Magnetic Field Effects on the Photochemical Electron-Transfer Reactions of 10-Methylphenothiazine and Dicyanobenzene Derivatives in Nonviscous Homogeneous Solutions

Sakaguchi, Yoshio; Hayashi, H.

doi:10.1021/jp961907f

Cited by 41 publications

(55 citation statements)

References 48 publications

(89 reference statements)

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“…Figure 5 shows the CW-TREPR spectra obtained by the 355 nm laser excitation of N-methylphenothiazine in the presence of electron acceptors of (a) 1,2,4,5-TCNB in the 4:1 (v/v) mixture of dimethyl sulfoxide (DMSO)-glycerol and (b) 1,4-DCNB in DMSO, respectively. The CIDEP spectrum in the N-methylphenothiazine-1,4-DCNB system (Figure 5b) agrees with that reported by Sakaguchi et al 26 The broad peaks were assigned to N-methylphenothiazine cation radical and the sharp ones to 1,4-DCNB anion radical (DCNB •-). In the CIDEP spectrum of Figure 5a, the cation radical is also observed and sharp peaks are assigned to the anion radical of TCNB •-which was reproduced with the reported hyperfine coupling constants (a H ) 0.111 mT (2H) and a N ) 0.115 mT (4N)).…”

Section: Resultssupporting

confidence: 90%

Chemically Induced Dynamic Electron Polarization Study on the Mechanism of Exchange Interaction in Radical Ion Pairs Generated by Photoinduced Electron Transfer Reactions

et al. 1999

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Photoinduced electron transfer reactions were studied by using the continuous wave time-resolved electron paramagnetic resonance and Fourier-transformed electron paramagnetic resonance spectroscopy in polar solvents. The chemically induced dynamic electron polarization was investigated in both singlet and triplet precursor intermolecular electron transfer systems. The signs of the exchange interaction, which are defined by the energy differences between the singlet and triplet radical ion pairs, depended on the free energy changes for the charge recombination processes. The results are interpreted in terms of the mechanism that the spin selective stabilization and destabilization are caused by the perturbation through the electronic coupling from the ground state and the locally excited triplet state of the donor-acceptor pair at the equilibrium nuclear coordinate. In the singlet precursor electron transfer systems, the positive exchange interaction resulted from the selective triplet stabilization in the radical ion pair, when the ion pair state crossed with the locally excited triplet state at the normal region. In the triplet precursor electron transfer systems, the negative exchange interaction resulted from the selective singlet stabilization when the ion pair state crossed with the singlet ground state at the normal region. When the free energy change is larger than about 1.8 eV, the positive exchange interaction resulted from the spin-selective destabilization in the singlet ion pair, since the level crossing occurs at the inverted region.

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Section: Resultssupporting

confidence: 90%

Chemically Induced Dynamic Electron Polarization Study on the Mechanism of Exchange Interaction in Radical Ion Pairs Generated by Photoinduced Electron Transfer Reactions

et al. 1999

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“…Now photoinduced ET or H abstraction produces radical pairs (RPs) and/or radical ion pairs (RIPs) as intermediates. It is known that an application of an external MF can modify the pathways of such reactions [5][6][7][8][9][10]. Actually, there is always an interconversion between singlet (S) and triplet (T 7 , T 0 ) states by the electron-nuclear hyperfine interactions present in the system [11].…”

Section: Introductionmentioning

confidence: 99%

Interactions between 9,10-anthraquinone and aromatic amines in homogeneous and micellar media: A laser flash photolysis and magnetic field effect study

Chowdhury

Basu

2006

Journal of Luminescence

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“…The magnetic field effect (MFE) on the yield of spin-selective RP recombination products directly reveals the magnitude of magnetic coupling between the spins of the RP and is proportional to V DA 2 (2, 16-18). The mechanistic details of the radical pair intersystem crossing mechanism (RP-ISC) and the theory behind the MFE have been researched extensively (19) and applied to many donor-acceptor systems (2,8,9,(20)(21)(22)(23)(24) …”

mentioning

confidence: 99%

Wire-like charge transport at near constant bridge energy through fluorene oligomers

Goldsmith

Sinks

Kelley

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

167

187

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The study of photoinitiated electron transfer in donor-bridgeacceptor molecules has helped elucidate the distance dependence of electron transfer rates and behavior of various electron transfer mechanisms. In all reported cases, the energies of the bridge electronic states involved in the electron transfer change dramatically as the length of the bridge is varied. We report here, in contrast, an instance in which the length of the bridge, and therefore the distance over which the electron is transferred, can be varied without significantly changing the energies of the relevant bridge states. A series of donor-bridge-acceptor molecules having phenothiazine (PTZ) donors, 2,7-oligofluorene (FLn) bridges, and perylene-3,4:9,10-bis(dicarboximide) (PDI) acceptors was studied. Photoexcitation of PDI to its lowest excited singlet state results in oxidation of PTZ via the FLn bridge. In toluene, the rate constants for both charge separation and recombination as well as the energy levels of the relevant FL n ؉• bridge states for n ‫؍‬ electron transfer ͉ hopping ͉ superexchange E fficient long-distance electron transfer is a prerequisite for molecular materials designed to serve as active components in solar cells and nanoscale devices. Being able to consistently achieve ''wire-like'' charge transport in synthetic systems requires a thorough understanding of the mechanisms involved. Recently progress has been made toward this goal (1, 2), but the complexity of even simple molecular systems poses a formidable challenge. In particular, the distance dependence of electron transfer has been shown to be a complex function of individual parameters, including molecular geometry and energetics (3,4). While the use of rigidly bound electron donor (D), bridge (B), electron acceptor (A) compounds has simplified the investigation of the distance dependence of electron transfer by keeping the donor-acceptor distance (r DA ) well defined, it is difficult to vary r DA by changing the length of the bridge without substantially altering the energy levels of the bridge.In this report we examine electron transfer in a system in which r DA can be changed considerably, whereas the oxidation potential of the intervening bridge changes very little. Approximate matching between the donor and bridge energy levels (2, 5, 6) has been shown to be critical for promoting incoherent, or ''wire-like,'' transport over coherent, or exponentially distance-dependent, superexchange transport (7). These earlier studies have shown how the energetic convergence of the relevant donor and bridge energy levels results in a minimal injection barrier for hole transfer to the bridge, leading to a striking change in mechanism as the bridge is lengthened.The relative importance of incoherent transport at larger values of r DA has been confirmed by independent measurements of the decreasing contribution of superexchange to the overall electron transfer rate with increasing length (8, 9). The indirect electronic coupling between the electron donor and acceptor via the br...

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Magnetic Field Effects on the Photochemical Electron-Transfer Reactions of 10-Methylphenothiazine and Dicyanobenzene Derivatives in Nonviscous Homogeneous Solutions

Cited by 41 publications

References 48 publications

Chemically Induced Dynamic Electron Polarization Study on the Mechanism of Exchange Interaction in Radical Ion Pairs Generated by Photoinduced Electron Transfer Reactions

Chemically Induced Dynamic Electron Polarization Study on the Mechanism of Exchange Interaction in Radical Ion Pairs Generated by Photoinduced Electron Transfer Reactions

Interactions between 9,10-anthraquinone and aromatic amines in homogeneous and micellar media: A laser flash photolysis and magnetic field effect study

Wire-like charge transport at near constant bridge energy through fluorene oligomers

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