Synthesis and environment-dependent fluorescence behavior of a biaryl-conjugated (diphenylmethylene)imidazolinone.

The newly designed green fluorescent protein (GFP) chromophore analog, bar-DAIN, which has a 2-biaryl-conjugated 5-(diphenylmethylene)imidazolinone structure, was effectively synthesized using the Suzuki coupling reaction. Bar-DAIN showed environment-dependent fluorescence behavior; for example, the thienyl analog emitted yellow-green fluorescence in viscous solution (λem: 535 nm), yellow-orange fluorescence in suspension (λem: 551 nm), and cyan fluorescence in a powder state (λem: 497 nm) although it showed almost no emission in common solvents such as dichloromethane. The dynamic discoloration of the fluorescence was observed by changing environmental conditions from suspension to viscous.