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Spirofluorene‐cored bis(difluoroboron β‐diketonate) complexes bearing terminal carbazoles (CbzBSF) and tert‐butylcarbazoles (TCbzBSF) have been synthesized. It was found that only TCbzBSF could form organogels in cyclohexane and methylcyclohexane, suggesting that tert‐butylcarbazole was essential for its organogelation directed by weak π–π interactions. It is worth noting that TCbzBSF could entrap ca. 5800 molecules of methylcyclohexane per gelator molecule, so this fully conjugated complex without traditional gelation group could be considered as a supergelator. The gained organogel showed reversible thixotropic and temperature‐dependent sol‐gel transitions. In particular, the orange red fluorescence of the xerogel‐based film of TCbzBSF could be quenched when exposed to gaseous aromatic amines of aniline, N‐methylaniline, and N,N‐dimethylaniline. The detection limit for aniline vapor of the xerogel‐based film was as low as 0.56 ppb. [ABSTRACT FROM AUTHOR]

Novel luminescent organogelators based on nucleoside functionalized with carbazole (UC8, UC12 and UC16) were designed and synthesized. Their gelation ability was tested and it was found that both UC12 and UC16 could form stable organogels in toluene/petroleum ether. The UV-vis absorption, fluorescence emission and IR spectral changes during the gelation of UC12 proved that the self-assembly was driven by H- bonding. The morphology of the xerogel UC16 obtained from toluene/petroleum ether (v/v = 1/1) displayed tough rod-like microstructures, and 3D networks formed from lots of nanofibers were observed for the xerogel UC16 obtained from toluene/petroleum ether (v/v = 2/1). It was interesting that the obtained organogels emitting blue light could be destroyed by the addition of F-, accompanied with the declining the emission intensity. Therefore, these organogels could be used as sensory materials to recognize F-. [ABSTRACT FROM AUTHOR]

Four new D-π-A-type difluoroboron β-carbonyl cyclic ketonate complexes that contain carbazole units ( TCCH, TCCP, CCH, and CCP) have been synthesized that exhibited reversible mechanofluorochromic (MFC) behaviors. Interestingly, TCCH and TCCP, which contained a tert-butyl carbazole group, exhibited high-contrast mechanofluorochromism compared with CCH and CCP, which just contained a carbazole group. For example, shifts of Δ δ=49 and 20 nm were detected during the mechanofluorochromism of TCCH and CCH, respectively. We found that tert-butyl carbazole derivatives existed as isolated molecules in the as-synthesized crystals, on account of the steric hindrance of the tert-butyl groups, and that J-aggregates were formed upon grinding. Transformation between the isolated and aggregated molecules, which was stimulated by mechanical force, led to clear changes in the emission properties. However, J-aggregates were formed in the as-synthesized crystals of carbazole derivatives, and grinding only weakened the strength of the π-π interactions, thereby resulting in low-contrast mechanofluorochromism. Therefore, this approach provides a useful strategy for the design of MFC dyes with high performance. [ABSTRACT FROM AUTHOR]

The simplest carbazole-based organogelator C1 (9-hexadecyl-9 H-carbazole) has been synthesized and can self-assemble into nanofibers in the gel phase directed by balanced π-π interactions. To extend the conjugation of the π gelator, we prepared linear carbazole-based trimer C3 and pentamer C5, which also exhibited gelation behavior in some organic solvents upon ultrasound stimulation. It is found that the xerogel of C3 emits strong blue light under UV irradiation. Notably, the emission of C3 in nanofiber-based films can be quenched upon exposure to vapors of TNT and DNT. The steady-state Stern-Volmer plots of C3 in toluene revealed that the fluorescent quenching induced by aromatic nitro compounds is due to photoinduced electron transfer. Therefore the emitting nanofibers fabricated from linear carbazole by organogelation can be used as fluorescent sensors to detect explosives. [ABSTRACT FROM AUTHOR]