Spectroscopic and magnetic properties of the pyridine-2-carbaldehyde thiosemicarbazonateiron(III) complexes:: [Fe(C7H7N4S)2]X•nH2O (X = Cl, ClO4, NO3, PF6).: Crystal structure of the hexafluorophosphate compound

The [Fe(C7H7N4S)(2)]X . nH(2)O (X = Cl (1), ClO4 (2), NO3 (3), PF6 (4); n = 0 (4), 1.5 (1), 0.5 (3)) compounds, where C7H8N4S is pyridine-2-carbaldehyde thiosemicarbazone, have been synthesized and characterized. The crystal structure of compound 4 has been solved. It crystallizes in the monoclinic P2(1)/n space group with a = 13.099(2), b = 12.153(5), c = 13.710(1) Angstrom, beta = 102.56(1)degrees, V = 2130(1) Angstrom(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 Huckel 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. (C) 1998 Elsevier Science S.A. All rights reserved.