Quaternary Phosphonium Salts Research Articles

Separation of Pt(IV), Pd(II), Ru(III) and Rh(III) from model chloride solutions by liquid-liquid extraction with phosphonium ionic liquids

The recovery of metals from waste is profitable not only from an economic but also from an ecological point of view. The natural resources of metals (especially platinum group metals – PGM) are limited, while the amount of waste containing the desired metals is still growing. The purpose of the work is the use of quaternary phosphonium salts, i.e. Cyphos IL 101 (trihexyl(tetradecyl)phosphonium chloride), Cyphos IL 102 (trihexyl(tetradecyl)phosphonium bromide) and Cyphos IL 104 (trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate), for the separation of palladium(II), platinum(IV), rhodium(III) and ruthenium(III) from their multi-component model mixtures of composition based on real solutions after leaching of PGM-containing wastes (e.g. automobile catalytic converters). Though, Pd(II) could not be separated from Pt(IV) by one-stage extraction, separation of Pd(II) from Pt(IV) was possible by stripping with 0.1 M thiourea in 0.5 M HCl. The extraction of Rh(III) from the four-component solution practically did not occur (Rh(III) stayed in raffinate), therefore Pt(IV) and Pd(II) could be selectively separated from Rh(III). As a result of the work, a separation procedure of successful separatation of Pd(II), Pt(IV), Ru(III) Rh(III) from four-component solutions has been developed based on two stages of extraction with ionic liquid solution (trihexyl(tetradecyl)phosphonium chloride) and two stages of stripping.

Symmetric quaternary phosphonium cation and perchlorate/chlorate anions: Crystal structure, Database study and Hirshfeld surface analysis

Two new quaternary phosphonium salts of 1,2-ethandiylbis (triphenylphosphonium) Diperchlorate (I), 1,2-ethandiylbis (triphenylphosphonium) Dichlorate (II) were prepared and used for oxidation of different benzylic alcohols to afford their corresponding carbonyl compounds. These new compounds were characterized by IR, NMR spectroscopy and single crystal X-ray analysis. The crystal structure and Hirshfield surface analysis of titled compounds revealed that the change of accompanying anionic moiety can affect the directional interactions of CH⋯O hydrogen bonds between anionic and cationic units which lead to various supramolecular aggregations on the crystal packing. In order to exploring the influence of crystal environment of anionic moieties on the geometry of main symmetric cationic unit, the relative contribution of various close contacts and 2D fingerprint plots of title compounds and twenty three analogous structures retrieved from Cambridge Structural Database (CSD) were investigated through the distortion of tetrahedral coordination geometry of P center of main cationic unit based on τ4 indices.

Ionic liquid-crystalline polymer-based quaternary phosphonium salt

ABSTRACTA series of quaternary phosphonium salts based on ionic liquid-crystalline polymers which were synthesised by triphenylphosphine and brominated polysiloxanes containing cholesteryl mesogens. The chemical structures, liquid crystalline properties and antimicrobial performance of [ChP]Brs were investigated by a series of test methods. [ChP]Brs showed smectic A mesophase with a wide temperature range of liquid crystalline phase in the heating and cooling cycles. The glass transition temperature and clearing point temperature decreased with the increase of triphenylphosphine content. While the increase of phosphorus content lead to the increase of antibacterial properties of polymers. The liquid crystal polymer provides full spatial support for complete contact between phosphorus ions and bacteria, So that the quaternary phosphonium salt can be fully sterilised.

In-vitro antitumor activity of new quaternary phosphonium salts, derivatives of 3-hydroxypyridine.

This work presents the results of in-vitro biological activity studies of three novel anticancer agents, phosphonium salts based on the 3-hydroxypyridine scaffold, including one derivative of 4-deoxypyridoxine. Proliferation and viability of cells treated with these compounds was assessed by the colony formation and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Effects of the compounds on apoptosis and cell cycle were studied by flow cytometry using annexin V-FITC/propidium iodide and propidium iodide staining, respectively. The influence of the compounds on mitochondrial membrane potential and intracellular reactive oxygen species was evaluated using tetramethyl rhodamine ethyl and DCFHA staining. Western blot analysis was used to study the changes in the expression of Bcl-xL, Bax, and caspase-3 apoptotic proteins. The treatment of ovarian adenocarcinoma cells OVCAR-4 with the tested compounds inhibited the growth and induced cell cycle arrest in the G1 phase. 3-Hydroxypyridine derivatives induced apoptosis by hyperexpression of Bax and caspase-3, whereas 4-deoxypyridoxine derivative induced cell death partly by reactive oxygen species generation and caspase-3 hyperexpression. These results indicate that the quaternary phosphonium salts studied represent potential therapeutic agents for the treatment of ovarian cancer.

