Study of Fluorescence Quenching of Coumarin Dye by Dimethyl Aniline In Binary Solvent Mixtures - A negative deviation (original) (raw)
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Effect of amino anilines on the fluorescence of coumarin derivative
Journal of Luminescence, 2018
The effect of stereo electronic factors of amino anilines such as orthophenylenediamine (OPD) and para-phenylenediamine (PPD) on the fluorescence of 5,6-benzo-4-azidomethyl coumarin (5BAMC) in polar aprotic and polar protic solvents has been studied. From UV absorption and 1 H NMR studies, observed blue shift in the presence of PPD is due to H-bonding with 5BAMC. Fluorescence quenching studies indicate the role of static and dynamic quenching mechanisms for both the quenchers and larger quenching efficiency of PPD than OPD. The sphere of action static quenching and finite sink approximation models reveal static effect in the excited state and diffusion limited bimolecular quenching reactions. Electrochemical analysis indicates that quenching efficiency of PPD is more than OPD based on the magnitudes of free energy change for electron transfer. Binding equilibria analysis confirms that the magnitude of binding between PPD and 5BAMC is stronger compared to OPD. It is also noticed that the binding between PPD and 5BAMC in polar protic solvents is stronger than that in aprotic solvents. Lastly, from the magnitudes of thermodynamic parameters, interaction between PPD and 5BAMC is hydrophobic and spontaneous. Thus from the present investigation, it is concluded that the separation between two -NH 2 groups in amino anilines plays role in their interaction with coumarin derivative 5BAMC.
Solvent Effect on Fluorescence Quenching of 7, 8 Benzo-4-azido Methyl Coumarin by Aniline
Fluorescence quenching of biologically active studies of 7, 8 benzo-4-azidomethyl coumarin (7BAMC) by aniline in four different organic solvents namely benzene, dioxane, tetrahydrofuran and acetonitrile has been carried out at room temperature with a view to understand the quenching mechanisms. The Stern–Volmer (S-V) plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the ground state complex formation and sphere of action static quenching models. Using these models various quenching rate parameters have been determined. The magnitudes of these parameters suggest that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R’ and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R’ and D with the values of the encounter distance R and the mutual coefficient D determined using the Edward‘s empirical relation and Stokes – Einstein relation.
On the Fluorescence Quenching of Substituted Coumarins
2015
In the present work the effect of different concentration of halide quenchers (Cl, Br, I) on 4-methyl-5-ethoxy-7-methoxy coumarin (1) and 4-methyl-5,7-diethoxy coumarin (2) in aqueous solutions have been carried out at 20 temperature. It was observed that the fluorescence intensity of these coumarin derivatives decrease with increase in the concentration of the quenchers except Cl quencher. Further, it was observed that the quenching due to halide ions proceeds via both a diffusional and static quenching process. The rate constants for diffusional as well as static component of quenching process have been calculated using modified Stern–Volmer relation. From the observed data it was found that I ion has very high quenching ability than Br ion and Cl ion behaves almost like a non-quencher. It was interpreted in terms of the sphere of action model by showing that the value of radius of sphere of action of the halide ion quencher is greater than the sum of the radii of the respective c...
Indian Journal of Pure and Applied Physics
Abstract Solvent effect of fluorescence quenching of biologically active studies of 6-methoxy-4-azidomethyl coumarin (6MAMC) by aniline in five different solvents namely dioxane, tetrahydrofuran, dichloroethane, dimethylformamide and acetonitrile has been carried out at room temperature with a view to understand the quenching mechanisms. The Stern–Volmer (S-V) plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the ground state complex formation and sphere of action static quenching models. Using these models various quenching rate parameters have been determined. The magnitudes of these parameters suggest that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check these bimolecular reactions as diffusio...
Solvent effect of fluorescence quenching of biologically active studies of 6-methoxy-4-azidomethyl coumarin (6MAMC) by aniline in five different solvents namely dioxane, tetrahydrofuran, dichloroethane, dimethylformamide and acetonitrile has been carried out at room temperature with a view to understand the quenching mechanisms. The Stern-Volmer (S-V) plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results, we have invoked the ground state complex formation and sphere of action static quenching models. Using these models, various quenching rate parameters have been determined. The magnitudes of these parameters suggest that sphere of action static quenching model agrees well with the experimental results. Hence, the positive deviation is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R' and mutual diffusion coefficient D. Finally, an effort has been made to correlate the values of R' and D with the values of the encounter distance R and the mutual coefficient D determined using the Edward's empirical relation and Stokes-Einstein relation.
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.
