Wide-Range Spectral Diffusion in Single Mg-Tetraazaporphyrin Molecules in a Polymer Matrix at Cryogenic Temperatures

Zero-phonon spectral lines of single Mg-tetraazaporphyrin molecules in a polymer matrix and their spectral trails are recorded using cryogenic fluorescence nanoscopy at a temperature of 6 K. Spectral diffusion (stochastic jumps of zero-phonon lines) in an anomalously wide spectral range up to several tens of inverse centimeters is revealed. The structure of the vibronic band in the fluorescence excitation spectrum of single molecules, including both a narrow zero-phonon line and a broad phonon sideband, is directly observed.     

Structures of the NH tautomers of tetraethylporphyrin and its isocyclic derivative

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 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.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 2, pp. 215–221, March–April, 1987.     

Vibronic interaction in the case of quasidegenerate electronic states. Formation of vibrational structure of the fluorescence spectra (letters to the editor)

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 359–361, September, 1991.     

Fluorescence fine-structure spectra of isomers of Zn-tetramethylporphyrin upon selective laser excitation at 4.2‡k

We have obtained the fluorescence fine-structure spectra for isomers of Zn-tetramethylporphyrin (TMP) (Zn-2, 3, 7, 8-TMP, Zn-2, 3, 12, 13-TMP, Zn-2, 8, 12, 18 TMP) in Isotropic media at 4.2K with selective laser excitation, For the phononless lines in the spectra of the indicated isomers, we have measured the values of the degree of polarization and have determined the symmetry of the vibrations in the electronic ground state. We have carried out theoretical calculations of the frequencies and forms of the normal vibrations of the given compounds and have carried out simultaneous analysis of the theoretical and experimental results. We have considered the effect of the location of the four methyl groups on the electronic-vibrational spectra of Zn-TMP isomers. We have shown that in Zn-2, 3, 7, 8-TMP, the direction of the transition moment S_o S₁ does not coincide with the symmetry axis of the molecules due to their interaction with the medium. We discuss the reasons for the splitting of the long-wavelength absorption band of Zn-alkylprophyrins having hydrogen atoms in positions of the pyrrole rings adjacent to one meso position.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 431–439, July–August, 1985.     

Fine-structure spectra of metal complexes of porphin in tetrahydrofuran at low temperatures: Manifestation of nonplanarity effects

The fine-structure fluorescence spectra of Mg and Zn porphins in solid tetrahydrofuran matrices at the liquid helium temperature are recorded for the first time. The fluorescence spectra of Mg porphin molecules deposited from the gas phase on a sapphire substrate simultaneously with tetrahydrofuran molecules are measured. Based on the data obtained from the fluorescence and fluorescence excitation spectra, it is ascertained that there are two noninteracting spectrally different long-and short-wavelength forms of metal complexes of porphins in the ground state. In the case of Mg porphin, the spectral gap for these two forms at 4.2 K amounts to 330 cm^?1. The short-wavelength form is attributed to the nonplanar saddle conformation of a porphin molecule, while the long-wavelength form is associated with the nonplanar domed conformation, in which the central metal ion is displaced out of the plane of the porphyrin ligand. The fine-structure fluorescence spectra of both forms of Mg and Zn porphins are measured in tetrahydrofuran at 4.2 K upon selective laser excitation. The frequencies of the normal vibrations in the ground electronic state are determined and the reasons for the differences in the vibrational frequencies of the forms are discussed.     

Shpolski effect in optical spectra of frozen solutions of the organic C60 fullerene derivative in toluene

Physics of the Solid State - The optical spectra of a solution of the C60 ethyl acetate (C60-EA) in toluene are investigated. The absorption spectra measured at T = 80 K reveal a combination of an...