Hysteretic four-step spin-crossover in a 3D Hofmann-type metal–organic framework with aromatic guest

Abstract

A new Hofmann-type metal–organic framework with bent pillar ligand, [Fe(dpoda){Ag(CN)₂}₂] (dpoda = 2,5-di-(pyridyl)-1,3,4-oxadiazole), was synthesized. Four-, two- and one-step spin-crossover (SCO) properties were obtained by using different sizes of aromatic guests. Most importantly, hysteretic four-step SCO behaviour with the sequence of LS ↔ HS_0.25LS_0.75 ↔ HS_0.5LS_0.5 ↔ HS_0.67LS_0.33 ↔ HS is observed for the first time.