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Shushkevich, I. K.; Першукевич, П. П.; Макарова, Е. А.; Соловьев, К. Н.

doi:10.1023/a:1013214521598

Journal of Applied Spectroscopy

2001

DOI: 10.1023/a:1013214521598

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I. K. Shushkevich

П. П. Першукевич

Е. А. Макарова

et al.

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Cited by 15 publications

(52 citation statements)

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“…They agree well with the above-given data of [1,2], in which another standard was used for determining ϕ F (a solution of the cresylic violet dye -oxazine-9 -in ethanol). The probabilities that were calculated for the radiative transition S 1 → S 0 and intercombination conversion S 1 L T 1 are equal to k F = 5.3⋅10 7 sec -1 and k ST = 2.4⋅10 8 sec -1 , respectively.…”

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Influence of a Solvent on the Quantum Yield and Duration of the Fluorescence of Tetraazoporphin

et al. 2005

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ev UDC 535.37In view of the discrepancies between the values available in the literature for the photophysical parameters of tetraazaporphin in solutions, we measured its quantum yield and duration of fluorescence in a number of solvents. It has been found that alcohols (isobutanol and isopropanol) quench the fluorescence appreciably. For a solution in toluene -a stable chemically inactive and low-polar solvent -the measured quantum yield of the fluorescence of tetraazaporphin is equal to 0.180 ± 0.015 and its duration is 3.4 ± 0.1 nsec.Keywords: tetraazaporphin, quantum yield of fluorescence, fluorescence duration.Introduction. The tetraazaporphin (H 2 TAP) molecule, or porphyrazine, is one of the fundamental structures in the porphin series, which is an intermediate between the biologically important class of porphyrins and classical dyes of the type of phthalocyanine, which are finding wide application in various fields of science and technology.In investigating the effect of hydrogenation of pyrrolic rings in porphyrazine macrocycles on the photophysical properties, in [1, 2] the quantum yield of fluorescence (ϕ F ) of H 2 TAP was measured as a basis for comparison with the data on dihydroderivatives. By comparing our results with the data of earlier investigations [3-6], we found that there were noticeable discrepancies between the values of ϕ F measured by various authors and also between the data on durations of fluorescence τ F . In [3,4], it was found that ϕ F = 0.12 and τ F = 3.7 nsec (see also the review [7]), in [5], ϕ F = 0.16 and τ F = 6.4 nsec; in [6], ϕ F = 0.12. Recently,in [8], the value ϕ F = 0.29 was obtained for H 2 TAP, whereas in [1, 2] ϕ F = 0.19 and τ F = 3.3 nsec.Since different solvents were used in the works cited, the idea arose that the quantity ϕ F of H 2 TAP can substantially depend on the nature of the solvent. The aim of the present work is to elucidate this influence and to arrange in an ordered fashion the data on the values of ϕ F and τ F for H 2 TAP.Experimental. Measurements of the quantum yield of fluorescence were performed by a relative method from the ratio between the areas of the fluorescence spectra of an object and a standard determined in terms of "quantum" intensities (I λ /hν) on an SDL-2 automated spectrofluorimeter (USSR) consisting of an MDR-12 light-transmission excitation monochromator and an MDR-23 registration monochromator. The excitation and registration axes were arranged at an angle of 90 o . A DKsSh-120 xenon lamp was used as the source of excitation. The light signal separated by the monochromator was registered with the aid of an FÉU-100 cooled photomultiplier (spectral range 200-800 nm) operating in the regime of photon counting. The spectral sensitivity of the recording monochromator-FÉU system was corrected with the aid of a TRSh 2850 standard ribbon tungsten lamp. The spectral width of the excitation monochromator slit did not exceed 4.8 nm in the entire spectral range studied, and that of the registration monochromator -2.6 nm in the 400-800-nm ...

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“…For all the solvents, the values of τ F were measured. These solvents were not selected at random -toluene was used in [1,2,6], isobutanol * in [3,4], EPIP in [5], and chloroform in [8].…”

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Influence of a Solvent on the Quantum Yield and Duration of the Fluorescence of Tetraazoporphin

et al. 2005

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“…Combination of these factors deserves consideration as a method for creating compounds with controlled properties. Spectral and luminescence characteristics of hydrogenated tetraazaporphine derivatives (also called porphyrazine) have been well studied [1][2][3][4][5][6][7][8].Studies showed that hydrogenation of one or two opposed pyrrole rings in tetraazaporphine (H 2 TAP) causes significant fluorescence quenching [1,3,5,8]. This quenching may be due to an increase of the probabilities for the two radiationless intramolecular processes of intersystem crossing S 1 ‫ב‬ T 1 , k ST , and internal conversion S 1 ‫ב‬ S 0 , i.e., energy exchange of the S 1 electronic state onto vibrations of the molecule in the ground state S 0 , the probability of which increases with lowering of the S 1 level.…”

