Specific O₂⁻ generation in corona discharge for ion mobility spectrometry

This study deals with O₂⁻ generation in corona discharge (CD) in point to plane geometry for single flow ion mobility spectrometry (IMS) with gas outlet located behind the ionization source. We have designed CD of special geometry in order to achieve the high O₂⁻ yield. Using this ion source we have achieved in zero air conditions that up to 74% all negative ions were O₂⁻ or O₂⁻(H₂O). It has been demonstrated that the non-electronegative nitrogen positively influences the efficiency of O₂⁻ generation in O₂/N₂ mixtures. The reduced ion mobility of 2.27 cm² V⁻¹ s⁻¹ has been measured for O₂⁻/O₂⁻(H₂O) ions in zero air. Additional ions detected in zero air (less than 200 ppb CO₂) using the mass spectrometric and IMS technique were, NO₂⁻, N₂O₂⁻ (2.37 cm² V⁻¹ s⁻¹), NO₃⁻, N₂O₃⁻ and N₂O₃⁻(H₂O). The CO₃⁻ and CO₄⁻ ions have been detected after the introduction of 5 ppm CO₂ into zero air.     

Conservation of [(C2H4NH3)3N]2·(ZrF7)2·H2O layers during the topotactic dehydration of [(C2H4NH3)3N]2·(ZrF7)2·9H2O

Tren amine cations [(C₂H₄NH₃)₃N]³⁺ and zirconate or tantalate anions adopt a ternary symmetry in two hydrates, [H₃tren]₂·(ZrF₇)₂·9H₂O and [H₃tren]₆·(ZrF₇)₂·(TaOF₆)₄·3H₂O, which crystallise in R32 space group with a_H = 8.871 (2) Å, c_H = 38.16 (1) Å and a_H = 8.758 (2) Å, c_H = 30.112 (9) Å, respectively. Similar [H₃tren]₂·(MX₇)₂·H₂O (M = Zr, Ta; X = F, O) sheets are found in both structures; they are separated by a water layer (O_w(2)-O_w(3)) in [H₃tren]₂·(ZrF₇)₂·9H₂O. Dehydration of [H₃tren]₂·(ZrF₇)₂·9H₂O starts at room temperature and ends at 90 °C to give [H₃tren]₂·(ZrF₇)₂·H₂O. [H₃tren]₂·(ZrF₇)₂·H₂O layers remain probably unchanged during this dehydration and the existence of one intermediate [H₃tren]₂·(ZrF₇)₂·3H₂O hydrate is assumed. O_w(1) molecules are tightly hydrogen bonded with -NH₃⁺ groups and decomposition of [H₃tren]₂·(ZrF₇)₂·H₂O occurs from 210 °C to 500 °C to give successively [H₃tren]₂·(ZrF₆)·(Zr₂F₁₂) (285 °C), an intermediate unknown phase (320 °C) and ZrF₄.     

Stabilisation of heterobimetallic networks by crown ethers and hydrogen-bonding in [Ni(H2O)6][Cu3Cl8(H2O)2] · (15-crown-5)2 · 2H2O: Structure and magnetism

[Ni(H₂O)₆][Cu₃Cl₈(H₂O)₂] · (15-crown-5)₂ · 2H₂O can be conveniently prepared by the interaction of NiCl₂ · 6H₂O, CuCl₂ · 2H₂O and 15-crown-5 in water. The X-ray crystal structure reveals an ionic complex involved in a hydrogen-bonded two dimensional network with the [Ni(H₂O)₆]²⁺ and [Cu₃Cl₈(H₂O)₂]²⁻ ions sandwiched between the 15-crown-5 macrocycles. The magnetic susceptibility data (4–300 K) and magnetisation isotherms (2–5.5 K; 0–5 T) are best interpreted in terms of intra-trimer ferromagnetic coupling within the [Cu₃Cl₈(H₂O)₂]²⁻ moieties, with J ∼ 6 cm⁻¹, and antiferromagnetic coupling between the trimers, the latter mediated by H-bonding pathways. Comparisons are made to other reported quaternary ammonium salts of [Cu₃Cl₈]²⁻ and [Cu₃Cl₁₂]⁶⁻, most of which display structures that involve close stacking of such Cu(II) trimers, rather than being of the present isolated, albeit H-bonded, types.     

