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For environmental safety, it is important to establish a simple, rapid, and sensitive method for emerging pollutants. Here, a dispersive solid-phase extraction (d-SPE) method based on an iron-based metal-organic framework (Fe-MIL-88-NH

In this paper, a new hollow fiber liquid-phase microextraction method was developed to improve the extraction of five fluorescent whitening agents that migrated from plastics food contact materials. Influencing factors, such as the types of membrane, the extraction solvent, the stirring speed, the addition of salt ion, and extraction time, were investigated in detail. Under the optimal conditions, high enrichment factors (71-205) can be obtained with 15 μL extraction solvent. The new method is advantageous; the polypropylene hollow fiber membrane modified by sepiolite nanoparticles had excellent solvent binding force and mass transfer effect compared with the conventional extraction technique. The extracts were analyzed by high performance liquid chromatography-tandem mass spectrometry, the limits of detection were 0.3 or 0.9 ng kg

Inflammation is a contributing factor to the initiation and progression of many diseases, and some food-derived biofunctional peptides show high anti-inflammatory activity. In our previous study, we demonstrated that peptides derived from trypsin hydrolysis of rice protein show good immunological activity. In the present study, proteins of broken rice were extracted and identified by macroporous resin fractionation and liquid chromatography/tandem mass spectrometry (LC-MS/MS). Subsequently, a bioinformatics prediction and in silico simulation approach was used to screen for peptides showing anti-inflammatory activity, including inhibition of the production of nitric oxide and proinflammatory cytokines (interleukin-1β, interleukin-6, and tumor necrosis factor-α) by lipopolysaccharide-stimulated RAW264.7 mice macrophages. Three peptides (DNIQGITKPAIR, IAFKTNPNSMVSHIAGK, and IGVAMDYSASSKR) that demonstrated the highest binding affinity were synthesized, and their in vitro anti-inflammatory activity was investigated. This is the first study that integrates LC-MS/MS identification and bioinformatics prediction for reporting the anti-inflammatory activity of anti-inflammatory peptides derived from broken rice protein. The study findings revealed that the peptides derived from the byproduct of rice milling could be potentially used as natural anti-inflammatory alternativities.

Imidacloprid as a widely used neonicotinoid insecticide can cause harmful pesticide residue inevitably. Metal-organic frameworks (MOFs) were innovatively composited to improve the light absorption and degradation performance of Bi2WO6 semiconductor, which expanded the photodegradation application in solving environmental problems. Based on the synergistic effect of Bi2WO6 and NH2-MIL-88B(Fe), a Bi2WO6/NH2-MIL-88B(Fe) (BNM) heterojunction photocatalyst with high-performance of photocatalytic degradation activities was successfully synthesized. The optimized BNM catalyst had a good degradation rate under visible light, which was mainly caused by generation of the active ·OH. Transient photocurrent response and electrochemical impedance tests verified that 1:2 BNM exhibits a highest charge separation and a lowest carrier recombination rate which were favorable to the photocatalytic activity. Cycle experiments show that the composite photocatalyst had good reusability and stability which were very important for potential industry applications.

The frequent exposure of the widely used dye, basic fuchsin (BF), is seriously threatening the health of human central nervous system. Thus, removing the environmental pollution caused by BF is crucial, and photocatalytic technology recently has been used to degrade the pollutions dye. In this study, the binary composite SrAl

The anion zinc-based metal–organic framework [HDMA]2n[Zn2n(DMA)2n(1,4-BDC)3n]·2nDMF·6nH2O (1, DMF = N,N-dimethylformamide, 1,4-H2BDC = 1,4-benzenedicarboxylic acid, DMA = dimethylamine) with open channels has been used as a luminescent sensor for Cd2+ detection, and was obtained by solvothermal synthesis and fully characterized. It shows excellent fluorescence stability in aqueous solution, which was further enhanced with a remarkable fluorescence shift upon introduction of Cd2+, while negligible effects occurred for Fe2+, Zn2+, Fe3+, Cu2+, Co2+, Ni2+, Mn2+ and Pb2+, respectively. The detection limit is 9.9 μM with a linear range between 50 and 600 μM for Cd2+. Furthermore, it can be used to detect Cd2+ in tap water and rice samples directly. Solid state 13C NMR spectra give direct evidence for the ion exchange between protonated dimethylamine and Cd2+ hydrates, which results in the increase of fluorescence and blue shift of the wavelength. The coordination of Cd2+ with the carboxyl groups of 1 in the interface of nano-channels can be also observed using IR spectra, where a structural model has been suggested in the confined channels. This may provide a new construction method for anion fluorescent MOF materials, where a confined sample has obvious influence on the detection of Cd2+. The maximum adsorption capacities are 10.36, 54.53, 103.06 and 8.78 mg g−1 for CH4, CO2, O2 and N2 at 30 bar respectively.

