Trivacant Keggin Research Articles

Syntheses, structures and properties of four organic–inorganic hybrid nicotinate-bridging rare-earth-containing phosphotungstates

Four novel organic–inorganic hybrid nicotinate-bridging dimeric rare-earth (RE)-containing phosphotungstates [H2N(CH3)2]8[RE(H2O)(NA)(α-HPW11O39)]2·24H2O (RE = HoIII for 1, ErIII for 2, TbIII for 3, DyIII for 4; HNA = nicotinic acid) have been synthesized from the reaction of trivacant Keggin precursor Na9[α-PW9O34]∙16H2O, RE(NO3)3·6H2O, HNA by employing dimethylamine hydrochloride as organic solubilizing agent in the conventional aqueous solution system, which have been further characterized by elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Structural analysis indicates that the hybrid dimeric {[RE(H2O)(NA)(α-HPW11O39)]2}8− polyoxoanion in 1–4 can be considered as two head-to-head mono-RE-containing Keggin [RE(H2O)(NA)(α-HPW11O39)]4− subunits bridged by two (η2,μ-1,1)-nicotinate linkers, which stands for the first organic–inorganic hybrid RE-containing phosphotungstates functionalized by nicotinate ligands. What's more, the solid-state photoluminescence properties and lifetime decay behaviors of 1–4 have been measured at room temperature and their photoluminescence spectra display the characteristic emission bands of corresponding trivalent RE cations.

The Hybrid Organic–Inorganic Assemblies Based on Monocapped Trivacant Keggin Arsenatomolybdate and CuI-Organic Units

A new arsenomolybdate compound [Cu(imi)2]5Na[(AsO4)Mo9O27(AsO3)]·5H2O(imi = imidazole) 1, has been prepared by hydrothermal method and structurally characterized by elemental analysis, IR, XRD, TG analysis and single-crystal X-ray diffraction analysis. Compound 1 represents the first example of monocapped trivacant Keggin [AsIIIAsVMo9O34]6− subunit as polydentate ligand bonded to five [Cu(imi)2] complexes through one covalent bond and four weak Cu···O bonds. The electrochemical behavior of 1-modified carbon paste electrode has been studied in detail. In addition, photoluminescence and photocatalysis properties of 1 have been investigated.

Lanthanide-Connecting and Lone-Electron-Pair Active Trigonal-Pyramidal-AsO3 Inducing Nanosized Poly(polyoxotungstate) Aggregates and Their Anticancer Activities.

By virtue of the stereochemical effect of the lone-electron pair located on the trigonal-pyramidal-AsO3 groups and the one-pot self-assembly strategy in the conventional aqueous solution, a series of novel lanthanide-bridging and lone-electron-pair active trigonal-pyramidal-AsO3 inducing nanosized poly(polyoxotungstate) aggregates [H2N(CH3)2]6 Na24H16{[Ln10W16(H2O)30O50](B-α-AsW9O33)8}·97H2O [Ln = EuIII (1), SmIII (2), GdIII (3), TbIII (4), DyIII (5), HoIII (6), ErIII (7), TmIII (8)] were prepared and further characterized by elemental analyses, IR spectra, UV spectra, thermogravimetric (TG) analyses and single-crystal X-ray diffraction. The most remarkable structural feature is that the polyanionic skeleton of {[Ln10W16(H2O)30O50](B-α-AsW9O33)8}46− is constructed from eight trivacant Keggin [B-α-AsW9O33]9− fragments through ten Ln centers and sixteen bridging W atoms in the participation of fifty extraneous oxygen atoms. Notably, 4 and 8 can be stable in the aqueous solution not only for eight days but also in the range of pH = 3.9–7.5. Moreover, the cytotoxicity tests of 4 and 8 toward human cervical cancer (HeLa) cells, human breast cancer (MCF–7) cells and mouse fibroblast (L929) cells were performed by the 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and the cell apoptosis processes were characterized by calcein AM/PI staining experiments, annexin V-FITC/PI staining experiments and morphological changes.

Trigonal Pyramidal {AsO2(OH)} Bridging Tetranuclear Rare-Earth Encapsulated Polyoxotungstate Aggregates.

