Synthesis of Thiosemicarbazones and Their Organoiodine Cocrystals: Cooperative Effects of Halogen and Hydrogen Bonding

Utilizing the facile addition–elimination reaction of thiosemicarbazide with acetone or aldehydes, nine thiosemicarbazones were synthesized. Aldehydes were chosen which contain additional heteroatoms to increase the diversity of possible intermolecular interactions. Further, the thiosemicarbazone synthesis was conducted in situ with one of the common halogen bond donors 1,2-, 1,3-, or 1,4-diiodotetrafluorobenzene, 1,3,5-trifluoro-2,4,6-triiodobenzene, or tetraiodoethylene. These reactions resulted in the characterization of 12 new cocrystals showcasing halogen bonding. The dimerization of two thiosemicarbazone units through a pair of N‒H···S hydrogen bonds was a universal feature of the solid-state structures in this series, with the hydrogen bond network often extending these motifs into chains. The organoiodines serve to link chains through either I···S or I···N halogen bonding, or less commonly, S···I chalcogen bonding. This variety of intermolecular interactions leads to the formation of double-stranded chains, ribbons, and sheets. Graphical Abstract Utilizing the facile addition–elimination reaction of thiosemicarbazide with acetone or aldehydes, nine thiosemicarbazones were synthesized, seven of which were isolated as cocrystals with common halogen bond donors. Significant N–H···S hydrogen bonding was observed in all, with S···I halogen and chalcogen bonding contributing to the long-range packing in the cocrystals.