Selective detection of minor prototropic tautomers in low-symmetry tetraazaporphyrin derivatives by the combined use of electronic absorption, MCD, and CI calculations

Ishii, Kazuyuki; Itoya, Hatsumi; Miwa, Hideya; Kobayashi, Nagao

doi:10.1039/b508500d

Cited by 13 publications

(18 citation statements)

References 33 publications

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“…The absorption spectra of the metal‐free Pzs 5a – c show a strong UV Soret transition at 333 nm with two shoulders at around 315 and 372 nm and two broad Q x ‐ and Q y ‐band transitions at around 647 and 710 nm, respectively, and a broad band of lesser intensity centered at 494 nm, which can be assigned to the S(n)→π* transition 17. The absorption spectra of compounds 5a – c are very similar to those reported for other low‐symmetry metal‐free Pzs in which two pyrrole protons should be bonded to the pyrrole ring in the x axial direction 18. Interestingly, the absorption spectra of 4c , with eight long alkyl chains, in a mixed solution of CH 2 Cl 2 /MeOH (0 → 40 % MeOH, v/v) reveal that 4c can be induced to form aggregates, as shown by a decrease and broadening of the band at 745 nm and an increase and blueshifting of the band at 678 nm (Q band at 678 nm → 673 nm; Figure 2, b) 1j…”

Section: Resultssupporting

confidence: 64%

Tetrakis(tetrathiafulvalene–tetrathiacrown ether)porphyrazine Triads: Synthesis, Photophysical, and Electrochemical Properties

Hou

Zhong

et al. 2012

Eur J Org Chem

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A series of tetrakis(tetrathiafulvalene‐tetrathiacrown ether)porphyrazine triads with long and flexible aliphatic side‐chains at the periphery have been synthesized and characterized. Electrochemical investigations show two reversible four‐electron oxidation waves, one reversible one‐electron oxidation wave and two irreversible one‐electron reduction waves, which indicates that these triads are good π‐electron donors. Selected triad 4a reacted with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) to form a charge‐transfer complex, which exhibits absorption bands at around 760 and 860 nm. Selected triads 4a and 5a bind silver(I) and mercury(II) ions. In the case of triad 4a, the addition of silver(I) ions led to dimerization of the triad, which fragmented to form monomeric 4:1 host–guest complexes when more than 2 equiv. of the metal ions were added. X‐ray scattering at room temperature showed that triad 5c is a highly ordered oblique columnar structure in the bulk state. The crystal structures of the precursors 3b,c were also determined by X‐ray diffraction analysis.

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Section: Resultssupporting

confidence: 64%

Tetrakis(tetrathiafulvalene–tetrathiacrown ether)porphyrazine Triads: Synthesis, Photophysical, and Electrochemical Properties

Hou

Zhong

et al. 2012

Eur J Org Chem

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“…However, in the case of the hydroporphyrin free-base compounds, the possibility of different tautomers exists − and needed to be addressed (Figure ). − In all the calculations, we found that the “ac” NH tautomers are at least ∼28 kcal/mol less stable than the corresponding NH tautomers. Thus, only the “bd” tautomers were considered.…”

Section: Resultsmentioning

confidence: 79%

Magnetic Circular Dichroism Spectroscopy of meso-Tetraphenylporphyrin-Derived Hydroporphyrins and Pyrrole-Modified Porphyrins

et al. 2016

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A large set of free-base and transition-metal 5,10,15,20-tetraphenyl-substituted chlorins, bacteriochlorins, and isobacteriochlorins and their pyrrole-modified analogues were investigated by combined UV-visible spectroscopy, magnetic circular dichroism (MCD), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches and their spectral characteristics were compared to those of the parent compounds, free-base tetraphenylporphyrin 1H2 and chlorin 2H2. It was shown that the nature of the pyrroline substituents in the chlorin derivatives dictates their specific UV-vis and MCD spectroscopic signatures. In all hydroporphyrin-like cases, MCD spectroscopy suggests that the ΔHOMO is smaller than the ΔLUMO for the macrocycle-centered frontier molecular orbitals. DFT and TDDFT calculations were able to explain the large broadening of the UV-vis and MCD spectra of the chlorin diones and their derivatives compared to the other hydroporphyrins and hydroporphyrin analogues. This study contributes to the further understanding of the electronic effects of replacing a pyrrole in porphyrins by pyrrolines or other five-membered heterocycles (oxazoles and imidazoles).

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“…22 As shown in Fig. 12, the systematic introduction of fused benzo-rings in metal-free TAPs results in "prototropic" tautomerism between X and Y, which is created by the difference in the positions of the two pyrrole protons with respect to the benzo-rings.…”

Section: Evaluations Of Prototropic Tautomers Of Low Symmetry Tapmentioning

confidence: 98%

“…A number of MCD studies on the effect of lowering the symmetry of metal-free TAPs have been carried out not only to clarify the degeneracy of the excited singlet states in these compounds but also to detect the tautomers generated by the positioning of the two pyrrole protons around the N4 ring. 22 As shown in Fig. 12, the systematic introduction of fused benzo-rings in metal-free TAPs results in "prototropic" tautomerism between X and Y, which is created by the difference in the positions of the two pyrrole protons with respect to the benzo-rings.…”

Section: Evaluations Of Prototropic Tautomers Of Low Symmetry Tap Der...mentioning

confidence: 99%

A novel aspect of spectroscopy for porphyrinic compounds under magnetic fields

Mulyana

Ishii

2014

Dalton Trans.

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The spectroscopies of a range of porphyrinic compounds performed under a magnetic field are reviewed, focusing on the molecular functions of the compounds. Characteristic molecular magneto-optical effects, such as the Kerr effects and magnetochiral dichroism (MChD), as well as time-resolved electron paramagnetic resonance (TREPR) are reviewed. A novel molecular magneto-optical memory is described on the basis of the results of a Kerr spectroscopic study of Si phthalocyanine coupled with a ferromagnetic substrate. The results of TREPR analyses of low-symmetry tetraazaporphyrin derivatives are discussed in order to determine the relationship between molecular symmetry and singlet oxygen yield, as knowing this relationship is essential for photodynamic therapy. Finally, the MChD of porphyrins is introduced as a new way of elucidating the asymmetry in biological systems. Further, it can lead to new asymmetric synthesis methods and form the basis for novel magneto-optical devices.

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Selective detection of minor prototropic tautomers in low-symmetry tetraazaporphyrin derivatives by the combined use of electronic absorption, MCD, and CI calculations

Cited by 13 publications

References 33 publications

Tetrakis(tetrathiafulvalene–tetrathiacrown ether)porphyrazine Triads: Synthesis, Photophysical, and Electrochemical Properties

Tetrakis(tetrathiafulvalene–tetrathiacrown ether)porphyrazine Triads: Synthesis, Photophysical, and Electrochemical Properties

Magnetic Circular Dichroism Spectroscopy of meso-Tetraphenylporphyrin-Derived Hydroporphyrins and Pyrrole-Modified Porphyrins

A novel aspect of spectroscopy for porphyrinic compounds under magnetic fields

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