On the Mechanism of Quenching by Amines: A New Method for Investigation of Interactions with Triplet States

1974 ◽  
Vol 52 (16) ◽  
pp. 2889-2893 ◽  
Author(s):  
Robert H. Young ◽  
D. Brewer ◽  
R. Kayser ◽  
R. Martin ◽  
D. Feriozi ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Charge Transfer ◽  
Singlet Oxygen ◽  
Rose Bengal ◽  
Rate Constants ◽  
Direct Method ◽  
Diffusion Limit ◽  
Triplet States ◽  
Novel Approach ◽  
Series Of Experiments

Rate constants for the quenching of singlet oxygen by a series of substituted N,N-dimethylanilines were obtained by a direct method employing a dye-laser. The Hammett ρ value obtained from the data (−1.71) suggests that a (partial) charge-transfer complex may be responsible for the quenching action. This rate data was combined with that obtained for the total quenching action on the sensitized photooxidation of 1,3-diphenylfuran. The quenching action on the photooxidation reaction is due to both the quenching of singlet oxygen and the quenching of the triplet state of the sensitizer (rose bengal or methylene blue). The combination of the data from each series of experiments resulted in rate constants of quenching of the triplet states of the sensitizers. A number of the N,N-dimethylanilines quenched the triplet states at the diffusion limit. Hammett ρ values (−1.86 for rose bengal and −4.19 for methylene blue) indicate that charge-transfer intermediates are probably responsible for the quenching action. This was confirmed by the observation of a transient intermediate assigned to the charge-transfer radical of methylene blue. The technique used here represents a novel approach to the investigation of triplet states.

Isomérisation photosensibilisée par des colorants et photoréduction de l'azobenzène en solution. II

1974 ◽  
Vol 52 (10) ◽  
pp. 1858-1867 ◽  
Author(s):  
Jacques Ronayette ◽  
René Arnaud ◽  
Jacques Lemaire
Keyword(s):  
Methylene Blue ◽  
Energy Transfer ◽  
Quantum Yield ◽  
Rose Bengal ◽  
Experimental Results ◽  
The Other ◽  
Eosin Y ◽  
Triplet States ◽  
Trans Form ◽  
Photochemical Isomerization

The photochemical isomerization of azobenzene in solution can be sensitized by dyes which have low-lying triplet states (rose Bengal, eosin Y, fluorescein, methylene blue) but cannot be inhibited by such compounds. The two triplet levels, Tβc and Tαc of the cis form are indistinguishable experimentally. On the other hand, the experimental results verify the existence of two triplet levels, Tβt and Tαt, with different properties, in the trans form. Population, by energy transfer, of the lower triplet, Tαt, leads to isomerization with a quantum yield near 0.5, whereas population of the triplet Tβt only rarely leads to isomerization (quantum yield about 0.03).The photoreduction of azobenzene in isopropanol also has been studied. Only the cis form is photoreducible and it is very difficult experimentally to determine whether this photoreduction can be sensitized.A Jablonski diagram of the two forms of azobenzene is presented to correlate these observations. [Journal translation]

The reaction of adamantylideneadamantane with singlet oxygen mediated by rose bengal and charge transfer complexes

Tetrahedron ◽  
1987 ◽  
Vol 43 (7) ◽  
pp. 1737-1745 ◽  
Author(s):  
Charles W. Jefford ◽  
Manuel Jimenez Estrada ◽  
Giacomo Barchietto
Keyword(s):  
Charge Transfer ◽  
Singlet Oxygen ◽  
Rose Bengal ◽  
Charge Transfer Complexes

Efficient photocatalytic oxygenation of alkenes by water soluble sensitizer in organic–water biphasic media

2016 ◽  
Vol 20 (06) ◽  
pp. 670-676 ◽  
Author(s):  
Mahdi Hajimohammadi ◽  
Hoda Ghasemi
Keyword(s):  
Methylene Blue ◽  
Visible Light ◽  
Singlet Oxygen ◽  
Molecular Oxygen ◽  
Rose Bengal ◽  
Room Temperature ◽  
Water Soluble ◽  
Oxygen Production ◽  
Oxidation Of Olefins ◽  
Major Route

A new green, environmentally and economically photooxygenation of olefins by molecular oxygen in the presence of 4-carboxyl tetra phenyl porphyrin (H2TCPP), Rose Bengal (RB), Methylene Blue (MB) and some metallosensitizers (MS) such as cobalt phthalocyaninesulfonate (Coph(SO3H)[Formula: see text], MnTCPPCl, FeTCPPCl and SbTPP(OH)2 as water–soluble sensitizers in organic–water biphasic media at room temperature under visible light was illustrated. The products were obtained with 100% conversion by H2TCPP and 100% selectivity by Coph(SO3H)4. Also in this study, singlet oxygen production as the major route for oxidation of olefins was proved.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

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