Composition Space Analysis in the Development of Copper Molybdate Hybrids Decorated by a Bifunctional Pyrazolyl/1,2,4-Triazole Ligand

Crown ether-like octanuclear molybdenum(V) clusters for cation binding and gas adsorption

Octanuclear polyoxomolybdenum-based porous materials, Na8[Mo8O8(μ2-O)8(μ2-OH)8(3-apz)4]2·26H2O (1, 3-Hapz = 3-aminopyrazole), K8[Mo8O8(μ2-O)8(μ2-OH)8(3-apz)4]2·7H2O (2) and (NH4)4[Mo8O8(μ2-O)8(μ2-OH)4(3-apz)8]·20.5H2O (3), have been successfully synthesized by a hydrothermal method and fully characterized. X-ray structural analyses show that microporous materials 1-3 contain round pores formed by octanuclear molybdenum-oxygen groups connected sequentially with pore sizes of 4.0, 4.0, and 4.8 Å, respectively. Both 1 and 2 are composed of two {Mo8} rings, which are connected by strong intramolecular hydrogen bonds between bridging hydroxy groups and oxygen atoms to form dimeric structures. The central pores in 1 and 2 are occupied by Na+ and K+, respectively, while they are empty in 3. This reflects the structural expansion and contraction effects induced by different cations. Through intermolecular stacking, 1-3 also exhibit channels with sizes of 14.0 × 6.4, 4.6 × 2.6, and 5.4 × 5.4 Å, respectively, which were used for the studies of gas adsorption. The results show that 1-3 can selectively adsorb CO2 and O2, including the empty hole in 3, while they show little or no affinity for gases H2, N2, and CH4. Moreover, an additional polyoxomolybdenum-based species (Mo8O26)n·4n(3-H2apz) (4) has been obtained with protonated 3-aminopyrazole in the absence of a reducing agent, which can serve as an intermediate for the polyoxomolybdenum-based porous products.

Synthesis and crystal structure of a new copper(II) complex based on 5-ethyl-3-(pyridin-2-yl)-1,2,4-triazole

The title compound, bis-[μ-3-ethyl-5-(pyridin-2-yl)-1H-1,2,4-triazol-1-ido]bis[acetato-(di-methyl-formamide)-copper(II)], [Cu2(C9H9N4)2(C2H3O2)2(C3H7NO)2] or [Cu2(L Et)2(OAc)2(dmf)2], is a triazolate complex, which contains two 3-(2-pyrid-yl)-5-ethyl-triazolates (L Et)- in bidentate-bridged coordination modes. Both copper atoms are involved in the formation of a planar six-membered metallocycle Cu-[N-N]2-Cu. The inversion center of the complex is located at the mid-point of the Cu⋯Cu vector. Each CuII atom has a distorted trigonal-bipyramidal environment formed by the three nitro-gen atoms of the deprotonated bridging 3-(2-pyrid-yl)-5-ethyl-triazolate unit, oxygen atoms of the OAc- group and dmf mol-ecule. In the crystal, C-H⋯O hydrogen bonds link the mol-ecules into chains running along the c-axis direction.

Two 1D Anderson-Type Polyoxometalate-Based Metal-Organic Complexes as Bifunctional Heterogeneous Catalysts for CO2 Photoreduction and Sulfur Oxidation

Sulfur oxides from the combustion of petrol and excessive emissions of carbon dioxide (CO₂) are currently the main causes of environmental pollution. Considerable interest has been paid to solving the challenge, and catalytic reactions seem to be the desired choice. Due to the high density of Lewis acid active sites, polyoxometalates are considered to be the ideal choice for these catalytic reactions. Herein, two captivating polyoxometalate-based metal-organic complexes, formulated as [Co(H₂O)₂DABT]₂[CrMo₆(OH)₅O₁₉] ({Co-CrMo₆}) and [Zn(H₂O)₂DABT]₂[CrMo₆(OH)₅O₁₉] ({Zn-CrMo₆}) (DABT = 3,3'-diamino-5,5'-bis(1H-1,2,4-triazole)) were successfully obtained under hydrothermal conditions. The structural analysis demonstrates that {Co-CrMo₆} and {Zn-CrMo₆} are isostructural with two different transition metal (Co/Zn) ions based on quadridentate Anderson-type [CrMo₆(OH)₅O₁₉]^4- polyanions. A fan-shaped unit of {Co-CrMo₆}/{Zn-CrMo₆} is linked to generate a one-dimensional (1D) ladder-like structure. Intriguingly, benefitting from rich Co centers with a suitable energy band structure, {Co-CrMo₆} displays better photocatalytic activity than {Zn-CrMo₆} for converting CO₂ into CO, endowing the CO formation of 1935.3 μmol g^-1 h^-1 with high selectivity. Meanwhile, {Co-CrMo₆} also exhibits a satisfactory removal rate of 99% for oxidizing dibenzothiophene at 50 °C, which suggests that {Co-CrMo₆} may be utilized as a potential dual functional material with immense prospects in photocatalytic CO₂ reduction and sulfur oxidation for the first time.

