Penzkofer, Alfons (2016) Absorption and emission spectroscopic investigation of alloxazine in aqueous solutions and comparison with lumichrome. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 314. pp. 114-124. ISSN 1010-6030,
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The absorption and emission spectroscopic behavior of alloxazine is studied in aqueous solutions at pH 4 (10(-4)M HCl) and pH 10 (10(-4)M NaOH). At pH 4 only the pure form of alloxazine is present, while at pH 10 about 9% of alloxazine is present in its tautomeric form of isoalloxazine. Absorption cross-section spectra, fluorescence emission quantum distributions, fluorescence excitation quantum distributions, excitation wavelength dependent fluorescence quantum yields, fluorescence lifetimes, and radiative lifetimes are determined. The spectroscopic behavior of alloxazine at pH 4 and pH 10 is compared with that of 7,8-dimethyl-alloxazine (lumichrome) at pH 4 and pH 10. Photo-induced (excited-state) tautomerization of alloxazine to isoalloxazine is observed which does not occur for lumichrome. In the case of alloxazine the highest occupied molecular n orbital (n-HOMO) is energetically well below the highest occupied molecular pi orbital (pi-HOMO) giving non-degenerate ground-state to first excited-state (pi pi*) transition. For isoalloxazine, lumichrome, and lumichrome-10H-tautomer n-HOMO is only slightly below pi-HOMO causing photo-induced ground-state n -> pi electron transfer with elongation of fluorescence lifetime and radiative lifetime. (C) 2015 Elsevier B.V. All rights reserved.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | PHOTOPHYSICAL PROPERTIES; FLUORESCENCE; RIBOFLAVIN; FLAVINS; PHOTOCHEMISTRY; BEHAVIOR; STATE; FILMS; PHOSPHORESCENCE; CYCLODEXTRINS; Alloxazine; Lumichrome; Photo-induced-tautomerization; Radiative lifetimes; n-HOMO and pi-HOMO level determination; Photo-induced n-HOMO ->pi-HOMO electron transfer |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Experimental and Applied Physics > Alumni or Retired Professors > Group Alfons Penzkofer |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 01 Mar 2019 12:36 |
| Last Modified: | 11 Mar 2019 09:54 |
| URI: | https://pred.uni-regensburg.de/id/eprint/2257 |
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