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Perylene derivative with circularly polarized luminescence (CPL) at aggregated state was seldom reported due to the strong ACQ (aggregation-caused quench) effect at aggregation. In this work, a novel cholesterol-tetraphenylethylene-perylene derivative (TPE-P) was designed and synthesized in moderate yield. It exhibited liquid crystalline behavior with orderly hexagonal columnar mesophase and good fluorescence emission at long wavelength (600-700 nm) not only in solution but also at aggregated states based on the AIE (aggregation-induced emission)-FRET (fluorescence resonance energy transfer) effect between tetraphenylethylene unit and perylene moiety. Moreover, the circular dichroism (CD) and CPL studies suggested the effective chiral transfer from cholesterol unit to tetraphenylethylene unit and perylene skeleton due to the spiral liquid crystalline self-assembly. The CD and CPL signals showed the order of THF

The chiral transfer from the nucleus to the periphery was observed for constructing columnar liquid crystals with excellent circularly polarized luminescence.

A novel fluorescein-bridged perylene bisimide (PBI) dimer for liquid crystal (LC) with geometrically symmetric structure was developed. The mesomorphic results indicated that the energetically stable and unstable conformers of fluorescein fragments could lead to the transformation of mesophases from a hexagonal columnar mesophase to an uncertain phase at 136.9 °C in heating, whilst a stable hexagonal columnar mesophase maintained between 175.6 °C and 58.6 °C in cooling. The selectively excited fluorescence characters in THF solution demonstrated that the fluorescence resonance energy transfer (FRET) effect between fluorescein fragments and PBI unites could provide a means to effectively impose strong fluorescence of the dimeric PBIs modified with suitable chromophore at the N-imide position, which alternatively serves as a platform for the further study of multi-functional PBI-based LCs.

The detection of cytosine is of significance for analyzing DNA bases, but no “turn-on” fluorescent sensor for cytosine in aqueous media has been reported so far. In this study, series of diamino-bridged biphenyl acrylonitriles 3a–3c were designed and synthesized with yields of 70–75%. The sensing experiments for 16 types of ions and biomolecules suggested that compound 3b with butanediamino bridges exhibited good selective sensing abilities towards cytosine based on “turn-on” fluorescence enhancement. The detection limit of compound 3b for cytosine attained 1.02 × 10−7 M. The selective sensing ability towards cytosine was little influenced by other species and remained stable between pH = 6–9. The sensing mechanism was proposed by the analysis of Job's plot, 1H NMR and MS binding spectra. The sensing ability for cytosine was successfully used for analysing urine samples with the recovery over 94%. Sample 3b also exhibited good bioimaging performance with bright blue-green fluorescence for sensing cytosine, implying the application prospect in complicated and living environment.

This paper reported not only the first fluorescein liquid crystals but also revealed the influence of peripheral alkyl chains on mesomorphic properties and photophysical properties. Novel fluorescein-triphenylene dimers 4a–4f with different alkyl chains were designed and synthesised in yields of 76–83%. Samples 4a, 4b, 4c and 4d with CH3 and C4H9 exhibited the columnar mesophase but samples 4e and 4f with C8H17 showed no mesophase. The longer alkyl chains on fluorescein units resulted in the lower phase transition temperature. The too long alkyl chain destroyed the liquid crystalline behaviour. Their fluorescence quantum yields were as high as 0.78–0.87 in CH2Cl2 solution and 0.11–0.17 in solid states. The longer alkyl chains leaded to the higher emission efficiencies.

The design and synthesis of novel fluorescence sensors for Fe3+ in aqueous media have important prospects for practical applications. In this work, the novel bis-biphenylacrylonitrile bridged with crown ether chains 3a–3c were prepared in yields of 73–80%. Compounds 3a–3c exhibited high fluorescence in aqueous media based on the AIE effect. The sensing abilities for a series of metal ions suggested that the compound 3b possessed the selective detection for Fe3+ in aqueous media with strong fluorescence quenching. The detection limit of compound 3b for Fe3+ was 1.67 × 10−7 M and the sensing mechanism was proposed with the assistance of 1H NMR and MS studies. Compound 3b displayed excellent fluorescence imaging properties with a sensing ability for Fe3+ in living cell systems, indicating the good application prospect for sensing Fe3+ in aqueous media and complex environments.

