Ammonium Polyuranates: Old Dog, New Structural Tricks.

The crystal structure of ammonium polyuranates xUO3·yNH3·zH2O has been investigated. Powder X-ray diffraction (PXRD) has been employed to define single-phase samples within a series of synthesized compounds, which are further characterized by elemental analysis to ascertain the stoichiometry, revealing compositions of 3UO3·NH3·5H2O and 2UO3·NH3·3H2O. Analysis using extended X-ray absorption fine structure and vibrational spectroscopy has elucidated that both 3UO3·NH3·5H2O and 2UO3·NH3·3H2O possess a local structure similar to the metaschoepite─layered U(VI) oxohydroxide UO3·2H2O, but with H2O and NH4+ groups in the interlayers. The structures of ammonium polyuranates are solved from PXRD data, revealing their relationship to the U(VI) oxohydroxide with the established composition of NH4[(UO2)3O2(OH)3]·3H2O and NH4[(UO2)2O2(OH)]·2H2O for 3UO3·NH3·5H2O and 2UO3·NH3·H2O, respectively. These structures maintain the arrangement of U-O polyhedra as pentagonal bipyramids. However, disparities in lattice parameters, space group, and layer topology from UO3·2H2O emphasize significant structural modifications resulting from the substitution of water by ammonium. Moreover, the anion topology of the NH4[(UO2)2O2(OH)]·2H2O has no analogues among uranium oxohydroxide minerals. Notably, ammonium polyuranates, when compared, have minimal alterations in lattice parameters regardless of the presence of ammonia within the structure. The revealed results contribute valuable insights into the UO3-NH3-H2O system and hold potential applications in the field of nuclear power as ammonium polyuranates form during actinide precipitation in back-end of the nuclear fuel cycle and also serve as precursors in the fabrication of nuclear fuel.

Application of mixed phosphorus/sulfur ligands based on terpenoids in Pd-catalyzed asymmetric allylic substitution and Rh-catalyzed hydrogenation.

A small library of easily prepared diamidophosphite-sulfides based on 1,3-thioether alcohols, primarily of terpenoid nature, was developed. Upon complexation with Pd(II) ions, these hemilabile ligands showed the ability to form both P,S-chelates and complexes with two ligands P-monodentately bonded to the metal. The structures of the ligands and their complexes were determined by 2D NMR spectroscopy and X-ray diffraction. The use of these stereoselectors provided up to 95% ee in the classic Pd-catalyzed asymmetric allylic substitution reactions of (E)-1,3-diphenylallyl acetate with C- and N-nucleophiles and up to 80% ee in the Pd-mediated allylic alkylation of cinnamyl acetate with ß-ketoesters. In addition, ee values of up to 90% with quantitative conversion were achieved in the Rh-catalyzed asymmetric hydrogenation of methyl esters of unsaturated acids. The effects of the structural parameters, reaction conditions and ligand-to-metal ratio on the catalytic results are discussed.

A Promising 1,3,5-Triazine-Based Anion Exchanger for Perrhenate Binding: Crystal Structures of Its Chloride, Nitrate and Perrhenate Salts.

The reaction of pyridine with cyanuric chloride was studied under microwave activation as well as in the presence of silver nitrate. The product of hydrolysis containing two pyridinium rings and chloride anion was isolated. The structures of these anion exchanger salts with chloride, nitrate and perrhenate anions are discussed.

Synthesis and the Crystal Structure of a New Chiral 1D Metal-Organic Coordination Polymer Based on L-Prolineamide-Substituted Diarylacetylenedicarboxylic Acid Derivative.

The new homochiral 1D metal-organic coordination polymer [Cu2(EDPB)•H2O]n was synthesized starting from the original 3,3'-ethyne-1,2-diylbis[6-(L-prolylamino)benzoic acid] (H4EDPB). The unique crystal structure of the new compound was established by powder X-ray diffraction. The [Cu2(EDPB)•H2O]n system shows catalytic activity and enantioselectivity in a Henry reaction of p-nitrobenzaldehyde with nitromethane.

Porphyrinylphosphonate-Based Metal-Organic Framework: Tuning Proton Conductivity by Ligand Design.

