N,N-Di- n-octyl- N,N-dimethyl and N,N-di- n-nonyl- N,N-dimethyl ammonium cholates: 13C and 15N CPMAS NMR, powder X-ray diffraction and thermoanalytical characterization

Abstract

N,N-Di- n-octyl- N,N-dimethyl cholate ( 1) and N,N-di- n-nonyl- N,N-dimethyl ammonium cholate ( 2) have been prepared by crystallization from equimolar mixtures of sodium cholate and quaternary N,N-di- n-alkyl- N,N-dimethyl ( n-octyl or n-nonyl) ammonium bromides. The formed crystalline materials have been structurally characterized by 13C and 15N cross polarization magic angle spinning (CPMAS) NMR, powder X-ray diffraction (PXRD) and thermoanalytical (TGA/DTA and DSC) methods and compared with each other. Powder X-ray diffraction patterns of 1 and 2 reveal clear similarities. Combined with the thermoanalytical data of these structures an existence of two hydrated polymorphs (most probably mono- and dihydrates) can be proposed. This presumption is further supported by 13C CPMAS NMR showing clearly double resonances for the carboxylic and majority of other carbons in these quaternary ammonium cholates. Owing to the endogenous character of cholate anion these ionic structures possess great potential in many pharmaceutical applications such as controlled drug delivery.