Metal-organic Fragments Research Articles

Analysis of the structure and chemical bonding of C5H5ScB40: A density functional study

The existence of uneven hexagon and heptagon on the surface of the borospherene B40 cage allows its interaction with transition metal–organic fragments to form complexes. Based on density functional theory calculations, the sandwich complex C5H5ScB40 was studied. Results show that when the B7-heptagon of B40 sandwiched with Sc, the isomer had the lowest energy. Detailed structural characterization and bonding analyses for the lowest energy isomer Cs C5H5ScB40 (1) show that both non-covalent and covalent interactions were present between Sc and C5H5 and B40. B40 can act as an inorganic ligand to bond with transition metals, in which the boron atoms that deviate from the heptagon play an important role in the bonding. At the same time, the IR, Raman, and UV–vis absorption spectra of Cs C5H5ScB40 (1) were theoretically simulated, and the findings can provide some theoretical guidance for future experimental synthesis.

Bifunctional Sensors Based on Phosphomolybdates for Detection of Inorganic Hexavalent Chromium and Organic Tetracycline.

Exploring effective sensors for detecting possible hazards in a water system are greatly significant. This work proposed a strategy for stable and effective bifunctional sensors via incorporating hourglass-type phosphomolybdates into metal-organic fragments to construct a high-dimensional framework. Two hourglass-type phosphomolybdate-based electrochemical sensors toward heavy metal ion Cr(VI) and tetracycline (TC) detection were designed with the formula [CoII2(H2O)4NaI2][CoII(Hbpe)][NaI(bpe)1.5]{CoII[PV4MoV6O31H6]2}·9H2O (1) and [CoII(H2O)4NaI3][CoII(Hbpe)][CoII(bpe)]{CoII[PV4MoV6O31H6]2}·9H2O (2) [bpe = 1,2-di(4-pyridyl)ethylene]. Structural analysis showed that hybrids 1 and 2 possess three-dimensional POM-supported network features with favorable stability and exhibit reversible redox properties. Experiments found that this kind of hybrids as efficient sensors have excellent electrochemical performance toward Cr(VI) detection with high sensitivities of 0.111 μA·μM-1 for 1 and 0.141 μA·μM-1 for 2, fast response time of 1 s, and low detection limits of 30 nM for 1 and 27 nM for 2, which far meet the standard of WHO for drinking water. Moreover, hybrids 1-2 also exhibit fast responses to TC detection with sensitivities of 0.0073 and 0.022 μA·mM-1 and detection limits of 0.426 and 0.084 mM. This work offers a novel strategy for the purposeful design of efficient POM-based electrochemical sensors for accurate determination of contaminants in a practical water system.

Metal-Organic Fragments with Adhesive Excipient and Their Utilization to Stabilize Multimetallic Electrocatalysts for High Activity and Robust Durability in Oxygen Evolution Reaction.

Multimetallic electrocatalysts have shown great potential to improve electrocatalytic performance, but their deteriorations in activity and durability are yet to be overcome. Here, metal‐organic fragments with adhesive excipient to realize high activity with good durability in oxygen evolution reaction (OER) are developed. First, a leaf‐like zeolitic–imidazolate framework (ZIF‐L) is synthesized. Then, ionized species in hydrogen plasma attack preferentially the organic linkers of ZIF‐L to derive cobalt–imidazole fragments (CIFs) as adhesive excipient, while they are designed to retain the coordinated cobalt nodes. Moreover, the vacant coordination sites at cobalt nodes and the unbound nitrogen at organic linkers induce high porosity and conductivity. The CIFs serve to stably impregnate trimetallic FeNiMo electrocatalysts (CIF:FeNiMo), and CIF:FeNiMo containing Fe contents of 22% and hexavalent Mo contents show to enable high activity with low overpotentials (203 mV at 10 mA cm−2 and 238 mV at 100 mA cm−2) in OER. The near O K‐edge extended X‐ray absorption fine structure proves further that high activity for OER originates from the partially filled eg orbitals. Additionally, CIF:FeNiMo exhibit good durability, as demonstrated by high activity retention during at least 45 days in OER.

