Structural diversity of uranyl acrylates

Abstract

A series of novel uranyl acrylate compounds with a general composition UO₂(CH₂CHCOO)₂·nH₂O, where n = 0, 2, 2.22, or 3, was synthesized and characterized by powder and single crystal X-ray diffraction, and IR spectroscopy. A comprehensive crystal structure analysis was performed by classical methods along with the method of Voronoi–Dirichlet tessellation to reveal the reasons of the unusual structural diversity of uranyl acrylates. Topological relations in hydrated compounds with molecular [UO₂(CH₂CHCOO)₂(H₂O)₂] complexes, which play the role of the main structural unit, were discussed. Single crystal X-ray diffraction performed at 150 and 250 K indicated a phase transition occurring in the structure of UO₂(CH₂CHCOO)₂·2H₂O. High temperature powder X-ray diffraction evidences a transformation of a sample of UO₂(CH₂CHCOO)₂·2H₂O to the waterless compound in the temperature range of 323–373 K.