Seven-coordinated iron(ii) spin-crossover molecules: some learning from iron substitution in [FexMn1−x(L222N3O2)(CN)2]·H2O solid solutions

Abstract

The purpose of this work is to study the influence of the substitution of Fe(II) by Mn(II) on the spin crossover behaviour of [Fe_xMn_1−x(L₂₂₂N₃O₂)(CN)₂]·H₂O solid solutions where L₂₂₂N₃O₂ is a macrocyclic ligand = 2,13-dimethyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]-octadeca-1(18),2,12,14,16-pentaene. The pure Fe(II) complex is known to present a change of the coordination number from 7 at high temperature to 6 at low temperature. The target of the solid solution study was to investigate the effect of metal dilution on this coordination change. We have then measured the thermal spin crossover features as well as the metastable HS state lifetime generated by rapid thermal quenching, which was probed through the determination of the T(TIESST) value. A discussion of the spin-state as a function of temperature is given based on the phase diagram of this series and based on the investigation of the crystal structure of the [Mn(L₂₂₂N₃O₂)(CN)₂]·H₂O complex and its comparison with the published [Fe(L₂₂₂N₃O₂)(CN)₂]·H₂O master compound.