Hydrothermal syntheses and crystal structures of crystalline catalysts based on 3-D Ln3+–pdc2− frameworks and [BW12O40]5− and their heterogeneous photocatalytic oxidation of thiophene

Five [BW₁₂O₄₀]^{5 ?} -containing metal-organic frameworks (MOFs), {K[Ln(H₂O)₄(pdc)]₄}[BW₁₂O₄₀]·2H₂O (Ln=La 1 and Ce 2, H₂pdc = pyridine-2,6-dicarboxylate) and {K[Ln(H₂O)₃(pdc)]₄}[BW₁₂O₄₀]·6H₂O (Ln=Tb 3, Dy 4 and Er 5), are synthesized hydrothermally. Ln³⁺ and pdc^2? are built into 3-D MOF segments containing large channels and cavities which are occupied by [BW₁₂O₄₀]^{5 ?} . Herein, we report MOF-containing polyoxometalates (POMs) as photocatalysts to oxidize thiophene with O₂ as the oxidant. Photo-excited state species ([BW₁₂O₄₀]^5??) are generated under UV irradiation and then H₂O is oxidized into OH˙ radicals and O₂ is reduced into O₂ ^2?. The active oxygen species (O₂ ^2?, OH˙) oxidize thiophene in the presence of photocatalysts and SO₃, CO₂, and H₂O are obtained as photoproducts. ESR measurements provide evidence that OH˙ species are generated during photocatalysis.     

The quenching of excited iodine atoms by oxygen molecules as studied by opto-acoustic spectroscopy

The opto-acoustic spectrum of I₂ in the presence of various quenching gases — NO, O₂, CH₃I, SO₂, C₃H_S, N₂, and He — has been studied. Of these, the I₂/O₂ spectrum is quite different due to the near-resonant energy transfer I(²P$\text{1}\text{2}$) + O₂(³Σ) → I(²P$\text{3}\text{2}$) + O₂(^IΔ), wherein the resistance of the O₂((^IΔ) species to collisional relaxation severely distorts the acoustic signal. The photochemical production of excited ²P$\text{1}\text{2}$ iodine atoms commences at wavelengths considerably longer than the dissociation limit of the I₂B? state.     

Low‐dimensional coordination polymeric structures in alkali metal complex salts of the herbicide (2,4‐dichlorophenoxy)acetic acid (2,4‐D)

The Li, Rb and Cs complexes with the herbicide (2,4‐dichlorophenoxy)acetic acid (2,4‐D), namely poly[[aqua[μ₃‐(2,4‐dichlorophenoxy)acetato‐κ³O¹:O¹:O^1′]lithium(I)] dihydrate], {[Li(C₈H₅Cl₂O₃)(H₂O)]·2H₂O}_n, (I), poly[μ‐aqua‐bis[μ₃‐(2,4‐dichlorophenoxy)acetato‐κ⁴O¹:O^1′:O^1′,Cl²]dirubidium(I)], [Rb₂(C₈H₅Cl₂O₃)₂(H₂O)]_n, (II), and poly[μ‐aqua‐bis[μ₃‐(2,4‐dichlorophenoxy)acetato‐κ⁵O¹:O^1′:O^1′,O²,Cl²]dicaesium(I)], [Cs₂(C₈H₅Cl₂O₃)₂(H₂O)]_n, (III), respectively, have been determined and their two‐dimensional polymeric structures are described. In (I), the slightly distorted tetrahedral LiO₄ coordination involves three carboxylate O‐atom donors, of which two are bridging, and a monodentate aqua ligand, together with two water molecules of solvation. Conjoined six‐membered ring systems generate a one‐dimensional coordination polymeric chain which extends along b and interspecies water O—H...O hydrogen‐bonding interactions give the overall two‐dimensional layers which lie parallel to (001). In hemihydrate complex (II), the irregular octahedral RbO₅Cl coordination about Rb⁺ comprises a single bridging water molecule which lies on a twofold rotation axis, a bidentate O_carboxy,Cl‐chelate interaction and three bridging carboxylate O‐atom bonding interactions from the 2,4‐D ligand. A two‐dimensional coordination polymeric layer structure lying parallel to (100) is formed through a number of conjoined cyclic bridges, including a centrosymmetric four‐membered Rb₂O₂ ring system with an Rb...Rb separation of 4.3312 (5) Å. The coordinated water molecule forms intralayer aqua–carboxylate O—H...O hydrogen bonds. Complex (III) comprises two crystallographically independent (Z′ = 2) irregular CsO₆Cl coordination centres, each comprising two O‐atom donors (carboxylate and phenoxy) and a ring‐substituted Cl‐atom donor from the 2,4‐D ligand species in a tridentate chelate mode, two O‐atom donors from bridging carboxylate groups and one from a bridging water molecule. However, the two 2,4‐D ligands are conformationally very dissimilar, with one phenoxyacetate side chain being synclinal and the other being antiperiplanar. The minimum Cs...Cs separation is 4.4463 (5) Å. Structure extension gives coordination polymeric layers which lie parallel to (001) and are stabilized by intralayer water–carboxylate O—H...O hydrogen bonds.     

