•Three conjugated fluorescence sensors forHg2+ have been achieved through the substitution of carbonyl O atom by S atom.•The structure-property relationship are investigated by the regulating effect of R group through steric-hindrance effect.•These congeneric fluorescent sensors show consistent optical properties in living mice comparing with the test in vitro.Three congeneric fluorescent sensors that utilize Rhodamine B were developed for the detection of mercury (II) ions. This series of sensors are functionalized by various differently substituted cinnamyl aldehyde, with CN Schiff base and CS structural motif as their core segment. The performance of these sensors adjusted by steric hindrance were investigated by absorption and fluorescence spectrum, and illuminated, summarized and confirmed using DFT calculations by frontier orbital theory and Fukui- function. In addition, living cell and living mice imaging demonstrated that all the sensors could serve as a potential fluorescent agent for quantitative mercury (II) ion imaging in living organism. The obvious morphology change reveal that the coordination of HgCl2 upon these sensors may have a great influence on the material performance to a certain extent. This approach provides a significant strategy for studying structure-property relationships and guiding the synthesis of sensors with various optical properties.Download high-res image (149KB)Download full-size image

A broad-spectrum fluorescent probe, which can be applied to monitoring H2S in various biological systems, has been rationally designed and synthesized. This specific probe was applied to localize the endogenous H2S in living Raw264.7 macrophage cells, HepG2 cells, and H9C2 cells. At the same time, the probe has successfully visualized CBS- and CSE-induced endogenous H2S production and monitored CBS and CSE activity in H9C2 cells. This probe could serve as a powerful molecular imaging tool to further explore the physiological function and the molecular mechanisms of endogenous H2S in living animal systems.

The inclusion behaviors of three native or modified CDs including β-CD, 2-hydroxypropyl-β-CD (2-Hp-β-CD) and 2,6-dimethyl-β-CD (Me-β-CD) toward 5-amino-6-methyl-2-benzimidazolone (AMBI) were comparatively investigated by NMR and fluorescence titration in combination with IR spectra, X-ray diffractometry and scanning electron microphotographs. The experimental results jointly demonstrated that the phenyl ring of AMBI entered into the cavity of the CDs and located close to the narrow rims accompanied by the formation of the 1:1 inclusion complex with large stability constant in aqueous solution. The introduction of the hydroxypropyl unit to the host improved the solubility, ultimately effecting an obvious promoting in the fluorescence intensity and the stability constantThe inclusion behaviors of three native or modified CDs including β-CD, 2-hydroxypropyl-β-CD (2-Hp-β-CD) and 2,6-dimethyl-β-CD (Me-β-CD) toward 5-amino-6-methyl-2-benzimidazolone (AMBI) were comparatively investigated by NMR and fluorescence titration in combination with IR spectra, X-ray diffractometry and scanning electron microphotographs. The experimental results jointly demonstrated that the phenyl ring of AMBI entered into the cavity of the CDs and located close to the narrow rims accompanied by the formation of the 1:1 inclusion complex with large stability constant in aqueous solution. The introduction of the hydroxypropyl unit to the host improved the solubility, ultimately effecting an obvious promoting in the fluorescence intensity and the stability constant.

The water soluble solid inclusion complex of three native or modified cyclodextrins (CDs) including β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (Hp-β-CD) and 2,6-di-o-methyl-β-cyclodextrin (DIME-β-CD) and Lomustine (CCNU) were presented with the orthogonal experiment investigation of the reaction conditions. The inclusion behaviors were comparatively investigated by nuclear magnetic resonance in combination with infrared spectroscopy, thermogravimetric analysis, X-ray diffractometry and scanning electron microphotographs. The experimental results jointly demonstrated that the entrance of CCNU into the cavity of the CDs by intermolecular forces as well as hydrophobic forces and resulting in the significantly improvement of the thermostability of CCNU.

