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Polarity of the Medium and Quenching of Fluorescence of Caratenoids and Phthalimides
Authors:V. S. Pavlovich
Affiliation:(1) Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 F. Skorina Ave., Minsk, 220072, Belarus
Abstract:The relation for the dependence of the rate of radiationless energy conversion of the S1 state kq on the polarity of the medium, obtained previously by the author, has been used to interpret the known literature data on the lifetime of the S1 state of solutions of some caratenoids and phthalimides. It has been shown that in alcohols and water (normal and deuterated ones) the fluorescence quenching of 4-amino-, 4-methylamino-, and 4-dimethylamino-N-methylphthalimides (4AMP, 4MAMP, and 4DMAMP) as well as of peridinine in alcohols is due to H-bond formation. It has been established that a twofold increase in the number of amine atoms of hydrogen on passing from 4MAMP to 4AMP, as well as deuteration of solvents in the case of 4DMAMP, is followed by a decrease in kq by a factor of 1.6 and 1.75, respectively. The mechanism of quenching in complexes formed with solvent molecules by means of the H-bond is discussed. It has been concluded that the quenching of fluorescence of phthalimides in such complexes is mainly due to the intersystem crossing initiated by the oscillations of the protons or deuterons of the H-bonds.
Keywords:intramolecular charge transfer  hydrogen bond  quenching of fluorescence  intersystem crossing  internal conversion  caratenoids  phthalimides
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