Towards a sulfur clean fuel: Deep extraction of thiophene and dibenzothiophene using polyethylene glycol-based deep eutectic solvents

In this work, extractive desulfurization of model fuel containing dibenzothiophene (DBT) and thiophene (Th) as sulfur compounds was carried out using 16 different Deep Eutectic Solvents (DES) based on polyethylene glycol (PEG) and its precursors. The aim of this study is the reduction of the sulfur content of fuels below the environmental regulation (10 ppm), using PEG-based DES as low-cost extraction media under mild conditions and to compare their extractive performance with that of PEG alone, which by itself is a green solvent. For that purpose, 7 different quaternary ammonium and phosphonium salts were combined with four different molecular weight grades of PEG and PEG precursors such as ethylene glycol and triethylene glycol. The best results were obtained for the DES composed of tetrabutylammonium chloride (TBAC) and PEG400, which showed that it is possible to achieve, in single extraction step, 85% and 68% of extraction efficiency, and deep desulfurization in 2 and 3 cycles, for DBT and Th, respectively. In addition, this DES is not soluble in the model fuel and its extraction capacity is independent on the starting sulfur concentration. Finally, after being reused six times, TBAC:PEG400 DES still maintained 53% and 17% of its capacity, for DBT and Th removal, respectively, and after a regeneration step the performance of the DES was fully recovered.

Quaternary aryl phosphonium salts as corrosion inhibitors for iron in HCl

Cathodic and anodic Tafel extrapolation data for the corrosion inhibition of iron in deaerated 1 M HCl at 22 °C are obtained for five synthesized phosphonium salts, 4-tolyltriphenyl-phosphonium chloride (TTPPC), 4-phenoltriphenylphosphonium chloride (PTPPC), 4-anilinetriphenylphosphonium bromide (ATPPB), 4-benzyl alcoholtriphenylphosphonium chloride (BATPPC), 4-hlorophenyltriphenylphosphonium bromide (CPTPPB), and two commercially available phosphonium salts, tetraphenylphosphonium bromide (TPPB) and methyltriphenylphosphonium bromide (MTPPB). The inhibitor concentrations ranged from 1 × 10−7 to 1 × 10−3 M. The inhibition of iron corrosion in 1 M HCl at 22 °C was found to be in the order TPPB > BATPPC > CPTPPB > PTPPC > MTPPB > TTPPC > ATPPB.

Nonmetallic Wurtz coupling reaction of perfluorohexyl iodide

It is shown for the first time that the Wurtz reaction can be realized by the action of an organic substance (triphenylphosphine) on an alkyl halide (perfluoroalkyl iodide) without the use of metals. It was found that when trying to prepare the bis(3,3′-aminophenyl)(fluoroalkyl)phosphine oxide by four-step synthesis, in the first stage of the reaction of perfluoro-1-iodohexane with triphenylphosphine does not proceed towards the formation of an intermediate quaternary phosphonium salt. Instead, the carbon chain of perfluoroalkyl iodide dimerizes to form perfluorododecane – Wurtz reaction product. We have proposed a new pathway for homocoupling of perfluoroalkylhalides into even-numbered perfluoroalkanes.

Synthesis of inulin derivatives with quaternary phosphonium salts and their antifungal activity

Inulin is a kind of renewable and biodegradable carbohydrate with good water solubility and numerous physiological functions. For further utilization of inulin, chemical modification can be applied to improve its bioactivities. In this paper, five novel inulin derivatives were synthesized via chemical modification with quaternary phosphonium salt. Their antifungal activity against three kinds of plant pathogens including Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum was assessed with radial growth assay in vitro. Results revealed that all the inulin derivatives exhibited improved antifungal activity compared with inulin. Particularly, inulin modified with triphenylphosphine (TPhPAIL) exhibited the best antifungal activity with inhibitory indices of 80.0%, 78.8%, and 87.4% against Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum at 1.0mg/mL respectively. The results clearly showed that chemical modification of inulin with quaternary phosphonium salt could efficiently improve derivatives' antifungal activity. Further analysis of results indicated that the antifungal activity was influenced by alkyl chain length or electron-withdrawing ability of the grafted quaternary phosphonium salts. Longer alkyl chain lengths or the stronger electron-withdrawing groups would lead to enhanced antifungal efficacy.

Structure and Properties Study of PA6 Nanocomposites Flame Retarded by Aluminium Salt of Diisobutylphosphinic Acid and Different Organic Montmorillonites.

