-methoxide dicopper(II) complexes: Syntheses, structures, magnetochemistry, spectroscopy and catecholase activity

Journal	Polyhedron
Publisher	-
ISSN	0277-5387
Open Access	No