An inorganic–organic hybrid supramolecular framework based on the γ‐[Mo8O26]4− cluster and cobalt complex of aspartic acid: X‐ray structure and DFT study

A new inorganic–organic hybrid based on an aspartate functionalized polyoxomolybdate, [pentaaquacobalt(II)]‐μ‐aspartate‐[γ‐octamolybdate]‐μ‐aspartate‐[pentaaquacobalt(II)] tetrahydrate, [Co₂(C₄H₆NO₄)₂(γ‐Mo₈O₂₆)(H₂O)₁₀]·4H₂O ( 1 ), has been synthesized under hydrothermal conditions from the reaction of an Evans–Showell‐type polyoxometalate, (NH₄)₆[Co₂Mo₁₀H₄O₃₈], and l ‐aspartic acid. The complex exhibits a supramolecular three‐dimensional framework structure in the crystal lattice. Compound 1 was structurally characterized by elemental analyses, IR and UV–Vis (diffuse reflectance) spectroscopy and single‐crystal X‐ray diffraction. In this compound, aspartic acid acts as a bridge between the two Co atoms and the Mo centres, with the –CH₂COOH side chain directly linked to the Mo centre in γ‐[Mo₈O₂₆]^4? and the α‐carboxylate side chain bound to the Co centre. Commonly, the binding of transition‐metal complexes to POMs involves coordination of the metal to a terminal O atom of the POM so that 1 , with a bridging ligand between Mo and Co atoms, belongs to a separate class of hybrid materials. While the starting materials are both chiral and one might expect them to form a chiral hybrid, the decomposition of the chiral Evans–Showell‐type POM and its conversion to the centrosymmetric γ‐octamolybdate POM, plus the presence of two aspartate ligands centrosymmetrically placed on either side of the POM, leads to the formation of an achiral hybrid. We have studied energetically by means of density functional theory (DFT) calculations and using the Bader's `atoms‐in‐molecules' analysis the electrostatically enhanced hydrogen bonds (EEHBs) observed in the solid state of 1 , which are crucial for the formation of one‐dimensional supramolecular assemblies.     

吡啶配位的夹心型杂多阴离子{[Na(H2O)2]3[Ni(C5H5N)]3(AsW9O33)2}9-的结构及磁学性质

The pyridine coordinated sandwich-type heteropolytungstate Na7[Ni（H2O）6] { [Na（H2O）2]3[Ni（C5H5N）]3（AsW9O33）2}·28H2O was obtained by the reaction of Na2WO4·2H2O, NaAsO2 and pyridine with NiCl2·6H2O at pH =7.0 and characterized by elemental analysis, IR, UV-Vis,^1H NMR spectra and magnetic measurement. The structure of this heteropolytungstate was determined by X-ray diffraction analysis, which crystallized in triclinic system, space group P1 with a= 1.3153（9） nm, b= 1.7228（12） nm, c=2.6866（19） nm, a=74.130（11）°,β=78.032（12）°, γ = 73.179（12）° and Z= 2, R1 = 0.0604, wR2 = 0.0915 [I〉 2σ（I）]. Polyanion {[Na（H2O）2]3[Ni（C5H5N）]3（AsW9O33）2}^9- has approximately C3 symmetry, and three pyridine coordinated Ni（C5H5N）^2＋ and three Na（H2O）2^＋ are encapsulated between two AsW9O33^9- . Magnetic measurements show that central Ni3 unit in the polyanion exhibits ferromagnetic Ni-Ni exchange interactions （J=6.17 cm^-1）.     

Synthesis and crystal structure of 2‐amino‐3‐hydroxypyridinium dioxido(pyridine‐2,6‐dicarboxylato‐κ3O2,N,O6)vanadate(V) and its conversion to nanostructured V2O5

2‐Amino‐3‐hydroxypyridinium dioxido(pyridine‐2,6‐dicarboxylato‐κ³O²,N,O⁶)vanadate(V), (C₅H₇N₂O)[V(C₇H₃NO₄)O₂] or [H(amino‐3‐OH‐py)][VO₂(dipic)], (I), was prepared by the reaction of VCl₃ with dipicolinic acid (dipicH₂) and 2‐amino‐3‐hydroxypyridine (amino‐3‐OH‐py) in water. The compound was characterized by elemental analysis, IR spectroscopy and X‐ray structure analysis, and consists of an anionic [VO₂(dipic)]⁻ complex and an H(amino‐3‐OH‐py)⁺ counter‐cation. The V^V ion is five‐coordinated by one O,N,O′‐tridentate dipic dianionic ligand and by two oxide ligands. Thermal decomposition of (I) in the presence of polyethylene glycol led to the formation of nanoparticles of V₂O₅. Powder X‐ray diffraction (PXRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the synthesized powder.     

