Potential energy surfaces excimer formation

Figure 15. Potential energy surface(s) for excimer formation. Reproduced with permission from Ref. [92a],...

Figure 5.22. Schematic representation of the potential energy surfaces for excimer formation and of the difference between monomer fluorescence and excimer fluorescence (adapted from Rehm and Weller, 1970a).

Figure 2.22 Left fluorescence spectra of pyrene in cyclohexane. Intensities are normalized to a common value of < f. A, 10-2m B, 7.75 x 10-3m C, 5.5 x 10-3m D, 3.25 x 10-3m E, 10-3m G, 10-4m. Reproduced by permission from ref. 109. Copyright 1970, John Wiley Sons, Ltd. Right potential energy surfaces for excimer formation />... P represents the distance between two pyrene molecules. The vibrational levels shown for the monomers at large separation refer to degrees of freedom other than rP... P...

Chemical reactions, particularly photochemical interactions, are characterized by distance-dependent rate constants rather than sharp spherical reaction boundaries. Furthermore, the detailed shapes of the potential energy surfaces for the kinds of interactions discussed in this chapter are largely unknown. Nevertheless if one is interested in a more qualitative assessment of the capture radius prediction, evidence should be available from a comparison of the cyclization rates of Py-poly-styrene-Py and DMA-polystyrene-Py. In polar and polarizable solvents, exciplex formation in the latter polymer should be preceded by rate-limiting electron transfer to generate the solvent separated ion pair. Estimates for this interaction distance are typically 7 A to 10 A (16), larger than the 5 A normally invoked for pyrene excimer formation (6). 

---