In the absence/presence of different N ancillary ligands, four copper(II)-pyrazolecarboxylate complexes, [Cu(HMPCA)2(ImH)2]·2H2O (1), [Cu2(MPCA)2(H2O)4] (2), [Cu2(MPCA)2(4,4′-bpy)(H2O)2]n·5nH2O (3) and [Cu3(MPCA)3(Phen)3]2·2EtOH·15H2O (4) (H2MPCA = 5-methyl-1H-pyrazole-3-carboxylic acid, ImH = imidazole, 4,4′-bpy = 4,4′-bipyridine and Phen = 1,10-phenanthroline) were obtained. All complexes have been structurally characterized. Compounds 2 and 3 containing the same bis(μ-pyrazolato)dicopper(II) planes range from dinuclear to 1D polymer. Trinuclear complex 4 contains the first reported cyclic-trinuclear copper(II)–pyrazolato structure without any μ3 ligand core. Magnetic susceptibility data show that complexes 2–4 exhibit antiferromagnetic couplings between the adjacent magnetic centers.
