Significant emission red-shift of BODIPY derivatives with strong electron-acceptor attached

A new red-fluorescent BODIPY derivative is designed and synthesized, which is configured by attaching an electron-withdrawing unit 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF). By virtue of the strong electron-accepting nature of TCF unit, the compound BT exhibits a large red-shift both in absorption and emission. In contrast to parent BODIPY, the absorption shifted about 90 nm. And the emission maximum shifted to red region with the peak centered around 620 nm. The CIE coordinate and fluorescence decay data uncovered its emission character. Theoretical calculation of BT confirmed that the electron density was altered dramatically by TCF and lowered the energy gap between ground state. The character of HOMO/LUMO distribution is well in agreement with that of experimental value.