Selective liquid and gas adsorptions are important for environmental control and industrial processes. Here, unique porous lanthanide–organic frameworks of [Ln2(1,3-pdta)2(H2O)2]n2n– {Ln = La (1), ...

A Fe3O4/mesoporous graphitized carbon (Fe3O4/m-GC) composite was prepared through a facile calcination method with iron-based metal–organic frameworks (Fe-MOFs) as a sacrificial template. After carbonization, the Fe3O4 nanoparticles were uniformly dispersed in the mesoporous carbon support, resulting in spatial structural stability. The mesoporous carbon support obtained was highly graphitized and exhibited eminent electrical conductivity, which accelerated the electron transfer between the Fe3O4 nanoparticles by Fe(II)/Fe(III) redox cycles and m-GC by C = Csp2/C-Csp3 redox cycles, leading to the excellent peroxidase-mimetic activity of Fe3O4/m-GC. Km values for tetramethylbenzidine (TMB) and H2O2 were 26.8 and 15.8 times lower than that of natural horseradish peroxidase, respectively. Taking advantage of the peroxidase-mimetic activity of Fe3O4/m-GC, a colorimetric assay was fabricated for detecting glucose in the range 0.5 ~ 200 μM, with a limit of detection of 0.24 μM. Fig 1 A Schematic illustration of the preparation process of Fe3O4/m-GC, B schematic illustration of a proposed synergistic catalytic mechanism of TMB oxidation by Fe3O4/m-GC.

Imidacloprid as a widely used neonicotinoid insecticide can cause harmful pesticide residue inevitably. Metal-organic frameworks (MOFs) were innovatively composited to improve the light absorption and degradation performance of Bi

A Fe

Coordination polymers (CPs) of mixed-ligand lanthanide complexes [Ln2(1,3-pdta)(TPA)(H2O)2]n·nH2O [Ln = La, 1; Ce, 2; Pr, 3; Nd, 4] (1,3-H4pdta = 1,3-propanediaminetetraacetic acid; H2TPA = terephthalic acid) were hydrothermally synthesized with flexible 1,3-pdta and rigid TPA ligands. Moreover, lanthanide propanediaminetetraacetates [Ln(1,3-Hpdta)(H2O)]2n·nH2TPA·xH2O [Ln = Sm, 5; Gd, 6] with multi-layered structures were also obtained. In 1–4, both 1,3-pdta and TPA coordinate with lanthanide ions through carboxyl oxygen and nitrogen atoms. In 5 and 6, only 1,3-Hpdta coordinates with the central lanthanide ion, where one nitrogen atom in 1,3-Hpdta is protonated, and TPAs are crystallized as H2TPA with the central multi-layered structures of [Ln(1,3-Hpdta)(H2O)]2n through very strong hydrogen bonds [2.504(4) Å]. Solid-state 13C NMR analysis of 1 revealed the coordination of carboxyl groups. However, the methylene groups of 1,3-pdta showed an obvious upfield shift, which can be attributed to the effects of the phenyl ring in TPA ligand. The successful synthesis of these mixed-ligand lanthanides provides a rational design of such lanthanide CPs with flexible and rigid ligands.

The design and construction of a novel magnetic resonance sensor (MRS) is presented for bisphenol A (BPA) detection. The MRS has been built based on the core component of magnetic Fe3O4 nanoparticles (~ 40 nm), which were uniformly distributed in nanoporous carbon (abbreviated as Fe3O4@NPC). The synthesis was derived from the calcination of the metal organic framework (MOF) precursor of Fe-MIL-101 at high temperature. Fe3O4@NPC was confirmed with enhanced transversal relaxation with r2 value of 118.2 mM−1 s−1, which was around 1.7 times higher than that of the naked Fe3O4 nanoparticle. This enhancement is attributed to the excellent proton transverse relaxation rate of Fe3O4@NPC caused by the reduced self-diffusion coefficient of water molecules in the vicinity of Fe3O4 nanoparticles in the nanoporous carbon. BPA antibody (Ab) and antigen (Ag)-ovalbumin (OVA) were immobilized onto the Fe3O4@NPC to form Ab-Fe3O4@NPC and Ag-Fe3O4@NPC, respectively. These two composites can cause the three-dimensional assembly of Fe3O4@NPC via immunological recognition. The presence of BPA can compete with antigen-OVA to combine with Ab-Fe3O4@NPC, thereby breaking the assembly process (disassembly). The difference in the change of the T2 value before and after adding BPA can thus be used to monitor BPA. The proposed MRS not only revealed a wide linear range of BPA concentration from 0.05 to 50 ng mL−1 with an extremely low detection limit of 0.012 ng mL−1 (S/N = 3), but also displayed high selectivity towards matrix interferences. The recoveries of BPA ranged from 95.6 to 108.4% for spiked tea π, and 93.4 to 104.7% for spiked canned oranges samples, respectively, and the RSD (n = 3) was less than 4.4% for 3 successive assays. The versatility of Fe3O4@NPC with customized relaxation responses provides the possibility for the adaptation of magnetic resonance platforms for food safety development.

