Anionic Metal Complexes Research Articles

Diphosphonic ionic liquids as anion-exchangers for palladium(II) and platinum(IV): Synthesis, complexation and selective extraction from hydrochloric solutions

The demand for platinum group metals (PGMs) continues to grow. To reduce the negative environmental impact, it is necessary to switch to secondary sources of PGMs and to improve the separation and purification processes of these metals. In this work, new phosphonium-based ionic liquids (diphosphonium salts) were synthesized as extractants for the selective recovery of palladium(II) and platinum(IV) from hydrochloric acid solutions. Substances synthesized contain a doubly-charged cation, which significantly affects the selectivity of extraction compared to singly charged phosphonium extractants. It was found that diphosphonium salts have a high extraction efficiency of metallic ions that form stable doubly-charged chloride anionic complexes. Thus, solutions of synthesized ionic liquids in 3-nitrobenzotrifluoride can selectively extract palladium(II) and platinum(IV) in the presence of all d‐metal ions studied, which are contained in PGMs secondary sources. The extraction efficiency under optimal conditions is 99.6 % and 98.5 % for palladium(II) and platinum(IV), respectively. The extraction mechanism has been investigated by X-ray diffraction, DFT calculations and 31P, 111Cd NMR spectroscopy. Extraction proceeds through the anion-exchange mechanism, however, in the case of the studied compounds, the significant role of bromide as a counterion of ligands was shown. It was found that bromide is likely included in the extracted ion pair, displacing chloride ions from anionic metal complexes during extraction.

Degradation of the AMP/PZ-based solvent CESAR1 and effects of solvent management in two longtime pilot plant tests

Two 24/7 longtime testing campaigns at the CO2 capture pilot plant at Niederaussem with an accumulated testing time of more than 40,000 h with the CESAR1 solvent, an aqueous solution of 26.7 wt% 2-amino-2-methylpropan-1-ol (AMP) and 12.9 wt% piperazine (PZ), provide a unique data base for the development of solvent management technologies and the evaluation of hypotheses on amine degradation. In the first campaign with a testing time of 34,000 h without replacement of the solvent inventory, three solvent management strategies with different effect mechanisms were investigated: adsorptive removal of trace elements from the solvent by two kinds of active carbon, removal of ionic contaminants by ion exchange using cation and anion exchange resins, and removal of NO2 from the flue gas by treatment with a thiosulfate/sulfite solution. After replacement of the solvent inventory the second campaign was conducted, in which none of the solvent management technologies mentioned have been applied for 10,000 h. The results of the two campaigns allow a direct comparison of the solvent degradation behavior. It is shown that active carbon does not significantly affect the accumulation rate of degradation products in CESAR1, and that an inappropriate kind of active carbon can cause foaming. Anionic degradation products, metal complexes, trace components and cationic contaminants can be effectively removed from the aged solvent by ion exchange. However, after their removal, accelerated formation of oxidative degradation products by a factor of up to 3 higher than before the anion exchange was observed. Removal of NO2 from the flue gas did not affect the NH3 emissions from the CO2 absorber, but it led to the highest observed increase rate of the accumulation of acidic degradation products for aged CESAR1. The results show that exaggerated efforts for solvent management are contra-productive and that a reassessment of the effect mechanisms of solvent management technologies is necessary.

Supramolecular Hybrids of Proteins from Habu Snake Venom with Discrete [Pt(CN)4]2- Complex.

The venom of the Habu snake Protobothrops flavoviridis (P. flavoviridis) is known to contain a diverse array of proteins and peptides, with a notable presence of phospholipase A2 (PLA2) enzymes. These PLA2 enzymes have been extensively studied for their function and molecular evolution. Nevertheless, several aspects, such as the physical properties and the self-assembly mechanism of hierarchical structure from the nanoscale to the microscale with different chemical compounds, remain poorly understood. This study aims to fill this knowledge gap by investigating the behavior of enzyme components purified from P. flavoviridis venom in the presence of anionic [Pt(CN)4]2- complexes, which have the potential for soft metallophilic interactions and interesting optical properties. The purified PLA2 isozymes were diluted in Dulbecco's phosphate buffered saline (D-PBS (-)) and combined with the anionic metal complex, resulting in the formation of microstructures several micrometers in size, which further grew to form fibrous structures. This novel approach of combining PLA2 enzymes with discrete functional metal complexes opens up exciting possibilities for designing flexible and functional supramolecular and biomolecular hybrid systems in aqueous environments. These findings shed light on the potential applications of snake venom enzymes in nanotechnology and bioengineering.

