Spectroscopy, Electrochemistry, and Molecular Orbital Calculations of Metal-Free Tetraazaporphyrin, -chlorin, -bacteriochlorin, and -isobacteriochlorin

Miwa, Hideya; Макарова, Е. А.; Ishii, Kazuyuki; Luk’yanets, E. A.; Kobayashi, Nagao

doi:10.1002/1521-3765(20020301)8:5<1082::aid-chem1082>3.0.co;2-u

Cited by 55 publications

(65 citation statements)

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“…Let us present available experimental data on the energies of electron transitions for isomers of H 2 iBC and its derivatives, including its cyano derivatives [17,18,23,[45][46][47], which may be obtained from the spectra of the molecules in solutions, including inert nonpolar n-alkanes.…”

Section: (Ii)mentioning

confidence: 43%

“…We note that in the MCD spectrum [45] we observe two maxima: at λ ≈ 540 nm and 500 nm (the deep minimum corresponds to the Q 1 (0-0) band). MCD spectra with a similar shape are also obtained for octaethylisobacteriochlorin [46] and meso-tetraazaisobacteriochlorin [47]. On the whole, analysis of the collective data shows that assignment of the λ ≈ 500 nm band to the transition G → Q 2 (0-0) transition is preferred, which gives E Q 2 = 20,000 cm -1 and ∆E Q 2 Q 1 = 2520 cm -1 .…”

Section: (Ii)mentioning

confidence: 97%

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Electronic structure and spectra of NH-isomers of isobacteriochlorin

2006

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ev UDC 539.19Using the restricted and unrestricted Hartree-Fock method (RHF and UHF) with the AM1 Hamiltonian, we have calculated the geometric structure of the NH-isomers of isobacteriochlorin and its meso-cyano derivative. We have used the CNDO/S method for all the considered structures to calculate the transitions to excited electronic states. We have analyzed the effect of taking into account electron correlation on the results of the calculations of the chemical and geometric structure and the electronic spectra. For the a isomer with the imino hydrogens opposite each other, we obtained a planar structure corresponding to literature x-ray diffraction data. For the aromatic c isomer and other isomers with the imino hydrogens adjacent to each other, the calculations lead to a substantial nonplanarity of the macrocycle (defined mainly by the tilt of the pyrrole rings) and also deviation of the NH bond from the plane of the pyrrole ring. The ground-state energies of the a and c isomers have close values, which generally explains the observed NH tautomerism. We calculated the dipole moments of the isomers in the ground state and the excited state. The results of the calculation of the characteristics of the excited states with UHF geometry on the whole seem to be preferred over those with RHF geometry. We show that only for the aromatic c isomer can we describe the electronic absorption spectrum within a four-orbital model.

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confidence: 43%

Section: (Ii)mentioning

confidence: 97%

Electronic structure and spectra of NH-isomers of isobacteriochlorin

2006

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confidence: 99%

“…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.…”

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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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A Switchable Near‐Infrared‐Absorbing Dye Based on Redox‐Bistable Benzitetraazaporphyrin

et al. 2023

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Activatable near‐infrared (NIR) dyes responsive to external stimuli are used in medical and other applications. Here, we describe the design and synthesis of bench‐stable 18π‐ and 20π‐electron benzitetraazaporphyrins (BzTAPs) possessing redox‐switchable NIR properties. X‐Ray, NMR, and UV/Visible‐NIR analyses revealed that 20π‐electron BzTAP 1 exhibits NIR absorption and antiaromaticity with a paratropic ring‐current, while 18π‐electron BzTAP 2 shows weakly aromatic character with NIR inertness. Notably, the NIR‐silent BzTAP 2 was readily converted to the NIR‐active BzTAP 1 in the presence of mild reducing agents such as amine. The intense NIR absorption band of BzTAP 1 is in sharp contrast to the very weak absorption bands of previously reported antiaromatic porphyrinoids. Molecular orbital analysis revealed that symmetry‐lowering perturbation of the 20π‐electron porphyrinoid skeleton enables the HOMO–LUMO transition of 1 to be electric‐dipole‐allowed. BzTAPs are expected to be useful for constructing activatable NIR probes working in reductive environments.

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Spectroscopy, Electrochemistry, and Molecular Orbital Calculations of Metal-Free Tetraazaporphyrin, -chlorin, -bacteriochlorin, and -isobacteriochlorin

Cited by 55 publications

References 24 publications

Electronic structure and spectra of NH-isomers of isobacteriochlorin

Electronic structure and spectra of NH-isomers of isobacteriochlorin

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

A Switchable Near‐Infrared‐Absorbing Dye Based on Redox‐Bistable Benzitetraazaporphyrin

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