Showing papers by "Hitoshi Ohtaki published in 1988"

An extended x‐ray absorption fine structure study of aqueous rare earth perchlorate solutions in liquid and glassy states

Abstract: Extended x‐ray absorption fine structure (EXAFS) measurements were performed for concentrated aqueous rare earth perchlorate solutions (R=28; R is the moles of water per mole of salt) in the liquid state at room temperature and in the glassy state at liquid nitrogen temperature. The quantitative analysis of the EXAFS data has revealed that the hydration number changes from about nine for light rare earth ions to about eight for heavy rare earth ions through the intermediate ions of Sm3+ ∼Eu3+ in both liquid and glassy states. The average Ln3+ –OH2 distances were determined and they are in agreement with previously reported values from x‐ray and neutron diffraction. The Debye–Waller factor of the average Ln3+ –OH2 bonds for the light rare earth ions was larger than that for the heavy ions, suggesting that the hydration shell of the light rare earth ions is statically disordered, consisting of different Ln3+ –OH2 bonds.

Liquid Structure of N,N-Dimethylformamide, Acetonitrile, and Their 1 : 1 Molar Mixture

Abstract: Liquid structures of pure N,N-dimethylformamide (DMF) and acetonitrile (AN) as well as of their 1 : 1 molar mixture were investigated by X-ray diffraction at 25 °C. The careful reinvestigation of pure DMF led to a good reproducibility of the previous result. Slight deviations in the structural parameters are discussed and a detailed parameter table is reported. A simple model in which each AN molecule has 2 neighbors at an average distance of 330 pm describes the more ordered first neighbor structure of pure AN. The main interaction forming the structure is of dipole–dipole type, in agreement with previous findings. In the 1 : 1 molar mixture a dipole–dipole model also leads to a satisfactory description of the first neighbor structure. The preferred orientation is that with dipoles in the antiparallel position. A central DMF molecule has 1.75 neighboring AN molecules in average at a distance of 316 pm. The same stands for DMF around AN. No evidence for other kinds of interaction, e.g., weak H-bond type i...

Solvation structure of copper(II) ion in N,N-dimethylformamide and N,N-dimethylformamide-acetonitrile mixtures determined by the X-ray diffraction method.

Abstract: The solvation structure of copper(II) ion in N,N-dimethylformamide (DMF) and N,N-dimethylformamide–acetonitrile (AN) mixtures has been investigated by means of X-ray diffraction at 25 °C. The X-ray scattering data for the copper(II) perchlorate DMF solution were well-interpreted in terms of the presence of the axially elongated octahedral [Cu(dmf)6]2+ ion in DMF. Among the six DMF molecules, four of them are at the distance of 203(3) pm at the equatorial position and the other two are at 243(5) pm at the axial one. On the other hand, in copper(II) perchlorate DMF–AN solutions with the Cdmf⁄CCu mole ratios of 5.308 and 7.435, where Ci denotes the total concentrations of species i, the copper(II) ion is coordinated with four DMF molecules within the square-plane and with no solvent molecule along the axis of the plane. The equatorial Cu–O bond length is 200(1) pm and practically the same as that within the [Cu(dmf)6]2+ ion in DMF. In copper(II) nitrate DMF solutions (1.086 and 1.500 mol dm−3), a nitrate ion...

Calorimetric and Raman Spectroscopic Studies of Cadmium(II) Thiocyanato Complexes in N,N-Dimethylformamide

Abstract: Formation of thiocyanato complexes of cadmium(II) ion has been calorimetrically studied in N,N-dimethylformamide (DMF) at 25 °C. Calorimetric data obtained were well explained in terms of the formation of a series of four mononuclear [CdXn](2−n)+ (n=1–4, X=SCN) complexes, and their formation constants, enthalpies, and entropies were determined. Raman band shifts for the C–S stretching vibration of SCN− ion indicated that SCN− ion binds to cadmium(II) ion only with the N end within the mono- or dithiocyanato complex, [Cd(NCS)]+ or [Cd(NCS)2]. Within the tri- and tetrathiocyanato complexes, thiocyanate ions binds with both the N and S ends, and the coordination modes, [Cd(NCS)2(SCN)]− and [Cd(NCS)3(SCN)]2−, were suggested. The coordination modes for the di- and tetrathiocyanato complexes in DMF, [Cd(NCS)2] and [Cd(NCS)3(SCN)]2−, are different from those in water, [Cd(NCS)(SCN)] and [Cd(NCS)2(SCN)2]2−. It is thus shown that the N-bonding becomes more favorable in DMF than in water. Such a result may mainly b...

Structural Study on Molten (7Li, K)Cl and (7Li, Na, K)Cl of the Eutectic Composition by Pulsed Neutron Diffraction

Abstract: Abstract Pulsed neutron diffraction Pulsed neutron diffraction measurements have been performed on molten (7Li, K)C1 and (7Li, Na, K)Cl mixtures of the eutectic composition to determine the nearest neighbour distance between Li+ and Cl- ions. Owing to the negative scattering length of the 7Li nucleus, this contribution becomes negative in the radial distribution function and can be separated from the other contributions. The nearest neighbour distance between Li+ ion and Cl- ion is found to be 240 pm in both the binary and ternary mixtures.