Faculty Profiles - SUNATSUKI Yukinari

Papers - SUNATSUKI Yukinari

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Schiff Base Ligands Derived from l-Histidine Methyl Ester: Characterization, Racemization, and Dimerization of Their Transition-Metal Complexes Reviewed

Rina Ogawa, Yukinari Sunatsuki, Takayoshi Suzuki

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY ( 16 ) 1733 - 1742 2018.4

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

Reactions of methyl (S)-2-[(2-hydroxybenzylidene)amino]-3-(1H-imidazol-4-yl)propanoate (S-H2LMe) and various transition-metal(II) salts (MX2: M = Mn, Fe, Co, and Ni; X = ClO4, Cl, OAc, etc.) are examined. During the reactions with Mn-II and Co-II salts, the M-II ion is oxidized by air to form a cationic complex with two mono-deprotonated ligands, [M-III(S-HLMe)(2)]X [M, X = Mn, ClO4 (S-1ClO(4)); Co, ClO4 (S-3ClO(4)); and Co, Cl (S-3Cl)], where (S-HLMe)(-) is coordinated to a M-III center in a tridentate O-3,N,N mode with a mer configuration. In contrast, the Ni-II ion is not oxidized; only one of the ligands is deprotonated to form a similar monocationic complex, [Ni-II(S-HLMe)(S-H2LMe)]PF6 (S-6PF(6)), which forms a dimer structure by double hydrogen bonds between the coordinating phenoxide and phenol groups in the crystal. Interestingly, the above complexes show slow racemization of the ligand, as confirmed by circular dichroism spectroscopy. Racemic Ni-II complexes of [Ni(HLMe)(H2LMe)](PF6 or Cl) (rac-6PF(6) or rac-6Cl) are isolated and their crystal structures are confirmed by X-ray diffraction analysis. In the case where Co(OAc)(2) is used as the metal(II) salt, a new ligand dimerization reaction takes place to afford a complex of [Co(H2LLMe)]Cl (7Cl, H4LLMe = methyl (E)-3-{[3-(1H-imidazol-4-yl)-1-methoxy-1-oxopropano-2-yl]amino}-2-[(1H-imidazol-4-yl)methyl]-2-[(2-hydroxybenzylidene)amino]-3-(2-hydroxyphenyl)propanoate).

DOI： 10.1002/ejic.201800137

Polymorphs of spin-crossover iron(II) complex fac-[Fe-II(HLn-Pr)(3)]Cl.PF6 (HLn-pr=2-methylimidazol-4-yl-methylideneamino-n-propyl): Assembly structures and scan rate dependent spin-crossover properties with thermal hysteresis Reviewed

Takahiro Ueno, Yuto Ii, Takeshi Fujinami, Naohide Matsumoto, Seiichiro Iijima, Yukinari Sunatsuki

POLYHEDRON 136 13 - 22 2017.11

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

Two polymorphs of iron(II) complex fac-[Fe-II(HLn-Pr)(3)]Cl.PF6, 1 and 2, were obtained (HLn-Pr = 2-methylimidazole-4-yl-methylideneamino-n-propyl ligand). Complex cations, fac-[Fe-II(HLn-Pr)(3)](2+), of 1 and 2 had similar octahedral and facial geometries coordinated with three bidentate HLn-Pr ligands. The three imidazole groups in fac-[Fe-II(HLn-Pr)(3)](2+) with Delta- and Lambda-enantiomorphs are hydrogen-bonded with three Cl- ions, forming one-dimensional (1D) and two-dimensional (2D) network structures in 1 and 2, respectively. Complex 1 had a ladder-like 1D structure formed by imidazole...chloride hydrogen bonds, with a circular binuclear net unit of {...fac-[Fe-II(HLn-Pr)(3)](2+)...Cl-...}(2), and showed two successive scan rate dependent spin crossover (SCO) processes with thermal hysteresis. Complex 2 had a 2D network structure formed by imidazole...chloride hydrogen bonds with circular binuclear and tetranuclear net units of {...fac-[Fe-II(HLn-Pr)(3)](2+)...Cl-...}(2),(4), and showed a one-step scan rate dependent SCO profile centered at 143 K with thermal hysteresis. The relaxation property was identified from the scan rate dependence of magnetic susceptibility and temperature dependent Mossbauer spectra and X-ray diffraction studies. The crystal structure of 2 was analyzed at 12 temperatures in a cooling cycle. Upon lowering the temperature, the crystal system transformed from a monoclinic to a triclinic lattice at 210 K in a high-spin state, and then transformed to a low-spin state at 150 K in the triclinic system. (c) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2017.03.028

