Journal ArticleDOI
Unprecedented structural variations in trinuclear mixed valence Co(II/III) complexes: theoretical studies, pnicogen bonding interactions and catecholase-like activities
Alokesh Hazari,Lakshmi Kanta Das,Ramakant Mahadeo Kadam,Antonio Bauzá,Antonio Frontera,Ashutosh Ghosh +5 more
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TLDR
Three new mixed valence trinuclear Co(II/III) compounds synthesized by reacting a di-Schiff base ligand with cobalt perchlorate hexahydrate and sodium azide show catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone.Abstract:
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) > 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).read more
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Non-covalent interactions in the synthesis of coordination compounds: Recent advances
Kamran T. Mahmudov,Kamran T. Mahmudov,Maximilian N. Kopylovich,M. Fátima C. Guedes da Silva,Armando J. L. Pombeiro +4 more
TL;DR: In this paper, a review describes how non-covalent interactions, such as hydrogen (inter-and intramolecular, resonance-and charge-assisted hydrogen bonding), halogen, chalcogen and pnicogen bonds, π-interactions, as well as other types of weak forces can influence and control the reactions in the synthesis, providing a class of highly directional stabilizing contacts that can be exploited in the design of coordination compounds.
Journal ArticleDOI
Catechol oxidase and phenoxazinone synthase: Biomimetic functional models and mechanistic studies
Suman Kr Dey,Arindam Mukherjee +1 more
TL;DR: The biomimetic studies strongly suggest that among the various metal ions probed for modeling the catalytic activity of CO and PHS, MnII/III based systems are so far the most promising candidates apart from the nature's choice CuII.
Journal ArticleDOI
Subtle Structural Changes in (CuIIL)2MnII Complexes To Induce Heterometallic Cooperative Catalytic Oxidase Activities on Phenolic Substrates (H2L = Salen Type Unsymmetrical Schiff Base).
Prithwish Mahapatra,Soumavo Ghosh,Sanjib Giri,Vinayak Rane,Ramakant Mahadeo Kadam,Michael G. B. Drew,Ashutosh Ghosh +6 more
TL;DR: The mechanisms of these biomimetic oxidase reactions are proposed for the first time involving any heterometallic catalyst on the basis of mass spectral analysis, EPR spectroscopy, and cyclic voltammetry.
Journal ArticleDOI
Strong ferromagnetic exchange interactions in hinge-like Dy(O2Cu)2 complexes involving double oxygen bridges.
TL;DR: The present result shows an advantage of doubly oxygen-bridged motifs to built strong ferromagnetic interactions between lanthanide and transition metal ions.
Journal ArticleDOI
Variations of Structures and Phenoxazinone Synthase-like Activity of the Complexes Based on (CuII)2MnII Node and Dicyanamide Spacer
TL;DR: In this paper, three new heterometallic Cu(II)-Mn(II) complexes, [{(CuL)2Mn}2(μ1,5-N(CN)2)(CH3CN) 2]-ClO4)3 (1), [(CuL] 2Mn[N[CN]2]·(H2O)
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Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate
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