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A 2023 study found that neutral 11a-boraolympicenes—a new family of fused, boron-containing molecules—were stable against air and moisture despite having no bulky groups shielding their boron atoms. The proposed reason is that the framework’s π electrons delocalize through boron’s otherwise vacant pz orbital. That finding does not extend to the molecules after reduction: the studied radical-anion salt was sensitive to air and moisture and persisted for a week only under inert glovebox conditions.
What the researchers made
Olympicene is a fused-ring molecular framework. In the compounds reported by Jing Guo and colleagues, a boron atom occupies the framework’s concave 11a position, producing what the authors call 11a-boraolympicenes. The molecules are planar and fully fused, rather than structures in which a boron-containing group is simply attached to the outside of a carbon framework.
The researchers prepared the family through a one-pot, triply borylation-based double-fold borocyclization. The synthesis also allowed substitution at several positions, giving the team a modular way to vary the molecules. Their paper, “Fully-fused boron-doped olympicenes: modular synthesis, tunable optoelectronic properties, and one-electron reduction,” appeared in Chemical Science in 2023 (DOI: 10.1039/D3SC00342F).
Why the neutral molecules resist air and moisture
Boron is strongly electron-deficient and can be highly Lewis acidic, so an exposed boron center might be expected to react readily with its surroundings. The reported neutral boraolympicenes behaved differently: the authors describe them as stable against air and moisture without bulky protecting groups around boron.
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The authors attribute this behavior to conjugation across the fused framework. Boron has a vacant pz orbital, and the study’s single-crystal structural analysis and theoretical calculations support significant π-electron delocalization involving that orbital. In the authors’ explanation, integrating boron into the conjugated framework helps stabilize the neutral molecules without relying on large protective substituents.
This is a reported result for the compounds and conditions studied, not a quantified shelf-life guarantee. The paper does not establish a duration or exposure threshold for the neutral molecules’ stability, and the finding should not be generalized to every boron-containing compound.
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Neutral molecules and the radical anion behave differently
The authors also tested what happens when one member of the family, 6-phenyl-11a-boraolympicene, gains an electron. Using cobaltocene, they prepared a radical-anion salt and characterized it with UV-vis-NIR absorption, electron spin resonance, and infrared spectroscopy. Its behavior is an important qualification to the air-and-moisture stability claim.
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Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →| Form studied | Reported condition | Reported result |
|---|---|---|
| Neutral 11a-boraolympicenes | Air and moisture | Described by the authors as chemically stable; no quantified exposure duration or threshold is given. |
| Radical-anion salt of 6-phenyl-11a-boraolympicene | Inert glovebox | No detectable spectral variation for one week. |
| Radical-anion salt of 6-phenyl-11a-boraolympicene | Air and moisture | Reported to be extremely sensitive. |
The one-week observation applies to the reduced salt in a glovebox, not to the neutral family in open air. The reduced and neutral forms are different electronic states, and the reported stability of one should not be substituted for the other.
What the electronic and optical results suggest
The study reports intense absorption spanning visible to near-infrared wavelengths and LUMO energy levels around −3.8 eV. The orbital-energy figure is a value reported for the studied compounds, not a constant for all boraolympicenes. Along with the modular substitution chemistry, these properties point to opportunities for tuning the molecules’ electronic and optical characteristics.
Crystal packing also varied with substituent structure, showing that changing the molecular decoration can affect how molecules arrange in the solid state. The paper reports synthesis and characterization findings; it does not demonstrate commercial device performance or establish a practical application.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the result does—and does not—establish
- Established in this study: a family of fully fused 11a-boraolympicenes was synthesized, and the neutral compounds were reported stable against air and moisture without bulky boron-protecting groups.
- Proposed explanation: the authors connect the stability to π-electron delocalization involving boron’s vacant pz orbital, supported by structural analysis and calculations.
- Separate reduced-state result: a radical-anion salt was sensitive to air and moisture, although it showed no detectable spectral change for a week in an inert glovebox.
- Not established: a quantified shelf life for the neutral compounds, independent replication, or performance in a commercial device.
The primary article is by Jing Guo, Kaihua Zhang, Yanpei Wang, Haipeng Wei, Wang Xiao, Kun Yang, and Zebing Zeng. It was first published on 7 March 2023 in Chemical Science, volume 14, pages 4158–4165 (Royal Society of Chemistry article record). For broader context, Chemistry World’s April 2023 coverage discusses the result in relation to the reactivity of carbon-based olympicenyl species.
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