Hidekazu Arii

Publications of Hidekazu Arii

• m-Carborane-based chiral NBN pincer-metal complexes: synthesis, structure, and application in asymmetric catalysis.

  Authors: Mohamed E El-Zaria, Hidekazu Arii, Hiroyuki Nakamura

  Inorganic chemistry. 03/2011; 50(9):4149-61.

  We have succeeded in synthesizing m-carborane-based chiral NBN-pincer ligands, 1,7-bis(oxazolinyl)-1,7-dicarba-closo-dodecaborane (Carbox) (7-9). The combination of bis(hydroxyamides) and 3 equiv ofWe have succeeded in synthesizing m-carborane-based chiral NBN-pincer ligands, 1,7-bis(oxazolinyl)-1,7-dicarba-closo-dodecaborane (Carbox) (7-9). The combination of bis(hydroxyamides) and 3 equiv of diethylaminosulfur trifluoride (DAST) is a key step for cyclization to form oxazoline rings in excellent yields. X-ray crystal structures of these ligands confirmed three donor sites, one central B and two flanking N atoms in fixed positions. The electrophilic halogenation of the Carbox pincer ligands with iodine and a catalytic amount of Lewis acid led to ring-opening of the oxazolines and afforded bis(haloamides) (13 and 14). The air- and moisture-stable Carbox pincer complexes of rhodium(III), nickel(II), and palladium(II) were synthesized by the oxidative addition of RhCl(3)·3H(2)O, Ni(COD)(2), and Pd(CH(3)CN)(4)[BF(4)](2) to the Carbox pincer ligands (7-9), respectively. The catalytic activity of the rhodium(III) complexes (18-20) was examined for the asymmetric conjugate reduction of α,β-unsaturated esters and reductive aldol reaction. Among these catalysts, [(S,S)-Carbox-iPr]Rh(OAc)(2)·H(2)O (18) showed the highest enantioselective catalytic ability for both asymmetric conjugate reduction and reductive aldol reaction.

• Syntheses of mono- and dinuclear silylplatinum complexes bearing a diphosphino ligand via stepwise bond activation of unsymmetric disilanes.

  Authors: Hidekazu Arii, Makiko Takahashi, Masato Nanjo, Kunio Mochida

  Dalton transactions (Cambridge, England : 2003). 07/2010; 39(28):6434-40.

  Zero-valence platinum complex [Pt(dppe)(eta(2)-C(2)H(4))] (1, dppe = 1,2-bis(diphenylphosphino)ethane) treated with disilanes HR(1)R(2)SiSiMe(3) (a, R(1) = R(2) = Me; b, R(1) = R(2) = Ph; c, R(1) =Zero-valence platinum complex [Pt(dppe)(eta(2)-C(2)H(4))] (1, dppe = 1,2-bis(diphenylphosphino)ethane) treated with disilanes HR(1)R(2)SiSiMe(3) (a, R(1) = R(2) = Me; b, R(1) = R(2) = Ph; c, R(1) = H, R(2) = Ph) afforded the corresponding disilanylplatinum hydrides [Pt(dppe)(H)(SiR(1)R(2)SiMe(3))] (2a-c) by oxidative addition of the Si-H bond to the platinum center. The 1,2-silyl migration in 2a,b led to the formation of bis(silyl)platinum complexes [Pt(dppe)(SiHR(1)R(2))(SiMe(3))] (3a,b) with a first-order rate constant of 7.2(2) x 10(-4) s(-1) at 25 degrees C for 2a and 3.86(4) x 10(-4) s(-1) at 40 degrees C for 2b, whereas 2c with R(1) = H followed by the transient generation of 3c dimerized rapidly to give the bis(mu-silylene)diplatinum complex [Pt(dppe)(mu-SiHPh)](2) (4c) in a mixture of cis/trans isomers. Heating of the toluene solution of 3b at 100 degrees C resulted in a similar dimerization to 4b. In addition, a trinuclear platinum complex [Pt(3)(dppe)(3)(mu(3)-SiPh)(2)] (5) with a trigonal bipyramidal Pt(3)Si(2) core arose from the reaction of 4c with 1 at 60 degrees C in toluene. Unsymmetric disilanes therefore accomplished the syntheses of various monomeric and dimeric platinum complexes via 1,2-hydrogen and silyl migration to the platinum center.

• 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;

• Self-assembled monolayer electrode of a diiron complex with a phenoxo-based dinucleating ligand: observation of molecular oxygen adsorptionldesorption in aqueous media.

