The quest for highly fluorescent chromophores: evaluation of 1H,3H-isochromeno[6,5,4-mna]xanthene-1,3-dione (CXD)

Abstract

Photophysical properties of the strongly fluorescent dye, 1H,3H-isochromeno[6,5,4-mna]xanthene-1,3-dione (CXD), are reported. This highly planar, rigid dye absorbs at around 420 nm, which is ideal for excitation with a blue laser diode, and is extremely stable towards prolonged illumination. Under near-UV excitation, the dye readily sensitises free-radical polymerisation, forming a plastic film with excellent optical transparency. Weakly structured emission is observed with a small Stokes' shift and remains essentially insensitive to changes in solvent polarity. For example, in tetrahydrofuran the fluorescence quantum yield is 0.96 while the excited-singlet state lifetime is 7.4 ns. Quantum chemical calculations provide further insight into the electronic nature of the dye in solution.