Koji Kubono

A high output low-pressure mercury lamp, 400 W L-Hg, was successfully used for the photolytic decomposition of dissolved oganic compounds as the pretreatment for the determination of trace metal ion in aqueous solution by stripping voltammetry. Various amino acids, showing interferences on voltammetric determination of metal ions, can be removed quite easily by intensive UV irradiation at room temperature. Effect of pH concentration of electrolyte and dissolved oxygen on the efficiency of photolysis are also described. This method uses no additional chemicals such as acids or oxidants and can be carried out in closed clean conditions.

Complexation equilibrium between iron(III) and N,N'-bis(2-hydroxyphenylmethyl)-N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine(H(2)bbpen), a colorless hydrophobic divalent hexadentate ligand, and potential use of the ligand far the spectrophotometric determination of iron(III) in aqueous solution was investigated. In the pH range 2.0 - 3.0, Fe(II) forms stable 1:1 complex with H(2)bbpen, and Fe(III) can be determined selectively as the purple Fe(bbpen)(+) complex (lambda(max) = 560 nm, epsilon = 4.3 x 10(3) dm(3) mol(-1) cm(-1), log beta(1) = 32.6 +/- 0.1). In this system, linear calibration range of Fe(III) was 5 x 10(-6) - 2 x 10(-4) mol dm(-3) (0.3 - 12 mu g cm(-3)) and detection limit was 3 x 10(-6) mol dm(-3) (0.2 mu g cm(-3)). Furthermore, most of foreign metal cations did not influence largely the determination of Fe(III).

For the selective extraction of trivalent lanthanides, the use of quadridentate divalent phenolic Schiff bases, such as N,N'-bis(5-nitrosalicilidene)ethylenediamine (H(2)Nsalen) and N,N'-bis(5-nitrosalicilidene)-o-phenylenediamine (H(2)Nsaloph), was investigated, Lanthanides made anionic 1:2 complexes with these ligands and could be extracted into nitrobenzene as ion-pairs with a suitable monovalent countercation in the aqueous phase, after which the ion-pair was dissociated almost perfectly. Although the order of the extractability of lanthanides between these ligands was H(2)Nsaloph > H(2)Nsalen, the mutual selectivity of them in the H(2)Nsalen system was higher than that in H(2)Nsaloph, Furthermore, with decreasing the size of the countercation, the mutual selectivity was enhanced although the extractability was lowered. A H(2)Nsalen-KCl extraction system, selected as an example, showed selectivity between lanthanides comparable with those of the better of other systems reported previously.

For the fundamental study on the development of novel extractants, extraction behavior of divalent first row transition metals such as manganese, nickel, copper and zinc was studied with using N,N'-bis(2-hydroxyphenylmethyl)-N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine (H(2)bbpen) and its derivatives as extractants. From the numerical analysis of the intricate extraction behavior of the metals, it was found that they were extracted into chloroform nor only as uncharged chelate complexes but also as ion-pairs of charged complexes with a counter anion in aqueous solution. In other words, these ligands seemed to act not only as divalent hexadentate extractants but also as monovalent tri-or tetra dentate ligands, forming positively charged complexes. Furthermore, the order of the extractabilities between the metals did not coincide with the Irving-Williams series of stability because of the 'cavity size' in the ligands and the structural rigidity of them. (C) 1997 Elsevier Science B.V.

The use of N,N,N',N-tetrakis(1'-pyrazolylmethyl)-1,2-diaminoethane (tpzen), N,N,N',N-tetrakis(3',5'-dimethypyrazol-1'-ylmethyl)-1,2-diaminoethane (Me(8)tpzen) and N,N,W,N'-tetrakis(2'-pyridylmethyl)-1,2-diaminoethane (tpen) as complexation reagents for ion-pair extraction of metal(II) cations into nitrobenzene was investigated. The order of extractability of the metals was tpen much greater than Me(8)tpzen > tpen. Although these molecules have four nitrogen-containing heterocyclic pendant arms and act as sexadentate ligands normally in aqueous solution, the result of numerical analysis concerning the extraction behavior indicated that they act as bidentate ligands in the extraction system. The pendant arms were not concerned in chelate formation and the arms acted to raise the hydrophobicity and the extractability of the complexes.

The polynuclear complexation of divalent 3d transition metal cations with N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine (tpen) in aqueous solution was investigated. It pas found that copper(II) forms a dinuclear complex with tpen in an aqueous solution containing chloride. The composition of the complex was determined as Cu2Cl2(tpen)(2+). Furthermore, the stability constant of the complex was determined and its structure was postulated to be (mu-Cl)(2).

The intensity of an ESR signal assigned to oxygen species or lattice defects was increased by photo-irradiation in Nb-doped TiO2. The excess electron was generated in the process of the formation of O- species or lattice defects on the surface layer of the sample. On the other hand, the rise of electric current appeared on the Nb-doped TiO2 by photo-irradiation. This behavior suggests that the generated electron by photo-irradiation is closely correlated to the rise of the current. The niobium-doped TiO2 was found to have the performance of oxygen-sensing. The oxygen-sensing under photo-irradiation was related to the paramagnetic behavior of oxygen introduced. In addition, NO-sensing was also observed for the Nb-doped TiO2. The function for oxygen-sensing was improved by a heat-treatment for the sample of Nb complex-doped TiO2.

Abstract Thin films of SiPc(OH)₂ (Pc = phthalocyanine) were formed epitaxially on the (001) surface of mica by vacuum deposition and were then polymerized by heat treatment. The molecular packing of the SiPc(OH)₂ was determined by electron diffraction and high‐resolution electron microscopy as triclinic\documentclass{article}\pagestyle{empty}\begin{document}${\rm P\bar 1} $\end{document} having dimensions a = 0.727, b = 1.307, c = 0.688 nm, α = 102.5, β = 104.2, and γ = 97.4°. This monomer crystal grows with its c‐axis parallel to the a‐axis of the substrate mica and its bc‐plane parallel to the (001) surface of mica. By heat treatment at 320°C, the SiPc(OH)₂ polymerized with the c‐axis of the polymer parallel to the c‐axis of the monomer. At 420°C, the c‐axis of the polymer became parallel to the a*‐axis of the monomer (i.e., perpendicular to the film surface). From high‐resolution electron microscopy of partially polymerized specimens, the polymerization was shown to start at the edges of small monomer crystals. This may be considered to be due to the volume expansion during the polymerization. © 1993 John Wiley & Sons, Inc.