Faculty Profiles - SUZUKI Takayoshi

Papers - SUZUKI Takayoshi

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Coordination Structure Conversion of Hydrazone-Palladium(II) Complexes in the Solid State and in Solution

Fumi Kitamura, Kana Sawaguchi, Asami Mori, Shoji Takagi, Takayoshi Suzuki, Atsushi Kobayashi, Masako Kato, Kiyohiko Nakajima

INORGANIC CHEMISTRY 54 ( 17 ) 8436 - 8448 2015.9

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

We prepared hydrazone palladium(II) complexes of [PdCl2(HLn)] and [PdCl(L-n)] (n = 1-3) by the reaction of [PdCl2(cod)] or [PdCl2(PhCN)(2)] and the hydrazone ligands of HLn {N'-(pyridin-2-ylmethylene)picolinohydrazide (HL1), N'-[1-(pyridin-2-yl)ethylidene]picolinohydrazide (HL2), and N'-[(6-methylpyridin-2-yOmethylene]picolinohydrazide (HL3)}. The structures of the complexes were determined by X-ray analysis. The hydrazone ligands had kappa N(pyl), kappa N(imine) and kappa N(amidate) kappa N(py2) bidentate coordination modes in [PdCl2(HLn] (1, n = 1; 2, n = 2) and in [PdCl2(HL3)] (3), respectively. In contrast, tridentate coordination modes of kappa N(pyl)), kappa N(imine), kappa N(py2) and kappa N(py1), kappa N(amidate), kappa N(py2) were observed in [PdCl(L-n)] (4, n = 1; 5, n = 2) and in [PdCl(L-n)] (6, n = 1; 7, n = 2; 8, n = 3). Thermal conversion of complexes 1-3 to complexes 6-8 proceeded in acetonitrile. Complexes 4 and 5 were obtained from complexes 1 and 2, respectively, in a basic acetonitrile solution under dark conditions. Complex 4 reverted immediately to complex 1 in an acidic acetonitrile solution that included hydrochloric acid. However, under room light, in the basic acetonitrile solution that included trimethylamine, complex 4 converted photochemically to complex 6. The thermochromic or vapochromic structure conversion of these complexes also occurred in the solid state. On heating at 180 degrees C, the color of the crystals of complexes 1, 2, and 3 changed from yellow to orange in the solid state. H-1 NMR and/or UV vis absorption spectroscopy confirmed that the orange complexes 6-8 were produced. The reddish-orange crystals of complexes 4 and 5 were exposed to hydrogen chloride vapor to yield the yellow products of complexes 1 and 2, respectively.

DOI： 10.1021/acs.inorgchem.5b01128

Crystal structures of dichloridopalladium(II), -platinum(II) and -rhodium(III) complexes containing 8-(diphenylphosphanyl) quinoline

Takayoshi Suzuki, Hiroshi Yamaguchi, Masayuki Fujiki, Akira Hashimoto, Hideo D. Takagi, H. Ishida

Acta Crystallographica Section E: Structure Reports Online 71 ( 5 ) 447 - 451 2015.5

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：International Union of Crystallography

The crystal structures of dichloridopalladium(II), -platinum(II) and - rhodium(III) complexes containing 8-(diphenylphosphanyl) quinoline, (SP-4)-[PdCl2(C21H16NP)], (1) [systematic name: dichlorido(8-diphenylphosphanyl-quinoline) palladium(II)], (SP-4)-[PtCl2(C21H16NP)]·CH2Cl2, (2) [systematic name: dichlorido(8-diphenylphosphanylquinoline) platinum(II) dichlorometh-ane monosolvate], and (OC-6-32)-[RhCl2(C21H16NP)2]PF6·0.5CH2Cl2·-0.5CH3OH, (3) [systematic name: cis-dichloridobis(8-diphenylphosphanyl-quinoline) rhodium(III) hexafluoridophosphate dichloromethane/methanol hemisolvate] are reported. In these complexes, the phosphanylquinoline acts as a bidentate ligand, forming a planar asymmetrical five-membered chelate ring. The palladium(II) and platinum(II) complex molecules in (1) and (2), respectively, show a typical square-planar coordination geometry and form a dimeric structure through an intermolecular π-π stacking interaction between the quinolyl rings. The centroid-centroid distances between the stacked six-membered rings in (1) and (2) are 3.633 (2) and 3.644 (2) Å, respectively. The cationic rhodium(III) complex in (3) has a cis(Cl),cis(P),cis(N) (OC-6-32) configuration of the ligands, in which two kinds of intramolecular π-π stacking interactions are observed: between the quinolyl and phenyl rings and between two phenyl rings, the centroid-centroid distances being 3.458 (2) and 3.717 (2) Å, respectively. The PF6 - anion in (3) is rotationally disordered, the site occupancies of each F atom being 0.613 (14) and 0.387 (14). The CH2Cl2 and CH3OH solvent molecules are also disordered and equal site occupancies of 0.5 are assumed.

