Mechanofluorochromic behaviors and latent fingerprint detection of triphenylamine-based compounds with mono-/bis-BF fluorophores.

To better understand the relationship between molecular structure of the mono-/bis-BF-core compounds and mechanofluoroboron behaviors, two pyridine-based difluoroboron compounds with triphenylamine group (TPA-ts-BF and TPA-ts-2BF) were designed and successfully synthesized, which TPA-ts-BF including a BF fluorophore and TPA-ts-2BF containing the bisBF fluorophores. Based on the photophysical properties measurements results, it was found that TPA-ts-2BF had more excellent intramolecular charge transfer characteristics than that of TPA-ts-BF, and exhibited significant aggregation-induced emission activity, however, TPA-ts-BF displayed typical aggregation-caused quenching phenomenon. Meanwhile, the emission spectrum of the solid powders of TPA-ts-2BF was red-shifted 52 nm after grinding, that of TPA-ts-BF was red-shifted 46 nm, which was resulted from crystalline state switching to amorphous state. According to the theoretical calculations, we conjectured that TPA-ts-BF with uncoordinated amide linkage moiety had a tendency to forming a more twisted conformance and higher molecular polarity, which made that mechanofluorochromic behavior was worse than that of TPA-ts-2BF. Additionally, TPA-ts-2BF was applied to latent fingerprint detection due to its prime aggregation-induced emission property.