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

Fluorene- and carl;azole-bridged dipyridyl ligands potentially useful for t he construction of supramolecules by self-assembly processes have been synt hesized by palladium-catalyzed cross-coupling reactions. They undergo facil e ring closure reactions with Re(CO)(5)X (X = Cl, Br) to form molecular geo metries of varied dimensions. Fluorene-bridged ditopic ligands facilitate t he formation of trimetallic triangles, while the angular carbazole-bridged ligands led to the formation of cyclic dimers. The ligands are strongly emi tting in the blue region, and the:supramolecules display emission of differ ent origins triggered by the bridging aromatic segment. Carbazole-containin g cyclic dimers emit green light that probably originates from a ligand-loc alized 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.