Phenothiazine Radical Cation Excited States as Super-oxidants for Energy-Demanding Reactions

Joseph A. Christensen, Brian T. Phelan, Subhajyoti Chaudhuri, Atanu Acharya, Victor S. Batista, Michael R. Wasielewski

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15 Citations (Scopus)

Abstract

We demonstrate that the 10-phenyl-10H-phenothiazine radical cation (PTZ+•) has a manifold of excited doublet states accessible using visible and near-infrared light that can serve as super-photooxidants with excited-state potentials is excess of +2.1 V vs SCE to power energy demanding oxidation reactions. Photoexcitation of PTZ+• in CH3CN with a 517 nm laser pulse populates a Dn electronically excited doublet state that decays first to the unrelaxed lowest electronic excited state, D1′ (τ < 0.3 ps), followed by relaxation to D1 (τ = 10.9 ± 0.4 ps), which finally decays to D0 (τ = 32.3 ± 0.8 ps). D1′ can also be populated directly using a lower energy 900 nm laser pulse, which results in a longer D1′→D1 relaxation time (τ = 19 ± 2 ps). To probe the oxidative power of PTZ+• photoexcited doublet states, PTZ+• was covalently linked to each of three hole acceptors, perylene (Per), 9,10-diphenylanthracene (DPA), and 10-phenyl-9-anthracenecarbonitrile (ACN), which have oxidation potentials of 1.04, 1.27, and 1.6 V vs SCE, respectively. In all three cases, photoexcitation wavelength dependent ultrafast hole transfer occurs from Dn, D1′, or D1 of PTZ+• to Per, DPA, and ACN. The ability to take advantage of the additional oxidative power provided by the upper excited doublet states of PTZ+• will enable applications using this chromophore as a super-oxidant for energy-demanding reactions.

Original languageEnglish
Pages (from-to)5290-5299
Number of pages10
JournalJournal of the American Chemical Society
Volume140
Issue number15
DOIs
Publication statusPublished - Apr 18 2018

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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