Synthesis and Photoinduced Electron‐Transfer Reactions in a La2@Ih‐C80–Phenoxazine Conjugate

Akasaka, Takeshi; Nakata, Akira; Rudolf, Marc; Wang, Wei Wei; Yamada, Michio; Suzuki, Masatatsu; Maeda, Yutaka; Aoyama, R.; Tsuchiya, Takahiro; Nagase, Shigeru; Guldi, Dirk M.

doi:10.1002/cplu.201600391

Cited by 11 publications

(12 citation statements)

References 52 publications

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“…The second spectrum shows TA bands at 560 nm and 600 nm and a GSB band at 537 nm, respectively. It has been reported that the absorption of PMI •– is at 600 and 780 nm and that of the PXZ radical cation is at 540 nm . The TA band at 600 nm for the mixture of diiodo-BDP / PMI–PXZ in acetonitrile is attributed to the PMI radical anion ( PMI •– ), which is also in agreement with the spectroelectrochemistry experiments (Figures a and S10).…”

Section: Resultssupporting

confidence: 89%

“…It has been reported that the absorption of PMI •− is at 600 and 780 nm 64 and that of the PXZ radical cation is at 540 nm. 93 The TA band at 600 nm for the mixture of diiodo-BDP/PMI−PXZ in acetonitrile is attributed to the PMI radical anion (PMI •− ), which is also in agreement with the spectroelectrochemistry experiments (Figures 5a and S10). Similar experiments were performed in n-hexane (Figure S18), and the PMI triplet state was observed.…”

Section: Resultssupporting

confidence: 84%

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Charge Transfer, Intersystem Crossing, and Electron Spin Dynamics in a Compact Perylenemonoimide-Phenoxazine Electron Donor–Acceptor Dyad

et al. 2021

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With phenoxazine (PXZ) as the electron donor and perylene-3,4-dicarboximide (PMI) as the electron acceptor, we prepared a compact, orthogonal electron donor−acceptor dyad (PMI−PXZ) to study the spin−orbit charge transfer-induced intersystem crossing (SOCT-ISC). A weak charge transfer (CT) absorption band, due to S 0 → 1 CT transition, was observed (ε = 2840 M −1 cm −1 at 554 nm, FWHM: 2850 cm −1 ), which is different from that of the previously reported analogue dyad with phenothiazine as the electron donor (PMI−PTZ), for which no CT absorption band was observed. A long-lived triplet state was observed (lifetime τ T = 182 μs) with nanosecond transient absorption spectroscopy, and the singlet oxygen quantum yield (Φ Δ = 76%) is higher than that of the previously reported analogue dyad PMI−PTZ (Φ Δ = 57%). Ultrafast charge separation (ca. 0.14 ps) and slow charge recombination (1.4 ns) were observed with femtosecond transient absorption spectroscopy. With time-resolved electron paramagnetic resonance spectroscopy (TREPR), we confirmed the SOCT-ISC mechanism, and the electron spin polarization phase pattern of the triplet-state TREPR spectrum is (e, e, a, e, a, a), which is dramatically different from that of PMI−PTZ (a, e, a, e, a, e), indicating that the triplet-state TREPR spectrum of a specific chromophore in the electron donor−acceptor dyads is not only dependent on the geometry of the dyads but also dependent on the structure of the electron donor (or acceptor). Even one-atom variation in the donor structure may cause significant influence on the electron spin selectivity of the ISC of the electron donor−acceptor dyads.

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Section: Resultssupporting

confidence: 89%

Section: Resultssupporting

confidence: 84%

Charge Transfer, Intersystem Crossing, and Electron Spin Dynamics in a Compact Perylenemonoimide-Phenoxazine Electron Donor–Acceptor Dyad

et al. 2021

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“…580 nm; , this assignment is also in agreement with the spectroelectrochemical results (Figure S62a, Supporting Information). A weak shoulder ESA band at 538 nm was observed, which is in agreement with the reported PXZ radical cation absorption (535 nm) and the spectroelectrochemical data (Figure S62b, Supporting Information) . The instant appearance of this band indicated the ultrafast CS in the dyad BDP-PXZ-1 .…”

