Zeolite-based heterogeneous photosensitizers containing triphenylpyrylium and dibenzotropylium cations. Modifications of the product selectivity in the cyclodimerization of 1,3-cyclohexadiene

Fornés, Vicente; Garcı́a, Hermenegildo; Miranda, Miguel A.; Mojarrad, Fatemeh; Sabater, Marı́a J.; Suliman, Nadia N.E.

doi:10.1016/s0040-4020(96)00343-2

Cited by 23 publications

(17 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Triphenylpyrylium (TPP + ) and dibenzotropylium (DT + ) cations were encapsulated in zeolite Y and MCM-41 and tested as photosensitizers in the dimerization of cyclohexadiene. The reaction was much faster in MCM-41 compared with zeolite Y, probably because of reduced diffusion limitations . In another photochemical study in MCM-41, the rate constants for the luminescence quenching of fluoranthene by molecular oxygen were evaluated …”

Section: Review Of Inclusion Chemistrymentioning

confidence: 99%

“…The reaction was much faster in MCM-41 compared with zeolite Y, probably because of reduced diffusion limitations. 67 In another photochemical study in MCM-41, the rate constants for the luminescence quenching of fluoranthene by molecular oxygen were evaluated. 68 The photosensitizer cation TPP + was either ion exchanged into MCM-41 or was synthesized within its channels from chalcone and acetophenone by Garcia et al 69 The sensitizer was four times more effective in the cis-stilbene isomerization than its tetrafluoroborate salt in solution.…”

Section: Ion Exchange and Complexationmentioning

confidence: 99%

See 1 more Smart Citation

Inclusion Chemistry in Periodic Mesoporous Hosts

1998

View full text Add to dashboard Cite

This review provides an overview of different aspects of inclusion chemistry in ordered mesoporous host materials such as MCM-41 or MCM-48 (Mobil codes). A rich field of inclusion chemistry has been explored in this context, including sorption, ion exchange, imbibition followed by reduction, grafting of reactive metal alkoxides, halides etc., grafting of silane coupling agents (sometimes followed by subsequent reactions), grafting of reactive metal complexes, and polymerization in the channels. Finally, co-condensation of reactive species during the mesopore synthesis is a method to incorporate functionality into the walls of the channel system. Important applications of these modified and functionalized systems are heterogeneous catalysis and photocatalysis involving bulky grafted catalysts and/or the conversion of large substrates. Other potential applications include ion exchange and separations, removal of heavy metals, chromatography, stabilization of quantum wires, stabilization of dyes, and polymer composites.

show abstract

Section: Review Of Inclusion Chemistrymentioning

confidence: 99%

Section: Ion Exchange and Complexationmentioning

confidence: 99%

Inclusion Chemistry in Periodic Mesoporous Hosts

1998

View full text Add to dashboard Cite

show abstract

“…This aspect of zeolite chemistry has received little attention. There are recent examples of the photosensitized electron transfer isomerization and dimerization of aryl alkenes in zeolites. − In these examples the triphenylpyrylium sensitizer was synthesized within the cavities of acidic HY zeolite. The use of zeolites as catalysts for thermal electron transfer cycloaddition chemistry has also been investigated …”

mentioning

confidence: 99%

Photoinduced Electron Transfer Reactions within Zeolites: Detection of Radical Cations and Dimerization of Arylalkenes¹