A novel metal-organic framework [Zn3 (Ni-H2 TPPP)(Ni-H4 TPPP)(Ni-H5 TPPP)⋅7(CH3 )2 NH2 ⋅DMF⋅7 H2 O] (where Ni-Hx TPPP (x=2,4,5) are partially deprotonated [5,10,15,20-tetrakis(3-(phosphonatophenyl)-porphyrinato(2-))]nickel(II) species), IPCE-2Ni, with outstanding proton conductivity (1.0×10-2  S cm-1 at 75 °C and 95 % relative humidity) has been obtained. The high concentration of free phosphonate groups and compensating dimethylammonium cations bound by hydrogen bonds in the unique crystal structure of IPCE-2Ni is a key factor responsible for the observed high proton conductivity, which is one order of magnitude higher than for the corresponding MOF based on 5,10,15,20-tetrakis(4-(phosphonatophenyl)porphyrinato(2-))]nickel(II) IPCE-1Ni and comparable with that of leaders among MOFs.

Impact of the Preparation Procedure on the Performance of the Microporous HKUST-1 Metal-Organic Framework in the Liquid-Phase Separation of Aromatic Compounds.

To date, metal-organic frameworks (MOFs) have been recognized as promising solid phases in high-performance liquid chromatography (HPLC). This research aimed to elucidate the role of the physico-chemical characteristics of the microporous HKUST-1 metal-organic framework in its operation as a selective adsorbent in HPLC. For this, the HKUST-1 samples were prepared by microwave-assisted synthesis and a solvothermal procedure. According to the chromatographic examinations, the HKUST-1 material synthesized in the microwave fields shows an efficient performance in the selective adsorption of aromatic compounds with different functionalities. This study revealed a significant impact of the preparation procedure on the mechanism of the liquid-phase adsorption on the HKUST adsorbents under conditions of the HPLC. An effect of the elution solvent with the different coordination ability to the Cu2+ sites in the HKUST-1 structure on the adsorption selectivity was observed.

Highly Proton-Conductive Zinc Metal-Organic Framework Based On Nickel(II) Porphyrinylphosphonate.

The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF (IPCE-1Ni), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10-3  S cm-1 at 75 °C and 80 % relative humidity).

A Study of the Influence of the HCl Concentration on the Composition and Structure of (Hydroxy)Arylsiloxanes from the Hydrolysis-Condensation Reaction of Aryltrichlorosilanes.

The hydrolysis-condensation reactions of m-tolyl, m-chlorophenyl, and α-naphtyl-trichlorsilanes, (1, 2, and 3, respectively) in water-acetone solutions were examined for how they were influenced by the change in the concentration of HCl (CHCl). The composition of the products was monitored by 29Si NMR spectroscopy and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The acidity of the medium was shown to affect the yields of the products, and so, what products were formed. For 3, e.g., APCI-MS showed peaks of α-naphtyl-T8 and α-naphtyl-T10 as the most abundant in the spectra taken after 48 and 240 h for the reaction conducted at CHCl = 0.037 mol L-1. Unlike this, at CHCl = 0.15 mol L-1, those peaks were of [α-naphtyl(HO)2SiO]2(α-naphtyl)(HO)Si and/or [α-naphtyl(HO)Si]3, [α-naphtyl(HO)Si]4,5, and α-naphtyl-T8 after 192 h. However, at both CHCl values, the main product (and an intermediate) after 24 h was trans-1,1,3,3-tetrahydroxy-1,3-di-α-naphtyldisiloxane. It was isolated and its structure established by 1H-, 29Si-NMR, and X-ray powder diffraction.

Stereoelectronic Control in the Ozone-Free Synthesis of Ozonides.

The value of stereoelectronic guidelines is illustrated by the discovery of a convenient, ozone-free synthesis of bridged secondary ozonides from 1,5-dicarbonyl compounds and H2 O2 . The tetraoxane products generally formed in reactions of carbonyl and dicarbonyl compounds with H2 O2 were not detected because the structural distortions imposed on the tetraoxacyclohexane subunit in [3.2.2]tetraoxanonanes by the three-carbon bridge leads to the partial deactivation of anomeric effects. The new procedure is readily scalable to produce gram quantities of the ozonides. This reaction enables the selective preparation of ozonides without the use of ozone.

Diversity Oriented Synthesis of Polycyclic Heterocycles through the Condensation of 2-Amino[1,2,4]triazolo[1,5-a]pyrimidines with 1,3-Diketones.

The acid-catalyzed condensation between 2-aminosubstituted [1,2,4]triazolo[1,5-a]pyrimidines and their analogues with various saturation of the pyrimidine ring and 1,3-diketones or 1,1,3,3-tetramethoxypropane was evaluated as a new approach for the synthesis of diversely substituted polycyclic derivatives of triazolopyrimidine. The reaction of 4,5,6,7-tetrahydro- or aromatic aminotriazolopyrimidines results in selective formation of the corresponding [1,2,4]triazolo[1,5-a:4,3-a']dipyrimidin-5-ium salts, and the condensation of substrates containing the 4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine fragment is accompanied by a cascade rearrangement with unusual recyclization of the dihydropyrimidine ring to yield partially hydrogenated [1,2,4]triazolo[1,5-a:4,3-a']dipyrimidin-5-ium or pyrimido[1',2':1,5][1,2,4]triazolo[3,4-b]quinazolin-5-ium salts. The proposed methodology exhibits a wide scope, providing rapid access to polycondensed derivatives of the [1,2,4]triazolo[1,5-a]pyrimidine scaffold. DFT calculations of the Gibbs free energies of possible isomers were performed to rationalize the experimentally observed reactivity and selectivity.

