Polymerization initiation and transient spectrometric studies of water-soluble and -insoluble tert-butyl aroylperbenzoates

Shah, Bela; Neckers, Douglas C.

doi:10.1016/j.jphotochem.2004.07.022

Cited by 4 publications

(2 citation statements)

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“…After absorbing a photon, triplet benzophenone is formed in a very efficient intersystem crossing (ISC) process with a quantum yield of unity (with a characteristic time of 6–10 ps , ). Accordingly, no fluorescence is observed.…”

Section: Introductionmentioning

confidence: 99%

“…The observations made in this study can be interpreted in terms of the simplified reaction mechanism presented in Scheme 1 for the benzophenone −2-propanol system. 19,22,23 After absorbing a photon, triplet benzophenone is formed in a very efficient intersystem crossing (ISC) process with a quantum yield of unity (with a characteristic time of 6−10 ps 24,25 ). Accordingly, no fluorescence is observed.…”

Section: ■ Introductionmentioning

confidence: 99%

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Substituent Effect on the Photoreduction Kinetics of Benzophenone

et al. 2013

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The kinetics of the photoreduction of four benzophenone derivatives by isopropyl alcohol was examined in acetonitrile, namely tetra-meta-trifluoromethyl-, di-para-trifluoromethyl-, di-paramethoxy benzophenone and for comparison the unsubstituted molecule itself. The basic spectroscopic (absorption and phosphorescence spectra) and photophysical (quantum yields, excited state energies) properties were established, and the key kinetic parameters were determined by the laser flash photolysis transient absorption technique. The rate coefficients of both the primary and secondary photoreduction reaction show remarkable dependence on ring substitution. This substantial effect is caused by the considerable change in the activation energy of the corresponding process. The experimental results as well as DFT quantum chemical calculations clearly indicate that these benzophenone derivatives all react as n-π* excited ketones, and the rate as well as the activation energy of the reduction steps change parallel with the reaction enthalpies, the determining factor being the stability of the forming aromatic ketyl 2 radicals. The secondary photoreduction of benzophenones by the aliphatic ketyl radical formed in the primary step occurs via a hydrogen bonded complex. The binding energy of the hydrogen bonded complex between the aliphatic ketyl radical reactant and a solvent molecule is a critical parameter influencing the observable rate of the secondary photoreduction.

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Section: Introductionmentioning

confidence: 99%