Circularly polarized luminescence studies of the adducts formed with mix-ligand Eu(III) β-diketone complexes and dimethyl sulfoxide or N,N-dimethyl formamide

The adducts formed by Eu(DK)₂(CDK) and Eu(DK)(CDK)₂ [DK = achiral β-diketone ligand, and CDK = chiral β-diketone ligand] with either dimethyl sulfoxide (DMSO) or N,N-dimethyl formamide (DMF) have been studied by means of circularly polarized luminescence spectroscopy. While extremely strong stereoselective effects had been observed in earlier studies involving Eu(CDK)₃ adducts, analogous phenomena were found to be much smaller in the mixed-ligand compounds. These observations imply that steric interactions involving bulky camphorato ligands are significantly greater than those involving the achiral (and planar) β-diketone ligands.     

The magnetic circular dichroism spectrum of matrix-isolated TaO

TaO has been matrix-isolated in an argon matrix at 14 K and 24 K and studied spectroscopically in the visible region (300–850 nm). Both adsorption and magnetic circular dichroism (MCD) spectra have been recorded and analyzed. A determination of the total angular momentum quantum numbers (ω) for fourteen excited electronic states has been made. The g factors for the ground ²Δ_{$\text{3}\text{2}$} and excited ²φ_{$\text{5}\text{2}$} states have been determined from a moment analysis of the MCD and absorption spectra of the 450.3 nm band. The present study indicates the power of the combination of magnetic circular dichroism and matrix isolation for the assignment of excited electronic states of high temperature molecules.     

Synthesis,characterisation and thermal properties of hydrazinium metal oxalate hydrates. crystal and molecular structure of hydrazinium copper oxalate monohydrate

Complexes of the formula (N₂H₅)₂M(C₂O₄)₂·nH₂O where M = Co, Ni, Cu and n = 3, 2, 1 respectively have been prepared and their spectral, magnetic and thermal properties investigated. The copper complex, (N₂H₅)₂Cu(C₂O₄)₂·H₂O has a square planar geometry with no coordination of hydrazinium cations as confirmed by a single crystal X-ray study. Nickel and cobalt form octahedral complexes and X-ray powder patterns reveal that the complexes are not isomorphous.     

The raman spectrum and structure of dicyclopentadienylberyllium

The Raman spectra of solid and liquid dicyclopentadienylberyllium are described. They suggest the presence of two π-bonded rings in the molecule, one pentahapto and one polyhapto coordinated to the Be atom.     

Enantiomers of polarized alkenes: chromatographic enrichment and thermal interconversion

(+)- and (?)-$\text{1}$ as well as (+)- and (?)-$\text{2}$ were partially separated by liquid chromatography on triacetylcellulose; racemizations resulted in the barriers (Table 2) to rotation via planarized transition states.     

X-ray K-absorption spectrum of yttrium in some yttrium pyrochlores

The X-ray K-absorption edge of yttrium in some pyrochlores of the type YLnFeSbO₇ have been investigated using a 400 mm bent crystal spectrograph. The position of the principal absorption edge was found to have shifted towards the low energy side when Ln was changed from lanthanum through erbium. On the basis of the extended absorption fine structure estimates about the bond lengths have been made using the Lytle's and Levy's techniques.     

A polarographic study of the mixed complexes of Pb(II) with oxalate and malonate ions

The coordinated mixed Pb(II)-oxalate-malonate system has been polarographically studied in aqueous medium. The ionic strength has been maintained constant at μ = 1.0 by using NaClO₄. Application of the Schaap and McMasters method detected only the existence of the [Pb-ox-mal]_2? complex, the overall stability constant of which was β₁₁ = 4.1 x 10⁵.The various coordination equilibria are discussed on the basis of statistical aspects.     

Electron spin resonance and optical absorption studies of copper-oxime chelates in dimethyl formamide and pyridine

ESR and optical absorption studies on Cu(II) chelates of 2-hydroxyacetophenone-, resacetophenone-, peonol- and 2-hydroxy-1-naphthaldoximes have been ma     

Formation constant and stoichiometry of the acetonitrile:18-crown-6 complex by nuclear magnetic resonance, raman and infrared spectroscopy

Crown ethers are increasingly used in a variety of chemical applications. While crown ether complexes with alkali-metal cations have been extensively studied, relatively little is known about their complexes with neutral molecules to form so-called host: guest complexes. The use of NMR is reported for the determination of the formation constant (2.1 +/- 0.1) for the acetonitrile: 18-crown-6 complex. The suitability of Raman spectroscopy for studies of the solid-phase complex is demonstrated and limitations in the use of infrared spectroscopy are discussed.     

