80 results on '"Akihiro Wakisaka"'
Search Results
2. Size-controlled Synthesis of Zeolitic Imidazolate Framework-67 (ZIF-67) Using Electrospray in Liquid Phase
- Author
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Mana Gotou, Kouhei Kikuchi, K Yasuda, Akihiro Wakisaka, Miho Omata, and Hiroki Konno
- Subjects
Crystal ,Electrospray ,Adsorption ,Chemical engineering ,Chemistry ,Diffusion ,Liquid phase ,General Chemistry ,Zeolitic imidazolate framework ,Catalysis - Abstract
To achieve rapid intraparticle diffusion when metal-organic frameworks are used as adsorbents and/or catalysts, it is preferable to reduce their crystal size and improve their monodispersity. The s...
- Published
- 2020
3. A Reactor System Using Electrospray in the Liquid Phase and Its Application in Selective Cyclosiloxane Synthesis
- Author
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Hitomi Kobara, Akihiro Wakisaka, Yohei Ido, and Kenichi Tominaga
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Electrospray ,Chemistry ,General Chemical Engineering ,Analytical chemistry ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,Electrostatics ,01 natural sciences ,Industrial and Manufacturing Engineering ,Product distribution ,0104 chemical sciences ,Reaction rate ,Surface tension ,Solvent ,Chemical engineering ,Yield (chemistry) ,0210 nano-technology - Abstract
Electrospraying is an electrochemical technique in which fine droplets are generated in the balance of electrostatic repulsion and surface tension. In this paper, we applied electrospray in the liquid phase in a new reactor system in which positively and negatively charged fine droplets collided with each other between two electrospray nozzles submerged in a solvent. When the hydrolysis of alkylchlorosilanes was carried out using this reactor, not only did the reaction rates increase, but also, the product distribution changed: the kinetically favored cyclotrimer was predominantly formed over the thermodynamically favored cyclotetramer. The yield of cyclotrimer increased with an increase in the voltage between the needles. Since the droplet size decreases with an increase in the applied voltage, the result suggests that the formed cyclotrimer could diffuse into the solvent before it was converted to the thermodynamically favored cyclotetramer.
- Published
- 2017
4. Phosphoester Coordination Polymer for the Mutual Separation of Lanthanide Ions
- Author
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Akihiro Wakisaka, Hirokazu Narita, Mikiya Tanaka, Yuiko Tasaki-Handa, and Kenta Ooi
- Subjects
Lanthanide ,chemistry.chemical_compound ,Chemistry ,Coordination polymer ,Phosphodiester bond ,Polymer chemistry ,Analytical Chemistry ,Ion - Published
- 2017
5. Selective Crystallization of Phosphoester Coordination Polymer for the Separation of Neodymium and Dysprosium: A Thermodynamic Approach
- Author
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Yuiko Tasaki-Handa, Hirokazu Narita, Kenta Ooi, Yukie Abe, Mikiya Tanaka, and Akihiro Wakisaka
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Aqueous solution ,Chemistry ,Coordination polymer ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Acid dissociation constant ,0104 chemical sciences ,Surfaces, Coatings and Films ,law.invention ,Metal ,chemistry.chemical_compound ,law ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Dysprosium ,Physical and Theoretical Chemistry ,Solubility ,Crystallization ,0210 nano-technology ,Phosphoric acid - Abstract
Thermodynamics of the formation of coordination polymers (CPs) or metal-organic frameworks (MOFs) has not been focused on, whereas many CPs or MOFs have been synthesized in a solution. With a view of separating Nd3+ and Dy3+ in an aqueous solution, we demonstrate that crystallization of the CPs of Nd3+ and Dy3+ based on dibutyl phosphoric acid (Hdbp) can be thermodynamically described; crystallization yields of [Ln(dbp)3] (Ln = Nd or Dy) complex are predicted well using a simple calculation, which takes the apparent solubility products (Kspa) for [Ln(dbp)3] and the acid dissociation constant of Hdbp into account. The Kspa values of [Nd(dbp)3] and [Dy(dbp)3] are experimentally determined to be (1.3 ± 0.1) × 10-14 and (2.9 ± 0.4) × 10-18 M4, respectively, at 20 °C. The ratio of these Kspa values, that is, ca. 4500, is significantly larger than the ratio of the solubility products for inorganic salts of Nd3+ and Dy3+. Therefore, Nd3+ and Dy3+ are selectively crystallized in an aqueous solution via the formation of CPs. Under optimized conditions, Dy3+ crystallization is preferable, whereas Nd3+ remains in the solution phase, where the ratio of the Dy molar content to the total metal content (i.e., Nd + Dy) in the crystal is higher than 0.9. The use of acids, such as HCl or HNO3, has no practical impact on the separation in an aqueous solution.
- Published
- 2016
6. Magnitude and Directionality of Halogen Bond of Benzene with C6F5X, C6H5X, and CF3X (X = I, Br, Cl, and F)
- Author
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Tadafumi Uchimaru, Seiji Tsuzuki, Akihiro Wakisaka, and Taizo Ono
- Subjects
Bromine ,Halogen bond ,010405 organic chemistry ,chemistry.chemical_element ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Acceptor ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,chemistry ,Pyridine ,Halogen ,Physical and Theoretical Chemistry ,Dispersion (chemistry) ,Benzene ,Basis set - Abstract
Geometries of benzene complexes with C6F5X, C6H5X, and CF3X (X is I, Br, Cl, and F) were optimized, and their interaction energies were evaluated. The CCSD(T) interaction energies at the basis set limit (Eint) of C6F5X (X is I, Br, Cl, and F) with benzene were -3.24, -2.88, -2.31, and -0.92 kcal mol(-1). Eint of C6H5X (X is I, Br, and Cl) with benzene were -2.31, -1.97, and -1.48 kcal mol(-1). The fluorination of halobenzenes slightly enhances the attraction. Eint of CF3X (X is I, Br, Cl, and F) with benzene (-3.11, -2.74, -2.22, and -0.71 kcal mol(-1)) were very close to Eint of corresponding C6F5X with benzene. In contrast to the halogen bond of iodine and bromine with pyridine (n-type halogen bond acceptor) where the main cause of the attraction is the electrostatic interactions, that of halogen bond with benzene (p-type acceptor) is dispersion interaction. In the halogen bonds with p-type acceptors (halogen-π interactions), the electrostatic interactions and induction interactions are small. The overall orbital-orbital interactions are repulsive. The directionality of halogen bonds with p-type acceptors is very weak, owing to the weak electrostatic interactions, in contrast to the strong directionality of the halogen bonds with n-type acceptors and hydrogen bonds.
- Published
- 2016
7. Separation of neodymium and dysprosium by forming coordination polymers
- Author
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Kenta Ooi, Mikiya Tanaka, Yuiko Tasaki-Handa, Yukie Abe, Akihiro Wakisaka, and Hirokazu Narita
- Subjects
chemistry.chemical_classification ,Materials science ,Precipitation (chemistry) ,Coordination polymer ,Inorganic chemistry ,chemistry.chemical_element ,Filtration and Separation ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Neodymium ,0104 chemical sciences ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Phase (matter) ,Dysprosium ,Solubility ,0210 nano-technology ,Phosphoric acid - Abstract
The increasing demand for neodymium (Nd)-magnets containing dysprosium (Dy) has necessitated the recovery of Nd and Dy from magnet scraps to ensure their supply. Thus, it is required to develop an environmentally friendly method for separating Nd3+ and Dy3+. Herein, we show that the formation of coordination polymers based on di(2-ethylhexyl) phosphoric acid (HDEHP) enables the fractional precipitation of Nd and Dy in ethanol–water solution because the solubility of the Dy coordination polymer is significantly lower than that of the Nd coordination polymer owing to coordination preference. The separation performance was found to be better in HNO3 than in HCl media. The characterization of the solid and liquid phases obtained from the Nd3+ and Dy3+ precipitation systems suggested that Nd3+– NO 3 - association inhibits the formation of Nd coordination polymers. The partial replacement of dehp− in the Nd coordination polymer by NO 3 - may weaken the binding strength of the framework, resulting in higher solubility. In addition, the formation of Nd(NO3)2+ in solution may shift the equilibrium against the precipitation reaction. However, when Nd3+ and Dy3+ coexist, Nd3+ precipitation is not accompanied by the replacement of dehp− by NO 3 - in the solid phase. This may be attributed to the incorporation of Nd3+ into the framework of the Dy coordination polymer. We conclude that the formation of Nd(NO3)2+ shifts the solution equilibrium and plays an important role in enhancing the separation performance in HNO3 than in HCl when Nd3+ and Dy3+ coexist.