Circular and Chainlike Copper(II)-Lanthanide(III) Complexes Generated by Assembly Reactions of Racemic and Chiral Copper(II) Cross-Linking Ligand Complexes with Ln(III)(NO3)(3)center dot 6H(2)O (Ln(II) = Gd-III, Tb-III, Dy-III) Reviewed

Takahiro Ueno, Takeshi Fujinami, Naohide Matsumoto, Masaki Furusawa, Ryo Irie, Nazzareno Re, Takuya Kanetomo, Takayuki Ishida, Yukinari Sunatsuki

INORGANIC CHEMISTRY 56 ( 3 ) 1679 - 1695 2017.2

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

The 1:1 assembly reaction of the racemic form of the crosslinking ligand complex Na[(CuLdpen)-L-II(1R2R/1S2S)] with Ln(III)(NO3)36H2O gave the centrosymmetric circular (Cu(II)Ln(III))(2) complex [(CuLdpen)-L-II(1R2R/1S2S)Ln(III)(NO3)2]2 (1Ln: Ln = Gd, Tb, Dy), while the reaction of the enantiopure form Na[(CuLdpen(1R2R))-L-II] with Ln(III)(NO3)36H2O gave the chiral chainlike (Cu(II)Ln(III))(1)8 complex [Cu(II)L(dpen(1R2R))Ln(III)(NO3)2(CH3CN)]18CH3CN (2Ln: Ln = Gd, Tb, Dy), where {(CuLdpen(1R2R))-L-II is (N((1R,2R)2(((E)3ethoxy2oxybenzylidene)amino)1,2diphenylethyl)2oxybenzamide)copper(II) and {(CuLdpen)-L-II(1R2R/1S2S) is the racemic mixture of {(CuLdpen(1R2R))-L-II and {(CuLdpen)-L-II(1S2S). The copper(II) component functions as a crosslinking ligand complex and bridges two Ln(III) ions at two phenoxo oxygen atoms and one ethoxy oxygen atom, as well as at an amido oxygen atom. For 1Ln, two binuclear species of [Cu(II)L(dpen(1R2R))Ln(III)(NO3)(2)] and [(CuLdpen)-L-II(1S2S)Ln(III)(NO3)(2)] with opposite chiralities are linked by two amido oxygen atoms O3 and O3* to form a centrosymmetric circular structure with GdCu = 3.370(1) A and GdCu* = 5.627(1) A. For 2Ln, binuclear species with the same chirality are bridged by GdO3* = 2.228(5) A to form a chiral chainlike structure with GdCu = 3.3348(9) A and GdCu* = 6.2326(9) A. The bridged angles through the amido group of GdO3*C7* are 133.9(5) and 177.6(4) for 1Gd and 2Gd, respectively. The magnetic susceptibilities of 1Gd and 2Gd were analyzed by the spinonly Hamiltonian on the basis of the circular tetranuclear ((CuGdIII)-Gd-II)(2) and linear chainlike ((CuGdIII)-Gd-II)(1)8 structures, respectively. The (CuGdIII)-Gd-II magnetic interactions through two phenoxo bridges and a threeatom NCO bridge, J(1) and J(2), are both ferromagnetic to be J1 = +4.6 cm(1) and J(2) = +1.8 cm(1) for 1Gd and J(1) = +4.2 cm(1) and J(2) = +0.037 cm(1) for 2Gd. The J(2) value of 2Gd is much smaller than that of 1Gd. When the temperature was lowered, 1Ln and 2Ln (Ln = Tb, Dy) showed a decrease in the Delta MT vs T plot due to crystal field effects on the Ln(III) ion (Stark splitting) and an increase due to the ferromagnetic Cu(II)Ln(III) interaction. The magnetization values of 1Ln and 2Ln (Ln = Tb, Dy) without liquid paraffin are considerably larger than the corresponding values with liquid paraffin, indicating the presence of strong magnetic anisotropy. 1Tb and 1Dy showed frequency dependence of ac magnetic susceptibility under zero external dc magnetic field, showing the behavior of singlemolecule magnets (SMMs). 2Tb and 2Dy showed no frequency dependence under a zero external magnetic field but showed a meaningful frequency dependence under an external magnetic field. Their energy barriers, Delta/k(B), estimated by the Arrhenius plots are 29.4(6) and 20.6(3) K for 1Tb and 2Tb under dc bias fields of 0 and 1000 Oe, respectively, and those of 1Dy and 2Dy are 13.1(9) K and 16.4(2) K under dc bias fields of 0 and 1000 Oe, respectively.

