Structural and Catalytic Characterization of a Heterovalent Mn(II)Mn(III) Complex That Mimics Purple Acid Phosphatases
Smith, Sarah J. and Riley, Mark J. and Noble, Christopher J. and Hanson, Graeme R. and Stranger, Robert and Jayaratne, Vidura and Cavigliasso, German and Schenk, Gerhard and Gahan, Lawrence R. (2009) Structural and Catalytic Characterization of a Heterovalent Mn(II)Mn(III) Complex That Mimics Purple Acid Phosphatases. Inorganic Chemistry, 48 . pp. 10036-10048. ISSN 0020-1669
The binuclear heterovalent manganese model complex [Mn(II)Mn(III)(L1)(OAc)2] ClO4 3 H2O (H2L1 = 2-(((3-((bis- (pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzyl)(pyridin-2-ylmethyl)amino)-methyl)phenol) has been prepared and studied structurally, spectroscopically, and computationally. The magnetic and electronic properties of the complex have been related to its structure. The complex is weakly antiferromagnetically coupled (J ∼ -5 cm-1, H =-2J S1 3 S2) and the electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectra identify the Jahn-Teller distortion of the Mn(III) center as predominantly a tetragonal compression, with a significant rhombic component. Electronic structure calculations using density functional theory have confirmed the conclusions derived from the experimental investigations. In contrast to isostructural M(II)Fe(III) complexes (M = Fe, Mn, Zn, Ni), theMn(II)Mn(III) system is bifunctional possessing both catalase and hydrolase activities, and only one catalytically relevant pKa (= 8.2) is detected. Mechanistic implications are discussed.
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