Turn-On Fluorescent Chemosensor for Fluoride Based on Pyreneamide Derivative

Abstract

On account of the important roles of anion in biological, clinical, environmental, catalysis, and chemical processes, the selective and efficient recognition of anion is an area of growing interest in supramolecular chemistry. In particular, the studies of chemosensors toward F− anion are quite intriguing because of its beneficial effects in human physiology. Also, fluoride is interest due to its established role in dental care and osteoporosis. However, an excess of fluoride ion can lead to fluorosis. Therefore, the development of reliable sensors for F− is needed for environment and human health care. Color changes that can be detected by the naked eye are widely used as signals for events owing to the inexpensive equipment required or no equipment at all. Among anion receptors, colorimetric and fluorescent chemosensors are important because they provide high sensitivity and convenience for monitoring the anion recognition. Especially, pyrenes are a particularly elegant basis for ratiometric based optical sensors, where the ratio of two emission wavelengths comprise the analytical signal. To date the pyrene excimer/monomer system has been exploited mainly for cation sensing and increasingly for anion sensing. In most fluorescent sensors involves photophysical changes such as photoinduced electron transfer (PET), photoinduced charge transfer (PCT), metal-to-ligand charge transfer (MLCT) for fluorescent chemosensors. Here, we report a novel pyreneamide chemosensor 1 with a specific optical response to F−. In pursuit of a selective fluoride chemosensor, a pyreneamide derivative 1 was synthesized, and its anion binding properties were investigated by H NMR, UV-vis spectroscopy, color changes, and fluorescence titration analysis. Pyreneamide derivative 1 was prepared by treating 3 with bipyridine in high yield. Finally, the chloride ion of 2 was replaced with PF6 − by a simple reaction with NaPF6 as shown in Scheme 1.