Sajadi, Mohsen and Obernhuber, Thorsten and Kovalenko, Sergey A. and Mosquera, Manuel and Dick, Bernhard and Ernsting, Nikolaus P. (2009) Dynamic Polar Solvation Is Reported by Fluorescing 4-Aminophthalimide Faithfully Despite H-Bonding. JOURNAL OF PHYSICAL CHEMISTRY A, 113 (1). pp. 44-55. ISSN 1089-5639,
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Solvation dynamics of 4-aminophthalimide (4AP) in methanol is measured by broadband upconversion of the fluorescence band. The peak emission frequency (v) over tilde (t) is determined from 100 fs onward with 85 fs time resolution. Polar solvation based on simple continuum theory, including solute polarizability, describes the temporal shape of P(t) quantitatively. Extrapolation (v) over tilde (t -> 0) points to an initial emission frequency which agrees with the result from stationary spectroscopy in a nonpolar solvent. The extent (4300 cm(-1)) of the dynamic Stokes shift is largely due (50%) to H-bonding, however. The observations imply that H-bonds with 4AP adiabatically follow the dielectric relaxation of the methanol network. The stimulated emission band is also used to measure solvation dynamics. The evolving band is monitored by transient absorption spectroscopy of supercontinuum probe pulses. But the excited-state absorption spectrum, its relative amplitude, and its evolution are needed to extract (v) over tilde (t) from such measurements. These key data are obtained by comparison with the upconversion results. Thus calibrated photometrically, 4AP transient absorption can be used to monitor solvation dynamics in any solvent. The excited-state absorption spectrum is assigned with the help of time-dependent density-functional calculations. Fluorescence excitation and double-resonance spectroscopy of isolated 4AP, cooled in a supersonic jet, is used to determine optically active modes. An intramolecular reorganization energy is inferred which is consistent with the value in 2-methylbutane (2025 cm-(1)). The crystal structure is also provided.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | STEADY-STATE SPECTROSCOPY; FEMTOSECOND SPECTROSCOPY; UP-CONVERSION; COUMARIN 153; ELECTRONIC SPECTRA; SOLVENTS; JET; EXCITATION; EMISSION; WATER; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) > Prof. Dr. Bernhard Dick |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 07 Oct 2020 09:45 |
| Last Modified: | 07 Oct 2020 09:45 |
| URI: | https://pred.uni-regensburg.de/id/eprint/29586 |
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