A Schiff fluorescent probe (E)-2-hydroxy-N-((4-hydroxy-2-oxo-2H-chromen-3-yl)methylene)benzoylhydrazine (LR) was designed and synthesized from 3-formyl-4-hydroxycoumarin. Probe LR was highly sensitive and selective for Zn2+/Al3+ ions and produced significant fluorescence changes (from no fluorescence to blue and green fluorescence) response in the mixed solvent DMSO/H2O (v/v = 9:1). The detection limits of probe LR for Al3+/ Zn2+ ions were 1.82 x 10-8 M and 8.32 x 10-7 M, respectively. In addition, the binding mode of probe LR with Al3+ /Zn2+ ions was determined to be 1:1 by the MS method and 1H NMR titration. The sensing mechanism of probe LR was attributed to the inhibition of free rotation of imine groups by the incorporation of Al3+/Zn2+, which effectively reduces non-radiative leaps and produces the CHEF effect, thus enhancing the fluorescence. The Probe LR test paper is capable of identifying Al3+/Zn2+ using natural light or specific wavelengths of UV light (365 nm), a process that does not rely on any costly equipment. In addition, the paper has been successfully used in real water samples to accurately detect trace amounts of aluminum and zinc ions. Importantly, LR has been successfully used to recognize Al3+/Zn2+ in zebrafish organisms, demonstrating the potential application of LR sensors in biological and environmental fields.

A Schiff-based fluorescent probe QS (6-aminobenzopyraone-2-hydroxybenzaldehyde) was synthesized for detection alkaline amino acids (arginine and lysine (Arg/Lys)) and Zn2+. The fluorescent probe QS has high sensitivity and selectivity to Arg/Lys and Zn2+ in DMSO/H2O (v/v = 9:1) solution, and significant fluorescence response (from no fluorescence to yellow fluorescence for Arg/Lys and bright green fluorescence for Zn2+). The limits of detection are 8.09x10(-)(7) M, 9.53x10(-)(7) M and 1.12x10(-)(8) M for Arg, Lys and Zn2+, respectively. The binding constants are 2.72 x 10(4) M-1, 1.72 x 10(4) M-1 and 2.35 x 10(5) M-1 for Arg, Lys and Zn2+, respectively. The fluorescence enhancement between the fluorescent probe QS and Arg/Lys is achieved by hydrogen bonding and excited state intramolecular proton transfer (ESIPT) effect, whereas the fluorescence enhancement with Zn2+ is achieved by chelation enhanced fluorescence (CHEF) effect. The binding ratio between QS and Arg/Lys was determined to be 1:1 by mass spectrometry. The single crystal structure of [Zn(QS)(2)] complex was obtained by single crystal X-ray diffraction method, and the binding ratio of QS to Zn2+ was 2:1. The QS has the advantages of strong anti-interference ability, and specific recognition of Arg/Lys and Zn2+. In addition, the QS has good applicability for the detection of Arg/Lys and Zn2+ in water samples and test strips, and has been successfully applied to zebrafish bioimaging, realizing the real-time monitoring of target analytes. This provides a strategy for biological analysis and environmental monitoring in related fields.

Three similar ligands were chosen for the syntheses of cobalt-based metal-organic frameworks (Co-MOFs): 1,4-Di(4-pyridyl)benzene (Dpb), 3,5-Bis(4-pyridyl)-1,2,4-triazolyl (Bpta), 2,5-Bis(4-pyridyl)-1,3,4-thiadiazole (Bpt), and 5-aminoisophthalic acid (NH(2)bdc). The catalysts were obtained by pyrolyzing the above-mentioned Co-MOFs at varying temperatures, and their electrocatalytic hydrogen evolution performances were studied in detail. The results revealed notable variations in the performance of the three derived catalysts, among them, the derived catalysts from Dpb-based MOFs demonstrating the highest electrocatalytic activity, an overpotential of 162 mV can achieve a current density of 10 mA cm(-2). The overpotentials of Bpta derived catalysts and Bpt derived catalysts were 295 mV and 427 mV respectively, which can drive a current density of 10 mA cm(-2). In addition, the C-dl value of the Dpb-based MOF-derived catalyst (36.5 mF cm(-2)) was higher than the C-dl value of the Bpta-based MOF-derived catalyst (6.5 mF cm(-2)) and the Bpt-based MOF-derived catalyst (0.5 mF cm(-2)). This work demonstrates optimizing electrocatalytic hydrogen evolution performance can be achieved by adjusting the ligand structures.

