Silver Ion Selective Electrode Based on Calix[4]arene Methyl Ketonic Derivative

Abstract

Calixarene has been studied as a selective complexing reagent for various metal ions and organic compounds to apply for separations and analyses. Calix [4]arene is well-known to be capable of taking several conformations, 1 among those conformations, cone conformation makes possible the selective complexation with specific metal ions due to its rigid steric molecular structure and preorganized coordination structure to form the metal complex.In our previous works, various functional groups have been introduced onto phenolic hydroxyl groups on the lower rim of calix [4]arene (focused to the cone conformation), and extractive separation characteristics have been examined. [2][3][4][5][6][7][8][9][10][11][12][13] In general, according to HSAB theory, ionophores having nitrogen or sulfur atoms in a molecule are favorable to complexation with soft heavy metal ions. For the sensing materials of silver ion-selective electrode, most works have been carried out on acyclic and cyclic poly ethers containing nitrogen and/or sulfur atoms, such as thia crown ethers and cryptands, with all or some oxygen atoms in poly ether bridge substituted by sulfur and/or nitrogen. 14-22 These compounds were employed as an ion-recognizable element of the silver ionselective electrode by the affinity of donor atom to silver ion as well as by a size effect of the cavity to each molecule during complexation. However, the ionophore having nitrogen atom as the coordination site tends to suffer from undesirable pH effects due to the interaction with hydrogen ion. Also, the compounds having sulfur atom as coordination site experience the lowering of silver ion selectivity against interfering ions due to the strong affinity of sulfur to soft metal ions. From our solvent extraction study, it was already revealed that 25,26,27,28-tetrakis (acetomethoxy)-5,11,17,23-tetrakis(1,1,3,3-tetramethylbutyl)-calix[4]arene (abbreviated to 1) has high selectivity for silver ion. Furthermore, such silver ion selectivity was maintained even in the highly acidic concentration region. 5 Basically, extractants containing nitrogen and sulfur atom as the binding sites have selectivity for multivalent metal ions among noble metal ions, such as palladium and gold. The development of the ionophore 1 as a solvent extraction reagent for silver ion was based on the strategy that the combination of both weak binding factors, fitting cavity size for silver ion and the coordination of hard and neutral carbonyl groups. The strategic aim was achieved and selectivity was brought to more preferable monovalent silver ion from multivalent hard and soft metal ions by a solvation extraction mechanism. However, from the viewpoint of solvent extraction technique, it is difficult to apply to commercial scale employment due to poor solubility of calixarene derivatives into organic solvents. That is the reason why we apply it as the ionophore for ion selective electrodes.Most research projects concerned with ion selective electrode using calixarene derivatives have been addressed to alkal...

Silver electrowinning from silver(I)–calixarene complexes by two-phase electrolysis

“…The application of two-phase electrolysis in the electrochemical synthesis of organic substances has been shown as an attractive method having several technological advantages [11,12]. Some calixarenes have been studied not only for the electrochemical determination of barium(II) [13], calcium(II) [14] but also silver(I) [15] and other metal species [16]; this encouraged the authors to investigate the electrochemical stripping of silver(I) bonded to calixarene in an organic phase.…”

Supramolecular Based Membrane Sensors

“…Shinohara et al, reported silver ion selective electrode based on calix[4]arene methyl ketonic derivative [62]. Seon Mook Lim et al, reported calix[2]furano[2]pyrrole and related compounds as the neutral carrier in silver ion-selective electrode [63].…”

Potentiometric Performance of Silver Ion-Selective Electrodes Based on Tridentate Schiff Base Derivatives

“…The response time (95% of the final signal; T 95 ), which is one of the important factors for ISEs, was shorter then 10 s, when changing the concentration of silver ion from 1.0 × 10 -3 to 1.0 × 10 -2 mol dm -3 . It is known [19][20][21] slope of these derivatives based electrodes is considered to be due to the low solubility to a membrane solvent. It is therefore, expected that the lowering can be improved by introducing a lipophilic substituent into the derivatives.…”