Réactions chimiques oscillantes III. Effets de la température et de la composition chimique sur la «période d'induction» des systèmes BrO/Ce4+/Cyclohexanone et BrO/Ce4+/Cyclopentanone

Oscillating Chemical Reactions. III. Effects of the Temperature and Chemical Composition on the ‘Induction Period’ of the BrO /Ce⁴⁺/Cyclohexanon and BrO /Ce⁴⁺/Cyclopentanon Systems A study of the influence of the temperature and composition of the BrO/Ce⁴⁺/cyclohexanon (S1) and BrO/Ce⁴⁺/cyclopentanon (S2) systems has shown a very particular behaviour for τ_ind. for a given ratio α of concentrations: Moreover, for 0.27 ? α ? 0.32, log¹/τ_ind. is no longer a linear function of the inverse of the temperature: a break in the line log¹/τ_ind. = f(1/T) occurs.     

Réactions de substitution dans l'anion tétrachloropalladate(II) avec des diamines. I. Ethylènediamine

The replacement of Cl^? by ethylenediamine (en) in PdCl has been followed spectrophotometrically at 25°C and μ = 1 (NaClO₄); it proceeds in two steps leading to Pd(en)Cl₂ and Pd(en), respectively. The observed rate constants are discussed in terms of the mechanism proposed by Reinhardt [1] for the successive ammination reactions of PdCl.     

A Transient Ion Pair (CCl · Cl−) in Irradiated Liquid CCl4: Evidence for a ‘delayed’ geminate ion neutralisation. (Preliminary communication)

Detailed cation scavenger studies in pulse-irradiated pure, liquid CCl₄ reveal that the 500 nm absorption has both, neutral and cationic characteristics, and that CCl₄⁺ must be the precursor. It is shown that all experimental results are compatible with the following ion neutralisation mechanism: CCl + Cl^? → (CCl · Cl^?) → CCl₄. The 500 nm band is assigned to the CCl₃⁺-cation (free or complexed). Its neutralisation therefore does not occur on ion recombination, but is delayed by the life time of the ion pair: τ_½ (ion pair) = 33 ± 3 ns at ?22°C with activation energy of 10.9 ± 2.1 kJ/mol. Possible reasons for the ion pair stability are briefly discussed.     

Negative ion fragmentations of deprotonated peptides containing post‐translational modifications. An unusual cyclisation/rearrangement involving phosphotyrosine; a joint experimental and theoretical study

The characteristic fragmentations of a pTyr group in the negative ion electrospray mass spectrum of the [M–H]^? anion of a peptide or protein involve the formation of PO (m/z 79) and the corresponding [(M‐H)^?–HPO₃]^? species. In some tetrapeptides where pTyr is the third residue, these characteristic anion fragmentations are accompanied by ions corresponding to H₂PO and [(M‐H)^?–H₃PO₄]^? (these are fragmentations normally indicating the presence of pSer or pThr). These product ions are formed by rearrangement processes which involve initial nucleophilic attack of a C‐terminal ‐CO [or ‐C(?NH)O^?] group at the phosphorus of the Tyr side chain [an S_N2(P) reaction]. The rearrangement reactions have been studied by ab initio calculations at the HF/6‐31+G(d)//AM1 level of theory. The study suggests the possibility of two processes following the initial S_N2(P) reaction. In the rearrangement (involving a C‐terminal carboxylate anion) with the lower energy reaction profile, the formation of the H₂PO and [(M‐H)^?–H₃PO₄]^? anions is endothermic by 180 and 318 kJ mol^?1, respectively, with a maximum barrier (to a transition state) of 229 kJ mol^?1. The energy required to form H₂PO by this rearrangement process is (i) more than that necessary to effect the characteristic formation of PO from pTyr, but (ii) comparable with that required to effect the characteristic α, β and γ backbone cleavages of peptide negative ions. Copyright © 2009 John Wiley & Sons, Ltd.     

