Quinoline-functionalized BODIPY dyes: Structural and photophysical properties

BODIPYs at different positions of quinolines show similar absorption spectra but very different visible emission efficiency. Single-crystal structures show different tilting angles of quinoline groups and BODIPY core structure. The emission efficiency decreases as the torsion angle between BODIPY core and quinoline becomes smaller in the order of 4-Q-BDP > 3-Q-BDP > 2-Q-BDP approximate to 2,9-Phen-BDP. The restoration of fluorescence in the presence of methanol and theoretical calculations indicate the photoinduced electron transfer from quinoline N to BODIPY core could be responsible for such a gradual fluorescence change.