In line with previous reports, 31 weak emission above 600 nm can be attributed to a charge transfer state between the pyrene and BODIPY subunits. The reported reduction potential EA/A-for the diethoxycarbonyl-BODIPY group is -0.87 eV (MeCN/SCE), which is +0.32 eV more positive than the value reported for the analogous tetramethyl BODIPY that has hydrogen atoms at the 2,6positions. This makes diethoxycarbonyl-BODIPY chromophore more susceptible to reduction and facilitates charge transfer. The oxidation potential (E D/D+) of pyrene group in acetonitrile is 1.16 eV, making the electron transfer to the BODIPY subunit thermodynamically favourable. Pyrene acts as an electron donor and the BODIPY as an acceptor, allowing this dipolar CT state to form. The emission observed for pyrene dyad 1b in polar solvents (Figure ) can be interpreted as a combination of fluorescence from the LE and CT state. When compared to the previously reported tetramethyl-substituted BODIPY-pyrene dyad without ethoxycarbonyl groups, which showed only moderate charge transfer efficiency in polar solvents; 31a it can be assumed that the addition of these substituents has promoted intramolecular charge transfer efficiency in the dyad.