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Effect of Solvent–Water Mixtures on the Prototropic Equilibria of Fluorescein and on the Spectral Properties of the Monoanion ¶
Author(s) -
Klonis Nectarios,
Sawyer William H.
Publication year - 2000
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(2000)0720179eoswmo2.0.co2
Subject(s) - solvent , chemistry , hydrogen bond , solvent effects , quantum yield , fluorescein , yield (engineering) , photochemistry , hydrogen , molecule , computational chemistry , fluorescence , organic chemistry , thermodynamics , optics , physics
A spectral resolution procedure was used to resolve the absorption, excitation and emission spectra of the fluorescein monoanion in a number of solvent–water mixtures. This permitted an analysis of the effect of the solvent environment on the spectral properties of the monoanion and on the lactone/monoanion/dianion transitions of fluorescein. The monoanion excitation and emission spectra show relatively small changes with changing environment, a behavior that is related to the hydrogen‐bonding environment of the solvent–water mixtures. There is also a general increase in the quantum yield of the monoanion from 0.36 in water to values up to 0.49 in the solvent–water mixtures. The presence of solvent also results in a general increase in the lactone content and in the monoanion:dianion and lactone:monoanion ratios. General polarity effects alone cannot account for the observed effects on the prototropic transitions indicating that specific solute–solvent effects involving hydrogen bonding perturb the prototropic equilibria of fluorescein.