A CPMAS C-13 NMR-STUDY OF MOLECULAR-CONFORMATIONS AND DISORDER OF N-OCTYLHEXONAMIDES IN MICROCRYSTALS AND SUPRAMOLECULAR ASSEMBLIES

Solid molecular mono- and bilayers in bulk aqueous media are usually m ade of amphiphiles with a chiral head group, a secondary amide group, and long alkyl chains. Their uniform helical pitches or rod and tubule diameters suggest uniform molecular conformations within the curved s upramolecular assemblies. These conformations are characterized by che mical shift patterns in CPMAS C-13-NMR solid state spectra. The assign ment of such spectra obtained for microcrystals and lyophilized fibrou s assemblies of five N-octylhexonamides is based on comparisons with ( i) known single crystal structures, (ii) unequivocally assigned C-13-N MR solution spectra, and (iii) application of established gauche effec ts. The crystal structure data may be taken from single crystal struct ures of corresponding amphiphiles, which are notoriously difficult to obtain, or from nonamphiphilic analogues. The procedure also detects c rystal disorders. It is generally applicable to assemblies of molecule s with at least four interconnected carbon atoms in a uniform conforma tion.