Abstract

So far, most reported open-shell singlet diradicaloids are based on planar π-conjugated molecules. Herein, we report the bridged corannulene dimer diradicaloids, Cor-D1 and Cor-D2, both showing a three-dimensional curved π-conjugated structure. Cor-D1 has a small diradical character (y0 = 5.4%) and behaves more like a closed-shell quinoidal compound at room temperature, while Cor-D2 is a typical open-shell diradicaloid with a larger diradical character (y0 = 16.9%). Both compounds exhibited paramagnetic activity at elevated temperatures, with a singlet-triplet energy gap (ΔES-T) of -8.4 and -3.0 kcal mol-1, respectively. X-ray crystallographic analysis revealed that both molecules have a dumbbell-shaped geometry, with the two terminal corannulene bowls bent to opposite directions. The spin is largely delocalized onto the two bowls in Cor-D2 and there are multiple [CH···π] interactions between the neighboring bowls. Chemical oxidation/reduction to their respective dications/dianions results in global aromaticity with [4n + 2] π-electrons delocalized through the periphery of the whole framework.

Highlights

  • There have been increasing research interests on openshell singlet diradicaloids due to their unique magnetic activity and potential applications in organic electronics, non-linear optics and spintronics.[1]

  • Its dication exhibits similar global aromaticity with 34 p electrons delocalized along the periphery

  • Rigid, p-QDM and 2,6-NQDM bridged corannulene dimers Cor-D1 and Cor-D2 were synthesized in stable form, which represent a new type of curved p-conjugated open-shell singlet diradicaloids

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Summary

Introduction

There have been increasing research interests on openshell singlet diradicaloids due to their unique magnetic activity and potential applications in organic electronics, non-linear optics and spintronics.[1]. Edge Article prepared and in all cases, the spin can be partially delocalized to the corannulene bowl.[4] The phenalenyl-fused corannulene anion was synthesized and fully characterized, but the property of its neutral radical Cor-PLY (Fig. 1a) was not reported, presumably due to its poor stability.[5] The corannulene-bridged phenoxyl diradical Cor-2PhO showed signi cant intramolecular magnetic interaction with a singlet–triplet energy gap (DES–T 1⁄4 2JkBÀ1) of À810 K (À1.61 kcal molÀ1).[6] Calculations reveal that the unpaired electronic spin in the triplet state is delocalized onto the corannulene skeleton from the phenoxyl moieties.

Results
Conclusion
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