Biphasic structure model for reversed micelles. Depressed acid dissociation of excited-state pyranine in the restricted reaction field

1982 ◽  
Vol 86 (24) ◽  
pp. 4826-4831 ◽  
Author(s):  
Hiroki Kondo ◽  
Ichiro Miwa ◽  
Junzo Sunamoto
Keyword(s):  
Excited State ◽  
Reversed Micelles ◽  
Acid Dissociation ◽  
Structure Model ◽  
Reaction Field

Excited state carbon acid dissociation and competing photorearrangements of 5H-dibenzo[a,c]cycloheptene derivatives

1996 ◽  
Vol 74 (8) ◽  
pp. 1447-1464 ◽  
Author(s):  
David. Budac. ◽  
Peter Wan
Keyword(s):  
Excited State ◽  
Fluorescence Quenching ◽  
Singlet State ◽  
Acid Dissociation ◽  
Excited Singlet ◽  
Deuterium Incorporation ◽  
Group A ◽  
Carbon Acids ◽  
Work Structure ◽  
Carbon Acid

The first examples of dissociating excited state carbon acids were reported by our group. A necessary structural feature is the 5H-dibenzocycloheptene ring system where the incipient carbanion is formally an antiaromatic system in S0. In this work, structure–reactivity studies of the excited singlet state carbon acid dissociation and competing formal di-π-methane rearrangement of several 5H-dibenzo[a,c]cycloheptene derivatives have been carried out in order to gain more insights into the photochemistry displayed by these compounds. Photolysis of 7-deuterio-5H-dibenzo[a,c]cycloheptene (9) in aqueous solution showed that the photogenerated carbanion is allylically delocalized. Derivative 7 was found to be less reactive than 3 with respect to carbon acid dissociation whereas 8 was unreactive. Ethanolamine (in CH3CN) was found to be an effective base in catalyzing carbon acid dissociation for 3, 7, and 9, as indicated by higher yields of deuterium incorporation and rates of fluorescence quenching. Binaphthyl derivatives 10 and 11 displayed contrasting photobehaviour. Photolysis of binaphthyl 11 resulted in only efficient (ΦP = 0.47) formal di-π-methane rearrangement under all conditions and no evidence was found for carbon acid dissociation, even in the presence of ethanolamine as base. On the other hand, the formal di-π-methane reaction was very inefficient for binaphthyl 10 (Φp < 0.001). Due to the conformational rigidity inherent in 10, the methylene protons at the 3-position are NMR resolvable as pseudo-axial and pseudo-equatorial protons. Photolysis in the presence of ethanolamine (in D2O–CH3CN) resulted in stereoselective deprotonation of the pseudo-axial proton (Φex ≈ 0.02), as indicated by deuterium exchange studies. The results show that excited state carbon acid dissociation is an observable general reaction of dibenzo and dinaphtho cycloheptenes only if more favourable photochemical pathways are not competing. Key words: excited state carbon acid, di-π-methane rearrangement, carbanion, stereoelectronic effect, fluorescence quenching.

Permanent Dipole Moment and Polarizability of a Gass of Merocyanine Dyes in Their Ground and First Excited Singlet State

1983 ◽  
Vol 38 (9) ◽  
pp. 995-1002 ◽  
Author(s):  
Wolfram Baumann
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Electric Field ◽  
Field Model ◽  
Singlet State ◽  
Excited Singlet State ◽  
Permanent Dipole Moment ◽  
Excited Singlet ◽  
Reaction Field ◽  
Merocyanine Dyes

Abstract The permanent dipole moment of a class of merocyanine dyes in their ground and first excited singlet state has been determined studying the influence of an external electric field on the absorption of the compounds in various solvents. Evaluation of the experimental results on the basis of the Onsager reaction field model also gives values for the polarizability in the ground and excited state, the latter approaches the value of a respective conducting ellipsoid with the longer chainlength molecules.

Dynamics of excited-state reactions in reversed micelles. 1. Proton transfer involving a hydrophilic fluorescent probe

1984 ◽  
Vol 88 (9) ◽  
pp. 1909-1913 ◽  
Author(s):  
Elisabeth Bardez ◽  
Bich Thui Goguillon ◽  
Erlend Keh ◽  
Bernard Valeur
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Fluorescent Probe ◽  
Reversed Micelles
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