Effect of Organic Ligands on Biological Availability of Inorganic Phosphorus in Soils

Citrate, oxalate, tartrate and malate were added into soils during the growthperiod of ryegrass to study the effect of different organic ligands on the release of variousinorganic P (Pi) fractions in a yellow-brown soil and a paddy soil. The results showed that oxalatewas most effective in promoting the release of total Pi in the yellow-brown soil and tartrate in thepaddy soil. The dominant Pi fractions released from the yellow-brown soil were calcium phosphate(Ca-P) and aluminum phosphate (Al-P) and those from the paddy soil were iron phosphate (Fe-P) andreductant soluble phosphate (O-P) mobilized by tartrate. Phosphorous-mobilizing capability oforganic acids in the yellow-brown soil revealed the following order: oxalate > citrate > malate >tartrate. In the paddy soil, the order was tartrate > citrate ≈ oxalate > malate. It wasdemonstrated that organic ligands were different in their capabilities of mobilizing Pi and the sameorganic ligand showed also a discrepancy in mobilizing P in different soils. Although the additionof organic ligands into soils could increase the amount of P taken up by ryegrass, the more uptakeof P, however, was not only due to the more release of Pi, but also partly from organic P. In manycases, organic ligands promoted the release of the total Pi, while different fractions showeddifferent trends: some increased and others decreased.

Organic Ligand,Competing Cation,and pH Effects on Dissolution of Zinc in Soils

A series of experiments were conducted to examine the interactive effects of an organic ligand,a competing cation, and pH on the dissolution of zinc (Zn) from three California soils,Maymen sandy loam,Merced clay,and Yolo clay loam.The concentrations of soluble Zn of the three soils were low in a background solution of Ca(NO3)2.Citric acid,a common organic ligand found in the rhizosphere,was effective in mobilizing Zn in these soils;its presence enhanced the concentration of Zn in soil solution by citrate forming a complex with Zn.The ability of Zn to form a complex with citric acid in the soil solution was dependent on the concentration of citric acid,pH,and the concentration of the competing cation Ca^(2+).The pH of the soil solution determined the extent of desorption of Zn in solid phase in the presence of citric acid.The amounts of Zn released from the solid phase were proportional to the concentration of citric acid and inversely proportional to the concentration of Ca(NO3)2 background solution,which supplied the competing cation Ca^(2+) for the formation of a complex with citrate.When the soil suspension was spiked with Zn,the adsorption of Zn by the soils was retarded by citric acid via the formation of the soluble Zn-citrate complex.The dissolution of Zn in the presence of citric acid was pH dependent in both adsorption and desorption processes.

Effects of Y(Ⅲ) Ions on the Fluorescence Properties of Ce(Ⅲ) Ion and the Organic Ligands in the Complex

The enhancement effects of Y ( Ⅲ) ions on the fluorescence of Ce ( Ⅲ) in Ce ( Ⅲ)-Y ( Ⅲ)-PMMA (polymethylmethacrylate ) or Ce ( Ⅲ)-Y ( Ⅲ)-PVC (polyvinyl chloride ) complex systems were observed. The influence of Y ( Ⅲ) ions on the emission spectra of PMMA ligands in PMMA-Y ( Ⅲ) and the fluorescent enhance- ment of Y( Ⅲ) on Ce( Ⅲ) emission in PMMA-Ce-Y by Y( Ⅲ) ion were studied. It was also of interest to note that when Y ( Ⅲ) ions were added into PMMA and into bpy(bipyridine ) , respectively , the emission spectrum of PMMA ligands was split into fine structure bands by Y ( Ⅲ) , and the fluorescence intensities of bpy ligands in bpy-Y ( Ⅲ) complexes were considerably increased.