DOI： 10.1107/S2056989015006076

Oxidation and Deprotonation of a Ruthenium(II) Complex with Quinoline-2-carbaldehyde (Pyridine-2-carbonyl)hydrazone and Formation of Hydrazonato-Bridged Heterodimetallic Complexes Reviewed

Asami Mori, Takayoshi Suzuki, Yukinari Sunatsuki, Masaaki Kojima, Kiyohiko Nakajima

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 88 ( 3 ) 480 - 489 2015.3

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Reactions of a ruthenium(II) complex containing quinoline-2-carbaldehyde (pyridine-2-carbonyl)hydrazone (HL), trans(P,P)-[RuCl2(PPh3)(2)(HL)] (1), and 3d-metal(II) chlorides resulted in heterodimetallic complexes, [RuCl2(PPh3)(2)-(mu-L)MCl2] (2M, M = Mn, Fe, Co, Ni, Cu, and Zn), in which the deprotonated hydrazonate (L-) bridged two metal ions in the mu-1(Ru)kappa N-2,O:2(M)kappa N-3',N '',N''' mode. The coordination bond lengths around the Ru and M centers suggested that the oxidation states in the complexes 2M could be assigned as Ru-III and M-II; this was also supported by magnetic, electrochemical, and spectroscopic measurements. In addition, oxidation of complex 1 by (NH4)(2)[Ce(NO3)(6)] gave the corresponding mononuclear Ru-III complex with the deprotonated hydrazonate, trans(P,P)-[RuCl2(PPh3)(2)(L)] (3). It is suggested that oxidation of the Ru center lead to the concerted deprotonation from the hydrazone ligand. Addition of excess HClO4 to complex 3 gave a doubly protonated Ru-III complex, 4(ClO4)(2); in this complex the hydrazonate moiety was not protonated, but both the quinolyl and pyridyl N atoms were protonated. Complexes 3 and 4(2+) could be interconverted by the addition of acid or base without changing the oxidation state of the Ru center.

DOI： 10.1246/bcsj.20140381

X-ray diffraction and vibrational spectroscopic study of trans-bis(acetylacetonato)-bis(4-methylpyridine)cobalt(III)

Sayyed Faramarz Tayyari, Mohammad Hossien Habibi, Elahe Shojaee, Mina Jamialahmadi, Robert Erik Sammelson, Koki Wada, Takayoshi Suzuki

SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 139 ( 1 ) 94 - 101 2015.3

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Trans-bis(acetylacetonato)-bis(4-methylpyridine)cobalt(III)hexafluorophosphate, [AMPC]PF6, was synthesized and characterized by X-ray diffraction and vibrational spectroscopy. The title compound C22H28-N2O4Co crystallizes with Z = 2 in space group P-1 (#2). The molecular structure and vibrational spectra of this compound were investigated by means of density functional theory (DFT) calculations and the results were compared with the experimental data. The measured IR bands were interpreted in terms of the calculated vibrational normal modes and compared with the tris(acetylacetonate)Co(III) (Co(acac)(3)) and 4-methylpyridine (4-Mepy) vibrational spectra. The scaled theoretical wavenumbers and the structural parameters were in excellent agreement with the experimental data. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.saa.2014.12.019

Crystal structure of bis(2, 2′-bipyridine)[N′-(quino-lin-2-ylmethylidene)pyridine-2-carbohydrazide]-ruthenium(II) bis(tetrafluoridoborate) dichloro-methane trisolvate

Asami Mori, Takayoshi Suzuki, Kiyohiko Nakajima, M. Weil

Acta Crystallographica Section E: Structure Reports Online 71 ( 2 ) 142 - 145 2015.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：International Union of Crystallography