A facile and efficient route for the synthesis of tetrasubstituted imidazoles from amidines and chalcones via FeCl3/I2-catalyzed aerobic oxidative coupling has been developed. This new strategy is featured by high regioselectivity and yields, good functional group tolerance, and mild reaction conditions.

•A solvent-dependent probe was presented for dual monitoring of Ag+ and Zn2+.•The probe exhibited special selectivity and sensitivity at physiological range.•The mechanism was investigated both experimentally and computationally.•The probe was highly suitable for mapping Ag+ and Zn2+ in biological samples.A novel, solvent-dependent “off–on” probe with benzoylthiourea moiety as the functional receptor and fluorescein as the fluorophore was designed for monitoring of Ag+ in EtOH–H2O (2:8, v/v) solution and Zn2+ in CH3CN–H2O (2:8, v/v) solution at physiological range with sufficient selectivity and sensitivity. The Ag+ promoted desulfurization of thiosemicarbazide functionality in formation of the 1,3,4-oxadiazole and the coordination of Zn2+ to the O atom and N atom of the spoirolactam moiety and the S atom of the benzoylthiourea moiety were investigated to be the power that promoted the fluorescent enhancement. This probe was tested highly suitable for mapping Ag+ and Zn2+ in living human osteosarcoma MG-63 cells and microbial cell–EPS–mineral aggregates, thus, providing a wonderful candidate for tracking Ag+ and Zn2+ in biological organisms and processes.

•Six novel rhodamine-based probes for TBT were designed, synthesized and tested.•The probes show high selectivity and sensitivity in the range from 6 to 20 mM of TBT.•The probe was used to map TBT in cell-EPS-mineral aggregates.•Here we present the first examples of fluorescent probes for microscopic TBT imaging.Here we present the first examples of fluorescent and colorimetric probes for microscopic TBT imaging. The fluorescent probes are highly selective and sensitive to TBT and have successfully been applied for imaging of TBT in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell-EPS-mineral aggregates and in cell suspensions of the marine cyanobacterium Synechococcus PCC 7002 by using confocal laser scanning microscopy.

Two functionalized rhodamine based probes have been rational designed and synthesized. The probes have sufficiently high selectivity and sensitivity for the detection of Fe3+ ion both by fluorescence and ultraviolet spectroscopy with strong ability of anti-interference performance. The detection process has been shown to be reversible and involves the fluoran ring-opening upon complexation with Fe3+. The obvious fluorescence image obtained from confocal laser scanning microscopy of the detection of Fe3+ in living L929 cells demonstrate that the probes could contribute to significant breakthroughs in understanding the critically important functions of Fe3+ in related cells and biological organs.

18 unprecedented tetrazines unsymmetrically substituted at C3 and C6 by an aromatic heterocycle have been successfully prepared by the S-induced reaction of aromatic nitriles with hydrazine hydrate under thermal conditions. The spectral property investigation suggests that compounds 4d, 4e, 4f, 4p, 4q, 4r, and 4v can display intense fluorescence in the visible region, and their fluorescent properties are affected by the substituents both in tetrazine and in phenyl rings. Moreover, the electrochemical behaviors of these synthesized tetrazines are demonstrated to be fully reversible. Furthermore, density functional theory (DFT) calculations for these compounds were performed to investigate their optimized structures, Fukui function and reactivity or selectivity in the inverse electron demand Diels–Alder reaction.