Circularly polarized luminescence controlled by both mechanics and temperature was observed for the first time. The cyano-distyrylbenzene-cholesterol liquid crystals exhibited not only mechanochromism and thermochromism but also mechanically induced and thermally induced circularly polarized.

Although some sensors for Cu

In previous studies, the increasing alkyl length of liquid crystalline molecules enhanced the chiral transfer and resulted in better CPL performance. But no work concerned the influence of alkyl lengths on CPL properties for non-liquid crystalline systems. In this research, three R-binaphthol-based cyanostilbene derivatives with various alkyl chains (BC-5, BC-8 and BC-12) were prepared in yields of 60–69%. They did not exhibit liquid crystalline behavior but were seen as soft materials at room temperature. They displayed excellent AIE fluorescence in aggregated states. Chiroptical investigations suggested good CD and CPL properties for their cyanostilbene units, indicating the successful chiral transfer from the binaphthol moieties to cyanostilbene units. Moreover, the values of gabs for CD signals and glum for CPL signals displayed the changing order of BC-5 > BC-8 > BC-12. These results suggested that the shorter alkyl chains for non-liquid crystalline systems led to stronger CPL emission, which was opposite to the results of the liquid crystalline molecules. This work provided a new strategy for the design and synthesis of chiroptical materials with good CPL properties based on non-liquid crystalline molecules.

The influence of different states of AIE derivative with columnar liquid crystalline phase on circularly polarized luminescence (CPL) was investigated in this work. Two novel tetraphenylethylene derivatives with multiple cholesterol units (TPE-C and TPE-SC) were prepared. They exhibited enantiotropic liquid crystalline behaviours with the ordered hexagonal columnar mesophase. They possessed excellent AIE properties in H2O-THF system. The fluorescence quantum yields of TPE-C and TPE-SC at solid state were as high as 28.8% and 22.6%, respectively. The chiral transfer from cholesterol units to TPE cores was confirmed by CD spectra. The studies on CPL spectra suggested that their CPL behaviors were tuned by the different states. They showed weak CPL properties at solid and isotropic state but strong CPL luminescence at liquid crystalline phase based on the orderly columnar self-assembly. The glum of TPE-SC at liquid crystalline phase reached 8.83 × 10−2.

By the typical Knoevenagel condensation of Bodipy with aldehyde derivatives, two novel Bodipy derivatives 3 and 6 with symmetric three and six alkyl chains were designed and prepared. The Bodipy derivative 3 with three alkyl chains showed no mesophase but the Bodipy derivative 6 with six alkyl chains possessed the orderly hexagonal columnar mesophase at room temperature. Both samples 3 and 6 exhibited the near-infrared fluorescence with high fluorescence quantum yields and larger Stokes shifts than their Bodipy precursors. Sample 6 was the first near-infrared fluorescent columnar liquid crystal with Bodipy core. This research presented a good strategy on constructing the near-infrared columnar Bodipy liquid crystal.

Porphyrins had long been used as near-infrared-emissive fluorescent materials, but the aggregation-caused quenching (ACQ) of porphyrins limited their performance in fluorescence imaging. In this work, a novel porphyrin derivative with an aggregation-induced emission characteristic was synthesized by introducing four diphenylacrylonitrile units onto the porphyrin skeleton. The strong aggregation induced emission–fluorescence resonance energy transfer (AIE–FRET) effect was first observed for diphenylacrylonitrile units and porphyrin units. The novel porphyrin derivative exhibited not only strong fluorescence in both solution and the solid state, but also exhibited an excellent fluorescence imaging ability for living cells.

