Catalymetric trace determination of molybdenum(VI) based on a Landolt type peroxoborate-iodide reaction using an ion-selective electrode

Summary Trace amounts of molybdenum(VI) have been determined by means of its catalytic effect on the peroxoborate-iodide reaction in acidic medium. The indicator reaction is transformed to a Landolt reaction by the addition ofl-ascorbic acid which reduces iodine to iodide. The end-point of the reaction (decrease of iodide) is potentiometrically monitored by the aid of an iodide ion-selective electrode. The relationship between the time required to reach the end-point (t in seconds) and the concentration of molybdenum(VI) was found to be 1/t=4.79 [Mo(VI)]+0.598 in the range of 0.5–5.0 M Mo(VI). Tungsten(VI) interferes. The method has been applied to the determination of molybdenum(VI) in sea water after its concentration by the chelating resin Chelex-100 (standard deviation 0.52 g/l for 8.62 g Mo/l).

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Katalymetrische Bestimmung von Molybdän(VI)spuren durch die Landoltsche Peroxoborat-Iodid-Reaktion mit Hilfe der Iodid-Elektrode

Zusammenfassung Das Verfahren beruht auf der katalytischen Wirkung des Molybdäns auf die Peroxoborat-Iodid-Reaktion. Durch Zugabe einer definierten Menge von Ascorbinsäure, die das zunächst entstehende Iod sofort reduziert, wird eine Landolt-Reaktion aufgebaut. Der Endpunkt (Verminderung an Iodid) wird potentiometrisch mit der Iodid-Elektrode indiziert. Zwischen der Zeitdauer bis zum Endpunkt (t in Sekunden) und der Molybdänkonzentration besteht die Beziehung 1/t=4,79 [Mo(VI)]+0,598 im Bereich von 0,5–5,0 M Mo(VI). Wolfram(VI) stört. Molybdän kann nach diesem Verfahren in Meerwasser nach Konzentration am Chelationenaustauscher Chelax-100 bestimmt werden (Standardabweichung 0,52 g/l für 8,62 g Mo/l).

     

Hidden Isolated OH at the Charged Hydrophobic Interface Revealed by Two-Dimensional Heterodyne-Detected VSFG Spectroscopy

Water around hydrophobic groups mediates hydrophobic interactions that play key roles in many chemical and biological processes. Thus, the molecular-level elucidation of the properties of water in the vicinity of hydrophobic groups is important. We report on the structure and dynamics of water at two oppositely charged hydrophobic ion/water interfaces, that is, the tetraphenylborate-ion (TPB⁻)/water and tetraphenylarsonium-ion (TPA⁺)/water interfaces, which are clarified by two-dimensional heterodyne-detected vibrational sum-frequency generation (2D HD-VSFG) spectroscopy. The obtained 2D HD-VSFG spectra of the anionic TPB⁻ interface reveal the existence of distinct π-hydrogen bonded OH groups in addition to the usual hydrogen-bonded OH groups, which are hidden in the steady-state spectrum. In contrast, 2D HD-VSFG spectra of the cationic TPA⁺ interface only show the presence of usual hydrogen-bonded OH groups. The present study demonstrates that the sign of the interfacial charge governs the structure and dynamics of water molecules that face the hydrophobic region.     

Successful preparation of metabolite of troglitazone by in-flow electrochemical reaction on coulometric electrode

A simple, rapid and efficient system utilizing a coulometric electrode was developed for the preparation of drug metabolites. Trace amounts of reactants are usually generated in electrochemical reactions, which are not suitable for the sufficient preparation of products to obtain NMR and other spectral data for chemical structure confirmation or to obtain data from pharmacological activity screening tests of products. In the developed system, called the "in-flow electrochemical reaction system," a drug, troglitazone, was dissolved in a volatile flow solvent, and pumped into a coulometric electrode under optimized conditions, and the effluent was evaporated. Without any further purification, milligram amounts of a pure oxidation product of troglitazone could be obtained within several hours. The amount obtained was enough for (1)H- and (13)C-NMR analysis by which the structure could be confirmed and was found to be identical to one of the metabolites of troglitazone detected in human plasma. This system will be useful to prepare standard compounds of the required amount for pharmacokinetic study and for toxicokinetic study.     

A Combined 6π-Azaelectrocyclization/Staudinger Approach to Protein and Cell Engineering: Noninvasive Tumor Targeting by N-Glycan-Engineered Lymphocytes

A Combined 6π-Azaelectrocyclization/Staudinger Approach to Protein and Cell Engineering: Noninvasive Tumor Targeting by N-Glycan-Engineered Lymphocytes

All authors

Katsunori Tanaka, Kaori Minami, Tsuyoshi Tahara, Eric R. O. Siwu, Koichi Koyama, Satoshi Nozaki, Hirotaka Onoe, Yasuyoshi Watanabe & Koichi Fukase

https://doi.org/10.1080/07328303.2010.483042

Published online:

02 June 2010

Graphical Abstract     

197.

Glass transition and dynamics of single and stacked thin films of poly(2-chlorostyrene)     

K. Fukao  Y. Oda  K. Nakamura  D. Tahara 《The European physical journal. Special topics》2010,189(1):165-171

The glass transition temperature and the dynamics of the α-process have been investigated using dielectric relaxation spectroscopy for single and stacked thin films of poly(2-chlorostyrene) (P2CS). The stacked film consists of 10 layers of single thin films with thickness of 12 nm or 18 nm. The glass transition temperature T _g of the single thin films of P2CS is found to decrease with decreasing film thickness in a similar way as observed for polystyrene thin films. The magnitude of the depression of T _g for the stacked thin films is larger than that of the single thin films with corresponding thickness. The depression of the temperature at which the dielectric loss shows a peak due to the α-process at a given frequency, T _α, is larger than that of the single thin films, although the magnitude is smaller than that of T _g . Annealing at a high temperature could cause the T _g and T _α of the stacked thin films to approach the values of the bulk system.     

