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A new series of benzoxazole-based two-photon absorption (2PA) chromophores (T1–5) were synthesized and fully characterized. Among them, T1–3 are linear donor (D)–π–acceptor (A) type fluorophores with various electron-donating groups, while T4 and T5 are multi-branched compounds stemming from T3. Their photophysical properties have been systematically investigated, and the two-photon absorption properties indicate that the highest 2PA cross-section (σ2PA) is 2702 GM for T5 (in DMF). Structure–property relationships of the chromophores are comprehensively discussed based on their optical properties, crystal structures and density functional theory (DFT) calculations. In addition, a two-photon fluorescence cell imaging experiment demonstrates the potential bio-application of T1–5 with good photostability and low cytotoxicity.

This study investigated the clean properties and combustion behavior of hydrochar from food waste (FW). The hydrochar was characterized by proximate analysis and HHVs, and the chemical forms were investigated by FTIR, XPS (Sulfur), and XANES (Chlorine). TG-FTIR was used to assess the combustion behaviors, and XRF was used to assess the fouling and slagging inclinations. Results showed that increasing temperature from 180 °C to 260 °C enhanced the removal of N, S, and Cl for hydrochar. Especially, aromatic-S and sulfate-S increased in contrast to sulfoxide-S, and more inorganic-S was produced in hydrochar; all samples had mainly inorganic-chlorine. Additionally, the release of HCl, SO2, and NO of hydrochar combustion were significantly reduced and the SI and FI index decreased to ranges of 0.18–0.16 and 0.32–0.17, respectively. However, hydrochar produced at temperature above 220 °C led increased NO emission possibly due to formation of more pyridine-N and quaternary-N.

Three benzothiazole-based two-photon absorption (2PA) chromophores (B1-3) were synthesized and the optical properties were investigated. The results illustrated the largest fluorescence quantum yield and effective 2PA cross-sections reached to 0.81 for compound B1 and 1013 GM for compound B3 in tetrahydrofuran solutions, respectively. Furthermore, the water-soluble fluorescent organic nanoparticles (FONs) possessing an embedded structure were prepared from the three compounds and Pluronic F127, which were successfully applied on two-photon nuclear envelope imaging.

A series of benzoxazole-pyridinium salt derivatives with two-photon excited fluorescence performance were synthesized and fully characterized. Among them, compounds 2, 3 and 4 were the isomers with different positions of pyridine N, while compounds 4N, 4S, 4P, 4F and 4B were derived from compound 4 through anion exchanging reaction. Their photophysical properties had been systematically investigated, and the results indicated that the position of pyridine N and the type of anions had a significant influence on their optical properties and bio-imaging application. Transforming the position of pyridine N could affect their fluorescence quantum obviously; the maximum fluorescence quantum is 0.21 for compound 3 in DMF. Meanwhile, we found that the altering anions might be used to regulate their two-photon fluorescence performance, only compounds 4N, 4P and 4B possessed excellent two-photon excited fluorescence emissions, and the highest two-photon cross-section was 1868.69 GM for compound 4B in DMF. In addition, two-photon fluorescence cell imaging experiment demonstrated the potential bio-application of partial compounds with good photostability and low cytotoxicity.

Six new benzoxazole-based compounds 1–6 of the donor-bridge-accepter (D-π-A) type with different anions were obtained by methylation and anion exchange reaction. The single crystals of 1, 3 and 6 were obtained by slow evaporation of acetonitrile and determined by X-ray crystallography. Ellipsoidal structures of the three compounds showed that the cationic parts all maintained good planarity, which was beneficial for two-photon absorption (2PA) properties and accorded with the results of two-photon excited fluorescence tests. Biological imaging experiments showed water-soluble six compounds had excellent penetrability in living cells and could located in cytoplasm in one- and two-photon cell imaging. Biological imaging result of compound 6 was more excellent than other compounds, which indicated synergy of anions and cations played a very important role in cell imaging.

