Now showing items 1-20 of 174

  • Concentration effects in pigment solutions 

    Gurinovich, G. P.; Losev, A. P.; Zenkevich, E. I. (1978)
    Gurinovich, G. P. Concentration effects in pigment solutions / G.P. Gurinovich, A.P. Losev, E.I. Zenkevich // Spectroscopy Letters. – 1978. - Vol 11, No 7. – P. 493-511.
  • Regularities of intermolecular interactions and energy transfer in mixed associates of chlorophyll and its analogs 

    Zenkevich, E. I.; Losev, A.P.; Kochubeev, G. A.; Gurinovich, G. P. (Elsevier Scientific Publishing Company, 1978)
    Regularities of intermolecular interactions and energy transfer in mixed associates of chlorophyll and its analogs / E.I. Zenkevich, A.P. Losev, G.A. Kochubeev, G.P. Gurinovich // Journal of Molecular Structure. – 1978. Vol. 45. – P. 423-436.
  • Directed energy transfer due to orientational broadenning of energy levels in photosynthetic pigment solutions 

    Rubinov, A. N.; Zenkevich, E. I.; Nemkovich, N. A.; Tomin, V. I. (1982)
    The directed non-radiative energy transfer through monomeric molecules of chlorophyll “a” and pheophytin “a” at high concentrations (c ~ 10⁻²) in a rigid matrix of polyvinylbutyral has been found by using the nanosecond laser spectrofluorimeter. The phenomenon is caused by orientational broadening of pigment molecular spectra owing to its interaction with a solvent. The observed ...
  • Radiationless intermolecular energy transfer with participation of acceptor excited triplet states 

    Gurinovich, G. P.; Zenkevich, E. I.; Sagun, E. I. (1982)
    Radiationless energy transfer between like and unlike molecules has been experimentally studied under conditions where acceptor molecules have been excited to the triplet state. Homogeneous singlet—triplet—triplet migration has been discovered in higbly concentrated chlorophyll “a” and pheophytin “a” solutions in castor oil at 183 K by measuring the variation of pigment relative ...
  • Spectral Рeculiarities of NH-Tautomerism in Isocycle-Containing Porphyrins and their Covalently Linked Dimers 

    Zenkevich, E. I.; Shulga, A. M.; Chernook, A. V.; Gurinovich, G. P. (1984)
    It has been found experimentally that a whole class of isocycle-containing porphyrins, including synthetic and natural objects and their covalently linked dimers, shows NH-tautomerism which manifests itself in isotropic solutions in normal electronic spectra both at 77 K and higher temperatures (up to 500 K).
  • NH-Tautomerism and Visible Absorption Spectra of Porphyrins with Nonsymmetrical substitution 

    Zenkevich, E. I.; Shulga, A. M.; Filatov, I. V.; Chernook, A. V.; Gurinovich, G. P. (1985)
    On the basis or experiments Ihe oscillator model has been established for individual NH tautomers or porphyrins with asymmetrical substitution. CNDO/2 calculations explain the inversion of Q ₓ (O.O) and Q y (O.O) electronic transition intensities in NH tautomers as a consequence of the inversion of LUMO coefficients c₁ and c₂ for fixed x and y molecular oscillators.
  • Resonance Raman spectra interpretation by molecular coherent state representation 

    Trifonov, N. Yu. (1992)
    In this paper the problem of exact summation over vibrational states of intermediate electronic level excited by resonance Raman scattering in a molecular system with an arbitrary number of vibrational modes is solved with the help of the coherent state representation. For matrix elements of the resonance Raman (RR) amplitude the expressions in the form of an integral and multiple ...
  • Energy transfer in ethane-bisporphyrins studied by fluorescence line narrowing and spectral hole burning 

