| Autor: |
Nahrstedt V; Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939 Cologne, Germany., Stadler D; Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939 Cologne, Germany., Fischer T; Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939 Cologne, Germany., Duchoň T; PGI-6, Research Centre, Juelich GmbH, Leo-Brandt-Str., 52428 Juelich, Germany., Mueller DN; PGI-6, Research Centre, Juelich GmbH, Leo-Brandt-Str., 52428 Juelich, Germany., Schneider CM; PGI-6, Research Centre, Juelich GmbH, Leo-Brandt-Str., 52428 Juelich, Germany., Mathur S; Institute of Inorganic Chemistry, University of Cologne, Greinstr. 6, 50939 Cologne, Germany. |
| Abstrakt: |
New heterometallic In-Fe alkoxides [InFe(O t Bu) 4 (PyTFP) 2 ] ( 1 ), [InFe 2 (O neo Pen) 9 (Py)] ( 2 ), and [InFe 3 (O neo Pen) 12 ] ( 3 ) were synthesized and structurally characterized. The arrangement of metal centers in mixed-metal framework was governed by the In:Fe ratio and the coordination preferences of Fe(III) and In(III) centers to be in tetrahedral and octahedral environments, respectively. 3 displayed a star-shaped so-called "Mitsubishi" motif with the central In atom coordinated with three tetrahedral {Fe(O neo Pen) 4 } - anionic units. The deterministic structural influence of the larger In atom was evident in 1 and 2 which displayed the coordination of neutral coligands to achieve the desired coordination number. Thermal decomposition studies of compounds 1 - 3 under inert conditions with subsequent powder diffraction studies revealed the formation of Fe 2 O 3 and In 2 O 3 in the case of 3 and 2 , whereas 1 intriguingly produced elemental In and Fe. In contrary, the thermal decomposition of 1 - 3 under ambient conditions produced a ternary oxide, InFeO 3 , with additional Fe 2 O 3 present as a secondary phase in a different stoichiometric ratio predetermined through the In:Fe ratio in 2 and 3 . The intimate mixing of different phases in InFeO 3 /Fe 2 O 3 nanocomposites was confirmed by transmission electron microscopy of solid residues obtained after the decomposition of 1 and 2 . The pure InFeO 3 particles demonstrated ferromagnetic anomalies around 170 K as determined by temperature-dependent field-cooled and zero-field-cooled magnetization experiments. A first-order magnetic transition with an increase in the ZFC measurements was explained by temperature-induced reduction of the Fe-Fe distance and the corresponding increase in superexchange. |
