Neptunyl(VI) Nitrate Coordination Polymer with Bis(2-pyrrolidone) Linkers Highlighting Crystallographic Analogy and Solubility Difference in Actinyl(VI) Nitrates

NpO2(NO3)2 units are connected by bis(2-pyrrolidone) linker molecules with trans-1,4-cyclohexyl bridging part (L1) to form a 1-dimensional coordination polymer, [NpO2(NO3)2(L1)] n. Molecular and crystal structures of this compound are nearly identical to that of UO22+ analogue, while its aqueous solubility is much enhanced probably due to weaker thermodynamic stability of complexation in NpO22+ compared with that in UO22+.