The one-pot assembly reaction of Na2WO4·2H2O, RE(NO3)3·6H2O, and NaAsO2 in the participation of dimethylamine hydrochloride as an organic solubilizing agent in the acidic aqueous solution led to a class of trigonal pyramidal {AsO2(OH)} bridging rare-earth substituted arsenotungstate (AT) aggregates [H2N(CH3)2]8Na8{[W3RE2(H2O)8AsO8(OH)][B-α-AsW9O33]2}2·65H2O [RE = Eu(III) (1), Gd(III) (2), Tb(III) (3), Dy(III) (4), Ho(III) (5), Y(III) (6)], which were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, and thermogravimetric (TG) analyses. The common structural feature of 1-6 is that their polyoxoanions consist of a novel tetrameric unit [(W3RE2(H2O)8AsO8(OH))(B-α-AsW9O33)2]2(16-) constituted by four trivacant Keggin [α-AsW9O33](9-) fragments linked through an unseen elliptical [W6RE4(H2O)16As2O16(OH)2](20+) moiety. Their polyoxoanionic infrastructures can also be described as a fusion of two equivalent dimeric subunits [(W3RE2(H2O)8O7)(B-α-AsW9O33)2](8-) bridged via two μ2-{AsO2(OH)} linkers. To the best of our knowledge, such a linking mode with trigonal pyramidal {AsO2(OH)} groups as linkers connecting adjacent RE containing polyoxometalate moieties together is very rare. The thermal stability of 1-6 was also investigated on the crystalline samples, and the thermal decomposition processes of 1, 4, and 6 were comparatively deeply studied. The fluorescent properties and decay times of 1, 3, and 4 were measured, and they exhibit the characteristic emissions of RE centers. The lifetimes of 1 and 3 mainly originate from the contribution of RE ions whereas the overall lifetime of 4 is contributed by the synergistic interactions of AT fragments and Dy(3+) ions.

Synthesis, structure and electrochemical properties of a FeIII–CeIII heterometallic sandwich-type tungstoantimonate with novel 2-D infinite structure [Ce(H2O)8][Ce(H2O)6][Fe4(H2O)10(B-β-SbW9O33)2]·16H2O

By the rational self-assembly of trivacant Keggin precursor [B-α-SbW9O33]9− with Fe3+ and Ce3+ cations in the conventional aqueous solution, a novel FeIII–CeIII heterometallic sandwich-type tungstoantimonate [Ce(H2O)8][Ce(H2O)6] [Fe4(H2O)10(B-β-SbW9O33)2]·16H2O (1) has been successfully synthesized and further structurally characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. Structural analysis indicates that the 2-D infinite sheet of 1 consists of the Krebs' sandwich-type [Fe4(H2O)10(B-β-SbW9O33)2]6− subunits and Ce3+ linkers. 1 represents the rare purely inorganic FeIII–CeIII heterometallic tungstoantimonate derivative with the 2-D infinite sheet. The electrochemical and electrocatalytic properties of 1 have been systemically studied in 0.5mol·L−1 Na2SO4+H2SO4 supporting electrolyte, moreover, 1 exhibits the obvious electrocatalytic activity towards the reduction of BrO3− and NO2−.

Syntheses, structures and properties of a series of 3s–5d–4f mixed metal substituted sandwich-type arsenotungstates

A class of 3s–5d–4f mixed metal substituted sandwich-type arsenotungstates [H2N(CH3)2]8H3[LnNa(H2O)4(OH)WO(H2O) (B-α-AsW9 O33)2]·8H2O [Ln=LaIII (1), CeIII (2), PrIII (3)] have been isolated from an aqueous solution reaction system (pH=4) of Na2WO4·2H2O, C2H7N·HCl, NaAsO2 and Ln(NO3)3·6H2O and structurally characterized by elemental analyses, IR spectra, UV spectra and single-crystal X-ray diffraction. It is the most prominent in 1–3 that the [LnNa(H2O)4(OH) WO(H2O)(B-α-AsW9O33)2]11− polyanion consists of two trivacant Keggin [B-α-AsW9O33]9− moieties linked by one [WO(H2O)]4+ group and a dimeric [LnNa(H2O)4(OH)]3+ group resulting in the special 3s–5d–4f mixed metal substituted sandwich-type assembly. Interestingly, lanthanide and sodium ions simultaneously occupy the two positions located at the central belt of 1–3 with the site occupancy of 50% for each position. Moreover, the electrochemical and electrocatalytic properties of only 1 and 2 have been measured by cyclic voltammetry (CV) in 0.5mol·L−1 Na2SO4+H2SO4 aqueous solution. 1 and 2 illustrate electrocatalytic activities for the hydrogen peroxide reduction.

