Probing the Local Magnetic Structure of the [FeIII(Tp)(CN)3]− Building Block Via Solid-State NMR Spectroscopy,Polarized Neutron Diffraction,and First-Principle Calculations

The local magnetic structure in the [Fe^III(Tp)(CN)₃]⁻ building block was investigated by combining paramagnetic Nuclear Magnetic Resonance (pNMR) spectroscopy and polarized neutron diffraction (PND) with first-principle calculations. The use of the pNMR and PND experimental techniques revealed the extension of spin-density from the metal to the ligands, as well as the different spin mechanisms that take place in the cyanido ligands: Spin-polarization on the carbon atoms and spin-delocalization on the nitrogen atoms. The results of our combined density functional theory (DFT) and multireference calculations were found in good agreement with the PND results and the experimental NMR chemical shifts. Moreover, the ab-initio calculations allowed us to connect the experimental spin-density map characterized by PND and the suggested distribution of the spin-density on the ligands observed by NMR spectroscopy. Interestingly, significant differences were observed between the pseudo-contact contributions of the chemical shifts obtained by theoretical calculations and the values derived from NMR spectroscopy using a simple point-dipole model. These discrepancies underline the limitation of the point-dipole model and the need for more elaborate approaches to break down the experimental pNMR chemical shifts into contact and pseudo-contact contributions.     

A Thermal and Structural Study On Lanthanum Hexacyanocobaltate(III) Pentahydrate, La[Co(CN)6]⋅5H2O

Thermal and structural changes of lanthanum hexacyanocobaltate(III) pentahydrate, La[Co(CN)₆]⋅5H₂O were investigated by means of thermal analysis, visible electronic spectra, IR, powder X-ray diffraction, EXAFS and TG-MS. The dehydration of La[Co(CN)₆]⋅5H₂O proceeded reversibly through three steps and steps corresponded to the losses of H₂O, 3H₂O and H₂O, and the enthalpy changes for these steps were 51.3, 211.0 and 38.7 kJ mol⁻¹, respectively. After the dehydration, the colour of the anhydride changed from white to blue around 290°C and an abrupt mass loss occurred at 350°C. The colour change seems to be attributable to the change of coordination geometry around the Co ions from an octahedral structure to a tetrahedral one. LnCoO₃ was obtained as a final product by heating the sample to 1000°C. This revised version was published online in August 2006 with corrections to the Cover Date.     

{Sn9[Si(SiMe3)3]3}− and {Sn8Si[Si(SiMe3)3]3}−: variations of the E9 cage of metalloid group 14 clusters

The disproportionation reaction of the subvalent metastable halide SnBr proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Hence, the neutral metalloid cluster compound Sn(10)[Si(SiMe(3))(3)](6) (3) was synthesized from the reaction of SnBr with LiSi(SiMe(3))(3). In the course of the reaction anionic clusters might also be present, and we now present the first anionic cluster compound {Sn(8)E[Si(SiMe(3))(3)](3)}(-) (E = Si, Sn), where one position in the cluster core is occupied by a silicon or a tin atom, giving further insight into structural variations of E(9) cages in metalloid group 14 cluster compounds.     

Structural,Electronic and Magnetic Properties of Co_nO(n = 2～10) Clusters: A Density Functional Study

The structural, electronic, and magnetic properties of Co_nO(n = 2～10) clusters have been systematically investigated within the framework of the generalized gradient approximation density functional theory. The results indicate that the O atom occupies the surface-capped position on Co_nO(n = 2～10) clusters. The stabilities of the host clusters are improved by adding one O atom. Maximum peaks of the second-order difference energy of the ground-state Co_nO clusters are found at n = 3, 6 and 8, indicating higher stability than their neighboring clusters. Compared with corresponding pure Con clusters, the O-doped cobalt clusters have larger gaps between the HOMO and LUMO energy levels, indicating their higher chemical stabilities. In addition, the doping of O atom exhibits different influence on the magnetism of the clusters. This is also further investigated by the local magnetic moment, deformation charge density and partial local density of states analysis.     