Thermal and X-ray diffraction analysis studies during the decomposition of ammonium uranyl nitrate

Two types of ammonium uranyl nitrate (NH₄)₂UO₂(NO₃)₄·2H₂O and NH₄UO₂(NO₃)₃, were thermally decomposed and reduced in a TG-DTA unit in nitrogen, air, and hydrogen atmospheres. Various intermediate phases produced by the thermal decomposition and reduction process were investigated by an X-ray diffraction analysis and a TG/DTA analysis. Both (NH₄)₂UO₂(NO₃)₄·2H₂O and NH₄UO₂(NO₃)₃ decomposed to amorphous UO₃ regardless of the atmosphere used. The amorphous UO₃ from (NH₄)₂UO₂(NO₃)₄·2H₂O was crystallized to γ-UO₃ regardless of the atmosphere used without a change in weight. The amorphous UO₃ obtained from decomposition of NH₄UO₂(NO₃)₃ was crystallized to α-UO₃ under a nitrogen and air atmosphere, and to β-UO₃ under a hydrogen atmosphere without a change in weight. Under each atmosphere, the reaction paths of (NH₄)₂UO₂(NO₃)₄·2H₂O and NH₄UO₂(NO₃)₃ were as follows: under a nitrogen atmosphere: (NH₄)₂UO₂(NO₃)₄·2H₂O → (NH₄)₂UO₂(NO₃)₄·H₂O → (NH₄)₂UO₂(NO₃)₄ → NH₄UO₂(NO₃)₃ → A-UO₃ → γ-UO₃ → U₃O₈, NH₄UO₂(NO₃)₃ → A-UO₃ → α-UO₃ → U₃O₈; under an air atmosphere: (NH₄)₂UO₂(NO₃)₄·2H₂O → (NH₄)₂UO₂(NO₃)₄·H₂O → (NH₄)₂UO₂(NO₃)₄ → NH₄UO₂(NO₃)₃ → A-UO₃ → γ-UO₃ → U₃O₈, NH₄UO₂(NO₃)₃ → A-UO₃ → α-UO₃ → U₃O₈; and under a hydrogen atmosphere: (NH₄)₂UO₂(NO₃)₄·2H₂O → (NH₄)₂UO₂(NO₃)₄·H₂O → (NH₄)₂UO₂(NO₃)₄ → NH₄UO₂(NO₃)₃ → A-UO₃ → γ-UO₃ → α-U₃O₈ → UO₂, NH₄ UO₂(NO₃)₃ → A-UO₃ → β-UO₃ → α-U₃O₈ → UO₂.     

Experimental determination of the rate constants of the reactions of HO2 + DO2 and DO2 + DO2

The rate constants of the reactions of DO₂ + HO₂ (R1) and DO₂ + DO₂ (R2) have been determined by the simultaneous, selective, and quantitative measurement of HO₂ and DO₂ by continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near infrared, coupled to a radical generation by laser photolysis. HO₂ was generated by photolyzing Cl₂ in the presence of CH₃OH and O₂. Low concentrations of DO₂ were generated simultaneously by adding low concentrations of D₂O to the reaction mixture, leading through isotopic exchange on tubing and reactor walls to formation of low concentrations of CH₃OD and thus formation of DO₂. Excess DO₂ was generated by photolyzing Cl₂ in the presence of CD₃OD and O₂, small concentrations of HO₂ were always generated simultaneously by isotopic exchange between CD₃OD and residual H₂O. The rate constant k₁ at 295 K was found to be pressure independent in the range 25–200 Torr helium, but increased with increasing D₂O concentration k₁ = (1.67 ± 0.03) × 10⁻¹² × (1 + (8.2 ± 1.6) × 10⁻¹⁸ cm³ × [D₂O] cm⁻³) cm³ s⁻¹. The rate constant for the DO₂ self-reaction k₂ has been measured under excess DO₂ concentration, and the DO₂ concentration has been determined by fitting the HO₂ decays, now governed by their reaction with DO₂, to the rate constant k₁. A rate constant with insignificant pressure dependence was found: k₂ = (4.1 ± 0.6) × 10⁻¹³ (1 + (2 ± 2) × 10⁻²⁰ cm³ × [He] cm⁻³) cm³ s⁻¹ as well as an increase of k₂ with increasing D₂O concentration was observed: k₂ = (4.14 ± 0.02) × 10⁻¹³ × (1 + (6.5 ± 1.3) × 10⁻¹⁸ cm³ × [D₂O] cm⁻³) cm³ s⁻¹. The result for k₂ is in excellent agreement with literature values, whereas this is the first determination of k₁.     

