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Luminescence spectra and basicity constants in the electron-excited state of 1-, 2-, and 1,2-substituted benzazoles

Luminescence spectra and basicity constants in the electron-excited state of 1-, 2-, and 1,2-substituted benzazoles. Kazakova, N. A.; Chipanina, N. N.; Cherednichenko, V. I.; Ponomareva, S. M.; Domnina, E. S.; Skvortsova, G. G.; Frolov, Yu. L. (USSR). Zh. Prikl. Spektrosk., 25(5), 827-31 (Russian) 1976. CODEN: ZPSBAX. DOCUMENT TYPE: Journal CA Section: 73 (Spectra by Absorption, Emission, Reflection, or Magnetic Resonance, and Other Optical Properties) Section cross-reference(s): 68 The absorption and fluorescence spectra of solns. of benzimidazole, 1-vinyl- and 1-ethylbenzimidazoles, 1-ethyl- and 1-vinyl-2-alkylbenzimidazoles, indazole, 1-vinyl-, 1-ethyl-, 2-vinyl-, and 2-ethylindazoles, benzotriazole, and 1-vinyl- and 1-ethylbenzotriazoles were studied. The ionization consts. of the above compds. in the ground state in Me2CO were detd. by emf. measurements. 5805-76-5 and 2764-84-3 are also in the experiment. All compds. displayed an intense fluorescence both in polar and nonpolar solvents at 300 K. The previously published conclusion (M. Kondo, H. Kuwano, 1969) about a simultaneous emission from the 1La and 1Lb levels was erroneous. Two bands in the spectrum belonged to a neutral and a cationic mol. form. The effect of solvent on the fluorescence spectra manifested itself in a decrease of energy of the 1st excited singlet state of a fluorescing mol. and can be caused by a reorientation of the solvent mols. in a temporal interval between the absorption and the emission. The large bands shift in the fluorescence spectra, as compared with the absorption ones was conditioned by an increase in dipole moment of the excited mol. The pKa values for the ground and electron-excited states of the compds. are given. .