Fe^III in a high-spin state in bis­(5-bromo­sali­cyl­alde­hyde 4-ethyl­thio­semicarbazonato-κ3O,N1,S)ferrate(III) nitrate monohydrate, the first example of such a cationic Fe^III com­plex unit

The synthesis and crystal structure (100 K) of the title compound, [Fe(C ₁₀H ₁₁BrN ₃OS) ₂]NO ₃·H ₂O, is reported. The asymmetric unit consists of an octahedral [Fe ^III(HL)2] ⁺cation, where HL ^-is H-5-Br-thsa-Et or 5-bromosalicylaldehyde 4-ethylthiosemicarbazonate(1-) {systematic name: 4-bromo-2-[(4-ethylthiosemicarbazidoidene)methyl]phenolate}, a nitrate anion and a noncoordinated water molecule. Each HL ^-ligand binds via the thione S, the imine N and the phenolate O atom, resulting in an Fe ^IIIS2N ₂O ₂chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. This [Fe(HL)2](anion)·H2O compound contains the first known cationic Fe ^IIIentity containing two salicylaldehyde thiosemicarbazone derivatives. The Fe ^IIIion is in the high-spin state at 100 K. In addition, a comparative IR spectroscopic study of the free ligand and the ferric complex is presented, demonstrating that such an analysis provides a quick identification of the degree of deprotonation and the coordination mode of the ligand in this class of metal compounds. The variable-temperature magnetic susceptibility measurements (5-320 K) are consistent with the presence of a high-spin Fe ^IIIion with a zero-field splitting D = 0.439 (1) cm ^-1