Heteroaromatic Donor–Acceptor π‐Conjugated 2,2′‐Bipyridines
A series of heteroaromatic 4,4′-π-conjugated 2,2′-bipyridines (bpy) bearing conjugated π-excessive and π-deficient heteroaromatic rings as donor (D) and acceptor (A) substituents, respectively, is presented. We have experimentally and computationally found that, upon variation of donor and acceptor properties of the heterocyclic subunits in combination with different structural symmetries (bpy-π-D or bpy-π-D-π-A), the absorption and emission maxima and molecular orbital energy levels can be easily tuned over a broad range. Properties of the new ligands can be efficiently exploited in metal complexes for dye-sensitized solar cells and in other materials for optical applications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)