Self-assembly molecular architectures incorporating fluorene- and carbazole-based bichromic oligopyridines. Novel photoactive materials

Fluorene- and carl;azole-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)pi-pi* and (MLCT)-M-3-based emissions with prolonged lifetimes.