Synthesis and crystal structures of two new uranyl coordination compounds obtained in aqueous solutions of 1-butyl-2,3-dimethylimidazolium chloride

<p>Two new uranyl coordination compounds, [C₉H₁₇N₂]₃[(UO₂)₂(CrO₄)₂Cl₂(H₂O)₂]Cl·5H₂O (<b>1</b>) and (C₉H₁₇N₂)[(UO₂)(C₂O₄)Cl] (<b>2</b>), have been synthesized by adding potassium dichromate (K₂Cr₂O₇) or oxalic acid dihydrate (H₂C₂O₄·2H₂O) solution into an aqueous solution of uranyl nitrate and 1-butyl-2,3-dimethylimidazolium chloride [Bmmim]Cl. [Bmmim]Cl provides the charge balance and Cl ions that coordinate with uranyl ions. The fundamental building units of <b>1</b> and <b>2</b> are UO₆Cl pentagonal bipyramidal structures. Compound <b>1</b> exhibits a graphene-like structure with a system molar ratio of 1:1 for U:Cr and crystallizes in the orthorhombic space group Pbca, with <i>a</i> = 25.644(3) Å, <i>b</i> = 12.996(14) Å and <i>c</i> = 29.198(4) Å. 16-Membered rings are formed by CrO₄²⁻ and UO₂²⁺ in the crystal structure of <b>1</b>. Compound <b>2</b> crystallizes in monoclinic space group P2₁/n, with <i>a</i> = 10.759(3) Å, <i>b</i> = 11.395(3) Å, <i>c</i> = 14.149(4) Å, <i>β</i> = 102.962(9)° and shows one-dimensional (1D) serrated chains. Within the crystal structures of <b>1</b> and <b>2</b>, C–H_[Bmmim]Cl⋯O hydrogen bonds are identified. O–H_water⋯Cl hydrogen bonds are also detected in the crystal structure for <b>1</b>.</p

Ionic Strength and pH Responsive Permeability of Soy Glycinin Microcapsules

Recently, hollow protein microcapsules have been made simply by heating the microphase separated soy glycinin microdomains. However, the properties (e.g., mechanical properties and permeability) that relate to the application of these microcapsules are unknown. In this study, the permeability of the soy glycinin microcapsules was investigated by confocal laser scanning microscopy (CLSM), as influenced by ionic strength and pH using fluorescein isothiocyanate-dextran (FITC-dextran). The glycinin microcapsules kept the integrity between pH 1 and 11.5, swelled when pH was below 3 or above pH 11, dissociated at pH above 11.5 and deswelled slightly at pH 1. When the pH increased above 11, the permeability of the microcapsule significantly increased. Remarkably, when the pH was below the isoelectric point of glycinin (≈pH 5), FITC-dextran spontaneously accumulated inside the microcapsule with a significantly higher concentration than that in bulk solution, as evidenced by the strong intensity increase of fluorescence. This unique feature significantly increased the loading amount of FITC-dextran. The permeability of microcapsules was also increased by adding salt but less significant than by adjusting pH. The surface of the microcapsules became coarser when the permeability increased, which was revealed by scanning electron microscopy. These results show that soy glycinin has a great potential to be used as a wall material to fabricate hollow microcapsules that could find applications in biomedicine and food industry

Uranyl-containing heterometallic coordination polymers based on 4-(4’-carboxyphenyl)-1,2,4-triazole ligand: structure regulation through subtle changes of the secondary metal centers

<p>Three uranyl-containing coordination polymers, Cd(UO₂)₂(cpt)₄(bdc)(H₂O)₂ (<b>1</b>), Zn(UO₂)₂(cpt)₄(bdc)(H₂O)₂ (<b>2</b>) and UO₂(OH)(cpt) (<b>3</b>) (Hcpt =4-(4’-carboxyphenyl)-1,2,4triazole, H₂bdc =1,4-benzenedicarboxylic acid), have been synthesized under hydrothermal conditions by employing a bifunctional ligand (Hcpt) with both O-donors and N-donors. Compound <b>1</b> represents a 3-D framework with the point symbol of (6²·8⁴)(6²·8)₂ by the intersection of two sets of 1-D [Cd₂(UO₂)₂(cpt)₄(bdc)]_n loop chains extended along different directions. Compound <b>2</b> exhibits a 2-nodal (3,4)-connected 2-D network with the point symbol (4·6²)₂(4²·6²·8²). Compound <b>3</b> shows a 2-D network by the assembly of uranyl dimers and the cpt^- anions. Although <b>1</b> and <b>2</b> have similar chemical formulas and the same coordination modes of ligands and metal centers, they possess totally different molecular frameworks, derived from the different radii of the secondary metal centers, Cd(II) and Zn(II). In addition, the optimal synthesis condition, thermal stability, luminescent properties, and IR spectra of <b>1</b> and <b>2</b> were also investigated.</p

