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The development of novel organic fluorescent materials with strong luminescence in the aggregate state as well as stimuli response under external forces is of great importance for practical applications in the solid state. It is established that triphenylethylene and tetraphenylethylene are propeller-type aromatic molecular structures present in the majority of organic emitters with aggregation-induced emission (AIE) properties to prevent aggregation-caused quenching (ACQ). In this study, we have incorporated a spiro-xanthene (SFX) core for the first time to design a new donor–π–acceptor–π–donor 4,4′-((3′,6′-dibutoxyspiro[fluorene-9,9′-xanthene]-2,7-diyl)bis(thiophene-5,2-diyl))bis(N,N-diphenylaniline) (SP-TH) luminescent material with aggregation induced emission (AIE) and mechano-responsive properties. DFT calculations were carried out to study the electronic properties of SP-TH. The photophysical and electrochemical properties of SP-TH were systematically investigated. The photophysical (UV-Vis and PL spectroscopies) studies indicate that SP-TH has AIE features. In addition, the mechano-stimuli response of SP-TH was also investigated, and a hypsochromic shift (yellowish green to bluish green) was observed upon grinding the SP-TH sample and was analyzed using PXRD. [ABSTRACT FROM AUTHOR]

A fluorescent polymer probe was developed by connecting tetraphenylethylene (TPE) with glucose via the formation of borate ester linkages. Based on the selective breaking of C–B bonds, the macroscopic and fluorescence detection of reactive oxygen species (ROS) in vitro and in cells was successfully realized. [ABSTRACT FROM AUTHOR]

Tetraphenylethylene functionalized arylimidazole derivatives G4, G3, G2, L-G4, L-G3 and L-G2 with different substituent groups and geometric structures have been designed and synthesized. All the compounds exhibited excellent aggregation-induced emission (AIE) properties due to the restricted intramolecular rotation (RIR) and the formation of J-aggregates. The solid compounds showed highly efficient emission with fluorescence quantum yields (ΦPL) of 67%, 72%, 67%, 40%, 52% and 48% for G4, G3, G2, L-G4, L-G3, and L-G2, respectively. The structure–property studies revealed that G4, G3 and G2 were more twisted structures and L-G4, L-G3 and L-G2 were partially planar conformations. The high quantum yields of the six solid compounds were driven by the synergistic effects of intramolecular electron transfer, molecular configuration and intermolecular interactions. On the other hand, the compounds also showed mechanochromism, acidochromism and picric acid-sensing properties. The compounds presented reversible mechanochromic behaviors between green and yellow emission and maintained highly solid emission (ΦPL about 50%) after grinding. The ΦPL values of the twisted molecules of G4, G3, and G2 decreased about 20% and those of the planar compounds showed a negligible change, which could be explained by the molecular structure planarization and the increased intermolecular interactions after grinding. Meanwhile, due to the excellent proton-binding properties of the imidazole group and pyridine group, the compounds were used as picric acid (PA) sensors with high selectivity and sensitivity in aqueous media and acid/base switches. The relative mechanism was ascribed to the photo-induced electron transfer (PET) and protonation, which were verified by 1H NMR spectra and theoretical calculations. [ABSTRACT FROM AUTHOR]

Highly emissive tetraphenylethylene chromophore appended thiophenylbipyridine pendant as a receptor (1) site has been successfully synthesized via a multistep reaction pathway. The synthesized chromophore 1 was well characterized by modern spectroscopy. In particular, the solid sample of 1 exhibits significant mechanochromic behavior upon grinding, fuming and heating. The yellow emissive chromophore 1 exhibits remarkable selectivity and sensitivity towards copper(II) perchlorate ions via a photoinduced electron transfer (PET) 'turn off–turn on' mechanism. When compared with competing metal ions, 1 shows little to no interference in selectivity towards Cu2+ ions in acetonitrile. Detailed colorimetric, UV-visible, emission, and 1H NMR spectral studies have been employed to understand the sensing mechanism of 1 towards Cu2+ ion interaction which is responsible for PET 'turn-on'. The binding constant of 1 with Cu2+ was shown to be 2.34 × 10−5 M with a limit of detection as low as 7.93 nM. The binding constant prompted us to explore chromophore 1 as a paper strip sensor for Cu2+ to develop kits for real-world practical utility. [ABSTRACT FROM AUTHOR]

