Premium
Highly Efficient Disproportionation of Dihydrogen Peroxide: Synthesis, Structure, and Catalase Activity of Manganese Complexes of the Salicylimidate Ligand
Author(s) -
Godbole Meenal D.,
Kloskowski Michael,
Hage Ronald,
Rompel Annette,
Mills Allison M.,
Spek Anthony L.,
Bouwman Elisabeth
Publication year - 2005
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200400621
Subject(s) - disproportionation , chemistry , hydrogen peroxide , catalase , catalysis , manganese , peroxide , turnover number , medicinal chemistry , ligand (biochemistry) , inorganic chemistry , coordination sphere , nuclear chemistry , stereochemistry , enzyme , organic chemistry , ion , biochemistry , receptor
Two complexes, [Mn 2 (etsalim) 4 (Hetsalim) 2 ](ClO 4 ) 2 ( 1 ), and [Mn(mesalim) 2 (OAc)(MeOH)]·MeOH ( 2 ), in which Hmesalim and Hetsalim are methyl and ethyl salicylimidate, respectively, have been synthesized, fully characterized by X‐ray analyses, magnetic susceptibility, UV/Vis and IR spectroscopy, and their catalase activity has been studied. Complex 1 is dinuclear and shows an Mn−Mn distance of 3.37 Å while complex 2 is mononuclear. Both complexes catalyze the disproportionation of hydrogen peroxide into water and dioxygen; they show very high catalase activity exhibiting saturation kinetics in the presence of NaOH. The rate and turnover number of the catalyzed reaction increase dramatically when a few equivalents of base (NaOH) are added to the reaction mixture. The turnover numbers for hydrogen peroxide disproportionation increase from approximately 200 to more than 1500 per manganese ion in less than 2 min for both complexes after addition of a few equivalents of NaOH. Kinetic studies of the catalyzed reaction performed on the dinuclear complex 1 in the presence of 5 equiv. of NaOH, gives k cat = 807 s −1 (± 16) and K M = 0.091 M (± 0.003). The effective catalytic efficiency is k cat / K M = 8900 M −1 s −1 . The kinetic parameters of the mononuclear complex 2 in the presence of 5 equiv. of NaOH, are k cat = 190 s −1 (± 4) and K M = 0.022 M (± 0.001). The effective catalytic efficiency is k cat / K M = 8600 M −1 s −1 . The catalase activity of the mononuclear complex, [Mn(mesalim) 2 Cl] ( 3 ) has also been studied, and it shows turnover numbers that are comparable to those of complex 2 . ESI‐MS analyses in deuterated solvents have been used to understand the nature of the active species formed on addition of 5 equiv. of NaOH. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)