Mikio Ouchi

Remarkable thallium(I) selectivity for ion sensors based on π-coordination of calix[4]arene neutral carriers

Calix[4]arene derivatives have been applied as neutral carriers for thallium(I)-selective electrodes, taking advantage of their π-coordination. Calix[4]arene derivatives without any t-butyl group at the upper rim, such as calix[4]arene tetra(propyl ether) and tetra(allyl ether), provided the thallium(I)-selective electrodes with high sensitivity and ion selectivity. t-Butylcalix[4]arene derivatives employed here did not afford very good results as for the thallium(I) neutral carrier. 1H-NMR spectroscopy indicated that thallium(I) complexation by the calixarene neutral carriers is made primarily by π-coordination of their skeletal aromatic rings. The ion-selective electrode based on calix[4]arene tetra(propyl ether) was successfully applied to thallium(I) assays in human urine.

Cation binding by thallium(I) selective crown ethers

Abstract The cation-binding abilities of crown ethers for thallium(I) ion are described. Unsubstituted symmetrical and unsymmetrical crown-5 and crown-6 ethers usually possess high thallium(I) ion binding ability; however, its selectivity against alkali metal ions is not so high. Unsymmetrical benzo-type crown ethers possess high thallium(I) ion selectivity especially against potassium and rubidium ions. This review deals with the cation-binding ability/selectivity for thallium(I) ion against alkali metal ions evaluated from the solvent extraction of metal picrates and PVC membrane thallium(I) ion-selective electrodes based on crown ethers.

Silver and thallium(I) complexation with dibenzo-16-crown-4

Dibenzo-16-crown-4 (1) indicates high silver and thallium(I) ion selectivity over sodium, potassium, and rubidium ion evaluated from the solvent extraction of metal picrates, while its cation-binding ability is lower than those of dibenzo-18-crown-6 (2) and dibenzo-22-crown-6 (3). Taking account of the highest thallium(I) ion selectivity for 1 obtained from extraction experiments, PVC membrane thallium(I)-selective electrodes based on 1 are prepared. The electrode shows the best potentiometric selectivity coefficients for thallium(I) over potassium and rubidium than those of 2 and 3, and commercially available bis(crown ether)s (4).

Synthesis and properties of a new ethyne-linked donor/acceptor pentamer

Abstract A new alternating π-donor/π-acceptor pentamer with ethyne linkage was synthesized by a bi-directional method using Sonogashira reactions. The pentamer showed small HOMO–LUMO gap compared with other π-conjugated oligomers.

Sodium ion selective electrodes based on lipophilic 16-crown-5-derivatives

Abstract Six kinds of lipopholic 16-crown-5 derivatives possessing double side-chains were synthesized. The Na+-selectivities were examined with poly(vinyl chloride) (PVC) matrix-membrane electrodes using these crown compounds. It is an effective way for obtaining high Na+-selectivity by introducing a bulky side-chain such as a benzyloxymethyl group into the 16-crown-5. The electrodes based on 16-crown-5 derivatives having both a methyl or ethyl group and a benzyloxymethyl group at the pivot carbon (C-15) (3 or 4, see Figure 1) exhibited excellent Na+-selectivity over K+ (log k Na.x = -2.65 and -2.75 for 3 and 4, respectively).

Extraction of sodium and potassium picrates with 15-(2,5-dioxahexyl)-15-methyl-16-crown-5 (lariat 16C5) into various organic solvents. Elucidation of fundamental equilibria which determine the extraction ability for Na(+) and K(+) and the selectivity.

To quantitatively elucidate the effects of the side chains and diluents on the extraction selectivity for sodium and potassium picrates of 15-(2,5-dioxahexyl)-15-methyl-16-crown-5 (L16C5) from the viewpoint of equilibrium, the constants for the overall extraction (K(ex)), the partition for various diluents of low dielectric constants (K(D,MLA)), and the aqueous ion-pair formation (K(MLA)) of L16C5-sodium and -potassium picrate 1:1:1 complexes were determined at 25 degrees C; the distribution constants of L16C5 were also measured at 25 degrees C. The log K(MLA) values for Na(+) and K(+) are 2.74+/-0.29 and 1.70+/-0.36, respectively. In going from 16-crown-5 (16C5) to L16C5, the side chains decrease the K(MLA) value, but do not increase the difference in K(MLA) between Na(+) and K(+). The distribution behavior of L16C5 and its 1:1:1 complexes with the alkali metal picrates closely obeys regular solution theory, except for chloroform. Molar volumes and solubility parameters of L16C5 and the 1:1:1 complexes were determined. The magnitude of K(ex) is mainly governed by the K(M(L16C5)A) value. For every diluent, L16C5 shows Na(+) extraction selectivity over K(+). The Na(+) extraction selectivity of L16C5 is determined completely by K(M(L16C5)A). The extraction ability and selectivity for sodium and potassium picrates by L16C5 are compared with those of 16C5 on the basis of the fundamental equilibrium constants.

