Phosphonate Ligands Research Articles

Interplay of anthracene luminescence and dysprosium magnetism by steric control of photodimerization.

Systematic control of the intermolecular pair-wise [4 + 4] photocycloaddition of a series of dysprosium phosphonates through fine-tuning of two different phosphonate ligands, one with a bidentate blocker and one with an anthracene antenna, both with alkyl substituents, reveals a size dependent rate. With bulky isopropyl on the diphosphonate blocker little response to UV light is observed. In contrast, compounds with ethyl which has less steric hindrance exhibit almost complete photocycloaddition. Interestingly, the alkyl substituents attached to anthracene monophosphonate have no evident effect on the reaction rate. Although no direct relationship can be found between the substitutions and the observed differences in field-induced single molecule magnetism, remarkable changes in magnetic dynamics are observed for complexes before and after the complete photocycloaddition reactions.

Structural and Luminescence Properties of Anthracene- and Biphenyl-Based Lanthanide Bisphosphonate Ester Coordination Polymers.

Coordinative networks containing lanthanide ions attached via phosphonate ester functionalities provide remarkable luminescence properties. On the basis of ditopic phosphonic ester ligands with biphenylene and 9,10-anthracenylene bridges, a series of compounds with formal composition {[M(NO3)3]L} n or {[M(NO3)3]2(L1)3} n (L = C28H40O6P2; L1 = C26H40O6P2) with M = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y have been synthesized, structurally characterized, and the luminescence behavior was explored in the visible and NIR spectral regions, where applicable. In contrast to closely related networks based on biphenyl bisphosphonate esters from previous work, no evidence for ligand-to-metal energy transfer could be observed, despite strong near-infrared emission in some cases. Unique behavior is found for the Eu derivative with the 9,10-anthracenylene bridge, which is nonemissive, showing neither ligand- nor metal-based emission.

One-step and scalable synthesis of Ni2P nanocrystals encapsulated in N,P-codoped hierarchically porous carbon matrix using a bipyridine and phosphonate linked nickel metal–organic framework as highly efficient electrocatalysts for overall water splitting

The development of highly active and durable noble-metal-free electrocatalysts for overall water splitting is a great challenge. Herein, a microdroplet flow reaction is used for ultrafast and continuous synthesis of a nickel metal–organic framework material with 4,4ʹ-bipyridine and phosphonate ligands. A one step pyrolysis of this metal–organic framework to various heat treatment temperatures and hold times at maximum temperature give a range of electrocatalysts, containing crystalline Ni2P nanoparticles dispersed in a porous carbonaceous matrix incorporating relatively high concentrations of both nitrogen and phosphorus derived from the original metal–organic framework. The Ni2P electrocatalysts inherite the morphology of the metal–organic framework precursor, have a uniform dispersion of Ni2P sites and Brunauer-Emmett-Teller surface areas in the range 558–754 m2 g−1. The Ni2P electrocatalysts exhibit excellent catalytic performance for both hydrogen and oxygen evolution reactions in 1.0 M KOH and an electrolyzer using Ni2P electrocatalysts as both cathode and anode generates a current density of 10 mA cm−2 at a voltage of 1.62 V with superior durability. This facile and scalable synthesis strategy for the rational design of electrocatalysts represents a proof-of-concept with the potential for scale-up for use in practical applications.

Bis-hexaaquasodium Decaaqua-monohydrogen-hexasodium-terbium(III)-bis-(nitrilo-tris-methylenephosphonate) Hexahydrate [TbNa6H(H2O)10{N(CH2PO3)3}2] [Na(H2O)6]2 · 6H2O

Bis-hexaaquasodium decaaqua-monohydrogen-hexasodium-terbium(III)-bis-(nitrilo-tris-methylenephosphonate) hexahydrate has been synthesized, and its crystal structure has been determined (sp. gr. P21/с, Z = 2). The terbium atom occupies the center of a cage consisting of two phosphonate ligand molecules, connected by six inorganic P–O–Na–O–P bridges, and a coordination polyhedron. The latter is an almost regular rhombohedron; two of its vertices, distant from the center, contain nitrogen atoms of two organic ligand molecules, and the other six vertices are occupied by oxygen atoms belonging to different PO3 groups. The complex contains six five-membered chelating cycles Tb–O–P–C–N, six eight-membered cycles Tb–O–P–C–N–C–P–O, and six heterometallic cycles O–Tb–O–Na.

