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1.
A photochemical method for the preparation of K6[Mo6[Mo2IVMoIV(CN)8O6]2H2O is discussed. The synthesis of this complex was achieved by photolysing aqueous solutions of K4Mo(CN)8 in contact with atmospheric oxygen.  相似文献   

2.
An in‐depth spectroscopic EPR investigation of a key intermediate, formally notated as [PVIVVVMo10O40]6? and formed in known electron‐transfer and electron‐transfer/oxygen‐transfer reactions catalyzed by H5PV2Mo10O40, has been carried out. Pulsed EPR spectroscopy have been utilized: specifically, W‐band electron–electron double resonance (ELDOR)‐detected NMR and two‐dimensional (2D) hyperfine sub‐level correlation (HYSCORE) measurements, which resolved 95Mo and 17O hyperfine interactions, and electron–nuclear double resonance (ENDOR), which gave the weak 51V and 31P interactions. In this way, two paramagnetic species related to [PVIVVVMo10O40]6? were identified. The first species (30–35 %) has a vanadyl (VO2+)‐like EPR spectrum and is not situated within the polyoxometalate cluster. Here the VO2+ was suggested to be supported on the Keggin cluster and can be represented as an ion pair, [PVVMo10O39]8?[VIVO2+]. This species originates from the parent H5PV2Mo10O40 in which the vanadium atoms are nearest neighbors and it is suggested that this isomer is more likely to be reactive in electron‐transfer/oxygen‐transfer reaction oxidation reactions. In the second (70–65 %) species, the VIV remains embedded within the polyoxometalate framework and originates from reduction of distal H5PV2Mo10O40 isomers to yield an intact cluster, [PVIVVVMo10O40]6?.  相似文献   

3.
A new trinuclear cyano-bridged CuII–MoIV–CuII compound has been prepared, characterized spectroscopically (UV–Vis and IR) and its structure determined by X-ray crystallography. The title complex 1 exhibits an antiferromagnetic exchange interaction between copper(II) ions mediated by [Mo(CN)8]4? diamagnetic units.  相似文献   

4.
Two new organic–inorganic hybrid compounds, [Cu(phen)(prz)]2[PMoV1MoVI7VIV2VV4O42]·4H2O (1) and [Ag2(phen)4]2[PMoV1MoVI7VIV2VV4O42] (2) (phen = 1,10-phenanthroline, prz = pyrazine), have been synthesized and characterized by IR, XPS, XRD, UV–vis, fluorescent spectra analyses, elemental analyses, X-ray diffraction analyses, TG analyses, and cyclic voltammetric measurements. Both compounds are formed by Keggin POM cores and transition metal fragments. Compound 1 exhibits an unprecedented 1-D chain structure constructed from [PMoV1MoVI7VIV2VV4O42]4? and [Cu(phen)(prz)]2+ in the –A–B↑–C–B↓– linking mode. Compound 2 shows a supramolecular structure formed by [PMoV1MoVI7VIV2VV4O42]4? and [Ag2(phen)4]2+.  相似文献   

5.
6.
Two polyoxometalate-based inorganic metal-organic hybrid supramolecular complexes [Cu(2,2′-bpy)2]2[VIV 2MoV 5MoVI 7O38(PO4)] (1) (2,2′-bpy?=?2,2′-bipyridine) and [Cu(2,2′-bpy)2]2[MoVMoVI 11O36(PO4)]?·?3H2O (2), have been hydrothermally prepared and structurally characterized by single-crystal X-ray diffraction. Both complexes are constructed from polyoxoanions (the bivanadyl capped α-Keggin polymolybdate anion [VIV 2MoV 5MoVI 7O38(PO4)]4? for 1 and the reduced 12-molybdophosphate anion [MoVMoVI 11O36(PO4)]4? for 2) and copper(II) complex cations [Cu(2,2′-bpy)2]2+, forming two-dimensional (2D) layer network structures, in which the polyoxoanion and the complex fragment cation connect with each other through Cu?···?Opolyoxoanion short contact weak interactions, which mediate ferromagnetic interaction.  相似文献   

7.
《Solid State Sciences》2004,6(7):689-696
Two interesting neutral tetrasupporting heteropolyoxometalates: [MoVI7MoVVIV8O40(PO4)][M(phen)2(OH)]2[M(phen)2(OEt)]2·xH2O (phen=1,10-phenanthroline, EtOH=ethanol, M=Co, x=7, 1; M=Ni, x=6, 2) were hydrothermally prepared and structurally characterized. The mixed molybdenum–vanadium polyoxoanion [MoVI7MoVVIV8O40(PO4)]4− exist in both two complexes, which acts as a bridge to covalently link two pairs of transition metal complex fragments, generating neutral windmill-like trimetallic nanocluster polyoxometalates. Variable-temperature magnetic susceptibility measurements of complexes 1 and 2 reveal that antiferromagnetic exchange interaction exists in this type of trimetallic tetrasupporting heteropolyoxometalates.  相似文献   