    Mauring, K.; Suisalu, A.; Kikas, J.; Zenkevich, E. I.; Chernook, A. V.; Shulga, A. M.; Gurinovich, G. P. (1995)
    The quasi-line fluorescence excitation spectrum of 1,2-bis (2,3,7,8,12,13,17,18-octaethyl-21H,23 H-porphino) ethane at 4.8 K consists of two subbands with the splitting mean value of 51cm⁻¹, that are ascribed to the donor and the acceptor half of the homodimer. The donor's fluorescence is quenched by an efficient energy transfer to the acceptor. The energy transfer rate of 10¹¹ ...
  • Spectroscopy of interchromophoric interactions in self-organized porphyrin and chlorin complexes 

    Zenkevich, E. I.; Shulga, A. M.; Chernook, A. V.; Rempel, U.; von Borczyskowski, C. (1995)
    Spectral-luminescent properties of multimolecular complexes (triads and pentads, complexation constants range from 5∙10⁶ to 5∙10⁷ M⁻¹) formed by two-fold coordination of dipyridyl and tetra-pyridyl substituted porphyrin or related molecules with Zn-porphyrin and Zn-chlorin dimers having various spacers between macrocycles (-CH₂-CH₂- or phenyl ring) have been studied in methylcyclohexane ...
  • Formation and optical properties of self-organized pentameric porphyrin arrays 

    Chernook, A. V.; Rempel, U.; von Borczyskowski, C.; Zenkevich, E. I.; Shulga, A. (1996)
    Principles of formation, electronic absorption and fluorescence spectra are reported for self-organized pentameric arrays of tetrapyrrolic macrocycles. In these arrays two molecules of Zn-porphyrin dimers, Zn(II)l,4-bis[5-(10,15,20-tri-p-hexylphenylporphyrinyl)]-benzene ((ZnHTPP)₂) are bound via one molecule of a tetrapyridyl-substituted free base of porphyrin or tetrahydroporphyrin. ...
  • Photophysical and photochemical properties of potential porphyrin and chlorin photosensitizers for PDT 

    Zenkevich, E.; Sagun, E.; Knyukshto, V.; Shulga, A.; Mironov, A.; Efremova, O.; Bonnett, R.; Pinda Songca, S.; Kassem, M. (1996)
    Structural and optical properties as well as photophysical and photochemical parameters (excited S₁ and T₁ state lifetimes at 77 K and in the presence of O₂ in solution at 293 K; efficiencies of singlet oxygen, ¹Δg, generation) are presented for porphyrins and chlorins with potential for the PDT of cancer: chlorin p₆ and its trimethyl ester, chlorin e₆ and its Na₃ and K₃ salts, ...
  • Fluorescence line narrowing study of cyclopentaneporphyrin chemical dimers at 4.2 K 

    Starukhin, A.; Zenkevich, E. I.; Shulga, A.; Chernook, A. (1996)
    The monomers of Zn-cyclopentanporphyrins (ZnOEP-cycle and ZnOEP-cycle=CH2) and their chemical dimers covalently linked via isocycles (Zn-cyclodimers) have been studied by the method of fluorescence line narrowing (FLN) in tetrahydrofurane-toluene (3:1) glassy matrixes at 4.2 K. Well-resolved fluorescence spectra upon laser excitation into the S₀→S₁ absorption band have been ...
  • Complexation and interchromophoric interactions in self-organized porphyrin and chlorin triads 

    Chernook, A. V.; Shulga, A. M.; Zenkevich, E. I.; Rempel, U.; von Borczyskowski, C. (1996)
    Spectral properties and equilibrium constants of multimolecular complexes (triads) formed by 2-fold coordination of dipyridyl-substituted free bases of porphyrin, chlorin, or tetrahydroporphyrin with Zn-porphyrin and Zn-chlorin dimers bridged by either of two different spacers between the monomeric entities have been studied in methylcyclohexane at room temperature. The ability ...
  • Investigations of Chl α aggregates cross-linked by dioxane in 3-methylpentane 

