Koichiro Jitsukawa

Publications of Koichiro Jitsukawa

• Formation of a bridged butterfly-type mu-eta2:eta2-peroxo dicopper core structure with a carboxylate group.

  Authors: Yasuhiro Funahashi, Tomohide Nishikawa, Yuko Wasada-Tsutsui, Yuji Kajita, Syuhei Yamaguchi, Hidekazu Arii, Tomohiro Ozawa, Koichiro Jitsukawa, Takehiko Tosha, Shun Hirota, Teizo Kitagawa, Hideki Masuda

  Journal of the American Chemical Society. 01/2009; 130(49):16444-5.

• Formation of a Bridged Butterfly-Type mu-eta(2):eta(2)-Peroxo Dicopper Core Structure with a Carboxylate Group.

  Authors: Yasuhiro Funahashi, Tomohide Nishikawa, Yuko Wasada-Tsutsui, Yuji Kajita, Syuhei Yamaguchi, Hidekazu Arii, Tomohiro Ozawa, Koichiro Jitsukawa, Takehiko Tosha, Shun Hirota, Teizo Kitagawa, Hideki Masuda

  Journal of the American Chemical Society. 12/2008;

• Preparation of a hydroperoxo zinc(II) intermediate.

  Authors: Akira Wada, Syuhei Yamaguchi, Koichiro Jitsukawa, Hideki Masuda

  Angewandte Chemie (International ed. in English). 10/2005; 44(35):5698-701.

• Self-assembled monolayers of optically active Co(III) complexes: a new promoter electrode recognizing the electron transfer site in cytochrome c.

  Authors: Isao Takahashi, Tomohiko Inomata, Yasuhiro Funahashi, Tomohiro Ozawa, Koichiro Jitsukawa, Hideki Masuda

  Chemical communications (Cambridge, England). 02/2005;

  A new-class of promoter electrode bearing a molecular recognition ability has been constructed; the chirality and/or orientation of promoter on the Au electrode surface have affected the electronA new-class of promoter electrode bearing a molecular recognition ability has been constructed; the chirality and/or orientation of promoter on the Au electrode surface have affected the electron transfer rate of cytochrome c.

• Synthesis, solution behavior, thermal stability, and biological activity of an Fe(III) complex of an artificial siderophore with intramolecular hydrogen bonding networks.

  Authors: Kenji Matsumoto, Tomohiro Ozawa, Koichiro Jitsukawa, Hideki Masuda

  Inorganic chemistry. 01/2005; 43(26):8538-46.

  Previously, an artificial siderophore complex, the iron(III) complex with tris[2-[(N-acetyl-N-hydroxy)glycylamino]ethyl]amine (TAGE), was constructed in order to understand the effect ofPreviously, an artificial siderophore complex, the iron(III) complex with tris[2-[(N-acetyl-N-hydroxy)glycylamino]ethyl]amine (TAGE), was constructed in order to understand the effect of intramolecular hydrogen bonding interaction on the siderophore function, and its structural characterization in the solid state was reported (Inorg. Chem. 2001, 40, 190). In this paper, the solution behavior of the M(III)-TAGE (M = Fe, Ga) system has been investigated using (1)H NMR, UV-vis, and FAB mass spectroscopies in efforts to characterize the biological implication of hydrogen bonding networks between the amide hydrogens and coordinating aminohydroxy oxygens of the complex. The temperature dependence of (1)H NMR spectra for Ga(III) complex of TAGE indicates that hydrogen bonding networks are maintained in polar solvents such as DMSO-d(6) and D(2)O. The UV-vis spectra of the Fe(III)-TAGE system under various pH conditions have shown that TAGE forms a tris(hydroxamato)iron(III) complex in an aqueous solution in the pH range 4-8. By contrast, tris[2-[(N-acetyl-N-hydroxy)propylamido]ethyl]amine (TAPE; TAGE analogue that is difficult to form intramolecular hydrogen bonding networks), which has been synthesized as a comparison of TAGE, forms both of bis- and tris(hydroxamato)iron(III) complexes in the same pH range. Both the stability constants (log beta(FeTAGE) = 28.6; beta(FeTAGE) = [Fe(III)TAGE]/([Fe(3+)][TAGE(3)(-)])) and pM (-log[Fe(3+)]) value for Fe(III)TAGE (pM 25) are comparable to those of a natural siderophore ferrichrome (log beta = 29.1 and pM 25.2). The kinetic study of the TAGE-Fe(III) system has given the following rate constants: the rate of the ligand exchange reaction between Fe(III)TAGE and EDTA is 6.7 x 10(-4) s(-1), and the removal rates of iron from diferric bovine plasma transferrin by TAGE are 2.8 x 10(-2) and 6.0 x 10(-3) min(-1). These values are also comparable to those of a natural siderophore desferrioxamine B under the same conditions. In a biological activity experiment, TAGE has promoted the growth of the siderophore-auxotroph Gram-positive bacterium Microbacterium flavescens, suggesting that TAGE mimics the activity of ferrichrome. These results indicate that the artificial siderophore with intramolecular hydrogen bonding networks, TAGE, is a good structural and functional model for a natural ferrichrome.

