Colourless p-phenylene-spaced bis-azoles for luminescent concentrators

We report on the synthesis of new push-pull imidazole-benzothiazole and thiazole-benzothiazole flu- orophores obtained in good yields by using direct CeH arylation synthetic strategies. Spectroscopic in- vestigations in CHCl3 solution evidenced that the 1,4-phenylene-spaced imidazole-benzothiazole bearing an electron-donating dimethylamino group achieved a trade-off between fluorescence maximum (516 nm), Stokes shift (165 nm) and a quantum yield higher than 0.4. Dispersions of the selected fluo- rophore in poly (methyl methacrylate) (PMMA) thin films mostly maintained the optical features in solution with significant light transmittance in the visible region (90% at 440 nm), and a brilliant green emission at 500 nm. Photocurrent experiments performed on PMMA thin films coated over high purity transparent glasses promoted their use in the development of colourless luminescent solar concentrators with optical efficiencies close to 6%.