A laser flash photolysis study of the behaviour of polyfluorophenyl ketones in solution

1989 ◽  
Vol 67 (5) ◽  
pp. 927-932 ◽  
Author(s):  
D. R. Boate ◽  
L. J. Johnston ◽  
J. C. Scaiano
Keyword(s):  
Charge Transfer ◽  
Hydrogen Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Oxidation Potential ◽  
Triplet States ◽  
Excellent Correlation ◽  
Triplet Energy ◽  
Keywords Laser

Decafluorobenzophenone triplets, which have a triplet energy very close to that of benzophenone, are much more reactive than benzophenone in quenching reactions that involve hydrogen transfer and/or charge transfer. An excellent correlation has been observed between the rate constants for charge transfer quenching and the oxidation potential of the substrate. In the case of 2-propanol, where the reactivity can be fully accounted for by hydrogen transfer, decafluorobenzophenone is 35 times more reactive than benzophenone. Pentafluorobenzophenone shows intermediate behaviour. Keywords: laser photolysis, benzophenones, triplet states, charge transfer, photoreduction.

Triplet energies of fumaronitrile and maleonitrile

1982 ◽  
Vol 60 (3) ◽  
pp. 339-341 ◽  
Author(s):  
Po Cheong Wong
Keyword(s):  
Charge Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Benzene Solution ◽  
Laser Flash ◽  
Transfer Mechanism ◽  
Triplet Energy ◽  
Charge Transfer Mechanism ◽  
A Charge

The triplet energies of fumaronitrile and maleonitrile measured by laser flash photolysis technique using the Herkstroeter–Hammond method are both 59 ± 2 kcal mol−1. Our results show that these olefins are classical triplet energy acceptors for non-electron donating sensitizers. With electron donating sensitizers, quenching through a charge-transfer mechanism also occurs in benzene solution.

Geometric and solvent effects on intramolecular phenolic hydrogen abstraction by carbonyl n,π* and π,π* triplets

2001 ◽  
Vol 79 (12) ◽  
pp. 1851-1863 ◽  
Author(s):  
Edward C Lathioor ◽  
William J Leigh
Keyword(s):  
Charge Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Hydrogen Abstraction ◽  
Phenoxyl Radical ◽  
Laser Flash ◽  
Acetonitrile Solution ◽  
Triplet States ◽  
Initial Charge ◽  
Phenolic Group

The photochemistry of a series of alkoxyacetophenone, -benzophenone, and -indanone derivatives, which contain a remote phenolic group linked to the ketone by a para,para'- or meta,meta'-oxyethyl spacer, has been studied in acetonitrile and dichloromethane solutions using laser flash photolysis techniques. The corresponding methoxy-substituted compounds and, in the case of the alkoxyindanones, derivatives bearing just a remote phenyl substituent, have also been examined. The triplet lifetimes of the phenolic compounds are determined by the rates of intramolecular abstraction of the remote phenolic hydrogen, and depend on the solvent, the geometry of attachment and the configuration of the lowest triplet state. In contrast to the large (>500-fold) difference in lifetime of the para,para'- and meta,meta'-alkoxyacetophenone derivatives, both of which have lowest π,π* triplet states, smaller differences are observed for the alkoxyindanone (lowest charge transfer triplet, ~twofold difference) and alkoxybenzophenone (lowest n,π* triplet, ~18-fold difference) derivatives in acetonitrile solution. The triplet lifetimes of the acetophenone and benzophenone are significantly shorter in dichloromethane than in acetonitrile, consistent with the intermediacy of a hydrogen-bonded triplet exciplex in the reaction. This is not the case with the para,para'-indanone derivative, sugesting that hydrogen abstraction in this compound is dominated by a mechanism involving initial charge transfer rather than hydrogen bonding. This is most likely due to orientational constraints that prevent the remote phenolic -O-H group from adopting a coplanar arrangement with the n-orbitals of the carbonyl group.Key words: photochemistry, aromatic ketone, phenol, triplet, intramolecular, quenching, hydrogen abstraction, phenoxyl radical, kinetics, kinetic isotope effect, laser flash photolysis.

