Catechol oxidase activity of dinuclear copper(II) complexes of Robson type macrocyclic ligands: Syntheses, X-ray crystal structure, spectroscopic characterization of the adducts and kinetic studies |
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| Authors: | Kazi Sabnam Banu Tanmay Chattopadhyay Arpita Banerjee Santanu Bhattacharya Ennio Zangrando Debasis Das |
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| Institution: | aDepartment of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata-700 009, India;bDepartment of Chemistry, Maharaja Manindra Chandra College, Kolkata-700 003, India;cDipartimento di Scienze Chimiche, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy |
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| Abstract: | Five dinuclear copper(II) complexes, Cu2L1(N3)2·2H2O] (1), Cu2L2(N3)2·2H2O] (2), Cu2L3(N3)2·2H2O] (3), Cu2L4(N3)2·2H2O] (4) and Cu2L5(N3)2·2H2O] (5) of Robson type macrocyclic Schiff-base ligands derived from 2 + 2] condensation of 4-methyl-2,6-diformylphenol with 1,3-diaminopropane (H2L1), 1,2-diaminoethane (H2L2), 1,2-diaminopropane (H2L3), 1,2-diamino-2-methylpropane (H2L4) and 1,2-diaminocyclohexane (H2L5), respectively have been synthesized and characterized. Catecholase activity of those complexes using 3,5-di-tert-butylcatechol as substrate has been investigated in two solvents, methanol and acetonitrile. The role of the solvent and of the steric properties of the macrocyclic ligand of these complexes on their catecholase activity has been examined thoroughly. Acetonitrile is observed to be a better solvent than methanol as far as their catalytic activity is concerned. However, methanol reveals to be a better choice to identify the enzyme–substrate adduct. The investigation also prompted that chelate ring size does affect on the catalytic efficiency: 6-membered ring (as in H2L1) exhibits better activity than its 5-membered counterpart (as in H2L2). The activity of the 5-membered counter parts also depend upon the steric factor. Moreover, the catalytic activity of the complexes is enhanced to a significant extent by increasing the bulkiness of the substituents on the backbone of macrocyclic H2L2 ligands. |
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| Keywords: | Catecholase activity Copper(II) Macrocyclic complexes Schiff-bases Template synthesis |
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