Temperature- and pressure-dependent kinetico-mechanistic studies on the formation of mixed-valence {(tetraamine)CoIIINCFeII(CN)5}− units

The reduction of Co^III in the tetraamine-encapsulating ligand complex [Co^III{(μ-ET)(Me₂)cyclen}(H₂O)₂]³⁺ by [Fe^II(CN)₆]^4? has been studied kinetico-mechanistically at different pH, temperatures, and pressures. The process agrees with the expected outer-sphere redox mechanism, with the value of the encounter-complex equilibrium constant large enough to allow for kinetic determination of the first-order electron transfer reaction rate constant. The value of the encounter-complex equilibrium constant, K_pre-eq, is not only dependent on the charge of the redox partners, but also on the establishment of an important network of hydrogen bonds. These can also explain the differences obtained in the activation volumes determined for the diaqua and bis-hydroxo complexes. Neither the leaching of Co^II nor the presence of [Fe^III(CN)₆]^3? is observed in the final reaction medium, which indicates that a fast sequence involving substitution on the transient Co^II complex followed by a fast inner-sphere electron transfer takes place. This sort of mechanism has already been established for encapsulating pentaamine ligand complexes, but this is the first example of such a sequential reaction occurring on a tetradentate ligand complex. Preliminary UV–Vis and electrochemical characterization experiments have been conducted on the final reaction mixtures, suggesting the formation of a stable cyanide-bridged Co^III/Fe^II mixed-valence complex of the same type reported in the literature for encapsulating {Co^III(N)₅} skeletons.     

3D-QSAR Study on Diindolylmethane and Its Analogues with Comparative Molecular Field Analysis (CoMFA)

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Two Co(Ⅱ) Coordination Polymers Based on 3,5-Di(4H-1,2,4-triazole-4-yl)benzoic Acid Ligand: Syntheses,Structures and Magnetic Property

Two Co(Ⅱ) coordination polymers, namely [Co(L)Cl]_n(1) and [Co(L)(CH_3 COO)]_n(2), {HL = 3,5-di(4 H-1,2,4-triazole-4-yl)benzoic acid}, were synthesized under hydrothermal conditions. Compound 1 crystallizes in orthorhombic system, space group Pmma with a = 7.032(5), b = 11.555(8), c = 8.185(5) ?, V = 665.1(7) ?~3, Z = 2, Dc = 1.746 g/cm3~, F(000) = 350, Mr = 349.61, μ = 1.504 mm~(-1), the final R = 0.0568 and w R = 0.1739 for 2312 observed reflections with I 2σ(I). Compound 2 crystallizes in orthorhombic system, space group Pmma with a = 7.7505(17), b = 11.391(3), c = 8.0298(18) ?, V = 708.9(3) ?~3, Z = 2, Dc = 1.748 g/cm~3, F(000) = 378, Mr = 373.20, μ = 1.245 mm-1, the final R = 0.0350 and w R = 0.0873 for 5239 observed reflections with I 2σ(I). Single-crystal X-ray analyses revealed that complexes 1 and 2 exhibit similar 2 D layer structures with uncoordinated carboxyl as dangling arms. The neighboring layers are further connected by these arms, leading to interest 2 D → 3 D polythreading frameworks. Moreover, the magnetic susceptibility study indicates compound 1 exhibits antiferromagnetic behavior.     

A Carboxylate-bridged Co(Ⅱ) Layer Complex: Synthesis,Structure and Magnetic Property

A 2D coordination polymer, [Co(NPA)(H_2 O)_2]_n(1, H_2 NPA = 3-nitrophthalic acid), has been synthesized by solvothermal method and characterized by single-crystal X-ray diffraction analysis, FT-IR spectroscopy, elemental analysis, thermogravimetric analysis and powder X-ray diffraction. Complex 1 crystallizes in orthorhombic space group Pbca with a = 7.2261(2), b = 14.6450(5), c = 19.6671(7) ?, V = 2081.31(11) ?~3, Z = 8, C_8 H_7 CoNO_8, M_r = 304.08, D_c = 1.941 mg/m~3, μ = 1.686 mm~(-1), S = 1.054, F(000) = 1224, the final R = 0.0248 and wR = 0.0603 for 1834 observed reflections(I 2σ(I)). The crystal structural analysis demonstrates that the Co(Ⅱ) ions in 1 are linked by single and double μ_2-1,3-bridging carboxylate bridges, forming a 2D layer structure. Moreover, magnetic property of 1 was also discussed.     

