Fluorescent 1-hydroxy-10-alkylacridin-9(10H)-one BF₂-chelates: Large Stokes shift and long emission decay times

New 1-hydroxy-10-alkylacridin-9(10H)-one BF₂-chelates absorb in the blue-green part of the electromagnetic spectrum and emit fluorescence with moderate quantum yields of 8–45% in toluene. The dyes show large Stokes shifts about 4300 cm⁻¹, decay times between 5 ns and 15 ns in toluene and high photostabilities. Introduction of a fluorine atom into the acridone cycle results in an increase of the fluorescence quantum yield and decay time whereas immobilization in a rigid polymer matrix (polystyrene) further extends the lifetime up to 18 ns. Large Stokes shifts and long emission decay time make this dye class an interesting platform for time-resolved imaging and sensing applications.