Crystal structure and spin crossover behavior of the [Fe(5-Cl-qsal)2][Ni(dmit)2]·2CH3CN complex

Abstract

The synthesis of the [Fe(5-Cl-qsal)2][Ni(dmit)2]·2CH3CN (1) is reported in the present work. The crystal structures of 1, solved at 150, 245, 255 and 294K, revealed the presence of low spin (LS) and high spin (HS) FeIII centers at 150 and 294K, respectively, and mixed HS/LS states ∼50:50 and 75:25 at 245 and 255K. The crystal structure is based on alternating cationic and anionic layers, where each layer is composed of an arrangement of chains of cations or anions. The anionic chains consist on the stacking of face-to-face pairs of [Ni(dmit)2]− anions. Extended ππ contacts, involving the 5-Cl-qsal ligands, were observed in the cationic chains. The contribution of the anions to the magnetization correlates well with an alternating chain, dominated by antiferromagnetic interactions. A spin crossover (SCO) process, assigned to the [Fe(5-Cl-qsal)2]+ cationic network was observed at high temperatures (T∼240K). The thermal dependence of the magnetization suggests the existence of an abrupt change at ∼233K from the LS state to a mixed 50:50 HS/LS state, followed by a gradual transformation at ∼256K to the HS state. A structural transformation consisting of the doubling of the unit cell was observed to be associated with the SCO process.