Noriyoshi Kon

Inclusion behavior of water-soluble thiacalix- and calix[4]arenes towards substituted benzenes in aqueous solution

Inclusion abilities of thiacalix- and calix[4]arenetetrasulfonate (3 and 4) towards mono-substituted benzenes were investigated in neutral aqueous solution. In general, the hosts regioselectively encapsulated the guests from the aromatic moiety except the complexation of toluene by 4, in which the guest penetrated from either the aromatic or the methyl group. Stabilities of the inclusion complexes increased with the electron-withdrawing ability of the substituent on the guest, suggesting pi-pi electronic interaction between the host and guest. In spite of the lower electron density of the aromatic ring, thiacalix[4]arene 3 showed higher inclusion ability than calix[4]arene 4, suggesting that the size rather than the electron density of the calix framework is a more important factor in determining the inclusion ability.

Synthesis of p-tert-butylthiacalix[n]arenes (n=4, 6, and 8) from a sulfur-bridged acyclic dimer of p-tert-butylphenol

The one-step method for the synthesis of p-tert -butylthiacalix[ n ]arenes TCnA s ( n =4 and 6) by reacting p-tert -butylphenol 1 with elemental sulfur in the presence of a base was advantageously replaced by a two-step procedure in which a sulfur-bridged linear dimer of 1 was prepared first to use as the starting material for the cyclo-condensation with sulfur to greatly improve the yields of TC4A (83%) and TC6A (5.3%). The present dimer method allowed the isolation of TC8A in an appreciable amount (4.3%) for the first time.

A POTASSIUM COMPLEX OF A FLUORINE-CONTAINING MACROCYCLIC CAGE COMPOUND : INTERACTIONS BETWEEN FLUORINE ATOMS AND METAL IONS

A new donor, the C-F unit, can be added to the field of host-guest chemistry. The interaction between fluorine atoms and a potassium ion was proven with the fluorine-containing cage compound 1 as a host. The six fluorine atoms of K+ ⊂1 are coordinated to K+ in a distorted octahedral fashion.

The C-F...cation interaction: an ammonium complex of a hexafluoro macrocyclic cage compound.

An ammonium complex of the hexafluoro cage compound 1 was isolated and its structure was elucidated by X-ray crystallographic analysis. The C-F bonds are elongated by the complexation, which is clear evidence of C-F...cation interaction. The driving force of NH4(+) inclusion is the C-F cation interaction, but the C-F...HN+ hydrogen bond does not contribute to this complexation. The crystal structure of the NH4+ complex 1 shows short C-F...HN+ contacts (2.286-2.662 A). Furthermore, it shows that closer F...H(+)(-N) distances give a larger F...H(+)-N angle. Although such structural features seem to indicate the existence of C-F...HN+ hydrogen bonds, the spectral data (1H NMR, 19F VT-NMR, and IR spectroscopy) did not support the existence of hydrogen bonds. Thermodynamic parameters, log K(s) (4.6 +/- 0.1, 298 K), deltaH (-5.3 +/- 0.1 kcal mol(-1)), and deltaS (3.2 +/- 0.3 cal mol(-1) K(-1)), of the complexation were obtained in CDCl3/CD3CN mixture.

Structurally isomeric two pyridino macrocycles: complexation and structures

Abstract Pyridine-based, structurally isomeric two macrocyclic compounds displayed a remarkably different complexation nature. The cage-type compound has an ideal structure for spherical cations, especially for the NH4+ ion, but the reaction with some transition metals and Ln3+ produced its protonated species. On the other hand, its isomer formed complexes with alkali metals and lanthanides (1:1) and also with transition metals. Some structures of the complexes were clarified by crystallographic analyses.

A PYRIDINE CAGE AS A BIRECEPTOR : INCLUSION OF CATIONS AND ANIONS

The bireceptor molecule 1 was synthesized in an one-step procedure. It binds cations under neutral conditions and anions in acidic media. The structure of K+ ⊂ 1 was clarified by X-ray crystallographic analysis.

CF···cation interactions: alkali metal complexes of hexafluoro cage compound

Abstract The covalently bonded fluorine atom acts as a donor towards alkali metal cations. The CF···M + interaction was proved by a complexation study between a hexafluoro cage compound and the alkali metal cations. The thermodynamic parameters of the complexation were estimated based on NMR spectroscopy. A 19 F 133 Cs spin coupling was observed at low temperatures in the 19 F NMR of the Cs + complex.

Stable Cu + , Ag + complexes of aza-bridged macrocyclic molecules: structure and chemical properties

The cage type compounds 1 and 2 form stable Cu+ or Ag+ complexes, which have been employed for the preparation of cation-free host molecules.A reaction between the potassium complex K+⊂1 and a CuII salt generates a CuI complex. The CuII/CuI redox potential is observed at +0.43 V (vs. SCE) in the cyclic voltammetry, which shows that the Cu+ state is stabilized by its rigid molecular skeleton and spatially fixed coordination sites. A reaction between Ag+ and K+⊂2 yields the dinuclear complex 2Ag+⊂2, which has a short Ag+ · · · Ag + distance (2.78 A). The halide anions (Cl-, Br-, I-) remove one Ag+ from 2Ag+⊂2 to give Ag+⊂2, but further demetallation does not occur. CV measurements show that these silver complexes are electrochemically stable. Both silver complexes are stable to sunlight. The first preparations of guest-free hosts have been achieved by treating Cu+⊂1 or 2Ag+⊂2 with CN-. Inclusions of neutral guests (NH3, BH3) have been attempted using these guest-free hosts.

Ein Kaliumkomplex einer fluorhaltigen makrocyclischen Käfigverbindung: Wechselwirkungen zwischen Fluoratomen und Metallionen

Ein neuer Donor fur die Wirt-Gast-Chemie: die C-F-Einheit. Die Wechselwirkungen zwischen Fluoratomen und einem Kaliumion wurden an einem Wirt/Gast-Komplex mit der fluorhaltigen Kafigverbindung 1 als Wirt nachgewiesen. Die sechs Fluoratome in K+⊂1 koordinieren das K+-Ion verzerrt oktaedrisch.

A Cage Compound containing Four Thiophene Rings: Synthesis and Structural Conversion by Desulfurization

A novel macrocyclic cage compound with four thiophene rings was synthesized following a one-step procedure and then structurally converted by disulfurization.