The work in this paper presents the syntheses, characterization, catecholase activity, and electrospray ionization mass spectroscopic (ESI-MS positive) study of three mixed-valence dinuclear CoIIICoII complexes of composition [CoIIICoIIL(N3) 3]·CH3CN (1), [CoIIICo IIL(OCN)3]·CH3CN (2), and [Co IIICoIIL(μ-CH3COO)2](ClO 4) (3), derived from a tetraimino diphenolate macrocyclic ligand H2L, obtained on [2 + 2] condensation of 4-ethyl-2,6-diformylphenol and 2,2′-dimethyl-1,3-diaminopropane. While 1 and 2 are diphenoxo-bridged, 3 is a heterobridged bis(μ-phenoxo)bis(μ-acetate) system. Utilizing 3,5-di-tert-butyl catechol (3,5-DTBCH2) as the substrate, the catecholase activity of all the three complexes has been checked in methanol/acetonitrile/N,N-dimethyl formamide. While 2 and 3 are inactive, complex 1 shows catecholase activity with turnover numbers of 482.16 h -1 and 45.38 h-1 in acetonitrile and methanol, respectively. Electrospray ionization mass (ESI-MS positive) spectra of complexes 1-3 have been recorded in acetonitrile solutions and the positive ions have been well characterized. The ESI-MS positive spectrum of complex 1 in the presence of 3,5-DTBCH2 has also been recorded and, interestingly, two positive ions [CoIIICoIIL(N3) 2(3,5-DTBCH-)H]+ and [CoIICo IIL(μ-3,5-DTBCH2-)Na]+ have been identified. © The Royal Society of Chemistry 2013.

SASANKA MOHANTA

Chemistry

S MAJUMDER

S MONDAL

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

Dalton Transactions

Three new mixed valence trinuclear Co(ii/iii) compounds cis-[Co3L2(MeOH)2(N3)2(μ1,1-N3)2] (1), trans-[Co3L2(H2O)2(N3)2(μ1,1-N3)2]·(H2O)2 (2) and [Co3LR2(N3)3(μ1,3-N3)] (3) have been synthesized by reacting a di-Schiff base ligand (H2L) or its reduced form [H2LR] (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine and H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine) with cobalt perchlorate hexahydrate and sodium azide. All three products have been characterized by IR, UV-Vis and EPR spectroscopies, ESI-MS, elemental, powder and single crystal X-ray diffraction analyses. Complex 1 is an angular trinuclear species in which two terminal octahedral Co(iii)N2O4 centers coordinate to the central octahedral cobalt(ii) ion through μ2-phenoxido oxygen and μ1,1-azido nitrogen atoms along with two mutually cis-oxygen atoms of methanol molecules. On the other hand, in linear trinuclear complex 2, in addition to the μ2-phenoxido and μ1,1-azido bridges with terminal octahedral Co(iii) centres, the central Co(ii) is bonded with two mutually trans-oxygen atoms of water molecules. Thus the cis-trans configuration of the central Co(ii) is solvent dependent. In complex 3, the two terminal octahedral Co(iii)N2O4 centers coordinate to the central penta-coordinated Co(ii) ion through double phenoxido bridges along with the nitrogen atom of a terminal azido ligand. In addition, the two terminal Co(iii) are connected through a μ1,3-azido bridge that participates in pnicogen bonding interactions (intermolecular N-N interaction) as an acceptor. Both the cis and trans isomeric forms of 1 and 2 have been optimized using density functional theory (DFT) calculations and it is found that the cis configuration is energetically more favorable than the trans one. However, the trans configuration of 2 is stabilized by the hydrogen bonding network involving a water dimer. The pnicogen bonding interactions have been demonstrated using MEP surfaces and CSD search which support the counter intuitive electron acceptor ability of the μ1,3-azido ligand. Complexes 1-3 exhibit catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone. Kinetic data analyses of this oxidation reaction in acetonitrile reveal that the catecholase-like activity follows the order: 1 (kcat = 142 h-1) &gt; 3 (kcat = 99 h-1) &gt; 2 (kcat = 85 h-1). Mechanistic investigations of the catalytic behaviors by X-band EPR spectroscopy and estimation of hydrogen peroxide formation indicate that the oxidation reaction proceeds through the reduction of Co(iii) to Co(ii). This journal is © The Royal Society of Chemistry 2015.