- Published
- 2016
8. Ln3+ Adsorption into an Yttrium-Hdehp Coordination Polymer through Exchange with Coordinated Yttrium Ion
- Author
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Akihiro Wakisaka, Mikiya Tanaka, Hiroaki Sato, Masaki Torimura, and Yuiko Tasaki-Handa
- Subjects
Lanthanide ,Chemistry ,Coordination polymer ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Yttrium ,Ion ,chemistry.chemical_compound ,Adsorption ,Atomic number ,Phosphoric acid ,Stoichiometry - Abstract
An exchange between lanthanide ions (Ln) in a solution and coordinated yttrium ions (Y) takes place in a coordination polymer (CP) formed by Y and di-(2-ethylhexyl) phosphoric acid (Hdehp). Through this cation exchange, Ln is adsorbed on the CP depending on the coordination power with Hdehp. Accordingly, the Ln with the larger atomic number is more preferably adsorbed into the CP. This adsorption is affected by the concentration of H, H C , in the solution. For example, at H C =10 M, Y is replaced directly by the incoming Ln with a 1:1 stoichiometry. In a limited higher H C region, the CP becomes a gel and the Ln/Y exchange is enhanced therein.
- Published
- 2014
9. Central metal ion exchange in a coordination polymer based on lanthanide ions and di(2-ethylhexyl)phosphoric acid: Exchange rate and tunable affinity
- Author
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Yukie Abe, Kenta Ooi, Akihiro Wakisaka, Mikiya Tanaka, and Yuiko Tasaki-Handa
- Subjects
Lanthanide ,Ionic radius ,Ion exchange ,Coordination polymer ,Inorganic chemistry ,Di-(2-ethylhexyl)phosphoric acid ,Crystal structure ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,Biomaterials ,Reaction rate ,chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,chemistry - Abstract
In this paper the exchange of lanthanide(III) ions (Ln(3+)) between a solution and a coordination polymer (CP) of di(2-ethylhexyl)phosphoric acid (Hdehp), [Ln(dehp)3], is studied. Kinetic and selectivity studies suggest that a polymeric network of [Ln(dehp)3] has different characteristics than the corresponding monomeric complex. The reaction rate is remarkably slow and requires over 600 h to reach in nearly equilibrium, and this can be explained by the polymeric crystalline structure and high valency of Ln(3+). The affinity of the exchange reaction reaches a maximum with the Ln(3+) possessing an ionic radius 7% smaller than that of the central Ln(3+), therefore, the affinity of the [Ln(dehp)3] is tunable based on the choice of the central metal ion. Such unique affinity, which differs from the monomeric complex, can be explained by two factors: the coordination preference and steric strain caused by the polymeric structure. The latter likely becomes predominant for Ln(3+) exchange when the ionic radius of the ion in solution is smaller than the original Ln(3+) by more than 7%. Structural studies suggest that the incoming Ln(3+) forms a new phase though an exchange reaction, and this could plausibly cause the structural strain.
- Published
- 2014
10. Molecular clustering inherent in the liquid state: Effect of relativity in intermolecular interaction energy
- Author
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Akihiro Wakisaka and Toru Iwakami
- Subjects
Aqueous solution ,Basis (linear algebra) ,Chemistry ,Binary number ,Thermodynamics ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Liquid state ,Theory of relativity ,Materials Chemistry ,Cluster (physics) ,Physical and Theoretical Chemistry ,Atomic physics ,Cluster analysis ,Spectroscopy ,Energy (signal processing) - Abstract
In alcohol–water binary mixtures, microheterogeneous clustering creates a non-ideal mixture. This molecular clustering in the binary mixture is controlled by relativity in the intermolecular interaction energies. This relativity-controlled clustering is inherent to the liquid state, irrespective of whether the solution is aqueous or non-aqueous. The vapor–liquid equilibrium for alcohol–water binary mixtures which represents non-ideality is correlated to relativity-controlled clustering. This paper was reviewed on the basis of our reported results, and presented at the 2012 EMLG/JMLG Annual Meeting in Eger.
- Published
- 2014
11. Preferential solvation of perfluorooctanoic acid (PFOA) by methanol in methanol–water mixtures: A potential overestimation of the dissociation constant of PFOA using a Yasuda–Shedlovsky plot
- Author
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Toru Iwakami, Hisao Hori, Shuzo Kutsuna, Takaaki Sonoda, and Akihiro Wakisaka
- Subjects
Dissociation constant ,Atmospheric Science ,chemistry.chemical_compound ,chemistry ,Inorganic chemistry ,Solvation ,Molecule ,Perfluorooctanoic acid ,Methanol ,Mole fraction ,Mass spectrometric ,General Environmental Science ,Methanol water - Abstract
Solvation of perfluorooctanoic acid (PFOA) in methanol–water mixed solvents was investigated by means of the mass spectrometric analyses of clusters in the solutions. The observed clusters were composed of PFOA, methanol, and water molecules. The molecular composition of the clusters showed that PFOA was preferentially solvated by methanol in the methanol–water mixed solvents, and that the ratio of methanol molecules in the PFOA solvation sphere was beyond 0.6 at the bulk methanol mole fraction (xMeOH) = 0.045. The microscopic environment of PFOA was almost occupied by the methanol from such lower xMeOH (xMeOH ≥ 0.045), and hence the ratio of methanol in the PFOA solvation sphere did not change at xMeOH ≥ 0.045 as much as the bulk xMeOH. This preferential solvation of PFOA by methanol suggested a potential overestimation on the dissociation constant (pKa) of PFOA extrapolated from a Yasuda–Shedlovsky plot.
- Published
- 2012
12. Magnitude and Origin of the Attraction and Directionality of the Halogen Bonds of the Complexes of C6F5X and C6H5X (X=I, Br, Cl and F) with Pyridine
- Author
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Akihiro Wakisaka, Takaaki Sonoda, Taizo Ono, and Seiji Tsuzuki
- Subjects
chemistry.chemical_classification ,Water dimer ,Bromine ,Halogen bond ,Molecular Structure ,Hydrocarbons, Halogenated ,Pyridines ,Hydrogen bond ,Stereochemistry ,Organic Chemistry ,chemistry.chemical_element ,Hydrogen Bonding ,General Chemistry ,Catalysis ,Crystallography ,chemistry ,Halogen ,Fluorine ,Thermodynamics ,Non-covalent interactions ,Molecular orbital - Abstract
The geometries and interaction energies of complexes of pyridine with C(6)F(5)X, C(6)H(5)X (X = I, Br, Cl, F and H) and R(F)I (R(F) = CF(3), C(2)F(5) and C(3)F(7)) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (E(int)) for the C(6)F(5)X-pyridine (X = I, Br, Cl, F and H) complexes at the basis set limit were estimated to be -5.59, -4.06, -2.78, -0.19 and -4.37 kcal mol(-1) , respectively, whereas the E(int) values for the C(6)H(5)X-pyridine (X = I, Br, Cl and H) complexes were estimated to be -3.27, -2.17, -1.23 and -1.78 kcal mol(-1), respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C(6)F(5)X. The values of E(int) estimated for the R(F)I-pyridine (R(F) = CF(3), C(2)F(5) and C(3)F(7)) complexes (-5.14, -5.38 and -5.44 kcal mol(-1), respectively) are close to that for the C(6)F(5)I-pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short-range (charge-transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C(6)F(5)I- and C(2)F(5)I-pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water-formaldehyde complex. The calculations suggest that the C-I and C-Br halogen bonds play an important role in controlling the structures of molecular assemblies, that the C-Cl bonds play a less important role and that C-F bonds have a negligible impact.
- Published
- 2011
13. Azeotropy of alcohol–water mixtures from the viewpoint of cluster-level structures
- Author
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Mamoru Takahashi, Akihiro Wakisaka, Makoto Uranaga, Taisuke Sekimoto, and Kazuo Matsuura
- Subjects
Ethanol ,Chemistry ,Analytical chemistry ,Alcohol ,Condensed Matter Physics ,Mass spectrometry ,Mass spectrometric ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Fragmentation (mass spectrometry) ,Materials Chemistry ,Cluster (physics) ,Organic chemistry ,Molecule ,Physical and Theoretical Chemistry ,Spectroscopy - Abstract
We showed that there is a close relation between evaporation properties and cluster-level structures in alcohol–water binary mixtures, on the basis of the mass spectrometric analyses of clusters generated through fragmentation of liquid droplets. The azeotropy for alcohol (ethanol, 1-propanol or 1-butanol)–water mixtures is caused by the change of the evaporation properties attributed to the cluster-level structures in the mixtures. When the hydrogen-bonding network of water molecules is stable at the cluster level in the water-rich mixtures, the alcohol molecules included in the water-rich clusters are evaporated primarily. On the other hand, when the alcohol self-association clusters are formed with an increase of the alcohol concentration in the mixtures, evaporation of the water existing around the alcohol self-association clusters is increased.
