Thermotropic phase behavior, structure and supramolecular organization of N, O-diacyl-β-alaninols with matched N- and O-acyl chains (n = 9-18)

Abstract

The thermotropic phase behavior, molecular structure and supramolecular organization of a homologous series of N,O-diacyl-β-alaninols (DABAOHs) with matched acyl chains (C9-C18) are reported. The C9-C11 DABAOHs showed a single thermotropic transition in DSC studies, whereas the longer chainlength compounds gave two transitions. Transition temperatures, enthalpies and entropies of the DABAOHs exhibited odd-even alternation, suggesting minor differences in the packing of odd- and even chain length compounds. Crystal structure of N,O-didecanoyl-β-alaninol revealed a bent geometry, with several N-H···O and C-H···O hydrogen bonds stabilizing the molecular packing. Powder X-ray diffraction studies suggested that all DABAOHs are packed in a tilted bilayer mode. These results provide a thermodynamic and structural basis for investigating the structure-function relationships of N,O-diacyl-β-alaninols.