4f/5d Hybridization Induced Single-Electron Delocalization in an Azide-Bridged Dicerium Complex.

Dilanthanide complexes with one-electron delocalization are important targets for understanding the specific 4f/5d-bonding feature in lanthanide chemistry. Here, we report an isolable azide-bridged dicerium complex 3 [{(TrapenTMS)Ce}2(µ-N3)]• [Trapen = tris (2-aminobenzyl)amine; TMS = SiMe3], which is synthesized by the reaction of tripodal ligand-supported (TrapenTMS)CeIVCl complex 2 with NaN3. The structure and bonding nature of 3 are fully characterized by X-ray crystal diffraction analysis, electron paramagnetic resonance (EPR), magnetic measurement, cyclic voltammetry, X-ray absorption spectroscopy, and quantum-theoretical studies. Complex 3 presents a trans-bent central Ce-N3-Ce unit with a single electron of two mixed-valent Ce atoms. The unique low-temperature (2 K) anisotropic EPR signals [g = 1.135, 2.003, and 3.034] of 3 indicate that its spin density is distributed on the central Ce-N3-Ce unit with marked electron delocalization. Quantum chemical analyses show strong 4f/5d orbital mixing in the singly occupied molecular orbital of 3, which allows for the unpaired electron to extend throughout the cerium-azide-cerium unit via a multicentered one-electron (Ce-N3-Ce) interaction. This work extends the family of mixed-valent dilanthanide complexes and provides a paradigm for understanding the bonding motif of ligand-bridged dilanthanide complexes.

Exploring the Valence Diversity of Uranium by Flux Growth of Uranium Silicate under Inert Atmosphere.

The attributes of good solubility and the redox-neutral nature of molten salt fluxes enable them to be useful for the synthesis of novel crystalline actinide compounds. In this work, a flux growth method under an inert atmosphere is proposed to explore the valence diversity of uranium, and a series of five uranium silicate structures, [K3Cl][(UVIO2)(Si4O10)] (1), Cs3[(UVO2)(Si4O10)] (2), K2[UIV(Si2O7)] (3), K8[(UVIO2)(UVO2)2(Si8O22)] (4), and Cs6[UIV(UVO)2(Si12O32)] (5), were synthesized using different metal halide salt and feeding U/Si ratios. Crystal structure analysis reveals that the utilization of argon atmosphere that helps to avoid possible oxidation of low-valence uranium generates a variety of oxidation states of uranium including U(VI), U(V), U(IV), mixed-valence U(V) and U(VI), and mixed-valence U(IV) and U(V). Characterization of physicochemical properties of representative compounds shows that all these uranium silicate compounds have bandgaps among the range of 2.0-3.4 eV, and mixed-valence uranium silicate compounds have relatively narrower bandgaps. Density functional theory calculations on formation enthalpies, lattice energies, and bandgaps of all five compounds were also performed to provide more structural information about these uranium silicates. This work enriches the library of variable-valence uranium silicate compounds and provides a feasible way to produce novel actinide compounds with intriguing properties through the flux growth method that might show potential application in relevant fields such as storage media for nuclear waste.

Transmembrane stem factor nanodiscs enhanced revascularization in a hind limb ischemia model in diabetic, hyperlipidemic rabbits.

Therapies to revascularize ischemic tissue have long been a goal for the treatment of vascular disease and other disorders. Therapies using stem cell factor (SCF), also known as a c-Kit ligand, had great promise for treating ischemia for myocardial infarct and stroke, however clinical development for SCF was stopped due to toxic side effects including mast cell activation in patients. We recently developed a novel therapy using a transmembrane form of SCF (tmSCF) delivered in lipid nanodiscs. In previous studies, we demonstrated tmSCF nanodiscs were able to induce revascularization of ischemia limbs in mice and did not activate mast cells. To advance this therapeutic towards clinical application, we tested this therapy in an advanced model of hindlimb ischemia in rabbits with hyperlipidemia and diabetes. This model has therapeutic resistance to angiogenic therapies and maintains long term deficits in recovery from ischemic injury. We treated rabbits with local treatment with tmSCF nanodiscs or control solution delivered locally from an alginate gel delivered into the ischemic limb of the rabbits. After eight weeks, we found significantly higher vascularity in the tmSCF nanodisc-treated group in comparison to alginate treated control as quantified through angiography. Histological analysis also showed a significantly higher number of small and large blood vessels in the ischemic muscles of the tmSCF nanodisc treated group. Importantly, we did not observe inflammation or mast cell activation in the rabbits. Overall, this study supports the therapeutic potential of tmSCF nanodiscs for treating peripheral ischemia.

