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¹H NMR: Complex Splitting

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A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
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Updated: Apr 15, 2026

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F⁻

Published on: July 27, 2018

Singlet fission in pentacene dimers.

Johannes Zirzlmeier¹, Dan Lehnherr², Pedro B Coto³

¹Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany;

Proceedings of the National Academy of Sciences of the United States of America

|April 11, 2015

Summary

Singlet fission (SF) can improve solar energy conversion beyond the Shockley-Queisser limit. This study demonstrates intramolecular SF in pentacene dimers, achieving high triplet yields and paving the way for advanced solar cells.

Keywords:

acene oligomers excited states multireference perturbation theory singlet fission time-resolved spectroscopy

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Area of Science:

Materials Science
Photochemistry
Renewable Energy

Background:

Singlet fission (SF) offers a route to exceed the 30% Shockley-Queisser limit for solar energy conversion.
Previous SF studies relied on intermolecular interactions between separate molecules.

Purpose of the Study:

To demonstrate unprecedented intramolecular SF within pentacene dimers.
To investigate the efficiency of SF induced by molecular proximity and coupling.

Main Methods:

Synthesis of regioisomeric pentacene dimers.
Spectroscopic analysis of photoexcited dimers in room-temperature solutions.
Measurement of triplet quantum yields.

Main Results:

Unambiguous evidence for intramolecular SF in pentacene dimers.
Observed triplet quantum yields as high as 156 ± 5%.
Demonstrated that proximity and coupling within dimers are sufficient to induce SF.

Conclusions:

Intramolecular SF is achievable in pentacene dimers.
This finding opens new avenues for designing efficient solar energy conversion materials.
Achieved high triplet yields suggest potential for surpassing current solar cell limitations.