A naked-eye colorimetric and fluorescent response dual-channel Schiff base chemosensor (L1) with simple structure and excellent performance was synthesized by the ammoniacal aldehyde condensation reaction of 6-amino coumarin with 4-methoxy salicylaldehyde. The chemical sensor L1 showed high sensitivity and selec-tivity to HSO4- that caused obvious colorimetric (from yellow to colorless) and fluorescent (from no fluorescence to orange fluorescence) response in mixed solvents (EtOH/H2O, v/v = 9:1). And the binding constants (Ka) and limit of detection (LOD) for HSO4 -were 6.4 x 103 M-1 and 4.63 x 10-7 M, respectively. The 1H NMR and HR-MS studies confirmed that the sensing mechanism for L1 was attributed to C--N hydrolysis cleavage promoted by HSO4-. L1-loaded test strips could be employed for detecting HSO4- under daylight and 365 nm UV light without resorting to any expensive instrumentation. In addition, it was also applied to the detection of trace HSO4 -in simulated water samples, including drinking water, and tap water. It was worth mentioning that L1 has been successfully used to recognition of HSO4 -in the Zebrafish organism, indicating that the practical application of sensor L1 in the field of biology and environment provided the possibility.

With increasing global industrialization, it is urgent and challenging to develop multifunctional species for detection and adsorption in the environment. For this purpose, a novel anionic heterometallic organic framework, [(CH3)2NH2][CaEu(CAM)2(H2O)2]·4H2O·4DMF (CaEuCAM), is hydrothermally synthesized based on chelidamic acid (H3CAM). Single crystal analysis shows that CaEuCAM features two different oxygen-rich channels along the c-axis in which one CAM3- bridges two sextuple-coordinated Ca2+ and two octuple-coordinated Eu3+ with a μ4-η1: η1: η1: η1: η1: η1 new chelating and bridging mode. The characteristic bright red emission and superior hydrostability of CaEuCAM under harsh acidic and basic conditions benefit it by acting as a highly sensitive sensor for Fe3+ and 3-nitrophenol (3-NP) with extremely low LODs through remarkable quenching. The combination of experiments and theoretical calculations for sensing mechanisms shows that the competitive absorption and interaction are responsible for Fe3+-induced selective emission quenching, while that for 3-NP is the result of the synergism of host-guest chemistry and the inner filter effect. Meanwhile, the assimilation of negative charge plus channels renders CaEuCAM a highly selective adsorbent for methylene blue (MB) due to a synergy of electrostatic affinity, ion-dipole interaction, and size matching. Of note is the reusability of CaEuCAM toward Fe3+/3-NP sensing and MB adsorption besides its fast response. These findings could be very useful in guiding the development of multifunctional Ln-MOFs for sensing and adsorption applications in water media.

The development of facile luminescent sensors for detecting nitrophenols in aqueous media is of great necessity for the safety of the environment and human health, as they are a class of widespread toxic organic pollutants that cause serious adverse effects upon consumption. Based on a new multidentate asymmetric ligand (H2L) in which salicylamide and 4-nitryl-salicylaldimine are spaced by 1,2-bis(2-ethoxy)ethyl, a new hydrostable lanthanide intercycle, [Tb2L2(NO3)2]·CH3CN (Tb-[2]c), was prepared to act as a new luminescent sensor for 4-NP in water media. Structural analysis indicated that two fully deprotonated L2- ligands in cis-configuration and μ2-L-κ2O1:κO2:κO4:κN2:κO5 coordination mode were interlocked by two TbIII ions to render the emitted TbIII encapsulated by L2- for lessening non-radiative transitions. The excellent sensitizing capability of the ligand L2- to TbIII was ascertained by both experimental methods and theoretical calculations. The sensing exploration indicated that Tb-[2]c exhibited highly sensitive and selective recognition of 4-NP against other nitroaromatics in aqueous media. The recognition mechanism could be attributed to the internal filtration effect (IFE) mechanism when DFT calculations and accumulating experimental evidence were combined.