• Preparation, structure characterization, and oxidation activity of ruthenium complexes with tripodal ligands bearing noncovalent interaction sites.

  Authors: Koichiro Jitsukawa, Yoshiyuki Oka, Syuhei Yamaguchi, Hideki Masuda

  Inorganic chemistry. 01/2005; 43(25):8119-29.

  Ruthenium(II/III) complexes with tripodal tris(pyridylmethyl)amine ligands bearing one, two, or three pivalamide groups (MPPA, BPPA, TPPA: amide-series ligands) or neopentylamine ones (MNPA, BNPA,Ruthenium(II/III) complexes with tripodal tris(pyridylmethyl)amine ligands bearing one, two, or three pivalamide groups (MPPA, BPPA, TPPA: amide-series ligands) or neopentylamine ones (MNPA, BNPA, TNPA: amine-series ligands) at the 6-position of the pyridine ring have been synthesized and structurally characterized. The X-ray structure analyses of the single crystals of these complexes reveal that they complete an octahedral geometry with the tripodal ligand and some monodentate ligands. The amide-series ligands prefer to form a Ru(II) complex, while the amine-series ones give a Ru(III) complex. In the presence of PhIO oxidant, the catalytic activities for epoxidation of olefins, hydroxylation of alkane, and dehydrogenation of alcohol have been investigated using the six ruthenium complexes [Ru(II)(tppa)Cl(2)] (1), [Ru(III)(tnpa)Cl(2)]PF(6) (2), [Ru(II)(bppa)Cl]PF(6) (3), [Ru(III)(bnpa)Cl(2)]PF(6) (4), [Ru(II)(mppa)Cl]PF(6) (5), and [Ru(III)(mnpa)Cl(2)]PF(6) (6). Among them, the amide-series complexes, 1, 3, and 5, showed a higher epoxidation activity in comparison with the amine-series ones, 2, 4, and 6. On the other hand, the latter showed a higher reactivity for hydroxylation, allylic oxidation, and C=C bond cleavage reactions compared with the former. Such a complementary reactivity is interpreted by the character of the ruthenium-oxo species involving electronically equivalent formulas, Ru(V)=O and Ru(IV)-O.

• Steric and hydrogen-bonding effects on the stability of copper complexes with small molecules.

  Authors: Akira Wada, Yasutaka Honda, Syuhei Yamaguchi, Shigenori Nagatomo, Teizo Kitagawa, Koichiro Jitsukawa, Hideki Masuda

  Inorganic chemistry. 10/2004; 43(18):5725-35.