8.
The photoinduced properties of the octacoordinated complex K4MoIV(CN)8⋅2 H2O were studied by theoretical calculations, crystallography, and optical and magnetic measurements. The crystal structure recorded at 10 K after blue light irradiation reveals an heptacoordinated Mo(CN)7 species originating from the light-induced cleavage of one Mo−CN bond, concomitant with the photoinduced formation of a paramagnetic signal. When this complex is heated to 70 K, it returns to its original diamagnetic ground state, demonstrating full reversibility. The photomagnetic properties show a partial conversion into a triplet state possessing significant magnetic anisotropy, which is in agreement with theoretical studies. Inspired by these results, we isolated the new compound [K(crypt-222)]3[MoIV(CN)7]⋅3 CH3CN using a photochemical pathway, confirming that photodissociation leads to a stable heptacyanomolybdate(IV) species in solution.  相似文献   

9.
The complex formation with CH3O? of AsIII, SbIII, GeIV, NbIV, SeIV, TeIV, TiIV, SnIV and MoV has been investigated in absolute methanolic solutions containing (CH3)4NCl, LiCl, or Lithiumtosylate (μ = 1; 20.0°) by means of pH-titrations. The relations between the stoichiometry of the reactions and the shape of the buffer regions, as well as the concentration-dependance of these buffer regions are discussed.  相似文献   

10.
The photoinduced properties of the octacoordinated complex K4MoIV(CN)8?2 H2O were studied by theoretical calculations, crystallography, and optical and magnetic measurements. The crystal structure recorded at 10 K after blue light irradiation reveals an heptacoordinated Mo(CN)7 species originating from the light‐induced cleavage of one Mo?CN bond, concomitant with the photoinduced formation of a paramagnetic signal. When this complex is heated to 70 K, it returns to its original diamagnetic ground state, demonstrating full reversibility. The photomagnetic properties show a partial conversion into a triplet state possessing significant magnetic anisotropy, which is in agreement with theoretical studies. Inspired by these results, we isolated the new compound [K(crypt‐222)]3[MoIV(CN)7]?3 CH3CN using a photochemical pathway, confirming that photodissociation leads to a stable heptacyanomolybdate(IV) species in solution.  相似文献   

11.
The first crystal structure of a molybdenum complex 9 with a hydrogenated pterin and a sulfur ligand contributes to the discussion about the active center of molybdenum and tungsten enzymes containing a molybdopterin cofactor. Complex 9 was synthesized through a redox reaction of [MoVIO2 (LN-S2)] ( 8 ; LN-S2 = pyridine-2, 6-bis(methanethiolato)) with 5, 6, 7, 8-tetrahydropterin ( 7 ). 2 HCl (H4Ptr.2 HCl). The complex crystallizes, with a non-coordinating Cl-atom acting as a counterion, in the monoclinic space group C2/c (No. 15) with cell dimensions a = 22.900(5), b = 10.716(2), c = 17.551(4) Å, β = 120.36(3)°, and Z = 8. We interpret 9 as [MoIVO(LN-S2)(H+-q-H2Ptr)]Cl (q = quinonoid; H2Ptr = dihydropterin), i.e., a MoIV monooxo center coordinated by a pyridine-2, 6-bis(methanethiolato) ligand and a protonated dihydropterin. The spectroscopic properties of this new complex are comparable to those of other crystalline molybdenum complexes of hydrogenated pterins without additional S-coordination. The slightly H2O-soluble complex 9 reacts with the natural enzyme substrate DMSO very slowly, possibly due to the lack of easily dissociable ligands at the metal center.  相似文献   

12.
《Polyhedron》2007,26(9-11):2054-2058
An intermediate in photoinduced magnetization process for the photomagnetic high-spin molecule [MoIV(CN)2(CN-CuL)6]8+ is studied with quantum chemistry calculations of the density functional theory and the ab initio multireference configuration interaction methods. It is found that the intramolecular electronic transfer from MoIV to CuII leads one trigonal-bipyamid coordinated CuII to be changed to the tetrahedral coordinated CuI with the light irradiation. The calculated magnetic properties show that the paramagnetic system [MoIV(CN)2(CN-CuIIL)6]8+ with six isolated spin 1/2 Cu ions is changed to ferromagnetic coupling high-spin system [MoV(CN)2(CN-CuIIL)5(CN-CuIL)]8+. These calculations will help to understand photoinduced magnetization phenomenon and provide a clue for the synthesization of new reversible photoinduced magnetic compounds.  相似文献   

