Study on the spectral and inclusion properties of a sensitive dye, 3-naphthyl-1-phenyl-5-(5-fluoro-2-nitrophenyl)-2-pyrazoline, in solvents and β-cyclodextrin

• Synthesis of a naphthalene–pyrazoline based fluorescence reagent.
• The reagent is a potential probe for primary amine analytes.
• The compound and its phenylephrine derivative exhibit interesting photo physical properties in various solvents.

3-Naphthyl-1-phenyl-5-(5-fluoro-2-nitrophenyl)-2-pyrazoline (NPFP), a fluorogenic probe and its derivative NPFP-Phenylephrine were synthesized and their absorption and fluorescence properties were recorded in solvents of varying polarity. Spectroscopic studies reveal that, the solvatochromic behavior of the compounds depend not only on the polarity but also on the hydrogen-bonding properties of the solvents. The effects of β-cyclodextrin on the fluorescence properties of both compounds were studied. It was found that there is an enhancement in the fluorescence intensity of labeled drug (NPFP-Phenylephrine) in the presence of β-cyclodextrin. In the present study, the molecular motions of NPFP-Phenylephrine embedded in a β-cyclodextrin cavity have been investigated by fluorescence techniques in steady-state and time resolved modes.

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