•A dithienopyrrole-based triphenylamine luminogen has been synthesized.•It exhibits reversible mechanochromic luminescence in the solid state.•The oxidized species show redox-switchable near-infrared absorptions in solution.•There exists considerable electron delocalization during the oxidation process.A dithieno[3,2-b:2′,3′-d]pyrrole-based luminogen 1 has been synthesized by appending two twisted triphenylamine units to the rigid conjugated dithieno[3,2-b:2′,3′-d]pyrrole core. This compound exhibits reversible mechanochromic luminescence in the solid state and near-infrared electrochromic switching behavior in solution. A reversible switching in fluorescence color between yellow-green and green can be observed through mechanical grinding and vapor fuming of solid powdered 1, which involves an interconversion between a crystalline form and an amorphous phase according to X-ray diffraction analysis. The associated oxidized species of 1 show intense redox-switchable near-infrared absorption and different fluorescence colors in solution in spectroelectrochemical and luminescence measurements. Density functional theory calculations have confirmed that there is considerable electron delocalization between the dithieno[3,2-b:2′,3′-d]pyrrole linker and two triphenylamine redox-active termini during the oxidation process.A dithieno[3,2-b:2′,3'-d]pyrrole (DTP)-based derivative has been synthesized by introducing a twisted triphenylamine (TPA) unit to the rigid conjugated DTP core. This compound exhibits reversible mechanochromic luminescence and near-infrared electrochromic switching behaviors in solid state and solution, respectively.

Formaldehyde, as one of the simplest reactive carbonyl species (RCS), is regarded as a potential carcinogen and a sick house syndrome gas. Recent studies have shown that abnormally high levels of formaldehyde may result in cognitive decline and spatial memory deficits, asthmatic symptoms, Alzheimer’s disease, and cancer. Due to the harmfulness of high levels of formaldehyde in nature and humans, it is of great significance to further elucidate the roles and functions of formaldehyde by a non-invasive detection approach. Fluorescence imaging has become a powerful and popular tool in monitoring bio-species owing to their high sensitivity and selectivity, excellent spatiotemporal resolution and non-invasion nature. Therefore, fluorescent probes are widely applied to track and detect formaldehyde in vitro and in vivo which have attracted more and more interest recently. This review focuses on various strategies to design the fluorescent probes for detecting formaldehyde based on different recognition groups.Formaldehyde is one of the simplest reactive carbonyl species. In view of the harmfulness of formaldehyde in nature and humans, it is of great significance to further elucidate roles and functions of formaldehyde by a noninvasive detection approach. Fluorescent probes have become a popular tool to track and detect formaldehyde in vitro and in vivo, which have attracted more and more interest recently. This review focuses on various reaction mechanisms to design the fluorescent probes for detecting formaldehyde.Download high-res image (85KB)Download full-size image

Developing the novel fluorescent dyes with a larger Stokes shift is still a challenge in the research of fluorescence probes. In this work, a naphthalimide-modified near-infrared cyanine dye with an emission at 785 nm has been synthesized for lysosome-targeting imaging. This fluorescent dye showed a large Stokes shift (up to 165 nm) and favorable lysosome-targeting property, which facilitated it to be a potential candidate for studying of lysosomal functions. The result also indicated that the probe is a promising contrast agent for in vivo imaging in mouse models.A naphthalimide-modified near-infrared cyanine dye (emission at 785 nm) with a large Stokes shift (up to 165 nm) has been synthesized and had favorable lysosome-targeting property.Download high-res image (118KB)Download full-size image

•Four oligomeric triarylamine compounds have been synthesized.•They all exhibit fascinating redox-tuned multiple NIR absorption characteristics.•They all exhibit completely reversible multicolor electrochromic behaviors.•All the associated mono-cations could be classified as moderately-coupled Robin–Day class II mixed-valence systems.Four oligomeric triarylamine compounds (diamine 1a, triamine 1b, tetramine 1c and pentamine 1d) were prepared and characterized by 1H NMR, mass spectrometry and elemental analysis. The combined results of cyclic voltammetry, square-wave voltammetry and UV–vis–NIR spectroelectrochemistry, as well as density functional theory, reveal that compounds 1a–1d display two to five steps of oxidation processes, respectively, and the ΔE1/2 and Kc values were still remarkable for the relatively long pentamine, though they all decreased with an increase of the triphenylamine unit. These four compounds all exhibit fascinating redox-tuned multiple NIR absorption characteristics, and a completely reversible multicolor electrochromism for each of them could be synchronously realized. The associated mono-cationic [1a]+–[1d]+ could be classified as moderately-coupled Robin–Day class II mixed-valence systems, which could be stabilized by spin delocalization over at least two adjacent amine units.Four oligomeric triarylamine compounds were prepared. These four compounds all exhibit fascinating redox-tuned multiple NIR absorption characteristics, and a completely reversible multicolor electrochromism for each of them could be synchronously realized. All the associated mono-cations could be classified as moderately-coupled Robin–Day class II mixed-valence systems, which could be stabilized by spin delocalization over at least two adjacent amine units.Download high-res image (334KB)Download full-size image

Molecular recognition based on hydrogen bond interaction plays a significant role in supramolecular self-assembly. In this work, we successfully developed a class of novel frameworks containing a urea in the recognition site and a carboxylate anion in the guest unit. The self-recognition model based on the interaction between urea and carboxylate anion could induce the molecules to assemble into a highly organized form. The crystal structures showed that they assembled in highly ordered two-dimensional architectures. The optical properties showed that the position of carboxylate anion on the diphenylacetylene backbone had an obvious influence on optical properties. The self-recognition strategy is useful for the construction of highly ordered self-assembled architectures.Download high-res image (193KB)Download full-size image

