Hideo Yamatera

X-ray photoelectron spectroscopy of rare-earth compounds

Abstract A variety of rare-earth (RE) compounds (oxides, sulfates and oxalates) have been studied by X-ray photoelectron spectroscopy. Except for Eu, the binding energies (BEs) of the RE 3 d and 4 d peaks for the sulfates and oxalates are respectively almost equal to and 1.3–3.1 eV higher than those for the oxides. In the Eu 3 d spectrum of europium(II) oxalate, distinct shake-down satellite peaks are present, and the BEs of these peaks are 10 eV lower than the parent ones. For the oxides, appreciable differences are found in the BEs of the O 1 s peaks, and a specific “inclined W” form is observed in plots of BE versus 1/ R (where R is the mean distance from the oxygen atom to the neighboring RE atom) and versus the RE oxidation-reduction potential (ORP). No characteristic differences are seen in the BEs (C 1 s , S 2 s and S 2 p ) of the other ligands.

Charge correction by gold deposition onto non-conducting samples in X-ray photoelectron spectroscopy

Abstract Gold deposited onto sample materials has been used as a calibrant for determining their absolute binding energies, and the optimum thickness of the gold decoration investigated. Polytetrafluoroethylene film and NaF and graphite pellets were used as the substrate materials. A series of depositions of gold layers up to ∼60 A thick was performed on each sample surface. The thickness of gold deposited influences the apparent binding energies, the precision of the charge-corrected binding energies, and the FWHMs of the Au 4f, C 1s and F 1s peaks. It seems that, for the instrument used in this study (which records photoelectrons at 45° to the sample surface), the optimum thickness of gold deposited onto a non-conducting sample surface is ∼ 6 A (ie., ∼9 A path-length through the layer).

The interaction of anionic surfactants with an Fe(II) chelate

Abstract The surface tension and light scattering of aqueous solutions of anionic surfactants (NaD), i.e., sodium dodecyl sulfate and sodium dodecanesulfonate, were measured in the presence of 5.0 × 10−5 M [Fe(phen)3](ClO4)2. The surface tension rapidly decreases with increasing concentration at a very dilute region, reaches a minimum, and then slightly increases with a further increase in concentration. Finally it reaches a constant value at the critical micelle concentration, after passing a maximum. The initial decrease in surface tension is mainly induced by the formation and adsorption of the 1:1 association complex, [Fe(phen)3]2+ · D−. The minimum is not the critical micelle concentration but is associated with the premicellar aggregation caused by the formation of the association complexes such as [Fe(phen)3]2+ · 2D− and [Fe(phen)3]2+ · 3D−. The critical micelle concentration can be definitely identified by the light scattering. A similar interpretation is applicable for the behavior of surface tension of aqueous solutions of sodium tetradecanesulfonate or sodium decanesulfonate containing [Fe(phen)3](ClO4)2. In the case of sodium octanesulfonate or sodium decanesulfonate, the micelle formation occurs more readily than the premicellar aggregation.

Effect of added salts on the rates of dissociation and racemization of tris(1,10-phenanthroline)iron(II) ion in aqueous methanol solutions

Abstract The kinetics of dissociation and racemization of [Fe(phen)3]2+ have been studied in aqueous methanol solutions containing perchlorate, chloride, and thiocyanate ions. The racemization rate was decreased by ClO−4 and increased by SCN−, while the dissociation rate was decreased by ClO−4 and increased slightly by Cl− and remarkably by SCN−. The effect of anions on the reaction rates became remarkable with the increase in methanol content of the solutions. The results were reasonably explained in terms of ion association. The dissociation rate of the complex ion in the ion-pair increased in the order, ClO−4

Ab initio calculation of the electronic structure of the [Co(CN)6]3− ion

Abstract Ab initio LCAO SCF MO calculations were carried out on the ion [Co(CN) 6 ] 3− with double-zeta type wavefunctions. The results showed differences with previous semi-empirical calculations in the relative energy level of the mainly metal-dπ molecular orbital and in other respects.