Syntheses,Structures and Characterizations of Two Vanadium(V) Complexes:[2-MePyH][V^vO2(C14H9N2O3Br)] and [2-EtPyH][V^VO2(C14H9N2O3Br)]

Two new oxovanadium(V) complexes, [2‐MePyH][V^vO₂(L)] (3) and[2‐EtPyH][V^vO₂,(L)] (4) (salicylaldehyde 5‐bromo salicyloylhydrazone is abbreviated as H₂L; 2‐MePyH is protonated 2‐Mepyridine; 2‐EtPyH presents protonated 2‐Et‐pyridine) were obtained from a reaction of VOSO₄ and H₂L in acetonitrile‐methanol with small quantity of 2‐Me‐pyridine or 2‐Et‐pyridine, and characterized by X‐ray diffraction and spectroscopic methods. Crystal data: [2‐MePyH][VO₂(L)] (3), C₂₀H₁₇N₃O₅BrV, M_r = 510.2, monoclinic, P2₁/n, a = 0.7363(1) nm, 6 = 0.9514(1) nm, c = 2.8594(2) nm, β = 95.305(2)°, Z = 4 and V=1.9946(3) nm³, μ(Mo Kα) = 2.539 mm^?1; [2‐EtPyH][VO₂(L)] (4), C₂₁H₁₉N₃ O₃BrV, M_r = 524.2, triclinic, P1 , a = 0.8051(1) nm, b = 0.9413(1) nm, c = 1.4648(2) nm, α=99.1900(10)°, α = 99.4530(10)°, γ = 104.6670(10)°, Z = 2 and V= 1.0355(2) nm³, μ(Mo Kα) = 2.448 mm^?1, X‐Ray analyses revealed that the crystal structures of 3 and 4 have similar packing modes.     

Modified polyoxometalate: a novel monocapped bi‐supporting and reduced α‐Keggin structure {PMo12O40[Cu(2,2′‐bpy)]}[Cu(2,2′‐bpy)(en)(H2O)]2

A novel modified polyoxometalate, {PMo₁₂O₄₀[Cu(2,2′‐bpy)]}[Cu(2,2′‐bpy)(en)(H₂O)]₂ [2,2′‐bpy is 2,2′‐bipyridyl (C₁₀H₈N₂) and en is ethylenediamine (C₂H₈N₂)], has been synthesized hydrothermally and structurally characterized by elemental analysis, TG, IR, XPS and single‐crystal X‐ray diffraction. The structural analysis reveals that the compound contains the reduced Keggin polyanion [PMo₁₂O₄₀]^6? as the parent unit, which is monocapped by [Cu(2,2′‐bpy)]²⁺ fragments via four bridging O atoms on an {Mo₄O₄} pit and bi‐supported by two [Cu(2,2′‐bpy)(en)(H₂O)]²⁺ coordination cations simultaneously. There exist strong intramolecular π–π stacking between the capping and supporting units, which play a stabilizing role during the crystallization of the compound. Adjacent POM clusters are further aggregated to form a three‐dimensional supramolecular network through noncovalent forces, hydrogen bonding and π–π stacking interactions. In addition, the photocatalytic properties were investigated in detail, and the results indicated that the compound can be used as a photocatalyst towards the decomposition of the organic pollutant methylene blue (MB).     

Darstellung und Kristallstruktur eines Ditelluridovanadium(IV)‐Komplexes: [(μ‐η1‐Te2)(μ‐NtBu)2V2Cp2]

Synthesis and Crystal Structure of a Ditelluridovanadium(IV) Complex: [(μ‐η¹‐Te₂)(μ‐N^tBu)₂V₂Cp₂] [(μ‐η¹‐Te₂)(μ‐N^tBu)₂V₂Cp₂] ( 2 ) is formed from [^tBuN = VCp(PMe₃)₂] ( 1 ) upon reaction with elemental tellurium. 1 and 2 are characterized by spectroscopic methods (MS; ¹H, ¹³C, ⁵¹V NMR), in addition 2 by single crystal X‐ray diffraction. The crystal structure indicates a folded cyclodivanadazen ring bridged by a bidentated ditellurido ligand, the first example of this structure type.     

