High-Temperature Spin Crossover in Two Solvent-Free Coordination Polymers with Unusual High Thermal Stability

Two
solvent-free two-dimensional (2D) coordination polymers, 2∞[Fe­(ptim)2] (1) and 2∞[Fe­(ptpy)2] (2)
(Hptim = 2-(5-(4-(1H-imidazol-1-yl)­phenyl)-4H-1,2,4-triazol-3-yl)­pyridine; Hptpy = 2-(5-(4-(pyridin-3-yl)­phenyl)-4H-1,2,4-triazol-3-yl)­pyridine), have been successfully prepared
by solvothermal reactions. Their iron atoms are bridged by the corresponding
multidentate anionic ligands into dense neutral structures. The magnetic
data reveal that complexes 1 and 2 are rare
examples exhibiting reversible one-step high-temperature spin crossover
behaviors with spin transition temperatures of 419 and 416 K, respectively.
Moreover, these structures also display remarkable thermal stability
up to 714 K (for 1) and 690 K (for 2), which
are confirmed by thermogravimetric and variable-temperature powder
X-ray diffraction analyses.