Diverse Ligand-Functionalized Mixed-Valent Hexamanganese Sandwiched Silicotungstates with Single-Molecule Magnet Behavior

Three Double-Layered {Ni8}@{Bn}2 (n = 3, 4, 6) Cluster Sandwiched Polyoxometalates

The reaction of [A-α-GeW9O34]10- with Ni2+ in the presence of inorganic boron sources yielded three unprecedented sandwiched Ni-added polyoxometalates (NiAPs): K6Na7H7[({Ni8(μ6-O)(OH)2}@{B3O6(OH)3}2)@(B-α-GeW9O34)2]·16H2O (1), K4Na4H12[({Ni8(μ6-O)}@{B4O8(OH)3}2)@(B-α-GeW9O34)2]·16H2O (2), and K10Na6[({Ni8(μ6-O)}@ {B6O9(OH)5}2)@(B-α-GeW9O34)2]·12H2O (3). The common feature of 1-3 is that a rare double-layered {Ni8}@{Bn}2 (n = 3,4,6) cluster is inlaid in their sandwich belts. The {Ni8} cluster is composed of two cubane {Ni4} clusters by six bridging oxygen atoms and sharing a μ6-O atom. The numbers of boron atoms in the {Ni8}@{Bn}2 (n = 3,4,6) clusters of 1-3 are different, namely, {Ni8}@{B3}2, {Ni8}@{B4}2, and {Ni8}@{B6}2 clusters. To the best of our knowledge, such architectures containing a double-layered {Ni8}@{Bn}2 (n = 3,4,6) cluster in the sandwich belts are the first observed in POM chemistry. Furthermore, 2 was investigated as an efficient heterogeneous catalyst for the Knoevenagel condensation of various aldehydes with malononitrile at room temperature.

Tetra-aqua-(ethane-1,2-di-amine-κ2N,N')nickel(II) naphthalene-1,5-di-sulfonate dihydrate

The reaction of ethane-1,2-di-amine (en, C2H8N2), the sodium salt of naphthalene-1,5-di-sulfonic acid (H2NDS, C10H8O6S2), and nickel sulfate in an aqueous solution resulted in the formation of the title salt, [Ni(C2H8N2)(H2O)4](C10H6O6S2)·2H2O or [Ni(en)(H2O)4](NDS)·2H2O. In the asymmetric unit, one half of an [Ni(en)(H2O)4]2+ cation and one half of an NDS2- anion, and one water mol-ecule of crystallization are present. The Ni2+ cation in the complex is positioned on a twofold rotation axis and exhibits a slight tetra-gonal distortion of the cis-NiO4N2 octa-hedron, with an Ni-N bond length of 2.0782 (16) Å, and Ni-O bond lengths of 2.1170 (13) Å and 2.0648 (14) Å. The anion is completed by inversion symmetry. In the extended structure, the cations, anions, and non-coordinating water mol-ecules are connected by inter-molecular N-H⋯O and O-H⋯O hydrogen bonding, as well as C-H⋯π inter-actions, forming a three-dimensional network.

A {Co9}-Added Polyoxometalate for Efficient Visible-Light-Driven Hydrogen Evolution

A polyanion cluster H₆Na₈Cs₃[Co₉(μ₃-OH)₃(H₂O)₆(HPO₄)₂(B-α-PW₉O₃₄)₃]Cl·40H₂O (1) was made with the guidance of the lacunary directing strategy under hydrothermal conditions. Compound 1 was characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and thermogravimetric analysis, respectively. Single-crystal X-ray diffraction analyses showed that 1 consists of three anions [B-α-PW₉O₃₄]^9- and a cyclic cationic [Co₉(μ₃-OH)₃(H₂O)₆]¹⁵⁺ and two anions HPO₄^2-. Variable-magnetic properties indicate antiferromagnetic interactions in 1. Visible-light-driven hydrogen evolution tests demonstrated that 1 was an efficient water reduction catalyst with an H₂ evolution rate of 1217.6 μmol h^-1 g^-1.

