Single Anion Research Articles

Structural characterization, spectroscopic properties, and Hirshfeld surface analysis of two copper(II) complexes with 3,14-dimethyl and 3,14-diethyl-2,6,13,17-diazadiazoniatricyclo[16.4.0.07,12]docosa-2,13-diene

Herein, two unsaturated macrocyclic copper(II) complexes, namely, [CuLA(ClO4)2] (1) [LA = 3,14-dimethyl-2,6,13,17-diazadiazoniatricyclo[16.4.0.07,12]docosa-2,13-diene) and [CuLB(ClO4)]ClO4 (2) (LB = 3,14‑diethyl-2,6,13,17-diazadiazoniatricyclo[16.4.0.07,12]docosa-2,13-diene), were synthesized. The complexes were characterized by single-crystal X-ray determination and physico-chemical methods. Complex 1 crystallized in the monoclinic P21/n space group with Z = 2, while complex 2 crystallized in the monoclinic P21/c space group with Z = 4. The asymmetric unit of complex 1 contained one half of the [CuLA]2+cation and a single perchlorate anion, whereas complex 2 comprised a single [CuLB(ClO4)]+ cation and one doubly disordered perchlorate anion. The Cu(II) ion in complex 1 adopted a six-coordinated tetragonal geometry coordinated by four N atoms of the macrocyclic ligand LA [Cu–Namine 2.000 (2) Å and Cu–Nimine 1.962 (3) Å] and two axial perchlorate O atoms [Cu–O 2.6736 (4) Å], while the Cu(II) ion in complex 2 adopted a five-coordinated square pyramidal geometry coordinated by four N atoms of LB [mean Cu–Namine 1.9892 (17) Å and Cu–Nimine 1.9915 (18) Å] and an apical perchlorate O-atom [Cu–O 2.6318 (5) Å]. The crystals were stabilized by hydrogen bonds involving the secondary amine NH groups of the macrocycles and O atoms of the perchlorate groups. Hirshfeld surface analysis with 2D fingerprint plots revealed that the H⋯H and O⋯H interactions in both complexes 1 and 2 were the main intermolecular interactions.

Consecutive methane activation mediated by single metal boride cluster anions NbB4.

Cleavage of all C-H bonds in two methane molecules by gas-phase cluster ions at room temperature is a challenging task. Herein, mass spectrometry and quantum chemical calculations have been used to identify one single metal boride cluster anions NbB4- that can activate eight C-H bonds in two methane molecules and release one H2 molecule each time under thermal collision conditions. In these consecutive reactions, the loaded Nb atoms and the support B4 units play different roles but act synergistically to activate CH4, which is responsible for the interesting reactivity of NbB4-. Moreover, there are some mechanistic differences in these two reactions, including the mechanisms for the first C-H bond activation steps, dihydrogen desorption sites, and major electron donors. This study shows that non-noble metal boride species are reactive enough to facilitate thermal C-H bond cleavages, and boron-based materials may be one kind of potential support material facilitating surface hydrogen transport.

Impact of borate on structure of antifreeze glycoproteins

Antifreeze glycoproteins (AFGPs) facilitate the survival of various organisms in the polar region by preventing internal ice accumulation via an adsorption-inhibition mechanism. Inhibition of AFGP antifreeze activity by the borate buffers has been widely acknowledged as the direct experimental evidence supporting the hydroxyl, rather than methyl, binding mechanism. On the other hand, perturbation of borate binding on the AFGP configuration, which might have considerable influence on the binding efficiency of not only the hydroxyl but also the methyl groups, has rarely been quantitatively examined. Herein we studied, using molecular dynamics simulations, the perturbation on the configuration of a solvated AFGP8 protein induced by the binding of one single borate anion. Near the freezing point, this binding not only makes the disaccharide groups adjacent to the borate-binding disaccharide close to each other but also affects the entire AFGP8 conformation. The structural changes induced by the binding of borate on different disaccharide sidechains exhibit clear site-specificities and the effect of borate binding on the structural changes is significantly reduced at higher temperatures. Our study is valuable for further understanding the relationship between the structure and antifreeze activity of these antifreeze glycoproteins.

Photoluminescence properties of quinary Ag–(In,Ga)–(S,Se) quantum dots with a gradient alloy structure for in vivo bioimaging

Mixed-anion Ag–(In,Ga)–(S,Se) QDs exhibited a tunable band-edge PL peak with the S/Se ratio and had superior durability for near-IR in vivo bioimaging in comparison with single anion counterparts.

