Synthesis and properties of polyenic oligosulfides derived from acetylene and elemental sulfur

Oligosulfides derived from ethyne-1,2-dithiol were synthesized in up to 96% yield via insertion of elemental sulfur into the Na-C_sp bond of sodium acetylides (HC≡CNa, NaC≡CSNa) in liquid ammonia, followed by hydrolysis and spontaneous oligomerization of ethynethiols, ethynedithiols, and mono-and bis-(polysulfanyl)ethynes (HC≡CSH, HSC≡CSH, HC≡CS_xH, HS_xC≡CS_yH). The resulting polyenic oligosulfides were isolated as brown powders melting in the temperature range from 122 to 203°C and containing up to 77% of sulfur; they are sparingly soluble in organic solvents and are high-resistance semiconductors (10^?13–10^?14 S cm^?1) possessing paramagnetic (10¹⁷–10¹⁸ spin g^?1) and redox properties. According to the data of IR and ESR spectroscopy and cyclic voltammetry, the oligomers obtained consist mainly of different oligosulfide units, including oligothienothiophene structures. They also ensure a high discharge capacity (345–720 mA h g^?1) of lithium sulfur rechargeable batteries.