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Guoyu Yang - One of the best experts on this subject based on the ideXlab platform.
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combination of lacunary polyoxometalates and high Nuclear Transition metal clusters under hydrothermal conditions ix a series of novel polyoxotungstates sandwiched by octa copper clusters
Chemistry: A European Journal, 2008Co-Authors: Junwei Zhao, Jie Zhang, Shoutian Zheng, Chunmei Wang, Guoyu YangAbstract:The reaction of CuCl(2).2 H2O with trivacant Keggin polyoxoanions K8Na2[A-alpha-GeW9O34].25 H2O or K10[A-alpha-SiW9O34].25 H2O in the presence of 1,2-diaminopropane (dap), ethylenediamine (en) or 2,2'-bipyridine (2,2'-bpy) under hydrothermal conditions afforded five novel hybrid inorganic-organic octa-Cu sandwiched polyoxotungstates (POTs): H4[CuII8(dap)4(H2O)2(B-alpha-GeW9O34)2].13 H2O (1), (H2en)2[CuII8-(en)4(H2O)2(B-alpha-GeW9O34)2].5 H2O(2), (H2en)2[CuII8(en)4(H2O)2(B-alpha-SiW9-O34)2].8 H2O (3), [CuII(H2O)2]H2[CuII8-(en)4(H2O)2(B-alpha-SiW9O34)2] (4), and [CuII2(H2O)2(2,2'-bpy)2]{[CuII(bdyl)]2-[CuII8(2,2'-bpy)4(H2O)2(B-alpha-GeW9-O34)2]}.4 H2O (bdyl=2,2'-bipyridinyl)(5). Additionally, CuCl(2).2 H2O reacts with the mixture of GeO2, Na2WO(4).2 H2O, H2SiW12O(40).2 H2O in the presence of 2,2'-bpy and 4,4'-bpy under hydrothermal conditions leading to another novel mixed-valent octa-Cu sandwiched POT hybrid: [CuI(2,2'-bpy)(4,4'-bpy)]2[{CuI2(2,2'-bpy)2(4,4'-bpy)]2[CuI2CuII6(2,2'-bpy)2(4,4'-bpy)2(B-alpha-GeW9O34)2}].2 H2O (6). 1, 2, and 3 are discrete dimers constructed from two trivacant Keggin [B-alpha-XW9O34]10- (X=GeIV/SiIV) fragments and an octa-Cu cluster whereas 4 displays the 3D (3,6)-connected nets with (4.6(2))(4(2).6(4).8(7).10(2)) topology, which are built by octa-Cu sandwiched polyoxometalate building blocks through copper cation bridges. 5 is a novel 2D layer based on octa-Cu sandwiched POT clusters and [CuII2(bdyl)] units. Interestingly, the rollover metalation of 2,2'-bpy is firstly observed in the system containing the copper complex under hydrothermal conditions. 6 is a discrete mixed-valent octa-Cu sandwiched POT supported by two CuI-complexes [CuI2-(2,2'-bpy)2(4,4'-bpy)]2+ through 4,4'-bpy bridges, which constructs a novel dodeca-copper cluster. Notably, the octa-Cu cluster in 6 is mixed-valent and is different from those in 1-5. To our knowledge, 1-6 represent a rare family of POTs incorporating novel octa-Nuclear Transition-metal clusters in polyoxometalate chemistry. They were structurally characterized by FT-IR spectra, elemental analysis, thermogravimetric analysis, and single-crystal X-ray diffraction. The magnetic properties of 1, 4, and 5 were quantitatively analyzed by the MAGPACK software package.
