Phase transitions involving re-ordering of the guest molecules in a solid organic inclusion compound: heptanoic anhydride–urea

Abstract

Phase transitions below ambient temperature in the heptanoic anhydride–urea inclusion compound have been investigated using X-ray diffraction and differential scanning calorimetry; one of these phase transitions (at ca. 179K on cooling) is associated with a change in the mode of three-dimensional ordering of the heptanoic anhydride guest molecules with no detectable change in the host (urea) structure, and represents the first reported example of this type of phase transition for urea inclusion compounds.