Copper/Zinc-Directed Heterometallic Uranyl-Organic Polycatenating Frameworks: Synthesis, Characterization, and Anion-Dependent Structural Regulation

By employing a multidentate ligand, 2,2′-bipyridine-5,5′-dicarboxylic acid (H₂bpdc), with both O-donors and N-donors, five uranyl-Cu­(II)/Zn­(II) heterometallic coordination polymers, (UO₂)­Cu­(μ₄-bpdc)­(μ₃-bpdc) (<b>1-Cu</b>), (UO₂)­Zn­(μ₄-bpdc)­(μ₃-bpdc) (<b>1′-Zn</b>), (UO₂)­CuCl­(μ₃-bpdc)­(μ₂-Hbpdc)­(H₂O) (<b>2-Cu</b>), (UO₂)₂Cu₂Cl₂­(μ₃-bpdc)₂­(μ₂-Hbpdc)₂­(H₂O)₃·2H₂O (<b>2-Cu′</b>), and (UO₂)₂Zn­(μ₃-SO₄)­(μ₄-bpdc)­(μ₃-bpdc)­(H₂O)₃ (<b>3-Zn</b>), were prepared under hydrothermal conditions. Thermal stability and luminescent properties of <b>1-Cu</b>, <b>1′-Zn</b>, <b>2-Cu</b>, and <b>3-Zn</b> were also investigated. Isostructural compounds <b>1-Cu</b> and <b>1′-Zn</b> both have a three-dimensional (3D) framework built by polycatenating of two sets of paralleling two-dimensional (2D) grids with octahedral transition metal cations (Cu or Zn) as the cross-linking nodes. As far as we know, compounds <b>1-Cu</b> and <b>1′-Zn</b> are the first two cases that possess polycatenated networks in heterometallic uranyl-organic coordination polymers. Compound <b>2-Cu</b> contains 3-fold interpenetrated 2D networks which are built by the connection of [(UO₂)₂(bpdc)₂­(Hbpdc)₂]^2– secondary building units and Cu­(II). A one-dimensional tilted ladder-like structure in <b>2-Cu′</b> is constructed by uranyl-bpdc chains connected by Cu­(II) and Hbpdc^–. Compound <b>3-Zn</b> displays a layered-like 2D network contain an unusual [(UO₂)₂Zn­(μ₃<i>-</i>SO₄)] unit. Interestingly, different anions could lead to the change of coordination sites of transition metal cations, resulting in structural diversity of heterometallic uranyl-organic frameworks

Bimetallic Uranyl Organic Frameworks Supported by Transition-Metal-Ion-Based Metalloligand Motifs: Synthesis, Structure Diversity, and Luminescence Properties

A bifunctional ligand, 2,2′-bipyridine-4,4′-dicarboxylic acid (H₂bpdc), has been used in the investigation of constructing bimetallic uranyl organic frameworks (UOFs). Seven novel uranyl–transition metal bimetallic coordination polymers, [(UO₂)­Zn­(bpdc)₂]_<i>n</i> (<b>1</b>), [Cd­(UO₂)­(bpdc)₂(H₂O)₂·2H₂O]_<i>n</i> (<b>2</b>), [Cu­(UO₂)­(bpdc)­(SO₄)­(H₂O)₃·2H₂O]_<i>n</i> (<b>3</b>), [CuCl­(UO₂)­(bpdc)­(Hbpdc)­(H₂O)₂·H₂O]_<i>n</i> (<b>4</b>), [Cu­(UO₂)­(bpdc)₂(H₂O)]_<i>n</i> (<b>5</b>), [Co₂(UO₂)₃(bpdc)₆]_<i>n</i> (<b>6</b>), and [Co₃(UO₂)₄(bpdc)₈(Hbpdc)­(H₂O)₂]_<i>n</i> (<b>7</b>), have been successfully constructed through the assembly of various transition-metal salts, uranyl ions, and H₂bpdc ligands under hydrothermal conditions. UOFs <b>1</b>, <b>5</b>, <b>6</b>, and <b>7</b> adopt three-dimensional (3D) frameworks with different architectures; UOFs <b>2</b> and <b>3</b> exhibit two-dimensional (2D) wavelike and stairlike layers, respectively, while UOF <b>4</b> is a one-dimensional (1D) chain assembly. These UOFs include a wide range of dimensionalities (1D–3D), interpenetrated frameworks, and cation–cation interaction species, suggesting that anion-dependent structure regulation based on the metalloligand [M­(bpdc)_<i>m</i>]^<i>n</i>− motifs, the coordination modes of the metal centers and bpdc^2– ligands, along with the reaction temperature, has a remarkable influence on the formation of bimetallic UOFs, which could be a representative system for the structural modulation of UOFs with various dimensionalities and structures. Furthermore, the thermal stability and luminescent properties of compounds <b>1</b>, <b>3</b>, and <b>6</b> are also investigated