Ion-Pairing Stereodynamic Probes for Circular Dichroism Chiral Sensing of Amines.

Tris(2-pyridylmethyl)amine (TPMA) and tris(2-phenolmethyl)amine (TPA) metal complexes have been extensively used for catalysis and molecular recognition applications. In particular, due to their ability to form stereodynamic complexes through the helical arrangement of the ligand around the metal in a propeller shape, chiroptical sensing has been extensively investigated. In particular, the capability of the analyte, usually a Lewis base, to bind the metal complex has been the predominant recognition motif. Herein, we report the synthesis and application of a zinc TPA-based stereodynamic probe for the sensing of chiral amines and amino-alcohols in which an ion-pair interaction between the anionic metal complexes and the ammonium ions is responsible for the recognition.

(Best Student Presentation) Is Solid-Electrolyte Interphase Formation Affected by Electrode Conductivity?

Accurate analysis of the mechanism of interphase formation and its composition is imperative for the development of stable and efficient lithium/sodium-ion batteries. One of the most practically scalable ways to optimize interphase chemistry and morphology for reversible charge transport is electrolyte engineering and the application of formation protocol with specific current/voltage conditions. In this sense, the analysis of structure and dynamics within the electrode/electrolyte interface, i.e., the so-called electric-double layer, is essential to predicting the possible chemistry and mechanism of interphase formation.The latest was recently advanced by understanding the effect of electrolyte chemistry, e.g., the chemical structure of solvent and salt, their ratio, the presence of additives etc.1–4 Although, the role of electrode material is often neglected which creates an impression that both metallic and semiconductive electrodes form an identical electric-double layer within the same electrolyte, therefore, the mechanism of interphase formation should be very similar regardless of the chemical nature of the electrode.Here, we used examples of sodium-salt-containing ionic liquids and carbonate electrolytes to demonstrate that structural changes at the electrified interface are greatly affected by the dielectric nature of electrode material. The key observation is attributed to the different abilities of electrified electrodes to form van der Waals interactions with the electrolyte species. This affects the concentration of metal-anion complexes in relation to organic solvent near the electrode, therefore, different interphase chemistry will be formed (inorganic-rich vs. organic-rich), and different formation protocols must be used. For example, Fig. 1 shows the summary of this phenomenon for ionic liquid electrolytes with 50 mol% sodium bis(fluorosulfonyl)imide. Besides, metallic and semiconductive electrodes demonstrated different affinity toward polar organic solvent, i.e., ethylene carbonate, in 1.0 M NaPF6 in EC:DMC (1:1 by volume) electrolyte. This presentation will discuss the details of these fundings and introduce future applications. Fig. 1 | Schematic relationships between solid-electrolyte interphase (SEI) composition, applied current of preconditioning cycling, and dielectric nature of anode material.References Zheng, X. et al. Toward High Temperature Sodium Metal Batteries via Regulating the Electrolyte/Electrode Interfacial Chemistries. ACS Energy Lett. 7, 2032–2042 (2022).Rakov, D. A. et al. Engineering high-energy-density sodium battery anodes for improved cycling with superconcentrated ionic-liquid electrolytes. Nat. Mater. 19, 1096–1101 (2020).Rakov, D. A. et al. Polar Organic Cations at Electrified Metal with Superconcentrated Ionic Liquid Electrolyte and Implications for Sodium Metal Batteries. ACS Mater. Lett. 4, 1984–1990 (2022).Rakov, D. et al. Stable and Efficient Lithium Metal Anode Cycling through Understanding the Effects of Electrolyte Composition and Electrode Preconditioning. Chem. Mater. (2021). doi:10.1021/acs.chemmater.1c02981 Figure 1

