Volumes of activation for the reactions of Pentacyanocobaltate(III) Complexes in aqueous solution

The volumes of activation in cm³ mol^?1 for the aquation of Co(CN)₅X^3? were determined at 40°C and μ = 1 M (NaClO₄) to be + 7.8 ± 0.5 for X = Cl^?, + 7.6 ± 0.6 for X = Br^?, + 14.0 ± 0.7 for X = I^?, and + 16.8 ± 0.5 for X = N₃^? (0.1 M HClO₄), respectively. The volumes of activation for the aquation of Co(CN)₅Cl^3? at μ = 0.1 M are + 10.0 ± 0.6 cm³ mol^?1 and ± 9.1 ± 0.3 cm³ mol^?1 at 40°C and 25°C, respectively. The corresponding values for the anation of Co(CN)₅OH₂^2? (at 40°C) and μ = 1 M by Br^?, I^?, and NCS^? are +8.4 ± 1.0, +9.4 ± 1.6, and +8.2 ± 0.9 cm³ mol^?1, respectively. These data are discussed in terms of a dissociative (D) mechanism.     

Komplexone XLVI. EDTA-Komplexe des Pt(II)-Ions mit und ohne einzähnige Fremdliganden

The formation of complexes between Pt(II)EDTA^2? and H⁺, OH^?, Cl^?, Br^?, SCN^?, CN^? and NH₃ was investigated using pH and UV.-spectrophotometric measurements at ionic strength 1.0 and 25°. The existence of the following species could be proved (charges are omitted): H_pPt(EDTA) (0 ≤ p ≤ 3), Pt(EDTA)X (X = OH, NH₃, Cl, Br, I, SCN), H_pPt(EDTA)X (1 ≤ p ≤ 3; X = Cl, Br) and H₄Pt(EDTA)Cl₂. They have been characterised by spectral data as well as with equilibrium constants. The different modes of attachment of EDTA are discussed.     

Thermal investigation of diamine complexes of Zn(II) in the solid state

The complexes [Zn(en)₃]X2·n H₂O, where en = ethylenediamine, X = Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄, n = 1 or 0.5, and [Zn(tn)₂]X₂·n H₂O, where tn=1,3-diaminopropane, X=Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄, n = 0 or 0.25, have been synthesized and their thermal investigations carried out. The complexes were characterized by elemental analysis and IR spectral data. These complexes have been observed to decompose through several isolable as well as non-isolable complex species as intermediates during heating. [Zn(tn)₂]SO₄ undergoes solid-state phase transition in the temperature range 126–145°C. ZnenSO₄ and ZntnX₂ (X = Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄) have been synthesized pyrolytically in the solid state from their corresponding mother diamine complexes. ZnenSO₄ and ZntnX₂ (X = Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄) complexes decompose through non-isolable hemidiamine species. ZnX₂ (X = Cl^? or Br^?) complexes of tn undergo melting after formation of the monodiamine species. In contrast, the corresponding en complexes undergo melting at non-stoichiometric composition. Diamine (en or tn) is found to be bridging in all monodiamine (en or tn) complexes; whilst their mother complexes possess chelated en or tn. The thermal stability sequence of en and tn complexes of Zn(II) is ZnCl₂ < ZnBr₂ < ZnSO₄. ΔH values are reported for some steps of decomposition. Possible mechanistic paths have been reported for each step of decomposition.     

Solvated positron chemistry. II. The reaction of hydrated positrons with Cl−, Br− and I− ions

The reaction of the hydrated positron, e_aq⁺ with Cl^?, Br^?, and I^? ions in aqueous solutions was studied by means of positron The measured angular correlation curves for [Cl^?, e⁺], [Br^?, e⁺, and [I^?, e⁺] bound states were in good agreement with th Because of this agreement and the fact that the calculated positron wavefunctions penetrate far outside the X^? ions in the [X^?, e⁺] sta propose that a bubble is formed around the [X^?, e⁺] state, similar to the Ps bubble found in nearly all liquids. F^?ions did not react w Preliminary results showed that CN^? ions react with e_aq⁺ while OH^?ions are non reactive. The rate constants were 3.9 × 10¹⁰ M^?1 s^?1, 4.4 × 10¹⁰ M^?1 s^?1, and 6.3 × 10¹⁰ M^?1 s^?1 for Cl^?, Br^?, and I^?, respectively, at low (? 0.03 M) X^? concentrations. A 25% decrease in the rate constant caused by the addition of 1 M ethanol to the I^? solutions was i The influence of halide ions on the positronium (Ps) yields in pure water was studied by use of lifetime measurements. The Cl^?, Br^?, and I^? ions reduced the Ps yields at low concentrations (? 0.03 M), while F^? ions only reduced the Ps-yield However, the Ps yields saturated (e.g. at ≈ 21% ortho-Ps yield in the Cl^? case) at higher concentrations. This saturation and the high-concentration effects-in the angular correlation results were interpreted as caused by rather complicated spur effects, wh It is proposed that spur electrons may pick off the positron from the [X^?, e⁺ states with an efficiency which depends on the structure of the     

