Anionic Motif Research Articles

Hydrolytic durability of uranium-containing sodium aluminum (iron) phosphate glasses

Normalized mass loss and leach rates of elements from the synthesized sodium aluminum phosphate and sodium aluminum iron phosphate glasses in relation to the content of uranium introduced into the glass-forming charge in the form of uranium dioxide or uranyl nitrate were determined by the РСТ procedure (variant А). The relationship between the element leaching parameters and the structure of the anionic motif of the glass network, up to the formation of a polyanionic structure from aluminum (iron)–phosphorus–oxygen network and uranium–oxygen polyanions, was determined. The resistance of the glasses to leaching of elements is on the same level as that of reference iron phosphate glasses.

Synthesis and Structural Characterization of Trimanganese‐Containing Polyoxovanadates with Carboxylate Ligands

A trimanganese core containing polyoxovanadate {Et4N}5[Mn3(OAc)(H2O)V10O30] (I; OAc = acetate) was synthesized by the reaction of {Et4N}[VO3] with Mn(OAc)2 (0.3 equiv.) in acetonitrile. The trimanganese core possesses a bridging acetate ligand. To demonstrate the ligand‐exchange properties of I, its reaction with benzoic acid (1 equiv.) was conducted and {Et4N}5[Mn3(OBz)(H2O)V10O30] (II; OBz = benzoate) was formed quantitatively. By using a dicarboxylate, the inorganic–organic–inorganic hybrid {Et4N}10[{Mn3(H2O)V10O30}2{OOC(CH2)nCOO}] [n = 3 (III) and n = 4 (IV)] compounds were synthesized. To compensate the negative–negative repulsion between the anionic groups with a 5– charge, tetraethylammonium cations are sandwiched between the anionic groups in the crystallographic packing. Despite the differences in the bridging carbon numbers, both complexes have the same orientation in the crystal state except for the conformation of the alkyl chains, which suggests the presence of a unique interaction with an anion–cation–anion motif to form V‐shaped dimer configurations.

Influence of the heat treatment procedure and irradiation on the structure of the anionic motif and crystallization of uranium-containing phosphate glasses

The solubility of UO3 in sodium almino(ferro)phosphate (SAFP) glasses prepared by quenching of melts reaches almost 50 wt %. The structure of the anionic motif of the network of such glasses is formed by polyanions and consists of alumino(ferro)phosphate and uranium–oxygen constituents. Irradiation with electrons of up to 8 MeV energy to an absorbed dose of 106 Gy does not lead to appreciable changes in the glass structure, except insignificant increase in the fraction of octahedrally coordinated aluminum. After annealing, samples of sodium aluminophosphate glasses with low content of uranium oxides (up to 10 wt %) partially crystallize with the formation of phosphotridymite, whereas high-uranium glasses (up to ~50 wt % UO3) remain X-ray amorphous. Samples of SAFP glasses at low concentrations of uranium oxides remain amorphous and at high concentrations undergo phase segregation with the formation of a SAFP glass phase enriched in uranium oxides and crystalline phase of sodium aluminum iron orthophosphate Na3(Al,Fe)2(PO4)3 containing impurity amounts of uranium ions. The incorporation of uranium ions is most probably due to the occurrence of redox processes between uranyl and iron ions.

Iron oxidation state and coordination, and hydrolytic durability of sodium-aluminum iron phosphate glasses

The structure of anionic motif, oxidation state and coordination of iron in the series of glasses (mol.%): 40 Na2O, (20-x) Al2O3, x Fe2O3, 40 P2O5 considered as matrices for immobilization of high Fe/Al legacy high level waste were determined by FTIR, Raman and Mössbauer study. The glass network is built from ortho- and pyrophosphate units linked by aluminum-oxygen and iron-oxygen polyhedra. Iron in all the glasses was present as primarily octahedrally coordinated Fe(III) and Fe(II). Fe(III) content in the glasses increased with the increase of the x value and reached ∼74% of total Fe in the glass with x = 15 while reduced to ∼67% of total Fe at x = 20. At the same time the lowest values of cumulative release from glasses into a deionized water for all the elements were found at x = 5. Thus no correlation between the Fe(III)/Fe(II) ratio and cumulative elemental release values was found and iron speciation seems to be not a key factor determining their chemical durability.

