Syntheses, crystal structures and supramolecular assemblies of two Cu(ii) complexes based on a new heterocyclic ligand: insights into C–H⋯Cl and π⋯π interactions

Abstract

A new heterocyclic ligand, N₃L [4-(1-methylimidazole)-2,6-di(pyrazinyl)pyridine] has been synthesized and characterized by several spectroscopic methods. The ligand (N₃L) was then used for the preparation of two complexes, namely, [Cu(N₃L)Cl₂] (complex 1) and [Cu(N₃L)(Cl)(μ-ONO₂)]_n (complex 2). The crystal structures of these complexes have been established by single-crystal X-ray diffraction analysis. Complex 1 is a mononuclear one whereas complex 2 is a 1D coordination polymer. The structural insights reveal that non-classical hydrogen bonding (C–H⋯Cl, C–H⋯O, C–H⋯N) and π⋯π stacking interactions play a crucial role in stabilizing various supramolecular architectures of the title complexes in the solid state. All the non-classical hydrogen bonding interactions are quantified through the infographic 2D fingerprint plots. Additionally, theoretical calculations (density functional theory) were carried out for both complexes to analyze these non-covalent interactions in the solid state including their characterization using Bader's theory of atoms in molecules and the noncovalent interaction (NCI) plot index.