To resolve the occurrence of unfulfillable detection in high-salts foods, we used fluorescence resonant energy transfer (FRET) sensors based on nanoparticle upconversion. In this study, we developed a novel FRET sensor for the detection of bisphenol A (BPA) in high-salt foods. We based this approach on the assembly of aptamer modified upconversion nanoparticles (DNA1-UCNPs) and complementary DNA modified metal organic frames (DNA2-MOFs), which possessed corresponding wavelength absorption. Targeting BPA signal transduction was performed using the BPA aptamer, via competitive recognition between the BPA analyte and complementary DNA sequences in a high-salt solution. Sensor adaption in high-salt samples was attributed to functional hydrophilic groups, modified in the MOFs, and the enhanced colloidal stability of these MOFs. The MOF-UCNP assembly displayed considerable analytical performance in terms of BPA detection, with a linear range of 0.1–100 nM, and a limit of detection (LOD) of 0.02 nM, in a 340 mM NaCl food sample (the energy drink, Gatorade). Thus, this method provides a solid basis for small molecules detection in high-salt foods.

A fluorescence resonance energy transfer (FRET)-labeled microenvironment-responsive immunosensor modulated by acetylcholinesterase (AChE) was designed to improve the sensitivity toward Aflatoxin B1 (AFB1). Specifically, the fluorescence of functional up-conversion nanoparticles (UCNPs) was quenched strongly by pH-sensitive dye fluorescein isothiocyanate (FITC). The immune-recognition-driven UCNPs-AChE assembly allows the reduction of microenvironment pH around the surface of UCNPs. This occurrence quenched the fluorescence of functional UCNPs, thereby achieving quantitative determination of AFB1. The pre-constructed FRET system (functional UCNPs) minimized the spatial distance between UCNPs and FITC, enhancing the effective FRET quenching. The quenching efficiency reached 95%. At the same time, the trace target-induced AChE archived functional UCNPs, thereby destroyed most UCNP-FITC (FRET system) for signal amplification. The AFB1 LODs were as low as 0.003 nM. We expect that the FRET-labeled microenvironment-responsive immunosensor will make up-conversion fluorescence sensing more efficient for future research.

The study aims at improving the solubility of rice protein (RP) by covalent coupling of proteins to polysaccharide via Maillard reaction in macromolecular crowding conditions. The formation of RP-dextran conjugates (RPC) was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, size exclusion chromatography and infrared spectra. The optimum conditions for the Maillard reaction between rice protein and dextran were 90 °C, pH 11, 60 min, and the mass ratio of RP to dextran was 1:3. The solubility of the RP-dextran conjugates in the buffer solution of pH 7–9 was greater than 80%. The high solubility of the RP-dextran conjugate was due to the introduction of dextran. Dextran covalently bound to RP has many hydrophilic hydroxyl groups, which reduced the ratio of hydrophobic groups on the surface of RP. At the same time, the emulsification and foaming properties of the RP-dextran conjugates were greatly improved compared to that of original RP. The application of crowded conditions can be used as a new way to enhance the reaction, improve the solubility of rice protein, while retaining the protein structure, thus contributing to the industrialized application of rice proteins.

The new food-derived bio-functional peptides are urgently needed globally, but the separation and purification process for obtaining the immunopeptides from food is low efficiency and highly time-consuming. In the present study, rice proteins were extracted and identified by using liquid chromatography/tandem mass spectrometry (LC-MS/MS). Furthermore, a strategy combining immuno-prediction and in silico simulation was used to screen for peptides showing immunomodulatory activity, including inhibition of the release of nitric oxide, tumor necrosis factor-α, and the interleukins IL-6 and IL-1β in lipopolysaccharide-induced RAW264.7 mouse macrophages. This LC-MS/MS identification and immuno-prediction method may provide insights for the potential identification of more food-derived immunopeptides.

