Nobumasa Kitajima

Synthetic Approach to the Structure and Function of Copper Proteins

Publisher Summary Copper is an essential component for living systems, although excess intake causes symptoms, such as Wilsons disease. Numerous copper-containing proteins are now known and can be categorized based on their functions that are as follows: (1) electron-transfer carrier: plastocyanin, azurin, and pseudoazurin, (2) dioxygen carrier: hemocyanin, (3) oxygenation: tyrosinase, dopamine β -hydroxylase, phenylalanine hydroxylase, and peptidylglycine  -amidating monooxygenase, (4) oxidation: galactose oxidase, amine oxidase, and ascorbate oxidase, (5) reduction: nitrite reductase and nitrous reductase, (6) disproportionation: superoxide dismutase, and (7) unknown: stellacyanin, umecyanin, and cucumber basic blue copper protein. Based on the spectroscopic properties, mainly electron paramagnetic resonance (EPR), the active sites of copper proteins have been classified into three groups, types I, II, and III. In this review, new nomenclature is used to classify the copper sites more precisely with respect to their structural features and spectroscopic properties along with their definitions. The synthesis, characterization, and reactivity of low-molecular-weight copper complexes with artificial ligands, designed to mimic structurally the copper sites in proteins, have been a major topic in current bioinorganic chemistry. The unusual spectroscopic properties of type I copper have been particularly fascinating to many inorganic chemists. Hemocyanin (Hc) is a widely occurring oxygen transport protein in invertebrates, arthropods, and mollusks. Hc contains type III copper that binds dioxygen reversibly as peroxide.

A model for methane mono-oxygenase: dioxygen oxidation of alkanes by use of a µ-oxo binuclear iron complex

Adamantane and cyclohexane are oxidised with dioxygen in CH2Cl2 in the presence of acetic acid, Zn powder, and a µ-oxo binuclear iron complex.

The synergism of AlCl3-CuCl2 mixtures in the low-temperature conversion of pentane

Abstract The conversion of pentane has been studied with the mixtures of aluminum chloride and cupric chloride as catalysts at 28–44.5 °C. In vapor-phase conversion the main product is isobutane, while in liquid-phase conversion the main product is isopentane at the early stage of the conversion. The mixture shows its highest activity with a composition of 40% AlCl 3 . The catalytic activities of mixtures of aluminum chloride and other halides have been also examined, and a combination of aluminum chloride and titanium trichloride (AA) has been found most active.

Formation of a µ-η2:η2-disulfide dinuclear copper(II) complex by thermal decomposition of a thiolate complex via C–S bond cleavage

Thermal decomposition of a thiolatocopper(II) complex Cu(SCPh3)(HB(3,5-Pri2pz)3)1 yields a novel µ-η2 : η2-disulfide dinuclear copper(II) complex {Cu[HB(3,5-Pri2pz)3]}2(S2)2 whose crystal structure was determined by X-ray crystallography.

Isomerization of pentane with AlCl3-CuSO4 mixtures

The isomerization of pentane over AlCl3-CuSO4 mixtures was studied in the temperature range of 5–23 °C. The catalytic activity of the mixtures was found to be proportional to the amount of CuSO4 and also to the specific surface area of the CuSO4 used. The reaction did not continue when the solid was removed from the system. Thus, it was concluded that the active species were located on the surface of the CuSO4. Traces of water added to the system have no influence on the reaction. The mixture has a strong acidity with 14.52 < Ho < −13.75. Complex formation between the two components on the CuSO4 surface was suggested.

Transition metal peroxo complexes relevant to metalloproteins

A series of dioxygen complexes of copper, iron, and manganese have been synthesized using bulky tripodal nitrogen ligands, hydrotris(3,5-dialkyl- 1-pyrazolyl)borate, as models for the active sites in the metalloproteins. A binuclear copper peroxo complex having p-q2:

Preparation of a highly dispersed ruthenium catalyst using a ruthenium(0) organometallic complex

coordination mode serves as an accurate model of the active site of oxy-hemocyanin. The reactivities of the complex and related peroxo copper complexes suggested a new radical type reaction mechanism for tyrosinase catalysis. Dioxygen complexes of iron are designed to provide structural and mechanical information for a non-heme oxygen carrier and monooxygenase, hemerythrin and tyrosine hydroxylase. A mononuclear dioxygen complex of manganese represents the first artificial example of hydrogen bond between the peroxide and proton in the ligand and binuclear manganese complexes do the models for the active intermediates of dioxygen evolution sites for PSII.

Oxidations of primary alcohols with a copper(II) complex as a possible galactose oxidase model

A highly dispersed ruthenium catalyst supported on SiO2(particle size, <10 A) is prepared by treatment of the support with (η4-cyclo-octa-1,5-diene)(η6-cyclo-octa-1,3,5-triene)Ru(0) followed by hydrogenolysis.

Two component friedel-crafts catalysts as solid superacids

N,N′-(2-Hydroxy-propane-1,3-diyl)bis(salicylaldiminato)copper(II) was found to be an effective catalyst for the oxidation of ethanol, n-propanol, or hydroxyacetone in the presence of KOH under O2; the X-ray crystal structure shows that the co-ordination geometry of the copper is significantly distorted toward tetrahedral from square planar with two oxygens and two nitrogens from salicyladimine moieties.

Isomerization of Pentane with Aluminum Chloride (Gallium Chloride)-Cupric Salt Complexes

Abstract The kneaded mixture composed of a Friedel-Crafts catalyst and a metal salt has very strong acidity comparable to those of superacids, and shows a remarkable catalytic activity for alkane isomerization at room temperature. The synergism was examined in detail, and Cu(AlCl 4 ) 2 and Cu(GaCl 4 ) 2 , novel ‘solid superacid’ substances, were isolated as the active species formed in AlCl 3 -CuCl 2 and GaCl 3 -CuCl 2 (or -CuSO 4 ) kneaded mixture respectively. The mechanism of pentane isomerization with Cu(AlCl 4 ) 2 , including the X-ray crystal structure of this compound, is described. Cu(AlCl 4 ) 2 is also effective for benzene polymerization.