Simultaneous Functionalization of Methane and Carbon Dioxide Mediated by Single Platinum Atomic Anions.

Mass spectrometric analysis of the anionic products of interaction among Pt-, methane, and carbon dioxide shows that the methane activation complex, H3C-Pt-H-, reacts with CO2 to form [H3C-Pt-H(CO2)]-. Two hydrogenation and one C-C bond coupling products are identified as isomers of [H3C-Pt-H(CO2)]- by a synergy between anion photoelectron spectroscopy and quantum chemical calculations. Mechanistic study reveals that both CH4 and CO2 are activated by the anionic Pt atom and that the successive depletion of the negative charge on Pt drives the CO2 insertion into the Pt-H and Pt-C bonds of H3C-Pt-H-. This study represents the first example of the simultaneous functionalization of CH4 and CO2 mediated by single atomic anions.

(Invited) Evolution of Structural, Transport and Electrical Properties of Binary Ionic Liquids in the Presence of Graphite

The flexibility to manipulate various interactions in ionic liquids by changing the cation, anion, or the various functional groups on the ions has drawn researchers to design tailor-made ionic liquids for a given application. Another approach that is gaining importance in tuning the properties of ionic liquids is to form binary, ternary, and reciprocal ionic liquid mixtures. Results from molecular simulations conducted in our research group have demonstrated that the binary ionic liquid mixtures in which two anions are combined in different molar ratios for a given cation can lead to either native or non-native structures in the bulk depending on the difference between the hydrogen bonding ability of the participating anions. The non-native structures differ markedly from those for the pure ionic liquid analogues and impact the physical dissolution mechanism for gases such as CO2.Given the importance of ionic liquids as electrolytes in the next-generation of batteries, it is likely that such ionic liquid mixtures will increasingly be investigated for their ability to transport ions to and from charged surfaces. However, very little is currently known regarding how the presence of a surface or an interface affects the local and long-range structures of binary ionic liquids. In this talk, we will present our findings from molecular simulation studies by examining the structural response of binary ionic liquid mixtures comprised of a single cation in combination with two anions when presented with a graphite surface. We will compare and contrast these structures to those obtained when binary ionic liquid mixtures are formed with a single anion and two cations and a graphite surface is introduced. Additionally, we will elucidate the influence of graphite on the transport and electrical properties of binary ionic liquids.

Color-adjustable CsPbBr3-xIx quantum dots glasses for wide color gamut display

CsPbBr3-xIx quantum dots (QDs) glasses have been fabricated by melt-quenching technique. Emission peaks are adjustable in 500–530 nm and 615–692 nm for CsPbBr3 and CsPbBr3-xIx respectively. FWHM varies from 20 to 50 nm. Emission peak and line-shape are independent of excitation wavelength. PL decay shows biexponential behavior with short and long lifetimes in the level of 10 ns and 100 ns respectively. Under excitation of 450 nm, PLQY is large for single anion CsPbBr3 QDs (46%) and CsPbI3 QDs (61%), but small (1.6%-25%) for double anion QDs. PL intensity decreases with temperature from ~25 to 125 °C and recovers after one cycle. Three primary colors for wide color gamut display have been researched using blue LED, green and red QDs glasses. Color purity is calculated as 98%, 91% and 100% (for both 630 nm and 670 nm red QDs) respectively. Color gamut areas 119% and 130% of NTSC have been realized for the case of 630 nm and 670 nm QDs.

Charge Transport and Dynamics in Imidazolium Chloroaluminate Ionic Liquids

Imidazolium based chloroaluminates were the first widely studied room-temperature ionic liquids. However, work in these systems has waned over the past 25 years in favor of ionic liquids with less reactive anions. Researchers are beginning to rediscover chloroaluminates because they possess some very advantageous properties that hold significant promise for applications such as energy storage, electrodeposition, and chemical synthesis. Chloroaluminates are not simple mixtures of a single cation with a single anion. It is more appropriate to think of these systems as binary mixtures of two ionic liquids which share the same cation. The binary nature of the chloroaluimates leads to highly tunable physical and chemical properties including liquidus range, electrochemical stability window, dc ionic conductivity, zero-shear viscosity, and static dielectric permittivity. However, the binary nature also leads to significant experimental challenges with respect to characterization of the structure and anion speciation in the chloroaluminates. The majority of work characterizing the imidazolium based chloroaluminate was conducted more than 25 years ago and focused on physical property measurements across limited compositions and/or narrow temperature/frequency ranges. The data from these early studies revealed important aspects of chloroaluminate physical properties; however, due to their limited scope they failed to make significant progress in understanding underlying structure-property relationships which are critical to realizing the full potential of chloroaluminate ionic liquids as electrolyte systems. Our current work seeks to reexamine imidazolium chloroaluminate ionic liquids leveraging the improved experimental tools and capabilities available today. In this presentation we will discuss our initial studies of imidazolium chloroaluminate ionic liquids using broadband dielectric spectroscopy, oscillatory shear rheology, and Raman spectroscopy. We will present preliminary work on the impact of changes in cation structure and ionic liquid composition on anion speciation, transport properties, and dynamics.