•A hemicyanine-based ratiometric fluorescent probe was synthesized.•The probe showed a high selectivity towards cysteine.•The probe was capable to selectively visualize the cysteine of living cell.A new ratiometric fluorescent probe based on a hemicyanine dye was synthesized. Investigation on the response behavior towards amino acids showed that the probe had a capability of rapidly and selectively detecting cysteine over other biothiols such as glutathione and homocysteine with similar structure and reactivity, and it also displayed a high selectivity and rapid response. Moreover, the probe had good water solubility, which authorized it could be applied in fluorescent bioimaging. The laser confocal fluorescence images indicated that the probe could visualize the intracellular cysteine. This work suggested that it could be utilized as a fluorescent indicator to discriminate the endogenous cysteine in living cells.Download high-res image (225KB)Download full-size image

AbstractTwo star-shaped molecules with benzene core and three naphthalene diimide (NDI) side arms were facilely prepared by two-step imidization reaction from the 1,4,5,8-naphthalenetetracarboxylic dianhydride. Two compounds showed the similar UV–vis absorption band as well as NDI. It was found that they displayed bathochromic shift of their UV–vis absorption and emission spectra in film compared with that in solution, ascribing to the aggregation between molecules in the solid state. Reversible reduction process was observed by cyclic voltammetry and low lying LUMO energy levels (−3.83 eV for 1a, −3.87 eV for 1b) were deduced, which suggest that these two compounds possessed good electron-acceptor property and can be used as potential n-type materials.

A fluorescent sensor for halogenated solvents termed AMN is reported. AMN shows strong fluorescence in most halogenated solvents (QE > 0.1) but weak fluorescence (QE<0.01) in most non-halogenated solvents. In chlorinated solvents, the fluorescence intensity decreased with the reduction of chlorine content. On the contrary, in brominated solvents the fluorescence intensity increased with the reduction of bromine content. It is worth mentioning that AMN displayed fluorescence emission centered at 520 nm in CCl4 with a quantum yield of 0.607, at 556 nm in CHCl3 with a quantum yield of 0.318, at 584 nm in CH2Cl2 with a quantum yield of 0.128, whereas in CHBr3 was centered at 441 nm with a quantum yield of 0.012. AMN was shown to have the ability to differentiate CCl4, CHCl3, CH2Cl2 and CHBr3 halogenated solvents.

A novel naphthalimide-based fluorescent probe employing a sulfonamide unit as a thiol-responsive group is reported. It is capable of efficiently distinguishing GSH from cysteine and homocysteine. Bioimaging shows that it has high selectivity in living cells and can visualize the level of GSH in lysosomes. It is worth mentioning that different groups on the imide unit can affect the selectivity and reaction dynamics of the probe towards thiols.

•Cyanine IR-780 can distinguish 2-amino thiophenols from position isomers.•The complex system of 2-amino thiophenol and IR-780 can be used to selectively detect the glutathione.•It was successfully applied to the imaging of 2-amino thiophenol and glutathione in living cells.Developing highly selective fluorescent probes for the determination of thiophenol is very significant due to its toxicity influence in biological system. In this work, we firstly found that the commercial available cyanine dye 3H-Indolium, 2-(2-(2-chloro-3-(2-(1,3-dihydro-3,3-dimethyl-1-propyl-2H-indol-2-ylidene)ethylidene)-1-cyclohexen-1-yl)ethenyl)-3,3-dimethyl-1-propyl-, iodide had a remarkable capability of determining the amino-substituted thiophenols. Especially, the 2-amino thiophenol induced a fluorescence change of this cyanine dye with the largest intensity in comparison to the 3- and 4-amino thiophenols, implying Cyanine IR-780 can distinguish 2-amino thiophenols from position isomers. Despite the 2-amino thiophenol quenched the fluorescence of cyanine dye, their complex system further played a role in detecting the glutathione with high selectivity over cysteine and homocysteine. It was worth mentioning that similar selectivity can also be observed in living cells.The commercial available cyanine dye (IR-780) had a remarkable capability of determining the amino-substituted thiophenols. Cyanine IR-780 can distinguish 2-amino thiophenols from its position isomers. Moreover, the complex system of 2-amino thiophenol and the fluorescence IR-780 played a role of detecting the glutathione (GSH) with high selectivity over cysteine (Cys) and homocysteine (Hcy).

A novel ammonium template containing three ammonium sites was synthesized. Two ammoniums located on the linear component served as template for cucurbit[6]uril to form the CB-based pseudo[2]rotacane while another one located on the macrocyclic component played a role of template for clipping reaction. As a result of a “threading-followed-by-clipping” approach, a novel hetero pseudo[2]rota[2]catenane was successfully constructed.A hetero pseudo[2]rota[2]catenane with novel topological structure was constructed by use of a “threading-followed-by-clipping” approach.

A new fluorene-based AIE-active gold(I) complex was designed and synthesized. The novel luminogen exhibits a crystallization-induced emission enhancement (CIEE) effect and reversible mechanochromic behavior with fluorescence changes between green and yellow emissions.

Hydrogen sulfide (H2S) is considered as the third signaling molecule in vivo and it plays an important role in various physiological processes and pathological processes in vivo, such as vasodilation, apoptosis, neurotransmission, ischemia/reperfusion-induced injury, insulin secretion and inflammation. Developing a highly selective and sensitive method that can detect H2S in the biological system is very important. In this work, a colorimetric and “turn-on” fluorescent probe is developed. Furthermore, this probe displays a highly selective response to H2S in aqueous solution and possesses good capability for bioimaging H2S without interference in living cells. The results suggest that a H2S-selective probe has good water-solubility, biocompatibility and cell-penetrability and can serve as an efficient tool for probing H2S in the cell level.

Tetraphenylethene (TPE) with aggregation-induced emission (AIE) behavior as a popular backbone is applied widely in the construction of functional supramolecular systems. In this work, a TPE-based linear molecule having amide and amine units is synthesized. Its ammonium template is used to construct the N-hetero crown ether-based [2]rotaxane by the template-directed clipping approach. Their structures are well-characterized by NMR, MALDI-TOF-MS and elemental analysis. Owing to the existence of the amide unit, [2]rotaxane possesses the function of a molecular shuttle. The shuttling motion of the macrocycle component between the ammonium station and the amide station can be driven by external acid–base stimuli in solution, accompanied by changes in visual behavior. Investigation on their AIE behavior shows that (1) ammonium reaches the aggregation state almost in the presence of same water with the deprotonated form of ammonium; (2) the [2]rotaxane that the macrocycle component locates at the site of ammonium forms the aggregation state in the presence of less water than the deprotonated [2]rotaxane that the macrocycle component locates at the site of the amide, attributed to stronger interaction between the crown ether component and the TPE unit of the template component when the distance between the two is shorter. The result indicates that the shuttling motion of the macrocycle component can adjust the aggregation state of AIE molecules.

