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Excited Singlet (S 1 )‐state Interactions of Nile Red with Aromatic Amines ¶
Author(s) -
Mohanty J.,
Pal H.,
Sapre A. V.
Publication year - 2003
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2003)0780153ession2.0.co2
Subject(s) - chemistry , nile red , quenching (fluorescence) , excited state , solvent , marcus theory , chemical physics , photochemistry , singlet state , electron transfer , computational chemistry , fluorescence , thermodynamics , atomic physics , reaction rate constant , kinetics , physics , quantum mechanics , organic chemistry
Both steady‐state (SS) and time‐resolved (TR) studies show that the fluorescence of the dye Nile red (NR) is quenched by various aromatic amines (ArA). Bimolecular quenching constants (k q ) from both SS and TR measurements are observed to match well, indicating that the interaction is dynamic in nature. The quenching interaction in the present systems has been attributed to electron transfer (ET) from ArA to excited NR, based on the variations in the k q values with the oxidation potentials of the amines. The k q values calculated within the framework of Marcus' outer‐sphere ET theory at different free‐energy changes (ΔG 0 ) of the ET reactions match well with the experimental ones, supporting the ET mechanism in the systems studied. The reorganization energy (λ) estimated from the correlation of the experimental and the calculated k q values is quite similar to the solvent reorganization energy (λ s ), calculated on the basis of the solvent dielectric continuum model along with the assumption that the reactants are the effective spheres. Although a modest error is involved in this λ s calculation, the similarity in λ and λ s values suggests that the solvent reorganization plays a dominant role in governing the ET dynamics in the present systems.