Selective enrichment of the highly active antioxidant peptides is required as the lack of an efficient method leads to long screening processes, hampering the research of antioxidant peptides. A simple synthetic metal–organic framework MIL-53 (Cr) was initially applied to extract specific antioxidant peptides from rice dreg protein hydrolysate. The highest active fraction was further purified by reversed-phase high-performance liquid chromatography. The antioxidant peptides with the highest antioxidant activities were identified as Gly-Asp-Met-Asn-Pro and Leu-Leu-Leu-Arg-Trp by LC–MS. These two peptides were synthesized and also exhibited good scavenging activity on the DPPH free radical, superoxide anion free radical and hydroxyl radical, and good chelating ability on Fe2+. The results confirmed that the angling method was effective for antioxidant peptide enrichment from protein hydrolysates.

In order to avoid the occurrence of false positives and false negatives caused by conventional enzyme-linked immunosorbent assay (ELISA), we established a novel indirect competitive MOF-linked immunosorbent assay (MOFLISA) method for the high throughput and high sensitive detection of aflatoxin B

Herein, a universal surface-enhanced Raman scattering (SERS) detection platform based on enzyme-guided crystal growth has been fabricated for the first time. In this system, the BPA-aptamer-modified enzyme glucose oxidase was mixed with the complementary DNA sequences of the BPA-aptamer-coated AuNSs, leading to the reduction in crystallization rate to form the core/shell structure and generate the SERS signal. Because of the different concentrations of the BPA target, the crystallization degree of the AuNS surface varied which led to the corresponding SERS signals. Our results showed that this method allowed a limit of detection of 5 × 10−17 g mL−1 for BPA. This work opens a new horizon for constructing promising SERS sensors for environmental monitoring and food safety.

Summary Dextran was grafted on to rice protein (RP) by the wet-heating Maillard reaction, and the structure and functional properties of the rice protein–dextran conjugates (RPDCs) were investigated. The RPDCs obtained by the Maillard reaction exhibited superior functionality compared with original RP. The solubility, emulsifying activity index, emulsifying stability index, foaming activity index and foaming stability of the RPDCs increased by factors of 7.50, 1.79, 2.20, 1.69 and 2.01, respectively, compared to original RP. The molecular weight, particle size distribution, surface hydrophobicity, secondary structures, amino acid compositions and chemical bonds of RPDCs were also characterised. The structure–function relationship was preliminary discussed, and the relationship suggests that the improvements in the functional properties were closely related to structural changes.

This investigation enables amino-functionalized metal–organic frameworks (MOFs) materials for the removal of imidacloprid (IMC). Two Fe-based MOF materials of NH2-MIL-88B(Fe) and NH2-MIL-101(Fe) both exhibited high adsorption capacity and Fenton-like degradation ability for IMC which were utilized to remove IMC from aqueous solution. Although the adsorption capacity of NH2-MIL-101(Fe) was higher than that of NH2-MIL-88(Fe), the degradation abilities of both MOF materials were similar. The removal efficiencies were evaluated through several basic studies, including concentrations of catalyst (0.12–0.3 g/L) and IMC (20–100 mg/L), pH of solution (3–11), and amounts of 30% H2O2 (0–2.0 μL/mL). By optimizing the above factors, the total removal ratio of IMC by NH2-MIL-88B(Fe) was as high as 93%, whereas the removal ratio of NH2-MIL-101(Fe) was 97%. Moreover, these MOF materials were proven to be stable and recyclable. The free radical quenching experiment and density functional theory calculation were applied to research the removal mechanism, and the hydroxyl radicals (·OH) was found to be the key active intermediate. The high catalytic efficiency can be attributed to the synergy of the Fe3+/Fe2+ redox cycle.

1,3-Propylenediaminetetraacetic acid (1,3-H4pdta, C11H18N2O8) is an aminopolycarboxylic acid and has been researched widely. It is a hexadentate (“six-toothed”) ligand as a typical chelating agent. In neutral solution, it mainly formed water-soluble monomeric coordination complexes [TM(1,3-pdta)(H2O)x]y− (TM = transition metal; x = 0,1; y = 1,2) when coordinated with first transition metals. When involving lanthanide complexes, monomeric and dimeric complexes, different kinds of one-dimensional (1D) and two-dimensional (2D) coordination polymers were isolated. In acidic solution, the coordination modes of 1,3-pdta ligand were widely increased with the variation of acidity and temperature of the solution.

