A coumarin-based fluorescent PET sensor utilizing supramolecular pK(a) shifts

作者：Saleh Na'il^*; Al Soud Yaseen A; Al Kaabi Leena; Ghosh Indrajit; Nau Werner M

来源：Tetrahedron Letters, 2011, 52(41): 5249-5254.

DOI：10.1016/j.tetlet.2011.07.138

• Photoinduced electron transfer (PET)
• pK(a) Shifts
• Fluorescence
• Sensors
• Host-guest systems
• Cucurbiturils
• Coumarin
• Benzothiazole
• Piperazine

A new coumarin derivative containing benzothiazole and piperazine substituents was synthesized. Preferential inclusion of the benzothiazole group, over the coumarin and piperazine groups, inside the cavity of the molecular container cucurbit[7]uril (CB7) was evidenced by using optical and NMR techniques. The binding constant of the new complex with CB7 is higher in its protonated forms (e.g., K = 2.8 x 10(6) M-1) than in its neutral forms, which led to an increase in the pK(a) value associated with protonation of the aza nitrogen on the benzothiazole ring of ca. 2.5 units. Such CB7-induced protonation disabled the photoinduced electron transfer (PET) in the included molecule, enhancing its coumarin fluorescence up to ca. 45-fold (pH 3.5, 410 nm). The results are discussed in the context of designing sensitive analytical tools for reversible monitoring of optically inactive analytes by competitive displacement experiments.

• 出版日期2011-10-12