UV absorption spectra of HO2, CH3O2, C2H5O2, and CH3C(O)CH2O2 radicals and mechanism of the reactions of F and Cl atoms with CH3C(O)CH3

Pulse radiolysis techniques were used to measure the gas phase UV absorption spectra of the title peroxy radicals over the range 215–340 nm. By scaling to σ(CH₃O₂)_{240 nm} = (4.24 ± 0.27) × 10^?18, the following absorption cross sections were determined: σ(HO₂)_{240 nm} = 1.29 ± 0.16, σ(C₂H₅O₂)_{240 nm} = 4.71 ± 0.45, σ(CH₃C(O)CH₂O₂)_{240 nm} = 2.03 ± 0.22, σ(CH₃C(O)CH₂O₂)_{230 nm} = 2.94 ± 0.29, and σ(CH₃C(O)CH₂O₂)_{310 nm} = 1.31 ± 0.15 (base e, units of 10^?18 cm² molecule^?1). To support the UV measurements, FTIR‐smog chamber techniques were employed to investigate the reaction of F and Cl atoms with acetone. The F atom reaction proceeds via two channels: the major channel (92% ± 3%) gives CH₃C(O)CH₂ radicals and HF, while the minor channel (8% ± 1%) gives CH₃ radicals and CH₃C(O)F. The majority (>97%) of the Cl atom reaction proceeds via H atom abstraction to give CH₃C(O)CH₂ radicals. The results are discussed with respect to the literature data concerning the UV absorption spectra of CH₃C(O)CH₂O₂ and other peroxy radicals. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 283–291, 2002     

Hydrogen bonded H3O, H2O, HF, F in fluoride metalates (Al, Cr, Fe, Zr, Ta) templated with tren (tris-(2-aminoethyl)amine)

The environment of H₃O⁺, H₂O, HF and F⁻ species (non-bonded to metals) is considered in fluoride metalates which crystallise from the (Al(OH)₃, Cr(OH)₃, FeF₃, ZrF₄, Ta₂O₅)-tren-HF_aq·-ethanol systems (microwave heating at 190 °C during 1 h). The presence of (H₃O)(H₂O)₆⁺ clusters or H₃O⁺ cations, of isolated or associated H₂O molecules, of (HF₂)⁻ and F⁻ anions is evidenced. The thermal stability of the solids depends strongly on the nature of the hydrogen-bonded species associated with the preceding cations or anions and on the formation of water ribbons or layers.     

3,3‐Bis(2‐methoxy­phenyl)‐3H‐benzo­[f]­chromene

The substituent methoxy group at the phenyl ortho position in the title compound, C₂₇H₂₂O₃, has an insignificant effect on the length of the Csp³—O bond and on the non‐planarity of the pyran ring. The cause of the changes in the photochemical properties is discussed.     

Kinetic studies of the deactivation of O2(1Σg+) and O(1D)

The kinetics of the deactivation of O₂(¹Σ_g⁺) is studied in real time. O₂(¹Σ_g⁺) is generated in this system by the O(¹D) + O₂ reaction following O₃laser flash photolysis in the presence of excess O₂, and it is monitored by its characteristic emission band at 762 nm. Quenching rate constants were obtained for O₂, O₃, N₂, CO₂, H₂O, CF₄and the rare gases. Since O(¹D) is the precursor for the formation of O₂(¹Σ_g⁺), the addition of an O(¹D) quencher effectively lowers the initial concentration of O₂(¹Σ_g⁺). By measuring the initial intensity of the 762 nm fluorescence signal, the relative quenching efficiencies were determined for O(¹D) quenching by N₂, CO₂, Xe, and Kr with respect to O₂; the results are in good agreement with literature values.     

