The absorption and fluorescence emission parameters of diethoxycarbonyl BODIPYs in a range of solvents are given in Table . Reference compounds 1 and 1a which lack electron donor groups and thus do not undergo intramolecular charge transfer showed optical properties typical for alkyl-substituted BODIPYs, i.e. narrow absorption and emission bands, high fluorescence QYs both in polar and non-polar solvents. For meso-phenyl BODIPY 1a (Figure ), position of the absorption and emission bands are nearly identical to the parent tetramethyl-substituted BODIPY without ethoxycarbonyl groups (λabs = 498 nm, λem = 508 nm in MeOH), indicating this substitution in the 2,6 positions has no major effect on optical characteristics. This is in line with the work of Gabe et al. describing the parent compound 1a and its analogue, meso-phenyl-2,6-diethyl-1,3,5,7-tetramethyl BODIPY. While the absorption and emission maxima remained the same for 1a compared to the parent tetramethyl-substituted BODIPY, the addition of ethyl groups to the 2,6-positions caused a bathochromic shift (λabs = 520 nm, λem = 534 nm in ACN) and a slight increase in the Stokes shift.