Ligand Ion Research Articles

Para-Selective C-H Borylation of Aromatic Quaternary Ammonium and Phosphonium Salts.

Aromatic ammonium and phosphonium salts are important synthetic intermediates and multifunctional materials, but para-selective functionalization of the aromatic salts remains a challenge. Here we develop an ionic ligand based on our newly designed "biphenyl-phenanthroline" skeleton and realize the Ir-catalyzed para-selective C-H borylation of seven types of aromatic quaternary ammonium and phosphonium salts. Gram-scale transformation, late-stage elaboration for drug molecule, and diversification of borylated products demonstrate the potential utility of this reaction. The mechanistic studies and computational analysis elucidate the origin of para-selectivity.

Identification of Wheat LACCASEs in Response to Fusarium graminearum as Potential Deoxynivalenol Trappers.

Fusarium graminearum (F. graminearum) can cause huge yield reductions and contamination of grain with deoxynivalenol (DON), and thus is one of the most problematic pathogen of wheat worldwide. Although great efforts have been paid and great achievements have been made to control the pathogens, there is still a wide gap for understanding the mechanism underlying F. graminearum resistance. Plant LACCASEs (LACs) catalyze the oxidative polymerization of monolignols by reinforcing cell-wall of various cell types to provide mechanical support, xylem sap transportation, and defense against pest and pathogens. To date, little has been known about LAC genes in bread wheat and their potential roles in wheat-F. graminearum interaction. Through systematic analysis of the genome-wide homologs and transcriptomes of wheat, a total of 95 Triticum aestivum laccases (TaLACs) were identified, and 14 of them were responsive to F. graminearum challenge. 3D structure modelings of the 14 TaLAC proteins showed that only TaLAC78 contains the entire activity center for oxidation and the others lack the type 1 copper ion ligand (T1Cu). Both amino acid sequence alignment and three-dimensional reconstruction after amino acid mutation showed that the loss of T1Cu is not only related to variation of the key amino acid coordinating T1Cu, but also closely related to the flanking amino acids. Significantly differential temporal expression patterns of TaLACs suggested that their subfunctionalization might occur. Promoter array analysis indicated that the induction of TaLACs may be closely associated with salicylic acid signaling, dehydration, and low-oxygen stress under F. graminearum infection. Molecular docking simulation demonstrated that TaLACs can not only catalyze lignin as a substrate, but also interact with DON, which may be docked into the binding position of the monolignols, where the LACs recognize substrates. The current study provides clues for exploring the novel functions of TaLACs in wheat resistance to F. graminearum, and TaLACs maybe candidates for conferring a high level of resistance against F. graminearum in wheat.

In-situ Raman spectroscopic analysis of dissolved silica structures in Na2CO3 and NaOH solutions at high pressure and temperature

The dissolved silica structures in quartz-saturated 0.50 and 1.50 m [mol kg H2O–1] Na2CO3 and 0.47 m NaOH solutions at up to 750 °C and 1.5 GPa were investigated by in-situ Raman spectroscopy using a Bassett-type hydrothermal diamond anvil cell. The solubility of quartz in the solutions was determined by in-situ observations of the complete dissolution of the grain. The Raman spectra of the quartz-saturated Na2CO3 and NaOH solutions at high pressures and temperatures exhibited the tetrahedral symmetric stretching band of silica monomers. The lower frequency and broader width of the band than those in pure H2O indicated the presence of both neutral and deprotonated monomers. In addition, we newly confirmed the intense bridging oxygen band and the tetrahedral symmetric stretching band of Q1 (silicate center having a single bridging oxygen atom) in the spectra of the Na2CO3 solutions. The integrated intensity ratios of the bridging oxygen band to the monomer band increased with the addition of Na2CO3 and NaOH to fluids, corresponding to an elevation of the measured quartz solubilities. These observations indicate that the formation of silica oligomers in addition to neutral and deprotonated monomers explains the high dissolved silica concentrations in the solutions. The presence of deprotonated monomers under the experimental conditions suggests that deprotonated oligomers exist in the solutions, because the production of the latter more significantly reduces the Gibbs free energy. The anionic silica species and oligomers formed in alkaline silicate fluids may act as effective ligands for certain metal ions or complexes in deep subduction zones.