Structure‐Modulated Complexation of Actinides with Phosphonates: A Combined Experimental and Quantum Chemical Investigation

AbstractPhosphonates have shown promising specificity and remarkable extractability towards actinide elements. Among all the organophosphorous compounds, phosphonates have the dual advantage of simplicity in preparation coupled with the flexibility to tailor‐make their carbon chain structure. In the present work the relationship between structure and metal binding affinity of phosphonates has been examined both experimentally and quantum mechanically. Symmetrical Diisobutylisobutyl, Diisoamylisoamyl and unsymmetrical Diisoamylhexyl and Diisoamylbutyl branched phosphonates were synthesised and characterised by NMR and GC‐MS. These ligands were used to bind Th(IV), U(VI), Pu(IV) and Am(III) at the liquid‐liquid interface. The ligands also were examined for their physicochemical properties of density, viscosity, aqueous solubility and dielectric constant which are significantly affected by changes in the alkyl chain structure. A combination of physico‐chemical parameters, as well as the structure modulated chemical nature of the extractants, cause variations in the distribution ratios towards metal ions. These effects have been probed in detail using Th(IV), U(VI), Pu(IV) and Am(III) ion extractions and found to correlate with the carbon chain length of the organic groups on the phosphoryl centre. Further, density functional theory was employed to understand the electronic structure of the extractants and metal complexes. The computed complexation energies in the formation of metal‐ligand complexes compared well with the trends observed in the experiments. Both experiment and quantum chemistry emphasizes the importance of the carbon chain structure on the actinide binding ability of phosphonate ligands.

Synthesis of Phosphonic Acid Ligands for Nanocrystal Surface Functionalization and Solution Processed Memristors

Here, we synthesized 2-ethylhexyl, 2-hexyldecyl, 2-[2-(2-methoxyethoxy)ethoxy]ethyl, oleyl, and n-octadecyl phosphonic acid and used them to functionalize CdSe and HfO2 nanocrystals. In contrast to branched carboxylic acids, postsynthetic surface functionalization of CdSe and HfO2 nanocrystals was readily achieved with branched phosphonic acids. Phosphonic acid capped HfO2 nanocrystals were subsequently evaluated as memristors using conductive atomic force microscopy. We found that 2-ethylhexyl phosphonic acid is a superior ligand, combining a high colloidal stability with a compact ligand shell that results in a record-low operating voltage that is promising for application in flexible electronics.

A series of zirconium-oxo cluster complexes based on arsenate or phosphonate ligands

A series of zirconium-oxo cluster complexes have been prepared by the reaction of Zr(OnPr)4 and arsenate or phosphonate ligands, namely, Zr6(μ3-O)2(4-aPhaa)4(OnPr)12 (Zr6-1, 4-aPhaa = 4-aminophenylarsonic acid), Zr6(μ3-O)2(tbpa)4(OnPr)12 (Zr6-2, tbpa = tert-butylphosphonic acid), H2[Zr6(μ3-O)(μ2-O)(tbpa)5(OnPr)12] (Zr6-3), and H4[Zr10(μ4-O)4(μ3-O)4(ppa)4(OnPr)20] (Zr10, ppa = phenylphosphonic acid). These complexes have been structurally characterized by the single-crystal X-ray diffraction. Interestingly, the {Zr10} cluster contains a [Zr10O4]32+ supertetrahedron core stabilized by the phosphate groups. In addition, thermal stabilities and phase purities were also investigated in detail.

From bidentate H-spirophosporane ligand to tridentate phosphonate ligand in palladium chemistry

Recrystallization of a palladium compound bearing bidentate H-spirophosporane [PdCl{P(OCH2CHi-PrNH)OCH2CHi-PrNH2}] from methanol in air atmosphere, gave rise to the palladium complex with tridentate NPN ligand [PdCl{P(O)(OCH2CHi-PrNH2)2}]. The structures of the complex and H-spirophosphorane ligand HP(OCH2CHi-PrNH)2 were determined using spectroscopic methods as well as by single-crystal X-ray diffraction.

Potent Half-Sandwich Iridium(III) and Ruthenium(II) Anticancer Complexes Containing a P^O-Chelated Ligand

We herein report the synthesis, characterization, and anticancer activity of a series of iridium(III) and ruthenium(II) half-sandwich complexes of the type [(Cpx/arene)M(P^O)Cl]PF6 (M = Ir, Cpx = pentamethylcyclopentadienyl (Cp*) or its phenyl (Cpxph = C5Me4C6H5) or biphenyl (Cpxbiph = C5Me4C6H4C6H5) derivatives; M = Ru, arene = p-cymene (p-cym); P^O = phosphine phosphonic amide ligand (PPOA)). The X-ray crystal structures of all complexes, in which the ligand can form six-membered rings with the metal center, have been determined. All of the complexes show remarkable anticancer activities toward HeLa and A549 cancer cells, activities which are higher than that of the clinical anticancer drug cisplatin. The incorporation of phenyl substituents on the Cp* ring for iridium(III) complexes results in little variation in their anticancer activities. These results can be attributed to the combinatorial action of the metal and PPOA ligand. Hydrolysis and DNA cleavage are not the major mechanisms of action. These...