Three novel 2-(4-methoxyphenyl)-1, 3, 4-thiadiazole based Schiff base derivatives (T1-T3) had been synthesized and characterized by 1H NMR, 13C NMR, MS and IR. The spectroscopic properties of T1-T3 were investigated by UV–vis absorption and fluorescence emission spectroscopy, which were coincident with theoretical calculations that three compounds possessed obvious intramolecular charge transfer (ICT) process. Their fluorescence emission performance in solution and aggregation state showed that three compounds all owned obvious aggregation-induced emission enhancement (AIEE) properties. To further understand AIEE nature, dynamic light scattering (DLS) and scanning electron microscopy (SEM) were comparatively investigated, which demonstrated that the small and uniform particles contributed to improve fluorescence emissions. Crystal structures of T1 and T3 showed that the twisted molecular conformation played an important role in AIEE. What's more, T2 and T3 had good biocompatibility, which were successfully applied in live-cell imaging.

Herein, we designed and synthesized two novel probes 4-(2-Hydroxy-phenylimino)-4′-(1, 4, 7, 10-tetraoxa-13-azacyclopentadecyl)-1- cyanostilbene (L1) and 4-(2-Hydroxy-phenylimino)-4′-(1, 4, 7, 10-tetraoxa-13-aza cyclopentadecyl) stilbene (L2) with aggregation induced emission behavior. L1 can directly recognize Cu2+ with high selectivity and specificity in water, L2 can distinguish Cu2+ with naked-eye in acetonitrile. Moreover, L1 and L2 with aggregation-induced emission could be applied to bio-imaging, and L1 showed a switchable color change feature based on mechanical grinding. The mechanism of the mechanochromic behavior was fully investigated by powder X-ray diffraction, single-crystal structures and differential scanning calorimetry measurements.

Four asymmetric bis-branched triphenylamine-cored compounds with different electron-withdrawing groups have been synthesized and their optical properties have been systematically investigated. The two-photon absorption cross-section (σ2PA) values were measured by two-photon excited fluorescence which revealed that the four compounds possessed large σ2PA values from 2011 to 4173 GM in the near-infrared region. Theoretical calculations revealed that the compounds were all provided with interesting intramolecular charge transfer generated from one branch to the other which contributed to the large σ2PA values. Cytotoxicity tests indicated that all these compounds had good biocompatibility for living cells, both one- and two-photon fluorescence microscopy studies showed the potential application of the four new compounds in cell imaging due to the large σ2PA and appropriate biocompatibility.

Two similar structural triphenylamine-based Schiff bases “off-on” fluorescent probes for detecting Al3+ through naked eye manner were prepared by changing their bridging groups, one via styrene (LW1), the other via phenethyl (LW2). This modification affected the performance remarkably in terms of selectivity, sensitivity and efficiency as well as recognition mechanism. The experimental results showed probe LW1 can selectively detect trivalent ion especially for Al3+ by hydrolysis-chelation-enhanced fluorescence with a detection limit of 1.22 × 10−7 M. However, probe LW2 can only highly selectively detect for Al3+ by the direct chelation-enhanced fluorescence with a detection limit of 2.99 × 10−7 M. Furthermore, benefiting from their good water solubility and biocompatibility, cell imaging and real-time monitoring of Al3+ in living HepG2 cells were successfully achieved.

Six D–π-A model compounds (compounds 1–6) were conveniently synthesized and characterized by 1H NMR, 13C NMR, MS and single crystal X-ray diffraction. One photon absorption and emission properties were studied by using a series of UV-visible and fluorescence spectra and theoretical calculations were applied to investigate the structure–property relationships, which showed that all six compounds possessed an obvious intramolecular charge transfer process which could be attributed to their optical properties. We simultaneously investigated their fluorescence emission performance in water/acetonitrile mixtures and found that they all have outstanding aggregation induced emission properties. Scanning electron microscopy testing illustrated that orderly aggregation was the main reason for their aggregation induced emission properties. Cytotoxicity tests indicated that all these compounds had good biocompatibility for living cells, and bio-imaging studies highlighted the potential application of the six compounds in one-photon fluorescence microscopy imaging domains.