Laser ablation of AgSbS2 and cluster analysis by time‐of‐flight mass spectrometry

Thin films of AgSbS₂ are important for phase‐change memory applications. This solid is deposited by various techniques, such as metal organic chemical vapour deposition or laser ablation deposition, and the structure of AgSbS₂(s), as either amorphous or crystalline, is already well characterized. The pulsed laser ablation deposition (PLD) of solid AgSbS₂ is also used as a manufacturing process. However, the processes in plasma have not been well studied. We have studied the laser ablation of synthesized AgSbS₂(s) using a nitrogen laser of 337 nm and the clusters formed in the laser plume were identified. The ablation leads to the formation of various single charged ternary Ag_pSb_qS_r clusters. Negatively charged AgSbS, AgSb₂S, AgSb₂S, AgSb₂S and positively charged ternary AgSbS⁺, AgSb₂S⁺, AgSb₂S, AgSb₂S clusters were identified. The formation of several singly charged Ag⁺, Ag, Ag, Sb, Sb, S ions and binary Ag_pS_r clusters such as AgSb, Ag₃S^?, SbS (r = 1–5), Sb₂S^?, Sb₂S, Sb₃S (r = 1–4) and AgS, SbS⁺, SbS, Sb₂S⁺, Sb₂S, Sb₃S (r = 1–4), AgSb was also observed. The stoichiometry of the clusters was determined via isotopic envelope analysis and computer modeling. The relation of the composition of the clusters to the crystal structure of AgSbS₂ is discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Ab initio calculations of many-body energy expansion in LiF− clusters

The effects of the basis-set size on many-body energy expansion in LiF^? clusters are investigated and correlated with previously reported values on LiCl^? analogs. Coulomb and non-Coulomb energies in LiF^? at different configurations are also examined. Although at the minimal STO -3G basis V^na(3, 4) and V^na(4, 4) nonadditivity terms were the smallest in the D₃h configuration, they were the largest at the extended 6-311 ++G basis. V(m, n) terms where m = n ≥ 3 were found to be playing a small role in the chemistry and physics of LiF^? clusters compared with V(3, n) terms in LiCl^? clusters.     

Neutral and Cationic Hexanuclear Rhenium Phosphine Clusters with μ3‐(Phosphido‐Chalcogenido), μ3‐(Arsenido‐Chalcogenido), and μ3‐(Imido or Oxo‐Chalcogenido) Hetero Ligand Shells

Reactions of dry THF/MeCN solutions of Ca[Re₆SCl(Cl^a)₆] with silylated derivatives E(SiMe₃)₂ (E = PhAs, PSiMe₃, HN, O, S) and addition of trialkylphosphine PPr₃ afford in high yields and at room temperature either the neutral clusters [Re₆SX(PPr₃)] ( 1 : X = As, 2 : X = P) or the ionic compounds [Re₆SX(PPr₃)]²⁺ · [Re₆S₆Cl₈]^2– ( 3 : X = NH, 4 : X = O, 5 : X = S). The compounds 1 – 5 were characterised by X‐ray crystal structure analysis. A di‐substitution reaction occurs on the {Re₆SCl}⁴⁺ cluster core, where the two inner μ₃‐chloro ligands Clⁱ are substituted by X (X = As, P, NH, O, S) and all six terminal chloro ligands Cl^a are exchanged by terminal PPr₃‐ligands.     

Kinetics of the solvolysis of [Co(3Rpy)4Cl2]+ ions (R = Me or Et) in water and in water + methanol mixtures

Rates of solvolysis of ions [Co(3Rpy)₄Cl₂]⁺ with R = Me and Et have been measured over a range of temperatures for a series of water-rich water + methanol mixtures to investigate the effect of changes in solvent structure on the solvolysis of complexes presenting a largely hydrophobic surface to the solvent. The variation of the enthalpies and entropies of activation with solvent composition has been determined. A free energy cycle relating the free energy of activation in water to that in water + methanol is applied using free energies of transfer of individual ionic species from water into water + methanol. Data for the free energy of transfer of chloride ions ΔG(Cl^?) from both the spectrophotometric solvent sorting method and the TATB method for separating ΔG(salt) into ΔG(i) for individual ions are used: irrespective of the source of ΔG(Cl^?), in general, ?ΔG(Co(Rpy)₄Cl²⁺) > ?ΔG(Co(Rpy)₄Cl₂⁺), where Rpy = py, 4Mepy, 4Etpy, 3Etpy, and 3Mepy, showing that changes in solvent structure in water-rich water + methanol mixtures generally stabilize the cation in the transition state more than the cation in the initial state for this type of complex ion. A similar result is found when the free energy cycle is applied to the solvolysis of the dichloro (2,2′,2″-triaminotriethylamine)cobalt(III) ion. The introduction of a Me or Et group on the pyridine ring in [Co(Rpy)₄Cl₂]⁺ has little influence on the difference {ΔG(Co(Rpy)₄Cl²⁺)?ΔG(Co(Rpy)₄Cl₂⁺)} in water + methanol with the mol fraction of methanol < 0.20.     

