NMR- and EPR spectroscopic characterization of S4N4 and (SN)x dissolved in [EMIm][OAc]

This work focuses on the reaction mechanism of poly(sulfur nitride) ((SN)x, (S15N)x), with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [EMIm][OAc]. We compare this with the reaction of the IL with S4N4 or its 15N labeled form S415N4, a precursor for the synthesis of (SN)x and (S15N)x. After purification of the S4N4-IL- and S415N4-system via column chromatography, we characterize the reaction products with 1H, 13C and 15N nuclear magnetic resonance (NMR) spectroscopy and with electron spray ionization time-of-flight mass spectrometry (ESI-ToF-MS). Furthermore, time-resolved electron paramagnetic resonance (EPR) spectroscopy as well as time-resolved ultraviolet-visible (UV/Vis) spectroscopy are carried out. Thus, radical intermediates are detected which are consumed with reaction progress. Finally, we postulate a reaction mechanism for the S4N4-IL- and S415N4-IL system and compare this with the respective data for the (SN)x-IL- and (S15N)x-IL-system.