Mono- and tetranuclear Fe(II,III) complexes with primary 1,3-diaminopropane: Synthetic aspects, magnetic properties and thermal behavior

Abstract

New iron carboxylate complexes with a aliphatic diamine, 1,3-diaminopropane (dap), were obtained under various synthesis conditions: in the air, [FeIII4O2(Piv)8(dap)2] (1, Piv is the pivalate anion), and in an inert atmosphere, [FeII(Piv)2(dap)2] (2). The structure of the compounds was determined by single crystal X-ray diffraction analysis. In mononuclear complex 2, the iron center coordinates two carboxylate ligands and two chelate dap. In the tetranuclear complex 1, the coordination environment of the metal ions is different, and only two ions coordinate the chelate dap. According to Mössbauer spectroscopy data, the Fe3+ ions in 1 and Fe2+ ion in 2 are in a high-spin state and in an octahedral environment of donor atoms. A DC magnetic susceptibility study and quantum-chemical analysis of intramolecular pathways using broken-symmetry density functional theory (DFT) showed that the magnetic exchange coupling between the Fe3+ ions of the central Fe2(μ-O)2 unit is weak (|J| ≤ 7 cm−1), while each of these ions is coupled by fairly strong antiferromagnetic exchange interactions with two other Fe3+ ions (J = −32.9/−43.2 cm−1). The thermal behavior of 1 and 2 was studied by simultaneous thermal analysis (STA).