Fluorescent boron dipyrromethene (Bodipy) dyes having two and four vinyl residues

Several new extended fluorescent dyes have been prepared by stepwise functionalisation of the methyl groups located in the 1, 3, 5, and 7 substitution positions of Bodipy dyes. In one case, a ferrocene residue has been connected, giving rise to severe fluorescence quenching and a rich redox behavior. The stepwise syntheses were largely based on Knoevenagel reactions allowing the attachment of three different modules in a tetravinyl configuration. Most of these dyes exhibit reversible formation of radical cations and radical anions, as well as an irreversible formation of dications and dianions. Spectroscopic examination of the dyes under various conditions including the presence of acid leads to the conclusion that the delocalization is more effective in the 3,5-substitution positions than in the 1,7-positions. These novel dyes have absorption and emission wavelengths spanning the ranges of 573–718 nm and 585–778 nm, respectively.