- Published
- 2011
14. Environmentally friendly separation of dysprosium and neodymium by fractional precipitation of coordination polymers
- Author
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Yuiko Tasaki-Handa, Kenta Ooi, Akihiro Wakisaka, Mikiya Tanaka, Yukie Abe, and Hirokazu Narita
- Subjects
Fractional Precipitation ,Materials science ,Ligand ,Precipitation (chemistry) ,General Chemical Engineering ,Metal ions in aqueous solution ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Neodymium ,Environmentally friendly ,chemistry.chemical_compound ,chemistry ,Dysprosium ,Phosphoric acid - Abstract
Against a backdrop of increasing demand, the recovery of neodymium (Nd) and especially dysprosium (Dy) from manufacturing scraps and used magnets has necessitated the development of Nd/Dy separation technologies. To this end, we suggest a simple and environmentally friendly separation method by fractional precipitation of coordination polymers (CPs)—extended complexes of metal ions and organic ligands. With the di(2-ethylhexyl) phosphoric acid ligand functioning as a precipitant, Dy was exclusively precipitated as a CP due to its precipitation equilibrium that is considerably different from that of Nd.
- Published
- 2014
15. Enantiodifferentiating endo-Selective Oxylactonization of ortho-Alk-1-enylbenzoate with a Lactate-Derived Aryl-λ3-Iodane
- Author
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Morifumi Fujita, Akihiro Wakisaka, Takashi Sugimura, Kazuyuki Miyata, and Yasushi Yoshida
- Subjects
chemistry.chemical_compound ,Aromatase inhibitor ,chemistry ,medicine.drug_class ,Stereochemistry ,Aryl ,medicine ,General Medicine ,General Chemistry ,Catalysis - Abstract
The present protocol is applied to the synthesis of the naturally occurring aromatase inhibitor (VII).
- Published
- 2010
16. Physicochemical Properties of Aqueous Solutions from the Viewpoint of Cluster Structures Analyzed by Mass Spectrometry
- Author
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Akihiro Wakisaka
- Subjects
Aqueous solution ,Chemistry ,Self assembling ,Analytical chemistry ,Cluster (physics) ,Mass spectrometry ,Analytical Chemistry - Abstract
溶液中の微視的構造に関する情報を得るために,液滴を真空チャンバー内でクラスターレベルに断片化し,その質量スペクトルを測定する分析技術を開発した.これにより水と有機化合物,及び電解質との相互作用によって形成されたクラスター構造とこれら水溶液の物性との関係を研究した.水-有機化合物系では,水-アルコール混合溶液のクラスター構造と,粘度,相分離特性,選択的溶媒和などの溶液の物性との関係を明らかにした.また,アルコール自己会合クラスターの生成が水によって促進されるのは,溶液中で生じる分子間相互作用の相対的関係によることを明らかにした.電解質水溶液系では,硝酸,硫酸,酢酸水溶液のクラスター構造を解析し,酸性度との関係を明らかにした.更に,水中の酢酸が水酸化ナトリウムにより中和され塩を生成する過程をクラスターレベルで観測した.
- Published
- 2010
17. Hydrogen-bonding self-association of 1-pentanol controlled by the relativity of interaction energies
- Author
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Akihiro Wakisaka, Toru Iwakami, Takahiro Ohki, and Miki Nakagawa
- Subjects
Chemistry ,Hydrogen bond ,Interaction energy ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Theory of relativity ,Chemical physics ,Materials Chemistry ,Molecule ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Atomic physics ,Solvent effects ,Adiabatic process ,Cluster analysis ,Spectroscopy ,Mixing (physics) - Abstract
Molecular clustering in the liquid state is controlled by the relativity of interaction energies. This means that the clustering is strongly promoted by the coexistence of relatively weakly interacting molecules in the solution. This relativity-controlled clustering was observed for 1-pentanol clustering through the mass spectrometry for clusters isolated from liquid droplets via adiabatic expansion in a vacuum chamber. The 1-pentanol clustering through hydrogen-bonding interaction was significantly promoted by the mixing with water, methanol, acetonitrile or dichloromethane, but it was not promoted by the mixing with 1-propanol or 1, 2-dichloroethane. This solvent effect on the 1-pentanol clustering is explained by the relativity of the 1-pentanol–1-pentanol interaction energy to the 1-pentanol–solvent interaction energy. Thermodynamic analysis on this solvent-induced clustering also supports that the clustering controlled by the relativity of interaction energy is inherent in the liquid state.
- Published
- 2009
18. Cluster Structure of Imidazolium Salts in Methanol Controlled by the Balance of Interactions: Cation-Anion, Cation-Solvent, and Anion-Solvent
- Author
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Akihiro Wakisaka, Yuichi Ishikawa, Satoshi Kitaoka, and Kaoru Nobuoka
- Subjects
Solvent ,Electrospray ,chemistry.chemical_compound ,Chemistry ,Inorganic chemistry ,Solvation ,Cluster (physics) ,Halide ,Methanol ,Mass spectrometry ,Analytical Chemistry ,Ion - Abstract
We have studied the cluster structure of 1-butyl-3-methylimidazolium halide, bmimX (X = Cl, Br, I), in methanol solution by means of an electrospray mass spectrometer, which is specially designed for analysis of clusters isolated from solution. In positive ion mode experiments, the ratio of solvated bmim(+), bmim(+)(MeOH)(n) and ion-pair clusters, bmim(bmim(+)X(-))(m) was dependent on the counter anion. As for bmimCl solutions, few solvated bmim(+) clusters were observed, and the ion-pair clusters were clearly observed. On the other hand, bmimBr and bmimI with large anions, the solvated bmim(+) clusters increased obviously, and the ion-pair clusters were in turn remarkably decreased. In negative ion-mode experiments, the solvation for Br(-) by the methanol is found to be the most prominent among those for Cl(-), Br(-), and I(-). These results were reasonably explained in consideration of the balance between ion-solvent and ion-counterion interactions.
- Published
- 2008
19. Nature of the chemical bond with the structural metal ion at the A9/G10.1 motif derived from hammerhead ribozymes
- Author
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Yoshiyuki Tanaka, Yasuhiro Kasai, Shunsuke Mochizuki, Akihiro Wakisaka, and Morita, Eugene H.; Chojiro Kojima; Atsushi Toyozawa; Yoshinori Kondo; Masumi Taki; Yasuomi Takagi; Atsushi Inoue; Kazuhiko Yamasaki; Kazunari Taira
- Subjects
Nucleotide sequencing -- Analysis ,Catalytic RNA -- Analysis ,Chemical bonds -- Analysis ,Metal ions -- Analysis ,Chemistry - Abstract
A study on the interaction between metal ions and the metal ion-binding motif in hammerhead ribozymes is presented. The findings suggest that the metal ion at this motif is not catalytic center of hammerhead .