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a combination of lacunary polyoxometalates and high Nuclear Transition metal clusters under hydrothermal conditions part ii from double cluster dimer and tetramer to three dimensional frameworks
Chemistry: A European Journal, 2007Co-Authors: Junwei Zhao, Hongpeng Jia, Jie Zhang, Shoutian Zheng, Guoyu YangAbstract:The hydrothermal reactions of trivacant Keggin A-alpha-XW(9)O(34) polyoxoanions (X=P(V)/Si(IV)) with Transition-metal ions (Ni(II)/Cu(II)/Fe(II)) in the presence of amines result in eight novel high-Nuclear Transition-metal-substituted polyoxotungstates [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][Ni(dap)(2)(H(2)O)(2)]4.5 H(2)O (1), [Cu(dap)(H(2)O)(3)](2)[{Cu(8)(dap)(4)(H(2)O)(2)}(B-alpha-SiW(9)O(34))(2)]6 H(2)O (2), (enH(2))(3)H(15)[{Fe(II) (1.5)Fe(III) (12)(mu(3)-OH)(12)(mu(4)-PO(4))(4)}(B-alpha-PW(9)O(34))(4)]ca.130 H(2)O (3), [{Cu(6)(mu(3)-OH)(3)(en)(3) (H(2)O)(3)}(B-alpha-PW(9)O(34))]7 H(2)O (4), [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]7 H(2)O (5), [{Ni(6)(mu(3)-OH)(3)(en)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))]7 H(2)O (6), [{Ni(6)(mu(3)-OH)(3)(dap)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))] 7 H(2)O (7), and [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-SiW(9)O(34))][Ni(0.5)(en)] 3.5 H(2)O (8) (en=ethylenediamine, dap=1,2-diaminopropane). These compounds have been structurally characterized by elemental analyses, IR spectra, diffuse reflectance spectra, thermogravimatric analysis, and X-ray crystallography. The double-cluster complex of phosphotungstate 1 simultaneously contains hepta- and hexa-Ni(II)-substituted trivacant Keggin units [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))](2-) and [{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]. The dimeric silicotungstate 2 is built up from two trivacant Keggin [B-alpha-SiW(9)O(34)](10-) fragments linked by an octa-Cu(II) cluster. The main skeleton of 3 is a tetrameric cluster constructed from four tri-Fe(III)-substituted [Fe(III) (3)(mu(3)-OH)(3)(B-alpha-PW(9) O(34))](3-) Keggin units linked by a central Fe(II) (4)O(4) cubane core and four mu(4)-PO(4) bridges. Complex 4 is an unprecedented three-dimensional extended architecture with hexagonal channels built by hexa-Cu(II) clusters and trivacant Keggin [B-alpha-PW(9)O(34)](9-) fragments. The common feature of 5-8 is that they contain a B-alpha-isomeric trivacant Keggin fragment capped by a hexa-Ni(II) cluster, very similar to the hexa-Ni(II)-substituted trivacant Keggin unit in 1. Magnetic measurements illustrate that 1, 2, and 5 have ferromagnetic couplings within the magnetic metal centers, whereas 3 and 4 reveal the antiferromagnetic exchange interactions within the magnetic metal centers. Moreover, the magnetic behavior of 4 and 5 have been theoretically simulated by the MAGPACK magnetic program package.
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combination between lacunary polyoxometalates and high Nuclear Transition metal clusters under hydrothermal conditions i from isolated cluster to 1 d chain
Chemical Communications, 2007Co-Authors: Shoutian Zheng, Hongpeng Jia, Jie Zhang, Guoyu Yang, Daqiang YuanAbstract:The hydrothermal reactions of [A-alpha-SiW(9)O(34)](10-)/[A-alpha-PW(9)O(34)](9-) with NiCl(2) x 6H(2)O and amines yielded four unprecedented hybrid high-Nuclear Ni-subsituted polyoxotungstates.
P. K. Rath - One of the best experts on this subject based on the ideXlab platform.
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Nuclear Transition matrix elements for neutrinoless double-β decay of 76Ge within mechanisms involving sterile neutrinos, Majorons and composite neutrinos
International Journal of Modern Physics E, 2021Co-Authors: P. K. Rath, Ashwani Kumar, Ramesh Chandra, P. K. Raina, R. Gautam, B. M. DixitAbstract:Using HFB wave functions generated with a realistic KUO and an empirical JUNE45 effective two-body interactions, Nuclear Transition matrix elements (NTMEs) [Formula: see text] for the [Formula: see text] Transition of neutrinoless double-[Formula: see text] decay of [Formula: see text]Ge isotope are calculated within mechanisms involving sterile neutrinos, Majorons and compositeness scenario. Uncertainties in Nuclear Transition matrix elements are estimated by calculating sets of 12 NTMEs with these two sets of wave functions, two alternative forms of finite size effects (FNS) and three different parametrizations of short range correlations (SRC). Uncertainties in NTMEs within mechanisms involving sterile neutrinos, Majorons and composite neutrinos turn out to be about 10%–36% depending on the mass of sterile neutrinos, 10% and 37%, respectively.