Impact of ultra-pulse carbon dioxide laser on the treatment of chronic refractory ulcer with bone exposure.

BACKGROUND: Chronic refractory ulcers with bone exposure present significant challenges in wound management and necessitate effective treatment strategies to facilitate healing and alleviate patient discomfort. This study aimed to investigate the impact of ultra-pulse carbon dioxide laser on treating chronic refractory ulcers with bone exposure. METHODS: This retrospective observational study enrolled patients diagnosed with chronic refractory ulcers with bone exposure admitted to the wound repair clinic of the Affiliated Hospital of Southwest Medical University between July 2018 and July 2019. RESULTS: A total of 64 patients with chronic refractory ulcers and bone exposure were included, of which 32 patients underwent ultra-pulse carbon dioxide laser drilling. Compared with patients who did not receive ultra-pulse carbon dioxide laser treatment, those who experienced the procedure demonstrated significantly higher wound healing rates on the fourth, eighth, 12th, 16th, and 20th days after treatment (all P < .001), lower scores on the visual analog scale for pain after 20 days of debridement (0.24 ± 0.05 vs 0.58 ± 0.12, P < .001), lower granulation color observation scores on the 12th, 16th, and 20th days (all P = .001), as well as reduced treatment costs (8200 ± 1600 yuan vs 15400 ± 3800 yuan, P < .001). CONCLUSION: Ultra-pulse carbon dioxide laser treatment may enhance the growth of granulation tissue, improve wound healing rates, reduce pain, and lower treatment costs for patients with chronic bone exposure wounds compared to those without such treatment.

Th6-Based Multicomponent Heterometallic Metal-Organic Frameworks Featuring 6,12-Connected Topology for Iodine Adsorption.

Its high coordination number and tendency to cluster make Th4+ suitable for constructing metal-organic frameworks (MOFs) with novel topologies. In this work, two novel thorium-based heterometallic MOF isomers (IHEP-17 and IHEP-18) were assembled from a Th6 cluster, a multifunctional organic ligand [4-(1H-pyrazol-4-yl)benzoic acid (HPyba)], and Cu2+/Ni2+ cations via the one-pot solvothermal synthesis strategy. The framework features a 6,12-connected new topology net and contains two kinds of supramolecular cage structures, Th36M4 and Th24M2, suitable for guest exchange. Both MOF materials can efficiently adsorb I2. X-ray photoelectron spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction indicate that the adsorbed iodine is uniformly distributed within the Th36M4 cage but not the Th24M2 cage in the form of I3-.

Thermally Induced Orderly Alignment of Porphyrin Photoactive Motifs in Metal-Organic Frameworks for Boosting Photocatalytic CO2 Reduction.

Efficient transfer of charge carriers through a fast transport pathway is crucial to excellent photocatalytic reduction performance in solar-driven CO2 reduction, but it is still challenging to effectively modulate the electronic transport pathway between photoactive motifs by feasible chemical means. In this work, we propose a thermally induced strategy to precisely modulate the fast electron transport pathway formed between the photoactive motifs of a porphyrin metal-organic framework using thorium ion with large ionic radius and high coordination number as the coordination-labile metal node. As a result, the stacking pattern of porphyrin molecules in the framework before and after the crystal transformations has changed dramatically, which leads to significant differences in the separation efficiency of photogenerated carriers in MOFs. The rate of photocatalytic reduction of CO2 to CO by IHEP-22(Co) reaches 350.9 µmol·h-1·g-1, which is 3.60 times that of IHEP-21(Co) and 1.46 times that of IHEP-23(Co). Photoelectrochemical characterizations and theoretical calculations suggest that the electron transport channels formed between porphyrin molecules inhibit the recombination of photogenerated carriers, resulting in high performance for photocatalytic CO2 reduction. The interaction mechanism of CO2 with IHEP-22(Co) was clarified by using in-situ electron paramagnetic resonance, in-situ diffuse reflectance infrared Fourier transform spectroscopy, in-situ extended X-ray absorption fine structure spectroscopy, and theoretical calculations. These results provide a new method to regulate the efficient separation and migration of charge carriers in CO2 reduction photocatalysts and will be helpful to guide the design and synthesis of photocatalysts with superior performance for the production of solar fuels.

