IUCr journals


Acta Cryst. (2003). E59, o693–o695

[Bisbenzimidazole structure]

Biphenyl-linked bis(imidazoles) (I) and bis(benzimidazoles) (II) act as flexible, geometrically constraining bidentate ligands containing four planar groups and three torsional degrees of freedom. They have been used in studies of electron self-exchange, to enforce near-tetrahedral coordination in transition metal complexes, in catalysis, and as proton sponges. In the solid state, II, R = ethyl adopts an unusual, compact, twisted-clamshell conformation with site symmetry 2 (ethyl groups trans). The shortest distances between C and N atoms of the nearly eclipsed, slightly diverging imidazole fragments range from 3.167(3) Å to 3.673(3) Å, indicative of strong intramolecular π–π interactions. In contrast, II, R = n-propyl exhibits an open structure with little evidence of intra- or intermolecular π–π interactions.

Robert T. Stibrany, Harvey J. Schugar and Joseph A. Potenza