Amorphous nickel-cobalt bimetal-organic framework nanosheets with crystalline motifs enable efficient oxygen evolution reaction: Ligands hybridization engineering

Development of high-efficiency and low-cost electrocatalyst for oxygen evolution reaction(OER) is very important for use at alkaline water electrolysis.Metal-organic frameworks(MOF) provide a rich platform for designing multi-functional materials due to their controllable composition and ultra-high surface area.Herein,we report our findings in the development of amorphous nickel-cobalt bimetal-organic framework nanosheets with crystalline motifs via a simple "ligands hybridization engineering" strategy.These complexes' ligands contain inorganic ligands(H_2 O and NO_3) and organic ones,hexamethylenetetramine(HMT).Further,we investigated a series of mixed-metal with multi-ligands materials as OER catalysts to explore their possible advantages and features.It is found that the Ni doping is an effective approach for optimizing the electronic configuration,changing lattice ordering degree,and thus enhancing activities of HMT-based electrocatalysts.Also,the crystalline-amorphous boundaries of various HMTbased electrocatalyst can be easily controlled by simply changing amounts of Ni-precursor added.As a result,the optimized ultrathin(Co,0.3 Ni)-HMT nanosheets can reach a current density of 10 mA cm^(-2)at low overpotential of 330 mV with a small Tafel slope of 66 mV dec^(-1).Our findings show that the electronic structure changes induced by Ni doping,2 D nanosheet structure,and MOF frameworks with multiligands compositions play critical roles in the enhancement of the kinetically sluggish electrocatalytic OER.The present study emphasizes the importance of ligands and active metals via hybridization for exploring novel efficient electrocatalysts.

The effect of organic ligand modification on protein corona formation of nanoscale metal organic frameworks

Nanoscale metal organic frameworks(NMOFs)have been widely reported in biomedical field for their unique porous structure and tunable multifunctionality.However,when administrated in vivo,the protein corona will be formed on the surface of NMOFs,significantly affecting their biodistribution,pharmacokinetics and drug release.Few studies paid attention to the protein corona formation process and its influencing factors of NMOFs.As a well-established strategy for altering structure features of NMOFs,the organic ligand modification may have effect on the protein corona formation process,which is to be investigated.In this study,the zirconium(Zr)-based UIO66 was chosen as model NMOFs,the organic ligand of which was modified with amino group(-NH_(2))or carboxyl group(-COOH)to synthesize UIO66-NH_(2)and UIO66-2COOH,respectively.Bovine serum albumin(BSA)was chosen as model protein to investigate the protein corona formation process of NMOFs.The current results showed that the-COOH modification remarkably enhanced the BSA adsorption on NMOFs while-NH_(2)slightly decreased the protein binding affinity.These differences may be ascribed to the two different dominate protein corona formation modes,i.e.,surface coating mode and porous embedded mode.The protein corona formation did not affect the crystal phase of NMOFs but increased the content ofα-helix of BSA.Ultimately,upon protein corona formation,the cellular uptake of NMOFs was significantly affected.We believe our study will provide a new research paradigm to the design and applications of NMOFs.

Distinct roles of pH and organic ligands in the dissolution of goethite by cysteine

Electron shuttles such cysteine play an important role in Fe cycle and its availability in soils,while the roles of pH and organic ligands in this process are poorly understood.Herein,the reductive dissolution process of goethite by cysteine were explored in the presence of organic ligands.Our results showed that cysteine exhibited a strong reactivity towards goethite-a typical iron minerals in paddy soils with a rate constant ranging from 0.01 to0.1 hr^(-1).However,a large portion of Fe(Ⅱ) appeared to be "structural species" retained on the surface.The decline of pH was favorable to generate more Fe(Ⅱ) ions and enhancing tendency of Fe(Ⅱ) release to solution.The decline of generation of Fe(Ⅱ) by increasing pH was likely to be caused by a lower redox potential and the nature of cysteine pH-dependent adsorption towards goethite.Interestingly,the co-existence of oxalate and citrate ligands also enhanced the rate constant of Fe(Ⅱ) release from 0.09 to 0.15 hr-1;nevertheless,they negligibly affected the overall generation of Fe(Ⅱ) in opposition to the pH effect.Further spectroscopic evidence demonstrated that two molecules of cysteine could form disulfide bonds(S-S) to generate cystine through oxidative dehydration,and subsequently,inducing electron transfer from cysteine to the structural Fe(Ⅲ) on goethite;meanwhile,those organic ligands act as Fe(Ⅱ) "strippers".The findings of this work provide new insights into the understanding of the different roles of pH and organic ligands on the generation and release of Fe induced by electron shuttles in soils.

