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1Author    Snezhana BakalovaRequires cookie*
 Abstract    o lv e n t E f fe c ts o n th e F lu o re s c e n c e P r o p e r tie s o f M e th y ld ih y d ro q u in o lin o n e s The absorption and fluorescence spectra and the fluorescence quantum yields of two methyl-2,3-dihydro-4(lH)-quinolinones in various solvents are reported. In some solvents deuteration-induced fluorescence enhancement has been observed. The solvent effects in aprotic solvents are consistent with the general type of solvent interaction. For protic solvents, solute-solvent complexation in the excited state is suggested. 
  Reference    Z. Naturforsch. 46a, 823—827 (1991); received May 24 1991 
  Published    1991 
  Keywords    Fluorescence, Dihydroquinolinones, Hydrogen bond 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-0823.pdf 
 Identifier    ZNA-1991-46a-0823 
 Volume    46 
2Author    HansE. Wilhelm, Horst Gebert, Wolfgang RegensteinRequires 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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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0837.pdf 
 Identifier    ZNA-1997-52a-0837 
 Volume    52 
3Author    Peter Nikolov, Irina Petkova, Stefan Stoyanov3Requires cookie*
 Title    Media Effect upon the Fluorescence Ability of Differently Substituted a-Cyanostilbenes  
 Abstract    The steady state and dynamic photophysical characteristics of a-cyanostilbene derivatives have been investigated in solution and in Polyvinylchloride (PVC) film at 300 K as well as in a frozen matrix at 77 K. While no emission is observed in solution, a significant fluorescence ability is registered both in PVC and frozen media. This fact is attributed to the matrix effect, which lessens the possible intramolecular motions around the central double bond. No phosphorescence at 77 K is observed. The fluorescence lifetimes at 77 K are compared with literature data for similar chemically fixed structures. 
  Reference    Z. Naturforsch. 56a, 447—451 (2001); received January 23 2001 
  Published    2001 
  Keywords    a-Cyanostilbene Derivatives, Fluorescence, Matrix Effect 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0447.pdf 
 Identifier    ZNA-2001-56a-0447 
 Volume    56 
4Author    I. Timtcheva, P. Nikolov, St Minchevand, N. SofronievRequires 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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 TEI-XML for    default:Reihe_A/42/ZNA-1987-42a-0289.pdf 
 Identifier    ZNA-1987-42a-0289 
 Volume    42 
5Author    J. Krzystek, H.J U C Von Schütz, Wolf, R.-D Stigler, J. J. StezowskiRequires 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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 TEI-XML for    default:Reihe_A/42/ZNA-1987-42a-0622.pdf 
 Identifier    ZNA-1987-42a-0622 
 Volume    42 
6Author    U. Eberl, A. Ogrodnik, M. E. Michel-BeyerleRequires cookie*
 Title    Access to Primary Charge Separation Mechanism in Photosynthetic Reaction Centers: Anisotropic Excitation Spectra of Electric Field Modulated Fluorescence Yields  
 Abstract    Two-step sequential and unistep, superexchange primary electron transfer form primary radical pair states which differ in the direction and magnitude of their dipole moments as revealed in the X-ray structure analysis. The direction can be measured by the excitation anisotropy of electric field induced changes of the fluorescence yield. This method determines angles between the dipole of the primary radical pair and photoselected transition moments (in absorption and emission) of cofactors in the reaction centers. Transitions particularly favourable for discrimination between the two models of primary electron transfer are discussed. 
  Reference    Z. Naturforsch. 45a, 763—770 (1990); received March 17 1990 
  Published    1990 
  Keywords    Electric field effect, Anisotropy, Fluorescence, Photosynthesis, Reaction center, Pri-mary charge separation 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0763.pdf 
 Identifier    ZNA-1990-45a-0763 
 Volume    45 
7Author    I. Grabchev, I. Moneva, E. Wolarz3, D. Bauman3, S. StoyanovbRequires cookie*
 Title    Spectral Properties of 3-Benzanthrone Derivative Dyes in Isotropic Solvents, Polymer Film and Liquid Crystal  
 Abstract    Some recently synthesized benzanthrone derivatives bearing azomethine and oxy groups at C-3 po­ sition have been systematically studied. The influence of the substituents and of the environment (iso­ tropic and anisotropic media) on the absorption and fluorescence of the dyes and their vibronic transi­ tions is discussed in this paper. 
  Reference    Z. Naturforsch. 56a, 291—296 (2001); received January 24 2001 
  Published    2001 
  Keywords    3-Benzanthrone Derivatives, Azomethine and Oxy substitutes, Absorption, Fluorescence, Vibronic Structure 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0291.pdf 
 Identifier    ZNA-2001-56a-0291 
 Volume    56