The Effect of Hydrothermal and Non-Hydrothermal Synthesis on the Formation of Holmium(III) Succinate Hydrate Frameworks

M. C. BERNINI; E. V. BRUSAU; G. E. NARDA; G. A. ECHEVERRÍA; C. G. POZZI; G. PUNTE; C. W. LEHMANN

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY

Wiley-VCH

Año: 2007 p. 684 - 693

1434-1948

Two novel hydrated holmium(III) succinates with formula [Ho2(C4H4O4)3(H2O)4]×6H2O (I) and [Ho2(C4H4O4)3(H2O)2]×H2O (II) have been synthesized from aqueous solution, under ambient and hydrothermal conditions, respectively. Single-crystal X- ray diffraction shows that Ho(III) is nine-coordinated in both compounds, however their structures are markedly different, the main distinctive features being the [H2O]/[C4H4O42-] ratio in the coordination sphere, the conformation and coordination ability of the succinate ions and the resulting framework dimensionality. Compound I is a 2D hybrid polymer and its crystal structure is unprecedented for rare-earth succinates. It consists of centrosymmetric dimers of edge-sharing HoO7(H2O)2 polyhedra linked by succinate ions in the [100] and [101] directions. Hydrogen-bonded hydration water molecules connect layers ensuring the three-dimensional stability. Compound II is built up from infinite chains of HoO8(H2O) polyhedra linked by succinates that results in a 3D architecture showing that hydrothermal conditions favor increasing overall dimensionality of these hybrids in agreement with theoretical considerations. The compounds were characterized by FTIR and Raman spectroscopies, thermal analysis and variable-temperature magnetic susceptibility measurements and the results are discussed in connection with the structural findings. The effect of the dimensionality on the thermal stability of both structures after hydration water molecules removal is also analyzed.