Faculty Profiles - SUNATSUKI Yukinari

Papers - SUNATSUKI Yukinari

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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

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

Abrupt Spin Transition with Thermal Hysteresis of Iron(III) Complex [Fe-III(Him)(2)(hapen)]AsF6 (Him = Imidazole, H(2)hapen = N,N '-Bis(2-hydroxyacetophenylidene)ethylenediamine)

Takeshi Fujinami, Masataka Koike, Naohide Matsumoto, Yukinari Sunatsuki, Atsushi Okazawa, Norimichi Kojima

INORGANIC CHEMISTRY 53 ( 4 ) 2254 - 2259 2014.2

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

The solvent-free spin crossover iron(III) complex [Fe-III(Him)(2)(hapen)]AsF6 (Him = imidazole, H(2)hapen = bis(2-hydroxyacetophenylidene)ethylenediamine), exhibiting thermal hysteresis, was synthesized and characterized. The Fern ion has an octahedral coordination geometry, with N2O2 donor atoms of the planar tetradentate ligand (hapen) and two nitrogen atoms of two imidazoles at the axial positions. One of two imidazoles is hydrogen-bonded to the phenoxo oxygen atom of hapen of the adjacent unit to give a hydrogen-bonded one-dimensional chain, while the other imidazole group is free from hydrogen bonding. The temperature dependencies of the magnetic susceptibilities and Mossbauer spectra revealed an abrupt spin transition between the high-spin (S = 5/2) and low-spin (S = 1/2) states, with thermal hysteresis.

DOI： 10.1021/ic402947u

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

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

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 410 122 - 125 2014.1

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

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 67 111 - 114 2014.1

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

Synthesis, Structure, Luminescent, and Magnetic Properties of Carbonato-Bridged Zn(2)(II)Ln(2)(II) Complexes [(mu(4)-CO3)(2){Zn(II)L(n)Ln(II)(NO3)}(2)) (Ln(III) = Gd-III, Tb-III, Dy-III; L-1 = N,N'-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L-2 = N,N'-Bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato)

Kiyomi Ehama, Yusuke Ohmichi, Soichiro Sakamoto, Takeshi Fujinami, Naohide Matsumoto, Naotaka Mochida, Takayuki Ishida, Yukinari Sunatsuki, Masanobu Tsuchimoto, Nazzareno Re

INORGANIC CHEMISTRY 52 ( 21 ) 12828 - 12841 2013.11

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

Carbonato-bridged Zn(2)(II)Ln(2)(III) complexes [(mu(4)-CO3)(2){Zn(II)L(n)Ln(III)(NO3)}(2)]center dot solvent were synthesized through atmospheric CO2 fixation reaction of [(ZnLn)-L-II(H2O)(2)]center dot xH(2)O, Ln(III)(NO3)(3)center dot 6H(2)O, and triethylamine, where Ln(III) = Gd-III, Tb-III, Dy-III; L-1 = N,N'-bis(3-methorry-2-oxybenzylidene)-1,3-propanediaminato, L-2 = N,N'-bis(3-ethorry-2-oxybenzylidene)1,3-propanediaminato. Each Zn(2)(II)Ln(2)(III) structure possessing an inversion center can be described as two di-mu-phenoxo-bridged {Zn(II)L(n)Ln(III)(NO3)} binuclear units bridged by two carbonato CO32- ions. The Zn-II ion has square pyramidal coordination geometry with N2O2 donor atoms of L-n and one oxygen atom of a bridging carbonato ion at the axial site. Ln(III) ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base L-n, two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9-300 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic susceptibilities under the direct current bias fields of 0 and 1000 Oe were measured. The magnetic properties of the Zn(2)(II)Ln(2)(III) complexes are analyzed on the basis of the dicarbonato-bridged binuclear structure, as the Zn-II ion with d(10) electronic configuration is diamagnetic. ZnGd1 (L-1) and ZnGd2 (L-2) show a ferromagnetic Gd-III-Gd-III interaction with J(Gd-Gd)Zn(2)(II)Ln(2)(III) = +0.042 and +0.028 cm(-1), respectively, on the basis of the Hamiltonian H = -2J(Gd-Gd)(S) over cap (Gd1).(S) over cap (Gd2). The magnetic data of the complexes (Ln(III) = D 11) were analyzed by a spin Hamiltonian including the crystal field effect on the Ln(III) ions and the Ln(III)-Ln(III) magnetic interaction. The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy. Luminescence spectra of (Zn2Tb2III)-Tb-II complexes were observed, while those of (Zn2Dy2III)-Dy-II were not detected. The fine structure assignable to the D-5(4) -> F-7(6) transition of ZnTb1 and ZnTb2 is in good accord with the energy pattern from the magnetic analysis. The Zn(2)(II)Ln(2)(III) complexes (Ln(III) = Tb-III, Dy-III) showed an out-of-phase signal with frequency-dependence in alternating current susceptibility, indicative of single molecule magnet. Under a dc bias field of 1000 Oe, the signals become significantly more intense and the energy barrier, Delta/k(B), for the magnetic relaxation was estimated from the Arrhenius plot to be 39(1) and 42(8) K for ZnTb1 and ZnTb2, and 52(2) and 67(2) K for ZnDyl and ZnDy2, respectively.

