Spin-crossover in an iron(iii) complex showing a broad thermal hysteresis

Abstract

A pentadentate Schiff-base ligand ^3,5Cl-L²⁻ and NCSe⁻ form an iron(III) mononuclear complex, namely [Fe(^3,5Cl-L)(NCSe)], which shows a thermally induced spin crossover with a broad hysteresis width of 24 K between 123 K (warming) and 99 K (cooling). Analogous complexes of the [Fe(^3,5X-L)(Y)] type, where X = Cl or Br and Y = Cl⁻, N₃⁻, NCS⁻, and NCSe⁻, are high-spin over the whole temperature interval.