Higher Excited States and Vibrationally Hot Excited States: How Important are they in Organic Photochemistry in Dense Media?

  • Josef Michl
  • Alain Castellan
  • Mark A. Souto
  • Jaroslav Kolc
Conference paper
Part of the The Jerusalem Symposia on Quantum Chemistry and Biochemistry book series (JSQC, volume 10)


In photochemical reactions of organic molecules in fluid or rigid solutions, and even in the gas phase at moderate to high pressures, it is usually assumed without question that internal conversion to the lowest excited electronic state and thermal equilibration of vibrational motion occur much more rapidly than any chemical transformations, so that direct irradiation first produces cool S1, or possibly directly cool T1 if special structural features greatly enhance the rate of intersystem crossing relative to thermalization (e.g., heavy atoms), and sensitization produces cool T1, before any chemical reactions occur. The reacting species is therefore assumed to be thermalized S1 or T1, except perhaps if S2 (or T2 is so close in energy as to be thermally accessible, and kinetic schemes are set up accordingly. These assumptions represent an analogy to Kasha’s rule which states that thermalized S1 and T1 states are the only ones from which significant light emission is observed in dense media.


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  1. 1.
    C. M. Lok, J. Lugtenburg, J. Cornelisse, and E. Havinga, Tet. Lett., 4701 (1970).Google Scholar
  2. 2.
    A. Couture, K. Ho, M. Hoshino, P. de Mayo, R. Suau, and W. R. Ware, J. Am. Chem. Soc., 98, 6218 (1976); P. de Mayo, Acc. Chem. Res., 9, 52 (1976); and references therein.Google Scholar
  3. 3.
    R. S. Becker and J. Michl, J. Am. Chem. Soc., 88, 5931 (1966); R. S. Becker, E. Dolan and D. E. Balke, J. Chem. Phys., 50, 239 (1969).CrossRefGoogle Scholar
  4. 4.
    R. V. Carr, B. Kim, J. K. McVey, N. C. Yang, W. Gerhartz, and J. Michl, Chem. Phys. Lett., 39, 57 (1976).CrossRefGoogle Scholar
  5. 5.
    E. F. Ullman, Acc. Chem. Res., 1, 353 (1968).CrossRefGoogle Scholar
  6. 6.
    For recent examples, see T. Wismonski-Knittel, G. Fischer, and E. Fischer, J. Chem. Soc., Perkin Trans. II, 1930 (1974); J. W. J. Gielen, H. J. C. Jacobs, and E. Havinga, Tet. Lett., 3751 (1976).Google Scholar
  7. 7.
    J. Gloor and K. Schaffner, Helv. Chim. Acta, 57, 1815 (1974); J. Am. Chem. Soc., 97, 4776 (1975); and references therein; F. Nobs, U. Burger and K. Schaffner, Helv. Chim. Acta, 60, in the press (1977).CrossRefGoogle Scholar
  8. 8.
    For a review, see R. Lesclaux and J. Joussot-Dubien, in “Organic Molecular Photophysics”, Vol. 1, J. B. Birks, Ed., Wiley, New York, N. Y., 1973.Google Scholar
  9. 9.
    F. P. Schwarz and A. C. Albrecht, J. Phys. Chem., 77, 2411, 2808 (1973).CrossRefGoogle Scholar
  10. 10.
    J. Michl and J. Kolc, J. Am. Chem. Soc., 92, 4148 (1970).CrossRefGoogle Scholar
  11. 11.
    J. Kolc and J. Michl, Abstracts, IVth IUPAC Symposium on Photochemistry, Baden-Baden, Germany, July 16–22, 1972, p. 167.Google Scholar
  12. 12.
    J. Kolc and J. Michl, J. Am. Chem. Soc. 95, 7391 (1973).Google Scholar
  13. 13.
    J. M. Labrum, J. Kolc, and J. Michl, J. Am. Chem. Soc., 96, 2636 (1974).CrossRefGoogle Scholar
  14. 14.
    K. Honda, A. Yabe, and H. Tanaka, Bull. Chem. Soc. Japan, 49, 2384 (1976).CrossRefGoogle Scholar
  15. 15.
    J. Meinwald, G. E. Samuelson, and M. Ikeda, J. Am. Chem. Soc., 92, 7604 (1970); N. J. Turro, V. Ramamurthy, R. M. Pagni, and J. A. Butcher, Jr., J. Org. Chem., 42, 92 (1977).CrossRefGoogle Scholar
  16. 16.
    J. Kolc, J. W. Downing, A. P. Manzara, and J. Michl, J. Am. Chem. Soc., 98, 930 (1976).CrossRefGoogle Scholar
  17. 17.
    Y. H. Meyer, R. Astier, and J. M. Leclercq, J. Chem. Phys., 56, 801 (1972).CrossRefGoogle Scholar
  18. 18.
    J. B. Birks, “Photophysics of Aromatic Molecules”, Wiley, New York, N. Y., 1970.Google Scholar
  19. 19.
    R. A. Keller and S. G. Hadley, J. Chem. Phys., 42, 2382 (1965).CrossRefGoogle Scholar
  20. 20.
    J. Michl, J. Am. Chem. Soc., 93, 523 (1971); Mol. Photochem., 4, 287 (1972); in “Chemical Reactivity and Reaction Paths”, G. Klopman, Ed., Wiley, New York, N. Y., 1974, p. 301.CrossRefGoogle Scholar
  21. 21.
    Not all such states are purely dissociative, as indicated by recent observations of weak Stokes-shifted fluorescence. See, e.g., P. Ausloos, Mol. Photochem., 4, 39 (1972); A. M. Halpern, Mol. Photochem., 5, 517 (1973).Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1977

Authors and Affiliations

  • Josef Michl
    • 1
  • Alain Castellan
    • 1
  • Mark A. Souto
    • 1
  • Jaroslav Kolc
    • 1
  1. 1.Department of ChemistryUniversity of UtahSalt Lake CityUSA

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