Donor-acceptor dyads dependence

The feasibility of intramolecular electron- and energy-transfer depends on distance and is usually studied in covalently linked systems. However, donor-acceptor dyads can be also arranged by self-assembly what resembles the situation of electron transfer in biological systems. Artificial dyads tethered by a small number of hydrogen bonds immediately dissociate in methanol or water. To improve the binding while keeping the reversibility, a photoinducible electron donor-acceptor dyad linked by a kinetically labile bond was designed. [19]... 

Regarding fullerene chemistry, whereas the covalent functionalisation of buckminsterfiillerene Ceo has seen dramatic development, the supramolecular aspects of its chemistry have not been explored to the same extent. In contrast to covalent bonds, the formation of H-bonds is reversible and their strength depends on the chemical environment, such as the solvent or temperature. This important difference has been skillfully used in the preparation of a variety of reversible donor-acceptor dyads. 

Studies on linkage length dependence of electron transfer in flexible chain-linked donor-acceptor dyads using cyclodextrin... 

When donor-acceptor systems are incorporated in LB films, it should be kept in mind that, in the case of flexible linkers, it is possible to favor one conformer over another due to the immobilization within the LB film matrix. In that case, the properties of the dyads in solution and in LB films can differ considerably (Figure 13.85). An example of this effect was reported by Tkachenko and Fukuzumi who incorporated the dyad 162 in LB filmsIn addition to the fact that, in LB films (22 layers), the fluorescence decay profiles were wavelength dependent, the authors have also observed a third, fast component with a significant amplitude in LB films that is not observed in solution studies. Table 13.18 summarizes the emission decay lifetimes of the species in LB films. 

The final example of the distance dependence of ET dynamics in norbomylogous bridged systems is photoinduced charge-shift ET in 22(4) and 22(6) which possess the A-methylpyridinium acceptor (Scheme 10).114 Local excitation of the DMN donor in the dyads results in charge-shift, from LD to LA, to form the distonic radical... 

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