X-ray investigation of bowl-like compounds

The mesophases of bowl-like compounds were first proposed in 1982, and the compounds have recently been synthesized. We have found that some bowl-like compounds can form disordered crystalline phase that have long-range positional order, but with strong fluctuations in position and orientation. Their side chains are in a molten state. X-ray diffraction has shown that two new homologues in the hexa-n-alkylcarboxytribenzocyclononene series are stacked in triclinic systems with space group P I. The parameters of an unit cell, the densities of the compounds and the expansion coefficient are given. Modelling of a unit cell is presented, which confirms the up-down asymmetry of the molecules, but there is no microscopic ferroelectricity. However, one-dimensional antiferroelectricity may exist. The results are compared with disc-like molecules, as well as with higher homologues of the bowl-like compounds.