  A series of the copper(II) complexes with tripodal tetradentate tris(pyridyl 2-methyl)amine-based ligands possessing the hydrogen-bonding 6-aminopyridine units (tapa, three amino groups; bapa, twoA series of the copper(II) complexes with tripodal tetradentate tris(pyridyl 2-methyl)amine-based ligands possessing the hydrogen-bonding 6-aminopyridine units (tapa, three amino groups; bapa, two amino groups; mapa, one amino group) have been synthesized, and their copper(II) complexes with a small molecule such as dioxygen and azide have been studied spectroscopically and structurally. The reaction of their Cu(II) complexes with NaN(3) have given the mononuclear copper complexes with azide in an end-on mode, [Cu(tapa)(N(3))]ClO(4) (1a), [Cu(bapa)(N(3))]ClO(4) (2a), [Cu(mapa)(N(3))]ClO(4) (3a), and [Cu(tpa)(N(3))]ClO(4) (4a) (tpa, no amino group). The crystal structures have revealed that the coordination geometries around the metal centers are almost a trigonal-bipyramidal rather than a square-planar except for 1a with an intermediate between them. The UV-vis and ESR spectral data indicate that the increase of NH(2) groups of ligands causes the structural change from trigonal-bipyramidal to square-pyramidal geometry, which is regulated by a combination of steric repulsion and hydrogen bond. The steric repulsion of amino groups with the azide nitrogen gives rise to elongation of the Cu-N(py) bonds, which leads to the positive shift of the redox potentials of the complexes. The hydrogen bonds between the coordinated azide and amino nitrogens (2.84-3.05 A) contribute clearly to the fixation of azide. The Cu(I) complexes with bapa and mapa ligands have been obtained as a precipitate, although that with tapa was not isolated. The reactions of the Cu(I) complexes with dioxygen in MeOH at -75 degrees C have given the trans-micro-1,2 peroxo dinuclear Cu(II) complexes formulated as [((tapa)Cu)(2)(O(2))](2+) (1c), [((bapa)Cu)(2)(O(2))](2+) (2c), and [((mapa)Cu)(2)(O(2))](2+) (3c), whose characterizations were confirmed by UV-vis, ESR, and resonance Raman spectroscopies. UV-vis spectra of 1c, 2c, and 3c exhibited intense bands assignable to pi(O(2)(2)(-))-to-d(Cu) charge transfer (CT) transitions at lambda(max)/nm (epsilon/M(-1)cm(-1)) = 449 (4620), 474 (6860), and 500 (9680), respectively. The series of the peroxo adducts generated was ESR silent. The resonance Raman spectra exhibited the enhanced features assignable to two stretching vibrations nu((16)O-(16)O/(18)O-(18)O)/cm(-1) and nu(Cu-(16)O/Cu-(18)O)/cm(-1) at 853/807 (1c), 858/812 (2c), 847/800 (3c), and at 547/522 (2c), 544/518 (3c), respectively. The thermal stability of the peroxo-copper species has increased with increase in the number of the hydrogen-bonding interactions between the peroxide and amino groups.

• An accurately-constructed structural model for an active site of Fe-containing superoxide dismutases (Fe-SODs).

  Authors: Syuhei Yamaguchi, Akinori Kumagai, Yasuhiro Funahashi, Koichiro Jitsukawa, Hideki Masuda

  Inorganic chemistry. 01/2004; 42(24):7698-700.

  A novel structural model, [Fe(bpga)(N(3))(OCH(3))] (1) (BPGA: bis(6-pivalamido-2-pyridylmethyl)(carboxy-methyl)amine), for an active site of Fe-containing SOD enzyme with N(3)(-) has been accuratelyA novel structural model, [Fe(bpga)(N(3))(OCH(3))] (1) (BPGA: bis(6-pivalamido-2-pyridylmethyl)(carboxy-methyl)amine), for an active site of Fe-containing SOD enzyme with N(3)(-) has been accurately designed and prepared, which has been characterized by X-ray structure analysis and UV-vis, ESR, and IR spectroscopies. Reaction of 1 with acid/base in methanol has shown that the superoxide-accessible site is the N(3)(-)-coordination site in the equatorial plane.

• Construction of a square-planar hydroperoxo-copper(II) complex inducing a higher catalytic reactivity.