Transmembrane Stem Factor Nanodiscs Enhanced Revascularization in a Hind Limb Ischemia Model in Diabetic, Hyperlipidemic Rabbits.

Therapies to revascularize ischemic tissue have long been a goal for the treatment of vascular disease and other disorders. Therapies using stem cell factor (SCF), also known as a c-Kit ligand, had great promise for treating ischemia for myocardial infarct and stroke, however clinical development for SCF was stopped due to toxic side effects including mast cell activation in patients. We recently developed a novel therapy using a transmembrane form of SCF (tmSCF) delivered in lipid nanodiscs. In previous studies, we demonstrated tmSCF nanodiscs were able to induce revascularization of ischemia limbs in mice and did not activate mast cells. To advance this therapeutic towards clinical application, we tested this therapy in an advanced model of hindlimb ischemia in rabbits with hyperlipidemia and diabetes. This model has therapeutic resistance to angiogenic therapies and maintains long term deficits in recovery from ischemic injury. We treated rabbits with local treatment with tmSCF nanodiscs or control solution delivered locally from an alginate gel delivered into the ischemic limb of the rabbits. After eight weeks, we found significantly higher vascularity in the tmSCF nanodisc-treated group in comparison to alginate treated control as quantified through angiography. Histological analysis also showed a significantly higher number of small and large blood vessels in the ischemic muscles of the tmSCF nanodisc treated group. Importantly, we did not observe inflammation or mast cell activation in the rabbits. Overall, this study supports the therapeutic potential of tmSCF nanodiscs for treating peripheral ischemia.

Sequential Water Sorption/Desorption of a Nonporous Adaptive Organic Ligand Bridged Coordination Polymer for Atmospheric Moisture Harvesting.

Moisture harvesters with favourable attributes such as easy synthetic availability and good processability as alternatives for atmospheric moisture harvesting (AWH) are desirable. This study reports a novel nonporous anionic coordination polymer (CP) of uranyl squarate with methyl viologen (MV2+ ) as charge balancing ions (named U-Squ-CP) which displays intriguing sequential water sorption/desorption behavior as the relative humidity (RH) changes gradually. The evaluation of AWH performance of U-Squ-CP shows that it can absorb water vapor under air atmosphere at a low RH of 20 % typical of the levels found in most dry regions of the world, and have good cycling durability, thus demonstrating the capability as a potential moisture harvester for AWH. To the authors' knowledge, this is the first report on non-porous organic ligand bridged CP materials for AWH. Moreover, a stepwise water-filling mechanism for the water sorption/desorption process is deciphered by comprehensive characterizations combining single-crystal diffraction, which provides a reasonable explanation for the special moisture harvesting behaviour of this non-porous crystalline material.

Tetravalent Uranium and Thorium Complexes: Elucidating Disparate Reactivities of AnIVCl2 (An = U, Th) Supported by a Pyridine-Decorated Dianionic Ligand.

Although synthesis, reactivity, and bonding of U(IV) and Th(IV) complexes have been extensively studied, direct comparison of fully analogous compounds is rare. Herein, we report corresponding complexes 1-U and 1-Th, in which U(IV) and Th(IV) are supported by the tetradentate pyridine-decorated dianionic ligand N2NN' (1,1,1-trimethyl-N-(2-(((pyridin-2-ylmethyl)(2-((trimethylsilyl)amino)benzyl)amino)methyl)phenyl)silanamine). Although 1-U and 1-Th are structurally very similar, they display disparate reactivities with TMS3SiK (tris(trimethylsilyl)silylpotassium). The reaction of (N2NN')UCl2 (1-U) and 1 equiv of TMS3SiK in THF unexpectedly formed [Cl(N2NN')U]2O (2-U) featuring an unusual bent U-O-U moiety. In contrast, a salt elimination reaction between (N2NN')ThCl2 (1-Th) and 1 equiv of TMS3SiK led to thorium complex 2-Th, in which the pyridyl group has undergone a 1,4-addition nucleophilic attack. Complex 2-Th serves as a synthon for preparing dimetallic bis-azide complex 3-Th by reaction with NaN3. The complexes were characterized by X-ray crystal diffraction, solution NMR, FT-IR, and elemental analysis. Computations of the formation mechanism of 2-U from 1-U suggest reduced U(III) as a key intermediate for promoting the cleavage of the C-O bonds of THF. The inaccessible nature of Th(III) as an intermediate oxidation state explains the very different reactivity of 1-Th versus 1-U. Given that reactants 1-U and 1-Th and products 2-U and 2-Th all comprise tetravalent actinides, this is an unusual case of very disparate reactivity despite no net change in the oxidation state. Complexes 2-U and 3-Th provide a basis for the synthesis of other dinuclear actinide complexes with novel reactivity and properties.

