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The dimanganese(II,II) complexes 1a [Mn(2)(L)(OAc)(2)(CH(3)OH)](ClO(4)) and 1b [Mn(2)(L)(OBz)(2)(H(2)O)](ClO(4)), where HL is the unsymmetrical phenol ligand 2-(bis-(2-pyridylmethyl)aminomethyl)-6-((2-pyridylmethyl)(benzyl)aminomethyl)-4-methylphenol, react with hydrogen peroxide in acetonitrile solution. The disproportionation reaction was monitored by electrospray ionization mass spectrometry (ESI-MS) and EPR and UV-visible spectroscopies. Extensive EPR studies have shown that a species (2) exhibiting a 16-line spectrum at g approximately 2 persists during catalysis. ESI-MS experiments conducted similarly during catalysis associate 2a with a peak at 729 (791 for 2b) corresponding to the formula [Mn(III)Mn(IV)(L)(O)(2)(OAc)](+) ([Mn(III)Mn(IV)(L)(O)(2)(OBz)](+) for 2b). At the end of the reaction, it is partly replaced by a species (3) possessing a broad unfeatured signal at g approximately 2. ESI-MS associates 3a with a peak at 713 (775 for 3b) corresponding to the formula [Mn(II)Mn(III)(L)(O)(OAc)](+) ([Mn(II)Mn(III)(L)(O)(OBz)](+) for 3b). In the presence of H(2)(18)O, these two peaks move to 733 and to 715 indicating the presence of two and one oxo ligands, respectively. When H(2)(18)O(2) is used, 2a and 3a are labeled showing that the oxo ligands come from H(2)O(2). Interestingly, when an equimolar mixture of H(2)O(2) and H(2)(18)O(2) is used, only unlabeled and doubly labeled 2a/b are formed, showing that its two oxo ligands come from the same H(2)O(2) molecule. All these experiments lead to attribute the formula [Mn(III)Mn(IV)(L)(O)(2)(OAc)](+) to 2a and to 3a the formula [Mn(II)Mn(III)(L)(O)(OAc)](+). Freeze-quench/EPR experiments revealed that 2a appears at 500 ms and that another species with a 6-line spectrum is formed transiently at ca. 100 ms. 2a was prepared by reaction of 1a with tert-butyl hydroperoxide as shown by EPR and UV-visible spectroscopies and ESI-MS experiments. Its structure was studied by X-ray absorption experiments which revealed the presence of two or three O atoms at 1.87 A and three or two N/O atoms at 2.14 A. In addition one N atom was found at a longer distance (2.3 A) and one Mn at 2.63 A. 2a can be one-electron oxidized at E(1/2) = 0.91 V(NHE) (DeltaE(1/2) = 0.08 V) leading to its Mn(IV)Mn(IV) analogue. The formation of 2a from 1a was monitored by UV-visible and X-ray absorption spectroscopies. Both concur to show that an intermediate Mn(II)Mn(III) species, resembling 4a [Mn(2)(L)(OAc)(2)(H(2)O)](ClO(4))(2), the one-electron-oxidized form of 1a, is formed initially and transforms into 2a. The structures of the active intermediates 2 and 3 are discussed in light of their spectroscopic properties, and potential mechanisms are considered and discussed in the context of the biological reaction.

Reactions of the unsymmetrical phenol ligand 2-(bis(2-pyridyimethyl)aminomethyl)-6-((2-pyridylmethyl)(benzyl)aminometh yl)-4-methylphenol with Mn(OAc)[sub 2]·4H[sub 2]O or Mn(H[sub 2]O)[sub 6](ClO[sub 4])[sub 2] in the presence of NaOBz affords the dimanganese(II) complexes 1(CH[sub 3]OH), [Mn[sub 2](L)(OAc)[sub 2](CH[sub 3]OH)](ClO[sub 4]), and 2(H[sub 2]O), [Mn[sub 2](L)(OBz)[sub 2](H[sub 2]O)](ClO[sub 4]), respectively. On the other hand, reaction of the ligand with hydrated manganese(III) acetate furnishes the mixedvalent derivative 3(H[sub 2]O), [Mn[sub 2](L)(OAc)[sub 2](H[sub 2]O)](ClO[sub 4])[sub 2]. The three complexes have been characterized by X-ray crystallography. 1(CH[sub 3]OH) crystallizes in the monoclinic system, space group P2[sub 1]/c, with a = 10.9215(6) Å, b = 20.2318(12) Å, c = 19.1354(12) Å, α = 90°, β = 97.5310(10)°, γ = 90°, V = 4191.7 A³, and Z = 4. 2(H[sub 2]O) crystallizes in the monoclinic system, space group P2[sub 1]/n, with a = 10.9215(6) Å, b = 20.2318(12) Å, c = 19.1354(12) Å, α = 90°, β = 97.5310(10)°, γ = 90°, V = 4191.7 ų, and Z = 4.3(H[sub 2]O) crystallizes in the monoclinic system, space group P2[sub 1]/c, with a = 11.144(6) Å, b = 18.737(10) Å, c = 23.949(13) Å, α = 90°, β = 95.910(10)°, γ = 90°, V-4974(5) ų, and Z = 4. Magnetic measurements revealed that the three compounds exhibit very similar magnetic exchange interactions -J = 4.3(3) cm[sup -1]. They were used to establish tentative magnetostructural correlations which show that for the dimanganese(II) complexes -J decreases when the Mn-O[sub phenoxo] distance increases as expected from orbital overlap considerations. For the dimanganese(II,III) complexes, crystallographic results show that the Mn[sup II]-O[sub phenoxo] and Mn[sup III]-O[sub phenoxo] bond lengths are inversely correlated. An... [ABSTRACT FROM AUTHOR]

Examines the properties of the dinuclear manganese complex. Outcome on the reaction of manganese compounds with ethylamines compounds; X-ray crystallography of the binuclear manganese compounds; Electrochemical behavior of the manganese complex.