Identification of [1,3]dithiolo[4,5-d]dithiazolyl radicals by in situ EPR spectroscopy and cyclic voltammetry

The synthesis of 1,3]dithiolo4,5-d]dithiazolium salts from readily available zinc chelate has been developed. Chlorination of 2-oxo and 2-(dicyanomethylene) (2-oxo-1,3-dithiole-4,5-diyl) diethanethioates with SO₂Cl₂ followed by condensation with Me₃SiN₃ produced 1,2,3-dithiazolium chlorides. The structure of 5-(dicyanomethylene)1,3]dithiolo4,5-d]1,3,2]dithiazol-1-ium tetrafluoroborate was confirmed by powder X-ray diffraction, and its chemical bonding pattern as well as charge transfer were studied within the QTAIM framework applied to the results of plane wave DFT periodic calculations. Reduction with triphenylantimony and electrochemical reduction of 1,3]dithiolo4,5-d]dithiazolium salts by cyclic voltammetry, chronoamperometry, and microelectrolysis at a controlled potential on a platinum electrode in acetonitrile revealed the formation of 1,3]dithiolo4,5-d]dithiazolyl radicals, which were characterized by EPR spectroscopy.