Nobuhiko Iki

Abstract The ability of tetra(p-t-butyl)tetrathiacalix[4]arenetetrol (TCA, H4L), a cyclic tetramer of p-(t-butyl)phenol bridged with four epithio groups, to bind metal ions was investigated via a solvent extraction study. Although tetra(p-t-butyl)calix[4]arenetetrol (CA) has very poor affinity for transition metal ions (M2+), TCA is an excellent extractant of these metal ions. The chemical formulae of the extracted TCA metal complexes were found by slope analysis to be neutral 1 : 1 complexes [M

5,11,17,23-Tetra-tert-butyl-2,8,14,20-tetrathiacalix[4]arene-25,26,27,28-tetrol (TCA) underwent facile tetra-O-alkylation by treatment with ethyl bromoacetate in the presence of an alkali carbonate as base catalyst in DMF or acetone to provide a mixture of conformational isomers (cone, partial cone, and 1,3-alternate) of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-2,8,14,20-tetrathiacalix[4]arene (1), the stereochemistries of which were unambiguously assigned by 1H

Abstract A new water soluble host molecule, thiacalix[4]arenetetrasulfonate(TCAS), was obtained by direct sulfonation of p-tert-butylthiacalix[4]arene. TCAS showed size- and shape-selectivity to bind small chlorinated organic molecules in its hydrophobic cavity by a 1:1 or 1:2 manner in aqueous solution.

New analogues of calix[4]arenetetrasulfonate (1) were prepared, in which the methylene bridges are replaced by S (2) and SO2 (3). The complexation ability of these calixarene ligands 1–3 toward Tb3+ ion and luminescence properties of the resulting complexes were examined. All the ligands formed complexes with lanthanide ions (Pr3+, Sm3+, Eu3+, Tb3+ and Dy3+), among which the Tb3+ complex exhibited strong energy transfer luminescence. The pH dependence of the luminescence intensity suggested that

Abstract Single-crystal X-ray analysis has shown that p-tert-butylthiacalix[4]arene (H4L) binds to Zn2+ ion by bridging sulfur atoms in addition to phenolic oxygen atoms to form [Zn4L(H2L)2].

Abstract Separation of 4-(2-pyridylazo)resorcinol (PAR) and its chelates of CoIII, FeII, NiII, and VV was accomplished within 6 min by simple capillary electrophoresis (CE) with a spectrophotometric detection. The detection limits, defined as 3σ of base-line noise were 1.80 × 10−7 mol dm−3 for CoIII and 1.41 × 10−7 mol dm−3 for NiII chelates, and those on a mass basis were 1.08 fmol (63.6 fg) and 0.84 fmol (49.3 fg) in 6.0 × 10−9 dm3 sample, respectively. A guideline on the ligand design for the

The acid–base properties of sulfur-bridged calixarenes, thiacalix[4]arenetetrasulfonate (4) and its sulfonyl analogue (5), have been investigated via potentio- and spectrophoto-metric studies, comparing them with the conventional methylene-bridged calix[4]arenetetrasulfonate (3). The titration curves revealed the acidity of the phenolic OH groups in the calix[4]arenes 3–5 to be in the order: 3 < 4 ≪ 5. In particular, the oxidation of the bridging sulfur to sulfone strongly enhanced the acidity o