Chiral Fluorescent Uranyl-Salen-Oligomer for Enantiomeric Supramolecular Recognition of Tryptophan

introduction: The development of enantioselective fluorescent sensors is of great interest for the detection of biologically relevant molecules such as amino acids. Tryptophan (Trp), in particular, plays a critical role in biochemical processes, and its selective recognition remains a challenging task. In this study, we report the synthesis and characterization of a new chiral oligomer based on an oligo-(p‑phenyleneethynylene) backbone functionalized with multiple Lewis acidic metal centers—specifically uranyl ions. This system represents the first example of a uranyl-salen oligomer exhibiting strong fluorescence and high selectivity toward Trp. materials and methods: The chiral oligomer was synthesized via a stepwise coupling of p‑phenyleneethynylene units, followed by complexation with uranyl ions to introduce Lewis acidic centers. The resulting oligomer was characterized using NMR, UV-Vis, fluorescence spectroscopy, and mass spectrometry. Enantioselective binding studies were conducted by fluorescence titration using L- and D-tryptophan. The formation of supramolecular assemblies upon Trp recognition was investigated by dynamic light scattering (DLS) to assess changes in particle size. results: The resulting uranyl-functionalized oligomer displayed significant fluorescence, making it the first example of a fluorescent uranyl-oligomer of this kind. The sensor demonstrated a high affinity for L-tryptophan, with an enantiodiscrimination ratio exceeding 40:1 over the D-enantiomer. The limit of detection was found to be in the sub-ppm range. DLS analysis confirmed the formation of micrometer-sized aggregates upon interaction with Trp, indicating non-covalent host–guest interactions and supramolecular organization. discussion: The unique conjugated structure of the oligomer, combined with the Lewis acidity of uranyl centers, provides a synergistic effect for selective and sensitive detection of L-tryptophan. The significant enantioselectivity observed suggests a specific chiral environment within the oligomeric scaffold, which is not replicated for the D-isomer. The fluorescence response and aggregation behavior further support the role of Trp in driving the formation of higher-order structures through molecular recognition. conclusion: This study presents the first fluorescent uranyl-salen oligomer capable of selectively recognizing L-tryptophan with high sensitivity and enantioselectivity. The system offers new insights into the design of supramolecular sensors based on metal-organic oligomers and opens new avenues for the development of chiral sensing platforms targeting biologically important molecules.