Photophysical and anion sensing properties of a triphenylamine–dioxaborinine trimeric compound

Herein, we report the synthesis and photophysical characterization of the novel tris(4-(2,2-difluoro-6-methyl-2H-1λ(3),3,2λ(4)-dioxaborinin-4-yl)phenyl)amine trimeric probe (A2) via the reaction between triphenylamine (1), acetic anhydride, and BF(3)·OEt(2) implying the twelve new bond formation in a one-pot manner. This highly fluorescent compound in solution (φ up to 0.91 at 572 nm) and solid state (φ = 0.24 at 571 nm) showed a better solvatofluorochromism than its analog monomeric A1 due to symmetry-broken charge transfer, which is consistent with high solvent dipolarity (SdP) response in Catalán's multiparametric regression. Notably, A2 had a high sensibility and selectivity for CN(−) or F(−) in solution (LODCN(−)/F(−) = 0.18/0.70 μM), and CN(−) can be discriminated from F(−) by the reaction of A2 with 3.0 equiv. of CN(−). In addition, A2 was impregnated on filter paper to prepare test strips that were applied to naked-eye qualitative sensing of CN(−) or F(−). Finally, the octupolar system in A2 allows for better action of two-photon excitation cross-section values when compared with that of the dipolar structure in A1. These findings provide further information for the design of new efficient two-photon absorption dyes.