Stable Cycloparaphenylene Diradical Dications with Macrocyclic Aromaticity
Peiyang Sun , Nan Yin , Li Zhang , Runbo Pei , Shusheng Wei , Yu Zhao , Yue Zhao , Wenqing Wang , Pingwu Du , Xinping Wang
Chinese Journal of Chemistry ›› 2025, Vol. 43 ›› Issue (24) : 3507 -3514.
Solid-state structures and aromaticity of open-shell cycloparaphenylene (CPP) dications remain elusive. This work reports the first isolation of open-shell cycloparaphenylene dications [9]CPP2•2+ and [11]CPP2•2+ through weakly coordinating anion-stabilized oxidation. X-ray crystallography confirms radially oriented π-delocalization, while EPR/SQUID analyses reveal antiferromagnetic coupling in open-shell singlet ground states with significant diradical character. Bidirectional aromaticity modulation emerges upon oxidation: diminished local benzene character versus enhanced global in-plane aromaticity, with macrocycle size governing diradical stability (ΔEOS-T, –3.11, –1.30, –0.99 kcal·mol–1 for [9]CPP2•2+, [10]CPP2•2+ and [11]CPP2•2+, respectively). Remarkably, size expansion preserves local aromaticity while reducing macrocyclic aromaticity, demonstrating electronic control over geometric constraints. These 3D spin-delocalized systems bridge Hückel aromaticity with curved π-topology, offering design principles for carbon nanotube-inspired organic spintronics and molecular multielectron storage architectures.
Cycloparaphenylene / Diradical dication / Macrocyclic aromaticity / Size-dependent properties / Curved π-system
2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
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