Solvatochromic effects in the fluorescence of a few diamino aromatic compounds (original) (raw)
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Fluorescence properties of aromatic asymmetric di-ketone compound in polar and non-polar solvents
Journal of Physics: Conference Series
Using the quantum chemical and solvatochromic shift technique aromatic unsymmetric di-ketone compound1-(4'-dodecyl-[1,1'-biphenyl]-4-yl)-3-(3,4,5trimethoxyphenyl)propane-1,3-dione (DK1) fluorescence properties were estimated. The excitation and emission band of recently synthesized DK1 have been examined in various dissolvable. The dipole moments evaluated utilizing Gaussian software and Solvatochromic correlations. Evaluated (μg) value by Gaussian method is comparatively larger than the solvatochromic shift methods. It is seen that the energized state dipole moments (μe) are more prominent than the ground state dipole moment (μg) which authorizes π → π* transition. The (Δμ) were also estimated both from solvatochromic shift method and microscopic solvent polarity parameter (ET N) and results are compared. The kinetic stability and chemical reactivity of the selected molecules have been studied with the help of quantum chemical properties of the molecule and Frontier molecular orbital analysis using DFT.
Solvatochromic Shifts on Absorption and Fluorescence Bands of N , N -Dimethylaniline
Journal of Chemical Theory and Computation, 2009
A theoretical study of the absorption and fluorescence UV/vis spectra of N,Ndimethylaniline in different solvents has been performed, using a method combining quantum mechanics, molecular mechanics, and the mean field approximation. The transitions between the three lowest-lying states have been calculated in vacuum as well as in cyclohexane, tetrahydrofuran, and water. The apparent anomalies experimentally found in water (a blue shift in the absorption bands with respect to the trend in other solvents, and an abnormally high red shift for the fluorescence band) are well reproduced and explained in view of the electronic structure of the solute and the solvent distribution around it. Additional calculations were done with a mixture of cyclohexane and tetrahydrofuran as solvent, which displays a nonlinear solvatochromic shift. Results, although not conclusive, are consistent with experiment and provide a possible explanation for the nonlinear behavior in the solvent mixture.
Molecules
The properties of 1,4-isocyanoaminonaphthalene (1,4-ICAN) and 2,6-isocyanoaminonaphthalene (2,6-ICAN) isomers are discussed in comparison with those of 1,5-isocyanoaminonaphthalene (1,5-ICAN), which exhibits a large positive solvatochromic shift similar to that of Prodan. In these isocyanoaminonaphthalene derivatives, the isocyano and the amine group serve as the donor and acceptor moieties, respectively. It was found that the positions of the donor and the acceptor groups in these naphthalene derivatives greatly influence the Stokes and solvatochromic shifts, which decrease in the following order: 1,5-ICAN > 2,6-ICAN > 1,4-ICAN. According to high-level quantum chemical calculations, this order is well correlated with the charge transfer character of these compounds upon excitation. Furthermore, unlike 1,5-ICAN, the 1,4-ICAN and 2,6-ICAN isomers showed relatively high quantum yields in water, that were determined to be 0.62 and 0.21, respectively. In addition, time-resolved fl...
Solvatochromic properties of a new isocyanonaphthalene based fluorophore
Journal of Photochemistry and Photobiology A: Chemistry, 2013
The photophysical properties of a new naphthalene based fluorophore, namely the 1-amino-5isocyanonaphthalene (ICAN) investigated by steady-state and time-resolved fluorescence methods are reported. The molecule showed positive solvatochromic properties, that is a more than v = 4800 cm −1 red-shift of the emission maximum was observed (from 409 nm in hexane to 513 nm in water). The fluorescence quantum efficiency was found to decrease with increasing solvent polarity, from an excellent F = 0.95 in 1,4-dioxane to ˚F = 0.04 in water. The Kamlet-Taft theory turned out to give the most appropriate description of the solvatochromic properties of the ICAN in various solvents including both protic and non-protic solvents. By carrying out experiments in cyclohexane/tetrahydrofuran binary mixtures of different compositions, evidence was found for the preferential solvation of ICAN. Based on laser light flash photometry measurements the radiative decay rate of ICAN was determined for six different solvents of largely different polarity. The decay rates show only minor solvent dependence and the life-times of the excited states are in the order of 10 ns which are in good agreement with the calculated values. The practical applicability of ICAN was demonstrated by determining the critical micelle concentration of sodium laurylsulfate in water.
Solvent effect on photophysical properties of a fluorescence probe: BMVC
Journal of Luminescence, 2006
The photophysical properties of N-methyl-1,8-naphthalimide (NI) and 4-phenoxy-N-methyl-1,8-naphthalimide (4-PNI) are studied by steadystate and time-resolved emission measurements. Both absorption and fluorescence spectra are red-shifted when the electron donor phenoxy group (-OPh) is introduced at the C-4 position. Compared to NI, the spectral shift in acetonitrile is 27 and 42 nm for the absorption and fluorescence, respectively. The 4-PNI shows high fluorescence emission in non-polar aprotic solvents that can be ascribed to stabilization of the S 1 state. The emission intensity of the 4-PNI decreases by addition of water to dioxane solution, and the fluorescence quenching occurs by combination of dynamic and static contribution ascribed to specific solute-solvent interaction.
Electronic Absorption and Fluorescence Spectra of Fluorescein in Aprotic Solvents
Spectroscopy Letters, 1990
Electronic absorption and fluorescence spectra of dipyridamole, a coronary vasodilator drug, were monitored in aqueous solutions as a function of pH in the range between 13 and 2. The spectra were decomposed into Gaussian components and the parameters were obtained and compared both in aqueous solution at different pHs and in several other solvents. The extinction coefficients were also obtained as well as the quantum yields and fluorescence lifetimes. At pH 7.0 e 415 = (5.4 ± 0.2)x10 3,~fluor = 0.95±0.05 and Tfluor = 17.8±0.4 ns, while at pH 5.0~-(4.8±0.2)x10, d~flaor = 0.16±0.01 and 1•fluor = 5.7±0.2ns. The decrease of pH is accompanied by sharp fluorescence changes in two different regions: in the range of pH 13-12 an increase of fluorescence is observed (pK 1 12.5) while in the range of pH 6.5-5.0 a dramatic decrease of fluorescence (pK2 5.7) is apparent. Changes in the position and shape of the absorption bands are also observed in this pH range (around pK2). A Förster cycle calculation using absorption and fluorescence data shows that the pKa of the excited state is around 1 unit below pK2. Similar changes are also observed in ethanolic solution of DIP with addition of acid. They could be explained as probably due to the protonation of two types of nitrogen atoms which are part of the structure of the DIP molecule. Changing the ionic strength of the solution in the range 0-0.1M gives only a slight (10%) decrease of the fluorescence intensity and does not affect the absorption spectrum of DIP. This suggests that ionic association is not very effective in changing the spectral properties of DIP.