Synthesis and spectroscopic properties of bodipy dimers with effective solid-state emission

Boron-dipyrromethenes (BODIPYs) dimers with phenyl and bulky triphenylsilylphenyl substituents were synthesized through oxidative self-coupling of the 2-position with FeCl₃. Spectroscopic properties of all the dyes in various solvents and on films have been investigated. In comparison with the corresponding monomers, the dimers exhibit higher molar absorption coefficients, relative moderate fluorescent quantum yields and redshifted wavelengths. The luminescence yields of the dimers are solvent polarity dependent and decrease dramatically in acetonitrile. More intensive solid-state emission of triphenylsilylphenyl substituted BODIPY dimer is observed with a quantum yield of 9.7% relative to the phenyl substituted dimer, which could be attributed to the introduction of the bulky group that inhibits aggregation.