To prepare immunomodulation peptides from rice protein hydrolysates (RPHs), trypsin was employed for enzymatic hydrolysis, and the immunomodulating activities of RPHs were studied using mouse peritoneal macrophage proliferation assay. The peptide fractions with the highest activity were further purified using macroporous adsorption resin, strong cation-exchange chromatography, gel filtration chromatography and reversed-phase high-performance liquid chromatography. The peptide sequence was identified as Tyr-Gly-Ile-Tyr-Pro-Arg (YGIYPR) by high-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometer. Evaluating its immunomodulatory activity showed that YGIYPR enhanced the proliferation of macrophage RAW 264.7 cells in the range of 12.5–100 μg/mL, and even a minimum dose achieved good proliferation. The results demonstrated that the RPHs prepared by trypsin could serve as a source of immunomodulating peptides and the immunomodulatory peptide YGIYPR is a potential natural ingredient for manufacture of functional foods or health care products.

A rapid surface-enhanced Raman scattering (SERS) method for Pb2+ detection has been developed based on l-cysteine-modified Ag-coated Au nanoparticles with core-shell nanostructure. Specifically, l-cysteine-functionalized Au@Ag core-shell probes bearing Raman-labeling molecules (4-ATP) are used to detect Pb2+ upon the formation of nanoparticle aggregates. The proposed SERS-based method shows a linear range between 5 pM and 10 nM, with an unprecedented limit of detection (LOD) of 1 pM for Pb2+; this LOD shows the method to be a few orders of magnitude more sensitive than the typical colorimetric approach that is based on the aggregation of noble metal nanoparticles. Real water samples diluted with pure water have been successfully analyzed. This SERS-based assay may provide a general and simple approach for the detection of other metal ions of interest, and so could have wide-ranging applications in many areas.

Water-soluble wheel-like icosanuclear peroxotitanate K16[Ti20(μ-O)8(HO2)8(O2)12(R,R-tart)12]·52H2O (1) chelated by tartrate has been successfully isolated. As the largest peroxotitanate reported, {...

In order to avoid the occurrence of false positives and false negatives caused by conventional enzyme-linked immunosorbent assay (ELISA), we established a novel indirect competitive MOF-linked immunosorbent assay (MOFLISA) method for the high throughput and high sensitive detection of aflatoxin B1. This method replaces the natural enzyme with functional MOFs to catalyze a chromogenic system. As a result, the limit of detection (LOD) of the MOFLISA method was 0.009 ng·mL−1 with a linear working range from 0.01 to 20 ng·mL−1. The developed MOFLISA method for AFB1 has a 20-fold improved LOD value compared with the conventional ELISA. The recoveries and relative standard deviations (RSD) ranged from 86.41 to 99.74% and 2.38–9.04%, respectively. The results demonstrate that the recovery rate and accuracy of this detection method is better than that of conventional ELISA, reducing risks of false positive and false negative results.

The effects of microwave treatment Maillard reaction on rice protein (RP) and dextran was investigated. Microwaving accelerated the Maillard reaction between RP and dextran. A solubility of 24.22% was reached by conventional heating for 5 min, whereas microwave treatment obtained a solubility of 64.25% over the same amount of time. The activation energy of the Maillard reaction by microwave treatment was calculated to be 28.52 kJ/mol which is lower than that by conventional heating. Molecular weight analysis and Fourier transform infrared spectroscopy (FTIR) demonstrated that the Maillard reaction induced changes in molecular weight and chemical structure. Spectral analysis showed that the Maillard reaction by microwaving allowed the RP tertiary structure to expand more widely, resulting in better solubility of conjugates. In general, microwave treatment Maillard reaction products (PM) showed higher improvement in functional properties than that of conventional heating Maillard reaction products (PC), this proved that microwave is more capable of improving functional properties. This research demonstrates an efficient method for the processing of RP to improve its functional properties, which can expand its application in the food, cosmetic, and pharmaceutical fields.