  Authors: Tomohiko Inomata, Kazuma Shinozaki, Yuya Hayashi, Hidekazu Arii, Yasuhiro Funahashi, Tomohiro Ozawa, Hideki Masuda

  Chemical communications (Cambridge, England). 02/2008;

  The phenoxo-based dinucleating ligand, 2,6-bis[bis(6-pivalamido-2-pyridylmethyl)amino-methyl-4-aminophenol (1), and its Fe2(II) complex, [Fe2(II)(1)(PhCOO)2](CF3SO3) (2), were prepared and 2The phenoxo-based dinucleating ligand, 2,6-bis[bis(6-pivalamido-2-pyridylmethyl)amino-methyl-4-aminophenol (1), and its Fe2(II) complex, [Fe2(II)(1)(PhCOO)2](CF3SO3) (2), were prepared and 2 deposited on the Au surface (2/Au) is much more stable than in solution and exhibits redox behavior in aqueous media as well as reversible adsorption/desorption of oxygen at room temperature.

• Co(III) complexes with N2(SO)2-type equatorial planar ligands similar to the active center of nitrile hydratase: role of the sulfenate group in the enzymatic reaction.

  Authors: Takuma Yano, Yuko Wasada-Tsutsui, Hidekazu Arii, Syuhei Yamaguchi, Yasuhiro Funahashi, Tomohiro Ozawa, Hideki Masuda

  Inorganic chemistry. 11/2007; 46(24):10345-53.

  In order to gain an understanding of the role of the sulfenyl group of nitrile hydratase (NHase), a new Co(III) complex with a sulfenyl-type ligand (LC=O:N2(SO)2), Na[CoIII(LC=O:N2(SO)2)(tBuNC)2]In order to gain an understanding of the role of the sulfenyl group of nitrile hydratase (NHase), a new Co(III) complex with a sulfenyl-type ligand (LC=O:N2(SO)2), Na[CoIII(LC=O:N2(SO)2)(tBuNC)2] (2), was synthesized. The compound includes two amide groups, two sulfenate sulfurs in the equatorial plane, and two tBuNC molecules in the axial positions. Characterization of the compound was performed by UV-vis spectroscopic, IR spectral, thermogravimetric (TG), and X-ray structure analytical methods. The results are discussed in the context of Co(III) complexes containing the corresponding sulfur-type (LC=O:N2S2) (1) and sulfinyl-type ligands (LC=O:N2(SO2)2) (3). Complex 2 crystallized with the formula Na[CoIII(LC=O:N2(SO)2)(tBuNC)2].urea.2H2O.0.5EtOH. The X-ray structure revealed that the Co(III) complex has an octahedral geometry with Co-S=av. 2.221 A, Co-N=av. 1.998 A, and Co-C=av. 1.87 A. The sulfenyl oxygen and amidate carbonyl oxygen are linked to urea, water, EtOH, and Na+ and participate in a hydrogen-bond and an electrostatic interaction. IR and TG measurements demonstrated that the coordination strength of tBuNC to the Co atom increases as follows: 1<2<3. Complex 2 has almost the same stability as 3 in all solutions tested, although 1 exhibits a release of axial ligands in nonaqueous solutions. DFT calculations for 1, 2, and 3 demonstrated that Milliken atomic charges of the Co(III) centers are +1.466, +1.536, and +1.542, respectively, indicating that the extent of oxidation of the sulfur atoms increases the Lewis acidity of the Co(III) centers. Interestingly, the solution-state IR spectrum of 2 exhibits a solvent-dependent S-O stretching frequency. The frequency decreases with an increase in the electrophilicity (acceptor number) of the solvent. This solvent dependence was not observed for 3, which has a sulfinate (SO2) group, suggesting that the sulfenyl oxygen atom has nucleophilic character and promotes strong binding of the tBuNC molecule to lower the reaction barrier. These findings may suggest that the sulfenate oxygen in native NHase acts as a base (proton acceptor) and contributes to the activation of a water molecule and/or nitrile molecule.

• Syntheses, characterization, and dioxygen reactivities of Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives: a Cu(III)2O2 intermediate exhibiting higher C-H activation.

  Authors: Yuji Kajita, Hidekazu Arii, Takahiro Saito, Yamato Saito, Shigenori Nagatomo, Teizo Kitagawa, Yasuhiro Funahashi, Tomohiro Ozawa, Hideki Masuda

  Inorganic chemistry. 05/2007; 46(8):3322-35.

