Benzimidazolene-2-thiones: A New Class of Molecules for the Engineering of Molecular Tapes in the Organic Solid State

Derivatives of benzimidazolene-2-thione differing in substitution at the 4 and 5 positions have been synthesized and studied by single-crystal X-ray diffraction and/or X-ray powder diffraction. These derivatives include five monosubstituted compounds (1-SX; X = Me, F, Cl, Br, I), four disubstituted compounds (1-SX2; X = Me, F, Cl, Br), the parent dihydro compound (1-SH2), and the naphthyl compound (2-SH2). Five of these molecules gave crystals suitable for single-crystal X-ray diffraction. In all of these crystals, the molecules pack as parallel, hydrogen-bonded tapes. Alternate molecules of a tape occupy two different planes that are separated by approximately 1 A. The resulting structure is named a stepped tape. These stepped tapes are divided into two classes based on packing:  tapes of 1-SH2, 1-SMe2, and 1-SF pack in flat, parallel planes. Tapes of 2-SH2, 1-SF2, and 1-SCl2 pack at an angle; of these, two (2-SH2 and 1-SF2) incorporate molecules of solvent. None of the structures is isomorphic.