The influence of the magnetic field on the photosubstitution reaction of coordination complexes

Photolyses of rhodium(III) complexes, Rh(NH₃)₅X²⁺ (X = Cl^? and Br^?), under intense magnetic fields, e.g. λ_excit = 360 nm and H = 24 kG, have been investigated. The magnetic field quenches the photoaquation of the ammonia and enhances the photoaquation of the acido ligand, X = Cl^? or Br^? by 10% for H = 24 kG. The implication of two different precursors in the formation of the photoproducts is discussed.     

An electrical conductivity (EC) study of the thermal dissociation of [Co(NH3)6]X3 and [Co(en)3]X3 complexes

The thermal dissociation of the [Co(NH₃)₆]X₃ (X = Cl^?, Br^?, I^?, and NO^?₃), [Co(en)₃]X₃ (X = Cl^?, Br^?, I^?, NO^?₃, HSO^?₄ and $\text{1}\text{2}$ C₂O^2?₄), cis- [Co(en)₂Cl₂]Cl, and trans-[Co(en)₂ClBr]NO₃ complexes was investigated by an electrical conductivity (EC) technique. During the thermal dissociation reactions, liquid or semi-liquid phases are formed which cause large increases in the EC of the compound. The effect of concentration of the complex in a matrix medium as well as the composition of the matrix material on the EC curves were also determined.     

[Pt(topy)(Htopy)(ONO2)] complex (Htopy = 2‐p‐tolylpyridine) and its analogs: 195Pt NMR spectra and fabrication of light‐emitting devices

We report fast, high‐yield syntheses of a series of [Pt(C^∧N)(HC^∧N)X] complexes, where HC^∧N is 2‐phenylpyridine (Hppy) or 2‐p‐tolylpyridine (Htopy) and X^? is Cl^?, Br^?, I^?, ONO₂^?, NO₂^? or SCN^?. The structure of [Pt(topy)(Htopy)(ONO₂)] was analyzed by single‐crystal X‐ray diffraction. Substitution of Cl^? with Br^? or I^? in our complexes shifted the ¹⁹⁵Pt NMR peaks upfield in the order Cl^? < Br^? < I^?, but the magnitudes of their shifts were one‐tenth those observed for non‐cyclometalated platinum(II) complexes. As the two nitrato complexes showed strong emissions in acetonitrile solution—three to six times those of other complexes—they were used to fabricate OLEDs. Although their emissions were not particularly strong, devices fabricated with platinum(II) complexes containing bulky ligands emitted green light with a short lifetime (τ). Copyright © 2009 John Wiley & Sons, Ltd.     

Complexes of Cu(II) and Co(II) with NN′-bis-8-quinolylethylenediamine

This article describes some complexes of Cu(II) and Co(II with NN′-bis-8-quinolylethylenediamine ligand (nn′). All the compounds are of stoichiometry [MX₂(nn′)] (M = Cu or Co; X = Cl^?, Br^?, I^?, NO^?₃ or SCN^?). The electronic spectra are consistent with distorted octahedral geometry around the ions, indicating the four coordination of the nn′ ligand. Magnetic susceptibility measurements down to 100 K show antiferromagnetic interactions in all the Cu(II) compounds demonstrating the existence of the ionic and bridging X group. Infrared spectra show the presence of ionic and bridging nitrate in the [M(NO₃)₂(nn′)] (M = Co or Cu) compounds and ionic and bridging NCS group in the [Cu(NCS)₂(nn′)] compound.     

