Synthesis, Structure, and Magnetic Electrochemical Properties of a Family of Tungstoarsenates Containing Just CoIICenters or Both CoIIand FeIIICenters.
The three polyoxotungstates [(NaOH2)2CoII2(As2W15O56)2]18-(1), [(NaOH2)(CoIIOH2)CoII2(As2W15O56)2]17-(2), and [(CoIIOH2)2CoII2(As2W15O56)2]16-(3) have been prepared in aqueous solution upon mixing cobalt(II) salts with the ligand [As2W15O56]12-. The reaction of 1 or 2 with the Fe3+ion leads invariably to the same species [(FeIIIOH2)(CoIIOH2)CoII2(As2W15O56)2]15-(4) possessing three cobalt atoms and a single iron atom. However, if the Fe-containing homologue of compound 1, that is, the polyoxotungstate [(NaOH2)2FeIII2(As2W15O56)2]16-(5), is employed instead to react with the Co2+ion, the species [(CoIIOH2)2FeIII2(As2W15O56)2]14-(6) is obtained, having two cobalt atoms and two iron atoms. The compounds 1, 2, 3, 4, and 6 are described for the first time and have been characterized by several physicochemical methods such as FTIR, UV-visible, ATG, and elemental analysis. Structural analysis by single-crystal X-ray diffraction has been carried out with compounds 2 (monoclinic space group P21/c, a = 17.0622(5) Å, b = 15.0828(4) Å, c = 32.0872(8) Å, β = 91.170(1)°, and Z = 2) and 3 (triclinic space group P1̅, a = 13.6137(7) Å, b = 13.8836(8) Å, c = 22.9276(6) Å, α = 89.906(3)°, β = 78.356(2)°, γ = 61.451(2)°, and Z = 1). Electrochemical studies undertaken with all the above-mentioned compounds and some of their homologues shed light on the influence of the chemical composition on their electrocatalytic properties toward substrates such as the nitrite ion and dioxygen. Magnetic measurements evidence anisotropic ferromagnetic interactions between Co2+ions and antiferromagnetic interactions between Fe3+ions. The nature and the strength of the Co2+-Fe3+interactions depend on the relative orientations of their 3d orbitals. The effective magnetic moment of the Co2+ions varies with the temperature and with the distortion of the octahedral sites in which they are located.
Equipe d'Electrochimie et de Photo-électrochimie, Laboratoire de Chimie Physique, Université Paris-Sud, UMR 8000 CNRS, Université Paris-Saclay , Orsay, F-91405, France.
Charyle S
CS
Ayingone Mezui
Equipe d'Electrochimie et de Photo-électrochimie, Laboratoire de Chimie Physique, Université Paris-Sud, UMR 8000 CNRS, Université Paris-Saclay , Orsay, F-91405, France.
Pedro
P
de Oliveira
Equipe d'Electrochimie et de Photo-électrochimie, Laboratoire de Chimie Physique, Université Paris-Sud, UMR 8000 CNRS, Université Paris-Saclay , Orsay, F-91405, France.
Anne-Lucie
AL
Teillout
Institut Lavoisier de Versailles, Université de Versailles St. Quentin, UMR 8180 CNRS, Université Paris-Saclay , Versailles, F-78035, France.
Jérôme
J
Marrot
Equipe Synthèse Propriétés et Modélisation des Matériaux, ICMMO, Université Paris-Sud, UMR 8182 CNRS, Université Paris-Saclay , Orsay, F-91405, France.
Patrick
P
Berthet
Institut Lavoisier de Versailles, Université de Versailles St. Quentin, UMR 8180 CNRS, Université Paris-Saclay , Versailles, F-78035, France.
Mounim
M
Lebrini
Equipe d'Electrochimie et de Photo-électrochimie, Laboratoire de Chimie Physique, Université Paris-Sud, UMR 8000 CNRS, Université Paris-Saclay , Orsay, F-91405, France.
Israël M
http://orcid.org/0000-0003-3440-8066
IM
Mbomekallé