Mechanically interlocked structures such as rotaxanes and catenanes provide a novel backbone for constructing functional materials with unique structural characteristics. In this study, we have designed and synthesized a series of photoswitchable rotaxanes and catenanes containing photochromic dithienylethene fragments using a template-directed clipping approach based on dynamic imine chemistry. Their structures have been confirmed using NMR, mass spectrometry and elemental analysis. Investigations into their photoisomerization properties indicated that these dithienylethene-based mechanically interlocked molecules have good reversibility and excellent fatigue resistance upon irradiation with UV or visible light. Interestingly, the mechanically interlocked molecules containing two dithienylethene backbones display around a 2-fold increase in the molar absorption coefficient compared with that of the mono dithienylethene derivative. Furthermore, the introduction of the fluorophore pyrene in the dithienylethene component facilitates these molecules to serve as fluorescent switches.

A new carbazole-based mononuclear gold(I) complex was designed and synthesized. The novel luminogen shows significative solid-state reversible mechanochromism, dual-responsive thermochromism and sensitive thin-film vapochromism properties. In addition, we obtained two kinds of crystals of the luminogen that may explain these interesting characteristics.

A series of novel [n]rotaxanes based on a tetraphenylethene (TPE) backbone were constructed by a template-directed clipping approach and their structures were well-characterized. Investigation of their optical properties showed that these rotaxanes and their corresponding ammonium salts showed aggregation-induced emission (AIE) behavior. However, there were obvious differences as follows: (1) rotaxanes reached the aggregation state in the presence of less water compared with the corresponding ammonium salt; (2) the rotaxanes with a long alkoxyl chain on the pyridine unit of the crown ether formed the aggregation state in the presence of less water than for those without an alkoxyl substituent and (3) a smaller distance between the TPE unit and N-hetero crown ether component resulted in the aggregation state being reached more easily than when there is a longer distance. The results suggest that the mechanically interlocked structures can adjust the aggregation state of AIE molecules.

•Two sulfonamide and urea-based compounds were successfully constructed.•They showed high selectivity towards cyanide and fluoride ions in CH3CN.•They only exhibited large changes in fluorescence in the presence of cyanide ions in CH3CN–H2O (95:5, v/v).•The compound having long alkoxyl chains could form a gel in DMSO.The detection of anions has attracted considerable interest because of their importance in various physiological processes. In this study, two sulfonamide and urea-based compounds (1a and 1b) were successfully developed and their spectroscopic and anion recognition properties were fully investigated. These results showed that: (1) compounds showed high selectivity towards cyanide and fluoride ions in CH3CN; (2) compounds only exhibited a large change in fluorescence in the presence of cyanide ions in CH3CN–H2O (95:5, v/v); and (3) compound 1b could act as a gel in dimethyl sulfoxide that transforms into a homogeneous solution upon exposure to cyanide ions. This research suggests that sulfonamide and urea can act as hydrogen-bond donors and provides an alternative approach to the design of novel anion chemosensors.Two sulfonamide and urea-based compounds were successfully developed and their spectroscopic and anion recognition properties were fully investigated. This research suggests that sulfonamide and urea can act as hydrogen-bond donors and provides an alternative approach to the design of novel anion chemosensors.

•A series of luminogens containing formamide or fluorenone units, based on fluorene, have been synthesized.•Fluorene-based luminogens with formamide units exhibited aggregate fluorescence change.•Fluorene-based luminogens with fluorenone unit exhibited AIEE characteristics.A series of luminogens containing formamide or fluorenone units, based on fluorene, have been synthesized and characterized by NMR spectroscopy, mass spectrometry and elemental analysis. Their aggregate fluorescence change and aggregation-induced emission enhancement (AIEE) characteristics were investigated by luminescence and UV/Vis spectroscopies. The results indicate that luminogens 1d and 2d, containing formamide units, exhibit significant fluorescence color changing upon aggregate formation, which is a newly observed uncommon and interesting aggregation-induced emission phenomenon. Although the luminogen 3d, with one fluorenone unit and one fluorene unit, was weakly emissive in solution, it was highly fluorescent in the aggregated state and demonstrates typical AIEE characteristics. In comparison with 3d, the luminogen 4d with one fluorenone unit and two fluorene units showed weaker AIEE behavior. In thin-films and in the solid state, luminogen 1d shows intense yellow-green emission, and other luminogens show strong yellow emitting. Among these luminogens, 4d exhibits the highest solid-state emission quantum yield.Fluorene-based luminogens with formamide units exhibited fluorescence change of aggregate formation, which is an uncommon and novel aggregation-induced emission phenomenon. Fluorene-based luminogens with fluorenone unit exhibited AIEE characteristics.

•Some dithienylethenes with different aromatic carbons were efficiently synthesized using a four-component Ugi reaction.•The dithienylethene derivatives exhibited photochromism and fluorescence switchable behavior.•The anthracene or pyrene-based dithienylethene derivatives exhibited high selectivity towards iodide or fluoride.A series of novel dithienylethenes with different aromatic carbons were efficiently synthesized using a four-component Ugi reaction and their structures confirmed by NMR spectroscopy, mass spectroscopy (MS) and elemental analysis. Their photochromic properties and fluorescence behaviors have been measured upon irradiation with UV light in solution. Investigations on their photochromic properties indicated that the dithienylethene derivatives had good reversibility upon irradiation with UV or visible light. In addition, they displayed excellent fluorescence switchable behavior. It was found that the degree of conjugation in the aromatic ring had a great effect on their photochromism and fluorescence properties. Moreover, the anthracene-based dithienylethene derivatives displayed high selectivity towards iodide and the pyrene-based dithienylethenes derivatives could act as a colorimetric fluoride sensor.A series of novel dithienylethenes with different aromatic carbons were efficiently synthesized using a four-component Ugi reaction. The dithienylethene derivatives exhibited photochromism, fluorescence switchable behavior and high selectivity towards iodide or fluoride.

