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Mn(ii) complexes of different nuclearity: synthesis, characterization and catecholase-like activity
Published in Royal Society of Chemistry (RSC)
Volume: 45
Issue: 2
Pages: 742 - 752

Two “end-off” compartmental ligands, 2-formyl-4-chloro-6-N-ethylmorpholine-iminomethylphenol (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 other 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 study of 2 and 3 have been performed and data analyses reveal that Mn centers are antiferromagetic coupled with J = - 9.15 cm-1 and J = - 46.89, respectively. Catecholase activity of all the complexes have been investigated using 3,5-di-tert-butyl catechol (3,5-DTBC). All are highly active with activity order on the basis of kcat value is 2>1>3. In order to unveil whether metal centered redox participation or radical pathway is responsible for the catecholase-like activity of the complexes detailed EPR and cyclic voltametric (CV) study have been performed. In addition to 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 catalyst, suggesting the formation of organic radical Page 1 of 31 Dalton Transactions Dalton Transactions Accepted Manuscript Published on 19 November 2015. Downloaded by UNIVERSITY OF OTAGO on 20/11/2015 03:32:46. View Article Online DOI: 10.1039/C5DT03659C 2 most likely ligand centered. CV experiment with the mixture of 3,5-DTBC and 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.

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JournalData powered by TypesetDalton Transactions
PublisherData powered by TypesetRoyal Society of Chemistry (RSC)
Open AccessNo