Phosphonium Ion Research Articles

Modulation by Phosphonium Ions of the Activity of Mitotropic Agents Based on the Chemiluminescence of Luminols.

Mitochondria-targeting drugs and diagnostics are used in the monitoring and treatment of mitochondrial pathologies. In this respect, a great number of functional compounds have been made mitotropic by covalently attaching the active moiety onto a triphenylphosphonium (TPP) cation. Among these compounds, a number of molecular detectors for reactive oxygen species (ROS) are based on fluorescent and chemiluminescent probes. In this regard, luminol (probably the most widely known chemiluminescent molecule) has been employed for a number of biological applications, including ROS detection. Its oxidation under specific conditions triggers a cascade of reactions, ultimately leading to the excited 3-aminophthalate (3AP *), which emits light upon deactivation. Hence, the photophysical interaction between the light-emitting species 3AP * and TPP cations needs to be evaluated, as it can add valuable information on the design of novel emission-based mitotropic systems. We herein investigate the quenching effect of ethyltriphenylphosphonium cation onto substituted 3-aminophthalates. These were prepared in situ upon hydrolysis of the corresponding anhydrides, which were synthesized from 3-aminophthalimides. Steady-state fluorescence and time-resolved experiments were employed for the evaluation of a possible electron transfer quenching by phosphonium ions. Our experimental results confirmed such quenching, suggesting it is mainly dynamic in nature. A minor contribution of static quenching that was also detected is attributed to complex formation in the ground state. Accordingly, the chemiluminescence of luminol was indeed strongly reduced in the presence of phosphonium ions. Our results have to be taken into account during the design of new chemiluminescent mitotropic drugs or diagnostic agents of the luminol family.

Phosphine addition to dehydroalanine for peptide modification.

Thiols are a functional group commonly used for selective reactions in a biochemical setting because of their high nucleophilicity. Phosphorus nucleophiles can undergo some similar reactions to thiols, but remain underexploited in this setting. In this work we show that phosphine nucleophiles react cleanly and quickly with a dehydroalanine electrophile, itself generated from cysteine, to give a stable adduct in a peptide context. NMR reveals the product to be a phosphonium ion and indicates some backbone conformational constraint, possibly arising from transient carbonyl coordination. The reaction proceeded quickly, with a pseudo-first order rate constant of 0.126 min-1 at 1 mM peptide (80% conversion in 10 min), and with no detectable side products on the peptide. A broad peptide sequence scope and water-soluble phosphines with alkyl as well as aromatic groups were all shown to react efficiently. Phosphine addition proved to be efficient on nisin as a model Dha-containing biologically-derived peptide and on an mRNA-displayed peptide, as well as on TCEP-modified agarose for peptide capture from solution. This reaction thus presents a promising approach for modification of peptides for cargo attachment or altered physical properties in peptide discovery.

Synthesis and Applications of Lewis Superacidic Catecholato Phosphonium Ions

Key words catecholato phosphonium ions - Lewis superacids - phosphorus–ligand cooperativity - electrophilic aromatic substitution

Lewis Superacidic Catecholato Phosphonium Ions: Phosphorus-Ligand Cooperative C-H Bond Activation.

A series of catecholato phosphonium ions, including the first stable bis(catecholato)-substituted derivatives, are isolated and fully characterized. The cations rank among the most potent literature-known Lewis acids on the Gutmann-Beckett and ion affinity scales. In contrast to halogenated or multiply charged phosphorus cations, Lewis superacidity is imparted by structural constraints, as disclosed by energy decomposition analysis. The modular access provides a tunable scaffold while maintaining extreme affinity, demonstrated by the synthesis of a chiral Lewis superacid. The combination of electrophilic phosphorus and basic oxygen substituents leverages new reactivity modes by phosphorus-ligand cooperativity. With this, a phosphorus-mediated C-H bond activation is accomplished.

