Molecular double chains and 3-D supramolecular frameworks with open channels assembled from 1D copper(II) maleate coordination polymers with chelating aromatic amine ligands by noncovalent interactions

Abstract

Two 1D coordination polymers, [Cu(mal)(Hdpa)] n ( 1) and {[Cu(mal)(tpy)] · 4H 2O} n ( 2) (mal = maleate, Hdpa = 2, 2′-dipyridylamine and tpy = 2,2′:6′,2″-terpyridine), have been synthesized and their crystal structures, IR spectra, thermal analyses, magnetic properties were determined. In 1 and 2, the maleate ligands link adjacent metal centers to form 1D coordination polymeric chains. Furthermore, the carboxylate oxygen atoms and the aromatic chelate ligands provide potential supramolecular recognition sites for noncovalent interactions to form higher dimensionality. In 1, each pair of 1D chains recognize each other through strong hydrogen bond formed by active amine (–NH–) hydrogen and aromatic π–π stacking interactions to generate a zipperlike double-stranded chain. In contrast, when the substitutions of tpy for dpa further enhance the π–π aromatic stacking interactions, complex 2 is directly constructed into 2D zipperlike layers by the unprecedented aromatic π–π stacking interactions that same orientated aromatic chelate ligands are simultaneously attached to both sides of the chain and the significant C–H⋯O hydrogen bonds. These layers are constructed through hydrogen bonds and result in a 3D supramolecular network with 1D open channels, in which exists an unprecedented one-dimensional water chain. Both were magnetically characterized, showing weak ferromagnetic behavior.