Noncomplexed Cucurbituril-Mediated Structural Evolution of Layered Uranyl Terephthalate Compounds

Template synthesis is one of the most feasible ways to explore new uranyl compounds with intriguing structures and properties. Here we demonstrate the preparation of six novel "sandwichlike" uranyl coordination polymers (UCPs) based on two-dimensional uranylterephthalate acid (H2TP) networks using CBn (n = 5, 6, 8) as template ligands in the presence of different cations (Na+, K+, Cs+, or H2N(CH3)(2)(+)). Compound 1 ([UO2(TP)(2)][Na-2(CB5)(H2O)](H2O)(5)) is composed of layered uranyl-TP networks with the complex of CB5 and sodium cations as template ligands. In compound 2 ([(UO2)(2)(TP)(3)](2) (CB6)(H2O)(10)), CB6 located between uranyl-TP networks contacts them by pi-pi interactions and hydrogen bonds. Compound 3 ([(UO2)(2)(TP)(3)](2) (TP)(3)](2) [Na-2(H2O)(10)(CB6)]) is the same as compound 2 except for sodium cations bonding with CB6. Similarly in compound 4 ([UO2)(2)(TP)(3)][Cs(H2O)(3)(CB6)]), CB6 is a capsulelike structure capped with two cesium cations and interacts with uranyl-TP networks through pi-pi and C-H center dot center dot center dot pi interactions. Compound 5([UO2)(2) (TP)(3)(HCOO)(2)][K-(H2O)(2)(CB5)](2)[H2N(CH3)(2)](2)(CB6)(H2O)(6)) consists of both templates of CB6 and CBS in which each CBS is capped with one potassium cation while the H2N(CH3)(2)(+) cation is held at CB6 portals. In compound ([UO2)(2)(TP)(3)](2)[UO2(TP)(2)(H2O)(2)][Cs(CB8)(3)(H2O)(4)](H2O)(16)), CB8 ligands are connected by cesium cations to form a triangle motif and are further located between the uranyl-TP networks as template agents. All of the 2D layered structures with free CBn or cation-anchored CBn intercalate into the laminates of uranyl-terephthalate and shows a cucurbituril-mediated structural evolution. The regulating role of CBn as structure-directing template agents for the construction of layered UCPs through outer-surface interactions with layers of uranyl terephthalate is demonstrated, especially for the case of CB6 with contractive interlayer spacing.