Tetrametallic Ln(III) (Ln = Gd, Dy) phosphonate clusters: Spin cooler and single-molecule magnet

We report herein convenient access to tetranuclear clusters of [Ln4(RPO3)2(RPO3H)(tBuCO2)7(tBuCO2H)3(H2O)3]·solvent Ln4 (Ln = Gd, Dy), from dinuclear lanthanide precursors [Ln2(O2CtBu)6(HO2CtBu)6] and a bulky phosphonate ligand (9-methyl-9H-fluoren-9-yl)phosphonic acid (RPO3H2). In the structures of Ln4, four Ln(III) ions are arranged at the vertices of an irregular quadrilateral that are wrapped by bulky hydrophobic fluorenyl groups. Magnetic studies show that Gd4 exhibits high magnetocaloric effect (MCE) with entropy change of 23.10 J kg−1 K−1 at 2.5 K for ΔH = 7 T, while Dy4 shows slow magnetic relaxation that is the character of a single-molecule magnet (SMM).

Proton-Rocking-Chair-Type Redox Capacitors Based on Indium Tin Oxide Electrodes with Multilayer Films Containing Ru Complexes.

A rechargeable proton-rocking-chair-type redox capacitor was fabricated using scalable layer-by-layer-(LbL)-assembled films composed of two dinuclear Ru complexes that exhibit proton-coupled electron-transfer (PCET) reactions with different Ru(II/III) redox potentials (RuNH-OH and RuCH-OH). RuNH-OH and RuCH-OH contain different coordination environments that involve two phosphonate linker ligands at both ends and bridging 2,6,2',6'-tetrakis(benzimidazol-2-yl)-4,4'-bipyridine or 1,3,1',3'-tetrakis(benzimidazol-2-yl)-5,5'-biphenyl ligands, respectively. The molecular units were assembled onto indium tin oxide (ITO) electrodes by complexation between the phosphonate groups and zirconium(IV) ions. The LbL growing process of these multilayer films was monitored by electrochemical or UV-vis spectroscopic measurements. The thus obtained LbL films on the ITO electrodes showed PCET reactions at different potentials, depending on the bridging ligands. The introduction of cyclometalated Ru-C bonds in the bridging ligand of RuCH-OH led to the stabilization of the ruthenium(III) oxidation state, and therefore, RuCH-OH exhibited lower p Ka values for the imino N-H protons in the bridging benzimidazole groups compared to those of the corresponding RuNH-OH complex. The proton movements that accompany the redox reaction in the Ru multilayer films on the ITO electrode were confirmed using a pH indicator probe. For the performance test of a proton-rocking-chair-type redox capacitor, a two-electrode system composed of RuNH-OH and RuCH-OH multilayer films on ITO electrodes was examined in an aqueous solution of NaClO4. Under galvanostatic conditions, stable, reversible, and repeatable charging/discharging processes occurred. The capacitance increased with an increasing number of LbL layers. For comparison, a similar redox capacitor composed of two RuNMe-OH and RuCMe-OH analogues, in which all four imino N-H protons on the benzimidazole moieties are protected by N-Me groups, was constructed and examined. In these complexes, the capacitance decreased by 77% compared to the PCET-type capacitor composed of a cell containing RuNH-OH and RuCH-OH; this result strongly suggests that the proton movement plays a more important role for the charge storage than the anion movement. In such LbL films composed of Ru complexes that exhibit PCET-type redox reactions, the capacitance is drastically improved with an increasing number of layers and using protons as charge carriers.