Tuning the surface electronic structure of noble metal aerogels to promote the electrocatalytic oxygen reduction

The sluggish kinetics of the oxygen reduction reaction(ORR)is the bottleneck for various electrochemical energy conversion devices.Regulating the electronic structure of electrocatalysts by ligands has received particular attention in deriving valid ORR electrocatalysts.Here,the surface electronic structure of Ptbased noble metal aerogels(NMAs)was modulated by various organic ligands,among which the electron-withdrawing ligand of 4-methylphenylene effectively boosted the ORR electrocatalysis.Theoretical calculations suggested the smaller energy barrier for the transformation of O^(*) to OH^(*) and downshift the d-band center of Pt due to the interaction between 4-methylphenylene and the surface metals,thus enhancing the ORR intrinsic activity.Both Pt3Ni and Pt Pd aerogels with 4-methylphenylene decoration performed significant enhancement in ORR activity and durability in different media.Remarkably,the 4-methylphenylene modified Pt Pd aerogel exhibited the higher halfwave potential of 0.952 V and the mass activity of 10.2 times of commercial Pt/C.This work explained the effect of electronic structure on ORR electrocatalytic properties and would promote functionalized NMAs as efficient ORR electrocatalysts.

Synthesis,fluorescence properties of Eu(Ⅲ) complexes with novel carbazole functionalized β-diketone ligand

A novel carbazole functionalized β-diketone, methyl 6-（9-ethylcarbazole-3-yl）-oxoacetyl-2-pyridinecarboxylate （MEP）, and its corresponding binary Eu（III） complexes Eu（MEP）y2H2O and ternary complex Eu（MEP）aPhen with 1,10-Phenanthroline （Phen） were prepared. The ligand was characterized based on elemental analysis, FT-IR, and ^1H NMR, and the complexes were characterized with elemental analysis, FT-IR and thermogravimetric and differential thermal analysis （TG-DTA）. The investigation of fluorescence properties of the complexes Eu（MEP）3·2H2O and Eu（MEP）3Phen showed that the Eu（III） ion could be sensitized efficiently by the ligand to some extent, in partitular, in the ternary system, the secondary ligand Phen acting as a light-harvesting center was involved in the highly efficient energy transfer process, and the emission was stronger than the binary complex. In addition, the introduction of the carbazole moiety enlarged the n-conjugated system of the ligand and enhanced the luminescent intensity of the complexes.

Two Zinc Architectures:A Mononuclear Complex and a 2D Wave-like Organic-inorganic Hybrid Layer

Self-assembly of Zn（NO3）2·6H2O and 2,3,5,6-tetrabromoterephthalic acid（H2TBTA） gave rise to two new zinc metal-organic frameworks,Zn（HTBTA）2（phen）2·H2O（1） and Zn（TBTA）1/2（μ2-OH）（H2O）·0.25EtOH（2）.Complex 1 is a mononuclear molecule.The hydrogen bonding interactions further connect the mononuclear molecules to generate a 2D supramolecular architecture.Complex 2 is a 2D organic-inorganic hybrid layer framework constructed from 1D rod-shaped secondary building units.

二炔基桥联双核钌配合物的电喷雾质谱研究

A rapid method is applied to analyze conjugated organic ligands bridged binuclear ruthenium complexes by electrospray ionization-tandem mass spectrometry (ESI MSn).Fragmentation pattern be discussed.

Fluorescence and Judd-Ofelt analysis of rare earth complexes with maleic anhydride and acrylic acid

Two kinds of Eu-complexes, Eu（TTA）2（Phen）（AA） and Eu（TTA）2（Phen）（MA） （HTTA=2-Thenoyltrifluoroacetone, Phen=1,10- phenanthroline, AA=acrylic acid, MA=Maleic anhydride）, which combined the excellent fluorescence properties of Eu（TTA）2（Phen）（H2O） and the reactivity of acrylic acid and maleic anhydride with radicals, were synthesized. The two complexes were characterized by elemental analysis, infrared （IR） spectra, and X-ray photoelectron spectroscopy （XPS）. Based on the data shown from the fluorescent spectra of the Eu-MA and Eu-AA complexes, the Ωλ （λ=2 and 4） experimental intensity parameters were calculated. The results demonstrated that the Ω2 intensity parameters for the two complexes were smaller than those for the Eu（TTA）2（Phen）（H2O） complex, indicating that a less symmetrical chemical environment existed in the complexes. It implied that the radiative efficiency of the ^5D0 of these two complexes could be enhanced by ligand of MA and AA, respectively. The luminescent lifetime of the Eu-AA （r=-7.26×10^-4 s） or Eu-MA complex （r=-8.12×10^-4 s） was higher than that of the Eu（TTA）2（Phen）（H2O） complex, which was attributed to the substitution of the water molecule （H2O） in Eu（TTA）2（Phen）（H2O） by the MA or AA ligand.