Synthesis of trioctyl polyvinyl chloride ammonium, membrane extraction properties, and electrodriven mass transfer behavior of Chromium (VI)

Trioctyl polyvinyl chloride ammonium (PVCTQAS) with quaternary ammonium salt content (QAS) of 25 % was synthesized by a nucleophilic substitution reaction of between polyvinyl chloride (PVC) and trioctylamine (TOA) for the first time. The mass transfer behavior of HCrO4−, CdCl3−, CoCl42−, FeCl4−, and CuCl42− metal complex anions within the plasticized PVCTQAS membrane followed a first-order kinetic rate equation. Taking the Cr(Ⅵ)-PVCTQAS system as a representative, the influences of plasticizer content and membrane thickness on the mass transfer performance were investigated, and the electrodriven mass transfer behavior of Cr(VI) was studied. The results showed that the mass transfer of HCrO4− in PVCTQASD followed a jumping mechanism, with a QAS content threshold of 22 %. In the Cr(VI)-PVCTQAS electrodriven mass transfer system, the PVCTQASD exhibited uniform electrochemical properties, and the membrane thickness had little influence on the mass transfer rate. The response of HCrO4− mass transfer rate to voltage depended on the distribution density of QAS in the membrane. The mass transfer performance of PVCTQASD with QAS between 15 % and 20 % had a high dependence on the voltage, while the permeability coefficient of Cr(VI)-PVCTQAS system became stable when the voltage exceeded 10 V after surpassing the QAS content threshold. 50 μm QAS 25 % Cr(VI)-PVCTQAS system had a treatment efficiency of 710 mg·m−2·h−1 for HCrO4− at 10 V, while maintaining exceptional selectivity and stability.

Spectroscopic and Electrochemical Investigation of Uranium and Neptunium in Chloride Room-Temperature Ionic Liquids.

To expand the breadth of knowledge of actinide chemistry in molten chloride salts, chloride room-temperature ionic liquids (RTILs) were used to probe the influence of RTIL cation on second-sphere coordination for anionic complexes of uranium and neptunium. Six chloride RTILs were studied to represent a range of cation polarizing strength, size, and charge density to correlate changes in the complex geometry and redox behaviors. Optical spectroscopy indicated that actinides were dissolved at equilibrium as octahedral AnCl62- (An = U, Np) as is observed in comparable high-temperature molten chloride salts. These anionic metal complexes were sensitive to the RTIL cation polarizing strength and hydrogen bond donating strength and displayed varying levels of fine structure and hypersensitive transition splitting depending on the degree of perturbation to the complex's coordination symmetry. Furthermore, voltammetry experiments on the redox-active complexes indicated a stabilizing effect on lower valence actinide oxidation states by more polarizing RTIL cations whereby the measured E1/2 potentials for both U(IV/III) and Np(IV/III) couples shifted positively by about 600 mV across the different systems. These results indicate that more polarizing RTIL cations inductively remove electron density from the actinide metal center over An-Cl-Cation bond networks to stabilize electron-deficient oxidation states. Electron-transfer kinetics were generally much slower than in molten chloride systems, partially due to lower temperatures and higher viscosities in the working systems and showed diffusion coefficients of 1.8 × 10-8 to 6.4 × 10-8 cm2 s-1 for UIV and 4.4 × 10-8 to 8.3 × 10-8 cm2 s-1 for NpIV. We also detect a one-electron oxidation of NpIV that we have attributed to the formation of NpV as NpCl6-. Overall, we observe a coordination environment for the anionic actinide complexes that is susceptible to even small changes in RTIL cation properties.

