A Study Of Spectral Properties Of Naphthalimide Derivatives

1,8-naphthalimides are a class of important fluorescent compounds. The change ofsubstituents and substitution position on the naphthalene ring will affect the spectrum of thecompound; the absorption and fluorescent spectra of the compound in different solvents aredifferent. The paper had studied the absorption and fluorescence spectra of a series of new1,8-naphthalimide derivatives.The absorption and fluorescent spectra of N-ethoxyethanol-1,8-naphthalimide （S3） and4,4’-coupling-N-ethoxyethanol-1,8-naphthalimide derivatives （D2） in different solvents weremeasured. Compared with the compound S3, the maximum absorption wavelength of D2hadred-shifted10nm, the maximum fluorescence wavelength of D2had red-shifted60nm. Andthe fluorescence quantum yield was significantly higher than that of compound S3.Red-shifted fluorescence spectra of the compounds D2were observed in aprotic solvents.The absorption and fluorescent spectra of N-butyl-3-amino-1,8-naphthalimide （S1）,N-butyl-4-amino-1,8-naphthalimide （S2）, N-ethoxyethanol-3-amino-1,8-naphthalimide （S4）and4,4’-coupling-N-butyl-3-amino-1,8-naphthalimide derivatives （D1） in solvent and theaffect of pH of the compound S1and D1were measured. Compared with S1, it found that thespectrum and fluorescence quantum yield of the S4and S1are essentially the similar; themaximum absorption wavelength of S2had red-shifted and the absorption peak in340nmdisappeared, and its maximum emission wavelength of S2had red-shifted about25nm. Inaprotic solvents, the maximum absorption wavelength of the S1and D1are almost the same.Red-shifted absorption spectra of D1were observed in nonprotic solvent. The maximumemission wavelength of D1had blue-shifted40nm. With the increase of pH, the fluorescenceintensity and absorbance of S1was enhanced, accompanying by the red-shifted emissionwavelength. The maximum absorption wavelength had no change; with the increase of pH,there had no change in absorption spectra, the fluorescence of D1was quenchedaccompanying by the red-shifted emission wavelength; but in the strong alkaline conditions,the fluorescence intensity decreased significantly.We used the self-emission fluorescence surfactant OP-10as fluorescent reagent, a newhighly selective method for fluorescence quenching detecting Hg²⁺was built.