Three branched molecules (T1–T3) were synthesized through simple step to realize or enhance two-photon absorption (2PA) in aggregates. Spectra data show that one- and two-branched molecules (T1 and T2) possessed remarkable AIE properties, which came from the formation of J-aggregation because of their partial planarization in an aggregated state. SEM and DLS illustrate that the ordered aggregation and the small particle size had an important influence on fluorescence emission. Open aperture Z-scan experiments show that T1 and T2 possessed excellent 2PA properties in the aggregated state. The largest 2PA cross section was 8314 GM for T2 in aggregates, which was about 13-fold higher than that in pure solution. All the results demonstrate that the compounds could obtain outstanding 2PA performance by rationally adjusting their structure or changing state, which could provide a reference for preparing strong 2PA compounds.

An easily available triphenylamine–isophorone-based Schiff base was synthesized and its specifically triple-addressable molecular photo-switching behaviour via copper ion recognition, trans–cis isomerization and ring closure were investigated in detail. Firstly, compound Lo was able to real-time monitor Cu2+ in an acetonitrile solution via displaying the “turn-on” emission in the near infrared region with high selectivity, and sensitivity. Furthermore, two independently photochromic phenomena based on the distinct mechanisms were found surprisingly, one through the ring closure of the thiosemicarbazide moiety based on a Michael addition reaction in tetrahydrofuran solution and another through the trans–cis isomerization of aldimine (–CN–) in the solid state under the stimuli of UV/visible light. Finally, fluorescence imaging experiments in living cells demonstrated the potential practical applications in biological systems.

Cis-trans isomer and polymorphism of 9-(4-(4-nitrostyryl)phenyl)-9H-carbzole (Dye 1 ) were obtained unexpectedly. Each isomer has two polymorphs, which was characterized by X-ray single crystal diffraction. Polymorphs T1 and T2 are trans -configuration and both crystallize in monoclinic space group P 21/c. Polymorphs C1 and C2 are cis -configuration and crystallize in triclinic space group P -1 and monoclinic space group P 21/c, respectively. Trans -isomer shows better stability and higher density than that of cis -isomer, but cis -isomer displays better solubility than that of trans -isomer. The molecular structures and packing arrangements of the four kinds of crystals show different features. The twisted conformation of cis -isomer effectively avoids π-π interactions and close packing. Both the trans and cis isomers show remarkable aggregation-induced emission effect in the acetonitrile/water mixture. In addition, fluorescence cell imaging experiment proves the potential application of the two isomers of dye 1 .

Six multi-branched compounds (1–6) were conveniently synthesized through condensation reaction, and characterized by 1H NMR, 13C NMR, MS and single crystal X-ray diffraction. One-, two-photon absorption and emission properties were studied and theoretical calculations were applied to investigate the structure–property relationships, which showed that all the six compounds possessed good two photon absorption (2PA) properties. Their 2PA cross sections increased with the isophorone's branch number, the highest 2PA cross-section was 9398.23 GM for 6 in 1, 4-dioxane. Cytotoxicity tests indicated that all these compounds had good biocompatibility for living cells, bio-imaging studies highlighted the potential application of compounds 1, 2, 4 and 6 in both one- and two-photon fluorescence microscopy imaging domains.

An efficient methodology has been developed for the oxidative cross-coupling of vinyl pyridine with various boronic acids catalyzed by palladium. In this reaction, vinyl pyridines reacted with various aryl boronic acids in the presence of 10 mol% palladium(II) trifluoroacetate, 10 mol% 1,10- phenanthroline, and 1 equivalent silver(I) oxide, to give the corresponding aryl vinyl pyridine products as a single stereoisomer, with N,N-dimethylformamide as the solvent and under 1 atmosphere of oxygen gas. The aryl vinyl pyridine products were obtained in moderate to good yields after 24 hours. A mechanism for the reaction is proposed.

In this paper, a novel easily available off–on fluorescent and colorimetric probe based on triphenylamine-isophorone-based Schiff base was synthesized and characterized by 1 H NMR, 13 C NMR, MS, FTIR. A comprehensive analysis on recognition ability of the target product toward metal ions was conducted by ultraviolet absorption and fluorescence emission spectra. Results showed that the target product was stable in pH 5–9, and had effectively selective and sensitive recognition toward Cu 2+ in acetonitrile, with no significant interference of other competitive metal ions. The limit of detection of this probe was calculated as low as 1.568 × 10 −6 M for Cu 2+ .

