Ion responsive near-IR BODIPY dyes: two isomers, two different signals

Tetrastyryl-substituted BODIPY dyes are likely to evolve into a new class of near IR fluorophores. In this work we demonstrate that 1,7 and 3,5-positions show marked differences in charge transfer characteristics. Using a Hg(ii) selective ligand, the signal transduction potentials were explored: one isomer shows a large blue shift in electronic absorption spectrum, while the other just shows an intensity increase in the emission spectrum. Electronic structure calculations were undertaken to elucidate the reasons for different signals on metal ion binding in relation to core BODIPY properties.