Tuning the Surface Reactivity and Tribological Performance of Phosphonium-Based Ionic Liquid at Steel/Steel Interfaces by Bromide/Phosphate Anion Mixtures

Phosphonium phosphate ionic liquids (ILs) are promising lubricant additives for engine oils owing to a combination of good tribological performance and attractive properties, such as high thermal stability and good miscibility with mineral and synthetic oils. Here, we evaluate the dependence of the lubricating performance of trihexyltetradecylphosphonium ([P6,6,6,14])-based ILs when used in steel/steel contacts on the relative concentration of bis(2-ethylhexyl)phosphate ([DEHP]) and bromide (Br-) anions. The results indicate no changes in friction and wear upon increasing the [P6,6,6,14]Br-to-[P6,6,6,14][DEHP] volume ratio up to 0.2:1, while a further increase in this ratio leads to a reduction of friction and wear. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry measurements highlight that the dependence of the lubricating properties of the ILs on the [P6,6,6,14]Br-to-[P6,6,6,14][DEHP] ratio originates from the balance between corrosivity and surface reactivity of this IL: while [DEHP] acts as corrosion inhibitor in the non-contact region, the formation of species containing phosphorus-oxygen moieties in the wear track as a result of the hydrolysis of phosphonium ions increases the surface coverage of phosphorus. This is proposed to decrease friction by decreasing adhesion at steel/steel contacts and lowering the interfacial shear strength.

Bulk Transparent Photon Upconverting Films by Dispersing High-Concentration Ionic Emitters in Epoxy Resins

It remains challenging to achieve efficient and air-stable photon upconversion (UC) in rigid, technologically valuable transparent films. Here, we report the first example of epoxy resins that show an air-stable and efficient triplet-triplet annihilation (TTA)-based UC. Epoxy resins are thermally cross-linked polymers widely used as coating and sealing materials in actual devices. To achieve efficient TTA-UC in rigid epoxy films, it is essential to execute both the triplet sensitization and triplet exciton diffusion processes without relying on molecular diffusion. This requires homogeneously dispersing emitter molecules without aggregation in three-dimensionally cross-linked rigid polymer networks at a high concentration (ca. 1000 mM) such that the inter-emitter distance is less than 1 nm, where dexter energy transfer can occur. This difficult requirement is solved by employing an ionic liquid emitter that consists of 9,10-diphenylanthracene sulfonate and lipophilic phosphonium ions bearing long alkyl chains. The obtained epoxy resins show a high TTA-UC efficiency (ηUC = 3.8%) and low threshold excitation intensity (Ith = 40 mW cm-2) in air. These UC parameters are achieved by virtue of a very high sensitizer-to-emitter triplet energy-transfer efficiency (92.8%) and a significantly long emitter triplet lifetime (17.8 ms) that reflect the high emitter concentration and the rigid chromophore environment, respectively. The bulk transparent upconverting resins can be prepared in air and function in air, which opens a new avenue toward a wide range of real-world applications.

Optimization of Green Technique Develop for Europium (III) Extraction by using Phosphonium Ionic Liquid and Central Composite Design Approach

Rare earth compounds widely used in industrial applications and new processes with green solvents are appropriate for recovering these elements. In this study, the ionic liquid application development was investigated to extract europium ions in single and binary systems. A green procedure for europium (III) extraction from aqueous chloride solution was investigated using phosphonium ionic liquid Cyphos IL 104. Comparative conditions were investigated for analyzing better results with the presence of organic extractant such as Cyanex272, D2EHPA in the batch experiments. The experiment design was carried out based on the central composite design principles to analyze the relationships between the responses and the significant parameters. The obtained data revealed that the quadratic equation has good desirability to predict the extraction percentage. Investigation of the extraction process showed that the ionic liquid Cyphos IL104 has selective power in the extraction of europium and the efficiency is higher than the organophosphorus extractants. Accordingly, optimum conditions for maximum removal of europium ions were obtained equal to 5.5, 1, 16 min, and 0.008 M for feed acidity (pH), phase ratio, time, Cyphos IL 104 concentration. Examination of binary systems of rare earth elements showed that ionic liquid had positive and negative effects on the separation factor. The high efficiency of ionic liquid in the reuse condition indicated that the system is appropriate from an economic perspective.

Easy Access to Enantiomerically Pure Heterocyclic Silicon-Chiral Phosphonium Cations and the Matched/Mismatched Case of Dihydrogen Release.