- Published
- 2004
20. Microheterogeneity of ethanol–water binary mixtures observed at the cluster level
- Author
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Kazuo Matsuura and Akihiro Wakisaka
- Subjects
Ethanol ,Analytical chemistry ,Binary number ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Physics::Fluid Dynamics ,chemistry.chemical_compound ,Fragmentation (mass spectrometry) ,chemistry ,Materials Chemistry ,Cluster (physics) ,Mass spectrum ,Physical and Theoretical Chemistry ,Spectroscopy - Abstract
The microscopic structures in ethanol–water binary mixtures were examined by analyzing the mass spectra of clusters generated through fragmentation of liquid droplets. From the effects of temperature and mixing ratios on the cluster structures, we have demonstrated that the ethanol–water binary mixtures have microscopic phase separation at the cluster level in wide mixing ratios: 10 vol.%
- Published
- 2006
21. Microscopic Structures in Water-propylene Glycol Monoalkyl Ether Binary Mixtures as Clarified by NMR and Mass Spectrometry
- Author
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Yuji Okauchi, Akihiro Wakisaka, Ryo Koike, Yamazaki Yoshihiro, and Tamura Shigeru
- Subjects
Aqueous solution ,Chemistry ,Hydrogen bond ,General Chemical Engineering ,Intermolecular force ,Analytical chemistry ,Ether ,General Medicine ,General Chemistry ,Mass spectrometry ,Polyvinyl alcohol ,chemistry.chemical_compound ,Amphiphile ,Mass spectrum ,sense organs - Abstract
Determination was made of the microscopic structures of binary mixtures of water and amphiphile (propyleneglycol-monomethylether (MPG) or propyleneglycol-monopropylether (PPG)) based on the NMR relaxation time (T1) of water and mass spectra of clusters isolated from solutions. The ratio of hydrating to non-hydrating water was derived from T1 and indicated water in MPG-water mixtures to be present more easily in the amphiphile hydration layer than in PPG-water mixtures. Hydrogen-bonded self-association clusters of MPG and PPG could be found in the aqueous solutions by mass spectrometry, the data from which showed MPG self-association clusters to undergo hydrogen bonding with water more readily than PPG self-association clusters. The results of NMR and mass spectrometry were found to be closely correlated. Microscopic structures and intermolecular interactions in aqueous solutions were accurately clarified.
- Published
- 2006
22. Clustering Structure of Aqueous Solution of Kinetic Inhibitor of Gas Hydrates
- Author
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Akihiro Wakisaka, Alexandre M. V. De Freitas, Wladmir F. De Souza, Yoshitaka Yamamoto, Taro Kawamura, and Michika Ohtake
- Subjects
Kinetic Inhibitor ,Aqueous solution ,Chemistry ,Inorganic chemistry ,Clathrate hydrate ,Nucleation ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Fragmentation (mass spectrometry) ,Materials Chemistry ,Mass spectrum ,Physical chemistry ,Physical and Theoretical Chemistry ,Hydrate ,Tetrahydrofuran - Abstract
Poly-[N-vinylcaprolactam] (PVCAP) and its related compounds are specific polymeric compounds for inhibiting hydrate formation. To clarify the inhibition mechanism of these compounds on hydrate nucleation at the molecular level, we measured the mass spectra of clusters generated from the fragmentation of liquid droplets including N-methylcaprolactam (NMCAP; functional group of PVCAP). By comparing the mass spectra of clusters of the solutions--pure D2O, tetrahydrofuran (THF)-D2O, NMCAP-D2O, and THF-NMCAP-D2O--it was found that the interaction of NMCAP with D2O was much stronger than that of THF with D2O. The relative intensity ratio of D+(NMCAP)m(D2O)n clusters to all the clusters observed for the NMCAP-D2O (1:250) mixed solution was 0.45. On the other hand, the relative intensity ratio of D+(THF)1(D2O)n clusters to all the clusters observed for the THF-D2O (1:17) mixed solution was 0.15. In the case of the THF-NMCAP-D2O three-component mixed solution, the NMCAP-D2O interaction was more predominant than the THF-D2O interaction, even at a lower NMCAP concentration. NMCAP reduces free mobile water molecules around NMCAP, but THF does not. This correlates with the facts that THF forms its hydrate below the freezing point and that PVCAP works as an inhibitor of gas hydrates.
- Published
- 2005
23. Cluster structures determined by ion–molecular interactions: preferential solvation and acid–base neutralization
- Author
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Akihiro Wakisaka
- Subjects
Molecular interactions ,Reaction mechanism ,Chemistry ,Inorganic chemistry ,Solvation ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Neutralization ,Electronic, Optical and Magnetic Materials ,Ion ,Crystallography ,Fragmentation (mass spectrometry) ,Materials Chemistry ,Cluster (physics) ,Molecule ,Physical and Theoretical Chemistry ,Spectroscopy - Abstract
The neutralization of CH 3 COOH by NaOH in water has been studied by the mass spectrometric analysis of clusters generated via fragmentation of liquid droplets. In water, CH 3 COOH molecules form self-association clusters at higher acid concentrations like the molar ratio of CH 3 COOH:H 2 O=1:10. At these concentrations, the neutralization takes place via interaction between the CH 3 COOH clusters and NaOH to afford Na + (CH 3 COOH) a (CH 3 COONa) b clusters. Furthermore, Na + is preferentially solvated by CH 3 COOH in water to form Na + (CH 3 COOH) α clusters. In consideration with these cluster structure, the reaction mechanism in solution can be realized more precisely.
- Published
- 2005
24. Phase separation of water–alcohol binary mixtures induced by the microheterogeneity
- Author
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Takahiro Ohki and Akihiro Wakisaka
- Subjects
chemistry.chemical_compound ,chemistry ,Fragmentation (mass spectrometry) ,Phase separation process ,Intermolecular force ,Mass spectrum ,Analytical chemistry ,Cluster (physics) ,Molecule ,Alcohol ,Physical and Theoretical Chemistry - Abstract
The relationship between liquid-liquid phase separation and microheterogeneity in water-primary alcohol mixtures was examined by analysing the mass spectra of clusters generated through the fragmentation of liquid droplets. By comparing the cluster structures of water-ethanol, -1-propanol, and -1-butanol binary mixtures at various alcohol concentrations, we discovered differences in the molecular clusters that control phase separation. We also studied the role of water in alcohol self-association. Alcohol self-association is promoted in the presence of a small amount of water (ca. 10 approximately 20 wt%), in which the water-water hydrogen-bonding network is weak and does not contribute to alcohol self-association. We have demonstrated that alcohol self-association is also promoted by non-ideal mixing with other alcohols. The self-association of alcohol molecules complements the loss of stabilization energy caused by the relatively weak coexisting interactions. This complementary relationship among intermolecular interactions is an inherent property of solutions, and plays a key role in the phase separation process.
- Published
- 2005
25. Cluster Formation of 1-Butanol–Water Mixture Leading to Phase Separation
- Author
-
Hitomi Kobara, Shunsuke Mochizuki, and Akihiro Wakisaka
- Subjects
Butanol ,Biophysics ,Analytical chemistry ,Alcohol ,Mass spectrometry ,Biochemistry ,Mass spectrometric ,chemistry.chemical_compound ,chemistry ,Fragmentation (mass spectrometry) ,Phase (matter) ,Cluster (physics) ,Qualitative inorganic analysis ,Physical and Theoretical Chemistry ,Molecular Biology - Abstract
Microscopic structures of 1-butanol (1-BuOH)–water mixtures in the presence and absence of salts are studied through the mass spectrometric analysis of clusters generated from the fragmentation of liquid droplets. The analysis of cluster structures provides information on the phase separation of 1-BuOH–water mixtures from the microscopic viewpoint. In a saturated solution of 1-BuOH in water, 1-BuOH exists as hydrated 1-BuOH clusters and self-associated 1-BuOH clusters. With further addition of 1-BuOH, a 1-BuOH rich phase is generated. When the salt (LiCl, NaCl, MgCl2, etc.) coexists in the 1-BuOH–water mixtures, the cation is preferentially solvated by the 1-BuOH to form M +(1-BuOH) m or M 2+(1-BuOH) m clusters: M + = Li+, Na+, Mg2+ = Mg2+, etc., m = 1, 2, 3, ... Since the formation of M +(1-BuOH) m corresponds to an increase of the self-associated 1-BuOH clusters in water, the presence of the salt induces the phase separation at lower 1-BuOH concentrations.
- Published
- 2004
26. Preferential Solvation and Self-Association in Alcohol−Acetonitrile Mixtures Observed through Mass Spectrometric Analysis of Clusters: Influence of Alkyl Chain Length
- Author
-
Akihiro Wakisaka, Giacomo Saielli, Alessandro Bagno, and Federico Rastrelli
- Subjects
preferential solvation ,mass spectrometry ,md simulations ,chemistry.chemical_classification ,Hydrogen bond ,Solvation ,Analytical chemistry ,Alcohol ,Surfaces, Coatings and Films ,Solvent ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Molecule ,lipids (amino acids, peptides, and proteins) ,Methanol ,Physical and Theoretical Chemistry ,Acetonitrile ,Alkyl - Abstract
Molecular clusters formed by fragmentation of liquid droplets of alcohol (methanol or n-butanol)-acetonitrile mixtures have been detected and analyzed by means of a specially designed mass spectrometer. In the methanol-acetonitrile mixture, methanol clusters retain a sizable magnitude through most of the composition range, whereas acetonitrile clusters decrease in intensity upon increasing the concentration of methanol. Hydrogen bonding among methanol molecules controls the clustering. On the other hand, in n-butanol-acetonitrile mixtures, self-association of n-butanol through hydrogen bonding is remarkably promoted by the mixing with acetonitrile. With decreasing the acetonitrile contents, however, n-butanol self-associated clusters disintegrate completely. The interaction among n-butanol molecules changes from hydrogen bonding to dispersive, depending on the mixing ratio. When phenol is added as a solute to these binary mixtures, the solvation of phenol is found to be controlled by the solvent molecular clustering.