Two different types of organic montmorillonite, namely quaternary ammonium salt intercalated MMT (CMMT) and quaternary phosphonium salt intercalated MMT (PMMT) were used as fillers in the flame-retardant polyamide (PA6) based on aluminium salts of diisobutylphosphinic acid (ABPA). The influence of different types of organic montmorillonite (OMMT) on the structure and properties of flame-retardant PA6 nanocomposites were systematically investigated. The X-ray diffraction and transmission electron microscopy results suggested that the introduction of OMMT improved the dispersion of the flame retardant particles independently of the type of OMMT. The derivative thermogravimetry (DTG) curve transformed to one peak from two peaks (representing the degradation of ABPA and PA6, respectively) after incorporation of the OMMT, which further confirmed better ABPA dispersion. Viscoelastic measurements demonstrated that a mechanically stable network structure was formed with the introduction of OMMT or ABPA and OMMT, while PA6/ABPA/PMMT presented the highest storage modulus and viscosity, suggesting a more efficient network structure. From UL-94 and limited oxygen index (LOI) tests, PA6/ABPA/PMMT presented the best flame performance, with a UL-94 of V-0 and a LOI of 33%. In addition, the PA6/ABPA/PMMT presented the lowest peak heat release rate (pHRR) among the investigated samples. Combined with the char layer analysis, it can be deduced that the introduction of PMMT improved the dispersion of ABPA, and promoted the formation of more efficient network structure, before promoting more compact char structures, which finally resulted in improved flame retardancy.

Green solvents: Applications in petroleum refinery

In the last two decades, Ionic Liquids (ILs) have attracted considerable attention in many fields of scientific research. ILs have drawn an increasing interest due to their unique physical and chemical properties that showed a great potential as an alternative media in many potential applications. ILs are defined as low melting point, lower than 100 °C, salts consisting of organic cations and organic/inorganic anions both of which are large ions and held together by electrostatic interactions. ILs has very low vapor pressure, non-flammable, tunable and can dissolve both polar and non-polar compounds. Owing to their low vapor pressure ILs were qualified as green solvents. However, the green affiliation of ILs is now contested by many research groups. The conventional technology used for oil extraction from oilseeds is by solvent extraction. In solvent extraction, n-hexane is used as a solvent for its attributes such as simple recovery, non-polar nature, low latent heat of vaporization (330 kJ/kg) and high selectivity to solvents. However, usage of hexane as a solvent has lead to several repercussions such as air pollution, toxicity and harmfulness that prompted to look for alternative options.The hazardous toxicity and the very poor biodegradability of many ILs have been reported in the literature. ILs with high purity is also required since impurities, even in trace amounts, affect their physical properties. These drawbacks together with the high price of common ILs delayed their industrial applications and new concepts were strongly needed in order to utilize these systems in a more rational way. To overcome these drawbacks, a new generation of solvents, named Deep Eutectic Solvents (DES), has emerged as alternative to ILs in many applications. Formation of these DESs can be obtained by simply mixing together two or more components that can be chosen to be cheap, renewable and biodegradable. These compounds are capable of forming a eutectic mixture with a melting point lower than that of each individual component. DESs are generally liquid at temperatures lower than 100 °C. Many DESs have similar physical-chemical properties to those of ILs, while being much cheaper and environmentally friendlier. Owing to these advantages, there is now of growing interest in DESs in many fields of research. DESs are chemically tailorable solvents since they can be designed by properly combining various quaternary ammonium or phosphonium salts with different Hydrogen Bond Donors (HBD) or complexing agents. Hence, task-specific DESs with different physical-chemical properties can be prepared. It should also be noted that although components of DESs are potentially reactive chemicals, their auto-association by a hydrogen bond drastically limits their reactivity, allowing their use in many fields of research. In this work, we discuss the application of both ILs and DESs in petroleum refining and petrochemical processes. Examples include, but are not limited to, separation of aromatics, de-sulfurization, de-nitrification and carbon dioxide capture.

Long sought synthesis of quaternary phosphonium salts from phosphine oxides: inverse reactivity approach

Quaternary phosphonium salts (QPS), a key class of organophosphorus compounds, have previously only been available by routes involving nucleophilic phosphorus. We report the realisation of the opposite approach to QPS utilising phosphine oxides as the electrophilic partner and Grignard reagents as nucleophiles. The process is enabled through the crucial intermediacy of the derived halophosphonium salts. The route does not suffer from the slow kinetics and limited availability of many parent phosphines and a broad range of QPS were prepared in excellent yields.