Unlike the most of α-alkoxy coordination in α-hydroxycarboxylates to vanadium, novel α-hydroxy coordination to vanadium(IV) has been observed for a series of chiral and achiral monomeric α-hydroxycarboxylato vanadyl complexes [VO(H2cit)(bpy)]·2H2O (1), [VO(Hmal)(bpy)]·H2O (2), [VO(H2cit)(phen)]·1.5H2O (3), [VO(Hmal)(phen)]·H2O (4), and [ΔVO(S-Hcitmal)(bpy)]·2H2O (5), [VO(H2cit)(phen)]2·6.5H2O (6), which were isolated from the reactions of vanadyl sulfate with α-hydroxycarboxylates and N-heterocycle ligands in acidic solution. The complexes feature a tridentate citrate, malate or citramalate that chelates to vanadium atom through their α–hydroxy, α–carboxy and β–carboxy groups; while the other β–carboxylic acidic group of citrate is free to participate strong hydrogen bonds with lattice water molecule. The neutral α-hydroxy group also forms strong intermolecular hydrogen bonds with water molecule and the negatively-charged α-carboxy group in the environment. The inclusion of a hydrogen ion in α–alkoxy group results in the formation of a series of neutral complexes with one less positive charge. There are two different configurations of citrate with respect to the trans-position of axial oxo group, where the complex with trans-hydroxy configuration seems more stable with less hindrance. The average bond distances of V–Ohydroxy and V–Oα-carboxy are 2.196 and 2.003 Å respectively, which are comparable to the V–O distance (2.15 Å) of homocitrate in FeV–cofactor of V–nitrogenase. A new structural model is suggested for R-homocitrato iron vanadium cofactor as VFe7S9C(R-Hhomocit) (H4homocit = homocitric acid) with one more proton in homocitrate ligand.

In acidic solution, a serials of water-soluble coordination polymers (CPs) were isolated as zonal 1D-CPs 1,3-propanediaminetetraacetato lanthanides [Ln(1,3-H3pdta)(H2O)5]n·2Cln·3nH2O [Ln=La, 1; Ce, 2; Pr, 3; Nd, 4; Sm, 5] (1,3-H4pdta=1,3-propanediaminetetraacetic acid, C11H18N2O8) in high yields. When 1 eq. mol potassium hydroxide was added to the solutions of 1D-CPs, respectively, two 1D-CPs [Ln(1,3-H2pdta)(H2O)3]n·Cln·2nH2O [Ln=Sm, 6; Gd, 7] were isolated at room temperature and seven 2D-CPs [Ln(1,3-H2pdta)(H2O)2]n·Cln·2nH2O [Ln=La, 8; Ce, 9; Pr, 10; Nd, 11; Sm, 12; Eu, 13; Gd, 14] were isolated at 70 °C. When the crystals of 1–4 were hydrothermally heated at 180 °C with 1–2 eq. mol potassium hydroxide, four 3D-CPs [Ln(1,3-Hpdta)]n·nH2O [Ln=La, 15; Ce, 16; Pr, 17; Nd, 18] were obtained. The two 2D-CPs [Ln(1,3-Hpdta)(H2O)]n·4nH2O (Sm, 19; Eu, 20) were isolated in similar reaction conditions. With the increments of pH value in the solution and reaction temperature, the structure becomes more complicated. 1–5 are soluble in water and 1 was traced by solution 13C{1H} NMR technique, the water-soluble lanthanides 1 and 5 show catalytic activity to ester hydrolysis reaction respectively, which indicate their important roles in the hydrolytic reaction. The europium complexes 13 and 20 show visible fluorescence at an excitation of 394 nm. The structure diversity is mainly caused by the variation of coordinated ligand in different pH values and lanthanide contraction effect. Acidic conditions are favorable for the isolations of lanthanide complexes in different structures and this may helpful to separate different lanthanides. The thermal stability investigations reveal that acidic condition is favorable to obtain the oxides at a lower temperature.

Tetranuclear copper dihydrogen 1,3-propanediaminetetraacetate [Cu4Cl4(1,3-H2pdta)2] (1) was obtained from an acidic solution, which was converted to one dimensional coordination polymer [Cu(1,3-H2pdta)]n (2) and its hydrated derivative [Cu4(1,3-pdta)2(H2O)4]·H2O (3) respectively (H4pdta = 1,3-propanediaminetetraacetic acid, C11H18N2O8) under heating condition. The four copper ions in 1 and 3 exist in quasi-symmetrical tetrahedral environments. Complex 1 consists of a tetrameric neutral unit [Cu4Cl4(H2pdta)2], which extents into a 3D supramolecular structure by inter-molecular hydrogen bonds [O3⋯Cl(1) 3.155(6) A]. In 2, [1,3-H2pdta]2− ligand links each copper ion to generate a neutral polymeric chain [Cu(1,3-H2pdta)]n with strong intra-molecular hydrogen bonds [O4⋯O2 2.620(7) A]. The protonated carboxy groups in 1 and 2 show weak coordination, while deprotonated nitrogen atoms are in coordination mode. All of the three complexes show catalytic activities to the conversions of cyclohexane to cyclohexanol and cyclohexanone with hydrogen peroxide in solution. This is attributed to the nano-constructed copper species (∼1.0 nm) and the copper coordination polymer. The chloride ion seems not related to the conversion, while unsaturated configuration is considered favorably for the conversion.

