Principal ZFS tensor axes versus optical transition moments of novel expanded porphyrins (texaphyrins). Time-resolved triplet EPR spectroscopy
1989; Elsevier BV; Volume: 160; Issue: 4 Linguagem: Inglês
10.1016/0009-2614(89)87618-3
ISSN1873-4448
AutoresAyelet Regev, Assia Berman, Haim Levanon, Toshiaki Murai, Jonathan L. Sessler,
Tópico(s)Photosynthetic Processes and Mechanisms
ResumoThe photoexcited triplet state of “expanded porphyrins”, namely free-base and cadmium complexes of texaphyrins, was investigated by laser-excitation-time-resolved EPR spectroscopy. Measurements were carried out at low temperatures, using glass matrices or uniaxial liquid crystals. The free-base exhibits in-plane ISC rates, independent of the matrix, while the ISC selectivity of the cadmium complexes strongly depend on the matrix, i.e. out-of-plane in the glass, and in-plane in the liquid crystal matrices. This is attributed to enhancement of the absorption of the in-plane (long X-axis) optical transition moment. Its direction in the molecular frame is determined from the anisotropy of the EPR signal intensities, in the liquid crystal, by an analysis similar to that utilized in optical dichroism measurements.
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