Photochromic materials have been widely used in many fields such as electro-optical functional materials and novel bio-materials. In this study, six cyanine-based dithienylethene compounds were successfully developed, and their photoisomerization and emission change properties were fully investigated. The results indicated that the UV/vis absorption of pyridinium-based compounds displayed near-infrared absorption, while their fluorescence showed quenching emission as a result of the changes in structure from open-ring isomers to closed-ring isomers. Therefore these cyanine-based compounds could be applied not only in photochromic materials, but also they could be used as fluorescence switches. Accordingly, one of these compounds was successfully used in the biological imaging of living cells. These results suggest that cyanine-based dithienylethenes may be used as photoswitchable bio-materials in the future.

In this paper, seven carbazole-based mononuclear gold(I) complexes with alkyl chains of different lengths have been synthesized and reported. All of these gold(I) complexes exhibit outstanding AIE characteristics. Furthermore, these various solid-state light-emitting AIE-active gold(I) complexes all show reversible mechanochromic fluorescent behaviors. The possible mechanism explaining these interesting AIE and mechanochromism phenomena involves a variation in weak multiple intermolecular C–H⋯F and π⋯π interactions and the formation or alteration of aurophilic interactions.

Copper is a crucial transition metal ion that plays an essential role in environmental, biological, and chemical systems. Therefore an efficient method for detection of copper ions is significant. In this work, a sulfonamide-based probe containing a dansyl fluorophore was synthesized in good yield. This probe exhibited good selectivity and sensitivity for copper ions in aqueous solution without any interference from other metal ions. And it displayed a very low detection limit (2.91 × 10−8 M) for Cu2+, which supported its further application in bioimaging. Its good water-solubility, bio-compatibility and cell permeability leads it to be employed as an efficient biomarker to monitor the level of Cu2+ in living cells. The binding model between fluorescent probe and Cu2+ was evaluated by density functional theory calculations.

Three new triazole-bridged dithienylethene compounds with pyrene or benzene units were synthesized using the azide alkyne Huisgen cycloaddition reaction. Their structures were well characterized by NMR spectroscopy and mass spectrometry. UV/Vis absorption spectra and fluorescence spectra indicated that these dithienylethene compounds displayed obvious photochromism and fluorescent switch properties. The open-ring isomer of compound 1 with two pyrene subunits showed intramolecular pyrene excimer fluorescence which arises from intramolecular association of two pyrene units, in contrast to compound 2 with one pyrene subunit.

A cyanine-based dithienylethene is developed. Its photoisomerization shows that (1) the irradiation of visible light can induce cyclization while the cycloreversion takes place upon irradiation with UV light and (2) the addition of CN– can lead to cyclization and cycloreversion upon irradiation of UV light and visible light, respectively.

Dinaphthothiophene has been reported as a promising p-type semiconductor. The development of high-performance n-type semiconductors is highly desirable. The introduction of an imide group into polycyclic aromatic hydrocarbons can lower their LUMO levels to meet the basic requirement of n-type organic semiconductor materials. In this work, we have synthesized four imide-modified dinaphthothiophenes and dinaphthothiophenedioxides. Their optoelectronic properties have been investigated. Their low-lying LUMO levels make them potential n-type semiconductor candidates.

A new fluorene-based white light-emitting gold(I) complex with aggregate fluorescence change is reported. The novel luminogen emits direct white light in the solid state without involving complex doping/mixing procedures.

The construction of novel mechanically interlocked structures has become a topic of great current interest due to the requirements of topology and their potential application in molecular machines and devices. Rotaxane and catenane as two basic topological frameworks can be used to construct the fused structures. In the current investigation, a class of novel ammonium backbones were synthesized. The ammonium group incorporated in the linear part of the molecule can be used for templating rotaxane formation while the macrocyclic part of the molecule can be used for templating catenane formation. Accordingly, they were subjected to dynamic covalent chemistry, resulting in a series of [n]rota[n]catenane structures (n = 2, 3, 4). In this process, the N-hetero crown ethers were installed on ammonium template sites of linear and macrocyclic components all at once by a template-directed clipping reaction. The results showed that these novel building blocks could be assembled with high efficiencies. Finally, this investigation provides a foundation for future studies aimed at constructing complicated integrated structures or polymers with multiple topological units.

The photochromic materials have been widely applied in many fields. In this article, we report a class of photochromic ammoniums with a dithienylethene backbone. They were utilized as templates to construct mechanically interlocked rotaxanes and pseudorotaxanes showing photo-responsive behavior by template-directed clipping reaction and the threading approach. The structures of novel rotaxanes were well defined. It is worth mentioning that the single crystal structure of [3]rotaxane containing two N-hetero crown ether units was obtained. Their photoisomerization behavior was investigated. These N-hetero crown ether-based rotaxanes displayed good reversibility and similar photochromic behaviors to their corresponding ammoniums when they underwent UV/vis photoirradiation. Interestingly, the cucurbit[6]uril-based pseudorotaxane showed better photoisomerization than its corresponding ammonium and those of N-hetero crown ether-based rotaxanes.

A series of novel dithienylethene-based macrocycles containing ammonium moieties has been synthesized. They have been employed as templates to construct [2]catenanes showing their photoisomerization properties by means of a dynamic covalent chemistry approach. Their structures have been reliably confirmed by NMR, ESI-MS or MALDI-QTOF-MS, and elemental analysis, and their energy-minimized structures of open- and closed-ring isomers were investigated by the theoretical calculation. Investigation of the photochromic properties of these dithienylethene-based [2]catenanes has revealed good reversibility and excellent fatigue resistance upon irradiation with UV or visible light. Notably, formation of the [2]catenanes enhanced the photochromic properties compared with those of the corresponding macrocyclic ammonium salt, implying that the non-covalently interacting components of the [2]catenanes could affect the photoswitchable properties.

