Coordination-driven self-assembly of discrete and polymeric copper(ii) and dicopper(ii) supramolecular structures based on oxacalix[2]benzene[2]pyrazines

Abstract

The reaction of oxacalix[2]benzene[2]pyrazines and with copper(ii) nitrate, as well as dimeric copper(ii) tetraacetate are presented. Ligands and , both adopt 1,3-alternate conformation, with the two exo-Lewis basic sites spatially oriented outwards. Ligand reacts with copper(ii) ions generated a discrete molecular cage by bridging two ligands via two Cu(2+) ions in the equatorial region. While the reaction of with dicopper(ii) tetraacetate unit resulted in the formation of a discrete supramolecular complex with 1 : 2 stoichiometry between the dicopper(ii) unit and ligand , due to the larger size and axial coordination mode of the dicopper(ii) unit. The conformationally flexible nature of ligand facilitated the formation of coordination polymers and upon interaction with copper(ii) and dicopper(ii) units, respectively. Coordination polymer featured a zigzag structure of alternating ligand and Cu(2+) ion, while in coordination polymer , ligand serves as an axial 2-connected node, propagating the "paddlewheel" dicopper(ii) unit along the polymeric chain.