Chemistry of Ruthenium Polypyridine Complexes: VI. Synthesis and Photochemistry of cis-[Ru(bpy)2(bipy)X]q Complexes

Complexes cis-[Ru(bpy)₂(bipy)(X)] ^{n +} [bpy = 2,2'-bipyridyl, bipy = 4,4'-bipyridyl, X = Br^-, ONO^-, CN^- (n = 1); MeCN, PPh₃ (n = 2), and NO⁺ (n = 3)] were synthesized. Irradiation of acetonitrile solutions of the complexes with X = Cl^-, Br^-, ONO^-, NO₂-, CN^-, NH₃, MeCN, and PPh₃ by visible light results in photosubstitution of 4,4'-bipyridyl by a solvent molecule. The electronic absorption spectra of the complexes were assigned on the basis of quantum-chemical calculations. A correlation was revealed between photolysis quantum yields and charges transferred from ligands X upon their coordination.     

The effects of temperature and pressure on the lifetime of benzophenone emission

The variation in the lifetime of flash-excited gaseous benzophenone with pressure and temperature indicates that (1) self-quenching is a relatively inefficient process for the long-lived emission, k_sq = 9 × 10⁵ M^?1 s^?1 (estimated from solution data) at 25°C and 1.2 × 10⁷ M^?1 s^?1 at 170°C and (2) the lifetime decreases with increasing temperature as a result of photochemical and photophysical decay pathways which have significant activation energies. The importance of diffusion to the walls on lifetime measurements is discussed.     

Darstellung und spektroskopische Charakterisierung der Nona-halogenodiiridate(III), [Ir2X9]3−, X = Cl,Br

Preparation and Spectroscopic Characterization of Nonahalogenodiiridates(III), [Ir₂X₉]^3?, X = Cl, Br The pure nonahalogenodiiridates(III), A₃[Ir₂X₉] (A = K, Cs, tetraalkylammonium; X = Cl, Br) have been prepared. They are formed from the monomer hexahalogenoiridates(III) which are bridged to confacial bioctahedral complexes by ligand abstraction in less polar organic solvents. The IR and Raman spectra exhibit bands in three characteristic regions; at high wavenumbers stretching vibrations with terminal ligands ν(Ir?Cl_t): 360?300, ν(Ir?Br_t): 250?220; in a middle region with bridging ligands ν(Ir?Cl_b): 290?235, ν(Ir?Br_b): 205?190 cm^?1; the deformation bands are observed at distinct lower frequencies. The distance between ν(Ir?X_t) and ν(Ir?X_b) increases with decreasing size of the cations. The electronic spectra measured at thin films of the pure complex salts at 10 K show some intensive charge transfer transitions in the UV and one or two weak d? d bands in the visible region.     

Synproportionierung am metallischen Substrat: CsCu2Cl3 und CsCu2Br3

CsCu₂Cl₃ and CsCu₂Br₃ by Synproportionation at the Metallic Substrate CsCu₂Cl₃ and CsCu₂Br₃ are obtained as single crystals via a dry route by synproportionation of mixtures of CsX/2 CuX (X = Cl, Br) and CsCuCl₃, respectively, with the copper of the surface of a closed copper cylinder as the metallic substrate. Lattice constants of CsCu₂Cl₃ (CsCu₂Br₃) are: a = 950.75(9) (987.3(1)), b = 1189.8(2) (1235.5(2)), c = 559.92(6) (581.80(9)) pm, orthorhombic, Cmcm, Z = 4. Details of the Cs? X polyhedra (X = Cl, Br, I) and the double chains of tetrahedra [Cu₂X₃]^? in CsCu₂Cl₃, CsCu₂Br₃, and CsCu₂I₃ are compared.     

X-ray crystal structure and raman spectrum of tribromine(1+) hexafluoroarsenate(V), Br3+AsF6−, and raman spectrum of pentabromine(1+) hexafluoroarsenate(V), Br5+AsF6−

A single crystal of Br₃⁺AsF₆^? was isolated from a sample of BrF₂⁺AsF₆^? which had been stored for 20 years. It was characterized by x-ray diffraction and Raman spectroscopy. It is shown that Br₃⁺AsF₆^? (triclinic, a = 7.644(7) Å, b = 5.641(6) Å, c = 9.810(9) Å, α = 99.16(8)°, β = 86.61(6)°, γ = 100.11(7)°, space group P1 R(F) = 0.0608) is isomorphous with I₃⁺AsF₆^?. The structure consists of discrete Br₃⁺ and AsF₆^? ions with some cation-anion interaction causing distortion of the AsF₆^? octahedron. The Br₃⁺ cation is symmetric with a bond distance of 2.270(5) Å and a bond angle of 102.5(2)°. The three fundamental vibrations of Br₃⁺ were observed at 297 (ν₃), 293 (ν₁), and 124 cm^?1 (ν₂). The Raman spectra of Cl₃⁺AsF₆^? and I₃⁺AsF₆^? were reinvestigated and ν₃(B₁) of I₃⁺ was reassigned. General valence force fields are given for the series Cl₃⁺, Br₃⁺, and I₃⁺. Reactions of excess Br₂ with either BrF₂⁺AsF₆^? or O₂⁺AsF₆^? produce mixtures of Br₃⁺AsF₆^? and Br₅⁺AsF₆^?. Based on its Raman spectra, the Br₅⁺ cation possesses a planar, centrosymmetric structure of C_2h symmetry with three semi-ionically bound, collinear, central Br atoms and two more covalently, perpendicularly bound, terminal Br atoms.     

