Synthesis, spectral and electrochemical properties of phenylated boron-dipyrromethenes

The synthesis, absorption, electrochemical and fluorescence properties of boron-dipyrromethenes (BODIPYs) containing one to six phenyl groups at the pyrrole carbons are described. The phenylated BODIPYs were prepared by coupling of appropriate brominated BODIPY with phenylboronic acid in THF/toluene/H2O (1:1:1) mixture in the presence of catalytic amount of Pd(PPh3)4/Na2CO3 at 80 °C for overnight. The effect of the number of phenyl substituents at the pyrrole carbons of BODIPY framework on absorption, electrochemical and fluorescence properties were investigated. The absorption and fluorescence studies showed a bathochromic shift in absorption and emission bands, increase in quantum yield and singlet state life time upto the presence of four phenyl groups at the pyrrole carbons of BODIPY but the properties were reversed for five and six phenyl substituted BODIPYs. The electrochemical studies indicated that with the increase of number of phenyl groups at the pyrrole carbons of BODIPY framework, the electron rich nature of BODIPY increases.

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► Synthesized a series of boron dipyrromethenes containing phenyl groups at the pyrrole carbons.
► The introduction of phenyl groups at the pyrrole carbon of the BODIPY core alters the electronic properties.
► Absorption and emission properties were systematically altered upto introduction of four phenyl groups.
► BODIPY core becomes electron rich and oxidation becomes easier with the increase of number of phenyl groups.