In this paper, we reported a conveniently prepared fluorescent probe for zinc ions detection, which constructed by the condensation reaction between p-(benzothiazolyl)aniline with 4, 4- diethylaminesalicylaldehyde. The sensing ability of the probe toward zinc ions in vitro was tested by a series of UV-Vis and fluorescence spectroscopy studies, which showed that the probe possessed high sensitivity with a detection limit of 5.8nM and a rapid response time of 10s. We also carried out fluorescent bio-imaging of the probe for zinc ions in human liver hepatocellular carcinoma cells (HepG2), which showed that the probe could be utilized to detect the intracellular endogenous zinc ions visually without introducing external zinc sources. Meanwhile, co-staining experiment with organelle selective trackers was performed to illustrate that the probe could locate at endoplasmic reticulum. Finally, we successfully used it as a zinc ion developer in plant tissue, which clearly demonstrated the distribution of zinc ions in the growth stage of plant tissue.

A series of new five-coordinated mercury(ΙΙ) coordination complexes (Hg(TpzT)(SCN)2·H2O (1), Hg(TpzT)I2·H2O (2), Hg(TpzT)Br2·H2O (3), 2Hg(TpzT)Cl2·HgCl2·2H2O (4)) have been synthesized by self-assembling the flexible ligand 2,4,6-tri(pyrazole-1-yl)-1,3,5-triazine (TpzT) with HgX2 (X = SCN, I, Br, Cl). Various weak interactions including hydrogen bonds (O−H···X, C−H···X), π−π interactions, and S···S contacts play significant roles in the final topological structures of the four compounds. Unexpectedly, 5 and 6 were obtained accidentally by self-assembling TpzT with MX2 (Zn(NO3)2·6H2O or CdI2) in methanol and were assessed by X-ray crystallography, which indicated that there are nucleophilic substitution reactions. Surprisingly, all the Hg−N bonds of approximately 2.70 A in length formed by the tridentate ligand and mercuric salt are rather unusual. So density functional theory (DFT) calculations (Amsterdam density functional, ADF) were employed to study the bond dissociation energies (BDE) of Hg−N bonds in...

Four photopolymerization initiators with D-π-D (D, donor; π, conjugation system) structure have been synthesized by solvent-free reaction and characterized by 1H NMR spectroscopy, IR and elemental analysis. The one-photon and two-photon excited fluorescence have been investigated in different solvents. Experimental results of the one-photon and two-photon absorption cross sections show different trends in OPA and TPA ability with different substitution groups in donor units.

An efficient methodology has been developed for the oxidative cross-coupling of vinyl pyridine with various boronic acids catalyzed by palladium. In this reaction, vinyl pyridines reacted with various aryl boronic acids in the presence of 10 mol% palladium(II) trifluoroacetate, 10 mol% 1,10- phenanthroline, and 1 equivalent silver(I) oxide, to give the corresponding aryl vinyl pyridine products as a single stereoisomer, with N,N-dimethylformamide as the solvent and under 1 atmosphere of oxygen gas. The aryl vinyl pyridine products were obtained in moderate to good yields after 24 hours. A mechanism for the reaction is proposed.

Two new triphenylamine-cored probes ( L1 , L2 ) with different receptor units have been synthesized and fully characterized by IR, NMR and MS spectra. Their photophysical properties have been investigated in detail. The recognition abilities of two probes were evaluated by a series of metal ions, which showed that L1 could recognize Cu 2+ over other metal ions. L2 could respond to Cu 2+ , Hg 2+ in a short time, which interferes with a little each other. The Job’s plot and 1 H NMR titration of L1 with Cu 2+ and L2 with Cu 2+ (Hg 2+ ) in CD 3 CN verified the coordination mode of complexes L1 -Cu 2+ , L2 -Cu 2+ and L2 -Hg 2+ , respectively. The limit of detection of L2 for Cu 2+ was lower than that of L1 towards Cu 2+ . The results demonstrated that the receptor units in the probes had remarkable effect on recognizing metal ions. Meanwhile, L1 and L2 showed potential application in bio-imaging after mixing with Cu 2+ .

Correction for ‘Intermolecular interactions boost aggregation induced emission in carbazole Schiff base derivatives’ by Xiaoping Gan, et al., Org. Biomol. Chem., 2017, 15, 256–264.