Tohoku University · Materials Science
Professor Nobuhiko Iki's research lab specializes in supramolecular chemistry, focusing on the design and synthesis of macrocyclic receptors such as calixarenes and thiacalixarenes for selective metal ion recognition and binding. The lab investigates the structural and electronic factors governing host-guest interactions, particularly the role of sulfur and oxygen donor atoms in enhancing affinity and selectivity toward transition and lanthanide ions. Key research directions include solvent extraction behavior, luminescent sensing using lanthanide complexes, and the development of water-soluble receptors for environmental and analytical applications.
Figures are computed from collected data and may differ slightly.
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
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