Intriguing H-Aggregate and H-Dimer Formation of Coumarin-481 Dye in Aqueous Solution As Evidenced from Photophysical Studies (original) (raw)
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Substituent and solvent effects on the photo-physical properties of some coumarin dyes
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2010
Absorption and fluorescence spectra of three coumarin dyes with various substituents and alkyl groups have been recorded in solvents in the range of 200-730 nm. The photo-physical behavior of dissolved dye depends on the nature of its environment, i.e. the solvatochromic behaviors of coumarin dyes and solvent/solute hydrogen bonding interactions can be analyzed by means of linear solvation energy relationships concept proposed by Kamlet and Taft. The intensity, shape, and maximum wavelength of the absorption and fluorescence band of these dyes in solution depend strongly on the solvent-solute interactions and solvent nature. Hydrogen bonding interactions (specific solute-solvent interactions) between these dye-solvent complex and dipolarity/polarizability (non-specific solute-solvent interactions) control reorientation of solvent molecules around the dye.
International journal of scientific research in computer science, engineering and information technology, 2019
Coumarin derivatives are extensively investigated in terms of their photo physical properties to understand excited state in regard to understand and innovate molecules. In this article we study steady state quenching of fluorescence of a coumarin derivative namely 3-Hydroxy-3-[2-oxo-2-(3-oxo-3H-benzo[f]chromen-2-yl)ethyl]-1,3-dihydro-indol-2-one (3HBCD) in binary mixture of acetonitrile and 1,4 dioxane. Dimethylaniline is used as quencher. A negative deviation is seen with modest quencher concentration in the Stern-Volmer (S-V) plots. The quenching ability of Dimethylaniline in reference to aniline is more due to its higher ionization energies.
Photochemistry and Photobiology, 2009
Photophysical studies on coumarin-7 (C7) dye in different protic solvents reveal interesting changes in the properties of the dye on increasing the solvent polarity (Df; Lippert-Mataga solvent polarity parameter) beyond a critical value. Up to Df 0.31,thephotophysicalpropertiesofthedyefollowgoodlinearcorrelationswithDf.ForDf>0.31, the photophysical properties of the dye follow good linear correlations with Df. For Df >0.31,thephotophysicalpropertiesofthedyefollowgoodlinearcorrelationswithDf.ForDf>0.31, however, the photophysical properties, especially the fluorescence quantum yields (F f), fluorescence lifetimes (s f) and nonradiative rate constants (k nr), undergo large deviations from the above linearity, suggesting an unusual enhancement in the nonradiative decay rate for the excited dye in these high polarity protic solvents. The effect of temperature on the s f values of the dye has also been investigated to reveal the mechanistic details of the deexcitation mechanism for the excited dye. Studies have also been carried out in deuterated solvents to understand the role of solute-solvent hydrogen bonding interactions on the photophysical properties of the dye. Observed results suggest that the fluorescence of the dye originates from the planar intramolecular charge transfer (ICT) state in all the solvents studied and the deviations in the properties in high polarity solvents (Df >$0.31) arise due to the participation of a new deexcitation channel associated with the formation of a nonfluorescent twisted intramolecular charge transfer (TICT) state of the dye. Comparing present results with those of a homologous dye coumarin 30 (C30; Photochem. Photobiol., 2004, 80, 104), it is indicated that unlike in C30, the TICT state of the C7 dye does not experience any extra stability in protic solvents compared to that in aprotic solvents. This has been attributed to the presence of intramolecular hydrogen bonding between the NH group (in the 3-benzimidazole substituent) of the C7 dye and its carbonyl group, which renders an extra stability to the planar ICT state, making the TICT state formation relatively difficult. Qualitative potential energy diagrams have been proposed to rationalize the differences observed in the results with C7 and C30 dyes in high polarity protic solvents.