Crystal structure of tetra-kis-(μ-4-benzyl-4H-1,2,4-triazole-κ2 N 1:N 2)tetra-fluoridodi-μ2-oxido-dioxidodisilver(I)divanadium(V)

The crystal structure of the title compound, [Ag2(VO2F2)2(C9H9N3)4], is presented. The mol-ecular complex is based on the heterobimetallic AgI-VV fragment {AgI 2(VVO2F2)2(tr)4} supported by four 1,2,4-triazole ligands [4-benzyl-(4H-1,2,4-triazol-4-yl)]. The triazole functional group demonstrates homo- and heterometallic connectivity (Ag-Ag and Ag-V) of the metal centers through the [-NN-] double and single bridges, respectively. The vanadium atom possesses a distorted trigonal-bipyramidal coordination environment [VO2F2N] with the Reedijk structural parameter τ = 0.59. In the crystal, C-H⋯O and C-H⋯F hydrogen bonds as well as C-H⋯π contacts are observed involving the organic ligands and the vanadium oxofluoride anions. A Hirshfeld surface analysis of the hydrogen-bonding inter-actions is also described.

Isolated molybdenum-based microporous POMs for selective adsorption of gases

Dodecanuclear, icosanuclear and octanuclear porous MOF-like POMs materials [MoV12O12(μ2-O)4(μ3-O)12(Htrz)4(trz)4]∙nH2O (n = 22, 1; n = 92, 2; Htrz = 1H-1,2,3-triazole), [MoV8O8(μ2-O)12(Htrz)8]½∙[MoV12O12(μ2-O)4(μ3-O)12(Htrz)4(trz)4]∙44H2O (3), and [MoV8O8(μ2-O)12(Htrz)8]·62H2O (4) have been obtained and well...

1,2,4-Triazolyl-4-acetate: a ditopic ligand combining soft and hard donor sites in homometallic (AgI) and heterometallic (AgI/UVI) coordination polymers

A 1,2,4-triazol-4-yl-acetic acid (trGly-H) was used for the synthesis of AgI and AgI/UVI coordination polymers. The composition space diagram was built for the AgNO3/trGly-H/UO2(NO3)2·6H2O system shows the crystallization fields of two AgI/UVI-compounds were found.

An Isopolymolybdate-Incorporated Metal-Organic Framework with Sulfite Oxidase-Mimicking Activity for Photocatalytic Oxidation of Sulfides Utilizing In Situ-Generated Singlet Oxygen

Developing new photocatalysts for sulfide oxidation utilizing in situ-generated 1O2 is very significant. Inspired by natural enzymatic processes, we synthesized a mimic sulfite oxidase (SO), {[Co(Mo4O13)(TPT)2]} (CoMo-TPT), by incorporating an isopolymolybdate anion [Mo4O13]2- into a 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT)-based metal-organic framework under mild hydrothermal conditions. In this structure, {Mo4O13} units with intrinsic SO-like catalytic sites are beneficial for the selective oxidation of sulfite and thioether. The ultraviolet-visible spectra of CoMo-TPT exhibited strong absorption from 250 to 650 nm and potential application in the utilization of solar energy. Mott-Schottky measurements indicated that CoMo-TPT is an n-type semiconductor with a LUMO value of -0.70 V (vs NHE) and a HOMO value of 1.39 V. The transient photocurrent responses with strong current density cycles with visible light indicated CoMo-TPT has a high photochemical activity. The lower resistance indicated that CoMo-TPT has a higher efficiency of photoinduced electron and hole separation. CoMo-TPT displayed a high efficiency of 99% and a selectivity of 97.3% in photocatalytic oxidation of sulfides by utilizing in situ-generated 1O2 through a tandem process of formation of H2O2 from O2 followed by catalyzed disproportionation of H2O2.

Hybrid compound based on diethylenetriaminecopper(ii) cations and scarce V-monosubstituted β-octamolybdate as water oxidation catalyst

Herein, we report on a new hybrid compound (NH₄){[Cu(dien)(H₂O)₂]₂[β-VMo₇O₂₆]}·1.5H₂O (1), where dien = diethylenetriamine, containing an extremely rare mixed-metal pseudo-octamolybdate cluster. An ex situ EPR spectroscopy provided insights into the formation of paramagnetic species in reaction mixture and in solution of 1. The magneto-structural correlations revealed weak antiferromagnetic exchange interactions between the [Cu(dien)]²⁺ cations transmitted by intermolecular pathways. The cyclic voltammetry showed the one-electron process associated with the Cu³⁺/Cu²⁺ oxidation followed by the multi-electron catalytic wave due to water oxidation with a faradaic yield of 86%. The title compound was thus employed in homogeneous water oxidation catalysis using tris(bipyridine)ruthenium photosensitizer. At pH 8.0, efficiency of the catalytic system attained 0.19 turnovers per second supported by the relatively mild water oxidation overpotential of 0.54 V.

