Metallo-supramolecular polyelectrolyte multilayers with cobalt(II):: preparation and properties

Metal ion mediated self-assembly of the ditopic ligand 1,4-bis(2,2':6',2"-terpyridine-4'-yl)benzene and Co(II) results in a metallo-supramolecular coordination polyelectrolyte (Co-MEPE), which is analyzed by spectroscopic methods, elemental analysis and cyclovoltammetry. The Co-MEPE shows a reversible one-electron redox transition in the potential range from -0.15 to 0.35 V with a half-wave potential of 87 mV. Thin films of Co-MEPE are fabricated by layer-by-layer self-assembly together with poly(styrenesulfonate) (PSS) on planar substrates and are analyzed by UV/vis spectroscopy, microgravimetry, and electrochemistry. The Co-ions in the multilayer can be removed and displaced by Fe-ions. The electrochemical activity of the Co-ions is fully maintained in the films. Charge transport through the multilayer is consistent with electron self-exchange reactions. The permeability of the multilayers is investigated by electrochemistry using K-3[Fe(CN)(6)] as electroactive probe. Compared to poly(allylamine hydrochloride) (PAH)/PSS films, the electroactive probe does not permeate through PSS/Co-MEPE multilayers, Fluorescence measurements with pyrene as polarity probe indicate that the Co-MEPE films are more hydrophobic than PAH/PSS multilayers. (C) 2002 Elsevier Science B.V. All rights reserved.