Hydrothermal combination of trilacunary Dawson phosphotungstates and hexanickel clusters: from an isolated cluster to a 3D framework.

Three novel hexa-Ni-substituted Dawson phosphortungstates [Ni6 (en)3 (H2O)6 (μ3-OH)3 (H3 P2 W15 O56 )]⋅14 H2O (1), [Ni(enMe)2 (H2O)][Ni6 (enMe)3 (μ3-OH)3 (H2O)6 (HP2 W15 O56)]⋅ 10 H2O (2), and [Ni(enMe)2 ]3 [Ni(enMe)2 (H2O)][Ni(enMe)(H2O)2][Ni6 (enMe)3 (μ3-OH)3 (Ac)2 (H2O)(P2 W15 O56)]2 ⋅6 H2O (3) (en=ethylenediamine, enMe=1, 2-diaminopropane, Ac=CH3 COO(-)) have been made under hydrothermal conditions and were characterized by IR spectroscopy, elemental analysis, diffuse reflectance spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The common structural features of compounds 1-3 contain the similar hexa-Ni-substituted Dawson polyoxometalate (POM) units that can be viewed as a [Ni6 (μ3-OH)3](9+) cluster capping on a [P2 W15 O56](12-) fragment. Compounds 1 and 2 are two isolated clusters, whereas compound 3 is the first 3D POM framework constructed from hexa-Ni-substituted Dawson POM units and Ni(enMe) complex bridges. The preparations of compounds 1-3 not only indicate that triangle coplanar Ni6 clusters are very stable fragments in both trivacant Keggin and trivacant Dawson POM systems, but also offer that the hydrothermal technique can act as an effective strategy for making novel Dawson-type high-nuclear transition-metal cluster substituted POMs by combination of lacunary Dawson precusors with transition-metal cations in the tunable role of organic ligands. In addition, magnetic measurements illustrate that there exist overall ferromagnetic interactions in compound 3.

A new 1-D chain based on the trivacant monocapped Keggin arsenomolybdate and the copper complex linker: synthesis, crystal structure, and ESI-MS analyses

A new organic–inorganic hybrid (H2en)2[[Cu(en)2]AsIIIAsVMoVI9O34]·6H2O (1), containing a 1-D helical chain based on the trivacant monocapped Keggin arsenomolybdate and the copper complex linker {[Cu(en)2][AsIIIAsVMoVI9O34]}n4n− (en = ethylenediamine), has been synthesized and characterized by IR spectra, TG analyses, single-crystal X-ray diffraction, and high-resolution electrospray ionization mass spectrometry (ESI-MS). Large voids are observed and a 1-D chain containing repeated (H2O)8 water units from lattice water molecules is formed along the a axis in the crystal structure. The high-resolution ESI-MS shows that the intact framework [Cu(en)2][AsIIIAsVMoVI9O34]4− exists in solution.

Self-assembly and thermotropic liquid crystal properties of a hexavacant germanomolybdate: [Ge2Mo16O58]12−

Two new hexavacant germanomolybdates, (H2enMe)3K2[Ge2Mo16O58]·4H3O·9H2O (1) (enMe = 1,2-propanediamine) and Na12[Ge2Mo16O58]·30H2O (2), were synthesized through the conventional aqueous method and characterized by X-ray crystallography, elemental analysis, IR spectra and thermogravimetry (TG) analysis. The polyoxoanions in compounds 1 and 2 contain two trivacant Keggin {β-A-GeMo9O34} units fused together by two {MoO6} octahedra. This structural type is different from that of the well-known basic structural types and rarely observed in the POM chemistry. Further, DODACl was used as the surfactant to encapsulate the hexavacant polyoxoanion, resulting in the surfactant-encapsulated cluster (SEC) [DODA]12[Ge2Mo16O58]·16H2O (SEC-Mo16). Polarized optical microscopy, differential scanning calorimetry (DSC), variable temperature X-ray diffraction (VT-XRD) and transmission electron microscopy (TEM) revealed that SEC-Mo16 exhibits characteristic thermotropic liquid crystal properties.

