Abstract

SOUZA, Gilmar P. et al. Synthesis and density functional calculations of the new molecule-based magnet precursor [Fe(H₂opba-i)(dmso)₂]Cl. J. Braz. Chem. Soc. [online]. 2006, vol.17, n.8, pp. 1534-1539. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532006000800008.

A new precursor of molecule-based magnetic systems, [Fe(H₂opba-i)(dmso)₂]Cl (1), with opba = ortho-phenylenebis(oxamato) in an iminoalcohol tautomeric form, was obtained as a product from the reaction between H₄opba and FeCl₃. Data from elemental analysis, IR and Mössbauer spectroscopies and magnetic measurements indicate that this precursor is composed of a mixture of trans (83%) and cis (17%) isomers. The c_MT value at 298K (2.1 emu K mol^-1) corresponds to Fe^III with spin state (S) between 3/2 and 5/2. Theoretical calculations (PBE/DZVP2) of trans- and cis-[Fe(H₂opba-i)(dmso)₂ ]⁺ show that both isomers have spin S = 1/2 in the ground state and S = 3/2 for the trans and S = 5/2 for the cis in the first excited state. The combination of these results leads to c_MT values of 0.375 and 2.3 emu K mol^-1, at low and high temperature respectively, which are in accordance with the experimental data for 1.

Keywords : molecule-based magnet; oxamate; iron(III); PBE/DZVP theoretical calculations; cis/trans isomerism.