Thin-layer chromatographic behavior of rare earths on silica gel with aqueous alkaline earth metal nitrate solutions as mobile phases

The TLC behavior of all the rare earths except Pm has been surveyed on silica gel (pH 7.0) pretreated with 0.1 mol L^–1 tris(hydroxymethyl)aminomethane and 0.1 mol L^–1 HCl with aqueous nitrate solutions of alkaline earth metals as mobile phases. The R_F values of the lanthanides varied in a regular and characteristic way accompanied by the tetrad effect with increasing atomic number, and when the mobile phases were changed the R_F values of each metal decreased in the order Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺, as the crystal ionic radii of the alkaline earth metals increased. This adsorption sequence was not observed with alkali metal nitrate and alkali metal chloride mobile phases. A brief discussion concerning the effect on R_F values of the solvent cations and the adsorption mechanism is included; also presented are typical chromatograms for the separation of multi-component mixtures containing adjacent lanthanides. Received: 9 October 2000 / Revised: 20 February 2001 / Accepted: 26 February 2001     

New antifungal 1,2,4-triazoles with difluoro(substituted sulfonyl)methyl moiety

New 1,2,4-triazoles (2) having a difluoro(substituted sulfonyl)methyl moiety were designed and synthesized via alpha,alpha-difluoro-alpha-(substituted thio)acetophenones (3). Compounds (2) showed potent antifungal activities against C. albicans, C. krusei, A. flavus and A. fumigatus in vitro and against C. albicans in vivo for oral and i.v. administrations. Especially, (-)-2a, (-)-2b and (-)-2d showed potent antifungal activities.     

Glochiflavanosides A-D: flavanol glucosides from the leaves of Glochidion zeylanicum (Gaertn) A. Juss.

From the leaves of Glochidion zeylanicum collected in Okinawa, four flavanol glucosides, named as glochiflavanosides A-D were isolated along with known flavone C-glucosides, vitexin and isoorientin. Their structures were elucidated by spectroscopic analyses.     

Latifolosides K and L, two new triterpenoid saponins from the bark of Llex latifolia.

Two new triterpenoid saponins, latifoloside K (1), 3-O-beta-D-glucopyranosyl-(1-->3)-[alpha-L-rhamnopyranosyl-(1-->2)-]-alpha-L-arabinopyranosyl 3beta-hydroxy-urs-12,18-dien-28-oic acid 28-O-beta-D-glucopyranosyl ester and latifoloside L (2), 3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->3)-[alpha-L-rhamnopyranosyl-(1-->2)-]-alpha-L-arabinopyranosyl 3beta,19alpha-dihydroxyursolic acid, were isolated from the bark of Ilex latifolia Thunb. Also isolated were two known compounds, ilekudinoside A (3) and kudinoside G (4). Structural assignments were established on the basis of spectroscopic data and chemical evidence.     

Microphase‐separated structure of 1,3‐cyclohexadiene/butadiene triblock copolymers and its effect on mechanical and thermal properties

We report the effect of microphase‐separated structure on the mechanical and thermal properties of several poly(1,3‐cyclohexadiene‐block‐butadiene‐block‐1,3‐cyclohexadiene) triblock copolymers (PCHD‐block‐PBd‐block‐PCHD) and of their hydrogenated derivatives: poly(cyclohexene‐block‐ethylene/butylene‐block‐cyclohexene) triblock copolymers (PCHE‐block‐PEB‐block‐PCHE). Both mechanical strength and heat‐resistant temperature (ex. Vicat Softening Temperature: VSPT) tended to increase with an increase in the 1,3‐cyclohexadiene (CHD)/butadiene ratio. On the other hand, heat resistance of the hydrogenated block copolymer was found to be higher than that of the unhydrogenated block copolymer. However, the mechanical strength was lower than those of the unhydrogenated block copolymer with the same ratio of CHD to butadiene. To clarify the relationship between the higher order structures of those block copolymers and their properties, we observed the microphase‐separated structure by transmission electron microscope (TEM). Hydrogenated block copolymers were found to have more finely dispersed microphase‐separated structures than those of the unhydrogenated block copolymers with the same CHD/Bd ratios through the use of TEM and the small‐angle X‐ray scattering (SAXS) technique. Those results indicated that the segregation strength between the PCHE block sequence and the PEB block sequence increased, depending on hydrogenation of the unhydrogenated precursor. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 13–22, 2001     

High-throughput characterization for organic pollutants in environmental waters using a capillary electrophoresis chip.

To evaluate organic pollution in water, we did preliminarily studies on high-throughput characterization of organic pollution in water using microchip-based capillary electrophoresis (CE) with laseer-induced fluorescence (LIF) detection. The applied voltage was investigated to control the gated valve injection and CE separation for conventional cross type microchips using a self-made personal computer (PC)-based controller as the voltage supply. We obtained high-throughput data for the reproducible separation of fluorescein isothiocyanate (FITC)-labeled river-water samples using a zwitter-ion based buffer solution to avoid adsorption of the labeled sample onto the channel of a microchip made from quartz glass. We used real samples from the Hino River that flows into Lake Biwa, from ten sampling points and obtained several reproducible peaks in different separation patterns for each sample within 2 min. We successfully demonstrated high-throughput characterization of dissolved organic carbon (DOC) in environmental water using the microchip.     