Chemisorption Synthesis of the Ion-Polymeric Heteronuclear Gold(III)–Bismuth(III) Complex ([Au{S2CN(C3H7)2}2]3[Bi2Cl9])n Based on [Bi2{S2CN(C3H7)2}6]: 13C MAS NMR,Supramolecular Structure,and Thermal Behavior

Russian Journal of Coordination Chemistry - Chemisorption synthesis on the basis of the binuclear compound [Bi2{S2CN(C3H7)2}6] (I) and preparative isolation of the ion-polymeric heteronuclear...     

Theoretical Study of the Structural,Electronic, and Magnetic Properties of Zirconium-doped Aluminum Clusters:Al_nZr(n = 1～14)

The geometrical structures, stabilities, electronic and magnetic properties of Al_nZr(n = 1~14) clusters have been systematically investigated using density functional theory. It is found that for the optimized clusters the zirconium atom prefers to remain on the surface, and the growth patterns are organized as follows: Zr substituted Al_(n+1) clusters or Zr capped Aln clusters as well as Al added Al_(n-1)Zr clusters. All doped clusters exhibit relatively larger average binding energies and magnetic behaviors compared with pure Al_(n+1) counterpart. The calculated fragmentation energies and second-order difference of energies exhibit pronounced odd-even alternation behavior as a function of the cluster size when n = 3~13. In all Al_nZr clusters, there exits internal hybridization in both Al and Zr atoms and charge transfer from Al to Zr atom, which reflects the strong interactions between the two kinds of atoms. The magnetic property analysis shows that the 4d electrons of Zr atom are the main origin for cluster magnetism.     

New Electrode Materials for Symmetrical Solid Oxide Fuel Cells Based on Perovskites (La,Ca)(Fe,Co,Mg,Mo)O3 – δ

Russian Journal of Electrochemistry - The conductivity of perovskites La0.3Ca0.7Fe0.6Mg0.175Mo0.225O3 – δ (LCF6) and...     

Syntheses,Crystal Structures and Magnetic Studies of Heterobimetallates Based on Paramagnetic Ruthenium(Ⅲ) Building Block [Ru~Ⅲ(salchda)(CN)_2]

The syntheses, crystal structures and magnetic properties of two cyano-bridged heterobimetallic compounds prepared from a paramagnetic Ru Ⅲ building block, transK[RuI II(salchda)(CN)_2](1, salchda = N,N?-bis(salicylidene)-o-cyclohexylenediamine), are described.1 reacts with hydrated CoCl_2 and [Mn Ⅲ(salchda)(Cl)(H_2O)] in MeOH to produce a trinuclear compound {[Ru~Ⅲ(salchda)(CN)]_2(μ-CN)_2[Co(MeOH)_4]?4MeOH}_n(2) and a dinuclear{[Ru~Ⅲ(salchda)(CN)](μ-CN)[Mn~Ⅲ(salchda)(MeOH)]?2MeOH}n(3), respectively. Both compounds exhibit intramolecular ferromagnetic coupling between Ru~Ⅲ and 3-d metal centers via the cyano bridge and intermolecular antiferromagnetic coupling. Moreover, 2 exhibits antiferromagnetic ordering below 3.4 K.     

Syntheses,Crystal Structures and Magnetic Studies of Two Mn(Ⅱ) Complexes Based on 2-Pyrimidineamidoxime

Two novel manganese(Ⅱ) complexes, [Mn(pmadH_2)_2(3-Sb)]n(1) and {[Mn(pmadH2)(Hssal)(H_2O)]·2 H_2O}n(2)(pmadH_2= 2-pyrimidineamidoxime, 3-Sb = 3-sulfobenzoate dianion, H_3ssal = 5-sulfosalicylic acid), have been successfully obtained. The two complexes were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermal gravimetric analysis, infrared spectra and elemental analysis. They are one-dimensional manganese polymer(1) and two-dimensional manganese complex(2), respectively. The values of χmT at 300 K of 1 and 2 are lower than the spin-only value for the non-interacting Mn(Ⅱ) ion(S = 5/2).     