Synthesis, Structures and Recognition Properties of Two Cadmium(II) Phosphonates for Highly Selective Sensing of Cr2O72− and CrO42− Anions

AbstractTwo cadmium (II) phosphonates, [Cd(MPBP)(2, 2′−bipy)(H2O)]⋅H2O (1) and [Cd(H2BPDP)(2,2′−bipy)2(H2O)]⋅H2O (2) [H2MPBP=4,4−Bis(monoethylphosphonomethyl)biphenyl, H4BPDP=biphenyl−4,4′−diylbis(methylene)diphosphonic acid, 2,2′−bipy=2,2′−bipyridine], had been successfully synthesized under hydrothermal conditions with different reaction temperatures by using H2MPBP as the phosphonate ligand and 2,2′−bipyridine as the second organic ligand. The compound 1 exhibited a 3D supramolecular structure, in which {CdN2O4} polyhedra and {CPO3} tetrahedra were interconnected by MPBP anions to form a 1D double chain via corner–sharing. Neighboring chains were linked into a 2D supramolecular sheet in the ac–plane by hydrogen bonding interactions, which were further assembled through π−π stacking interactions to form a 3D supramolecular structure. Compound 2 was assembled through π−π stacking and hydrogen bonding interactions to form a 1D supramolecular structure. Furthermore, both compounds exhibited remarkable luminescent properties, and could be applied as the high selective and sensitive luminescent sensors in the sensing of Cr2O72− and CrO42− anions through the luminescence quenching effect with a low–detection limit of 3.5 × 10−7 M and 4.6 × 10−7 M (for 1) and 6.1 × 10−7 M and 4.3 × 10−7 M (for 2), respectively. Additionally, the probable mechanisms for the quenching behaviour for the two compounds had also been investigated in detail.

Pair Distribution Function Analysis of ZrO₂ Nanocrystals and Insights in the Formation of ZrO₂-YBa₂Cu₃O₇ Nanocomposites.

The formation of superconducting nanocomposites from preformed nanocrystals is still not well understood. Here, we examine the case of ZrO2 nanocrystals in a YBa2Cu3O7−x matrix. First we analyzed the preformed ZrO2 nanocrystals via atomic pair distribution function analysis and found that the nanocrystals have a distorted tetragonal crystal structure. Second, we investigated the influence of various surface ligands attached to the ZrO2 nanocrystals on the distribution of metal ions in the pyrolyzed matrix via secondary ion mass spectroscopy technique. The choice of stabilizing ligand is crucial in order to obtain good superconducting nanocomposite films with vortex pinning. Short, carboxylate based ligands lead to poor superconducting properties due to the inhomogeneity of metal content in the pyrolyzed matrix. Counter-intuitively, a phosphonate ligand with long chains does not disturb the growth of YBa2Cu3O7−x. Even more surprisingly, bisphosphonate polymeric ligands provide good colloidal stability in solution but do not prevent coagulation in the final film, resulting in poor pinning. These results thus shed light on the various stages of the superconducting nanocomposite formation.

Bis(nitrilo)tris(methylenephosphonato)dodecaaquatrihydrohexasodium Europium(III) [EuNa6H3(H2O)12{N(CH2PO3)3}2]: Synthesis and Structure

The crystal structure of bis(nitrilo)tris(methylenephosphonato)dodecaaquatrihydrohexasodium europium(III) [EuNa6H3(H2O)12{N(CH2PO3)3}2] was determined; sp. gr. $$P\bar 1$$ , Z = 2, a = 11.0801(3) A, b = 11.5992(3) A, c = 14.6879(4) A, α = 70.096(3)°, β = 77.730(2)°, γ = 80.452(2)°. The coordination polyhedron of the Eu atom can be described as a distorted dodecadeltahedron (snub disphenoid), with two vertices occupied by nitrogen atoms of two phosphonate ligands and the other six vertices occupied by oxygen atoms of six PO3 groups. The chelate complex contains six five-membered rings Eu–O–P–C–N and six eight-membered rings Eu–O–P–C–N–C–P–O.

High-Nuclearity Heterometallic tert-Butylethynide Clusters Assembled with tert-Butylphosphonate.

tert-Butylphosphonic acid and lanthanide precursors were employed to construct two high-nuclearity hybrid silver(I)-ytterbium(III) phosphonate clusters: compound 1 consists of a Ag16 ethynide cluster fused with a trinuclear hydroxoytterbium phosphonate cluster, whereas compound 2 is composed of two Ag16 ethynide clusters bridged by a hexanuclear oxo/hydroxoytterbium phosphonate cluster. Using transition-metal-substituted lacunary polyoxotungstates in place of the lanthanide reactant, new phosphonate-functionalized silver(I)-copper(II) ethynide clusters [Ag34 Cu6 (3) and Ag37 Cu6 (4)] and silver(I) ethynide clusters [Ag51 (5) and Ag72 (6)] were obtained. The structures of complexes 3-6 feature core-shell arrangements, in which silver(I)-copper(II) or silver(I) ethynide cluster shells stabilized by peripheral phosphonate ligands enclose different kinds of tungstate core templates.

