Hidefumi Sakamoto

High stability constants for multivalent metal ion complexes of crown ether derivatives incorporating two spirobenzopyran moieties

The metal ion complexing behavior of diazacrown ether derivatives possessing two spirobenzopyran moieties has been studied under dark conditions. Introduction of two spirobenzopyran moieties into diazacrown ethers resulted in interesting metal ion complexation abilities, along with isomerization of the spirobenzopyran moieties to the corresponding merocyanine form. The extremely high affinity for multivalent metal ions observed is due to an ionic interaction between the two phenolate anions and the multivalent metal ion. This finding is supported by absorption spectral measurements and electrospray ionization mass spectrometry. Stability constants for complex formation with various metal ions in methanol under dark conditions have been determined for the first time using mass spectrometry. It was found that the stability constants for crowned bis(spirobenzopyran) complexes with high charge density metal ions are much greater than those for the parent crown ether rings. Specifically, the La3+complex of the diaza-18-crown-6 derivative carrying two spirobenzopyran moieties possesses an extraordinarily high stability constant of greater than 1011 M−1 in methanol.

Excellent mercury(II) ion selectivefluoroionophore based on a 3,6,12,15-tetrathia-9-azaheptadecane derivativebearing a nitrobenzoxadiazolyl moiety

Selective and drastic fluorescence enhancement for mercury ion was observed in 1,4-dioxane–water (60/40) using a fluoroionophore bearing a nitrobenzoxadiazolyl group linked to a 3,6,12,15-tetrathia-9-azaheptadecane moiety.

Adsorption and concentration of silver ion with polymer-supported polythiazaalkane resins

Novel ion-exchange resins bearing various kinds of polythiazaalkane moiety were prepared by using polystyrene and TOYOPEARL, which is composed of poly(vinyl alcohol), as matrixes. The adsorption of silver ion from aqueous solution was completed within 1 h by TOYOPEARL based resins, while that by polystyrene based resins was not accomplished for 24 h. All resins bearing polythiazaalkane moiety exhibited the selective adsorption for silver ion, and the efficiency of silver ion absorption was primarily governed by the number of sulfur atoms and the structures of polythiazaalkane moieties. The adsorption and the elution behavior of the TOYOPEARL based resin packed into columns for silver ion were examined in the flow system, and the highly selective enrichment of silver ion was observed using the resin with monothiazaalkane.

Evaluation of photoinduced changes in stability constants for metal-ion complexes of crowned spirobenzopyran derivatives by electrospray ionization mass spectrometry

The photoinduced changes of metal-ion complexing ability of crowned spirobenzopyran derivatives were studied by using electrospray ionization mass spectrometry (ESI-MS). Stability constants for the complexation with various metal ions in methanol under visible-irradiation conditions were determined for the first time by ESI-MS. It was found that the stability constants of crowned bis(spirobenzopyran) derivatives with metal ions are decreased dramatically by visible irradiation due to the disappearance of powerful ionic interaction between phenolate anion(s) of the merocyanine form of their spirobenzopyran moiety and a metal ion bound to their crown ether moiety, and the decrease in the stability constants is more pronounced for the multivalent metal-ion complexes. A theoretical consideration was also made to attain reliable values of stability complexes for metal-ion complexes of crown compounds.

Studies on metal-ion complex formation of crown ether derivatives incorporating a photoionizable spirobenzopyran moiety by electrospray ionization mass spectrometry

Metal-ion complexation of crown ether derivatives incorporating one and two spirobenzopyran units was investigated by electrospray ionization mass spectrometry. The crowned spirobenzopyran derivatives exhibited very different metal ion-complexing behavior from their corresponding parent crown ether rings, preferring multivalent to monovalent metal ions owing to the additional ionic interaction with the nitrophenolate anion of the merocyanine moiety. The on-line photochemical reaction for mass spectrometry indicated that the metal ion-complexing ability and ion selectivities of the crowned spirobenzopyrans can be switched photochemically, taking advantage of the difference between the spiropyran and merocyanine isomers.

