Crystal structure of K2[Mo3(PdPPh3)S4(C2O4)3(H2O)3]·0.5H2O

By the reaction of [Mo₃S₄(C₂O₄)₃(H₂O)₃]²⁻ with PdCl₂ and NH₄H₂PO₂ as a reducing agent, followed by the addition of PPh₃, a new oxalate cuboidal cluster complex [Mo₃(PdPPh₃)S₄(C₂O₄)₃(H₂O)₃]²⁻ is obtained. It was isolated and structurally characterized as K₂[Mo₃(PdPPh₃)S₄(C₂O₄)₃(H₂O)₃]·0.5H₂O. Original Russian Text Copyright ? 2008 by A. L. Gushchin, M. N. Sokolov, D. Yu. Naumov, and V. P. Fedin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 4, pp. 775–778, May–June, 2008.     

Synthesis and crystal structure of new one-dimensional copper(II) complex [Cu4(En)2(μ1,1-N3)4(μ1,1,1-N3)2(μ1,3-N3)2]n

A new polymer azido-bridged copper(II) complex [Cu₄(En)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂(μ_1,3-N₃)₂] _n (I) (En = ethylenediamine) has been synthesized and crystallography characterized. Complex I shows one-dimensional coordination polymeric structure based on a tetranuclear cluster unit [Cu₄(En)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂(μ_1,3-N₃)₂], in which the azido ions display three different bridging modes.     

Synthesis of Mo(CO)2(η-PPh2(o-C6H4)C(O)H)2 and its reaction with C60

Reaction of Mo(CO)₃(NCMe)₃ and PPh₂(o-C₆H₄)C(O)H (abbreviated as PCHO) at room temperature affords Mo(CO)₂(η³-PCHO)₂ (1), while compound 1 and the phosphine-imine complex Mo(CO)₄(η²-PPh₂(o-C₆H₄)CHNMe) (2) are obtained by using Mo(CO)₃(η³-(MeNCH₂)₃) as the reactant. Thermal reaction of 1 with C₆₀ products Mo(CO)₂(η⁴-(PPh₂(o-C₆H₄)CH)₂)(η²-C₆₀) (3) in low yield, apparently through coupling of the formyl moieties. The structures of 1 and 3 have been determined by an X-ray diffraction study. The two aldehyde groups of 1 and C₆₀ ligand of 3 are coordinated to the molybdenum atom in a π-fashion.     

Oxidative addition of the Mo-Cl bond to the Pt0 complex. Synthesis and structure of Cp′Mo(μ-CO)2(C2Ph2)Pt2(PPh3)2(CO)Cl

A reaction of Cp′Mo(CO)₃Cl(Cp′ = MeC₅H₄) with (PPh₃)₂Pt(C₂Ph₂) gave the heterometallic cluster Cp′Mo(μ-CO)₂(C₂Ph₂)Pt₂(PPh₃)₂(CO)Cl (I) as the sole product. According to X-ray diffraction data, complex I contains single Pt-Mo bonds (2.7962(5) and 2.7699(5) ?) but no Pt-Pt bond (Pt…Pt 2.9746(3) ?). The coordinated diphenylacetylene molecule forms two Pt-C σ-bonds (2.054(6) and 2.083(5) ?) and a π-bond to the Mo atom (Mo-C 2.265(6) and 2.272(5) ?; C≡C 1.387(8) ?). Original Russian Text ? A.A. Pasynskii, I.V. Skabitskii, Yu.V. Torubaev, S.S. Shapovalo, 2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 6, pp. 410–413.     

Sandwich-type Uranium-Substituted of Bismuthotungstate: Synthesis and Structure Determination of [Na(UO2)2(H2O)4(BiW9O33)2]13?

