Syntheses, characterizations, and properties of 1,4-phenylene and 4,4′-biphenylene bridged BOBPY dimers

Abstract

Two novel phenylenes (1,4-phenylene and 4,4[Formula: see text]-biphenylene) bridged dimeric BOBPY (Boron complexed N2O-type benzopyrromethenes) were designed and synthesized from the one-pot condensation of pyrrole with formylisoindole and subsequent complexation with diboronic acid. These novel dyes were fully characterized by NMR spectroscopy, HRMS, absorption and fluorescence emission spectroscopy, and cyclic voltammetry. These resulting BOBPY dimers are highly photostable and show intense absorption and emission in the region of 618 to 644 nm with high absorption coefficients and solvent-dependent fluorescence quantum yields. The electronic interactions between BOBPY units are related with length of the linker. And the dimer with short 1,4-phenylene linker was more sensitive to the polarity of the solvents than that of the other dimer, suggesting that the short linkage allowed stronger electronic communication between the two BOBPY units.