- Published
- 2004
27. Molecular Association in Binary Mixtures of tert-Butyl Alcohol−Water and Tetrahydrofuran−Heavy Water Studied by Mass Spectrometry of Clusters from Liquid Droplets
- Author
-
Toshiko Fukasawa, Akihiro Wakisaka, and Yasunori Tominaga
- Subjects
Heavy water ,chemistry.chemical_compound ,tert-Butyl alcohol ,chemistry ,Mixing ratio ,Analytical chemistry ,Molecule ,Alcohol ,Physical and Theoretical Chemistry ,Mass spectrometry ,Mole fraction ,Tetrahydrofuran - Abstract
The cluster structures observed by means of mass spectrometry for binary mixtures-tert-bulyl alcohol (TBA)-H 2 O and tetrahydrofuran (THF)-D 2 O-with varying mixing ratios exhibit striking contrast, even though both TBA andTHF are miscible with water at any mixing ratio. In the TBA-H 2 O mixtures at TBA mole fractions of (X T B A ) ≤ 0.01-0.025, some of the H 2 O molecules in the H 2 O clusters are replaced by TBA molecules. For 0.01-0.025 ≤ X T B A ≤ 0.2-0.3, the self-aggregation of TBA forms dominant cluster structures, and the hydrogen-bonded water clusters are disintegrated with increasing X T B A . This TBA self-aggregation is reduced with further increasing TBA at X T B A ≥ 0.3. However, in the THF-D 2 O mixtures, THF molecules have a weak additional interaction with D 2 O clusters, and the self-aggregation of THF is not promoted in the THF-D 2 O mixtures. The D 2 O clusters still exist, even at a THF mole fraction of X T H F = 0.3. On the basis of the observed cluster structure, the mechanism for the mixing between water and the organic solvent and the controlling factors in the self-aggregation are proposed.
- Published
- 2003
28. Interactions of a Nucleoside Cytidine with Metal Ions in Water Observed through Mass Spectrometry: Clustering Controlled by Electrostatic Interaction and Coordinating Interaction
- Author
-
Shunsuke Mochizuki and Akihiro Wakisaka
- Subjects
Aqueous solution ,Chemistry ,Metal ions in aqueous solution ,Inorganic chemistry ,Cytidine ,Mass spectrometry ,Mass spectrometric ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Materials Chemistry ,Physical and Theoretical Chemistry ,Cluster analysis ,Nucleoside ,Electrostatic interaction - Abstract
The effect of metal ions on the molecular clustering of cytidine in aqueous solution was studied by mass spectrometric analysis of clusters isolated from liquid droplets, and two types of cytidine ...
- Published
- 2003
29. A mass spectrometric study of solvated clusters of ions and ion pairs generated from lithium halide solutions in polar solvents: Acetonitrile compared to methanol
- Author
-
Akihiro Wakisaka, Tünde Megyes, and Tamás Radnai
- Subjects
chemistry.chemical_classification ,Inorganic chemistry ,Solvation ,chemistry.chemical_element ,Salt (chemistry) ,Halide ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Ion ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Cluster (physics) ,Physical chemistry ,Lithium ,Methanol ,Physical and Theoretical Chemistry ,Acetonitrile ,Spectroscopy - Abstract
Mass spectrometric study on cluster structure of solutions of lithium halides (LiX = LiBr and LiI) in acetonitrile is reported. Solvated ions Li+(CH3CN)n, X−(CH3CN)n, and salt clusters Li+(LiX)m(CH3CN)n and X−(LiX)m(CH3CN)n, were observed in the spectra. The mechanism of cluster formation is discussed in terms of a competition between solvation interactions and electrostatic interactions. This helps to explain the differences between clustering in methanol and acetonitrile, since the latter one has much larger dipole moment than the former one. Therefore appearance of solvated clusters, including the solvated salt clusters, is more favourable in methanol solutions' spectra.
- Published
- 2003
30. Complementary Relation between Ion−Counterion and Ion−Solvent Interaction in Lithium Halide−Methanol Solutions
- Author
-
Tamás Radnai, Tünde Megyes, and Akihiro Wakisaka
- Subjects
chemistry.chemical_classification ,Inorganic chemistry ,Solvation ,Halide ,chemistry.chemical_element ,Ion ,Solvent ,chemistry ,Mass spectrum ,Molecule ,Physical chemistry ,Lithium ,Physical and Theoretical Chemistry ,Counterion - Abstract
Mass spectrometric study on the cluster structure of methanol solutions containing lithium halides (LiX = LiCl, LiBr, and LiI) is reported. Solvated ions: Li+(CH3OH)n and X-(CH3OH)k, and salt clusters: Li+(Li+X-)s(CH3OH)m and X-(Li+X-)p(CH3OH)r, were observed in the mass spectra. The number of methanol molecules around Li+, especially in Li+(Li+X-)s(CH3OH)m clusters, increased when changing the anions from Cl- to I-, which suggested that there was a complementary relation between a Li+−CH3OH interaction and a Li+−X- interaction. In the case of X- = I-, the Li+−CH3OH interaction was enhanced in comparing with the case of X- = Cl-, because a Li+−I- interaction is weaker than a Li+−Cl- interaction. This observed complementary relation is a kind of intrinsic property of a liquid phase. Furthermore, mass distribution of the solvated ions and the salt clusters had correlations with physicochemical properties such as solvation energies and molar conductivities.
- Published
- 2002
31. Solvation for Ions and Counterions: Complementary Relation between Ion−Counterion and Ion−Solvent Interaction
- Author
-
Akihiro Wakisaka and Shunsuke Mochizuki
- Subjects
chemistry.chemical_classification ,Solvent ,chemistry.chemical_compound ,chemistry ,Inorganic chemistry ,Solvation ,Methanol ,Physical and Theoretical Chemistry ,Counterion ,Solvated electron ,Mass spectrometric ,Ion - Abstract
The microscopic environments around a cation and its counterion were experimentally studied for methanol solutions of CsCl, LiCl, LiI, and LiClO4 through mass spectrometric analysis of clusters gen...
- Published
- 2002
32. Cluster Structures in Aqueous HNO3 and H2SO4 Solutions: In Relation with Equivalent Conductivity
- Author
-
Takashi Ibusuki, Akihiro Wakisaka, Hitomi Kobara, and Koji Takeuchi
- Subjects
Delocalized electron ,Aqueous solution ,Mass distribution ,Chemistry ,Cluster (physics) ,Analytical chemistry ,Molecule ,Protonation ,Physical and Theoretical Chemistry ,Conductivity ,Mass spectrometry - Abstract
A part of microscopic structure in aqueous HNO3, and H2SO4 solutions was directly observed as ionic clusters isolated from these aqueous solutions by means of a specially designed electrospray mass spectrometer. The difference in the hydration structure for these acids was partially visualized on the basis of the molecular composition in the observed ionic clusters. For aqueous HNO3 solutions, the protonated water clusters, H+(H2O)n: n = 1, 2, 3 ..., which have similar mass distribution to the inherent water clusters, were observed predominantly. This is in good agreement with microscopic picture that the protons released from HNO3 are hopping and delocalized among water clusters. Such a cluster structure was independent of the HNO3 concentrations of [HNO3] < 1 mol/dm3. On the other hand, for aqueous H2SO4 solution, cluster structure was drastically changed with varying H2SO4 concentration. For diluted H2SO4 solution, clusters that consisted of only water molecules were mainly observed. This means that t...
