Voltammetric study of the transfer of fluoride ion at the nitrobenzene / water interface assisted by tetraphenylantimony.

The transfer of F- ion assisted by an organometallic complex cation tetraphenylantimony (TPhSb+) across the polarized nitrobenzene / water (NB / W) interface has been studied by means of ion-transfer voltammetry. A well-defined voltammetric wave was observed within the potential window at the NB / W interface when tetraphenylantimony tetrakis(4-chlorophenyl) borate and F- ion were present in NB and W, respectively. The voltammogram can be interpreted as being due to the reversible transfer of F- ion assisted by the formation of the TPhSbF complex through the coordination of F- to Sb atom in NB. The formal formation constant of TPhSbF in NB has been determined to be 10(1.95 +/- 0.2 M(-1). No voltammetric wave due to the TPhSb(+)-assisted transfer of other anions such as Cl-, Br, I-, NO3-, CH3COO- and H2PO4(-) ions has been observed within the potential window.     

Halogen-free water-immiscible ionic liquids based on tetraoctylammonium cation and dodecylsulfate and dodecylbenzenesulfonate anions, and their application as chelate extraction solvent.

The tetraoctylammonium cation forms water-immiscible room temperature ionic liquids with dodecylsulfate and dodecylbenzenesulfonate anions. The ionic liquids are halogen-free and can be considered environmentally friendly solvents. At 25 degrees C, the solubilities of water in tetraoctylammonium dodecylsulfate and tetraoctylammonium dodecylbenzenesulfonate were 2.8 and 4.0%, respectively, and the densities were 0.92 and 0.93 g cm(-3). The ionic liquids formed stable interfaces with water at 25 degrees C. The possible use of tetraoctylammonium dodecylsulfate as chelate extraction solvent was evaluated by using 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione as extractant. Tetraoctylammonium dodecylsulfate showed high extraction performance for divalent transition metal cations.     

Molecular design of calixarene-based ion-selective electrodes

In order to obtain insights into relationships between the calix[4]arene structure and the ion selectivity in the electrode system, 20 ionophoric calix[4]arenes were synthesized and their ion selectivity (with Na⁺ as a standard) estimated. Among these ionophoric calix[4]arenes, 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-t-octylcalix[4]arene afforded the highest logK _NA,M ^pot value (–3.1) in the presence of 2-fluorophenyl-2-nitrophenylether (10) as the best of 13 plasticizers. This is the first example in which the Na⁺/K⁺ selectivity exceeds a factor of 10³ in the electrode system based on the neutral carrier. The high Na⁺ selectivity is attributed to modification of the upper rim which ostensibly has no relation with the component of the cavity. This paper demonstrates the potential relationships between the unique structure of the calix[4]arene-based ligands and selectivity performance for the design of ion-selective electrodes.     

Voltammetric study of interfacial electron transfer between bis(cyclopentadienyl)iron in organic solvents and hexacyanoferrate in water.

The electron-transfer reaction between bis(cyclopentadienyl)iron(II) ([Fe(II)(C5H5)2]) in nitrobenzene and a hexacyanoferrate redox couple ([Fe(II/III)(CN)6](4-/3-)) in water at the nitrobenzene / water interface was studied using normal pulse voltammetry. The voltammetric results indicate that the electron-transfer reaction takes place by way of a so-called ion-transfer (IT) mechanism, of which the forward and backward rate constants of the homogeneous electron-transfer reaction between [Fe(II/III)(C5H5)2](0/+) and [Fe(II/III)(CN)6](4-/3-) in the water phase have been determined. The electron-transfer reaction between [Fe(II)(C5H5)2] in 1,2-dichloroethane and [Fe(II/III)(CN)6](4-/3-) in water at the 1,2-dichloroethane / water interface was shown to also take place by the IT-mechanism.     

Stable triplex formation using the strong stacking effect of consecutive thionucleoside moieties

In this study, it was found that the arrangement of consecutive thiocarbonyl groups of s(2)T and m(5)s(2)C remarkably stabilized the pre-protonated form of the triplex, and that the stabilization of the pre-protonated form increased the pKa value of a cytosine derivative in the triplex.     

