Masayasu Iida

Ionic Liquids of Bis(alkylethylenediamine)silver(I) Salts and the Formation of Silver(0) Nanoparticles from the Ionic Liquid System

We have prepared novel ionic liquids of bis(N-2-ethylhexylethylenediamine)silver(I) nitrate ([Ag(eth-hex-en)(2)]NO(3) and bis(N-hexylethylenediamine)silver(I) hexafluorophosphate ([Ag(hex-en)(2)]PF(6)), which have transition points at -54 and -6 degrees C, respectively. Below these transition temperatures, both the silver complexes assume amorphous states, in which the extent of the vitrification is larger for the eth-hex-en complex than for the hex-en complex. The diffusion coefficients of both the complex cations, measured between 30 (or 35) and 70 degrees C, are largely dependent on temperature; the dependence is particularly large in the case of the eth-hex-en complex cation below 40 degrees C. Small-angle X-ray scattering studies showed that the bilayer structure of the metal complex is formed in the liquid state for both the silver complexes. A direct observation of the yellowish [Ag(eth-hex-en)(2)]NO(3) liquid by transmission electron microscopy (TEM) indicates the presence of nanostructures, as a microemulsion, of less than 5 nm. Such structures were not clearly observed in the [Ag(hex-en)(2)]PF(6) liquid. Although the [Ag(eth-hex-en)(2)]NO(3) liquid is sparingly soluble in bulk water, it readily incorporates a small amount of water up to [water]/[metal complex] = 7:1. Homogeneous and uniformly sized silver(0) nanoparticles in water were created by the reduction of the [Ag(eth-hex-en)(2)]NO(3) liquid with aqueous NaBH(4), whereas silver(0) nanoparticles were not formed from the [Ag(hex-en)(2)]PF(6) liquid in the same way.

Properties of ionic liquids containing silver(I) or protic alkylethylenediamine cations with a bis(trifluoromethanesulfonyl)amide anion.

Ionic liquids of an N-alkylethylenediamine-silver(I) complex cation (alkyl=hexyl, 2-ethylhexyl, and octyl) or a protic N-alkylethylenediaminium cation (alkyl=butyl, hexyl, 2-ethylhexyl, octyl, decyl, and dodecyl) with a bis(trifluoromethanesulfonyl)amide counter anion (Ag-ILs and PILs, respectively) were prepared and their physicochemical properties were investigated. The trend of solidification decreased in the order octyl≫hexyl>2-ethylhexyl for the Ag-ILs, and butyl>dodecyl>decyl>octyl>hexyl≫2-ethylhexyl for the PILs. The diffusion coefficients of the cations indicated stronger intermolecular interactions in PILs than in the Ag-ILs because of hydrogen-bonding networks, and it has been revealed that the intermolecular interactions increase in the order, hexyl<octyl<2-ethylhexyl for the Ag-ILs, and hexyl≈2-ethylhexyl<butyl≈octyl<decyl≈dodecyl for the PILs. The ionicity of the PILs was nearly independent (0.38-0.43) of the lengths of the alkyl chain. The octyl Ag-IL provided uniform silver(0) nanoparticles upon reaction with aqueous NaBH(4) solution, whereas the 2-ethylhexyl and hexyl complexes did not form silver(0) sols. This difference can be attributed to the ordering of the nanostructures in the Ag-ILs.

Self-motion of a camphoric acid boat sensitive to the chemical environment

As a simple example of an autonomous motor, the characteristic patterns in the self-motion of a camphoric acid boat depending on the chemical environment were investigated at the air/aqueous interface. The uniform motion of a camphoric acid boat changed to intermittent motion and its period increased depending on the concentration of phosphate ions. The nature of the self-motion changed reversibly with the addition of chemical stimuli to the air/aqueous interface. The camphoric acid layer adsorbed on a mica surface was observed by atomic force microscopy (AFM) to investigate how the microscopic state of the camphoric acid layer varied with pH. The nature of the self-motion was reproduced by a numerical calculation in relation to the surface tension, which depends on the surface concentration of the camphoric acid layer.

Solvation Structure of a Copper(II) Ion in Protic Ionic Liquids Comprising N-Hexylethylenediamine

The fine and dynamic structure of the copper(II) ion solvated in a protic ionic liquid (PIL) comprising monoprotonated N-hexylethylenediaminium (HHexen(+)) and bis(trifluoromethanesulfonyl)amide (Tf2N(-)) [or trifluoroacetate (TFA(-))] was determined using NMR, visible electronic, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The chelate-diamine group in the cationic unit facilitates advantageous dissolution of transition-metal salts in the present PIL. The interaction of the copper(II) ion with the chelate-diamine PIL was explored by the addition of copper(II) salts to the PIL, demonstrating competitive complexation between the ligand of the added copper(II) salt and the components of the ionic liquid to the copper(II) ion. The favorable mode of interaction of the present chelating PIL with the copper(II) ion was clarified based on a comparison of the interactions with analogous liquids, including the monoprotonated hexylaminium HHexam(Tf2N)-PIL, neat N-hexylethylenediamine (Hexen), and neat ethylenediamine (En). The coordination modes of the bis-Hexen and tris-Hexen copper(II) complexes in molecular liquids and in solids were also studied for comparison of the coordination structures around the copper(II) ion with those in the present PILs. The paramagnetic-induced relaxations derived from (13)C (ΔT(1p)(-1)) and (15)N (ΔT(2p)(-1)) NMR, the visible electronic spectra, and EXAFS analysis showed that the copper(II) ion tends to form a bis-Hexen complex in the HHexen-PIL despite the electrostatic repulsion and the fact that the counteranions are located at the axial sites, whereas in the HHexam(Tf2N)-PIL, the copper(II) ion exhibits affinity for the Tf2N anion over the protonated amines. The lifetime of the copper(II) complex formed in the PIL was determined to be ≈10(-4) s based on (13)C (ΔT(1p)(-1)) and (14)N (ΔT(2p)(-1)) NMR, which is appreciably longer than that in conventional molecular solvents.

