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A hydrogen bonded complex could self-assemble into one-dimensional fibers in its gel phase. The fibrous film could be used as a sensor to detect and discriminate aromatic and aliphatic amines.

Being different from common sensing molecules existing as monomer in solution, the gelators as sensing molecules self-assembled together in gels. Therefore, the interaction strength between gelators is believed as an important factor for gels to recognize selectively anions. In this paper, we choose two gelators, presenting similar binding sites for anions, but different strengths in intermolecular interaction. Moreover, their anion responsive behaviors in organogels were examined by observing phase state and measuring UV-vis and fluorescence spectra. We found that the organogel formed by 2 with strong intermolecular interaction could selectively recognize fluoride anion. However, the gels of 1 could be transformed into sol phases by addition of F(-), Cl(-), Br(-), AcO(-) and H(2)PO(4)(-) because of the small aggregate constant of 1 in o-dichlorobenzene, presenting poor selectivity. Moreover, their UV-vis and emission spectra acting as testing methods also suggested the same conclusion.

A new D-pi-A type gelator based on a phenothiazine derivative, which can gel cyclohexane, hexane, and ethanol/water under ultrasound treatment, has been synthesized. Because such gelators can act as twisted intermolecular charge transfer (TICT) probes, their emission in solution can be tuned by varying the polarity of the solvents. It is notable that an unusual aggregation-induced blue shift of the emission has been detected on account of the suppression of TICT in the gel phase.

Glutamine derivative 1 with two-photon absorbing units has been synthesized and was found to show gelation ability in some solvents. Its self-assembly in the gel phase could be controlled by the solvent and speed of gelation. For example, in DMSO the organogelator self-assembled into H-aggregates with weak exciton coupling between the aromatic moieties. On the other hand, in DMSO/diphenyl ether (1:9, v/v) the molecules formed 1D aggregates, but with strong exciton coupling due to the small distance between the chromophores. Moreover, the formation of these two kinds of aggregates could be adjusted by the ratio of DMSO to diphenyl ether. In DMSO/toluene, DMSO/butanol, DMSO/butyl acetate, and DMSO/acetic acid systems similar results were observed. Therefore, conversion of the packing model occurs irrespective of the nature of the solvent. Notably, a unique sign inversion in the CD spectra could be realized by controlling the speed of gelation in the DMSO/diphenyl ether (1:9, v/v) system. It was found that a low speed of gelation induces the gelator to adopt a packing model with strong pi-pi interactions between the aromatic units. Moreover, the gels, when excited at 800 nm, emit strong green fluorescence and the quantum chemical calculations suggest that intramolecular charge transfer leads to two-photon absorption of the gelator molecule.

tert-Butyl groups can modulate the self-assembling properties of carbazole derivatives; organogel fibers with a bright blue emission are generated, directed by the cooperation of hydrogen bonding as well as pi-pi interactions.

A new cholesterol organogelator 1 was synthesized, which was confirmed as an effective gelator for various organic solvents and could self-assemble into network fibers in some organic solvents. Moreover, gelator 1 could act as templates for the synthesis of various CuS nanofibers with different helical pitches. For example, when H(2)S was used as the sulfur source, straight and bending helical CuS nanofibers with a pitch of 100-200 nm could be fabricated in butyl acetate and benzene-butanol gel systems, respectively, while bending CuS nanofibers with a similar helical pitch (ca. 50 nm) could be obtained when thioacetamide was used as the sulfur source in both gel systems. It was first found that the morphologies of inorganic nanofibers could be controlled by the binding sites between the inorganic precursor and the organogel.

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]

We have synthesized a series of new β-iminoenolates and their corresponding difluoroboron complexes without any traditional gelation moieties, and some of them were able to gelatinize organic solvents. It was found that the presence of halogen atoms as substituents had a significant effect on gelation ability. In particular, bromo-containing compounds 4 A and 4 B exhibited excellent gelation abilities compared with other halogen-substituted gelators. By analyses of the single-crystal structure, the PXRD pattern of the xerogel, and electronic spectral changes during gelation, we deemed that π-π, C−H⋅⋅⋅F, and C−H⋅⋅⋅Br interactions were the driving forces for the gelation of 4 B. Interestingly, ( Z)-1-(4-bromophenyl)-2-(3-methylpyrazin-2-yl)ethen-1-ol ( 8 A), prepared in this work, is the lowest-molecular-weight organogelator to have been reported. It should be noted that although β-iminoenolates 3 A- 5 A are nonemissive in solution, they emit strong yellow light in organogels, which suggests aggregation-induced emissive activity, whereas the difluoroboron complexes 3 B- 5 B show strong fluorescence in solutions, organogels, and xerogel-based films. Moreover, we found that the emission of 4 B in a nanofiber-based film could be quenched significantly upon exposure to gaseous trifluoroacetic acid and that the decay time and detection limit were 0.5 s and 0.17 ppm, respectively. Thus, through this work we have provided a new strategy for the design of nontraditional π gelators by introducing halogen atoms into π-conjugated systems with moderate polarities. [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]

Fluorescent organic molecules with C3-symmetry consisting of tris{2-cyano-2-[4-(dodecyloxybenzoylamino)phenyl]-1-ethenyl}phenylbenzene (CN-DBAPPBn, n = 1, 2, 3) were synthesized. It was observed that these compounds can spontaneously self-assemble into organogels in many organic solvents. Scanning electron microscopy (SEM), light microscopy, and fluorescence microscopy images of the air-dried gels showed the presence of either heavily entangled amorphous or fibrous structures, or rods. FTIR, UV/Vis absorption, excitation and emission spectra suggest that π-π interactions and H-bonding are the driving forces for the formation of the gel phases. Moreover, spherical or cubic fluorescent nanoparticles based on CN-DBAPPBn were prepared by using a reprecipitation method in a mixture of tetrahydrofuran and water. It is interesting that aggregation-induced emission behavior of CN-DBAPPBn was detected in both the gel phase and in the nanoparticle suspensions. The fluorescent molecular aggregates of CN-DBAPPBn with different architectures and emission properties fabricated by using these self-assembling methods could find potential applications in sensors and optoelectronic devices. [ABSTRACT FROM AUTHOR]