The title compound, [Ru(C&lt
inf&gt
10&lt
/inf&gt
H&lt
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8&lt
/inf&gt
N&lt
inf&gt
2&lt
/inf&gt
)&lt
inf&gt
2&lt
/inf&gt
(C&lt
inf&gt
16&lt
/inf&gt
H&lt
inf&gt
12&lt
/inf&gt
N&lt
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4&lt
/inf&gt
O)](BF&lt
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4&lt
/inf&gt
)&lt
inf&gt
2&lt
/inf&gt
·3CH&lt
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2&lt
/inf&gt
Cl&lt
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2&lt
/inf&gt
, crystallizes with one complex dication, two BF&lt
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4&lt
/inf&gt
&lt
sup&gt
-&lt
/sup&gt
counter-anions and three dichloromethane solvent molecules in the asymmetric unit. The central Ru&lt
sup&gt
II&lt
/sup&gt
atom adopts a distorted octahedral coordination sphere with two 2, 2′-bipyridine (bpy) and one quinoline-2-carbaldehyde (pyridine-2-carbonyl)hydrazone (HL) ligand. The hydrazone ligand has a Z form and coordinates to the Ru&lt
sup&gt
II&lt
/sup&gt
atom via the amide-O and imine-N atoms, affording a planar five-membered chelate ring, while its pyridine-N and quinoline-N donor atoms in the substituents are non-coordinating. The hydrazone N - H group forms an intramolecular hydrogen bond with the quinoline-N atom. In the crystal, the quinoline moiety of HL shows the shortest π-π stacking interaction with the pyridine substituent of HL in a neighbouring complex, the centroid-to-centroid distance being 3.793 (3) Å.

DOI： 10.1107/S2056989015000122

Thyminate(2-)-bridged cyclic tetranuclear rhodium(III) complexes formed by a template of a sodium, calcium or lanthanoid ion

Ayana Kashima, Mika Sakate, Hiromi Ota, Akira Fuyuhiro, Yukinari Sunatsuki, Takayoshi Suzuki

CHEMICAL COMMUNICATIONS 51 ( 10 ) 1889 - 1892 2015

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

In the thyminate(2-)-bridged tetranuclear Cp*Rh-III complexes incorporating a Na+, Ca2+ or Ln(3+) cation, homochiral aggregation of four Rh-III centres was achieved to form metallacalix[4] arene-type clusters. The thyminate(2-) bridged two RhIII and the third metal ionwith a mu(3)-1 kappa N-1:2 kappa N-2(3),O-2:3 kappa O-2 mode in the Na+ and Ca2+ complexes, while in the Ln(3+) analogues it exhibited a different bridging mode, mu(3)-1 kappa N-1:2 kappa N-2(3),O-4:3 kappa O-2.

DOI： 10.1039/c4cc09087j

Flipping of the coordinated triazine moiety in Cu(I)-L-2 and the small electronic factor, kappa(el), for direct outer-sphere cross reactions: syntheses, crystal structures and redox behaviour of copper (II)/(I)-L-2 complexes (L=3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)

Atsutoshi Yamada, Takuya Mabe, Ryohei Yamane, Kyoko Noda, Yuko Wasada, Masahiko Inamo, Koji Ishihara, Takayoshi Suzuki, Hideo D. Takagi

DALTON TRANSACTIONS 44 ( 31 ) 13979 - 13990 2015

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Six-coordinate [Cu(pdt)(2)(H2O)(2)](2+) and four-coordinate [Cu(pdt)(2)](+) complexes were synthesized and the cross redox reactions were studied in acetonitrile (pdt = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). Single crystal analyses revealed that [Cu(pdt)(2)(H2O)(2)](BF4)(2) was of pseudo-D-2h symmetry with two axial water molecules and two symmetrically coordinated equatorial pdt ligands, while the coordination structure of [Cu(pdt)(2)]BF4 was a squashed tetrahedron (dihedral angle = 54.87 degrees) with an asymmetric coordination by two pdt ligands: one pdt ligand was coordinated to Cu(I) through pyridine-N and triazine-N2 while another pdt ligand was coordinated through pyridine-N and triazine-N4, and a stacking interaction between the phenyl ring on one pdt ligand and the triazine ring on another pdt ligand caused the squashed structure and non-equivalent Cu-N bond lengths. The cyclic voltammograms for [Cu(pdt)(2)(H2O)(2)](2+) and [Cu(pdt)(2)](+) in acetonitrile were identical to each other and quasi-reversible. The reduction of [Cu(pdt)(2)(H2O)(2)](2+) by decamethylferrocene and the oxidation of [Cu(pdt)(2)](+) by [Co(2,2'-bipyridine)(3)](3+) in acetonitrile revealed that both cross reactions were sluggish through a gated process (the structural change took place prior to the electron transfer) accompanied by slow direct electron transfer processes. It was found that the triazine ring of the coordinated pdt ligand rotates around the C-C bond between the triazine and pyridine rings with the kinetic parameters k = 51 +/- 5 s(-1) (297.8 K), Delta H-double dagger = 6.2 +/- 1.1 kJ mol(-1) and Delta S-double dagger = -192 +/- 4 J mol(-1) K-1. The electron self-exchange process was directly measured using the line-broadening method: k(ex) = (9.9 +/- 0.5) x 10(4) kg mol(-1) s(-1) (297.8 K) with Delta H-double dagger = 44 +/- 7 kJ mol(-1) and Delta S-double dagger = 0.2 +/- 2.6 J mol(-1) K-1. By comparing this rate constant with the self-exchange rate constants estimated from the cross reactions using the Marcus cross relation, the nonadiabaticity (electronic) factors, kappa(el), for the direct electron transfer processes between [Cu(pdt)(2)](+/2+) and non-copper metal (Fe2+ and Co3+) complexes were estimated as ca. 10(-7), indicating that the electronic coupling between the d orbitals of copper and of non-copper metals is very small.