ChemInform Abstract: A Lewis Acid Catalytic Core Sandwiched by Inorganic Polyoxoanion Caps: Selective H2O2‐Based Oxidations with [AlIII4(H2O)10 (β‐XW9O33H)2]6‐(X: AsIII, SbIII).

The AlIII-containing polyanions [AlIII4(H2O)10(β-XW9O33H)2]4− with X = AsIII (1) and SbIII (2) feature four aluminum(III) centers sandwiched by two trivacant (β-XW9O33) Keggin units, and trigger peroxide catalysis as well as substrate coordination via multiple Lewis acid site interactions.

Hydrothermal synthesis and structural characterization of an organic–inorganic hybrid sandwich-type tungstoantimonate [Cu(en)2(H2O)]4[Cu(en)2(H2O)2][Cu2Na4(α-SbW9O33)2]·6H2O

An organic–inorganic hybrid sandwich-type tungstoantimonate [Cu(en)2(H2O)]4[Cu(en)2(H2O)2][Cu2Na4(α-SbW9O33)2]·6H2O (1) has been synthesized by reaction of Sb2O3, Na2WO4·2H2O, CuCl2·2H2O with en (en=ethanediamine) under hydrothermal conditions and structurally characterized by elemental analysis, inductively coupled plasma atomic emission spectrometry, IR spectrum and single-crystal X-ray diffraction. 1 displays a centric dimeric structure formed by two equivalent trivacant Keggin [α-SbW9O33]9− subunits sandwiching a hexagonal {Cu2Na4} cluster. Moreover, those related hexagonal hexa-metal cluster sandwiched tungstoantimonates have been also summarized and compared. The variable-temperature magnetic measurements of 1 exhibit the weak ferromagnetic exchange interactions within the hexagonal {Cu2Na4} cluster mediated by the oxygen bridges.

Synthesis and characterization of a new Hervé-type tungstoantimonite based on α-[SbW9O33]9− unit

A sandwich-type polyoxotungstate, {[Na(H2O)2]H8[KNa2(H2O)6][Cu(H2O)]3(SbW9-O33)2}n⋅4nH2O⋅4n(tn) (1) (tn=1,3-Propanediamine) has been synthesized and characterized by IR, UV-DRS, single-crystal X-ray diffraction analysis, TGA, XPS, magnetic-dependent 2D-IR correlation spectroscopy (2D-COS IR). The Hervé-type polyanion {[KNa2(H2O)6][Cu(H2O)]3(SbW9O33)2}9− of compound 1 consists of two trivacant Keggin moieties [SbW9O33]9− which are linked by three Cu2+ ions, and the space between the three Cu2+ ions is occupied by two sodium ions and one potassium ion forming a six-membered ring, and resulting in the polyanion with C2v symmetry. Compound 1 exhibits a 1D ribbon-like structure in which the adjacent polyanions were connected by the K+ in the central belt and Na+, which is rarely reported for Hervé-type polyanion. The magnetic-dependent 2D-IR correlation spectroscopy display obvious magnetic response signal of the groups which Cu2+ ions attached to.

Synthesis, structure and magnetic properties of a two-dimensional polymer based on sandwich-type tetra-cobalt(II)-substituted polyoxotungstate anions and 1-D potassium-chains

A 2-D coordination polymer, (C7N4H16)2{NH(CH3)3}[{K(H2O)}4Na(H2O)5{Co4(H2O)2(B-α-PW9O34)2}]·2H2O (1), was hydrothermally synthesized and structurally characterized by IR spectroscopy, elemental analysis, X-ray powder diffraction, and X-ray single-crystal crystallography. Crystal structure analysis shows a triclinic space group Pī with a = 12.4677(8) Å, b = 12.5054(8) Å, c = 18.5745(1) Å, α = 73.3220(1)°, β = 87.1890(1)°, γ = 62.2710(1)°, and V = 2443.4(3) Å3. Sandwich-type tetra-cobalt(II)-substituted [Co4(H2O)2(B-α-PW9O34)2]10− of 1 consists of two trivacant Keggin [B-α-PW9O34]9− moieties and a rhomb-like Co4O16 unit. Each sandwich-type polyoxotungstate subunit connects 12 K(1) and K(2) centers from two adjacent 1-D K-chain units resulting in an interesting 2-D layer framework. Magnetic properties of 1 have been investigated.

