Structural and catalytic characterization of a heterovalent Mn(II)Mn(III) complex that mimics purple acid phosphatases.
The binuclear heterovalent manganese model complex [Mn(II)Mn(III)(L1)(OAc)(2)] ClO(4) x H(2)O (H(2)L1 = 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 approximately -5 cm(-1), H = -2J S(1) x S(2)) 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), the Mn(II)Mn(III) system is bifunctional possessing both catalase and hydrolase activities, and only one catalytically relevant pK(a) (= 8.2) is detected. Mechanistic implications are discussed.
Smith
Sarah J
SJ
School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia.
Riley
Mark J
MJ
Noble
Christopher J
CJ
Hanson
Graeme R
GR
Stranger
Robert
R
Jayaratne
Vidura
V
Cavigliasso
Germán
G
Schenk
Gerhard
G
Gahan
Lawrence R
LR
D000135:Acid Phosphatase / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D006023:Glycoproteins / Q000737:chemistry*; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008954:Models, Biological; D015394:Molecular Structure
D006023:Glycoproteins; D008345:Manganese; C091137:purple acid phosphatase; D000135:Acid Phosphatase