2-{2-[4-(Dimethylamino)phenyl]-6-methyl-4H-pyran-4-ylidene}malononitrile: a colorimetric and fluorescent chemosensor for low pH values.

For developing intramolecular charge transfer (ICT) chemosensors for low pH values, 2-{2-[4-(dimethylamino)phenyl]-6-methyl-4H-pyran-4-ylidene}malononitrile (DPM) was designed and synthesized. The spectroscopic and pH-sensing properties of DPM were investigated by UV-Vis and fluorescence spectroscopy. This sensor exhibited a pH-dependent ratiometric absorption property in the range of pH 0-3, along with a reversible color change from yellow to colorless with increasing acid concentration. The fluorescence intensity of the sensor was increased with increasing pH within the pH range of 0-2.