Phosphorus-containing Ligands Research Articles

Ligand-Assisted Phase Engineering of Nanomaterials.

ConspectusThe synthesis of monodisperse colloidal nanomaterials with well-defined structures is important for both fundamental research and practical application. To achieve it, wet-chemical methods with the usage of various ligands have been extensively explored to finely control the structure of nanomaterials. During the synthesis, ligands cap the surface and thus modulate the size, shape, and stability of nanomaterials in solvents. Besides these widely investigated roles of ligands, it has been recently discovered that ligands can affect the phase of nanomaterials, i.e., their atomic arrangement, providing an effective strategy to realize the phase engineering of nanomaterials (PEN) by selecting appropriate ligands. Nanomaterials normally exist in the phases that are thermodynamically stable in their bulk states. Previous studies have shown that under high temperature or high pressure, nanomaterials can exist in unconventional phases which are unattainable in the bulks. Importantly, nanomaterials with unconventional phases exhibit unique properties and functions different from conventional-phase ones. Consequently, it is feasible to utilize the PEN to tune the physicochemical properties and application performance of nanomaterials. During wet-chemical synthesis, ligands binding to the surface of nanomaterials can modify their surface energy, which could significantly affect the Gibbs free energy of nanomaterials and thus determine the stability of different phases, making it possible to obtain nanomaterials with unconventional phases at mild reaction conditions. For instance, a series of Au nanomaterials with unconventional hexagonal phases have been prepared with the assistance of oleylamine. Therefore, the rational design and selection of different ligands and deep understanding of their effect on the phase of nanomaterials would significantly accelerate the development of PEN and the discovery of novel functional nanomaterials for diverse applications.In this Account, we briefly summarize the recent progress in ligand-assisted PEN, elaborating the important roles of different ligands in the direct synthesis of nanomaterials with unconventional crystal phases and amorphous phase as well as the phase transformation of nanomaterials. We first introduce the background of this research topic, highlighting the concept of PEN and why ligands can modulate the phase of nanomaterials. Then we discuss the usage of four kinds of ligands, i.e., amines, fatty acids, sulfur-containing ligands, and phosphorus-containing ligands, in phase engineering of different nanomaterials, especially metal, metal chalcogenide, and metal oxide nanomaterials. Finally, we provide our personal views of the challenges and future promising research directions in this exciting field.

Solvent Extraction and Complexation Studies of Pyridine-di-Phosphonates with Lanthanides(III) in Solutions

ABSTRACT In this work, we studied the complex formation (1H, 31P NMR-titration, UV–vis titration, luminescent titration) and solvent extraction of lanthanides with pyridine diphosphonates. The stoichiometry of the complexes was determined: ML and ML2 forms are present. This is confirmed by all of the above methods. It was found that the pyridine ring and P=O groups are involved in the coordination of the metal cation. The coordination environment of the Eu(III) cation was studied more thoroughly using the EXAFS method in solution. Coordination numbers and distances were determined for the complex in solution. The influence of the lanthanide radius on the value of the stability constant was shown. The change in extraction efficiency in the series of lanthanide is described. A new pattern, unusual for other phosphorus-containing ligands, was obtained. To explain the change in the parameters of complexation depending on the system, DFT calculations were carried out. The effect of various initial states of the extracted cations was shown. The initial state with a large amount of nitrates corresponds to a two-phase system during extraction, and with a smaller amount, to a single-phase system with acetonitrile. Additionally, the luminescent properties of the complexes were described in detail as one more applied aspect of the work. .

Preliminary Study: Micropropagation Using Five Types of Chelated Iron and the Subsequent Acclimation of Blue Honeysuckle (Lonicera caerulea var. kamtschatica Sevast.)

