Photophysical and Electrochemical Properties of Thiophene-Based 2-Arylpyridines

Two families of thiophene-based 2-arylpyridines, in which aryl is phenyl and 2,4-difluorophenyl, have been developed. The pyridine ring of the new compounds is substituted at the 4-position with pi-conjugated electron-rich and electron-poor thiophene-based fragments to tune the optical and energetic properties. The high-yielding synthetic access, which consists of two sequential Suzuki coupling reactions, the first of which is completely regioselective, is of wide applicability and allows access to a large variety of derivatives. The absorption/emission and redox features, as well as the HOMO and LUMO energy levels, have been investigated; the results show that the optical and electronic properties can be tuned over a broad range. The diversity of the characteristics may be effectively exploited by using the thiophene-substituted 2-arylpyridines as ligands in cyclometalated sensitizers for dye-sensitized solar cells and other optoelectronic applications.