Catalytic oxidation of 3,5-di-tert-butylcatechol by a manganese(III) 18-azametallacrown-6 compound: Synthesis, crystal structure, fluorescence, magnetic and kinetic investigation |
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Authors: | Arpi Majumder Stuart R. Batten Joan Ribas |
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Affiliation: | a Department of Chemistry, Jadavpur University, Raja S.C. Mallik Road, Kolkata 700 032, West Bengal, India b Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, West Bengal, India c School of Chemistry, P.O. Box 23, Monash University 3800, Australia d Department de Quimica Inorganica, Universitat de Barcelona, Marti I Franques, 1-11, 08028 Barcelona, Spain |
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Abstract: | A new macrocyclic hexanuclear manganese(III) 18-azametallacrown-6 compound, [Mn6(ashz)6(CH3OH)3(H2O)3] · 3H2O · 3DMF (1), has been prepared using a trianionic pentadentate ligand N-acetylsalicylhydrazide (ashz3−) and characterised by various techniques such as elemental analysis, IR, UV-vis and fluorescence spectroscopy, cyclic voltammetry and X-ray diffraction. Six ashz3− ligands connect six metal ions to form the cyclic skeleton based on the M-N-N-M linkage. Due to the meridional coordination of the ligand to the Mn3+ ion, the ligand enforces the stereochemistry of the Mn3+ ions as a propeller configuration with alternating Δ/Λ forms. The kinetic studies on catecholase activity of 1 for the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) by O2 were done using UV-Vis absorption spectra method. Compound 1 has been evaluated as a model system for the catechol oxidase enzyme and it is found that the compound shows high catecholase activity. It exhibits the activity with a turnover number of 270 h−1. A kinetic treatment on the basis of the Michaelis-Menten model has been applied. The magnetic susceptibility (300-5 K) study indicates antiferromagnetic exchange interactions with J = −2.6 cm−1 between the adjacent Mn3+ ions. |
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Keywords: | Metallamacrocycle Hexanuclear Mn(III) cluster Pentadentate ligand Crystal structure Fluorescence Catecholase activity study Antiferromagnetic coupling |
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