Blue honeysuckle (Lonicera caerulea var. kamtschatica Sevast.) is a valuable berry crop with a unique biochemical composition. It is rich in vitamins, minerals, and biologically active substances. Different species and cultivars of honeysuckle require different cultivation conditions in the field of accelerated reproduction in vitro. Taking into account the high clonal replication potential of the plant, we conducted research on the chelated-iron form’s influence on the micropropagation productivity of the blue honeysuckle “Lulia” cultivar at the multiplication, rooting, and subsequent acclimatization stages of microplants. In a preliminary study, five types of iron chelates were tested with carboxyl- and phosphorus-containing ligands: Fe(III)-EDTA, Fe(III)-DTPA, Fe(III)-EDDHA, Fe(III)-HEDP, and Fe(II)-HEDP. Each type of iron chelate was applied at four concentrations: standard, decreased by 2 times, and increased by 1.5 times and 2 times in the basic Murashige and Skoog (MS) nutrient medium. It was found that the blue honeysuckle “Lulia” had a selectivity to the type of iron chelate that was used. The nutrient-medium modifications with iron chelates, which caused the plant response, contributed to a significant improvement in the plant’s physiological status and increased its survival rate during the microplant’s acclimation to the nonsterile conditions stage. At the rooting stage, an increase in the rooting rate of up to 100% (Fe (III)-EDDHA), an increase in the number of shoots by 1.5–2 times, and an increase in the number of roots by 1.4–1.9 times were observed. The positive effect of the iron’s chelated forms was also observed at the acclimation stage. According to the results of the research, the most suitable iron forms for clonal micropropagation of blue honeysuckle were carboxyl-containing Fe(III)-EDDHA and phosphonate-containing Fe(II)-HEDP. Moreover, the effectiveness of both complexonates was confirmed in a wide concentration range: Fe(III)-EDDHA from (×1.0) to (×2.0), and Fe(II)-HEDP from (×0.5) up to (×1.5).

A Review of Phosphorus Structures as CO2 Reduction Photocatalysts.

Effective photocatalytic carbondioxide(CO2 ) reduction into high-value-added chemicals is promising to mitigate current energy crisis and global warming issues. Finding effective photocatalysts is crucial for photocatalytic CO2 reduction. Currently, metal-based semiconductors for photocatalytic CO2 reduction have been well reviewed, while review of nonmetal-based semiconductors is almost limited to carbon nitrides. Phosphorus is a promising nonmetal photocatalysts with various allotropes and tunable band gaps, which has been demonstrated to be promising non-metallic photocatalysts. However, no systematic review about phosphorus structures for photocatalytic CO2 reduction reactions has been reported. Herein, the progresses of phosphorus structures as photocatalysts for CO2 reduction are reviewed. The fundamentals of photocatalytic CO2 reduction, corresponding properties of phosphorus allotropes, photocatalysts with phosphorus doping or phosphorus-containing ligands, research progress of phosphorus allotropes as photocatalysts for CO2 reduction have been reviewed in this paper. The future research and perspective of phosphorus structures for photocatalytic CO2 reduction are also presented.

In vitro Effect of Replacement Mineral Salts of Trace Elements with P-containing Chelates to Improve Rooting of Cherry Rootstock (cv. VC-13)

In this paper, we studied the effect of modified culture medium based on Murashige and Skoog (Murashige T. Skoog F., 1962) on the in vitro rhizogenesis of clonal rootstock of stone cultures - VC-13. For the first time, the nutrient medium was modified with complexes of all incoming trace elements based on a phosphorus-containing ligand of the bisphosphonate class. The effect of 3 levels of concentrations of chelated trace elements was studied: 1.25, 2.5 and 5 ml/l without the use of increased doses of BMI, and a comparative analysis was carried out in comparison with the modification of trace elements based on EDTA. The maximum effect – 100% rooting after 30 days of subcultivation was found at a concentration of chelated trace elements of 5 ml/l. When modifying EDTA, rooting did not occur. Also, the modification of the nutrient medium by phosphorus-containing complexes contributed to a change in the nature of the formation of the root system of micro-gears. Micro-plants had from 3 to 6 short strong roots, convenient for washing from the nutrient medium and then planting at the stage of adaptation to non-sterile conditions. Repeated tests of the effect of culture medium modification on rhizogenesis in vitro on a larger scale confirmed the high efficiency of this approach. The rooting rate of micro-gears of the VC-13 clone rootstock was more than 80%. The results obtained allow us to conclude about the key role of the nature of the chelating agent.

Tolman's Electronic Parameter of the Ligand Predicts Phase in the Cation Exchange to CuFeS2Nanoparticles.