Fluorescence quenching of coumarins by halide ions
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2004
Fluorescence quenching of 4-methyl-7-methoxy coumarin (1) and 4-methyl-5-ethoxy-7-methoxy coumarin (2) in aqueous solutions have been studied at different concentrations of halide ions (Cl − , Br − , I − ), at room temperature ∼20 • C. It is observed that the fluorescence intensity of both the coumarin compounds (1 and 2) decrease with increase in the concentration of Br − and I − ions but remains almost constant in case of Cl − ion. It is observed that the quenching due to halide ions proceeds via both a diffusional and static quenching processes. The rate constants for diffusional as well as static component of quenching process have been calculated using modified Stern-Volmer relation. It is further observed, that I − ion has very high quenching ability than Br − ion and Cl − ion almost behaves as a non-quencher. It is explained in terms of the sphere of action model by showing that the value of radius of sphere of action of the halide quencher is greater than the sum of the radii of the respective coumarin and quencher. Further, pattern of the quenching ability of the halide quenchers is found to be as I − > Br − > Cl − and interestingly this is in the same order as of their ionization energy. Finally, the present quenching process has been attributed to the electron transfer resulting between colliding species.
Quenching of the excitation energy of coumarin dyes by aniline 1
Canadian Journal of Physics, 2013
Quenching mechanisms of coumarin dyes, namely 6-bromo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (6BDTC) and 8-methoxy-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (8MDTC), were carried out in toluene by adopting two methods, namely steady-state and time-resolved methods, to understand the role of diffusion in the quenching mechanism. The solute molecules were excited by UV radiation of wavelength 360 and 330 nm. Various quenching parameters like frequency of encounter (k d ), probability of quenching per encounter (p and p=), and quenching rate parameter (k q and kЈ q ) were experimentally determined in all the solvents. Activation energy of quenching (E a and EЈ a ) was also determined by using the literature values of activation energy of diffusion (E d ). It was found that the values of E a (and EЈ a ) were less than E d indicating that the quenching reactions are more significantly influenced by diffusion. PACS Nos.: 33.50.D, 33.50.-j, 87.64.i, 31.70.Hq. Résumé : À l'aide des méthodes stationnaire et résolue dans le temps, afin de comprendre le rôle de la diffusion dans le mécanisme d'extinction (de luminescence), nous avons activé dans le toluène les mécanismes d'extinction de colorants coumarine, nommément le 6-bromo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarine (6BDTC) et 8-methoxy-3-[1-(4,5-dicarbomethoxy-1,2,3triazoloacetyl)]coumarine (8MDTC). Les molécules de soluté ont été excitées par radiation UV de longueur d'onde 360 et 330 nm. Nous avons déterminé expérimentalement, dans tous les solvants, différents paramètres de désactivation, comme la fréquence de collision (k d ), la probabilité de désactivation par collision (p et p=) et le paramètre de taux de désactivation (k q et kЈ q ). Utilisant les valeurs de la littérature pour l'énergie d'activation de la diffusion (E d ), nous avons déterminé les énergies d'activation de désactivation (E a et EЈ a ). Nous trouvons que E a (et EЈ a ) sont plus petites que E d , ce qui indique que les réactions de désactivation sont significativement plus affectées par la diffusion. [Traduit par la Rédaction] ). 1 This manuscript is part of the special issue Mid-and Far-Infrared Spectroscopy: Techniques and Applications published in memoriam of our colleague Arvid Schultz. 976 Can. J. Phys. 91: 976-980 (2013) dx.
Analysis of Fluorescence Quenching of Coumarin Derivatives by 4-Hydroxy-TEMPO in Aqueous Solution
Journal of Fluorescence, 2013
The fluorescence quenching of different coumarin derivatives (7-hydroxy-4-methylcoum arin, 5,7dimethoxycoumarin, 7-amino-4-methyl-3-coumarinylacetic acid, 7-ethoxy-4-methylcoumarin, 7-methoxycoumarin, 7hydroxycoumarin, 7-hydroxy-4-methyl-3-coumarinylacetic acid and 7-amino-4-methylcoumarin) by 4-hydroxy-TEMPO in aqueous solutions at the room temperature was studied with the use of UV-Vis absorption spectroscopy as well as a steady-state and time-resolved fluorescence spectroscopy. In order to understand the mechanism of quenching the absorption and fluorescence emission spectra of all coumarins along with fluorescence decays were recorded under the action of 4hydroxy-TEMPO. The Stern-Volmer plots (both from timeaveraged and time-resolved measurements) displayed no positive (upward) deviation from a linearity. The fluorescence quenching mechanism was found to be entirely dynamic, what was additionally confirmed by the registration of Stern-Volmer plots at different temperatures. The Stern-Volmer quenching constants and bimolecular quenching rate constants were obtained for all coumarins studied at the room temperature. The findings demonstrate the possibility of developing an analytical method for the quantitative determination of the free radicals' scavenger, 4-hydroxy-TEMPO.