title: Mn(II) complexes of different nuclearity: synthesis, characterization and catecholase-like activity.
abstract: Two "end-off" compartmental ligands, 2-formyl-4-chloro-6-N-ethylmorpholine-iminomethyl-phenol (HL1) and 2-formyl-4-methyl-6-N-ethylpyrrolidine-iminomethyl-phenol (HL2) have been designed and three complexes of Mn(ii), one mono-, one di- and a polynuclear, namely Mn(L1)(SCN)2(H2O)] (), [Mn2(L1)(OAc)2](BPh4)] (), and [Mn2(L2)(OAc)2(dca)]n () have been synthesized and structurally characterized. Variable temperature magnetic studies of and have been performed and data analyses reveal that Mn centers are antiferromagnetic coupled with J = -9.15 cm(-1) and J = -46.89, respectively. Catecholase activity of all the complexes has been investigated using 3,5-di-tert-butyl catechol (3,5-DTBC). All are highly active and the activity order on the basis of the kcat value is > > . In order to unveil whether the metal centered redox participation or the radical pathway is responsible for the catecholase-like activity of the complexes, detailed EPR and cyclic voltammetric (CV) studies have been performed. In addition to the six-line EPR spectrum characteristic to Mn(ii), an additional peak at g ∼ 2 is observed when the EPR study is done with the mixture of 3,5-DTBC and the catalyst, suggesting the formation of an organic radical, most likely ligand centered. The CV experiment with the mixture of 3,5-DTBC and the catalyst reveals ligand centered reduction rather than reduction of Mn(ii) to Mn(i). It is thus inferred that complexes show catecholase-like activity due to radical generation.
authors.affiliation: Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700009, India and Department of Chemistry, Amity University, Newtown, Kolkata, West Bengal 700156, India.
authors.forename: Prateeti
authors.initials: P
authors.lastname: Chakraborty
authors.affiliation: Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700009, India.
authors.forename: Ishani
authors.initials: I
authors.lastname: Majumder
authors.affiliation: Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700009, India.
authors.forename: Kazi Sabnam
authors.initials: KS
authors.lastname: Banu
authors.affiliation: Department of Chemistry, Indian Institute of Engineering, Science and Technology, Shibpur, Howrah-711103, India.
authors.forename: Bipinbihari
authors.initials: B
authors.lastname: Ghosh
authors.affiliation: Department of Physics, Faculty of Science and Art, Balikesir University, 10145 Balikesir, Turkey and Department of Physics, Faculty of Science, Mugla Sıtkı Koçman University, Mugla, Turkey.
authors.forename: Hulya
authors.initials: H
authors.lastname: Kara
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy.
authors.forename: Ennio
authors.initials: E
authors.lastname: Zangrando
authors.affiliation: Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700009, India.
authors.forename: Debasis
authors.initials: D
authors.lastname: Das
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D004156:Catechol Oxidase / Q000378:metabolism; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D004578:Electron Spin Resonance Spectroscopy; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008968:Molecular Conformation
chemical_list: D001672:Biocompatible Materials; D056831:Coordination Complexes; D008024:Ligands; D008345:Manganese; D004156:Catechol Oxidase