Raman Spectroscopic Study on Alkyl Chain Conformation in 1‐Butyl‐3‐methylimidazolium Ionic Liquids and their Aqueous Mixtures

Ionic liquids of 1‐butyl‐3‐methylimidazolium ([BMIM]) cation with different anions (Cl^?, Br^?, I^?, and BF₄^?), and their aqueous mixtures were investigated by using Raman spectroscopy and dispersion‐included density functional theory (DFT). The characteristic Raman bands at 600 and 624 cm^?1 for two isomers of the butyl chain in the imidazolium cation showed significant changes in intensity for different anions as well as in aqueous solutions. The area ratio of these two bands followed the order I^?>Br^?>Cl^?>BF₄^? (in terms of the anion X in [BMIM]X), indicating that the butyl chain of [BMIM]I tends to adopt the trans conformation. The butyl chain was found to adopt the gauche conformation upon dilution, irrespective of the anion type. The Raman bands in the butyl C?H stretch region for [BMIM]X (X=Cl^?, Br^?, and I^?) blueshifted significantly with the increase in the water concentration, whereas that for [BMIM]BF₄ changed very little upon dilution. The blueshift in the C?H stretch region upon dilution also followed the order: [BMIM]I>[BMIM]Br>[BMIM]Cl>[BMIM]BF₄, the same order as the above trans conformation preference of the butyl chain in pure imidazolium ionic liquids, which suggested that the cation‐anion interaction plays a role in determining the conformation of the chain.     

EPR Study of some Copper(II) Coordination Compounds with substituted Biguanides. III

Copper(II) coordination compounds with p-chlorphenylbiguanide of the type: [Cu(Cl-PhBig)₂]X₂ and [Cu(Cl–PhBig)X₂] with X =Cl^?, Br^? NO₃, OH^?, NCS^?, NCO^?, N₃, have been studied by EPR spectroscopy using polycrytalline powders and solutions in DMF. The parameters of the EPR spectra have been used to estimate molecular orbital coefficient, in these compounds and to discuss details of the chemical bonding.     

Ni(II) complexes with 8-aminoquinoline derivatives

Some Ni(II) complexes with 5,7-dicloro-8-aminoquinoline (dcaq), 5,7-dibromo-8-aminoquinoline(dbaq) and 5,7-diiodo-8-aminoquinoline(diaq) are described. The compounds are of stoichiometry NiL₂X₂(L= dcaq, dbaq, diaq; X= NO^?₃ and L= dbaq; X= Cl^?, Br^?, I^?, NCS^?) and NiLX₂·H₂O(L= dcaq, diaq; X= Cl^?). The electronic spectra and magnetic susceptibility data at room temperature, are consistent with octahedral geometry for the Ni(II) in each compound. I.r. spectra show the presence of ionic and bridging nitrate groups in the compounds NiL₂(NO₃)₂(L= dcaq, dbaq, diaq) and we assign them polymeric structures. Polymeric structures with bridging chloride are proposed for the compounds NiLCl₂·H₂O(L= dcaq, diaq) and monomeric octahedral structures for NiL₂X₂(L= dbaq; X= Cl, Br, I, NCS).     