ChemInform Abstract: Recent Advances in Pillar[n]arenes: Synthesis and Applications Based on Host—Guest Interactions

AbstractReview: 92 refs.

The effect of electron irradiation on the structure and iron speciation in sodium aluminum (iron) phosphate glasses

The effect of 8 MeV electron irradiation on the structure of glasses in the series 40 Na2O, (20-x) Al2O3, x Fe2O3, 40 P2O5 (mol.%) and on the iron speciation in these samples was studied by FTIR and Mössbauer spectroscopic techniques. Irradiation up to a dose of 1.0 MGy has no appreciable effects on the character of the bonds within anionic motif of the glass network. Electron irradiation increases the fraction of aluminum in octahedral coordination. Iron in both unirradiated and irradiated glasses is present mainly as Fe(III) (60–75% of the total amount) in the glasses and partly as Fe(II) and the ratio of two forms remains constant up to a dose of 1.0 MGy.

Phase composition and structure of sodium aluminophosphate based glass materials depending on their synthesis conditions

The effect of the method of synthesis on the structure of aluminophosphate glasses intended for immobilization of high level waste from uranium–graphite channel reactor spent nuclear fuel reprocessing has been studied by X-ray powder diffraction and Fourier transform IR spectroscopy. Slow cooling in a furnace, both spontaneous cooling in a switched-off furnace and cooling simulating the conditions of glass cooling in their disposal canisters, or additional heat treatment (annealing) led to partial crystallization of glasses with segregation of different modifications of aluminum orthophosphate. For orthoand pyrophosphate based glasses with similar anionic motifs, their phase composition and degree of crystallization depend not so much on the chemical composition of a sample as on its heat treatment history.

Recent advances in pillar[n]arenes: synthesis and applications based on host-guest interactions.

Pillar[n]arenes (n = 5-15) are a novel class of macrocyclic molecules with hydroquinone as the repeating unit linked by methylene bridges at para-positions. Introduced by T. Ogoshi for the first time in 2008, pillararenes have attracted increasing interest and have been widely studied during the last eight years, due to their unique structural advantages as host molecules, such as symmetrical rigid architecture, electron-rich cavities and facile functional modification. In this review, we first describe the syntheses of pillar[n]arenes including cyclooligomerization of pillar[n]arenes and modification of pillar[n]arenes after cyclooligomerization, summarising almost twenty different kinds of guest motifs and dividing them into three types: cationic, neutral and anionic motifs. The main section of this review examines the applications of pillar[n]arenes based on the host-guest interactions in different research fields, including biology, materials science and environmental science. Finally, future research directions and potential for novel applications are discussed.

Crystal structure of a new hybrid compound based on an iodido-plumbate(II) anionic motif.

Crystals of the one-dimensional organic-inorganic lead iodide-based compound catena-poly[bis-(piperazine-1,4-diium) [[tetra-iodido-plumbate(II)]-μ-iodido] iodide monohydrate], (C4N2H12)2[PbI5]I·H2O, were obtained by slow evaporation at room temperature of a solution containing lead iodide and piperazine in a 1:2 molar ratio. Inorganic lead iodide chains, organic (C4N2H12)(2+) cations, water mol-ecules of crystallization and isolated I(-) anions are connected through N-H⋯·I, N-H⋯OW and OW-H⋯I hydrogen-bond inter-actions. Zigzag chains of corner-sharing [PbI6](4-) octa-hedra with composition [PbI4/1I2/2](3-) running parallel to the a axis are present in the structure packing.

FTIR and Mössbauer spectroscopic study of sodium–aluminum–iron phosphate glassy materials for high level waste immobilization

Complex sodium-aluminum-iron phosphate glassy materials with various Al2O3 to Fe2O3 ratio containing high level waste (HLW) surrogate were characterized by X-ray diffraction and scanning electron microscopy and studied in details by Fourier transform infrared (FTIR) spectroscopy. The samples with high Al2O3 content and not containing Fe2O3 were predominantly amorphous but subjected to devitrification under annealing. Addition of B2O3 and partial Fe2O3 substitution for Al2O3 in the materials increases their resistance to devitrification whereas further substitution and NiO incorporation significantly increase the tendency to devitrification. FTIR spectra demonstrate changes in the structure of glassy materials caused by both structural variations in the anionic motif and occurrence of crystalline phases in the materials. According to Mössbauer spectroscopy data, iron in the glassy samples is present as octahedrally coordinated Fe3+ ions while in the partly devitrified samples iron is partitioned among vitreous and crystalline phases entering the vitreous phase mainly as Fe3+O6 units and crystalline phases as major Fe3+ and minor Fe2+ ions in a magnetically ordered state and participating in a “fast” electronic exchange.

