Synthesis,\nCharacterization, and Electrochemical Polymerization\nof Some 5,5-Fused Ring Terthiophene Tricarbonyl Manganese Complexes

Polythiophenes are of great interest for use in electronic\nmaterials\ndue to their stability and favorable materials properties. Thiophene-based\nelectronic materials provide an attractive alternative to conventional\ninorganic semiconductors. We have targeted hybrid materials that combine\nthe versatility of transition metals with oligo- and polythiophenes.\nWe report here terthiophenes in which the [<i>c</i>]-edge\nof the central thiophene is fused to a cyclopentadienyltricarbonylmanganese\ngroup. These thiapentalenyl complexes, [Mn{η<sup>5</sup>-SC<sub>7</sub>H<sub>3</sub>-1,3-R<sub>2</sub>}(CO)<sub>3</sub>], were prepared\nin moderate to good yields (50–80%) via ring closure of 1,2-diacylcymantrenes,\n[Mn{η<sup>5</sup>-1,2-C<sub>5</sub>H<sub>3</sub>(COR)<sub>2</sub>}(CO)<sub>3</sub>] (R = thienyl, 5-methylthienyl, 5-chlorothienyl,\n5-bromothienyl) with Lawesson’s reagent. These complexes display\nhigh environmental stability and were characterized via spectroscopic\nmethods as well as X-ray crystallography. Cyclic voltammetry shows\nthat the unsubstituted terthiophene manganese complex is susceptible\ntoward electrochemical polymerization, whereas the 5-methyl complex\nis not. X-ray photoelectron spectroscopy (XPS) confirmed the presence\nof manganese in the polymeric films and indicated a nearly identical\nbonding environment of manganese in the monomer and the films.