The metastable and thermodynamically favored phases of CuFeS2 are shown to be alternatively synthesized during partial cation exchange of hexagonal Cu2S using various phosphorus-containing ligands. Transmission electron microscopy and energy dispersive spectroscopy mapping confirm the retention of the particle morphology and the approximate CuFeS2 stoichiometry. Powder X-ray diffraction patterns and refinements indicate that the resulting phase mixtures of metastable wurtzite-like CuFeS2 versus tetragonal chalcopyrite are correlated with the Tolman electronic parameter of the tertiary phosphorus-based ligand used during the cation exchange. Strong L-type donors lead to the chalcopyrite phase and weak donors to the wurtzite-like phase. To our knowledge, this is the first demonstration of phase control in nanoparticle synthesis using solely L-type donors.

Spectral-Luminescent Properties of Mixed-Ligand Europium(III) Complexes with O-Methoxybenzoic Acid and Phosphorus-Containing Neutral Ligands

The spectral-luminescent properties of europium(III) complexes with o-methoxybenzoic acid and phosphorus-containing neutral ligands with an island structure and the compositions Eu(MOBA)3 · 3H2O and Eu(MOBA)3 · L, where MOBA is o-methoxybenzoic acid and L is hmpa (hexamethylphosphortriamide, tppo (triphenylphosphinoxide), and Et6pa (hexaethylphosphortriamide), are studied. It is found that the excitation energy transfer to the europium ion occurs from the levels of both o-methoxybenzoic acid and phosphorus-containing neutral ligands. The electronic absorption and luminescence excitation spectra, as well as the Stark structure of the 5D0−7Fj ( j = 0–2) electronic transitions in the luminescence spectra of mixed-ligand complexes of europium(III) o-methoxybenzoates, are analyzed. The highest luminescence intensity is demonstrated by europium(III) methoxybenzoate with triphenylphosphinoxide.

Mixed-Ligand Complex Compounds of Europium(III) with ortho-Methoxybenzoic Acid and Phosphorus-Containing Neutral Ligands

Luminescent coordination mixed-ligand compounds of europium(III) with ortho-methoxybenzoic acid and phosphorus-containing neutral ligands of the isle-like structure Eu(MOBA)3 · 3H2O and Eu(MOBA)3 · L have been synthesized. MOBA—ortho-methoxybenzoic acid, L—hmpa (hexamethylphosphotriamide), tppo (triphenylphosphinoxide), Et6pa (hexaethylphosphotriamide). Thermal properties of the complex mixed-ligand compounds of europium(III) have been investigated. It has been shown that thermolysis results in the splitting of a neutral ligand molecule proceeding within one stage along with an endothermic effect. The complex compound appeared to be stable up to 280°C. The composition and structure of the synthesized complexes have been established. Based on the IR spectroscopy data, it has been demonstrated that in ortho-methoxybenzoates of europium(III) ortho-methoxybenzoic acid is coordinated to a europium(III) ion bidentately.

Spectral-Luminescent Properties of Mixed-Ligand Europium(III) Complexes with p-Methylbenzoic Acid

The spectral-luminescent properties of europium(III) complexes with p-methylbenzoic acid and nitrogen- and phosphorus-containing neutral ligands of compositions [Eu(p-MBA)3 · D]2 · xH2O and [Eu(p‑MBA)3 · 2H2O]n, where p-MBA is the anion of p-methylbenzoic acid and D is 1,10-phenanthroline (phen), 2,2' dipyridyl (dipy), triphenylphosphine oxide (tppo) (х = 0), hexamethylphosphortriamide (hmpa) (x = 1), or benzotriazole (bt) (x = 2) are studied. The electronic absorption spectra, the luminescence excitation spectra, and the Stark structure of 5D0−7Fj ( j = 0–2) electronic transitions in low-temperature luminescence spectra of complex europium(III) p-methylbenzoates are analyzed. It is found that the excitation energy transfer to europium ions occurs from the levels of both p-methylbenzoic acid and neutral ligands.

Luminescent Properties of Europium(III) Compounds with Quinolinic Acid and Phosphorus-Containing Neutral Ligands

Luminescent mixed-ligand europium(III) complexes with quinolinic acid and phosphorus-containing neutral ligands with a dimeric structure of the composition Eu2(QA)3 · 3Н2О, Eu2(QA)3 · D · 2Н2О, where QA is quinolinic acid and D is hmpa (hexamethylphosphortriamide), tppo (triphenylphosphinoxide), (hmpa), or Et6pa (hexaethylphosphortriamide), are synthesized. The thermal and spectral-luminescent properties of the synthesized complex mixed-ligand europium(III) compounds are studied. It is shown that the detachment of water and neutral ligand molecules during thermolysis occurs in two stages with endothermic effects and that the complex compounds are stable at temperatures up to 320°С. It is found by IR spectroscopy that quinolinic acid coordinates to the europium(III) ion by two carboxylate ions. The low luminescence intensity of mixed-ligand europium(III) quinolinates is explained by inefficient electronic excitation energy transfer from quinolinic acid and phosphorus-containing neutral ligands to europium ions.

