Synthesis and optical properties of 1-ethyl-indol-3-yl-substituted aza-BODIPY dyes at the 1,7-positions

New aza-BODIPYs with significant bathochromic shifts in their UV–vis absorption spectrum were synthesized by the installation of 1-ethyl-indol-3-yl moieties at 1,7-positions aza-BODIPY core bearing 4-substituted phenyl or thien-2-yl groups 3,5-positions. The compounds described herein show strong NIR absorptions up to 779 nm, and emissions 805 nm chloroform solution, present large molar extinction coefficients. emission bands aza–BODIPYs significantly red-shifted, ca 100 relative 3,5-dianisyl-1,7-diphenyl aza-BODIPY. TD-DFT calculations indicate an effective electronic conjugation between substituents. Absorption studied derivatives corresponds a charge transfer from donor substituents toward boron-centered core. Moreover, computational results that all HOMO–LUMO band gap values are organic semiconductor range.