The [Fe(C 7H 7N 4S) 2]X·ηH 2O (X = Cl ( 1), ClO 4 ( 2), NO 3 ( 3), PF 6 ( 4); n = 0 ( 4), 1.5 ( 1), 0.5 ( 3)) compounds, where C 7H 8N 4S is pyridine-2-carbaldehyde thiosemicarbazone, have been synthesized and characterized. The crystal structure of compound 4 has been solved. It crystallizes in the monoclinic P/2 1 n space group with a = 13.099(2), b = 12.153(5), c = 13.710(1)Å, β = 102.56(1)°, V = 2130(1)Å 3, Z = 4. The framework consists of discrete monomeric cationic entities containing low-spin iron(III) ions in a distorted octahedral environment. The metal ion is bonded to one sulfur and two nitrogen atoms of each thiosemicarbazone molecule. The hexafluorophosphate molecules act as counterions. Extended Hu¨ckel MO calculations for complex 4 reveal a high delocalization and an important charge transfer contribution from the ligands to the metal. EPR spectra of compounds 1, 2, 3 and 4 show rhombic signals. Their main features, which can be expressed as a relatively low anisotropy in g values and a g 3 value which is greater than usual, are due to the low symmetry and the electronic delocalization.