Designing a new organic-inorganic arsenomolybdate by modification of traditional Keggin-type building fragment

A rare monocapped trivacant Keggin fragment [A-α-AsIIIAsVMo9O34]6– has been captured and an organic-inorganic hybrid arsenomolybdate (H2en)[Ni(en)2(H2O)]{[Ni(en)2][AsIIIAsVMo9O34]}∙3H2O (1) was obtained under hydrothermal conditions. The structure of 1 was determined by X-ray single-crystal diffraction and further characterized by IR spectroscopy, X-ray powder diffraction (XRPD), scanning electron microscope with energy dispersive X-ray (EDX-SEM) and X-ray photoelectron spectroscopy (XPS). Single-crystal structural analysis indicates that 1 contains the peculiar monocapped trivacant [A-α-AsIIIAsVMo9O34]6– fragment derived from the rare trivacant Keggin type [A-α-AsVMo9O34]9– unit capped by a triangular pyramidal {AsO3} group. 1 represents the first Ni-substituted inorganic-organic arsenomolybdate containing the [A-α-AsIIIAsVMo9O34]6– subunit.

A Lewis acid catalytic core sandwiched by inorganic polyoxoanion caps: selective H2O2-based oxidations with [AlIII4(H2O)10(β-XW9O33H)2]6− (X = AsIII, SbIII)

The Al(III)-containing polyanions [Al(III)4(H2O)10(β-XW9O33H)2](4-) with X = As(III) (1) and Sb(III) (2) feature four aluminum(III) centers sandwiched by two trivacant (β-XW9O33) Keggin units, and trigger peroxide catalysis as well as substrate coordination via multiple Lewis acid site interactions.

Triangular {Mn(OH)}36+ fragment encapsulated in trivacant [A-R-SiW9O34]10− ligand

[{Mn III (OH)(H 2 O)} 3 SiW 9 O 34 ] 4 − 1a , has been isolated from the reaction of Na 9 [β-SiW 9 O 34 H]·23H 2 O and [Mn 3 O(O 2 CMe) 6 (HIm) 3 ](O 2 CMe) (Im = imidazole C 3 H 4 N 2 ) in aqueous solution. The trimetal-substituted polyoxometalate (TMSP) 1 has been fully characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, and infrared spectroscopy. This monomeric anion is composed of one trilacunary Keggin fragment A-α-SiW 9 O 34 and three manganese ions encapsulated resulting in a triangular {Mn(OH)} 3 6 + ring core. Experimental structural and magnetism aspects of the material are reported and discussed. A new complex displays trilacunary Keggin ligand [A-α-SiW 9 O 34 ] 10 − encapsulating triangular {Mn(OH)} 3 6 + fragment, in which hydroxo bridges connect the high-spin Jahn–Teller (JT) distorted Mn III centers with antiferromagnetic coupling predominates throughout the cluster. ► {Mn(OH)} 3 6+ encapsulated in trivacant Keggin anion SiW 9 O 34 10− was obtained ► Magnetism measurement convinced spin frustration in the Mn 3 core ► Mn ions in complex 1 show evident Jahn–Teller (JT) distortion

Synthesis, structural characterization and properties of a novel 1D helical chain arsenomolybdate {[Cu(en)2][Cu(en)(H2O)][(Cu(en)2(H2O)] [AsIIIAsVMo9O34)]}·2H2O

Abstract An organic–inorganic hybrid 1D helical chain arsenomolybdate {[Cu(en) 2 ][Cu(en)(H 2 O)][(Cu(en) 2 (H 2 O)] [As III As V Mo 9 O 34 )]} · 2H 2 O ( 1 ) (en = ethylenediamine) has been hydrothermally synthesized and characterized by elemental analyses, IR, UV and CD spectrum, powder X-ray diffraction, TG-DTA and single-crystal X-ray diffraction. The asymmetric unit of 1 consists of a monocapped trivacant Keggin [As III As V Mo 9 O 34 ] 6 − subunit, a pendant [Cu(en) 2 (H 2 O)] 2 + cation, a pendant [Cu(en)(H 2 O)] 2 + cation, one bridging [Cu(en) 2 ] 2 + cation and two lattice water molecules. It should be noted that 1 illustrates a one-dimensional (1D) helical chain assembled by {[Cu(en)(H 2 O)][(Cu(en) 2 (H 2 O)][As III As V Mo 9 O 34 )]} 2 − clusters and [Cu(en) 2 ] 2 + linkers.