198.

Lewis-Pairing-Induced Electrochemiluminescence Enhancement from Electron Donor-Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector     

Takashi Ikeda  Dr. Keishiro Tahara  Dr. Ryoichi Ishimatsu  Prof. Toshikazu Ono  Dr. Luxia Cui  Momoka Maeda  Prof. Yoshiki Ozawa  Prof. Masaaki Abe 《Angewandte Chemie (International ed. in English)》2023,62(21):e202301109

This study reports an effective peripheral decoration of organic donor-acceptor diads with B(C₆F₅)₃ for stabilizing electrogenerated radical ions. By employing a common p-type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156-fold increase compared to that of the parent diad. The unprecedented Lewis-pairing-induced ECL enhancement is attributed to the multiple roles of B(C₆F₅)₃: 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C₆F₅)₃ converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π-stacks. This robust, highly ordered columnar nanostructure allowed red-shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal-free ECL systems.     

199.

Determination of Absolute Configuration of Decipinone,a Diterpenoid Ester with a Myrsinane‐Type Carbon Skeleton,by NMR Spectroscopy.     

Amir Reza Jassbi  Yukiharu Fukushi  Satoshi Tahara 《ChemInform》2002,33(44):25-25

     

200.

Copolymerization of 2‐butene and ethylene with catalysts based on titanium and zirconium complexes     

C.‐H. Ahn  M. Tahara  T. Uozumi  J. Jin  S. Tsubaki  T. Sano  K. Soga 《Macromolecular rapid communications》2000,21(7):385-389

The polymerization of 2‐butene and its copolymerization with ethylene have been investigated using four kinds of dichlorobis(β‐diketonato)titanium complexes, [ArN(CH₂)₃NAr]TiCl₂ (Ar = 2,6‐ⁱPr₂C₆H₃) and typical metallocene catalysts. The obtained copolymers display lower melting points than those produced of homopolyethylene under the same polymerization conditions. ¹³C NMR analysis indicates that 9.3 mol‐% of 2‐butene units were incorporated into the polymer chains with Ti(BFA)₂Cl₂‐MAO as the catalyst system. With the trans‐2‐butene a higher copolymerization rate was observed than with cis‐2‐butene. A highly regioselective catalyst system for propene polymerization, [ArN(CH₂)₃NAr]TiCl₂ complex using a mixture of triisobutylaluminium and Ph₃CB(C₆F₅)₄ as cocatalyst, was found to copolymerize a mixture of 1‐butene and trans‐2‐butene with ethylene up to 3.1 mol‐%. Monomer isomerization‐polymerization proceeds with typical metallocene catalysts to produce copolymers consisting of ethylene and 1‐butene.     

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Glass transition and dynamics of single and stacked thin films of poly(2-chlorostyrene)

The glass transition temperature and the dynamics of the α-process have been investigated using dielectric relaxation spectroscopy for single and stacked thin films of poly(2-chlorostyrene) (P2CS). The stacked film consists of 10 layers of single thin films with thickness of 12 nm or 18 nm. The glass transition temperature T _g of the single thin films of P2CS is found to decrease with decreasing film thickness in a similar way as observed for polystyrene thin films. The magnitude of the depression of T _g for the stacked thin films is larger than that of the single thin films with corresponding thickness. The depression of the temperature at which the dielectric loss shows a peak due to the α-process at a given frequency, T _α, is larger than that of the single thin films, although the magnitude is smaller than that of T _g . Annealing at a high temperature could cause the T _g and T _α of the stacked thin films to approach the values of the bulk system.     

Lewis-Pairing-Induced Electrochemiluminescence Enhancement from Electron Donor-Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector

This study reports an effective peripheral decoration of organic donor-acceptor diads with B(C₆F₅)₃ for stabilizing electrogenerated radical ions. By employing a common p-type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156-fold increase compared to that of the parent diad. The unprecedented Lewis-pairing-induced ECL enhancement is attributed to the multiple roles of B(C₆F₅)₃: 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C₆F₅)₃ converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π-stacks. This robust, highly ordered columnar nanostructure allowed red-shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal-free ECL systems.     

Copolymerization of 2‐butene and ethylene with catalysts based on titanium and zirconium complexes

The polymerization of 2‐butene and its copolymerization with ethylene have been investigated using four kinds of dichlorobis(β‐diketonato)titanium complexes, [ArN(CH₂)₃NAr]TiCl₂ (Ar = 2,6‐ⁱPr₂C₆H₃) and typical metallocene catalysts. The obtained copolymers display lower melting points than those produced of homopolyethylene under the same polymerization conditions. ¹³C NMR analysis indicates that 9.3 mol‐% of 2‐butene units were incorporated into the polymer chains with Ti(BFA)₂Cl₂‐MAO as the catalyst system. With the trans‐2‐butene a higher copolymerization rate was observed than with cis‐2‐butene. A highly regioselective catalyst system for propene polymerization, [ArN(CH₂)₃NAr]TiCl₂ complex using a mixture of triisobutylaluminium and Ph₃CB(C₆F₅)₄ as cocatalyst, was found to copolymerize a mixture of 1‐butene and trans‐2‐butene with ethylene up to 3.1 mol‐%. Monomer isomerization‐polymerization proceeds with typical metallocene catalysts to produce copolymers consisting of ethylene and 1‐butene.