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Nuclear Transition matrix elements for neutrinoless double-β decay of 76Ge within mechanisms involving sterile neutrinos, Majorons and composite neutrinos
International Journal of Modern Physics E-nuclear Physics, 2021Co-Authors: P. K. Rath, Ashwani Kumar, Ramesh Chandra, R. B. Gautam, P. K. Raina, B. M. DixitAbstract:Using HFB wave functions generated with a realistic KUO and an empirical JUNE45 effective two-body interactions, Nuclear Transition matrix elements (NTMEs) M(K) for the 0+ → 0+ Transition of neutri...
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Nuclear Transition matrix elements for neutrinoless double-β decay within Rp-violating squark-neutrino mechanism
International Journal of Modern Physics E, 2020Co-Authors: P. K. Rath, Ramesh Chandra, K. Chaturvedi, B. Shukla, V. K. Nautiyal, P. K. RainaAbstract:Within the squark-neutrino mechanism of [Formula: see text]-violating SUSY, sets of 12 Nuclear Transition matrix elements (NTMEs) are calculated for the neutrinoless double-[Formula: see text] decay [Formula: see text] of [Formula: see text]Zr, [Formula: see text]Mo, [Formula: see text]Pd, [Formula: see text]Te and [Formula: see text]Nd isotopes. Specifically, four sets of HFB wave functions generated with four different parametrizations of the pairing plus multipolar two-body interactions, dipole form factor and three different parametrizations of the Jastrow short-range correlations are employed in the calculation of NTMEs with two possible prescriptions for the hadronization, namely the two-nucleon mode and the pionic mode. Without (with) Miller–Spencer parametrization of short-range correlation, uncertainties in average NTMEs [Formula: see text] (QBM), [Formula: see text] (NRQM), [Formula: see text] (FF3) and [Formula: see text] turn out be 11–18% (29–37%), 11–16% (27–31%), 5–12% (13–17%) and 3–13% (9–15%), respectively.
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Nuclear Transition Matrix Elements for Double-β Decay Within PHFB Model
Frontiers in Physics, 2019Co-Authors: P. K. Rath, Ramesh Chandra, K. Chaturvedi, P. K. RainaAbstract:Employing the projected-Hartree-Fock-Bogoliubov (PHFB) approach, Nuclear Transition matrix elements (NTMEs) have been calculated to study the three complementary modes of $\beta ^{-}\beta ^{-}$ decay, namely two neutrino $% \beta ^{-}\beta ^{-}$ (2$\nu \beta ^{-}\beta ^{-}$) decay, neutrinoless $% \beta ^{-}\beta ^{-}$ (0$\nu \beta ^{-}\beta ^{-}$) decay within mass mechanism and Majoron accompanied 0$\nu \beta ^{-}\beta ^{-}$ (0$\nu \beta ^{-}\beta ^{-}\chi $) decay. Reliability of HFB wave functions generated with four different parametrizations of the pairing plus multipolar type of effective two-body interaction has been ascertained by comparing a number of Nuclear observables with the available experimental data. Specifically, the calculated NTMEs $M^{(2\nu )}$ of 2$\nu \beta ^{-}\beta ^{-}$ decay have been compared with the observed data. Effects due to different parametrizations of effective two-body interactions, form factors and short-range correlations have been studied. It has also been observed that deformation plays a crucial role in the Nuclear structure aspects of 0$\nu \beta ^{-}\beta ^{-}$ decay. Uncertainties in NTMEs calculated with wave functions generated with four different parametrizations of the pairing plus multipolar type of effective two-body interaction, dipole form factor and three different parametrizations of Jastrow type of short-range correlations within mechanisms involving light Majorana neutrinos, heavy Majorona neutrinos, sterile neutrinos and Majorons have been statistically estimated.
