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2,2'‐Bipyridine Equipped with a Disulfide/Dithiol Switch for Coupled Two Electron and Proton Transfer

[1,2]dithiino[4,3‐b:5,6‐b']dipyridine (1) and its protonated open form 3,3'‐dithiol‐2,2'‐bipyridine (2) were synthesised and their interconversion investigated. The X‐ray structure of 2 revealed an anti orientation of the two pyridine units and a zwitterionic form. In depth electrochemical studies in combination with DFT calculations lead to a comprehensive picture of the redox chemistry of 1 in the absence and presence of protons. Initial one electron reduction at E1 = −1.97 V results in the formation of the radical anion 1red with much elongated S‐S bond, which readily undergoes further reduction at E2 = −2.15 V. Water triggers a potential inversion (E ≥ −1.9 V for the second reduction) as the radical anion 1red is protonated at its basic N atom. DFT studies revealed that S−S bond breaking and twisting of the pyridine units generally occurs after the second reduction step while the potential inversion induced by protonation is a result of charge compensation. The CV data were simulated to derive rate constants for the individual chemical and electrochemical reactions for both scenarios in the absence and presence of protons.

Authors:   Mauricio Cattaneo, Christine Schiewer, Anne Schober, Sebastian Dechert, Inke Siewert, Franc Meyer
Journal:   Chemistry - A European Journal
Year:   2018
Pages:   n/a
DOI:   10.1002/chem.201705022
Publication date:   17-Jan-2018
Facts, background information, dossiers
  • reductions
  • pyridine
  • Inversion
  • water
  • protons
  • Proton
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