Ž . Synthetic Metals 109 2000 277–280 www.elsevier.comrlocatersynmet Synthesis, electrochemical and electroluminescent properties of oligothiophene-based conjugated polymers L. Trouillet a , M. Lapkowski b, ) , O. Stephan c , S. Guillerez a a Departement de Recherche Fondamentale sur la Matiere Condensee, SI3Mr EMSI, CEA Grenoble, 17, rue des Martyrs, ´ ` ´ 38054 Grenoble Cedex 09, France b Department of Chemistry, Silesian UniÕersity of Technology, Ks. M. Strzody 9, 44100 Gliwice, Poland c Laboratoire de Spectrometrie Physique, UniÕersite Joseph Fourier, Domaine UniÕersitaire Saint-Martin-d’Heres-Gieres, 38041 Grenoble Cedex 9, France Received 26 June 1999; received in revised form 30 June 1999; accepted 10 September 1999 Abstract The paper deals with a new conjugated polymer having the possibility to form a complex with transition metals. The conjugated backbone is constituted by the alternation of regioregular alkylated oligothiophene of variable size and of 2,2 X -bipyridine as the chelating Ž . unit. Electrochemical studies were conducted on both the non-metalated and Ru II complex forms together with the in-situ conductance measurement showing that p- and n-doping occur. The non-metalated form was showed to exhibit electroluminescent properties. q 2000 Elsevier Science S.A. All rights reserved. Ž. Keywords: Pd 0 catalyzed cross-coupling; Conjugated polymer; Metal-containing conjugated polymer; Conductivity; n-Doping; Electroluminescence 1. Introduction Metal-containing conjugated polymers constitute an emerging class of materials designed with the aim of combining as intimately as possible the electronic proper- ties of transition metal complexes with those of conducting w x polymers 1–16 . From this strong interaction, new tunable electrochemical, photophysical, magnetic or transport properties are expected to evolve, leading to materials with potential interest in various fields of research such as electrocatalysis, molecular recognition, photoconductivity and molecular electronics. As shown in Scheme 1, we developed a chemical synthesis of novel all conjugated polymers based on the alternation of oligothiophene and bipyridine units. The oligothiophene sequence is regioregularly alkylated in or- der to provide the final polymer with reproducible proper- ties and to enhance its solubility in usual organic solvents. The complexing unit 2,2 X -bipyridine is inserted into the conjugated backbone by its 5,5 X positions in order to allow ) Corresponding author. E-mail: lapkowsk@zeus.polsl.gliwice.pl formal electronic delocalization along the polymer chain and to allow the formation of octahedral complexes of the Ž . nq Ž . type M bipy M s Fe, Ru, Os, etc. . 3 2. Results and discussion Bis-stanylated regioregular alkylated oligothiophenes 2 4 and 2 were obtained from the corresponding a-chloro- 6 w x substituted oligothiophenes 1 and 1 17 by reductive 4 6 dehalogenation with Bu SnH under radical conditions, 3 giving up to 95% of the free-end oligomers. By lithiation with 2.5 equivalents of n-BuLi and quenching of the dianions with trimethyltin chloride, we obtained the bis- functionalized oligomers with nearly quantitative yields. A Ž. Pd 0 catalyzed Stille cross-coupling reaction between X X w x 5,5 -dibromo-2,2 -bipyridine 3 18 , and 2 and 2 con- 4 6 ducted to polymers P4 and P6, respectively. The crude polymers were extracted successively with boiling ethanol, hexane, 1,2-dimethoxyethane to remove inorganic impuri- ties and low molecular weight oligomers. Finally, an ex- traction with chloroform allowed the isolation of pure polymers P4 and P6 with yields of 55% and 61%, respec- 0379-6779r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. Ž . PII: S0379-6779 99 00245-3