DOI： 10.1039/c5dt01808k

Palladium(II) mononuclear and palladium(II)/ruthenium(II) heterodinuclear complexes containing 2-quinolyl-substituted (pyridine-2-carbonyl)hydrazone

Asami Mori, Takayoshi Suzuki, Yuichi Nakatani, Yukinari Sunatsuki, Masaaki Kojima, Kiyohiko Nakajima

DALTON TRANSACTIONS 44 ( 36 ) 15757 - 15760 2015

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

A reaction of [PdCl2(cod)] (cod = 1,5-cyclooctadiene) and an E/Z mixture of quinoline-2-carbaldehyde (pyridine-2-carbonyl) hydrazone (HL) gave two kinds of Pd-II mononuclear complexes, [PdCl-(Z-L-kappa N-3,N',N '')] (1) and [PdCl2(E-HL'-kappa N-2,N')] (2), where L- is the deprotonated hydrazonate anion and HL' is the quinolinium-hydrazonate zwitterionic form of HL. Complex 2 is gradually converted to 1 in solution, and complex 1 is a good precursor to prepare a Pd-II/Ru-II heterodinuclear complex bridged by hydrazonate, trans(Cl, Cl)-[RuCl2(PPh3)(2)(mu-L)PdCl] (3).

DOI： 10.1039/c5dt02345a

Syntheses, Crystal Structures and Ligand Field Properties of Iron(II) Complexes with PNP Ligands: Origin of Large Ligand Field by a Phosphorous Donor Atom

Takuya Mabe, Hiroshi Yamaguchi, Masayuki Fujiki, Kyoko Noda, Koji Ishihara, Masahiko Inamo, Refat Moustafa Hassan, Satoshi Iwatsuki, Takayoshi Suzuki, Hideo D. Takagi

JOURNAL OF SOLUTION CHEMISTRY 43 ( 9-10 ) 1574 - 1587 2014.10

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER/PLENUM PUBLISHERS

New iron(II) complexes were synthesized with two tridentate hybrid ligands having phosphorous and nitrogen donor sites, in order to quantitatively estimate the difference of the ligand-field strengths of phosphorous and nitrogen donor sites in cationic metal complexes. Iron(II) complexes with bis(dimethylphosphinoethyl)amine (PNP) and 2,6-bis(diphenylphosphinomethyl)pyridine (PpyP) ligands crystallized as un-symmetric facial-[Fe(PNP)(2)](PF6)(2)center dot CH3NO2 and mer-[Fe(PpyP)(2)](CF3SO3)(2), respectively, as expected from the steric congestion and from the tendency to avoid the mutual trans influence between two phosphorous donor sites. Both complexes are in the low-spin electronic state up to 400 K. The pseudo-D (4h) coordination geometry of the PpyP complex made it possible to separate axial (2 x N) and equatorial (4 x P) contributions to the overall ligand-field by means of a spectrometric method: the difference in the ligand-field strengths by the equatorial Ph2P-donor sites and by the axial 2,6-disubstituted pyridine donor sites is ca. 13,200 cm(-1). A significantly reduced inter-electronic repulsion parameter (425 cm(-1) for both PNP and PpyP complexes) from the value of the free ion (1,060 cm(-1)) indicates covalent interaction between the Fe(II) and P atoms even in these cationic metal complexes. It is shown that the degree of covalency as well as the coordination bond strengths between various metal ions and phosphorous/nitrogen donor atoms is successfully explained by the relative energy levels of interacting atomic orbitals calculated on the basis of the Thomas-Fermi-Dirac potential.