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Nuclear Transition matrix elements for neutrinoless double-β decay of 76Ge isotope within PHFB approach
International Journal of Modern Physics E, 2019Co-Authors: P. K. Rath, Ashwani Kumar, Ramesh Chandra, R. B. Gautam, P. K. Raina, B. M. DixitAbstract:Employing projected–Hartree–Fock–Bogoliubov (PHFB) model, Nuclear Transition matrix elements (NTMEs) M(K) for the neutrinoless double-β− decay of 76Ge isotope are calculated within mechanisms invol...
Adriana Pálffy - One of the best experts on this subject based on the ideXlab platform.
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tailoring laser generated plasmas for efficient Nuclear excitation by electron capture
Physical Review Letters, 2018Co-Authors: Jonas Gunst, Christoph H. Keitel, Adriana PálffyAbstract:The optimal parameters for Nuclear excitation by electron capture in plasma environments generated by the interaction of ultrastrong optical lasers with solid matter are investigated theoretically. As a case study we consider a 4.85 keV Nuclear Transition starting from the long-lived $^{93\mathrm{m}}\mathrm{Mo}$ isomer that can lead to the release of the stored 2.4 MeV excitation energy. We find that due to the complex plasma dynamics, the Nuclear excitation rate and the actual number of excited nuclei do not reach their maximum at the same laser parameters. The Nuclear excitation achievable with a high-power optical laser is up to twelve and up to six orders of magnitude larger than the values predicted for direct resonant and secondary plasma-mediated excitation at the x-ray free electron laser, respectively. Our results show that the experimental observation of the Nuclear excitation of $^{93\mathrm{m}}\mathrm{Mo}$ and the subsequent release of stored energy should be possible at laser facilities available today.
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Laser-induced electronic bridge for characterization of the 229mTh → 229gTh Nuclear Transition with a tunable optical laser with a tunable optical laser
New Journal of Physics, 2018Co-Authors: Pavlo V. Bilous, Ekkehard Peik, Adriana PálffyAbstract:An alternative method to determine the excitation energy of the $~^{229\rm{m}}\rm{Th}$ isomer via the laser-induced electronic bridge is investigated theoretically. In the presence of an optical or ultra-violet laser at energies that fulfill a two-photon resonance condition, the excited Nuclear state can decay by transfering its energy to the electronic shell. A bound electron is then promoted to an excited state by absorption of a laser photon and simultaneous de-excitation of the nucleus. We present calculated rates for the laser-induced electronic bridge process and discuss the experimental requirements for the corresponding setup. Our results show that depending on the actual value of the Nuclear Transition energy, the rate can be very high, with an enhancement factor compared to the radiative Nuclear decay of up to $10^8$.
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Electric-dipole-forbidden Nuclear Transitions driven by super-intense laser fields
Physical Review C, 2008Co-Authors: Adriana Pálffy, Joerg Evers, Christoph H. KeitelAbstract:Electric-dipole-forbidden Transitions of nuclei interacting with super-intense laser fields are investigated by considering stable isotopes with suitable low-lying first excited states. Different classes of Transitions are identified, and all magnetic sublevels corresponding to the near-resonantly driven Nuclear Transition are included in the description of the Nuclear quantum system. We find that large Transition matrix elements and convenient resonance energies qualify Nuclear M1 Transitions as good candidates for the coherent driving of nuclei. We discuss the implications of resonant interaction of intense laser fields with nuclei beyond the dipole approximation for the controlled preparation of excited Nuclear states and important aspects of possible experiments aimed at observing these effects.
Ekkehard Peik - One of the best experts on this subject based on the ideXlab platform.
