Synthesis, structure, topology and magnetic properties of new coordination polymers based on 5(-Br/-COOH)-substituted nicotinic acid

Nine new coordination polymers of 5-substituted nicotinic acid (with either -Br, HBNA, or -COOH, 3,5-H2PDC) with d-transition (Co, Ni, Zn and Cd) and f-lanthanoid (La, Ce, Sm and Tb) metal ions have been synthesized. The two metal complexes [Co-2(BNA)(4)(H2O)](n)center dot H2O (1a) and [Cd(BNA)(2)](n) (1b) have polymorphic/isomeric structures to those of metal-organic-frameworks (MOFs) with similar structural building units (SBUs) reported earlier. Modified reaction conditions yielded new isomeric metal complexes in the present case. Reactions of the 3,5-H2PDC linker with different metal ions led to the formation of polymeric complexes [Mn-3(3,5-PDC)(3)(DMA)(3)](n)center dot DMA (2a), [Zn(3,5-PDC)(DMA)](n)center dot DMA (2b) and [Cd-2(3,5-PDC)(2)(DMA)(4)](n) (2c), as well as lanthanoid MOFs [Sm(3,5-PDC)(1.5)(DMF)](n)center dot DMF (2d, as well as isomorphous products with La (2f) and Ce (2g) ions) and [Tb-2(3,5-PDC)(3)(DMF)(2)](n)center dot DMF (2e). Networking diversity observed in these coordination polymers with the conformationally rigid 5-substituted nicotinic acid ligand is discussed. The magnetic properties of 2a, 2d and 2e have been studied as well.