Synthesis and Characterization of a New Soluble, Structurally Well-Defined Conjugated Polymer Alternating Regioregularly Alkylated Thiophene Oligomer and 2,2‘-Bipyridine Units: Metal-Free Form and Ru(II) Complex

Abstract

The Pd-catalyzed Stille cross-coupling reaction has been used to synthesize novel π-conjugated polymers based on regioregular 3-(octylthiophene) tetramers alternated with either 2,2‘-bipyridine or its Ru(II) complex (Ru(bipy)32+). A preliminary optimization of the cross-coupling conditions enabled the synthesis of high molecular, structurally defined, and defect-free copolymers. Both are well-soluble in common organic solvents, which allowed their easy characterization by standard 1H NMR and UV−visible spectroscopies as well as by electrochemical techniques. Interestingly, 1H NMR spectra not only confirmed the structure of the synthesized polymers but also contributed to estimating the length of polymer chains together with gel permeation chromatography and light-scattering experiments. UV−visible experiments indicated that the delocalization of π-orbitals occurs efficiently in our conjugated structures and involves both oligothiophene and metal-free or ruthenium chelating bipyridine units, while electrochemical experiments revealed electronic interactions between the conjugated backbone and the ruthenium complexes in the metal-containing polymer.