An examination of the relationship between the x-ray diffraction-derived molecular structure of chloro (1,11-diamino-3,6,9-trithiaundecane)cobalt(III) cation and its inner sphere reduction by iron(II)

The crystal structure of racemic [Co(NSSSN)Cl](ClO₄)Cl was determined by X-ray diffraction methods. It crystallizes in the monoclinic system, space group P2₁/c, with cell constants of a = 9.795(3), b = 10.412(3) and c = 16.323(8) Å, and β = 93.87(4)°; V = 1661 ųd (meas.; flotation) = 1.85 gm-cm^?3, d (calc.; Z = 4 molecules/unit cell) = 1.88 gm-cm^?3. The molecules, a racemic mixture, have the absolute configurations λλδλ or δδλδ at each of the four five-membered rings and resemble, in general, the so called αα conformer already described by Snow¹ in his study of the Co(tetraen)Cl²⁺ cation. However, the torsional angles at C2, C3 and C8, C9 in the two terminal C-C-NH₂ fragments are quite different in the two systems. For Co(tetraen)Cl²⁺ they are 44.7° and ?20.2° respectively, whereas for Co(NSSSN)C²⁺ the values –52.3° and –44.6° obtain. Also, the ring Co-S1-C3-C2-N1 does not have the classical, low energy conformation found in Co(tetraen)Cl²⁺. The presence of the larger Co-S bonds causes the two terminal -NH₂ groups to be pushed toward each other, and to minimize steric hindrance between adjacent -NH₂ hydrogens and ligand twists C2 down and staggers the terminal hydrogens. We visualize the propagation of these distortion effects in solution as being transferred from one side to the other across the entire ligand chain with concomittant effects on the activation of the precursor complex in electron transfer reactions, resulting in ~10⁷ rate enhancement over the Co(tetraen)Cl² system. Kinetic data for the reduction of Co(NSSSN)X²⁺ and Co(NSNSN)X²⁺ (X = Cl^?, Br^?) by Fe(II) is also presented and discussed.     

Hydrolyse acide des diazocétones secondaires: Participation des nucléophiles

In the acid hydrolysis of two secondary diazoketones showing rate-determining protonation, 3-diazo-butan-2-one ( 1 ) and 1-phenyl-1-diazo-acetone ( 4 ), the nature of the (rapid) decomposition step of the intermediate diazonium ion was studied by product analysis. In the presence of strong nucleophiles, the reaction with Cl^?, Br^?, I^? and SCN^? follows the Swain-Scott relationship. SCN^? formed thiocyanates; isothiocyanates could not be detected. Both results indicate nucleophilic participation in the substitution step. For the accompanying elimination reaction (the amount of which is independent of added base) the isotope effect k_H/k_D = 2,4 in the hydrolysis of 1–d₃ is in favour of an E2 type mechanism. – Addition of HSCN to methyl-vinylketone at 0° yields nearly exclusively 4-thiocyanato-butan-2-one, which at 25° in the presence of HSCN is slowly rearranged to 4-isothiocyanato-butan-2-one.     

Further studies on the dissociation of HBr behind shock waves

Previously reported shock tube studies of the dissociation of HBr in the temperature range of 2100–4200°K have been extended to lower temperatures (1450–2300°K) in pure HBr. The course of reaction was followed by monitoring the radiative recombination emission in the visible spectrum from Br atoms. The results imply that, in the lower range of temperatures, the activation energy of dissociation, E in the expression AT^?2e^?E/RT, can be approximated by the HBr bond energy (88 kcal/mole). It was also found that, in this temperature range, the rate of HBr dissociation is sensitive to the Br₂ dissociation rate and the HBr + Br exchange rate. When these rates were adjusted to bring computed reaction profiles into agreement with experimental ones, it was found that the higher-temperature data could also be fitted reasonably well with an HBr dissociation activation energy of 88 kcal/mole, contrary to the conclusions of our previous work, which favored an activation energy of 50 kcal/mole. The “best value” for k₁^Ar, the rate coefficient for HBr dissociation in the presence of Ar as chaperone, appears to be 10^{21.78 ± 0.3} T^?2 10^?88/θ cc/mole sec, where θ = 2.3 RT/1000; that for k₁^HBr, is 10^22.66T^?210^?88/θ. A detailed review is given of the rate coefficients for the other pertinent reactions in the H₂–Br₂ system, viz., Br₂ dissociation and reactions of HBr with H and Br.     

Synthesis and Characterization of Antimony (V)-Polycobalticinium Esters

Antimony (V) polycobalticinium esters, where the anion was PF₆ ^?, Cl^?, Br^? and NO₃ ^?, were synthesized. A number of factors were found to be important in the synthesis, including anion exchange and pH. The products containing PF₆ ^? are oligomeric (DP _w = 7) whereas the other products are di-and trimeric. The products undergo oxidative degradation beginning about 100 to 225°C. They are near semiconductors with resistivities about 10⁵ to 10⁷ ohm-cm.