In neutral media, reactions of gadolinium ethylenediaminetetraacetates with phosphorous acid result in the formation of the mixed-ligand polymeric complex K3n[Gd(EDTA)(HPO3)]n·7nH2O (1) and dimeric complex Na6[Gd2(EDTA)2(HPO3)2]·2.5NaCl·21H2O (2) (H4EDTA = ethylenediaminetetraacetic acid) in warm solution. Further substitution with citric acid gives the monomeric gadolinium citrate with EDTA (NH4)2Na[Gd(EDTA)(H2cit)]·4H2O (3). The compounds were characterized by elemental analysis, single crystal X-ray diffraction, FT-IR, ESI-MS and thermogravimetric analysis. Structural analysis indicates that three coordinated water molecules in the gadolinium ethylenediaminetetraacetate trihydrates are replaced by phosphite ions (HPO32−) in the compounds 1 and 2. Gadolinium atoms are octa-coordinated by EDTA and the phosphite ion, the latter links adjacent Gd–EDTA units to generate an infinite one-dimensional chain in compound 1 and a dimeric octatomic ring in 2. In complex 3, coordinated water molecules were substituted by the α-hydroxy, α-carboxy and β-carboxy groups of citrate. Citrate is favourable for inhibiting the formation of Gd–EDTA phosphite. All the complexes are very easily soluble in water. The solution behavior of the isostructural lanthanum complexes was probed with 13C and 31P NMR spectra in D2O for comparison. ESI-MS analysis and recrystallization proved that complexes 1 and 2 dissociate to the monomeric unit of Gd–EDTA and free HPO32− in aqueous solution. Substitutions of gadolinium ethylenediaminetetraacetates to 1 and 2 are attributed to be the cause of nephrogenic systemic fibrosis in some way.

Investigations on aminopolycarboxylato molybdates resulted in the isolation of two interesting decameric species of iminodiacetato γ-octamolybdates (NH4)8{γ-Mo8O26[MoO3(ida)]2}·6H2O (1) (H2ida = iminodiacetic acid) and its partially reduced form, K8{γ-Mo8VI/VO26[MoVO2(ida)]2}·12H2O (2). 1 is comparable with its formal polymeric coupling form of polyaminopolycarboxylato molybdate (NH4)8n{γ-Mo8O26[Mo2O6(1,3-pdta)]}n·30nH2O (3) from 1,3-propanediaminetetraacetate (H4pdta = 1,3-propanediaminetetraacetic acid). The basic construction unit of the iminodiacetato γ-octamolybdates was isolated as a monomeric complex (NH4)4[MoO3(ida)]2·3H2O (4). While those for propanediaminetetraacetato γ-octamolybdate are a dimeric species of (NH4)5[Mo2O6(1,3-pdta)]Cl·2H2O (5) and K4[Mo2O6(1,3-pdta)]·3H2O (6) respectively. Moreover, polymeric octamolybdates with ammonium cations (NH4)6n(Mo8O27)n·4nH2O (7) and (NH4)4n(Mo8O26)n (8) were obtained under heating and hydrothermal conditions, respectively. Monomeric iminodiacetato molybdate 4 can be transformed to its decanuclear species 1 with [Mo8O26]4− anion. Mixed-valence complex 2 processes a unique deca-molybdenum core with a metallic Mo(V)–Mo(V) bond [2.573(2) A]. The complexes have been characterized by elemental analyses, spectral, X-ray structural analyses and bond valence calculations. Complexes 1–6, except for 3, showed an obvious decomposition in solution, based on solution 13C NMR observations. NMR analyses revealed that the γ-Mo8O26 units in 1 and 2 show an effect on the carbon signals. This is attributed to the Mo–O–Mo bond between the Mo8O26 and MoO3ida units. The dimeric species 5 and 6 dissociated to free ligands in ∼5% and ∼27%, respectively, based on 1H NMR spectra.