Colossal negative thermal expansion in a cucurbit[8]uril-enabled uranyl-organic polythreading framework via thermally induced relaxation.

It is an ongoing goal to achieve the effective regulation of the thermal expansion properties of materials. In this work, we propose a method for incorporating host-guest complexation into a framework structure and construct a flexible cucurbit[8]uril uranyl-organic polythreading framework, U3(bcbpy)3(CB8). U3(bcbpy)3(CB8) can undergo huge negative thermal expansion (NTE) and has a large volumetric coefficient of -962.9 × 10-6 K-1 within the temperature range of 260 K to 300 K. Crystallographic snapshots of the polythreading framework at various temperatures reveal that, different from the intrinsic transverse vibrations of the subunits of metal-organic frameworks (MOFs) that experience NTE via a well-known hinging model, the remarkable NTE effect observed here is the result of a newly-proposed thermally induced relaxation process. During this process, an extreme spring-like contraction of the flexible CB8-based pseudorotaxane units, with an onset temperature of ∼260 K, follows a period of cumulative expansion. More interestingly, compared with MOFs that commonly have relatively strong coordination bonds, due to the difference in the structural flexibility and adaptivity of the weakly bonded U3(bcbpy)3(CB8) polythreading framework, U3(bcbpy)3(CB8) shows unique time-dependent structural dynamics related to the relaxation process, the first time this has been reported in NTE materials. This work provides a feasible pathway for exploring new NTE mechanisms by using tailored supramolecular host-guest complexes with high structural flexibility and has promise for the design of new kinds of functional metal-organic materials with controllable thermal responsive behaviour.

Syndecan-4 proteoliposomes enhance revascularization in a rabbit hind limb ischemia model of peripheral ischemia.

Regenerative therapeutics for treating peripheral arterial disease are an appealing strategy for creating more durable solutions for limb ischemia. In this work, we performed preclinical testing of an injectable formulation of syndecan-4 proteoliposomes combined with growth factors as treatment for peripheral ischemia delivered in an alginate hydrogel. We tested this therapy in an advanced model of hindlimb ischemia in rabbits with diabetes and hyperlipidemia. Our studies demonstrate enhancement in vascularity and new blood vessel growth with treatment with syndecan-4 proteoliposomes in combination with FGF-2 or FGF-2/PDGF-BB. The effects of the treatments were particularly effective in enhancing vascularity in the lower limb with a 2-4 increase in blood vessels in the treatment group in comparison to the control group. In addition, we demonstrate that the syndecan-4 proteoliposomes have stability for at least 28 days when stored at 4°C to allow transport and use in the hospital environment. In addition, we performed toxicity studies in the mice and found no toxic effects even when injected at high concentration. Overall, our studies support that syndecan-4 proteoliposomes markedly enhance the therapeutic potential of growth factors in the context of disease and may be promising therapeutics for inducing vascular regeneration in peripheral ischemia. STATEMENT OF SIGNIFICANCE: Peripheral ischemia is a common condition in which there is a lack of blood flow to the lower limbs. This condition can lead to pain while walking and, in severe cases, critical limb ischemia and limb loss. In this study, we demonstrate the safety and efficacy of a novel injectable therapy for enhancing revascularization in peripheral ischemia using an advanced large animal model of peripheral vascular disease using rabbits with hyperlipidemia and diabetes.

Unveiling Structural Diversity of Uranyl Compounds of Aprotic 4,4'-Bipyridine N,N'-Dioxide Bearing O-Donors.

