Na+ Selective Fluorescent Tools Based on Fluorescence Intensity Enhancements Lifetime Changes and on a Ratiometric Response

摘要

Over the years, we developed highly selective fluorescent probes for K⁺ in water, which show K⁺‐induced fluorescence intensity enhancements, lifetime changes, or a ratiometric behavior at two emission wavelengths (cf. Scheme 1, >K1–>K4). In this paper, we introduce selective fluorescent probes for Na⁺ in water, which also show Na⁺ induced signal changes, which are analyzed by diverse fluorescence techniques. Initially, we synthesized the fluorescent probes >2, >4, >5, >6 and >10 for a fluorescence analysis by intensity enhancements at one wavelength by varying the Na⁺ responsive ionophore unit and the fluorophore moiety to adjust different K d values for an intra‐ or extracellular Na⁺ analysis. Thus, we found that >2, >4 and >5 are Na⁺ selective fluorescent tools, which are able to measure physiologically important Na⁺ levels at wavelengths higher than 500 nm. Secondly, we developed the fluorescent probes >7 and >8 to analyze precise Na⁺ levels by fluorescence lifetime changes. Herein, only >8 (K d=106 mm) is a capable fluorescent tool to measure Na⁺ levels in blood samples by lifetime changes. Finally, the fluorescent probe >9 was designed to show a Na⁺ induced ratiometric fluorescence behavior at two emission wavelengths. As desired, >9 (K d=78 mm) showed a ratiometric fluorescence response towards Na⁺ ions and is a suitable tool to measure physiologically relevant Na⁺ levels by the intensity change of two emission wavelengths at 404 nm and 492 nm.