Three new mixed ligand CuIIN2O2 complexes, namely, [CuII(2-A-6-MBT)2(m-NB)2] (1), [CuII(2-ABT)2(m-NB)2] (2), and [CuII(2-ABT)2(o-NB)2] (3), (2-A-6-MBT = 2-amino-6-methoxybenzothiazole, m-NB = m-nitrobenzoate, 2-ABT = 2-aminobenzothiazole, and o-NB = o-nitrobenzoate), have been prepared by the biomimetic synthesis strategy, and their structures were determined by X-ray crystallography studies and spectral methods. These complexes exhibited the effective superoxide dismutase (SOD) activity and catecholase activity. On the basis of the experimental data and computational studies, the structure–activity relationship for these complexes was investigated. The results reveal that electron-accepting abilities of these complexes and coordination geometries have significant effects on the SOD activity and catecholase activity. Then, we found that 1 and 2 exerted potent intracellular antioxidant capacity in the model of H2O2-induced oxidative stress based on HeLa cervical cancer cells, which were screened out by the cytotoxicity assays of different kinds of cells. Furthermore, 1–3 showed the favorable biocompatibility in two different biological models: Saccharomyces cerevisiae and human vascular endothelial cells. These biological experimental data are indicative of the promising application potential of these complexes in biology and pharmacology.

A copper-catalyzed cascade coupling and aerobic oxidation of aromatic nitriles and 2-aminobenzylamine for the synthesis of 3,4-dihydroquinazolines and quinazolineshas been achieved. The catalytic system, characterized by not adding additives and using molecular oxygen as the sole oxidant, exhibited exquisite substrate specificity and operated under mild conditions through inherently “green” processes.

A series of novel and convenient fluorescent probes with Schiff base functionality were presented for direct detection of OCl−via the irreversible OCl−-promoted oxidation and hydrolyzation reaction in formation of the ring-opened product, fluorescein. Prominent high sensitivity, selectivity and anti-interference OCl−-induced fluorescence and color change over a wide range of tested metal ions performance were observed for each probe under physiological conditions, thus making the probes well suitable for sensing of OCl− in living cells.A series of novel and convenient fluorescent probes with Schiff base functionality are presented for direct detection of OCl−via the irreversible OCl−-promoted oxidation and hydrolyzation reaction in the formation of the ring-opened product fluorescein. Prominent high sensitivity, selectivity and anti-interference performance were observed for each probe under physiological conditions, thus making the probes well suited for sensing of OCl− in living cells.

A new complex, bis[2-(1H-benzimidazol-2-yl)benzoato]nickel(II) (NiL2), has been synthesized and characterized. It was used as catalyst for synthesis of dimethyl carbonate (DMC) from methanol and CO2 in the presence of dicyclohexyl carbodiimide (DCC) as promoter. The effects of temperature, reaction time, and amount of catalyst on the reaction, and the reusability of the catalyst, were investigated. A catalytic mechanism is proposed. The results revealed that NiL2 + DCC had excellent catalytic activity, because this catalytic system promoted facile formation of DMC, with acceptable yield, in the presence of a small amount of NiL2 and under moderate conditions (80 °C, 1.0 MPa). Moreover, the catalyst has been consecutively used five times without significant loss of activity.

A novel rhodamine based probe with a unique six-membered spirocycle was rationally designed for detection of Hg2+ with greatly improved selectivity, sensitivity, and photostability. The probe has been shown to be suitable for Hg2+ imaging in living cells and mapping Hg2+ distribution in living cell–EPS–mineral aggregates under anoxic conditions.

Two novel fluorescein-based OCl− chemosensors were designed, synthesized and characterized. Both fluorescence probes utilize an irreversible OCl−-promoted oxidation reaction to trigger the activation of fluorescence. These probes were shown to be highly selective for OCl−, and showed real time responses as well as a positive linear relationship to OCl− concentrations. The probes were successfully applied for the detection of OCl− in tap water and for fluorescence imaging of OCl− in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell–EPS–mineral aggregates.