Controlling and tuning CO2 hydrate nucleation and growth by metal-based ionic liquids

The complex kinetic process of CO2 hydrate formation limits its applications of CO2 capture and sequestration et al. In this work, the effects of metal-based ionic liquids with different cations and anions on CO2 hydrate nucleation and growth was studied. The results showed that CO2 hydrate nucleation was promoted by the anions of [NiCl3]-, [MnCl3]-, [FeCl4]-, [C8MIM]+ and [C16MIM]+ ions due to the enhancement of local hydrogen-bonding network to construct crystal nuclei. The induction time of CO2 hydrate nucleation was decreased by 75.0% in the [C16MIM]FeCl4 aqueous solution. However, CO2 hydrate nucleation was inhibited by [C2MIM]+ and [ZnCl3]- anion. The gas storage capacity of CO2 hydrate was increased by mass transfer channels around the metal complex anions which could accelerate the diffusion rate of H2O and CO2 molecules. The co-effect between [C16MIM]+ cations and [FeCl4]- anions on CO2 hydrate growth was the strongest, which increased gas storage capacity by 16.1%. Hence, CO2 hydrate formation can be controlled and tuned by changing cations and anions of metal-based ionic liquids.

Metal complexes of new thiocarbohydrazones of Cu(I), Co(II), and Ni(II); identification by NMR, IR, mass, UV spectra, and DFT calculations

Substituted thiocarbohydrazones were synthesized to study their complexation capability towards Cu(I), Co(II), and Ni(II) salts. The Cu(I) complexes showed ligation of one mole of Cu(I)Br to one of the synthesized ligands to form a cationic–anionic metal complex. Co(II) and Ni(II) complexes were determined due to the chelating of equal equivalents of both ligands and metal salts to form monodentate metal dihalogenated complexes. Metal complexes were characterized by mass spectrometry, IR, NMR, UV spectra, and elemental analyses. Theoretical calculations were performed using density functional theory (DFT) at the B3LYP level with 6–31 + G(d) and LANL2DZ basis sets to access reliable results to the experimental values. The calculations were performed to obtain the optimized molecular geometry, charge density distribution, extent of distortion from regular geometry, the HOMO (highest occupied molecular orbital), the LUMO (lowest unoccupied molecular orbital), the molecular electrostatic potential (MEP), reactivity index (ΔE), dipole moment (D), global hardness (η), softness (σ), electrophilicity index (ω), and chemical potential. The calculations confirmed that the investigated complexes have a reliable geometry, agreeing with the experimental observation.

Formation of an active layer for charge accumulation in NiCo2O4 spinel

Discussion about the mechanism of pseudocapacitance led to the hypothesis that on the surface of pseudocapacitive materials there is an intermediate layer responsible for charge accumulation. Cyclic voltammetry revealed the presence of a hydroxylated layer on the surface of NiCo2O4 film.It was proven that the hydroxylated layer is formed as a result of the interaction of NiCo2O4 with alkali and consists of anionic metal complexes at the phase boundary. The redox switching process is considered as the loss of protons from water molecules or the removal of OH− ions in the environment of a metal ion. The presence of structurally bound hydroxyl groups on the surface was confirmed by TG-DSC, NMR 1H MAS and XPS. According to the results of ARXPS measurements, the thickness of the surface layer is ∼0.4 nm.

Localized Corrosion Mechanisms – a Bayesian Reasoning Perspective

The mechanisms for localized corrosion proposed over the last several decades are fall into two two major categories: (1) defect generation in the passive film of the open surface leading to breakdown and enhanced local dissolution and (2) the maintenance of a local electrolyte chemistry that promotes continued localized corrosion. A qualitative argument was proposed by Frankel et al. [1] to bridge the gap between passive film and local chemistry mechanisms. They suggest that passive film breakdown was more important for alloy-environment situations where pit initiation was more difficult, whereas local chemistry was more relevant for situations where pit initiation was more facile. Another difficulty arises when modeling the effect of local chemistry on stabilization of local corrosion. Is it the formation of critical pH, critical metal-anion complexes, or metal-anion salt film that is responsible for the stabilization of localized corrosion? These effects are interrelated because high concentration of metal cations can lead to acidification and salt film formation. Specific experimental techniques may bias conclusions with respect to one mechanism or another. Furthermore, uncertainties exist in the data used to validate models as conditions assumed in the models may be difficult to access. It is convenient under these circumstances to take a probabilistic approach based on Bayesian network (BN) to assess the likelihood of validity of a causal mechanism [2]. In this presentation, the importance of local acidity versus metal-salt formation on localized corrosion is examined through a Bayesian network model. The Bayesian network consists of nodes connected through cause-effect relationships characterized by conditional probabilities. The network computes the marginal probability of an event given causal events. Conversely, given an evidence, the preceding causes are evaluated using Bayes theorem. Thus, BN provides a probabilistic framework for cause-effect evaluations based on experimental evidence. Results from the literature and recent experiments are presented to illustrate the approach. Limitations of the approach are also presented. Frankel, G.S., T. Li, and J.R. Scully, Localized Corrosion: Passive Film Breakdown vs Pit Growth Stability. J. of The Electrochemical Society, 2017. 164(4): p. C180-C181.Pearl, J., Causality. 2009: Cambridge university press.

