Clathration of Five-Membered Aromatic Rings in the Bimetallic Spin Crossover Metal-Organic Framework [Fe(TPT)2/3{MI(CN)2}2]•G (MI = Ag, Au)

Six clathrate compounds of the three-dimensional spin crossover metal-organic framework formulated [Fe(TPT)(2/3){M-I(CN)(2)}(2)]center dot nG, where TPT is 2,4,6-tris(4-pyridyl)-1,3,5-triazine, M-I = Ag or Au and G represent the guest molecules furan, pyrrole and thiophene, were synthesized using slow diffusion techniques. The clathrate compounds were characterized by single-crystal X-ray diffraction at 120 and 300 K, thermogravimetric analysis and thermal dependence of the magnetic susceptibility. All compounds crystallize in the R (3) over barm trigonal space group. The Fe-II defines a unique [FeN6] crystallographic site with the equatorial positions occupied by four dicyanometallate ligands while the axial positions are occupied by the TPT ligands. Each TPT ligand links three Fe-II sites, while the dicyanometallate ligands bridge two Fe-II sites thereby generating two interlocked three-dimensional frameworks with the NbO topology. The choice of the TPT ligand favors the generation of pores where the guest molecules are located. The thermal dependence of the magnetic susceptibility of samples constituted of single crystals was investigated for the six compounds to assess the influence of the guest molecules on the spin crossover behavior. In general, the magnetic properties of the six clathrates suggest a gradual stabilization of the high-spin state as the molecular volume of the guest increases.