15N NMR studies of cobalt(III) complexes: [Co(NH3)5(15NH3)]3+ and [Co(15NH2CH2CH215NH2)3]3+

Abstract 15 N Fourier-transform nuclear magnetic resonance spectroscopy enabled the determination of spin-spin coupling constants 1 J ( 59 Co 15 N) and spin-lattice relaxation times T 1 ( 59 Co) for hexaamminecobalt(III) complex [Co(NH 3 ) 5 ( 15 NH 3 )] 3+ and tris-(ethylenediamine[ 15 N, 15 N])cobalt(III) complex. The obtained values are as follows: 1 J ( 59 Co 15 N) = 62.5 (± 1.0)Hz, T 1 ( 59 Co) = 38 msec for the hexaamminecobalt complex, and 1 J ( 59 Co 15 N) = 63.8 (± 1.0)Hz, T 1 ( 59 Co) = 13 msec for the tris(ethylenediamine)cobalt(III) complex. These T 1 ( 39 Co) values are well consistent with the values obtained from multi-pulse spin-echo measurement.

The adsorption of an association complex of anionic surfactants with an Fe(II) chelate on aqueous surfaces

Abstract The surface tension of aqueous solutions of sodium dodecanesulfonate (NaD) has been measured in the presence of different concentrations of Fe(phen) 3 ](ClO 4 ) 2 . An expression of the Gibbs adsorption isotherm is derived for these solutions, by postulating formation of a 1:1 association complex, [Fe(phen) 3 ] 2+ · D − cation, and it is applied for the data of surface tension obtained at dilute surfactant concentrations. Assuming a value of the association constant, the total surface excess densities of surfactant and metal chelate are derived as functions of concentration. From a consideration of the observed molecular area, it is found that the adsorbed layer consists mostly of the association complex. An approximate method for determining the total surface excess density of surfactant is given and applied for previous data on aqueous solutions of interacting systems. Treatments of the Gibbs adsorption isotherm including higher association complexes, [Fe(phen) 3 ] 2+ . p D − ( p > 1), are also given, and the relationship of the isotherm for the ternary system with that for the quaternary system containing NaClO 4 is discussed.

Structural determination of solvated copper species in formamide solution by EXAFS

The EXAFS studies on CuBr2 –LiBr solutions in formamide showed that the existing species remained to be [Cu(formamide)4 ]2+ with the Cu–O distance of 1.97 A even when the bromide concentration was increased. From the analysis of two other peaks in the EXAFS Fourier transform, the structure of the solvated species has been proposed.

EXAFS studies on the methanol and ethanol solutions of cobalt(II) bromides

The results of an EXAFS investigation of methanol and ethanol solutions of CoBr2 are reported. The curve fitting analysis gives the coordination numbers and the Co−Br and Co-solvent distances. The results for both 0.2M and 3.8M CoBr2 in ethanol show the existence of [CoBr2(C2H5OH)2] as the dominant species, although a considerable amount of octahedral species also exists in the solutions. In 0.2 and 3.3M CoBr2 methanol solutions, the dominant species are [Co(CH3OH)6]2+ and [CoBr(CH3OH)5]+, respectively.

17 O nuclear magnetic resonance study of the rotational motion of the sulphate ion in aqueous solution

Linewidths of 17O n.m.r. spectra of the sulphate ion in D2O solutions have been measured at temperatures ranging from 4 to 70 °C. The dependence of the linewidth on concentration has been investigated in various alkali-metal and tetra-alkylammonium sulphate solutions. The electric-field gradient at the oxygen site of an isolated sulphate ion has been calculated using the ab initio molecular-orbital method. This gave a field gradient of 1.52 atomic unit for the component along the O—S bond. The field gradient at the sulphate oxygen caused by a nearby single positive charge has also been calculated. This calculation showed that the fluctuation of the field gradient caused by the movement of the surrounding ions and water molecules is of secondary importance in its effect on the 17O linewidth of the sulphate ion in aqueous solutions. The rotational correlation times of the sulphate ion, τ, in solution have been obtained from the measured linewidths and the calculated field gradient (1.52 a.u.). A plot of the rotational correlation time at infinite dilution, τ(0), against the ratio of viscosity to temperature (η/T) curved downward at low temperatures. τ(0) values at various temperatures are well represented by the Arrhenius relation with an activation energy of 13 kJ mol–1 for rotation of the sulphate ion. The rotational correlation time of the sulphate ion increased with increasing salt concentration and showed a good correlation with the decrease in mobility of water molecules in the hydration sphere of the cation contained in the solution.