金属离子(Na~+、K~+、Ca~(2+)、Mg~(2+)、Zn~(2+))与鸟嘌呤异构体配合物的稳定性

在B3LYP/6-311++G**水平上用极化连续介质模型(PCM)系统研究了金属离子(M+/2+=Na+,K+,Ca2+,Mg2+,Zn2+)和十三种鸟嘌呤异构体形成的配合物GnxM+/2+(n为鸟嘌呤异构体的编号,x表示M+/2+与鸟嘌呤异构体的结合位点)在气(g)液(a)两相中的稳定性顺序.着重探讨了液相中配合物的稳定性差异,并且从溶质-溶剂效应、结合能、形变能及异构体的相对能量等几个方面分析了造成稳定顺序发生变化的原因.报道了溶液中这五种金属离子与鸟嘌呤异构体结合形成的六种基态配合物:aG1N2,N3Na+,aG1N2,N3K+,aG1O6,N7Ca2+,aG1N2,N3Mg2+(aG1O6,N7Mg2+),aG2N3,N9Zn2+.可以看出,除了在Zn2+配合物中鸟嘌呤异构体为G2外,构成其余四种金属离子配合物的鸟嘌呤异构体都是G1,但结合位点不同.同时对气相中各类配合物稳定性也进行了系统的排序,并报道了几种较稳定的配合物,如:gG3N1,O6K+,gG5N1,O6K+,gG3N1,O6Ca2+/Mg2+,gG4O6,N7Ca2+/Mg2+.     

Ag2.54Tl2Mo12Se15: a new structure type containing Mo6 and Mo9 clusters

The novel structure‐type Ag_2.54Tl₂Mo₁₂Se₁₅ (silver thallium molybdenum selenide) is built up of Mo₆Seⁱ₈Se^a₆ and Mo₉Seⁱ₁₁Se^a₆ cluster units in a 1:2 ratio, which are three‐dimensionally connected to form the Mo–Se network. The Ag and Tl cations are distributed in several voids within the cluster network. Three of the seven independent Se atoms and one Tl atom lie on sites with 3.. symmetry (Wyckoff sites 2c or 2d).     

Rb4Mo21Se24 containing Mo12 and Mo15 clusters

Rubidium molybdenum selenide, Rb₄Mo₂₁Se₂₄, crystallizes in the trigonal space group R. Its crystal structure consists of a mixture of Mo₁₂Se₁₄Se₆ and Mo₁₅Se₁₇Se₆ cluster units in a 1:2 ratio. Both units are interconnected through Mo—Se bonds. The Rb⁺ cations occupy large voids between the different cluster units.     

Synthesis and structure of a new octahedral molybdenum thiocyanide cluster complex K7[Mo6(μ3-S)8(CN)6]·8H2O

The new octahedral molybdenum thiocyanide cluster complex K₇[Mo₆S₈(CN)₆]·8H₂O was synthesized by excision of the cluster core (the reaction of ZnMo₆S₈ with a melt of KCN). The structure of the complex was established by X-ray diffraction analysis. The reaction of Mo₆Se₈ with a KCN—KSCN mixture afforded the mixed-ligand cluster anions [Mo₆(Se,S)₈(CN)₆]^7–. The salt of composition K_1.5Cs_5.5[Mo₆Se_6.8S_1.2(CN)₆]·8H₂O was obtained. The complexes are isostructural to each other and to the selenium analog described previously. The magnetic properties and the electronic and IR spectra were measured and discussed.     