Polyoxometalates decorated with metal-organic moieties as new molecular photo- and electro-catalysts

Three new polyoxometalate-based organic-inorganic hybrid compounds (POIHCs), [Cu(PBI)2(H2O)][{Cu(PBI)(OH)(H2O)}{PW12O40}]·5H2O (1), [Cu(PBI)2(H2O)][{Cu(PBI)2(H2O)}{SiW12O40}]·4H2O (2) and [Cu4(HPO4)(PO4)(H2O)2(PBI)4][PMo12O40]·H2O (3) (PBI =2-(pyridin-2-yl)-1H-benzo[d]imidazole), have been synthesized under hydrothermal conditions. All three compounds were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. In 1 and 2, the Keggin-type polyoxometalate (POM) units are decorated by the {Cu/PBI} metal-organic fragments, together with additional {Cu/PBI} isolated cations, which further stack into 3-D supramolecular frameworks with porous structural features. Compound 3 consists of a rare cationic cluster [Cu4(HPO4)(PO4)(H2O)2(PBI)4]3+ and the Keggin-type POM anion, forming a 3-D supramolecular framework with limited interspaces for the entry of guest molecules. Comparable photocatalytic properties of 1–3 were investigated by the use of methylene blue (MB) and Rhodamine B (RhB) degradation under UV light. All compounds showed good catalytic activity for the degradation of MB in contrast to RhB. The possible catalytic mechanism was discussed based on the size of dye molecules, the low adsorption ability and crystal packing mode of the as-synthesized compounds. Additionally, the electrochemical properties of 1–3 have also been investigated, exhibiting good electrocatalytic performance for nitrite reduction.

Solvent-tuned polyoxometalate-based supramolecular hybrids constructed from different metal-organic motifs: Various structures and adsorption properties for dyes

By changing the solvents, three polyoxometalate (POM)-based supramolecular hybrids, [Co2L3][SiW12O40]·17H2O (1), [Co2L2(H2O)4][SiW12O40]·2EtOH·2H2O (2) and [Co2L3][SiW12O40]·9DMA·6H2O (3), have been synthesized under hydrothermal or solvothermal conditions. All three hybrids show various supramolecular structures, which contain two kinds of different metal-organic motifs. A kind of metal-organic cationic cage [Co2L3]4+ is formed in the presence of H2O for 1, DMA/H2O for 3, and a metal-organic cationic circle [Co2L2]4+ is constructed in the presence of EtOH/H2O for 2. That is to say, the solvents show a key role in tuning the architectures of metal-organic fragments and the final POM-based supramolecular structures. The adsorption properties of 1–3 for different organic dyes have also been investigated.

Two porous coordination polymers containing helix-based metal-organic nanotubes based on trigonal N-donor ligand

Two isostructural 3D porous metal-organic frameworks (MOFs), namely [Co2(Htpim)2(odpa)]·8H2O (1) and [Ni2(Htpim)2(odpa)]·8H2O (2) (Htpim=2,4,5-tri(4-pyridyl)-imidazole, odpa=4,4′-oxydiphthalate), were prepared and characterized by elemental analyses, single crystal X-ray diffraction, powder X-ray diffraction, IR spectra and thermal analyses. The 3D architectures of compounds 1 and 2 are built from 1D metal-organic nanotubes (MONTs) which connect with each other by bridging ligands, and every 1D MONT is generated by linking the vertexes of helical chain with metal-organic fragments. In addition, the magnetic properties of 1 and 2 have also been studied.

Four Polyoxonibate-Based Inorganic–Organic Hybrids Assembly from Bicapped Heteropolyoxonibate with Effective Antitumor Activity

Four novel heteropolyoxonibate-based inorganic–organic hybrids {Cu(en)2}6{GeNb12VIV2O42}·20H2O (1), {Cu(en)2}3K2Na4{GeNb12VIV2O42}·23H2O (2), {Cu(en)2}6{SiNb12VIV2O42}·18H2O (3), and {Cu(en)2}3K2Na4{SiNb12VIV2O42}·19H2O (4) (en = ethanediamine), composed of polyoxoanions [TNb12O40]16– (T = Si and Ge) and [Cu(en)2]2+ building blocks, were successfully synthesized under hydrothermal conditions by reaction of K7HNb6O19·13H2O, Cu(Ac)2·3H2O, Na2VO3, Na2SiO3, or GeO2 and en molecules. Polyoxoanion [TNb12VIV2O42]12– (T = Si and Ge) can be best described as a α-Keggin core [TNb12O40] with two [VO] units capping on its two “opened windows”. Compounds 1 and 3 are both composed of the bicapped heteropolyoxonibate core surrounded by a shell consisting of twelve [Cu(en)2]2+ groups, which represent a promising structural model toward core–shell nanostructures. Compounds 2 and 4 are also composed of a bicapped polyoxoanion [TNb12VIV2O42]12– (T = Si, Ge) decorated by three metal–organic fragments [Cu(en)2]2+, forming a trisupporting polyoxoanion {[Cu(en)2]3[TNb12O42VIV2]}6–. Antitumor, electrochemical study, and UV–vis spectra indicate that compounds 1–4 exhibit effective antitumor activity against SGC7901 cells and HepG2 cells and could keep the structural integrity in this process.

