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Triphenylamine functionalized salicylaldimine difluoroboron complexes bearing different substituents have been synthesized. The photophysical results showed that these complexes exhibited intramolecular charge transfer (ICT) emission and solvatochromism. The fluorescence of these complexes could be well-tuned by the substituents in the ligands. The introduction of tert-butyl groups causes the complex TST to show obvious aggregation-induced emission (AIE) activity. In particular, the complexes without other substitutions or with the substitutions of bromo, tert-butyl and methoxyl on salicylaldimine moieties displayed reversible mechanofluorochromic (MFC) behaviors. XRD patterns and DSC curves of the complexes in different solid states suggested that the transformation between crystalline and amorphous states was responsible for the MFC properties. The relationship between the molecular structures and MFC properties suggested that the high polarity of the conjugated skeletons in difluoroboron complexes was beneficial for realizing high-contrast performance in mechanofluorochromism. [ABSTRACT FROM AUTHOR]

New D–π–A-type triphenylamine-containing benzimidazoles, benzoxazoles and benzothiazoles have been synthesized. It was found that the introduction of a cyano group in vinyl and methyl in triphenylamine was favorable for producing mechanofluorochromism of the fused heterocyclic derivatives. The single crystal X-ray diffraction data revealed that the intermolecular interactions of the H-bonding formed from the cyano group and the C–H…π interaction formed from the methyl group would rigidify the molecular conformations, leading to strong solid-state emission. Interestingly, the solid-state emission of the synthesized triphenylamine-containing fused heterocycles bearing cyano and/or methyl groups could be tuned by external mechanical forces on account of the transition between crystalline and amorphous states or between a highly ordered crystalline state and a less ordered state. [ABSTRACT FROM AUTHOR]

Abstract New D-π-A type quinoline derivatives (CbzVQ and TPAVQ) were synthesized via Knoevenagel condensation reactions. They exhibited reversible high-contrast mechanofluorochromic (MFC) behavior under grinding/fuming treatment. Taking CbzVQ as an example, its fluorescence could be switched from blue to greyish green by grinding the as-synthesized sample into ground powders, and the fluorescence emission was red-shifted from 449 nm (with shoulders at 475 nm and 520 nm) to 578 nm (with shoulders at ca. 450 nm and 500 nm). Such large shift of the maximal emission peak during MFC processes was rare reported. In addition, the casting films of CbzVQ and TPAVQ emitted blue and green light, respectively, which was turned to red rapidly induced by TFA (trifluoroacetic acid) vapor. Moreover, the emission could be recovered stimulated by TEA (triethylamine) vapor, so the quinoline derivatives exhibited reversible fluorescent sensory properties. TPAVQ showed better performance in the detection of TFA vapor than CbzVQ due to the strong electron-donating ability of triphenylamine compared with carbazole. The detection limit and the decay time of TPAVQ towards TFA vapor were 163 ppb and 0.22 s, respectively. Apparently, the D-π-A type quinoline derivatives are candidates as multi-stimuli responsive fluorescent materials. Graphical abstract Image 1 Highlights • New D-π-A type quinoline derivatives bearing carbazole and triphenylamine are synthesized. • Quinoline derivatives show reversible high-contrast mechanofluorochromism. • The shift of the maximal emission for CbzVQ reaches 129 nm during mechanofluorochromic processes. • The emitting color of quinoline derivatives is turn to red from blue or green rapidly stimulated by TFA vapor. [ABSTRACT FROM AUTHOR]

Two push-pull compounds, which are comprised of triphenylamine (TPA) (electron donor units) and functionalized β-diketones difluorboron complexes (electron acceptor units) are probed by many spectroscopies, which offers the relationship between electron acceptor and the intrinsic excited state properties of push–pull chromophores. We found that the photoluminescence (PL) intensity would enhance with the number of electron acceptor. Transient absorption (TA) data shows that intramolecular charge transfer (ICT) process really exists in the two molecules after photoexcitation and this process would be prolonged through increasing the electron-acceptor, which would be responsible for the improvement of PL property. [ABSTRACT FROM AUTHOR]