Über Oxocadmate: K2Cd2O3

New obtained is K₂Cd₂O₃ (brownish red), which – according to single crystal work [487 h 01–h 41, Mo? Kα, R = 9.7₃%, R′ = 10.7₆%] – crystallises monoclinic with a = 6.41₇, b = 6.72₃, c = 6.58₆ Å, β = 116.0° in P2₁/c–C [K⁺, Cd²⁺ and O(1)^2? in 4(e), O(2)^2? in 2(a)] and is isotypic with Na₂Zn₂O₃. [Parameters see text]. The Madelung Part of Lattice Energy is calculated and discussed.     

Different coordination modes of trans‐2‐{[(2‐methoxyphenyl)imino]methyl}phenoxide in rare‐earth complexes: influence of the metal cation radius and the number of ligands on steric congestion and ligand coordination modes

A simple and effective synthetic route to homo‐ and heteroleptic rare‐earth (Ln = Y, La and Nd) complexes with a tridentate Schiff base anion has been demonstrated using exchange reactions of rare‐earth chlorides with in‐situ‐generated sodium (E)‐2‐{[(2‐methoxyphenyl)imino]methyl}phenoxide in different molar ratios in absolute methanol. Five crystal structures have been determined and studied, namely tris(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐κ³O¹,N,O²)lanthanum, [La(C₁₄H₁₂NO₂)₃], ( 1 ), tris(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐κ³O¹,N,O²)neodymium tetrahydrofuran disolvate, [La(C₁₄H₁₂NO₂)₃]·2C₄H₈O, ( 2 )·2THF, tris(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato)‐κ³O¹,N,O²;κ³O¹,N,O²;κ²N,O¹‐yttrium, [Y(C₁₄H₁₂NO₂)₃], ( 3 ), dichlorido‐1κCl,2κCl‐μ‐methanolato‐1:2κ²O:O‐methanol‐2κO‐(μ‐2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐1κ³O¹,N,O²:2κO¹)bis(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato)‐1κ³O¹,N,O²;2κ³O¹,N,O²‐diyttrium–tetrahydrofuran–methanol (1/1/1), [Y₂(C₁₄H₁₂NO₂)₃(CH₃O)Cl₂(CH₄O)]·CH₄O·C₄H₈O, ( 4 )·MeOH·THF, and bis(μ‐2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐1κ³O¹,N,O²:2κO¹)bis(2‐{[(2‐methoxyphenyl)imino]methyl}phenolato‐2κ³O¹,N,O²)sodiumyttrium chloroform disolvate, [NaY(C₁₄H₁₂NO₂)₄]·2CHCl₃, ( 5 )·2CHCl₃. Structural peculiarities of homoleptic tris(iminophenoxide)s ( 1 )–( 3 ), binuclear tris(iminophenoxide) ( 4 ) and homoleptic ate tetrakis(iminophenoxide) ( 5 ) are discussed. The nonflat Schiff base ligand displays μ₂‐κ³O¹,N,O²:κO¹ bridging, and κ³O¹,N,O² and κ²N,O¹ terminal coordination modes, depending on steric congestion, which in turn depends on the ionic radii of the rare‐earth metals and the number of coordinated ligands. It has been demonstrated that interligand dihedral angles of the phenoxide ligand are convenient for comparing steric hindrance in complexes. ( 4 )·MeOH has a flat Y₂O₂ rhomboid core and exhibits both inter‐ and intramolecular MeO—H…Cl hydrogen bonding. Catalytic systems based on complexes ( 1 )–( 3 ) and ( 5 ) have demonstrated medium catalytic performance in acrylonitrile polymerization, providing polyacrylonitrile samples with narrow polydispersity.     