Roles of Organic Fragments in Redirecting Crystal/Molecular Structures of Inorganic-Organic Hybrids Based on Lacunary Keggin-Type Polyoxometalates

Lacunary polyoxometalates (LPOMs) are key precursors for the synthesis of functional POMs. To date, reviews dedicated to behavioral studies of LPOMs often comprise the role of metal ions, including transition metal (TM) and rare earth (RE) ions, in extending and stability of high-nuclearity clusters. In contrast, the role of organic ligands in the structures and properties of lacunary-based hybrids has remained less explored. In this review, we focus on the role of organic fragments in the self-assembling process of POM-based architectures and discuss relationships between the nature and structure of organic ligand and properties such as the topology of hybrid inorganic–organic material in RE and TM-RE heterometallic derivatives of lacunary Keggin-type POMs. The effects of organic fragment in mixed ligand hybrids are also briefly reviewed.

Core-Shell Structured Layered Lanthanide-Organic Complexes with Stilbazolium-type Dye Encapsulation for Multifunctional Performances

Host-guest encapsulation of functional organic dye into a porous metal-organic framework can give rise to the development of new functional materials. In this work, by intercalating the stilbazolium-type dye (DEAST)I (4'-diethylamino-N-methyl stilbazolium) into four lanthanide layered metal-organic complexes (Ln-LMOCs), i. e. {[Ln(BTB)(H₂ O)₂ ]⋅3(DMF)⋅2(H₂ O)}_n (Ln=La (1), Nd (2), Sm (3), Er (4)), four responsive (DEAST)I@Ln-LMOC composites have been prepared, serving as multifunctional performance platform. The core-shell structures of (DEAST)I@Ln-LMOC composites have been fully characterized by IR, UV/Vis, PXRD, SEM, TEM, TGA and ESR. Significantly, after intercalation of dyes, the (DEAST)I@Ln-LMOC composites exhibit enhanced luminescent sensing properties in detecting Fe³⁺ with much higher water stabilities. The luminescent sensing behavior stems from the fluorescence resonance energy transfer (FRET) from the π-electron-rich BTB ligands to the Fe³⁺ , and their higher water stabilities are induced by electrostatic interactions and lower porosity. Specially, the characteristic emissions of Sm³⁺ will not be affected after the encapsulation guest dyes, which provide a theoretical guide for the modulation of luminescence devices. Finally, better ion conductivities and diminished photocurrents can be achieved after the embedding of the functional organic dye. In all, the formation of (DEAST)I@Ln-LMOC composites with core-shell structures can be utilized as a multifunctional platform with good stability.

Two new hexa-Ni-substituted polyoxometalates in the form of an isolated cluster and 1-D chain: syntheses, structures, and properties

Two new hexa-Ni-substituted polyoxometalates are made and characterized, exhibiting electrochemical performance and photocatalytic activity for the degradation of organic dyes under UV irradiation.

A new octa-Mn-substituted poly(polyoxotungstate)

A novel octa-Mn-substituted silicotungstate (ST) tetramer [H₂N(CH₃)₂]₈H₁₉Na₄{[K(H₂O)₄WO₄] [SiMnII2W₁₀O₃₈]₃}[SiMnIII2W₁₀O₃₈]·27H₂O (1) was prepared, and its electrochemistry, thermal stability and magnetic properties were investigated.

Two mononuclear dysprosium(iii) complexes with their slow magnetic relaxation behaviors tuned by coordination geometry

We report here two field-induced single-ion magnets of Dy(iii), which present octahedral and pentagonal–bipyramidal coordination geometries, respectively, with their magnetic performances tuned by the coordination geometries of Dy(iii).