The effect of Fe2O3 substitution for Al2O3 on the phase composition and structure of sodium–aluminum–iron phosphate glasses

The phase composition and structure of sodium–aluminum (iron) phosphate glasses and glass crystalline materials at Fe2O3 substitution for Al2O3 in the glasses of the series (mol%) 40 Na2O, (20−x) Al2O3, x Fe2O3, 40 P2O5 (I) and 35 Na2O, (20−x) Al2O3, x Fe2O3, 45 P2O5 (II) were studied by Fourier Transform Infrared (FTIR), Raman, and Mössbauer spectroscopy techniques. The products in series I poured onto a metal plate were found to be amorphous (glasses) while the annealed samples were partly devitrified except for the sample at x=10 which remained amorphous. The quenched samples of series II contained AlPO4 at high Al2O3 content (x=0 and x=5) and were amorphous at high iron content while the annealed samples were mostly devitrified with segregation of ortho- and pyrophosphate phases. The anionic motif of the glasses in both series is mainly composed of ortho- (Q0) and pyrophosphate (Q1) structural units. In the structure of the glasses in series I the Q0 to Q1 ratio remains the same at Al2O3 substitution for Fe2O3 within the whole x range whereas in the structure of the glasses in series II the Q0 to Q1 ratio changes in favor of the Q1 units. Annealing of the quenched samples resulted in splitting of the bands in FTIR due to de-degeneration at formation of crystalline phases. Iron in the glasses is present as major Fe(III) and minor Fe(II) both in primarily octahedral oxygen environment.

Adsorption of Cd2+ and Cu2+ ions from aqueous solutions by a cross-linked polysulfonate–carboxylate resin

A new cross-linked polyzwitterion (CPZ) was synthesized through cyclocopolymerization of 3-[diallyl(carboxymethyl)ammonio]propane-1-sulfonate (92.5mol%), and a cross-linker 1,1,4,4-tetraallylpiperazine-1,4-diium chloride (7.5mol%) in the presence of tert-butylhydroperoxide. The cross-linked polyzwitterion/anion (CPZA) was obtained by the basification of CPZ with NaOH. The adsorption data fit both Temkin and Freundlich isotherm models. The adsorption trend on CPZA is as Cu2+>Cd2+ and both followed pseudo-second-order kinetic model. The negative ΔG and positive ΔH values ascertained the spontaneous and endothermic nature of the adsorption process. The effectiveness of a zwitterionic–anionic motif consisting of quaternary nitrogen, sulfonate and carboxylate groups has been tested for the first time for capturing Cd2+ and Cu2+ ions at low concentrations.

Preclinical Validation of the Heparin-Reactive Peptide p5+14 as a Molecular Imaging Agent for Visceral Amyloidosis.

Amyloid is a complex pathologic matrix comprised principally of paracrystalline protein fibrils and heparan sulfate proteoglycans. Systemic amyloid diseases are rare, thus, routine diagnosis is often challenging. The glycosaminoglycans ubiquitously present in amyloid deposits are biochemically and electrochemically distinct from those found in the healthy tissues due to the high degree of sulfation. We have exploited this unique property and evaluated heparin-reactive peptides, such as p5+14, as novel agents for specifically targeting and imaging amyloid. Herein, we demonstrate that radiolabeled p5+14 effectively bound murine AA amyloid in vivo by using molecular imaging. Biotinylated peptide also reacted with the major forms of human amyloid in tissue sections as evidenced immunohistochemically. Furthermore, we have demonstrated that the peptide also binds synthetic amyloid fibrils that lack glycosaminoglycans implying that the dense anionic motif present on heparin is mimicked by the amyloid protein fibril itself. These biochemical and functional data support the translation of radiolabeled peptide p5+14 for the clinical imaging of amyloid in patients.