Luminescent Properties of Europium(III) Compounds with Quinaldic Acid and Neutral Phosphorus-Containing Ligands with a Dimeric Structure

New luminescent mixed-ligand complexes of europium(III) with quinaldic acid and neutral phosphorus-containing ligands with a dimeric structure are synthesized. The structure and the thermal, spectral, and luminescent properties of mixed-ligand europium(III) complexes are studied. It is shown that the quinaldinate ion is coordinated to a europium(III) ion in a bidentate fashion. It is found that the excitation energy transfer to europium (III) ion occurs from levels of quinaldic acid and neutral phosphorus-containing ligands.

New Approaches for Biaryl-Based Phosphine Ligand Synthesis via P═O Directed C–H Functionalizations

Given the important influence of phosphine ligands in transition metal-catalyzed reactions, chemists have searched for straightforward and efficient methodologies for the synthesis of diverse phosphine ligands. Although significant progress has been made in this aspect over the past decades, the development of new phosphorus-containing ligands with properties superior to their predecessors remains a central task for chemists. Recently, researchers have demonstrated that biphenyl monophosphine ligands function as highly efficient ligands for transition-metal-catalyzed organic transformations, especially for reactions where chelating bisphosphine ligands cannot be used. In 1998, Buchwald introduced a new class of air-stable phosphine ligands based on the dialkylbiaryl phosphine backbone. These ligands have been successfully used for a wide variety of palladium-catalyzed carbon-carbon, carbon-nitrogen, and carbon-oxygen construction processes as well as serving as supporting ligands for a number of other reactions. At the same time, the use of the biphenyl monophosphine ligands often allows reactions to proceed with short reaction times and low catalyst loadings and under mild reaction conditions. However, the synthesis of chiral biphenyl monophosphine ligands, especially those the chirality of which is due to biaryl axial chirality, is very limited. In this Account, we summarize our methodologies for the synthesis of this kind of biphenyl monophosphine ligands including the P═O directed C-H functionalization, P═O directed diastereoselective C-H functionalization, P═O directed enantioselective C-H functionalization, and metal-free diastereoselective radical oxidative C-H amination under mild reaction conditions. With these methods, a series of biphenyl phosphine ligand precursors containing achiral or axially chiral centers and precursors possessing both axial chirality and a chirogenic phosphorus center with different electronic properties and steric effect have been obtained under different reaction conditions. For the preparation of chiral biphenyl monophosphine ligands, which not only possess axial chirality but in many cases also possess chirality at phosphorus, the primary means of introducing chirality is through the use of the menthyl phenylphosphinate. As a chiral auxiliary group, the menthyl phenylphosphinate has some unique features: (i) it is easy to prepare; (ii) the products contain both axial chirality and central chirality on the phosphorus atom; (iii) the menthyl group could easily be transformed into other functional groups, which is crucial for the diversity of the corresponding biphenyl ligands. In our reaction, the P═O group not only acts as the directing group but also facilitates the construction of the phosphine ligands. In addition, the application of these products in asymmetric catalysis has also been studied with good results obtained in some reactions. The further application of these ligands, especially the chiral biphenyl monophosphine ligands in catalysis reactions is underway in our laboratory, and we hope different kinds of reactions will be achieved with these ligands.

Effect of P-Containing Ligands on the Structural and Optical Properties of (CdSe)n (n = 3, 6, 10) Clusters

The effect of phosphorus-containing ligands on the structure, energetics and properties of the (CdSe)n clusters (n = 3, 6, and 10) with different number of PH3 and PMe3 ligands were studied by using density functional theory calculations. The P atom in the ligand interacts with Cd and forms a strong Cd–P coordination bond. The introduction of ligands does not change the cluster architecture, but leads to considerable changes in Cd–Se bondlength, charge distribution, binding energy, HOMO–LUMO gap and optical absorption. The ligand influence is enhanced with increasing ligand coverage. A blueshift in absorption band was predicted for the clusters with increasing ligands, resulting from the electron donating characteristics of the ligands that hamper electron transition from Se to Cd. As P-containing ligands are often used in the preparation of CdSe nanocrystals, our calculations reveal the influence of ligand-cluster interaction on the cluster geometrical and electronic properties, which would be helpful for the nanocrystal design and synthesis.

