Powder crystalline metal-organic frameworks (MOF), M(N 3) 2(bpy) (where M Ni, Co, Cu, and bpy 4,4′-bipyridine), were successfully synthesized by mixing M(II) salts with solutions of 4,4′-bipyridine and NaN 3. All three MOFs crystallize in an orthorhombic crystal system with the space group Cmmm (No. 65), which is isostructural to that of 2D-Fe(N 3) 2(bpy). The M(II) ions are coordinated with four azide ligands (N 3) in equatorial plane forming linear magnetic chains. Isothermal magnetization, magnetic susceptibility, and heat capacity measurements were performed. No clear phase transitions were observed. The intra-chain magnetic interaction was found to be ferromagnetic for the Co and Ni compounds, and antiferromagnetic for the Cu compound. The data were fit to theoretical models, and the variation in the exchange interactions was interpreted in terms of the geometric distortions on the octahedral M(II) sites.
ASJC Scopus subject areas
- Physics and Astronomy(all)