Imide-modified polycyclic aromatic hydrocarbons can be widely applied in the field of optoelectronic materials. In this work, we have synthesized four novel functionalized benzopicenes and characterized their solid structures and optoelectronic properties. The fluorescence of the four functionalized benzopicenes showed red shifts with increasing solvent polarity; the quantum yields are high in the solution state and moderate in the solid state. The single crystal structures show that the benzopicenes adopt a lamellar motif π-stacking. Their good solubility and optoelectronic properties make them potential solution-processable candidates for organic devices, bioimaging and biolabeling.

We report a structurally simple 1,8-naphthalimide-based fluorescent molecule. Its solid shows an intense blue emission with an absolute fluorescence quantum yield of up to 82.33%. The novel luminogen exhibits reversible thermochromism and vapochromism behaviors.

Three fluorinated 1,8-napthalimides were synthesized from acenaphthene. Their structures were characterized by NMR and EI-MS analyses. The structures of compounds 1b and 1c were also confirmed by X-ray diffraction analysis, which showed that they possessed different packing models. Their optoelectronic properties were investigated. The results indicated that all of the naphthalimides possess good solubility and low LUMO energy level, which make them good solution processing candidates in n-type semiconductor.Three fluorinated 1,8-napthalimides were synthesized from acenaphthene. All of naphthalimides are solution processing candidates in n-type semiconductor.

A series of dendritic ammonium salts have been designed and synthesized. Subsequently, they were used to construct the corresponding [2]rotaxanes by a template-directed clipping approach. Unusually, two unsymmetrical dendritic [2]rotaxanes containing fluorophore (pyrene units) were also obtained; their optical properties, such as UV/vis absorption and fluorescence, were measured. The results indicate that these two rotaxanes possess stronger intermolecular interaction in the solid state than in solution. As a result, solutions of high concentration readily formed the excimer. These special rotaxanes might be applied in dynamic fluorescence-reponsive materials, and the rotaxane structure will also be used as a strategy to adjust the aggregated behaviors of fluorescent molecules.

•Some dithienylethenes containing gold(I) have been synthesized.•These compounds show photochromic behavior.•Their photochromic properties are highly dependent on acetylide gold(I) sites.We report the synthesis and characterization of two new bisacetylide compounds, 1,2-bis(2-ethynyl-5-methyl-3-thienyl)perfluorocyclopentene and 1-[2-methyl-5-phenyl-3-thienyl]-2-[4-methyl-2,5-bis(ethynyl)-3-thienyl]hexafluorocyclopentene together with three dinuclear acetylide gold(I) complexes LAu-CC-dithienylethene-CC-AuL in which L = PPh3 or PCy3, containing the photochromic dithienylethene unit. The photophysical properties of these new complexes are compared and contrasted with those of some previously reported dithienylethene complexes. It has been revealed that these compounds with dithienyletehene units show photochromic behavior, but their absorption spectra, cyclization/cycloreversion quantum yields, and efficiencies of the photochromic process and conversions from the open- to the closed-ring isomers in the photostationary state, are all highly dependent on the substitution sites of the bisalkynyl moiety and whether or not there is bisalkyne metalation. The photochromic process was also found to show complete reversibility by alternating irradiation with UV and visible light.Some bisacetylide and binuclear acetylide gold(I) compounds containing the dithienylethene unit have been synthesized and their photochromic properties are investigated.

Polycyclic aromatic hydrocarbons are of great interest as a result of their self-assembly properties and excellent charge-transfer abilities. They are therefore promising candidates for organic semiconducting devices. In order to develop better optoelectronic devices, chemists have made considerable effort to investigate synthetic methods for polycyclic aromatic hydrocarbons. Among many building blocks, arynes are a promising reactive intermediate for the construction of polycyclic aromatic hydrocarbons and so have been studied over many decades. In this review, we will summarize recent progress on the construction of polycyclic aromatic hydrocarbons using arynes as starting materials.

Three switchable macrocycles based on photochromic dithienylethene were synthesized under the template of dibenzylammonium hexafluorophosphate. Their structure were well-confirmed by NMR, ESI-MS and X-ray diffraction. Their photochromism indicated that they showed good reversibility in solution. Additionally, the theoretical calculation suggested that photoirradiation can change the cavity of macrocycles.Three switchable macrocycles based on photochromic dithienylethene were synthesized under the template of dibenzylammonium hexafluorophosphate. Their structure were well-confirmed by NMR, ESI-MS and X-ray diffraction. Their photochromism indicated that they showed good reversibility in solution. Additionally, the theoretical calculation suggested that photoirradiation can change the cavity of macrocycles.

A novel intermolecular Alder-ene reaction based on aryne and olefins was developed. We performed this transformation under mild conditions such as at room temperature, and this reaction displayed high selectivity and good yields only in the presence of CsF. Hence, the intermolecular Alder-ene reaction of aryne with olefins provides an effective route to synthesize derivatives of olefins.A novel intermolecular Alder-ene reaction based on aryne and olefins was developed. We performed this transformation under mild conditions such as at room temperature, and this reaction displayed high selectivity and good yields only in the presence of CsF. Hence, the intermolecular Alder-ene reaction of aryne with olefins provides an effective route to synthesize derivatives of olefins.

Heterorotaxanes, one class of topological organic structures, have attracted increasing interesting during the past two decades. In general, two types of heterorotaxane structures exist, one in which two or more different macrocycles are threaded onto one dumbbell-shaped molecule and the other where one macrocycle is threaded onto two or more different dumbbell-shaped molecules. In comparison to these traditional types, another family of topologically interesting heterorotaxanes can be envisaged as arising from polyfunctional molecules that possess both host (crown ether) and guest (ammonium templates). In the present investigation, we have explored the construction of selected members of this new heterorotaxane family, which possess crown ether moieties that are wrapped around a dumbbell-shaped molecule. These structures are prepared by routes in which “stitching” processes, involving template-directed clipping reaction or olefin metathesis reactions, are used to install crown ether ring systems encircling ammonium cation centers. This is then followed by implementation of a threading-followed-by-stoppering sequence to install a second encircling crown ether ring. The results show that the polyfunctional building blocks assemble with high efficiencies. Finally, this investigation provides a foundation for future studies aimed at constructing more complicated heterorotaxane architectures, such as switchable systems, self-assembling polymers, and functional molecular machines.