Synthesis of 5'-terminal capped oligonucleotides using O-N phosphoryl migration of phosphoramidite derivatives

Trivalent phosphoramidite derivatives could be readily converted by reacting with 1-hydroxy-7-azabenzotriazole to phosphotriester intermediates; these intermediates reacted smoothly with phosphorylated compounds to give pyrophosphate derivatives. This new phosphorylation approach enabled a facile and rapid synthesis of 5'-adenylated DNA oligomers (A(5')ppDNA) on resins using a silyl-type linker. Our new approach could be applied to the synthesis of a 2'-OMe-RNA oligomer containing the 5'-terminal 2,2,7-trimethylguanosine cap structure.     

Ion-transfer voltammetry at 1,6-dichlorohexane|water and 1,4-dichlorobutane|water interfaces

The usefulness of 1,6-dichlorohexane (1,6-DCH) and 1,4-dichlorobutane (1,4-DCB) as organic solvent (O) for ion-transfer voltammetry at O|water (W) interface has been examined, and the results are compared with those with 1,2-dichloroethane (1,2-DCE). The width of potential window of the 0.1 M tetraoctylammonium tetrakis(4-chlorophenyl)borate (O)|0.05 M Li₂SO₄ (W) interface increased in the sequence: O = 1,6-DCH > 1,4-DCB > 1,2-DCE. The voltammetric behavior of the transfer of various cations and anions at the 1,6-DCH|W and 1,4-DCB|W interfaces has been shown to be of reversible nature, and the midpoint potentials or the reversible half-wave potentials have been determined. The midpoint potentials of hydrophilic ions have also been determined by the analysis of anodic final rise or cathodic final decent of the voltammograms with the O|W interfaces, where the W contains a salt of the hydrophilic ion. Also, the effect of ion-pair formation in O on the midpoint potentials has also been discussed.     

Cyclic Voltammetry of Ion Transfer for Phenylpropanolamine Hydrochloride at Water|Nitrobenzene Interface

The transfer on phenylpropanolamine ion, PPAH⁺, has been studied at the Interface between Two Immiscible Solutions (ITIES). The polarizable potential range was determined by cyclic voltammetry at the interface between an aqueous solution of lithium chloride (LiCl) and a nitrobenzene (NB) solution of electrolyte tetrabutylammonium tetraphenylborate (TBATPB). The half‐wave potential of ion transfer for phenylpropanolamine accross the water|NB interface was found 465.3 mV. The peak separation, the diffusion coefficient, and the standard ion transfer potential of PPAH⁺ were observed to be 59.1 mV, 1.7 × 10^?6 cm²/s, and 104.6 mV, respectively. The temperature of experiment was kept constantly at 25 ± 1 °C using water flow thermostate.     

Formation of new base pairs between inosine and 5-methyl-2-thiocytidine derivatives

In this paper, we report DNA and 2'-OMe-RNA probes containing 5-methyl-2-thiocytidine (m(5)s(2)C) residues that can bind selectively and strongly to the corresponding RNA targets containing inosine residues by the significant stacking effect and steric hindrance of the 2-thiocarbonyl group.     

Highly Dispersed Pd Species Active in the Suzuki–Miyaura Reaction

Structures of Pd/zeolites immersed in solvents were measured by in situ X‐ray absorption fine structure (XAFS). Systematic studies revealed that the selection of an appropriate support (USY‐zeolite), thermal treatment temperature of USY, solvent (o‐xylene), H₂ partial pressure (6 %), and the use of a Pd amine complex affect the structure of Pd. As a result, we found that monomeric Pd can be obtained in the USY support with H₂ bubbling in o‐xylene. The structural properties of Pd correlate well with its catalytic performance in the Suzuki–Miyaura coupling reactions; a very high TON of up to 11 000 000 was obtained over the monomeric Pd.