Circularly polarized luminescence (CPL) is important to chiral photonic technologies. In molecular systems, besides their intrinsic chemical structures, architectures of molecular assemblies at the mesoscopic scale also account for the final macroscopic CPL properties. Herein, tunable CPL responses can be induced through architectural regulation of these molecular assemblies in suspension and solid states. A liquid crystalline assembled system of DPCE-ECh exhibiting a smectic C* phase with a high dissymmetry factor (gCD = −0.20 and glum = +0.38) is reported. The intense and apparent CD and CPL of the film stem from the intrinsic helical structure of the molecular assembles with a weak contribution of Bragg reflection, where the helical axis is perpendicular to the optical axis and parallel to the direction of the glass substrate. To the best of our knowledge, this large glum factor is very rare for organic compounds even in the assembled state formed by annealing at the smectic liquid crystalline temperature. Interestingly, a strong CPL signal with a glum value of +0.18 is still recorded when DPCE-ECh is annealed in a chiral isotropic liquid (Iso*) state. On the other hand, DPCE-ACh can form two coexisting phases of chiral hexagonal and smectic liquid-crystalline phases due to intermolecular hydrogen bonding. The non-periodic molecular orientations of DPCE-ACh break its helical structure to give a weak negtive CPL signal of the order of 10−3. This work thus provides a new insight for developing efficient chiroptical materials in the aggregate state that have profound implications for high-performance CPL-based devices.

Porphyrins are good near-infrared fluorescent materials, but the strong self-assembly stacking resulted in the aggregation-caused quenching (ACQ) effect, limiting their emissive performance in aggregated states. In this work, a novel diphenylacrylonitrile-porphyrin derivative with multiple polyglycol chains on the periphery was designed and synthesized as an excellent near-infrared-emissive liquid crystalline material in both solution and aggregated states, which was first observed for porphyrin liquid crystals. It exhibited a high self-assembly ability with the ordered hexagonal columnar mesophase between 70 and 120 °C approximately. The strong AIE-FRET effect was produced based on the overlap of the emission wavelength of diphenylacrylonitrile and the absorption wavelength of the porphyrin, resulting in the excellent near-infrared emission in both solution and aggregated states. The pseudo Stokes shift was as large as 210 nm and the fluorescence quantum yield reached 0.12 in the solid state. Moreover, this porphyrin liquid crystal displayed low biotoxicity and excellent fluorescence bio-imaging ability in living cells, opening a new application prospect for porphyrin liquid crystalline materials.

Aggregation-induced emission (AIE) provides a new strategy for preparing fluorescent sensors in aggregated state. In this paper, a series of crown ether-bridged bis-tetraphenylethylene compounds were synthesized in 78-84% yield by a simple procedure. The molecules exhibited excellent AIE properties in THF/H2O solutions and solid films. The investigation on sensing abilities for various biomolecules and metal ions suggested that Bis-TPE-1 possessed obvious response to folic acid, with fluorescence enhancement and blue shift of maximum emission wavelength from 380 nm to 365 nm. The detection limit for folic acid was 6.36 × 10-7 M, and the sensor's selectivity for folic acid was little interfered by the other species. The sensor mechanism was studied by FT-IR, 1H NMR, MS spectra and fluorescence Jobs' plot. The selective sensor for folic acid was applied in test paper and the analyses of real samples of mung bean and spinach. The superior bioimaging performance of Bis-TPE-1 for sensing folic acid was confirmed by the live cell imaging experiments, which indicated its good practical application potential for detecting folic acid.