As an aprotic O-donor ligand, 4,4'-bipyridine N,N'-dioxide (DPO) shows good potential for the preparation of uranyl coordination compounds. In this work, by regulating reactant compositions and synthesis conditions, diverse coordination assembly between uranyl and DPO under different reaction conditions was achieved in the presence of other coexisting O-donors. A total of ten uranyl-DPO compounds, U-DPO-1 to U-DPO-10, have been synthesized by evaporation or hydro/solvothermal treatment, and the possible competition and cooperation of DPO with other O-donors for the formation of these uranyl-DPO compounds are discussed. Starting with an aqueous solution of uranyl nitrate, it is found that an anionic nitrate or hydroxyl group is involved in the coordination sphere of uranyl in U-DPO-1 ((UO2)(NO3)2(H2O)2·(DPO)), U-DPO-2 ((UO2)(NO3)2(DPO)), and U-DPO-3 ((UO2)(DPO)(µ2-OH)2), where DPO takes three different kinds of coordination modes, i.e. uncoordinated, monodentate, and biconnected. The utilization of UO2(CF3SO3)2 in acetonitrile, instead of an aqueous solution of uranyl nitrate, precludes the participation of nitrate and hydroxyl, and ensures the engagement of DPO ligands (4-5 DPO ligands for each uranyl) in a uranyl coordination sphere of U-DPO-4 ([(UO2)(CF3SO3)(DPO)2](CF3SO3)), U-DPO-5 ([UO2(H2O)(DPO)2](CF3SO3)2) and U-DPO-6 ([(UO2)(DPO)2.5](CF3SO3)2). Moreover, when combined with anionic carboxylate ligands, terephthalic acid (H2TPA), isophthalic acid (H2IPA), and succinic acid (H2SA), DPO works well with them to produce four mixed-ligand uranyl compounds with similar structures of two-dimensional (2D) networks or three-dimensional (3D) frameworks, U-DPO-7 ((UO2)(TPA)(DPO)), U-DPO-8 ((UO2)2(DPO)(IPA)2·0.5H2O), U-DPO-9 ((UO2)(SA)(DPO)·H2O), and U-DPO-10 ((UO2)2(µ2-OH)(SA)1.5(DPO)). Density functional theory (DFT) calculations conducted to probe the bonding features between uranyl ions and different O-donor ligands show that the bonding ability of DPO is better than that of anionic CF3SO3 -, nitrate, and a neutral H2O molecule and comparable to that of an anionic carboxylate group. Characterization of physicochemical properties of U-DPO-7 and U-DPO-10 with high phase purity including infrared (IR) spectroscopy, thermogravimetric analysis (TGA), and luminescence properties is also provided.

Transmembrane Stem Factor Nanodiscs Enhanced Revascularization in a Hind Limb Ischemia Model in Diabetic, Hyperlipidemic Rabbits.

Therapies to revascularize ischemic tissue have long been a goal for the treatment of vascular disease and other disorders. Therapies using stem cell factor (SCF), also known as a c-Kit ligand, had great promise for treating ischemia for myocardial infarct and stroke, however clinical development for SCF was stopped due to toxic side effects including mast cell activation in patients. We recently developed a novel therapy using a transmembrane form of SCF (tmSCF) delivered in lipid nanodiscs. In previous studies, we demonstrated tmSCF nanodiscs were able to induce revascularization of ischemia limbs in mice and did not activate mast cells. To advance this therapeutic towards clinical application, we tested this therapy in an advanced model of hindlimb ischemia in rabbits with hyperlipidemia and diabetes. This model has therapeutic resistance to angiogenic therapies and maintains long term deficits in recovery from ischemic injury. We treated rabbits with local treatment with tmSCF nanodiscs or control solution delivered locally from an alginate gel delivered into the ischemic limb of the rabbits. After eight weeks, we found significantly higher vascularity in the tmSCF nanodisc-treated group in comparison to alginate treated control as quantified through angiography. Histological analysis also showed a significantly higher number of small and large blood vessels in the ischemic muscles of the tmSCF nanodisc treated group. Importantly, we did not observe inflammation or mast cell activation in the rabbits. Overall, this study supports the therapeutic potential of tmSCF nanodiscs for treating peripheral ischemia.

SSR identification and phylogenetic analysis in four plant species based on complete chloroplast genome sequences.

