On the importance of electronic symmetry for triplet state delocalization
The influence of electronic symmetry on triplet state delocalization in linear zinc porphyrin oligomers is explored by electron paramagnetic resonance (EPR) techniques. Using a combination of transient continuous wave (cw) and pulse Electron Nuclear DOuble Resonance (ENDOR) spectroscopies, it is dem...
| Main Authors: | , , , , , |
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| Format: | Journal article |
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American Chemical Society
2017
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| Summary: | The influence of electronic symmetry on triplet state delocalization in linear zinc porphyrin oligomers is explored by electron paramagnetic resonance (EPR) techniques. Using a combination of transient continuous wave (cw) and pulse Electron Nuclear DOuble Resonance (ENDOR) spectroscopies, it is demonstrated experimentally that complete triplet state delocalization requires the chemical equivalence of all porphyrin units. These results are supported by DFT calculations, showing uneven delocalization in a porphyrin dimer in which a terminal ethynyl group renders the two porphyrin units inequivalent. When the conjugation length of the molecule is further increased upon addition of a second terminal ethynyl group which restores the symmetry of the system, the triplet state is again found to be completely delocalized. The observations suggest that electronic symmetry is of greater importance for triplet state delocalization than other frequently invoked factors such as conformational rigidity or fundamental length-scale limitations. |
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