Molecular-level behavior of imidazolium-based ionic liquid mixtures

Understanding the molecular-level organization of anions and cations in a mixture of different ionic liquids (ILs) is challenging, but it can be very important for designing solvents and IL-based membrane materials. Here, we perform all-atom molecular dynamics (MD) simulations to understand the intermolecular interactions and structuring of both neat and mixed IL compositions containing 1-benzyl-3-methylimidazolium [ZMIM+], 1-butyl-3-methylimidazolium [BMIM+], bistriflimide [Tf2N−], and tetrafluoroborate [BF4−]. We observe very strong underlying molecular-level migrations in these mixtures, and this tends to mainly involve the anion species. As compared to the systems with a single anion, the mixed anions lead to large increases/decreases in the radial distribution function peak heights, whereas the cation mixing is relatively benign. The [BF4−] anions have a strong tendency to displace the [Tf2N−] anions in the mixtures, and this is seen with respect to both [BMIM+] and [ZMIM+].

A bis(silylene)-stabilized diphosphorus compound and its reactivity as a monophosphorus anion transfer reagent

In contrast to the well-established transition-metal-mediated activation of white phosphorus (P4), the metal-free direct functionalization of P4 has remained rare. The conversion of P4 into a reactive zero-valent diphosphorus compound (P2) has proven challenging to carry out without relying on metal reactivity. Herein, we describe the facile degradation of P4 mediated by two divalent silicon atoms in a bis(silylene) scaffold, resulting in a silylene-stabilized zero-valent P2 complex. The presence of two lone pairs of electrons on each P atom in the silylene-stabilized P2 complex enables a rich reactivity towards small molecules; reaction of the P2 species with CO2, water or a borane leads to the formation of P-C, P-H or P-B bonds, respectively. Notably, the P2 complex also serves as a single phosphorus anion (P-) transfer reagent towards metal carbonyls and a chlorogermylene compound, leading to the synthetically valuable phosphaketenide (PCO-) ligand and a phosphinidene germylene complex, respectively.

Supramolecular networks supported by the anion...π linkage of Keggin-type heteropolyoxotungstates.

Anion...π interactions are newly recognized weak supramolecular forces which are relevant to many types of electron-deficient aromatic substrates. Being less competitive with respect to conventional hydrogen bonding, anion...π interactions are only rarely considered as a crystal-structure-defining factor. Their significance dramatically increases for polyoxometalate (POM) species, which offer extended oxide surfaces for maintaining dense aromatic/inorganic stacks. The structures of tetrakis(caffeinium) μ12-silicato-tetracosa-μ2-oxido-dodecaoxidododecatungsten trihydrate, (C8H11N4O2)4[SiW12O40]·3H2O, (1), and tris(theobrominium) μ12-phosphato-tetracosa-μ2-oxido-dodecaoxidododecatungsten ethanol sesquisolvate, (C7H9N4O2)3[PW12O40]·1.5C2H5OH, (2), support the utility of anion...π interactions as a special kind of supramolecular synthon controlling the structures of ionic lattices. Both caffeinium [(HCaf)+ in (1)] and theobrominium cations [(HTbr)+ in (2)] reveal double stacking patterns at both axial sides of the aromatic frameworks, leading to the generation of anion...π...anion bridges. The latter provide the rare face-to-face linkage of the anions. In (1), every square face of the metal-oxide cuboctahedra accepts the interaction and the above bridges yield flat square nets, i.e. {(HCaf+)2[SiW12O40]4-}n. Two additional cations afford single stacks only and they terminate the connectivity. Salt (2) retains a two-dimensional (2D) motif of square nets, with anion...π...anion bridges involving two of the three (HTbr)+ cations. The remaining cations complete a fivefold anion...π environment of [PW12O40]3-, acting as terminal groups. This single anion...π interaction is influenced by the specific pairing of (HTbr)+ cations by double amide-to-amide hydrogen bonding. Nevertheless, invariable 2D patterns in (1) and (2) suggest the dominant role of anion...π interactions as the structure-governing factor, which is applicable to the construction of noncovalent linkages involving Keggin-type oxometalates.