DOI： 10.1021/ic4022273

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

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/ic401667v

Carbonato-Bridged NO(2)(II)Ln(2)(III) (Ln(III) = Gd-III, Tb-III, Dy-III) Complexes Generated by Atmospheric CO2 Fixation and Their Single-Molecule-Magnet Behavior: [(mu(4)-CO3)(2){Ni-II(3-MeOsaltn)(MeOH or H2O)Ln(III)(NO3)}(2)]center dot solvent [3-MeOsaltn = N,N '-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato]

Soichiro Sakamoto, Takeshi Fujinami, Koshiro Nishi, Naohide Matsumoto, Naotaka Mochida, Takayuki Ishida, Yukinari Sunatsuki, Nazzareno Re

INORGANIC CHEMISTRY 52 ( 12 ) 7218 - 7229 2013.6

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

Atmospheric CO2 fixation of [Ni-II(3-MeOsaltn)(H2O)(2)]center dot 2.5H(2)O [3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene) -1,3-propanediaminato], Ln(III)(NO3)(3)center dot 6H(2)O, and triethylamine occurred in methanol/acetone, giving a first series of carbonato-bridged Ni-2(II),Ln(2)(III) complexes [(mu(4)-CO3)(2){Ni-II(3-MeOsaltn)(MeOH)-Ln(III)(NO3)}(2)] (1Gd, 1Tb, and 1Dy). When the reaction was carried out in acetonitrile/water, it gave a second series of complexes [(mu(4)-CO3)(2){Ni-II(3-MeOsaltn)(H2O)-Ln(III)(NO3)}(2)]center dot 2CH(3)CN center dot 2H(2)O (2Gd, 2Tb, and 2Dy). For both series, each Ni(2)(II)Ln(2)(III) structure can be described as two di-mu-phenoxo-bridged Ni(II)Ln(III) binuclear units bridged by two carbonato CO32- units to form a carbonato-bridged (mu(4)-CO3)(2){Ni(2)(II)Ln(2)(III)) structure. The high-spin Ni-II ion has octahedral coordination geometry, and the Ln(III) ion is coordinated by O-9 donor atoms from Ni-II(3-MeOsaltn), bidentate NO3-, and one and two oxygen atoms of two CO32- ions. The NO3- ion for the first series roughly lie on Ln-O(methoxy) bonds and are tilted toward the outside, while for the second series, the two oxygen atoms roughly lie on one of the Ln-O(phenoxy) bonds due to the intramolecular hydrogen bond. The temperature-dependent magnetic susceptibilities indicated a ferromagnetic interaction between the Ni-II and Ln(III) ions (Ln(III) = Gd-III, Tb-III, Dy-III) for all of the complexes, with a distinctly different magnetic behavior between the two series in the lowest-temperature region due to the Ln(III)-Ln(III) magnetic interaction and/or different magnetic anisotropies of the Tb-III or Dy-III ion. Alternating-current susceptibility measurements under the 0 and 1000 Oe direct-current (dc) bias fields showed no magnetic relaxation for the (Ni2Gd2III)-Gd-II complexes but exhibited an out-of-phase signal for (Ni2Tb2III)-Tb-II and (Ni2Dy2III)-Dy-II, indicative of slow relaxation of magnetization. The energy barriers, Delta/k(B), for the spin flipping were estimated from the Arrhenius plot to be 12.2(7) and 6.1(3) K for 1Tb and 2Tb, respectively, and 18.1(6) and 14.5(4) K for 1Dy and 2Dy, respectively, under a dc bias field of 1000 Oe. Compound 1Dy showed relatively slow relaxation of magnetization reorientation even at zero dc applied field with Delta/k(B) = 6.6(4) K.