- Published
- 2002
33. Self-Association of m-Cresol in Aqueous Organic Solvents: Relation to Enzymatic Polymerization Reaction
- Author
-
Hiroyuki Tonami, Hiroshi Uyama, Shin-ichiro Tawaki, Shiro Kobayashi, Akihiro Wakisaka, and Takahisa Oguchi
- Subjects
m-Cresol ,chemistry.chemical_classification ,Aqueous solution ,Inorganic chemistry ,Formaldehyde ,Polymer ,Surfaces, Coatings and Films ,Solvent ,chemistry.chemical_compound ,chemistry ,Polymerization ,Materials Chemistry ,Methanol ,Physical and Theoretical Chemistry ,Water content - Abstract
Oxidative polymerization of phenols using horseradish peroxidase (HRP) in aqueous organic solvents (1,4-dioxane-water and methanol-water), which is an attractive pathway for synthesis of a new class of polyphenols withoutuse of toxic formaldehyde, was remarkably influenced by the water content. The present study is focused on the self-association of m-cresol in such a solvent to understand the effect of solvent on its polymerization. The change of the molecular weight of the polymer with varying the water content was found to be related to the molecular clustering in the solution, observed through the difference UV absorption spectroscopy and the mass spectrometry for clusters. In mixed solvents of 1,4-dioxane and aqueous 0. 1 M phosphate buffer (pH 7), number-average molecular weight had a maximum at the aqueous buffer content of 50 vol %, whereas in methanol-aqueous buffer mixtures, the molecular weight had a small maximum at 20 vol % aqueous buffer content and gradually decreased with increase of the aqueous buffer content. As for the m-cresol clustering, the effect of the water content was also in significant contrast between the above aqueous organic solvent systems. The m-cresol clusters were not formed in 1,4-dioxane, but its clustering was remarkably promoted by an increase of the water content. On the other hand, the m-cresol clusters were formed favorably in methanol and were readily hydrated with increase of the water content in the solution. These effects of the water content on the clustering are related to the enzymatic polymerization. The polymer would be obtained in high yields when the m-cresol clusters were formed in the solution; however, the hydration of the m-cresol cluster would restrain the polymerization.
- Published
- 2002
34. On the Origin of Microheterogeneity
- Author
-
Jan B.F.N. Engberts, Jan W. Wijnen, Akihiro Wakisaka, and Dong Nam Shin
- Subjects
Aqueous solution ,Dimethyl sulfoxide ,Analytical chemistry ,Solvation ,MOLECULAR ASSOCIATION ,NOESY NMR-SPECTROSCOPY ,Mole fraction ,Mass spectrometry ,AQUEOUS-SOLUTION ,Surfaces, Coatings and Films ,PK VALUES ,chemistry.chemical_compound ,chemistry ,ACID ,Materials Chemistry ,Cluster (physics) ,Phenol ,Organic chemistry ,SOLVENT MIXTURES ,Physical and Theoretical Chemistry ,LIQUID-CHROMATOGRAPHY ,Acetonitrile ,ADIABATIC EXPANSION ,CLUSTERS ,PREFERENTIAL SOLVATION - Abstract
The microscopic structures of acetonitrile-water and DMSO-water binary mixed solvents and their influence on the solvation for solutes (some alcohols and phenol) have been studied on the basis of the cluster structures observed through a specially designed mass spectrometer. In acetonitrile-water mixtures, the water clusters were observed at water mole fractions: Xw > 0.2; on the other hand, in DMSO-water mixtures, the water clusters were observed only at much higher water mole fractions: Xw > 0.93. In the mixing processes, the water clusters were stabilized in the acetonitrile-water mixtures, whereas the DMSO clusters were stabilized in the DMSO-water mixtures. It is demonstrated that these microscopic structures directly affect the solvation for alcohols and phenol in these binary mixed solvents.
- Published
- 2002
35. Theoretical study on the structure and stability of the clusters of tropylium ion solvated by methanol molecules
- Author
-
Akiya Suzuki, Kazunari Yoshizawa, Tomomi Kinoshita, Ken'ichi Takeuchi, and Akihiro Wakisaka
- Subjects
Range (particle radiation) ,Chemistry ,Hydrogen bond ,solvated cluster ,Condensed Matter Physics ,Chemical communication ,hydrogen bonding ,Biochemistry ,tropylium ion ,Ion ,chemistry.chemical_compound ,Crystallography ,magic-numbered species ,Computational chemistry ,Cluster (physics) ,Molecule ,Density functional theory ,Methanol ,Physical and Theoretical Chemistry ,density functional theory - Abstract
Density functional theory (DFT) B3LYP calculations characterize the structure and stability of the clusters of tropylium ion (Tr+) coordinated by methanol molecules Tr+(MeOH)n with n=1–7. Methanol molecules are bound together through strong O–H⋯O type hydrogen bonds, resulting in a cyclic structure when n≥3, and the methanol cluster thus formed coordinates to Tr+ through weak C–H⋯O type hydrogen bonds. Thus, the formation of the Tr+(MeOH)n clusters is mediated by two kinds of hydrogen bonds. Calculated distances of the O–H⋯O hydrogen bonds lie in the range 1.570–1.991 A (1.712 A in average) while those of the C–H⋯O hydrogen bonds lie in the range 2.083–2.319 A (2.160 A in average). Mass spectroscopic experiments demonstrated that Tr+(MeOH)4 is a dominant, magic-numbered species and that Tr+(MeOH)3 and Tr+(MeOH)5 are minor [Chemical Communication, (2001) in press]. The experimental result is analyzed from the viewpoint of energetics. The specific size effect on the stability of Tr+(MeOH)n is a direct consequence of the stability of the (MeOH)n fragment itself.
- Published
- 2001
36. Steric effect involved in Ln3+/Ce3+ exchange in a coordination polymer based on di(2-ethylhexyl)phosphoric acid
- Author
-
Yuiko Tasaki-Handa, Yukie Abe, Mikiya Tanaka, Kenta Ooi, and Akihiro Wakisaka
- Subjects
Inorganic Chemistry ,Steric effects ,Crystallinity ,chemistry.chemical_compound ,Crystallography ,Ionic radius ,chemistry ,Ion exchange ,Coordination polymer ,Stereochemistry ,Ionic bonding ,Di-(2-ethylhexyl)phosphoric acid ,Phosphoric acid - Abstract
Coordination polymers can be attractive ion exchange materials because of their crystallinity and semi-flexibility, which are rather opposing properties, and play integral and synergistic roles in introducing unique ion-exchange behavior. In this paper, Ln(3+)/Ce(3+) exchange (Ln(3+) = Nd(3+), Gd(3+), Dy(3+), or Lu(3+)) in a coordination polymer, [Ce(dehp)3], based on di(2-ethylhexyl)phosphoric acid (Hdehp) is studied by distribution coefficient measurements, ion-exchange isotherms, Kielland plot analysis, and morphology observation. The ion-exchange selectivity is in the order Nd(3+)Gd(3+)Dy(3+)Lu(3+) when a small amount of Ln(3+) is loaded, but Lu(3+) ≈ Nd(3+)Gd(3+) ≈ Dy(3+) for a high loading ratio. The Kielland plot suggests that a steric effect is involved in the reactions, which becomes stronger in the order of Nd(3+)/Ce(3+)Gd(3+)/Ce(3+)Dy(3+)/Ce(3+)Lu(3+)/Ce(3+) for exchange systems. This trend is attributable to the differences in the ionic sizes between an incoming Ln(3+) and original Ce(3+). Scanning electron microscopy observations reveal the generation of a new phase via the Ln(3+)/Ce(3+) exchange. Such a phenomena results from solid-solid transformation, rather than dissolution-recrystallization. The small steric strain in the Nd(3+)/Ce(3+) system leads to the formation of a Nd(3+)-and-Ce(3+) solid-solution, whereas the morphological change is possibly restrained by the strong strain caused by loaded Ln(3+) with an ionic size significantly smaller than the original Ce(3+).
- Published
- 2013
37. Molecular Self-Assembling of Butan-1-ol, Butan-2-ol, and 2-Methylpropan-2-ol in Carbon Tetrachloride Solutions as Observed by Near-Infrared Spectroscopic Measurements
- Author
-
Yukihiro Ozaki, Hideyo Matsuzawa, Norihisa Katayama, Akihiro Wakisaka, Masayuki Suzuki, Makio Iwahashi, and Mirosław A. Czarnecki
- Subjects
chemistry.chemical_classification ,Hydrogen bond ,Overtone ,010401 analytical chemistry ,Near-infrared spectroscopy ,Inorganic chemistry ,Alcohol ,Polymer ,01 natural sciences ,0104 chemical sciences ,010309 optics ,chemistry.chemical_compound ,Monomer ,chemistry ,0103 physical sciences ,Carbon tetrachloride ,Molecule ,Physical chemistry ,Instrumentation ,Spectroscopy - Abstract
The self-associations of butan-1-ol, butan-2-ol, and 2-methylpropan-2-ol ( tert-butanol) in the pure liquid state and in carbon tetrachloride solutions have been studied mainly through near-infrared spectroscopic observation at various temperatures. A new analysis assuming a successive association process for the alcohol molecules was applied to the sharp band around 1410 nm (the first-overtone band of the OH stretching vibration mode attributed to free OH monomer and partly to OH polymer); it became clear that the mean association number for each alcohol increases with increasing concentration and decreases with increasing temperature. Comparisons of the association numbers at various constant temperatures for the three kinds of alcohols show that the association abilities are on the order butan-1-ol > butan-2-ol > 2-methylpropan-2-ol.
