Single-site spectra of NH-tautomers of nonsymmetrical tetraethylporphyrinsin an n-octane matrix at 10K

Single-site fluorescence and fluorescence excitation spectroscopy are repor ted in n-octane matrix at 10 K for two different NH-tautomers of 2,3,12,13- tetraethyl-21H, 23H-porphine (H2TEP), the same compound in which the centra l protons have been replaced by deuterons (D2TEP) and 2,3,12,13-tetraethyl- 7-bromo-21H, 23H-porphine (H2TEP-Br). The vibrational frequencies of the gr ound electronic state and the first singlet excited state were determined f rom the spectra. On the basis of the spectral data, the behaviour of normal vibrations involving of NH deformation and the results of the normal coord inate analysis the positions of protons for two tautomers has been establis hed. The possibility of spectral manifestation of the third NH-tautomer wit h adjacent positions of protons is discussed. (C) 2001 Elsevier Science B.V . All rights reserved.