title: Photocatalytic Oxygenation of Substrates by Dioxygen with Protonated Manganese(III) Corrolazine.
abstract: UV-vis spectral titrations of a manganese(III) corrolazine complex [Mn(III)(TBP8Cz)] with HOTf in benzonitrile (PhCN) indicate mono- and diprotonation of Mn(III)(TBP8Cz) to give Mn(III)(OTf)(TBP8Cz(H)) and [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] with protonation constants of 9.0 × 10(6) and 4.7 × 10(3) M(-1), respectively. The protonated sites of Mn(III)(OTf)(TBP8Cz(H)) and [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] were identified by X-ray crystal structures of the mono- and diprotonated complexes. In the presence of HOTf, the monoprotonated manganese(III) corrolazine complex [Mn(III)(OTf)(TBP8Cz(H))] acts as an efficient photocatalytic catalyst for the oxidation of hexamethylbenzene and thioanisole by O2 to the corresponding alcohol and sulfoxide with 563 and 902 TON, respectively. Femtosecond laser flash photolysis measurements of Mn(III)(OTf)(TBP8Cz(H)) and [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] in the presence of O2 revealed the formation of a tripquintet excited state, which was rapidly converted to a tripseptet excited state. The tripseptet excited state of Mn(III)(OTf)(TBP8Cz(H)) reacted with O2 with a diffusion-limited rate constant to produce the putative Mn(IV)(O2(•-))(OTf)(TBP8Cz(H)), whereas the tripseptet excited state of [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] exhibited no reactivity toward O2. In the presence of HOTf, Mn(V)(O)(TBP8Cz) can oxidize not only HMB but also mesitylene to the corresponding alcohols, accompanied by regeneration of Mn(III)(OTf)(TBP8Cz(H)). This thermal reaction was examined for a kinetic isotope effect, and essentially no KIE (1.1) was observed for the oxidation of mesitylene-d12, suggesting a proton-coupled electron transfer (PCET) mechanism is operative in this case. Thus, the monoprotonated manganese(III) corrolazine complex, Mn(III)(OTf)(TBP8Cz(H)), acts as an efficient photocatalyst for the oxidation of HMB by O2 to the alcohol.
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea.
authors.forename: Jieun
authors.initials: J
authors.lastname: Jung
authors.affiliation: Department of Chemistry, The Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Neu
authors.affiliation: Department of Chemistry, The Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States.
authors.forename: Pannee
authors.initials: P
authors.lastname: Leeladee
authors.affiliation: Department of Chemistry, The Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States.
authors.forename: Maxime A
authors.initials: MA
authors.lastname: Siegler
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea.|Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency (JST) , Suita, Osaka 565-0871, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Ohkubo
authors.affiliation: Department of Chemistry, The Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States.
authors.forename: David P
authors.initials: DP
authors.lastname: Goldberg
authors.affiliation: Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea.|Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency (JST) , Suita, Osaka 565-0871, Japan.|Faculty of Science and Engineering, Meijo University, ALCA and SENTAN, Japan Science and Technology Agency (JST) , Nagoya, Aichi 468-0073, Japan.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry; D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008345:Manganese / Q000737:chemistry*; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D010083:Oxidants, Photochemical / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011522:Protons; D013440:Sulfides / Q000737:chemistry
chemical_list: D001555:Benzene Derivatives; D056831:Coordination Complexes; D008665:Metalloporphyrins; D010083:Oxidants, Photochemical; D011522:Protons; D013440:Sulfides; C583828:corrolazine; D008345:Manganese; C093850:methylphenylsulfide; C091695:hexamethylbenzene; D010100:Oxygen