Copper(II) coordination polymers containing neutral trinuclear or anionic dinuclear building units based on pyrazole-3,5-dicarboxylate: Synthesis, structures and magnetic properties

Abstract

Four novel copper(II) coordination polymers, namely {[Cu3(pzdc)2(pyz)(H2O)6](H2O)}n (1), {[Cu3(pzdc)2(bpy)(H2O)8](H2O)6}n (2), {[Cu4(Hpzdc)2(pzdc)2(bpy)2][Cu(bpy)(H2O)4]n(H2O)4}n (3), and {[Cu3(pzdc)2(ampy)(H2O)5](H2O)3}n (4) (H3pzdc=pyrazole-3,5-dicarboxylic acid, pyz=pyrazine, bpy=4,4′-bipyridine and ampy=2-aminopyrazine) were synthesized and characterized. Compounds 1, 2 and 4 were synthesized by layering method at room temperature while 3 was prepared under solvothermal reaction. Compounds 1 and 2 are one-dimensional (1D) chain coordination polymers, while 3 shows 1D cationic chain coordination polymer with anionic tetranuclear Cu(II) cluster. Compound 4 exhibits 1D ladder-like chain structure. Compounds 1, 2 and 4 consist of neutral trinuclear [Cu3(pzdc)2] building unit which is constructed by μ2-pzdc3− bridging (5-6-5), (6-6-6), and (6-5-5) sequences of Cu(II) geometries for 1, 2 and 4, respectively. Each trinuclear unit is extended via N,N′-linkers giving polymeric chain structure. In contrast, anionic tetranuclear cluster of 3 is built up from two anionic dinuclear metallacyclic [Cu2(Hpzdc)(pzdc)]− building units and double μ2-bpy spacers. The magnetic properties of 1, 2 and 4 exhibit weak antiferromagnetic interactions among Cu(II) centers.