Self-Assembly Molecular Architectures Incorporating Fluorene- and Carbazole-Based Bichromic Oligopyridines. Novel Photoactive Materials

Fluorene- and carbazole-bridged dipyridyl ligands potentially useful for the construction of supramolecules by self-assembly processes have been synthesized by palladium-catalyzed cross-coupling reactions. They undergo facile ring closure reactions with Re(CO) 5 X (X = Cl, Br) to form molecular geometries of varied dimensions. Fluorene-bridged ditopic ligands facilitate the formation of trimetallic triangles, while the angular carbazole-bridged ligands led to the formation of cyclic dimers. The ligands are strongly emitting in the blue region, and the supramolecules display emission of different origins triggered by the bridging aromatic segment. Carbazole-containing cyclic dimers emit green light that probably originates from a ligand-localized excited state. However, in the fluorene-based triangles emission was observed only at low temperature, and it displayed 3 π−π* and 3 MLCT-based emissions with prolonged lifetimes.