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

Single-site fluorescence and fluorescence excitation spectroscopy are reported in n-octane matrix at 10 K for two different NH-tautomers of 2,3,12,13-tetraethyl-21 H, 23H-porphine (H2TEP), the same compound in which the central protons have been replaced by deuterons (D2TEP) and 2,3,12,13-tetraethyl-7-bromo-21 H, 23H-porphine (H2TEP-Br). The vibrational frequencies of the ground electronic state and the first singlet excited state were determined from the spectra. On the basis of the spectral data, the behaviour of normal vibrations involving of NH deformation and the results of the normal coordinate analysis the positions of protons for two tautomers has been established. The possibility of spectral manifestation of the third NH-tautomer with adjacent positions of protons is discussed.