Publications scientifiques
Coustel M. N. Choubeu
Bridget N. Ndosiri
* (Auteur correspondant)
Hervé Vezin
Autres affiliations : Université de Lille · Laboratoire de Spectroscopie pour les Interactions, la Réactivité et l'Environnement
Claire Minaud
Autres affiliations : Université de Lille
James B. Orton
Simon J. Coles
Journal of Coordination Chemistry
By modifying the stoichiometric ratio of starting materials, two tris(oxalato)chromate(III) salts, (C7H11N2)3[Cr(C2O4)3] (1) and (C5H8N3)2(NH4)[Cr(C2O4)3]·2H2O (2) {(C7H11N2)+ = 2-amino-4,6-dimethylpyridinium, (C5H8N3)+ = 2,6-diaminopyridinium}, were synthesized and characterized by elemental and thermal analyses, single-crystal X-ray diffraction, IR and UV − Vis spectroscopies, EPR and SQUID measurements. Salt 1 exhibits a 3-D supramolecular framework based on [Cr(C2O4)3]3- and 2-amino-4,6-dimethylpyridinim cations, (C7H11N2)+, via N–H···O hydrogen bonds. Interestingly, π–π stacking interactions between pyridine rings contribute to the stabilization of the crystal packing. In contrast to salt 1, no π–π stacking interactions are observed in the mixed-cation salt 2 and its crystal packing is consolidated by N–H···O and O − H···O hydrogen bonds. EPR spectra of 1 and 2 are consistent with the oxidation state +3 of the chromium center in an octahedral environment. Temperature-dependence of the magnetic susceptibility data investigated from 2 to 300 K revealed the existence of zero-field splitting effects (ZFS) for Cr(III) ions in both compounds.