  Six Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives (R3CY, R = Et, iBu, and Bn), [Cu(MeCN)(Et3CY)]SbF6 (1), [Cu(MeCN)(iBu3CY)]SbF6 (2), [Cu(MeCN)(Bn3CY)]SbF6 (3),Six Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives (R3CY, R = Et, iBu, and Bn), [Cu(MeCN)(Et3CY)]SbF6 (1), [Cu(MeCN)(iBu3CY)]SbF6 (2), [Cu(MeCN)(Bn3CY)]SbF6 (3), [Cu(CO)(Et3CY)]SbF6 (4), [Cu(CO)(iBu3CY)]SbF6 (5), and [Cu(CO)(Bn3CY)]SbF6 (6), were prepared to probe the ability of copper complexes to effectively catalyze oxygenation reactions. The complexes were characterized by elemental analysis, electrochemical and X-ray structure analyses, electronic absorption spectroscopy, IR spectroscopy, 1H NMR spectroscopy, and ESI mass spectrometry. The crystal structures of 1-3 and 6 and the CO stretching vibrations (nuCO) of 4-6 demonstrate that the ability of R3CY to donate electron density to the Cu(I) atom is stronger than that of the previously reported ligands, 1,4,7-triazacyclononane (R3TACN) and 1,4,7-triazacyclodecane (R3TACD). Reactions of complexes 1-3 with dioxygen in THF or CH2Cl2 at -105 to -80 degrees C yield bis(mu-oxo)dicopper(III) complexes 7-9 as intermediates as confirmed by electronic absorption spectroscopy and resonance Raman spectroscopy. The Cu-O stretching vibrations, nu(Cu-O) for 7 (16O2: 553, 581 cm-1and 18O2: 547 cm-1) and 8 (16O2: 571 cm-1 and 18O2: 544 cm-1), are observed in a lower energy region than previously reported for bis(micro-oxo) complexes. The decomposition rates of complexes 7-9 in THF at -90 degrees C are 2.78 x 10-4 for 7, 8.04 x 10-4 for 8, and 3.80 x 10-4 s-1 for 9. The decomposition rates of 7 and 8 in CH2Cl2 were 5.62 x 10-4 and 1.62 x 10-3 s-1, respectively, and the thermal stabilities of 7-9 in CH2Cl2 are lower than the values measured for the complexes in THF. The decomposition reactions obeyed first-order kinetics, and the H/D isotope experiments for 8 and 9 indicate that the N-dealkylation reaction is the rate-determining step in the decomposition processes. On the other hand, the decomposition reaction of 7 in THF results in the oxidation of THF (acting as an exogenous substrate) to give 2-hydroxy tetrahydrofuran and gamma-butyrolactone as oxidation products. Detailed investigation of the N-dealkylation reaction for 8 by kinetic experiments using N-H/D at -90 degrees C showed a kinetic isotope effect of 1.25, indicating that a weak electrostatic interaction between the N-H hydrogen and mu-oxo oxygen contributes to the major effect on the rate-determining step of N-dealkylation. X-ray crystal structures of the bis(micro-hydroxo)dicopper(II) complexes, [Cu2(OH)2(Et3CY)2](CF3SO3)2 (10), [Cu2(OH)2(iBu3CY)2](CF3SO3)2 (11), and [Cu2(OH)2(Bn3CY)2](ClO4)2 (12), which have independently been prepared as the final products of bis(micro-oxo)dicopper(III) intermediates, suggest that an effective interaction between N-H and mu-oxo in the Cu(III)2(micro-O)2 core may enhance the oxidation ability of the metal-oxo species.

• Design of Salen-type Ni(II) complexes for recognition of DNA base sequence.

  Authors: Koji Takahashi, Kazuma Fukiura, Hidekazu Arii, Makoto Chikira

  Nucleic acids symposium series (2004). 02/2007;

  The DNA binding properties of cationic salen-type Ni(II) complexes (Fig. 1) have been studied by CD and NMR measurements. The binding constants estimated for poly(dA-dT)2 and poly(dA)poly(dT)The DNA binding properties of cationic salen-type Ni(II) complexes (Fig. 1) have been studied by CD and NMR measurements. The binding constants estimated for poly(dA-dT)2 and poly(dA)poly(dT) revealed that (1) binds more preferentially to poly(dA)poly(dT) than to poly(dA-dT)2, and vice versa for (2). The intermolecular NOE and chemical shift change of the oligonucleotides, d(CGCGAATTCGCG)2 (ODN1) and d(CGCGTATACGCG)2 (ODN2) indicated that the two complexes bound to the minor grooves at AT-rich site of the ODNs from the "en" bridging side. The difference in the sequence specificity between (1) and (2) was attributed to the difference in the width of the minor groove; (2) recognized the wider minor groove of ODN2 'TATA' region. In contrast to (1) and (2), the asymmetric complex (3) bound to the major groove at terminal GC-rich site of ODN1. In this study, we could reveal that hydrophobic interaction is an important factor for base sequence recognition and an appropriate modification of the salen could switch the binding site from minor to major groove of DNA.