National Science Foundation of China [21073150]; National Basic Research Program of China [2010CB732303]

Ministry of Science Technology [2005CB221408]; National Science Foundation of China [20571061]; PCSIRIC [IRT 1036]

In neutral and acidic solution, homonuclear s-block metal complexes [Sr2(1,3-pdta)(H2O)3.5] n (1), {[Ba2(1,3-pdta)(H2O)6]·H2O} n (2), {[Sr(1,3-H2pdta)]·(H2O)} n (3), and [Ba(1,3-H2pdta)(H2O)3] n (4) {1,3-H4pdta=1,3-propanediamine-N,N,N′,N′-tetraacetic acid, CH2[CH2N(CH2CO2H)2]2} were isolated. In 1 and 2, hexadentate 1,3-pdta joins two metal ions via the diamine chain. In 3 and 4, the nitrogens of 1,3-H2pdta were protonated and show no coordination. There is no coordinated water in 3, unusual coordination for strontium. In 4, the coordination number is nine and there are three coordinated waters for each barium. One carboxy group of pdta is free without coordination. Thermal decomposition shows that temperatures of ligand elimination start at 408, 423, 298, and 250 °C for 1–4, respectively. Acidic condition is favorable for preparation of metal oxide at low temperature.

National Science Foundation of China [21073150]; National Basic Research Program of China [2010CB732303]

Highly water-soluble lanthanum and cerium citrates or malates with ethylenediaminetetraacetate (NH(4))(8)[Ln(2)(Hcit)(2)(EDTA)(2)]·9H(2)O [Ln = La, 1; Ce, 2], K(8)[La(2)(Hcit)(2)(EDTA)(2)]·16H(2)O (3) and K(6)[Ln(2)(Hmal)(2)(EDTA)(2)]·14H(2)O [Ln = La, 4; Ce, 5] (H(4)cit = citric acid, H(3)mal = malic acid, and H(4)EDTA = ethylenediaminetetracetic acid) were prepared from the reactions of lanthanide ethylenediaminetetraacetate trihydrates with citric or malic acid at pH 5.0-6.5. These compounds were characterized by elemental analyses, IR, TG-DTG, solution (13)C{(1)H} NMR, solid state (13)C NMR spectra and X-ray structural analyses. The main structural feature of the compounds consists of a dinuclear unit deca-coordinated by EDTA and citrate or malate. The α-hydroxy and α-carboxy groups of citrate and malate chelate in five-membered ring with one lanthanide ion, while one of the β-carboxy group coordinates with the other lanthanide ion, forming a dimeric structure. The other pendent β-carboxy groups in 1-3 form very strong intramolecular hydrogen bond with α-hydroxy groups [O1O7 2.594(4), 2.587(8) and 2.57(1) Å for 1-3 respectively]. (13)C NMR spectra of the lanthanum compounds show obvious downfield shifts based on solid and solution NMR measurements, indicating the coordinations of mixed-ligand in lanthanum complexes, while highfield shifts are observed in cerium complexes.

National Science Foundation of China[21073150]; National Basic Research Program of China[2010CB732303]

From neutral solutions, dimeric 1,3-propanediaminetetraacetato lanthanides (NH4)2[Ln2(1,3-pdta)2(H2O)4]·8H2O [Ln = La, 1; Ce, 2] and K2[Ln2(1,3-pdta)2(H2O)4]·11H2O [Ln = La, 3; Ce, 4] (1,3-H4pdta = 1,3-propanediaminetetraacetic acid, C11H18N2O8) were isolated in high yields. The reaction of excess strontium nitrate with 1 resulted in the formation of a two dimensional coordination polymer [La2(1,3-pdta)2(H2O)4]n·[Sr2(H2O)6]n·[La2(1,3-pdta)2(H2O)2]n·18nH2O (5) at 70 °C. Complexes 1-4 show a similar central molecular structure. The lanthanide ions are coordinated by two nitrogen atoms, four carboxy oxygen atoms from one 1,3-pdta ligand, two from the neighboring 1,3-pdta ligand forming a four-membered ring and two water molecules. Complex 5 has two kinds of dimeric lanthanum unit and extends into a 2D coordination polymer through strontium ions and bridged oxygen atoms, and forms a fourteen membered ring linked by oxygen atoms from carboxy groups of pdta. Complexes 1-4 are soluble in water. The (13)C{(1)H} NMR experiments for complex 1 were tested in solution. Thermal products from 1 and 5 show good catalytic activities towards the oxidative coupling reaction of methane (OCM). The conversion of methane and selectivity to C2 reached 29.7% and 51.7% at 750 °C for the product of 5. From TGA, XRD and SEM analyses, the thermal products from 1 and 5 are rod- and poly-shaped, which are assigned as lanthanum oxocarbonate and a mixture of La2O3, SrCO3 and La2O2CO3 for 1 and 5, respectively. The precursor method is favorable for the formation of regular shaped mixed oxides.