Viologen-Based Uranyl Coordination Polymers: Anion-Induced Structural Diversity and the Potential as a Fluorescent Probe

Four novel uranyl coordination polymers (CPs) have been synthesized by the utilization of viologen derivative ligand, 1,1'-bis(3,5-dicarboxyphenyl)-4,4'-bipyridinium (H(4)bdbp . 2Cl), and uranyl nitrate under hydrothermal reactions through the regulation of different kinds of inorganic acids (HF, HCl, HNO3, HClO4, H2SO4). Compound 1 features a unique triple-stranded helix structure with a helical pitch of 31.578 angstrom. The ligands in compounds 2-4 have similar configurations, while their 3D structures are completely different due to the presence of different kinds of anions. The anions play different roles in the frameworks of these uranyl CPs. In addition, compound 2 possesses strong fluorescence both in solid-state and aqueous suspension-state. It is demonstrated that compound 2 can selectively detect Fe3+ over several competing metal cations in aqueous solution.