Synthesis of 1‐Methyl‐3‐aryl‐substituted Titanocene and Zirconocene Dichlorides and Crystal Structure of Bis[η5‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium Dichloride

The syntheses of a series of l‐methyl‐3‐aryl‐substituted titanocene and zirconocene dichlorides are reported. These complexes are synthesized by the reaction of 2‐ and 3‐methyl‐6, 6‐dimethylfulvenes (1:4) with aryllithium, followed by the reaction with TiCl₄·2THF, ZrCl₄ and (CpTiCl₂)₂O respectively, to give complexes 1–5. The complex [η⁵‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium dichloride has been studied by X‐ray diffraction. The red crystal of this complex is monoclinic, space group P2_t/C with unit cell parameters: a =6.973(6) × 10^?1 nm, b =36.91(2) × 10^?1 nm, c = 10.063(4) × 10^?1 nm, α=β= γ = 93.35(5)°, V = 2584(5) × 10^?3 nm³ and Z = 4. Refinement for 1004 observed reflections gives the final R of 0.088. There are four independent molecules per unit cell.     

A Molecular Paddlewheel with a Sliding Organometallic Latch: Syntheses,X‐Ray Crystal Structures and Dynamic Behaviour of [Cr(CO)3{η6‐2‐(9‐triptycyl)indene}], and of [M(CO)3{η5‐2‐(9‐triptycyl)indenyl}] (M=Mn,Re)

Metal clamping in operation! Deprotonation of [η⁶‐2‐(9‐triptycyl)indene]tricarbonylchromium induces a haptotropic shift of the organometallic fragment from the six‐membered to the five‐membered ring, as in a→b . In the anion, rotation of the molecular paddlewheel is blocked by the bulky tripod. X‐ray crystal structures provide pictures of the system in both its “ON” and “OFF” states.

     

Hydrothermal Assembly and Structural Characterization of an Octamolybdate Supported Copper(Ⅰ) Tetramer:[Cu2(1,10-phen)2(4,4'-bpy)]2[Mo8O26]·4H2O

A hydrothermal reaction of copper acetate with ammonium molybdate, 4,4'-bpy (4,4'-bipyridine) and 1,10-phen (1,10-phenanthroline) led to the formation of brown crystals of [Cu2(1,10-phen)2(4,4'-bpy)]2 [Mo8O26]@4H2O 1. Single-crystal X-ray analysis has revealed that 1 C68H56N12O30Cu4Mo8 crystallizes in the triclinic system, space group P ī with a = 11.270(3), b = 13.113(6), c = 13.906(3)A, α = 103.33(4),α = 98.54(2),β= 101.29(2)°, V = 1920.1(1)A3, Mr = 2542.9(3), Z = 1, Dc = 2.199 g/cm3, μ= 2.435 mm-1, F(000)= 1240, the final R = 0.0445, wR = 0.1082 and S = 1.021 for 5052 observed reflections with I>σ2(I).It consists of copper Ⅰ tetramer units and α-[Mo8O26]4- anions, which are further attached into a three-dimensional framework through hydrogen bonding and π-π stacking interactions.     

新型杂多阴离子[{Na2(H2O)3}Ni(H2O)VOAs4W40O140]21-的结构及表征

在pH=4.5的水溶液中,Na27[NaAs4W40O140]·60H2O与NiCl2·6H2O, NaVO3·4H2O和NH4Cl反应得到了不同过渡金属离子占据S2位的新型杂多钨酸盐(NH4)21[{Na2(H2O)3}Ni(H2O)VOAs4W40O140]·53H2O,用X射线单晶衍射法和元素分析确定了其结构.晶胞参数为a=2.3305(14) nm, b=2.9467(19) nm, c=1.2671(16) nm, V=8.701(9) nm3, Z=2,空间群Pmmn.在杂多阴离子[{Na2(H2O)3}Ni(H2O)VOAs4W40O140]21-中,配体{As4W40}的1个中心位和4个S2位可以选择性地被不同的金属离子所占据,其中相对的2个S2位被Ni2+和V5+统计性地占据,每种离子占据的概率为50%;{As4W40}中的另2个S2位分别被2个Na+占据,2个Na+间通过一配位水分子桥连.讨论了标题化合物的IR, TG和磁学性质.     