Gamma-ray induced decomposition of some divalent and trivalent nitrates

Gamma-ray induced decomposition of some divalent nitrates, viz. Mg(NO₃)₂·6H₂O, Ca(NO₃)₂·4H₂O, Sr(NO₃)₂, Ba(NO₃)₂, Zn(NO₃)₂·6H₂O, Cd(NO₃)₂·4H₂O, Hg(NO₃)₂·2H₂O, Mn(NO₃)₂·4H₂O, Cu(NO₃)₂·3H₂O and trivalent nitrates, viz. Al(NO₃)₃·9H₂O, Fe(NO₃)₃·9H₂O, Cr(NO₃)₃·9H₂O, Y(NO₃)₃·6H₂O, In(NO₃)₃·3H₂O, La(NO₃)₃·6H₂O, Ce(NO₃)₃·6H₂O, Pr(NO₃)₃·6H₂O, Bi(NO₃)₃·5H₂O has been studied in solid state at room temperature. G(NO ₂ ^– ) values (after applying appropriate dose correction) have been found to vary in the range 0.12–3.16 and 0.069–2.15 for divalent and trivalent nitrates respectively. G'-values were calculated by dividing G by the ratio of number of electrons in nitrate ion to the total number of electrons in the nitrate salt. Cation size, its polarizing power, available free space in the crystal lattice and the number and location of water molecules seem to play a dominant role in radiolytic decomposition. For Zn, Sr, In, La and Ce nitrates dose variation studies have been carried out.     

Reactivity of the unsaturated manganese dihydrides [Mn2(μ-H)2(CO)6(μ-L2)] [L2 = (EtO)2POP(OEt)2, Ph2PCH2PPh2, Me2PCH2PMe2] toward silicon and tin hydrides

The dimanganese hydride complexes [Mn₂(μ-H)₂(CO)₆(μ-L₂)] [L₂ = (EtO)₂POP(OEt)₂ (tedip), Ph₂PCH₂PPh₂ (dppm)] react with primary and secondary silanes H₂SiPhR (R = Ph, Me, H) to give the corresponding derivatives [Mn₂(μ-H₂SiPhR)(CO)₆(μ-L₂)] having a silane molecule displaying a relatively unusual μ-κ²:κ² coordination mode (averaged values are ca. Mn-H = 1.59 Å, H-Si = 1.69 Å and Mn-Si = 2.381 Å, when R = Ph and L₂ = tedip). These complexes display in solution cis and/or trans arrangement of the bridging silane relative to the diphosphorus ligands (and facial and/or meridional arrangements of the corresponding carbonyl ligands), depending on the bridging groups. The novel unsaturated dihydride [Mn₂(μ-H)₂(CO)₆(μ-dmpm)] (dmpm = Me₂PCH₂PMe₂) has been prepared through the reaction of [Mn₂(μ-Cl)₂(μ-dmpm)(CO)₆] and 5 equiv of Li[BH₂Me₂] in tetrahydrofuran followed by addition of water. The dihydride complexes [Mn₂(μ-H)₂(CO)₆(μ-L₂)] (L₂ = tedip, dppm, dmpm) react with HSnPh₃ to give different mixtures of products strongly dependent on the particular reaction conditions. We have thus been able to isolate and characterize five new types of dimanganese-tin derivatives: [Mn₂(μ-SnPh₂)₂(CO)₆(μ-L₂)], [Mn₂(μ-H)(μ-Ph₂SnO(H)SnPh₂)(CO)₆(μ-L₂)] (average values are Mn-Sn = 2.54 Å, Sn-O = 2.11 Å, when L₂ = tedip), [Mn₂(μ-H)(μ-κ¹:κ²-HSnPh₂)(CO)₆(μ-L₂)], [Mn₂(μ-H)(μ-κ¹:κ¹-O(H)SnPh₂)(CO)₆(μ-L₂)], and [Mn₂(μ-H)(SnPh₃)(CO)₇(μ-L₂)] (Mn-Mn = 3.237(1) Å, Mn-Sn = 2.642(1) Å, when L₂ = dppm).     

