Synthesis, Structure, and Photomagnetic Properties of a Hydrogen-Bonded Lattice of [Fe(bpp)2]2+ Spin-Crossover Complexes and Nicotinate Anions

In this paper, we report on the synthesis, crystal structure, and photomagnetic properties of the spin-crossover salt of formula [Fe(bpp)2](C6H4NO2)2&middot
4H2O (1&middot
4H2O) (bpp = 2,6-bis(pyrazol-3-yl)pyridine
C6H4NO2&minus
= nicotinate anion). This compound exhibits a 3D supramolecular architecture built from hydrogen bonds between iron(II) complexes, nicotinate anions, and water molecules. As synthesized, the hydrated material is low-spin and desolvation triggers a low-spin (LS) to high-spin (HS) transformation. Anhydrous phase 1 undergoes a partial spin crossover (T1/2= 281 K) and a LS to HS photomagnetic conversion with a T(LIESST) value of 56 K.