Development of Large-Scale Downstream Processing for Lentiviral Vectors

The interest in lentiviral vectors (LVs) has increased prominently for gene therapy applications, but few have reached the later stages of clinical trials. The main challenge has remained in scaling up the manufacturing process for the fragile vector to obtain high titers for in vivo usage. We have previously scaled up the LV production to iCELLis 500, being able to produce up to 180 L of harvest material in one run with perfusion. The following challenge considers the purification and concentration of the product to meet titer and purity requirements for clinical use. We have developed a downstream process, beginning with clarification, buffer exchange, and concentration, by tangential flow filtration. This is followed by a purification step using single membrane-based anion exchange chromatography and final formulation with tangential flow filtration. Different materials and conditions were compared to optimize the process, especially for the chromatography step that has been the bottleneck in lentiviral vector purification scale-up. The final infectious titer of the lentiviral vector product manufactured using the optimized scale-up process was determined to be 1.97 × 109 transducing units (TU)/mL, which can be considered as a high titer for lentiviral vectors.

Helical Anion Foldamers in Solution.

Using anions to induce molecular structure is a rapidly growing area of dynamic and switchable supramolecular chemistry. The emphasis of this review is on helical anion foldamers in solution, and many of the beautiful complexes described herein are accentuated by their crystal structures. Anion foldamers are defined as single- or multistrand complexes-often helical-that incorporate one or more anions. The review begins by discussing foldamer structure and nomenclature and follows with discourse on the anions which are employed. Recent advances in functional foldamers that bind a single anion are examined, including: induced chirality, stimuli-responsive dynamics, fluorescence changes, organocatalysis, anion transport, and halogen bonding. The review then inspects multianion foldamers, and this section is organized by the number of strands within the foldamer-from single- to triple-strand foldamers. Finally, the review is punctuated by recent hydrogen- and halogen-bonding triple-strand anion foldamers.

Valence State of Iron and Molybdenum Cations under Conditions of Anionic Deficiency in Sr2FeMoO6–δ

The activation energy of oxygen diffusion in strontium ferromolybdate Sr2FeMoO6–δ is determined by the Merzhanov technique based on the temperature dependences of the oxygen desorption dynamics. The activation energy has a minimum value of 76.7 kJ mol−1 at δ = 0.005 and a maximum value of 156.3 kJ mol−1 at δ = 0.06. It is suggested that with an increase in the concentration of oxygen vacancies, an interaction occurs between them and the nearest cations, with the subsequent formation of associates of various types that are less mobile than the single anion vacancies. According to Mössbauer spectroscopy data, it has been established that the appearance of oxygen vacancies and their ordering contribute to the isomer shift, and some of the iron ions occupy the tetrahedral (or close to it) positions in the lattice. This indicates the formation of associates of oxygen vacancies. The results of X‐ray photoelectron spectroscopy (XPS) studies show that the increase in the concentration of oxygen vacancies results in a decrease of the Mo6+ and Fe2+ concentrations. At the same time, the number of Mo5+ and Fe3+ cations increases due to the redistribution of the electron density, and molybdenum cations in a different valence state (Mo4+) appear.

Co3S4 nanosheets on Ni foam via electrodeposition with sulfurization as highly active electrocatalysts for anion exchange membrane electrolyzer

Co3S4 nanosheets on Ni foam (NS/NF) were prepared by sulfurization for various time after calcination of electrodeposited Co(OH)2. In our FE-SEM images, we observed that Co3S4 NS was vertically, or obliquely, deposited on the Ni foam. As a result, the structure contained more active sites, and active sites were highly accessible to the electrolyte for the hydrogen evolution reaction (HER). Furthermore, results of XPS and XRD analysis confirmed S-conversion from Co3O4 to Co3S4 during sulfurization. 3-Co3S4 NS/NF with sulfurization for 3 h exhibited the highest sulfur content, while Co3S4 began to desulfurize to Co9S8 after sulfurization for 4 h. The 3-Co3S4 NS/NF electrocatalyst showed a lowest overpotential of 93 mV at −10 mA/cm2, with a Tafel slope of −55.1 mV/dec in N2-purged 1 M KOH. Also, the single cell anion exchange membrane water electrolyzer (AEMWE) showed a high current density of 431 mA/cm2 with cell voltage 2.0 Vcell at 40–45 °C.

