Dual-State Ambipolar Charge Transport in Antiaromatic [4]cyclodibenzopentalene Single-Molecule Nanohoops

Feng, Sai and Almughathawi, Renad and Weber, Andrej and Hou, Songjun and Zhang, Chengyang and Wössner, Jan S. and Esser, Birgit and Lambert, Colin and Wu, Qingqing and Li, Yueqi and Li, Jinghong (2025) Dual-State Ambipolar Charge Transport in Antiaromatic [4]cyclodibenzopentalene Single-Molecule Nanohoops. Journal of the American Chemical Society, 147 (22). pp. 18475-18483. ISSN 0002-7863

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Abstract

Antiaromatic compounds are of great interest due to their narrow highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps, high reactivity, and enhanced charge mobility, yet their role in single-molecule electronics is still not well understood. Using electrochemically controlled scanning tunneling microscopy break junction (ECSTM-BJ) measurements, we compared the energy-alignment-dependent conductance of the aromatic [10]cycloparaphenylene ([10]CPP) and the antiaromatic [4]cyclodibenzopentalene ([4]CDBP). While [10]CPP showed a single conductance state via the HOMO, [4]CDBP exhibited two distinct states involving both the HOMO and LUMO. Our analysis and DFT calculations attribute this dual-state behavior to unique anchoring mode and energy-level realignment within a narrow HOMO-LUMO gap. This property enables electron- and hole-dominated pathways that depend on the anchoring configuration and coexist at a fixed gate potential. This phenomenon, also observed in the [4]CDBP⊃C60 structure, highlights the potential of antiaromatic molecules for advanced molecular electronics.