Phosphonium ions are widely used in preparative organic synthesis and catalysis. The provision of new types of cations that contain both functional and chiral information is a major synthetic challenge and can open up new horizons in asymmetric cation‐directed and Lewis acid catalysis. We discovered an efficient methodology towards new Si‐chiral four‐membered CPSSi* heterocyclic cations. Three synthetic approaches are presented. The stereochemical sequence of anchimerically assisted cation formation with B(C6F5)3 and subsequent hydride addition was fully elucidated and proceeds with excellent preservation of the chiral information at the stereogenic silicon atom. Also the mechanism of dihydrogen release from a protonated hydrosilane was studied in detail by the help of Si‐centered chirality as stereochemical probe. Chemoselectivity switch (dihydrogen release vs. protodesilylation) can easily be achieved through slight modifications of the solvent. A matched/mismatched case was identified and the intermolecularity of this reaction supported by spectroscopic, kinetic, deuterium‐labeling experiments, and quantum chemical calculations.

Oxidative addition, reduction and reductive coupling: the versatile reactivity of subvalent gallium cations.

Inspired by the successful oxidative addition of a P-H bond to univalent Ga[Al(ORF)4] that gives the unprecedented dicationic gallium hydride complex [H-Ga(PPh3)3][Al(ORF)4]2 (ORF = OC(CF3)3), the oxidative addition of E-Cl containing substrates was investigated. The reductive coupling of three PPh2Cl to the catenated phosphorus cation [P3Ph6]+ hinted towards a formal two-electron-three-halide reduction (2e--3X- reduction). Similarly, from SbCl3, a cationic formal SbI compound and from RhCl3, [RhI(HMB)(COD)]+ and [RhI(COD)2]+ (HMB = C6Me6, COD = 1,5-cyclooctadiene) are formed as [Al(ORF)4]- salts when reacted with Ga+. Thus, Ga[Al(ORF)4] allows for a one-pot 2e--3X- reduction with the concomitant introduction of a weakly coordinating anion (WCA).

Phosphonium-Based Polyzwitterions: Influence of Ionic Structure and Association on Mechanical Properties

This manuscript describes a synthetic strategy and structure–property investigation of unprecedented phosphonium-based zwitterionic homopolymers (polyzwitterions) and random copolymers (zwitterionomers). Free radical polymerization of 4-(diphenylphosphino)styrene (DPPS) provided neutral polymers containing reactive triarylphosphines. Quantitative postpolymerization alkylation of these pendant functionalities generated a library of polymers containing various concentrations of neutral phosphines, phosphonium ions, and phosphonium sulfobetaine zwitterions. The zwitterionic homo- and copolymers exhibited significantly higher glass transition temperatures (Tg) and enhanced mechanical reinforcement in comparison to neutral and phosphonium analogues. These changes in Tg and mechanical properties were attributed to nanoscale morphological domains, which formed due to electrostatic interactions between zwitterionic groups, as revealed by X-ray scattering and broadband dielectric spectroscopy (BDS). BDS revealed increased static dielectric constants (>25) for the phosphonium zwitterionomers compared to ionomeric or neutral analogues. These high static dielectric constants for the solvent-free polyzwitterions supported their stronger polarization response in comparison with polymers containing neutral phosphines and phosphonium ions, and these interactions accounted for morphological differences and enhanced mechanical behavior. This work describes a versatile strategy for modulating electrostatic interactions with tunable mechanical properties for an unprecedented family of zwitterionic polymers.

Recovery of Samarium and Cobalt from Sm–Co Magnet Waste Using a Phosphonium Ionic Liquid Cyphos IL 104

