A QUANTITATIVE STUDY OF THE EFFECT OF SOLVENT ON THE ELECTRONIC ABSORPTION AND FLUORESCENCE-SPECTRA OF SUBSTITUTED PHENOTHIAZINES - EVALUATION OF THEIR GROUND AND EXCITED SINGLET-STATE DIPOLE-MOMENTS
C. Parkanyi et al., A QUANTITATIVE STUDY OF THE EFFECT OF SOLVENT ON THE ELECTRONIC ABSORPTION AND FLUORESCENCE-SPECTRA OF SUBSTITUTED PHENOTHIAZINES - EVALUATION OF THEIR GROUND AND EXCITED SINGLET-STATE DIPOLE-MOMENTS, Spectrochimica acta. Part A: Molecular spectroscopy, 49(12), 1993, pp. 1715-1725
Electronic absorption and fluorescence excitation and emission spectra
of five phenothiazines (phenothiazine, promethazine, thionine, methyl
ene blue and Azure A) were determined at room temperature (293 K) in s
everal solvents of various polarities (cyclohexane, dioxane, ethyl eth
er, chloroform, ethyl acetate, 1-butanol, 2-propanol, ethanol, methano
l, acetonitrile, dimethylformamide and dimethyl sulfoxide). The effect
of the solvents upon the spectral characteristics was studied. In com
bination with the ground state dipole moments of these phenothiazines,
the spectral data were used to evaluate their first excited singlet-s
tate dipole moments by means of the solvatochromic shift method (Bakhs
hiev's and Kawski-Chamma-Viallet correlations). The theoretical ground
and excited singlet-state dipole moments for phenothiazines were calc
ulated as a vector sum of the pi component (obtained by the Pariser-Pa
rr-Pople method) and the sigma component (obtained from sigma-bond mom
ents). A reasonable agreement was found with the experimental values.
For most phenothiazines under study, excited singlet-state dipole mome
nts were found to be significantly higher than their ground-state coun
terparts. The application of the Kamlet-Abboud-Taft solvatochromic par
ameters to the solvent effect on spectral properties of phenothiazines
is discussed.