A general synthetic route to 3,5-substituted boron dipyrromethenes: applications and properties.

An efficient protocol for the direct synthesis of 3-substituted and 3,5-disubstituted BODIPY derivatives via electrophilic attack with NBS was developed. Various substituents like ethers, sugar, hydroxyl, thiophene, sulfur, azide, tertiary amines, alkyne, vinyl, or phosphonate groups were obtained in moderate to excellent yields. The amine-substituted derivatives display unusual spectroscopic and electrochemical properties which were analyzed in solution in the presence of HCl. The diethylamino-substituted derivative has a proton association constant of log β = 4.7, and the disubstituted derivative has two association constants of log β = 6.2 and 12.1 in ethanol. In both cases, the quenching of the fluorescence is explained by photoinduced electron transfer from the tertiary amine to the Bodipy excited state.