The sandwich-type [Na(UO₂)₂(H₂O)₄(BiW₉O₃₃)₂]¹³⁻ uranium (VI) has been synthesized by reacting the trivacant species of B-α-[BiW₉O₃₃]⁹⁻ with and investigated by IR and UV–Vis spectroscopy, and elemental analysis. The X-ray single crystal analysis was carried out on Na₁₃[Na(UO₂)₂(H₂O)₄(BiW₉O₃₃)₂] · 33H₂O (I) which crystallizes in the orthorhombic system, space group Pna2₁ with a = 33.8454(19) ?, b = 21.1484(12) ?, c = 13.2403(7) ?, α = 90°, β = 90°, γ = 90°, and Z = 4. The polyanion consists of two lacunary B-α-[BiW₉O₃₃]⁹⁻ groups which sandwich two uranyl cations and one sodium cation. The uranium atoms adopt distorted pentagonal–bipyramidal coordination, achieved by two equatorial bonds to each BiW₉O₃₃ unit and one external water ligand. The coordination of each uranium atom is evident by the shift of ν_as(W–O_b–W) and ν_as(Bi–O) stretching vibrational bonds. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Pyridine-2-thione (pySH) derivatives of silver(I): Synthesis and crystal structures of dinuclear [Ag2Cl2(μ-S-pySH)2(PPh3)2] and [Ag2Br2(μ-S-pySH)2(PPh3)2] complexes

Reaction of silver(I) halides with PPh₃ in acetonitrile and then with pyridine-2-thione (pySH) chloroform (1:1:1 molar ratio) has yielded sulfur bridged dimers of general formula, [Ag₂X₂(μ-S-pySH)₂(PPh₃)₂] (X = Cl, 1, Br, 2). Both these complexes have been characterized using analytical data, NMR spectroscopy and single crystal X-crystallography. The central Ag₂S₂ cores form parallelograms with unequal Ag–S bond distances (2.5832(8), 2.7208(11) Å) in 1 and (2.6306(4), 2.6950(7) Å) in 2, respectively. The Ag?Ag contacts of compounds 1 and 2 are 3.8425(8) and 3.8211(4) Å, respectively. The angles around Ag (in the range 87.19(2)–121.71(2)° in 1 and 87.81(2)–121.53(2)° in 2) reveal highly distorted tetrahedral geometry. There are inter dimer π–π stacking interactions between pyridyl rings (inter ring distances of 3.498 and 3.510 Å in complexes 1 and 2, respectively). The solution state ³¹P NMR spectroscopy has shown the existence of both monomers and dimers. The studies reveal relatively weaker intramolecular –NH?Cl hydrogen bonding in case of AgCl vis-à-vis that in CuCl which favored both a monomer and a dimer with AgCl, and only a monomer with CuCl.     

Synthesis and structures of Cs4[(UO2)2(C2O4)(SO4)2(NCS)2] · 4H2O and (NH4)4[(UO2)2(C2O4)(SO4)2(NCS)2] · 6H2O

Single crystals of Cs₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 4H₂O (I) and (NH₄)₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 6H₂O (II) have been synthesized and studied by X-ray diffraction. The crystals of both compounds are orthorhombic with the space group Pbam, Z = 2, and unit cell parameters a = 12.0177(3) ?, b = 18.6182(5) ?, c = 6.7573(10) ?, R = 0.0376 (I); a = 11.6539(9) ?, b = 18.3791(13) ?, c = 6.7216(5) ?, R = 0.0179 (II). The main structural units of crystals I and II are [(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂]⁴⁻ chains belonging to the crystal-chemical group A₂K⁰²B₂²M₂¹ (A = UO₂²⁺, K⁰² = C₂O₄²⁻, B² = SO₄²⁻, M¹ = NCS⁻) of the uranyl complexes. The uranium-containing chains are joined into a three-dimensional framework due to a system of electrostatic interactions with the cesium or ammonium ions in the structure of I. In the structure of II, this framework is additionally stabilized by hydrogen bonds involving the outer-sphere water molecules and ammonium ions. Original Russian Text ? I.V. Medrish, A.V. Virovets, E.V. Peresypkina, L.B. Serezhkina, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 7, pp. 1115–1120.     