Synthesis, fluorescence properties of Tb(Ⅲ) complexes with novel mono-substituted β-diketone ligands

Two novel pyridine-2,6-dicarboxylic acid derivatives of mono-β-diketone named methyl 6-biphenylacetyl-2-pyridinecarboxylate (MBP) and 6-biphenylacetyl-2-pyridinecarboxylic acid (BAA) and their corresponding binary complexes Tb(MBP)3.6H2O and Tb(BAA)3·6H2O were synthesized. The ligands were characterized by elemental analysis, FT-IR and 1H-NMR, and the complexes were characterized with elemental analysis, FT-IR, 1H-NMR and thermogravimetric and differential thermal analysis(TG-DTA). The investigation of fluo...

Well-defined coordination environment breaks the bottleneck of organic synthesis:Single-atom palladium catalyzed hydrosilylation of internal alkynes

Single-atom site(SAS)catalysts have attracted considerable attention due to their excellent performance.However,most of the current research models of SAS catalysts are based on inorganic catalysts,where“metal and coordination atom interaction”cannot simulate the fine-tuning effect of organic ligands on metal catalytic centers in homogeneous catalysts.Therefore,certain chemical transformations in homogeneous catalysis cannot be perfectly replicated.Here,we used porous organic ligand polymers as the carrier,which effectively changes the charge regulation of nanoparticles and monoatomic metal catalysts.Drawing lessons from traditional homogeneous metal/ligand catalysis,we introduced various functional groups into the ligand polymers to adjust the electronic properties,and successfully realized the hydrosilylation of internal alkynes with high catalytic performance.The selectivity and catalytic efficiency under the Pd@POL-1 catalyst system were improved compared with previous studies.The internal alkynes with various structures can complete this reaction,and the ratio of E/Zcan reach up to 100:1.

自还原法合成超小尺寸钯加氢催化剂

负载型超小尺寸金属纳米颗粒在多相催化过程中表现出优异的催化性能.虽然已经发展了一些合成方法,但仍缺少便捷地合成超小尺寸催化剂的方法.通常情况下,加氢金属催化剂往往需要经过高温还原过程.但过量的还原剂,如H2,会导致金属纳米颗粒的聚集.本研究利用含有有机配体的钯前驱体合成了金属氧化物负载的超小尺寸钯催化剂.在惰性气氛下,通过简单的煅烧即可得到尺寸均一、超小的Pd纳米颗粒(~1 nm).有机配体中的-CHx基团与氧化物载体的表面氧物种反应促进了Pd物种的还原.同时,反应过程中原位产生的CO和氧空位稳定了超小尺寸纳米颗粒.该方法所制备得到的催化剂具有较高的抗烧结能力、优异和稳定的催化加氢反应性能.

A mini review on strategies for heterogenization of rhodium-based hydroformylation catalysts

Hydroformylation has been widely used in industry to manufacture high value-added aldehydes and alcohols, and is considered as the largest homogenously catalyzed process in industry. However, this process often suffers from complicated operation and the difficulty in catalyst recycling. It is highly desirable to develop a heterogeneous catalyst that enables the catalyst recovery without sacrificing the activity and selectivity. There are two strategies to afford such a catalyst for the hydrofromylation： immobilized catalysts on solid support and porous organic ligand （POL）-supported catalysts. In the latter, high concentration of phosphine ligands in the catalyst framework is favorable for the high dispersion of rhodium species and the formation of Rh-P multiple bonds, which endow the catalysts with high activity and stability respectively. Besides, the high linear regioselectivity could be achieved through the copolymerization of vinyl functionalized bidentate ligand （vinyl biphephos） and monodentate ligand （3vPPh3） into the catalyst framework. The newly-emerging POL-supported catalysts have great perspectives in the industrial hydroformylation.