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

• We synthesized a new push–pull conjugate (D–π–A structure) dye which displays ICT process.
• This dye shows ratiometric pH-sensing in the low pH region.
• This dye exhibits a reversible color change from yellow to colorless with increasing pH in the pH range of 0–3.
• This dye is also useful as a fluorescent pH sensor 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.

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