13.
A huge increase in the magnetization of two coordination chains based on tetravalent octacyanidometalates (WIV and MoIV) is observed on irradiation with 436 nm light, while no such behavior is observed for the NbIV analogue. A photomagnetic response based solely on [WIV(CN)8]4− is demonstrated for the first time. The observed behavior is attributed to the light‐induced excited spin state trapping (LIESST) effect at the octacyanidometalate, and to the resulting magnetic exchange ON/OFF photoswitching between the MnII center and the photoinduced high‐spin (S =1) WIV or MoIV centers.  相似文献   

14.
Oxidation of benzoic acid hydrazide by bromate in the presence of octamolybdomanganate(II), [MnIIMo8O27]4−, was studied in hydrochloric acid medium. The mechanism of the reaction involves oxidation of the catalyst to [MnIVMo8O27]2− by bromate which then forms a complex with the unoxidized catalyst. Both the complex and [MnIVMo8O27]2− react with the substrate in rate-determining steps to generate an intermediate acyl diimide, RCONNH. The reaction of water with the diimide then leads to the formation of benzoic acid and nitrogen as products through an NH–NH intermediate. There was no formation of free radical, indicating the involvement of only two-electron transfer steps in the mechanism. The order of more than unity in catalyst concentration is due to the formation of complex between the catalyst and the oxidized form of the catalyst. A rate law explaining all the kinetic results has been derived and verified. The effects of ionic strength and solvent polarity have also been studied, and the thermodynamic parameters were determined. A less solvated transition state as a result of interaction between the complex and oxidized form of the catalyst satisfactorily explains all the effects observed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

15.
Synthesis, structure characterization, and magnetic properties of three novel cyano-bridged complexes {[MnII(bpy)(DMF)2]2[MoIV(CN)8]·1.5H2O} n (1), [CuII(L)]2[MoIV(CN)8]·6.75H2O (2), and [MnII(bpy)2]4[MoIV(CN)8]2·4MeOH·4H2O (3) (where DMF = N,N′-dimethylformamide; bpy = 2,2-bipyridine and L = 1,3,6,8,11,14-hexaazatricyclo[12.2.1.18,11]octadecane) have been studied. The X-ray single-crystal structure reveals that 1 is a cyanide-bridged 1D infinite chain with the alternating of MnII(bpy)(DMF)2 and MoIV(CN)8 moieties. The neighboring chains interact with each other by hydrogen bonding to form a sheet-like network, and the layers further extend to a 3D network due to the face-to-face π···π stack interactions. For 2, the MoIV center adopts a distorted square antiprism coordination environment, while the CuII center adopts a distorted square pyramidal geometry. The weak Mo–CN···Cu interactions between neighboring molecules lead to a 2D network structure of 2. For 3, basic structural unit is centrosymmetric and contains four MnII centers bridged by two octacyanomolybdate(IV). Here, their magnetic properties have also been studied. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

16.
The crystal structure of La5Mo6O21 (penta­lanthanum hexa­molybdenum henicosa­oxide) is made up of Mo3O13 units containing triangular {MoIV}3 clusters, three distorted MoVO6 octa­hedral units and six inter­stitial LaIII atoms. The Mo3O13 unit consists of three edge‐sharing MoIVO6 units involving Mo—Mo bonding. The three MoVO6 octa­hedra share their corners or edges with each other and with the Mo3O13 units.  相似文献   

17.
Cleavage of dihydrogen is an important step in the industrial and enzymatic transformation of N2 into ammonia. The reversible cleavage of dihydrogen was achieved under mild conditions (room temperature and 1 atmosphere of H2) by the molecular uranium nitride complex, [Cs{U(OSi(OtBu)3)3}2(μ‐N)] 1, leading to a rare hydride–imide bridged diuranium(IV) complex, [Cs{U(OSi(OtBu)3)3}2(μ‐H)(μ‐NH)], 2 that slowly releases H2 under vacuum. This complex is highly reactive and quickly transfers hydride to acetonitrile and carbon dioxide at room temperature, affording the ketimide‐ and formate‐bridged UIV species [Cs{U(OSi(OtBu)3)3}2(μ‐NH)(μ‐CH3CHN)], 3 and [Cs{U(OSi(OtBu)3)3}2(μ‐HCOO)(μ‐NHCOO)], 4 .  相似文献   