  Authors: Tatsuya Fujii, Asako Naito, Syuhei Yamaguchi, Akira Wada, Yasuhiro Funahashi, Koichiro Jitsukawa, Shigenori Nagatomo, Teizo Kitagawa, Hideki Masuda

  Chemical communications (Cambridge, England). 12/2003;

  A novel hydroperoxo-copper(II) complex with a square-planar geometry has been prepared, which has exhibited a higher selectivity and catalytic reactivity for dimethyl sulfide, in contrast to thatA novel hydroperoxo-copper(II) complex with a square-planar geometry has been prepared, which has exhibited a higher selectivity and catalytic reactivity for dimethyl sulfide, in contrast to that with a trigonal-bipyramidal one.

• Kinetic resolution of rac-phenylalanine by stereoselective complexation to a chiral cobalt complex through pi-pi stacking interaction.

  Authors: Koichiro Jitsukawa, Akira Katoh, Kentaro Funato, Nayumi Ohata, Yasuhiro Funahashi, Tomohiro Ozawa, Hideki Masuda

  Inorganic chemistry. 11/2003; 42(20):6163-5.

  A cobalt(III) complex with chiral ligand, H2cpel (N-carboxymethyl-N-pyridylethyl-l-leucine), was prepared for chiral recognition of amino acids. Through the competitive coordination of racemicA cobalt(III) complex with chiral ligand, H2cpel (N-carboxymethyl-N-pyridylethyl-l-leucine), was prepared for chiral recognition of amino acids. Through the competitive coordination of racemic phenylalanine to the chiral cobalt complex, [Co(cpel)(CO(3))](-) (1), enantioselective recognition was achieved on the ternary complex, which was determined on the basis of HPLC analysis with a chiral column. The formation rate for the [Co(cpel)(l-phe)] complex (2) was 6-times superior to that of [Co(cpel)(d-phe)] (3). The preferential formation of 2 might be illustrated by the interligand pi-pi stacking interaction. Crystal structural analysis for 2 and 3 revealed that aromatic rings, pyridine ring of CPEL and phenylalanine sidechain, in 2 were very close each other but those in 3 were far apart. Such interligand aromatic interaction in 2 was also examined by the use of (1)H NMR spectra.

• Reactivity of hydroperoxide bound to a mononuclear non-heme iron site.

  Authors: Akira Wada, Seiji Ogo, Shigenori Nagatomo, Teizo Kitagawa, Yoshihito Watanabe, Koichiro Jitsukawa, Hideki Masuda

  Inorganic chemistry. 03/2002; 41(4):616-8.

  The first isolation and spectroscopic characterization of the mononuclear hydroperoxo-iron(III) complex [Fe(H(2)bppa)(OOH)](2+) (2) and the stoichiometric oxidation of substrates by the mononuclearThe first isolation and spectroscopic characterization of the mononuclear hydroperoxo-iron(III) complex [Fe(H(2)bppa)(OOH)](2+) (2) and the stoichiometric oxidation of substrates by the mononuclear iron-oxo intermediate generated by its decomposition have been described. The purple species 2 obtained from reaction of [Fe(H(2)bppa)(HCOO)](ClO(4))(2) with H(2)O(2) in acetone at -50 degrees C gave characteristic UV-vis (lambda(max) = 568 nm, epsilon = 1200 M(-1) cm(-1)), ESR (g = 7.54, 5.78, and 4.25, S = (5)/(2)), and ESI mass spectra (m/z 288.5 corresponding to the ion, [Fe(bppa)(OOH)](2+)), which revealed that 2 is a high-spin mononuclear iron(III) complex with a hydroperoxide in an end-on fashion. The resonance Raman spectrum of 2 in d(6)-acetone revealed two intense bands at 621 and 830 cm(-1), which shifted to 599 and 813 cm(-1), respectively, when reacted with (18)O-labeled H(2)O(2). Reactions of the isolated (bppa)Fe(III)-OOH (2) with various substrates (single turnover oxidations) exhibited that the iron-oxo intermediate generated by decomposition of 2 is a nucleophilic species formulated as [(H(2)bppa)Fe(III)-O*].