Syntheses and X-ray crystal structure studies of four new coordination complexes and salts based on proton-transferred pyridine-2,6-dicarboxylic acid N-oxide

Four new supramolecular coordination complexes and salts based on proton-transferred pyridine-2,6-dicarboxylic acid N-oxide formulated as (Htata)(Hpydco)·H2O (1), (Htata)2(pydco)·2H2O (2), (H9a-acr)2[Zn(pydco)2(H2O)2]·4H2O (3), and (H9a-acr)2[Co(pydco)2(H2O)2]·4H2O (4) (where H2pydco = pyridine-2,6-dicarboxylic acid N-oxide, tata = 2,4,6-triamino-1,3,5-triazine (melamine) and 9a-acr = 9-aminoacridine) have been synthesized by proton transfer from H2pydco as ligand and to tata and 9a-acr. The structures of 1–4 were characterized by elemental analysis, infrared spectroscopy, and single crystal X-ray diffraction methods. Compounds 1 and 2 are salts of proton-transferred H2pydco and melamine with two separate formulas. There is a difference between the anionic fragment in 1 and 2, the anionic part of 1 retains one acid proton (Hpydco−) which is involved in a strong, intramolecular hydrogen bonding with the oxygen attached to nitrogen, while the acid units in 2 are fully deprotonated (pydco2−). The linear chains of melaminium cations with an anionic motif and water molecules lead to 2-D zipper layers in 1 and 2-D zigzag layers in 2. These layers are held together via an extensive network of hydrogen bonds, π+–π+ stacking, N+–H⋯π+, and lp⋯π+ interactions to extend the structures into the 3-D supramolecular framework. Single-crystal studies revealed that 3 and 4 are isostructural with distorted octahedral geometry about the metal consisting of two pydco2− ligands acting in bidentate fashion and two trans-disposed water molecules. They also adopt alternating cationic and anionic layers with 9-aminoacridinium cations and transition metal complex anions which are linked to each other by a variety of noncovalent interactions such as ion pairing, hydrogen bonding and π–π stacking.

Raman scattering study of molten alkali-metal molybdates and tungstates rich in basic oxides

Structural transformations of alkali-metal (Li, K, and Na) mono- and dimolybdates and tungstates have been studied by Raman scattering spectroscopy from room temperature to above their melting point. The structure of the Mo-O and W-O complexes in the form of isolated [MoO4] and [WO4] tetrahedra in crystalline monomolybdates and monotungstates has been shown to persist in the molten state. At the same time, the mixed anion motif made up of tetrahedra and octahedra in dimolybdate and tungstate crystals transforms on melting into complexes made up of two corner-sharing tetrahedra. We have identified the internal vibrational modes of such complexes in molten alkali-metal dimolybdates and ditungstates. Using rapid quenching of K2O · 2MoO3 and K2O · 2WO3 melts, we have obtained transparent glasses whose Raman spectra suggest that they have the same anion motif as the corresponding melts.

Raman scattering study of molten alkali-metal molybdates ricn in MoO3

Raman scattering spectroscopy has been used to study the melting behavior and structure of Mo-O complexes alkali-metal molybdates rich in MoO3: Li4Mo5O17, K2Mo3O10, and M2Mo4O13 (M = Li, Na, K). The complex structure of the anion motif in these molybdates, made up of edge-sharing [MoO6] octahedra, transforms on melting into short chains of [MoO4] tetrahedra. We discuss the general trends in the variation of the chain structure of the anion motif in melts across the series of alkali-metal molybdates as the MoO3 concentration increases from mono- to tetramolybdate compositions.

Structure and Vibrational Spectra of Slags Produced from Radioactive Waste

The structure of the anionic motif of aluminosilicate and aluminoborosilicate glasses containing simulated slags from a solid radioactive waste incinerator was studied by IR and Raman spectroscopy. Spectra of melted slag were consistent with Si–O tetrahedra with various numbers of bridging O ions and Al–O tetrahedra embedded in the Si–O network in the slag vitreous and crystalline phases (nepheline, nagelschmidtite). Vibrations of doubly and triply bound Si–O tetrahedra and Al–O tetrahedra embedded between them were mainly responsible for the spectra as the content of sodium disilicate fl ux and the glass fraction in the materials increased. Addition of sodium tetraborate fl ux caused the appearance of B–O vibrations of predominantly three-coordinate B and a tendency toward chemical differentiation preceding phase separation.