Due to outstanding thermal stability and corrosion resistance, samarium–cobalt alloy is being used in rare earth magnet. So, this permanent magnet waste can be a potential source for rare earth metal samarium and critical metal cobalt. Recovery and reuse of Sm, Co from Sm–Co magnet waste can reduce the burden on primary resources and environmental issues related to primary resources. In this work, a hydrometallurgical method for recovery of samarium and cobalt from Sm–Co magnet waste has been developed using an ionic liquid Cyphos IL 104. The optimum separation condition for cobalt and samarium has been determined by varying the concentration of HCl, NaCl, and mixture of HCl and NaCl in the leach liquor. The McCabe–Thiele plot is constructed using 0.075 mol/L Cyphos IL 104. Three counter-current stages at A:O ratio of 1:1.5 are needed for complete extraction of cobalt into the ionic liquid phase leaving samarium in the raffinate. Precipitation stripping of cobalt from the loaded organic is carried out using oxalic acid and the cobalt oxalate, thus formed, is calcined at 450 °C to form Co3O4. The raffinate obtained from the counter-current extraction contains 2.02 g/L Sm and 0.02 mg/L Co. Sm2O3 from raffinate is produced by precipitation of samarium with oxalic acid followed by calcination of samarium oxalate at 800 °C. Both the oxide products are confirmed by XRD.

Micellization Behavior of Conventional Cationic Surfactants within Glycerol-Based Deep Eutectic Solvent.

The aggregation behavior of two cationic surfactants, i.e., cetyldimethylethanolammonium bromide (CDMEAB) and cetyltributylphosphonium bromide (CTBPB), within an aqueous deep eutectic solvent (DES) is studied. The synthesized DES is composed of 1:2 mole ratio of choline chloride and glycerol and is further characterized by Fourier transform infrared (FTIR) and 1H NMR spectroscopy techniques. The critical micellar concentration (CMC), micellar size, and intermolecular interaction in surfactants within Gly-based DES solutions are investigated by various techniques including surface tension, conductivity, fluorescence, dynamic light scattering (DLS), FTIR, 1H NMR, and two-dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY). The various interfacial properties and thermodynamic parameters are determined in the presence of 5 wt % glyceline (Gly)-based DES in an aqueous solution. The CMC, aggregation number (Nagg), and Stern–Volmer constant (Ksv) have also been determined by a steady-state fluorescence method. DLS is used to obtain information regarding the size of the aggregates formed by the cationic surfactants in DES solutions. FTIR spectroscopy is used to study the surfactant–DES interactions that tune the micellar structure of the surfactants within the Gly-based DES solution. The functional groups involved in the interactions (H-bonding and electrostatic) are the head groups (HO–CH2–CH2–N+ ion for CDMEAB and quaternary phosphonium (P+) ion for CTBPB) of the surfactants with the −OH-containing Gly DES. The hydrophobic moieties are involved in the hydrophobic interactions. The 1H NMR data show that differences in chemical shifts can provide significant information about the interactions taking place within the system. 1H NMR and NOESY techniques are further employed to strengthen our claim on the feasible structural arrangements within the aqueous surfactant–DES self-assembled structures. It is observed that both the cationic surfactants, i.e., CDMEAB and CTBPB, form self-assembled nanostructures in the Gly-based DES solutions. The present results are expected to be useful for colloidal solutions of DES and their mixtures with water.

Simulation of Wetting and Interfacial Behavior of Quaternary Ammonium and Phosphonium Ionic Liquid Nanodroplets Over Face-Centered Cubic Metal Surfaces.

We studied the behavior of quaternary ammonium- and phosphonium-based ([N2225][NTf2] and [P2225][NTf2]) ionic liquid (IL) nanodroplets on copper (Cu) and platinum (Pt) metal surfaces using classical molecular dynamics simulations. Solid-liquid interactions were underpinned by studying the dynamic spreading, contact angle, time-dependent binding energies, mean-square displacements, number and charge density profiles, and orientational distribution of these two IL nanodroplets. In particular, the role and importance of different crystallographic facets of face-centered cubic metal surface [Cu(100), Cu(111), Pt(100), and Pt(111)] were investigated. The results indicate a vast variety of properties that are dictated highly by the structure of different crystallographic facets of the metal substrate. The nature of the facet (e.g., the atomic arrangement symmetry, the extent of closed packed, and the unit cell size) leads to an extended scale spreading of the ILs on the surface with the (111) index but not with the (100) index, while the nature of metals itself plays a role.