Abstract The DNA binding and the antibacterial activities of metal organic compounds have great significance for the development of anticancer drugs. In this study, a copper coordination network, [Cu2L(H2O)2]n (CuNet), based on H4L where 2,6-pyridine-dicarboxylic acid moieties are spaced by p-benzyloxy, is prepared hydrothermally. Single crystal X-ray analysis demonstrates that the fully deprotonated ligand L4– with high planarity in CuNet adopts a bis-µ2-η1: η1: η2 coordination mode to bind four Cu(II) to render a graphene-like network, which is further propped up to a 3D supramolecular framework through the hydrogen bonds between coordinated water and uncoordinated carboxyl oxygen. Considering its highly planar structural feature and excellent antibacterial properties of Cu(II), the DNA binding and antibacterial performance were explored. The UV-Visible absorption titration and EB-DNA competition determination exhibited that CuNet bound DNA in an intercalation mode with the higher binding constant Kb of 2.42 × 105 M− 1, and the comparable quenching constant Ksv of 1.62 × 104 M− 1 upon compared with the documented DNA linkers. In addition, the antibacterial activity test demonstrates that CuNet exhibits comparable inhibitory effect on Escherichia coli with that of cefradine at the concertation of 0.70 mg/mL. This work has certain significance for the development of metal drugs.

Abstract The DNA binding and the antibacterial activities of metal organic compounds have great significance for the development of anticancer drugs. In this study, a copper coordination network, [Cu 2 L(H 2 O) 2 ] n ( CuNet ), based on H 4 L where 2,6-pyridine-dicarboxylic acid moieties are spaced by p -benzyloxy, is prepared hydrothermally. Single crystal X-ray analysis demonstrates that the fully deprotonated ligand L 4– with high planarity in CuNet adopts a bis-µ 2 -η 1 : η 1 : η 2 coordination mode to bind four Cu(II) to render a graphene-like network, which is further propped up to a 3D supramolecular framework through the hydrogen bonds between coordinated water and uncoordinated carboxyl oxygen. Considering its highly planar structural feature and excellent antibacterial properties of Cu(II), the DNA binding and antibacterial performance were explored. The UV-Visible absorption titration and EB-DNA competition determination exhibited that CuNet bound DNA in an intercalation mode with the higher binding constant K b of 2.42 × 10 5 M − 1 , and the comparable quenching constant K sv of 1.62 × 10 4 M − 1 upon compared with the documented DNA linkers. In addition, the antibacterial activity test demonstrates that CuNet exhibits comparable inhibitory effect on Escherichia coli with that of cefradine at the concertation of 0.70 mg/mL. This work has certain significance for the development of metal drugs.

A dual-responsive luminescent Zn(II) coordination polymer as sensor for the detection of acetylacetone and Fe ion XU-PENG ZHANG, LI JUAN LIU and GUI-YING DONG* College of Chemical Engineering, Hebei Key Laboratory for Environment Photocatalytic and Electrocatalytic Materials, North China University of Science and Technology, No. 21 Bohai Road, Caofeidian new-city, Tangshan, Hebei, 063210, P. R. China. Department of Engineering, Caofeidian College of Technology, No. 25 Xingzhi Road, Caofeidian New-city, Tangshan, Hebei, 063200, P. R. China. Corresponding author: Gui-Ying Dong E-mail: tsdgying@126.com

One zinc coordination polymer based on 5-(4-(tetrazol-5-yl) phenyl) m-phthalic acid (tpia) was synthesized. It was characterized by powder X-ray diffraction. Fluorescence titration experiments show that 1 is a multifunctional probe for metal ions and antibiotics. In addition, its electrocatalytic performance was improved and optimized by doping cobalt ions and pyrolysis, that is 1-Co-700. 1-Co-700 has a low initial potential (-423 mV), Tafel efficiency (101.9 mV.dec(-1)) and good cycle stability (stable after at least 1000 cycles).

Three novel N-4-cavity Cu(II), Ni(II) and Zn(II) mononuclear complexes, [Cu(L)(NO3)(2)][Cu(L)(NO3)]NO3 (1) [Ni (T)(NO3)(2)] (2) and [Zn(L)(NO3)(2)] (3) were successfully synthesized via the reactions of a pyridine-containing N-4-cavity bisoxime ligand L (L = 2,2'-[Ethylenedioxobis(azetidinyl)]pyridine) with Cu(II), Ni(II) and Zn(II) nitrates, respectively. Complexes 1-3 were characterized via elemental analysis, IR, UV-Vis spectra and X-ray crystallography. All three complexes are monoclinic systems, containing one M(II) atom and one (L) ligand moiety. Complexes 2 and 3 form centrosymmetric molecules. In addition, supramolecular interactions, Hirshfeld surface analysis were used to analyze the crystal properties that have been studied.

