Hisanori Imura

Cloud point extraction equilibrium of lanthanum(III), europium(III) and lutetium(III) using di(2-ethylhexyl)phosphoric acid and Triton X-100.

The cloud point extraction behaviors of lanthanoids(III) (Ln(III)=La(III), Eu(III) and Lu(III)) with and without di(2-ethylhexyl)phosphoric acid (HDEHP) using Triton X-100 were investigated. It was suggested that the extraction of Ln(III) into the surfactant-rich phase without added chelating agent was caused by the impurities contained in Triton X-100. The extraction percentage more than 91% for all Ln(III) metals was obtained using 3.0x10(-5)moldm(-3) HDEHP and 2.0% (v/v) Triton X-100. From the equilibrium analysis, it was clarified that Ln(III) was extracted as Ln(DEHP)(3) into the surfactant-rich phase. The extraction constant of Ln(III) with HDEHP and 2.0% (v/v) Triton X-100 were also obtained.

Solvent effect of ionic liquids on the distribution constant of 2-thenoyltrifluoroacetone and its nickel(II) and copper(II) chelates and the evaluation of the solvent properties based on the regular solution theory

Distribution constants of 2-thenoyltrifluoroacetone (Htta) and its Ni(II)and Cu(II) chelates between 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C(n)mimTf(2)N; n=4, 6, and 8) as ionic liquid (IL) and an aqueous phase were determined. The enol fraction of Htta in ILs was spectrophotometrically measured to calculate the distribution constant of the enol form (K(D,HE)) of Htta. The K(D,HE) values in ILs were evaluated by comparing those in various molecular solvents such as alkanes, aromatic hydrocarbons, chlorohydrocarbons, ethers, ketones, and esters previously reported on the basis of the regular solution theory (RST). It was elucidated that the IL solutions of Htta (enol) can be taken as apparently regular solutions as expected in the organic solvents. On the other hand, the effect of ILs on the distribution constant of metal(II) chelates (K(D,M)) was fairly complicated. The Cu(tta)(2)-IL solutions behaved like the alkane and aromatic hydrocarbon solutions but the Ni(tta)(2)-IL (C(4)mimTf(2)N) like ether and ketone solutions. In the Ni(II) case, some specific interactions between the Ni(II) chelate and IL was suggested. Finally, the solubility parameters of ILs were calculated using K(D,HE) by RST and were in good agreement with the literature values obtained by the enthalpy of vaporization.

Cooperative intramolecular interaction of diazacrown ether bearing β-diketone fragments on an ionic liquid extraction system

A novel extractant beta-diketone-substituted diaza-18-crown-6 demonstrated very efficient extraction of Sr(2+) due to an intramolecular synergistic effect on the ionic liquid extraction system and recovery of Sr(2+) from the ionic liquid was successfully achieved under acidic conditions.

Vitamin B6 Prevents IL-1β Protein Production by Inhibiting NLRP3 Inflammasome Activation

Vitamin B6 includes six water-soluble vitamers: pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), and their phosphorylated forms. Pyridoxal 5′-phosphate (PLP) is an important cofactor for many metabolic enzymes. Several lines of evidence demonstrate that blood levels of PLP are significantly lower in patients with inflammation than in control subjects and that vitamin B6 has anti-inflammatory effects, with therapeutic potential for a variety of inflammatory diseases. Although one of our group previously demonstrated that PL inhibits the NF-κB pathway, the molecular mechanism by which vitamin B6 suppresses inflammation is not well understood. Here, we showed that both PL and PLP suppressed the expression of cytokine genes in macrophages by inhibiting Toll-like receptor (TLR)-mediated TAK1 phosphorylation and the subsequent NF-κB and JNK activation. Furthermore, PL and PLP abolished NLRP3-dependent caspase-1 processing and the subsequent secretion of mature IL-1β and IL-18 in LPS-primed macrophages. In contrast, PM and PN had little effect on IL-1β production. PLP, but not PL, markedly reduced the production of mitochondrial reactive oxygen species (ROS) in peritoneal macrophages. Importantly, PL and PLP reduced IL-1β production induced by LPS and ATP, or by LPS alone, in mice. Moreover, PL and PLP protected mice from lethal endotoxic shock. Collectively, these findings reveal novel anti-inflammatory activities for vitamin B6 and suggest its potential for preventing inflammatory diseases driven by the NLRP3 inflammasome.

