The coumarin conjugate: synthesis, photophysical properties and the ratiometric fluorescence response to water content of organic solvent

A new fluorescent probe based on coumarin conjugate has been synthesized which shows high quantum yield because of strong ICT effect. The absorption and fluorescence spectra of probe were measured in a variety of solvents and the Stokes shifts were found to be in linear relationship with the orientation polarizability of the solvents. The fluorescence intensity of probe decreased with a rise in water content which could be an effective fluorescence water sensor in organic solvents. Moreover, the probe presents a highly linear ratiometric fluorescence response to water content under the excitation of ultraviolet light. The detection results by the ratio metric fluorescence probe are in good agreement with that by the well-established standard Karl Fischer method. This ratiometric fluorescent probe provides another accessible tool for the quantitative determination of water content and may replace the Karl Fischer method for specific applications.