Thermochemical properties of U(VI) hybrid materials containing uranyl tetrachloride anions

The enthalpies of formation from simpler components of four hybrid materials bearing the [UO2Cl4]2− anion have been measured and compared to that of Cs2[(UO2)Cl4]. The hybrids contain protonated amines as charge balancing cations that form bifurcated H-bonding interactions with the chloro ligands of the anions. The structure of each material contains similar motifs and the driving force for the formation of the hybrids appears to be the enthalpy of organic cation formation (protonation). The hybrids are energetically much more stable than the corresponding cesium salt without a protonated organic cation.