3+2] Fragmentation of an [RP5Cl]+ Cage Cation Induced by an N‐Heterocyclic Carbene

The cage compound [DippP5 Cl][GaCl4 ] (Dipp=2,6-diisopropylphenyl) reacts with an NHC (N-heterocyclic carbene) by an unprecedented [3+2] fragmentation of the P5 (+) core. This yields an imidazoliumyl-substituted P3 species featuring a triphosphaallyl anion motif and a neutral P2 compound. The mechanism of the fragmentation reaction was elucidated by means of experimental and quantum chemical methods.

Structures and magnetic properties of copper(ii) and manganese(ii) polymers derived from pseudohalides and a flexible zwitterionic dicarboxylate ligand

The flexible zwitterionic dicarboxylate ligand 1,4-bis(4-carboxylato-1-pyridinium)butane (bcpb) assumes different conformations to collaborate with pseudohalides in various coordination modes to produce coordination polymers in which distinct anionic motifs with mixed carboxylate and pseudohalide bridges are interlinked by the cationic butylenebis(pyridinium) tethers. The Cu(II) compound, [Cu2(bcpb)(N3)4]n·nH2O (1), is a 1D coordination polymer based on the defective dicubane-like [Cu4(μ3-1,1,1-N3)2(μ-1,1-N3)2(μ-1,1-OCO)2] cluster. With Mn(II), four distinct 3D coordination polymers, [Mn4(bcpb)4(N3)(H2O)4]n(ClO4)7n·nCH3OH·3nH2O (2), [Mn2.5(bcpb)(N3)5(H2O)2]n (3), [Mn2(bcpb)(N3)4]n·nH2O (4), and [Mn2(bcpb)(NCO)4]n·nH2O (5), were characterized. 2 is the first Mn(II) compound with the rare μ4-1,1,3,3 azide bridge and exhibits an unusual 3D framework based on the [Mn4(μ4-1,1,3,3-N3)(μ-1,3-OCO)6] cluster. In 3, the unique undulated honeycomb-like [Mn2(μ-1,3-N3)3]n layers are interlinked into a 3D framework by disordered [Mn(μ-1,1-N3)4(μ-1,3-OCO)2] and [(O(aqua)-H)2···OCO]2 moieties, and the bcpb ligands serve as additional interlayer linkers to lead to the rare self-catenated 6(6) net. 4 and 5 show 3-fold interpenetrated 3D frameworks based on the chains with (μ-1,1-N3)2(μ-1,3-OCO) and (μ-N,N-NCO)2(μ-1,3-OCO) bridges, respectively. Magnetic studies indicated that 1 shows competing ferromagnetic and antiferromagnetic interactions. Compounds 2-5 all show antiferromagnetic coupling between Mn(ii) ions, while 3 shows 3D ordering. Analyses of magneto-structural data suggest a general trend that the antiferromagnetic interaction through (μ-1,1-N3)2(μ-1,3-OCO) or (μ-N,N-NCO)2(μ-1,3-OCO) increases with a decrease of the Mn···Mn distance.

True and quasi-isomorphism in tetrakis(acetonitrile)coinage metal(i) salts

Salts of the family [M(NCMe)4]+X− (M = Cu, Ag; X− = [BF4]−, [ClO4]−, [PF6]− crystallize in the space groups Pna21 or P212121 with very similar cell dimensions. This gives rise to two sets of true isomorphs (four members in Pna21, two in P212121), and a solvated species (Cu/PF6/MeCN) with a distorted P212121 lattice. Across the two space groups and regardless of the choice of metal atom or anion, the underlying basic structures are virtually identical in the six unsolvated cases, consisting of alternate sheets of cations and anions, mainly held together by C–H⋯C,N and C,N⋯C,N interactions, and a columnar cation–anion motif perpendicular to the sheets maintained by C–H⋯F,O interactions. The pair of concomitant polymorphs found with Cu/BF4 in both Pna21 and P212121 can readily be described as being quasi-isomorphous. Using a Hirshfeld surface approach and a tri-cationic structural synthon extracted from the asymmetric units, the common underlying pattern of close intercomponent approaches has been analysed and quantified. The structure of the Ag/PF6 complex is new; low-temperature redeterminations are recorded for the Ag/ClO4 and the Cu/PF6/MeCN complexes.