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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 phenothiazine-modified 2-hydroxychalcone analogues PTNn (n = 2, 4, 8, 12, and 16) have been synthesized, and they exhibited reversible mechanofluorochromism. Notably, the emission of PTNn in different solid-states was in the range of 600–800 nm, and red-emitting mechanofluorochromic (MFC) materials were seldom reported. The as-synthesized crystals of PTN16 emitted red light centered at 667 nm, and were changed into deep red emitting ground powders after grinding. The fluorescence emission could be recovered to the original state when the ground powders were fumed with the DCM vapor or heated. The MFC processes were accompanied by the transformation between crystalline and amorphous states, which could be confirmed based on the results of XRD patterns in different solid-states. Additionally, it was found that the length of the alkyl chain affected the performance in mechanofluorochromism for PTNn. The dye bearing a short carbon chain showed high-contrast MFC behavior compared with the one bearing a long carbon chain. Moreover, PTN12 and PTN16 bearing long carbon chains could self-assemble into organogels in a certain amount of organic solvents, and gelation-induced emission enhancement was observed during organogelation. [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]

New carbazole modified salicylaldimine derivatives 1a–3a and their difluoroboron complexes 1b–3b were synthesized. It was found that 3a and 3b bearing both tert-butyl and trifluoromethyl could form stable gels in some organic solvents, while no gel could be formed from 1a–1b and 2a–2b without tert-butyl or trifluoromethyl, respectively. It suggested that both tert-butyl and trifluoromethyl played key roles in the gel formation because they could tune the solubility of the compounds and adjust the strength of intermolecular interactions. It should be noted that there is no traditional gelation moiety involved in gelators 3a and 3b. The main driving force for the gelation of such nontraditional π-gelators was π–π interaction. Meanwhile, aggregation-induced emission (AIE) was detected during the organogelation process of 3a, and the gel–sol transition took place upon adding F−. Interestingly, complexes 1b and 3b exhibited reversible piezofluorochromic (PFC) behaviors upon grinding/fuming, which originated from the transformation between crystalline and amorphous states. Herein, we provided a new strategy for designing new stimuli-responsive multifunctional soft materials. [ABSTRACT FROM AUTHOR]

Cyanostyrene-based D–π–A type conjugated compounds bearing triphenylamine units (G1, G1-N and G2) have been synthesized. By tuning the conjugated skeleton and the electron withdrawing ability of the acceptor, green, orange and red light emitters were achieved. It is interesting that although their emissions in solutions were weak, we observed strong emission in solid states. For example, the ΦF of the dendritic molecule G2 in powder reached 0.67, which was more than 20 times of that in THF. The single crystal X-ray diffraction data revealed that the intermolecular H-bonds of C–H…O, C–H…N and C–H…π led to the increased rigidity of the molecular skeleton, which would restrict the intramolecular rotation, yielding high ΦF in solid states. These AIE compounds may become candidates for emitting materials. [ABSTRACT FROM AUTHOR]