Synthesis, structure, and catalase-like activity of dimanganese(III) complexes of 1,5-bis[(2-hydroxy-5-X-benzyl)(2-pyridylmethyl)amino]pentan-3-ol (X = H, Br, OCH3).
New diMn(III) complexes of general formula [Mn(2)L(mu-OR)(mu-OAc)]BPh(4) (H(3)L = 1,5-bis[(2-hydroxy-5-X-benzyl)(2-pyridylmethyl)amino]pentan-3-ol, 1: X = H, R = Me, 2: X = OMe, R = Me, 3: X = Br, R = Me, 4: X = Br, R = Et) have been prepared and structurally characterized. The synthesized complexes possess a triply bridged (mu-alkoxo)(2)(mu-acetato)Mn(2)(3+) core, a short intermetallic distance of 2.95/6 A modulated by the aliphatic spacers between the central alcoholato and N-amino donor sites, and the remaining coordination sites of the two Mn(III) centers occupied by the six donor atoms of the polydentate ligand. In dimethylformamide, complexes 1-3 are able to disproportionate more than 1500 equiv of H(2)O(2) without significant decomposition, with first-order dependence on catalyst and saturation kinetic on [H(2)O(2)]. Spectroscopic monitoring of the reaction mixtures revealed that the catalyst converts into [Mn(2)(III)(mu-O)(mu-OAc)L], which is the major active form during cycling. Overall, kinetics and spectroscopic studies of H(2)O(2) dismutation by these complexes converge at a catalytic cycle between Mn(III)(2) and Mn(II)(2) oxidation levels. Comparison to other alkoxo-bridged complexes suggests that the binding mode of peroxide to the metal center of the Mn(III)(2) form of the catalyst is a key factor for tuning the Mn oxidation states involved in the H(2)O(2) dismutation mechanism.
Biava
Hernán
H
Instituto de Química Rosario-CONICET, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina.
Palopoli
Claudia
C
Duhayon
Carine
C
Tuchagues
Jean-Pierre
JP
Signorella
Sandra
S
D002374:Catalase / Q000378:metabolism; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007700:Kinetics; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D000439:Pentanols / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared
C540722:1,5-bis((2-hydroxy-5-X-benzyl)(2-pyridylmethyl)amino)pentan-3-ol; D008024:Ligands; D009942:Organometallic Compounds; D000439:Pentanols; D011725:Pyridines; D008345:Manganese; D002374:Catalase