Spectroscopic properties of ironthiosemicarbazone compounds. Structure of [Fe(C 7H 7N 4S) 2]·1.25H 2O

Abstract

The reaction of FeCl 3 and HL, where HL=C 7H 8N 4S, pyridine-2-carbaldehyde thiosemicarbazone, at physiological pH values in air gives rise to a powder of composition C 14H 16Cl 0.3FeN 8O 1.2S 2 which contains iron(II)– and iron(III)–thiosemicarbazone species. This fact confirms the reducing character of the ligand in neutral and basic media. The [Fe(C 7H 7N 4S) 2]·1.25H 2O compound has been isolated. The crystal structure consists of discrete monomeric cationic entities containing low-spin iron(II) ions in a distorted octahedral environment. The metal ion is bonded to one sulfur and two nitrogen atoms of each thiosemicarbazone molecule. The powdered X-band EPR spectra of C 14H 16Cl 0.3FeN 8O 1.2S 2 show a significant variation with temperature which can be explained considering an ‘exchange narrowing’ phenomenon, in good accordance with the presence of antiferromagnetic interactions. The Mössbauer measurements are in good agreement with the existence of one iron(II) and two iron(III) low-spin species, with relative areas of 69, 17 and 14%, respectively.