Efficient solvent-free fixation of CO2 catalyzed by new recyclable bifunctional metal complexes

A series of metal complexes containing a metal ion (Zn, Cu, Pb, Ni, Co) and two quaternary phosphonium salt units anchored on the ligands were designed and synthesized as efficient single-component bifunctional catalyst for the solvent-free coupling reaction of CO2 and epoxides without any co-catalysts. The effects of various reaction variables on the catalytic activity were investigated systematically and the optimized reaction conditions were screened as (130°C, 1MPa and 5h). The order of the catalytic activity for these single-component bifunctional metal complexes was found to be Zn-PPBCl (96%)>Co-PPBCl (90%)≈Ni-PPBCl (90%)>Pb-PPBCl (86%)>Cu-PPBCl (15%). Notably, a high turnover frequency (TOF) value (1230h−1) for bifunctional catalyst Zn-PPBCl was achieved via adjusting reaction variables. Moreover, this series of catalysts can also catalyze the coupling reaction at atmospheric pressure, and most of them showed high conversion of epoxide (propylene carbonate (PC) yield>90%) within 7h. The catalysts are also applicable to a variety of epoxides and good catalytic performances were achieved for producing the corresponding cyclic carbonates in most cases. Furthermore, the catalyst can be easily recycled and reused for at least five times without dramatic activity loss after simple filtration and drying. Finally, kinetic studies were carried out preliminarily for four metal (Zn, Co, Ni, Pb) catalysts and the formation activation energies (Ea) of cyclic carbonate were obtained. The apparent activation energy Ea catalyzed by Zn-PPBCl is only 37.6kJ/mol, while the Ea (Pb-PPBCl) is 70.0kJ/mol, Ea (Ni-PPBCl) is 65.6kJ/mol, and Ea (Co-PPBCl) is 43.1kJ/mol. The sequence of Ea agrees well with the catalytic activity. Based on the kinetic studies and experimental results, an inferred mechanism was deduced.

Synthesis and Biological Activity of Azine Heterocycle Functionalized Quaternary Phosphonium salts

Various azine heterocycles (pyrazine, quinoxaline and quinoline) possessing phosphonium salts (3a-3c) were prepared as cationic biocides. The structural characterization of the phosphonium compounds was confirmed by FTIR, NMR and HR-Mass spectroscopy. These compounds has shown excellent bactericidal activity against two Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae). Quinoline functionalized phosphonium has shown more antibacterial activity than pyrazine and quinoxaline.

New insights into the alkoxycarbonylation of propargyl alcohol

The challenging carbonylation of propargyl alcohol is effectively catalyzed by Pd(OAc)2 in combination with diphenyl-(6-methyl-pyridin-2-yl)phosphine and methanesulfonic acid. In dichloroethane at 20–50°C, the reaction affords with almost complete regioselectivity alkyl 2-(hydroxymethyl)acrylates. Turnover frequency numbers (TOF) of up to 450h−1 can be achieved working at 50°C, while a maximum turnover number (TON) of about 730 is obtained at 30°C. The catalyst longevity is limited because the carbonylation product reacts with the phosphorus atom of the ligand to give a quaternary phosphonium salt. This reaction leads to deactivation of the catalyst and eventually to palladium black formation.

Mechanical strength of epoxy/organoclay/carbon fiber hybrid composites

The influence of organoclay (bentonite BS) modified with quaternary ammonium (QAS) and phosphonium salts (QPS) on the mechanical properties of epoxy/organoclay/carbon fiber hybrid composites was investigated. The longitudinal flexural strength of the composites containing 1 wt % ­BSQAS and BSQPS increased by 4 and 10 %, respectively, compared to the reference sample (epoxy resin/carbon fiber). Moreover, there was also a significant improvement, up to 13 %, of Young's modulus and transverse elastic modulus for the composites with modified bentonites. On the basis of the atomic force microscopy cross-section analysis (AFM), it was found that the composites with matrix containing the modified bentonites were characterized with larger interfacial surface, about 50 %, than that of unmodified matrix (epoxy resin/carbon fiber).

Preparation and Characterization of Novel Cationic Chitosan Derivatives Bearing Quaternary Ammonium and Phosphonium Salts and Assessment of Their Antifungal Properties.