The sensor for thymine detection has a great significance in the analysis of deoxyribonucleic acid in living organisms. In this work, a series of bis-BODIPY derivatives, namely, 3a–3c with diamido bridges were designed and prepared in yields of 74–77% through a simple procedure. The sensing abilities of compounds 3a–3c for adenine, guanine, cytosine, thymine, glucose, urea and haemoglobin were examined by UV-vis and fluorescence spectra. Sample 3b was demonstrated to be a good selective sensor for thymine among all the other tested species. The detection limit of sample 3b was as low as 1.53 × 10−6 M for thymine. The competitive experiments suggested that the selective sensor for thymine was influenced slightly by the other species. The proposed sensing mechanism was confirmed by FT-IR, 1H NMR and MS spectra. Sample 3b exhibited good bioimaging performance with bright green fluorescence in living cell imaging. The significant fluorescence quenching phenomenon after the addition of thymine implied the sensing ability of sample 3b for thymine in living cells.

A series of novel tetraphenylethylene aromatic acylhydrazone derivatives 11, 12 and 13 with 4, 8 or 12 alkyl chains were designed and synthesized in yields of 82–85%. Studies on the mesomorphic properties suggested the ordered hexagonal columnar mesophase for compounds 11, 12 and 13. The increase in the number of alkyl chains was favourable for decreasing the phase-transition temperatures and extending the mesophase temperature range. Further, samples 11, 12 and 13 presented an excellent AIE effect. The fluorescence intensities increased by 70, 84 and 43 times for samples 11, 12 and 13, respectively. The absolute fluorescence quantum yields were 18.7%, 27.4% and 23.8% in solid films at room temperature and 6.7%, 24.2% and 17.3% in the mesophase. These results suggested that the number of alkyl chains greatly influenced the fluorescence emission and sample 12 with 8 alkyl chains exhibited the strongest fluorescence emission. Sample 12 also displayed the electroluminescence performance on OLED device.

Three novel rufigallol derivatives with four alkyl chains and two cholesteric units 6a, 6b and 6c were prepared in yields of 83–88%. The mesomorphic properties were investigated by DSC, POM and XRD analysis, suggesting that compounds 6a, 6b and 6c possess the ordered hexagonal columnar mesophase. The long alkyl chains contribute to the low phase transition temperature. Sample 6c with four dodecyl chains and two cholesterol units is a room temperature liquid crystal between 31°C and 87°C. Compounds 6a, 6b and 6c also have good fluorescence emission between 400 nm and 500 nm. The studies on CD spectra implied that the chiralities of cholesterol moieties are successfully transferred to the liquid crystalline core. Samples 6a, 6b and 6c are the first fluorescence liquid crystal based on rufigallol core with chiral cholesterol units.

This work focused on design, synthesis and application of an AIE and FRET-based BODIPY pH sensor bearing large Stoke shift. The cyano-diphenylethylene- conjugated BODIPY derivative 4 was prepared by condensating 4-hydroxybenzene acetonitrile with 4-(diethoxymethyl)benzaldehyde and then following the typical procedure of synthesizing BODIPY derivative. Compound 4 exhibited strong fluorescence in all kinds of THF/H2O solutions due to the AIE and FRET effect. The Stoke shift of compound 4 was as large as 138 nm based on the excitation of cyano-diphenylethylene moiety and the emission of BODIPY moiety. Compound 4 showed good fluorescent response to the change of pH with the pKa value at 9.79. The mechanism of compound 4 as pH probe was confirmed by 1H NMR spectra and theoretical calculation. Compound 4 was successfully used to CO32− detection among 13 kinds of common anions both in solution and by tested strips. The experiments of living cell imaging suggested that compound 4 possessed superior bioimaging performance and presented sensitive change to pH values between 9 and 10 in living cells.