Approach for the preparation of various classes of peroxides based on the reaction of triketones with H2O2: first examples of ozonide rearrangements.

The reaction of ß,δ-triketones with an ethereal solution of H2O2 catalyzed by heteropoly acids in the presence of a polar aprotic co-solvent proceeds via three pathways to form three classes of peroxides: tricyclic monoperoxides, bridged tetraoxanes, and a pair of stereoisomeric ozonides. The reaction is unusual in that produces bridged tetraoxanes and ozonides with one of the three carbonyl groups remaining intact. In the synthesis of bridged tetraoxanes, the peroxide ring is formed by the reaction of hydrogen peroxide with two carbonyl groups at the ß positions. The synthesis of ozonides from ketones and hydrogen peroxide is a unique process in which the ozonide ring is formed with the participation of two carbonyl groups at the δ positions. Rearrangements of ozonides were found for the first time after more than one century of their active investigation. Ozonides are interconverted with each other and rearranged into tricyclic monoperoxides, whereas ozonides and tricyclic monoperoxides are transformed into bridged tetraoxanes. The individual reaction products were isolated by column chromatography and characterized by NMR spectroscopy, mass spectrometry, and elemental analysis. One representative of each class of peroxides was characterized by X-ray diffraction.

Two polymorphs of 2-ethyl-3-hydroxy-6-methylpyridinium hydrogen N-acetyl-L-glutamate from powder diffraction data.

The title salt, C8H12NO(+)·C7H10NO5(-), crystallizes in two polymorphic modifications, viz. monoclinic (M) and orthorhombic (O). The crystal structures of both polymorphic modifications have been established from laboratory powder diffraction data. The crystal packing motifs in the two polymorphs are different, but the conformations of the anions are generally similar. In M, the anions are linked by pairs of hydrogen bonds of the N-H···O and O-H···O types into chains along the b-axis direction, and neighbouring molecules within the chain are related by the 21 screw axis. The cations link these chains via O-H···O and N-H···O hydrogen bonds into layers parallel to (001). In O, the anions are linked by O-H···O hydrogen bonds into helices along [001], and neighbouring molecules within the helix are related by the 21 screw axis. The neighbouring helical turns are linked by N-H···O hydrogen bonds. The cations link the helices via O-H···O and N-H···O hydrogen bonds, thus forming a three-dimensional network.

Zoledronic acid: monoclinic and triclinic polymorphs from powder diffraction data.

The crystal structures of the monoclinic and triclinic polymorphs of zoledronic acid, C5H10N2O7P2, have been established from laboratory powder X-ray diffraction data. The molecules in both polymorphs are described as zwitterions, namely 1-(2-hydroxy-2-phosphonato-2-phosphonoethyl)-1H-imidazol-3-ium. Strong intermolecular hydrogen bonds (with donor-acceptor distances of 2.60 Šor less) link the molecules into layers, parallel to the (100) plane in the monoclinic polymorph and to the (1-10) plane in the triclinic polymorph. The phosphonic acid groups form the inner side of each layer, while the imidazolium groups lie to the outside of the layer, protruding in opposite directions. In both polymorphs, layers related by translation along [100] interact through weak hydrogen bonds (with donor-acceptor distances greater than 2.70 Å), forming three-dimensional layered structures. In the monoclinic polymorph, there are hydrogen-bonded centrosymmetric dimers linked by four strong O-H...O hydrogen bonds, which are not present in the triclinic polymorph.

Two polymorphs of afobazole from powder diffraction data.

Afobazole {systematic name: 2-[2-(morpholin-4-yl)ethylsulfanyl]-1H-benzimidazole} is a new anxiolytic drug and Actins, Auzins & Petkune [(2012). Eur. Patent EP10163962] described four polymorphic modifications. In the present study, the crystal structures of two monoclinic polymorphs, 5-ethoxy-2-[2-(morpholin-4-ium-4-yl)ethylsulfanyl]-1H-benzimidazol-3-ium dichloride, C15H23N3O2S(2+)·2Cl(-), (II) and (IV), have been established from laboratory powder diffraction data. The crystal packing and conformation of the dications in (II) and (IV) are different. In (II), there are channels in the [001] direction, which offer atmospheric water molecules an easy way of penetrating into the crystal structure, thus explaining the higher hygroscopicity of (II) compared with (IV).

