Cocrystallization of thioamide and bipyridine-type molecules

Cocrystallization experiments conducted between thiocarbamide derivatives, (E)-O-alkyl N-aryl-thiocarbamide, of the general formula ROC(=S)N(H)R', for R = Me, Et and iPr and R' = Ph and C₆H₄NO₂-4 containing an active pharmaceutical ingredient (API), i.e., -C(=S)-N(H)-, and bipyridine-type molecules, e.g., 4,4'-bipyridine, trans-1,2-bis(4-pyridyl)ethene and 1,2-bis(4-pyridyl)ethane, showed the formation of stable binary 2:1 cocrystals, e.g., {[ROC(=S)N(H)R']₂(bipyridine-type molecule)}. Novel species were formed by grinding and solvent drop grinding methods, and characterized by X-ray powder diffraction methods. Five 2:1 cocrystals were isolated as single crystals by slow evaporation methods and subjected to full characterization by spectroscopic and X-ray crystallographic methods. This study shows that the eight-membered {...H-N-C=S}₂ homosynthon found in the parent thiocarbamides is readily disrupted in the presence of bipyridine-type molecules to enable the formation of the stable heterosynthon, {N...H-N}.