A laser flash photolysis study of the triplet states of the red and the blue forms of Blepharisma japonicum pigment

1992 ◽  
Vol 13 (3-4) ◽  
pp. 315-321 ◽  
Author(s):  
Francesco Ghetti ◽  
Giovanni Checcucci ◽  
Francesco Lenci ◽  
Paul F. Heelis
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Triplet States ◽  
Blepharisma Japonicum

Laser flash photolysis of iodine dissolved in hydroxylic solvents. Identification of iodine atom charge transfer complexes

1973 ◽  
Vol 19 (2) ◽  
pp. 251-253 ◽  
Author(s):  
Philipe Fornier de Violet ◽  
Roland Bonneau ◽  
Jacques Joussot-Dubien
Keyword(s):  
Charge Transfer ◽  
Iodine Atom ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Charge Transfer Complexes

Properties of singlet- and triplet-excited states of hemicyanine dyes

2014 ◽  
Vol 68 (8) ◽  
Author(s):  
Daniel Mártire ◽  
Walter Massad ◽  
Hernán Montejano ◽  
Mónica Gonzalez ◽  
Paula Caregnato ◽  
...  
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Laser Flash ◽  
Quantum Yields ◽  
Triplet States ◽  
Fluorescence Emission Spectra ◽  
Fluorescence Quantum Yields ◽  
Hemicyanine Dyes

AbstractThe fluorescence emission spectra and fluorescence quantum yields of hemicyanine dyes LDS 698, LDS 722, and LDS 730 were measured in different media. No transient species was detected in the laser flash-photolysis experiments performed with Ar-saturated solutions of the dyes in methanol. However, in the presence of 0.08 M potassium iodide, the absorption of the triplet states was clearly observed. Oxygen consumption measurements in the absence and presence of a chemical trap (furfuryl alcohol) in MeOH: H2O (φ r = 1: 1) solutions of the dyes containing KI confirmed the generation of singlet molecular oxygen.

A reinvestigation of the interaction between triplet states of cyclohexenones and amines

1988 ◽  
Vol 66 (10) ◽  
pp. 2595-2600 ◽  
Author(s):  
D. Weir ◽  
J. C. Scaiano ◽  
D. I. Schuster
Keyword(s):  
Triplet State ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Radical Cations ◽  
Laser Flash ◽  
Triplet States ◽  
New Evidence

Laser flash photolysis studies lead to the conclusion that the short-lived triplet states of cyclohexenones are readily quenched by amines. For example, in the case of 2-cyclohexen-1-one (1) its triplet state (τT = 40 ns in acetonitrile) is quenched by triethylamine with a rate constant of (9.0 ± 0.8) × 107 M−1 s−1. Cyclohexenone triplets are also quenched efficiently by DABCO and by triphenylamine leading to the formation of the corresponding amine radical cations. The new evidence reported rules out the involvement of long-lived detectable exciplexes.

Dynamics of the transient species generated upon photolysis of diarylmethanes within zeolites — Deprotonation and oxidation reactions

2005 ◽  
Vol 83 (9) ◽  
pp. 1637-1648 ◽  
Author(s):  
Suzanne Shea ◽  
Norman P Schepp ◽  
Amy E Keirstead ◽  
Frances L Cozens
Keyword(s):  
Radical Cation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Radical Cations ◽  
Laser Flash ◽  
Oxidation Potential ◽  
Oxidation Reactions ◽  
Oxidation Potentials ◽  
Multistep Process ◽  
Acid Zeolites

The oxidation of diarylmethanes is a multistep process involving initial formation of a radical cation, deprotonation of the radical cation to the radical, and oxidation of the radical to the carbocation. The dynamics and efficiency of the last two steps in this process, namely deprotonation and oxidation, in acidic zeolites and non-acid zeolites are examined in the present work as a function of the acidity of the diarylmethane radical cations and the oxidation potential of the diarylmethyl radicals. Our results indicate that rate constants for deprotonation strongly depend on the acidity of the radical cations, but not on the composition of the zeolites. In addition, oxidation of the radicals to the diarylmethyl cations is strongly dependent on both the oxidation potential of the radicals and the oxidizing ability of the zeolite. This dependence allows oxidation potentials of the zeolites to be estimated.Key words: radical cations, carbocations, zeolites, laser flash photolysis.

Laser flash photolysis of metal oxide supported vanadyl catalysts. Spectroscopic evidence for the ligand-to-metal charge-transfer state

2006 ◽  
Vol 16 (2) ◽  
pp. 216-220 ◽  
Author(s):  
Hermenegildo García ◽  
Jose Manuel López-Nieto ◽  
Emilio Palomares ◽  
Heinz D. Roth ◽  
Benjamín Solsona
Keyword(s):  
Charge Transfer ◽  
Metal Oxide ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Charge Transfer State ◽  
Metal Charge ◽  
Spectroscopic Evidence ◽  
Metal Charge Transfer ◽  
Transfer State
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