An Organic–Inorganic Hybrid Semiconducting Quantum Spin Liquid Candidate: (BEDT-TTF)3[Cu2(μ-C2O4)3·CH3CH2OH·1.2H2O]

The organic–inorganic hybrid (BEDT-TTF)3[Cu2(μ-C2O4)3·CH3CH2OH·1.2H2O] (I) was obtained using the electrocrystallization method. It comprises a θ21-phase organic donor layer and a two-dimensional inorganic antiferromagnetic honeycomb lattice. Cu(II) is octahedrally coordinated by three bisbidenetate oxalates, exhibiting Jahn–Teller distortion. CH3CH2OH and H2O molecules are located within the cavities of the honeycomb lattice. The total formal charge of the three donor molecules was assigned to be +2 based on the bond lengths in the TTF core, which corresponded to the Raman spectra. It is a semiconductor with σrt = 0.04 S/cm and Eα = 40 meV. No long-range ordering was observed above 2 K from zero-field cooling/field cooling magnetization, as confirmed by specific heat measurements. The spin frustration with f > 10 from the antiferromagnetic copper-oxalate-framework was observed. It is a candidate quantum spin liquid.