    Oksanen, J. A. I.; Zenkevich, E. I.; Knyukshto, V. N.; Pakalnis, S.; Hynninen, P. H.; Korrpi-Tommola, J. E. I. (1997)
    In this work, dioxane-bound aggregates of chlorophyll a are prepared in 3-methylpentane. The properties of the aggregates are studied by using steady-state and time-resolved spectroscopies. The Qy-region absorption spectrum of the chlorophyll α-dioxane aggregate shows four clearly resolvable narrow bands with comparable intensities. The band maxima are located at 683, 689, 698 ...
  • Unusual dynamic relaxation of triplet-excited meso-phenyl-substituted porphyrins and their chemical dimers at room temperatures 

    Knyukshto, V.; Zenkevich, E.; Sagun, E.; Shulga, A.; Bachilo, S. (1998)
    It has been found that for mono- and di-meso-phenyl-substituted octaethylporphyrin (OEPs), etioporphyrins, corresponding Zn complexes and OEP chemical dimers (with a meso-phenyl spacer) a drastic shortening of triplet lifetimes from a ms to μs timescale in deaerated toluene solutions at 295K takes place without any changes of the spectral-kinetic parameters of the S₀ and S₁ states. ...
  • Electron transfer in porphyrin multimolecular self-organized nanostructures 

    Zenkevich, E. I.; Bachilo, S. M.; Shulga, A. M.; Rempel, U.; Willert, A.; von Borczyskowski, C. (1998)
    On the base of of covalent and non-covalent bonds nanoscale self-assembling multiporphyrin arrays with well-defined geometry, the controllable number of interacting components and their spectral and photophysical properties were formed. The deactivation of excited singlet and triplet states was studied using steady-state, time-resolved picosecond fluorescence (∆½≈30 ps) and ...
  • Pathways for photoinduced electron transfer in meso-nitro-phenyl-octaethylporphyrins and their chemical dimers 

    Knyukshto, V.; Zenkevich, E.; Sagun, E.; Shulga, A.; Bachilo, S. (1999)
    The photophysical properties of meso-nitro-phenyl-octaethylporphyrins and their dimers with electron-accepting NO₂ groups in the para-, meta- and ortho-positions of the phenyl ring were studied. For the ortho-NO₂ case in deaerated toluene at 295 K, strong fluorescence quenching is caused by the intramolecular electron transfer from the porphyrin S₁ state in the absence of phenyl ...
  • Competition between electron transfer and energy migration in self-assembled porphyrin triads 

    Zenkevich, E. I.; Willert, A.; Bachilo, S. M.; Rempel, U.; Kilin, D. S.; Shulga, A. M.; von Borczyskowski, C. (2001)
    The photoinduced electron transfer (ET) and the energy migration (EM) processes have been studied in liquid solutions and polymeric (PMMA) films for the triads consisting of the Zn-octaethylporphyrin chemical dimer (the energy and electron donor, D) and dipyridyl substituted tetrapyrrole extra-ligands (porphyrins, chlorin, tetrahydroporphyrin) as the acceptors, A. On the basis ...
  • Photoinduced electron transfer dynamics for self-assembled porphyrin arrays in solutions and films 

    Zenkevich, E. I.; Kilin, D. S.; Willert, A.; Bachilo, S. M.; Shulga, A. M.; Rempel, U.; von Borczyskowski, C. (2001)
    Electronic excitation energy deactivation in self-assembled porphyrin triads has been studied by the time correlated single photon counting technique as a function of the solvent polarity (toluene-acetone mixtures), temperature (77-350 K), and mutual spatial arrangement of the donor and acceptor subunits. The donor (Zn-octaethylporphyrin chemical dimer) fluorescence quenching ...
  • Manifestation of nonplanarity effects and charge-transfer interactions in spectral and kinetic properties of triplet states of sterically strained octaethylporphyrins 

    Knyukshto, V. N.; Sagun, E. I.; Shulga, A. M.; Starukhin, D. A.; Bachilo, S. M.; Zenkevich, E. I. (2001)
    Properties of the triplet states of octaethylporphyrins with the steric hindrance (free bases and Pd complexes) are studied by the methods of stationary and kinetic spectroscopy in the temperature range from 77 to 293 K. The mono-mesophenyl substitution results in a decrease in the quantum yield and shortening of the phosphorescence lifetime of Pd complexes by 250–3500 times in ...