Phenanthrene, triplet state energy

Oxygen quenching of phenanthrene phosphorescence involves an exchange mechanism which also operates for triplet state energy transfer involving phenanthrene in biphenyl 2i. Radiationless processes of excited states of 5,6-diazaphenanthrene in hexane and hexafluoroisopropanol have been studied by both triplet and singlet lumi ne s cen ce 2 2 extremely fast radiationless transition in the... 

Figure 8. Energy level scheme for 33 and 34. Excitation with 226 nm light populates BP, which undergoes efficient energy transfer to PE and NP. Subsequent energy transfer and intersystem crossing populate the triplet state of the phenanthrene, PE. Excitation to the PE state with 488 nm light results in stepwise energy transfer to BP and NP, the latter of which acts as an energy well.

They are well known as compounds which are photoohemically very reactive. The excited singlet and triplet states are the photochemically reactive states,and they also can participate in energy transfer reactions (2,3i10,11). Some of these compoxmds such as anthracene,phenanthrene,pyrene added to polyethylene effect the photodegradation of polymer (118,... 

Little attention has so far been paid to studying exchange energy-transfer processes in media so viscous that a steady-state is no longer established. Butler and Pilling [200] specifically sought experimental evidence for time-dependent rate coefficients of the form of eqn. (98). They chose to study triplet phenanthrene in methanol—water mixtures and used cupric chloride as the acceptor since it is readily soluble and a very efficient quencher of triplet phenanthrene. To observe even the t 1/2 dependence of the time-dependent rate coefficient, concentrations [A] > 10-2 are required that is with Re 1 nm and [A] > 10 mmol... 

Triplet—triplet energy transfer from benzophenone to phenanthrene in polymethylmethacrylate at 77 and 298 K was studied by steady-state phosphorescence depolarisation techniques [182], They were unable to see any clear evidence for the orientational dependence of the transfer probability [eqn. (92)]. This may be due to the relative magnitude of the phosphorescence lifetime of benzophenone ( 5 ms) and the much shorter rotational relaxation time of benzophenone implied by the observation by Rice and Kenney-Wallace [250] that coumarin-2 and pyrene have rotational times of < 1 ns, and rhodamine 6G of 5.7 ns in polymethyl methacrylate at room temperature. Indeed, the latter system of rhodamine 6G in polymethyl methacrylate could provide an interesting donor (to rose bengal or some such acceptor) where the rotational time is comparable with the fluorescence time and hence to the dipole—dipole energy transfer time. In this case, the definition of R0 in eqn. (77) is incorrect, since k cannot now be averaged over all orientations. 

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