One-pot synthesis and properties of well-defined butadiynylene-BODIPY oligomers.

A homogeneous series of well-defined butadiynylene-BODIPY oligomers containing up to four BODIPY moieties have been synthesized from a "one-pot" oxidative homocoupling reaction of 2,6-di((trimethylsilyl)ethynyl)BODIPY. Further derivation of the resultant BODIPY dimer generates a water-soluble, red-emitting butadiyne-linked BODIPY dimer with pyridinium ions, which can ratiometrically detect viscosity, based on the two fluorescent conformers with the two BODIPY cores twisted and planar to each other depending on the viscosity of the environment.