White-light-emitting materials have attracted significant attention due to their broad applications in displays and lighting. Herein, a quadruple-stranded helicate with white-light emission was constructed by co-assembly of bis-β-diketone featuring cyan fluorescence and red light emitting Eu3+ ions in a 2 : 1 stoichiometric ratio. The cyan emission from bis-β-diketone originated from the pendent tetraphenylethylene (TPE), a typical AIE molecule featuring strong emission in the aggregation state. The formation of the helicate was verified by 1H NMR, 1H DOSY and high-resolution MS analyses. Upon excitation at 390 nm, the helicate realized the tunable emission with the colors changing from white light to green in the solid state. After hybridization with a polymer, a white-light hybrid material was prepared with the CIE coordinate locating at (0.322, 0.332). The absolute luminescence quantum yields were measured to be 16.9%. [ABSTRACT FROM AUTHOR]

Improving the reactive oxygen species (ROS) generation ability is of tremendous significance in designing photosensitizers (PSs). In this paper, a heavy atom free 4,4′-bis(1,2,2-triphenylvinyl)-1,1′-biphenyl (denoted as BTPE) with aggregation induced emission (AIE) was designed and synthesized by a Suzuki coupling reaction. Then nanoprecipitation with 1,2-distearoyl-sn-glycero-3-phospho-ethanolamine-N-[methoxy(polyethyleneglycol)]-2000 (DSPE-PEG-2000) was used to prepare the NPs. Singlet oxygen sensor green (SOSG) used under irradiation suggests better 1O2 generation ability of BTPE than monomer TPE. In vitro MTT assay on human cervical carcinoma cancer cells (HeLa) demonstrates that BTPE NPs with a half maximal inhibitory concentration (IC50) of 8.4 μg mL−1 are superior to TPE NPs (17.2 μg mL−1), indicating the higher phototoxicity of BTPE NPs. Furthermore, an in vivo study suggests that BTPE NPs are capable of inhibiting tumor proliferation with irradiation but the normal organs, including heart, lungs, liver, spleen and kidneys, suffer from no side effects. Our results indicate that BTPE is able to improve the phototherapy efficacy and simultaneously retains the low toxicity and good biocompatibility, compared with TPE. [ABSTRACT FROM AUTHOR]

Binding of a series of cationic tetraphenylethylene (TPE) derivatives with a cucurbit[10]uril (CB[10]) host has been investigated. Compared to the free forms, all guests exhibit fluorescence enhancement upon encapsulation by CB[10]. Thus, by restricting intramolecular rotation through host–guest encapsulation instead of aggregation, fluorescence enhancement of TPE derivatives can be realized in water. [ABSTRACT FROM AUTHOR]

Mono and tetra phenothiazine (PTZ) functionalized tetraphenylethylene (TPE) derivatives PTZTPE-1 and PTZTPE-4 were designed and synthesized by the Suzuki cross-coupling reactions between PTZ boronate ester and bromo TPEs. The PTZTPE-1 and PTZTPE-4 are highly emissive in the solid state, which is crucial for a molecule to show mechanofluorochromism. The strong donor ability of PTZ could affect the donor ability of TPE leading to changes in the electronic and photophysical properties of the target molecules. The number of PTZ moieties attached to TPE could vary the twisting in the molecules, which could further affect the mechanochromic properties. The photophysical, electrochemical, solvatochromic, mechanochromic and AIE properties of PTZTPE-1 and PTZTPE-4 were studied. Both PTZTPE-1 and PTZTPE-4 show significant mechanochromic behavior and comparable spectral shift on grinding. The single crystal X-ray analysis of PTZTPE-1 reveals a twisted confirmation of PTZ and TPE phenyl rings confirming strong AIE characteristics and reversible mechanochromic behavior. [ABSTRACT FROM AUTHOR]

