Air-Stable Cyclohexasulfur as Cocrystal

Abstract

A new stable cyclohexasulfur (cyclo-S₆) was discovered in the crystal of 3,5-diphenyl-1,2,4-dithiazol-1-ium (dpdti); dpdti was synthesized via an oxidation reaction of thiobenzamide with iodine in benzene, under reflux. Two kinds of crystal habitsbrick-shaped (crystal-<b>A</b>) and needle-shaped (crystal-<b>B</b>)were obtained following recrystallization from acetonitrile solvent. Single-crystal structure analysis using synchrotron X-ray radiation showed that both crystal-<b>A</b> and -<b>B</b> consist of a dpdti cation and an iodine anion. Furthermore, neutral cyclo-S₆ molecules are present in crystal-<b>A</b> as cocrystals, enclosed by the dpdti cation and the iodide anion. This is akin to cyclosulfur of <i>S</i>_<i>n</i> in zeolites and sodalities, suggesting a contribution to the stabilization of cyclo-S₆ molecules. The results show that crystal engineering of cocrystals may be used as a method to control the stability and activity of sulfur, for improved utilization