pi-conjugated ligand polymers entwined around copper centres

We describe conjugated polymers entwined around Cu-I with alternating alpha -quaterthienyl (poly[Cu(T-2)(2)]) or 3',4',3'''',4''''-tetrahexyl-alpha-sex ythienyl (poly[Cu(T-3)(2)]) moieties and 1,10-phenanthroline complexing sit es. Our strategy is to synthesise the 2,9-bis(oligothienyl)-1,10-phenanthro line precursors, then to assemble these ligands by means of Cu-I templating followed by electropolymerisation. Poly[Cu(T-2)(2)] shows separate electro activities for Cu redox centres and conjugated backbones, whereas the elect roactivities overlap in the case of poly[Cu(T-3)(2)]. An X-ray absorption s tudy on these polymers in their reduced state at the Cu-K edge identifies, in both cases, four nitrogen atoms as the closest copper(I) neighbours. For poly[Cu(T-2)(2)], the Cu-I environment is a distorted tetrahedron similar to a monomer model compound, but with a slightly higher number of steric co nstraints. The Cu-I environment for poly[Cu(T-3)(2)] is a less distorted te trahedron with an unusually short Cu-I-N average bond length. Cu-I removal in poly[Cu(T-2)(2)] induces an irreversible collapse of the structure, wher eas the reversibility of Cu-I binding is almost perfect for poly[Cu(T-3)(2) ], as the hexyl chains prevent irreversible gliding of the wires after copp er removal. Combined electrochemical and resistance measurements reveal tha t the Cu centres in poly[Cu(T-2)(2)] play the role of mechanical support fo r the structure with no significant electronic interactions with the conjug ated backbone, whereas in the case of poly[Cu(T-3)(2)] copper centres contr ibute to the conductivity of the structure.