The thermal decomposition,IR spectrum and crystal structure of ammonium manganese(II) tris(hydrogenselenite), NH4Mn(HSeO3)3

The compound NH₄Mn(HSeO₃)₃ has been prepared and its IR spectrum and thermal behaviour have been investigated. It crystallizes in the monoc     

The ferric chloride α-DI-imine systemVI: Electronic structure of the dimethyl formamide addcut of mono-1,10-phenanthroline ferric chloride and the by-product,tris-1,10-phenanthroline ferrous μ-oxo-bis[trichloro ferrate(III)]; field induced slow paramagnetic relaxation in monomeric ferric complexes

Magnetic susceptibility (1.45–300 K), zero and high field Mössbauer spectroscopy, IR and solution conductivity measurements were used to characterize the title DMR adduct, Fe(phen)Cl₃·DMF. The absence of magnetic hyperfine splitting in zero external field is correlated with D positive corresponding to an isolated, rapidly relaxing ground (M_s = ± $\text{1}\text{2}$ Kramers doublet. X-ray data show that the ferric ion centres are apparently sufficiently close (～ 7 Å) to allow for rapid spin-spin relaxation via dipolar interactions. The application of longitudinal magnetic fields (0–5 Tesla for 1.7–4.2 K) slows relaxation and results in fully resolved Zeeman split Mössbauer spectra for which the effective internal field, H_n = 354 kG at 1.7 K for H₀ = 5T. The complex [Fe(phen)₃] [O(FeCl₃)₂] contains an unusual binuclear anion based on tetrahedral FeOCl₃ units as recently found in [pyridinium]₂[O(FeCl₃)₂] and is obtained as a trace by-product in our preparation of Fe(phen)Cl₃·DMF. Further magnetic characterization of the latter pyridinium compound is presented.     

ICP argon emission in the near infrared 1–2μm by high resolution Fourier transform spectrometry

The emission characteristics of the inductively coupled plasma in the near infrared spectral region from 0.9 to 2.0μm have been recorded by high resolution Fourier transform spectrometry. This region contains many strong atomic argon lines. The 109 lines with signal-to-noise ratio greater than four in the observed spectrum are identified and reported here with wavenumber accuracy on the order of 0.001 cm^?1. Also reported are relative intensities and line widths. This information is useful for determining spectral interferences to be expected in the development of analytical applications for the ICP in the near infrared.     

Rotational isomerism in divinylether studied by gas phase electron diffraction, microwave spectroscopy, infrared band profile simulation and ab initio calculations

The conformational behaviour of divinyl ether in the gas phase was explored by infrared band profile simulations and joint analysis of electron diffraction and microwave data. At 300 K the rotameric mixture contains 80% [sp, ac] and 20% [ap, ap] forms. Geometries have been studied using constraints taken from ab initio 4-21G gradient geometry and force field calculations. Differences between some unresolved bond distances and angles were constrained to the calculated values. Scale factors for the ab initio force field were refined from the diffraction data. In addition the transferability of scale factors from methyl vinyl ether to divinyl ether was tested. The investigation demonstrates that molecular orbital constrained models are consistent with and rationalize all experimental gas phase results. Subject to the ab initio constraints, the analysis yields the following model (r_g-distances, r-angles; numbers in parentheses are 6 times the least-squares ESDs): (C---H) = 1.103(12) A, (C---C) = 1.337(2) A, (C---O) = 1.389(2) A. Torsion angles for the [sp, ac] form are −13(6)° and 145(4)°.     

A spectrometric study of a 40 MHz inductively coupled plasma—VII: Continuum of a binary mixture in the visible region of the spectrum

The continuum of an argon-hydrogen plasma is determined both theoretically and experimentally using the determination of physical parameters of the ICP. Similarly to pure argon plasma, radiative recombination is the main process in the continuum formation, below 500 nm. The presence of hydrogen results in an increase of the excitation temperatures and the electron number density, linked with an enhancement of the continuum. On the other hand, easily ionizable elements such as Na and K have no influence on these parameters. The injection of hydrogen via water is the main cause of variation of the ICP physical parameters.     

Solvent effects on the electronic spectrum of the hexathiocyanatochromate (III) anions. A revised octahedral crystal field splitting parameter for the thiocyanate ion

An early report on the solvent dependence of the electronic spectra of complex ions considered the electrostatic effect of solvent molecules in the second coordination sphere, on the position of the absorption bands.¹ Solvent effects on the ligand field bands for solutions of K[Cr(NH₃₂(NCS)₄] have been discussed by Adamson² who emphasised a correlation between the solvent shifts in the spin-allowed bands and the shifts in the quartet-doublet bands. This work describes the effects of various solvents on the electronic absorption spectra of [Cr(CNS)₆]^3?.     