Two unexpected tetranuclear supramolecular boxes, [Zn-4(L')(4)(CH3OH)(2)]center dot 2CH(3)OH (1) and [Co-4(L)(2)(L')(2)(CH3OH)(2)]center dot acetone (2), with M-4(mu(3)-O)(2)(mu(2)-O)(4) core were obtained through reacting coumarin Schiff base H2L (H2L = 4-hydroxy-3-((2-hydroxyphenyl-imino)-methyl)-2hchrome-2-one) with Zn(OAc)(2)center dot 4H(2)O and Co(OAc)(2)center dot 4H(2)O, respectively. Interestingly, the original ligand (H2L) has changed into a new structure (H2L') in the process of forming single crystals. The structures of 1 and 2 were characterized by X-ray single crystal diffraction. 1 and 2 are tetranuclear structures including four metal centers (Zn(II) or Co(II)), four completely deprotonated ligands (four new (L')(2-) in 1, two original (L)(2-) and two new (L')(2-) in 2), two coordinated methanol molecules and several crystalline solvent molecules. Significantly, due to the action of Zn(II) and Co(II), the original Schiff base H2L completely changed from coumarin skeleton to quinoline skeleton to form a new ligand (H2L') in 1, while in 2 half of the ligands H2L involved in coordination changed to H2L' configuration, the other half maintained the original structure. In 1, Zn1 ions are six-coordinate octahedral configuration and Zn2 are five-coordinate distorted square-pyramidal configuration with tau = 0.38. In 2, Co1 are six-coordinate octahedral configuration and Co2 are five-coordinate triangular bipyramidal configuration with tau = 0.66.

A simple, fast response and aggregation-induced emission (AIE) fluorescent chemical sensor 2,2'-(hydrazine-1,2-diylidenebis(methaneylylidene))diphenol (SX) based on o-hydroxybenzaldehyde had been designed and synthesized. Interestingly, the increase of water content, the color of the SX solution changed from colorless to bright yellow in solution, and the chemical sensor SX showed the unique AIE properties. The chemical sensor SX exhibited high selectivity and sensitivity to Zn2+ without Cu2+ in DMSO/H2O (4:1, v/v) solution, and the limit of detection was 6. 8 x 10(-8) M. In addition, the in situ generated [SX + Zn2+] system was used for the relay detection of Cu2+ without separation and purification and exhibited a new fluorescence quenching signal under the same conditions, and limit of detection [SX + Zn2+] to Cu2+ was 2.3 x 10(-8) M. Furthermore, the chemical sensor SX had been successfully applied to detect and analyze Zn2+ and relay detect Cu2+ in environmental water samples. (C) 2021 Elsevier B.V. All rights reserved.

As multifunctional luminescence sensor, EU MOF has good thermal stability and water stability. It is used for the detection of Fe3+, Cr2O72−, CrO42− and aspartic acid in water system with low detection limit. And it has good recycling performance.

Mononuclear Zn complexes and binuclear Ni complex based on coumarin Schiff base ligands, [Zn(L =6-((4-diethylamino-2-hydroxy-benzylidene amino)-benzopyran-2-one), [Co(L] ( 2) (HL =6-((4-methoxy - 2 - hydroxy - benzylidene - amino) - benzopyran - 2 one and [Ni] (3) (H =4 -hydroxy - 3 - ((4 - methoxy 2 hydroxy benzylidene) amino) benzopyran 2 one), were synthesized and characterized by elemental analysis, IR, UV Vis, fluorescence spectra and X-ray single crystal diffraction analysis. The crystal structure analysis represents that the complexes 1 and 2 possess mononuclear structure composed of one metal ion.

A simple Schiff base fluorescent probe (SW) composed of oxime and salicylaldehyde units was designed and synthesized. The probe has high selectivity and sensitivity for Zn2+ ion in mixed solvent (DMSO/H2O, V/V = 9:1). The fluorescence has obvious redshift phenomenon and visible color change. The stoichiometric ratio of the probe to Zn2+ ion was confirmed to be 1:2 (mole) by 1H NMR, MS analysis and job curves. And the detection limit of fluorescence response of the SW to Zn2+ is down to 2.53 × 10–8 mol/L. At the same time, the probe SW can be applied to the test paper detection of Zn2+ ions under 365 nm UV light and the detection of Zn2+ ions in actual water samples.

