Negative solvatochromism of merocyanine dyes: Application as water content probes for organic solvents

Two new merocyanine dyes derived from 7-hydroxycoumarin were prepared, and their signaling ability to detect water content in organic solvents was investigated. The dyes exhibited a pronounced negative solvatochromism, and dramatic changes in absorption spectra and λ_max as a function of water content were observed. Solvatochromic behavior was pronounced in regions of less than 5% water content; therefore, these dyes could be used as chromogenic probes for detecting water in common water miscible organic solvents.