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.

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.

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.

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.

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.

2D MOFs with Ni(II), Cu(II), and Co(II) as Efficient Oxygen Evolution Electrocatalysts: Rationalization of Catalytic Performance vs Structure of the MOFs and Potential of the Redox Couples.

Earth-abundant transition-metal-based metal-organic frameworks (MOFs) are of immense interest for the development of efficient and durable heterogeneous water splitting electrocatalysts. This repot explores the design of two-dimensional (2D) MOFs with redox-active metal centers (Ni(II), Co(II), and Cu(II)) containing two types of electron-rich linkers such as bis(5-azabenzimidazole), linear L1 and angular L2, and aromatic dicarboxylates. The electron-rich linkers are considered to stabilize the higher oxidation state of the redox-active metal centers in the course of the electrocatalytic oxygen evolution reaction (OER) process. The 2D MOFs of L1 and L2 with Co(II) (1 and 3) and Ni(II) (2 and 4) have been produced via the conventional hydrothermal synthesis, while the MOFs of Cu(II) (Cu@1 and Cu@3) are obtained by the postsynthetic transmetallation reaction of MOFs 1 and 3. The electrocatalytic OER activities of the six MOFs have been studied to explore the influence of the redox potential of the transition-metal quasi-reversible couples and the coordination environment around the redox-active metal centers in the electrocatalytic activity. The lowest overpotential of 370 mV exhibited by MOF 2 with the highest current density and TOF value indicates the importance of the presence of coordinated water molecules and the lowest redox potential value of the most favorable quasi-reversible couple Ni+2/Ni+3. These catalysts exhibit a remarkable stability up to 1000 OER cycles. These studies pave the way for the design of MOF materials toward the development of a promising heterogeneous OER electrocatalyst.

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.

Diamidophosphites from ß-hydroxyamides: readily assembled ligands for Pd-catalyzed asymmetric allylic substitution.

Two groups of modular chiral diamidophosphite ligands were easily synthesised from accessible N-Boc-amino alcohols and pseudodipeptides. The reaction of these compounds with [Pd(allyl)Cl]2 in the presence of AgBF4 yielded complexes [Pd(allyl)(L)2]BF4. In addition, metallochelates [Pd(allyl)(L)]BF4 with (S)-methioninol-based P,S-bidentate ligands were prepared. The structures of the novel ligands and complexes were elucidated by means of 2D-NMR and were confirmed by single-crystal X-ray diffraction, as well as by DFT calculations. Asymmetric inducers of this type exhibited high enantioselectivities in the Pd-mediated allylic substitution of (E)-1,3-diphenylallyl ethyl carbonate with CH2(CO2Me)2 (up to 98% ee) and (CH2)4NH (up to 92% ee). Ee values of up to 86% and 73% were obtained in the Pd-catalyzed allylic alkylation of cinnamyl acetate with ethyl 2-oxocyclohexane-1-carboxylate and ethyl 2-oxocyclopentane-1-carboxylate, respectively. The effects of the structural modules, such as the nature of the phosphorus-containing ring or exocyclic substituent, on the catalytic activity and enantioselectivity were investigated.

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.

Adsorption of 2,4-dichlorophenoxyacetic acid in an aqueous medium on nanoscale MIL-53(Al) type materials.

A series of flexible metal-organic frameworks (MOFs) belonging to the MIL-53 family, such as MIL-53(Al), its amino-functionalized analog NH2-MIL-53(Al), and MIL-53(Al) type materials with Al3+ ions and mixed benzene-1,4-dicarboxylate and 2-aminobenzene-1,4-dicarboxylate linkers (MixLR) in various proportions were prepared in a nanocrystalline form using MW-activation under atmospheric pressure according to the original solvothermal procedure. The MIL-53(Al) and NH2-MIL-53(Al) samples feature nanocrystals with sizes of 200-300 nm, while MixLR matrices synthesized in this manner are composed of small nanoparticles with sizes of about 20-30 nm. MIL-53(Al) type materials (MIL-53(Al), NH2-MIL-53(Al) and MixLR) were probed in the adsorption of a typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in an aqueous medium. This study revealed a strong impact of the flexibility and porosity of the synthesized MIL-53(Al) type matrices on their physicochemical characteristics. MIL-53(Al) type materials show much higher 2,4-D adsorption rates than an activated carbon matrix (CSAC). The structural characteristics of the studied MIL-53(Al) type materials were established with a high resolution X-ray powder diffractometer equipped with a synchrotron radiation source. The obtained results can be used for the development of advanced adsorbents based on MIL-53(Al) type materials for water remediation.

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).

Optically active derivatives of terephthalic acid: four crystal structures from two powder patterns.

A novel important class of nanoporous crystalline solids, metal-organic frameworks (MOFs), composed of organic ligands (linkers) and metal ions, is now considered as a platform for the development of various functional hybrid materials. In order to design new MOF-based asymmetric catalysts, two terephthalic acid derivatives, namely 2-{[1-(1-tert-butoxycarbonyl)-L-prolyl]amino}terephthalic acid, C18H22N2O7, (1), and 2-(L-prolylamino)terephthalic acid, C13H14N2O5, (2), which could find potential applications as chiral linkers for the construction of enantioselective MOFs, were synthesized and their powder samples were measured at synchrotron station ID22 (ESRF). Each sample contained two unknown crystalline phases, so four new crystal structures were determined, namely, the 2.24-hydrate of (1), (1a) (space group C2221), and the 2.08-hydrate of (1), (1b) (P2221), which are crystallohydrates, and two polymorphs of (2), i.e. (2a) (C2221) and (2b) (P212121), and were validated with DFT-d (dispersion-corrected density functional theory) optimizations.

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.

The Oxime Derivatives of 1-R-1H-Naphtho[2,3-d][1,2,3]triazole-4,9-dione 2-oxides: Synthesis and Properties.

OBJECTIVE: To synthesize a novel chemotype based on the naphthoquinone scaffold with retained cytotoxicity and provisionally low intracellular oxidation potential. BACKGROUND: Derivatives of naphthoquinone, although potent anticancer agents, can exert heart toxicity due to generation of free oxygen species. METHODS: In this study, we modified the scaffold by replacing one carbonyl group with the oxime moiety. Interestingly, only one carbonyl group in 1-R-1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione 2-oxides reacted with hydroxylamine. The spatial structure was determined by X-ray analysis. New compounds were tested for the ability to form stable complexes with double stranded DNA by spectroscopy and molecular docking and to induce death of tumor cell lines and non-malignant counterparts. RESULTS: The resulting 1-R-1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione 4-oxime 2-oxides were further acylated to produce a series of 1-R-1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione 4-(O-acyloxime) 2-oxides. Newly synthesized compounds demonstrated a higher (in submicromolar or low micromolar range) cytotoxic potency against human colon and breast adenocarcinoma cell lines than to non-malignant skin fibroblasts. Spectroscopic measurements revealed that, unlike other classes of quinone derivatives, new naphthotriazoledione oxides did not form stable complexes with double stranded DNA regardless of their fitting to the DNA minor groove (as determined by molecular modeling). CONCLUSION: Thus, our chemical modifications yielded a new chemotype with good cytotoxic properties and yet-to-be-identified intracellular target(s).

Polymeric structure of a coproporphyrin I ruthenium(II) complex: a powder diffraction study.

Porphyrin complexes of ruthenium are widely used as models for the heme protein system, for modelling naturally occurring iron-porphyrin systems and as catalysts in epoxidation reactions. The structural diversity of ruthenium complexes offers an opportunity to use them in the design of multifunctional supramolecular assemblies. Coproporphyrins and metallocoproporphyrins are used as sensors in bioassay and the potential use of derivatives as multiparametric sensors for oxygen and H+ is one of the main factors driving a growing interest in the synthesis of new porphyrin derivatives. In the coproporphyrin I RuII complex catena-poly[[carbonylruthenium(II)]-µ-2,7,12,17-tetrakis[2-(ethoxycarbonyl)ethyl]-3,8,13,18-tetramethylporphyrinato-κ5N,N',N'',N''':O], [Ru(C44H52N4O8)(CO)]n, the RuII centre is coordinated by four N atoms in the basal plane, and by axial C (carbonyl ligand) and O (ethoxycarbonylethyl arm from a neighbouring complex) atoms. The complex adopts a distorted octahedral geometry. Self-assembly of the molecules during crystallization from a methylene chloride-ethanol (1:10 v/v) solution at room temperature gives one-dimensional polymeric chains.