Electron transfer in zeolites: formation of aminium and bipyridinium cation radicals

Brunel, Daniel; Nagy, J.B.; Daelen, Guy; Derouane, Éric G.; Geneste, P.; Vanderveken, D. J.

doi:10.1016/0926-860x(93)85036-o

Cited by 5 publications

(6 citation statements)

References 21 publications

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“…Accordingly, HY developed a very weak yellow coloration when treated with a CH 2 Cl 2 solution of TOH. These results are also in agreement with recent reports of incorporation of TOH on HY as well as with the lack of adsorption of similarly shaped triarylamines on Y faujasites …”

Section: Resultssupporting

confidence: 93%

“…These results are also in agreement with recent reports of incorporation of TOH on HY 49 as well as with the lack of adsorption of similarly shaped triarylamines on Y faujasites. 50 In contrast, preparation of substituted trityl cations was successfully achieved by condensation of benzaldehydes with electron-rich aromatic compounds, catalyzed by the acid sites of large pore zeolites (Scheme 1). It is well known 51 that hydroxyalkylation of arenes with aldehydes affords initially benzylic alcohols which are much more reactive than the starting carbonyl compound and hence undergo further alkylation to R,Rdiarylalkanes under the reaction conditions.…”

Section: Preparation and Characterization Of Triarylmethyliummentioning

confidence: 99%

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Triarylmethylium Cations Encapsulated within Zeolite Supercages

et al. 1996

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A series of substituted triarylmethylium cations, including malachite green, tris(4-methoxyphenyl)methylium, and bis(4-methoxyphenyl)phenylmethylium cations, has been prepared adsorbed on tridirectional large pore zeolites Y and β in their H+ or La3+ form, as well as within the novel mesoporous aluminosilicate MCM-41, by ship-in-a-bottle synthesis from the corresponding benzaldehyde and N,N-dimethylaniline or anisole. The resulting composites exhibit diffuse reflectance and IR spectra characteristic of these trityl dyes. The cation content was determined by thermogravimetry−differential scanning calorimetry. Preparation of these triarylmethylium cations exclusively on the external surface of ZSM-5, a medium pore zeolite whose internal voids are too small to accommodate these cations, is also possible. Therefore, the methodology based in the diffusion of smaller precursors does not guarantee itself the intrazeolite location of the synthesized guests. In this work, we have experimentally determined that the dyes are blocked in the interior of the faujasite pores. Thus, direct evidence showing the location of the organic material inside the zeolite supercages was obtained using X-ray diffraction and X-ray photoelectron spectroscopy. These dyes incorporated within microporous solids can act as heterogeneous photosensitizers to promote the sensitized dimerization of 1,3-cyclohexadiene.

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Section: Resultssupporting

confidence: 93%

Section: Preparation and Characterization Of Triarylmethyliummentioning

confidence: 99%

Triarylmethylium Cations Encapsulated within Zeolite Supercages

et al. 1996

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“…261 With the benefit of hindsight, these choices were unfortunate: 103 gave rise to the blue species (again assigned to 103 •+ ); 70 probed only the external surface because it is too large to pass through the 0.74 nm pore opening. 193 Pulse radiolysis studies produced "authentic" UV-Vis spectra of 103 •+ (λ max 550 nm) and a dimer radical cation, [103‚‚‚103] •+ , (λ max 520 nm), 337,338 both different from the maximum of the "blue species". However, nanosecond laser flash studies of p-substituted derivatives revealed that 103 •+ is highly reactive in solution and unlikely to be detected in pulse radiolysis.…”

Section: Vb3 the Nature Of The Blue Species Generated Upon Adsorption...mentioning

confidence: 99%

“…A plethora of organic radical cations can be generated in zeolites, either spontaneously upon inclusion of their precursors or by action of light, anodic oxidation, or radiation. ,,− The rigid microporous solids serve as excellent matrices, stabilizing otherwise reactive or unstable radical cations, , due to the combined contributions of the intense electrostatic fields inside the zeolite and from topological restrictions that prevent access of external reagents. Following early work aimed to probe the activities of active solids, the role of their physicochemical parameters in radical cation generation was evaluated.…”

Section: Spontaneous Generation Of Radical Cations In Zeolitesmentioning

confidence: 99%

Generation and Reactions of Organic Radical Cations in Zeolites

2002

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“…Numerous organic radical cations have been generated spontaneously by inclusion of their precursors into zeolites. [1][2][3][4][5][6][7][8][9][10][11] In many cases, these rigid microporous solids provide excellent matrices to stabilize these otherwise very reactive intermediates. 12, 13 The remarkable stabilization within the zeolite host arises from the combined contribution of the intense electrostatic fields inside the zeolite and from geometrical restrictions that impede the approach of external reagents.…”

Section: Introductionmentioning

confidence: 99%