DOI： 10.1021/ic4008312

Syntheses, Structures, and Magnetic Properties of Acetato- and Diphenolato-Bridged 3d-4f Binuclear Complexes. [M(3-MeOsaltn)(MeOH)(x)(ac)Ln(hfac)(2)] (M = zn(II), Cu-II, Ni-II, Co-II; Ln = La-III, Gd-III, Tb-III, Dy-III; 3-MeOsaltn = N,N '-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato; ac = Acetato; hfac = Hexafluoroacetylacetonato; x=0 or 1)

Masaaki Towatari, Koshiro Nishi, Takeshi Fujinami, Naohide Matsumoto, Yukinari Sunatsuki, Masaaki Kojima, Naotaka Mochida, Takayuki Ishida, Nazzareno Re, Jerzy Mrozinski

INORGANIC CHEMISTRY 52 ( 10 ) 6160 - 6178 2013.5

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

A series of 3d-4f binuclear complexes, [M(3-MeOsaltn)(MeOH)(x)(ac)Ln(hfac)(2)] (x = 0 for M = Cu-II, Zn-II; x = 1 for M = Co-II, Ni-II; Ln Gd-III, Dy-III, La-III), have been synthesized and characterized, where 3-MeOsaltn, ac, and hfac denote N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propane-diaminato, acetato, and hexafluoroacetylacetonato, respectively. The X-ray analyses demonstrated that all the complexes have an acetato- and diphenolato-bridged M-II-Ln(III) binuclear structure. The Cu-II-Ln(III) and Zn-II-Ln(III) complexes are crystallized in an isomorphous triclinic space group PT, where the Cu-II or Zn-II ion has square pyramidal coordination geometry with N2O2 donor atoms of 3-MeOsaltn at the equatorial coordination sites and one oxygen atom of the bridging acetato ion at the axial site. The Co-II-Ln(III) and Ni-II-Ln(III) complexes are crystallized in an isomorphous monoclinic space group P2(1)/c, where the Co-II or Ni-II ion at the high-spin state has an octahedral coordination environment with N2O2 donor atoms of 3-MeOsaltn at the equatorial sites, and one oxygen atom of the bridged acetato and a methanol oxygen atom at the two axial sites. Each Ln(III) ion for all the complexes is coordinated by four oxygen atoms of two phenolato and two methoxy oxygen atoms of "ligand-complex" M(3-MeOsaltn), four oxygen atoms of two hfac(-), and one oxygen atom of the bridging acetato ion; thus, the coordination number is nine. The temperature dependent magnetic susceptibilities from 1.9 to 300 K and the field-dependent magnetization up to 5 T at 1.9 K were measured. Due to the important orbital contributions of the Li-III (Tb-III, Dy-III) and to a lesser extent the M-II (N-III, Co-II) components, the magnetic interaction between M-II and Ln(III) ions were investigated by an empirical approach based on a comparison of the magnetic properties of the M-II-Ln(III), Zn-II-Ln(III), and complexes. The differences of chi T-M and M(H) values for the M-II-Ln(III), Zn-II-Ln(III) and those for the M-II-La-III complexes, that is, Delta(T) = (chi T-M)(MLn) - (chi T-M)(znLn)-(chi T-M)(MLa) = J(MLn)(T) and Delta(H) = M-MLn(H) - M-ZnLn(H) - M-MLa(H) = J(MLn)(H), give the information of 3d-4f magnetic interaction. The magnetic interactions are ferromagnetic if M-II = (Cu-II, Ni-II, and Co-II) and Ln = (Gd-III, Tb-III, and Dy-III) The magnitudes of the ferromagnetic interaction, J(MLn)(T) and J(Mln)(H), are in the order Cu-II-Gd-III > Cu-II-Dy-III > Cu-II-Tb-III, while those are in the order of M-II-Gd-III approximate to M-II-Tb-III > M-II-Dy-III for M-II = Ni-II and Co".Alternating current (ac) susceptibility measurements demonstrated that the Ni-II-Dy-III and Co-II-Tb-III complexes showed out-of-phase signal with frequency-dependence and the Ni-II-Dy-III and Co-II-Dy-II complexes showed small frequency-dependence. The energy barrier for the spin flipping was estimated from the Arrhenius plot to be 14.9(6) and 17.0(4) K for the (NiII-TbIII) and Co-II-Tb-III complexes, respectively, under a dc bias field of 1000 Oe.

