Hydrogen-Bonding Interactions in Crystalline Solids of Cyclic Thioureas

Abstract

The crystal structures of three cyclic thioureas (4,5-disubstituted benzimidazolene-2-thiones) are reported. Each compound forms a tape motif in the solid state. Two of the three compounds assemble into tapes via N−H- - -S hydrogen bonds. These tapes pack into planar sheets. The third compound assembles into tapes via C−H- - -Br hydrogen bonds. These tapes pack at angles relative to each other, generating puckered sheets. The patterns of packing of these three cyclic thioureas are compared to those observed in the crystalline solids of cyclic ureas that have analogous molecular structures. The patterns of packing adopted by cyclic thioureas are rationalized in terms of molecular structure, solvent of crystallization, and energies and efficiencies of packing.