Photocatalytic Oxygenation of Substrates by Dioxygen with Protonated Manganese(III) Corrolazine

Jieun Jung, Heather M. Neu, Pannee Leeladee, Maxime A. Siegler, Kei Ohkubo, David P. Goldberg, Shunichi Fukuzumi

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


UV-vis spectral titrations of a manganese(III) corrolazine complex [MnIII(TBP8Cz)] with HOTf in benzonitrile (PhCN) indicate mono- and diprotonation of MnIII(TBP8Cz) to give MnIII(OTf)(TBP8Cz(H)) and [MnIII(OTf)(H2O)(TBP8Cz(H)2)][OTf] with protonation constants of 9.0 × 106 and 4.7 × 103 M-1, respectively. The protonated sites of MnIII(OTf)(TBP8Cz(H)) and [MnIII(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 [MnIII(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 MnIII(OTf)(TBP8Cz(H)) and [MnIII(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 MnIII(OTf)(TBP8Cz(H)) reacted with O2 with a diffusion-limited rate constant to produce the putative MnIV(O2•-)(OTf)(TBP8Cz(H)), whereas the tripseptet excited state of [MnIII(OTf)(H2O)(TBP8Cz(H)2)][OTf] exhibited no reactivity toward O2. In the presence of HOTf, MnV(O)(TBP8Cz) can oxidize not only HMB but also mesitylene to the corresponding alcohols, accompanied by regeneration of MnIII(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, MnIII(OTf)(TBP8Cz(H)), acts as an efficient photocatalyst for the oxidation of HMB by O2 to the alcohol.

Original languageEnglish
Pages (from-to)3218-3228
Number of pages11
JournalInorganic Chemistry
Issue number7
StatePublished - 18 Apr 2016

Bibliographical note

Publisher Copyright:
© 2016 American Chemical Society.


Dive into the research topics of 'Photocatalytic Oxygenation of Substrates by Dioxygen with Protonated Manganese(III) Corrolazine'. Together they form a unique fingerprint.

Cite this