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The thorium-229 low-energy isomer and the Nuclear clock
Nature Reviews Physics, 2021Co-Authors: Kjeld Beeks, Thorsten Schumm, Tomas Sikorsky, Johannes Thielking, Maxim V. Okhapkin, Ekkehard PeikAbstract:The ^229Th nucleus has an isomeric state at an energy of about 8 eV above the ground state, several orders of magnitude lower than typical Nuclear excitation energies. This has inspired the development of a field of low-energy Nuclear physics in which Nuclear Transition rates are influenced by the electron shell. The low energy makes the ^229Th isomer accessible to resonant laser excitation. Observed in laser-cooled trapped thorium ions or with thorium dopant ions in a transparent solid, the Nuclear resonance may serve as the reference for an optical clock of very high accuracy. Precision frequency comparisons between such a Nuclear clock and conventional atomic clocks will provide sensitivity to the effects of hypothetical new physics beyond the standard model. Although laser excitation of ^229Th remains an unsolved challenge, recent experiments have provided essential information on the Transition energy and relevant Nuclear properties, advancing the field. A Nuclear clock, based on a radiative Transition in the nucleus, is less sensitive to external perturbations and therefore potentially more precise than established atomic clocks that are based on Transitions in the electron shell. The ^229Th nucleus is the prime candidate for the realization of a Nuclear clock because it possesses a low-energy (8 eV) excited state that is amenable to resonant laser excitation from the Nuclear ground state, with an expected natural linewidth in the millihertz range. Recent experiments have provided essential information on the Nuclear properties of ^229Th (half-life 7,920 years), such as the Nuclear moments, decay modes of the isomer and a more precise value of the isomer excitation energy, which is required to achieve laser excitation. Thorium-229 is studied as trapped atomic ions in vacuum or doped into transparent crystals such as CaF_2. Because the Nuclear Transition energy is in the range of Transitions of valence electrons, the electronic state may influence the Nuclear excitation and decay rates. Because of a fine balance of contributions from the strong and electromagnetic interactions to the Nuclear Transition energy, a ^229Th clock would be sensitive to predicted effects of physics beyond the standard model, such as temporal or spatial variations of fundamental constants. A clock using the excitation of a low-energy excited state in the ^229Th nucleus promises high accuracy and sensitivity to new physics. The recently measured properties of this nucleus will lead to Nuclear laser spectroscopy with trapped Th ions and Th-doped crystals.
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Laser-induced electronic bridge for characterization of the 229mTh → 229gTh Nuclear Transition with a tunable optical laser with a tunable optical laser
New Journal of Physics, 2018Co-Authors: Pavlo V. Bilous, Ekkehard Peik, Adriana PálffyAbstract:An alternative method to determine the excitation energy of the $~^{229\rm{m}}\rm{Th}$ isomer via the laser-induced electronic bridge is investigated theoretically. In the presence of an optical or ultra-violet laser at energies that fulfill a two-photon resonance condition, the excited Nuclear state can decay by transfering its energy to the electronic shell. A bound electron is then promoted to an excited state by absorption of a laser photon and simultaneous de-excitation of the nucleus. We present calculated rates for the laser-induced electronic bridge process and discuss the experimental requirements for the corresponding setup. Our results show that depending on the actual value of the Nuclear Transition energy, the rate can be very high, with an enhancement factor compared to the radiative Nuclear decay of up to $10^8$.
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Experimental search for the low-energy Nuclear Transition in 229Th with undulator radiation
New Journal of Physics, 2015Co-Authors: A Yamaguchi, Michael Kolbe, Hendrik Kaser, T Reichel, Alexander Gottwald, Ekkehard PeikAbstract:To search for the lowest energy Nuclear isomeric Transition in 229Th in solid samples, a novel adsorption technique which prepares 229Th atoms on a surface of CaF2 is developed. Adsorbed 229Th is exposed to highly intensive undulator radiation in the wavelength range between 130 and 320 nm, which includes the indirectly measured Nuclear resonance wavelength 160(10) nm. After the excitation, fluorescence from the sample is detected with a VUV sensitive photomultiplier tube. No clear signal relating to the Nuclear Transition is observed and possible reasons are discussed.
Junwei Zhao - One of the best experts on this subject based on the ideXlab platform.