Structural and spectroscopy studies of complexes of the uranyl ion with 2,2′-bipyridine-N,N′-dioxide

2,2′-Bipyridine-N,N′-dioxide (bypO₂ = L) complexes of the composition [UO₂(bypO₂)₂(NO₃)₂]·2H₂O (UO₂–L₂–NO₃), [UO₂(bypO₂)₂H₂O](ClO₄)₂ (UO₂–L₂–ClO₄) and [UO₂bypO₂(H₂O)₂SO₄] (UO₂–L–SO₄) have been prepared by the reactions of the respective hydrated uranyl salts with the bypO₂ ligand in water. The structures of the complexes were elucidated using elemental and thermal analyses, IR and luminescence spectroscopy as well as luminescence lifetime measurements. The IR spectra show that the bonding between uranium and bypO₂, as well as uranium and water or a counter ion (NO₃⁻ and SO₄²⁻) is formed. The nitrate or sulfate groups coordinate to the central metal ions in a monodentate manner. From TG–DTA curves, the nature of the water molecules present in the complexes and the decomposition temperature of the dehydrated uranyl complexes were determined. The thermal stability of the anhydrous uranyl complexes increases in the series: (UO₂–L₂–NO₃) < (UO₂–L₂–ClO₄) < (UO₂–L–SO₄). All the compounds show green-yellow intense luminescence. The main fluorescence bands and the emission lifetimes in these complexes were determined. The luminescence spectra of all the prepared complexes differ from each other with respect to their peak maxima positions. The luminescence lifetimes also vary. The structure of the (UO₂–L–SO₄) complex was determined by X-ray single-crystal analysis.     

Kinetics of the Formation of the Blue Complex CrO(O2)2 Formed by Dichromate and H2O2 in Acid Solutions. A Stopped-Flow Investigation Using Rapid-Scan UV-VIS Detection

 The kinetics of the CrO(O₂)₂ formation by H₂O₂ and Cr₂O₇ ²⁻ in aqueous acidic media was measured at 293 ± 2 K in a pH range between 2.5 and 3.3. Using the stopped-flow method with rapid scan UV-VIS detection, the rate law of the formation of CrO(O₂)₂ was determined. For the media HClO₄, HNO₃ and CH₃COOH, the reaction order in the Cr₂O₇ ²⁻ concentration was found to be 0.5. For [H₂O₂] as well as for [H⁺], the reaction was first order in all acids used. In HCl and H₂SO₄ media the reaction was first order in Cr₂O₇ ²⁻. At T = 293 ± 2 K the rate constant for the formation of Cr(O)(O₂)₂ was found to be (7.3 ± 1.9) · 10² M^−3/2 s⁻¹ in HClO₄.     

Kinetics of the Formation of the Blue Complex CrO(O2)2 Formed by Dichromate and H2O2 in Acid Solutions. A Stopped-Flow Investigation Using Rapid-Scan UV-VIS Detection

Summary.  The kinetics of the CrO(O₂)₂ formation by H₂O₂ and Cr₂O₇ ²⁻ in aqueous acidic media was measured at 293 ± 2 K in a pH range between 2.5 and 3.3. Using the stopped-flow method with rapid scan UV-VIS detection, the rate law of the formation of CrO(O₂)₂ was determined. For the media HClO₄, HNO₃ and CH₃COOH, the reaction order in the Cr₂O₇ ²⁻ concentration was found to be 0.5. For [H₂O₂] as well as for [H⁺], the reaction was first order in all acids used. In HCl and H₂SO₄ media the reaction was first order in Cr₂O₇ ²⁻. At T = 293 ± 2 K the rate constant for the formation of Cr(O)(O₂)₂ was found to be (7.3 ± 1.9) · 10² M^−3/2 s⁻¹ in HClO₄. Corresponding author. E-mail: grampp@ptc.tu-graz.ac.at Received January 30, 2002; accepted (revised) June 5, 2002     

