Polyoxometalate-Incorporated Metal-Organic Network as a Heterogeneous Catalyst for Selective Oxidation of Aryl Alkenes

Selective oxidation of aryl alkenes is important for chemical synthesis reactions, in which the key lies in the rational design of efficient catalysts. Herein, four polyoxometalate (POM)-incorporated metal-organic networks, with the formulas of [Co(ttb)(H₂O)₃]₂[SiMo₁₂O₄₀]·2H₂O (1), [Co(ttb)(H₂O)₂]₂[SiW₁₂O₄₀]·8H₂O (2), [Zn(Httb)(H₂ttb)][BW₁₂O₄₀]·9H₂O (3) and {[Zn(H₂O)₃(ttb)]₄[Zn₃(H₂O)₆]}[H₃SiW_10.5Zn_1.5O₄₀]₂·24H₂O (4) (ttb = 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene), were hydrothermally synthesized and structurally characterized. Structural analysis showed that compound 1 consists of a POM-encapsulated three-dimensional (3-D) supramolecular framework; compound 2 is composed of a POM-supported 3-D coordination network; and compounds 3-4 show POM-incorporated 3-D supramolecular networks. Using selective catalytic oxidation of styrene as the model reaction, compounds 1-4 as heterogeneous catalysts display excellent performance with the double advantages of high styrene conversion and benzaldehyde selectivity owing to the synergistic effect among POM anions and transition metal (TM) centers. Among them, compound 1 exhibits the highest performance with ca. 96% styrene conversion and ca. 99% benzaldehyde selectivity in 3 h. In addition, compound 1 also displays excellent substrate compatibility, good reusability, and structural stability. Thus, a plausible reaction pathway for the selective oxidation of styrene is proposed. This study on the structure-function relationship paves a way for the rational design of POM-based heterogeneous catalysts for important catalysis applications.

Various amide derivatives induced Keggin-type SiW12O404−-based cobalt complexes: assembly, structure, electrochemical sensing and dye adsorption properties

Three new [SiW12O40]4−-based complexes assembled from three amide derivative ligands displayed excellent electrochemical sensing activities for BrO3−, NO2− and Cr(vi) ions and showed good adsorption capacities for methylene blue and neutral red dyes.

Various amide-derived ligands induced five octamolybdate-based metal–organic complexes: synthesis, structure, electrochemical sensing and photocatalytic properties

Five octamolybdate-based complexes with diverse architectures employing three new amide-derived organic ligands can be used as promising electrochemical sensors and photocatalysts.

Four octamolybdate complexes constructed from a quinoline–imidazole–monoamide ligand: structures and electrochemical, photocatalytic and magnetic properties

Four octamolybdate-based complexes synthesized by employing N-(quinoline-5-yl)-1H-imidazole-4-carboxamide as a ligand exhibit excellent electrocatalytic activities, photocatalytic properties and antiferromagnetic behavior.

Hydrogen bonding assisted formation of sandwich-type titanium-containing heteropolymolybdates: water-soluble and photoelectroactive

Two water-soluble titanium-containing polyoxomolybdates have been synthesized by means of a hydrogen bonding assisted strategy. Their applications in the photoelectrochemical sensing of bisphenol A in aqueous solution were also investigated.

Synthesis, characterization and bioactivities of a new covalent copper(II) compound derived from {P2Mo5O23}6- and thiosemicarbazones

In this article, a new compound H₂[{Cu(HL)(H₂O)}₂(P₂Mo₅O₂₃)]·5H₂O (1) (HL = 2-acetylpyrazine thiosemicarbazone) has been synthesized and structurally characterized by single-crystal X-ray diffraction of and other detection techniques. Interestingly, the structure of 1 is different from many reported copper-based complexes, in which the [P₂Mo₅O₂₃]^6-, two Cu²⁺ ions and two HL were directly connected by covalent bands. Biological studies demonstrated that 1 indicated moderate antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and a better cytotoxicity against human hepatic cancer line (SMMC-7721) than Mitoxantrone (Mito), the current clinical anticancer drug. Besides, the antibacterial mechanisms of 1 have been studied by the membrane integrity disruption, the destructive reactive oxygen species generation (ROS), the glutathione (GSH) depletion and the depressed enzymatic activity of respiratory chain dehydrogenases (RCD). These results revealed that the combination of HL, Cu²⁺, [P₂Mo₅O₂₃]^6- shows a higher antibacterial and cytotoxic activity.

