Naphthalene fluorescence

Similarly, 2,3-dimethyl-l,3-butadiene quenches naphthalene fluorescence (1.7 x 107 M-1 sec-1) but does not rearrange ... 

A singlet naphthalene or a singlet exciplex is thought to be the reactive species in this reaction since the quantum yield of cycloaddition parallels the quenching of naphthalene fluorescence by acrylonitrile. 

Photo-oxidation of protoporphyrin IX and its dimethyl ester Norrish type II reaction of amphiphilic ketoacid Quenching of naphthalene fluorescence by Ni2 +... 

The aqueous cores of reverse micelles are of particular interest because of their analogy with the water pockets in bioaggregates and the active sites of enzymes. Moreover, enzymes solubilized in reverse micelles can exhibit an enhanced catalytic efficiency. Figure B4.3.1 shows a reverse micelle of bis(2-ethylhexyl)sulfosuccinate (AOT) in heptane with three naphthalenic fluorescent probes whose excited-state pK values are much lower than the ground-state pK (see Table 4.4) 2-naphthol (NOH), sodium 2-naphthol sulfonate (NSOH), potassium 2-naphthol-6,8-disulfonate (NSOH). The spectra and the rate constants for deprotonation and back-recombination (determined by time-resolved experiments) provide information on the location of the probes and the corresponding ability of their microenvironment to accept a proton , (i) NDSOH is located around the center of the water pool, and at water contents w = [H20]/[A0T] >... 

Similarly, the luminescence of complexes 38,39,40,41, and 42 can be modulated by changing the redox states of the respective metal ions. Complexes 38 and 39 show emission in the Ni(II) state, whereas the emission is quenched in the Ni(III) state generated after oxidation.46 The fluorescence due to the naphthalene unit in complex 40 is observed in the Ni(II) state after reduction to the corresponding Ni(I) state the naphthalene fluorescence is distinctly reduced.47 Water-soluble complexes 41 and 42 also works as redox-responsive fluorescence switches in a similar way 48... 

Assuming that the true encounter distance is about 1.20 nm (the exact value is not very important), feact > 4 x 109 dm3 mol-1 s-1. The quenching of 1,2-benzanthracene and naphthalene fluorescence by carbon tetrabromide can also be followed by illuminating a solution with light of constant intensity and measuring the fluorescence intensity, /, for a number-of solutions containing different quencher concentrations. These steady-state experiments of Nemzek and Ware [7] are discussed in Sect. 5.5. 

Fig. 10. The kinetics [291 of the decay of naphthalene fluorescence in the presence of CC14 in ethanol. Concentration of CC14 1, 0M 2, 2M 3, 2.5 M 4, 3M. The points indicate the experimental data the broken lines were calculated using eqn. (11) the solid lines were calculated using eqn. (12). O, T = 77 K , T = 140K. I is the fluorescence intensity in arbitrary units.

Dienes quench naphthalene fluorescence although they have no excited state of lower energy than the Sx state of naphthalene. Apparently, quenching is due to an exciplex that either undergoes radiationless transition to ground-... 

The decay of naphthalene fluorescence. Emission wavelength Is 333 nm (a) silica gel heated in open air for 4 hours at 800 C (b) silica gel was heated in vacuum for 4 hours at 800°C. (Reproduced by permission from Canadian Journal of Chemistry. 62. 1279. 1984.)... 

Using the temperature effect, it was proven that non-emitting exciplex intermediates were also involved in the cycloaddition. For example, in the reaction of naphthalene with diphenylacetylene, with increasing temperature both the quantum yields of photoaddition and the quenching of the naphthalene fluorescence by acetylene decrease by the same magnitude [65],... 

When considering the rates of chemical processes in polymers which require diffusion of reagents and products, it is necessary to estimate the internal viscosity q. to substitute in expressions such as Equations 6 and 7. We ave made estimates for q in solid polyethylene from luminescence quenching of naphthalene fluorescence in ethylene -OO copolymers [24]. (Table VII)... 

Photoinitiated SET has been used to drive a molecular machine and absorption and fluorescence spectroscopy have been used to monitor it. A 1 1 pseudoro-taxane forms spontaneously in solution as a consequence of the donor-acceptor interactions between the electron-rich naphthalene moiety of the thread (380) and the electron-deficient bipyridinium units of the cyclophane (381). The threading process is monitored by the appearance of a charge transfer absorption band and disappearance of the naphthalene fluorescence. Excited state SET from 9-anthracenecarboxylic acid (9-ACA) reduces a bipyridinium moiety of the cyclophane, lessening the extent of interaction between the thread and the cyclophane and dethreading occurs. On addition of oxygen the reduced cyclophane is reoxidised and threading reoccurs. ... 

The product e N G (t) is the decay function for the monomer naphthalene singlet state where kj is the unperturbed naphthalene lifetime and Cjj(t) is a general, non-exponential function that describes the naphthalene fluorescence decay In the presence of X mole fraction of mergy accepter. Using our multlexponentlal... 

Tx state of benzene (B) was used as an energy carrier to populate the Tx level of emfo-dicyclopentadiene (E). Population of the Tx state of E can be easily monitored since it undergoes an internal cycloaddition. Figure 7 shows the linear Stern-Volmer plot obtained as a function of benzene concentration. Intermolecular intersystem crossing ( N + E -> N + 3E) can be dismissed as a possible means of accounting for the results since naphthalene fluorescence is unaffected by benzene.244... 

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