Unprecedented structural variations in trinuclear mixed valence Co(ii/iii) complexes: Theoretical studies, pnicogen bonding interactions and catecholase-like activities

This report describes the syntheses, characterization, crystal structures and magnetic properties of five dinuclear FeIIINiII compounds derived from two Robson-type tetraiminodiphenol macrocyclic ligands H2L1 and H2L2, which are the [2+2] condensation products of 4-ethyl-2,6-diformylphenol and 1,3-diaminopropane (for H2L1) or 2,2-dimethyl-1,3-diaminopropane (for H2L2). The compositions of the compounds are [FeIII(N3)2L1NiII(H2O)2](ClO4) (1), [FeIII(benzoato)L1NiII(H2O)(μ1,3-benzoato)](ClO4) (2), [FeIII(benzoato)L2NiII(H2O)(μ1,3-benzoato)](ClO4) (3), [FeIIIL2NiII(μ1,3-acetato)2](ClO4)·H2O (4) and [FeIIIL2NiII(μ1,3-propionato)2](ClO4)·H2O (5). The bridging moieties between the two metal ions and the azido and carboxylato moieties in these compounds are of the following types: (1) In 1, the bridging moiety is a bis(μ-phenoxido) ligand, and two azido ligands are monodentate to the FeIII centre; (2) In 2 and 3, the bridging moiety is a bis(μ-phenoxido)-μ1,3-benzoato ligand, and the second benzoato ligand is monodentate to the FeIII centre; (3) In 4 and 5, the bridging moiety is a bis(μ-phenoxido)bis(μ1,3-acetato/propionato) ligand. Variable-temperature and variable-field magnetic data reveal ferromagnetic interactions in 2-5 and an antiferromagnetic interaction in 1 with J values of -9.22 cm-1 for 1, 0.50 cm-1 for 2, 5.65 cm-1 for 3, 13.00 cm-1 for 4 and 14.57 cm-1 for 5. An excellent magnetostructural correlation and interesting structural aspects regarding the bond lengths to the FeIII or NiII centres in some structures have been obtained. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

European Journal of Inorganic Chemistry

Structures and magnetic properties of bis(Î¼-phenoxido), bis(Î¼-phenoxido)-Î¼-carboxylato and bis(Î¼-phenoxido)bis(Î¼-carboxylato) FeIIINiII compounds - Magnetostructural correlations

Abstract The work in this report deals with syntheses, crystal structures, catechol oxidase activity and ESI-MS (positive) studies of two mononuclear cobalt(III) compounds [CoIIILOEt-en(N<inf>3</inf>)<inf>2</inf>⊃(H<inf>3</inf>O+)]·2MeOH (1) and [CoIIILOEt-en(NCS)(H<inf>2</inf>O)]·DMF·H<inf>2</inf>O (2), where H<inf>2</inf>LOEt-en is N,N′-ethylenebis(3-ethoxysalicylaldiimine). The metal center in both the compounds occupies N(imine)<inf>2</inf>O(phenoxo)<inf>2</inf> compartment. Two apical coordination positions are occupied by one anionic ligand (thiocyanate) and one neutral ligand (water) in 2 but by two anionic ligands (azide) in 1. The extra negative charge in [CoIIILOEt-en(N<inf>3</inf>)<inf>2</inf>]- is balanced by an oxonium ion (H<inf>3</inf>O+), which is trapped in the O(phenoxo)<inf>2</inf>O(ethoxy)<inf>2</inf> compartment to result in the formation of host-guest species [CoIIILOEt-en(N<inf>3</inf>)<inf>2</inf>⊃;(H<inf>3</inf>O+)] in 1. Both the compounds show catechol oxidase activity (1 in MeCN, 2 in DMF) as monitored by the UV-Vis spectroscopy of the aerial oxidation of 3,5-DTBCH<inf>2</inf> to 3,5-DTBQ. The kinetic parameters have been determined using Michaelis-Menten approach. The K<inf>cat</inf> values for 1 in MeCN and 2 in DMF are 10.0 h-1 and 11.2 h-1, respectively. ESI-MS (positive) of 1 and the mixture of 1 and 3,5-DTBCH<inf>2</inf> have been recorded and the positive ions have been well assigned. Interestingly, a 1:2 adduct of composition [CoIILOEt-en(3,5-DTBQ)<inf>2</inf>+H+]+ has been identified from the spectrum of the mixture of 1 and 3,5-DTBCH<inf>2</inf>. Unique features of 1 and 2 in terms of showing catechol oxidase activity and, more importantly, unique structural features of compound 1 have been discussed. © 2015 Elsevier B.V.