Two non-linear azide containing heteronuclear complexes: crystal structure and thermal decomposition

Bis-N,N′(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH₂) has a high tendency to form polynuclear complexes. Two trinuclear complexes were obtained using this ligand and azide ions; (CuLDM)₂ · Mn(N₃)₂ · (DMF)₂, [(C₁₉H₂₀N₂O₂Cu)₂ · Mn(N₃)₂ · (C₃H₇NO)₂] and (CuLDM)₂ · Cd(N₃)₂ · (DMF)₂, [(C₁₉H₂₀N₂O₂Cu)₂ · Cd(N₃)₂ · (C₃H₇NO)₂]. The structures were identified with X-ray methods. TG and DSC methods were also employed to these complexes. Studies showed the (CuLDM)₂ · Mn(N₃)₂ · (DMF)₂ and (CuLDM)₂ · Cd(N₃)₂ · (DMF)₂ to be non-linear. Also μ-bridges were not encountered for the azide ions but were seen to form between the Cu and other metal via phenolic oxygens. Thermal analysis showed exothermic degradation of the azide ions destroying the trinuclear structure. Although azide containing structures show explosive characteristics, this was not observed for the present compounds.     

Hydroformylation of oct-1-ene catalyzed by dinuclear gem-dithiolato-bridged rhodium(I) complexes and phosphorus donor ligands

The dinuclear gem-dithiolato bridged compounds [Rh₂(μ-S₂Cptn)(cod)₂] (1) (CptnS₂²⁻ = 1,1-cyclopentanedithiolato), [Rh₂(μ-S₂Chxn)(cod)₂] (2) (ChxnS₂²⁻ = 1,1-cyclohexanedithiolato), [Rh₂(μ-S₂CBn₂)(cod)₂] (3) (Bn₂CS₂²⁻ = 1,3-diphenyl-2,2-dithiolatopropane) and [Rh₂(μ-S₂CⁱPr₂)(cod)₂] (4) (ⁱPr₂CS₂²⁻ = 2,4-dimethyl-2,2-dithiolatopentane) dissolved in toluene in the presence of monodentate phosphine or phosphite P-donor ligands under carbon monoxide/hydrogen (1:1) atmosphere are efficient catalysts for the hydroformylation of oct-1-ene under mild conditions (6.8 atm of CO/H₂ and 80 °C). The influence of the gem-dithiolato ligand, the P-donor co-catalyst and the P/Rh ratio on the catalytic activity and selectivity has been explored. Aldehyde selectivities higher than 95% and turnover frequencies up to 245 h⁻¹ have been obtained using P(OMe)₃ as modifying ligand. Similar activity figures have been obtained using P(OPh)₃ although the selectivities are lower. Regioselectivities toward linear aldehyde are in the range 75–85%. The performance of the catalytic systems [Rh₂(μ-S₂CR₂)(CO)₂(PPh₃)₂]/PPh₃ has been found to be comparable to the systems [Rh₂(μ-S₂CR₂)(cod)₂] at the same P/Rh ratio. The system [Rh₂(μ-S₂CBn₂)(cod)₂] (3)/P(OPh)₃ has been tested in the hydroformylation-isomerization of trans-oct-2-ene. Under optimized conditions up to 54% nonanal was obtained. Spectroscopic studies under pressure (HPNMR and HPIR) evidenced the formation of hydrido mononuclear species under catalytic conditions that are most probably responsible for the observed catalytic activity.     

Recent studies on chemistry of novel μ-CO-containing butterfly Fe/E (E=S,Se,Te) cluster salts

This article describes recent developments in chemical study on a series of butterfly-shaped μ-CO-containing Fe/E (E = S, Se, Te) cluster salts. These salts include eleven novel cluster anions, which are the single butterfly one μ-CO-containing [(μ-RE)(μ-CO)Fe2(CO)6]- (A), the double butterfly two μ-CO-containing {[(μ-CO)Fe2(CO)6]2(μ-EZE-μ)}2- (B, E = S; C, E = Se), the triple butterfly three μ-CO- containing {[(μ-CO)Fe2(CO)6]3[(μ-SCH2CH2)3N]}3- (D), {[(μ-CO)Fe2(CO)6]3[1,3,5-(μ-SCH2)3C6H3]}3- (E), {[(μ- CO)...     