Section: Results and Discussionmentioning

confidence: 99%

Spin–Orbit Charge-Transfer Intersystem Crossing (SOCT-ISC) in Bodipy-Phenoxazine Dyads: Effect of Chromophore Orientation and Conformation Restriction on the Photophysical Properties

et al. 2019

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The spin–orbit charge-transfer-induced intersystem crossing (SOCT-ISC) in Bodipy-phenoxazine (BDP-PXZ) compact electron-donor/-acceptor dyads was studied. PXZ is the electron donor, and BDP is the electron acceptor. The molecular geometry is varied by applying different steric hindrance on the rotation about the linker between the two subunits. Charge-transfer (CT) absorption bands were observed for the dyads with more coplanar geometry (electronic coupling matrix elements is up to 2580 cm–1). Ultrafast charge separation (0.4 ps) and slow charge recombination (3.8 ns, i.e., SOCT-ISC process) were observed. Efficient ISC (ΦT = 54%) and long triplet-state lifetime (τT = 539 μs) were observed for the dyads. Notably, the triplet-state lifetime is 2-fold of that accessed with heavy-atom effect, indicating the advantage of using a heavy-atom-free photosensitizer. The low-lying CT state in the dyads in polar solvents was confirmed with intermolecular triplet photosensitizing method. Time-resolved electron paramagnetic resonance spectroscopy show that the electron spin polarization of the triplet state formed by the SOCT-ISC is the same as that of spin–orbit-ISC (SO-ISC). 3CT and localized excited triplet states (3LE) were simultaneously observed for one of the dyads, which is rare. Normally, the CT state was observed as spin-correlated radical pair. The dyads were used as triplet photosensitizers for triplet–triplet annihilation upconversion, the quantum yield is up to 12.3%. A large anti-Stokes shift (5905 cm–1) was achieved by excitation into the CT absorption band, not the conventional LE absorption band.

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“…The negative band at 700 nm is assigned to stimulated emission (SE) of the localized singlet state ( 1 StyrylBDP * ). However, no obvious absorption band of the PXZ radical cation (around 540 nm, Supporting Information, Figure S23b) and the styryl BODIPY radical anion (around 670 nm, Supporting Information, Figure S23a) were observed.…”

Section: Resultsmentioning

confidence: 99%

Long‐Lived Triplet Excited State Accessed with Spin–Orbit Charge Transfer Intersystem Crossing in Red Light‐Absorbing Phenoxazine‐Styryl BODIPY Electron Donor/Acceptor Dyads

Elmalı

Zhao

et al. 2020

ChemPhysChem

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Orthogonal phenoxazine‐styryl BODIPY compact electron donor/acceptor dyads were prepared as heavy atom‐free triplet photosensitizers (PSs) with strong red light absorption ( ϵ =1.33×10 5 M −1 cm −1 at 630 nm), whereas the previously reported triplet photosensitizers based on the spin‐orbit charge transfer intersystem crossing (SOCT‐ISC) mechanism show absorption in a shorter wavelength range (<500 nm). More importantly, a long‐lived triplet state (τ T =333 μs) was observed for the new dyads. In comparison, the triplet state lifetime of the same chromophore accessed with the conventional heavy atom effect (HAE) is much shorter (τ T =1.8 μs). Long triplet state lifetime is beneficial to enhance electron or energy transfer, the primary photophysical processes in the application of triplet PSs. Our approach is based on SOCT‐ISC, without invoking of the HAE, which may shorten the triplet state lifetime. We used bisstyrylBodipy both as the electron acceptor and the visible light‐harvesting chromophore, which shows red‐light absorption. Femtosecond transient absorption spectra indicated the charge separation (109 ps) and SOCT‐ISC (charge recombination, CR; 2.3 ns) for BDP‐1 . ISC efficiency of BDP‐1 was determined as Φ T =25 % (in toluene). The dyad BDP‐3 was used as triplet PS for triplet‐triplet annihilation upconversion (upconversion quantum yield Φ UC =1.5 %; anti‐Stokes shift is 5900 cm −1 ).

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Synthesis and Photoinduced Electron‐Transfer Reactions in a La₂@I_h‐C₈₀–Phenoxazine Conjugate

Cited by 11 publications

References 52 publications

Charge Transfer, Intersystem Crossing, and Electron Spin Dynamics in a Compact Perylenemonoimide-Phenoxazine Electron Donor–Acceptor Dyad

Charge Transfer, Intersystem Crossing, and Electron Spin Dynamics in a Compact Perylenemonoimide-Phenoxazine Electron Donor–Acceptor Dyad

Spin–Orbit Charge-Transfer Intersystem Crossing (SOCT-ISC) in Bodipy-Phenoxazine Dyads: Effect of Chromophore Orientation and Conformation Restriction on the Photophysical Properties

Long‐Lived Triplet Excited State Accessed with Spin–Orbit Charge Transfer Intersystem Crossing in Red Light‐Absorbing Phenoxazine‐Styryl BODIPY Electron Donor/Acceptor Dyads

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