A novel off–on fluorescence chemosensor for Ca2+ based on Rhodamine–Coumarin Schiff base derivative

A novel sensor, 7-Hydroxy-4-methylcoumarin-8-carbaldehyde-(rhodamine) hydrazone (l) has been synthesized and investigated as a fluorescence chemosensor for Ca2+ in acetonitrile. The compound is found preferential binding to Ca2+ in presence of large excess of other competitive ions with associated changes in its optical and fluorescence spectral behavior. Upon the addition of Ca2+, an overall emission change of 64-fold was observed. Photoinduced electron transfer (PET) process, coupled with the intramolecular charge transfer (ICT) process, are proposed to explain the observed spectral response.