Three Dy(iii) single-ion magnets bearing the tropolone ligand: structure, magnetic properties and theoretical elucidation

Three Dy(iii) SIMs bearing the tropolone ligand are reported here with the tuning effect on their performances by ancillary ligands revealed via experimental magnetic investigations and theoretical calculations.

Bis[(4-chlorophenoxy)acetato-κO](ethylenediamine-κ2 N,N′)zinc

The mononuclear title complex, [Zn(C8H6ClO3)2(C2H8N2)], was obtained by the reaction of zinc(II) acetate dihydrate with p-chlorophenoxyacetic acid (pCPA) and ethylenediamine (EDA) in a water/ethanol mixture. The ZnII cation has a distorted tetrahedral coordination sphere involving two carboxylate O atoms of two monodentate pCPA ligands and two N atoms of one chelating EDA ligand. The pCPA ligands coordinate asymmetrically to the ZnII cation with two different Zn—O distances of 1.967 (3) and 1.978 (3) Å. In the crystal, molecules are linked by N—H...O hydrogen bonds, forming chains propagating parallel to [100]. These chains are linked by C—H...O hydrogen bonds, C—H...π stacking and Cl...Cl interactions, generating a three-dimensional supramolecular network.

A Series of Weakley-type Polyoxomolybdates: Synthesis, Characterization, and Magnetic Properties by a Combined Experimental and Theoretical Approach

Using DCC as the dehydrating agent, a series of Weakley-type polyoxomolybdates [Bu₄N]₃{Ln[Mo₅O₁₃(OMe)₄(NO)]₂} (Ln = Tb, Dy, Ho, Er) were synthesized in a one-pot reaction and structurally characterized by elemental, IR, UV-vis analysis, PXRD, and single-crystal X-ray diffraction. Furthermore, the static and dynamic measurements were utilized to investigate their magnetic performances. Typically, slow relaxation of magnetization was observed for Dy analogues with an energy barrier for the reversal of the magnetization of 50 K, which is the highest barrier height observed on the polyoxomolybdates-based single-molecule magnets (SMMs). For a deep understanding of the appearance of the SMM behavior on Weakley-type polyoxomolybdates series, ab initio calculations on {Dy[Mo₅O₁₃(OMe)₄(NO)]₂}^3- have been conducted.

Probing Frontier Orbital Energies of {Co9(P2W15)3} Polyoxometalate Clusters at Molecule-Metal and Molecule-Water Interfaces

Functionalization of polyoxotungstates with organoarsonate coligands enabling surface decoration was explored for the triangular cluster architectures of the composition [CoII9(H2O)6(OH)3(p-RC6H4AsVO3)2(α-PV2WVI15O56)3]25- ({Co9(P2W15)3}, R = H or NH2), isolated as Na25[Co9(OH)3(H2O)6(C6H5AsO3)2(P2W15O56)3]·86H2O (Na-1; triclinic, P1̅, a = 25.8088(3) Å, b = 25.8336(3) Å, c = 27.1598(3) Å, α = 78.1282(11)°, β = 61.7276(14)°, γ = 60.6220(14)°, V = 13888.9(3) Å3, Z = 2) and Na25[Co9(OH)3(H2O)6(H2NC6H4AsO3)2(P2W15O56)3]·86H2O (Na-2; triclinic, P1̅, a = 14.2262(2) Å, b = 24.8597(4) Å, c = 37.9388(4) Å, α = 81.9672(10)°, β = 87.8161(10)°, γ = 76.5409(12)°, V = 12920.6(3) Å3, Z = 2). The axially oriented para-aminophenyl groups in 2 facilitate the formation of self-assembled monolayers on gold surfaces and thus provide a viable molecular platform for charge transport studies of magnetically functionalized polyoxometalates. The title systems were isolated and characterized in the solid state, in aqueous solutions, and on metal surfaces. Using conducting tip atomic force microscopy, the energies of {Co9(P2W15)3} frontier molecular orbitals in the surface-bound state were found to directly correlate with cyclic voltammetry data in aqueous solution.