Long-range Triplet Energy Transfer

It is noteworthy that triplet energy transfer in acetylene-bridged porphyrin dimers has been interpreted in terms of the conformational flexibility of the system [215]. Thus, rapid relaxation between triplet levels occurs in a series of meso- 

It has long been suggested that the extent of electronic coupling along poly(phenylene)-based wires should depend on the mutual orientation of adjacent rings. This problem has been difficult to study by experimental methods but recent 

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In fluid solutions only the third mechanism is of importance in transfer of triplet excitation. The trivial mechanism is usually excluded because most molecules do not phosphoresce in solution, and the second mechanism seems to be excluded because the transition moments for the T - S process in the donor and the T - S transition of the acceptor should both be vanishingly small. An interesting possibility which has yet to be explored experimentally is that heavy atom-containing solvents might so enhance T <- S transition probabilities that long-range triplet energy transfer may become important. 

Holmlin RE, Tong RT, Barton JK (1998) Long-range triplet energy transfer between metal lointerca-lators tethered to DNA Importance of intercalation, stacking, and distance. J Am Chem Soc 120 9724-9725... 

K5 rychenko, A. and B. Albinsson (2002). Conformer-dependent electronic coupling for long-range triplet energy transfer in donor-bridge-acceptor porphyrin dimers. Chem. Phys. Lett. 366(3-4), 291-299. 

Kyrychenko A and Albinsson B. Conformer-Dependent Electronic Coupling for Long-Range Triplet Energy Transfer in Donor-Bridge-Acceptor Porphyrin Dimers. Chem. Phys. Lett. 2002 366 291-299. 

Figure 2.33. Examples of mixed-metal Ru"/Os" poly(pyridine) complexes built for long-range triplet energy transfer.

G. L Closs, M. D. Johnson, J. R. Miller, P. Piotrowiak, A Connection between Intramolecular Long-Range Electron, Hole, and Triplet Energy Transfers , J. Am Chem Soc 1989, 111, 3751-3753. 

The Coulombic mechanism would require that both 3D — 3D and 1A —> 3A were allowed transitions, which clearly they are not as both are spin-forbidden processes. Thus, triplet-triplet energy transfer by the long-range Coulombic mechanism is forbidden. 

H. E. Zemel and B. M. Hoffman, Long-range triplet-triplet energy transfer within metal-substituted hemoglobins, J. Not. Chem. Soc. 103, 1192-1201 (1981). 

Under these same experimental conditions, long-range triplet-triplet annihilation has been observed for phenanthrene, the process amounting to a dipole-dipole induced energy transfer from one triplet into the triplet manifold of another.147 Phenanthrene triplets have also... 

Closs GL, Johnsson MD, Miller JR, and Piotrowiak P. A connection between intramolecular long-range electron, hole, and triplet energy transfers. 1989 111 3751-3753. 

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