Forster singlet energy transfer

The most important mechanism for singlet energy transfer is the Forster resonance transfer ... 

The small effect that has been observed can be quantitatively accounted for via Forster-type long-range singlet energy transfer,(1,46,48)... 

Forster, Th 211, 278, 282, 285 Forster resonance energy transfer, 282 Forster singlet energy transfer, 378 Franck-Condon factors, 23 Franck-Condon principle, 5 Franck-Condon transition, 5 French, C. S., 555 Friedman, G., 353 Fritzsche, J., 37 Frosch, R. P 252, 267, 269 Fumaronitrile, photodimerization in solid state, 478... 

It is possible to estimate the rate of vertical singlet energy transfer (9.31) and (9.33) (when Forster-type energy transfer is negligible, spectral overlap integral is very small) from the relation... 

The theory of resonance transfer of electronic excitation energy between donor and acceptor molecules of suitable spectroscopic properties was first presented by Forster.(7) According to this theory, the rate constant for singlet energy transfer from an excited donor to a chromophore acceptor which may or may not be fluorescent is proportional to r 6, where r is the distance... 

Forster Transfer. Singlet energy transfer has actually been known for many years, as evidenced by numerous studies of the sensitized fluorescence of dyes.161,162 In these cases strong overlap of donor emission with acceptor absorption results in Forster type transfer but the acceptor undergoes no photochemistry. 

Fluorescein is an energy acceptor for chromophores such as naphthalene and anthracene and acts as energy donor toward Eosin and Rhodamine, so derivatives have been used for singlet-singlet energy transfer studies. According to Forster s theory [68] the rate constant for energy transfer increases... 

The Forster [62,63] and Dexter [64] theory in photo-induced energy transfer is discussed. For the singlet-singlet energy transfer [65,66]... 

The lack of energy transfer in 24 is in marked contrast to the results for a variety of other bichromophoric molecules where singlet energy transfer occurs over many tens of angstroms via the Forster dipole-dipole mechanism. Since the effidency of Forster energy transfer depends upon the fluorescence quantum yield of the donor, we postulated that the lack of energy transfer in 24 was due to the very low fluorescence quantum yield of the carotenoid, and further concluded that energy transfer from carotenoid polyenes to chlorophyll in photosynthetic reaction centers could therefore not occur by the dipole-dipole mechanism [72]. 

The distance between the chromophores Is approximately 21 8 as measured on molecular models and no ground state Interaction could be observed. In dioxane, the singlet energy transfer occurs by a Forster-type mechanism. On the basis of this mechanism, the distance can be calculated from the transfer efficiency. For [16a] a value of 21.211.6 X was found, while for [I6b] one obtained a value of 16.7 1.4 X. This latter discrepancy was explained on the basis of preferential orientation of the chromophores. That this phenomenon Indeed plays an Important role, was proved by Leermakers (59,60) In a series of indole alkaloids. The same author (59) also Illustrated the absence of triplet-triplet transfer at low temperature in compound [16b]. 

Keller and Dolby (51,62) found that In the blchromophorlc systems [17a] and [17b] efficient singlet energy transfer occurred according to a Forster mechanism. A distance of 15 X for [17b] and 14 X for [17a] was found on the basis of transfer efficiency,... 

Frechet and coworkers [85,86] synthesized a series of dendrimers whose energy transfer mechanism is exclusively through-space. By designing dendrimers in which the donor periphery chromophores are effectively separated from the interior acceptors, the dendrimer architecture becomes simply a structural scaffold upon which chromophores can be placed. Chromophores were carefully chosen to satisfy the requirements of FOrster energy transfer (i.e. emission of donor overlaps absorbance of acceptor), so that any photons absorbed by a molecule on the periphery undergo intramolecular singlet energy transfer to the core moiety and emission from that core ensues. 

All of the examples of singlet energy transfer we have considered take place via the long-range resonance mechanism. When the oscillator strength of the acceptor is very small (for example, n ir transitions) so that the Forster critical distance Ro approaches or is less than the collision diameter of the donor-acceptor pair, then all evidence indicates that the transfer takes place at a diffusion-controlled rate. Consequently, the transfer mechanism should involve exchange as well as Coulomb interaction. Good examples of this type of transfer have been provided by Dubois and co-workers. " ... 

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