Abstract
Vibronic spectra with detailed structure have been recorded in the fluorescence of the NH tautomers of 2,3,12,13-tetraethylporphyrin (TEP), 13′,15′-cyclo-13′-methyl-2,3,12-triethylporphyrin (TEPC), and derivatives of these deuterated at the center, which has involved the use of selective laser excitation at 4.2 K. The degrees of polarization have been measured for the individual phonon-free lines. The vibrational structures and 1H NMR data (two independent methods) have given the structures of the NH tautomers. The short-wave (main) tautomer of TEP has the imine protons on the pyrrole rings containing ethyl substituents, while the long-wave one has them on the pyrrole rings containing protons in the β positions. The intensities of the lines relating mainly to vibrations of the ethyl groups are sensitive to the positions of the central protons. A difference from the tetraalkylporphyrins is that the main TEPC tautomer has the central protons positioned on opposite pyrrole rings not linked to the isocycle as being more favored by energy considerations.
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Literature cited
C. B. Storm and Y. J. Teklu, “Nitrogen-hydrogen tautomerism in porphyrins and chlorines,” J. Am. Chem. Soc., 94, No. 5, 1745–1747 (1972).
E. I. Zenkevich, A. M. Shulga, A. V. Chernook, and G. P. Gurinovich, “Spectral peculiaritie. of NH-tautomerism in isocyclocontaining poryphyrins and their covalently linked dimers, Chem. Phys. Lett., 109, No. 3, 306–311 (1984).
E. I. Zenkevich, A. M. Shul'ga, A. V. Chernook, and G. P. Gurinovich, “Spectral signs of NH tautomerism in cyclopentaneporphyrins,” Dokl. AN BSSR, 28, No. 12, 1082–1085 (1984).
E. I. Zen'kevich, A. M. Shul'ga, A. V. Chernook, et al., “NH tautomerism in porphyrins containing isocycles and in chemical dimers of them,” Zh. Prikl. Spektr., 42, No. 5, 772–779 (1985).
A. M. Shul'ga, “Synthesis of 10,15,20-tripropylcyclopentaneporphyrin and the structures of NH tautomers,” Khim. Geterotsikl. Soedin., No. 1, 132–133 (1985).
R. I. Personov, E. I. Al'shits, and L. A. Bykovskaya, “Fine structure in fluorescence spectra of polyatomic molecules on laser excitation,” Pis'ma Zh. Éksp. Teor. Fiz., 15, No. 10, 609–612 (1972).
A. S. Starukhin, A. M. Shul'ga and I. V. Stanishevskii, “A method of obtaining high-resolution fluorescence spectra from NH tautomers of substituted porphyrins in solid solution,” Opt. Spektr., 58, No. 4, 936–939 (1985).
A. M. Shul'ga, L. L. Gladkov, I. V. Stanishevskii, and A. S. Starukhin, “A study of NH tautomers of alkyl derivatives of porphine by low-temperature spectroscopy with selective excitation,” Teor. Éksp. Khim., 21, No. 5, 554–560 (1985).
H. Fisher and H. Orth, Die Chemie des Pyrrols, Akad. Verlag, Leipzig (1937).
G. P. Gurinovich, A. N. Sevchenko, and K. N. Solov'ev, The Spectroscopy of Chloroform and Related Compounds [in Russian], Nauka i Tekhnika, Minsk (1968).
G. V. Ponomarev and A. M. Shul'ga, “The first synthesis of bisporphyrin covalently bonded on the cyclopentane rings,” Dokl. Akad. Nauk SSSR, 271, No. 2, 365 (1983).
A. M. Shul'ga and G. V. Ponomarev, “Synthesis of octapropylporphyrin by monopyrrole cyclotetramerization of 5-carboxy-2-methoxymethyl-3,4-dipropylpyrrol,” Khim. Geterotsikl. Soedin., No. 7, 922–927 (1984).
I. A. Chaudry, P. S. Clezy, and A. H. Mirza, “Chemistry of pyrrolic compounds. Benzyl β-ketopropionate porphyrins: a new synthesis of deoxophylloerythroacetioporphyrin and harderoporphyrin,” Austr. J. Chem., 33, No. 6, 1095–1104 (1980).
G. V. Ponomarev and A. M. Shul'ga, “Oxidation of porphyrins containing cyclopentane rings at the surface of silica gel: the chemical properties of oxycyclopentaneporphyrins,” Khim. Geterotsikl. Soedin., No. 4, 485–489 (1984).
L. A. Bykovskaya, A. T. Gradyushko, R. I. Personov, et al., “Polarized fluorescence of porphine derivatives on selective laser excitation,” Zh. Prikl. Spektr., 29, No. 6, 1088–1098 (1978).
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Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 2, pp. 215–221, March–April, 1987.
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Shul'ga, A.M., Gladkov, L.L., Stanishevskii, I.V. et al. Structures of the NH tautomers of tetraethylporphyrin and its isocyclic derivative. Theor Exp Chem 23, 202–207 (1987). https://doi.org/10.1007/BF00534584
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DOI: https://doi.org/10.1007/BF00534584