The effective utilization of traditional Chinese medicine (TCM) has been challenged by the difficulty to accurately distinguish between similar plant varieties. The stability and conservation of the chloroplast genome can aid in resolving genotypes. Previous studies using nuclear sequences and molecular markers have not effectively differentiated the species from related taxa, such as Machilus leptophylla, Hanceola exserta, Rubus bambusarum, and Rubus henryi. This study aimed to characterize the chloroplast genomes of these four plant species, and analyze their simple sequence repeats (SSRs) and phylogenetic positions. The results demonstrated the four chloroplast genomes consisted of 152.624 kb, 153.296 kb, 156.309 kb, and 158.953 kb in length, involving 124, 130, 129, and 131 genes, respectively. They also contained four specific regions with mononucleotide being the class with the most members. Moreover, these repeating types of SSR were various in individual class. Phylogenetic analysis showed that M. leptophylla was clustered with M. yunnanensis, and H. exserta was confirmed as belonging to the family Ocimeae. Additionally, R. bambusarum and R. henryi were grouped together but differed in their SSR features, indicating that they were not the same species. This research provides evidence for resolving species and contributes new genetic information for further studies.

Role of molecular symmetry in the magnetic relaxation dynamics of five-coordinate Dy(III) complexes.

A new family of low-coordinate mononuclear DyIII single-molecule magnets [(TrapenTMS)Dy(LB)] (Trapen = tris(2-aminobenzyl)amine; TMS = SiMe3; LB = THF 1, pyridine 2, ONMe33) has been synthesized and structurally characterized by single crystal X-ray diffraction. The five-coordinate DyIII ions exhibit distorted triangular bipyramidal geometries, among the different neutral ligands LB on the apex and the same TrapenTMS ligand, making the pyramid base of the trigonal bipyramid. Magnetic data analysis reveals that 1-3 are characteristic of SMM behaviors without a dc field, accompanying an unambiguous quantum tunneling of magnetization. Under an extra dc field of 500 Oe, field-induced slow magnetic relaxation behaviors occur with Raman and/or QTM processes. Ab initio calculations were also performed to rationalize the observed discrepancy in the magnetic behaviors, and the result illustrates that the SMM behavior could be effectively manipulated by the axial symmetry of the triangular bipyramidal DyIII motifs.

Supramolecular Shish Kebabs: Higher Order Dimeric Structures from Ring-in-Rings Complexes with Conformational Adaptivity.

Use of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring-in-ring(s) system comprising a hydrogen-bonded macrocycle and cyclobis(paraquat-o-phenylene) tetracation (o-Box) or cyclobis(paraquat-p-phenylene) tetracation (CBPQT4+ , p-Box) that assembles to construct discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR spectroscopy, and single-crystal X-ray diffraction analysis, this ring-in-ring(s) system features the box-directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1 a/o-Box) and H5G (1 a/o-Box). Remarkably, a dimeric shish-kebab-like ring-in-rings superstructure H7G2 (1 a/o-Box) or H8G2 (1 a/p-Box) is formed from the coaxial stacking of two ring-in-rings units. The formation of such unique dimeric superstructures is attributed to the large π-surface of this 2D planar macrocycle and the conformational variation of both host and guest.

Bioinspired Macrocyclic Molecule Supported Two-Dimensional Lamellar Membrane with Robust Interlayer Structure for High-Efficiency Nanofiltration.

2D lamellar membranes (2DLMs) are used for efficient desalination and nanofiltration. However, weak interactions between adjacent stacked nanosheets result in susceptibility to swelling that limits practical applicability. Inspired by the super adhesion of multi-point suction cups on octopus tentacles, a 2DLM is constructed from Ti3 C2 Tx MXene supported by the macrocyclic "multi-point" molecule cucurbit[5]uril (CB5) and demonstrated for nanofiltration of methyl blue (MB) and enrichment of uranyl carbonate. Experimental results and density functional theory calculations indicate that CB5 rivets to the surface of the nanoflakes through strong stable interactions between its multiple binding sites and surface hydroxyl functional groups on MXene nanosheets. This novel 2DLM exhibits excellent nanofiltration performance (69 L m-2 h-1 bar-1 permeance with 93.6% rejection for MB) and can be recycled at least 30 times without significant degradation. The 2DLM exhibits excellent swelling resistance at high salinity, with a demonstration of selective enrichment of uranyl carbonate from artificial water and natural seawater. The results provide a new strategy for constructing highly stable 2DLMs with interlayer spacing controllable from sub-nano to nanometer scales, for size-selective sieving of molecules and ions, high-efficiency nanofiltration, and other applications.

Synthesis of Trapen Ligand-Based U(IV) and Th(IV) 2-Phosphaethynolate Complexes and Comparison of Covalency with Corresponding Ti(IV) Analogues.