Investigation of Molecular Iridium Fluorides IrFn (n=1–6): A Combined Matrix-Isolation and Quantum-Chemical Study

The photo-initiated defluorination of iridium hexafluoride (IrF₆) was investigated in neon and argon matrices at 6 K, and their photoproducts are characterized by IR and UV-vis spectroscopies as well as quantum-chemical calculations. The primary photoproducts obtained after irradiation with λ=365 nm are iridium pentafluoride (IrF₅) and iridium trifluoride (IrF₃), while longer irradiation of the same matrix with λ=278 nm produced iridium tetrafluoride (IrF₄) and iridium difluoride (IrF₂) by Ir−F bond cleavage or F₂ elimination. In addition, IrF₅ can be reversed to IrF₆ by adding a F atom when exposed to blue-light (λ=470 nm) irradiation. Laser irradiation (λ=266 nm) of IrF₄ also generated IrF₆, IrF₅, IrF₃ and IrF₂. Alternatively, molecular binary iridium fluorides IrF_n (n=1–6) were produced by co-deposition of laser-ablated iridium atoms with elemental fluorine in excess neon and argon matrices under cryogenic conditions. Computational studies up to scalar relativistic CCSD(T)/triple-ζ level and two-component quasirelativistic DFT computations including spin-orbit coupling effects supported the formation of these products and provided detailed insights into their molecular structures by their characteristic Ir−F stretching bands. Compared to the Jahn-Teller effect, the influence of spin-orbit coupling dominates in IrF₅, leading to a triplet ground state with C_4v symmetry, which was spectroscopically detected in solid argon and neon matrices.     

A New Tetranuclear Cubane-like Ni(Ⅱ) Complex Based on Schiff-base Ligand: Synthesis,Crystal Structure and Magnetic Properties

A new Ni(Ⅱ) cubane-like complex, namely, [Ni(L)(CH_3OH)]_4·(CH_3OH)_2, has been obtained via self-assembly of nickel(Ⅱ) and Schiff base, where the ligand L is a raceme of(R)-2-[(2-hydroxy-1-phenyl-ethylimino)-methyl]-6-methoxy-phenol. X-ray diffraction analysis reveals that the complex shows a cubane-like [Ni_4O_4] cluster and similar coordination environment around the metallic centers. Magnetic measurements indicate there is ferromagnetic interaction within the Ni_4 cluster.     

A Novel 3D Pillar-layered Co(Ⅱ)-MOF with(4,8)-Connected Topology: Synthesis,Structure and Magnetic Properties

By using pillaring strategy, a new Co(Ⅱ)-MOF, [Co_2(abtc)(bimb)_2]·2H_2O(1, H_4abtc = 3,3?,5,5?-azobenzenetetracarboxylic acid, bimb = 4,4?-bis(imidazole-1-ylmethyl)biphenyl), has been solvothermally synthesized and structurally characterized. The structural determination revealed that 1 features a 3D pillar-layered framework with(4,8)-connected {4~4.6~2}{4~8.6~(20)} topology based on dinuclear Co(Ⅱ)-SBUs. The magnetic investigation shows that the dominant antiferromagnetic coupling is observed in compound 1.     

Study on the Bond Covalency and Bond Susceptibility in NdCr_(1-x)M_xO_3 (M=Mn, Fe, Co)

IntroductionNdCrl-.M.Os(M=Mn,Fe,Co)'-'haveanorthorhombicperovskite-typestrUcture,andareallp-typesendconductors.lnNdCr,-.Mn.O,'andNdCr,-.Fe.O,',theaverage(Cr,Mn)-Oand(Cr,Fe)-Obonddistancesandeffectivemagneticmomentincreasewiththeincreasingdopinglevel,indicatingthatMn3 andFe3 ionsareinhigh-spinstateswith(dE)'(dY)'and(dE)'(dY)'electronconfigurationsrespectively.However,forNdCr,x.Co.O,'atlowtemperatures,theaverage(Cr,Co)-Obonddistancesandeffectivemagneticmomentsdecrease,suggestingtha…     