Theoretical Probing of Size-Selective Crown Ether Macrocycle Ligands for Transplutonium Element Separation.

Effective separation and recovery of chemically similar transplutonium elements from adjacent actinides is extremely challenging in spent fuel reprocessing. Deep comprehension of the complexation of transplutonium elements and ligands is significant for the design and development of ligands for the in-group separation of transplutonium elements. Because of experimental difficulties of transplutonium elements, theoretical calculation has become an effective means of exploring transplutonium complexes. In this work, we systematically investigated the coordination mechanism between transplutonium elements (An = Am, Cm, Bk, Cf) and two crown ether macrocyclic ligands [N,N'- bis[(6-carboxy-2-pyridyl)methyl]-1,10-diaza-18-crown-6 (H2bp18c6) and N,N'-bis[(6-methylphosphinic-2-pyridyl)methyl]-1,10-diaza-18-crown-6 (H2bpp18c6)] through quasi-relativistic density functional theory. The extraction complexes of [Anbp18c6]+ and [Anbpp18c6]+ possess similar geometrical structures with actinide atoms located in the cavity of the ligands. Bonding nature analysis indicates that the coordination ability of the coordinating atoms in pendent arms is stronger than that in the crown ether macrocycle because of the limitation of the macrocycle. Most of the coordination atoms of the H2bp18c6 ligand have a stronger ability to coordinate with metal ions than those of the H2bpp18c6 ligand. In addition, the bonding strength between the metal ions and ligands gradually weakens from Am to Cf, which is mainly attributed to the size selectivity of the ligands. Thermodynamic analysis shows that the H2bp18c6 ligand has a stronger extraction capacity than the H2bpp18c6 ligand, while the H2bpp18c6 ligand is superior in terms of the in-group separation ability. The extraction capacity of the two ligands for metal ions gradually decreases across the actinide series, indicating that these crown ether macrocycle ligands have size selectivity for these actinide cations as a result of steric constraint of the crown ether ring. We hope that these results offer theoretical clues for the development of macrocycle ligands for in-group transplutonium separation.

Polynomials of Degree-Based Indices of Metal-Organic Networks

Aim and Objective: Metal-organic network (MON) is a special class of molecular compounds comprising of groups or metal ion and carbon-based ligand. These chemical compounds are examined employing one, two- or threedimensional formation of porous ore and subfamilies of polymers. Metal-organic networks are frequently utilized in catalysis for the parting & distillation of different gases and by means of conducting solid or super-capacitor. In various scenarios, the compounds are observed balanced in the procedure of deletion or diluter of the molecule and can be rebuilt with another molecular compound. The physical solidity and mechanical characteristics of the metal-organic network have attained great attention due to the mention properties. This study was undertaken to find the polynomials of MON. Methods: Topological descriptor is a numerical number that is utilized to predict the natural correlation amongst the physico-chemical properties of the molecular structures in their elementary networks. Results: After partitioning the vertices based on their degrees, we calculate different degree-based topological polynomials for two distinct metal-organic networks with an escalating number of layers containing both metals and carbon-based ligand vertices. Conclusion: In the analysis of the metal-organic network, topological descriptors and their polynomials play an important part in modern chemistry. An analysis between the calculated various forms of the polynomials and topological descriptors through the numeric values and their graphs is also comprised.