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Transient absorption spectra of tetraazaporphine and its reduced derivatives upon picosecond excitation

et al. 2009

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Transient absorption spectra of tetraazaporphine and substituted derivatives of tetraazachlorin and tetraazabacteriochlorin were obtained upon picosecond excitation with various probe pulse delay times in order to resolve the open question about the reasons for fluorescence quenching in tetraazaporphine hydrogenated derivatives. The quantum yield of triplet state T 1 formation has been estimated. It has been shown that in all investigated cases radiationless de-excitation of the fluorescent level S 1 occurs by two channels: S 1 ‫ב‬ T 1 and S 1 ‫ב‬ S 0 , the latter being predominant. As the S 1 level becomes lower, the transition rate for this channel increases. For tetraazaporphine and its derivatives, a quasi-photochemical mechanism is proposed that accounts for the anomalous efficiency of the S 1 ‫ב‬ S 0 channel in the dissipation of the electronic excitation energy.Introduction. Bridging tetraaza-substitution in the tetrapyrrole macrocycle and hydrogenation of the pyrrole rings is one of the factors capable of causing fundamental changes in the electronic spectra of porphine derivatives. Combination of these factors deserves consideration as a method for creating compounds with controlled properties. Spectral and luminescence characteristics of hydrogenated tetraazaporphine derivatives (also called porphyrazine) have been well studied [1][2][3][4][5][6][7][8].Studies showed that hydrogenation of one or two opposed pyrrole rings in tetraazaporphine (H 2 TAP) causes significant fluorescence quenching [1,3,5,8]. This quenching may be due to an increase of the probabilities for the two radiationless intramolecular processes of intersystem crossing S 1 ‫ב‬ T 1 , k ST , and internal conversion S 1 ‫ב‬ S 0 , i.e., energy exchange of the S 1 electronic state onto vibrations of the molecule in the ground state S 0 , the probability of which increases with lowering of the S 1 level. Preference has been given to the first de-excitation channel [1, 3, 5] on the basis of indirect literature data, in particular, a comparison with fluorescence of bacteriochlorin [9] and 2,3-naphthalocyanine [10] derivatives. In these instances, lowering of the S 1 level was also accompanied by fluorescence quenching although the quenching was weaker. Both pathways were mentioned in another study [8].The kinetics of absorption spectra upon picosecond excitation of H 2 TAP, dibenzobarrelene-substituted tetraazachlorin (H 2 TAC t ), and dibenzobarrelene-substituted tetraazabacteriochlorin (H 2 TABC

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“…Tetraaza derivatives of H 2 iBC that contain peripheral diarenobarrelene moieties were prepared [19,20]. We have studied the spectral-luminescent properties of hydrogenated H 2 TAP derivatives with one or two opposing hydrogenated pyrrole rings [21][22][23]. Quantum-chemical calculations in addition to experimental studies were performed [23].…”

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“…Both hydrogenation of pyrrole rings and aza-substitution are structural factors that have a substantial effect on the electronic states of the molecule. Their combination can produce complicated effects that require a comprehensive analysis [20][21][22][23].…”

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Effect of bridging aza-substitution on electronic structure and spectral-luminescent properties of isobacteriochlorin NH-isomers

et al. 2007

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UDC 535.37We have investigated the spectral characteristics, quantum yield ϕ F , lifetime τ F , and polarization of fluorescence of NH-isomers of dibenzobarrelene disubstituted tetraazaisobacteriochlorin at 293 and 77 K. The following information has been obtained from low-temperature measurements: 1) the weak shoulder on the edge of the long-wavelength 0-0 absorption band disappears at 77 K and, therefore, can be assigned to the cis-NH-isomer [the principal component of the tautomeric mixture is the trans-isomer a (b)]; 2) the low value of ϕ F at room temperature is due to temperature-viscosity quenching whereas ϕ F at 77 K is close to 1 and τ F = 5.3 nsec; 3) the energy of the weak electronic transition G → Q 2 and the interval ∆E Q 2 Q 1 ≈ 2750 cm -1 have been determined. Quantum-chemical calculations found that replacing the methine bridges by nitrogen stabilizes the non-aromatic trans-isomer a (b) whereas the non-planarity of the macrocycle and the alternation of bond lengths increase for the cis-isomers. The calculated electronic absorption spectra of the a isomer reproduce rather well the experimental data. It is shown that the four-orbital model is applicable for the lower excited states Q 1 and Q 2 for all NH-isomers.

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Cited by 15 publications

References 1 publication

Influence of a Solvent on the Quantum Yield and Duration of the Fluorescence of Tetraazoporphin

Influence of a Solvent on the Quantum Yield and Duration of the Fluorescence of Tetraazoporphin

Transient absorption spectra of tetraazaporphine and its reduced derivatives upon picosecond excitation

Effect of bridging aza-substitution on electronic structure and spectral-luminescent properties of isobacteriochlorin NH-isomers

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