Photophysical Properties of Coumarin-30 Dye in Aprotic and Protic Solvents of Varying Polarities¶
Photochemistry and Photobiology, 2004
Experimental results on various photophysical properties of coumarin-30 (C30) dye, namely, Stokes' shift (Av), fluorescence quantum yield (Qf), fluorescence lifetime (q), radiative rate constant (kf) and nonradiative rate constant (knr), as obtained using absorption and fluorescence measurements have been reported. Though in most of the solvents the properties of C30 show more or less linear correlation with the v o s t e d on the website on 28 May 2004 *To whom conespondence should be addressed Radiation Chemistry and
Part I. Photophysics of Coumarin 343 at liquid/liquid interface
2005
Pico-second time-resolved time-correlated single photon counting (TCSPC) technique under the total internal reflection (TIR) condition has been used to study the photophysical properties of Coumarin 343 (C343) dye molecules adsorbed at the water/1,2-dichloroethane (DCE) interface. The fluorescence decay profile of C343 under TIR condition at the water/DCE interface was non-exponential and fitted to the double exponential decay function with the fluorescence lifetimes 0.3 and 3.6 ns, which proved the existence of two different forms of C343 species having largely different lifetimes at the interface. The longer fluorescence lifetime component of C343 at the interface is attributed to the emission from the monomeric form of the dye molecules and the shorter lifetime component is due to the aggregation of dye molecules. The penetration depth dependence of decay curves indicated no change in the fluorescence lifetime components, however, the amplitude corresponding to the lifetime of aggregate increased and the amplitude corresponding to the lifetime of monomer decreased with the decrease in penetration depth of the aqueous phase from the interface. Aggregation is significant in the interfacial layer. The decrease in monomer lifetime at the interface compared to that in the bulk solution is interpreted in terms of excitation energy migration between the dye molecules.
Time-resolved spectra of coumarin 30-rhodamine 6G dye mixture
Pramana
The effect of acceptor concentration on the energy transfer from Coumarin 30 (donor) to Rhodamine 6G (acceptor) has been studied. The nature of energy transfer reaction has been studied through lifetime measurements by recording the time-resolved fluorescence decay curves. The energy transfer parameters calculated were used to confirm the occurrence of energy transfer on the basis of the emission-reabsorption effect.
Indian Journal of Pure and Applied Physics
Studies of steady state and time resolved methods of fluorescence quenching of excitation energy of three coumarin dyes by aniline were carried out in toluene solvent only to understand the role of diffusion in the quenching mechanism. The coumarin dyes (dye1, dye2 and dye3) were excited directly by UV radiation of 350 nm and probabilities of quenching per encounter p (or p') were determined in the toluene solvent. Further, the activation energy E'a (or E'a) of quenching was determined using the literature values of activation energy of diffusion Ed and the experimentally determined values of p (or p'). Magnitudes of p (or p') as well as the values of Ea (or E'a) suggest that the quenching reaction is predominantly controlled by material diffusion.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2000
Ground and excited state properties of a pre-twisted 7-diethylaminocoumarin dye (BC I) belonging to the family of coumarinyl benzopyrano pyridines are reported in isooctane -AOT -formamide reversed micelles. In reversed micelles, BC I, albeit soluble in formamide, is found to remain out of the polar solvent pool. But the photophysical properties of the probe dye are sensitive to the changes in the polarity of the interfacial region caused by increase in F 0 =[formamide]/[AOT]. The spectroscopic properties and dynamics are indicative of dual emission due to the solubilization of the dye in two different environments (the nonpolar solvent and the interfacial region). Results of the steady-state fluorescence anisotropy experiments also support the presence of two different environments. The present study once again proves that molecular size is an important parameter in the study of the photophysical properties of the flexible aminocoumarin dyes in reversed micelles.
Effect of binary solvent mixtures (DMSO/water) on the dipole moment and lifetime of coumarin dyes
Journal of Molecular Structure, 2008
Absorption and fluorescence spectra of four coumarin laser dyes, Coumarin 440 (C440), Coumarin 450 (C450), Coumarin 466 (C466) and Coumarin 151 (C151), have been recorded in binary mixtures of DMSO and water at room temperature (298 K) to study the solvent effect and to evaluate the ground and excited state dipole moments using solvatochromic shift method. The anomalous feature in the complex systems of these mixtures due to the structural heterogeneities is discussed. The effect of solvent polarity parameters of binary mixture on the ground and excited state dipole moments was examined. Experimental results indicate that the dipole moments in the excited state, for all the molecules investigated, are higher than the corresponding values in the ground state. The ground and excited state dipole moments of these probes have also been computed from ab initio calculations and compared with those obtained experimentally. Fluorescence lifetimes of all the probes measured using time domain fluorescence spectrometer employing time correlated single photon counting technique, show a nonlinear variation with the composition of binary mixture.