Abstract
An analysis of the symmetry of frontier molecular orbitals makes it possible to determine the molecular orbitals which take part in the redox conversions of stable radicals of various classes. In agreement with experimental data, it has been shown that the lowest barrier to reactions involving the electron disproportionation of stable phenoxyl, nitroxide, and verdazyl radicals is realized only when high-lying excited MO's participate. Conversely, the redox reaction between free verdazyl and phenoxyl radicals is allowed for the doublet ground states of the radicals, but the analogous reaction between verdazyl and nitroxide radicals requires the participation of excited molecular orbitals.
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Literature cited
R. B. Woodward and R. Hoffman, The Conservation of Orbital Symmetry, Academic Press, New York (1970).
R. G. Pearson, Symmetry Rules for Chemical Reactions: Orbital Topology and Elementary Processes, Wiley-Interscience, New York (1976).
J. W. McIver, “The structure of transition states: are they symmetric?” Acc. Chem. Res., 7, No. 3, 72–77 (1974).
P. Pechukas, “On simple saddle points of a potential surface, the conservation of nuclear symmetry along paths of steepest descent, and the symmetry of transition states,” J. Chem. Phys., 64, No. 4, 1516–1521 (1976).
M. Quack, “Detailed symmetry selection rules for chemical reactions,“ in: Symmetries and Properties of Non-rigid Molecules: Proc. Intern. Symp.: A Comprehensive Survey, Paris, July 1–7, 1982, Amsterdam (1983), pp. 355–378.
H. Fujimoto and K. Fukui, “Intermolecular interactions and chemical reactivity,“ in: Chemical Reactivity and Reaction Paths, G. Klopman (ed.), Wiley, New York (1974), 30–62.
G. Klopman, “Chemical reactivity and the concept of charge- and frontier-controlled reactions,” J. Am. Chem. Soc., 90, No. 2, 223–234 (1968).
A. Streitwieser, Molecular Orbital Theory for Organic Chemists, Wiley, New York (1961).
G. J. Hojtink, “Electrochemiluminescence of aromatic hydrocarbons,” Discuss. Faraday Soc., 45, No. 1, 22–44 (1968).
V. D. Pokhodenko, A. A. Beloded, and V. G. Koshechko, Redox Reactions of Free Radicals [in Russian], Naukova Dumka, Kiev (1977).
L. N. Ganyuk, N. F. Guba, and V. D. Pokhodenko, “Photoactivated electron disproportionation of the galvinoxyl phenoxyl radical,” Teor. Éksp. Khim., 14, No. 4, 542–546 (1978).
A. I. Bogatyreva and A. L. Buchachenko, “Reactions of electronically excited radicals and quenching of excited states by radicals,” Usp. Khim., 44, No. 12, 2171–2204 (1975).
A. I. Bykh, R. F. Vasil'ev, and N. N. Ryzhitskii, Electrochemiluminescence of Solutions of Organic Compounds. Progress in Science and Technology. Radiation Chemistry. Photochemistry [in Russian], Vol. 2, VINITI, Moscow (1979).
É. P. Platonova, E. Yu. Skuridin, and L. S. Degtyarev, “Electrochemical oxidation and reduction of complexes of tetra-4-tert-butylphthalocyanine with ions of group II and group III metals,” Zh. Obshch. Khim., 54, No. 4, 925–928 (1984).
J. A. Barltrop and J. D. Coyl, Excited States in Organic Chemistry, Wiley, New York (1975).
L. S. Degtyarev, E. I. Kapinus, and E. Yu. Skuridin, “Formation of exciplexes during the deactivation of a triplet state of magnesium phthalocyanine by nitroxide radicals,” Khim. Vys. Énerg., 18, No. 1, 56–59 (1984).
D. E. Williams, “The structure of galvinoxyl, a stable phenoxyl radical,” Mol. Phys., 16, No. 2, 145–151 (1969).
D. E. Williams, “Structure of 3,4-dihydro-2,4,6-triphenyl-s-tetrazin-1(2H)-yl free radical by crystal-packing analysis and x-ray diffraction,” J. Am. Chem. Soc., 91, No. 5, 1243–1245 (1969).
A. L. Buchachenko and A. N. Vasserman, Stable Radicals [in Russian], Khimiya, Moscow (1968).
P. Bischof, “Unrestricted open-shell calculations by MINDO/3. Geometries and electronic structure of radicals,“ J. Am. Chem. Soc., 98, No. 22, 6844–6849 (1976).
L. K. Lee, N. H. Sabelli, and P. R. Le Breton, “Theoretical characterization of phthalocyanine, tetraazaporphyrin, tetrabenzoporphyrin, and porphyrin electronic spectra,” J. Phys. Chem., 86, No. 20, 3926–3931 (1982).
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Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 86–91, January–February, 1987.
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Degtyarev, L.S. Influence of the symmetry of frontier orbitals on the height of the barriers to redox reactions of stable free radicals. Theor Exp Chem 23, 81–85 (1987). https://doi.org/10.1007/BF00534980
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DOI: https://doi.org/10.1007/BF00534980