Intercalation of [Ni(bpy)3]2+ complex cation into synthetic saponite: Preparation, characterization and magnetic properties

The magnetic properties of the hybrid materials formed by coordination compounds and clay minerals represent one of the main challenges in material science. The investigation of the intercalation of tris(2,2′-bipyridine)nickel(II) cations [Ni(bpy)3]2+ present in the solution with chloride anions into synthetic saponite (Sap) was carried out by direct exchange of the sodium ions by nickel(II) complex. The final intercalated [Ni(bpy)3]2+ saponite complex was characterized by powder X-ray diffraction (XRD), infrared (IR) spectroscopy, carbon and thermal analysis, and for the first time also by magnetic measurements. The carbon analysis proved a full replacement of Na+ with [Ni(bpy)3]2+ cations. Furthermore, significant increase of the d001 value of the intercalated saponite confirmed the presence of the [Ni(bpy)3]2+ in Sap interlayers. Only limited effect of the saponite layers on the ring C-H or skeletal vibrations of the [Ni(bpy)3]2+ complex was observed. The thermal stability of the [Ni(bpy)3]2+ increased after its intercalation into saponite. The magnetic properties of the [Ni(bpy)3]2+ saponite complex revealed similar magnetic response as the starting compound [Ni(bpy)3]Cl2·nH2O suggesting that the local surroundings of the Ni(II) atoms in [Ni(bpy)3]2+ intercalated into saponite remained unchanged.