Publications scientifiques
Colince Nde
Bridget N. Ndosiri
Idelle N. Kamga
Ledoux S. Pouamo
Justin Nenwa* (Auteur correspondant)
Adam Bouraima
Frédéric Capet
Autres affiliations : École Nationale Supérieure de Chimie de Lille · Université de Lille · Unité de catalyse et de chimie du solide de Lille · Université d'Artois · École Centrale de Lille
Michel Foulon
Polyhedron
An oxalato-bridged heterometallic heptanuclear [K 5 I Fe 2 III ] hybrid salt, (CH 6 N 3 )[K 5 (H 2 O) 4 Fe 2 (C 2 O 4 ) 6 ] ( 1 ) (CH 6 N 3 + = guanidinium cation) has been synthesized and characterized by elemental and thermal analyses, IR spectroscopy, single-crystal X-ray diffraction, EPR and SQUID magnetometry. The asymmetric unit in 1 is composed of a dimetallic heptanuclear [K 5 (H 2 O) 4 Fe 2 (C 2 O 4 ) 6 ] − anionic complex and a guanidinium CH 6 N 3 + cation insuring the charge compensation. Each Fe 3+ center in the anionic complex is six-coordinate in a distorted octahedron defined by three chelating oxalato(2-) ligands. In contrast, the coordination numbers for K + centers range from 7 to 9. The structural feature of focal interest in 1 is formation of an extended anionic network encapsulating guanidinium cations. This structure can be considered a sheet-MOF, where metal ions and oxalates (linkers) form infinite 2D units. The 3-D supramolecular architecture is stabilized by O H∙∙∙O and N H∙∙∙O hydrogen bonds linking polymeric oxalato-bridged anionic assemblies and organic cations. The thermal studies confirmed the anhydrous character of salt 1 and showed a three-step decomposition to yield a mixture of Fe 2 O 3 and K 2 O as final residue. EPR spectrum of 1 is in accordance with the oxidation state + 3 of the iron center in an octahedral environment. Temperature-dependence susceptibility measurements investigated in the temperature range 2–300 K revealed weak antiferromagnetic coupling at low temperatures in salt 1 . The distributions of different types of intermolecular interactions in the crystal structure were quantified by Hirshfeld surface analysis and their associated fingerprint plots.
