Pyrimidine-containing β-iminoenolate difluoroboron complexes acting as non-traditional π-gelators and mechanofluorochromic dyes

New pyrimidine-containing beta-iminoenolates and their difluoroboron complexes were synthesized. It was found that the ligand and the complex bearing tert-butyl could self-assemble into organogek in methyl-cyclohexane/1,4-dioxane and other solvents, but no organogel could be formed from the carbazole derivatives. This suggested that tert-butyl played a key role in the gel formation. It should be noted that no traditional gelation moiety was involved in the fully conjugated TCPPA ((Z)-2-(6-chloropyrimidin-4-yl)-1-(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)et-hen-1-ol and TCPPAB (6-chloro-3-(4-(3,6-ditert-butyl-9H-carbazol-9-yl)phenyl)-1,1-diflu-oro-1H-1l4,9l4-pyrimido[1,6-c][1,3,2]oxazaborinine), and pi - pi interactions were found to be the main driving forces for the gelation. Moreover, the xerogekbased film of TCPPAB emitting strong yellow Eight could be used as a turn-off fluorescent sensor to detect TFA vapor with the decay time and detection Limit of 0.8 s and 260 ppb, respectively. On the other hand, the beta-iminoenolate difluoroboron complexes exhibited reversible mechanofluorochromic behavior. The as-synthesized crystals of TCPPAB emitted strong green Eight and could be transformed into powders emitting orange Eight upon grinding, and the fluorescence could be recovered when the ground powders were fumed with CH2Cl2. Such reversible MFC processes for TCPPAB were suggested to have resulted from the transformation between crystalline and amorphous states. Herein, we provide a strategy for designing new multi-stimuli-responsive soft materials.