A nanochanneled silver-deficient oxalatocobaltate(III) complex anion with hydronium as counter cation: Synthesis, crystal structure, thermal analysis and magnetism

Abstract

A novel cobalt(III) salt, (H3O)0.6[Ag2.4Co(C2O4)3]·6H2O (1), a member of the rare paramagnetic CoIII-open framework materials, has been synthesized in water and characterized by standard methods, including elemental and thermal analyses, IR, UV-Vis and EDX spectroscopies, and single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic I2/a space group. In the crystal structure, the Co(III) centers are pseudo-octahedrally chelated by three oxalato ligands with usual propeller orientation. The structure can be best described as an anionic silver-deficient oxalatocobaltate(III) [Ag2.4Co(C2O4)3]0.6- framework with isolated nanochannels parallel to the a axis, hosting highly disordered water molecules carrying protons (hydronium ions). Thermal analysis showed significant weight losses corresponding to the elimination of crystal water molecules followed by the decomposition of the network. Temperature-dependence susceptibility measurements investigated in the temperature range 2–300 K revealed antiferromagnetic ordering at low temperatures (T ≤ 25 K), the Curie–Weiss constants being C = 1.60 emu Oe−1 K and θ = -50 K.