Single Au Anion Can Catalyze Acetylene Hydrochlorination: Tunable Catalytic Performance from Rational Doping

In this work, for the first time it is demonstrated that supported single Au in either a positive or a negative charge state can catalyze acetylene hydrochlorination competitively with regard to ot...

Synthesis and Doping Strategies to Improve the Photoelectrochemical Water Oxidation Activity of BiVO4 Photoanodes

Abstract BiVO4 is one of the most investigated and most promising metal oxide based photoanode materials for photoelectrochemical (PEC) water oxidation. Although it has several advantages (suitable band gap around 2.4 eV, suitable valence-band position for water oxidation, low toxicity, high abundance), it suffers from slow charge-carrier transport properties, high surface recombination, and limited water-oxidation activity. In the present work, we review the synthesis and doping strategies that we developed in the last years to improve the PEC performance of BiVO4 photoanodes. Strategies ranging from single anion doping or cation doping to anion and cation co-doping will be presented for fluoride and molybdenum as anion and cation dopants, respectively. One major result is that co-doping allows combining the most important PEC specific benefits of each type of dopant, i.e. an increased charge-injection efficiency in case of fluoride as well as an increased charge-separation efficiency in case of molybdenum.

One step Purification and Characterisation of Abrin Toxin from Abrus Precatorius Seeds

Abrin is a plant toxin obtained from Abrus precatorius seeds. It belongs to the type II ribosomal inactivating proteins (RIPs) consisting of two chains namely, catalytically active A chain and sugar binding B chain linked by a single disulphide bond. Due to high toxicity of abrin, its exposure or consumption can lead to serious public health problems. In the present work, we have extracted and purified the abrin toxin from Abrus precatorius seeds. The toxin was purified using a single step anion exchange chromatography. The purified protein was characterized by SDS-PAGE and MALDI- TOF to confirm its purity. The toxicity of purified abrin toxin was also confirmed by injecting the toxin in mice. The purified protein was further used to raise antibodies in mice and characterized by indirect Enzyme Linked Immunosorbent Assay. The results of present study established the use of single step ion exchange chromatography to purify abrin toxin for further development of its detection system.

The encapsulation selectivity for anionic fission products imparted by an electride

The nanoporous oxide 12CaO·7Al2O3 (C12A7) can capture large concentrations of extra-framework species inside its nanopores, while maintaining its thermodynamical stability. Here we use atomistic simulation to predict the efficacy of C12A7 to encapsulate volatile fission products, in its stoichiometric and much more effective electride forms. In the stoichiometric form, while Xe, Kr and Cs are not captured, Br, I and Te exhibit strong encapsulation energies while Rb is only weakly encapsulated from atoms. The high electronegativities of Br, I and Te stabilize their encapsulation as anions. The electride form of C12A7 shows a significant enhancement in the encapsulation of Br, I and Te with all three stable as anions from their atom and dimer reference states. Successive encapsulation of multiple Br, I and Te as single anions in adjacent cages is also energetically favourable. Conversely, Xe, Kr, Rb and Cs are unbound. Encapsulation of homonuclear dimers (Br2, I2 and Te2) and heteronuclear dimers (CsBr and CsI) in a single cage is also unfavourable. Thus, C12A7 offers the desirable prospect of species selectivity.

Anomalous Conductivity in the Rutile Structure Driven by Local Disorder.

Many rutile-type materials are characterized by a softness in shear with pressure which is coupled to a Raman-active librational motion. Combining direct studies of anion positions in SnO2 with measurements of its electronic properties, we find a correlation between O sublattice disorder between 5 and 10 GPa and an anomalous decrease up to 4 orders of magnitude in electrical resistance. Hypotheses into the atomistic nature of the phenomenon are evaluated via ab initio calculations guided by extended X-ray absorption fine structure spectroscopy analysis, and the most likely mechanism is found to be the displacement of single anions resulting from the pressure-induced softening of the librational mode. On the basis of this mechanism, we propose that the same behavior should feature across all materials exhibiting a rutile → CaCl2 phase transition and that conductivity in other rutile-type materials could be facilitated at ambient pressure by appropriate design of devices to enhance defects of this nature.