Air-Stable Cyclohexasulfur as Cocrystal

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-A) and needle-shaped (crystal-B)were obtained following recrystallization from acetonitrile solvent. Single-crystal structure analysis using synchrotron X-ray radiation showed that both crystal-A and -B consist of a dpdti cation and an iodine anion. Furthermore, neutral cyclo-S6 molecules are present in crystal-A as cocrystals, enclosed by the dpdti cation and the iodide anion. This is akin to cyclosulfur of Sn 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.