Three tetraphenylethylene (TPE) decorated benzaldehyde isomers were designed and synthesized via the Suzuki–Miyaura coupling reaction with higher yields by changing the linking positions of the peripheral TPE units to demonstrate the isomeric effects on the photophysical and MFC properties. The changes of the linking positions could alter the molecular packing modes, and thus, their solid-state fluorescence properties exhibit remarkable isomeric effects. Interestingly, the three isomers are all aggregation induced emission (AIE) and MFC dyes. And the MFC activities of the three compounds are increased with the sequence of m-TPEC (45 nm) ＞ p-TPEC (39 nm) ＞ o-TPEC (8 nm). X-ray structural analysis, XRD, DSC and theoretical studies suggest that the change from a crystalline phase with a twisted molecular structure to a more planar amorphous phase should be responsible for the MFC properties. These findings suggest that subtle manipulation of the end groups capped at benzaldehyde could significantly alter and tune the photophysical properties. And these results will be of great help in understanding the structure–property relationships of MFC mechanisms and designing more new MFC materials. [ABSTRACT FROM AUTHOR]

Tetraphenylethylene-naphthopyran (TPE-NP) and tetraphenylethylene-spirooxazine (TPE-SO) with conjugated photochromic groups and fluorophores were designed and synthesized. Both of them exhibit the comprehensive effects of aggregation-induced emission (AIE) and photochromism while different photochromic groups lead to a unique photochromic rate and fluorescence intensity. Among them, TPE-NP has significant photochromic and fluorescence effects with good stability. Therefore, it could be used as an anti-counterfeiting ink and is expected to be used in fluorescence switches in the future. [ABSTRACT FROM AUTHOR]

Tetrasulfonate-tetraphenylethylene (Su-TPE) is non-emissive in water and upon addition of a good solvent such as THF (fTHF = 95%) it displays strong fluorescence emission with a quantum yield of 6.33%. In the presence of spermine, emission of Su-TPE produces higher quantum yields i.e. 1 : 48 molecular ratio gives 7.21%. Furthermore, interaction of spermine with Su-TPE is also shown to be pH dependent. Scanning electron microscopy (SEM) of Su-TPE molecule self-assemblies demonstrates that it produces various supramolecular structures at different Su-TPE : spermine molecular ratios. Nanobelts were obtained at 1 : 12, evolving into microsheets at 1 : 24, microglobular morphology at 1 : 36 and microtubes at 1 : 48 molecular ratios, respectively. Additionally, enhanced fluorescence emission was observed upon increasing the molar ratio of spermine with Su-TPE at pH 7. The physical characterisation of the system was performed using dynamic light scattering and zeta potential measurements. [ABSTRACT FROM AUTHOR]