DOI： 10.1007/s10953-014-0182-3

Crystal Structure and Spectroscopic Properties of Cyclic Dipeptide: A Racemic Mixture of cyclo(D-Prolyl-L-Tyrosyl) and cyclo(L-Prolyl-D-Tyrosyl)

Yong Pyo Hong, Sung-Hong Lee, Jong-Ha Choi, Ayana Kashima, Go Nakamura, Takayoshi Suzuki

BULLETIN OF THE KOREAN CHEMICAL SOCIETY 35 ( 8 ) 2299 - 2303 2014.8

Language：English Publishing type：Research paper (scientific journal) Publisher：KOREAN CHEMICAL SOC

Two diastereoisomers of cyclo(Pro-Tyr) have been synthesized simultaneously. The crystal structures and conformations of both cyclo(L-Pro-L-Tyr) and a racemic mixture of cyclo(D-Pro-L-Tyr) and cyclo(L-Pro-D-Tyr), abbreviated as rac-cyclo(D-Pro-L-Tyr/L-Pro-D-Tyr), have been determined by a single-crystal X-ray diffraction study at low temperature. The crystals of rac-cyclo(D-Pro-L-Tyr/L-Pro-D-Tyr) belong to orthorhombic space group Pna2(1) with a = 10.755 (1), b = 12.699 (1), c = 9.600 (1) angstrom and Z = 4. The tyrosine side chain is folded towards the diketopiperazine (DKP) ring. The DKP ring adopts a twist boat conformation with pseudo symmetry C-2v. The pyrrolidine ring has an envelope conformation with the N5, C4, C7 and C8 atoms in a plane. The crystal of rac-cyclo(D-Pro-L-Tyr/L-Pro-D-Tyr) is stabilized by hydrogen bonds between amide N2-H2 and carbonyl oxygen O2 in the neighbor. The hydroxyl group of tyrosine residue is also hydrogen bonded to the oxygen of the carbonyl group of the DKP ring in the next molecule. The spectroscopic properties of both isomers are also described.

DOI： 10.5012/bkcs.2014.35.8.2299

Chiral Crystal Structure of a P2(1)2(1)2(1) Kryptoracemate Iron(II) Complex with an Unsymmetric Azine Ligand and the Observation of Chiral Single Crystal Circular Dichroism

Yukinari Sunatsuki, Kunihiro Fujita, Hisashi Maruyama, Takayoshi Suzuki, Hiroyuki Ishida, Masaaki Kojima, Robert Glaser

CRYSTAL GROWTH & DESIGN 14 ( 8 ) 3692 - 3695 2014.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A chiral complex, [Fe(HL)(2)](PF6)(2) (1), where HL denotes 2-pyridylmethylidenehydrazono-4-(2-methylimidazoly)methane, was prepared. X-ray structure analysis revealed that it crystallizes as a kryptoracemate of sesquihydrate chiral crystals in the orthorhombic non-centrosymmetric space group P2(1)2(1)2(1) (Z = 8, Z' = 2). Two diastereomeric cationic complexes with opposite configuration reside within the asymmetric unit. KBr pellets prepared using selected single crystals showed enantiomorphous circular dichroism patterns.

DOI： 10.1021/cg500635q

Electrochemical Behavior of Phosphine-Substituted Ruthenium(II) Polypyridine Complexes with a Single Labile Ligand

Go Nakamura, Masaya Okamura, Masaki Yoshida, Takayoshi Suzuki, Hideo D. Takagi, Mio Kondo, Shigeyuki Masaoka

INORGANIC CHEMISTRY 53 ( 14 ) 7214 - 7226 2014.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A series of phosphine-substituted ruthenium poly-pyridine complexes, cis(P,Cl)-[Ru(trpy)(Pqn)Cl]PF6 (cis-Cl), trans(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)](PF6)(2) (trans-PN), cis(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)] (PF6)(2) (cis-PN), and [Ru(trpy)(dppbz)(MeCN)] (PF6)(2) (PP), were synthesized and crystallographically characterized (trpy = 2,2':6',2 ''-terpyridine, Pqn = 8-(diphenylphosphanyl)quinoline, and dppbz = 1,2-bis(diphenylphosphanyl)benzene). In electrochemical measurements for cis-PN and PP, the reduction of cis-PN resulted in the formation of trans-PN via cis trans isomerization and that of PP proceeded via a two-electron-transfer reaction. The mechanism of the electrochemical behaviors is discussed through consideration of five-coordinated species, [Ru(trpy)(Pqn)](n+) or [Ru(trpy)(dppbz)](n+) (n = 0-2), formed by liberation of a monodentate labile ligand.