DOI： 10.1021/acs.inorgchem.6b02668

Thyminato-bridged cyclic tetranuclear rhodium(III) complexes containing a sodium, calcium or lanthanoid ion as a template metal core Reviewed

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

INORGANICA CHIMICA ACTA 452 205 - 213 2016.10

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

Reactions of [(Cp*Rh)(2)(mu-OH)(3)]OH (Cp*=eta(5)-C5Me5-) and thymine (=H(2)thym) in methanol in the presence or absence of a certain metal salt were examined. From the reaction mixture without any template metal salt, a dinuclear hydroxido-bridged complex bearing monodentate monodeprotonated thyminato ligands,1[Cp*Rh(Hthym-kappa N-1))(2)(mu-OH)(2)], was isolated after recrystallization from water. In the presence of a metal salt MXn{=NaPF6, NaBF4, NaNO3, Ca(NO3)(2), Ca(ClO4)(2), La(NO3)(3), Eu(NO3)(3), Dy(NO3)(3) and Er (NO3)(3)) were deposited orange crystals (1P, 1B, 1N, 2N, 2C, 3N, 4N, 5N and 6N, respectively) which consist of a thyminato(2-)-bridged tetranuclear Cp*Rh complex incorporating a Mn+ cation, [(Cp*Rh)(4)(mu-thym)(4)M](n+). All complexes were characterized by the single-crystal X-ray diffraction method, which revealed that homochiral aggregations of four Rh-III centers were achieved to give metallacalix[4]arene-type clusters. It was also observed that the bridging modes of thyme(2-) ligands were dependent on the template metal ion. In the Na+-incorporated clusters (1X, X = P, B or N) a thyme(2-) ligand bridged two Rh-III and the third Na+ ions with a mu(3)-1 kappa N-1:2 kappa N-2(3),O-2:3 kappa O-2 mode, while in the Ln(3+) analogs (Ln = La, Eu, Dy or Er: 3N-6N) thyme(2-) exhibited a different bridging mode, mu(3)-1 kappa N-1:2 kappa N-2(3),O-4:3 kappa O-2. In the cases of Ca2+-incorporated clusters, the bridging mode is further dependent on the associated anion; only the mu(3)-1 kappa N-1:2 kappa N-2(3),O-2:3 kappa O-2-type cluster was obtained in the NO3- salt (2N), but the ClO4- salt (2C) afforded both types of the bridging clusters piled up alternatively in the crystals. The tetranuclear structures with a template metal cation, [(Cp*Rh)(4)(mu-thym)(4)M](n+), are maintained in solution. The magnetic behaviors of the Dy3+- and Er3+-incorporated complexes (5N and 6N) are also reported. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2016.01.023

Preparation, structures and properties of manganese complexes containing amine-(amido or amidato)-phenolato type ligands Reviewed

Ryoji Mitsuhashi, Rina Ogawa, Ryuta Ishikawa, Takayoshi Suzuki, Yukinari Sunatsuki, Satoshi Kawata