We have designed and developed a tetraphenylethene (TPE)–anthracene–(aminomethyl)-4-cyanophenylboronic acid ester (AminoMeCNPhenylBPin) structure (RS-1) and a diphenyldibenzofulvene (DPDBF)–anthracene–AminoMeCNPhenylBPin structure (RS-2) possessing PET (photo-induced electron transfer) and AIEE (aggregation-induced emission enhancement) characteristics as PET/AIEE hybrid fluorescence sensors for detection of water in the low and high water content regions in solvents, where the TPE or DPDBF unit is directly attached to the 10-position on the anthracene skeleton. For both RS-1 and RS-2 the enhancement of the fluorescence band at around 430 nm in the low water content region below 1.0 wt% is attributed to the fluorescence emission originating from the anthracene skeleton due to the formation of PET inactive species RS-1(H2O) and RS-2(H2O), respectively, upon addition of water molecules. Furthermore, the appearance of new and broad fluorescence bands at around 450 nm for RS-1 and 530 nm for RS-2 in the high water content region of over 60–70 wt% is attributed to the AIEE characteristics due to the restricted intramolecular rotation (RIR) of the TPE or DPDBF unit associated with aggregate formation (RS-1(H2O)-A and RS-2(H2O)-A). It is worth noting that a big difference in the enhancement of the fluorescence band originating from the anthracene skeleton due to the suppression of the PET characteristics and the appearance of a fluorescence band due to the AIEE characteristics with aggregate formation between RS-1 and RS-2 was observed: for RS-2 the separation of fluorescence peak wavelengths originating from the anthracene skeleton (at ∼430 nm) and due to the RIR of the DPDBF unit with the aggregate formation (at ∼530 nm) is clear, but for RS-1 the separation of fluorescence peak wavelengths is completely indistinct. Consequently, this work indicates that RS-2 having a DPDBF unit on the anthracene skeleton can act as a PET/AIEE hybrid-based dual-fluorescence emission sensor for detection of water in the low and high water content regions in solvents. [ABSTRACT FROM AUTHOR]

A photoactivatable benzo[c][1,2,5]oxadiazole-dressing tetraphenylethylene (TPE) was developed. The optical performance results indicate that UV-irradiation can lead to remarkable emission enhancement in solution states due to the cyclization of the TPE component. Application in the solid state confirmed that it has a potential to serve as a photoactivatable visualized material. [ABSTRACT FROM AUTHOR]

Herein, a chiral thiourea Schiff base derived from (1R,2R)-1,2-cyclohexanediamine and tetraphenylethylene (TPE) was applied as a highly effective chiral sensor for the enantioselective discrimination of various acids and amines via ion-pair and hydrogen-bond interaction. Compared to the case of the sensors 5 and 6, the additional thiourea and hydrogen groups of sensor 4 were essential and greatly enhanced the enantioselectivity of chiral guests. In addition, for amino acids, the sensor 4 showed high enantioselectivity, and precipitates visible by the naked eye appeared; however, for chiral amines, the enantioselectivity decreased. This was attributed to weaker hydrogen bond interaction between the amino groups of chiral amines and the sensor. Both the thiourea and acidic hydroxyl groups are essential for chiral TPE thiourea to provide an appropriate chiral environment for highly efficient enantioselective discrimination of chiral substrates. Our findings will be of great value in the design of new chiral sensors. [ABSTRACT FROM AUTHOR]

Three novel boron dipyrromethene (BODIPY) derivatives containing tetraphenylethene (TPE) with emissions ranging from orange to red were synthesized and characterized. Spectroscopic properties of the dyes in various solvents and in the solid state have been investigated. They all exhibit high fluorescence intensity in solution and moderate fluorescence in the solid state, due to inhibiting intermolecular π–π stacking resulting from tetraphenylethene substituents. Cyclic voltammetry and time-dependent density functional theory (TD-DFT) calculations were carried out to explore the electronic coupling between the tetraphenylethene group and the BODIPY unit, giving consistent results with photophysical measurements. [ABSTRACT FROM AUTHOR]

A new piezofluorochromic aggregation-induced emission compound was synthesized. The compound had morphology-alterable emission property and its amorphous and crystalline aggregates with various emissions were obtained through evaporation from the solutions in different solvent systems. The spectroscopic properties and morphological structures of the compound were reversed upon pressing and annealing (or fuming). The results show that the piezofluorochromic nature is generated through crystalline–amorphous phase transformation under external pressure. The reason for the phase transformation is ascribed to the twisted conformation of the molecule which leads to poor solid molecular packing and formation of some cavities in the interfaces of lamellar layers, as confirmed by single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Correction for 'Spermine-directed supramolecular self-assembly of water-soluble AIE-active tetraphenylethylene: nanobelt, nanosheet, globular and nanotubular structures' by Duong Duc La et al., New J. Chem., 2018, 42, 15379–15386, DOI: 10.1039/C8NJ02636J. [ABSTRACT FROM AUTHOR]