Synthesis, structure, and magnetic properties of a new eight-connected metal-organic framework (MOF) based on Co4 clusters

A hydrothermal reaction of cobalt nitrate, 4,4'-oxybis(benzoic acid) (OBA), 1,2,4-triazole, and NaOH gave rise to a deep purple colored compound Co(4)(triazolate)(2)(OBA)(3)], I, possessing Co(4) clusters. The Co(4) clusters are connected together through the tirazolate moieties forming a two-dimensional layer that closely resembles the TiS(2) layer. The layers are pillared by the OBA units forming the three-dimensional structure. To the best of our knowledge, this is the first observation of a pillared TiS(2) layer in a metal-organic framework compound. Magnetic studies in the temperature range 1.8-300 K indicate strong antiferromagetic interactions for Co(4) clusters. The structure as well as the magnetic behavior of the present compound has been compared with the previously reported related compound Co(2)(μ(3)-OH)(μ(2)-H(2)O)(pyrazine)(OBA)(OBAH)] prepared using pyrazine as the linker between the Co(4) clusters.