Impact of Electronic Asymmetry on Photoexcited Triplet-State Spin Distributions in Conjugated Porphyrin Oligomers Probed via EPR Spectroscopy
| Autor: | Michael J. Therien, Paul J. Angiolillo, H. Tetsuo Uyeda, and Timothy V. Duncan |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Chemistry
Exciton Relaxation (NMR) Atmospheric temperature range Photochemistry Porphyrin Molecular physics Surfaces Coatings and Films law.invention chemistry.chemical_compound Delocalized electron law Materials Chemistry Physical and Theoretical Chemistry Triplet state Spectroscopy Electron paramagnetic resonance |
| Zdroj: | The Journal of Physical Chemistry B. 108:11893-11903 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/jp040032z |
| Popis: | The photophysics of triplet excitons in a series of electronically asymmetric “push−pull” π-conjugated meso-to-meso ethyne-bridged (porphinato)metal oligomers, along with electronically symmetric analogues, were studied by X-band electron paramagnetic resonance (EPR) spectroscopy under continuous-wave (CW) optical pumping conditions in the 4−100 K temperature range. In all of the systems studied, the spatial extent of the triplet wave function, as inferred from the |D| zero-field splitting (ZFS) parameter, never exceeds the dimensions of a single porphyryl moiety and its meso-pendant ethynyl groups. The |D| values determined for an oligomeric series of these electronically asymmetric species that span one through four porphyryl units are respectively 0.0301, 0.0303, 0.0300, and 0.0301 cm-1, indicating a common triplet wave function spatial delocalization of approximately 0.4−0.45 nm. Electron spin−spin and spin−lattice relaxation times were determined over the 4−30 K temperature range using progressive mi... |
| Databáze: | OpenAIRE |
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