Thermal and photoinduced spin-crossover of mononuclear FeII complexes based on bppCHO ligand

Two new iron(o) complexes (Fe(bppCHO)(2)](ClO4)(2) (1 center dot ClO4) and (Fe(bppCHO)(2))(BF4)(2)center dot H2O (1.BF4) were synthesized by using 2,6-di(1H-pyrazol-1-yl)isonicotinaldehyde (bppCHO) as the ligand. The structures and spin states of the complexes were characterized by single-crystal X-ray diffraction and magnetic susceptibility measurements. Complex 1 center dot ClO4 exhibits light-induced excited spin state trapping (LIESST) up to 53 K and two-step spin-crossover (SCO) over room temperature, in which the first step shows a thermal hysteresis of 26 K, whereas 1 center dot BF4 exhibits a gradual SCO behavior. A magnetostructural study reveals that the difference in the SCO property is related to the supramolecular interactions and crystal packing effect.

Automated summary

The study of two iron(o) complexes reveals that the spin states and spin-crossover behavior are influenced by supramolecular interactions and crystal packing effects. Complex 1·ClO4 shows light-induced excited spin state trapping and two-step spin-crossover at room temperature, while complex 1·BF4 exhibits gradual spin-crossover behavior. Magnetostructural analysis provides insight into the differences in the spin-crossover properties of the two complexes.