Radiationless deactivation of excited molecules of 4-aminonaphthalimides

Abstract

The effects of alkylation of the 4-amino group, polarity and viscosity of a solvent, and temperature on the fluorescence of N-(2,4-dimethylphenyl)imides of 4-aroino-1,8-naphthalenedicarboxylic acid were studied. A decrease in the temperature and polarity of a solvent and an increase in its viscosity cause the rate of radiationless deactivation of 4-dimethylaminonaphthalimide to decrease and have almost no effect on the rate of eroissive deactivation of excited state. The abnormally low efficiency of fluorescence of 4-dimethylaminonaphthalimide in polar low-viscosity media at room temperature is associated with the formation of a nonfluorescent charge-transfer state. The increase in the rate of radiationless deactivation of 4-aminonaphthalimide in the alkylation of its amino group is associated with the increase in its electron-donor ability.Key words: 4-aminonaphthalimide, fluorescence, radiationless deactivation, donor-acceptor interaction.Derivatives of 4-aminonaphthalimides are used as active laser media I and fluorescent labels, z The luminescent properties of these compounds are strongly dependent on the structure of the molecule and solvent. The fluorescence of naphthalimides containing the 4-amino-or 4-monoalkylamino group is characterized by a high quantum yield independent of the solvent, whereas the quantum yield of fluorescence of 4-(N,Ndialkylamino)naphthalimides is strongly dependent on the nature of the solvent, z,3 The nineteen-fold decrease in the quantum yield of fluorescence in ethanol on going from 4-amino-to 4-(N,N-dialkylamino)naphthalimide has been explained by the violation of planarity of the dialkylaminonaphthalimide molecule) The strong effect of substitution in the amino group on luminescent properties of derivatives of 4-aminobenzonitriles, coumarins, and other compounds is associated with a change in the extent of the charge transfer in the excited state 4-~ and in the molecular structure (with a change in hybridization 5 and rotation of the fragments4,6). A rearrangement of the closest environment of the molecule or a change in its structure in the excited state results in the dependence of the efficiency of fluorescence of such systems on the viscosity and polarity of the medium. 4,6 In this work, the effects of the structure of the 4-amino substituent, of the polarity and viscosity of a solvent, as well as the effect of temperature on the fluorescent properties of N-(2,4-dimethylphenyl)imides of 4-amino-1,8-naphthalenedicarboxylic acid were studied to elucidate the reasons for the different fluorescent ExperimentalAbsorption and fluorescence spectra were recorded on a Shimadzu UV-3100 spectrophotometer and an Elyumin 2M spectrofluorimeter, respectively. The kinetics of fluorescence was studied on a nanosecond ORTEC spectrometer by photon counting. The quantum yield of fluorescence (g~) was determined by comparing the areas under the curves of corrected fluorescence spectra of the compound under study with those of a solution of quinine bisulfate in I N H2SO 4 (cp = 0.546). 7 Polym...

Controlling photophysics of styrylnaphthalimides through TICT, fluorescence and E,Z-photoisomerization interplay

“…Hence, the changes in the dipole moment of 20.78 D, 21.96 D and 22.95 D correspond to unit charge separation by 4.33 Å, 4.58 Å and 4.78 Å, which is clear evidence of charge transfer state formation, and also is in a good agreement with the (m e m g ) values obtained for 1,8-naphthalimides with different electron-donating groups at the 4th position of the naphthalene ring. 32,[48][49][50][51][52] Fluorescence quantum yields of compounds NI1-3 were dramatically influenced by the solvent polarity (Table 1), however, the character of changes was quite complex to be understood only on the basis of the steady-state spectroscopy data. Apparently, to get a deeper insight into the processes occurring after the photoexcitation, time-resolved experiments were strongly needed.…”

“…Indeed, in most of the cases, TICT states of 4-amino-1,8-naphthalimides are not fluorescent or weakly fluorescent, which is a reason commonly used to explain the quenching effect of polar protic solvents on the emission intensity. [51][52][53] With this point of view, compounds NI1 and NI2 appear to be very interesting, because their TICT fluorescence remains approximately at the constant level when the polarity of a protic (for NI1) or aprotic (for NI2) solvent increases.…”

Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers

“…18, 19 1,8-Naphthalimide, in particular 4-amino-1,8-naphthalimide, derivatives are a well-studied class of environmentalsensitive dyes. [23][24][25][26][27][28][29] This a priori non-ionic chromophore shows intense absorbance and emission in a convenient range of the visible spectrum, while it is rather insensitive to photooxidation and to quenching by oxygen. Also, due to the relatively small size and the rather polar, yet non-ionic character, it is less prone to hydrophobic self-aggregation in water and to unspecic electrostatic interactions than most of the standard uorescent labels, such as pyrene, uorescein or rhodamine.…”

Influence of the configuration of the amine nitrogen atom on the efficiency of fluorescence of 4-aminonaphthalimide derivatives

“…The efficiency of fluorescence of N,N-diaklyl derivatives of 4-aminonaphthalimide, on the contrary, appreciably decreases with increasing solvent polarity. Strong influence of substitution in the amino group on the luminescence properties of 4-aminonaphthalimides is attributed to variation of the extent of the charge transfer in the excited state [2]. A considerable decrease in the quantum yield of the fluorescence in going from unsubstituted 4-aminonaphthalimide to 4-(dimethylamino)naphthalimide in polar solvents (by a factor of 28 in ethanol) is due to an increase in the efficiency of formation of the nonfluorescing chargetransfer state with an increase in the electron-donor power of the amino group [3].…”

“…The spectral and luminescence properties of alkyl-substituted 4-aminonaphthalimide derivatives are determined by the solvent and the structure of the amino group at the 4-position [2]. Fluorescence of 4-aminonaphthalimide and its mono-4-N-alkyl derivatives is characterized by the high quantum yield in all the examined solvents.…”