Facile reduction of sodium and bipyridinium cations within zeolites with Tesla spark-coil

Park, Y.S.; Um, S.Y.; Yoon, Kyung Byung

doi:10.1016/0009-2614(96)00164-9

Cited by 8 publications

(1 citation statement)

References 24 publications

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“…It has been demonstrated that ET takes place from the framework to photosensitized electron acceptors such as pyrene, − tetracyanobenezene, 1,4-dicyanobenzene, pyromellitic dianhydride, and methyl viologen (MV 2+ ) . In close relation to the above, zeolite frameworks have been known to eject electrons upon exposure to high-energy radiations such as γ-ray, X-ray, electron beams, , and high-energy UV (such as 185, 193, and 248 nm). , The electrons generated from the framework by the high-energy radiations have been shown to reduce clusters of alkali metal ions (such as 4 Na + ), MV 2+ , , and O 2 . Thus, the donor property of Z n - has been unambiguously established.…”

Section: Resultsmentioning

confidence: 99%

Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)₃²⁺as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen

et al. 2002

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K(+)-exchanged, Ru(bpy)(3)(2+)-encapsulating zeolite-Y [K(+)-Ru(bpy)(3)(2+)Y] and N-[3-(dicyclohexylmethyl)oxypropyl-N'-methyl-4,4'-bipyridinium [DCH-MV(2+)] were prepared, and visible light-induced electron transfer from the zeolite-encapsulated Ru(II) complex to the size-excluded viologen was studied in acetonitrile. Addition of a series of crown ethers (CEs) into the heterogeneous solution leads to over a 10-fold increase in the yield of DCH-MV(*)(+), where the yield linearly increases as the formation constant of CE with K(+) [K(f)(K(+))(CE)] increases. The following two sequential events are attributed to be responsible for the above novel phenomenon. First, K(+) ions are liberated from the zeolite to solution during interfacial electron transfer from the photoexcited Ru(II) complexes to DCH-MV(2+). Second, the liberated K(+) ions form strong host-guest complexes with the added CE molecules, which leads to retardation of the reverse flow of the cations, hence the charge-balancing electrons, from the solution to the zeolite. Surprisingly, the yield of DCH-MV(*)(+) reaches more than approximately 50 times the amount of Ru(bpy)(3)(2+) situated in the outermost supercages, despite the absence of electron relay in the zeolite. This is attributed to photosensitized electron pumping from the zeolite framework to viologen by the outermost Ru(bpy)(3)(2+) ions. In support of the above conclusion, Ru(bpy)(3)(3+) does not accumulate in the zeolite host while DCH-MV(*)(+) accumulates in the supernatant solution. Consistent with the above, the independently prepared hexafluorophosphate salt of Ru(bpy)(3)(3+) is reduced to Ru(bpy)(3)(2+) in acetonitrile upon contact with Ru(bpy)(3)(2+)-free M(+)Y (M(+) = Li(+), Na(+), K(+), Rb(+), and Cs(+)), where the yield increases as the donor strength of the framework oxygen increases. Although small, thermal electron transfer also takes place from the zeolite framework to DCH-MV(2+), where the yield increases upon increasing the donor strength of the framework, concentration of DCH-MV(2+), temperature, and K(f)(K(+))(CE) (when K(+)Y is the zeolite host). The photoyield is always higher than the thermal yield by 4-30 times, confirming that the zeolite-encapsulated Ru(bpy)(3)(2+) serves as the photosensitized electron pump.

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Section: Resultsmentioning

confidence: 99%

Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)₃²⁺as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen

et al. 2002

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Highly selective epoxidation of cyclohexene by reductive activation of molecular dioxygen using hexylviologen as catalyst

Tsuda

Matsui

Takahashi

1999

Journal of Molecular Catalysis A: Chemical

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Charge-Transfer Interaction of Methyl Viologen with Zeolite Framework and Dramatic Blue Shift of Methyl Viologen−Arene Charge-Transfer Band upon Increasing the Size of Alkali Metal Cation

Park

Yoon

1999

J. Am. Chem. Soc.

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A series of alkali metal-exchanged zeolites X and Y co-exchanged with small amounts (1 per unit cell) of methyl viologen (MV 2+ ) were prepared. The diffuse reflectance UV-vis spectra of the dried zeolites showed broad absorption bands in the 220-320-nm region. Decomposition of the bands revealed that each absorption band consists of two Gaussian bands. Of the two, the one that appears at the higher energy region is always more intense and much broader than the other that appears at the lower energy region. The broader, higher energy band (BHEB) progressively red-shifted upon increasing the electropositivity of the alkali metal cation, while the narrower, lower energy band (NLEB) remained stationary. The BHEB was assigned as the charge-transfer (CT) band between MV 2+ and the zeolite framework on the basis of the linear relationship established between the energy of the absorption maximum and Sanderson's partial charge of the framework oxygen. The remaining, stationary NLEB was consequently assigned as the absorption band of MV 2+ in the zeolite media. Subsequent formation of CT complexes of MV 2+ with guest arene donors such as anthracene, 1-methoxynaphthalene, and pentamethylbenzene within the zeolites showed a dramatic blue shift of MV 2+arene CT bands upon increasing the size of alkali metal cation. The possible reasons for the dramatic, cationdependent spectral shift of MV 2+ -arene CT bands are discussed.

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Facile reduction of sodium and bipyridinium cations within zeolites with Tesla spark-coil

Cited by 8 publications

References 24 publications

Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)₃²⁺as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen

Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)₃²⁺as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen

Highly selective epoxidation of cyclohexene by reductive activation of molecular dioxygen using hexylviologen as catalyst

Charge-Transfer Interaction of Methyl Viologen with Zeolite Framework and Dramatic Blue Shift of Methyl Viologen−Arene Charge-Transfer Band upon Increasing the Size of Alkali Metal Cation

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Facile reduction of sodium and bipyridinium cations within zeolites with Tesla spark-coil

Cited by 8 publications

References 24 publications

Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)32+as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen

Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)32+as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen

Highly selective epoxidation of cyclohexene by reductive activation of molecular dioxygen using hexylviologen as catalyst

Charge-Transfer Interaction of Methyl Viologen with Zeolite Framework and Dramatic Blue Shift of Methyl Viologen−Arene Charge-Transfer Band upon Increasing the Size of Alkali Metal Cation

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Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)₃²⁺as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen

Long-Lived Charge-Separation by Retarding Reverse Flow of Charge-Balancing Cation and Zeolite-Encapsulated Ru(bpy)₃²⁺as Photosensitized Electron Pump from Zeolite Framework to Externally Placed Viologen