Synthesis of a dihydroquinoline based merocyanine as a 'naked eye' and 'fluorogenic' sensor for hydrazine hydrate in aqueous medium and hydrazine gas

1,2,2,4-Tetramethyldihydroquinoline (TMDQ) is formylated at the 6-position and the resulting quinoline aldehyde is condensed with 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one to obtain a merocyanine 6-pyrazolinyl TMDQ. The merocyanine is a selective and sensitive sensor for hydrazine hydrate in aqueous ethanolic medium and also for hydrazine gas. The merocyanine detects hydrazine hydrate selectively in less than 5 s over other amines, anions, and metals. The detection can be done simply by the naked eye and quantification can be done by absorbance/fluorescence spectroscopy. Hydrazine hydrate as well as hydrazine gas can be detected by the TLC plate technique.