- Published
- 2000
38. Small-angle X-ray scattering investigation of water droplets in mist
- Author
-
Kazuyuki Kaneko, Kazuo Matsuura, Yohko F. Yano, Yoshio Katsuya, Akihiro Wakisaka, Hitomi Kobara, Masahiko Tanaka, Atsushi Kumagai, Fusatsugu Abe, Masato Okui, and Tetsuo Fukazu
- Subjects
Physics::Fluid Dynamics ,Range (particle radiation) ,Beamline ,Scattering ,Chemistry ,Small-angle X-ray scattering ,Physics::Atomic and Molecular Clusters ,Analytical chemistry ,Mist ,Flow cell ,Ultrasonic atomization ,General Biochemistry, Genetics and Molecular Biology - Abstract
Small-angle X-ray scattering measurements of water droplets in a mist were carried out using the BL15XU beamline at SPring-8. The diameter of the water droplets generated by ultrasonic atomization was found to be ≥ 50 nm and had no distribution in the range under 50 nm, as predicted. The study also showed how difficult it is to measure the small-angle scattering of low-density materials, such as liquid droplets in a mist.
- Published
- 2007
39. Acid–base interaction from the viewpoint of molecular clustering Effects of solvent, pKa and size of alkyl group
- Author
-
Akihiro Wakisaka, Yoshiharu Usui, and Shunsuke Mochizuki
- Subjects
chemistry.chemical_classification ,Carboxylic acid ,Solvation ,Medicinal chemistry ,chemistry.chemical_compound ,chemistry ,Pyridine ,Organic chemistry ,Propionitrile ,Physical and Theoretical Chemistry ,Solvent effects ,Weak base ,Brønsted–Lowry acid–base theory ,Alkyl - Abstract
Acid–base interactions were investigated by mass spectrometry of clusters isolated from solutions containing a carboxylic acid (propionic, butyric or hexanoic acid), an aromatic base (pyridine or pyrazine) and a solvent (water, acetonitrile or propionitrile). In water, self-aggregation of the carboxylic acid molecules due to hydrophobic interaction to form carboxylic acid clusters, such as (butyric acid)n, was prominent, and acid–base interaction proceeded between the carboxylic acid clusters and the basic molecules. In acetonitrile, the acid–base interaction was sensitive to the relative strength of the base. When pyridine (relatively strong base) was used as a base, clustering proceeded through the formation of a polarized acid–base complex, (acid)δ-(base)δ+. However, when pyrazine (relatively weak base) was used as a base, self-aggregation of the acid molecules became favorable. In propionitrile, such clusters were not observed because each molecule was separated by individual solvation. This solvent effect is related to the solvation structure, which determines the balance between the self-aggregation of the acid molecules and the formation of the polarized acid–base complex. It has also been demonstrated that the balance of the above intermolecular interactions is also dependent on the size of the alkyl group of the carboxylic acid. The results of the mass spectrometry partially show the microscopic view for the effect of solvent, pKa and the size of the alkyl group on the acid–base interaction in solution.
- Published
- 1998
40. Solvent effect on acid–base clustering between acetic acid and pyridine
- Author
-
Yoshikatsu Akiyama, Kengo Sakaguchi, Fujio Mizukami, and Akihiro Wakisaka
- Subjects
chemistry.chemical_classification ,Solvent ,chemistry.chemical_compound ,Acetic acid ,Base (chemistry) ,chemistry ,Pyridine ,Polymer chemistry ,Inorganic chemistry ,Molecule ,Solvent effects ,Brønsted–Lowry acid–base theory ,Acetonitrile - Abstract
The solvent effect on the acid–base interaction between acetic acid and pyridine has been studied by the mass spectrometric analysis of clusters isolated from liquid droplets. The clusters resulting from the acetic acid–pyridine, acid–base, interaction in water are quite different from those in acetonitrile solvent. In water (acetic acid∶pyridine∶water = 1∶1∶10) the acid–base interaction occurs through the intercluster interaction between acetic acid and pyridine clusters. On the other hand, in acetonitrile (acetic acid∶pyridine∶acetonitrile = 1∶1∶10), the acid–base interaction proceeds through an intermonomer interaction between an acetic acid molecule and pyridine molecule, and the clusters are produced through the aggregation of a polar (acetic acid)δ–(pyridine)δ+ complex. This solvent effect is mainly attributed to the cluster structure of acetic acid and pyridine in water and acetonitrile solvent.
- Published
- 1998
41. Rigid or floppy water-containing dipole-bound dimer anions
- Author
-
Jean-Pierre Schermann, Yves Bouteiller, Akihiro Wakisaka, Charles Desfrançois, and H. Abdoul-Carime
- Subjects
Bond dipole moment ,Proton ,Hydrogen bond ,Dimer ,Chemical polarity ,Atomic and Molecular Physics, and Optics ,Ion ,Dipole ,chemistry.chemical_compound ,Crystallography ,chemistry ,Molecule ,Physics::Atomic Physics ,Physics::Chemical Physics ,Atomic physics ,Physics::Atmospheric and Oceanic Physics - Abstract
We here report a comparative experimental and theoretical study of dipole-bound electron attachment on four polar hydrogen-bonded dimers containing one water molecule (water-water, ammonia-water, phenol-water and pyridine-water). When the water molecule is the proton acceptor in the neutral complex, with a trans-linear hydrogen bond (water-water and phenol-water), it is shown that the equilibrium geometry of the dipole-bound anion tends to a cis-linear hydrogen bond for which the total dipole moment is larger. On the contrary, when the water molecule is the proton donor to a nitrogen atom (ammonia-water and pyridine-water), dipole-bound electron attachment does not lead to subsequent modifications of the complex geometry.
- Published
- 1997
42. Non-covalent binary interactions between some organic acids and bases
- Author
-
C. Desfrancois, Akihiro Wakisaka, J. P. Schermann, H. Takeo, V. Periquet, J. Flugge, and H. Abdoul-Carime
- Subjects
Valence (chemistry) ,Chemistry ,Dimer ,Intermolecular force ,Binding energy ,Cyclohexanol ,Photochemistry ,Crystallography ,chemistry.chemical_compound ,Rydberg atom ,Pyridine ,Physics::Atomic and Molecular Clusters ,Molecule ,Physics::Chemical Physics ,Physical and Theoretical Chemistry - Abstract
Very-low-energy electron attachment to homogeneous and mixed pyridine, phenol and cyclohexanol dimers is studied by means of collisions with laser-excited Rydberg atoms and several new dipole-bound anions are observed. The corresponding structures and binding energies of their neutral parents are determined by model calculations of the intermolecular interactions between these polar closed-shell molecules. In the case of the phenol–pyridine dimer, a valence negative ion is observed. The geometry of its neutral parent is obtained from both abinitio and model calculations.
- Published
- 1997
43. Molecular self-assembly composed of aromatic hydrogen-bond donor[ndash ]acceptor complexes
- Author
-
Tetsuo Koyama and Akihiro Wakisaka
- Subjects
Crystallography ,chemistry.chemical_compound ,Chemistry ,Stereochemistry ,Hydrogen bond ,Dimer ,Monolayer ,Cluster (physics) ,Molecule ,Molecular self-assembly ,Acid–base reaction ,Physical and Theoretical Chemistry ,Acceptor - Abstract
Molecular self-assembling systems derived from the clustering of acid and base molecules have been investigated by mass spectrometric analysis of clusters isolated from liquid droplets. N–H···N and O–H···N hydrogen-bonded acid–base systems were compared. When heteroaromatic N–H···N hydrogen-bonding acid–base systems, such as 7-azaindole dimer, the indole–quinoline pair, etc. were used as acid–base pairs, the clusters composed of equimolar acid and base molecules were generated. This means that the hydrogen-bonding acid–base complex, N–H···N, behaves like a single molecule in cluster formation. On the other hand, clustering of the aromatic O–H···N hydrogen-bonding systems, such as phenol–pyridine, phenol–pyrazine, etc., was controlled by the acid–base interaction determined by the pKa values, giving a multilayer structure for a relatively strong acid–base pair and a monolayer structure for a relatively weak acid–base pair. Molecular self-assembling systems containing hydrogen-bond donor and acceptor molecules have been systematically described here.
