Synthesis, Magnetic Properties and X‐ray Structure Analysis of a 1‐D Chain Iron( II ) Spin Crossover Complex with wide Hysteresis

The reaction of [FeL(MeOH)2] (L being a tetradentate [N2O2]2− coordinating Schiff base like ligand [([3,3′]‐[1,2‐phenylenebis(iminomethylidyne)]bis(2,4‐pentane‐dionato)(2‐)N,N′,O2,O2′], MeOH = methanol) with 4,4′‐bipyridine (bipy) results in the formation of a new iron(II) spin crossover coordination polymer of the formula [FeL(bipy)] (1). T‐dependent susceptibility measurements revealed an abrupt HS ↔ LS spin transition with an approximately 18 K‐wide thermal hysteresis loop (T1/2↑ = 237 K and T1/2↓ = 219 K). The isolation of crystals suitable for X‐ray structure analysis allowed the determination of the motive of the molecule structure of the first 1‐D chain compound with hysteresis in the HS form at 250 K. Despite the low qualtity of the data, we were able to obtain some insight into the interplay of covalent and elastic interactions that are both responsible for the high cooperative interactions during the spin transition in this compound.