Temperature-Dependent Structural Properties of the 1,10-Decanedicarboxylic Acid/Urea Inclusion Compound

Abstract

Periodic structural properties of the 1,10-decanedicarboxylic acid/urea inclusion compound have been investigated at ambient temperature (high-temperature phase) and at 173 K (low-temperature phase). In the high-temperature phase, the inclusion compound has the hexagonal urea tunnel structure of the conventional urea inclusion compounds, with substantial orientational disorder of the guest molecules. In the low-temperature phase, the urea tunnel structure distorts to form an orthorhombic structure, based on a 2×2×1 supercell of the orthohexagonal cell of the high-temperature structure. There are four independent types of tunnel exhibiting different modes of distortion. Within each type of tunnel there is a comparatively narrow distribution of guest molecule orientations, which correlates well with the observed distortion of the tunnel. The reported results for the 1,10-decanedicarboxylic acid/urea inclusion compound highlight several issues of wider relevance within the context of structural properties of solid inclusion compounds, and these issues are discussed in detail.