A series of new polyoxometalate-based metal-organic complexes with different rigid pyridyl-bis(triazole) ligands: assembly, structures and electrochemical properties

Five new polyoxometalate (POM)-based metal-organic complexes (MOCs) with different rigid pyridyl-bis(triazole) ligands, namely, H{Co2(Hpyttz-I)2(H2O)6[CrMo6(OH)6O18]}·8H2O (1), {Co2(H2pyttz-I)2(H2O)4[TeMo6O24]}[Co(H2O)6]·3H2O (2), {Co3(Hpyttz-II)2(H2O)6[γ-Mo8O26]}·10H2O (3), {Ni3(Hpyttz-II)2(H2O)6[γ-Mo8O26]}·10H2O (4), {Ni3(Hpyttz-III)2(H2O)8[γ-Mo8O26]}·10H2O (5) (H2pyttz-I = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H2pyttz-II = 3-(pyrid-3-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H2pyttz -III = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), were successfully synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 is a two-dimensional (2D) supramolecular network based on the binuclear complex unit: [Co2(Hpyttz-I)2(H2O)6 [CrMo6(OH)6O18]]. Complex 2 is a 1D supramolecular chain derived from the binuclear cobalt complex: {Co2(H2pyttz-I)2(H2O)4[TeMo6O24]}2-, the discrete [Co(H2O)6]2+ units act as counter cations. Complexes 3 and 4 are isostructural with different center metals (M = Co or Ni), the adjacent γ-Mo8O26 4- anions are linked by the MII ions to form a 1D M-γ-Mo8O26 inorganic chain. Then 1D M-γ-Mo8O26 inorganic chains are linked together by the 1D metal-organic M-(Hpyttz-II) chains to form a 3D framework. In complex 5, γ-Mo8O26 4- anions are bridged by the NiII ions to give a 1D Ni-γ-Mo8O26 inorganic chain, the adjacent 1D Ni-γ-Mo8O26 chains are connected through [Ni(Hpyttz-III)2] units to form a 2D layer. The effect of POM type and coordination site of the ligands on the structures of the title complexes were discussed. The title complexes 1, 2 and 5 exhibit excellent bifunctional electrocatalytic activities toward the reduction of bromate/hydrogen peroxide and the oxidation of ascorbic acid. In addition, the redox potentials of complexes 1, 2 and 5 are highly sensitive to pH and may be used as a kind of potential pH sensor.

The crystal structure of poly[tetraaqua-tris(μ2-2,6-di(1H-imidazol-1-yl)naphthalene-κ2 N:N′)-bis(thiophene-2,5-dicarboxylato-κ1 O)]dicobalt(II), C30H24CoN6O6S

C30H24CoN6O6S, monoclinic, P21/c (no. 14), a = 11.892(6) Å, b = 11.206(6) Å, c = 20.694(11) Å, β = 93.558(13)°, V = 2752(3) Å3, Z = 4, R gt(F) = 0.0413, wR ref(F 2) = 0.1030, T = 293(2) K.

Synthesis, X-ray crystallography, thermogravimetric analysis and spectroscopic characterization of isostructural one-dimensional coordination polymers as sorbents for some anions

A new series of coordination polymers capable of adsorbing anions have been synthesized by employing a dipyridine substituted diazacrown macrocycle as linker.

Novel polyoxometalate-based cobalt complexes based on rigid pyridyl-triazole-tetrazole and pyridyl-bis(triazole) ligands

Three novel polyoxometalate (POM)-based cobalt complexes have been synthesized and structurally characterized. The adsorption activities for organic dyes and electrochemical properties have been studied in detail.

Crystal structure of bis(μ 3-2,2′-azanediylbis(ethan-1-olato)-κ5 O:O,N,O′:O′)-tetrachlorido-bis(μ 2-2-((2-hydroxyethyl)amino)ethan-1-olato-κ3 N,O:O)dicobalt(II)dicobalt(III), C16H38Cl4Co4N4O8

C16H38Cl4Co4N4O8, monoclinic, P21/c (no. 14), a = 9.070(3) Å, b = 15.201(5) Å, c = 20.786(6) Å, β = 111.385(11)°, V = 2668.5(15) Å3, Z = 4, R gt(F) = 0.0646, wR ref(F 2) = 0.1743, T = 293 K.