Mechanism of fluoride loss from fluoropolytungstates possessing the keggin structure

The fluoropolytungstates [H₂W₁₂F₂O₃₈]^4? and [HW₁₂F₃O₃₇]^4?, which are of the metatungstate type with the fluoride ions occupying inner sites, lose fluoride ion and form more higly charged species [H₂W₁₂FO₃₉]^5? and [HW₁₂F₂O₃₈]^5? in aqueous solution about pH 3 in media of suitable ionic strength. Kinetic results are presented here consistent with a mechanism involving less condensed species containing 11 tungsten and 1, 2 or 3 fluoride atoms. Involvement of such species is supported by the isolation of the aluminotungstates [HW₁₁AlF₃O₃₆(H₂O)] (TMA)₅², 30H₂O and [H₂W₁₁AlF₂O₃₇(H₂O)](TMA)₅, 17H₂O.     

Overlooked Formation of Carbonate Radical Anions in the Oxidation of Iron(II) by Oxygen in the Presence of Bicarbonate

Iron(II), (Fe(H₂O)₆²⁺, (Fe^II) participates in many reactions of natural and biological importance. It is critically important to understand the rates and the mechanism of Fe^II oxidation by dissolved molecular oxygen, O₂, under environmental conditions containing bicarbonate (HCO₃⁻), which exists up to millimolar concentrations. In the absence and presence of HCO₃⁻, the formation of reactive oxygen species (O₂⋅⁻, H₂O₂, and HO⋅) in Fe^II oxidation by O₂ has been suggested. In contrast, our study demonstrates for the first time the rapid generation of carbonate radical anions (CO₃⋅⁻) in the oxidation of Fe^II by O₂ in the presence of bicarbonate, HCO₃⁻. The rate of the formation of CO₃⋅⁻ may be expressed as d[CO₃⋅⁻]/dt=[Fe^II[[O₂][HCO₃⁻]². The formation of reactive species was investigated using ¹H nuclear magnetic resonance (¹H NMR) and gas chromatographic techniques. The study presented herein provides new insights into the reaction mechanism of Fe^II oxidation by O₂ in the presence of bicarbonate and highlights the importance of considering the formation of CO₃⋅⁻ in the geochemical cycling of iron and carbon.     

Nd[Al(iPrO)4]3, a novel tetranuclear alkoxide forming merohedrally twinned crystals

The new tetranuclear alkoxide hexa‐μ₂‐isopropoxy‐1:2κ⁴O;1:3κ⁴O;1:4κ⁴O‐hexaisopropoxy‐2κ²O,3κ²O,4κ²O‐trialumin­ium(III)­neodymium(III), [Nd{Al(C₃H₇O)₄}₃], has a metal–oxy­gen NdAl₃O₁₂ core which consists of four metal atoms arranged in an approximately planar triangular geometry. The central Nd atom is six‐coordinated by O atoms and the Al atoms are four‐coordinated by O atoms.     

Thermal decomposition of trifluoromethoxycarbonyl peroxy nitrate,CF3OC(O)O2NO2

The thermal decomposition of trifluoromethoxycarbonyl peroxy nitrate, CF₃OC(O)O₂NO₂, has been studied between 278 and 306 K at 270 mbar total pressure using He as a diluent gas. The pressure dependence of the reaction was also studied at 292 K between 1.2 and 270 mbar total pressure. The rate constant reaches its high‐pressure limit at 70 mbar. The first step of the decomposition leads to CF₃OC(O)O₂ and NO₂ formation, that is, CF₃OC(O)O₂NO₂ + M ? CF₃OC(O)O₂ + NO₂ + M (k₁, k_?1). Reaction (?1) was prevented by adding an excess of NO that reacts with the peroxy radical intermediate and leads to carbonyl fluoride (CF₂O), carbon dioxide (CO₂), nitrogen dioxide (NO₂), and small quantities of CF₃OC(O)O₂C(O)OCF₃. The kinetics of reaction (1) was determined by following the loss of CF₃OC(O)O₂NO₂ via IR spectroscopy. The temperature dependence of the decomposition follows the equation k₁(T) = 1.0 × 10¹⁶ e^{?((111±3)/(RT))} for the exponential term expressed in kJ mol^?1. The values obtained for the kinetic parameters such as k₁ at 298 K, the activation energy (E_a), and the preexponential factor (A) are compared with literature data for other acyl peroxy nitrates. The atmospheric thermal stability of CF₃OC(O)O₂NO₂ and its dependence with altitude is discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 831–838, 2008     