Effect of Surface Alignment on Connectivity in Phosphonium-Containing Diblock Copolymer Anion-Exchange Membranes

The performance of ion-exchange membranes in fuel cells is critically linked to their ion-conducting morphology. In this report, we analyzed the connectivity of anion-exchange membranes (AEMs) by electrostatic force microscopy (EFM). As a tapping-mode AFM-based technique, EFM probes height, phase, and electrostatic force gradient through two-pass interleave scans, which reveals the direct relationship between membrane surface morphology and connectivity of the ionic domain. The AEMs are diblock copolymers of a polyisoprene (PIp) block and a polystyrenic block containing the phosphonium ion (P(R3P+)MS). Different alignments of cylinders were observed in the bulk and on the surface for AEMs with different ion-exchange capacities (IECs) and preparation methods. The impacts of the cylinder alignment on the connectivity of the ionic domain were then investigated by EFM. For AEM 13 with IEC = 0.44 mmol/g and a hexagonal morphology, cylinders aligned parallel to the surface, which led to many disconnected regions observed throughout the membrane. In contrast, the perpendicularly aligned channels of AEM 16 with IEC = 0.87 mmol/g consisted only of a well-connected ionic phase throughout the membrane.

Effect of Ionomer Solvents for Pore Size Control of Imidazolium-Base Ionomers in Aemfc

Anion exchange membrane fuel cells (AEMFCs) have a low activation overvoltage due to the fast oxygen reduction reaction (ORR) response to alkaline conditions compared to the acidic condition of proton exchange membrane fuel cells (PEMFCs). The reasons for low activation overvoltage in AEMFCs are diversely studied. Recently, the binder ionomer in the catalyst layer of polymer electrolyte membrane fuel cells has attracted increasing attention because of its critical role in power performance and the durability of the catalyst layer. Ionomer covers the catalyst surfaces, providing anion transport between the catalyst surfaces and the membrane, as well as mechanical connection. Several requirements as a binder are to have high ion conductivity, gas permeability, and electron conductivity. For durability of membrane electrode assembly (MEA), the binder must have high oxidative stability, and mechanical integrity, less excessive swelling is detrimental. Unususally as AEMs and binder materials, functional groups such as quaternary ammonium (QAs), phosphonium, guanidinium, tertiary sulfonium, pyridinium, and imidazolium ionic liquid (IILs) are used as cation groups. Among them, the QAs has higher chemical and thermal stability than phosphonium, guanidinium and tertiary sulfonium ions. However, the QAs groups tend to be degraded by OH- counterion in high pH environments. In this study, we prepared a binder using IILs instead of the commonly used QAs. Imidazolium-based binders are uncomplicated to design the polymer and easy to synthesize. Furthermore, effect of different alcohols in ionomer binder solution on the shale and pore size of catalyst layer is presented here. The aim of this study is to find out the effect of alcohols in binder ionomers for alkaline fuel cell performance. Figure 1

Synthesis and Evaluations of “1,4‐Triazolyl Combretacoumarins” and Desmethoxy Analogs

1,4‐Triazolyl combretacoumarins have been prepared by linking the trimethoxyarene unit of combretastatin A4 with coumarins, via a 1,2,3‐triazole. For this, 4‐azidocoumarins were accessed by a sequential two‐step, one‐pot reaction of 4‐hydroxycoumarins with (benzotriazol‐1‐yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), followed by reaction with NaN3. In the reaction with BOP, a coumarin‐derived phosphonium ion intermediate seems to form, leading to an O 4‐(benzotriazolyl)coumarin derivative. For the CuAAC reaction of azidocoumarins with 5‐ethynyl‐1,2,3‐trimethoxybenzene, catalytic [(MeCN)4Cu]PF6 in CH2Cl2/MeOH with 2,6‐lutidine, at 50 oC, was suitable. The 4‐azidocoumarins were less reactive as compared to PhN3 and the NBO coefficients of the azido groups were compared by DFT analysis. Compound solubility was a problem in biological assays. On the basis of the biological and solubility data of one 1,4‐triazolyl combretacoumarin, four analogs lacking one or two methoxy groups were synthesized. Reactivity differences among the phenylacetylenes were noted and the NBO coefficients of the alkynes were compared by DFT analysis. In cytotoxicity assays, 1‐phenyl‐4‐(3,4,5‐trimethoxyphenyl)‐1H‐1,2,3‐triazole showed activity in CEM and MDA‐MB‐231 cell lines by apoptosis. The desmethoxy 6‐bromo‐4‐(4‐(4‐methoxyphenyl)‐1H‐1,2,3‐triazol‐1‐yl)‐2H‐chromen‐2‐one also showed cytotoxicity against the two cell lines, but this did not appear to be consistent with apoptosis. The antiviral activity of the compounds was unremarkable.