Inorganica Chimica Acta

Syntheses, structures and catecholase activity of two cobalt(III) complexes derived from N,Nâ€²-ethylenebis(3-ethoxysalicylaldiimine): A special host-guest system from a special ligand

This report describes the syntheses, characterization, crystal structures and magnetic properties of five dinuclear (FeNiII)-Ni-III compounds derived from two Robson-type tetraiminodiphenol macrocyclic ligands H2L1 and H2L2, which are the [2+2] condensation products of 4-ethyl-2,6-diformylphenol and 1,3-diaminopropane (for H2L1) or 2,2-dimethyl-1,3-diaminopropane (for H2L2). The compositions of the compounds are [Fe-III(N-3)(2)(LNiII)-Ni-1(H2O)(2)](ClO4) (1), [Fe-III(benzoato)(LNiII)-Ni-1(H2O)((1,3)-benzoato)](ClO4) (2), [Fe-III(benzoato)(LNiII)-Ni-2(H2O)((1,3)-benzoato)](ClO4) (3), [(FeLNiII)-L-III-Ni-2((1,3)-acetato)(2)](ClO4)H2O (4) and [(FeLNiII)-L-III-Ni-2((1,3)-propionato)(2)](ClO4)H2O (5). The bridging moieties between the two metal ions and the azido and carboxylato moieties in these compounds are of the following types: (1) In 1, the bridging moiety is a bis(-phenoxido) ligand, and two azido ligands are monodentate to the Fe-III centre; (2) In 2 and 3, the bridging moiety is a bis(-phenoxido)-(1,3)-benzoato ligand, and the second benzoato ligand is monodentate to the Fe-III centre; (3) In 4 and 5, the bridging moiety is a bis(-phenoxido)bis((1,3)-acetato/propionato) ligand. Variable-temperature and variable-field magnetic data reveal ferromagnetic interactions in 2-5 and an antiferromagnetic interaction in 1 with J values of -9.22 cm(-1) for 1, 0.50 cm(-1) for 2, 5.65 cm(-1) for 3, 13.00 cm(-1) for 4 and 14.57 cm(-1) for 5. An excellent magnetostructural correlation and interesting structural aspects regarding the bond lengths to the Fe-III or Ni-II centres in some structures have been obtained.

Structures and Magnetic Properties of Bis(mu-phenoxido), Bis(mu-phenoxido)-mu-carboxylato and Bis(mu-phenoxido) bis(mu-carboxylato) (FeNiII)-Ni-III Compounds - Magnetostructural Correlations

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

This paper deals with the diprotonated salt, [H4L](ClO 4)2 (1), of the tetraiminodiphenolate macrocyclic ligand, H2L which is the [2 + 2] condensation product of 4-ethyl-2,6- diformylphenol and 2,2′-dimethyl-1,3-diaminopropane, and two diphenoxo-bridged dicopper(II) complexes [Cu2L(ClO4) 2] (2) and [Cu2L(ClO4)](ClO4) (3). The syntheses, characterization and crystal structures of 1-3 and the magnetic and electrochemical properties of the metal complexes 2 and 3 are presented. The cationic macrocycle [H4L]2+ is stabilized by four intramolecular and symmetric NH...O...HN hydrogen bonds involving phenoxo oxygen and imino nitrogen atoms. One metal center in 3 is tetracoordinated and in a square planar geometry. The second metal ion of 3 and both the metal ions in 2 are pentacoordinated and in a square pyramidal geometry; one perchlorate oxygen atom occupies the apical position in each case. Both 2 and 3 exhibit quasireversible two-step one-electron couples in the reduction window. The E (ΔEp) values (in mV) for the Cu IICuII/CuIICuI couple is -0.466 V (0.067 V) for 2 and -0.490 V (0.076 V) for 3, while the E (ΔEp) values (in mV) for the CuIICuI/CuICu I couple is -0.953 V (0.060 V) for 2 and -0.985 V (0.069 V) for 3. Variable-temperature (2-300 K) magnetic susceptibility measurements of the two compounds reveal that the metal centers in both of the complexes are coupled by strong antiferromagnetic interactions with 2J values (H = -JS 1·S2) of -780 and -820 cm-1 for 2 and 3, respectively. © 2012 Elsevier B.V. All rights reserved.

Journal	Dalton Transactions
Publisher	-
ISSN	1477-9226
Open Access	No