Mechanosynthesis of Stable Salt Hydrates of Allopurinol with Enhanced Dissolution, Diffusion, and Pharmacokinetics.

Allopurinol (ALO) is a medication that treats gout and kidney stones by lowering uric acid synthesis in the blood. The biopharmaceutics classification system (BCS) IV drug exhibits poor aqueous solubility, permeability, and bioavailability. To overcome the bottlenecks of ALO, salts with maleic acid (MLE) and oxalic acid (OXA) were synthesized using the solvent-assisted grinding method. The novel multicomponent solids were characterized by PXRD, DSC, TGA, FT-IR, and SEM images. The crystal structures of these salts with variable stoichiometry were obtained using Rietveld refinement from the high-resolution PXRD data. The proton from the dicarboxylic acid is transferred to the most basic pyrimidine "N" of ALO. The N-H···N hydrogen-bonded ALO homodimer is replaced by the N+-H···O- ionic interactions in ALO-OXA (2:1:0.4) and ALO-MLE (1:1:1) salt hydrates. The organic salts improved solubility and dissolution up to 5-fold and the diffusion permeability up to 12 times compared to the native drug in a luminal pH 6.8 phosphate buffer medium. The salt hydrates were exceptionally stable during storage at 30 ± 5 °C and 75 ± 5% relative humidity. Superior dissolution and diffusion permeability of the ALO-MLE salt resulted in improved pharmacokinetics (peak plasma concentration) that offers a promising solid dosage form with enhanced bioavailability and lower dosage formulation.

An anionic porphyrinylphosphonate-based hydrogen-bonded organic framework: optimization of proton conductivity through the exchange of counterions.

Hydrogen-bonded organic frameworks (HOFs) possessing high crystallinity, simple synthetic procedure and easy regeneration provide high efficiency as multifunctional systems, including applications as proton conductors. Porphyrinylphosphonates having acidic moieties, which can form multiple hydrogen bonds, together with tunable physical-chemical properties of a macrocycle may significantly improve the proton conductivity of such materials. Herein, the synthesis, characterization and proton-conducting properties of a novel anionic HOF based on a new complex of palladium(II) with meso-tetrakis(4-(phosphonatophenyl))porphyrin, HOF-IPCE-1Pd, are reported. Directed structural transformation of the framework by the exchange of dimethylammonium counterions for ammonium cations along with the absorption of ammonia and water molecules led to the formation of a more hydrolytically stable structure of HOF-IPCE-1Pd-NH3, demonstrating the proton conductivity of 1.27 × 10-3 S cm-1 at 85 °C and 85% RH, which is one of the highest among all known HOFs based on porphyrins. It is noteworthy that the reversible absorbance of water/ammonia molecules preserves the crystal structure of HOF-IPCE-1Pd-NH3.

Selective synthesis of cyclic peroxides from triketones and H2O2.

A method for the assembly of tricyclic structures containing the peroxide, monoperoxyacetal, and acetal moieties was developed based on the acid-catalyzed reaction of ß,δ-triketones with H(2)O(2). Tricyclic compounds are formed selectively in yields from 39% to 90% by the reactions with the use of large amounts of strong acids, such as H(2)SO(4), HClO(4), or HBF(4), which act both as the catalyst and as the co-solvent. The reaction is unusual in that, despite the diversity of possible peroxidation pathways giving cyclic compounds and oligomers, the reaction proceeds with high selectivity and produces tricyclic peroxides via the monoperoxidation of the carbonyl groups in the ß-positions and the transformation of the δ-carbonyl group into the acetal one. The syntheses are scaled up to tens of grams, and the resulting peroxides can be easily isolated from the reaction mixture.

Understanding the Working Mechanism of the Novel HKUST-1@BPS Composite Materials as Stationary Phases for Liquid Chromatography.