A novel rhodamine based probe has been synthesized as an “off–on” chemosensor for Fe3+. Upon coordination with Fe3+, the probe displayed good brightness and fluorescent enhancement. A linear relationship was observed to exist between the relative fluorescence intensity of this probe and the concentration of Fe3+ in the range of 5 μM–20 μM with a detection limit of 5 μM. It offered highly sensitive toward Fe3+ over other ions. The recognizing behaviors toward Fe3+ have been investigated both experimentally and computationally. It can be expected that Fe3+ coordinated with the N atom of thiazole moiety in the probe accompanied by the transferring of electrons of the phenylthiazole resulted in the opening of the spiro-ring.Highlights► A novel rhodamine derived fluorescent probe has been synthesized. ► The probe shows an intense fluorescent intensity and a clear color change. ► It offers highly sensitive toward Fe3+ over other cations. ► Its recognizing behavior towards Fe3+ has been investigated.

Three new rhodamine-based probes Y1–Y3 were synthesized as “off–on” chemosensors for Fe3+ imaging in living cells. The recognizing behaviors were investigated both experimentally and computationally. The crystal structure of the complex Y3-Fe3+ revealed that Fe3+ preferred to coordinate with the N atom of benzothiazole moiety rather than the O atom of carboxyl group.

Eight chlorinated fluoresceins have been synthesized by the reaction of chlorinated resorcinols with 4, 5, 6, 7-tetrachlorophthalic anhydride or 3, 6-dichloro-4-carboxyphthalic anhydride in the presence of methanesulfonic acid. The spectral properties of the chlorinated fluoresceins were studied. It was found that they have absorption and emission maxima at long wavelengths and high fluorescence quantum yields. Emission spectra of chlorinated fluoresceins shifted towards long wavelength with increase in chlorine. pH-dependent properties of chlorinated fluoresceins were studied in detail. These compounds showed a strongly pH-sensitive range of 3.0–7.0. These chlorinated fluoresceins will be used as pH probes for pH measurement of the cell because of the high quantum yield and strong pH-sensitivity.Research highlights► Eight chlorinated fluoresceins have been synthesized in the presence of methanesulfonic acid. ► Emission spectra of these compounds shifted towards long wavelength with increase in chlorine. ► Eight chlorinated fluoresceins showed a strongly pH-sensitive range of 3.0–7.0. ► They have emission maxima at long wavelengths and high fluorescence quantum yields.

A rapid and efficient method for the synthesis of 2-imidazolines and their N-hydroxyethyl derivatives from the reaction of aromatic nitriles with ethylenediamine (EDA) or N-(2-aminoethyl)ethanolamine (AEEA) using cupric indole-3-acetate (Cu(II)–(IAA)2) as a reusable catalyst under reflux and microwave conditions is reported. And seven new N-hydroxyethyl-imidazolines were reported for the first time.

A fluorescent chemosensor for Fe3+, rhodamine-aminobenzothiazole conjugate has been synthesized and characterized by 1H NMR, 13C NMR and X-ray crystallography. The sensor demonstrates strong Fe3+- selective orange fluorescence and a pink color switch. Furthermore, the recognizing behavior has been investigated both experimentally and computationally.

Eight chlorinated fluoresceins have been synthesized by the reaction of chlorinated resorcinols with 4, 5, 6, 7-tetrachlorophthalic anhydride or 3, 6-dichloro-4-carboxyphthalic anhydride in the presence of methanesulfonic acid. The spectral properties of the chlorinated fluoresceins were studied. It was found that they have absorption and emission maxima at long wavelengths and high fluorescence quantum yields. Emission spectra of chlorinated fluoresceins shifted towards long wavelength with increase in chlorine. pH-dependent properties of chlorinated fluoresceins were studied in detail. These compounds showed a strongly pH-sensitive range of 3.0–7.0. These chlorinated fluoresceins will be used as pH probes for pH measurement of the cell because of the high quantum yield and strong pH-sensitivity.Research highlights► Eight chlorinated fluoresceins have been synthesized in the presence of methanesulfonic acid. ► Emission spectra of these compounds shifted towards long wavelength with increase in chlorine. ► Eight chlorinated fluoresceins showed a strongly pH-sensitive range of 3.0–7.0. ► They have emission maxima at long wavelengths and high fluorescence quantum yields.