Gels composed of low mol. wt. gelators (LMWGs) are fascinating research targets from the viewpoint of applications because their functionalities are easily modified by designing their mol. structures. Some reliable gelator design approaches were developed. However, new classes of mol. gelators are sometimes discovered unexpectedly, suggesting that there remain unknown aspects about gelators. To obtain knowledge regarding gelation and crystn. ability, the crystal structure of N,N'-diperfluorooctanoyl-(1R,2R)-1,2-diaminocyclohexane (RR-CF8), which is a deriv. of 1,2-diaminocyclohexane, one of the most famous LMWGs, was studied in addn. to the vibrational CD (VCD) measurements. The crystal structure was solved from powder x-ray diffraction patterns because recrystn. of RR-CF8 afforded no suitable single crystals for single crystal x-ray diffraction measurement. Two unusual structural features were confirmed. One is that the perfluoroalkyl chain (PFC) of RR-CF8 forms a pseudoracemic helix, or a mixt. of right- (P) and left-handed (M) helixes, while elsewhere, PFCs generally have one-handed helicity. The other is that an oxygen atom of one of the amide groups is free of hydrogen bonds, reducing the stability of one-dimensional hydrogen-bonded assemblies. These unique structural features let us propose the reasonable explanations for the gelation and crystn. ability of RR-CF8. Furthermore, a factor of environment-dependent chirality inversion of RR-CF8 supermols. was clarified by combining x-ray crystallog. and solid-state VCD spectroscopy. [on SciFinder(R)]
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