Structure and luminescence of [Tb0.5(C6NO2H5)3(H2O)2]2n·(H3O)4n(ZnCl5)n(ZnCl4)2n

A novel bimetallic 4f-3d metal-isonicotinic acid inorganic-organic hybrid complex [Tb_0.5(C₆NO₂H₅)₃(H₂O)₂]_2n ·(H₃O)_4n (ZnCl₅) _n (ZnCl₄)_2n (1) is synthesized. It has a one-dimensional polycationic chain-like structure. Photoluminescent investigation reveals that it displays interesting emissions in the violet, blue, green, and yellow regions.     

Diverse coordination of two ligands in ferromagnetic [Cu(μ-HCO2)2(3-pyOH)]n and [Cu2(μ-HCO2)2(μ-3-pyOH)2(3-pyOH)2(HCO2)2]n

Two novel polynuclear complexes with methanoate anions and 3-hydroxypyridine ligands [Cu(μ-HCO₂)₂(3-pyOH)]_n (1) and [Cu₂(μ-HCO₂)₂(μ-3-pyOH)₂(3-pyOH)₂(HCO₂)₂]_n (2), respectively, were synthesized and characterized. The central copper atom in 1 is surrounded by four methanoates and a 3-pyOH molecule, forming a square-pyramidal CuO₃NO chromophore. All the methanoates are bidentate and serve as bridges between the adjacent copper ions via syn-anti and anti–anti coordination. The basal square coordination axes are formed by O(syn), N(3-pyOH) (1.974(2), 2.016(2) Å) and O(anti), O(anti) (1.945(2), 1.960(2) Å), while the third O(anti) (2.247(2) Å) is on the top of the pyramid. A ferromagnetic transition with an exchange constant 2J/k_B = 9.2 cm⁻¹ is found for 1 below 20 K. This interaction probably takes place through two syn-anti methanoates extended in a chain through the 2D structure. On the other hand, two monoatomic Cu–O–Cu intra-dinuclear asymmetric (1.986(2), 2.415(2) Å) bridges of two methanoates in [Cu₂(HCO₂)₄(3-pyOH)₄] (2) are present. An elongated distorted octahedral coordination sphere around each copper(II) atom is completed by an additional monodentate terminal methanoate (1.975(2) Å), two N-coordinated 3-pyOH (2.005(2), 2.002(2) Å) and the third weakly O-coordinated 3-pyOH (2.732(2) Å). Although a shorter Cu?Cu distance is noticed in 2 than in 1 (4.690(1) Å 1, 3.442(1) Å 2), much weaker ferromagnetism is found in 2.     

Formation of the silylene-bridged complex Fe2(CO)6(μ2-SiCl2)3 from cis-Fe(CO)4(SiCl3)2: an experimental and computational study

Abstract  

Thermolysis of cis-Fe(CO)₄(SiCl₃)₂ results in the formation of the novel compound Fe₂(CO)₆(μ₂-SiCl₂)₃, which was characterized by single crystal X-ray diffraction. Density functional theory calculations were carried out to elucidate possible reaction steps leading to the formation of Fe₂(CO)₆(SiCl₂)₃, including CO dissociation and chlorine abstraction by a SiCl₃ radical generated from homolytic Fe–Si bond cleavage involving a singlet–triplet intersystem crossing.     