et al. 1998

View full text Add to dashboard Cite

Photosensitized electron transfer reactions between excited singlet acceptors and arylalkenes included within NaX zeolites have been studied using a combination of product studies, fluorescence spectroscopy, and diffuse reflectance laser flash photolysis. Steady-state and time-resolved fluorescence quenching of cyanoaromatic and ionic sensitizers by arylalkenes demonstrates that singlet quenching occurs predominantly by a static process. Diffuse reflectance flash photolysis studies indicate that quenching of singlet cyanoaromatic sensitizers by trans-anethole and 4-vinylanisole occurs via electron transfer and yields relatively long-lived radical cations. Signals due to trapped electrons (Na4 3+) are also observed, suggesting that photoionization of the cyanoaromatic sensitizer occurs in competition with electron transfer quenching of the excited singlet by the alkene. The long lifetimes of the radical cations indicate the utility of the zeolite environment for controlling the energy-wasting back electron transfer step. Photosensitized electron transfer reactions of five alkenes (trans-anethole, 4-vinylanisole, phenyl vinyl ether, and two indenes), using both ionic and cyanoaromatic sensitizers, lead to predominantly dimeric cyclobutane products as in solution. However, the dimer ratios are substantially different with the cis/syn cyclobutanes formed preferentially in the zeolite reactions, presumably as a result of constraints imposed by the restricted space of the zeolite supercage. In fact the zeolite environment is more important in determining the geometry of the dimeric products than is the method (direct or sensitized photocycloaddition vs radical ion initiation) for their generation.

show abstract

“…These reactions were also accompanied by extensive decomposition of the pyrylogen sensitizer. On the other hand the cycloaddition of 1,3‐cyclohexadiene occurred with 95% conversion in one‐hour with less than 5% decomposition of the pyrylogen sensitizer. The formation of transient HPY + ˙ and stilbene radical cations were directly confirmed by UV–Visible spectroscopy and by laser flash photolysis in the 1,3‐cyclohexadiene cycloaddition and the cyclobutane cycloreversion reactions , respectively.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Characterization, Photophysics and Photochemistry of Pyrylogen Electron Transfer Sensitizers

Clennan

Liao

2013

Photochem & Photobiology

View full text Add to dashboard Cite

A series of new dicationic sensitizers that are hybrids of pyrylium salts and viologens has been synthesized. The electrochemical and photophysical properties of these "pyrylogen" sensitizers are reported in sufficient detail to allow rationale design of new photoinduced electron transfer reactions. The range of their reduction potentials (+0.37-+0.05 V vs SCE) coupled with their range of singlet (48-63 kcal mol(-1)) and triplet (48-57 kcal mol(-1)) energies demonstrate that they are potent oxidizing agents in both their singlet and triplet excited states, thermodynamically capable of oxidizing substrates with oxidation potentials as high as 3.1 eV. The pyrylogens are synthesized in three steps from readily available starting materials in modest overall 11.4-22.3% yields. These sensitizers have the added advantages that: (1) their radical cations do not react on the CV timescale with oxygen bypassing the need to run reactions under nitrogen or argon and (2) have long wavelength absorptions between 413 and 523 nm well out of the range where competitive absorbance by most substrates would cause a problem. These new sensitizers do react with water requiring special precautions to operate in a dry reaction environment.

show abstract

Zeolite-based heterogeneous photosensitizers containing triphenylpyrylium and dibenzotropylium cations. Modifications of the product selectivity in the cyclodimerization of 1,3-cyclohexadiene

Cited by 23 publications

References 18 publications

Inclusion Chemistry in Periodic Mesoporous Hosts

Inclusion Chemistry in Periodic Mesoporous Hosts

Photoinduced Electron Transfer Reactions within Zeolites: Detection of Radical Cations and Dimerization of Arylalkenes¹

Synthesis, Characterization, Photophysics and Photochemistry of Pyrylogen Electron Transfer Sensitizers

Contact Info

Product

Resources

About

Zeolite-based heterogeneous photosensitizers containing triphenylpyrylium and dibenzotropylium cations. Modifications of the product selectivity in the cyclodimerization of 1,3-cyclohexadiene

Cited by 23 publications

References 18 publications

Inclusion Chemistry in Periodic Mesoporous Hosts

Inclusion Chemistry in Periodic Mesoporous Hosts

Photoinduced Electron Transfer Reactions within Zeolites: Detection of Radical Cations and Dimerization of Arylalkenes1

Synthesis, Characterization, Photophysics and Photochemistry of Pyrylogen Electron Transfer Sensitizers

Contact Info

Product

Resources

About

Photoinduced Electron Transfer Reactions within Zeolites: Detection of Radical Cations and Dimerization of Arylalkenes¹