ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Supramolecular ensembles stable at room temperature (complexation constant and activation energy ... more Supramolecular ensembles stable at room temperature (complexation constant and activation energy range from 5 (DOT) 106 M-1 to 5 (DOT) 107 M-1 and from 0.5 to 1.0 eV correspondingly) containing up to five macrocyclic fragments have been constructed using two-fold ligation of Zn-porphyrin and Zn-chlorin chemical dimers by pyridyl substituted porphyrin or related molecules. Spectral, photophysical and thermodynamic properties of triadic and pentadic arrays have been studied in a temperature range from 140 to 360 K. Kinetic behavior of the complexes was investigated using a fluorescent picosecond laser setup ((Delta) t approximately equals 30 ps) with 2-D (wavelength-lifetime) registration. Observed spectral properties are explained in terms of extra-ligation (red shift of all electronic bands <EQ 550 cm-1)) and excitonic splitting ((Delta) E < 1900 cm-1). Nonradiative for- and backward excitation energy transfer (K > 1010 c-1), electron transfer and d-(pi) interactions are discussed as the main paths of electronic excitation deactivation in the complexes.
Journal of Applied Spectroscopy - J APPL SPECTROSC, 2003
Quantum-chemical investigation of the electronic structure and properties of the excited states o... more Quantum-chemical investigation of the electronic structure and properties of the excited states of porphyrin dimers, in which monomeric subunits are linked by the phenyl spacer, is performed by semiempirical methods. The molecular orbitals of the monomeric subunits are shown to interact with each other via molecular orbitals of the phenyl ring. Comparison of the experimental absorption data and quantum-chemical calculations of electronic absorption spectra for different conformations of Zn-tetraphenylporphyrin dimer is performed and the main conformation of the dimer in a solution at 295 K, in which the planes of tetrapyrrole macrocycles are located at an angle of about 60°, is substantiated.
Journal of Photochemistry and Photobiology B: Biology, 1990
On the basis of spectral fluorescence and polarization measurements and results obtained on the l... more On the basis of spectral fluorescence and polarization measurements and results obtained on the luminescence quenching of the membrane fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) by incorporated chlorin e6 (chl e6) molecules, it is shown that the interaction of the water-soluble pigment with smaller unilamellar lipid vesicles occurs by a mechanism of partition between the aqueous and lipid phases (partition coefficient Kp = 6.7 x 10(3) and provides rigid fixing of chl e6 monomers at the boundary between the polar and non-polar parts of the lipid membrane. In terms of inductive resonance electronic excitation energy transfer between DPH and chl e6 (R0 = 36.2 A), we have analysed data on DPH fluorescence quenching under different conditions of chl e6 localization in the lipid bilayer and have concluded that the incorporation of the pigment molecules into the vesicles from the aqueous phase occurs mainly into the external monolayer.
The monomers of Zn-cyclopentanporphyrins (ZnOEP-cycle and ZnOEP-cycle=CHz) and their chemical dim... more The monomers of Zn-cyclopentanporphyrins (ZnOEP-cycle and ZnOEP-cycle=CHz) and their chemical dimers cova-lently 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 So-+Sl absorption band have been observed. In contrast to this, it has been shown that the excitation into the region of SO+& absorption band leads to FLN disappearance for individual monomers. On the basis of this effect positions of the SO+& electronic transitions in the energy scale have been determined. The normal coordinate treatment of FLN spectra of ZnOEP-cycle=CHz and those for the Zn-cyclodimers permitted us to determine the normal modes which are connected with the formation of the dimeric species. The weak interaction of Q-transitions of donor (D, ZnOEP-cycle) and acceptor (A, ZnOEP-cycle=CHz) subunits in Zn-cyclodimers manifests ...
Physical chemistry chemical physics : PCCP, Jan 11, 2018
Nanoassemblies formed via self-assembly based on colloidal CdSe quantum dots (QDs) and porphyrin ... more Nanoassemblies formed via self-assembly based on colloidal CdSe quantum dots (QDs) and porphyrin (H2P) dye molecules show Fluorescence Resonant Energy Transfer (FRET) and non-FRET quenching of QD photoluminescence (PL). We present a procedure to unravel and quantify these two relaxation pathways via dynamic and static PL quenching experiments. Accordingly, FRET amounts at maximum to 10% of the total quenching efficiency. Since the degree of ligand coverage is inhomogeneously distributed across the QD ensemble PL quantum yields vary broadly. The attachment of H2P molecules occurs preferentially to those QDs with low ligand coverage. Along with that, nanoassembly formation deviates strongly from Poisson statistics. Like FRET, non-FRET depends on the QD size. We assign non-FRET quenching to the formation of specific new Cd2+ trap states following depletion of several ligands by the spacious dye molecules. While FRET follows quantitatively the Förster model, non-FRET appears on time sca...