Advantages of the Ns group in the reactions of N-SO2R inosines with benzylamine and with NH3

The reactivity of N¹-alkylsulfonyl- and N¹-arylsulfonyl-2′,3′,5′-tri-O-acetylinosine with benzylamine and with ¹⁵NH₃, regarding the attack on C2, has been shown to be in the order CF₃SO₂ (Tf) > 2,4-(NO₂)₂C₆H₃SO₂ (DNs) ? 4-NO₂C₆H₄SO₂ (pNs) ≈ C₆F₅SO₂ (PFBs) > 2-NO₂C₆H₄SO₂ (Ns) ? CH₃SO₂ (Ms) > 4-CH₃C₆H₄SO₂ (Ts) > 2,4,6-(CH₃)₃C₆H₂SO₂ (Mts). In spite of its intermediate reactivity, the Ns group is the most appropriate, since in this case the formation of by-products is minimised during the ring-opening and ring-closing steps of the process. Another advantage of the Ns group is thus disclosed.     

Enhancement of hydrolysis through the formation of mixed hetero-metal species

In order to analyze the formation of hetero-metal polynuclear hydrolytic species, in this paper, we reported some results of an investigation (at I = 0.16 mol L⁻¹ in NaNO₃, at t = 25 °C by potentiometry, ISE-H⁺, glass electrode) on the hydrolysis of several mixtures (in different ratios) of two couples of cations: dioxouranium(VI)/copper(II) and dioxouranium(VI)/diethyltin(IV). The elevated total concentrations of cations 0.005 ≤ ΣC_M mol L⁻¹ ≤ 0.05) adopted in these measurements induced us to study again the hydrolysis of uranyl, for which no suitable literature data are available in these particular experimental conditions. All measurements were performed by two different operators, using completely independent instruments and reagents. Many different speciation models were considered in the calculations, including the simultaneous refinement of homo- and hetero-metal species, and a statistical analysis of obtained results was proposed too. Main results can be summarized as follows: UO₂²⁺ and Cu²⁺ form three hetero-metal polynuclear hydrolytic species [(UO₂)Cu(OH)³⁺, (UO₂)Cu₂(OH)²⁺ and (UO₂)₂Cu₄(OH)²⁺, with log β_pqr = −2.93 ± 0.01, −7.34 ± 0.03 and −13.78 ± 0.03, respectively], all those common to their simple speciation without the other cation; UO₂²⁺ and (C₂H₅)₂Sn²⁺ form seven mixed hydrolytic species [(UO₂)(DET)(OH)³⁺, (UO₂)(DET)₂(OH)²⁺, (UO₂)₂(DET)₄(OH)²⁺, (UO₂)(DET)₂₄(OH)²⁺, (UO₂)₂(DET)⁺₅(OH), (UO₂)(DET)₂⁺₅(OH) and (UO₂)₂(DET)⁻₇(OH), with log β_pqr = −2.5 ± 0.2, −4.74 ± 0.02, −10.70 ± 0.06, −10.34 ± 0.03, −15.70 ± 0.06, −15.58 ± 0.06 and −27.9 ± 0.1, respectively] that are of the same kind of those formed by uranyl; formation of mixed hydrolytic species causes a significant enhancement of the percentage of hydrolyzed metal cations, modifying the solubility and, therefore, the bioavailability of these cations. We also determined, for dioxouranium(VI)/copper(II) system, the corresponding complex formation enthalpies and entropies by direct calorimetric measurements. We obtained ΔH₁₁₂ = 47.9 ± 0.6 and ΔH₂₁₄ = 92.9 ± 0.5 kJ mol⁻¹, TΔS₁₁₂ = 6 ± 1 and TΔS₂₁₄ = 14 ± 1 kJ mol⁻¹ (±S.D.), respectively, for the formation of (UO₂)(Cu)₂(OH)²⁺ and (UO₂)₂(Cu)₄(OH)²⁺ species (according to reaction 2). We also calculated the single enthalpic and entropic contributes to the extra-stability that these species show with respect to the corresponding homo polynuclear ones.     

