Photocatalysis by transition-metal coordination compounds in homogeneous phase. The role of ligand photodissociation

Moggi, L.; Juris, Alberto; Sandrini, D.; Manfrin, M. F.

doi:10.1007/bf03052415

Cited by 42 publications

(6 citation statements)

References 163 publications

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“…Photogenerated catalysis Catalyzed photolysis photoinduced catalytic reactions [18] catalyzed photochemistry [17] (Stoeichiometric photogenerated catalysis [15]) catalyzed photoreactions [17,20] sensitized photoreactions [17,18] photosensitized reactions [21] photo-assisted catalysis [18,22] (stoichiometric photogenerated catalysis [15]) substance-assisted photoreactions [23] substance-catalyzed photoreactions [23] which designates the number of reagent molecules consumed or product molecules formed per surface active site per unit time, and (b) turnover frequency (TOF) which denotes the number of reactant molecules consumed, or product molecules formed, per active site per unit time (note the confusing similarity with turnover rate-however, see below). Laidler [24] noted that because turnover numbers (and by extension, turnover rates and turnover frequencies) vary with temperature, concentration and other experimental conditions, TON is not a useful quantity in kinetic work.…”

Section: Catalytic In Photons Non-catalytic In Photonsmentioning

confidence: 99%

Suggested terms and definitions in photocatalysis and radiocatalysis

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Emeline

2002

International Journal of Photoenergy

162

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This document has two principal goals. First, it summarizes some of the issues that pertain to the complexities encountered in photocatalysis. Secondly, it presents suggested terms and definitions proposed to describe those phenomena, which fall under the umbrella of “photocatalysis” and “radiocatalysis”. A distinction is made between the different phenomena that are related to either or both photochemistry and photocatalysis, and to radiation chemistry and radiocatalysis. Consistent definitions of terms in these areas are given. Definitions of important parameters that describe photocatalytic and radiocatalytic phenomena quantitatively are also proposed. As with the related Glossary of Terms in Photochemistry, this document is a dynamic working document to provide the base for lively discussion and debate by the interested community. The terms and definitions will no doubt need to be revisited from time to time as the fields of photocatalysis and radiocatalysis progress and new discoveries reported. Some of the terms used in photochemistry are also given for completion, either verbatim or modified to address the issues of photocatalysis.

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Section: Catalytic In Photons Non-catalytic In Photonsmentioning

confidence: 99%

Suggested terms and definitions in photocatalysis and radiocatalysis

Serpone

Emeline

2002

International Journal of Photoenergy

162

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“…Later it was shown that SnCl 4 shows a similar effect on the [2 + 2] photodimerization of dibenzylideneacetone and the solid-state reaction was further investigated by Alcock et al, who confirmed the structure of the [2 + 2] photodimer . While the influence of metal catalysts on various photochemical reactions was investigated in the 1970s and 1980s, specific studies regarding the influence of Lewis acids on [2 + 2] photocycloaddition reactions of α,β-unsaturated carbonyl compounds in solution were reported by Lewis et al in 1983 . It was found that the photodimerization of coumarin was catalyzed by BF 3 ·OEt 2 , and the syn head-to-tail dimer was obtained as a single product upon irradiation of an equimolar solution of coumarin and BF 3 ·OEt 2 in >85% yield.…”

Section: Introductionmentioning

confidence: 98%

Enantioselective Lewis Acid Catalysis in Intramolecular [2 + 2] Photocycloaddition Reactions: A Mechanistic Comparison between Representative Coumarin and Enone Substrates

2015

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The intramolecular [2 + 2] photocycloaddition of three 4-(alk-4-enyl)coumarins and three 1-(alk-4-enoyl)-2,3-dihydropyridones was studied in the absence and in the presence of Lewis acids (irradiation wavelength λ = 366 nm). Spectral and kinetic data were collected for the respective parent compounds with a pent-4-enyl and a pent-4-enoyl chain. For the substrates with a methyl group in cis- or trans-position of the terminal alkene carbon atom (hex-4-enyl and hex-4-enoyl substitution), the stereochemical outcome of the [2 + 2] photocycloaddition was investigated. The mechanistic course of the uncatalyzed coumarin reactions was found to be a singlet pathway, whereas Lewis acid-catalyzed reactions proceeded with higher reaction rates in the triplet manifold. Contrary to that, the dihydropyridones underwent a fast triplet reaction in the absence of the Lewis acid. In the presence of a chiral Lewis acid the reactions slowed down but, due to the high extinction coefficient of the Lewis acid/dihydropyridone complexes at λ = 366 nm, still resulted in high enantioselectivity.

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“…Due to this high reactivity, the "active species" are generally difficult to handle and thus are not directly applicable as catalysts. CO-ligands in carbonyl complexes can conveniently be removed photochemically [8]. This can in many cases be accomplished by the use of a stabilizing ligand.…”

Section: Introductionmentioning

confidence: 99%