Optical, zero-field ODMR and EPR studies of the triplet states from singlet fission in biphenyl-TCNQ and biphenyl-tetrafluoro-TCNQ charge-transfer crystals
1993; Elsevier BV; Volume: 173; Issue: 2 Linguagem: Inglês
10.1016/0301-0104(93)80139-z
ISSN1873-4421
AutoresGiancarlo Agostini, Carlo Corvaja, Giovanni Giacometti, Luigi Pasimeni,
Tópico(s)Photochemistry and Electron Transfer Studies
ResumoAbstract Biphenyl-TCNQ and biphenyl-tetrafluoro-TCNQ crystals, when excited with visible light, give rise to triplet excitons which were investigated by optical, EPR and zero-field (ZF) ODMR spectroscopies in a wide temperature range. The analysis of spin polarization carried by EPR and ZF ODMR spectra at room temperature enabled us to reveal the singlet depletion path S→ (T, T) which is thermally activated. The activation energies are Δ E = 1940 cm −1 for B-TCNQ and Δ E = 1720 cm −1 for B-TCNQF 4 . From the relation 2 E T = E S +Δ E the energies of the triplet state in the CT complexes were derived: E T =9770 ± 100 cm −1 for B-TCNQ and E T =8695 ± 100 cm −1 for B-TCNQF 4 . It was also established that the triplet species detected by ODMR at 1.8 K are populated by ISC.
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