Manabu Harata

STRUCTURAL AND SPECTROSCOPIC CHARACTERIZATION OF A MONONUCLEAR HYDROPEROXO- COPPER(II) COMPLEX WITH TRIPODAL PYRIDYLAMINE LIGANDS

A model for the key intermediate in copper oxygenase reactions, the Cu(II)-OOH complex, was prepared with the novel tripodal pyridylamine ligand, bis(6-pivalamide-2-pyridylmethyl)(2-pyridylmethyl)amine. The HOO- moiety is stabilized by hydrogen bonding to two amine H atoms (see structure on the right).

SOD activities of the copper complexes with tripodal polypyridylamine ligands having a hydrogen bonding site

Abstract As a structural mimic of the Arg 141 residue near copper site in native bovine Cu,Zn–superoxide dismutase (Cu,Zn–SOD), four mononuclear copper complexes with tris(2-pyridylmethyl)amine derivatives having a hydrogen bonding site (pivalamido, neopentylamino, or amino groups) at the pyridine 6-position, [Cu(tnpa)(OH)]ClO4 (1), [Cu(tapa)Cl]ClO4 (2), [Cu(tapa)(OH)]ClO4 (3), and [Cu(bppa)](ClO4)2 (4), and two analogous dinuclear copper complexes, [Cu2(tppen)(H2O)2](ClO4)4 (5) and [Cu2(tppen)Cl4] (6), were prepared, and the correlation between the coordination structures of the copper complexes and their superoxide dismutation activities were examined. Their structures in both solution and solid states were characterized by electronic absorption and ESR spectroscopic (for all the complexes) and by X-ray analytical methods (for 1, 2, 5 and 6), respectively. The coordination geometries around the copper ions were determined to be five-coordinate trigonal bipyramidal for 1, 2 and 3 and to be an intermediate of five-coordinate trigonal bipyramidal and square pyramidal for 5 and 6 in both crystal and solution phases, in contrast to four-coordinate square planar structure for 4 reported previously. The cyclic voltammetry measurement of the mononuclear complexes 1–4 showed quasi-reversible redox potentials (Cu(II)/Cu(I) couple) in the range between −330 mV (vs. NHE at pH 7; O2/O2 −) and +890 mV (vs. NHE at pH 7; O2 −/H2O2), which are in the range responsible for superoxide dismutation (SOD) reaction, although the dinuclear copper complexes, 5 and 6, gave only reduction potentials. The SOD activities of complexes 1, 2, and 3 were moderate and those of 5 and 6 were rather high, although 4 showed the lowest activity of all. Those of 1, 2 and 3 with a trigonal bipyramidal structure and hydrogen bonding interaction site are slightly high in comparison with that of the corresponding Cu(II) complex without hydrogen bonding site, [Cu(tpa)(H2O)](ClO4)2 (7). Relatively higher SOD activity observed in complexes 5 and 6 may be explained in terms of higher flexibility in the conformation and cooperativity by dinuclear copper ions.

Synthesis, Structure, and Spectroscopic Properties of [Feiii(tnpa)(OH)(PhCOO)]ClO4: A Model Complex for an Active Form of Soybean Lipoxygenase-1

The cis configuration between the hydroxo and the carboxylato and the three amino groups of the tetradentate, tripodal ligand tris(6-neopentylamino-2-pyridylmethyl)amine favors the formation of hydrogen bonds which stabilize the hydroxo-Feiii complex 1. Thus, its structure closely resembles that of the active center of Feiii -soybean lipoxygenase-1, which also contains a six-coordinate Feiii atom.

Strukturelle und spektroskopische Charakterisierung eines einkernigen Hydroperoxo‐Kupfer(II)‐Komplexes mit tripodalem Pyridylaminliganden

Ein Modell fur die Schlusselintermediate bei der Reaktion von Kupferoxygenasen ist der Kupfer(II)-OOH-Komplex mit dem neuartigen, tripodalen Pyridylaminliganden Bis(6-pivalamid-2-pyridylmethyl)(2-pyridylmethyl)amin. Der HOO−-Rest wird hierin durch zwei Amin-H-Atome uber Wasserstoffbrucken stabilisiert (siehe Strukturbild rechts).

PREPARATION, STRUCTURE AND PROPERTIES OF A COPPER(II) COMPLEX WITH A NEW TRIPODAL TETRADENTATE LIGAND, BIS{(6-PIVALOYLAMINO-2-PYRIDYL)METHYL}{(5-CARBOXY-2-PYRIDYL)METHYL}AMINE (BPCA), AND REACTION OF ITS Cu(I) COMPLEX WITH DIOXYGEN

Abstract A copper complex with a new tripodal tetradentate ligand, bis{(6-pivaloylamino-2-pyridyl)-methyl}{(5-carboxyl-2-pyridyl)methyl}amine (BPCA), has been prepared as a model metal centre of copper enzymes that react with dioxygen, the behaviour of which in solution has been examined on the basis of absorption and ESR spectra. Addition of NaN3 to an H2O/CH3OH solution containing Cu(ClO4)2 6H2O-BPCA with 1:1 molar ratio has afforded the complex [Cu-(bpca)(N3)]ClO4. It crystallizes in the monoclinic space group P2/a, a= 17.478(3), b= 9.773(1), c = 22.388(5) A, β = 102.92(2)°, Z = 4. The crystal structure reveals that the coordination around the central metal ion forms a trigonal bipyramid with three pyridine nitrogen atoms of BPCA (Cu-N(2) = 2.01(2), Cu-N(3) = 2.09(1) and Cu-N(4) = 2.22(1) A), in the trigonal plane and with a tertiary amino nitrogen atom of BPCA (Cu-N(l)= 1.99(1)A) and an azide anion (Cu-N(7) = 1.96(2) A) in axial positions. The azide ion is coordinated in an end-on configuration, the c...