DOI： 10.1021/ic400594u

Syntheses, three types of hydrogen-bonded assembly structures, and magnetic properties of [Fe-III(Him)(2)(hapen)]Y center dot solvent (Him = imidazole, hapen = N,N '-bis(2-hydroxyacetophenylidene)ethylenediamine, Y = BPh4-, CF3SO3-, PF6-, ClO4-, and BF4-)

Masataka Koike, Keishiro Murakami, Takeshi Fujinami, Koshiro Nishi, Naohide Matsumoto, Yukinari Sunatsuki

INORGANICA CHIMICA ACTA 399 185 - 192 2013.4

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

Five iron(III) complexes of [Fe-III(Him)(2)(hapen)]Y center dot solvent with five different counter anions were synthesized, where Him = imidazole, H(2)hapen = N,N'-bis(2-hydroxyacetophenylidene)ethylenediamine, Y = BPh4- (1), CF3SO3- (2), PF6- (3), ClO4- (4), and BF4- (5), and solvent = methanol or H2O. Each Fe-III ion has octahedral coordination geometry with N2O2 donor atoms of the equatorial tetradentate ligand (hapen) and two nitrogen atoms of two imidazoles at the axial positions. The imidazole group is hydrogen-bonded to the phenoxo oxygen atom of hapen of the adjacent unit and/or to the counter anion or solvent molecule, to give three types of assembly structures involving linear dimer, cyclic dimer, and one-dimensional zigzag chain. Compound 1, with a cyclic dimer, and 2 and 3, with a one-dimensional chain, showed spin-equilibrium behavior between high-spin (S = 5/2) and low-spin (S = 1/2) states, whereas 4 and 5, with linear dimers, are high-spin complexes. Compound 3 shows abrupt spin transition with small thermal hysteresis. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2013.01.021

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) Publisher：ELSEVIER SCIENCE SA

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 H-1 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 {L2(2) = 2-amino-1-(2-oxybenzamido) propane; L3(2) = trans-1-amino-2-(2-oxybenzamido)cyclohexane}, [Co(L3)(2)] showed diastereoselectivity while [Co(L2)(2)] did not. Furthermore, PPh4[Co(L1)(2)] (L1(2) = 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. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2013.01.011

Facial and meridional geometrical isomers of tris(2-methylimidazol-4-yl-methylideneaminobenzyl)iron(II) with Delta- and Lambda-con figurations and their enantio-discriminative assembly via imidazole ... chloride hydrogen bonding and spin cross-over properties (Reprinted from Polyhedron, vol 44, pg 194, 2012)