Binuclear Co-III complex [Co-2(L)(3)(DMF)(3)] containing a Schiff ligand H2L was synthesized and analyzed by elemental analysis, single crystal X-ray crystallography, FT-IR, UV-Vis absorption spectroscopy, Hirshfeld surface analysis and DFT calculation. The Co-III complex was a 3:2 ((L)(2-) : Co-III) binuclear structure. The spatial configuration of central Co-III ions was six-coordinated slightly twisted octahedron. The 3D supramolecular network structure was linked by intermolecular hydrogen bonds, C-H center dot center dot center dot pi and pi center dot center dot center dot pi stacking interactions. The Schiff ligand H2L exhibits weak luminescence, but this weak fluorescence is turned on after coordination with the Zn-II ion. Furthermore, H2L could as an "OFF-ON" chemosensor for fluorescent recognition of Zn-II.

The Schiffbase binuclear Zn(II) complexes, [Zn-2(L)(2)center dot(H2O)(2)]center dot 2DMF (1) and its coordination polymer [Zn-2(L)(2)center dot( 4,4 -bpy)(2)] ln (2) (H2L = 3-[(5-chloro-2-hydroxy-benzylidene)-amino]-4-hydroxy-chromen-2-one, 4,4' -bpy = 4,4' -bipyridine), were synthesized under the same experimental condition without or with the auxiliary ligand 4,4'-bpy, respectively. The structural analysis revealed that complexes 1 and 2 have different crystal structures. The complex 1 was a centrosymmetric binuclear structure. It is noteworthy that the linker 4,4'-bpy was introduced during the synthesis of complex 2, so that two water molecules in complex 1 were replaced by two 4,4'-bpy linkers to form one-dimensional (1D) chain-like coordination polymer. The central Zn(II) ions in complex 1 were penta-coordinated distorted square pyramid geometry with tau = 0.42. However, the Zn(II) ions of complex 2 were hexa-coordinated distorted octahedral geometry. The fluorescence spectrum showed the complex 2 containing 4,4'-bpy was substantially quenching of the fluorescence as compared with the complex 1. In addition, it could be seen from the DFT calculation the energy gaps of the complexes 1 and 2 were both reduced compared to the ligand H2L. However, the LUMO and HOMO orbits of the complex 2 were occupied by the 4,4'-bpy, which is different from complex 1, resulting in 1 and 2 had different spectral properties. (C) 2020 Elsevier B.V. All rights reserved.

A highly selective turn-on fluorescent and naked-eye colourimetric dual-channel probe for cyanide anions (CNˉ) has been designed and characterized. In the mixed solution (DMSO / H2O, 9:1, v / v), only CNˉ could cause an increase in the UV absorption intensity and the corresponding fluorescence intensity increased, and other anions had no significant effect on the probe. After treatment with cyanide in the probe solution, the solution showed a noticeable colour change, from light yellow to purple. Moreover, a fluorescence spectrophotometer can be used to observe that the fluorescence intensity of the solution is significantly enhanced. The response of the colourimetric and fluorescent dual-channel probe to CNˉ was attributed to nucleophilic addition, and the mechanism was determined by 1H NMR spectroscopy. In addition, this probe was used to detect CNˉ in actual water samples, including river water, drinking water, and tap water. The spiked CNˉ recovery rate is very high (97.2%-100.06%), and analytical precision is also very high (RSD < 2%), which shows its feasibility and reliability for detecting cyanide ions in actual water samples.

A new colorimetric method of detecting Hg2+ in aqueous solutions was proposed, based on the three color changes of gold nanoparticles (AuNPs) with the assistance of ascorbic acid (AA) and multi-sulfhydryl functionalized hyperbranched polyethylenimine (SH-HPEI). The mechanism of sensing is based on the formation of Au-Hg alloy and its aggregation, along with the corresponding three color changes from red (AuNPs) through sandy beige (Au-Hg alloy) to celandine green (larger Au-Hg alloy). Compared with usual colorimetric assays with only one color change progress from red to blue or red to purple of reported AuNPs, this assay is highly selective for Hg2+ detection due to the fact that the appearing probability of identical three color changes triggered by interfering agents or the possibility of false positive results is very, very low. The detection limit of 8.76 x 10(-9) M is lower than the guideline value of Hg2+ (30 nM) in drinking water defined by the World Health Organization (WHO). Meanwhile, the concentration range (from 8.76 x 10(-9) to 1.27 x 10(-4)M) of this new detection method is the widest one that has been reported. Moreover, this method'is successfully applied to detecting Hg2+ in real water sample. More importantly, this novel colorimetric sensor based on multiple color changes may open a new avenue for the development of Hg2+ sensing probes. (C) 2017 Elsevier B.V. All rights reserved.