Synthesis and properties of hexaarylated AzaBODIPYs. Issue 40 (7th October 2015) - Kumar, Sunit
Abstract: Sterically crowded 1, 2, 3, 5, 6, 7-hexaarylated azaBODIPYs were synthesized in 25–35% yields by coupling 1, 3, 5, 7-tetraaryl azaBODIPYs with six different aryl boronic acids under Pd(0) coupling conditions. The moderate reaction yields were attributed to steric congestion caused by two additional aryl groups introduced at the tetraaryl azaBODIPY core. The compounds were characterized by HRMS, 1D and 2D NMR spectroscopic techniques. The 1 H, 19 F and 11 B NMR studies of hexaarylated azaBODIPYs showed slight upfield shifts compared to tetraaryl azaBODIPY indicating the slight alteration of electronic properties of azaBODIPY core upon introduction of two additional aryl groups on tetrararyl azaBODIPY. The absorption and fluorescence bands of hexaarylated azaBODIPYs experienced 7–10 nm hypsochromic shifts compared to tetraaryl azaBODIPY. The hexaarylated azaBODIPYs are weakly fluorescent with significant reduction in quantum yields and singlet state lifetimes compared to tetraarylated azaBODIPY. Graphical abstract: A series of 1, 2, 3, 5, 6, 7-hexaarylated azaBODIPYs were synthesized by coupling of 2, 6-dibromo-1, 3, 5, 7-tetraaryl azaBODIPY with different substituted aryl boronic acids under Pd(0) coupling conditions and their spectral and electrochemical properties were investigated.