Synthesis, structure and DFT study of a chelidamic acid based Cu coordination polymer: On the importance of π–π interactions and hexameric water clusters

Abstract

One-dimensional coordination polymer, i.e., {(Hampy)[Cu(chel)(H2O)]⋅2H2O}n (1, ampy=2-amino-6-methylpyridine, H3chel=chelidamic acid), has been synthesized and characterized by elemental analysis, IR spectroscopy, solution studies and X-ray single-crystal diffraction. In the monomeric unit of compound 1 the metal center exhibits a distorted square–pyramidal coordination sphere. The Cu(II) ion is coordinated to chelidamic acid and water. These monomers are interlinked generating a 1D polymer by means of the para hydroxyl group of the ligand. Protonated 2-amino-6-methylpyridine rings act as counter cations. The crystal lattice is aggregated through intermolecular interactions, such as electrostatic attraction, N–H⋯O, O–H⋯O and C–H⋯O hydrogen bonding and aromatic π stacking interactions. Hydrogen bond interactions between the water molecules led to formation of six-membered rings with chair conformation. These assemblies are described and analyzed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks.