Regioselective Thiol-yne Reaction of Thiol with ((Methyl-d3)sulfonyl)ethyne: Synthesis of (2-((Methyl-d3)sulfonyl)vinyl)sulfides.

Herein, we have developed a new method for the synthesis of ((methyl-d3)sulfonyl)ethyne, which is cost-effective and environmentally friendly and can be synthesized at the gram level. As an ideal thiol-yne reagent, it can be reacted with various types of thiols to afford (Z)- and (E)-type vinyl sulfides under different conditions with high selectivity. In addition, it can complete the conformational transition from Z- to E-type products under suitable conditions, and can also carry out further derivatization smoothly. The deuterium content of all products was greater than 99%. The preliminary mechanistic studies support the visible light-mediated radical course, and herein provide a novel and efficient synthetic strategy for the direct introduction of deuterated methyl groups, enriching the methods for the construction of C-S bond-containing compounds.

Regioselective 1,4-/1,3-Difunctionalization of 1,3-Enynes with Selenosulfonates in Water.

1,4-/1,3-Regioselective bifunctionalization of 1,3-enynes with selenosulfonates in water under catalyst-free conditions for the construction of sulfonyl allene and 1,3-disulfonyl-conjugated dienes respectively have been developed. The reactions feature mild reaction conditions in aqueous solution and remarkable regioselectivity controlled by substrates.

Copper-Catalyzed Synthesis of S-S Bond-Containing Silanols from SCBs and Trisulfide-1,1-dioxides.

In this work, an efficient method for the copper-catalyzed ring-opening hydrolysis of silacyclobutanes to silanols was developed. This strategy has the advantages of friendly reaction conditions, simple operation, and good functional group compatibility. No additional additives are required in the reaction, and the S-S bond can also be introduced into the organosilanol compounds in one step. Furthermore, the success at the gram scale demonstrates the great potential of the developed protocol for practical industrial applications.

Photoinduced Construction of Thieno[3,4-c]quinolin-4(5H)-ones/Selenopheno[3,4-c]quinolin-4(5H)-ones Using Diphenyl Disulfide or Diphenyl Diselenide as Sulfur or Selenium Sources.

A photocatalytic synthesis of thieno[3,4-c]quinolin-4(5H)-ones/selenopheno[3,4-c]quinolin-4(5H)-ones using diphenyl disulfide or diphenyl diselenide as sulfur or selenium sources was developed. Two C-S/Se bonds and one C-C bond were constructed simultaneously without transition metals and other additives.

Nickel-Catalyzed Acid Chlorides with Tetrasulfides for the Synthesis of Thioesters and Acyl Disulfides.

Herein, we report a novel method for the synthesis of thioesters and acyl disulfides via nickel-catalyzed reductive cross-electrophile coupling of acid chlorides with tetrasulfides. This approach for the synthesis of thioesters and acyl disulfides is convenient and practical under mild reaction conditions, relying on easy availability. In addition, a wide range of thioesters and acyl disulfides were obtained in medium to good yields with good functional group tolerance. Moreover, thioesters and acyl disulfides can also be prepared at the gram scale, indicating that they have certain potential for industrial application.

Successful Decontamination of 99 TcO4 - in Groundwater at Legacy Nuclear Sites by a Cationic Metal-Organic Framework with Hydrophobic Pockets.

99 Tc contamination at legacy nuclear sites is a serious and unsolved environmental issue. The selective remediation of 99 TcO4 - in the presence of a large excess of NO3 - and SO4 2- from natural waste systems represents a significant scientific and technical challenge, since anions with a higher charge density are often preferentially sorbed by traditional anion-exchange materials. We present a solution to this challenge based on a stable cationic metal-organic framework, SCU-102 (Ni2 (tipm)3 (NO3 )4 ), which exhibits fast sorption kinetics, a large capacity (291 mg g-1 ), a high distribution coefficient, and, most importantly, a record-high TcO4 - uptake selectivity. This material can almost quantitatively remove TcO4 - in the presence of a large excess of NO3 - and SO4 2- . Decontamination experiments confirm that SCU-102 represents the optimal Tc scavenger with the highest reported clean-up efficiency, while first-principle simulations reveal that the origin of the selectivity is the recognition of TcO4 - by the hydrophobic pockets of the structure.

Emergence of Uranium as a Distinct Metal Center for Building Intrinsic X-ray Scintillators.

The combination of high atomic number and high oxidation state in UVI materials gives rise to both high X-ray attenuation efficiency and intense green luminescence originating from ligand-to-metal charge transfer. These two features suggest that UVI materials might act as superior X-ray scintillators, but this postulate has remained substantially untested. Now the first observation of intense X-ray scintillation in a uranyl-organic framework (SCU-9) that is observable by the naked eye is reported. Combining the advantage in minimizing the non-radiative relaxation during the X-ray excitation process over those of inorganic salts of uranium, SCU-9 exhibits a very efficient X-ray to green light luminescence conversion. The luminescence intensity shows an essentially linear correlation with the received X-ray intensity, and is comparable with that of commercially available CsI:Tl. SCU-9 possesses an improved X-ray attenuation efficiency (E>20 keV) as well as enhanced radiation resistance and decreased hygroscopy compared to CsI:Tl.

Identifying the Recognition Site for Selective Trapping of 99TcO4- in a Hydrolytically Stable and Radiation Resistant Cationic Metal-Organic Framework.

Effective and selective removal of 99TcO4- from aqueous solution is highly desirable for both waste partitioning and contamination remediation purposes in the modern nuclear fuel cycle, but is of significant challenge. We report here a hydrolytically stable and radiation-resistant cationic metal-organic framework (MOF), SCU-101, exhibiting extremely fast removal kinetics, exceptional distribution coefficient, and high sorption capacity toward TcO4-. More importantly, this material can selectively remove TcO4- in the presence of large excesses of NO3- and SO42-, as even 6000 times of SO42- in excess does not significantly affect the sorption of TcO4-. These superior features endow that SCU-101 is capable of effectively separating TcO4- from Hanford low-level waste melter off-gas scrubber simulant stream. The sorption mechanism is directly unraveled by the single crystal structure of TcO4--incorporated SCU-101, as the first reported crystal structure to display TcO4- trapped in a sorbent material. A recognition site for the accommodation of TcO4- is visualized and is consistent with the DFT analysis results, while no such site can be resolved for other anions.

Substitutional Disorder of SeO32-/IO3- in the Crystalline Solid Matrix: Insights into the Fate of Radionuclides 79Se and 129I in the Environment.

As the crucial soluble species of long-lived radionuclides 129I and 79Se, iodate and selenite anions commonly share similar geometry of the trigonal pyramid XO3 (X = I, Se) but in different valence states. Although large amounts of investigations have been performed aiming at understanding the environmental behavior of these two anions individually, studies on cases when they coexist are extremely scarce. Structurally well-characterized natural/synthetic crystalline solids simultaneously incorporating these two anions as potential solubility-limiting products at the nuclear waste geological depository remain elusive. We report here a crystalline solid Th(IO3)2(SeO3) representing the first example of aliovalent substitution between IO3- and SeO32- sharing the same structural site, as demonstrated by single crystal X-ray diffraction, laser-ablation inductively coupled plasma mass spectrometry analysis, and spectroscopic techniques including infrared, Raman, and X-ray absorption spectroscopies. Sequentially, in the Eu(IO3)3 solid matrix, we demonstrated that the IO3- site can be sufficiently substituted by SeO32- in the presence of Th4+ via simultaneous incorporation of Th4+ and SeO32- in a charge-balancing mechanism. The obtained results provide insights into the environmental behavior of fission products 79Se and 129I: they may cocrystallize in one solid matrix and may be efficiently immobilized by incorporation into each other's solid phase through solid solution.

Mild Periodic Acid Flux and Hydrothermal Methods for the Synthesis of Crystalline f-Element-Bearing Iodate Compounds.

f-element-bearing iodate compounds are a large family mostly synthesized by hydrothermal reactions starting with actinide/lanthanide ions and iodic acid or iodate salt. In this work, we introduce melting periodic acid flux as a new reaction medium and provide a safe way for single-crystal growth of a series of new f-element iodate compounds including UO2(IO3)2·H2O (1), UO2(IO3)2(H2O)·HIO3 (2), α-Th(IO3)2(NO3)(OH) (3), ß-Th(IO3)2(NO3)(OH) (4), and (H3O)9Nd9(IO3)36·3HIO3 (5). The structures of these compounds deviate from those afforded from hydrothermal reactions. Specifically, compounds 1 and 2 exhibit pillared structures consisting of uranyl pentagonal bipyramids and iodate trigonal pyramids. Compounds 3 and 4 represent two new thorium iodate compounds that are constructed from subunits of thorium dimers. Compound 5 exhibits a flower-shaped trivalent lanthanide iodate structure with HIO3 molecules and H3O+ cations filled in the channels. The aliovalent replacement of f elements in 5 is available from a hydrothermal process, further generating compounds of Th2(IO3)8(H2O) (6) and Ce2(IO3)8(H2O) (7). The distinct absorption features are observed in isotypic compounds 5-7, where 7 shows typical semiconductor behavior with a band gap of 2.43 eV. Remarkably, noncentrosymmetric 1, 6, and 7 exhibit strong second-harmonic-generation efficiencies of 1.3, 3.2, and 9.2 times, respectively, that of the commercial material KH2PO4. Additionally, the temperature-dependent emission spectra of 1 and 2 were also collected showing typical emission features of uranyl units and a negative correlation between the intensities of the emissions with temperature. Clearly, the presented low-temperature melting inorganic acid flux synthesis would provide a facile and effective strategy to produce a large new family of structurally versatile and multifunctional f-element inorganic compounds.

Selenium Sequestration in a Cationic Layered Rare Earth Hydroxide: A Combined Batch Experiments and EXAFS Investigation.

Selenium is of great concern owing to its acutely toxic characteristic at elevated dosage and the long-term radiotoxicity of 79Se. The contents of selenium in industrial wastewater, agricultural runoff, and drinking water have to be constrained to a value of 50 µg/L as the maximum concentration limit. We reported here the selenium uptake using a structurally well-defined cationic layered rare earth hydroxide, Y2(OH)5Cl·1.5H2O. The sorption kinetics, isotherms, selectivity, and desorption of selenite and selenate on Y2(OH)5Cl·1.5H2O at pH 7 and 8.5 were systematically investigated using a batch method. The maximum sorption capacities of selenite and selenate are 207 and 124 mg/g, respectively, both representing the new records among those of inorganic sorbents. In the low concentration region, Y2(OH)5Cl·1.5H2O is able to almost completely remove selenium from aqueous solution even in the presence of competitive anions such as NO3-, Cl-, CO32-, SO42-, and HPO42-. The resulting concentration of selenium is below 10 µg/L, well meeting the strictest criterion for the drinking water. The selenate on loaded samples could be desorbed by rinsing with concentrated noncomplexing NaCl solutions whereas complexing ligands have to be employed to elute selenite for the material regeneration. After desorption, Y2(OH)5Cl·1.5H2O could be reused to remove selenate and selenite. In addition, the sorption mechanism was unraveled by the combination of EDS, FT-IR, Raman, PXRD, and EXAFS techniques. Specifically, the selenate ions were exchanged with chloride ions in the interlayer space, forming outer-sphere complexes. In comparison, besides anion exchange mechanism, the selenite ions were directly bound to the Y3+ center in the positively charged layer of [Y2(OH)5(H2O)]+ through strong bidentate binuclear inner-sphere complexation, consistent with the observation of the higher uptake of selenite over selenate. The results presented in this work confirm that the cationic layered rare earth hydroxide is an emerging and promising material for efficient removal of selenite and selenate as well as other anionic environmental pollutants.

Efficient and Selective Uptake of TcO4- by a Cationic Metal-Organic Framework Material with Open Ag+ Sites.

99Tc is one of the most problematic radioisotopes in used nuclear fuel owing to its combined features of high fission yield, long half-life, and high environmental mobility. There are only a handful of functional materials that can remove TcO4- anion from aqueous solution and identifying for new, stable materials with high anion-exchange capacities, fast kinetics, and good selectivity remains a challenge. We report here an 8-fold interpenetrated three-dimensional cationic metal-organic framework material, SCU-100, which is assembled from a tetradentate neutral nitrogen-donor ligand and two-coordinate Ag+ cations as potential open metal sites. The structure also contains a series of 1D channels filled with unbound nitrate anions. SCU-100 maintains its crystallinity in aqueous solution over a wide pH range from 1 to 13 and exhibits excellent ß and γ radiation-resistance. Initial anion exchange studies show that SCU-100 is able to both quantitatively and rapidly remove TcO4- from water within 30 min. The exchange capacity for the surrogate ReO4- reaches up to 541 mg/g and the distribution coefficient Kd is up to 1.9 × 105 mL/g, which are significantly higher than all previously tested inorganic anion sorbent materials. More importantly, SCU-100 can selectively capture TcO4- in the presence of large excess of competitive anions (NO3-, SO42-, CO32-, and PO43-) and remove as much as 87% of TcO4- from the Hanford low-level waste melter off-gas scrubber simulant stream within 2 h. The sorption mechanism is well elucidated by single crystal X-ray diffraction, showing that the sorbed ReO4- anion is able to selectively coordinate to the open Ag+ sites forming Ag-O-Re bonds and a series of hydrogen bonds. This further leads to a single-crystal-to-single-crystal transformation from an 8-fold interpenetrated framework with disordered nitrate anions to a 4-fold interpenetrated framework with fully ordered ReO4- anions. This work represents a practical case of TcO4- removal by a MOF material and demonstrates the promise of using this type of material as a scavenger for treating anionic radioactive contaminants during the nuclear waste partitioning and remediation processes.

Hydrolytically Stable Nanoporous Thorium Mixed Phosphite and Pyrophosphate Framework Generated from Redox-Active Ionothermal Reactions.

The first thorium framework compound with mixed-valent phosphorus-based (phosphite and pyrophosphate) ligands, [BMMim]2[Th3(PO3)4(H2P2O7)3] (ThP-1), was synthesized by ionothermal reactions concurrent with the partial oxidation of phosphoric acid. The overall structural topology of ThP-1 highly resembles that of MOF-5, containing only one type of three-dimensional channels with a window size of 11.32 Å × 11.32 Å. ThP-1 has a free void volume of 50.8%, making it one of the most porous purely inorganic actinide-based framework materials. More importantly, ThP-1 is highly stable in aqueous solutions over an extremely wide pH range from 1 to 14 and thus may find potential applications in selective ion exchange and catalysis.

First Cationic Uranyl-Organic Framework with Anion-Exchange Capabilities.

By controlling the extent of hydrolysis during the self-assembly process of a zwitterionic-based ligand with uranyl cations, we observed a structural evolution from the neutral uranyl-organic framework [(UO2)2(TTTPC)(OH)O(COOH)]·1.5DMF·7H2O (SCU-6) to the first cationic uranyl-organic framework with the formula of [(UO2)(HTTTPC)(OH)]Br·1.5DMF·4H2O (SCU-7). The crystal structures of SCU-6 and SCU-7 are layers built with tetranuclear and dinuclear uranyl clusters, respectively. Exchangeable halide anions are present in the interlaminar spaces balancing the positive charge of layers in SCU-7. Therefore, SCU-7 is able to effectively remove perrhenate anions from aqueous solution. Meanwhile, the H2PO4(-)-exchanged SCU-7 material exhibits a moderate proton conductivity of 8.70 × 10(-5) S cm(-1) at 50 °C and 90% relative humidity, representing nearly 80 times enhancement compared to the original material.

Umbellate distortions of the uranyl coordination environment result in a stable and porous polycatenated framework that can effectively remove cesium from aqueous solutions.

Searching for new chemically durable and radiation-resistant absorbent materials for actinides and their fission products generated in the nuclear fuel cycle remain highly desirable, for both waste management and contamination remediation. Here we present a rare case of 3D uranyl organic framework material built through polycatenating of three sets of graphene-like layers, which exhibits significant umbellate distortions in the uranyl equatorial planes studied thoroughly by linear transit calculations. This unique structural arrangement leads to high ß and γ radiation-resistance and chemical stability in aqueous solutions within a wide pH range from 3 to 12. Being equipped with the highest surface area among all actinide compounds known to date and completely exchangeable [(CH3)2NH2](+) cations in the structure, this material is able to selectively remove cesium from aqueous solutions while retaining the polycatenated framework structure.

Boosting Proton Conductivity in Highly Robust 3D Inorganic Cationic Extended Frameworks through Ion Exchange with Dihydrogen Phosphate Anions.

The limited long-term hydrolytic stability of rapidly emerging 3D-extended framework materials (MOFs, COFs, MOPs, etc.) is still one of major barriers for their practical applications as new solid-state electrolytes in fuel cells. To obtain hydrolytically stable materials, two H2 PO4 (-) -exchanged 3D inorganic cationic extended frameworks (CEFs) were successfully prepared by a facile anion-exchange method. Both anion-exchanged CEFs (YbO(OH)P and NDTBP) show significantly enhanced proton conductivity when compared with the original materials (YbO(OH)Cl and NDTB) with an increase of up to four orders-of-magnitude, reaching 2.36×10(-3) and 1.96×10(-2)  S cm(-1) at 98 % RH and 85 °C for YbO(OH)P and NDTBP, respectively. These values are comparable to the most efficient proton-conducting MOFs. In addition, these two anion-exchanged materials are stable in boiling water, which originates from the strong electrostatic interaction between the H2 PO4 (-) anion and the cationic host framework, showing a clear advance over all the acid-impregnated materials (H2 SO4 @MIL-101, H3 PO4 @MIL-101, and H3 PO4 @Tp-Azo) as practical solid-state fuel-cell electrolytes. This work offers a new general and efficient approach to functionalize 3D-extended frameworks through an anion-exchange process and achieves water-stability with ultra-high proton conductivity above 10(-2)  S cm(-1) .

Unravelling the Proton Conduction Mechanism from Room Temperature to 553 K in a 3D Inorganic Coordination Framework.

The preparation of proton-conducting materials that are functional and stable at intermediate temperatures (393-573 K) is a focal point of fuel cell development. The purely inorganic material, HNd(IO3)4, which possesses a dense 3D framework structure, can reach a maximum of 4.6 × 10(-4) S·cm(-1) at 353 K and 95% relative humidity and exhibit a high conductivity of 8.0 × 10(-5) S·cm(-1) from 373 to 553 K under the flow of wet N2. HNd(IO3)4 exhibits a variety of improvements including high thermal stability, low solubility in water, and resistance to reducing atmosphere. The proton conductivity in such a wide temperature range originates from the intrinsic liberated protons in the structure and the resulting 1D hydrogen-bonding network confirmed by bond valence sum calculation and solid-state NMR analysis. Moreover, two different activation energies are observed in different temperature regions (0.23 eV below 373 K and 0.026 eV from 373 to 553 K), indicating that two types of proton motion are responsible for proton diffusion, as further domenstrated by temperature-dependent open-circuit voltage hysteresis in a tested fuel cell assembly as well as variable-temperature and double quantum filtered solid-state NMR measurements.

Insertion of Trivalent Lanthanides into Uranyl Vanadate Layers and Frameworks.

Two new uranyl vanadates have been prepared from hydrothermal reactions and structurally characterized by single-crystal X-ray diffraction. The structure of (H3O)UO2VO4 (UVO-1) consists of anionic layers containing UO2(2+) pentagonal bipyramids coordinated by edge-sharing VO5 square pyramids, with the charge balanced by interlaminar H3O(+) cations. Vanadium in (UO2)3(VO4)2(H2O)3 (UVO-2) exists as monomeric VO4 tetrahedra coordinating to UO2(2+) pentagonal bipyramids, forming a 3D uranyl(VI) vanadate framework. Similar reactions with the addition of Ln(NO3)3 (Ln = Nd, Eu) afford the three heterobimetallic lanthanide uranyl vanadate frameworks Nd(UO2)3(VO4)3(H2O)11 (NdUVO-1), Eu(UO2)3(VO4)3(H2O)10 (EuUVO-1), and Eu2(UO2)12(VO4)10(H2O)24 (EuUVO-2). In NdUVO-1 and EuUVO-1, Ln(3+) cations are inserted into the interlayer space of UVO-1 substituting for H3O(+) and further bridging adjacent layers into 3D frameworks. Similarly, EuUVO-2 adopts the same sheet topology as UVO-2, with Eu(3+) ions replacing some of the interlayer uranyl ions in UVO-2. Our work has demonstrated that uranyl vanadate extended structures are excellent hosts for further incorporation of trivalent lanthanide/actinide cations and has provided a new way to create new heterobimetallic 4f-5f and 5f-5f compounds.

Probing the influence of phosphonate bonding modes to uranium(VI) on structural topology and stability: a complementary experimental and computational investigation.

Systematic control of the reactions between U(VI) and 1,4-phenylenebis(methylene))bis(phosphonic acid) (pmbH4) allows for alterations in the bonding between these constituents and affords three uranyl phosphonate compounds with chiral one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) structures, namely, [TPA][UO2(pmbH3)(pmbH2)H2O]·2H2O (1), [NH4]2[UO2(pmb)] (2), UO2(pmbH2) (3), and the first uranyl mixed phosphite/phosphonate compound [TMA]2[(UO2)2(pmb)(HPO3)] (4) (TPA = NPr4+, TMA = NMe4+). These compounds crystallize in the space groups P212121, P1̅, P21/c, and Cmcm, respectively. Further investigation of the local uranyl coordination environment reveals that in 1 only oxygen atoms from P=O moieties ligate the uranium centers; whereas in 2 only P-O(-) oxygen atoms are involved in bonding and yield a layered topology. Compound 3 differs sharply from the first two in that conjugated P=O and P-O(-) oxygen atoms chelate the uranium centers resulting in a 3D framework. In compound 4, a phosphonate group bridges three uranyl centers further coordinated with a phosphite ligand HPO32­, which is a product of pmbH4 decomposing, forming a 2D layered structure. Compounds 3 and 4 also contain a different coordination environment for U(VI) than that found in 1 or 2. In this case, tetragonal bipyramidal UO6 units occur instead of the far more common UO7 pentagonal bipyramids found in 1 and 2. Interestingly, 1 converts to 3 at elevated reaction temperatures, indicating that the formation of 1 is likely under kinetic control. This is supported by thermal analysis, which reveals that 3 has higher thermal stability than 1 or 2. UV-vis-near-IR absorption and fluorescence spectroscopy show that the absorption and photoluminescence intensity increases from 1 to 4. Density functional theory electronic structure calculations provide insight into the nature of the interactions between U(VI) and the phosphonate ligands.

In situ confinement of ultra-small metal nanoparticles in redox-active zirconium MOFs for catalysis.

Herein, we successfully fabricated ultra-small metal nanoparticles into two stable Zr-based metal-organic frameworks via in situ redox reactions between triphenylamine and the corresponding metal ions to afford Pd NPs@1 and Pd NPs@2, which exhibit excellent activity and reusability for Suzuki coupling reactions as heterogeneous catalysts.