Two-color emission of Zn2SiO4:Mn from ionic liquid mediated synthesis

Yellow emitting β-Zn₂SiO₄:Mn²⁺ and green emitting α-Zn₂SiO₄:Mn²⁺ nanoparticles are synthesized by nucleation applying a zinc-containing ionic liquid. As-prepared material is non-agglomerated and very uniform with a mean diameter of 32 nm. According to X-ray diffraction (XRD) two crystallographic different modifications of Zn₂SiO₄ can be realized by annealing of as-prepared and non-crystalline nanomaterial at 750 and 1000 °C. Surprisingly, these crystalline materials are still nanosized, non-agglomerated and redispersible. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) confirm particle diameters of 18 nm (β-Zn₂SiO₄:Mn²⁺) and 14 nm (α-Zn₂SiO₄:Mn²⁺). Photoluminescence indicates Mn²⁺-related emission at an average wavelength of 579 nm and 528 nm, and a quantum yield of 7% and 12% for β-Zn₂SiO₄:Mn²⁺ and α-Zn₂SiO₄:Mn²⁺, respectively.     

White-light-emitting long-lasting phosphorescence in Dy-doped SrSiO3

We report on a luminescent phenomenon in Dy³⁺-doped SrSiO₃ long-lasting phosphor. After irradiation by a 254-nm UV lamp for 5 min, the Dy³⁺-doped SrSiO₃ phosphor emits white light-emitting long-lasting phosphorescence for more than 1 h even after the irradiation source has been removed. Photoluminescence, long-lasting phosphorescence and thermoluminescence (TL) spectra are used to explain this phenomenon. Photoluminescence spectra reveal that the white light-emitting long-lasting phosphorescence originated from the two mixtures of Dy³⁺ characteristic luminescence, the 480-nm blue emission (⁴F_9/2→⁶H_15/2) and the 572-nm yellow emission (⁴F_9/2→⁶H_13/2). TL spectra shows that the introduction of Dy³⁺ ions into the SrSiO₃ host produces a highly dense trapping level at 377 K (0.59 eV), which is responsible for the long-lasting phosphorescence at room temperature. A possible mechanism of the long-lasting phosphorescence based on the experimental results is proposed. It is considered that the long-lasting phosphorescence is due to persistent energy transfer from the electron traps to the Dy³⁺ ions, which creates the persistent luminescence of Dy³⁺ to produce the white light-emitting long-lasting phosphorescence.     

Effet Jahn-Teller cooperatif et affinite tétraedrique des ions Mn2+ et Zn2+ dans le système Mn3O4Zn2SnO4

Comparison between synthesis in air and in vacuum of the solid solution tMn₃O₄ + (1 ? t)Zn₂SnO₄, and cristallographic study of the nonoxidized compounds allowed us to establish the distribution and the electronic configuration of cations in tetrahedral (A) and octahedral (B) sites. The competitive aspect of Zn²⁺ and Mn²⁺ ions to occupy tetrahedral site is discussed. In air, the non-oxidizable character of Mn²⁺ on an A-site is clearly borne out, whereas the B-site displaced manganese oxidizes to Mn³⁺. In vacuum, the critical concentration of Mn³⁺ ion at the octahedral site, involving a cooperative Jahn-Teller effect, is about 50%.An important fact has also been put forward: the microscopic distortion of the oxygen octahedra, which the ratio of long and short anion-cation distances expresses, is equal to the unit-cell macroscopic deformation that the ratio $\text{c}\text{a}\text{√2}$ represents.     

A novel highly selective ratiometric fluorescent sensor for relay recognition of Zn2+ and H2PO4−

A novel fluorescent sensor (AQTF1) based on the N-(quinolin-8-yl) tetrahydrofuran-2-carboxamide was designed and synthesized. This new sensor demonstrated high selectivity for the Zn²⁺ without the interference from Cd²⁺. The detection limit of this probe was calculated to be 10.8 nM for Zn²⁺. The in situ prepared AQTF1-Zn²⁺ complex was used for detection of H₂PO₄^? and displayed good selectivity from the common anions. Furthermore, the AQTF1 displayed good ratiometric response for the relay recognition for Zn²⁺ and H₂PO₄^?.     