Indium metal-organic framework with catalytic sites coated conductive graphene for high-performance lithium-sulfur batteries

Metal-organic frameworks (MOFs) with abundant active sites and stable frame structures have great advantages for inhibiting the "shuttle effect" and alleviating volume expansion in lithium-sulfur (Li–S) batteries. However, their inherent poor conductivity hinders their application in Li–S batteries. Herein, with isophthalic acid (IPA) as the organic ligand and indium ions as the central metal, a tetrahedral cubic indium MOF (In-IPA) was synthesized and employed for the first time as a sulfur host. Experimental results suggest that In-IPA has a good catalytic effect on the conversion of polysulfides. Furthermore, three-dimensional In-IPA was coated with reduced graphene oxide (rGO) by the hydrothermal method (In-IPA@rGO). The interlaced rGO network not only significantly enhances the conductivity of In-IPA but also improves the reduction of kinetic reactions and promotes electron transport. Finally, In-IPA@rGO exhibited excellent electrochemical performance as a sulfur host. In particular, it exhibited a considerable initial capacity of 1672.3 mAh g−1 at 0.2 C and a reversible capacity of 898.7 mAh g−1 after 100 cycles. In addition, the initial capacity reached 1376.7 mAh g−1 and retained 519.8 mAh g−1 after 200 cycles at 0.5 C. This work proves that nontransition metal-organic frameworks prepared along with highly conductive rGO have synergistic advantages in Li–S battery applications.

Synthesis, Characterization and Redox studies of perchlorate-coordinated-Cu(II)N4-macrocyclic complex and its application as potent antibacterial agent

Macrocyclic ligands afford a powerful means to manipulate the geometry of metal complexes and ultimately to control their kinetics, electronic structure and reactivity. In this study, two different ring sized Cu(II)N4-macrocyclic complexes have been synthesized using a template method. The analytical techniques such as IR, UV-Vis, mass spectral analysis and cyclic voltammetry were used to investigate the synthesized macrocyclic complexes. Spectral studies of these complexes suggested that both complexes possessed saddle shaped geometry. Redox studies revealed a good electrochemical potential for the synthesized complex with significant ΔEp values. Further, the biological investigations of both complexes were carried out against E. coli, P. aeruginosa, B. cereus and S. aureus as well as antifungal activity against C. albicans and indicated a comparable antimicrobial efficacy to standard Gentamycin. The result is compatible with solvating process of released metal ion and macrocyclic ligands. Additionally, these complexes were also tested for their antibacterial activity against gram +ve and gram –ve bacteria and it was found that Cu(II) complex can be served as potential model for antimicrobial.

Ligand confinement and pure aqueous medium synthesis of novel ion imprinted membranes for advanced rare earth separation

Molecular imprinting technology has been proved an efficient strategy for separation, however ion imprinting was not so high-performance. Pure aqueous phase synthesis and ligand assistance are two prominent improvement strategies so far. This article developed a novel rare earth yttrium(Y) ion imprinted membrane (Y-IIM) in pure aqueous phase, and applied a high-performance rare earth extractant Cyanex272 as ligand in membrane basement to confine the imprinted polymerization process. Firstly, polymer inclusion membrane (PIM) containing copolymer poly(vinyl alcohol-co-ethylene) as hydrophilic additive and Cyanex272 as interior ion ligand was synthesized. Then ion imprinting in aqueous phase was initiated through redox polymerization. Results confirmed that Y-IIMs performed superior hydrophility and Cyanex272 presented improved thermal stability. Imprinted aggregates distributed separately on membrane surfaces and inner walls, as a result of the confinement by the coordination between Y and Cyanex272 ligand. The adsorption capacity on Y was 3 times that of non-imprinted membranes, and the Y-IIMs exhibited superior permeation ability for Y than Ho and Er, indicating the realization of expected specific recognition affinity for Y through ligand confinement and aqueous medium synthesis.

Visible-Light Switching of Metallosupramolecular Assemblies.

