Synthesis of thiophene-substituted aza-BODIPYs and their optical and electrochemical properties

A series of novel thiophene-substituted aza-BODIPY dyes were synthesized by means of a standard procedure and complemented by a Stille-coupling of a brominated species with 2-tributylstannylthiophene. The optical as well as the electrochemical properties of the compounds were investigated and compared to result of density functional theory (DFT) calculations. The influence of the thiophene substituents is discussed in dependence of the position at the aza-BODIPY core regarding the HOMO and LUMO frontier orbitals. The different distributions of the HOMO and LUMO coefficients over the BODIPY core lead to a variable influence of the thiophene substituents on the HOMO and LUMO energies, being the origin of the tunable optical and electrochemical properties.