| | 1 | Author
| HansE. Wilhelm, Horst Gebert, Wolfgang Regenstein | Requires cookie* | | | Title
| Effect of Substituents on the Viscosity Dependence of Fluorescence and on the S l -T l Energy Gap of Donor-Acceptor Substituted Trans-Stilbenes  | | | | Abstract
| The dependence of fluorescence quantum yields and Sj-lifetimes of donor-acceptor substituted trans-stilbenes on temperature was measured in the temperature range from 298 to 100 K, using solutions of stilbenes in 3-methylpentane (3-MP). Measurements of fluorescence and phosphores-cence spectra show that the triplet energy is almost independent of the acceptor. The S[-energy and the S r Ti energy gap decrease with increasing acceptor strength. For all compounds intersystem crossing (ISC) S, —» T, is negligible. | | | |
Reference
| Z. Naturforsch. 52a, 837—842 (1997); received November 18 1997 | | | |
Published
| 1997 | | | |
Keywords
| Stilbenes, Fluorescence, Phosphorescence, Singlet-Triplet Energy Gap, Rate Constants | | | |
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| default:Reihe_A/52/ZNA-1997-52a-0837.pdf | | | | Identifier
| ZNA-1997-52a-0837 | | | | Volume
| 52 | |
| 2 | Author
| Shozi Yamashita, Mizuki Yoshida, Giiti Tomita | Requires cookie* | | | Title
| Photoionization of Indole in Alkaline Aqueous Solutions at 77 °K | | | | Abstract
| The photoionization process of indole in alkaline aqueous solutions at 77 °K and the recombination process of trapped electron with its mother molecule were investigated. The fluorescence spectrum of indole in these glassy media depended on the NaOH concentration; the disappearance of the 325 nm band at the NaOH concentrations higher than 5 M with the appearance of a fluorescence band at 375 nm. The latter emission is possibly ascribed to the fluorescence of indole anion formed by proton dissociation in the excited singlet state of indole. The intensities of the 375 nm band and the ESR signal due to trapped electrons were dependent on the NaOH concentration and increased steeply with increasing the NaOH concentration. There was a parallel relation between the indole anion concentration and the trapped electron density to some extent. The dependence of the ESR signal intensity on irradiation intensity suggested that the photoionization of indole in alkaline aqueous solution occurred through a two photon process. The presence of a photoactive intermediate for absorbing the second photon was further investigated with simultaneous irradiation of two different wavelength lights. The trapped electron was detrapped with the irradiation of visible light (e.g. 580 nm), and its recombination with mother molecule caused an emission with the same spectrum as indole phosphorescence. The molecular species of the photoactive intermediate in alkaline aqueous solutions seems to be the indole anion. The photoionization in NaOH aqueous solution at 77 °K was also compared with that in methanolic glassy solution. | | | |
Reference
| (Z. Naturforsch. 31b, 361—366 [1976]; received April 28/July 22 1975) | | | |
Published
| 1976 | | | |
Keywords
| Photoionization, Phosphorescence, ESR, Trapped Electron, Indole | | | |
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| default:Reihe_B/31/ZNB-1976-31b-0361.pdf | | | | Identifier
| ZNB-1976-31b-0361 | | | | Volume
| 31 | |
| 3 | Author
| I. Timtcheva, P. Nikolov, St Minchevand, N. Sofroniev | Requires cookie* | | | Title
| Luminescence Properties of Some 4-or 5-Aminosubstituted Indan-13-Diones | | | | Abstract
| The photophysical characteristics of some 4(5)-amino-2-aryl-and 4(5)-amino-2-aryl-2-carboxy-methyl-l,3-indandiones have been studied in solvents of different polarity at room temperature and at 77 °K. In contrast to the 2-arylindan-l,3-diones unsubstituted in the phthaloyl fragment, the compounds investigated are photostable and fluoresce in the region 25 000-18 000 cm -1 with fluorescence quantum yields between 0.1 and 0.5. | | | |
Reference
| Z. Naturforsch. 42a, 289—292 (1987); received October 22 1986 | | | |
Published
| 1987 | | | |
Keywords
| 4-and 5-amino indan-l, 3-diones, absorption, fluorescence, phosphorescence | | | |
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| default:Reihe_A/42/ZNA-1987-42a-0289.pdf | | | | Identifier
| ZNA-1987-42a-0289 | | | | Volume
| 42 | |
| 4 | Author
| J. Krzystek, H.J U C Von Schütz, Wolf, R.-D Stigler, J. J. Stezowski | Requires cookie* | | | Title
| Characterization of the Phenanthrene-Tetrachlorophthalic Anhydride (P/TCPA) 1:1 Charge-Transfer Crystal: Spectroscopic and Structural Investigations | | | | Abstract
| The 1:1 phenanthrene-tetrachlorophthalic anhydride (P/TCPA) charge-transfer complex crystalizes with monoclinic symmetry, space group P2,, with two magnetically inequivalent stacks in the unit cell. The noncentrosymmetric space group is very unusual for CT-complexes. The optical emission spectra at low temperature are characterized by a strong CT phospho-rescence and a weak CT fluorescence and delayed fluorescence. The S, band lies at 22 800 ± 100 cm" 1 , the T, band at 21 200 ± 100 cm" 1 . Above 15 K triplet excitons, moving along the stacks are revealed by ESR. They have a CT character of about 30%, coinciding with that of the shallow X-traps found by ODMR at jow temperatures. A further trap, with zero-field-splitting (zfs) parameters of £> = ±0.0617, E = + 0.0116 cm" 1 has a much larger CT character of 50% as found in the isolated complex in low-temperature glass [1]. A structural model is proposed. | | | |
Reference
| Z. Naturforsch. 42a, 622—630 (1987); received February 28 1987 | | | |
Published
| 1987 | | | |
Keywords
| Charge-transfer crystal, crystal structure, fluorescence, phosphorescence, triplet excitons | | | |
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| default:Reihe_A/42/ZNA-1987-42a-0622.pdf | | | | Identifier
| ZNA-1987-42a-0622 | | | | Volume
| 42 | |
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