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.

Key Words:

• hydrogen bonding
• inclusion compounds
• host-guest compounds
• supramolecular synthons
• hydroxy groups
• enantiomeric packing