An investigation on the structural diversification of metal phosphonates in varying combinations of phosphonate ligand, metal ions and auxiliary ligands

Five new metal diphosphonates, namely, [Cu(H2L1)(2,2′-bipy)] (1), [Cu(H2L1)0.5(H3L1)(2,2′-bipy)][(H2O)3] (2), [Cu3(H2L1)1.5(H3L1)3(2,2′-bipy)3][H2O] (3), [Ni(4,4′-bipy)(H2O)4][H2L1] (4), [Cd(H2L1)(1,10-phen)(H2O)2][(H2O)2] (5), (H4L1 = (2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene))bis(phosphonic acid, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, 1,10-phen = 1,10-phenanthroline) have been synthesized from a methylated phosphonate ligand and characterized systematically. The single-crystal X-ray diffraction analyses reveal weak interactions play important roles in the speciation of metal phosphonates. The photophysical property of compound 5 was also investigated.

Phosphine phosphonic amide nickel catalyzed ethylene polymerization and copolymerization with polar monomers.

The phosphine phosphonic amide ligand platform is highly versatile, with three positions that can be independently tuned. In this contribution, we wish to study the nickel complexes based on this ligand system. Interestingly, the nickel dibromide and nickel allyl complexes are not active in ethylene polymerization. In contrast, the nickel phenyl chloride complexes are highly active in ethylene polymerization in the presence of a sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate cocatalyst. In addition, these nickel complexes can initiate ethylene copolymerizations with polar functionalized comonomers including methyl 10-undecenoate, 6-chloro-1-hexene and 5-acetoxy-1-pentene. More interestingly, these nickel complexes can oligomerize 1-hexene and 6-chloro-1-hexene.

Conjugated microporous polymers bearing phosphonate ligands as an efficient sorbent for potential uranium extraction from high-level liquid wastes

Conjugated microporous polymers bearing phosphonate ligands are stable and efficient for uranium extraction under highly acidic and strong radioactive conditions.

Sequestration of U(VI) from Acidic, Alkaline, and High Ionic-Strength Aqueous Media by Functionalized Magnetic Mesoporous Silica Nanoparticles: Capacity and Binding Mechanisms.

Uranium(VI) exhibits little adsorption onto sediment minerals in acidic, alkaline or high ionic-strength aqueous media that often occur in U mining or contaminated sites, which makes U(VI) very mobile and difficult to sequester. In this work, magnetic mesoporous silica nanoparticles (MMSNs) were functionalized with several organic ligands. The functionalized MMSNs were highly effective and had large binding capacity for U sequestration from high salt water (HSW) simulant (54 mg U/g sorbent). The functionalized MMSNs, after U exposure in HSW simulant, pH 3.5 and 9.6 artificial groundwater (AGW), were characterized by a host of spectroscopic methods. Among the key novel findings in this work was that in the HSW simulant or high pH AGW, the dominant U species bound to the functionalized MMSNs were uranyl or uranyl hydroxide, rather than uranyl carbonates as expected. The surface functional groups appear to be out-competing the carbonate ligands associated with the aqueous U species. The uranyl-like species were bound with N ligand as η2 bound motifs or phosphonate ligand as a monodentate, as well as on tetrahedral Si sites as an edge-sharing bidentate. The N and phosphonate ligand-functionalized MMSNs hold promise as effective sorbents for sequestering U from acidic, alkaline or high ionic-strength contaminated aqueous media.

Stabilization of Colloidal Ti, Zr, and Hf Oxide Nanocrystals by Protonated Tri-n-octylphosphine Oxide (TOPO) and Its Decomposition Products

Although TiO2, ZrO2, and HfO2 nanocrystals are often synthesized in tri-n-octylphosphine oxide (TOPO), it is unclear whether TOPO also serves as ligand. Using liquid and solid state 1H and 31P nuclear magnetic resonance spectroscopy and X-ray fluorescence spectroscopy, we show that the nanocrystal surface is capped by several derivatives of TOPO. In the 31P NMR spectrum, di-n-octylphosphinate (δ = 57 ppm) and P,P′-(di-n-octyl) pyrophosphonate (δ = 20 ppm) are found coordinated to the nanocrystal. In addition, hydrogen chloride associates with the metal oxide nanocrystal surface and protonates TOPO. The resulting hydroxyl-tri-n-octylphosphonium, [HO-PR3]+, is tightly associated with the nanocrystal surface (δ(31P) = 73 ppm) due to electrostatic interactions and hydrogen bonding. To simplify the complex surface composition, we exchange the original surface species for carboxylate or phosphonate ligands. The protonation of TOPO is an unexpected example of lyophilic ion pairing between an acidic metal oxide n...