• Synthesis and Characterization of Novel Alkylperoxo Mononuclear Iron(III) Complexes with a Tripodal Pyridylamine Ligand: A Model for Peroxo Intermediates in Reactions Catalyzed by Non-Heme Iron Enzymes.

  Authors: Akira Wada, Seiji Ogo, Yoshihito Watanabe, Masahiro Mukai, Teizo Kitagawa, Koichiro Jitsukawa, Hideki Masuda, Hisahiko Einaga

  Inorganic chemistry. 09/1999; 38(16):3592-3593.

• Nucleobase Stacking Evidenced on Ternary Metal (Palladium(II), Copper(II)) Complexes with Nucleobase Amino Acids and Aromatic Diimines.

  Authors: Mamoru Mizutani, Ichiro Kubo, Koichiro Jitsukawa, Hideki Masuda, Hisahiko Einaga

  Inorganic chemistry. 03/1999; 38(3):420-421.

• A novel diiron complex as a functional model for hemerythrin

  Authors: Hidekazu Arii, Shigenori Nagatomo, Teizo Kitagawa, Tomohiro Miwa, Koichiro Jitsukawa, Hisahiko Einaga, Hideki Masuda

  Journal of Inorganic Biochemistry.

  Diiron(II) complexes with a novel dinucleating polypyridine ligand, N,N,N′,N′-tetrakis(6-pivalamido-2-pyridylmethyl)-1,3-diaminopropan-2-ol (HTPPDO), were synthesized as functional models ofDiiron(II) complexes with a novel dinucleating polypyridine ligand, N,N,N′,N′-tetrakis(6-pivalamido-2-pyridylmethyl)-1,3-diaminopropan-2-ol (HTPPDO), were synthesized as functional models of hemerythrin. Structural characterization of the complexes, [FeII2(Htppdo)(PhCOO)](ClO4)3 (1), [FeII2(Htppdo)((p-Cl)PhCOO)](ClO4)3 (2), [FeII2(Htppdo)((p-Cl)PhCOO)](BF4)3 (2′) and [FeII2(tppdo)((p-Cl)PhCOO)](ClO4)2 (3), were accomplished by electronic absorption, and IR spectroscopic, electrochemical, and X-ray diffraction methods. The crystal structures of 1 and 2′ revealed that the two iron atoms are asymmetrically coordinated with HTPPDO and bridging benzoate. One of the iron centers (Fe(1)) has a seven-coordinate capped octahedral geometry comprised of an N3O4 donor set which includes the propanol oxygen of HTPPDO. The other iron center (Fe(2)) forms an octahedron with an N3O3 donor set and one vacant site. The two iron atoms are bridged by benzoate (1) or p-chlorobenzoate (2). On the other hand, both Fe atoms of complex 3 are both symmetrically coordinated with N3O4 donors and two bridging ligands; benzoate and the propanolate of TPPDO. Reactions of these complexes with dioxygen were followed by electronic absorption, resonance Raman and ESR spectroscopies. Reversible dioxygen-binding was demonstrated by observation of an intense LMCT band for O22− to Fe(III) at 610 (1) and 606 nm (2) upon exposure of dioxygen to acetone solutions of 1 and 2 prepared under an anaerobic conditions at −50°C. The resonance Raman spectra of the dioxygen adduct of 1 exhibited two peaks assignable to the ν(O–O) stretching mode at 873 and 887 cm−1, which shifted to 825 and 839 cm−1 upon binding of 18O2. ESR spectra of all dioxygen adducts were silent. These findings suggest that dioxygen coordinates to the diiron atoms as a peroxo anion in a μ-1,2 mode. Complex 3 exhibited irreversible dioxygen binding. These results indicate that the reversible binding of dioxygen is governed by the hydrophobicity of the dioxygen-binding environment rather than the iron redox potentials.