Template Syntheses of Copper(II) Complexes from Arylhydrazones of Malononitrile and their Catalytic Activity towards Alcohol Oxidations and the Nitroaldol Reaction: Hydrogen Bond‐Assisted Ligand Liberation and E/Z Isomerisation

A one‐pot template condensation of 2‐(2‐(dicyanomethylene)hydrazinyl)benzenesulfonic acid (H₂L¹, 1 ) or 2‐(2‐(dicyanomethylene)hydrazinyl)benzoic acid (H₂L², 2 ) with methanol (a), ethylenediamine (b), ethanol (c) or water (d) on copper(II), led to a variety of metal complexes, that is, mononuclear [Cu(H₂O)₂(κO¹,κN² L^1a] ( 3 ) and [Cu(H₂O)(κO¹,κN³ L^1b)] ( 4 ), tetranuclear [Cu₄(1 κO¹,κN²:2 κO¹ L^2a)₃‐(1 κO¹, κN²:2 κO² L^2a)] ( 5 ), [Cu₂(H₂O)(1 κO¹, κN²:2 κO¹ L^2c)‐(1 κO¹,1 κN²:2 κO¹,2 κN¹‐ L^2c)]₂ ( 6 ) and [Cu₂(H₂O)₂(κO¹,κN²‐ L^1dd)‐(1 κO¹,κN²:2 κO¹ L^1dd)(μ‐H₂O)]₂ ? 2 H₂O ( 7? 2 H₂O), as well as polymer‐ ic [Cu(H₂O)(κO¹,1 κN²:2 κN¹ L^1c)]_n ( 8 ) and [Cu(NH₂C₂H₅)(κO¹,1 κN²:2 κN¹L^2a)]_n ( 9 ). The ligands 2‐SO₃H‐C₆H₄‐(NH)N?C{(CN)[C(NH₂)‐(?NCH₂CH₂NH₂)]} (H₂L^1b, 10 ), 2‐CO₂H‐C₆H₄‐(NH)N?{C(CN)[C(OCH₃)‐(?NH)]} (H₂L^2a, 11 ) and 2‐SO₃H‐C₆H₄‐(NH)N?C{C(?O)‐(NH₂)}₂ (H₂L^1dd, 12 ) were easily liberated upon respective treatment of 4 , 5 and 7 with HCl, whereas the formation of cyclic zwitterionic amidine 2‐(SO₃^?)? C₆H₄? N?NC(? C?(NH⁺)CH₂CH₂NH)(?CNHCH₂CH₂NH) ( 13 ) was observed when 1 was treated with ethylenediamine. The hydrogen bond‐induced E/Z isomerization of the (HL^1d)^? ligand occurs upon conversion of [{Na(H₂O)₂(μ‐H₂O)₂}(HL^1d)]_n ( 14 ) to [Cu(H₂O)₆][HL^1d]₂ ? 2 H₂O ( 15 ) and [{CuNa(H₂O)‐(κN¹,1 κO²:2 κO¹ L^1d)₂}K_0.5(μ‐O)₂]n ? H₂O ( 16 ). The synthesized complexes 3 – 9 are catalyst precursors for both the selective oxidation of primary and secondary alcohols (to the corresponding carbonyl compounds) and the following diastereoselective nitroaldol (Henry) reaction, with typical yields of 80–99 %.     

Crystal structures and Hirshfeld surface analysis of transition‐metal complexes of 1,3‐azolecarboxylic acids

The crystal structures of five new transition‐metal complexes synthesized using thiazole‐2‐carboxylic acid (2‐Htza), imidazole‐2‐carboxylic acid (2‐H₂ima) or 1,3‐oxazole‐4‐carboxylic acid (4‐Hoxa), namely diaquabis(thiazole‐2‐carboxylato‐κ²N,O)cobalt(II), [Co(C₄H₂NO₂S)₂(H₂O)₂], 1 , diaquabis(thiazole‐2‐carboxylato‐κ²N,O)nickel(II), [Ni(C₄H₂NO₂S)₂(H₂O)₂], 2 , diaquabis(thiazole‐2‐carboxylato‐κ²N,O)cadmium(II), [Cd(C₄H₂NO₂S)₂(H₂O)₂], 3 , diaquabis(1H‐imidazole‐2‐carboxylato‐κ²N³,O)cobalt(II), [Co(C₄H₂N₂O₂)₂(H₂O)₂], 4 , and diaquabis(1,3‐oxazole‐4‐carboxylato‐κ²N,O⁴)cobalt(II), [Co(C₄H₂NO₃)₂(H₂O)₂], 5 , are reported. The influence of the nature of the heteroatom and the position of the carboxyl group in relation to the heteroatom on the self‐assembly process are discussed based upon Hirshfeld surface analysis and used to explain the observed differences in the single‐crystal structures and the supramolecular frameworks and topologies of complexes 1 – 5 .     

