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 [Co₄(triazolate)₂(OBA)₃], I, possessing Co₄ clusters. The Co₄ clusters are connected together through the tirazolate moieties forming a two-dimensional layer that closely resembles the TiS₂ 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 TiS₂ layer in a metal–organic framework compound. Magnetic studies in the temperature range 1.8–300 K indicate strong antiferromagetic interactions for Co₄ clusters. The structure as well as the magnetic behavior of the present compound has been compared with the previously reported related compound [Co₂(μ₃-OH)­(μ₂-H₂O)­(pyrazine)­(OBA)­(OBAH)] prepared using pyrazine as the linker between the Co₄ clusters.