The structure of metallo-supramolecular polyelectrolytes in solution and on surfacesThis paper contains work as a result of a collaborative research project of the German Science Foundation (DFG Sonderforschungsbereich 448) on "Mesoscopically organized composites".Electronic supplementary information (ESI) available: NMR spectra of Zn-MEPE-1 with metal to ligand rations (y) = 0.75, 0.98 and 2.00. See DOI: 10.1039/b926783b

Metal ion induced self-assembly of the rigid ligand 1,4-bis(2,2′:6′,2″-terpyridine-4′-yl)benzene ( 1 ) with Fe( ii ), Co( ii ), Ni( ii ) and Zn( ii ) acetate in aqueous solution results in extended, rigid-rod like metallosupramolecular coordination polyelectrolytes (MEPE- 1 ). Under the current experimental conditions the molar masses range from 1000 g mol −1 up to 500 000 g mol −1 . The molar mass depends on concentration, stoichiometry, metal-ion and time. In addition, we present viscosity measurements, small angle neutron scattering and AFM data. We introduce a protocol to precisely control the stoichiometry during self-assembly using conductometry. The protocol can be used with different terpyridine ligands and the above-mentioned metal ions and is of paramount importance to obtain meaningful and reproducible results. As a control experiment we studied the mononuclear 4′-(phenyl)-2,2′:6′,2″-terpyridine ( 3 ) complex with Ni( ii ) and Zn( ii ) and the flexible ligand 1,3-bis[4′-oxa(2,2′:6′,2″-terpyridinyl)]propane ( 2 ) with Ni( ii ) acetate (Ni-MEPE- 2 ). This ligand does not form extended macro-assemblies but likely ring-like structures with 3 to 4 repeat units. Through spin-coating of Ni-MEPE- 1 on a solid surface we can image the MEPEs in real space by AFM. SANS measurements of Fe-MEPE- 1 verify the extended rigid-rod type structure of the MEPEs in aqueous solution. Conductivity, rheology, AFM and neutron scattering measurements prove that metal-ion induced self-assembly of ditopic ligands in solution results in the formation of linear rigid-rod like macro-assemblies.