Cyclic hexapeptoids with N-alkyl side chains: solid-state assembly and thermal behaviour

Abstract

The solid state assembly of two cyclic hexapeptoids decorated respectively with five and six carbon N-alkyl side chains is analyzed by single crystal X-ray diffraction, intermolecular energies and lattice energy calculations. Thermal analysis and variable temperature X-ray powder diffraction were also carried out to analyze their thermal behaviour. The crystal structures of the two compounds feature architectural similarities, but also small relevant differences due to side chains-to-side chains interactions, which can explain the observed differences in the thermal properties. The compound with N-pentyl side chains exhibits a phase transition upon cooling down from room temperature to 100 K, while that with N-hexyl side chains features no phase transformation on cooling, instead a phase transformation occurs at 335 K upon heating.