Singlet Excitation Energy Migration in the Glassy and Single Crystalline States of 1,3-Diphenyl-5-(p-chlorophenyl)-2-pyrazoline

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Abstract
Comparative studies have been made of the singlet excitation energy migration of 1,3-diphenyl-5-(p-chlorophenyl)-2-pyrazoline between the glassy and single crystalline states at near room temperature. The rate parameter for the singlet excitation energy migration, i.e., frequency of excitation hopping, was determined from the fluorescence quenching by the guest molecule, dimethylterephthalate, the quenching process being the migration controlled charge-transfer. The results are discussed in terms of both kinetic and random migration models. The results show that the singlet excitationenergy migrates over 523 ± 9 molecules in the glassy state and (3.71 ± 0.06) ∗ 105 molecules in the single crystalliner state at 10°C within its lifetime which temperature dependent, the apparent activation energy being ∼ 0.052 ev in the glassy state and ∼ 0.012 ev in the single crystalline state. It is indicated that the difference of the two or three orders of magnitued in the efficiency of migration between the disordered and ordered system is mainly due to the difference of the preexponential frequency factor rather than of the activation energy.