Daisuke Furushou, Tomotaka Hashibe, Takeshi Fujinami, Koshiro Nishi, Hiroaki Hagiwara, Naohide Matsumoto, Yukinari Sunatsuki, Masaaki Kojima, Seiichiro Iijima

POLYHEDRON 52 1489 - 1498 2013.3

Language：English Publisher：PERGAMON-ELSEVIER SCIENCE LTD

A bidentate 2-methylimidazol-4-yl-methylideneaminobenzyl ligand (HLMe-Renz) reacts with (FeCl2)-Cl-II center dot 4H(2)O and NaPF6 at a 3:1:1 molar ratio to yield a tris(2-methylimidazol-4-yl-methylideneaminobenzyl)iron(II) chloride hexafluorophosphate solvate with the formula of [Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot solvent. Meridional and facial geometrical isomers, i.e., mer-[Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot 1.5H(2)O (1 center dot PF6.1.5H(2)O) and fac[Fell( [Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot EtOH.H2O (2-PF6 center dot EtOH center dot H2O), were selectively crystallized from methanol and ethanol solutions, respectively. fac-[Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot H2O (2.SbF6 center dot 1.H2O) and fac-[Fe-II (HLMe-Benz)(3)]C1 center dot EtOH center dot H2O(2.ClO4 center dot EtOH2O) are synthesized in ethanol, using the corresponding anions. Each Fell ion has an octahedral coordination geometry with N6 donor atoms from three bidentate ligands. All three imidazole groups in both thefac- and mer-[Fe-II (HLMe-Benz)(3)](2+) cations are hydrogen-bonded to neighboring three Cl- ions, and each Cl- ion is hydrogen-bonded to three imidazole groups of three neighboring complex cations; this results in the formation of hydrogen-bonded assembly structures. mer-Complex 1.PF6.1.5H(2)O forms a heterochiral two-dimensional (2D) network structure comprised of cyclic [Fe-II (HLMe-Benz)(3)](2+) ... Cl-}(4) units with an Delta Delta Delta or Lambda Lambda Delta configuration; the PF6- ions occupy the spaces between the 2D layers. All the fac-complexes have isomorphous cubane-like tetrameric structures, i.e.,.Cl},. C114. The tetranuclear structure comprises four homo-chiral {fac-[Fe-II (HLMe-Benz)(3)](2+) ... Cl-3(-)} cations and four Cl- ions interconnected by twelve imidazole-chloride hydrogen bonds to form a chiral cubane supramolecule that encapsulates one counter anion. In the crystal lattice, the cubane-like tetramers with opposite chiralities are alternately arrayed. The temperature dependence of the magnetic susceptibilities and Mossbauer spectra reveal that the fac-complexes show incomplete spin crossover behavior, while the mer-complex shows a gradual spin crossover between high-spin (HS, S= 2) and low-spin (LS, S = 0) states. (C) 2013 Published by Elsevier Ltd.

DOI： 10.1016/j.poly.2013.02.003

Stepwise Spin Transition and Hysteresis of a Tetrameric Iron(II) Complex, fac-[Tris(2-methylimidazol-4-ylmethylidene-n-hexylamine)]iron(II) Chloride Hexafluorophosphate, Assembled by Imidazole center dot center dot center dot Chloride Hydrogen Bonds

Koshiro Nishi, Hiroki Kondo, Takeshi Fujinami, Naohide Matsumoto, Seiichiro Iijima, Malcolm A. Halcrow, Yukinari Sunatsuki, Masaaki Kojima

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY ( 5-6 ) 927 - 933 2013.2

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

A spin-crossover iron(II) complex, fac-[Fe-II(HLn-Hx)(3)]Cl center dot PF6 (1), that exhibits stepwise spin transition and thermal hysteresis was synthesized by using the ligand 2-methylimidazol-4-ylmethylidene-n-hexylamine (HLn-Hx). Four complex cations (fac-[Fe-II(HLn-Hx)(3)](2+)) and four Cl- anions associate through twelve imidazole center dot center dot center dot Cl- H bonds to give a tetrameric cubane-like assembly, and one PF6- anion is encapsulated within the cavity of the cubane. Magnetic susceptibility measurements showed a three-step spin transition, and the spin-crossover profile became less pronounced as the sweep rate increased. At a sweep rate of 0.5 K min(-1), the midpoint temperatures of the three steps are T-c(up arrow) = 131.2, 144.2, and 154.2 K in the heating mode and T-c(down arrow) = 116.8, 137.8, and 151.8 K in the cooling mode. The respective thermal hystereses were evaluated to be 14.4, 6.3, and 2.4 K wide.