New artificial host compounds containing galactose end groups for binding chiral organic amine guests: chiral discrimination and their complex structures

New linear host (1) and cyclic hosts (2 and 3), which have galactopyranose skeletons as chiral origins and oxyethylenes skeletons as binding sites, were designed based on the structural features extracted from the fructo-oligosaccharide derivatives, having a large chiral discrimination ability, and were then synthesized. These hosts showed chiral discrimination toward chiral organic ammonium salts. For example, the chiral discrimination ability (the ratio of association constants: K(R)/K(S)) of host 1, which has the highest value among them, was K(R)/K(S) = 3 for Trp-O-(i)Pr(+) and K(R)/K(S) = 0.7 for 1-(1-naphthyl)ethylammonium (NEA(+)) at 298 K in CHCl(3). It was clarified that host 1 changed the conformation from a linear structure to the pseudo-ring structure by complexation with cations such as alkali metallic ions and chiral organic ammonium ions. The (1)H NMR induced shifts of host 1 by adding the NEA(+) guests showed that the host-guest complex structures are clearly different, depending upon the chirality of the guest; in the complex with (R)-NEA(+), the naphthyl group of the guest is located above the oxyethylene skeleton of the host and in the complex with (S)-NEA(+), and the naphthyl group is located between the edges of the pseudo-ring of the host. The clearly different structure of the complex of host 1 with NEA(+) may be caused by the dynamic molecular recognition, thus the induced-fitting mechanism.     

High-Pressure Synthesis, Crystal Structure, and Metal–Semiconductor Transitions in the Tl2Ru2O7−δPyrochlore

Thallium ruthenium oxides, Tl₂Ru₂O_7−δ, with the pyrochlore structure were synthesized under a pressure of 1–5 GPa and 1173 K and characterized by resistivity, magnetization, and TOF neutron-diffraction measurements. The oxygen vacancy,δ, varied with the synthesis conditions and significantly affected their electrical properties. The pyrochlores synthesized at high pressure and atmospheric pressure are classified into four groups which depend on their oxygen nonstoichiometry. (i) Nonstoichiometric Tl₂Ru₂O_6.71shows a metallic conductivity with almost temperature-independent magnetization. (ii) Stoichiometric Tl₂Ru₂O₇synthesized under high oxygen pressure using KClO₄shows a metallic–semiconducting transition at 120 K with magnetization anomalies at 120 and 40 K. (iii) Slightly nonstoichiometric Tl₂Ru₂O_6.96shows spin-glass-like behavior around 40 K accompanying a resistivity increase at the transition. (iv) Tl₂Ru₂O₇synthesized at 773 K and atmospheric pressure is semiconducting with magnetization anomalies at 120 and 40 K. The change from the metallic to semiconducting state is discussed from the viewpoint of structure changes.     

Synthesis of Vinylene-Co,N-Linked Multi(porphyrin)s by the Addition of Free-Base Porphyrins to a C(2)H(2) Complex of Cobalt(III) Porphyrin and Their Oxidative Rearrangement to Vinylene-N,N'-Linked Multi(porphyrin)s

The nucleophilic addition reaction of a pyrrole nitrogen of free-base porphyrins to a pi-complexed acetylene ligand in a cationic Co(III) porphyrin intermediate afforded good yields of vinylene-Co,N'-linked bis(porphyrin)s, (Por)Co(III)-CH=CH-(N-Por)H(2). N-substituted porphyrin free bases are N-vinylated regioselectively at the pyrrole adjacent to the original N-substituted pyrrole in this reaction. Tris- and tetrakis(porphyrin)s have been prepared by reacting a vinylene-N,N'-linked bis(meso-tetraarylporphyrin) with (OEP)Co(III)(H(2)O)(2)ClO(4) (OEP: octaethylporphyrin dianion) and acetylene. The tetrakis(porphyrin) proved to be a 1:1 mixture of C(i)()- and C(2)-symmetric regioisomers. These organometallic Co(III) complexes underwent facile oxidative migration of the Co-bound vinyl group to a porphyrin pyrrole nitrogen when treated with Fe(III) salts or HClO(4) to provide moderate to good yields of Co(II) vinylene-N,N'-linked multi(porphyrin) complexes. (Vinylene-N,N')bis(porphyrin) free bases with combinations of different porphyrins have been obtained by this procedure. The homobinuclear (2Co(II), 2Cu(II), and 2Zn(II)) and heterobinuclear (Co(II)Cu(II) and Co(II)Zn(II)) complexes have been prepared and characterized spectroscopically. The single-crystal X-ray analysis of (CH=CH-N,N')[(OEP)Co(II)Cl][(TPP)Zn(II)Cl] (TPP: meso-tetraphenylporphyrin dianion) showed a face-to-face structure with an average inter-ring separation of 4.39 ? (triclinic P&onemacr;; Z = 2; a = 14.806(4), b = 18.703(10), c = 13.796(3) ?, alpha = 97.69(3), beta = 99.57(2), gamma = 96.74(3) degrees ).     

Synthesis and binding properties of a noncovalent molecularly imprinted testosterone-specific polymer

In this study, molecular imprinting was used to develop a method based on noncovalent interactions for synthesis of a testosterone-specific polymer. The effect of the different template–monomer ratios, the particle sizes of polymers, and chromatographic mobile phases on steroid–polymer interactions are discussed. The polymer obtained was found to interact specifically with testosterone, while other steroids under study were eluted close to the void volume in the HPLC experiments. Batch rebinding studies in acetonitrile were undertaken to quantitatively evaluate the affinity of the polymer for testosterone. During this experiment, the testosterone concentration was measured in two ways: spectrophotometrically and by HPLC on a column with testosterone-specific imprinted polymer synthesized by us. Both methods resulted in similar values of association constants and the number of binding sites. However, the second method has obvious advantages when the analyzed solution contains a mixture of optically dense compounds. The results obtained focus on the two-point binding nature of the imprinted polymer–testosterone interaction and the significant role of hydrogen bonds between the OH group of testosterone and carboxy group of methacrylic acid residues inside specific recognition sites of the imprinted polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1725–1732, 1998