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Mn(II) complexes of different nuclearity: Synthesis, characterization and catecholase-like activity
P CHAKRABORTY, I MAJUMDER, K S BANU, B GHOSH, E ZANGRANDO, D DAS,
Published in Royal Society of Chemistry
2016
Volume: 45
   
Issue: 2
Pages: 742 - 752
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)] (1), [Mn2(L1)(OAc)2](BPh4)] (2), and [Mn2(L2)(OAc)2(dca)]n (3) have been synthesized and structurally characterized. Variable temperature magnetic studies of 2 and 3 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 2 > 1 > 3. 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 1-3 show catecholase-like activity due to radical generation. © The Royal Society of Chemistry 2016.
About the journal
JournalData powered by TypesetDalton Transactions
PublisherData powered by TypesetRoyal Society of Chemistry
ISSN1477-9226