Structural variation and supramolecular isomerism in the C-methylcalix[4]resorcinarene/bipyridine system

Five supramolecular compounds [CMCR.2bipyl] 1, [CMCR.3bipyl] 2, [CMCR.2bipy.2H(2)O] 3, [2CMCR].1.5bipy.5H(2)O 4, and [CMCR.bipyl].3.5ethanol.H2O-bipy 5 (where the square brackets enclose framework components, CMCR = C-methylealix[4]resoreinarene, bipy = 4,4'-bipyridine), prepared hydrothermally and from solution, are described. CMCR adopts a chair conformation in 1 and 2, and a flattened cone conformation in 3-5. The framework structures vary from 2D stepped-sheet (1), 3D stepped sheet (2), brick-wall (3 and 5) to a network consisting of perpendicular nonintersecting ribbons of CMCR molecules (4). The supramolecular architectures found in the current study are compared with those of other multicomponent CMCR/bipy system reported in the literature. The nature of the enclosed cavities in the brick-wall type structures is a function of the number of phenoxyl OH groups not involved in the framework hydrogen bonding, and thus available for bonding to guest molecules. The number of solvent-binding phenoxyl groups per CMCR ranges from two to zero in the brick-wall structures surveyed here.