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rare sandwich type polyoxomolybdates constructed from di tetra Nuclear Transition metal clusters and trivacant keggin germanomolybdate fragments
Inorganic Chemistry, 2009Co-Authors: Junwei Zhao, Jingyang Niu, Jingping WangAbstract:Two types of rare sandwich-type germanomolybdates [Na12(H2O)36][Cu2(β-Y-GeMo9O33)2]·3H2O (1), [N(CH3)4]4 [Na6(H2O)24][Cr2(β-Y-GeMo9O33)2]·7H2O (2), and [Na11(H2O)25]H[M4(H2O)2(α-B-GeMo9O34)2]·6H2O (M = NiII for 3, M = MnII for 4 and M = CoII for 5) have been synthesized and characterized by elemental analyses, ICP spectra, IR spectroscopy, UV spectroscopy, thermogravimetry (TG) analyses (for 1−3), X-ray photoelectron spectroscopy (XPS) (for 1 and 3), X-ray powder diffraction (XRPD) (for 1 and 3) and single-crystal X-ray diffraction. To our knowledge, 1−5 represent the first sandwich-type germanomolybdates containing both {β-Y-GeMo9O33}/{α-B-GeMo9O34} fragments and Transition-metal clusters. Interestingly, 1 and 2 display the rare diNuclear Transition-metal substituted sandwich-type structures with unusual trivacant {β-Y-GeMo9O33} germanomolybdate units whereas 3−5 exhibit the first tetraNuclear Transition-metal substituted sandwich-type structures with familiar trivacant {α-B-GeMo9O34} germanomolybdate un...
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combination of lacunary polyoxometalates and high Nuclear Transition metal clusters under hydrothermal conditions ix a series of novel polyoxotungstates sandwiched by octa copper clusters
Chemistry: A European Journal, 2008Co-Authors: Junwei Zhao, Jie Zhang, Shoutian Zheng, Chunmei Wang, Guoyu YangAbstract:The reaction of CuCl(2).2 H2O with trivacant Keggin polyoxoanions K8Na2[A-alpha-GeW9O34].25 H2O or K10[A-alpha-SiW9O34].25 H2O in the presence of 1,2-diaminopropane (dap), ethylenediamine (en) or 2,2'-bipyridine (2,2'-bpy) under hydrothermal conditions afforded five novel hybrid inorganic-organic octa-Cu sandwiched polyoxotungstates (POTs): H4[CuII8(dap)4(H2O)2(B-alpha-GeW9O34)2].13 H2O (1), (H2en)2[CuII8-(en)4(H2O)2(B-alpha-GeW9O34)2].5 H2O(2), (H2en)2[CuII8(en)4(H2O)2(B-alpha-SiW9-O34)2].8 H2O (3), [CuII(H2O)2]H2[CuII8-(en)4(H2O)2(B-alpha-SiW9O34)2] (4), and [CuII2(H2O)2(2,2'-bpy)2]{[CuII(bdyl)]2-[CuII8(2,2'-bpy)4(H2O)2(B-alpha-GeW9-O34)2]}.4 H2O (bdyl=2,2'-bipyridinyl)(5). Additionally, CuCl(2).2 H2O reacts with the mixture of GeO2, Na2WO(4).2 H2O, H2SiW12O(40).2 H2O in the presence of 2,2'-bpy and 4,4'-bpy under hydrothermal conditions leading to another novel mixed-valent octa-Cu sandwiched POT hybrid: [CuI(2,2'-bpy)(4,4'-bpy)]2[{CuI2(2,2'-bpy)2(4,4'-bpy)]2[CuI2CuII6(2,2'-bpy)2(4,4'-bpy)2(B-alpha-GeW9O34)2}].2 H2O (6). 1, 2, and 3 are discrete dimers constructed from two trivacant Keggin [B-alpha-XW9O34]10- (X=GeIV/SiIV) fragments and an octa-Cu cluster whereas 4 displays the 3D (3,6)-connected nets with (4.6(2))(4(2).6(4).8(7).10(2)) topology, which are built by octa-Cu sandwiched polyoxometalate building blocks through copper cation bridges. 5 is a novel 2D layer based on octa-Cu sandwiched POT clusters and [CuII2(bdyl)] units. Interestingly, the rollover metalation of 2,2'-bpy is firstly observed in the system containing the copper complex under hydrothermal conditions. 6 is a discrete mixed-valent octa-Cu sandwiched POT supported by two CuI-complexes [CuI2-(2,2'-bpy)2(4,4'-bpy)]2+ through 4,4'-bpy bridges, which constructs a novel dodeca-copper cluster. Notably, the octa-Cu cluster in 6 is mixed-valent and is different from those in 1-5. To our knowledge, 1-6 represent a rare family of POTs incorporating novel octa-Nuclear Transition-metal clusters in polyoxometalate chemistry. They were structurally characterized by FT-IR spectra, elemental analysis, thermogravimetric analysis, and single-crystal X-ray diffraction. The magnetic properties of 1, 4, and 5 were quantitatively analyzed by the MAGPACK software package.
