Structural, Spectroscopic, Magnetic and Thermal Properties in the [SrM(C3H2O4)2(H2O)5]· 2 H2O (M = Mn, Fe, Co, Ni) System: Precursors of SrMO3–x Mixed Oxides

Abstract

The [SrM(C3H2O4)2(H2O)7] (M = Mn, Fe, Co, Ni) compounds have been prepared and characterised by chemical analysis and X‐ray diffraction. The crystal structure of [SrCo(C3H2O4)2(H2O)5] · 2 H2O has been solved [monoclinic, P21/c, Z = 4, a = 6.880(1), b = 14.360(2), c = 15.800(2) Å. β = 101.69(1)°]. The compound exhibits a three‐dimensional chain/snake structure consisting of –CoO6–[SrO7]∞–CoO6– repeating units parallel to the [0 1 1] and [0 –1 1] directions. UV/Vis data are consistent with the cations being in a high‐spin octahedral symmetry. Magnetic measurements show antiferromagnetic interactions for all compounds with approximate θ values of –0.5 K, except for the cobalt compound (–24.5 K) where the decrease of the χmT curve can also be attributed to the spin‐orbit coupling. Thermal analyses performed in air and under nitrogen show three consecutive steps: dehydration, ligand pyrolysis, and inorganic residue evolution. Thermal treatments in tubular furnaces were performed in order to obtain pure SrMO3–x phases. In all cases the oxides are nonstoichiometric and oxygen‐deficient with structures related to that of perovskite. Lower temperatures and reaction times than those given in the literature have been used when using the ceramic method. These “soft” treatments gave rise to homogeneous particles of small grain size.

Poly[[μ2-aqua-tetraaquadi-μ3-malonato-nickel(II)strontium(II)] dihydrate]

“…The average Sr1-O distance are 2.649 (2) Å, slightly shorter than those in [SrCo(mal) 2 (H 2 O) 5 ].2H 2 O (Gil de Muro et al, 1999). The strontium polyhedra are linked to a dimer via bridge atoms O2 and O2 i as a common edge.…”

“…For the cobalt-containing analogue of the title compound and the previous unit-cell determination, see: Gil de Muro et al (1999). For a related structure, see: Gil de Muro et al (2000).…”

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Key indicators: single-crystal X-ray study; T = 294 K; mean (C-C) = 0.006 Å; R factor = 0.035; wR factor = 0.098; data-to-parameter ratio = 12.5.The unit-cell parameters for the title mixed-metal coordination polymer, {[NiSr(C 3 H 2 O 4 ) 2 (H 2 O) 5 ]Á2H 2 O} n , which is isostructural with its Co-containing analogue, were reported previously [Gil de Muro et al (1999). Eur.

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“…The unit-cell parameters for the title mixed-metal coordination polymer, {[NiSr(C 3 H 2 O 4 ) 2 (H 2 O) 5 ]Á2H 2 O} n , which is isostructural with its Co-containing analogue, were reported previously [Gil de Muro et al (1999). Eur.…”

Synthesis, DFT calculations of structure, vibrational and thermal decomposition studies of the metal complex Pb[Mn(C3H2O4)2(H2O)2]

“…The malonato anion, with two neighboring carboxylate groups, is a very versatile ligand and it has been used for the synthesis of crystalline coordination materials of diverse architectures, as the result of its various potential binding modes to transition metals as well as its participation in perovskite-type oxides [7][8][9][10][11]. The thermal decomposition of metallo-organic precursors allowed us to prepare metastable or stable phases at lower temperatures containing smaller grain sizes than those obtained from the ceramic method [7][8][9][10][11]. Using this method of synthesis, the diffusion distances between metal centres are remarkably reduced and, as a consequence, the reaction times and temperatures are reduced compared with other methods of synthesis.…”