Hydrogen atom vs electron transfer in catecholase-mimetic oxidations by superoxometal complexes. Deuterium kinetic isotope effects.
Dioximato-cobalt(II), -iron(II) and -manganese(II) complexes (1)-(6), acting as functional catecholase and phenoxazinone synthase models, exhibit a deuterium kinetic isotope effect predicted by theory (k4H/k4D < or = 3) in the catalytic oxidative dehydrogenation of 3,5-di-tert-butylcatechol and 2-aminophenol by O2. KIEs in the range of (k4H/k4D approximately 1.79-3.51) are observed with (1) and (2) as catalysts, pointing to hydrogen atom transfer in the rate-determining step from the substrate hydroxy group to the metal-bound superoxo ligand. Less significant KIEs (1.06-1.20) are exhibited by catalysts systems (3)-(6), indicating that proton-coupled electron transfer is the preferred route in those cases.
Simándi
Tatiana M
TM
Chemical Research Center, Institute of Surface Chemistry and Catalysis, Hungarian Academy of Sciences, PO Box 17, 1525 Budapest, Hungary. simandi@chemres.hu
May
Zoltán
Z
Szigyártó
Imola Cs
IC
Simándi
László I
LI
D000627:Aminophenols / Q000737:chemistry; D032701:Biomimetics; D002384:Catalysis; D004156:Catechol Oxidase / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry; D003903:Deuterium / Q000737:chemistry*; D004579:Electron Transport; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry; D010100:Oxygen / Q000494:pharmacology; D011868:Radioisotopes / Q000737:chemistry; D013481:Superoxides / Q000737:chemistry
D000627:Aminophenols; D002396:Catechols; D011868:Radioisotopes; D013481:Superoxides; C027667:2-aminophenol; D006859:Hydrogen; D003903:Deuterium; D010088:Oxidoreductases; D004156:Catechol Oxidase; C023944:2-aminophenol oxidase; D010100:Oxygen