Conformational study of S-alkylated isothiosemicarbazones

A theoretical investigation of the conformational preferences of S-alkylated isothiosemicarbazones was performed. The structures of such compounds cluster in two groups, according to the different orientation of the -SR group with respect to the hydrazine N atom of the thiosemicarbazide. While the trans arrangement may be more stable for the isolated molecules, owing to N-H...N intramolecular interactions, the cis form is preferred by most compounds in the solid state, as the result of interplay between intra- and intermolecular effects.