Synthesis and structure of a new molecular octahedral cluster complex Mo<Subscript>6</Subscript>Se<Subscript>8</Subscript>(Ph<Subscript>3</Subscript>P)<Subscript>6</Subscript>·2H<Subscript>2</Subscript>O

Mo₆Se₈(Ph₃P)₆·2H₂O cluster complex has been synthesized and its structure has been defined. The compound is triclinic, space group P1ˉ, with unit cell parameters a = 14.3356(5) Å, b = 15.7882(4) Å, c = 25.3949(8) Å, = 95.9750(10)°, β = 91.1030(10)°, γ= 112.2570(10)°, V = 5279.8(3) ų, Z = 2, ρ_calc = 1.772 g/cm³. The complex has a molecular structure. The molybdenum atoms of the {Mo₆Se₈} cluster nucleus are coordinated by the phosphorus atoms of triphenylphosphine molecules. Original Russian Text Copyright ? 2007 by Yu. V. Mironov, Zh. S. Kozhomuratova, D. Yu. Naumov, and V. E. Fedorov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 2, pp. 389–393, March–April, 2007.     

Stabilization of Mo6S8 by halogens; new superconducting compounds: Mo6S6Br2, Mo6S6I2

We present a study of the properties of the series Mo₆X_8?xY_x (X = S, Se, Te; Y = Br, I) having the hexagonal rhombohedral structure of the PbMo₆S₈ type. For X = S we have found two new superconducting compounds Mo₆S₆Br₂ and Mo₆S₆I₂, having critical temperatures of 13.8 and 14.0°K, respectively. We further find that Mo₆Te₈ becomes superconducting (T_c ≈ 2.6°K) upon substitution of Te by small quantities of iodine, and that in the case of Mo₆Se₈ substitution of a Se atom by a halogen, raises T_c up to about 7.6°K.     

Rb5Mo27Se31, a novel ternary reduced molybdenum selenide containing Mo12 and Mo15 clusters

The crystal structure of Rb₅Mo₂₇Se₃₁, penta­rubidium hepta­cosa­molybdenum hentria­conta­selenium, consists of a mixture of Mo₁₂Se₁₄Se₆ and Mo₁₅Se₁₇Se₆ cluster units in a 1:1 ratio. Both types of cluster are interconnected through inter‐unit Mo—Se bonds. Rb⁺ cations occupy large voids between the different cluster units.     

Novel Complexes [M(DMF)6][Mo6Br8(NCS)6] (M = Mn2+, Co2+, Ni2+, Cu2+, and Cd2+): Synthesis,Structure Determination,and Properties

A series of novel complexes [M(DMF)₆][Mo₆Br₈(NCS)₆] (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Cd²⁺) was synthesized. Compounds with M = Co and Mn were examined using X-ray diffraction analysis and found to be isostructural. A cobalt-containing complex was used to illustrate their essential structural features. The NCS ligands are coordinated through the nitrogen atom. The IR spectra of all the compounds obtained correlate well with the X-ray diffraction data. When heated, the complexes release all of their DMF molecules to give MMo₆Br₈(NCS)₆ salts (TGA data). The magnetic properties of the compounds indicate a weak interaction between the paramagnetic cations.     

Syntheses and structures of Tetranuclear Cluster complexes of molybdenum [Mo4(μ3-S)2(μ2-S)4 X 2-(PMe3)6] (X = SH,Cl, Br,I, SCN) and [Mo4(μ3-S)2-(μ2-S)4 (dtc)2(PMe3)4] (dtc = diethyldithiocarbamate)

A molybdenum cluster complex [Mo₄(μ₃-S)₂(μ₂-S)₄)(SH)₂(PMe_{3 6}] has been synthesized by the reaction of (NH₄)₂Mo₃S₁₃ with trimethylphosphine. The cluster core is composed of four molybdenum atoms arranged in the rhombus bridged by two capping and four bridging sulfur atoms. Two SH and six tri-methylphosphine ligands are coordinated to the terminal positions. The mean oxidation stares of molybdenum is +3.5 and there are five Mo-Mo bonds consistent with ten metal cluster electrons. The complex has been converted into [Mo₄(μ₃-S)₂(μ₂-S)₄ X ₂(PMe₃)₆] (X=Cl, Br, I, SCN) and [Mo₄μ₃-S₂(μ₂-S)₄ (die)₂(PMe₃)₄] (dtc - diethyldithiocarbamate). In the case of the dtc complex, two terminal trimetlaylphosphine ligands are displaced and dtc ligands are coordinated in chelate fashion. The structures of the SH, Cl, Br, and dtc complexes have been determined by X-ray crystallography. Molecular orbital calculations with DV-Xα method has shown large HOMO-LUMO gaps (1.52-1.74eV) for [Mo₄S₆ X ₂(PH₃)₄] (X= SH, Cl, and Br).     

