Radiative and nonradiative electron transfer in donor–acceptor phenoxazine and phenothiazine derivatives

Borowicz, P.; Herbich, Jerzy; Kapturkiewicz, Andrzej; Opałło, Marcin; Nowacki, Jacek

doi:10.1016/s0301-0104(99)00265-7

Cited by 43 publications

(47 citation statements)

References 40 publications

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“…24 The planar phenoxazine core versus the bent phenothiazine core can be visualized in the X-ray crystal structures of the PCs (Figure 6). The electrostatic potential (ESP) mapped electron density of the 3 PC* state of these compounds reveal that electron density is transferred to the naphthalene substituent (red region) in phenoxazine upon photoexcitation and ISC from 1 PC, even more so with dihydrophenazines, while electron density remains localized on the phenothiazine core (Figure 7).…”

Section: Resultsmentioning

confidence: 99%

Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts

et al. 2016

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N-Aryl phenoxazines have been synthesized and introduced as strongly reducing metal-free photoredox catalysts in organocatalyzed atom transfer radical polymerization for the synthesis of well-defined polymers. Experiments confirmed quantum chemical predictions that, like their dihydrophenazine analogs, the photoexcited states of phenoxazine photoredox catalysts are strongly reducing and achieve superior performance when they possess charge transfer character. We compare phenoxazines to previously reported dihydrophenazines and phenothiazines as photoredox catalysts to gain insight into the performance of these catalysts and establish principles for catalyst design. A key finding reveals that maintenance of a planar conformation of the phenoxazine catalyst during the catalytic cycle encourages the synthesis of well-defined macromolecules. Using these principles, we realized a core substituted phenoxazine as a visible light photoredox catalyst that performed superior to UV-absorbing phenoxazines as well as previously reported organic photocatalysts in organocatalyzed atom transfer radical polymerization. Using this catalyst and irradiating with white LEDs resulted in the production of polymers with targeted molecular weights through achieving quantitative initiator efficiencies, which possess dispersities ranging from 1.13 to 1.31.

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Section: Resultsmentioning

confidence: 99%

Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts

et al. 2016

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“…9 It must be pointed out that, the radiationless depopulation of the lowest excited 1 CT state was mostly controlled by two competitive mechanisms: the intersystem crossing to the triplet manifold and a direct radiationless charge recombination process in the singlet manifold. 5,9,10,26 The direct radiationless charge recombination channel is the dominant radiationless deactivation path in the polar solvent, which can be proved by the CT fluorescence intensity decreased with the increase of solvent polarity in our phenothiazine system. However, in nonpolar or lowly polar solvents the ISC process is an important radiationless deactivation path.…”

Section: Excited Ct State Depopulationmentioning

confidence: 67%

“…The photophysical behavior of a particular A-D system 5,[9][10][11] can be predicted from the properties of its donor and acceptor subunits alone. The acceptable strategy to design a particular A-D system can select the acceptor and donor subunits with appropriate redox potentials to make the energy of the CT 1,3 (A --D ＋ ) states lowered with respect to those of the locally excited triplet states 3 (A-D) * .…”

Section: -11mentioning

confidence: 99%

“…The nonradiative depopulation of the excited 1 (A --D ＋ ) state is usually controlled by two competitive mechanisms. 5,[9][10][11] The first corresponds to a direct radiationless charge recombination (DRCR with the rate constant k nr ) in the singlet manifold, which leads to the ground state S 0 of the particular A-D molecule. In the second the lowest excited triplet 3 (A-D) * state, localized typically in the A or D subunit, is populated most probably via a CT triplet state 3 (A --D ＋ ) by the inter-system crossing process (ISC with the rate constant k isc ).…”

Section: -11mentioning

confidence: 99%

“…On the other hand, the electronic interactions stabilize the 3 CT states in the highly polar solvents, thus these states are energetically located below the locally excited triplet ones. 5,9,10,26 Figure 6 presents the corresponding processes and energy level diagrams.…”

Section: Excited Ct State Depopulationmentioning

confidence: 99%

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Charge Transfer in Excited Donor‐acceptor Phenothiazine Derivatives

Liu¹,

Wei²,

Yuan³

et al. 2005

Chin. J. Chem.

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A series of N-bonded donor-acceptor derivatives of phenothiazine containing phenyl (PHPZ), anisyl (ANPZ), pyridyl (PYPZ), naphthyl (NAPZ), acetylphenyl (APPZ), and cyanophenyl (CPPZ) as an electron acceptor have been synthesized. Their photophysical properties were investigated in solvents of different polarities by absorption and emission techniques. These studies clearly revealed the existence of an intramolecular charge transfer (ICT) excited state in the latter four compounds. The solvent dependent Stokes shift values were analyzed by the modified Lippert-Mataga equation to obtain the excited state dipole moment values. The large excited state dipole moment suggests that the full (or nearly full) electron transfer take place in the A-D systems. In the system of A-D phenothiazine derivatives, the transition dipole moments M flu were determined mainly by direct interactions between the solvent-equilibrated fluorescence 1 CT state and ground state because of their lack of significant change with increase of the solvent polarity. The electron structure and molecular conformation of phenothiazine derivatives will be significantly changed with the increase of the electron affinity of the N-10 substituent.

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Cationic photopolymerization of tetrahydrofuran: A mechanistic study on the use of a sulfonium salt-phenothiazine initiation system

Rodrigues

Neumann

2000

J. Polym. Sci. A Polym. Chem.

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The kinetics aspects of the photoinitiated polymerization of tetrahydrofuran with triphenylsulfonium hexafluoroarsenate and sensitized by phenothiazine was studied under visible‐light irradiation. A photosensitizer mechanism was proposed involving electron transfer from phenothiazine to the triphenylsulfonium salt, forming a cation radical, the true precursor of the polymerization. An initial complex in the ground state between the phenothiazine and the triphenylsulfonium was formed prior to the excitation, and this complex actually activated the photopolymerization rate. The polymerization conversion presented an S‐shaped curve, suggesting an induction period caused by the existence of two pathways responsible for the beginning of the polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 46–55, 2001

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Radiative and nonradiative electron transfer in donor–acceptor phenoxazine and phenothiazine derivatives

Cited by 43 publications

References 40 publications

Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts

Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts

Charge Transfer in Excited Donor‐acceptor Phenothiazine Derivatives

Cationic photopolymerization of tetrahydrofuran: A mechanistic study on the use of a sulfonium salt-phenothiazine initiation system

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