New difluoro-boradiazaindacene shaped with gallate platforms

Abstract

The present account describes the synthesis of difluoro-boradiazaindacenes (F-Bodipy) functionalized at the central 8-position by phenylamino or phenyldiamino moieties conveniently transformable into phenyl amide scaffoldings. Molecules carrying three linear or branched chains, or six linear chains were prepared and fully characterized. Four X-ray crystal structures were determined and the packing is discussed in terms of molecular interactions, a key feature for the formation of aggregates or thin films. With the exception of nitro derivatives quenched by a photo-induced reductive electron transfer and the amino-derivatives partially quenched, all dyes are highly fluorescent with quantum yields lying between 50 and 90%. The few nanosecond excited-state lifetimes and the weak Stokes shifts are in keeping with singlet excited states. Reversible reduction and oxidation processes occur around −1.34 and +0.97 V in solution and the electroactivity and photoluminescence are maintained in thin films. Interestingly, two distinct emissions are observed at 550 and 635 nm by electroluminescence of the trimethoxyphenyl-Bodipy derivative, corresponding, respectively, to the luminescence of isolated molecules and aggregates. Dispersion of the Bodipy into a fluorescent poly(N-vinylcarbazole) polymer (PVK) (approximately 3 mol% per repeating unit of PVK) by solution processing exclusively produces yellow emission due to isolated Bodipy fluorophore.