DOI： 10.1021/ic5003644

Chiral Incomplete-cubane-type (Mn3O4)-O-III Clusters Containing a mu(3)-Methoxido or Hydroxido

Marina Inoue, Takayoshi Suzuki, Yukinari Sunatsuki, Akira Fuynhiro, Nazzareno Re

CHEMISTRY LETTERS 43 ( 6 ) 784 - 786 2014.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Two new cluster compounds having chiral incomplete-cubane-type (Mn3O4)-O-III cores were synthesized using (2S)-2-hydroxy-4-(salicylideneamino)butyrate (H2L-) and characterized by X-ray analysis as well as magnetic susceptibility and spectroscopic measurements. Compound 1 contains a [Mn-3(III)(L)(3)(mu(3)-OMe)](-) cluster anion, while compound 2 prepared in water has a heptanuclear structure bearing two [Mn-3(III)(L)(3)(mu(3)-OH)](-) clusters connected by a Mn-II(H2O)(4) fragment. In both compounds, a moderate intracluster (MnMnIII)-Mn-III center dot center dot center dot)31 ferromagnetic interaction was observed. It was also found that the (Mn3O4)-O-III cluster cores are maintained in solution.

DOI： 10.1246/cl.140067

Linkage and Geometrical Isomers of Dichloridobis(triphenylphosphine)ruthenium(II) Complexes with Quinoline-2-carbaldehyde (Pyridine-2-carbonyl)hydrazone: Their Molecular Structures and Electrochemical and Spectroscopic Properties

Asami Mori, Takayoshi Suzuki, Yukinari Sunatsuki, Atsushi Kobayashi, Masako Kato, Masaaki Kojima, Kiyohiko Nakajima

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2014 ( 1 ) 186 - 197 2014.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

The reactions of quinoline-2-carbaldehyde (pyridine-2-carbonyl)hydrazone (HL) and [RuCl2(PPh3)(3)] in various solvents at different temperatures gave the three geometrical isomers trans(Cl,Cl)-, cis(Cl,Cl),trans(P,N)-, and trans(P,P)-[RuCl2(PPh3)(2){HL-O(amide),N(imine)}] (1, 2, and 3, respectively) as well as a linkage isomer trans(P,P)-[RuCl2(PPh3)(2){HL-N(imine),N(quin)}] (4). The molecular and crystal structures of 1-4, together with both E and Z configurational isomers (with respect to the C=N double bond) of the free ligand HL, were determined by X-ray analysis. The ligand HL adopted a Z form and acted as a O(amide),N(imine) bidentate ligand in 1-3, whereas it was an E isomer with a N(imine),N(quin) coordination mode in 4. The gradual thermal conversions of 1 to 2 and of 2 to 3 were observed in dichloromethane and ethanol, respectively, but an interconversion between 3 and 4 was not detected. In dichloromethane, all complexes have a reversible Ru-III/II redox couple in the range 110-412 mV (vs. Ag/Ag+), and the redox potential was largely dependent on the coordination mode of HL and on the mutual configuration of the two PPh3 ligands. Such a potential shift can be interpreted as a combination of Cl-/amide O -donor and PPh3/quinoline N -acceptor orbital contributions to the Ru-II d orbitals [highest occupied molecular orbitals (HOMOs)]. Complexes 3 and 4 in acetonitrile showed a gradual spectral change, probably because of the substitution of the Cl- ligand by the acetonitrile solvent. In addition, 2-4 showed solvatochromic behavior even in noncoordinating solvents that resulted from a blueshift of the metal-to-ligand charge-transfer (MLCT) transition band in polar solvents. These electrochemical and spectroscopic properties are also supported by DFT and time-dependent DFT (TD-DFT) calculations.

DOI： 10.1002/ejic.201301150

Preparation, crystal structures, and spectroscopic properties of cobalt(III) complexes bearing 2,4-pentanedionate (acac(-)) and 2-cyanoethylphosphines: trans-[Co(acac)(2){P(CH2CH2CN)(n)Ph3-n}]BF4 (n=1-3)

Keiko Kihara, Syohei Yamaguchi, Yasuo Kawahata, Masakazu Kita, Takayoshi Suzuki, Yukinari Sunatsuki, Masaaki Kojima, Kazuo Kashiwabara

POLYHEDRON 67 ( 1 ) 111 - 114 2014.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