Syntheses,Crystal Structures and Properties of Mn(Ⅱ) and Co(Ⅱ) Coordination Complexes Based on 1,10-Phenanthroline Derivative

Two new coordination complexes[Mn(L)₂(DNSA)](1) and[Co(L)(1,4-bdc)]_n (2) have been achieved under hydrothermal conditions (H₂DNSA=3,5-dinitro-salicylic acid,1,4-bdc=1,4-benzenedicarboxylic acid and L=2-(2-fluoro-6-fluorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline).1 crystallizes in monoclinic,space group P2_1/c with a=15.871(3),b=17.274(4),c=16.078(3)A,β=113.03(3)^o,V=4056.6(16)A³,Z=4,C₄₅H₂₂Cl₂F₂Mn N₁₀O₇,M_r=978.57,D_c=1.602 g/cm³,F(000)=1980,μ(Mo Ka)=0.536 mm^–1,R=0.0437 and w R=0.1065.2 belongs to the monoclinic system,space group C2/c with a=14.665(2),b=30.856(4),c=11.237(2)A,β=111.166(2)^o,V=4742.0(12)A³,Z=8,C₂₇H₁₄Cl Co FN₄O₄,M_r=517.80,D_c=1.602 g/cm³,F(000)=2312,μ(Mo Ka)=0.889 mm^–1,R=0.0364 and w R=0.0862.The central Mn(II) ion in 1 is six-coordinated by four nitrogen atoms from two L ligands and two oxygen atoms from one DNSA anion.In 2,the two kinds of 1,4-bdc ligands link neighboring Co(II) atoms to yield a two-dimensional layer structure.The luminescence of 1 has been studied in detail.Moreover,thermal behaviors of 1 and 2 are also investigated.     

3D－QSAR Study on Diindolylmethane and Its Analogues with Comparative Molecular Field Analysis(CoMFA)

Comparative molecular field analysis (CoMFA),a three dimensional quantitative structure-activity relationship (3D-QSAR) method was applied to a series of diindolylmethane(DIM) analogs to study the relationship between their structure and their induction of CYP 1A1-associated ethoxyresorufin-O-deethylase(EROD) activity.A DISCO model of pharmacophore was derved to guide the superposition of the compounds.The coefficient of cross-validation (q^2) and non cross-validation(r^2) for the model established by the study are 0.827 and 0.988 respectively,the value of variance ratio (F) is 103.53 and standard error estimate (SEE)is 0.044.These values indicate that the CoMFA model derived is significant and might have a good prediction for the catalytic activity of DIM compounds.As a consequence,the predicted activity values of new designed compounds were all higher than that of the reported value.     

Platinum(II) cyclo-hexamethylenedithiocarbamate complex, [Pt{S2CN(CH2)6}2] and its solvated form, [Pt{S2CN(CH2)6}2] · CHCl3: Crystal and molecular structures, 13C CP/MAS NMR data, and thermal behavior

Platinum(II) cyclo-hexamethylenedithiocarbamate (HmDtc) complex, [Pt{S₂CN(CH₂)₆}₂] (I), and its solvated form, Pt{S₂CN(CH₂)₆}₂] · CHCl₃ (II), are synthesized and characterized by the ¹³C MAS NMR data. The HmDtc ligands in structure I are not equivalent, whereas the solvation of the complex is accompanied by the structural unification of the initially nonequivalent HmDtc ligands. In addition, the spectra are characterized by the ¹³C-¹⁹⁵Pt spin-spin coupling. The noncentrosymmetric molecular structure of compound I determined by X-ray diffraction analysis includes two nonequivalent dithiocarbamate ligands coordinated by the metal in the S,S′-bidentate mode. The central atom forming the [PtS₄] chromophore (intraorbital dsp ²-hybrid state of platinum) shifts from the plane of four sulfur atoms by 0.07 Å in the vertex of the flattened tetragonal pyramid. The seven-membered heterocycles ?N(CH₂)₆ of the HmDtc ligands are oppositely directed in space relative to the [S₄] plane (trans orientation). The thermal behavior of compounds I and II are studied by simultaneous thermal analysis. In both cases, the final product of the multistage thermal destruction of the complexes is reduced metallic platinum.