Synthesis, EPR and Mossbauer spectral studies of new iron(III) complexes with 2-benzoylpyridine-N(4), N(4)-(butane-1,4-diyl) thiosemicarbazone (HBpypTsc):: X-ray structure of [Fe(BpypTSC)2]FeCl4 • 2H2O and the free ligand

Three novel iron(III) complexes of 2-benzoylpyridine N(4), N(4)-(butyl-1,4-diyl) thiosemicarbazone (HBpypTsc), [Fe(BpypTsc)(2)]ClO4 (1), [Fe(BpypTsc)(2)]NO3 (2) and [Fe(BpypTSC)(2)]FeCl4 (3) were synthesized and physico-chemically characterized by means of partial elemental analyses, magnetic measurements (polycrystalline state), UV-Vis and IR spectroscopies. The spin Hamiltonian parameters, isomer shifts and quadrupolar splitting values of the complexes were assigned by variable temperature EPR and Mossbauer spectra. The presence of a spin-paired iron(Ill) cation with d(xz)(2)d(yz)(2)d(xy)(1), ground state is revealed by the simulated EPR spectral data. The structures of the free ligand HBpypTsc and one of the complexes [Fe(BpypTsc)(2)]FeCl4 (3) were solved by single crystal X-ray diffraction which authenticated a FeN4S2 octahedral coordination in the complex, as envisaged from the spectral data. All complexes except [Fe(BpypTsc)(2)]FeCl4 (3) were found to be low-spin S = 1/2 (T-2(2g)), whereas 3 was found to have both low-spin (T-2(2g)) and high-spin ((6)A(1)) centres. (C) 2004 Elsevier Ltd. All rights reserved.