Clicking the Arsenic-Carbon Triple Bond: An Entry into a New Class of Arsenic Heterocycles.

Arsaalkynes can undergo regioselective and quantitative [3+2] cycloaddition reactions with organic azides to give hitherto unknown 3H-1,2,3,4-triazaarsole derivatives. The reaction product was obtained as a white, air- and moisture-stable solid, and the presence of a planar, five-membered arsenic heterocycle was unambiguously verified by means of X-ray crystallography. DFT calculations gave insight into the electronic structure of these novel compounds compared to tetrazoles and triazaphospholes. The coordination chemistry towards Re(I) was investigated and compared with the structurally related phosphorus-containing ligand. These preliminary investigations pave the way for a new class of arsenic heterocycles and fill the gap between the azaarsoles already known.

Water-Stable Anionic Metal-Organic Framework for Highly Selective Separation of Methane from Natural Gas and Pyrolysis Gas.

A 3D water-stable anionic metal-organic framework [Zn4(hpdia)2]·[NH2(CH3)2]·3DMF·4H2O (FJI-C4) was constructed based on an elaborate phosphorus-containing ligand 5,5'-(hydroxyphosphoryl)diisophthalic acid (H5hpdia). FJI-C4 with narrow one-dimensional (1D) pore channels exhibits high selectivity of C3H8/CH4 and C2H2/CH4. It is the first time for the MOF which contains phosphorus for selective separation of methane from natural gas and pyrolysis gas.

Facile iron(iii)-mediated ATRP of MMA with phosphorus-containing ligands in the absence of any additional initiators

Fe(iii)-mediated ATRP using phosphorus reagents was studied without any additional initiator and reducing agent. The polymerization was demonstrated as reverse ATRP, in which phosphorus reagents acted as both ligand and thermal radical initiator.

Luminescence of ytterbium(III) in mixed-ligand compounds with cinnamic acid and neutral phosphorus-containing ligands

The luminescence spectral characteristics of mixed-ligand compounds of ytterbium(III) with cinnamic acid and neutral phosphorus-containing ligands were studied by luminescence spectroscopy. The intensity of luminescence of the compounds was determined. The highest intensity of luminescence was found for the ytterbium(III) compound with triphenylphosphine oxide.

Synthesis and Complexing Properties of Phosphorus-Substituted Pyridine-2-Carboxylic Acid Anilides

Novel phosphorus-containing ligands have been synthesized by the condensation of 2-(thio)phosphorylated anilines with 2,6-dichloro- and 4-chloropyridine-2-carbonyl chlorides in the presence of Et3N and unsubstituted pyridine-2-carboxylic acid using P(OPh)3 as a coupling agent. The compounds derived readily form complexes with a range of transition metals (M=Re(I), Pd(II), and Cu(II)), serving as bi- or tridentate monoanionic ligands. The composition and structure of the resulting metallocycles depend both on the presence/amount of the Cl atoms in the pyridine ring and on the nature of the donor atom X in the P=X moiety. The novel compounds were characterized by multinuclear NMR and IR spectroscopy as well as X-ray crystallography.

Polymethoxyphenyl-substituted [2-(5-chloro-2-hydroxy-4-methylphenyl)-2-phenylvinyl]phosphine oxides: Synthesis and complexation with Eu(TTA)3

New di- and trimethoxyphenyl-substituted phosphorus-containing ligands, (Z)-[2-(5-chloro-2-hydroxy-4-methylphenyl)-2-phenylvinyl]bis(3,4-di- and 3,4,5-trimethoxyphenyl)phosphine oxides, have been synthesized, and their adducts with europium(III) 2-thenoyltrifluoroacetonate have been obtained. High luminescence intensity of the synthesized complexes suggests prospects in using them for the design of various materials possessing unique photophysical properties.

ChemInform Abstract: Lanthanide Acylpyrazolonates: Synthesis, Properties and Structural Features

AbstractReview: 75 refs.