A photoswitchable ligand and palladium(II) ions form a dynamic mixture of self‐assembled metallosupramolecular structures. The photoswitching ligand is an ortho‐fluoroazobenzene with appended pyridyl groups. Combining the E‐isomer with palladium(II) salts affords a double‐walled triangle with composition [Pd3L6]6+ and a distorted tetrahedron [Pd4L8]8+ (1 : 2 ratio at 298 K). Irradiation with 410 nm light generates a photostationary state with approximately 80 % of the E‐isomer of the ligand and results in the selective disassembly of the tetrahedron, the more thermodynamically stable structure, and the formation of the triangle, the more kinetically inert product. The triangle is then slowly transformed back into the tetrahedron over 2 days at 333 K. The Z‐isomer of the ligand does not form any well‐defined structures and has a thermal half‐life of 25 days at 298 K. This approach shows how a thermodynamically preferred self‐assembled structure can be reversibly pumped to a kinetic trap by small perturbations of the isomer distribution using non‐destructive visible light.

A Strong and Rigid Coordination Adaptable Network that Can Be Reprocessed and Recycled at Mild Conditions

A Strong and Rigid Coordination Adaptable Network that Can Be Reprocessed and Recycled at Mild Conditions

Structure and Magnetic Properties of a Trinuclear Copper(II) Complex with Bridging Carboxy-Phenyl Nitronyl Nitroxides

A new complex {(NITPBAH)2[Cu(hfac)2]3} 1 derived from carboxy-phenyl-substituted nitronyl nitroxide radical (NITPBAH) and Cu(hfac)2(H2O)2 (NITPBAH = 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac = hexafuoroacetylacetonato) has been synthesized as well as characterized structurally and magnetically. The single-crystal X-ray diffraction analyses indicated that the complex {(NITPBAH)2[Cu(hfac)2]3} 1 consists of trinuclear five-spin molecule system. Each NITPBAH ligand is bound to two copper atoms with its two oxygen atoms from ONCNO group. Copper atoms display two different coordination types. The central copper atom lies on an inversion center and is six-coordinated in an elongated octahedron using two hfac molecules and two oxygen atoms of ONCNO group from two different NITPBAH ligands. Two terminal copper atoms are five-coordinated in a distorted square-pyramidal environment formed by two hfac molecules and one oxygen atom of ONCNO group from one NITPBAH ligand. The magnetic susceptibility study of the complex {(NITPBAH)2[Cu(hfac)2]3} 1 shows strong antiferromagnetic interactions between Cu(II) ion and NITPBAH radical ligand.

Advances in N-methyl-D-aspartate Receptor Signaling Pathway and Mechanism of the Pathway-mediated Apoptosis

N-methyl-D-aspartate receptor (NMDAR),an important ionic glutamate receptor and a ligand and voltage-gated ion channel characterized by complex composition and functions and wide distribution,plays a key role in the pathological and physiological process of diseases or stress states.NMDAR can mediate apoptosis through different pathways such as mitochondrial and endoplasmic reticulum damage,production of reactive oxygen species and peroxynitrite,and activation of mitogen-activated protein kinase and calpain.This paper reviews the structure,distribution,and biological characteristics of NMDAR and the mechanisms of NMDAR-mediated apoptosis.

Quinolinium modified β-cyclodextrin: An ionic ligand towards sustainable A3-coupling and tandem cyclisation reactions of aldehydes, amines and alkynes

An ionic Cu(I) complex (Cu(I)@Qun-β-CD), stabilized by water soluble quinolinium modified β-cyclodextrin (Qun-β-CD) with an 8-N-pentyl side chain, was prepared and characterized by ESI-Mass, NMR and UV-Visible spectroscopies and also molecular modeling studies. The synthesized Cu(I)@Qun-β-CD was found to be highly efficient in promoting A3-coupling reaction of various aldehydes, amines and terminal alkynes to yield propargylamines in acetonitrile medium. The prepared Qun-β-CD (C) alone, without any metal ion, follows a different course exhibiting excellent catalytic efficiency in an intramolecular tandem cyclisation reaction of the same reagents to yield quinolines in aqueous medium. From the point of the environmental concerns, the work presented here has the merits of both three-component reaction, environmentally friendliness, easy separation, simple work-up, good yields, the avoidance of organic solvents and use of an inexpensive catalyst. The catalyst was recycled more than five consecutive cycles without any significant loss in its activity in both reactions.

