Effect of ring size in macrocyclic dinuclear manganese(ii) complexes upon their'structure, properties and reactivity towards H2O2

Takanori Aono, Hisae Wada, Masami Yonemura, Masaaki Ohba, Hisashi Okawa, David E. Fenton

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Abstract

A dinuclear manganese(ii) complex [Mn2L4,4(O2CMe)2] has been prepared and its structure, properties and catalase-Iike function studied in comparison with the analogous [Mn2Lm,n(O2CMe)2] [m,n = 2,3; 2,4; or 3,3; (L1m,n)2 denotes macrocycles containing two 2,6-bis(iminomethyl)-4-methylphenolate entities bridged through two lateral chains, (CH2)m and (CH2)n, at the imino nitrogens]. In the centrosymmetric [Mn2L4,4(O2CMe)2] a pair of manganese(n) ions are bridged by two phenolic oxygens of (L4,4)2- in the equatorial plane and by two acetate groups at the axial sites. The configuration about each Mn is pseudo:pctahedral. The Mn ⋯ Mn separation is 2.978( 1 ) Å. Cryomagnetic studies (4.2-300 K.) indicated a significantly strong antiferromagnetic interaction (J= -5.0 cm-1 based on //= -2JS1S1). The complex is oxidized at +0.35 V (vs. saturated calomel electrode) at a platinum electrode to a Mn2lun complex. It catalyses the disproportionation of hydrogen peroxide in aqueous dimethylformamide. Based on ESR and visible spectroscopic studies, a catalytic mechanism involving the interconversion between MnIIMnIII(OH) and Mn"MnIV(=O) species is proposed.

Original languageEnglish
Pages (from-to)1527-1531
Number of pages5
JournalJournal of the Chemical Society - Dalton Transactions
Issue number9
DOIs
Publication statusPublished - 1997

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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