| Abstract
| - The UV laser flash photolysis (248 nm, 10 ns) of biphenyl (BP) occluded in void space of aluminum richfaujasitic X zeolites Nan(AlO2)n(SiO2)192-n with n = 85, 96 has been investigated by diffuse reflectance transientUV−visible absorption (DRTUV) and time-resolved resonance Raman (TR3) measurements on the nano-and microsecond time scales. TR3 measurements were carried out using an 8 ns probe pulse at 370 nm.Delays between pump and probe pulses (50 ns to 100 μs) provide evidence of triplet state BP(T1), radicalcation BP•+, and radical anion BP•- with planar quinoidal structures. Self-modeling mixture analysis(SIMPLISMA) of DRTUV data sets resolved pure absorption spectra of BP(T1), BP•+, BP•-, and trappedelectron as Na43+. Data processing determines also the decays of the corresponding concentrations between0.5 and 340 μs for loading values corresponding to 1, 2, 4, and 8 BP per unit cell. All the decays of specificconcentration were found to fit a model of dispersed heterogeneous kinetics. At lower laser fluence, BP(T1)was found to be the major transient species for all the loading values. Lifetime mean values of BP(T1) werefound to be 40 and 110 μs at low and high loading, respectively. Photoionization was found to be dominantat higher pump laser fluence. At low loading, Na43+ cluster and BP•+ are produced in high yield with relativelydifferent lifetimes, 10 μs and ∼500 μs, respectively. The recombination process includes probablysupplementary electron transfers with the zeolite framework. At high loading, BP•- (20 μs) concomitantlyforms BP•+ (12 μs) as a result of photoejected electron capture by BP(S0). The most important role of poroussolids with large pores such as X faujasite with respect to photophysical and photochemical BP behaviors insolution appears to be the efficient trapping of photoejected electron in the solid network.
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