Complete assignment of spin sublevels in the lowest excited triplet state of corrole compounds by time-resolved EPR spectroscopy

Yamauchi, Seigo; Tanabe, Mana; Ohba, Yasunori; Sugisaki, Kenji; Toyota, Kazuo; Sato, Kazunobu; Takui, Takeji; Saltsman, Irena

doi:10.1016/j.cplett.2011.11.040

Cited by 9 publications

(13 citation statements)

References 32 publications

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“…What is another energy dissipation channel besides IC and fluorescence? From our previous study 22 and other papers 11,30 corroles can arrive in its excited triplet state (T 1 ) after excitation to the S 1 state and the TA peaks of T n ←T 1 are also located at ca. 460 nm, 22 which overlap with that of S n ←S 1 absorption in this study.…”

Section: Transient Absorption Studiesmentioning

confidence: 95%

Photophysical properties of electron-deficient free-base corroles bearing meso-fluorophenyl substituents

Zhang

Liu

Zhan

et al. 2015

Photochem Photobiol Sci

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The ultrafast photophysical behaviors of a series of meso-fluorophenyl substituted electron-deficient free base corroles F0C, F5C, F10C and F15C in toluene have been investigated using femtosecond time resolved absorption spectroscopy and steady-state spectroscopy. The S2→S1* transformation was found to be accelerated with the enhancement of electron-deficiency (from 550 fs for F0C to 140 fs for F15C), while S1*→S1 prolonged from ∼9 ps for F0C to ∼24 ps for F15C, which was assigned to an intermolecular vibrational cooling process. The intersystem crossing process was directly observed. The intersystem crossing rate constant (kISC) from S1 to T1 was found to increase significantly with the fluorophenyl substituents (from F0C to F10C), while it does not totally follow the trend of the increase of the atomic number of the peripheral fluorine atoms. The order of ISC time constants from larger to smaller is F0C < F5C < F10C > F15C. It indicates that the electron-withdrawing effect of fluorophenyl substitutions, together with the heavy atom effect, influences the photophysical properties of excited states of corroles.

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Section: Transient Absorption Studiesmentioning

confidence: 95%

Photophysical properties of electron-deficient free-base corroles bearing meso-fluorophenyl substituents

Zhang

Liu

Zhan

et al. 2015

Photochem Photobiol Sci

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“…This is in agreement with the previous report that the in-plane T X and T Y sublevels will be predominantly populated given the heavy atom is in the plane of a planar molecule. 74 The D value of PMI-Br was determined as 1400 MHz. To the best of our knowledge, this is the first report of the TREPR feature of the triplet state of PMI chromophore.…”

Section: = ×mentioning

confidence: 99%

Study of the Spin–Orbit Charge Transfer Intersystem Crossing of Perylenemonoimide–Phenothiazine Compact Electron Donor/Acceptor Dyads with Steady-State and Time-Resolved Optical and Magnetic Spectroscopies

et al. 2019

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Compact electron donor/acceptor dyads were prepared, with perylenemonoimide (PMI) as the electron acceptor and phenothiazine (PTZ) as the electron donor, to study the relationship between the molecular geometry and the spin−orbit charge transfer (CT) intersystem crossing (SOCT-ISC) efficiency. The photophysical properties of the dyads were studied with steadystate and time-resolved optical and magnetic resonance spectroscopies. We found that PTZ is an ideal chromophore for molecular conformation restriction in the compact dyads, which exerts a significant effect on the electronic coupling between the donor and acceptor and thus on the photophysical properties such as UV−vis absorption, fluorescence, and ISC efficiency. Anomalous intensified fluorescence at elevated temperatures was observed, which can be fully rationalized by the bright twisted charge transfer (CT) state. The singlet oxygen quantum yields (Φ Δ ) of the dyads are up to 57%, which are highly solvent-polarity-dependent. Femtosecond transient absorption and fluorescence spectroscopies indicate that the charge separation proceeds within 1 ps and the charge-recombination-induced ISC takes 2.8 ns. With time-resolved electron paramagnetic resonance spectroscopy, we confirmed the SOCT-ISC mechanism of the dyad, for which the electron spin polarization and the population rates of the sublevels of the triplet state (zero-field states T X , T Y and T Z ) are drastically different from those of the spin−orbit-couplinginduced ISC (for monobrominated PMI). Photodriven intermolecular energy-transfer and electron-transfer processes in the presence of a triplet energy acceptor or a sacrificial electron donor were also studied. The radical anion of PMI was reversibly produced with photoreduction for which near-IR absorption band in the range of 750−850 nm was observed.

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“…We quantitatively fitted the delay time dependence of the transverse magnetizations in Figure S7 with taking into account the time-dependent sublevel populations determined by depletion rates (k-X, k-Y and k-Z in Figure 5a Figure S4b obtained by the CIS method. 35,[51][52][53] The details on the calculations are described in section 1-4 of SI. The relation of D SS = 1.4 D agrees with the correlations between the computed D SS and the D values (Table S1) (Table S2 and S3) The validity of utilizing the (U)B3LYP levels of theory 54,55 in the model molecules is detailed in section 1-4 and in Table S2, demonstrating the reversal relationship between the aromaticity and the antiaromaticity in the S0 and T1 states, respectively.…”

Section: Toc Graphicsmentioning

confidence: 99%

“…This well explains CT:LE = 1:5 obtained from the CI coefficients in the triplet state, as described above. We also calculated the D value ( D SS = −746 MHz as the spin-spin contribution) from the unpaired orbital distributions in Figure S4b obtained by the CIS method. ,− Details of the calculations are described in sections 1–4 of the SI. The relation of D SS = 1.4 D agrees with the correlations between the computed D SS and the D values (Table S1) obtained for tetraphenylporphyrins and hexaphyrins, supporting the coexistence of the LE and CT characters in the twisted [28]Hex .…”

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confidence: 99%

Charge-Transfer Character Drives Möbius Antiaromaticity in the Excited Triplet State of Twisted [28]Hexaphyrin

Ema

Tanabe

Saito

et al. 2018

J. Phys. Chem. Lett.

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Möbius aromatic molecules have attracted great attention as new functional materials because of their π-orbital cyclic conjugations lying along the twisted Möbius topology. To elucidate the electronic character of the lowest excited triplet (T) state of a Möbius aromatic [28]hexaphyrin, we employed a time-resolved electron paramagnetic resonance (TREPR) method with applied magnetophotoselection measurements at 77 K. Analyses of the EPR parameters have revealed that the T state possesses intramolecular charge-transfer (CT) character together with local excitation character residing at one side in the Möbius strip ring. We have also demonstrated that the CT character between orthogonal unpaired orbitals triggers quick triplet deactivation by spin-orbit coupling. This deactivation can be an important barometer to represent the "antiaromaticity" because of a connection between the orthogonal CT character and instability by a weakened spin-spin exchange coupling in the T state.

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Complete assignment of spin sublevels in the lowest excited triplet state of corrole compounds by time-resolved EPR spectroscopy

Cited by 9 publications

References 32 publications

Photophysical properties of electron-deficient free-base corroles bearing meso-fluorophenyl substituents

Photophysical properties of electron-deficient free-base corroles bearing meso-fluorophenyl substituents

Study of the Spin–Orbit Charge Transfer Intersystem Crossing of Perylenemonoimide–Phenothiazine Compact Electron Donor/Acceptor Dyads with Steady-State and Time-Resolved Optical and Magnetic Spectroscopies

Charge-Transfer Character Drives Möbius Antiaromaticity in the Excited Triplet State of Twisted [28]Hexaphyrin

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