Synthesis, Single Crystal X-ray Structure, Spectroscopy and Substitution Behavior of Niobium(V) Complexes Activated by Chloranilate as Bidentate Ligand

Chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone, caH2) as a bidentate ligand for Nb(V) as a metal center is presented. The different coordination behavior of caH2 is well illustrated by a monomeric (Et4N)cis-[NbO(ca)2(H2O)OPPh3]·3H2O.THF (5) and a novel tetranuclear compound (Et4N)4[Nb4O4(ca)2(μ2-O)2Cl8]·2CH3CN (6) via self-assembly, respectively. These were obtained in >80% yields and characterized by IR, UV/Vis and NMR (1H, 13C{1H}, 31P{1H}) spectroscopy and single crystal X-ray diffraction, and they included a systematic assessment of the solid-state behavior. The anionic metal complexes showed different coordination modes at the Nb(V): [Nb4O4(ca)2(μ2-O)2Cl8]4− (6a; distorted octahedral) and cis-[NbO(ca)2(H2O)(OPPh3)]− (5a; D5h distorted pentagonal bipyramidal), respectively. The tetranuclear complex 6a is substitution inert, while cis-[NbO(ca)2(H2O)OPPh3]− (5a) allowed a systematic ligation kinetic evaluation. The substitution of the coordinated triphenylphosphine oxide by a range of pyridine-type entering nucleophiles, 4-N,N-dimethyl-aminopyridine (DMAP), pyridine (py), 4-methylpyridine (4Mepy), 3-chloropyridine (3Clpy) and 3-bromopyridine (3Brpy) in acetonitrile at 31.2 °C was carefully evaluated. The subtle interplay between the main group ligand systems and the hard, early transition metal Nb(V) complex (5a) was well illustrated. The entering monodentate ligands showed a 15-fold reactivity range increase in the order 3Brpy < 3Clpy < 4Mepy < py < DMAP in broad agreement with the Brønsted-donating ability of the nucleophiles. The activation parameters determined for the reaction of 5a with DMAP as the entering ligand yielded ΔH≠kf = 52 ± 1 kJ mol−1 and ΔS≠kf = −108 ± 3 J K−1 mol−1 for the enthalpy and entropy of activation, respectively, indicating an associative substitution mechanism. The study presents an important contribution to the structure/reactivity relationships in Nb(V) complexes stabilized by chloranilic acid as a bidentate ligand.

On the Synthesis and Reduction of Trigonal Halido Bis(silylamido) Metalates of Chromium to Cobalt

AbstractA series of halido bis(silylamido) metalates of chromium to cobalt is reported. Reaction of [NBu4]Br with linear metal silylamides ML2 (M=Mn−Co, L=−N(SiMe3)2, −N(Dipp)SiMe3; Dipp=2,6‐iPr−C6H3) leads to NBu4[M(Br)L2] whereas for chromium either intramolecular deprotonation (L=−N(SiMe3)2) or ligand exchange (L=−N(Dipp)SiMe3) is observed. Attempts for their reduction with KC8 showed in part the formation of linear metal(I) silylamide complexes but also degradation. In contrast, analogous compounds bearing a [K{18c6}]+ counter ion of cobalt and iron, obtained from reaction of anionic linear metal(I) complexes [M{N(SiMe3)2}2]− with allyl bromide – can be cleanly reduced. The adduct formation studies are also extended to benzyl potassium yielding [KM(Bn)L2] (M=Mn, Co) and subsequently the salt separated [K{18c6}][M(Bn)L2] using 18‐crown‐6 as sequestrating agent.

