Role of the (O‒H)6 Synthon in the Construction of Organic Inclusion Compounds

Abstract

The racemic diol 5 crystallises from ethanol in the orthorhombic space group Cmca (a 19.05, b 14.93, c 10.12 Å) as the cocrystalline solid 5°C2H5OH. In contrast, the racemic diol 6 crystallises from benzene in the cubic space group Ia3 (a 19.85 Å) as a clathrate compound. The principal supramolecular synthon involved in both cases is a cyclic hexamer of hydrogen bonded hydroxy groups, (O-H)6. While the former cycle is almost planar, rather uncommonly the latter is cyclohexane-like in geometry. A major function of the (O-H)6 cycle is to allow efficient packing between opposite enantiomers within the crystal lattice.