Non-vertical energy transfer to oximes: role of structural changes

Lalevée, Jacques; Allonas, Xavier; Fouassier, Jean‐Pierre; Tachi, Hideki; Izumitani, Akihito; Shirai, Masamitsu; Tsunooka, Masahiro

doi:10.1039/b104163k

Cited by 17 publications

(13 citation statements)

References 10 publications

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“…Indeed, the five-membered ring of Ia gives a planar geometry at the ground state, in contrast to the six- or seven-membered ring systems of IIa and IVa , respectively, which distorted the planarity of the π system. As observed in a previous work, the flexible structure of IIIa exhibits an intermediate twisted geometry, β being 20.4°.…”

Section: Resultssupporting

confidence: 81%

“…Indeed, the Sandros model for the triplet energy transfer applied only in the case of rigid chromophores (fluorenone- O -acyloxime) but does not fit the experimental results obtained with flexible molecules (acetophenone- O -acyloxime). Therefore, a first set of compounds was used to clarify the behavior of oximes toward energy-transfer reaction, showing that two molecular rearrangements, π system flattening and C−N bond twist in the triplet state, are particularly important to affect the NVET character of the oximes …”

Section: Introductionmentioning

confidence: 99%

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Role of Structural Changes in the Triplet−Triplet Energy Transfer Process to Oxime Derivatives

2002

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The triplet energy accepting properties of bridged hydroxy and methyl derivatives of acetophenone oxime were examined. Sandros and Agmon−Levine−Balzani (ALB) models were used to deduce the oxime triplet energies, , and the reorganizational intrinsic barriers, ΔG #(0), associated with the reaction. It is found for the first time that these compounds exhibit different degrees of nonvertical energy transfer (NVET) behavior, depending on their chemical structure. These structural properties have been investigated at both the AM1 and the B3LYP/6-31+G(d) levels of theory. The flexibility of the ground-state molecule and the structural changes occurring during the S0 → T1 sensitized transition seem to play crucial roles. It appears that two important rearrangements are involved, namely, rotation about the C−N double bond and a π system flattening associated with a torsion about the formal C−C single bond. To relate the NVET character to these structural changes, the energy variations associated with these latter were evaluated and successfully related to ΔG #(0). Moreover, the role of the thermal activation of the molecular coordinates is evidenced through the calculations of the ground and triplet potential energy surfaces (PESs) at DFT and CIS levels. A simple model, based on the Sandros equation, was derived to include the influence of such torsional modes on the energy-transfer behavior. Finally, the experimental quenching data were fitted to this model, leading to the conclusion that, although both C−N double bond and C−C single bond torsions occur during the sensitization, the thermal activation of C−C single bond torsion plays the major role in the NVET character of oxime derivatives.

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Section: Resultssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Role of Structural Changes in the Triplet−Triplet Energy Transfer Process to Oxime Derivatives

2002

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“…The relatively high value of Δ G P3T # (0) highlights a large molecular reorganization of the compounds after the reaction. As the structure of the Ru complex is quite rigid, this would indicate that the triplet states of the RAFT agents are distorted with respect to their ground states . This may somehow be related to a predissociative triplet state.…”

Section: Methodsmentioning

confidence: 99%

Elucidation of the Key Role of [Ru(bpy)₃]²⁺ in Photocatalyzed RAFT Polymerization

et al. 2016

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Photocatalysis reactions using [Ru(II) (bpy)3 ](2+) were studied on the example of visible-light-sensitized reversible addition-fragmentation chain transfer (RAFT) polymerization. Although both photoinduced electron- and energy-transfer mechanisms are able to describe this interaction, no definitive experimental proof has been presented so far. This paper investigates the actual mechanism governing this reaction. A set of RAFT agents was selected, their redox potentials measured by cyclic voltammetry, and relaxed triplet energies calculated by quantum mechanics. Gibbs free-energy values were calculated for both electron- and energy-transfer mechanisms. Quenching rate constants were determined by laser flash photolysis. The results undoubtedly evidence the involvement of a photoinduced energy-transfer reaction. Controlled photopolymerization experiments are discussed in the light of the primary photochemical process and photodissociation ability of RAFT agent triplet states.

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“…Laser flash photolysis set-up. It has been recently shown that laser flash photolysis was suitable for the direct observation of peroxyl radicals 40 (ROO ) resulting from the interaction of radicals (R ) generated upon UV irradiation to oxygen. The experimental procedure requires the formation of tert-butoxyl radical (B) from the irradiation of di-tert-butyl peroxide (A) at 355 nm (Fig.…”

Section: Hybrid Film Photopolymerisationmentioning

confidence: 99%

Influence of zirconium propoxide on the radical induced photopolymerisation of hybrid sol–gel materials

et al. 2008

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Non-vertical energy transfer to oximes: role of structural changes

Abstract: Energy transfer to aromatic ketone oximes can exhibit nonvertical behaviour depending on the planarity of ground state equilibrium geometry, a fact discussed in terms of structural changes of ground and triplet states.

Cited by 17 publications

References 10 publications

Role of Structural Changes in the Triplet−Triplet Energy Transfer Process to Oxime Derivatives

Role of Structural Changes in the Triplet−Triplet Energy Transfer Process to Oxime Derivatives

Elucidation of the Key Role of [Ru(bpy)₃]²⁺ in Photocatalyzed RAFT Polymerization

Influence of zirconium propoxide on the radical induced photopolymerisation of hybrid sol–gel materials

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Non-vertical energy transfer to oximes: role of structural changes

Abstract: Energy transfer to aromatic ketone oximes can exhibit nonvertical behaviour depending on the planarity of ground state equilibrium geometry, a fact discussed in terms of structural changes of ground and triplet states.

Cited by 17 publications

References 10 publications

Role of Structural Changes in the Triplet−Triplet Energy Transfer Process to Oxime Derivatives

Role of Structural Changes in the Triplet−Triplet Energy Transfer Process to Oxime Derivatives

Elucidation of the Key Role of [Ru(bpy)3]2+ in Photocatalyzed RAFT Polymerization

Influence of zirconium propoxide on the radical induced photopolymerisation of hybrid sol–gel materials

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Elucidation of the Key Role of [Ru(bpy)₃]²⁺ in Photocatalyzed RAFT Polymerization