Four novel imidazole-based dithienylethenes have been successfully synthesized in good yields. Their structures have been confirmed by NMR spectrometry, mass spectrometry, and elemental analyses. UV/Vis absorption spectra indicated that these dithienylethenes can easily isomerize between the open-ring and closed-ring isomers upon irradiation with UV or visible light in solution, and that the respective closed-ring isomers show decreased fluorescence properties compared with the open-ring isomers. Moreover, the open-ring and closed-ring isomers display high selectivity toward Fe3+, such that the addition of Fe3+ obviously suppresses their fluorescence intensity.Highlights► Four imidazole-based dithienylethenes show decreased fluorescence properties upon irradiation with UV light. ► The open-ring and closed-ring isomers display high selectivity toward Fe3+. ► The addition of Fe3+ obviously suppress their fluorescence intensity.

A series of binuclear gold (I) complexes were synthesized. Their structures were characterized by elemental analyses, IR spectrometry, UV–Vis spectroscopy and single crystal X-ray diffraction. Their fluorescent mechanochromic (tribochromic) properties were investigated. The results of the mechanochromic studies suggested that the gold complexes with methylsubstituted phenyl bridges exhibited mechanochromism and a 100 nm red-shift of fluorescent spectrum could be observed after grinding. The complex with a diphenylmethane bridge exhibited mechanochromism with a change in fluorescence from green to blue (25 nm red-shift after grinding). The ground complexes reverted to their original states by treatment with CH2Cl2. No mechanochromism was observed for either the biphenyl or diphenylethane containing complexes.Graphical abstractThe diisocyano-based bimetallic gold (I) complexes displayed mechanochromic properties, and the different organic bridge can affect their mechanochromism. Highlights► The mechanochromic activity of diisocyano bridge gold (I) complexes are described. ► Crystal structures of diisocyano bridge gold (I) complexes are discussed. ► The nature of the bridging ligands upon the mechanochromic response are reported.

The construction of coronenes using simple building blocks is a challenging task. In this work, triphenylene was used as a building block to construct functionalized coronenes, and their solid structures and optoelectronic properties were investigated. The single crystal structures showed that coronenes have different packing motifs. Their good solubility and photostability make them potential solution-processable candidates for organic devices.

A series of [2]catenanes were efficiently synthesized in high yields by a template-directed clipping approach with the formation of one macrocycle around another macrocycle containing a dialkylammonium recognition site. Their structures were identified by the NMR spectra and ESI mass spectrometry, and their geometries were investigated by the theoretical calculation.

A versatile amide- and urea-functionalized dithienylethene has been successfully synthesized. Upon irradiation with UV or visible light, the compound showed excellent fatigue resistance. As a synthetic receptor, the dithienylethene displayed switchable affinities for Cl– and Br– anions when the UV/vis light was introduced. The switchable binding ability also had good reversibility.

Two dithienylethene-based binuclear gold complexes and a palladium chlorine-bridged macrocycle bearing bis(phosphine) ligands have been synthesized. Their structures have been thoroughly characterized by NMR spectrometry, single-crystal X-ray diffraction, and elemental analyses. The two binuclear gold complexes display excellent photoisomerization properties upon irradiation with UV/Vis light in CH2Cl2. Moreover, we found that the introduction of metal atoms can stabilize the dithienylethene-based bis(phosphine) ligands, and that the absorption spectra of gold complexes 3 and 4 showed 6–12 nm red-shifts upon irradiation with UV light compared with those of the ligands 1 and 2. However, no such isomerization was observed when the palladium chlorine-bridged macrocycle 5 in CH2Cl2 was irradiated with UV light, but it showed excellent catalytic activity for the Suzuki coupling reaction. Moreover, we found that the non-photochromic macrocycle 5 can perform the photochromic reaction when the solution of CH3CN was irradiated by UV light.Highlights► Dithienylethene bis(phosphine) gold complexes can easily isomerize. ► A palladium chlorine-bridged macrocycle was obtained. ► The macrocycle can catalyze the Suzuki coupling reaction. ► The macrocycle can perform photochromic reaction in CH3CN, not in CH2Cl2.

A series of symmetrical imidazole- and N-methylated imidazole-based diarylethenes were synthesized, and the structures have been well characterized by NMR spectroscopy and mass spectrometry. Their photochromism were investigated upon UV/vis light irradiation in DMF solution. A significant red-shift of UV absorption was observed after irradiation with UV light when substituents on the benzene ring (such as methoxyl group) were introduced. But N-methylation on the two imidazole rings will result in a blue-shift of UV absorption. The photophysical properties can be adjusted by changing the substituents, which provides a new strategy for the design of diarylethenes with excellent properties.

A series of binuclear bis-terpyridyl ruthenium complexes with different substituents were synthesized and characterized by physico-chemical and spectroscopic methods. The UV/Vis and fluorescence spectra indicated that the non-substituted binuclear bis(terpyridyl) ruthenium(II) complex has similar properties to those with electron-donating groups such as methyl and alkoxyl on the organic conjugated bridge units. Furthermore, similar oxidation–reduction potentials were observed according to their electrochemical properties in CH2Cl2 solution.

Condensation of dialdehyde 1 with different aromatic amines gave a series of symmetrical diarylethenes containing Schiff-base moieties, which were reduced with NaBH4 to give the corresponding diarylethene amines. The structures of all new compounds were confirmed by NMR spectroscopy, mass spectrometry, X-ray diffraction and elemental analysis. Their photochromic properties were also investigated, revealing that diarylethene imines displayed better photochromic properties in solution than their amine analogues. Furthermore, we found that by varying the aromatic amine precursor, diarylethenes with different polychromic behavior could be obtained. A number of different aromatic amines were investigated, including different carbon skeletons and substitution with different halogens in various positions, to tune the polychromic behavior.Condensation of dialdehyde with different aromatic amines gave a series of symmetrical diarylethenes containing Schiff-base units, which were reduced by NaBH4 to give the corresponding diarylethene amines. Their photochromic properties were also investigated, revealing that diarylethene imines displayed better photochromic properties in solution than their amine analogues. Furthermore, we found that by varying the aromatic amine precursor, diarylethenes with different polychromic behavior could be obtained. A number of different aromatic amines were investigated, including different carbon skeletons and substitution with different halogens in various positions, to tune the polychromic behavior.

