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Synthesis and Properties of Various Catanionic Cholate Surfactant Salts

The bile acids play divergent roles in biology and in supramolecular and biomimetic chemistry. In the context of host–guest chemistry these compounds can be used as an architectural component of supramolecular hosts suitable for molecular recognition of a wide variety of organic substances by size, shape, polarity, chirality and chemical environment. The interactions between anionic amphiphilic biomolecular compound sodium cholate, and oppositely charged cationic surfactants (conventional alkylammonium, gemini or oligomeric quaternary ammonium halogenides, and also 18-crown-6) have been studied in aqueous solutions. The series of new solid catanionic salts/complexes of different corresponding cholates, with the 1 : 1 cationic : anionic surfactant molar ratio, has been synthesized and their physicochemical properties characterised by spectroscopic analysis (NMR solid and liquid state), differential scanning calorimetry, X-ray diffraction and microscopic observations. The strong synergism in the examined mixtures, arrangements and preferred shapes of catanionic supramolecular aggregates are consequence of primarily electrostatic interactions, preferred hydrophilic and hydrophobic orientations of the abovementioned combinations of molecular structures and the H-bond networks. On the contrary to the typical catanionic "sandwich-type" bilayer arrangements with alkylammonium cations, the 18-crown-6 cholate aduct (owing to the coordination of metal ion in their central cavity) is characterized as smectic liquid crystal.

bile acid; catanionic surfactants

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