Measurement and correlation of solubilities of oxygen in aqueous solutions containing galactose and fructose

Abstract The solubilities of oxygen in aqueous solutions containing galactose and fructose were measured by a saturation method. These sugars are usually included in the fermentation media. The measurements were carried out at 298.15, 303.15 and 310.15 K, as these temperatures are close to the fermentation conditions. The extended scaled-particle theory proposed by Hu et al. (1985), of which flexibility for correlation of gas solubilities was exhibited, was used to correlate the solubilities of oxygen in the solutions measured in this work. By determining the potential parameters for sugars, good correlation results were obtained.

Complexation of cobalt(II) perchlorate with crown ethers. Synthesis, properties and structure of complexes of cobalt(II) perchlorate with 16-crown-5 and its lariat derivatives

Complexes of cobalt(II) perchlorate with 16-crown-5 (L1) and its two lariat derivatives, 15,15-dimethyl-16-crown-5 (L2) and 15-(2,5-dioxahexyl)-15-methyl-16-crown-5 (L3), have been prepared and characterized. The crystal structure of [Co(L3)H2O)](ClO4)_2 has been determined by X-ray crystallography. The cobalt(II) ion is heptacoordinated with five crown ether oxygen atoms at the equatorial plane, a side arm oxygen atom and a water molecule at the apical position. The coordination polyhedron of cobalt is a distorted pentagonal bipyramid with the average Co-O(crown) distance of 2.20(2)Å.

Complexation thermodynamics of crown ethers. Part 4. Ring-enlargement effects upon cation complexation with dibenzo-18 to dibenzo-22-crown-6

Abstract Calorimetric titrations have been performed in methanol and acetonitrile at 25°C to give the complex stability constants (K) and the thermodynamic parameters for the complexation of sodium thiocyanate and potassium thiocyanate with the dibenzo-crown ethers: 2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca-2,11-diene (dibenzo-18-crown-6) (1); 2,3,12,13-dibenzo-1,4,7,10,15,18-hexaoxacycloeicosa-2,12-diene(dibenzo-20-crown-6) (2); 2,3,12,13-dibenzo-1,5,8,11,15,18-hexaoxacycloeicosa-2,12-diene) (dibenzo-20-crown-6) (3); and 3,4,14,15-dibenzo-1,6,9,12,17,20-hexaoxacyclodocosa-3,14-diene) (dibenzo-22-crown-6) (4). Data analyses assuming 1:1 stoichiometry were successfully applied to all of the crown ether-cation combinations employed. The complex stability constants, reaction enthalpies and entropies were calculated directly by using a calorimeter connected to a CA-033 microcomputer. The thermodynamic parameters obtained and the examination of CPK molecular models reveal that the less-symmetrical arrangement of donor oxygen is induced by increasing methylene in the dibenzo-18-crown-6 molecule and leads to an unfavorable conformation for complexation compared with the parent crown ether. The complex stability constants are lower than those of dibenzo-18-crown-6 (1) for the ligands (2)–(4) with Na + and K + , but the relative cation selectivity for K + Na + is increased respectively. The effects of the molecular structure of crown ether and the cation diameter, and of solvent upon complex stability are discussed from a viewpoint of thermodynamics.

Synthesis of 2-(substituted methyl)quinolin-8-ols and their complexation with Sn(II)

A new method for the synthesis of 2-(substituted methyl)quinolin-8-ol is described. 2-Methyl-8-methoxyquinoline 3 was prepared as a key building block; lithiation of 3 with LDA and subsequent addition of alkyl halides followed by reaction in 48% HBr afforded the 2-alkylquinolin-8-ols 6a,b. On the other hand, the use of alkanediyl dihalides as the electrophile gave bis(quinolin-8-ol) derivatives containing an alkyl bridge 12. The complexation of 2-alkyl-8-hydroxyquinolines with SnCl2 in alkaline methanol produced the bis(quinolin-8-ol) complexes 13a,b, whereas in the case of the bis(quinolin-8-ol) derivatives, intractable solids were obtained. The molecular structure of 13b was elucidated by X-ray analysis.