Perylene. fluorescence quenching

Popovic et al. (1985) investigated photogeneration of a series of peiylene diimides by delayed-field and field-induced fluorescence quenching techniques. The results for N.N-bis(phenyl)perylene-3,4.9.10-tetracaiboxyldiimide (PPECI)... 

Other experimental studies in this area are fluorescence quenching of excited perylene by Co + ions which occurs via energy transfer in viscous and nonviscous... 

The undesired fluorescence quenching could be overcome in perylene bisimide-based squares 7, which show fluorescence quantum yields of almost unity in chloroform [46,47]. The square assemblies were quantitatively accessible by mixing an equimolar amount of perylene bispyridyl imide Ugands and corresponding metal corner units in dichloromethane at room temperature. Because the pyridyl moieties are located at the imide positions of the... 

Fluorescent small molecules are used as dopants in either electron- or hole-transporting binders. These emitters are selected for their high photoluminescent quantum efficiency and for the color of their emission. Typical examples include perylene and its derivatives 44], quinacridones [45, penlaphenylcyclopenlcne [46], dicyanomethylene pyrans [47, 48], and rubrene [3(3, 49]. The emissive dopant is chosen to have a lower excited state energy than the host, such that if an exciton forms on a host molecule it will spontaneously transfer to the dopant. Relatively small concentrations of dopant are used, typically in the order of 1%, in order to avoid concentration quenching of their luminescence. 

D + 3A —> D + 3A (higher triplet). This type of transfer requires overlap of the fluorescence spectrum of D and the T-T absorption spectrum of A (e.g. quenching of perylene by phenanthrene in its lowest triplet state). 

Ferrocene has been widely investigated as an electron donor and its electron donating ability can be tuned by redox reactions. As anticipated, when a ferrocene unit is covalently connected to an electron acceptor moiety that shows intrinsic fluorescence, the fluorescence of the acceptor moiety would be largely quenched because of the photoinduced electron transfer between ferrocene and the fluorescent acceptor. For instance, triad 15 that contains perylene diimide flanked by two ferrocene moieties, shows rather weak fluorescence due to the photoinduced electron transfer between perylene diimide and ferrocene units. Either chemical or electrochemical oxidation of ferrocene unit lead to fluorescence enhancement. This is simply because the electron donating ability of ferrocene is reduced after oxidation and accordingly the photoinduced electron transfer is prohibited. In this way, the fluorescence intensity of 15 can be reversibly modulated by sequential electrochemical oxidation and reduction. Therefore, a new redox fluorescence switch can be established with triad 15.25... 

The quantum yield of fluorescence of many fluorescent substances in solution decreases with increasing concentration. In some cases, e.g., with aqueous solutions of thionine and Methylene Blue, this selfquenching is due to formation of stable dimers in equilibrium with the monomer.78 In other cases, e.g., with solutions of anthracene, perylene, and coronene in solvents such as benzene, chloroform, and kerosene, Bowen and co-workers have shown that quenching takes place by collision17 the self-quenching rate constants obtained are very close to those given in Table I (see also ref. 19). 

Popovic et al. (1987) studied photogeneration of N,N-bis(methyl)perylene-3,4,9,10-tetracarboxyldiimide by field modulation of the time-resolved fluorescence. The results show that the field increases the rate of decay of fluorescence but leaves the initial intensity unchanged. The results were described by a process which occurs by the field-assisted dissociation of the first-excited singlet state. The absence of quenching of the initial fluorescence (amplitude quenching) was interpreted as evidence that the photogeneration process cannot be described by Onsager theories. 

In an article which is critical of many generally accepted molecular fluorescence parameters of aromatic molecules (and by inference the parameters for other systems), Birks emphasizes the precautions necessary to eliminate errors due to self-absorption secondary fluorescence and/or self-quenching.1 The points are made that reliable data for rf and Of are available for only a few compounds, e.g. diphenylanthracene (DPA), perylene, quinine bisulphate, and acridone, and that these provide suitable standards. The value of Of (DPA) is now set at 0.83. The importance of solvent effects on Of and t( of DPA is stressed in a publication which reports Tf for DPA in cyclohexane and benzene.2 The value of 6.95 0.04 ns for benzene solution is in good agreement with the earlier work of Birks and Dyson3 and Ware and Baldwin 4 7 (7.35 0.05 ns). The value obtained for cyclohexane solution, 7.58 0.04 ns, although in poor agreement with earlier results, is probably the most acceptable. The absolute fluorescence quantum yield of quinine bisulphate has also been redetermined (Of = 0.56).8... 

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