Copper complexes with 1,10-phenanthrolines tethered to a cyclotriphosphazene platform

The synthesis of two ligands, L¹ and L², each containing two 2-oxy-1,10-phenanthroline moieties attached to the same phosphorus atom of a substituted cyclotriphosphazene ring via an oxy-bridge, but differing in substitution on the biphenyl capping groups, is described. The single-crystal X-ray structure of L¹ · 2CH₂Cl₂ shows an ordered structure in the lattice with channels, containing dichloromethane molecules, running parallel to the a-axis. The reactions of L¹ and L² with [Cu(MeCN)₄](PF₆) afford the dimetallic copper(I) derivatives, [(CuL¹)₂] (PF₆)₂ · CH₂Cl₂ and [(CuL²)₂](PF₆)₂. The single-crystal X-ray structure of the former complex shows that the L¹ ligands of the cation [(CuL¹)₂]²⁺ act as a bridges coordinating to the two copper(I) centres in a helical fashion. The copper atoms have distorted tetrahedral geometries with the interligand dihedral angle being 85°. With copper(II) chloride and copper(II) perchlorate, the monomeric copper(II) complexes, [CuL¹Cl]Cl · 2CH₂Cl₂, [CuL²Cl]Cl · CH₂Cl₂, [CuL¹(OMe)]PF₆ · 2H₂O, [CuL²(OMe)]PF₆ · 2H₂O, [CuL¹(OH₂)](ClO₄)₂ and [CuL²(OH₂)](ClO₄)₂ · H₂O are obtained. The single-crystal X-ray structure of [CuL¹Cl]Cl · 2CH₂Cl₂ shows the copper to be in a square-base pyramidal distorted trigonal-bipyramidal (SBPDTB) environment (τ = 0.57) with L¹ acting as a κ⁴N donor, coordinating via the four nitrogen atoms of the two tethered 1,10-phenanthrolines. In CH₃CN, this complex undergoes hydrolysis via the presence of adventitious water losing one oxyphenanthroline arm to form the centrosymmetric dimetallic species, [(CuL³Cl)₂] · 4CH₃CN · 3H₂O (L³ = [N₃P₃(biph)₂(ophen)O]⁻ where biph = 2,2′-dioxybiphenyl and O replaces an oxyphenanthroline and is attached to the phosphorus of the phosphazene ring). The two monomeric units, which are linked by bridging chlorine atoms, have a distorted square-based pyramidal geometry about the copper with the basal plane made by the ‘ON₂Cl’ ligand set. Spectroscopic (mass spectral, electronic and ESR) and magnetic moment data for the complexes are discussed.     

N,N-polymethylene-bisadenine complexes with d metal ions

The reaction of N⁹,N^9′-(tri or tetramethylene)-bisadenines (Ade₂C_x; x = 3 or 4) in HCl 2 M at 50 °C with MCl₂ · 2H₂O [M = Zn(II), Cd(II)] yields outer sphere compounds like the previously described [(H-Ade)₂C₃][ZnCl₄] · H₂O (3) and [(H-Ade)₂C₃]₂[Cd₂Cl₈(H₂O)₂] · 4H₂O (4) for Ade₂C₃ and the new {[(H-Ade)₂C₄][Cd₂Cl₆(H₂O)₂] · 2H₂O}_n (5) for Ade₂C₄. On the other hand, only in case of Zn(II) complexes by changing [HCl] to 0.1 M, the inner sphere compounds [H-(Ade)₂C₃(ZnCl₃)] (6) and [H-(Ade)₂C₄(ZnCl₃)] · 1.5H₂O (7) are obtained. X-ray diffraction study of compound 6, which represents the first inner sphere complex with a N⁹,N^9′-bisadenine, shows a zwitterionic form with one adenine ring protonated at N(1) while the other ring is coordinated via N(7) to a ZnCl₃ moiety as in other alkyl-adenine derivatives. In addition, with Ade₂C₄, is also possible to obtain another inner sphere complex: [(H-Ade)₂C₄(ZnCl₃)₂] · 3H₂O (8).     