- Published
- 1997
44. Clustering of a hydrogen-bonding complex between indole and isoquinoline Correlation with nucleation of intermolecular compounds
- Author
-
Akihiro Wakisaka and Yoshitaka Yamamoto
- Subjects
Indole test ,Hydrogen bond ,Intermolecular force ,Nucleation ,Mass spectrometry ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Polymer chemistry ,Organic chemistry ,Physical and Theoretical Chemistry ,Crystallization ,Isoquinoline ,Acetonitrile - Abstract
Upon crystallization from mixtures containing indole and isoquinoline, intermolecular compounds of 1:1 molecular ratio have been isolated as crystals. This crystallisation process, i.e., molecules→clusters→nucleus was studied in a specially designed mass spectrometer. From the mass spectrometric analysis of clusters isolated from liquid droplets containing indole, isoquinoline and acetonitrile, clusters composed of equimolecular indole and isoquinoline, i.e. (indole) n (isoquinoline) n : n=1, 2, 3,..., were observed as prominent species. This suggested that the hydrogen-bonded complex of indole and isoquinoline works as a unit species for the nucleation of the intermolecular compounds.
- Published
- 1997
45. Clusters in the Liquid and on the Surface
- Author
-
Kenji Koga, Akihiro Wakisaka, and Harutoshi Takeo
- Subjects
Surface (mathematics) ,Field (physics) ,law ,Chemical physics ,Chemistry ,Molecule ,Crystallization ,Atomic physics ,Chemical reaction ,law.invention - Abstract
Clusters, ensemble of atoms and/or molecules with less number enough to form stable bulk, are thought to play important roles in various phenomena such as, crystallization, phase separation, chemical reactions, etc. Several techniques to produce clusters have been developed and studies in this field are becoming active. Two new methods to produce clusters and the investigations on their characteristics are described in this paper. One is the characteristics of clusters formed from liquid (solution), and the other is the formation and the stabilization of clusters on the surface and their structural investigation.
- Published
- 1997
46. Camphor Ionic Liquid: Correlation between Stereoselectivity and Cation−Anion Interaction
- Author
-
Masashi Iio, Kazuya Kunimitsu, Satoshi Kitaoka, Yuichi Ishikawa, and Akihiro Wakisaka, Kaoru Nobuoka, and Thomas Harran
- Subjects
chemistry.chemical_compound ,Camphor ,Sulfonate ,chemistry ,Organic Chemistry ,Ionic liquid ,Organic chemistry ,Stereoselectivity ,Medicinal chemistry ,Ion - Abstract
[structure: see text] As a halogen-free anion for an imidazolium room temperature ionic liquid, the use of a camphorsulfonate causes an increase in the number of free (naked) imidazolium cations, which produces an effective endo/exo stereoselective Diels-Alder reaction.
- Published
- 2005
47. CCSD(T) level interaction energy for halogen bond between pyridine and substituted iodobenzenes: origin and additivity of substituent effects
- Author
-
Akihiro Wakisaka, Taizo Ono, Seiji Tsuzuki, Tadafumi Uchimaru, and Takaaki Sonoda
- Subjects
chemistry.chemical_compound ,Halogen bond ,Iodobenzenes ,Electronic correlation ,chemistry ,Computational chemistry ,Halogen ,Pyridine ,Substituent ,General Physics and Astronomy ,Interaction energy ,Physical and Theoretical Chemistry ,Basis set - Abstract
The CCSD(T) level interaction energies at the basis set limit (E(int)) were calculated for 33 halogen bonded pyridine complexes with substituted iodobenzenes. The CCSD(T) level electron correlation correction substantially decreases the magnitude of attraction in comparison with the MP2. The E(int) for the pyridine complexes with mono substituted iodobenzenes varies from -3.14 to -4.42 kcal mol(-1), depending on the substituent. The electron-withdrawing substituents such as NO2 enhance the attraction, while the effects of electron-donating substituents reduce. The additivity of the substituent effects is observed for the E(int) of the pyridine complexes with multiple substituted iodobenzenes. The electrostatic interactions are mainly responsible for the substituent effects on the magnitude of the attraction in the halogen-bonded complexes. The electrostatic energy depends significantly on the substituent. They have a strong correlation with the E(int). On the other hand the effects of the substituent on the dispersion energy are small, however the dispersion does contribute greatly to the attraction.
- Published
- 2013
48. Molecular self-assembly controlled by acid–base non-covalent interactions: a mass spectrometric study of some organic acids and bases
- Author
-
Kengo Sakaguchi, Yoshitaka Yamamoto, Yoshikatsu Akiyama, Harutoshi Takeo, Theo Engst, Akihiro Wakisaka, Fujio Mizukami, and Harold Jones
- Subjects
chemistry.chemical_classification ,Base (chemistry) ,chemistry ,Computational chemistry ,Monolayer ,Stacking ,Analytical chemistry ,Non-covalent interactions ,Molecular self-assembly ,Molecule ,Acid–base reaction ,Physical and Theoretical Chemistry ,Mass spectrometry - Abstract
Molecular clusters generated from vacuum adiabatic expansion of liquid droplets including acid and base molecules provide an insight into molecular self-assembly through non-covalent interactions. The mass spectrometric analysis for the resulting clusters indicates a systematic structure change which is dependent on the acid–base interaction: a multilayer stacking structure for relatively strong acid–base pairs (phenol–pyridine, phenol–N,N-dimethylaniline, etc.), and a monolayer structure for relatively weak acid–base pairs (phenol–pyrazine, cyclohexanol–pyridine, etc.). As another viewpoint, mass spectrometry of the molecular clusters composed of acid and base molecules can be presented as a new method to characterise the acid–base interaction.
- Published
- 1996
49. Solvation-controlled clustering of a phenol–pyridine acid–base pair
- Author
-
Yoshitaka Yamamoto, Harutoshi Takeo, Kengo Sakaguchi, Fujio Mizukami, Akihiro Wakisaka, and Yoshikatsu Akiyama
- Subjects
chemistry.chemical_classification ,Nitrile ,Chemistry ,Solvation ,Photochemistry ,Solvent ,chemistry.chemical_compound ,Polymer chemistry ,Pyridine ,Propionitrile ,Physical and Theoretical Chemistry ,Solvent effects ,Acetonitrile ,Alkyl - Abstract
Solvent effects on acid–base interactions between phenol and pyridine have been observed via mass spectrometry of solutions containing phenol, pyridine and water, alcohol and nitrile solvents. In the solvents having sufficiently long alkyl chains to solvate phenol and pyridine, such as propan-1-ol and propionitrile, the phenol–pyridine interaction was limited to the inter-unimolecular interactions. However, in the solvents having short alkyl chains such as methanol and acetonitrile, and in water, clustering between phenol and pyridine was observed as a result of inter-cluster interactions. The phenol molecules also formed clusters in methanol and acetonitrile, but not in propan-1-ol or propiontrile. This indicates that the observed clusters are controlled by the solvation structure depending on the solvent alkyl-chain length.
- Published
- 1996
50. Preferential solvation controlled by clustering conditions of acetonitrile–water mixtures
- Author
-
Nobuyuki Nishi, Satoru Takahashi, and Akihiro Wakisaka
- Subjects
Solvent ,chemistry.chemical_compound ,chemistry ,Clathrate hydrate ,Analytical chemistry ,Solvation ,Phenol ,Molecule ,Organic chemistry ,Emission spectrum ,Physical and Theoretical Chemistry ,Mole fraction ,Acetonitrile - Abstract
Experimental evidence for the preferential solvation of phenol in a mixed solvent of acetonitrile and water has been obtained by mass spectrometric analysis of the clusters isolated from liquid droplets by the adiabatic expansion. The effect of temperature on the formation of phenol–hydrate clusters, (C6H5OH)(H2O)n : n= 1,2,3, …, showed that phenol molecules are solbated preferentially by acetonitrile molecules at xw(water mole fraction) < 0.85, the phenol–hydrate clusters were hardly observed at temperatures lower than 50 °C but appeared at higher temperatures. On the contrary, at xw 0.85, hydrate formation became preferable at lower temperatures. The observed temperature effect confirmed microscopically inhomogeneous clustering of the solvent and solute molecules in the mixtures. A. similar temperature effect was also observed in the emission spectra of 2-naphthol in the same mixtures.
- Published
- 1995
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