Darstellung,Schwingungsspektrum und Kristallstruktur von (n‐Bu4N)2[(W6Cl)F] · 2 CH2Cl2 und 19F‐NMR‐spektroskopischer Nachweis der gemischten Clusteranionen [(W6Cl)FCl]2–, n = 1–6

Synthesis, Vibrational Spectra, and Crystal Structure of ( n ‐Bu₄N)₂[(W₆Cl )F ] · 2 CH₂Cl₂ and ¹⁹F NMR Spectroscopic Evidence of the Mixed Cluster Anions [(W₆Cl )F Cl ]^2–, n = 1–6 The reaction of (n‐Bu₄N)₂[(W₆Cl)Cl] with CF₃COOH in dichloromethane gives intermediately a mixture of the cluster anions [(W₆Cl)(CF₃COO)Cl]^2–, n = 1–6. By treatment with NH₄F the outer sphere coordinated trifluoracetato ligands are easily substituted and the components of the series [(W₆Cl)FCl], n = 1–6 are formed and characterized by their distinct ¹⁹F NMR chemical shifts. An X‐ray structure determination has been performed on a single crystal of (n‐Bu₄N)₂[(W₆Cl)F] · 2 CH₂Cl₂ (orthorhombic, space group Pbca, a = 15.628(4), b = 17.656(3), c = 20.687(4) Å, Z = 4). The low temperatur IR (60 K) and Raman (20 K) spectra are assigned by normal coordinate analysis based on the molecular parameters of the X‐ray determination. The valence force constants are f_d(WW) = 1.89, f_d(WF) = 2.43 and f_d(WCl) = 0.93 mdyn/Å.     

Über ternäre Oxocuprate. X. Zur Kenntnis von Ba2Cu3O4Cl2

About Ternary Oxocuprates. X. On Ba₂Cu₃O₄Cl₂ The preparation of Ba₂Cu₃O₄Cl₂ and results by single crystal X-ray methods are described (a = 5.517, c = 13.808 Å; Space group D–I4/mmm). A so far unknown arrangement of square coordinated Cu²⁺ was detected. The Cu²⁺/O^2?-squares are partly completed to a distorted octahedral coordination by two Cl^?.     

Beiträge zur Chemie des Hydrazins und seiner Derivate. XVIII. Darstellung und Eigenschaften von Salzen des Triazans

The reaction of N₃H₇SO₄ with barium compounds BaX₂ in aqueous solutions yields under precipitation of BaSO₄ solutions which contain the corresponding salts of triazane N₃H₆X (X = NO, ClO, Cl^?, CH₃COO^?, N₃, CN^?, Br^?, OH^?). Due to the instability of the triazanium ion, NH₂? NH₂? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document}H₂, the solid triazanium salts could only be isolated in mixture with the also formed BaSO₄. The properties of these compounds are described.     

Structures and Electrical Properties of Some New Organic Conductors Derived from the Donor Molecule TMET (S,S,S,S,-Bis(dimethylethylenedithio) tetrathiafulvalene)

Crystal structures and electrical properties of radical-cation salts of the chiral organic donor TMET (S,S,S,S,-bis-(dimethylethylenedithio)tetrathiafulvalene) are described. Two structural types, 2:1 with octahedral anions Pf, AsF, SbF, I (incommensurate), and 3:2 with tetrahedral anions BF^?₄, CIO^?₄, ReO^?₄ are observed. Resistivity measurements between 2 and 298 K indicate that the 3:2 types are organic metals, while the other compounds are semiconductors. (TMET)₃(CIO₄)₂ is metallic down to about 120 K at ambient pressure and remains metallic down to 2 K at 8 kbar.     

Rate constants for some reactions of free radicals with haloacetates in aqueous solution

The kinetics of the acqueous-phase reactions of the free radicals ·OH, ·Cl, and SO· with the halogenated acetates, CH₂FCOO^?, CHF₂COO^?, CF₃COO^?, and with CH₂ClCOO^?, CHCl₂COO^?, CCl₃COO^? were investigated. Generally, the reactivity decreases with increasing halogen substitution and is in the order k(·OH) > k(SO·) > k(·Cl), but there is no general relation between the effect on reactivity of chlorine and fluorine substitution. © 1995 John Wiley & Sons, Inc.     