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a combination of lacunary polyoxometalates and high Nuclear Transition metal clusters under hydrothermal conditions part ii from double cluster dimer and tetramer to three dimensional frameworks
Chemistry: A European Journal, 2007Co-Authors: Junwei Zhao, Hongpeng Jia, Jie Zhang, Shoutian Zheng, Guoyu YangAbstract:The hydrothermal reactions of trivacant Keggin A-alpha-XW(9)O(34) polyoxoanions (X=P(V)/Si(IV)) with Transition-metal ions (Ni(II)/Cu(II)/Fe(II)) in the presence of amines result in eight novel high-Nuclear Transition-metal-substituted polyoxotungstates [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][Ni(dap)(2)(H(2)O)(2)]4.5 H(2)O (1), [Cu(dap)(H(2)O)(3)](2)[{Cu(8)(dap)(4)(H(2)O)(2)}(B-alpha-SiW(9)O(34))(2)]6 H(2)O (2), (enH(2))(3)H(15)[{Fe(II) (1.5)Fe(III) (12)(mu(3)-OH)(12)(mu(4)-PO(4))(4)}(B-alpha-PW(9)O(34))(4)]ca.130 H(2)O (3), [{Cu(6)(mu(3)-OH)(3)(en)(3) (H(2)O)(3)}(B-alpha-PW(9)O(34))]7 H(2)O (4), [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]7 H(2)O (5), [{Ni(6)(mu(3)-OH)(3)(en)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))]7 H(2)O (6), [{Ni(6)(mu(3)-OH)(3)(dap)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))] 7 H(2)O (7), and [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-SiW(9)O(34))][Ni(0.5)(en)] 3.5 H(2)O (8) (en=ethylenediamine, dap=1,2-diaminopropane). These compounds have been structurally characterized by elemental analyses, IR spectra, diffuse reflectance spectra, thermogravimatric analysis, and X-ray crystallography. The double-cluster complex of phosphotungstate 1 simultaneously contains hepta- and hexa-Ni(II)-substituted trivacant Keggin units [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))](2-) and [{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]. The dimeric silicotungstate 2 is built up from two trivacant Keggin [B-alpha-SiW(9)O(34)](10-) fragments linked by an octa-Cu(II) cluster. The main skeleton of 3 is a tetrameric cluster constructed from four tri-Fe(III)-substituted [Fe(III) (3)(mu(3)-OH)(3)(B-alpha-PW(9) O(34))](3-) Keggin units linked by a central Fe(II) (4)O(4) cubane core and four mu(4)-PO(4) bridges. Complex 4 is an unprecedented three-dimensional extended architecture with hexagonal channels built by hexa-Cu(II) clusters and trivacant Keggin [B-alpha-PW(9)O(34)](9-) fragments. The common feature of 5-8 is that they contain a B-alpha-isomeric trivacant Keggin fragment capped by a hexa-Ni(II) cluster, very similar to the hexa-Ni(II)-substituted trivacant Keggin unit in 1. Magnetic measurements illustrate that 1, 2, and 5 have ferromagnetic couplings within the magnetic metal centers, whereas 3 and 4 reveal the antiferromagnetic exchange interactions within the magnetic metal centers. Moreover, the magnetic behavior of 4 and 5 have been theoretically simulated by the MAGPACK magnetic program package.
