Naphthalene triplet state energy

Thus, the photo-activity of poly[bis(4-benzoylphenoxy)phosphazene] under illumination could be finely tuned by irradiating the polymer in the presence of variable amount of naphthalene, a typical triplet state energy quencher [474]. The same polymer could be used as polymeric photosensitizer to induce the... 

Intermolecular triplet-state energy transfer is well known in photochemistry. McDowell et al. (334) first demonstrated by ESR the triplet energy transfer from benzophenone to naphthalene in a rigid glass. The excitation transfer is found to be independent of orientation (335a), while the probability of excitation transfer per lifetime is dependent on concentration (335b). 

The energy available in the reaction (aromatization of two benzene rings) should be sufficient to put the product in one of the naphthalene triplet states. 

Figure 6.3 Energy level diagram for the triplet state of naphthalene (D = 0.1003 cm-1, E= -0.0137 cm-1, g = 2.003). Solid lines correspond to orientation of the magnetic field along the z-axis, dashed lines for orientation along the x-axis. Arrows show the allowed transitions for 9.50 GHz microwave radiation.

By contrast, in the pulse radiolysis of naphthalene and xenon mixtures in the gaseous phase, the triplet state of naphthalene was produced almost instantaneously (< 0.5 /isec)109. This was attributed to energy transfer by direct impact of sub-excitation electrons. 

Anthracene and substituted anthracenes are also known to sensitize the dimerization of 1,3-cyclohexadiene, another triplet state process [E(7,) for 1,3-cyclohexadiene = 53 kcal/mol] [28]. In similar experiments, the 72 state of naphthalene was also shown to undergo energy transfer to quenchers [29]. 

From now on, we wish, in the spirit of the site percolation in electrokinetics (Section IV.C.4.a), to neglect the bond correlations. Thus, we consider an effective medium around the energy vA where the excitation will propagate it is clear that this medium correctly describes the propagation, but that it will not correctly describe, for example, the density-of-states distribution, since it contains also fictitious B sites at the energy vA. Therefore, by means of this restriction, the HCPA method is then directly transferable to the naphthalene triplet lattice, with probability cL = cA of having a passing bond (4.83). The curves of Fig. 4.18 are likewise transferable, but, because of the fictitious B sites, the density of states around vA is not normalized at the real concentration of the A sites (as was possible for the CPA cases cf. Fig. 4.11). 

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