Supramolecular assemblies and magnetic behaviors of the M(II)/p-aminopyridine/malonate (M = Ni, Mn, Cu, Co) systems

The coordination compounds [Ni(μ-mal)(apy)2(H2O)]·2.8H2O (1), [Mn(μ-mal)(H2O)2] (2), (apyH)2[Cu(μ-mal)2] (3) and (apyH)2[Co(mal)2(H2O)2] (4) (mal = malonate, apy = p-aminopyridine) have been synthesized and characterized by elemental analysis, vibrational spectroscopy, single crystal X-ray diffraction and magnetometry. With exception of 4, the malonate group acts as bridging ligand leading to the formation of one-dimensional polymeric chains. In compound 1 it was observed the coordination of the p-aminopyridine in the axial positions of the distorted octahedral coordination sphere. The solid-state structure exhibits a high complex 3D network formed by several supramolecular interactions. Magnetic properties were determined for all members of the series and indicate that the materials behave are normal paramagnets, except the Mn polymer 2 which exhibits an antiferromagnetic ground state.

Graphical abstractThe new 1D polymer [Ni(μ-mal)(apy)2(H2O)]·2.8H2O (1) with the simultaneous coordination of malonate (mal) and 4-aminopyridine (apy) ligands has been synthesized. Different non-covalent interactions are responsible for the crystal packing in a brickwall-like supramolecular network. Magnetic measurements revealed that 1 follows the Curie–Weiss law down to 0.4 K, and the related compounds (apyH)2[Cu(μ-mal)2] (3) and (apyH)2[Co(mal)2(H2O)2] (4) present paramagnetic behavior above T = 2 K. The [Mn(μ-mal)(H2O)2] polymer (2) displays an antiferromagnetic phase transition around T = 4 K.Figure optionsDownload full-size imageDownload as PowerPoint slide