Conducting-Polymer Electrochemical Switching as an Easy Means for Control of the Molecular Properties of Grafted Transition Metal Complexes Claire Mangeney, [a] Jean-Christophe Lacroix,* [a] Kathleen I. Chane-Ching, [a] Mohamed Jouini, [a] Françoise Villain, [b] Souad Ammar, [a] Nouredine Jouini, [a] and Pierre-Camille Lacaze [a] Dedicated to Professor Olivier Kahn Abstract: Copper( ii )3',4'-bis(N,N'-oxa- mato)terthiophene has been synthesized and electropolymerized. The copper( ii )- complex centers are not affected by the polymerization process, which involves coupling between C a carbon atoms of the terthiophene units and leads to a new conjugated polymer consisting of polythiophene chains bearing bis(oxa- mato) ± Cu II groups regioregularly graft- ed onto the polymer backbone. The polymer is stable with respect to poly- thiophene electroactivity, and no de- metallation or modification of the Cu oxidation state occurs over a large potential range. In this material, the two moieties exhibit direct electronic interaction, which makes it possible to use the conductive polymer backbone as a molecular wire or a nanocontact capable of inputting to the bis(oxama- to) ± Cu II groups through the polythio- phene-switching reaction. FTIR, XPS, and XAS spectroscopies have been used to study the effect of the state of the conducting polymer upon the properties of the copper( ii ) center (electron density, ligand field strength, size of cavity, force constants of some bonds). These proper- ties can be controlled to some extent by the potential applied to this device. From the point of view of the copper(ii ) center, this effect is similar to the graft- ing of substituents with various elec- tronic properties. Keywords: conducting materials ´ electrochemical switching ´ EXAFS spectroscopy ´ molecular electronics ´ polythiophene Introduction In the field of materials science, conducting polymers have attracted great interest for both fundamental and potential applications. The grafting of a transition metal complex onto a conductive polymer backbone has been widely used in order to add a specific function to the material. [1] When the metal complex is separated from the backbone by a saturated spacer there is no direct electronic interaction between the two parts and any interaction is mainly steric. In contrast, when the polymer is functionalized through a conjugated spacer the complex is in direct electronic communication with the p- conjugated backbone, and the interaction between the two subunits of the material modifies their properties. [2±10] Several studies devoted to such materials have focused on the influence of conjugated grafted groups upon the con- ductive backbone. Ruthenium has been used to enhance the photosensitivity of the parent organic polymer. [2] Poly(phe- nylenevinylene) that incorporates 2,2'-bipyridine units has been studied, and conformational changes of the backbone upon coordination of metal ions demonstrated. [3] Applica- tions of this material in capting devices were proposed. Electrochromic materials, with colors unique to each metal, have been reported. [4] Other studies have focused upon the use of the conjugated polymer backbone to promote electron transfer between metal centers. Yamamoto et al. reported the synthesis of poly(bipyridine) (poly(bpy)) and post-metallation with Ru II , Ni II , and Cu I . [5] They showed that even though post-metal- lation is somewhat inefficient, the conductivity of poly- (bpy)Ru is several orders of magnitude higher than that of poly(bpy). Furthermore, they interpreted electrochemical broadening of the Ru III /Ru II redox peak as evidence for electronic interactions between ruthenium through the poly- (bpy) backbone. However, no such effect was seen in later [a] Prof. J.-C. Lacroix, Dr. C. Mangeney, Dr. K. I. Chane-Ching, Prof. M. Jouini, Prof. S. Ammar, Prof. N. Jouini, Prof. P.-C. Lacaze Institut de Topologie et de Dynamique des Syste Ámes Universite  Paris 7-Denis Diderot, associe  au CNRS 1 rue Guy de la Brosse, 75005 Paris (France) Fax: ( 33) 144-276-814 E-mail: lacroix@paris7.jussieu.fr [b] Dr. F. Villain Laboratoire de Chimie Inorganique et Mate  riaux Mole  culaires Universite  Paris 7-Pierre et Marie Curie Ba Ãt. F 74, 4 Place Jussieu, 75252 Paris Cedex 05 (France) or Laboratoire pour l'Utilisation du Rayonnement Electromagne  tique Universite  Paris-Sud, BP 34, 91898 Orsay Cedex (France) FULL PAPER Chem. Eur. J. 2001, 7 , No. 23  WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001 0947-6539/01/0723-5029 $ 17.50+.50/0 5029