Uranyl oxamate hydrates: hydrothermal synthesis, crystal structure, photophysical properties, and selective crystallization

Abstract

Presented here are two isostructural uranyl coordination polymers [UO2(EDO)(H2O)]·H2O (1) and [UO2(BDO)(H2O)]·2H2O (2) (EDO2-=ethylene-1,2-dioxamate; BDO2-=butylene-1,2-dioxamate) with identical stepwise zigzag chain structure and distinct interchain hydrogen bonding interaction, prepared from hydrothermal reaction of DEEDO or DEBDO (DEEDO=diethyl ethylene-1,2-dioxamate; DEBDO=diethyl butylene-1,2-dioxamate) with uranyl ions. The monomeric uranyl-based fluorescence emissions of compounds 1 and 2 are red-shifted by about 6 and 5 nm respectively, compared to that of uranyl nitrate hexahydrate. Compound 1 has stronger emission than compound 2, but both their emissions exhibit triple-exponential decay. The photophysics of uranyl oxalate trihydrate was also investigated for comparison. The selective crystallization of compound 1 in alkaline solution was applied to the sequestration of uranyl ions, showing a kinetic preference.