Mononuclear discrete complexes and coordination polymers based on metal(II) chelidonate complexes with aromatic N,N-chelatingligands

The versatile coordination chemistry of the anion chelidonate (chelidonic acid, H(2)chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) allowed for the synthesis of different mixed-ligand complexes with the N,N'-chelating ligands 2,2'-bipyridine and 1,1'-phenanthroline. We describe here the synthesis and structural characterization of a series of compounds that illustrate the structural diversity of which 4-oxo-4H-pyran-2,6-dicarboxylate ligands are capable: the 2D coordination polymer [Cu(chel)(bipy)] (1), the 1D coordination polymer [Zn(chel)(bipy)(OH2)]center dot 1/2H(2)O (2), the discrete neutral mononuclear compounds [Zn(chel)(phen)(OH2)(2)] (3) and [M(chel)(phen)(OH2)(3)]center dot nH(2)O, M = Zn and n = 1 (4), M = Ni and n = 2 (5), and the discrete mononuclear cationic complex [Zn(OH2)(2)(phen)(2)]chel center dot 3.3H(2)O (6). The effects of the weak interactions on the crystal packing were also analyzed. The thermal behaviour of the hydrated compounds was investigated. The study of the magnetic properties of 1 revealed weak antiferromagnetic coupling between the copper(II) centres.