The involvement of the 2-phosphaethynolate anion species with ambident nucleophilic properties serves as an essential protocol for synthesizing oxygen-bound or phosphorus-bound complexes. This work mainly describes the synthesis and characterization of U, Th, and Ti phosphaethynolate complexes featuring a preferential O-coordination fashion. Among these complexes, the first examples of a Ti(IV)-OCP complex 3A, Th(IV)-OCP complex 3B, and U(IV)-OCP complex 3C were assembled by a salt metathesis reaction between M(TrapenTMS)(Cl) (M = Ti, Th, U) and NaOCP(dioxane)2.5 and were all crystallographically characterized. The structural similarity of this series of phosphaethynolate complexes allows us to compare the bonding properties of d- and f-block elements in the corresponding compounds. The well-established density functional theory (DFT) computational method was employed to explore the electronic structures and covalency in M-O bonding, and the results showed a consistent pattern. The calculation result showed that 2-phosphaethynolate complexes exhibited the covalency trend of U-O > Th-O > Ti-O due to the involvement of 5f orbitals.

Modular Assembly of Isostructural Mixed-Ligand Uranyl Coordination Polymers Based on a Patterning Strategy.

Controlling the orderly assembly of molecular building blocks for the formation of the desired architectural, chemical, and physical properties of the resulting solid-state materials remains a long-term goal and deserves to be examined. In this work, we propose a patterning strategy for modular assembly and structural regulation of mixed-ligand uranyl coordination polymers (CPs) through the combination of couples of organic ligands with complementary molecular geometry and well-matched coordination modes. By using a 5-(p-tolyldiazenyl)isophthalic acid ligand (H2ptdi) with different rigid linear bicarboxylic acid linkers to construct a well-defined ladder-like pattern, five novel isostructural uranyl coordination polymers, [(UO)2(ptdi)(bdc)0.5](dma) (1), [(UO)2(ptdi)(bpdc)0.5](dma) (2), [(UO)2(ptdi)(tpdc)0.5](dma) (3), [(UO)2(ptdi)(ndc)0.5](dma) (4), and [(UO)2(ptdi) (pdc)0.5](dma) (5) {H2bdc, 1,4-dicarboxybenzene; H2bpdc, 4,4'-biphenyldicarboxylic acid; H2tpdc, terphenyl-4,4″-dicarboxylic acid; H2ndc, 2,6-naphthalenedicarboxylic acid; H2pdc, 1,6-pyrenedicarboxylic acid; [dma]+, [(CH3)2NH2]+}, were successfully synthesized. Structural analysis reveals that 1-5 have similar ladder-like units but different sizes of one-dimensional nanochannels and interlayer spacing due to the different lengths and widths of the linkers. Because of the changes in interlayer spacing of these isostructural cationic frameworks, differences in the performance of Eu3+ ion exchange with [dma]+ are observed. Moreover, those compounds with high phase purity have been further characterized by thermogravimetric analysis, infrared spectroscopy, and luminescence spectroscopy, element analysis, PXRD and UV spectroscopy. Among them, compound 3 with strong fluorescence can selectively detect Fe3+ over several competing metal cations in aqueous solution. This work not only provides a feasible patterning method for effectively regulating the modular synthesis of functional coordination polymers but also enriches the library of uranyl-based coordination polymers with intriguing structures and functionality.

Circular RNA: An emerging frontier in RNA therapeutic targets, RNA therapeutics, and mRNA vaccines.

Circular RNAs (circRNA) is a class of natural (biogenic) or synthetic closed RNA without 5' or 3' ends. Meanwhile, their unique covalently-closed structures of circRNA prevent RNA degradation by exonucleases, thereby empowering them with high pharmaceutical stability and biostability relative to current standard-of-care linear mRNA. Natural circRNA can be non-coding RNAs as well as protein-coding RNA, the latter of which was recently discovered. The physiological functions of biogenic circRNAs, which largely remain elusive, include protein and gene sponges, cell activity modulators, and protein translation. The discovery that the circRNA levels can be correlated with some human diseases empowers circRNA with the potential as a novel type of disease biomarkers and a noncanonical class of therapeutic targets. Recently, synthetic circRNA have been engineered to explore their applications as a novel class of mRNA therapeutics and vaccines. In this review, we will discuss the current understanding of the biogenesis and physiological functions of natural circRNAs, the approaches to circRNA synthesis, and current research in the exploration of endogenous circRNAs as novel therapeutic targets and testing circRNAs as an emerging class of RNA therapeutics and vaccines.