18.
Oxophthalocyaninato(2–)molybdenum(IV), activated by bromine oxidation prior to use, reacts with fused triphenylphosphine in the presence of bis(triphenylphosphine)iminium bromide to yield linear-bis(triphenylphosphine)iminium trans-dibromophthalocyaninato(2–)molybdate(III), l(PNP)trans[Mo(Br)2pc2?]. It crystallizes triclinic with crystal data: a = 10.506(1) Å, b = 12.436(2) Å, c = 12.918(2) Å, α = 76.186(1)°, β = 67.890(1)°, γ = 68.689(1)°; space group P1 (No. 2); Z = 1. MoIII is in a pseudo-octahedral coordination geometry with the bromo ligands in trans-arrangement. The Mo? Np and Mo? Br distance is 2.043(10) and 2.588(1) Å, respectively. The PNP cation adopts a linear conformation. In the IR spectrum vas(Mo? Br) is observed at 218 cm?1 and vas(P? N) of the linear (P? N? P) core at 1406 cm?1. Cyclic and differential-pulse voltammetry show two quasi-reversible cathodic processes at ?1.15 and ?0.53 V vs. Ag/AgCl. The first is assigned to a phthalocyaninate directed reduction (pc2?/pc3?), while the latter arises from a Mo directed reduction (MoIII/MoII). Spectral monitoring confirms the reversible MoIII/MoII reduction. Two quasi-reversible anodic processes at 0.60 and 1.27 V are assigned to the successive Mo directed oxidation with redox couples MoIII/MoIV and MoIV/MoV. For the first time, three very intense spin-allowed trip-quartet transitions are observed in the electronic absorption spectra at 7140 (TQI), 16890 (TQ2) and 18700 cm?1 (TQ3) together with a sing-quartet transition at 15850 cm?1 and characteristic ?Q”? region with maximum at 28500 cm?1 and ?N”? region at 37400 cm?1. All electronic excitations are of comparable intensity. A prominent low temperature emission at 6690 cm?1 is assigned to a spin-forbidden trip-sextet.  相似文献   

19.
The bridged dimer of molybdenum(V), Mo2O42+ (aq) is oxidized to Mo(VI) by carboxylato-bound chromium(V). Reaction of bis(chelated) Cr(V) with excess (MoV)2 yields a chelated Cr(III) complex, but this conversion proceeds through a pink Cr(IV) intermediate, indicating that the oxidation of (MoV)2 entails a series of le? steps, passing through a reactive transient, the mixed valence complex, MoVMoVI. When experiments are carried out in buffers of the ligating acid, 2-ethyl-2-hydroxybutanoic acid, two stages of ligation of (MoV)2 by the ligand anion, characterized by rate constants near 104 and 0.14 M?1 s?1 (19°C; pH 3.0; μ = 0.6 M) must be considered. In quick mixing experiments, the first, but not the second, of these proceeds before the redox reaction gets under way, and autocatalytic redox profiles are observed. If the slower ligation is allowed to reach completion before Cr(V) is added, reduction to Cr(IV) is greatly accelerated and conforms to the superposition of two processes, whereas the reduction of Cr(IV) to Cr(III) is slow and exhibits a rate independent of [CrIV]. A proposed sequence applicable to the latter conditions includes reductions of Cr(V) at two ligation levels, slow unimolecular conversion of (MoV)2 to an activated form, and rapid reduction of the latter with Cr(IV). Here Cr(IV) has assumed the role of a scavenger for the reactive form of (MoV)2.  相似文献   

20.
The in situ spectrocyclic voltammetric investigations of the dimeric ruthenium complex used for water oxidation, [(bpy)2(H2O)Ru–O–Ru(H2O)(bpy)2]4+ (H2O–RuIII–RuIII–OH2), were carried out in a homogeneous aqueous solution and in a Nafion membrane under different pH conditions. The in situ absorption spectra recorded for the dimer show that the dimer H2O–RuIII–RuIII–OH2 complex underwent reactions initially to give the detectable H2O–RuIII–RuIV–OH and H2O–RuIII–RuIV–OH2 complexes, and at higher positive potentials, this oxidized dimer underwent further oxidation to produce a presumably higher oxidation state RuV–RuV complex. Since this RuV–RuV complex is reduced rapidly by water molecules to H2O–RuIII–RuIV–OH2, it could not be detected by absorption spectrum. Independent of the pH conditions and homogeneous solution/Nafion membrane systems, the dimer RuIII–RuIV was detected at higher potentials, suggesting that the dimer complex acts as a three-electron oxidation catalyst. However, in the Nafion membrane system it was suggested that the dimer complex may act as a four-electron oxidation catalyst. While the dimer complex was stable under oxidation conditions, the reduction of the dimer RuIII–RuIII to RuII–RuII led to decomposition, yielding the monomeric cis-[Ru(bpy)2(H2O)2]2+.  相似文献   

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