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Supramolecular ensembles stable at room temperature (complexation constant and activation energy ... more Supramolecular ensembles stable at room temperature (complexation constant and activation energy range from 5 (DOT) 106 M-1 to 5 (DOT) 107 M-1 and from 0.5 to 1.0 eV correspondingly) containing up to five macrocyclic fragments have been constructed using two-fold ligation of Zn-porphyrin and Zn-chlorin chemical dimers by pyridyl substituted porphyrin or related molecules. Spectral, photophysical and thermodynamic properties of triadic and pentadic arrays have been studied in a temperature range from 140 to 360 K. Kinetic behavior of the complexes was investigated using a fluorescent picosecond laser setup ((Delta) t approximately equals 30 ps) with 2-D (wavelength-lifetime) registration. Observed spectral properties are explained in terms of extra-ligation (red shift of all electronic bands <EQ 550 cm-1)) and excitonic splitting ((Delta) E < 1900 cm-1). Nonradiative for- and backward excitation energy transfer (K > 1010 c-1), electron transfer and d-(pi) interactions are discussed as the main paths of electronic excitation deactivation in the complexes.
Journal of Applied Spectroscopy - J APPL SPECTROSC, 2003
Quantum-chemical investigation of the electronic structure and properties of the excited states o... more Quantum-chemical investigation of the electronic structure and properties of the excited states of porphyrin dimers, in which monomeric subunits are linked by the phenyl spacer, is performed by semiempirical methods. The molecular orbitals of the monomeric subunits are shown to interact with each other via molecular orbitals of the phenyl ring. Comparison of the experimental absorption data and quantum-chemical calculations of electronic absorption spectra for different conformations of Zn-tetraphenylporphyrin dimer is performed and the main conformation of the dimer in a solution at 295 K, in which the planes of tetrapyrrole macrocycles are located at an angle of about 60°, is substantiated.
Journal of Photochemistry and Photobiology B: Biology, 1990
On the basis of spectral fluorescence and polarization measurements and results obtained on the l... more On the basis of spectral fluorescence and polarization measurements and results obtained on the luminescence quenching of the membrane fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) by incorporated chlorin e6 (chl e6) molecules, it is shown that the interaction of the water-soluble pigment with smaller unilamellar lipid vesicles occurs by a mechanism of partition between the aqueous and lipid phases (partition coefficient Kp = 6.7 x 10(3) and provides rigid fixing of chl e6 monomers at the boundary between the polar and non-polar parts of the lipid membrane. In terms of inductive resonance electronic excitation energy transfer between DPH and chl e6 (R0 = 36.2 A), we have analysed data on DPH fluorescence quenching under different conditions of chl e6 localization in the lipid bilayer and have concluded that the incorporation of the pigment molecules into the vesicles from the aqueous phase occurs mainly into the external monolayer.
The monomers of Zn-cyclopentanporphyrins (ZnOEP-cycle and ZnOEP-cycle=CHz) and their chemical dim... more The monomers of Zn-cyclopentanporphyrins (ZnOEP-cycle and ZnOEP-cycle=CHz) and their chemical dimers cova-lently 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 So-+Sl absorption band have been observed. In contrast to this, it has been shown that the excitation into the region of SO+& absorption band leads to FLN disappearance for individual monomers. On the basis of this effect positions of the SO+& electronic transitions in the energy scale have been determined. The normal coordinate treatment of FLN spectra of ZnOEP-cycle=CHz and those for the Zn-cyclodimers permitted us to determine the normal modes which are connected with the formation of the dimeric species. The weak interaction of Q-transitions of donor (D, ZnOEP-cycle) and acceptor (A, ZnOEP-cycle=CHz) subunits in Zn-cyclodimers manifests ...
Physical chemistry chemical physics : PCCP, Jan 11, 2018
Nanoassemblies formed via self-assembly based on colloidal CdSe quantum dots (QDs) and porphyrin ... more Nanoassemblies formed via self-assembly based on colloidal CdSe quantum dots (QDs) and porphyrin (H2P) dye molecules show Fluorescence Resonant Energy Transfer (FRET) and non-FRET quenching of QD photoluminescence (PL). We present a procedure to unravel and quantify these two relaxation pathways via dynamic and static PL quenching experiments. Accordingly, FRET amounts at maximum to 10% of the total quenching efficiency. Since the degree of ligand coverage is inhomogeneously distributed across the QD ensemble PL quantum yields vary broadly. The attachment of H2P molecules occurs preferentially to those QDs with low ligand coverage. Along with that, nanoassembly formation deviates strongly from Poisson statistics. Like FRET, non-FRET depends on the QD size. We assign non-FRET quenching to the formation of specific new Cd2+ trap states following depletion of several ligands by the spacious dye molecules. While FRET follows quantitatively the Förster model, non-FRET appears on time sca...
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