Composite materials have been used based on coordination polymers or microporous metal-organic frameworks (MOFs) combined with mesoporous matrices for adsorption-related techniques, which enable outflanking some adverse phenomena manifested during pristine components operation and enhance the performance and selectivity of the resulting materials. In this work, for the first time, the novel HKUST-1@BPS composites synthesized by the microwave-assisted (MW) technique starting from microporous HKUST-1 (Cu3(btc)2) MOF and biporous silica matrix (BPS) with bimodal mesopore size distribution were comparatively studied as materials for liquid-phase adsorption techniques utilizing the high-performance liquid chromatography (HPLC) method and benzene as a model adsorbate. It was established that the studied HKUST-1@BPS composites can function as stationary phases for HPLC, unlike the pristine HKUST-1 and bare BPS materials, due to the synergetic effect of both components based on the preliminary enhanced adsorbate mass transfer throughout the silica mesopores and, subsequently, its penetrating into HKUST-1 micropores. The suggested mechanism involves the initial deactivation of open metal Cu2+ sites in the HKUST-1 framework structure by isopropanol molecules upon adding this polar component into the mobile phase in the region of the isopropanol concentration of 0.0 to 0.2 vol.%. Thereafter, at the medium range of varying the isopropanol concentration in the eluent of 0.2 to 0.3 vol.%, there is an expansion of the previously inaccessible adsorption centers in the HKUST-1@BPS composites. Subsequently, while further increasing the isopropanol volume fraction in the eluent in the region of 0.3 to 5.0 vol.%, the observed behavior of the studied chromatographic systems is similar to the quasi-normal-phase HPLC pattern. According to the obtained thermodynamic data, benzene adsorption into HKUST-1 micropores from solutions with a vol.% of isopropanol in the range of 0.4 to 5.0 follows the unique entropy-driven mechanism previously described for the MIL-53(Al) framework. It was found that HKUST-1 loading in the composites and their preparation conditions have pronounced effects on their physicochemical properties and adsorption performance, including the adsorption mechanism.

Hydroamination of Phenylacetylene with Aniline over Gold Nanoparticles Embedded in the Boron Imidazolate Framework BIF-66 and Zeolitic Imidazolate Framework ZIF-67.

The hydroamination of alkynes is an atom-economy process in the organic synthesis for the C-N bond formation, thereby allowing the production of fine chemicals and intermediates. However, direct interaction between alkynes and amines is complicated due to the electron enrichment of both compounds. Therefore, efficient hydroamination catalysts, especially heterogeneous ones, are in great demand. This work aimed at the development of novel heterogeneous catalysts based on zeolite-like metal-organic frameworks for phenylacetylene hydroamination. The sodalite (SOD) type zeolitic imidazolate framework ZIF-67 (Co(meim)2, meim = 2-methylimidazolate) and boron imidazolate framework BIF-66 ({Co[B(im)4]2}n, im = imidazolate) were studied as the carriers for the gold nanoparticles (Au-NPs). Au-NPs were embedded in the ZIF-67 and BIF-66 matrices by incipient wetness impregnation. Au@ZIF-67 and Au@BIF-66 hybrids were studied for the first time in the liquid phase hydroamination of phenylacetylene with aniline in an air atmosphere and have shown high activity and selectivity in respect to imine in this process. The pronounced impact of the nature of the metal-organic carrier, Au source, and reducing agent on the catalytic performance of the synthesized nanomaterials was found. To the best of our knowledge, it is the first example of using the zeolitic imidazolate framework and boron-imidazolate framework as the components of the gold-containing catalytic systems for the alkyne hydroamination.

Proton conductivity as a function of the metal center in porphyrinylphosphonate-based MOFs.

The rational design of metal-organic frameworks (MOFs) is highly important for the development of new proton conductors. Porphyrinylphosphonate-based MOFs, providing the directed tuning of physical and chemical properties of materials through the modification of a macrocycle, are potentially high-conducting systems. In this work the synthesis and characterization of novel anionic Zn-containing MOF based on palladium(ii) meso-tetrakis(3-(phosphonatophenyl))porphyrinate, IPCE-2Pd, are reported. Moreover, the proton-conductive properties and structures of two anionic Zn-containing MOFs based on previously described nickel(ii) and novel palladium(ii) porphyrinylphosphonates, IPCE-2M (M = Ni(ii) or Pd(ii)), are compared in details. The high proton conductivity of 1.0 × 10-2 S cm-1 at 75 °C and 95% relative humidity (RH) is revealed for IPCE-2Ni, while IPCE-2Pd exhibits higher hydrolytic and thermal stability of the material (up to 420 °C) simultaneously maintaining a comparable value of conductivity (8.11 × 10-3 S cm-1 at 95 °C and 95% RH). The nature of the porphyrin metal center is responsible for the features of crystal structure of materials, obtained under identical reaction conditions. The structures of IPCE-2Pd and its dehydrated derivative IPCE-2Pd-HT are determined from the synchrotron powder diffraction data. The presence of phosphonic groups in compared materials IPCE-2M affords a high concentration of proton carriers that together with the sorption of water molecules leads to a high proton conductivity.