Photophysical and electrochemical properties of sterically crowded polyarylated boron-dipyrromethenes

The absorption, fluorescence and electrochemical properties of six polyarylated BODIPYs were investigated in solution. The presence of aryl substituents at all pyrrole carbons of BODIPY significantly alters the electronic properties of the dye. Compared to unsubstituted meso-aryl BODIPY, the polyarylated BODIPYs exhibited large bathochromic shifts in absorption and emission bands, large Stokes shifts, fluorescence quantum yields and singlet state lifetimes. These changes are attributed to the aryl groups which create steric crowding and induces nonplanarity in the BODIPY core altering the electronic properties of the dyes. The polyarylated BODIPYs were stable under redox conditions and exhibited reversible/quasi-reversible oxidation and reduction.