Mixed-Ligand Uranyl Polyrotaxanes Incorporating a Sulfate/Oxalate Coligand: Achieving Structural Diversity via pH-Dependent Competitive Effect

A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on <b>C6BPCA</b>@CB6 (<b>C6BPCA</b> = 1,1′-(hexane-1,6-diyl)­bis­(4-(carbonyl)­pyridin-1-ium), CB6 = cucurbit[6]­uril) ligand, <b>UPS1</b> (UO₂(<b>L</b>)_0.5(SO₄)­(H₂O)·2H₂O, <b>L</b> = <b>C6BPCA</b>@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl polyrotaxane sheet structure of <b>UPS1</b> is based on uranyl-sulfate ribbons connected by the <b>C6BPCA</b>@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl polyrotaxane compounds, <b>UPO1</b>–<b>UPO4</b>, have been acquired by tuning reaction pH and ligand concentration: <b>UPO1</b> (UO₂(<b>L</b>)_0.5(C₂O₄)_0.5(NO₃)·3H₂O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) and <b>UPO2</b> (UO₂(<b>L</b>)­(C₂O₄)­(H₂O)·7H₂O)­obtained at a higher pH value range (4.31–7.21). By lowering the amount of oxalate, another two uranyl polyrotaxane network <b>UPO3</b> ((UO₂)₂(<b>L</b>)_0.5(C₂O₄)₂(H₂O)) and <b>UPO4</b> ((UO₂)₂O­(OH)­(<b>L</b>)_0.5(C₂O₄)_0.5(H₂O)) could be acquired at a low pH value of 1.98 and a higher pH value over 6, respectively. The <b>UPO1</b>–<b>UPO4</b> compounds, which display structural diversity via pH-dependent competitive effect of oxalate, represent the first series of mixed-ligand uranyl polyrotaxanes with organic ligand as the coligand. Moreover, the self-assembly process and its internal mechanism concerning pH-dependent competitive effect and other related factors such as concentration of the reagents and coordination behaviors of the coligands were discussed in detail

Silver Ion-Mediated Heterometallic Three-Fold Interpenetrating Uranyl–Organic Framework

A unique case of a uranyl-silver heterometallic 3-fold interpenetrating network (U-Ag-2,6-DCPCA) from a multifunctionalized organic ligand, 2,6-dichloroisonicotinic acid, in the presence of uranyl and silver ions is reported. It is the first report of a heterometallic uranyl–organic interpenetrating network or framework. Notably, a (4,4)-connected uranyl building unit in U-Ag-2,6-DCPCA, which is available through combined influences of structural halogenation and silver ion additive on uranyl coordination, plays a vital role in the formation of a 3-fold interpenetrating network. Halogen substitution effectively changes structural features and coordination behaviors of isonicotinate ligand and contributes to the control of uranyl coordination. Meanwhile, it exerts influence on the stabilization of 3-fold interpenetrating networks by halogen–halogen interactions. Theoretical calculation suggests that the silver ion should mainly serve as an inductive factor of uranyl species through strong Ag–N binding affinity, directly leading to the formation of a (4,4)-connected uranyl building unit and finally a heterometallic 3-fold interpenetrating network. Related experimental results, especially an interesting postsynthetic metalation, afford further evidence of this induction effect

Stepwise ortho Chlorination of Carboxyl Groups for Promoting Structure Variance of Heterometallic Uranyl–Silver Coordination Polymers of Isonicotinate

