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A series of novel monodisperse, structurally well defined vinylene‐linked phenothiazine oligomers containing up to 7 phenothiazine units have been designed and synthesized by Heck reaction and McMurry reaction with a convergent approach. These conjugated oligomers showed a progressive bathochromic shift of the absorption maxima and high fluorescence quantum yields in solutions. Notably, the oligomers without strong donor and acceptor units exhibit two‐photon absorption properties, and the two‐photon absorption cross sections (δ) increase with the number of covalently linked phenothiazine units, and δ reaches up to 2071 GM for the one with 7 phenothiazine units at 800 nm. The oligomers might be used as models to study structure–property relationship for their corresponding polymers or applied in organic electronic materials. [ABSTRACT FROM AUTHOR]

An L-phenylalanine derivative ( C12PhBPCP) consisting of a strong emission fluorophore with benzoxazole and cyano groups is designed and synthesized to realize dual responses to volatile acid and organic amine vapors. The photophysical properties and self-assembly of the said derivative in the gel phase are also studied. C12PhBPCP can gelate organic solvents and self-assemble into 1 D nanofibers in the gels. UV/Vis absorption spectral results show H-aggregate formation during gelation, which indicates strong exciton coupling between fluorophores. Both wet gel and xerogel emit strong green fluorescence because the cyano group suppresses fluorescence quenching in the self-assemblies. Moreover, the xerogel film with strong green fluorescence can be used as a dual chemosensor for quantitative detection of volatile acid and organic amine vapors with fast response times and low detection limits owing to its large surface area and amplified fluorescence quenching. The detection limits are 796 ppt and 25 ppb for gaseous aniline and trifluoroacetic acid (TFA), respectively. [ABSTRACT FROM AUTHOR]

Nanofibers based on phenanthroimidazole derivatives PCC, PDC, and PSC were fabricated by organogelation processes, and their fluorescence sensory properties towards acid were investigated. It was found that the emission of PCC in the nanofiber-based film could be quenched significantly upon exposure to gaseous TFA due to the formation of protonated PCC, in which ICT (intramolecular charge transfer) would occur. On the other hand, TFA vapor led to the emitting colors of PDC and PSC in the nanofiber-based films to turn to yellow and green from sky blue and blue, respectively. Additionally, we found that the decay times of PCC were 0.1 s and 1.9 s in probing the saturated vapor of TFA in nanofiber-based film and in spin-coated film, respectively. The results suggested that the high surface-to-volume ratio and large interspace in the nanofiber-based networks favored the enhanced adsorption, accumulation, and diffusion of gaseous molecules, resulting in such a high performance. [ABSTRACT FROM AUTHOR]

Two L-phenylalanine derivatives with 5,8-bis(2-(carbazol-3-yl)vinyl)quinoxaline ( PCQ) and 5,8-bis[2-(carbazol-3-yl)]-2,3-dimethylquinoxaline ( DCQ) as fluorophores were synthesized, and their photophysical properties were measured and compared. The two compounds were found to gelate some organic solvents and self-assemble into 1D nanofibers in gels. The wet gel of PCQ emitted a weak orange fluorescence, but the DCQ gel had a strong green one. This result can be due to the presence of two methyl groups and the nonplanar conformation of fluorophore in DCQ. The gel film of DCQ also showed significantly stronger fluorescence than that of PCQ. Thus, the wet gel and xerogel film of DCQ were selected to study their sensing properties to acids. The yellow wet gel of DCQ transformed into a brown sol upon the addition of 0.2 equiv trifluoroacetic acid (TFA), accompanied by emission quenching. The xerogel film of DCQ rapidly responded to volatile acids, such as TFA, HCl, and HOAc. The fluorescence of the xerogel film was gradually quenched with increased concentration of volatile acid vapors. The fibrous film exhibited low detection limits for volatile acid. The detection limits of the thin films for TFA, HCl, and HOAc reached 43, 122, and 950 ppb, respectively. [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]

We study the photophysical characters of two oligofluorenes-functionalized anthracenes molecules with different fluorine-vinylene ( FV) units, which exhibits that 'excimer' state appears in the solution after photoexcitation. The dynamic data shows that two mechanisms are responsible for the generation of 'excimer'. The fast one is controlled by the arene-arene interaction between molecules and the slow one is influenced by the diffusion motion of molecules. Increasing the number of FV units may suppress the DM-dependent 'excimer' and enhance the yield of intrinsic fluorescence, which finally improves the fluorescence property of molecules in solution. [ABSTRACT FROM AUTHOR]

A glutamide gelator, 1, was synthesized,and a weakemission enhancement was observed during its gelation. In addition, 1could be an excellent scaffold for successfully embeddingan energy acceptor, 2, into its aggregate to obtain highlyefficient energy transfer. An amplification of the emission enhancementwas observed in the two-component gels compared to that of the neatgel of 1during gel formation. For example, 1induced only a 2.5-fold increase in emission intensity, whereasa 23-fold enhanced emission could be observed in the two-componentgel with only 1.6 mol % 2. Furthermore, two-componentgels had an excited proton response. In systems with low acceptorconcentrations, the hot solution red-shifted the fluorescence fromblue to yellow upon the addition of a proton, which continuously blue-shiftedwith decreasing temperature to form the gel given that the bindingof the gelator to the proton is weakened during coassembly. Moreover,the casting film formed by the two-component wet gel had an excellentresponse to volatile acids such as hydrochloric acid, trifluoroaceticacid, and so on and could be reversibly recovered by exposure to NH3. [ABSTRACT FROM AUTHOR]

