Preparation of cucurbit[5]uril - Ln 3+ - based supramolecular assemblies and its effective detection of L -Tryptophan

By introducing Co 2+ ions as a structural inducer, we have successfully synthesized five new Ln 3+ -cucurbit[5]uril-based supramolecular assemblies within the cucurbit[5]uril (Q[5]) system with rare-earth elements (Pr 3+, Sm 3+, Eu 3+, Gd 3+ and Dy 3+ ) by solvent evaporation method. A meticulous analysis of the crystal structure uncovers that the aforementioned assemblies constitute isomorphic 3D frameworks, which are stabilized through outer-surface interactions of cucurbit[n]uril (OSIQ). Within these frameworks, Q[5] directly coordinates with rare-earth metal ions to generate simple “Ln 3+ -Q[5]” molecular bowl structure. Six of these molecular bowls then arrange themselves to create a 3D honeycomb-like framework with channels occupied by the structure-guiding agent [Co(H 2 O) 6 ] 2+ through H-bond. Additionally, we explored the fluorescence sensing capabilities of the assembly 5 for amino acids, which indicate that it holds promise as a fluorescent sensor material, particularly for detecting L -Tryptophan ( L -Try).