Zero‐, one‐ and two‐dimensional hydrogen‐bonded structures in the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with the monocyclic heteroaromatic Lewis bases 2‐aminopyrimidine,nicotinamide and isonicotinamide

The structures of the anhydrous 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid (DCPA) with the monocyclic heteroaromatic Lewis bases 2‐aminopyrimidine, 3‐(aminocarbonyl)pyridine (nicotinamide) and 4‐(aminocarbonyl)pyridine (isonicotinamide), namely 2‐aminopyrimidinium 2‐carboxy‐4,5‐dichlorobenzoate, C₄H₆N₃⁺·C₈H₃Cl₂O₄⁻, (I), 3‐(aminocarbonyl)pyridinium 2‐carboxy‐4,5‐dichlorobenzoate, C₆H₇N₂O⁺·C₈H₃Cl₂O₄⁻, (II), and the unusual salt adduct 4‐(aminocarbonyl)pyridinium 2‐carboxy‐4,5‐dichlorobenzoate–methyl 2‐carboxy‐4,5‐dichlorobenzoate (1/1), C₆H₇N₂O⁺·C₈H₃Cl₂O₄⁻·C₉H₆Cl₂O₄, (III), have been determined at 130 K. Compound (I) forms discrete centrosymmetric hydrogen‐bonded cyclic bis(cation–anion) units having both R₂²(8) and R₁²(4) N—H...O interactions. In (II), the primary N—H...O‐linked cation–anion units are extended into a two‐dimensional sheet structure via amide–carboxyl and amide–carbonyl N—H...O interactions. The structure of (III) reveals the presence of an unusual and unexpected self‐synthesized methyl monoester of the acid as an adduct molecule, giving one‐dimensional hydrogen‐bonded chains. In all three structures, the hydrogen phthalate anions are essentially planar with short intramolecular carboxyl–carboxylate O—H...O hydrogen bonds [O...O = 2.393 (8)–2.410 (2) Å]. This work provides examples of low‐dimensional 1:1 hydrogen‐bonded DCPA structure types, and includes the first example of a discrete cyclic `heterotetramer.' This low dimensionality in the structures of the 1:1 aromatic Lewis base salts of the parent acid is generally associated with the planar DCPA anion species.     

The crystal and molecular structures of three copper‐containing complexes and their activities in mimicking galactose oxidase

The structures of three copper‐containing complexes, namely (benzoato‐κ²O,O′)[(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O]copper(II) dihydrate, [Cu(C₇H₅O₂)(C₁₃H₁₉N₂O)]·2H₂O, 1 , [(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O](2‐phenylacetato‐κ²O,O′)copper(II), [Cu(C₈H₇O₂)(C₁₃H₁₉N₂O)], 2 , and bis[μ‐(E)‐2‐({[3‐(diethylamino)propyl]imino}methyl)phenolato]‐κ⁴N,N′,O:O;κ⁴O:N,N′,O‐(μ‐2‐methylbenzoato‐κ²O:O′)copper(II) perchlorate, [Cu₂(C₈H₇O₂)(C₁₂H₁₇N₂O)₂]ClO₄, 3 , have been reported and all have been tested for their activity in the oxidation of d ‐galactose. The results suggest that, unlike the enzyme galactose oxidase, due to the precipitation of Cu₂O, this reaction is not catalytic as would have been expected. The structures of 1 and 2 are monomeric, while 3 consists of a dimeric cation and a perchlorate anion [which is disordered over two orientations, with occupancies of 0.64 (4) and 0.36 (4)]. In all three structures, the central Cu atom is five‐coordinated in a distorted square‐pyramidal arrangment (τ parameter of 0.0932 for 1 , 0.0888 for 2 , and 0.142 and 0.248 for the two Cu centers in 3 ). In each species, the environment about the Cu atom is such that the vacant sixth position is open, with very little steric crowding.     

