Clathration of Five-Membered Aromatic Rings in the
Bimetallic Spin Crossover Metal–Organic Framework [Fe(TPT)<sub>2/3</sub>{M<sup>I</sup>(CN)<sub>2</sub>}<sub>2</sub>]·G (M<sup>I</sup> = Ag, Au)
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Abstract
Six
clathrate compounds of the three-dimensional spin crossover
metal–organic framework formulated [Fe(TPT)<sub>2/3</sub>{M<sup>I</sup>(CN)<sub>2</sub>}<sub>2</sub>]·nG, where TPT is 2,4,6-tris(4-pyridyl)-1,3,5-triazine,
M<sup>I</sup> = 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 <i>R</i>3̅<i>m</i> trigonal space
group. The Fe<sup>II</sup> defines a unique [FeN<sub>6</sub>] 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<sup>II</sup> sites, while the dicyanometallate
ligands bridge two Fe<sup>II</sup> 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