Unprecedented structural variations in trinuclear mixed valence Co(II/III) complexes derived from a Schiff base and its reduced form: Theoretical studies, pnicogen bonding interactions and catecholase-like activities

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dc.contributor.author Hazari, Alokesh
dc.contributor.author Das, Lakshmi Kanta
dc.contributor.author Kadam, Ramakant M.
dc.contributor.author Bauzá Riera, Antonio
dc.contributor.author Frontera Beccaria, Antonio
dc.contributor.author Ghosh, Ashutosh
dc.date.accessioned 2018-09-27T10:49:55Z
dc.identifier.uri http://hdl.handle.net/11201/147813
dc.description.abstract [eng] 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 [Co3LR 2(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) > 3 (kcat = 99 h−1) > 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).
dc.format application/pdf
dc.relation.isformatof Versió postprint del document publicat a: https://doi.org/10.1039/C4DT03446E
dc.relation.ispartof Dalton Transactions, 2015, vol. 44, p. 3862-3876
dc.rights (c) Hazari, Alokesh et al., 2015
dc.subject.classification 54 - Química
dc.subject.other 54 - Chemistry. Crystallography. Mineralogy
dc.title Unprecedented structural variations in trinuclear mixed valence Co(II/III) complexes derived from a Schiff base and its reduced form: Theoretical studies, pnicogen bonding interactions and catecholase-like activities
dc.type info:eu-repo/semantics/article
dc.type info:eu-repo/semantics/acceptedVersion
dc.date.updated 2018-09-27T10:49:55Z
dc.date.embargoEndDate info:eu-repo/date/embargoEnd/2075-01-01
dc.embargo 2075-01-01
dc.rights.accessRights info:eu-repo/semantics/embargoedAccess
dc.identifier.doi https://doi.org/10.1039/C4DT03446E


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