The uranyl tetrachloride anion as a tecton in the assembly of U(VI) hybrid materials

Abstract

Seven compounds containing the uranyl tetrachloride anion ([UO₂Cl₄ ]²⁻) have been synthesized through room temperature reactions of uranium (VI) oxyacetate with several pyridinium cations in highly acidic Cl⁻ solutions. The resulting compounds have been characterized viasingle-crystal X-ray diffraction and fluorescence spectroscopy. These compounds represent an importat step in the synthesis of novel uranium-bearing materials in that their assembly explicitly employs the use of non-covalent bonds, specifically through a systematic pairing of [UO₂Cl₄]²⁻ with protonated pyridyl species. Four of these compounds exhibit a bifurcated hydrogen bond (NH⋯Cl₂U) that leads to the formation of a linear “ribbon motif” which has been previously explored in similar perhalometallate systems. The remaining three compounds exhibit different bonding motifs, that likely result from the non-linear geometry of their organic cations.