A Bridge Too Far: Testing the Limits of Polypyridyl Ligands in Bridging Soluble Subunits of a Coordination Polymer

Starting with a coordination polymer, {[Cu­(<b>L</b>)]₂}_<i>n</i> (<b>1</b> where H₂<b>L</b> = salicylidene-2-aminophenol), we have explored the ability of polypyridyl ligands (<b>P</b>) to bridge the monomer complex to form nine {[Cu­(<b>L</b>)]₂(<b>P</b>)} complexes. The identity and solution stability of the [Cu­(<b>L</b>)] units has been investigated through a novel combined UV–vis/EPR experiment and it has been found to be a stable supramolecular building unit for the construction of discrete complexes and coordination polymers. The reorganization of [Cu­(<b>L</b>)] units to a new coordination polymer on addition of 4,4′-bipyridine markedly changes the connectivity of the structure and the magnitude of the antiferromagnetic interactions through reorientation of the Cu­(II) orbitals. We also present the structure of <b>1</b>, 80 years after its synthesis was first reported