New heterometallic pivalates with FeIII and ZnII ions: Synthesis, structures, magnetic, thermal properties

3 years ago

New heterometallic pivalates with FeIII and ZnII ions: Synthesis, structures, magnetic, thermal properties

Techniques for synthesizing Zn(II)-Fe(III) heterometallic molecular complexes [Fe2Zn4O2(Piv)10] (1), [Fe4Zn3O3(Piv)12(H2O)]·1.5Et2O (2) and [Fe3Zn2O2(Piv)9(1,10-phen)] (3) (where HPiv is pivalic acid, 1,10-phen – C12H8N2) have been developed. It has been found that recrystallization of the solid product formed from reaction mixture of Fe(NO3)3, Zn(NO3)2, KOH and HPiv (in the 3:2:13:34 ratio) in water («Reagent A») from acetone results in hexanuclear complex 1, whereas thermolysis of «Reagent A» at 130°C in air followed by crystallization of the thermolysis products from ether makes it possible to isolate complex 2. It has been found that dissolution of thermolyzed «Reagent A» in MeCN in the presence of 1,10-phenanthroline leads to formation of complex 3. The structures of complexes 1–3 were determined by single crystal X-ray diffraction analysis. The doublet Mössbauer spectra of complexes 1 and 2 correspond to high-spin Fe³⁺ ions in an octahedral environment of oxygen atoms, while the non-equivalence of the environment of iron ions in compound 3 (FeO6 and FeO4N2) is reflected by two observed doublets with different intensities. Based on the results of magnetic data simulation and quantum-chemical calculations, it has been shown that antiferromagnetic exchange coupling exists in complexes 1 and 2 (J 12 =−3.05cm⁻¹ for 1 and J 12 =−0.4, J 13 =−13.5, J 23 =−3.6, J 24 =−27.2 and J 34 =−30.1cm⁻¹ for 2). The value of the exchange integral between pairs of metal ions correlates with the Fe-O distances and the Fe-O-Fe angles in the bridging oxo ligands. Processes of thermal destruction have been studied for complexes 1 and 2 in argon atmosphere in the temperature range of 25–500°C.

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DOI: S0277538717305594