Mononuclear Manganese(III) Superoxo Complexes: Synthesis, Characterization, and Reactivity

Yen Hao Lin, Hanna Hinrika Cramer, Maurice Van Gastel, Yi Hsuan Tsai, Chi Yi Chu, Ting Shen Kuo, I. Ren Lee, Shengfa Ye, Eckhard Bill, Way Zen Lee

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Metal-superoxo species are typically proposed as key intermediates in the catalytic cycle of dioxygen activation by metalloenzymes involving different transition metal cofactors. In this regard, while a series of Fe-, Co-, and Ni-superoxo complexes have been reported to date, well-defined Mn-superoxo complexes remain rather rare. Herein, we report two mononuclear MnIII-superoxo species, Mn(BDPP)(O2 •-) (2, H2BDPP = 2,6-bis((2-(S)-diphenylhydroxylmethyl-1-pyrrolidinyl)methyl)pyridine) and Mn(BDPBrP)(O2 •-) (2′, H2BDPBrP = 2,6-bis((2-(S)-di(4-bromo)phenylhydroxyl-methyl-1-pyrrolidinyl)methyl)pyridine), synthesized by bubbling O2 into solutions of their MnII precursors, Mn(BDPP) (1) and Mn(BDPBrP) (1′), at -80 °C. A combined spectroscopic (resonance Raman and electron paramagnetic resonance (EPR) spectroscopy) and computational study evidence that both complexes contain a high-spin MnIII center (SMn = 2) antiferromagnetically coupled to a superoxo radical ligand (SOO• = 1/2), yielding an overall S = 3/2 ground state. Complexes 2 and 2′ were shown to be capable of abstracting a H atom from 2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPO-H) to form MnIII-hydroperoxo species, Mn(BDPP)(OOH) (5) and Mn(BDPBrP)(OOH) (5′). Complexes 5 and 5′ can be independently prepared by the reactions of the isolated MnIII-aqua complexes, [Mn(BDPP)(H2O)]OTf (6) and [Mn(BDPBrP)(H2O)]OTf (6′), with H2O2 in the presence of NEt3. The parallel-mode EPR measurements established a high-spin S = 2 ground state for 5 and 5′.

Original languageEnglish
Pages (from-to)9756-9765
Number of pages10
JournalInorganic Chemistry
Issue number15
Publication statusPublished - 2019 Aug 5

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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