Effect of complex formation on the mass transfer during anodic dissolution of rotating disk electrode

The effect of complexation on the mass transfer during the anodic dissolution of metal rotating disk electrode involving anions of electrolyte with the formation of stable and unstable metal-anion complexes is theoretically studied. The unstable complexes can decompose with the formation of anions, which can be involved in the electrochemical reaction, i.e. the catalytic mechanism of anodic metal dissolution is realized. The developed mathematical model enables us to solve numerically the problem without using the approximations of the Nernst diffusion layer, equal diffusion coefficients of all solution components, and the condition of equilibrium complexation reaction.For several special cases (solution within the model of the Nernst diffusion layer, equal ionic diffusion coefficients), the analytical solution of the problem was compared with the numerical one. The conditions for the limiting current of anodic dissolution are determined. The role of convection and migration of solution components is revealed.The factors that have the strongest effect on the efficiency of the catalytic mechanism of metal dissolution with the formation of unstable intermediate complex are revealed.

Reductions of M{N(SiMe3)2}3 (M = V, Cr, Fe): Terminal and Bridging Low-Valent First-Row Transition Metal Hydrido Complexes and "Metallo-Transamination".

The reaction of the vanadium(III) tris(silylamide) V{N(SiMe3)2}3 with LiAlH4 in diethyl ether gives the highly unstable mixed-metal polyhydride [V(μ2-H)6[Al{N(SiMe3)2}2]3][Li(OEt2)3] (1), which was structurally characterized. Alternatively, performing the same reaction in the presence of 12-crown-4 affords a rare example of a structurally verified vanadium terminal hydride complex, [VH{N(SiMe3)2}3][Li(12-crown-4)2] (2). The corresponding deuteride 2D was also prepared using LiAlD4. In contrast, no hydride complexes were isolated by reaction of M{N(SiMe3)2}3 (M = Cr, Fe) with LiAlH4 and 12-crown-4. Instead, these reactions afforded the anionic metal(II) complexes [M{N(SiMe3)2}3][Li(12-crown-4)2] (3, M = Cr; 4, M = Fe). The reaction of the iron(III) tris(silylamide) Fe{N(SiMe3)2}3 with lithium aluminum hydride without a crown ether gives the "hydrido inverse crown" complex [Fe(μ2-H){N(SiMe3)2}2(μ2-Li)]2 (5), while treatment of the same trisamide with alane trimethylamine complex gives the iron(II) polyhydride complex Fe(μ2-H)6[Al{N(SiMe3)2}2]2[Al{N(SiMe3)2}(NMe3)] (6). Complexes 2-6 were characterized by X-ray crystallography, as well as by infrared, electronic, and 1H and 13C (complex 6) NMR spectroscopies. Complexes 1 and 6 are apparently formed by an unusual "metallo-transamination" process.

Effective capture of aqueous uranium using a novel magnetic goethite: Properties and mechanism

A large amount of uranium-containing wastewater is produced by the nuclear industry, which causes harm to human health and the environment. Goethite (α-FeOOH) is highly insoluble in water and has a net positive surface charge, making it an effective sorbent for metal–anion complexes in aqueous solutions. In this study, goethite (α-FeOOH) and Fe2+-modified magnetic goethite (M-α-FeOOH) were prepared using an easy one-pot chemical precipitation method and used to remove uranium from solution. The adsorbents were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), BET surface area analysis, fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM). When Fe2+ partially substitutes for Fe3+, the material is magnetic, has a larger specific surface area and can be rapidly separated in a magnetic field. The uranium adsorption performance of M-α-FeOOH was substantially better than that of α-FeOOH, and its maximum adsorption capacity increased by 46.09%. The data fitted well with the quasi-second order kinetic model and the Langmuir isothermal adsorption model. According to the results of this study, the increase in the uranium removal performance of M-α-FeOOH was attributed to its higher specific surface area, better dispersion, and larger quantity of activated adsorption sites. These results, along with its low-cost, environmentally friendly, and facile synthesis, reveal M-α-FeOOH is a promising material for uranium capture.

