Synthesis and spectral properties of fluorescent dyes based on 4-styryl-1,8-naphthalimide

Abstract

The paper reports on synthesis and spectroscopic study of novel N-butyl-4-styryl-1,8-naphthalimide dyes bearing methoxy (1), dimethoxy (2), and dimethylamino (3) groups in the styryl fragment. It is shown that all synthesized compounds demonstrate positive solvatochromism, high values of Stokes shift in polar solvents, and fluorescence in the long wavelength part of visible range. These facts indicate a potential application of these compounds as fluorescent dyes in the biochemistry. The changes in the dipole moments of the molecules caused by excitation were estimated using Lippert—Mataga equation. The obtained results could be assigned to the formation of the excited states with intramolecular charge transfer. The formation of the twisted states with charge transfer was suggested in the case of compound 3, while the fluorescence quantum yield was significantly reduced in polar protic solvents.