Abstract: Four new well-defined monodisperse linear oligofluorenes with anthracene core An-OFVn (n =1–4) have been synthesized through Heck and Wittig reaction. These conjugated oligomers exhibit good solubility in common organic solvents. It is found that the conjugation length of the oligomers can be extended and the formation of excimers can be suppressed with increasing the number of fluorene–vinylene units linked in the 9,10-positions of anthracene. [Copyright &y& Elsevier]

Abstract: A new D–π–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. [Copyright &y& Elsevier]

Abstract: Novel monodisperse linear 3,9-linked oligocarbazoles (OCAs) were prepared stepwise using Ullmann coupling reaction in seal-tubes. The resulting OCAs were soluble in common organic solvents. The UV–vis spectra of OCAs exhibited small red shift and their intensities increased linearly with the increase of the carbazole moieties, suggesting that no intramolecular π-interactions appeared at ⩽8-mer. All the OCAs gave strong fluorescence and it was found that the conjugated degree of linear OCAs would be saturated when the number of carbazole units reaches four. [Copyright &y& Elsevier]

Triphenyl pyrazoline derivative, 1,3-diphenyl-5-{4-[2-(4-(phenylazo)phenoxy)ethyloxy]phenyl}-2-pyrazoline (compound III), was synthesized and its optical properties were studied by UV–VIS and fluorescence spectroscopies. The UV–VIS spectrum showed that the electronic transition bands of azobenzene and triphenyl pyrazoline groups were overlapped at ≈350 nm. The fluorescent emission band appeared at 450 nm, which was located at the range of n–π* transition band of azobenzene. It was found that the fluorescence intensity of pyrazoline moiety could be modulated by irradiation with UV and visible light due to the reversible trans–cis–trans photoisomerization reaction of azobenzene moiety. It indicated that the intramolecular electronic energy transfer from pyrazoline moiety to azobenzene one happened and the degree of energy transfer was determined by the content of cis-isomer of azobenzene moiety. [Copyright &y& Elsevier]

New dimesitylborylthiophene derivative with terminal tetraphenylethene TPETB has been synthesized. It was found that TPETB exhibited aggregation-induced emission behavior and reversible mechanofluorochromism. For instance, the emission intensity of TPETB in THF/H 2 O with water fraction of 90% was ca. 21 times higher than that in THF. In addition, grinding the as-prepared crystal of TPETB the emitting color changed from sky blue to yellowish green. Meanwhile, the ground powder could recover to crystalline structure with sky blue emission when it was exposed to CH 2 Cl 2 vapor. It was suggested that the transformation between crystalline and amorphous states led to the changes of solid emitting colors in response to external mechanical forces. It should be noted that TPETB could detect F − selectively, and the detection limit was 1.67 × 10 −8 mol/L in CH 2 Cl 2 . [ABSTRACT FROM AUTHOR]

Abstract: We report on the synthesis and self-assembly of a new discotic organogelator based on π-conjugated triphenylbenzene with three peripheral chiral substituents. It is found that the introduction of chiral groups to the C 3-symmetric molecule led to a hexagonal columnar chiral stacking of the molecules in a clockwise direction in the organogel fibers. And the fluorescent emission of the gel decreased significantly compared to the monomer state at the same concentration, as a result of the aggregation of the nonplanar triphenylbenzene core in the gel phase. [Copyright &y& Elsevier]

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]

Abstract New carbazole-modified pyrazole derivatives were synthesized. It was found that tert -butylcarbazole derivatives of TCPDP , TCPHP , TCPPM and TCPPF exhibited reversible mechanofluorochromic (MFC) behavior under the treatment of grinding/fuming with CH 2 Cl 2. Particularly, the emission of the as-synthesized crystals of TCPDP was weak and emerged in the ultraviolet region, while the grinding led to significant red-shift of the emission to the visible-light region, accompanied with the significant fluorescence enhancement on account of the formation of J -aggregates. Thus, TCPDP showed intriguing fluorescence switching in visible-light region during MFC processes, which could be easily observed visually. Additionally, TCPDP , TCPHP , TCPPM and TCPPF could form stable organogels in some organic solvents. Notably, the solutions of TCPPM and TCPPF were almost non-emissive, but gelation-induced blue emission was achieved. Thus, the fluorescence could be also turned on due to the AIE (aggregation-induced emission) during the gel formation. Graphical abstract Image 1 Highlights • New carbazole-modified pyrazole derivatives were synthesized. • Tert -butylcarbazole derivatives showed reversible mechanofluorochromism and good gelation abilities. • High-contrast mechanofluorochromism of TCPDP was achieved via fluorescence switching in visible-light region. • Gelation-induced emission of TCPPM and TCPPF was detected. [ABSTRACT FROM AUTHOR]

Abstract: Two new star-shaped difluoroboron β-diketonate complexes (TBC) 3 Ph and (TBF) 3 Ph, in which the terminal groups of triphenylamine functionalized difluoroboron β-diketonates were bridged by carbazole or fluorene to the core of 1,3,5-benzene, have been synthesized. It was found that they gave high molar extinction coefficients, meaning strong light-harvesting ability, and emitted intense yellow light with fluorescence quantum yields (Φ F) of 0.73 and 0.67 for (TBC) 3 Ph and (TBF) 3 Ph, respectively, in toluene as well as red light in solid states with Φ F of 0.36 and 0.27, respectively. The electrochemical behaviors suggested that they had considerably higher electron affinities than tris(8-hydroxyquinoline)aluminum (AlQ3), which indicated that they could be used as electron-transporting materials besides emitting materials. [Copyright &y& Elsevier]