Spectroelectrochemical characterization of dendrimer-porphyrin associates at polarized liquid|liquid interfaces

Molecular encapsulation of anionic porphyrins in NH2-terminated polyamidoamine (PAMAM) dendrimers and the interfacial behavior of the dendrimer-porphyrin associates were studied at the polarized water|1,2-dichloroethane (DCE) interface. Formation of the ion associates was significantly dependent on the pH condition and on generation of dendrimers. 5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin (ZnTPPS(4-)) associated with the positively charged fourth-generation (G4) PAMAM dendrimer was highly stabilized in acidic aqueous solution without protolytic demetalation in a wide range of pH values (pH > 2). In contrast to the zinc(II) complex, the free base porphyrin (H2TPPS(4-)) was readily protonated under acidic conditions even in the presence of the dendrimers. In addition, the J-aggregates of diprotonated species, (H4TPPS(2-))n, were preferably formed on the dendrimer. The interfacial mechanism of the dendrimer-porphyrin associates was analyzed in detail by potential-modulated fluorescence (PMF) spectroscopy. PMF results indicated that the dendrimers incorporating porphyrin molecules were transferred across the positively polarized water|DCE interface via adsorption step, whereas the transfer responses of the porphyrin ions released from the dendrimers were observed at negatively polarized conditions. A negative shift of the transfer potential of porphyrin ions compared to the intrinsic transfer potential was apparently observed for each ion association system. The ion association stability between the dendrimer and the porphyrin molecules could be estimated from a negative shift of the transfer potential. ZnTPPS(4-) exhibited relatively strong interaction with the higher generation dendrimer, whereas H2TPPS(4-) was less effectively associated with the dendrimers.

Specific Cooperative Effect of a Macrocyclic Receptor for Metal Ion Transfer into an Ionic Liquid

An intramolecular cooperative extraction system for the removal of strontium cations (Sr(2+)) from water by use of a novel macrocyclic receptor (H(2)βDA18C6) composed of diaza-18-crown-6 and two β-diketone fragments in ionic liquid (IL) is reported, together with X-ray spectroscopic characterization of the resulting extracted complexes in the IL and chloroform phases. The covalent attachment of two β-diketone fragments to a diazacrown ether resulted in a cooperative interaction within the receptor for Sr(2+) transfer, which remarkably enhanced the efficiency of Sr(2+) transfer relative to a mixed β-diketone and diazacrown system. The intramolecular cooperative effect was observed only in the IL extraction system, providing a 500-fold increase in extraction performance for Sr(2+) over chloroform. Slope analysis and potentiometric titration confirmed that identical extraction mechanisms operated in both the IL and chloroform systems. Extended X-ray absorption fine structure spectroscopy revealed that the average distance between Sr(2+) and O atoms in the Sr(2+) complex was shorter in IL than in chloroform. Consequently, Sr(2+) was held by H(2)βDA18C6 more rigidly in IL than in chloroform, representing an important factor dominating the magnitude of the intramolecular cooperative effect of H(2)βDA18C6 for Sr(2+). Furthermore, competitive extraction studies with alkaline earth metal ions revealed that the magnitude of the intramolecular cooperative effect depended on the suitability between metal ion size and the cavity size of H(2)βDA18C6. Sr(2+) was successfully recovered from IL by controlling the pH in the receiving phase, and the extraction performance of H(2)βDA18C6 in IL was maintained after five repeated uses.

An 8-sulfonamidoquinoline derivative with imidazolium unit as an extraction reagent for use in ionic liquid chelate extraction systems

To evaluate the superiority of using a task-specific onium salt (TSOS), a novel TSOS reagent 1-methyl-3-[2-(8-quinolinylaminosulfonyl)ethyl]imidazolium chloride (HmimesqCl) was synthesized, and its performance in extraction of different divalent metal cations was investigated. This TSOS reagent has both a cationic imidazolium unit and an anionic (proton-dissociable) complexation unit for the extraction of metal cations into an ionic liquid. In the use of HmimesqCl, relatively high extraction of metals resulted in comparison with the use of its non-imidazolium analogs, without changing the extraction selectivity.