Heterogeneous surface saponification of suspension‐polymerized monodisperse poly(vinyl acetate) microspheres using various ions

Poly(vinyl alcohol) (PVA)/poly(vinyl acetate) (PVAc) microspheres with a skin/core structure were prepared through the heterogeneous surface saponification of PVAc microspheres suspension‐polymerized. The PVA skin formed through the heterogeneous saponification was hydrogel swellable in water. In addition, to obtain monodisperse PVA/PVAc microspheres having various skin/core ratios and morphologies, the ion‐specificities to the heterogeneous saponification were investigated using SO, Cl^?, NO, Br^?, and I^? for anions and Li⁺, Na⁺, and K⁺ for cations, respectively. The ions were not specific significantly to the rate of the heterogeneous saponification, while were related to the degree of saponification (DS). DSs had different values between by weight loss (DS_w) and by proton nuclear magnetic resonance spectroscopy (DS_NMR) measurements. The order of DS_ws was SO < Cl^? < NO < Br^? < I^? for anions and K⁺ < Na⁺ < Li⁺ for cations, and that of DS_NMRs, I^? < Br^? < NO < Cl^? < SO for anions and Li⁺ < Na⁺ < K⁺ for cations. The differences in values between DS_ws and DS_NMRs were caused by the dissolution of PVA skin and were significantly decreased for SO. The peaks at melting temperature of PVA were sharp and their areas were large for ions deswelling PVA skins.     

Zur Stabilität der Metallkomplexe von Methantriessigsäure und cis,cis-1,3,5-Cyclohexantricarbonsäure

The stabilities of the Mn²⁺-, Co²⁺-, Ni²⁺-, Cu²⁺- and Zn²⁺-complexes with 2-(carboxymethyl)glutaric acid ( 2 ) and cis,cis-1,3,5-cyclohexanetricarboxylic acid ( 3 ) were measured potentiometrically at 25° and I = 0.5 (KNO₃). Beside the complexes ML^? protonated species MLH and MLH are also formed. Their stability constants are given in Table 1. A comparison between the stabilities of 2 or 3 and those of acetate, as a model for a monocarboxylate, or succinate and glutarate, as examples for dicarboxylates, indicates that in all species only one carboxylate is strongly bound whereas the second and third ones are probably not. The observation that Δlog K₁ = log K ? log K as well as Δlog K₂ = log K ? log K are practically constants with values of 0.34 ± 0.05 and 0.49 ± 0.07, respectively, for both ligands and the five metal ions studied is also in line with the proposed monodentate structures of the complexes ML^?, MLH and MLH.     

A chiral polymer‐based turn‐on fluorescent sensor for specific recognition of hydrogen sulfate

A new kind of polymeric chemosensor containing chiral naphthaldimine moiety in the side chain was synthesized by the reversible addition‐fragmentation chain transfer polymerization of N‐{[2‐(4‐vinylbenzyloxy)‐1‐naphthyl]‐methylene}‐(S)‐2‐phenylglycinol (VNP). The resulting polymers (PVNP) showed high selectivity for hydrogen sulfate relative to other anions including F^?, Cl^?, Br^?, H₂PO, CH₃CO, and NO in tetrahydrofuran (THF) solution as judged from UV?vis, fluorescence, and circular dichroism spectrophotometric titrations. Compared with its monomer, the polymer has proven to be more attractive for detection of HSO in terms of sensitivity and reproducibility. Upon addition of the anion it gives remarkable spectral responses concomitant with detectable color change from colorless to pale yellow. Furthermore, the HSO‐induced CD or fluorescence signal can be totally reversed with addition of base and eventually recovered the initial state, leading to a reproducible molecular switch with two distinguished “on” and “off” states. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Schwingungsspektren der Clusterverbindungen (M6X)X · 8 H2O,M = Nb,Ta; Xi = CI,Br; Xa = CI,Br, I

Vibrational Spectra of the Cluster Compounds (M₆X₁₂ⁱ) · 8H₂O, M = Nb, Ta; Xⁱ = Cl, Br; X^a = Cl, Br, I IR and, for the first time, Raman spectra at 80 K of the cluster compounds (M₆X)X · 8H₂O; M = Nb, Ta; Xⁱ = Cl, Br; X^a = Cl, Br, I, have been recorded, characterized by typical frequencies of the (M₆X) unit, which are only slightly influenced by the terminal X^a ligands. The most intense line with the depolarisation ≈? 0.2 in all Raman spectra is caused by inphase movement of all atoms and assigned to the symmetric metal-metal vibration v₁, observed for the clusters (Nb₆Cl) at 233–234, for (Nb₆Br) at 186–187, for (Ta₆Cl) at 199–203, and for (Ta₆Br) at 176–179 cm^?1. The IR spectra exhibit in the same series intense bands at 233, 204, 207, and 179 cm^?1, assigned to the antisymmetric metal-metal vibration. The metal-metal frequencies are significantly higher than discussed before. The tantalum clusters show on excitation with the krypton line 647.1 nm in the region of a d–d transition at 645 nm a resonance Raman effect with series of overtones and combination bands. In case of (Ta₆Br) another polarisized band is observed at 229 cm^?1 and assigned to the Ta? Brⁱ vibration v₂. From the progressions of v₁ and v₂ anharmonicity constants of about ?3 cm^?1 are calculated indicating a strong distortion of the potential curves.     

