Intramolecular Thiiranocyclobutane-Open Chain Isomerization of 3,3'-Dithioxo Sulfide Derivatives: A Quantum-Chemical Study

The thermodynamic stability and structural and electronic characteristics of thiabicyclic structures, expected products of photochemical isomerization of bis(3-thioxo-1-phenylpropenyl), bis(3-thioxo-1-propenyl), and bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfides, were evaluated by quantum-chemical calculations. The energy in the thiabicyclic structures is accumulated owing to formation of metastable highly strained fused systems. The heats of dark isomerization of thiabicyclic structures into acyclic ones range from 50 to 250 kJ mol^-1. The activation energy of thermal transformations into acyclic isomers are 90-310 kJ mol^-1. Higher thermal effects and lower activation energies are obtained when the polarity of the medium is taken into account. The calculation results show that this class of compounds is promising for solar energy conversion.