Although some reports on sensing ClO

Although various AIE liquid crystals have been studied, AIE ionic liquid crystals (ILCs) are almost unknown to date. In this work, a series of novel AIE ILCs based on diphenylacrylonitrile-imidazole salts bridged by soft spacers with different anions were prepared in yields of 63-80%. The mesomorphic, photophysical and electrochemical properties were investigated systematically to elucidate the relationship between structures and properties. The results implied that they were the first room-temperature AIE ILCs with wide ranges of mesomorphic temperature, good fluorescence emission in both the solid state and mesophase, and stable electrochemical behaviour. The samples with one alkyl chain possessed the SmA2 mesophase while the samples with two alkyl chains prefered the Colh mesophase. The larger anions resulted in the bigger layer spacing length for the SmA2 mesophase and smaller values of ncell in each slice of Colh mesophase. The fluorescence quantum yields in the mesophase maintained reasonable values (0.15-0.22), which decreased a little in comparison with that in solid films (0.18-0.26) due to the orderly molecular stacking in the mesophase. The cyclic voltammetry experiments confirmed that all of them possessed similar and stable electrochemical behaviour. This research not only presented the first room-temperature AIE ILCs with excellent mesomorphic, photophysical and electrochemical properties, but also elucidated the relationship between structures and properties to a certain degree, contributing to the further construction of novel AIE ILCs with excellent mesomorphic, photophysical and electrochemical properties.

This work reported two novel liquid crystals with good fluorescence in aggregated states. Two tetraphenylethylene-rufigallol-tetraphenylethylene trimers (compounds 6a and 6b) were prepared in simple procedure. The columnar liquid crystalline behaviors of 6a and 6b were confirmed by the analysis of differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction. Compound 6b exhibited an ordered hexagonal columnar mesophase. They possessed excellent AIE fluorescence properties in THF-H2O solution, solid film and mesophase. The fluorescence quantum yields of compounds 6a and 6b were 12% and 22% in solid films, 14% and 24% in mesophase, respectively. The experimental results showed that the liquid crystalline properties and fluorescence properties were tuned by the lengths of the terminal alkyl chains.

The selective detection of salicylaldehyde skeleton is of great significance in phytochemistry and biological research but rarely reported. In this research, a simple and highly selective “turn-on” fluorescence sensor (CDB-Am) for salicylaldehyde skeleton was developed based on switch of photoinduced electron transfer (PET) and aggregation-induced emission (AIE). CDB-Am bearing amino-cyanodistyrene structure responded to salicylaldehyde in the range of 3.1 to 40 μM with a detection limit of 0.94 μM. The sensing process of formation of Schiff-base adduct CDB-SA was confirmed by 1H NMR, MS, and FT-IR spectra, revealing that a recovered AIE property accounted for the turn-on fluorescence response of CDB-Am and the intramolecular hydrogen bonding played a crucial role in the disruption of PET process. This sensing ability was successfully applied for both fluorescence qualitative test of salicylaldehyde skeleton on TLC analysis and quantitative detection of salicylaldehyde skeleton with good accuracy in the root bark of Periploca sepium, suggesting the extensive applications in phytochemistry and traditional Chinese herbal medicine. Furthermore, CDB-Am exhibited the first excellent fluorescence imaging ability in detecting salicylaldehyde skeleton in a living system. This work supplied a new strategy of preparing a novel “turn-on” fluorescence probe for detecting salicylaldehyde skeleton in complex environments and living bodies.

Previously reported fluorescent sensors for Th

This paper reported the first triphenylene-fluorescein-triphenylene trimers (3a and 3b), which exhibited stable hexagonal columnar mesophase and good fluorescence in comparison with the similar triphenylene-fluorescein dimers. The trimers 3a and 3b bridged by -C3H6- and -C6H12- group were conveniently prepared in yields of 67% and 73%. They exhibited the stable hexagonal columnar mesophase, high fluorescence quantum yields, and the large Stokes shifts due to the influence of two triphenylene units. The highest fluorescence quantum yield attained 0.91 for 3b and the largest Stokes shift reached 105 nm for 3a. This work revealed that trimers were a good strategy to construct novel columnar liquid crystals with stable columnar mesophase and high fluorescence.