• Copper(II) complexes of 1,10-phenanthroline-derived ligands: studies on DNA binding properties and nuclease activity.

  Authors: Tomoya Hirohama, Yuko Kuranuki, Eriko Ebina, Takashi Sugizaki, Hidekazu Arii, Makoto Chikira, Pitchumony Tamil Selvi, Mallayan Palaniandavar

  Journal of inorganic biochemistry. 06/2005; 99(5):1205-19.

  A series of copper(II) complexes of the type [Cu(L)]2+, where L = N,N'-dialkyl-1,10-phenanthroline-2,9-dimethanamine and R = methyl (L1), n-propyl (L2), isopropyl (L3), sec-butyl (L4), or tert-butylA series of copper(II) complexes of the type [Cu(L)]2+, where L = N,N'-dialkyl-1,10-phenanthroline-2,9-dimethanamine and R = methyl (L1), n-propyl (L2), isopropyl (L3), sec-butyl (L4), or tert-butyl (L5) group, have been synthesized. The interaction of the complexes with DNA has been studied by DNA fiber electron paramagnetic resonance (EPR) spectroscopy, emission, viscosity and electrochemical measurements and agarose gel electrophoresis. In the X-ray crystal structure of [Cu(HL2)Cl2]NO3, copper(II) is coordinated to two ring nitrogens and one of the two secondary amine nitrogens of the side chains and two chloride ions as well and the coordination geometry is best described as trigonal bipyramidal distorted square based pyramidal (TBDSBP). Electronic and EPR spectral studies reveal that all the complexes in aqueous solution around pH 7 possess CuN3O2 rather than CuN4O chromophore with one of the alkylamino side chain not involved in coordination. The structures of the complexes in aqueous solution around pH 7 change from distorted tetragonal to trigonal bipyramidal as the size of the alkyl group is increased. The observed changes in the physicochemical features of the complexes on binding to DNA suggest that the complexes, except [Cu(L5)]2+, bind to DNA with partial intercalation of the derivatised phen ring in between the DNA base pairs. Electrochemical studies reveal that the complexes prefer to bind to DNA in Cu(II) rather than Cu(I) oxidation state. Interestingly, [Cu(L5)]2+ shows the highest DNA cleavage activity among all the present copper(II) complexes suggesting that the bulky N-tert-butyl group plays an important role in modifying the coordination environment around the copper(II) center, the Cu(II)/Cu(I) redox potential and hence the formation of activated oxidant responsible for the cleavage. These results were compared with those for bis(1,10-phenanthroline)copper(II), [Cu(phen)2]2+.

• Effect of a conjugated acridine moiety on the binding and reactivity of Cu(II)[9-acridinylmethyl-1,4,7-triazacyclononane] with DNA.

  Authors: Tomoya Hirohama, Hidekazu Arii, Makoto Chikira

  Journal of inorganic biochemistry. 11/2004; 98(11):1778-86.

  The DNA binding orientation and dynamic behavior of Cu(II) complexes of 1,4,7-triazacyclononane ([9]aneN(3)), 1, and an acridine conjugate, 2, were investigated by DNA fiber EPR (EPR=electronThe DNA binding orientation and dynamic behavior of Cu(II) complexes of 1,4,7-triazacyclononane ([9]aneN(3)), 1, and an acridine conjugate, 2, were investigated by DNA fiber EPR (EPR=electron paramagnetic resonance) spectroscopy. Crystal and molecular structure of 2 were determined by X-ray diffraction. It has been shown that 1 binds to DNA in two different modes at room temperature; one species is rapidly rotating and the other is immobilized randomly on the DNA. The introduction of acridine to [9]aneN(3) fixed the [Cu([9]aneN(3))](2+) moiety of 2 in two different environments on the DNA: the g(mid R:mid R:) axis of one species (g( parallel)=2.26) is aligned perpendicularly to the DNA fiber axis whereas that of the other (g( parallel)=2.24) aligns<90 degrees with the DNA fiber axis. The different DNA binding structures of 1 and 2 are reflected also in their different efficiencies of DNA cleavage; 2 was found to be more effective both in oxidative and hydrolytic cleavage reactions.

• 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.