Lattice water molecules tuned spin-crossover for an iron(ii) complex with thermal hysteresis

Abstract

A new iron(II) complex based on the 4,4′-dimethyl-2,2′-bipyridine ligand [Fe(4,4′-dmbpy)₃(ClO₄)(SCN)·3H₂O (1·3H₂O)] has been prepared and characterized. Structural studies and Hirshfeld surface analysis for complex 1·3H₂O at three different temperatures (300, 240 and 130 K) are described. The UV-vis absorption spectrum of a water-free sample (1) in methanol solution and magnetic susceptibility measurements for solid-state samples 1·3H₂O and 1 revealed that the removal of lattice water molecules from complex 1·3H₂O changed the magnetic properties from the low-spin state (1·3H₂O) to the complete spin-crossover (1) between 350–220 K with a thermal hysteresis of 7 K, and was accompanied by a colour change from brown to red.