Crystal structure of catena-poly[aqua-(μ3-1,3,5-benzenetricarboxylato-κ3 O:O′:O′′)-[μ3hydroxy-(1,3-di-(μ2-1,2,4-triazole-4-yl)benzoato-κ2 N:N′)copper(II)], C19H16Cu2N6O9

C19H16Cu2N6O9, monoclinic, P21/n (no. 14), a = 7.9182(8) Å, b = 11.7533(12) Å, c = 22.7024(19) Å, V = 2015.7(3) Å3, Z = 4, R gt(F) = 0.0309, wR ref(F 2) = 0.0692, T = 293(2) K.

Crystal structure of poly[aqua-(μ3-3,5-di(4H-1,2,4-triazolyl-4-κ3 N,N′:N′′)benzenecarboxylato)silver(I)], C11H9AgN6O3

C11H9AgN6O3, monoclinic, P21/c (no. 14), a = 3.8210(13) Å, b = 15.427(5) Å, c = 21.969(7) Å, β = 90.275(4)°, V =1295.0(8) Å3, Z = 4, R gt(F) = 0.0457, wR ref(F 2) = 0.1096, T = 296(2) K.

Crystal structure of poly[diaquabis(μ4-benzene-1,3,5-tricarboxylato-κO 1,κO 2:κO 3,κO 4:κO 5:κO 6)-bis(μ2-4,4′-benzene-1,3-diylbis(4H-1,2,4-triazole-κ2 N:N′)tricadmium(II)] tetrahydrate, C38H34Cd3N12O18

C38H34Cd3N12O18, monoclinic, C2/c (no. 15), a = 35.076(3) Å, b = 7.5997(7) Å, c = 18.5480(18) Å, β = 117.8560(10)°, V = 4371.3(7) Å3, Z = 6, R gt (F) = 0.0314, wR ref (F 2 ) = 0.1265, T = 296(2) K.

A series of Anderson-type polyoxometalate-based metal–organic complexes: their pH-dependent electrochemical behaviour, and as electrocatalysts and photocatalysts

Seven novel polyoxometalate-based metal–organic complexes are synthesized and structurally characterized, exhibiting high electrochemical sensitivity to pH and photocatalytic activities for the degradation of organic dyes under UV irradiation.

A series of Keggin-based compounds constructed by conjugate ring-rich pyrazine and quinoxaline derivatives

Ligands L¹ and L² are utilized in POM chemistry for the first time. Different Keggin anions induce distinct 2D structures of compounds 1/2 and 3/4 in Ag–L¹ and Ag–L² systems, respectively. By adding Ag^I and Cu^I to the PMo₁₂–L² system different 3 and 5 were formed.

Three multi-nuclear clusters and one infinite chain induced by a pendant 4-butyl-1H-pyrazole ligand for modification of Keggin anions

By utilizing a pendant 4-butyl-1H-pyrazole, four POM-based multi-nuclear clusters or infinite chain subunits are formed: tetra-, tri- and penta-nuclear clusters in 1, 3 and 4 and an infinite chain in 2.

Two novel octamolybdate nanoclusters as catalysts for dye degradation by air under room conditions

Two new octamolybdate-based hybrid materials as catalysts for the wet air oxidation of dyes under mild conditions.

Construction of POMOFs with different degrees of interpenetration and the same topology

Three POMOFs with different degrees of interpenetration are reported and the influence of the organic molecules on the degree of interpenetration of the compounds is discussed.

Tuning the topology structures of polymolybdate-based hybrids from interpenetrated framework to interdigitated architecture via changing polymolybdate clusters

Three distinct hybrids were synthesized by modulating polyoxomolybdates, which suggests that both the size and the charge of polyoxometalates play a key role in the assembling.

Isopolymolybdate-induced organic–inorganic hybrid assemblies with copper ions and bichelate-bridging ligands

Heptamolybdate is used as a “molecular adaptor” to modulate the metal–organic coordination building units in the hydrothermal environment, with new polyoxometalate-induced hybrid assemblies isolated demonstrating good photocatalytic activity.