Photoinduced Electron Transfer of PAMAM Dendrimer–Zinc(II) Porphyrin Associates at Polarized Liquid|Liquid Interfaces

The heterogeneous photoinduced electron-transfer reaction of the ion associates between NH2-terminated polyamidoamine (PAMAM) dendrimers and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato zinc(II) (ZnTPPS(4-)) was studied at the polarized water|1,2-dichloroethane (DCE) interface. The positive photocurrent arising from the photoreduction of ZnTPPS(4-) by a lipophilic quencher, decamethylferrocene, in the interfacial region was significantly enhanced by the ion association with the PAMAM dendrimers. The photocurrent response of the dendrimer-ZnTPPS(4-) associates was dependent on the pH condition and on the generation of dendrimer. A few cationic additives such as polyallylamine and n-octyltrimethyammonium were also examined as alternatives to the PAMAM dendrimer, but the magnitude of the photocurrent enhancement was rather small. The high photoreactivity of the dendrimer-ZnTPPS(4-) associates was interpreted mainly as a result of the high interfacial concentration of photoreactive porphyrin units associated stably with the dendrimer which was preferably adsorbed at the polarized water|DCE interface. The photochemical data observed in the second and fourth generation PAMAM dendrimer systems demonstrated that the higher generation dendrimer which can incorporate a porphyrin molecule more completely in the interior is less efficient for the photocurrent enhancement at the interface. These results indicated that the photoreactivity of ionic reactant at a polarized liquid|liquid interface can readily be modified via ion association with the charged dendrimer.

Equilibrium and ab initio computational studies on the adduct formation of 1,3-diketonato-lithium(I), -sodium(I) and -potassium(I) with 1,10-phenanthroline and its 2,9-dimethyl derivatives.

Highly effective and selective synergistic extraction of Li+ has been found using 2-naphthoyltrifluoroacetone (Hnta) as an acidic chelating agent and 2,9-dimethyl-1,10-phenanthroline (dmp) or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmdpp) as a neutral ligand (denoted as L) in toluene. The synergism was ascribed to the adduct formation in the organic phase, and the composition and the formation constants of the adducts for alkali metal ions (M+) were determined by the extraction equilibrium analysis. The adducts found were M(nta)L for Li+ and Na+, while M(nta)L and M(nta)L2 for K+. To understand thermodynamics of the adduct formation with the bidentate amines, quantum chemical calculations of the 1:1 and 1:2 adduct formations with dmp and 1,10-phenanthroline (phen) were performed. The electronic and steric effects of the methyl groups at 2,9-positions of phen on the thermodynamic functions of adduct formation as well as the high lithium selectivity were quantitatively elucidated.

Role of Tf2N− anions in the ionic liquid–water distribution of europium(III) chelates

The role of bis(trifluoromethanesulfonyl)imide (Tf2N−) anions in the ionic liquid–water distribution systems of Eu(III) chelates with 2-thenoyltrifluoroacetone (Htta) was investigated by liquid–liquid distribution and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The extraction constants of neutral Eu(tta)3 and anionic Eu(tta)4− chelates in 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cnmim][Tf2N]) were determined by analyzing the distribution equilibrium. The effect of the ionic liquids on the distribution constant of the neutral Eu(tta)3 chelate was evaluated by the regular solution theory. The distribution constant of Eu(tta)3 in [Cnmim][Tf2N] was increased dramatically by the solvation effects of Eu(tta)3 in [Cnmim][Tf2N]. TRLFS for [Eu(tta)3(H2O)3] synthesized revealed that the Eu(tta)3 chelate was almost completely dehydrated in a series of [Cnmim][Tf2N] (n = 2–10). The Eu(tta)3 chelate exists as di- or tri-hydrates in 1-ethyl-3-methylimidazolium perchlorate ([C2mim][ClO4]) containing 20 mol dm−3 water, whereas mono-hydrated chelate was formed in [C2mim][Tf2N, ClO4] in the presence of 0.50 mol dm−3 Tf2N− and 20 mol dm−3 water. These results show that the coordinated water molecules of [Eu(tta)3(H2O)3] were replaced by the Tf2N− anions. In fact, an anionic adduct, [Eu(tta)3(Tf2N)]−, was observed by electrospray ionization mass spectrometry in the presence of [C4mim][Tf2N].