Application of Solid-State Molybdenum Sulfide Clusters with an Octahedral Metal Framework to Catalysis: Ring-Opening of Tetrahydrofuran to Butyraldehyde

Solid-state molybdenum sulfide clusters with an octahedral metal framework, the superconducting Chevrel phases, are applied to catalysis. The cluster of copper salt, Cu _x Mo₆S₈ (x = 2.94), stored in air is treated in a hydrogen stream above 300 °C. The activated cluster exhibits catalytic activity for the ring-opening of tetrahydrofuran, yielding butyraldehyde. Cyclic ethers such as trimethylene oxide and tetrahydropyran are also converted to the corresponding aldehydes. The cluster contains nonstoichiometric defects of sulfur atoms. Oxygen atoms are incorporated at the sulfur-deficient sites upon storage in air, but they are removed from the sites by the activation in a hydrogen stream. The resulting coordinatively unsaturated molybdenum atoms are catalytically active for the ring-opening reaction. The molybdenum atom in an intermediate oxidation state around 2+ is moderately coordinated by the oxygen of tetrahydrofuran and favorably releases the produced aldehyde. The neutral cluster Mo₆S₈, which has such sulfur-deficient sites, also catalyzes the reaction.     

Ternary molybdenum cluster sulfides: electrochemical and chemical behavior of in situ pulsed laser deposited thin films

The electrochemical deinsertions and insertions in recently synthesised PLD molybdenum cluster sulfide films are presented. We prove that Cu_xMo₆S₈ can be electrochemically converted to Mo₆S₈. The copper, cadmium, zinc and lead intercalation performed by electrochemistry on deintercalated films has succeeded. During this study, we also report that the use of a chemical process allows the formation of PbMo₆S₈ and SnMo₆S₈ thin films, that means that the intercalation of large cations is effective like the one of small cations.     

Raman spectroscopy in AB2X4 pseudoternary layered compounds

We have synthesized several pseudoternary layered compounds by cation or anion cross substitution in ternary AB₂X₄ compounds. Here we report on the low frequency Raman spectra obtained from Zn_xCd_1-xIn₂S₄, Zn(In_xGa_1-x)₂S₄ and ZnIn₂(S_xSe_1-x)₄ single crystals. Within these systems we have identified five compositionally or dynamically different phases. Each of these phases may be characterized by its peculiar low frequency Raman spectrum which is connected to the dynamics of the layers in the unit cell. Abrupt structural/dynamical changes are observed as a function of composition between different phases. Within each phase compositional changes cause only smooth and small spectral variations.     

Collision-Induced Decomposition (CID) of Triangular [Mo3S7-xSex]4+ Complexes (x = 0,3,7). A liquid SIMS and FTMS/MS study of [Mo3S7-xSex(Et2NCS2)3] +

