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Dexter-type electron exchange

As mentioned earlier, triplet energy transfer can occur by way of Forster-type through-space interactions [100] or via Dexter-type electron exchange [101], In the former case, the rate constant for Forster-type triplet energy transfer (kp) can be expressed as follows ... [Pg.40]

Baldo et al. [ 164] used the platinum complex of 2,3,7,8,12,13,17,18-octaethyl-21 //,23//-porphine (PtOEP, 66) as efficient phosphorescent material. This complex absorbs at 530 nm and exhibits weak fluorescence at 580 nm but strong phosphorescence from the triplet state at 650 nm. Triplet transfer from a host like Alq3 was assumed to follow the Dexter mechanism. Dexter-type excitation transfer is a short-range process involving the exchange of electrons. In contrast to Forster transfer, triplet exciton transfer is allowed. [Pg.132]

Figure 4.6 Simplified representation of Dexter-type triplet energy transfer as a correlated two-electron exchange process. Figure 4.6 Simplified representation of Dexter-type triplet energy transfer as a correlated two-electron exchange process.
If the charge distributions of the D and A overlap than a new class of interactions has to be considered, namely the exchange interaction between the electrons on D and on A. This type of energy transfer is called Dexter transfer [80, 96,98], Here we briefly outline the physical principles involved. [Pg.61]

Energy transfer requires electronic interactions and therefore its rate decreases with increasing distance, r. Depending on the electronic interaction mechanism, the distance dependence may follow a 1/r (resonance, also called Fdrster-type, mechanism) or e (exchange, also called Dexter-t5rpe, mechanism) (6). In both cases, energy transfer is favored when the emission spectrum of the donor overlaps the absorption spectrum of the acceptor. [Pg.111]

The second possibility of energy transfer is known as exchange type or Dexter energy transfer. Dexter ET is based on quantum mechanical exchange interactions, therefore it needs strong spatial overlap of the involved wavefunctions of D and A. Since the overlap of electronic wavefunctions decays exponentially with distance, it is expected that the rate constant koA decreases even more rapidly with distance R than observed in the case of singlet transfer. A schematic presentation of Dexter ET is shown in Fig. 21. Dexter ET occurs typically over distances which are similar to the van-der-Waals distance, i.e. R = 0.5 - Inm. The rate constant drops exponentially with the distance Rda between D and A ... [Pg.209]


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