Synthesis, structure, and characterization of a 1D monocopper substituted Dawson-type arsenotungstate (H2En)0.5[Cu(En)2]0.5{[Cu(En)2(H2O)]2[Cu(En)2] (α1-As2W17CuO61)} · 8H2O

A new 1D organic-inorganic hybrid monocopper substituted Dawson-type arsenotungstate (H2En)0.5[Cu(En)2]0.5{[Cu(En)2(H2O)]2[Cu(En)2](α1-As2W17CuO61)} · 8H2O (I) has been hydrothermally synthesized by the reaction of Na8[A-α-HAsW9O34] · 11H2O, CuCl2 · 2H2O, YCl3, with enthylenediamine (En) and characterized by elemental analyses, IR spectra, UV spectra, powder X-ray diffraction, thermogravimetric analysis, as well as single-crystal X-ray diffraction. Single-crystal structural analysis shows that I displays an interesting 1D chain constructed from [α1-As2W17CuO61]8− subunits by means of common oxygen atoms and [Cu(En)2]2+ bridges. It should be noted that the structural transformation of the trivacant Keggin polyoxoanion [A-α-AsW9O34]9− to the monovacant Dawson [α-As2W17O61]10− polyoxoanion was observed. The TG curve of I exhibits three stages of weight loss.

Two new sandwich-type tungstobismuthates constructed from trivacant Keggin units, estertin and transition metals

Two new sandwich-type tungstobismuthates containing carboxyethyltin groups and transition metals, Na8K2[{Co(H2O)3}2{Sn(CH2)2COO}2·(B-β-BiW9O33)2]·25H2O (1) and K10[{Mn(H2O)3}2{Sn(CH2)2COO}2·(B-β-BiW9O33)2]·30H2O (2) have been synthesized in the aqueous solutions and characterized by IR, TG, NMR and XRD. Single crystal X-ray diffraction analysis reveals that two 3d-transition metal (TM) cations and two organometallic (OM) groups in the central belt of the two complexes are all sandwiched by two B-β-[BiW9O33]9− units. The two compounds represent the first transition metal and carboxyethyltin-decorated polyoxometalate complexes. Structural analyses reveal that the reaction processes involving the α → β isomerization of [BiW9O33]9− unit and the hydrolysis of ester group. Both compounds have high thermal stabilities.

Two dysprosium-incorporated tungstoarsenates: synthesis, structures and magnetic properties

Two dysprosium-containing tungstoarsenates [C(NH(2))(3)](11)[Dy(2)(Hcit)(2)(AsW(10)O(38))]·9H(2)O (1) and K(8-n)H(3-n)[Dy(3-n)K(n)(H(2)O)(3)(CO(3))(A-α-AsW(9)O(34))(A-β-AsW(9)O(34))]·22H(2)O (n = 0 or 1) (2) have been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, thermogravimetric analyses and infrared spectroscopy. Compound 1 is a citrate-decorated Keggin type di-substituted Ln/POM derivative with the two non-adjacent substituted sites occupied. Compound 2 is composed of two different trivacant Keggin unit isomers [A-α-AsW(9)O(34)](9-) and [A-β-AsW(9)O(34)](9-), linked to each other via one {Dy(3-n)K(n)(H(2)O)(3)(CO(3))}((7 - 2n)+) (n = 0 or 1) unit, where CO(3)(2-) is encapsulated in the triangle plane, resulting in a stable dysprosium carbonate-containing sandwich-type polyoxoanion with D(2h) symmetry. The investigation on both static and dynamic magnetic properties of 1 and 2 show that the magnetic relaxation behavior of 2 appear in a static magnetic field of 5000 Oe, while 1 shows no positive out-of-phase ac susceptibility.