High-Temperature Spin Crossover Behavior in a Nitrogen-Rich FeIII-Based System

A nitrogen-rich ligand bis(1H-tetrazol-5-yl)­amine (H3bta) was employed to isolate a new FeIII complex, Na2NH4[FeIII(Hbta)3]·3DMF·2H2O (1). Single crystal X-ray diffraction revealed that complex 1 consists of FeIII ions in an octahedral environment where each metal ion is coordinated by three Hbta2– ligands forming the [FeIII(Hbta)3]3– core. Each unit is linked to two one-dimensional (1-D) Na+/solvent chains creating a two-dimensional (2-D) network. In addition, the presence of multiple hydrogen bonds in all directions between ammonium cation and ligands of different [FeIII(Hbta)3]3– units generates a three-dimensional (3-D) network. Magnetic measurements confirmed that the FeIII center undergoes a Spin Crossover (SCO) at high temperature (T1/2 = 460(10) K).