Four anthracene-based bimetallic ruthenium vinyl complexes, in which two ruthenium units are attached at different positions (the 9,10-, 1,5-, 2,6-, and 1,8-positions) of the anthracene moiety, have been synthesized by treating the appropriate anthracene-based ethynes with [RuHCl(CO)(PPh3)3]. These bimetallic complexes have been thoroughly characterized by NMR, X-ray diffraction, and elemental analysis. According to the single-crystal X-ray structures, the 2,6-disubstituted ruthenium vinyl complex has a more planar structure compared with the 9,10-disubstituted complex, possibly because it has less steric hindrance. Furthermore, we have investigated the optical electronic properties of these complexes, such as their UV/vis absorption spectra, fluorescence spectra, and electrochemical properties. The optical electronic results indicated that the 2,6-disubstituted ruthenium vinyl complex displayed the strongest fluorescence emission due to the more planar structure of its organic conjugated bridge, and the electrochemical studies showed that the two ruthenium centers displayed obvious differences in electronic communication when they are located at different positions on the anthracene unit, with the 9,10- and 1,8-disubstituted ruthenium vinyl complexes exhibiting better electronic communication and higher stability of the mixed-valence complex than the 1,5- and 2,6-disubstituted complexes.

•A indolo[3,2-b]carbazole-based diphenylamine compound has been synthesized.•It exhibits reversible near-infrared electrochromic behavior.•It exhibits reversible electroluminochromic property.•Its fluorescence undergoes obvious changes with the aggregation forming.A new indolo[3,2-b]carbazole-based compound (1) has been developed by linking two redox-active diphenylamine moieties to the rigid π-conjugated indolo[3,2-b]carbazole core. Its first two completely reversible oxidation steps are mainly related to the two terminal amine centers, and a moderate electron coupling between these amine centers has been determined. The associated oxidized species 1+ and 12+ both exhibited strong NIR absorptions, and a completely reversible conversion among three different colors (light-yellow, red, and blue, corresponding to neutral, monocationic and dicationic states, respectively) could be realized. In addition, reversible switching between turn-off and turn-on of its fluorescence could be accomplished by electrochemical oxidation and reduction, respectively. Compound 1 also exhibited obvious fluorescence color changes during its aggregate-forming process, and its solid showed bright-yellow fluorescence with a high emission quantum yield of 30%.A new indolo[3,2-b]carbazole-based derivative has been synthesized by introducing a redox-active diphenylamineunit to the rigid conjugated indolo[3,2-b]carbazole core. This compound exhibits remarkable near-infrared electrochromic, electroluminochromic and aggregation-induced fluorescence change properties.

A fluorescent sensor for halogenated solvents termed AMN is reported. AMN shows strong fluorescence in most halogenated solvents (QE > 0.1) but weak fluorescence (QE<0.01) in most non-halogenated solvents. In chlorinated solvents, the fluorescence intensity decreased with the reduction of chlorine content. On the contrary, in brominated solvents the fluorescence intensity increased with the reduction of bromine content. It is worth mentioning that AMN displayed fluorescence emission centered at 520 nm in CCl4 with a quantum yield of 0.607, at 556 nm in CHCl3 with a quantum yield of 0.318, at 584 nm in CH2Cl2 with a quantum yield of 0.128, whereas in CHBr3 was centered at 441 nm with a quantum yield of 0.012. AMN was shown to have the ability to differentiate CCl4, CHCl3, CH2Cl2 and CHBr3 halogenated solvents.

Supramolecular chemistry and self-assembly provide a valuable chance to understand the complicated topological structures on a molecular level. Two types of classical mechanically interlocked molecules, rotaxanes and catenanes, possess non-covalent mechanical bonds and have attracted more attention not only in supramolecular chemistry but also in the fields of materials science, nanotechnology and bioscience. In the past decades, the template-directed clipping reaction based on imine chemistry has become one of the most efficient methods for the construction of functionalized rotaxanes and catenanes. In this review, we outlined the main progress of rotaxanes and catenanes using the template-directed clipping approach of imine chemistry. The review contains the novel topological structures of rotaxanes and catenanes, functions and applications.

Tetraphenylethene (TPE) with aggregation-induced emission (AIE) behavior as a popular backbone is applied widely in the construction of functional supramolecular systems. In this work, a TPE-based linear molecule having amide and amine units is synthesized. Its ammonium template is used to construct the N-hetero crown ether-based [2]rotaxane by the template-directed clipping approach. Their structures are well-characterized by NMR, MALDI-TOF-MS and elemental analysis. Owing to the existence of the amide unit, [2]rotaxane possesses the function of a molecular shuttle. The shuttling motion of the macrocycle component between the ammonium station and the amide station can be driven by external acid–base stimuli in solution, accompanied by changes in visual behavior. Investigation on their AIE behavior shows that (1) ammonium reaches the aggregation state almost in the presence of same water with the deprotonated form of ammonium; (2) the [2]rotaxane that the macrocycle component locates at the site of ammonium forms the aggregation state in the presence of less water than the deprotonated [2]rotaxane that the macrocycle component locates at the site of the amide, attributed to stronger interaction between the crown ether component and the TPE unit of the template component when the distance between the two is shorter. The result indicates that the shuttling motion of the macrocycle component can adjust the aggregation state of AIE molecules.

