Ryosuke Machida

Further studies on superoxide dismutase activities of macrocyclic polyamine complexes of copper(II)

The superoxide dismutase (EC 1.15.1.1) activities of new series of macrocyclic complexes with copper(II) have been measured. Chemical modifications in macrocyclic ring size, donor atom, donor atom number, substituents on the macrocyclic skeletons, and length of bridges linking two macrocycles are shown to have profound effects on the superoxide dismutase activities of the metal complexes. The quantitative measurement by the standard xanthine-xanthine oxidase assay, which depends on the conversion of nitroblue tetrazolium to formazan, has been corroborated by a direct assay method using an oxygen electrode.

A new platinum(II)–dioxocyclam complex and its application to selective extraction of ptII from aqueous metal ion mixtures

Selective extraction of platinum(II) is achieved by utilizing unique complexation properties of macrocyclic dioxotetra-amine (1) specific for PtII at low pH in the presence of Na2S2O3.

A proton-driven copper(II) ion pump with a macrocyclic dioxotetra-amine. A new type of carrier for solvent extraction of copper

The macrocyclic dioxotetra-amine (2) acts as a carrier for the membrane transport of copper(II) ions against the concentration gradient by the coupled counter-transport of protons and is potentially useful for solvent extraction of copper.

A mono-ozygenase model for selective aromatic hydroxylation with nickel(II)-macrocyclic polyamines

In a new model reaction for biological mono-oxygenases, a 17O atom from 17O2 is directly incorporated into an aromatic ring as an hydroxy group via the novel 1:1 Ni–O2complexes (2) formally existing as Ni3+–O2–.

Metal chelates of sulphur-containing polyamine macrocycles and oxygenation of the corresponding cobalt(II) complexes

The protonation and complex formation of macrocyclic polyamines containing a sulphur donor atom, 1-thia-4,7,10-triazacyclododecane (L4) and 1-thia-4,7,11,14-tetra-azacyclohexadecane (L5), have been investigated with the metal ions CoII, NiII, CuII, HgII, and FeII. The equilibrium and kinetic constants for formation of the dioxygen adducts of the cobalt(II) chelates in aqueous solutions are also reported, and compared with previous data for the analogous macrocycles containing nitrogen, oxygen, and pyridine instead of sulphur. The values of log KML for the macrocyclic polyamines follow the trend N > S > O. Oxygenation of the cobalt(II) complexes of L4 and L5 yields µ-peroxo-adducts as with the nitrogen and oxygen analogues, and the O2-affinity order is N S > O.

Co-ordination of a 16-membered dioxopenta-amine macrocycle to high-spin nickel(II). X-Ray study of structural requirements for a mono-oxygenase model

X-Ray crystal structure analysis of the nickel(II) 16-membered dioxopenta-amine macrocyclic complex (1) reveals that the constrained ligand configuration and the possible electron-sink properties of the deprotonated amide donors could be favourable for its interaction with O2.