Solvent effects of the electronic absorption and photophysical properties of poly(3-methoxythiophene), a conducting oligomer: evaluation of the dipole moment and specific solute-solvent interactions in the first excited singlet-state

The electronic absorption and fluorescence spectra, and fluorescence quantu m yields (phi(F)) Of Poly(3-methoxythiophene) (PMOT) were determined at roo m temperature (298 K) in a variety of solvents with different polarities (h exane, cyclohexane, 2-propanol, ethyl acetate, methanol, ethanol, acetonitr ile, ethylene glycol, dioxane, propylene carbonate, dimethylformamide, and dimethyl sulfoxide). The solvent effects on the PMOT spectral and photophys ical characteristics (absorption and fluorescence wavenumbers) were studied quantitatively, using the Kamlet-Abboud-Taft solvation relationships. The spectral data were used, in combination with the PMOT ground-state dipole m oment (mu(g)), to evaluate its first excited singlet-state dipole moment (m u(e)). A mu(e)/mu(g) ratio of 5.8 was obtained by means of the solvatochrom ic shift method (Bakhshiev's and Kawski-Chamma-Viallet's correlations). The Kamlet-Abboud-Taft solvatochromic parameters were applied to determine the solute-solvent interactions in the PMOT ground and excited singlet states. (C) 2000 Elsevier Science Ltd. All rights reserved.