We report the syntheses and characterization of four new heterometallic uranyl–silver compounds from isonicotinic acid derivatives with a stepwise ortho chlorination of carboxyl group, that is, isonicotinic acid (H-<b>PCA</b>), 3-chloroisonicotinic acid (H-3-<b>MCPCA</b>), and 3,5-dichloroisonicotinic acid (H-3,5-<b>DCPCA</b>). Compound <b>1</b>, (UO₂)­Ag₄­(3,5-<b>DCPCA</b>)₆­(3,5-<b>DCPy</b>)₂, from H-3,5-<b>DCPCA</b> displays a heterometallic three-dimensional (3D) framework through the connection of 3,5-DCPCA and in situ-formed 3,5-dichloropyridine (3,5-<b>DCPy</b>) with the aid of multiple argentophilic interactions. Compounds <b>2</b> ((UO₂)­Ag­(3-<b>MCPCA</b>)₃) and <b>3</b> ((UO₂)­Ag₂­(3-<b>MCPCA</b>)₄), which differ from each other in coordination modes of uranyl center, are both heterometallic 3D reticular frameworks from 3-<b>MCPCA</b> based on highly coordinated silver nodes. All these heterometallic uranyl–silver compounds are different from the hydrothermal products from chlorine-free H-<b>PCA</b> ligand in the presence of uranyl and silver ions, U–Ag-<b>PCA</b> ((UO₂Ag­(OH)­(<b>PCA</b>)₂)) and <b>4</b> ((UO₂)­Ag₂­(OH)­(H₂O)₂(<b>PCA</b>)₄) due to highly coordinated silver ions found in <b>1</b>–<b>3</b>, among which carboxyl groups of isonicotinate expected to coordinate with uranyl are the biggest contributors. Detailed structural analysis reveals that the inclination of the carboxyl group of isonicotinate driven by large steric hindrance from bulky ortho chlorine atoms at its ortho positions enables it to participate in the coordination sphere of silver ion and promote the formation and structure variance of 3D heterometallic uranyl–silver frameworks

Automated Modular Synthesis of Aptamer–Drug Conjugates for Targeted Drug Delivery

Aptamer–drug conjugates (ApDCs) are promising targeted drug delivery systems for reducing toxicity while increasing the efficacy of chemotherapy. However, current ApDC technologies suffer from problems caused by the complicated preparation and low controllability of drug–aptamer conjugation. To solve such problems, we have designed and synthesized a therapeutic module for solid phase synthesis, which is a phosphoramdite containing an anticancer drug moiety and a photocleavable linker. Using this module, we have realized automated and modular synthesis of ApDCs, and multiple drugs were efficiently incorporated into ApDCs at predesigned positions. The ApDCs not only recognize target cancer cells specifically, but also release drugs in a photocontrollable manner. We demonstrated the potential of automated and modular ApDC technology for applications in targeted cancer therapy

Large-Pore Layered Networks, Polycatenated Frameworks, and Three-Dimensional Frameworks of Uranyl Tri(biphenyl)amine/Tri(phenyl)amine Tricarboxylate: Solvent-/Ligand-Dependent Dual Regulation

In this work, we present the syntheses of four novel uranyl complexes of tri­(biphenyl)­amine tricarboxylate (<b>L1</b>) or triphenylamine tricarboxylate (<b>L2</b>), <b>1</b>–<b>4</b>, with layered networks or three-dimensional (3D) frameworks through solvothermal/hydrothermal reactions. Using dimethylformamide (DMF) as the solvent, compound <b>1</b> ([NH₂(CH₃)₂]­[UO₂(<b>L1</b>)]­·3DMF) and <b>3</b> ([NH₂(CH₃)₂]­[UO₂(<b>L2</b>)]­·DMF) give nearly identical (6,3)-connected large-pore layered networks in spite of the slight difference in packing mode (“ABC-ABC” pattern in <b>1</b> vs “AB-AB” pattern in <b>3</b>). When mixed DMF/water solvents were used, compound <b>2</b> ([NH₂(CH₃)₂]₂­[UO₂(<b>L1</b>)]₂­(NO₃)₂­·H₂O) with a two-dimensional (2D) + 2D → three-dimensional (3D) polycatenasted framework and compound <b>4</b> ([NH₂(CH₃)₂]­[UO₂(<b>L2</b>)]­·2H₂O) with a (10,3)-connected 2-fold interpenetrating 3D framework were achieved from H₃<b>L1</b> and H₃<b>L2</b>, respectively, which might be attributed to the induction of water molecules with strong hydrogen-bonding capacity. Most remarkably, the difference between a 2D + 2D → 3D polycatenated framework and (10,3)-connected 2-fold interpenetrating 3D framework demonstrates the vital role of conformation flexibility of ligand on the final structure of uranyl compounds, which should be related to the increased amount of phenyl groups of the <b>L1</b> ligand endowing its molecular skeleton more freedom and adjusting molecular conformation more easily. Their physicochemical properties were also studied by powder X-ray diffraction, thermogravimetric analysis, IR spectroscopy, and luminescence spectroscopy