[Fe(TPT)2/3{MI(CN)2}2]*nSolv (MI = Ag, Au): New bimetallic porous coordination polymers with spin-crossover properties
Résumé
Two new heterobimetallic porous coordination polymers with the formula [Fe(TPT)2/3{MI(CN)2}2]*nSolv {TPT = [2,4,6-tris(4-pyridyl)-1,3,5-triazine]; MI = Ag (nSolv = 0, 1MeOH, 2CH2Cl2), Au (nSolv = 0, 2CH2Cl2)} have been synthesized and their crystal structures were detd. at 120 K and 293 K by single-crystal x-ray anal. These structures crystd. in the trigonal R-3m space group. The FeII ion resides at an inversion center that defines a [FeN6] coordination core. Four dicyanometallate groups coordinate at the equatorial positions, while the axial positions are occupied by the TPT ligand. Each TPT ligand is centered in a ternary axis and bridges three crystallog. equiv. FeII ions, while each dicyanometallate group bridges two crystallog. equiv. FeII ions that define a 3D network with the topol. of NbO. There are two such networks, which interpenetrate each other, thereby giving rise to large spaces in which very labile solvent mols. are included (CH2Cl2 or MeOH). Crystallog. anal. confirmed the reversible structural changes that were assocd. with the occurrence of spin-crossover behavior at the FeII ions, the most significant structural variation being the change in unit-cell vol. (about 59 Å3 per FeII ion). The spin-crossover behavior has been monitored by thermal dependence of the magnetic properties, Moessbauer spectroscopy, and calorimetry. [on SciFinder(R)]