Effects of metal–counterion interactions on the percolation in microemulsions composed of bis(N-octylethylenediamine)metal(II) complexes in water/benzene and water/chloroform systems

Abstract Self-diffusions and electric conductivities of microemulsions composed of surfactant metal complexes, dianionobis(N-octylethylenediamine)zinc(II) (aniono=chloro or nitrato), dichlorobis(N-octylethylenediamine)cadmium(II), and bis(N-octylethylenediamine) palladium(II) chloride (=ZnCl2(oct-en)2, Zn(NO3)2(oct-en)2, CdCl2(oct-en)2, and [Pd(oct-en)2]Cl2, respectively) were studied in water/benzene or water/chloroform mixed solvent system. The electric conductivities of the solutions increase in the order, CdCl2(oct-en)2

Aggregation in methanol and formation of molecular glasses for europium(III) N-acylaminocarboxylates: effects of alkyl chain length and head group

Europium(III) complexes of N-acyl-DL-alaninates (acyl=acetyl, butanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl and tetradecanoyl), N-octanoyl-DL-phenylalaninate, and N-octanoyl-L-serinate were prepared to understand the effects of alkyl chain length and the type of head group on the formation of glassy states and on the aggregation behaviour in solutions. The acylalaninate complexes had a tendency to form a transparent glass, whereas Eu(ala)3 (ala=DL-alaninate) was easily crystallized. Of the C2(acetyl)-C14(tetradecanoyl) chains in the ligands, the C4-C8 chains were the most favourable to assume a stable glassy state by solvent vaporization. The europium(III) complexes having an acyl chain of C6 (hexanoyl) or longer exhibited a peak below 2theta=5 degrees due to the presence of a bilayer structure in the glassy state. The octanoylserinate complex easily formed an anisotropic glass by a solvent-cast method, while the octanoylphenylalaninate complex transformed from a transparent glass to an anisotropic glass by an annealing treatment. The trend of glass formation was related with the aggregation behaviour of the complexes in methanol detected by self-diffusion and luminescence properties.

“The Third Phase” of Extraction Processes in Fuel Reprocessing, (III): 31P-NMR Study of Coordination Behavior of Zirconium Dibutylphosphates

The coordination and complexation behavior of Zr-dibutylphosphate was investigated by 31P-NMR measurement, in order to clarify the mechanism of the previously reported phenomena that the precipitates once formed at low HDBP/Zr mole ratio of 2 in an organic solution disappears with increasing HDBP/Zr. As the results of 31P-NMR spectrum measurements, following two steps were identified. (1) Species having Zr:DBP=1:3 immediately reacts with free HDBP to form species having Zr : DBP=1:4 with increasing HDBP/Zr, (2) Under the presence of higher HDBP/Zr concentration, species having more DBPs than 4 to one Zr are observed. DBP− (or HDBP) ligands in these species bridge two Zr ions to form three-dimensional net-work structure and have an interaction with HDBP in the solvent. Consequently, the mechanism was elucidated for the re-dissolution of Zr-DBP precipitates with sufficient free HDBP producing highly viscous oilyliquid.

Specific effects of simple organic sulphonate anions on the mercury ion-assisted aquation of chlorocobalt(III) complexes: Deviations from the primary s

Abstract Kinetic effects of various 1-1 electrolytes on the CoClLn2 + Hg2 reaction (Ln: neutral ligands) were studied with varying concentra

PRELIMINARY COMMUNICATIONS: SUBSTITUTION OF tris(2,2′-BIPYRIDINE)COBALT(III) BY CARBONATE ION

Abstract This communication reports the instability of tris(2,2′-bipyridine)cobalt(III) toward ligand substitution. 2,2′-Bipyridine(“bpy”) has been recognized as one of the most potent ligands and used to prepare many kinds of metal complexes. Nevertheless, one of the authors1 reported the preparation of [Co(CN)2(bpy)2]Cl, which was obtained by the reaction of [Co(bpy)3]3+ with cyanide ion in water. The reaction was reported to occur within five minutes at room temperature. The strong nucleophilicity of the cyanide ion might be responsible for this kind of substitution.

Ion-pairing effects on the 59Co electric field gradients in the NMR relaxations of tripositive cobalt(III) complex ions

Abstract 59Co NMR relaxation rates for the [Co(chxn)3]3+ (chxn = trans-(1R,2R)-1,2-diaminocyclohexane) and [Co(en)3]3+ (en = ethylenediamine) ions were measured in the presence of sulfate or oxalate ions. 1H relaxation rates for the chxn ligands in the same systems were also measured. The ratios of the 59Co relaxation rates to the 1H ones indicate that the 59Co electric field gradient of [Co(chxn)3]3+ is appreciably decreased by the formation of the 1:1 ion pair with the sulfate ion. The difference of the concentration dependence of the 59Co NMR relaxations between the sulfate and the oxalate ions can be attributed to the faster change in the configuration of the 1:1 ion pair of the oxalate ion.