Halogenaustausch an Re3-Clustern: Ein neuer Syntheseweg für binäre und ternäre Rhenium(III)-bromide. Kristallstrukturen von Cs2[Re3Br11] und Cs3[Re3Br3Cl9]

Halogen Exchange at Re₃-Clusters: A New Synthetic Route to Binary and Ternary Rhenium(III) Bromides. Crystal Structures of Cs₂[Re₃Br₁₁] and Cs₃[Re₃Br₃Cl₉] The substitution of “inner” ligands in transition metal clusters in aqueous HX solutions is hitherto unknown. For the first time the substitution of bridging and terminal chloride for bromide ions was observed at rhenium clusters, [Re₃(μ-Cl^i,b)₃(Cl)(Cl^i,t)_(3?x)(H₂O^i,t)_x]^(3?x)? (x = 0–3), via the reaction of “ReCl₃ · 2 H₂O” in hot hydrobromic acid solution under an inert gas atmosphere. This establishes a new synthetic route to ternary Re(III) bromides as well as to ReBr₃. However, ternary Re(IV) bromides, A₂ReBr₆ (A = Rb, Cs), are dominating in the presence of oxygen, rhenium(III) bromides are only by-products. Dark brown rods of Cs₂[Re₃Br₁₁] are obtained from argon saturated, hot hydrobromic acid solutions of “ReCl₃ · 2 H₂O” and CsBr. The crystal structure (orthorhombic, Pnma (Nr. 62); a = 955.51(5); b = 1 610.29(10); c = 1 372.70(9); Z = 4; V_m = 318.0(2) cm³mol^?1; R = 0.084, R_w = 0.058) consists of defect clusters [Re₃BrBrBr□^i,t]^2? in which one in plane, terminal position is not occupied. The substitution of “inner” ligands has been observed in the case of chloride for bromide only, the Br^i,b and I^i,b ligands in ReBr₃ and ReI₃, respectively, are not substituted in hydrochloric acid even at temperatures as high as 100°C. Bordeaux red square pyramids of CsReBrCl₃ = Cs₃[Re₃(μ-Br^i,b)₃ClCl] are obtained from hot hydrochloric acid solutions of ReBr₃ · 2/3 H₂O upon evaporation. CsReBrCl₃ (orthorhombic, C2cm (Nr. 40); a = 1 419.0(1); b = 1 419.2(1); c = 1 080.30(8) pm; Z = 4; V_m = 327.6(3) cm³mol^?1; R = 0.033, R_w = 0.028) is isostructural to the corresponding chloride CsReCl₄.     

Laser ablation of ternary As‐S‐Se glasses and time‐of‐flight mass spectrometric study

Ternary chalcogenide As‐S‐Se glasses, important for optics, computers, material science and technological applications, are often made by pulsed laser deposition (PLD) technology but the plasma composition formed during the process is mostly unknown. Therefore, the formation of clusters in a plasma plume from different glasses was followed by laser desorption ionization (LDI) or laser ablation (LA) time‐of‐flight mass spectrometry (TOF MS) in positive and negative ion modes. The LA of glasses of different composition leads to the formation of a number of binary As_pS_q, As_pSe_r and ternary As_pS_qSe_r singly charged clusters. Series of clusters with the ratio As:chalcogen = 3:3 (As₃S, As₃S₂Se⁺, As₃SSe), 3:4 (As₃S, As₃S₃Se⁺, As₃S₂Se, As₃SSe, As₃Se), 3:1 (As₃S⁺, As₃Se⁺), and 3:2 (As₃S, As₃SSe⁺, As₃Se), formed from both bulk and PLD‐deposited nano‐layer glass, were detected. The stoichiometry of the As_pS_qSe_r clusters was determined via isotopic envelope analysis and computer modeling. The structure of the clusters is discussed. Copyright © 2009 John Wiley & Sons, Ltd.