RESUMEN
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 (C96 H24 Ar6 )2 (Ar=2,6-dimethylphenyl) (12 ) was transformed to a triply negatively charged species 12 3.- , 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). 12 3.- 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 conjugated sp2 carbon atoms. Spin frustration is observed with the frustration parameter f>31.8 at low temperatures in 12 3.- , which indicates graphene upon reduction doping may behave as a quantum spin liquid.
RESUMEN
The monoradical cation 1Ë+ and anion 1Ë- based on tetracene were generated by one-electron oxidation and one-electron reduction of the bulky tetracene (1), respectively, which contain the largest π-fused skeletons reported to date. For monoradical species, 1Ë+ and 1Ë-, EPR spectra and DFT calculation results indicate the spin density delocalized over the whole molecules. Notably, in the solid state, 1Ë+ and 1Ë-, respectively, pack into (1Ë+)n and (1Ë--K-crown)n, characterized by single-crystal X-ray diffraction studies. The intermolecular interactions of 1Ë+ and 1Ë- are, respectively, through van der Waals forces and exchange couplings supported by metal ions. The monoradical cation polymer (1Ë+)n was the first example based on PAHs. The EPR spectra at 90 K of 1Ë+ and 1Ë- all show forbidden transitions (Δms = ±2), indicating the existence of electronic coupling between the neighboring radicals, with respective 2J = -6.54 K and 2J = -0.22 K characterized by SQUID measurements.