[Mo₃S(S₂)₃(dtc)₃]I, [Mo₃S(SeS)₃(dtc)₃](dtc), and [Mo₃Se(Se₂)₃(dtc)₃](dtc) (dtc = N,N-diethyldithiocarbamate) were investigated by liquid SIMS-FTMS. The fragmentation pathways were essentially the same for the three compounds and can be explained by two types of fragmentation processes: stepwise abstraction of S/Se atoms as exemplified by the series [Mo₃X_z(dtc)₃]⁺ (4 ? z ? 7, X = S, Se), and ligand dissociation, as indicated by the generation of [Mo₃X_z(dtc)₂]⁺ (5 ? z ? 7, X = S, Se). The exclusive elimination of the Se-atoms from [Mo₃S(S_ax-Se_eq)₃(dtc)₃]⁺ confirmed the inequivalent reactivity of the bridging atoms in axial and equatorial position as observed in previous studies. Collision-induced decomposition (CID) of [Mo₃S₇(dtc)₃]⁺ ( 1 ), [Mo₃S₆(dtc)₃]⁺ ( 2 ), [Mo₃S(S_ax–Se_eq)₃(dtc)₃]⁺ ( 3 ), and [Mo₃Se₇(dtc)₃]⁺ ( 4 ) revealed distinctly different fragmentation reactions for the SIMS and CID mode. CID of 1, 3 , and 4 resulted in a two-step reaction with the exclusive elimination of diatomic molecules XY (X,Y = S/Se). In the case of 3 , the selective elimination of Se₂ indicated the abstraction of two Se-atoms located in equatorial positions of two different bridging groups. This result is discussed in terms of mechanisms, based on labile M? X_eq and inert M? X_ax bonds with an intramolecular formation of a X₄ fragment prior to the elimination of X₂.     

Bichromophoric naphthalene derivatives of diethylenetriaminepentaacetate (DTPA): fluorescent response to H+, Ca2+, Zn2+, and Cd2+

As an effort to design selective fluorescent sensors toward Ca²⁺, Zn²⁺ and Cd²⁺, synthetic and fluorometric studies were performed on four bichromophores, each of which consists of two naphthyl or methynaphthyl units (1- and 2-isomers) linked with a diethylenetriaminepentaacetate (DTPA) chain. Every bichromophore exhibits naphthalene-monomer emission at 370 nm and excimer emission at 405 nm. Emission intensities show sensitive pH dependence, from which protonation constants were determined. Fluorometric titrations with the metal ions were performed at the physiological pH and the conditional formation constants were determined. Naphthyl rings define the stoichiometry and stability of the complexes. The insertion of CH₂ spacer intensifies the emission and enhances the selective response to metal ions: the excimer emission is strengthened by 70?100 % with Cd²⁺ coordination, weakened by 60 % with Zn²⁺, and insensitive to Ca²⁺. The high response of methylnaphthyl bichromophores to Cd²⁺ is advantageous in fluorometric analyses.     

Gitterschwingungsspektren XVIII.1 Chromthio- und Chromselenospinelle mit 1:1-Ordnung auf den Tetraederpl?tzen

The infrared spectra of spinel-type compounds A⁺A³⁺ Cr₄X₈ (A⁺ = Li, Cu, Ag; A³⁺ = Al, Ga, In; X = S, Se) have been measured. The spectra show that the spinels LiGaCr₄S₈, LiInCr₄S₈, CuGaCr₄S₈, CuInCr₄S₈, AgInCr₄S₈, CuGaCr₄Se₈, CuInCr₄Se₈, and AgInCr₄Se₈, whose structures cannot be determined by X-ray methods in all cases, have a structure with 1:1 ordering on the tetrahedral site (space group $\text{F}\text{4}\text{3m}$). No ordering takes place in AgGaCr₄S₈. The spectra of the ordered spinels are discussed in relation to two-mode type spectra of spinel mixed crystals.     

First example of monodispersed (Mo3Se3)1∞ clusters

The close relationship of the structure of ternary molybdenum chalcogenides to molecular cluster compounds suggests that these chalcogenides might be synthesized from such clusters or be solubilized as clusters. However, in contrast to molybdenum halide clusters which can be obtained in solution from the solid phase, many attempts to solubilize these chalcogenide clusters were unsuccessful. This is the first report that some of the pseudo-one-dimensional compounds (M₂Mo₆X₆, X = Se, Te; M = Li, Na) can be dissolved when exposed to highly polar solvents such as dimethylsulfoxide or N-methylformamide. We show using optical microscopy, TEM, and light scattering that some of these solutions contain individual (Mo₃X₃)¹_∞ chains. This is also the first example of a purely inorganic transition-metal polymer solution. The behavior with respect to flocculation is consistent with the double layer theory. We show that the (Mo₃X₃)¹_∞ chains can be oriented in solution.     

