Multifrequency TREPR Investigation of Excited-State ZnTPP/Nitroxide Radical Complexes

Valery F. Tarasov, Saiful S.M. Islam, Yasunori Ohba, Malcolm D.E. Forbes, Seigo Yamauchi

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


Multiple-frequency (X-band and W-band) time-resolved electron paramagnetic resonance spectra of Zn-tetraphenylporphyrin (ZnTPP) triplet states coordinated to two different stable nitroxide moieties are presented and discussed. The position of the pyrimidyl nitroxide relative to the ZnTPP plane is the only structural change made between the two complexes, from ortho to para. This changes the angle between the interacting orbitals of the three-spin system with only a minor change in the distance between the unpaired electron of the nitroxide and the TPP ring system. Changes in the electron spin polarization patterns at the two different frequencies of observation are discussed in terms of a radical-triplet pair spin-state mixing model, including the intersystem crossing processes. It is determined that the inclusion of an additional spin-selective relaxation process to the computational model for the spectral shapes gives adequate reproduction of the experimental results using the same parameters at each frequency.

Original languageEnglish
Pages (from-to)175-193
Number of pages19
JournalApplied Magnetic Resonance
Issue number2-4
Publication statusPublished - 2011 Dec

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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