Ligands directed versatile cadmium-bis(triazole) metal–organic fragments to generate three new two dimensional complexes based on polymolybdenum phosphate

Three new two dimensional (2D) polymolybdenum phosphate-based cadmium complexes, [Cd2.5(btp)2(H2O)3][Cd0.5(PO4)(HPO4)3(MoO2)6(OH)3]·2H2O (1), [Cd(Hbtb)(H2O)]4[Cd(PO4)4(HPO4)4(MoO2)12(OH)6]·6H2O (2) and [Cd(H2O)2][Cd(H2O)(Hbth)]2[Cd0.5(H2O)(bth)]2[Cd(PO4)4(HPO4)2(H2PO4)2(MoO2)12(OH)6]·4H2O (3) (btp=1,3-bis(1,2,4-triazol-1-yl)propane, btb=1,4-bis(1,2,4-triazol-1-yl)butane and bth=1,6-bis(1,2,4-triazol-1-yl)hexane), have been synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. Single crystal X-ray diffraction analyses reveal that all the compounds are based on the polymolybdenum phosphate [P4Mo6O28(OH)3]9− ([P4Mo6]) units, which are further connected into sandwich-type [Cd(P4Mo6)2] dimers by cadmium ions, and different multi-nuclear CdII subunits. There exist penta-nuclear subunits in 1, which are further connected by btp ligands to form 1D chains; tetra-nuclear fragments in 2; and a 1D zigzag Cd–O–P chains based on tri-nuclear CdII units in 3, all of which are extended into different 2D networks by [Cd(P4Mo6)2] dimers. The –(CH2)n– spacers of the bis(triazole)-based ligands play an important role in the formation of multi-nuclear CdII subunits and the ultimate 3D supramolecular frameworks. Moreover, the thermal stabilities, electrochemical properties of the title compounds have been investigated in this paper.

Hydrothermal synthesis and structural characterization of a new inorganic–organic hybrid compound with photocatalytic activity based on Keggin-type polyanion and cadmium-1, 2, 4-triazolate units

Abstract A new inorganic–organic hybrid compound constructed from Keggin-type polyoxometalate and cadmium-organic units, namely, [Cd(Htrz)3]2[SiW12O40]·2H2O (1), [Htrz = 1-H-1,2,4-triazole], has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR, TG, and UV–vis absorption spectra. In compound 1, each [SiW12O40]4 − cluster is modified by six [Cd(Htrz)3]2 + metal–organic fragments, meanwhile, each [Cd(Htrz)3]2 + also connects with three [SiW12O40]4 − to built up a binodal (3,6)-connected 2D planar network with the (43)2(46·66·83)-kgd topology. Interestingly, [SiW12O40]4 − cluster exhibits a rare coordination mode acting as a hexadentate ligand, in which all of the six terminal oxygen atoms in the equatorial plane are synchronously participated in coordination. The diffuse reflectivity spectrum shows it can be regarded as a wide gap semiconductor. Moreover, the photocatalytic performance shows good photocatalytic activity for the degradation of Rhodamine B.

Self-assembly of a 2D helical coordination polymer from Keggin-type polyoxoanion and metal-organic fragment by in situ ligand transformation

A new two-dimensional (2D) polyoxometalate (POM)-based helical coordination polymer, [Cu3(μ2-OH)(pdon)3(pca)(H2O)3][SiW12O40]·6H2O (1) (pdon = 1,10-phenanthroline-5,6-dione, Hpca = pyridine-4-carboxlic acid), has been synthesized by in situ generation of pyridine-4-carboxlic acid and 1,10-phenanthroline-5,6-dione from 2-(4-pyridine)imidazo[4,5-f]1,10-phenanthroline under hydrothermal condition, and characterized by elemental analysis, IR spectra, TGA and single-crystal X-ray diffraction. In complex 1, each [SiW12O40]4− (SiW12) cluster connects with three trinuclear [Cu3(μ2-OH)(pdon)3(pca)(H2O)3]4+ metal-organic fragments, meanwhile, each metal-organic fragment also links with three SiW12 polyoxoanions to form two types of one dimensional (1D) helical chains. The adjacent 1D chains with different spiral orientations are connected by the terminal oxygen atom of SiW12 polyoxoanions, leading to the formation of a 2D layer network. Moreover, the photochemical catalysis and electrochemical properties of complex 1 are also reported.