Studies on Synthetic Inorganic Ion Exchangers-III Quantitative Separations of Mg2+ -Pb2+, Zn2+ - Pb2+ Cu2+ - Pb2+, Al3+ - Pb2+, Zn2+ - Cd2+, and Mg2+ - Cd2+ on Lead Antimonate Columns

Abstract

A new inorganic ion exchanger, lead antimonate has been synthesized having an Pb:Sb ratio of 1:5 and cation exchange capacity of 1.46 mequiv./g. It is fairly stable in water and dilute solutions of acids, bases and salts. Ion distribution studies on twenty metal ions have been determined on this gel at pH 1,2,3 and 5. The following mixtures have been separated: Mg²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Cu²⁺ - Pb²⁺, Al³⁺ - Pb²⁺, Zn²⁺ - Cd²⁺ and Mg²⁺ - Cd²⁺. Mg²⁺ and Al³⁺ were removed with 0.4 M ammonium nitrate, Cu²⁺ and Zn²⁺ with 0.4 M ammonium nitrate + 0.1M nitric acid (1:1), Pb²⁺ with 0.5M nitric acid and Cd²⁺ with 0.25M nitric acid. A tentative structure of this material is proposed on the basis of chemical analysis, pH titrations, thermogravimetry and IR spectrophotometry.     

New alkali-metal-molybdenum(VI)-selenium(IV) oxides: syntheses, structures, and characterization of A2SeMoO6 (A=Na, K, or Rb)

Three new quaternary selenites, A₂SeMoO₆ (A=Na⁺, K⁺, or Rb⁺), were synthesized through the solid-state reaction of A₂MoO₄ with SeO₂ at 400°C. Although the reported materials are ‘stoichiometrically equivalent’, the compounds exhibit strikingly different crystal structures. Whereas Na₂SeMoO₆ has a three-dimensional crystal structure, K₂SeMoO₆ and Rb₂SeMoO₆ are molecular and uni-dimensional, respectively. However, all of the new materials have structures containing Mo⁶⁺ octahedra linked to Se⁴⁺ trigonal pyramids. Although the Mo⁶⁺ and Se⁴⁺ cations are in local asymmetric environments in all three materials, only Na₂SeMoO₆ is non-centrosymmetric. Single crystal X-ray data: Na₂SeMoO₆, cubic, space group, P2₁3 (no. 198), a=8.375(5) Å, Z=4, R(F)=0.0143; K₂SeMoO₆, monoclinic, space group, P2₁/c (no. 14), a=6.118(8) Å, b=15.395(2) Å, c=7.580(9) Å, β=112.39(4)°, Z=4, R(F)=0.0281; Rb₂SeMoO₆, orthorhombic, space group, Pnma (no. 62), a=7.805(9) Å, b=6.188(7) Å, c=14.405(4) Å, Z=4, R(F)=0.0443.     

Preparation and physical properties of BiMo6S8 and SbMo6S8

The compounds Me₁Mo₆S₈ (Me = Bi, Sb) were prepared by low-temperature diffusion of Bi and Sb into the binary phase Mo₆S₈. The homogeneity range of the ternary elements is very narrow and centered about Me = 1.0, implying that the ternary metal is located at the origin position of the rhombohedral unit cell. The observed lattice parameters (BiMo₆S₈, a_h = 9.194, c_h = 11.325; SbMo₆S₈, a_h = 9.122, c_h = 11.282) are consistent with this hypothesis and suggest that these atoms enter the structure as trivalent cations. No superconducting transition is observed for these materials above 2 K. A small temperature-independent paramagnetism is present in the magnetic susceptibility of these compounds. The magnitude of this paramagnetism is less than that found in other ternary molybdenum chalcogenides with trivalent cations, suggesting that a reduced density of states is responsible for the observed lack of superconductivity. Attempts to prepare MeMo₆(S_1−xSe_x)₈ (Me = Sb and Bi) with x > 0 failed to yield ternary phases, instead producing mixtures of the unreacted ternary metal and the corresponding binary phase.