A new [Ni4] distorted cubane assembly on four solvent derived μ3-OMe corners: Solvent dependent formation and cleavage of exogenous bridges

A new Ni₄ distorted cubane complex [Ni₄(μ₃-OMe)₄Q₄(MeOH)₄] (1) (where Q⁻ is the anion of 8-quinolinol) is obtained from the reaction of NaQ with Ni(OAc)₂ · 4H₂O in refluxing MeOH via solvent derived μ₃-OMe assisted self-assembly of four nickel(II) centres. The periphery of [Ni₄(OMe)₄] cubane is covered by four Q⁻ and four MeOH molecules. This methanol specific reaction is not supported in solvent glycinol (Hgl; NH₂(CH₂)₂OH), an amine substituted ethanol, producing monomeric [NiQ₂(Hgl)₂] · 2H₂O (2 · 2H₂O) instead and is able to cleave 1 to yield 2 · 2H₂O. The cryomagnetic susceptibility data of powdered 1 can be modeled by a two J equation yielding J₁ = −1.8(1) cm⁻¹, J₂ = 3.9(1) cm⁻¹ and g = 2.24.     

A Raman spectroscopic study of the XeOF4/XeF2 system and the X-ray crystal structure of α-XeOF4·XeF2

The mixed oxidation state complexes, α-XeOF₄·XeF₂ and β-XeOF₄·XeF₂, result from the interaction of XeF₂ with excess XeOF₄. The X-ray crystal structure of the more stable α-phase shows that the XeF₂ molecules are symmetrically coordinated through their fluorine ligands to the Xe(VI) atoms of the XeOF₄ molecules which are, in turn, coordinated to four XeF₂ molecules. The high-temperature phase, β-XeOF₄·XeF₂, was identified by low-temperature Raman spectroscopy in admixture with α-XeOF₄·XeF₂; however, the instability of the β-phase precluded its isolation and characterization by single-crystal X-ray diffraction. The Raman spectrum of β-XeOF₄·XeF₂ indicates that the oxygen atom of XeOF₄ interacts less strongly with the XeF₂ molecules in its crystal lattice than in α-XeOF₄·XeF₂. The ¹⁹F and ¹²⁹Xe NMR spectra of XeF₂ in liquid XeOF₄ at −35 °C indicate that any intermolecular interactions that exist between XeF₂ and XeOF₄ are weak and labile on the NMR time scale. Quantum-chemical calculations at the B3LYP and PBE1PBE levels of theory were used to obtain the gas-phase geometries and vibrational frequencies as well as the NBO bond orders, valencies, and NPA charges for the model compounds, 2XeOF₄·XeF₂, and XeOF₄·4XeF₂, which provide approximations of the local XeF₂ and XeOF₄ environments in the crystal structure of α-XeOF₄·XeF₂. The assignments of the Raman spectra (−150 °C) of α- and β-XeOF₄·XeF₂ have been aided by the calculated vibrational frequencies for the model compounds. The fluorine bridge interactions in α- and β-XeOF₄·XeF₂ are among the weakest for known compounds in which XeF₂ functions as a ligand, whereas such fluorine bridge interactions are considerably weaker in β-XeOF₄·XeF₂.     

Removal of multiple pollutants from water using noble Ag/Au/magnetite/graphene/H2O2 system under light and ultrasound irradiation

Ag/Au/Fe₃O₄/graphene composites prepared by a hydrothermal method demonstrated excellent activation of H₂O₂ and were used to degrade methylene blue (MB) in solution in the presence of organic acids and inorganic ions under light and ultrasound irradiation. The physicochemical properties of the obtained composites were characterized using various methods. The results showed that the composites exhibited excellent magnetic properties, crystallinity, and stability. The results of catalysis experiments revealed that the removal efficiency of MB increased when Ag and Au were both incorporated into the Fe₃O₄/graphene/H₂O₂ system compared with the removal efficiency achieved with separate Ag-Fe₃O₄/graphene/H₂O₂ and Au-Fe₃O₄/graphene/H₂O₂ systems, indicating a substantial synergistic interaction between the two metallic nanoparticles and the Fe₃O₄/graphene/H₂O₂ systems. The presence of an organic acid accelerated degradation of the MB/H₂O₂ system, whereas almost all of the investigated anions inhibited the degradation of MB; their inhibition effects followed the order CO₃^2? > NO₃^? > Cl^? > F^? > H₂PO₄^? > SO₄^2? > I^?. Cations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ also suppressed MB degradation, likely because of the influence of Cl^? coexisting in the solutions.