A study of infrared absorption in the oxidation of zinc-substituted magnetites to defect phase γ and hematite

The effect of substitution extent on formation of superstructure-ordered vacancies in zinc-substituted lacunar spinels of type $\text{(}\text{Zn}{}^{\mathrm{2+}}{}_{\mathrm{x}}\text{Fe}{}^{\mathrm{3+}}{}_{\mathrm{1?x}}\text{)}{}_{\mathrm{A}}\text{(}\text{Fe}{}^{\mathrm{3+}}{}_{\mathrm{<mtext>(5+x)</mtext><mtext>3</mtext>}}\text{□}{}_{\mathrm{<mtext>(1?x)</mtext><mtext>3</mtext>}}\text{)}{}_{\mathrm{B}}\text{O}{}^{\mathrm{2?}}{}_4$ was investigated using ir spectrometry. Only those lacunar phases whose substitution extent x is less than about 0.3 show a vacancy ordering on octahedral sites. In addition, referring to the disappearance of the 635-cm^?1 absorption band, which is characteristic of these lacunar spinels, we show that the transformation temperature of the γ phases into αFe₂O₃ increases with zinc substitution extent. For the α phase obtained at 700°C we have found a linear variation between the intensity difference of the 390- and 450-cm^?1 absorption bands and the percentage of αFe₂O₃.     

Temperature dependence of the Mössbauer spectrum and magnetic susceptibility [Fe(uridine)Cl2]∞: Novel magnetic ordering of transition metal complexes based on nucleoside ligands

The zero-field Mössbauer spectra and magnetic susceptibility of a polycrystalline sample of the polymeric material [Fe(uridine)Cl₂]_∞ have been measured in the temperature range 1.7-300 K. The compound exhibits two magnetic transitions. The isomer shift and quadrupole splitting indicate a distorted pseudo-octahedral FeCl₄O₂ chromophore resulting from condensation to a network structure via chloro and uridine ligand bridging.     

The pyrolysis of trimethylgermane and trimethylsilane

The number of products and the H₂/CH₄ ratio obtained from the flow pyrolyses of (CH₃)₃GeH and (CH₃)₃SiH were very different. The (CH₃)₃GeH decomposition is consistent with the following mechanism:

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The pyrolysis of (CH₃)₃SiH was found to be much more complex, presumably due to the formation of silicon-carbon double bonded intermediates and the (CH₃)₂Si(H)CH₂ radical. We also present data which supports the presence of a H atom chain sequence during this pyrolysis.     

The synthesis and structure of potassium cyanotrimethylaluminate

The reaction of KCN with Al(CH₃)₃ to form K[Al(CH₃)₃CN] is greatly facilitated by the presence of an aromatic solvent: for p-xylene a solid complex, K[Al(CH₃)₃CN]·C₆H₄(CH₃)₂, has been isolated. The crystal structure of potassium cyanotrimethylaluminate has been determined from three-dimensional X-ray data measured by counter methods. K[Al(CH₃)₃CN] crystallizes in the monoclinic space group C2/c with cell dimensions a = 19.902(7), b = 9.211(4), c = 9.615(4) Å, β = 107.74(5)°, and p_calcd. = 1.09 g cm^?1 for Z = 8. Least squares refinement gave a conventional weighted R factor of 4.9% for 807 independent reflections. The monomeric [Al(CH₃)₃CN]^? units possess no crystallographic symmetry, and the packing in the unit cell is such that the nitrogen atoms on three such units approach the potassium atom to within 3.11 Å. The average aluminum-methyl carbon bond distance is 1.971 (7) Å, while the aluminum-cyano carbon distance is 2.047 (7) Å. This significant lengthening is attributed to partial electron deficiency in the aluminum-cyano carbon bond.     

The reduction of oxygen in molten lithium carbonate

Oxygen reduction on immersed gold electrodes has been studied in Li₂CO₃ melt under steady-state conditions and by the potential-sweep method. Reaction order measurements have established that the species being reduced is not molecular oxygen, but the peroxide ion. The latter is in chemical equilibrium with molecular oxygen and oxide ions. The rate-determining step is the primary charge transfer

where (O^?) is a transient species. The exchange current densities and activation energies have been determined. Under conditions where O₂^2? diffusion is not limiting (e.g. meniscus electrodes) the rate of neutralization of oxide by CO₂ at the electrode surface is probably rate-determining.