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Abstract The chemical reduction of π‐conjugated bilayer nanographene1(C138H120) with K and Rb in the presence of 18‐crown‐6 affords [K+(18‐crown‐6)(THF)2][{K+(18‐crown‐6)}2(THF)0.5][C138H1223−] (2) and [Rb+(18‐crown‐6)2][{Rb+(18‐crown‐6)}2(C138H1223−)] (3). Whereas K+cations are fully solvent‐separated from the trianionic core thus affording a “naked”1.3−anion, Rb+cations are coordinated to the negatively charged layers of1.3−. According to DFT calculations, the localization of the first two electrons in the helicene moiety leads to an unprecedented site‐specific hydrogenation process at the carbon atoms located on the edge of the helicene backbone. This uncommon reduction‐induced site‐specific hydrogenation provokes dramatic changes in the (electronic) structure of1as the helicene backbone becomes more compressed and twisted upon chemical reduction, which results in a clear slippage of the bilayers.
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A Triply Negatively Charged Nanographene Bilayer with Spin Frustration
Abstract We report on the largest open‐shell graphenic bilayer and also the first example of triply negatively charged radical π‐dimer. Upon three‐electron reduction, bilayer nanographene fragment molecule (C96H24Ar6)2(Ar=2,6‐dimethylphenyl) (12) was transformed to a triply negatively charged species123.−, which has been characterized by single‐crystal X‐ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and magnetic properties on a superconducting quantum interference device (SQUID).123.−features a 96‐center‐3‐electron (96c/3e) pancake bond with a doublet ground state, which can be thermally excited to a quartet state. It consists of 34 π‐fused rings with 96 conjugatedsp2carbon atoms. Spin frustration is observed with the frustration parameterf>31.8 at low temperatures in123.−, which indicates graphene upon reduction doping may behave as a quantum spin liquid.
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- Award ID(s):
- 2107820
- PAR ID:
- 10396076
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 62
- Issue:
- 8
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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