Tatsuo Higashiyama

“Armed thia-crown ether”: a specific carrier for soft metal cation

Abstract Macrocyclic polythiaether having two ligating “arms” for soft metal cations showed new and specific transport ability for Ag + ion, based on cooperative actions of parent thia-crown ring and side arms.

Specific Ag+ ion binding and transport properties of ‘tripod’ type open-chain cryptands

Tripod-type host molecules have shown new and characteristic cation binding and transport properties especially for Ag+ ion; they have a flexible open-chain skeleton as well as cryptand-like geometry. 1H N.m.r. and binding studies have shown that the Ag+ ion is completely enveloped by the tripod molecule and, in consequence, barely exchanged with K+ and other alkali-metal cations. Such three-dimensional complexation, although similar to that of related double armed crown ethers and cryptands, because of its flexible nature, offers unique and specific transport of Ag+ ion.

Cation-binding properties of new armed macrocyclic host molecules and their applications to phase-transfer reactions and cation membrane transport

A new series of armed macrocyclic host molecules was prepared; the macrocycles were characterized by parent macrocyclic ligands and cation-ligating donor arms. Their cation-binding properties were significantly controlled by co-ordination characteristics of their parent macro-ring and donor side-arms, and chemical modifications of their basic structures provided interesting chemical functions. For example, a furan-bearing double armed crown ether showed high catalytic activity in some phase-transfer reactions; a multi-armed cyclam containing furan-oxygen atoms discriminated NH4+ion from K+ and other related cations effectively. Such chemical functions of these armed macrocycles were not attained with common crown ethers and cryptands. Hence, further variations of ligand structures may lead to a new series of host molecules showing unique and important chemical functions.

Lipophilic polyamine and polyamide macrocycles for membrane transport of amino acid esters and related cations

A variety of polyamine and polyamide macrocycles have been shown to be new and excellent cation-carriers for the transport of amino acid ester salts. Their transport properties were largely different from those of common polyether macrocycles, and essentially controlled by factors such as the natures of donor sites incorporated, ring sizes of macrocyclic systems, and hydrophobicities of co-transported anions. By appropriate choice of these factors, selective transport of various amino acid derivatives was successfully realized.

1H NMR Studies on Cationic Motions in Solid tert-Butylammonium Hexachlorostannate (IV)

Abstract The temperature dependences of the 1H spin-lattice relaxation time (T1) and the second moment (M2) of NMR absorptions were measured for anhydrous tert-butylammonium hexachlorostannate(IV) and its partially deuterated analogs [(CD3)3CNH3]2SnCl6 and [(CH3)3CND3]2SnCl6. Three kinds of cationic motions were revealed: the reorientations of the CH3 group about their C - C bonds, the NH+3 group about its C - N bond, and the tert-butyl group about the C - N bond. Their motional parameters were determined. Among the three motions, the NH+3 motion occurs at the lowest temperature with quite a small activation energy (9.9-10.0 kJ mol-1 ) .

Biomimetic transport of unusual metal cations and amino acid ester salts mediated by monensin and lasalocid A

The biological ionophores monensin and lasalocid A mediate transport of unnatural guest cations such as amino acid ester salts, and heavy metal and transition metal cations across a liquid membrane.

New "Open-Chain Cryptands" with Specific Ion Transport Abilities

A new family of macrocyclic polyethers and polyamines having pendant “arms” available for cation binding were prepared and examined as synthetic ion carriers. They offered characteristic cation transport phenomena, based on their unique ligand topology. By appropriate choice of parent macgocyclic ligand and pendant donor group, specific transport of K+, Ba2+, Pb2+, and NH4 + cations was realized.