DOI： 10.1002/ejic.201201298

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

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

Carbonate-bridged tetranuclear (Ni2Gd2III)-Gd-II complex generated by atmospheric CO2 fixation

Soichiro Sakamoto, Suguru Yamauchi, Hiroaki Hagiwara, Naohide Matsumoto, Yukinari Sunatsuki, Nazzareno Re

INORGANIC CHEMISTRY COMMUNICATIONS 26 20 - 23 2012.12

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

Atmospheric CO2 fixation by a basic reaction mixture of [Ni-II(3-MeOsaltn)(H2O)(2)] and Gd-III(NO3)(3)center dot 6H(2)O gave a carbonate-bridged tetranuclear (Ni2Gd2III)-Gd-II complex, (mu(4)-CO3)(2)[Ni-II(3-MeOsaltn)(MeOH)Gd-III(NO3)](2)center dot H2O, where 3-MeOsaltn denotes N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato. The tetranuclear structure possessing an inversion center can be described as two [(NiGdIII)-Gd-II] binuclear units bridged by two carbonate CO32- ions: two oxygen atoms of the carbonate ion bridge the high-spin Ni-II and Gd-III ions of a binuclear unit and the remaining oxygen atom of the carbonate ion coordinates to a Gd-III ion of the adjacent binuclear unit. The temperature-dependent magnetic susceptibilities, from 1.9 to 300 K, follow the Curie-Weiss equation of chi T-M= C/(T - theta) with theta = +2.3 K and C = 18.24 cm(3) K mol(-1), suggesting a ferromagnetic interaction. The magnetic data were well reproduced assuming two independent [Ni-II-Gd-III] binuclear units with the parameters of J(Ni-Gd) = +1.2 cm(-1) and D = +2.1 cm(-1). (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.inoche.2012.08.022

Synthesis, structures, and magnetic properties of iron(II) complexes, [Fe-II(HLMe)(2)] (ClO4)(2) and its ethanol adduct [Fe-II(HLMe)(2)](ClO4)(2)center dot EtOH (HLMe=2-methylimidazol-4-yl-methylideneamino-2-ethylpyridine): Their structural distortion and spin states

Hiroaki Hagiwara, Suguru Yamauchi, Naohide Matsumoto, Yukinari Sunatsuki

POLYHEDRON 48 ( 1 ) 110 - 116 2012.11

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

Two new iron(II) complexes, [Fe-II(HLMe)(2)](ClO4)(2) (1) and its ethanol adduct [Fe-II(HLMe)(2)](ClO4)(2)center dot EtOH (2) were synthesized by selective crystallization in methanol and ethanol, respectively, where HLMe is a tridentate N-3 ligand, 2-methylimidazol-4-yl-methylideneamino-2-ethylpyridine, and their structures and magnetic properties were investigated. Each compound contains the same octahedrally N-6 coordinated complex-cation [Fe-II(HLMe)(2)](2+) and two ClO4- ions. The non-solvated compound 1 is the HS (S = 2) complex without spin transition over the 5-300 K temperature range, and has the homochiral 1D helical-chain structure constructed of the intermolecular NH center dot center dot center dot O- hydrogen bonds between ClO4- ions and neighboring imidazole NH groups of the [Fe-II(HLMe)(2)](2+) cations. The ethanol adduct 2 shows a gradual one-step spin transition between the HS (S = 2) and LS (S = 0) states, and has two crystallographically independent iron(II) sites with two NH(imidazole)center dot center dot OH(EtoH)center dot center dot center dot O(ClO4-) hydrogen bonds of Fe(1) site and two NH(imidazole)center dot center dot center dot O(ClO4-) hydrogen bonds of Fe(2) site. There are no further intermolecular interactions to produce an extended structure in a crystal lattice of 2. The presence or absence of thermal spin transition is related to the structural distortion of each HS molecule of these perchlorate salts associated with their surroundings of intermolecular hydrogen bonds. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2012.09.010