A series of cobalt(III) complexes containing 2-cyanoethylphosphines, [Co(acac)(2){P(CH2CH2CN)(n)Ph3-n}(2)]-BF4 {acac = 2,4-pentanedionate; n = 1 (1), 2 (2), and 3 (3)} have been prepared, and their molecular and crystal structures have been determined. The X-ray diffraction study revealed that these complexes are the trans isomers in the crystals. The Co-P bond lengths are little affected by the number of 2-cyanoethyl substituents on the P atom, which is consistent with a small change of the sigma-donicity among these phosphines. The trans configuration of these complexes is maintained in solution, as revealed by 1H NMR spectroscopy. The 2-cyanoethylphosphines could not form stable cis-isomers of [Co(acac)(2){P(CH2CH2CN)(n)Ph3-n}(2)](+), like the corresponding methylphosphines (PMenPh3-n,). This fact probably results from a strong electron-withdrawing property of a terminal cyano group of phosphine substituent. In the UV-Vis absorption spectra of complexes 1-3, the LMCT transition band is observed in the range of 20500-24000 cm(-1), which is comparable to the analogous PMenPh3-n, complexes, but their intensity is characteristically weaker than that of the corresponding PMenPh3-n complexes. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2013.09.001

Molecular structure and spectroscopic properties of [Co( Me(2)dtc)(2) {(Ph2PO)(2)BF2}] (Me(2)dtc = N,N-dimethyldithiocarbamate)

Kyohei Sakano, Syohei Yamaguchi, Takayoshi Suzuki, Yukinari Sunatsuki, Masaaki Kojima, Kazuo Kashiwabara

INORGANICA CHIMICA ACTA 410 ( 1 ) 122 - 125 2014.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Oxidation of a blue ethanolic mixture containing Co(BF4)(2)center dot 6H(2)O and PClPh2 by tetramethylthiuram disulfide afforded a red- colored complex having a cis-[Co-III(Me(2)dtc)(2)(P)(2)] environment (Me(2)dtc = N, N-dimethyldithiocarbamate), although the yield was relatively low. Single- crystal X- ray crystallography revealed that the product was [Co(Me(2)dtc)(2){(Ph2PO)(2)BF2}] (1), where bis(diphenylphosphinito) difluoroborate was probably formed by hydrolysis of PClPh2 followed by reaction with BF4 in ethanol. The same complex was also prepared by hydrolysis of cis-[Co(Me(2)dtc)(2)(PHPh2)(2)]BF4 in a mixture of acetonitrile, methanol and water. The molecular structure and spectroscopic properties of complex 1 were compared with those of the corresponding Ph2POMe complex, cis-[Co(Me(2)dtc)(2)(Ph2POMe)(2)]BF4. (C) 2013 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.ica.2013.10.028

Efficient and eco-friendly syntheses of 1,5-benzothiazepines and 1,5-benzodiazepines catalyzed by [Hmim][NO<inf>3</inf>] under mild conditions

Loghmani-Khouzani, H., Tamjidi, P., Mohammadpoor-Baltork, I., Yaeghoobi, M., Rahman, N.A., Khosropour, A.R., Moghadam, M., Tangestaninejad, S., Mirkhani, V., Habibi, M.H., Kashima, A., Suzuki, T.

Journal of Heterocyclic Chemistry 51 ( 1 ) 2014

Four-Electron Oxidative Dehydrogenation Induced by Proton-Coupled Electron Transfer in Ruthenium(III) Complex with 2-(1,4,5,6-Tetrahydropyrimidin-2-yl)phenolate

Ryoji Mitsuhashi, Takayoshi Suzuki, Yukinari Sunatsuki

INORGANIC CHEMISTRY 52 ( 17 ) 10183 - 10190 2013.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

New rutheniurn(II or III) complexes with general formula [Ru(O-N)(bpy)(2)](n+) (O-N = unsymmetrical bidentate phenolate ligand; bpy = 2,2'-bipyridine) were synthesized, and their crystal structures and electrochemical properties were characterized. Ru-II complexes with, 2-(2-imidazolinyl)phenolate (Himn(-)) or 2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolate (Hthp(-)) could be deprotonated by addition of excess KO'Bu, although the deprotonated species were easily reprotonated by. exposure to air. Unlike these Run complexes, their Ru-III analogs showed interesting ligand oxidation reactions upon addition of bases. With Ru-III (Himn)(bpy)(2)](2+), two electron oxidation of Himn(-) and reduction of the Rum center resulted in conversion of the 2-irnidazolinyl group, to a 2-imidazolyl group. On the other hand, the corresponding Hthp- complex exhibited four electron oxidation of the ligand to form 2-(2-pyrirnidyl)phenolate (pym-). These aromatization reactions of imidazolinyl and 1,4,5,6-tetrahydropyrimidyl groups were also achieved by the electrochemically generated Rum complexes.'

