Template-Driven Assembly of Rare Hexameric Uranyl-Organic Rotaxane Networks Threaded on Dimeric Uranyl Chains

Despite the rise of uranyl-organic rotaxane compounds along with the prosperity of uranyl-organic frameworks, uranyl-based polyrotaxane compounds with high nuclearity have been rarely reported. In this work, a novel twofold nested uranyl polyrotaxane compound (1, [ (UO2)3O(OH)3(C4CA4@CB6)1.5]·[(UO2)(OH) (H2O) (C4CA4@CB6)0.5)]) with two different moieties, hexameric networks and dimeric chains, has been synthesized from C4CN4@CB6 (L1) using C4N4@CB6 (L3) as the induction agent. It is worth noting that the hexameric uranyl SBUs found here represent the highest nuclearity of uranyl found by far in uranyl-organic rotaxane frameworks. When starting from C4CN3@CB6, a positional isomer of C4CN4@CB6 (L2), compound 2 ([(UO2)(H2O)(NO3)(C4CA3@CB6)]·[(C4CA3@CB6)]) was obtained, which contains a one-dimensional polyrotaxane chain linked by another set of noncoordinated C4CA3@CB6 motifs through hydrogen bonding. Further characterization of compound 1 by fluorescence, IR, and Raman spectra was performed to analyze the f...