EPR spectroscopic studies in (30 − x) Li2O-xK2O-10CdO-59B2O3-1MnO2 multi-component glass system

EPR studies were carried out in (30 - x) Li₂O-xK₂O-10CdO-59B₂O₃-1MnO₂ multi-component glass system to understand the effect of the variation in the alkali ratios on the EPR parameters. The observed EPR spectra of Mn²⁺ ion exhibits resonances at g = 2.0, 3.3 and 4.3. The resonance at g = 2.0 is due to Mn²⁺ ions in an environment close to the octahedral symmetry, where as the resonances at g = 3.3 & 4.3 are due to the rhombic surroundings of Mn²⁺ ions. Hyperfine splitting constant values at g = 2.0 and number of paramagnetic centers & paramagnetic susceptibility at different observed resonances were evaluated. These parameters show non linear variation with progressive substitution of Li⁺ ion with K⁺ ions may be due to the changes in cation field strengths and local structural variation due to the variation in mixed alkali ion ratios.     

Selective turn-on fluorescence for Zn and Zn + Cd metal ions by single Schiff base chemosensor

Chemosensor based on Schiff base molecules (1, 2) were synthesized and demonstrated the selective fluoro/colorimetric sensing of multiple metal ions (Mn²⁺, Zn²⁺ and Cd²⁺) in acetonitrile–aqueous solution. Both 1 and 2 showed a highly selective naked-eye detectable colorimetric change for Mn²⁺ ions at 10⁻⁷ M. Fluorescence sensing studies of 1 and 2 exhibited a strong fluorescence enhancement (36 fold) selectively upon addition of Zn²⁺ (10⁻⁷ M, λ_max = 488 nm). Fluorescence titration and single crystal X-ray analysis confirmed the formation of 1:1 molecular coordination complex between 1 and Zn²⁺. Interestingly, a rare phenomenon of strong second turn-on fluorescence (190 fold, λ_max = 466 nm) was observed by the addition of Cd²⁺ (10⁻⁷ M) into 1 + Zn²⁺ or Zn²⁺ (10⁻⁷ M) into 1 + Cd²⁺. Importantly both 1 and 2 exhibited different fluorescence λ_max with clearly distinguishable color for both Zn²⁺ and Cd²⁺.     

Electronic behavior of three oxygen non-stoichiometric Fe/Fe oxoperovskites

For comparison with the Mn⁴⁺/Mn³⁺ oxoperovskites at the crossover from localized to itinerant behavior of the σ-bonding e electrons, the electronic properties of three oxygen non-stoichiometric, mixed-valent Fe⁴⁺/Fe³⁺ oxoperovskites were explored by measuring their resistivity ρ(T), thermoelectric power α(T), and magnetic susceptibility χ(T). Oxidation of Ca₂Fe₂O₅ by annealing in ozone progresses by oxygen insertion to give conductive CaFeO₃ perovskite clusters in a localized-electron, weakly oxidized brownmillerite Ca₂Fe₂O_5+δ matrix. Removal of 0.12 oxygen per formula unit from La_1/3Sr_2/3FeO₃ lowers somewhat its cooperative disproportionation reaction, and fivefold-coordinated ions neighboring oxygen vacancies in the more ionically bonded slabs act as donors to the covalently bonded Fe(V)O₆ planes. Single-crystal SrFeO_2.83 exhibited bad-metal behavior with superparamagnetic, electron-rich fluctuations below 240 K that, on cooling below 190 K, become progressively trapped by the oxide-ion vacancies as an immobile second phase; long-range antiferromagnetic order is stabilized below a T_N≈60 K.     

