Convenient Method To Access New 4,4-Dialkoxy- and 4,4-Diaryloxy-diaza-<i>s</i>-indacene Dyes: Synthesis and Spectroscopic Evaluation

A straightforward method for the synthesis of original 4,4-dialkoxy- or 4,4-diaryloxy-diaza-s-indacenes (BODIPY) derivatives obtained by treatment of BODIPY 1 with various alcohols in the presence of AlCl3 is described. The novel compounds are characterized by spectroscopic properties similar to those of the parent BODIPY 1, absorption and emission spectra with similar band shapes, high molar absorption coefficients (ελmax ≈ 80 000 M-1 cm-1), and for most of them high fluorescence quantum yields (Φexp from 0.52 to 0.71). Among all of the new compounds synthesized, the dye 2h exhibits higher fluorescence quantum yield (0.71) and lifetime (4.09 ns) than compound 1 and a good chemical stability toward conditions compatible with biological cell-based assays.