Acyclic and cyclic polythiamonoaza- and polythiadiaza-alkane hydrazone derivatives as chromogenic extractants for silver ion

Acyclic and cyclic dithiaza-, tetrathiaza- and tetrathiadiazaalkane derivatives bearing 6-trifluoromethyl-2,4-dinitrophenylhydrazono moieties as chromogenic groups on the nitrogen atoms of the alkanes were synthesized and used as extractants for some class ab and b metal ions in liquid–liquid extraction. The extraction behavior was estimated by using the spectral change in the organic phase containing the chromoionophore. All of these compounds exhibited high Ag+ selectivity relative to other class ab and b metal ions, which are soft Lewis acids, even against Hg2+. In the extraction of silver nitrate from aqueous acidic and basic phases, interestingly, the absorption maxima of the organic phases containing the chromoionophores in the visible absorption region shifted to shorter and longer wavelengths, respectively. Among the chromoionophores used here, the acyclic tetrathiazaalkane hydrazone 4b extracted Ag+ most effectively from an aqueous phase into a 1,2-dichloroethane phase under all the extraction conditions studied. A linear calibration graph up to 5.5 × 10–5 mol dm–3 Ag+ in the aqueous neutral phase was obtained spectrophotometrically by using the acyclic tetrathiazaalkane hydrazone 4b and the determination of Ag+ in a silver solder sample was achieved from the calibration graph.

Highly Silver Ion-selective Transport Through Liquid Membranes Containing Cyclic and Acyclic Polythiamonoazaalkanes Bearing an Easily Ionizable Moiety

Liquid membranes containing cyclic and acyclic tetrathiazaalkanes bearing a hydrazone moiety as a proton-dissociable group exhibited effective uphill silver ion transport behavior in the proton-driven cation transport. Excellent silver ion selectivities relative to other class ab and class b metal ions were observed for these membranes when citric acid was used for adjusting pH and for preventing hydrolysis of several metal ions in the source phase. Complete recovery of silver ion from a silver solder sample was selectively achieved using the liquid membrane containing acyclic tetrathiazaalkane hydrazone.

Flow injection of lithium ion using chromogenic 14-crown-4 derivatives as extraction-spectrophotometric reagents

A system for flow injection of Li+ has been designed, with use of proton-dissociable chromogenic 14-crown-4 derivatives as the extraction-spectrophotometric reagents, and the analytical conditions have been optimised. This flow injection system showed high selectivity for Li+ reflecting the cation-complexing property of the chromogenic crown ethers. The determination of Li+ in the clinical range in blood under a high Na+ background of 130-160 mM was feasible, with a small sample size (50 microliters) and high sampling rate (more than 100 injections per hour), with this method. The proposed extraction-spectrophotometric flow injection system was, therefore, found to be promising for the efficient determination of Li+ in biological samples, such as blood sera, with a high Na+ background.

Synthesis and cation-extraction study of chromogenic 14-crown-4 derivatives for spectrophotometric determination of lithium

Three kinds of proton-dissociable chromogenic 14-crown-4 ethers have been synthesized, all of which possess a dinitrophenol chromophore. Proton-dissociation behavior of the chromogenic crown ethers in aqueous 1,4-dioxane (1/1), and extraction equilibria between the 1,2-dichloroethane solution containing the chromogenic crown ether and aqueous solutions of alkali-metal ions have been investigated spectrophotometrically. An excellent lithium-ion-selective chromogenic 14-crown-4 derivative was obtained by introducing a bulky decalino subunit and dinitrophenol chromophore, which has small pKa value, into the ethano-bridge section of the 14-crown-4 ring.

Proton-driven cation transport through polyamic acid membranes incorporating crown ether moiety

Abstract Proton-driven cation transport against cation concentration gradient has been investigated using films of polyamic acid 18-crown-6 (1) and polyamide 18-crown-6 (3)/polyamic acid (5) mixtures as the polymeric membrane. Both membrane systems containing the crown ethers were found to act as efficient alkali metal ion pumps. The ion-transportability of the polyamic acid 18-crown-6 membrane decreased in the order K+ > Cs+ > Na+ > Li+, which is reflected in the cation-complexing ability of the 18-crown-6 moiety. The transport selectivity, however, was varied remarkably by the combined use of polyvinylpyrrolidone with (1) and, therefore, by the resulting increase in hydrophilicity of the membrane. The ion-selectivity in the transport through mixed membranes of (3) and (5) was also dependent on the membrane composition. For the proton-driven cation transport two mechanisms are proposed; in one of the transport mechanisms, the carboxylic group cooperates with the crown ether moiety and in the other the carboxylic group participates independently.