Preparation, Crystal Structures, and Behavior in Solution of Cobalt(III) Complexes Containing 2-Cyanoethylphosphines: trans-[Co(Me2dtc)(2){P(CH2CH2CN)(n)Ph3-n}]BF4 (n=1-3; Me(2)dtc(-): N,N-Dimethyldithiocarbamate)

Keiko Kihara, Takayoshi Suzuki, Masakazu Kita, Yukinari Sunatsuki, Masaaki Kojima, Hideo D. Takagi

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 85 ( 10 ) 1160 - 1166 2012.10

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

A series of cobalt(III) complexes containing 2-cyanoethylphosphines, [Co(Me(2)dtc)(2){P(CH2CH2CN)(n)Ph3-n}(2)]BF4 {Me(2)dtc(-): N,N-dimethyldithiocarbamate; n =1 (1), 2 (2), and 3 (3)} have been prepared, and their molecular structures in the crystals and in solution have been characterized. X-ray analysis revealed that all complexes isolated as single-crystals were the trans-isomers. The Co-P bond lengths for the 2-cyanoethylphosphines in complexes 1-3 are almost invariant to the number of 2-cyanoethyl substituent groups. Unlike related complexes with other monodentate P-donor ligands, complexes 1-3 in solution showed dissociation and isomerization equilibriums, which were achieved immediately after dissolving the crystals. These characteristic features of the complexes would result from the weak sigma-donor and pi-acceptor abilities of 2-cyanoethylphosphines. Furthermore, mixing of complex 1 and NaN3 in acetonitrile gave cis-[Co(Me(2)dtc)(2)(N-3){P(CH2CH2CN)Ph-2}] quantitatively, and refluxing the mixture resulted in the phosphine-tetrazolate complex, [Co(Me(2)dtc)(2)(Ph2PCH2CH2CN4-(KP)-P-2,N-1)] (4).

DOI： 10.1246/bcsj.20120148

Facial and meridional geometrical isomers of tris(2-methylimidazol-4-yl-methylideneaminobenzyl)iron(II) with Delta- and Lambda-configurations and their enantio-discriminative assembly via imidazole center dot center dot center dot chloride hydrogen bonding and spin cross-over properties

Daisuke Furushou, Tomotaka Hashibe, Takeshi Fujinami, Koshiro Nishi, Hiroaki Hagiwara, Naohide Matsumoto, Yukinari Sunatsuki, Masaaki Kojima, Seiichiro Iijima

