Regioselective synthesis of tetraphenyl-1,3-butadienes with aggregation-induced emission.

In the presence of substoichiometric amounts of Co2(CO)8, internal bisarylalkynes undergo reductive dimerization with good to excellent yields. The Co2(CO)8-induced reactions described are experimentally quite simple and provide a very useful synthetic procedure for the synthesis of tetraphenylbutadienes which exhibit aggregation-induced emission enhancement, i.e., weak emission in good solvents but strong fluorescence in solvents that lead toward formation of aggregates or in the solid state.