Syntheses and X-Ray Crystal Structures of Novel Oxonium Ion-12-Crown-4 Complexes Isolated From Liquid Clathrate Media

Abstract

The reactions of Mo(CO)₆ and W(CO)₆ with HCl_(g) in the presence of 12-crown-4 and H₂O have been investigated in toluene. For both reactions, two products were isolated, depending on the oxidation of the metal center. For molybdenum, the Mo^III species, [H₃O⁺ · 12-crown-4]₃[Mo₂Cl₉ ^3-], 1, was obtained from the liquid clathrate layer in the reaction mixture. Upon air oxidation of the reaction mixture, the Mo^v complex, [H₇O₃ ^? · H₄O₂ ⁺ · (12-crown-4)₂][MoOCl₄(H₂O)^?]₂, 2, rapidly formed. For tungsten, the W^II species, [(H₅O₂ ⁺)₂ · 12-crown-4][W(CO)₄Cl^? ₃]₂, 3, deposited from the liquid clathrate layer which upon oxidation formed the W^v complex, [H₃O⁺· 12-crown-4][WOCl₄(H₂O)^?], 4. These reactions were promoted by UV radiation and formed liquid clathrates almost immediately upon reaction. X-ray crystal structures were performed on each compound. Complexes 1 and 4 have H₃O⁺ oxonium ions involved in complex hydrogen bonded arrays with the 12-crown-4 acceptor molecules. The H₅O₂ ⁺ oxonium ions in 2 and 3 contain extremely short O…O separations, equivalent to the shortest O-H…O bonds known. Also isolated in complex 2 was the H₇O₃ ⁺ oxonium ion which contains an unusual linear O…O…O core.     

Syntheses,Structures and Magnetic Properties of Three New Extended Iron‐containing Heteropolytungstates

Three new extended iron‐containing heteropolytungstates were synthesized and structurally characterized: K₆[{Fe^II(H₂O)₄}₂(H₂W₁₂O₄₂)]·15H₂O ( 1 ), Na₅[{Fe(H₂O)₃}₂{Fe(H₂O)₄}_0.5(H₂W₁₂O₄₂)]·30H₂O ( 2 ) and (H₃O)⁺₂[{Fe(H₂O)₄Fe(H₂O)₃}₂(H₂W₁₂O₄₂)]·20H₂O ( 3 ). 1 and 3 crystallize in the monoclinic system, space group P2₁/n with a = 14.9967(5), b = 10.3872(3), c = 18.8237(6)Å, β = 93.407(1)°, V = 2927.1(2)ų and D_c = 4.151 g cm^—3 for 1 , and space group P2₁/c with a = 12.1794(4), b = 22.4938(4), c = 11.6941(3) Å, β = 105.731(2)°, V = 3083.7(1) ų, and D_c = 4.043 g cm^—3 for 3 . 2 is triclinic, space group P1¯, with a = 12.121(2), b = 12.426(3), c = 13.247(3)Å, α = 68.33(3), β = 71.33(3), γ = 71.44(3)°, V = 1710.7(6)ų and D_c = 3.735 g cm^—3. In all cases, the structures are based on paradodecatungstate polyoxoanions, which are linked by iron ions into chains, layers and a three‐dimensional structure for 1 , 2 and 3 , respectively.     

Modeling Chemical Composition for an Atmospheric Pressure DC Discharge in Air with Water Cathode by 0-D model

This paper reports the results of the chemical composition modeling for an atmospheric pressure DC air discharge with water cathode. The modeling was based on the combined solution of Boltzmann equation for electrons, equations of vibrational kinetics for ground states of N₂, O₂, H₂O and NO molecules, equations of chemical kinetics and plasma conductivity equation. Calculations were carried out using experimental values of E/N and gas temperatures for the discharge currents range of 20–50 mA. The effect of H₂O concentration on the plasma composition was studied. The main particles of plasma were shown to be O₂(a¹Δ, b¹Σ), O(³P), NO, NO₂, HNO₃, H₂O₂ and OH. Effective vibrational temperatures of molecules were higher than gas temperature and they did not depend on the discharge current. Distribution functions on vibrational levels for N₂, O₂, H₂O and NO ground states were non-equilibrium ones.