Hydrogen sulfide (H2S) is considered as the third signaling molecule in vivo and it plays an important role in various physiological processes and pathological processes in vivo, such as vasodilation, apoptosis, neurotransmission, ischemia/reperfusion-induced injury, insulin secretion and inflammation. Developing a highly selective and sensitive method that can detect H2S in the biological system is very important. In this work, a colorimetric and “turn-on” fluorescent probe is developed. Furthermore, this probe displays a highly selective response to H2S in aqueous solution and possesses good capability for bioimaging H2S without interference in living cells. The results suggest that a H2S-selective probe has good water-solubility, biocompatibility and cell-penetrability and can serve as an efficient tool for probing H2S in the cell level.

Imide-modified polycyclic aromatic hydrocarbons can be widely applied in the field of optoelectronic materials. In this work, we have synthesized four novel functionalized benzopicenes and characterized their solid structures and optoelectronic properties. The fluorescence of the four functionalized benzopicenes showed red shifts with increasing solvent polarity; the quantum yields are high in the solution state and moderate in the solid state. The single crystal structures show that the benzopicenes adopt a lamellar motif π-stacking. Their good solubility and optoelectronic properties make them potential solution-processable candidates for organic devices, bioimaging and biolabeling.

A new fluorene-based AIE-active gold(I) complex was designed and synthesized. The novel luminogen exhibits a crystallization-induced emission enhancement (CIEE) effect and reversible mechanochromic behavior with fluorescence changes between green and yellow emissions.

The photochromic materials have been widely applied in many fields. In this article, we report a class of photochromic ammoniums with a dithienylethene backbone. They were utilized as templates to construct mechanically interlocked rotaxanes and pseudorotaxanes showing photo-responsive behavior by template-directed clipping reaction and the threading approach. The structures of novel rotaxanes were well defined. It is worth mentioning that the single crystal structure of [3]rotaxane containing two N-hetero crown ether units was obtained. Their photoisomerization behavior was investigated. These N-hetero crown ether-based rotaxanes displayed good reversibility and similar photochromic behaviors to their corresponding ammoniums when they underwent UV/vis photoirradiation. Interestingly, the cucurbit[6]uril-based pseudorotaxane showed better photoisomerization than its corresponding ammonium and those of N-hetero crown ether-based rotaxanes.

A series of novel dithienylethene-based macrocycles containing ammonium moieties has been synthesized. They have been employed as templates to construct [2]catenanes showing their photoisomerization properties by means of a dynamic covalent chemistry approach. Their structures have been reliably confirmed by NMR, ESI-MS or MALDI-QTOF-MS, and elemental analysis, and their energy-minimized structures of open- and closed-ring isomers were investigated by the theoretical calculation. Investigation of the photochromic properties of these dithienylethene-based [2]catenanes has revealed good reversibility and excellent fatigue resistance upon irradiation with UV or visible light. Notably, formation of the [2]catenanes enhanced the photochromic properties compared with those of the corresponding macrocyclic ammonium salt, implying that the non-covalently interacting components of the [2]catenanes could affect the photoswitchable properties.

Mechanically interlocked structures such as rotaxanes and catenanes provide a novel backbone for constructing functional materials with unique structural characteristics. In this study, we have designed and synthesized a series of photoswitchable rotaxanes and catenanes containing photochromic dithienylethene fragments using a template-directed clipping approach based on dynamic imine chemistry. Their structures have been confirmed using NMR, mass spectrometry and elemental analysis. Investigations into their photoisomerization properties indicated that these dithienylethene-based mechanically interlocked molecules have good reversibility and excellent fatigue resistance upon irradiation with UV or visible light. Interestingly, the mechanically interlocked molecules containing two dithienylethene backbones display around a 2-fold increase in the molar absorption coefficient compared with that of the mono dithienylethene derivative. Furthermore, the introduction of the fluorophore pyrene in the dithienylethene component facilitates these molecules to serve as fluorescent switches.

The construction of novel mechanically interlocked structures has become a topic of great current interest due to the requirements of topology and their potential application in molecular machines and devices. Rotaxane and catenane as two basic topological frameworks can be used to construct the fused structures. In the current investigation, a class of novel ammonium backbones were synthesized. The ammonium group incorporated in the linear part of the molecule can be used for templating rotaxane formation while the macrocyclic part of the molecule can be used for templating catenane formation. Accordingly, they were subjected to dynamic covalent chemistry, resulting in a series of [n]rota[n]catenane structures (n = 2, 3, 4). In this process, the N-hetero crown ethers were installed on ammonium template sites of linear and macrocyclic components all at once by a template-directed clipping reaction. The results showed that these novel building blocks could be assembled with high efficiencies. Finally, this investigation provides a foundation for future studies aimed at constructing complicated integrated structures or polymers with multiple topological units.

A new fluorene-based white light-emitting gold(I) complex with aggregate fluorescence change is reported. The novel luminogen emits direct white light in the solid state without involving complex doping/mixing procedures.

A series of novel [n]rotaxanes based on a tetraphenylethene (TPE) backbone were constructed by a template-directed clipping approach and their structures were well-characterized. Investigation of their optical properties showed that these rotaxanes and their corresponding ammonium salts showed aggregation-induced emission (AIE) behavior. However, there were obvious differences as follows: (1) rotaxanes reached the aggregation state in the presence of less water compared with the corresponding ammonium salt; (2) the rotaxanes with a long alkoxyl chain on the pyridine unit of the crown ether formed the aggregation state in the presence of less water than for those without an alkoxyl substituent and (3) a smaller distance between the TPE unit and N-hetero crown ether component resulted in the aggregation state being reached more easily than when there is a longer distance. The results suggest that the mechanically interlocked structures can adjust the aggregation state of AIE molecules.

A new carbazole-based mononuclear gold(I) complex was designed and synthesized. The novel luminogen shows significative solid-state reversible mechanochromism, dual-responsive thermochromism and sensitive thin-film vapochromism properties. In addition, we obtained two kinds of crystals of the luminogen that may explain these interesting characteristics.

A novel naphthalimide-based fluorescent probe employing a sulfonamide unit as a thiol-responsive group is reported. It is capable of efficiently distinguishing GSH from cysteine and homocysteine. Bioimaging shows that it has high selectivity in living cells and can visualize the level of GSH in lysosomes. It is worth mentioning that different groups on the imide unit can affect the selectivity and reaction dynamics of the probe towards thiols.