Theoretical description of the ligand function for ionoselective electrodes reversible to metal anion complexes. 3. Modeling of the electrode response in ligand and foreign ions solutions using the multi-species approach model

A description for the ligand function of the tetrathiocyanatozincate selective electrode, has been proposed, using a multi-species approach model. This model takes into account simultaneous phase-boundary, diffusion-controlled, processes of ion exchange between tetrathiocyanatozincate, thyocyanate and foreign ions unable to form zinc complexes, as well as distribution of the neutral zinc complex between phases, partial decomposition of quaternary ammonium tetrathiocyanatozincate salt and stepwise complex formation processes in water phase. The model is based on solving the system of equations describing several interphase and intraphase equilibria, assuming that diffusion flows of all membrane and solution components at the phase boundary are stationary. It provides the adequate description of tetrathiocyanatozincate selective electrode in solutions of the ligand, foreign ions and mixed solutions of the above, and predicts the effect of zinc chloride concentration in the sample solution upon electrode function slopes, lower detection limits and selectivity coefficients.

POSS and imidazolium-constructed ionic porous hypercrosslinked polymers with multiple active sites for synergistic catalytic CO2 transformation.

In this work, we reported a facile one-pot approach to construct polyhedral oligomeric silsesquioxane (POSS) and imidazolium-based ionic porous hypercrosslinked polymers (denoted as iPHCPs) with multiple active sites towards efficient catalytic conversion of carbon dioxide (CO2) to high value-added cyclic carbonates. The targeted iPHCPs were synthesized from a rigid molecular building block octavinylsilsesquioxane (VPOSS) and a newly-designed phenyl-based imidazolium ionic crosslinker through the AlCl3-catalyzed Friedel-Crafts reaction. The desired multiple active sites come from the mixed anions including free Cl- and Br- anions, and in situ formed Lewis acidic metal-halogen complex anions [AlCl3Br]- within imidazolium moieties and POSS-derived Si-OH groups during the synthetic process. The typical polymer iPHCP-12 possesses a hierarchical micro-/mesoporous structure with a high surface area up to 537 m2 g-1 and shows a fluffy nano-morphology. By virtue of the co-existence of free nucleophilic Cl- and Br- anions, the metal complex anion [AlCl3Br]- with both electrophilic and nucleophilic characters and electrophilic hydrogen bond donor (HBD) Si-OH groups, iPHCP-12 is regarded as an efficient recyclable heterogeneous catalyst for synergistic catalytic conversion of CO2 with various epoxides into cyclic carbonates under mild conditions. The present work provides a succinct one-pot strategy to construct task-specific ionic porous hypercrosslinked polymers from easily available modules for the targeted catalytic applications.

Why halides enhance heterogeneous metal ion charge transfer reactions.

The reaction kinetics of many metal redox couples on electrode surfaces are enhanced in the presence of halides (i.e., Cl−, Br−, I−). Using first-principles metadynamics simulations, we show a correlation between calculated desorption barriers of V3+–anion complexes bound to graphite via an inner-sphere anion bridge and experimental V2+/V3+ kinetic measurements on edge plane pyrolytic graphite in H2SO4, HCl, and HI. We extend this analysis to V2+/V3+, Cr2+/Cr3+, and Cd0/Cd2+ reactions on a mercury electrode and demonstrate that reported kinetics in acidic electrolytes for these redox couples also correlate with the predicted desorption barriers of metal–anion complexes. Therefore, the desorption barrier of the metal–anion surface intermediate is a descriptor of kinetics for many metal redox couple/electrode combinations in the presence of halides. Knowledge of the metal–anion surface intermediates can guide the design of electrolytes and electrocatalysts with faster kinetics for redox reactions of relevance to energy and environmental applications.

Synthesis and characterization of 1-butyl-4-amino-1,2,4-triazolium energetic ionic liquids with transition-metal complex anions

Energetic ionic liquids based on 1-butyl-4-amino-1,2,4-triazolium cation and transition metal complex anions, namely [Co(NO2)6]3−, [Co(CN)6]3−, [Co(NCS)4]2− and [Fe(CN)6]3−, were synthesized.