Isolation of octahedral to tetrahedral cobalt-azido molecular assemblies based on cationic influence

Two novel cobalt-azido compounds [Me4N]2[NaCo(EE-N3)6] 1 and [Ph4P]2[Co(N3)4] 2; where Me4N = tetramethyl ammonium ion, EE = end-to-end, Ph4P = tetraphenyl phosphonium ion, have been synthesized and characterized by single crystal X-ray crystallography. Two compounds were synthesized by varying the size of the cations. The size of the cations effects remarkably producing different cobalt-azido compounds. Depending on the cation size the framework dimensionality changes from 3D to mononuclear complex. The smaller cation leads to a 3D framework which is an interesting Prussian Blue analogue type structure but the bigger cation produces a discrete mononuclear unit.

A nickel foam modified with electrodeposited cobalt and phosphor for amperometric determination of dopamine.

Considering the importance of dopamine (DA) detection for neuroscience and disease diagnosis, herein, an electrochemical sensor for dopamine is described. It is based on the use of a Ni-Co-P nanostructure fabricated on nickel foam via electrode position from cobalt chloride and ammonium phosphate for 10min. Time-dependent experiments show the transformation of Ni-Co-P nanoparticles to spheres. The resulting electrode display excellent electrochemical response to DA. Figures of merit include (a) a working potential of 0.55V (vs. Ag/AgCl); (b) an electrochemical sensitivity of 5262μAmM-1cm-2; (c) a wide linear range (from 0.5 to 2350μM), and (d) a 1μM detection limit. The outstanding electrochemical performance is explained by the synergistic effects of large surface area, improved electron transfer, presence of free binders, and the presence of three active components (nickel, cobalt and phosphonium ion). Graphical abstract A Ni-Co-P nanostructure was electrodeposited on nickel foam to obtain an electrochemical sensor for amperometric determination of dopamine with outstanding performance.

Structure, Anion, and Solvent Effects on Cation Response in ESI-MS.

The abundance of an ion in an electrospray ionization mass spectrum is dependent on many factors beyond just solution concentration. Even in cases where the analytes of interest are permanently charged (under study here are ammonium and phosphonium ions) and do not rely on protonation or other chemical processes to acquire the necessary charge, factors such as cation structure, molecular weight, solvent, and the identity of the anion can affect results. Screening of a variety of combinations of cations, anions, and solvents provided insight into some of the more important factors. Rigid cations and anions that conferred high conductivity tended to provide the highest responses. The solvent that most closely reflected actual solution composition was acetonitrile, while methanol, acetonitrile/water, and dichloromethane produced a higher degree of discrimination between different ions. Functional groups that had affinity for the solvent tended to depress response. These observations will provide predictive power when accounting for analytes that for reasons of high reactivity can not be isolated.

Development of palladium catalysts immobilized on supported phosphonium ionic liquid phases

The application of heterogeneous palladium catalysts supported on phosphonium ion modified silica was investigated in aminocarbonylation reactions of aryl iodides. In contrast to catalysts immobilized on supports decorated with imidazolium ions, the application of phosphonium type supported ionic liquid phases made it possible to carry out double carbonylation with good selectivity in apolar toluene which led to a considerable decrease in the amount of leached palladium. An even better stabilization of the palladium catalyst could be achieved by introducing dicationic organic moieties incorporating both imidazolium and phosphonium ions on the surface of the support. At the same time, the former catalyst, obtained from the supported phosphonium ionic liquid phase was found to be superior in monocarbonylations. The amide products were obtained in good yields by the proper choice of the reaction conditions, such as reaction temperature and pressure and that of the base.