The first observation that metal chalcogenide supertetrahedral cluster is corner-coordinated by neutral amine group

Reported here is a new organic–inorganic hybrid compound {[(Ga10S17)(H+–AEP)2]·(H+–AEP)2} (1) with an one-chain structure and an unprecedented corner-coordination mode between the amine group from the 1-(2-aminoethyl)piperazine ligand and gallium ions in metal chalcogenide supertetrahedral cluster. This is the first observation that a metal chalcogenide supertetrahedral cluster is corner-coordinated by an amine group from alicyclic ammonia. The characterization of UV–Vis diffuse reflectance spectroscopy and optoelectronic properties on 1 indicated its potential application in semiconductor devices and photoelectric sensors.

Anion-assisted Fe(III)-coordination supramolecular systems based on 2,6-diacetylpyridine dihydrazone

Six new iron coordination complexes were obtained as a result of the direct interaction of the Fe3+ ion and Schiff base ligands in the presence of anions with weak, moderate and high coordinating ability in order to study their role in the construction of diverse supramolecular assemblies. All the crystalline solids present mononuclear complexes: [Fe(H2L1)(H2O)1.5(MeOH)0.5](ClO4)3·1.75H2O (1), [Fe(H2L2)(H2O)2](ClO4)3·H2O (2), [Fe(HL1)(NCS)2]·0.25H2O (3), [Fe(HL2)(NCS)2]·2.33H2O (4), [Fe(L1)(N3)(H2O)]·H2O (5) and [Fe(L2)(H2O)2]OH·4H2O (6), where H2L1 = 2,6-diacetylpyridine bis(isonicotinoylhydrazone) and H2L2 = 2,6-diacetylpyridine bis(nicotinoylhydrazone), which were characterized by IR spectroscopy and single crystal X-ray diffraction. The Schiff base ligands in the perchlorate-assisted compounds adopt a double zwitterion tautomeric form and these coordinate as neutral ligands. In the isothiocyanate complexes, the Schiff base coordinates as a single zwitterionic monoprotonated ligand, while the presence of the N3– anion in the reaction leads to the bisdeprotonation of both 2,6-diacetylpyridine dihydrazones. The crystal structures of all the coordination compounds show different types of weak intermolecular interactions, which were confirmed by the analysis of their Hirshfeld surfaces and the corresponding fingerprint diagrams.

Rapid Preparation of Dual Cross-Linked Mechanical Strengthening Hydrogels via Frontal Polymerization for use as Shape Deformable Actuators

The hydrogel artificial muscle has demonstrated enormous potential in various applications, such as soft robotics and actuators. However, the poor mechanical properties have always limited the practical applications of hydrogels. Here, we designed a Zr4+ coordinated and vinyl hybrid silica nanoparticle (VSNP) grafted poly(acrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid) (VSNP@poly(AM-co-AMPS)-Zr4+) via frontal polymerization (FP). Benefiting from the synergistic effect of the polymer–nanocomposite interaction (VSNP nanocomposite) and metal ion–ligand interactions (Zr4+–sulfonate group coordination), the mechanical properties of hydrogels can be extremely improved. In addition, a deformable hydrogel with gradient structure and swelling ratio was designed through introducing Zr4+ to one side of the hydrogel, which can serve as an artificial muscle to accomplish multiple moving activities, such as bending and grabbing. This work offers an easy-to-perform strategy to construct mechanically strong hydrogels, which might promote the development of artificial muscle materials.

