Intrazeolite photochemistry. VI. Diffuse reflectance laser flash photolysis and product studies of diphenylmethyl radicals on solid supports

Kelly, G. P.; Willsher, C. J.; Wilkinson, Frances; Netto‐Ferreira, José Carlos; Olea, Andrés F.; Weir, D.; Johnston, Linda; Scaiano, J. C.

doi:10.1139/v90-129

Cited by 59 publications

(48 citation statements)

References 22 publications

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“…Accordingly, we have examined the behavior of several model ketones (1-7) on three solid supports (silica gel, Na-X zeolite, and cellulose) using a combination of diffuse reflectance laser flash photolysis and product studies. The diffuse reflectance flash photolysis techniques developed by Wilkinson and coworkers over the last decade have considerable potential for studying transients such as triplets, radicals, and radical ions in opaque solids (18)(19)(20)(21)(22)(23)(24)(25)(26). The present studies provide insight into the manner in which the initial photochemistry and the behavior of photogenerated radical pairs are modified for lignin model ketones in a constrained environment.…”

Section: Omementioning

confidence: 81%

Photochemistry of lignin model compounds on solid supports

Hurrell¹,

Johnston²,

Mathivanan³

et al. 1993

Can. J. Chem.

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. Can. J. Chem. 71, 1340 (1993).The photochemistry of several substituted a-(aryloxy)acetoveratrones that are models for chromophores in lignin has been studied using a combination of laser flash photolysis and product studies in solution and on silica, Na-X zeolite, and cellulose. The lifetimes of the triplet ketones vary substantially with the electron-donating ability of the substituents in the a-aryloxy ring, with values ranging from 30 ns for the 4-methoxy derivative to 5.5 ps for the 4-cyano ketone in acetonitrile. The triplet ketones are considerably longer lived on a silica surface than in solution and do not decay with first-order kinetics; however, they are all shorter lived than triplet acetoveratrone under the same conditions, indicating that P-phenyl quenching and (or) P-cleavage dominate their decay. The same triplets show quite different kinetic behavior in Na-X or cellulose and there is no indication in these systems for the importance of either P-phenyl quenching or P-cleavage in determining the rates of triplet decay. Product studies for a-guaiacoxyacetoveratrone indicate that Pcleavage from the singlet excited state is responsible for product formation; in contrast to solution results, the phenacyl-phenoxyl radical pairs react exclusively by geminate recombination to give rearranged ketones resulting from ortho and para ring coupling of the two radicals. Product formation is very inefficient for this ketone in cellulose, indicating either a low singlet reactivity or efficient geminate recombination of the initial radical pair to regenerate starting material. Utilisant une combinaison de photolyse Cclair au laser et une Ctude des produits en solution, sur de la silice, sur une zColite Na-X et sur de la cellulose, on a CtudiC la photochimie de plusieurs a-(aryloxy)acCtovCratrones qui sont des modkles pour les chromophores de la lignine. Les temps de vie dcs cCtones triplet varient beaucoup avec les capacitts des substituants du cycle aryloxy ?i donner des Clectrons; les valeurs varient de 30 ns pour le dCrivC 4-mtthoxy 5 5,5 ps pour la 4-cyanocCtone dans I'acCtonitrile. Les cCtones triplet ont des temps de vie beaucoup plus ClevCs sur une surface de silice qu'en solution et leur dCgCnCrescence n'est pas du premier ordre; toutcfois, leurs temps de vie sont tous plus courts que celui du triplet de I'acCtovCratrone dans les mCmes conditions et ces rksultats indiquent que la relaxation P-phknyle et (ou) un clivage P dominent leur dCgCnCrescence. Les mCmes triplets prtsentent un comporternent cinCtique trks diffCrent avec Na-X ou la cellulose et il ne semble pas que, dans ces systi-mes, la relaxation P-phCnyle ou un clivage P joue un r6le important dans la determination de la vitesse de dCgCnCrescence de I'Ctat triplet. Des etudes de produit pour l'a-guai'acoxyacttovCratrone indiquent que le clivage P B partir de 1'Ctat singulet excitC est responsable pour la formation des produits; par opposition aux rksultats obtenus en solution, Ics paires de radicaux phenacyle-phCnoxyle rkagissent exclusivement p...

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Section: Omementioning

confidence: 81%

Photochemistry of lignin model compounds on solid supports

Hurrell¹,

Johnston²,

Mathivanan³

et al. 1993

Can. J. Chem.

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“…The software package has been developed in the LabVIEW environment from National Instruments and compiled as a stand-alone application. Fundamentals [13] and details [14] of similar time-resolved laser setups has been published elsewhere. The samples contained in a Suprasil quartz 0.7 × 0.7 cuvette were capped with a septum and purged with N 2 for at least 15min before laser experiments.…”

Section: Synthesis Ofmentioning

confidence: 99%

Synthesis and Photophysical Properties of the 4‐(Biphenyl‐4‐yl)‐2,6‐bis(4‐iodophenyl)pyrylium Ion

et al. 2006

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A triarylpyrylium ion containing iodo and biphenyl substituents has been synthesized and its photophysical properties measured. Compared to its parent triphenylpyrylium ion,the photophysical data recorded for 4‐(biphenyl‐4‐yl)‐2,6‐bis(4‐iodophenyl)pyrylium are significantly influenced by substitution. Remarkable decreases in fluorescence and phosphorescence quantum yields, a shorter singlet lifetime, and lower energies of the singlet and triplet excited states are observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…The signal from the monochromator/photomultiplier detection system was captured by a Tektronix 2440 digitizer and transferred to a PC computer that controlled the experiment and provided suitable processing and data storage capabilities. Fundamentals [39][40] and details [41] of similar time-resolved diffuse reflectance laser set up has been published elsewhere.…”

Section: Methodsmentioning

confidence: 99%

Organosilica Spheres Covalently Functionalized with Diphenylanthracene and Viologen Units

Álvaro¹,

Bizzoca²,

Ferrer³

et al. 2010

ChemPhysChem

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Organosilica spheres functionalized with two different photoactive units, diphenylanthracene, DPA@SPH, and viologen, VIO@SPH, covalently linked to the silica framework are prepared. These new materials have a uniform diameter, 300 nm for the DPA@SPH and 550 nm for the VIO@SPH, and exhibit the typical photochemical response of the organic moieties. It is observed that organic radical cations incorporated in the structure of the functionalized silica spheres are remarkably persistent. Due to their morphology and regular diameter DPA@SPH do not tend to aggregate and they form a highly regular, ordered and homogeneous multilayer film of high surface coverage which is employed as the active layer for the preparation of an electroluminescence cell.

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Intrazeolite photochemistry. VI. Diffuse reflectance laser flash photolysis and product studies of diphenylmethyl radicals on solid supports

Cited by 59 publications

References 22 publications

Photochemistry of lignin model compounds on solid supports

Photochemistry of lignin model compounds on solid supports

Synthesis and Photophysical Properties of the 4‐(Biphenyl‐4‐yl)‐2,6‐bis(4‐iodophenyl)pyrylium Ion

Organosilica Spheres Covalently Functionalized with Diphenylanthracene and Viologen Units

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