A 2D Semiquinone Radical-Containing Microporous Magnet with Solvent-Induced Switching from T_c = 26 to 80 K

The incorporation of tetraoxolene radical bridging ligands into a microporous magnetic solid is demonstrated. Metalation of the redox-active bridging ligand 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (LH₂) with Fe^II affords the solid (Me₂NH₂)₂[Fe₂L₃]·2H₂O·6DMF. Analysis of X-ray diffraction, Raman spectra, and Mössbauer spectra confirm the presence of Fe^III centers with mixed-valence ligands of the form (L₃)^8- that result from a spontaneous electron transfer from Fe^II to L^2-. Upon removal of DMF and H₂O solvent molecules, the compound undergoes a slight structural distortion to give the desolvated phase (Me₂NH₂)₂[Fe₂L₃], and a fit to N₂ adsorption data of this activated compound gives a BET surface area of 885(105) m²/g. Dc magnetic susceptibility measurements reveal a spontaneous magnetization below 80 and 26 K for the solvated and the activated solids, respectively, with magnetic hysteresis up to 60 and 20 K. These results highlight the ability of redox-active tetraoxolene ligands to support the formation of a microporous magnet and provide the first example of a structurally characterized extended solid that contains tetraoxolene radical ligands.