A new hybrid compound (NH₄){[Cu(dien)(H₂O)₂]₂[β-VMo₇O₂₆]}·1.5H₂O was employed in homogeneous water oxidation catalysis. At pH 8.0, its efficiency attains 0.19 turnovers per second, supported by the relatively mild water oxidation overpotential of 0.54 V.

Solvothermally-derived MoO3-benzotriazole hybrid structures for nanocontainer depot systems

Layered MoO₃ containing intercalated benzotriazole (up to 40 mol%) shows much promise as a container system for corrosion protection.

A 3D Cu(ii) tetrazolate coordination polymer based on pentanuclear units with a large coercive field

A 3D Cu(ii) coordination polymer with the ligand 1,2-bis(tetrazol-5-yl) exhibits spin-canting magnetic behavior with a large coercive field of 2.3 kOe.

On the Border between Low-Nuclearity and One-Dimensional Solids: A Unique Interplay of 1,2,4-Triazolyl-Based {CuII5(OH)2} Clusters and MoVI-Oxide Matrix

A pentanuclear Cu^II₅-hydroxo cluster possessing an unusual linear-shaped configuration was formed and crystallized under hydrothermal conditions as a result of the unique cooperation of bridging 1,2,4-triazole ligand ( trans-1,4-cyclohexanediyl-4,4'-bi(1,2,4-triazole) ( tr₂ cy)), Mo^VI-oxide, and CuSO₄. This structural motif can be rationalized by assuming in situ generation of {Cu₂Mo₆O₂₂}^4- anions, which represent heteroleptic derivatives of γ-type [Mo₈O₂₆]^4- further interlinked by [Cu₃(OH)₂]⁴⁺ cations through [ N- N] bridges. The framework structure of the resulting compound [Cu₅(OH)₂( tr₂ cy)₂Mo₆O₂₂]·6H₂O (1) is thus built up from neutral heterometallic {Cu₅(OH)₂Mo₆O₂₂} _n layers pillared with tetradentate tr₂ cy. Quantum-chemical calculations demonstrate that the exclusive site of the parent γ-[Mo₈O₂₆]^4- cluster into which Cu^II inserts corresponds with the site that has the lowest defect ("MoO₂ vacancy") formation energy, demonstrating how the local metal-polyoxomolybdate chemistry can express itself in the final crystal structure. Magnetic susceptibility measurements of 1 show strong antiferromagnetic coupling within the Cu₅ chain with exchange parameters J₁ = -500(40) K (-348(28) cm^-1), J₂ = -350(10) K (-243(7) cm^-1) and g = 2.32(2), χ² = 6.5 × 10^-4. Periodic quantum-chemical calculations reproduce the antiferromagnetic character of 1 and connect it with an effective ligand-mediated spin coupling mechanism that comes about from the favorable structural arrangement between the Cu centers and the OH^-, O^2-, and tr₂ cy bridging ligands.

Two new POM-based compounds containing a linear tri-nuclear copper(II) cluster and an infinite copper(II) chain, respectively

Using the pendent organic ligand 1-butyl-1H-(1,3,4)triazole (btz), two new polyoxometalate (POM)-based compounds, [Cu3(btz)6(H2O)4(H3P2W18O62)2]·6H2O (1) and [Cu2(btz)(tz)(H2O)2(SiMo12O40)]·5H2O (2) (tz=1H-(1,3,4)triazole), have been synthesized under hydrothermal conditions. In compound 1, three CuII ions are fused by six btz ligands to form a linear tri-nuclear CuII cluster, with water as bridging molecules. Two Wells-Dawson anions offer two terminal O atoms to link two apical CuII atoms of this tri-nuclear cluster. In compound 2, the btz and tz molecules connect CuII ions to construct an infinite CuII chain still with water molecules as bridges. The adjacent chains are linked by one type of POM anions to build a 2D grid-like layer. Considering the long-range coordinative Cu–O bonds, the other types of POM anions connect adjacent layers to form a 3D framework. The electrochemical and photocatalytic properties of compounds 1 and 2 were also studied.

A series of organic–inorganic hybrid materials consisting of flexible organic amine modified polyoxomolybdates: synthesis, structures and properties

A series of hybrid materials consisting of Tris[(2-pyridyl)methyl]amine modified polyoxomolybdates were obtained and some complexes have efficient photocatalytic activities to degrade pararosaniline hydrochloride dye molecules.