DOI： 10.1021/ic401662v

Hydrogen-bonding interactions, geometrical selectivity and spectroscopic properties of cobalt(III) complexes with unsymmetrical tridentate amine-amidato-phenolato type ligands

Ryoji Mitsuhashi, Takayoshi Suzuki, Yukinari Sunatsuki, Masaaki Kojima

Inorganica Chimica Acta 399 131 - 137 2013.4

Language：English Publishing type：Research paper (scientific journal)

Four cobalt(III) complexes with the formula of [Co(Ln)2] - bearing tridentate amine-amidato-phenolato-type ligands (Ln: n = 1-4) were synthesized. All of the complexes were characterized by 1H NMR spectroscopy and X-ray analysis. The geometrical selectivity was found to depend on the flexibility of the amine-amidato chelate in combination with the planar 2-oxybenzamido 6-membered chelate
that is, the amine-amidato 5-membered chelate took the mer-type geometry, and the 6-membered chelate took the fac-type geometry. In most of the mer-type complexes, intermolecular double hydrogen bonds via amidato(O) and amino group were selectively formed between their enantiomeric pairs of mononuclear complexes. In the case of two chiral ligands {L22- = 2-amino-1-(2-oxybenzamido)propane
L32- = trans-1-amino-2-(2-oxybenzamido)cyclohexane}, [Co(L3)2]- showed diastereoselectivity while [Co(L2)2]- did not. Furthermore, PPh4[Co(L1)2] (L12- = 2-amino-1-(2-oxybenzamido)-2-methylpropane) showed an apparent solvatochromic behavior in several solvents. Although the molecular structures of [Co(L2 or L3)2]- are quite similar to that of [Co(L1) 2]-, these complexes did not exhibit such a solvatochromic behavior. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2013.01.011

Comparison of ancillary ligand effects between 2,2 '-bipyridine and 2-(2 '-pyridyl)phenyl in the linkage and bridging isomerism of 5-methyltetrazolato iridium(III) and/or rhodium(III) complexes

Asuka Takayama, Takayoshi Suzuki, Miyu Ikeda, Yukinari Sunatsuki, Masaaki Kojima

DALTON TRANSACTIONS 42 ( 40 ) 14556 - 14567 2013

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Several new iridium(III) and rhodium(III) complexes bearing 5-methyltetrazolate (MeCN4-) have been prepared, and their structures in the crystals and in solution have been determined by X-ray analysis and by NMR spectroscopy, respectively. In the crystals of the mononuclear complexes, kappa N-2-coordination of MeCN4- was observed when the ancillary ligand was 2,2'-bipyridine (bpy): [Cp*M(bpy)(MeCN4-kappa N-2)]PF6 (Cp* = eta(5)-C5Me5; M = Ir: 1 and Rh: 2), while the corresponding complexes with 2-(2'-pyridyl)phenyl (ppy(-)) were confirmed to have the kappa N-1-coordination of MeCN4-: [Cp*M(ppy)(MeCN4-kappa N-1)] (M = Ir: 3 and Rh: 4). In solution, the Ir-III complexes (1 and 3) were robust enough to maintain their molecular structures, but the Rh-III complexes (2 and 4) existed as an equilibrium mixture of the kappa N-1- and kappa N-2-isomers. In addition to the Ir-III-Ir-III and Rh-III-Rh-III homodinuclear complexes bridged by MeCN4- (5-8), the corresponding heterodinuclear Ir-III-Rh-III complexes (9-12) were prepared using the mononuclear Ir-III complexes (1 and 3) as precursors. The molecular structures of these dinuclear complexes were also characterised. Interestingly, both of the heterodinuclear complexes comprised of Cp*M(bpy)(2+) and Cp*M'(ppy)(+) fragments, [Cp*M(bpy)(mu-MeCN4)M'(ppy)Cp*](PF6)(2) (M = Ir, M' = Rh: 10 and M = Rh, M' = Ir: 11), exhibited selective crystallisation of a specific mu-kappa N-1(M'-ppy):kappa N-3(M-bpy) isomer. In solution, the dinuclear complexes with a Rh-N(MeCN4) bond and more than one positive charge (6 and 9-11) showed a dissociation equilibrium, while monocationic MeCN4-bridged complexes (7, 8 and 12) were inactive for dissociation. Furthermore, the heterodinuclear complexes of 9-12, as well as the Rh-III-Rh-III complex of 8, exhibited a bridging isomerisation, which would proceed via a eta(2):eta(2)-intermediate without dissociation of Cp*M(bpy or ppy) fragments.

DOI： 10.1039/c3dt51667a

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