Chitosan is an abundant and renewable polysaccharide, its derivatives exhibit attractive bioactivities and the wide applications in various biomedical fields. In this paper, two novel cationic chitosan derivatives modified with quaternary phosphonium salts were successfully synthesized via trimethylation, chloride acetylation, and quaternization with tricyclohexylphosphine and triphenylphosphine. The structures and properties of synthesized products in the reactions were characterized by FTIR spectroscopy, 1H-NMR, 31P-NMR, elemental and thermogravimetric analysis. The antifungal activities of chitosan derivatives against four kinds of phytopathogens, including Phomopsis asparagi, Watermelon fusarium, Colletotrichum lagenarium, and Fusarium oxysporum were tested using the radial growth assay in vitro. The results revealed that the synthesized cationic chitosan derivatives showed significantly improved antifungal efficiency compared to chitosan. It was reasonably suggested that quaternary phosphonium groups enabled the obviously stronger antifungal activity of the synthesized chitosans. Especially, the triphenylphosphonium-functionalized chitosan derivative inhibited the growth of Phomopsis asparagi most effectively, with inhibitory indices of about 80% at 0.5 mg/mL. Moreover, the data demonstrated that the substituted groups with stronger electron-withdrawing ability relatively possessed greater antifungal activity. The results suggest the possibility that cationic chitosan derivatives bearing quaternary phosphonium salts could be effectively employed as novel antifungal biomaterials for application in the field of agriculture.

Evaluation of quaternary phosphonium salt as the collector in bauxite reverse flotation

Organic phosphorous compounds recently have received more attention because of the stronger affinity towards metals and metal oxides. In the present study, tributyltetradecylphosphonium chloride (TTPC), a quaternary phosphonium salt (cationic type), was introduced and evaluated in the system of bauxite reverse flotation. Although there were some limitations in the preliminary tests, the results still showed that TTPC exhibited superiority in bauxite reverse flotation to dodecyl trimethyl ammonium chloride. Quaternary phosphonium salts might have the promising application values in chemical engineering areas where quaternary ammonium salts were extensively applied.

Halogenation of quaternary phosphonium salts containing prop-1(2)-enyl group

Bromination of prop-2-enyltributyl- and -triphenylphosphonium bromides affords the products of addition to the double bond. The structure of the triphenylphosphonium adduct was established by X-ray diffraction analysis. The latter is formed also by radical bromination of prop-1-enyltriphenylphosphonium bromide. The chlorination of prop-1- and 2-enyltriphenylphosphonium bromides leads to the formation of 3-chloroprop-1-enyltriphenylphosphonium bromide.

Thermal characterization and non-isothermal kinetics of 4-fluorobenzyltriphenylphosphonium chloride crystal

4-Fluorobenzyltriphenylphosphonium chloride (4-FBTC), a quaternary phosphonium salt, was synthesized, a single crystal was grown by slow evaporation method, and the structure was confirmed by single crystal XRD and spectral analyses. The single crystal XRD analysis showed the triclinic crystal structure with molecular formula, C50H48P2F2Cl2O3. Thermal studies were carried out at three different heating rates (5, 10 and 15 °C min−1) under N2 atmosphere, which shows the single-stage decomposition at all heating rates. The conventional, non-isothermal decomposition kinetic studies using model-free method were carried out to calculate the kinetic parameters like activation energy, pre-exponential factor, half-life and rate constant at various conversion percentages (1, 2.5, 5, 10 and 20%). Lifetime of 4-FBTC at room temperature for different conversion percentages was calculated to estimate the stability of the compound. Specific heat capacity and change in enthalpy were calculated using DSC analysis at 10 °C min−1 heating rate under N2 atmosphere.

Design, synthesis of novel chitosan derivatives bearing quaternary phosphonium salts and evaluation of antifungal activity

Two novel chitosan derivatives modified with quaternary phosphonium salts were successfully synthesized, including tricyclohexylphosphonium acetyl chitosan chloride (TCPACSC) and triphenylphosphonium acetyl chitosan chloride (TPPACSC), and characterized by FTIR, 1H NMR, and 13C NMR spectra. The degree of substitution was also calculated by elemental analysis results. Their antifungal activities against Colletotrichum lagenarium, Watermelon fusarium, and Fusarium oxysporum were investigated in vitro using the radial growth assay, minimal inhibitory concentration, and minimum bactericidal concentration assay. The fungicidal assessment revealed that the synthesized chitosan derivatives had superior antifungal activity compared with chitosan. Especially, TPPACSC exhibited the best antifungal property with inhibitory indices of over 75% at 1.0mg/mL. The results obviously showed that quaternary phosphonium groups could effectively enhance antifungal activity of the synthesized chitosan derivatives. Meanwhile, it was also found that their antifungal activity was influenced by electron-withdrawing ability of the quaternary phosphonium salts. The synthetic strategy described here could be utilized for the development of chitosan as antifungal biomaterials.