POLYHEDRON 44 ( 1 ) 194 - 203 2012.8

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

A bidentate 2-methylimidazol-4-yl-methylideneaminobenzyl ligand (HLMe-Benz) reacts with (FeCl2)-Cl-II center dot 4H(2)O and NaPF6 at a 3:1:1 molar ratio to yield a tris(2-methylimidazol-4-yl-methylideneaminobenzyl)iron(11) chloride hexafluorophosphate solvate with the formula of Well( HLMe-Benz)3]Cl center dot PF6.solvent. Meridional and facial geometrical isomers, i.e., mer-(Fe-II (HLMe-Benz)(3)]Cl center dot PF6.1.5H(2)O (1.PF6.1.5H(2)O) and fac-[Fe-II(HLMe-Benz)(3)]Cl.PF6 center dot EtOH center dot H2O (2-PF6.EtOH center dot H2O), were selectively crystallized from methanol and ethanol solutions, respectively. fac-[Fe-II(HLMe-Be1z)(3)]Cl center dot SbF6 center dot H2O (2.SbF6 center dot H2O) and fac-[Fe-II(HLMe-Benz)(3)]Cl. ClO4 center dot EtOH center dot H2O (2.ClO4 center dot EtOH center dot H2O) are synthesized in ethanol, using the corresponding anions. Each Fell ion has an octahedral coordination geometry with N-6 donor atoms from three bidentate ligands. All three imidazole groups in both the fac- and mer-[Fe-II(HLMe-Benz)(3)](2+) cations are hydrogen-bonded to neighboring three Cl- ions, and each Cl- ion is hydrogen-bonded to three imidazole groups of three neighboring complex cations; this results in the formation of hydrogen-bonded assembly structures. met-Complex 1.PF6-15H(2)O forms a heterochiral two-dimensional (2D) network structure comprised of cyclic (mer[Fe-II(HLMe-Benz)(3)](2+)center dot center dot center dot Cl-)3 units with an Delta Delta Lambda or Lambda Lambda Delta configuration; the PF6- ions occupy the spaces between the 20 layers. All the fac-complexes have isomorphous cubane-like tetrameric structures, i.e., {fac-[Fe-II(HLMe-Benz)(3)](2+)center dot center dot center dot Cl-)(4). The tetranuclear structure comprises four homo-chiral fac-Delta- or fac-Lambda-[Fell(HLMe-Benz)(3)](2+) I cations and four Cl- ions interconnected by twelve imidazole-chloride hydrogen bonds to form a chiral cubane supramolecule that encapsulates one counter anion. In the crystal lattice, the cubane-like tetramers with opposite chiralities are alternately arrayed. The temperature dependence of the magnetic susceptibilities and Mossbauer spectra reveal that the fac-complexes show incomplete spin crossover behavior, while the mer-complex shows a gradual spin crossover between high-spin (HS, S = 2) and low-spin (LS, S = 0) states. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2012.06.085

Enantioselective assembling into tetra- and octanuclear structures by deprotonation of copper(II) complexes of N-[(5-methylimidazol-4-yl)methylidene]-DL-phenylalanine and its L-form ligand

Tomohiro Oishi, Tomotaka Hashibe, Saori Takahashi, Hiroaki Hagiwara, Naohide Matsumoto, Yukinari Sunatsuki

POLYHEDRON 33 ( 1 ) 209 - 217 2012.2

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

Two copper(II) complexes with the protonated ligands [(CuCIHLDL)-C-II] and [(CuCIHLL)-C-II] were prepared, where HLDL, denotes N-[(5-methylimidazol-4-yl)methylidenel-DL-phenylalanine and HLL denotes its L-form ligand. The deprotonation of [(CuCIHLDL)-C-II] at the imidazole moiety gave an imidazolato-bridged cyclic tetranuclear arrayed [(CuLo)-L-II(H2O)] and [(CuLL)-L-II(H2O)] species, while the deprotonation of [(CuCIHLL)-C-II] gave an octanuclear structure [(Cu8L8L)-L-II center dot 4H(2)O] in which two cyclic tetranuclear species are linked by an intertetramer Cu-O (carboxylate) coordination bond. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2011.11.024

Conglomerate crystallization, chiral recognition and spin-crossover in a host-guest complex consisting of Fe-III complexes (host) and [Cr(ox)(3)](3-) (guest)

Yukinari Sunatsuki, Sho Miyahara, Yuu Sasaki, Takayoshi Suzuki, Masaaki Kojima, Naohide Matsumoto

CRYSTENGCOMM 14 ( 20 ) 6377 - 6380 2012

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

A host-guest complex, [Fe-III(H3L)][Fe-III(L)][Cr-III(ox)(3)]center dot 3H(2)O (1), where H3L and L3- serve as hexadentate ligands, was prepared. In 1, three properties are united: the homochiral assembly of chiral [Fe-III(H3L)](3+) and [Fe-III(L)] into a conglomerate structure, the chiral recognition of the host Fe-III assembly to the guest [Cr-III(ox)(3)](3-) and the spin-crossover of [Fe-III(H3L)](3+).

DOI： 10.1039/c2ce25612f

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