Reasons for the line broadening in the epr spectra of copper ions in Li2-2x Zn2+x (MoO4)3 lithium-zinc molybdate crystals

An EPR study of Li_2?2x Zn_2+x (MoO₄)₃ crystals activated by copper ions shows that they occupy the M2 site, one of the three possible sites of both lithium and zinc. In the EPR spectra of Cu²⁺ copper a broadening of HFS lines and a nonequidistant splitting between them, which are unusual for the orientation H‖g _zz , A _zz , are observed. In this work possible reasons for such a broadening of HFS lines from copper ions are analyzed: a distortion of the oxygen octahedron due to the introduction of copper ions, second order perturbation theory corrections, superposition of HFS from ⁶³Cu and ⁶⁵Cu isotopes, and the effect of the charge redistribution in the oxygen octahedron because the cation vacancy providing charge compensation can be located at different distances from the copper ion. It is shown that the first three reasons do not explain the features observed in the EPR spectra. In the case of cation vacancies located in the M3 site and remote at different distances from the copper ion, the charge redistribution in the oxygen octahedron of copper should occur along with the dispersion of HFS parameters and the g-factor. The studies performed in X and Q bands confirm this assumption. The width of HFS lines from copper ions in the EPR spectra measured in the Q band is three times more compared to that measured in the X band.     

Magnetic and vibrational properties and crystal structure of Sr9.2Co1.3(PO4)7 with disordered arrangements of some strontium, cobalt, and phosphate ions

Solid solutions of Sr_9+xCo_1.5−x(PO₄)₇ were found in the compositional range of 0.05?x?0.30. The structure of Sr_9.2Co_1.3(PO₄)₇ (x=0.2) was determined from single crystal X-ray diffraction (space group (No. 166); Z=3; and ; ; ; ) and refined to R₁=0.0343 and wR₂=0.0633 for 586 reflections with I>2σ(I). Sr_9.2Co_1.3(PO₄)₇ is structurally related to β-Ca₃(PO₄)₂ and Sr₃(PO₄)₂ and has disordered arrangements of some Sr²⁺, Co²⁺, and PO₄³⁻ ions. Sr²⁺ ions at a 9e site are statistically disordered among four positions near the center of symmetry. Co²⁺ and Sr²⁺ ions are split along the c-axis to occupy a 6c site that is 75% vacant. The P1O₄ tetrahedra are orientationally disordered. Sr²⁺ ions at an 8-fold coordinated 18h site, Co²⁺ ions at an octahedral 3a site, and the P2O₄ tetrahedra are ordered in the structure of Sr_9.2Co_1.3(PO₄)₇. Features of Raman spectra are discussed in relation to the crystallographic structure of Sr_9.2Co_1.3(PO₄)₇ and in comparison with Raman spectra of β-Ca₃(PO₄)₂-type and Sr₃(PO₄)₂-type compounds. Sr_9.2Co_1.3(PO₄)₇ is paramagnetic between 2 and 300 K with an effective magnetic moment of 4.98μ_B per Co²⁺ ion.     

Sorption of silicic acid from non-saturated aqueous solution by a complex of zinc ions with poly(vinylamine)

Silicifying organisms (diatom algae, sponges, etc.) build multifarious silica and composite nano-structures which attracts rapt attention of specialists in nanotechnology. These organisms can capture monomeric silicic acid from diluted solutions (<1 mM) and molecular mechanism of this process is still unknown. Some hypotheses include mediatorial role of zinc ions coordinated with a special protein transporter. We have studied several basic hydrogels and their complexes with double charged metal ions in sorption of silicic acid from non-saturated solutions. Cross-linked poly(vinylamine) coordinated with Zn²⁺ was able to capture silicic acid from 0.1 to 1.7 mM solutions. The other ions (Cu²⁺, Fe²⁺, Ni²⁺, Co²⁺, Cd²⁺ and Mn²⁺) and less basic poly(1-vinylimiazole) were not active in the sorption. A mechanism included oligomerization of silicic acid and formation of triple complex poly(vinylamine)-Zn²⁺-oligosiloxane was proposed. FTIR, NMR and EDS data confirm this conclusion. The found capture of silicic acid from diluted solutions with polyamine-zinc complex shows possibility in principle of the zinc-mediated transmembrane transport of Si(OH)₄ in silicifying organisms. On the other hand, the ability of zinc ions immobilized on the polyamine support to capture oligosilicates could be used in directed assembly of nanocomposite structures by the “bottom-up” approaches.