Triphenylide-Based Molecular SolidA New Candidate for a Quantum Spin-Liquid Compound

The reduction of polycyclic aromatic hydrocarbons with alkali metals results in solids having intriguing magnetic properties the understanding of which has been hitherto severely hampered by the lack of single-phase samples. Here, we report on the successful reduction of triphenylene with stoichiometric amount of potassium in 1,2-dimethoxyethane (DME) solution. Comprehensive diffraction measurements of the obtained K2(C18H12)2(DME) solid demonstrate the importance of cation-π interactions as responsible for the characteristic stacking of the triphenylide molecular ions. Electron paramagnetic resonance and magnetization measurements reveal K2(C18H12)2(DME) is a Mott insulator with strikingly strong nearest neighbor antiferromagnetic interactions between S = 1/2 spins of (C18H12)•– radical anions. Low dimensionality hinders long-range magnetic ordering and establishes a spin state that resembles gapped quantum spin liquid state.