Ammonium Bis(salicylaldehyde Thiosemicarbazonato)ferrate(iii), a Supramolecular Material Containing Low-Spin FeIII

The synthesis and crystal structure (100 K) of the title compound, ammonium bis[salicylaldehyde thiosemicarbazonato(2−)-κ3O,N1,S]iron(III), NH4[Fe(C8H7N3OS)2], is reported. The asymmetric unit consists of an octahedral [FeIII(thsa)2]−fragment, where thsa2−is salicylaldehyde thiosemicarbazonate(2−), and an NH4+cation. Each thsa2−ligand bindsviathe thiolate S, the imine N and the phenolate O donor atoms, resulting in an FeIIIS2N2O2chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms incisand the N atoms intranspositions. The FeIIIion is in the low-spin state at 100 K. The crystal structure belongs to a category I order–disorder (OD) family. It is a polytype of a maximum degree of order (MDO). Fragments of the second MDO polytype lead to systematic twinning by pseudomerohedry.