A Designed Three‐Stranded β‐Sheet in an α/β Hybrid Peptide

The incorporation of β‐amino acid residues into the antiparallel β‐strand segments of a multi‐stranded β‐sheet peptide is demonstrated for a 19‐residue peptide, Boc‐LV^βFV^DPGL^βFVVL^DPGLVL^βFVV‐OMe (BBH19). Two centrally positioned ^DPro–Gly segments facilitate formation of a stable three‐stranded β‐sheet, in which β‐phenylalanine (^βPhe) residues occur at facing positions 3, 8 and 17. Structure determination in methanol solution is accomplished by using NMR‐derived restraints obtained from NOEs, temperature dependence of amide NH chemical shifts, rates of H/D exchange of amide protons and vicinal coupling constants. The data are consistent with a conformationally well‐defined three‐stranded β‐sheet structure in solution. Cross‐strand interactions between ^βPhe3/^βPhe17 and ^βPhe3/Val15 residues define orientations of these side‐chains. The observation of close contact distances between the side‐chains on the N‐ and C‐terminal strands of the three‐stranded β‐sheet provides strong support for the designed structure. Evidence is presented for multiple side‐chain conformations from an analysis of NOE data. An unusual observation of the disappearance of the Gly NH resonances upon prolonged storage in methanol is rationalised on the basis of a slow aggregation step, resulting in stacking of three‐stranded β‐sheet structures, which in turn influences the conformational interconversion between type I′ and type II′ β‐turns at the two ^DPro–Gly segments. Experimental evidence for these processes is presented. The decapeptide fragment Boc‐LV^βFV^DPGL^βFVV‐OMe (BBH10), which has been previously characterized as a type I′ β‐turn nucleated hairpin, is shown to favour a type II′ β‐turn conformation in solution, supporting the occurrence of conformational interconversion at the turn segments in these hairpin and sheet structures.     

Bildung und Struktur von [μ‐(1,2 : 2‐η‐tBu2P–P){Mo(CO)2cp′}2]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XXIV. Formation and Structure of [μ‐(1,2 : 2‐η‐^tBu₂P–P){Mo(CO)₂cp′}₂] [cp′Mo(CO)₂]₂ (cp′ = C₅H₄^tBu) reacts with ^tBu₂P–P=P(Me)^tBu₂ to yield the compound [μ‐(1,2 : 2‐η‐^tBu₂P–P){Mo(CO)₂cp′}₂], which crystallizes in the space group P2₁2₁2₁ with a = 1202.42(7), b = 1552.48(8), and c = 1765.3(1) pm.     

Synthese und Strukturuntersuchungen von Ba2H[α-FeO4W12O36] · 26 H2O

Synthesis and Structure Studies of Ba₂H[α-FeO₄W₁₂O₃₆] · 26 H₂O The heteropolyanion compound Ba₂H[α-FeO₄W₁₂O₃₆] · 26 H₂O (I) crystallizes in the tetragonal space group P4 n2 with the lattice parameters a = 12.398(6), c = 18.721(6) Å; Z = 2; D_x = 4.128 g · cm^?3. The structure was solved on a twinned crystal from 1029 observed reflections and refined to an index R of 7.6%. The calculations were done by means of a modified ORFLS-programme by Eitel and Bärnighausen. The heteropolyanion [α-FeO₄W₁₂O₃₆]^5? has the well known α-Keggin structure. The average distance of the four central oxygen atoms to the Fe^III position (0, 0, 0) is 1.84 Å. The angles ? O? Fe? O are 112.3° (4X) and 103.9 (2X), respectively, which leads to an disphenoidal distortion of the FeO₄ tetrahedron. The powder and single crystal ESR spectra of I show the anisotropy of the Fe^III fine structure transition 1/2 ? ?1/2. The Mößbauer spectra confirm the tetragonal distortion of the central FeO₄ tetrahedron (quadrupole splitting Δ ≈ 0.50 mm · s^?1).     

Ein neues Syntheseverfahren für Vanadiumbronzen. Die Kristallstruktur von β?Ag0,33V2O5. Verfeinerung der Kristallstruktur von ϵ?Cu0,76V2O5

A Novel Means of Synthesis for Vanadium Bronzes. Crystal Structure of β? Ag_0.33V₂O₅. Refinement of the Crystal Structure of ?? Cu_0.76V₂O₅ Ag_0.33V₂O₅ and Cu_0.76V₂O₅ were obtained by heating equimolar mixtures of AgI + V₂O₅ (700°C) and CuI + V₂O₅ (525°C), respectively, in sealed quartz glass ampoules. In each case, one of the well-formed crystals served for an X-ray structure analysis. Ag_0.33V₂O₅ has the structure known of the β phase of the vanadium bronzes, i. e. layers of edge-sharing, distorted VO₆ octahedra are liked by certain common octahedron vertices, the Ag atoms randomly occupy two positions with occupation probabilities of 0.5. Cu_0.76V₂O₅ has the previously determined structure of the ? phase, however, its space group is not Cm but C2/m.