Inorganic–organic hybrid compounds based on octamolybdates and metal–organic fragments with flexible multidentate ligand: syntheses, structures and characterization

Six polyoxometalate-based (POM) hybrid materials based on octamolybdate building blocks and metal-organic fragments with flexible multidentate ligand, namely [Cu(II)(2)(ttb)(2)(β-Mo(8)O(26))(H(2)O)(2)]·2H(2)O (1), Cu(I)(4)(ttb)(2)(β-Mo(8)O(26))(H(2)O) (2), [Cu(I)(4)(ttb)(3)(β-Mo(8)O(26))] (3), [Ni(2)(ttb)(2)(β-Mo(8)O(26))(H(2)O)(6)]·2H(2)O (4), [Zn(2)(ttb)(2)(α-Mo(8)O(26))(H(2)O)(2)] (5), and [Ag(4)(ttb)(2)(β-Mo(8)O(26))] (6), where ttb = 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethyl benzene, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, TGA, IR spectra, and electrochemistry. Compounds 1 and 2 exhibit three-dimensional (3D) 2-fold interpenetrating frameworks with (3,6)-connected (4(1)·6(2))(4(2)·6(10)·10(3)) and (3,4)-connected (6(2)·8(1))(2)(6(2)·8(4)) topologies, respectively. We are not aware of any other examples of interpenetrating (3,6)- and (3,4)-connected frameworks which involves the octamolybdates. Compound 3 shows a rare two-dimensional (2D) 2-fold interpenetrating network structure. In compound 4, a 3D supramolecular framework with the channels is constructed by the hydrogen-bonding interactions between (β-Mo(8)O(26))(4-) polyanions and the Ni-ttb double layers, in which the guest (β-Mo(8)O(26))(4-) anions are included. If ZnO interactions are considered, the structure of 5 is a 3D (3,4)-connected framework with (4·8(2))(4·8(2)·10(3)) topology. In 6, the ttb ligand as a tetradentate ligand links the Ag atoms to yield a 2D POM-based network. By careful inspection of the structures of 1-6, it can be seen that the ttb ligand, the metal ion and the coordination mode of the octamolybdate anion play important roles in the formation of the POM-based MOFs.

Keggin polyoxometalates-supported assembly of 2D supramolecular isomers: Synthesis, crystal structures and characteristics of two novel hybrid host–guest complexes

Two novel hybrid host–guest architectures based on metal-organic fragments and Keggin polyoxometalates, namely [α-Cu 12(trz) 8][PMo 12O 40] · H 2O ( 1) and [β-Cu 12(trz) 8][PMo 12O 40] · 2H 2O ( 2) (trz = 1,2,4-triazole), have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction (XRD), elemental analysis, powder XRD, ESR, FT-IR, UV–Vis, and thermogravimetric analysis (TGA). The [Cu 12(trz) 8] 4+ hosts in compounds 1 and 2 are two-dimensional (2D) supramolecular isomers, which present 4 4 topology based on Cu 4(trz) 4 cyclic units and 6 3 topology based on Cu 3(trz) 3 cyclic units, respectively. The metalmacrocyclic Cu 8(trz) 8 and Cu 9(trz) 9 rings represent the largest examples in the coordination chemistry of 1,2,4-triazole. 2D metal-organic fragments and Keggin anions both are connected via hydrogen bonds and Cu⋯O short contacts to form interesting 3D host–guest architectures of 1 and 2.

Sulfur-capped cyclodextrins: a new class of cavitands with extroverted as well as introverted donor functionalities

Ansa-cyclodextrins were obtained in high yields by reaction of sodium sulfide with A,B-di- or A,B,D,E-tetramesylated alpha-CD precursors; the resulting thiocavitands are suitable for forming nanotubular molecules, as well as for hosting metal-organic fragments.