Dynamic Metal-Ligand Interaction of Synergistic Polymers for Bistable See-Through Electrochromic Devices.

Bistable electrochromic materials are a promising alternative solution to reduce energy consumption in displays. Limited by the mechanism and lack of a design strategy, only a few electrochromic materials have truly been able achieve bistability. Herein, a novel strategy is proposed to design bistable electrochromic materials based on polymer-assisted dynamic metal-ligand coordination. The mechanism and materials of such unconventional electrochromic systems are proved by sufficient characterization. Synergistic stabilization of polymerized switchable dyes and the ionic ligand polymer are attracted to each other by supramolecular forces. The color states of the dye molecules are controlled and stabilized by valence changes of the metal ions. Meanwhile, through the polymerization of the electrochromic material and the nearby metal-ligand material, the metal ions of the electroinduced valence change are tightly fixed, and the related diffusion problem of the active EC component is also almost completely suppressed. This strategy successfully enables preparation of the corresponding transparent electrochromic displays with good performances, such as, the display information is clearly visible for more than 1.5 h without consuming energy.Furthermore, the new way of dynamic coordination or dissociation bistable displays could likely prosper the development of the electrochromic area and inspire other fields.

Cation and polyhedron substitution strategies: Effects on local crystal structure and on Bi3+ and Eu3+ co-doped inverse garnet phosphors’ luminescence property

Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg3Gd2Ge3O12: Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO4] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs.

Synthesis and crystal structure of cytotoxic copper(II) complex with 1,10-phenanthroline-5,6-dione and isothiazole derivative

Oligopyridine based copper(II) complexes are of interest to scientists as possible anticancer agents due to promising cytotoxic and DNA binding/cleaving properties. In this study, copper(II) complex [Cu(phendione)L2]·C2H5OH with 1,10-phenanthroline-5,6-dione (phendione) and 4,5-dichloro-isothiazole-3-carboxylic acid (HL) was synthesized and characterized by elemental analysis, IR-spectroscopy, X-ray powder diffraction and single-crystal X-ray diffraction. According to X-ray diffraction data, obtained compound is mononuclear complex with square pyramidal coordination environment of the central atom which is surrounded by two isothiazolate molecules and one phendione ligand. The X-ray diffraction data are confirmed by IR-spectroscopy data showing the presence of characteristic stretching vibration bands of the carbonyl and carboxyl groups of oligopyridine ligand and isothiazolate ions, respectively. Density functional theory (DFT) calculations for complex were carried out using the ADF software package to perform geometry optimization and frequency calculations that were in a good agreement with experimental IR spectrum. Cytotoxicity of complex and initial reagents was tested in vitro against HepG2 (human hepatocellular carcinoma) and MCF-7 (human breast adenocarcinoma) cell lines. The complex showed high dose-dependent cytotoxic activity with the IC50 values of 0.60±0.03 µM and 0.96±0.13 µM, respectively, which is higher than the activity of cisplatin against these cell lines. The activity of the complex is due to the presence of phendione ligand, which exhibits a similar cytotoxic activity.

Base on spectroscopic properties response fluorescence probe for rapid, sensitive and selective detection of aluminum ions in wastewater

In this paper, three compounds with Schiff-base functional group were successfully synthesized by several simple reactions. These three compounds can be used as good ligands for metal ions. Fluorescent probe has been favored by researchers because of its high sensitivity, high selectivity, practicability and simple operation method. A new fluorescent probe for the detection of Al3+ is the focus of this paper. From the photoluminescence spectrum, after the addition of Al3+, the maximum emission wavelengths of the three compounds have a large distance bathochromic shift, and a new emission peak appears on the right side of the maximum emission peak of the original compound. In order to verify the binding sites of aluminum ions, electronic calculation results show that after binding with Al3+, the HOMO and LUMO energy levels and energy gap values of the complexes decrease, indicating that the complexes become more stable. It is practical and feasible to detect Al3+ in wastewater.