The multiple BODIPY derivatives could exhibit higher fluorescence than mono-BODIPY derivatives but also might produce the stronger aggregation-induced quenching effect. It is important to investigate the relationship between fluorescence and numbers of BODIPY units. In this work, series of multiple BODIPY derivatives 2–5 with 1,3,5-triazine as core were designed and synthesized in high yields. A subtle balance between the fluorescence enhancement of multiple BODIPY units and fluorescence quenching based on H-aggregation of multiple BODIPY units was observed for these multiple BODIPY derivatives. Compound 3 bearing two BODIPY units with triazine as core presented the strongest fluorescence emission and highest fluorescence quantum yield. Compound 3 was successfully applied in viscosity measurement, exhibiting the linear relationship between fluorescence intensity (or steady-state emission anisotropy) and viscosity.

By step-by-step etherification on cyanuric chloride with BODIPY unit and cholesterol units, two novel cholesterol-triazine-BODIPY trimers (compounds 6 and 7 with one and two cholesterol unit, respectively) were designed and synthesized in high yields. The investigation on mesomorphic properties suggested that compound 6 with one cholesterol unit was a nematic liquid crystal but compound 7 with two cholesterol units was a hexagonal columnar liquid crystal. Both compounds 6 and 7 exhibited the strong fluorescence with high quantum yields and larger Stokes shifts than their precursors. The cholesterol-triazine moiety played crucial role for producing liquid crystalline property and enhancing fluorescence.

The first perylene liquid crystals bearing six peripheral alkyl substituents on both 1,6,7,12-bay positions and imides positions were designed and synthesized in yields of 72–77%. The studies on their mesomorphic behaviors suggested that they possessed good ordered hexagonal columnar mesophase with low phase transition temperatures and wide ranges of mesophase temperature in comparison with their precursors with chloric groups and the similar perylene liquid crystal with 4-tert-butylphenolic groups on bay positions. Their photophysical properties revealed that they also had higher fluorescence intensities and fluorescence quantum yields than that of their precursors with chloric groups and the similar perylene liquid crystal with 4-tert-butylphenolic groups on bay positions. The good fluorescence in both solution and solid film were observed for the first time for perylene liquid crystals. This research indicated that the introduction of long p-nonylphenol units on bay position is an effect strategy to obtain perylene liquid crystal with good liquid crystalline behavior and excellent fluorescent property.

Series of novel CTV derivatives with one, two and three triphenylene units were designed and synthesized via click reaction in 72–84% yields. The influences of the numbers of triphenylene units on mesomorphic behaviors were investigated. The results suggested that one triphenylene unit could not counteract the rigidity of CTV skeleton, resulting in no mesophase for CTV derivative 6 with one triphenylene unit. The strong induction of more triphenylene units leaded to the mesophase for CTV derivative 7 with two triphenylene units and 8 with three triphenylene units. The more triphenylene units decreased the phase transition temperatures. The XRD analysis suggested that compound 8 possessed higher ordered hexagonal columnar mesophase than compound 7, implying that the more triphenylene units were favorable for improving the structural symmetry and produced the ordered columnar stacking. Compound 8 was the first example of high ordered hexagonal columnar liquid crystalline molecule based on CTV skeleton.

Herein, a series of mesogenic perylene bisimide (PBI) dyes including 1,6,7,12-tetrachloroperylenebisimides 11a, 11b and 11c with 2, 4 and 6 peripheral alkyl chains at the imide positions and 1,6,7,12-tetra-p-nonylphenol bay-substituted perylene bisimides 12a, 12b and 12c with 6, 8 and 10 peripheral alkyl chains at both the imide and bay-positions were synthesized and characterized. The influence of multiple peripheral alkyl chains on the mesomorphic and photophysical properties was investigated. The results suggested that all of them possessed hexagonal columnar mesophases. The presence of more alkyl chains contributed to lower phase transition temperature and more orderly hexagonal mesophases. These novel perylene liquid crystals exhibited excellent fluorescence properties with fluorescence quantum yields of 0.90–0.96 in solution. The compounds 12a, 12b and 12c presented larger Stoke shifts and higher ΦF values than the compounds 11a, 11b and 11c; this indicated that more peripheral alkyl chains at both the imide and bay-positions contributed to the excellent fluorescence properties in both solution and thin films.