INORGANICA CHIMICA ACTA 447 113 - 120 2016.6

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

Complexation of 2-hydroxy-N-(n-aminoalkyl)benzamides, where n-aminoalkyl substituents are 2-amino-2-methylpropyl (H(2)L2(Me2)), (R)-2-aminopropyl {(R)-H(2)L2(Me)} and 3-aminopropyl (H(2)L3), with manganese(II)chloride or perchlorate were examined. With the 2-aminopropyl derivatives, dinuclear methoxido-bridged manganese(III) complexes bearing the dianionic ligands, [{Mn(L2(Me2) or (R)-L2(Me)) (MeOH)}(2)(mu-OMe)(2)] (2 or 4), were isolated and their crystal structures were determined. There was a weak antiferromagnetic interaction between two axially distorted Mn-III centers in 2. Also, with the ligand of (L2(Me2))(2) a mononuclear manganese(IV)complex, [Mn(L2(Me2))(2)]center dot DMF (3 center dot DMF) was obtained. In the crystal of 3 center dot DMF a heterochiral dimerization via the intermolecular double hydrogen-bonds was observed. In the case of reactions with H(2)L3, mononuclear manganese(III)complexes, [Mn(H(2)L3 ')(2)Cl-2] Cl (6)and [Mn(H(2)L3 ')(2)(MeOH)(2)]Cl-2(ClO4)(7), were afforded, where the ligand (H(2)L3 ')has a phenolateamide-ammonium type zwitterionic form of H(2)L3 and coordinates to a Mn-III center via the phenolato-O and amide-O atoms to form a six-membered chelate ring. Furthermore, a tetranuclear (Mn2Mn2III)-Mn-II double incomplete-cubane type cluster compound, [Mn-4(HL3)(2)Cl-2(OMe)(6)(MeOH)(2)]center dot 4MeOH (5a center dot 4MeOH) was revealed by the single-crystal X-ray diffraction study, although the bulk crystals (5)obtained from the reaction mixture showed a different PXRD pattern. The elemental analysis of the bulk crystals of 5 suggested that they consist of the same tetranuclear clusters. It is interesting that the bulk crystals of 5 were highly efflorescent, and it was suggested that their coordinated MeO and MeOH ligands were easily substituted by OH and H2O, respectively, in atmospheric air. This conversion changed their magnetic behaviors drastically. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2016.03.036

Luminescent Dy-III single ion magnets with same N6O3 donor atoms but different donor atom arrangements, 'fac'-[Dy-III(HLDL-ala)(3)]center dot 8H(2)O and 'mer'-[Dy-III(HLDL-phe)(3)]center dot 7H(2)O Reviewed

Daisuke Hamada, Takeshi Fujinami, Suguru Yamauchi, Naohide Matsumoto, Naotaka Mochida, Takayuki Ishida, Yukinari Sunatsuki, Masanobu Tsuchimoto, Cecilia Coletti, Nazzareno Re

POLYHEDRON 109 120 - 128 2016.4

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

Two Dym complexes with same N603 donor atoms but different donor atom arrangements 'fac'-[Dy-III(HLDL-ala)(3)]center dot 8H(2)O (1) and 'mer'-[Dy-III(HLDL-phe)(3)]center dot 7H(2)O (2) were synthesized, where H2LDL-ala and H2LDL-phe are tridentate NNO ligands of N-Rimidazol-4-yl)methylidene]-DL-alanine and N-[(imidazol-4-yl)methylidene]-DL-phenylalanine, respectively. Each Dy-III ion is coordinated by three mono-deprotonated mono-negative NNO tridentate ligands to form a nona-coordination geometry of a tricapped trigonal prism (TTP). 1 consists of enantiomers 'fac'-[Dy-III(HLD-ala)(3)], and 'fac'-[Dy-III(HLL-ala)(3)], while 2 consists of 'mer'-[Dy-III(HLD-phe)(2)(HLL-phe)] and 'mer'-[Dy-III(HLD-phe)(HLL-ala)(2)]. The temperature dependence of the magnetic susceptibilities and field-dependence of the magnetization of two complexes showed the different magnetic profiles and the Stark splitting of the ground state H-6(15/2) due to the crystal field effect on Dy-III ion (4f(9), J = 15/2, S = 5/2, L = 5, g(J) = 4/3, H-6(15/2)). Luminescence spectra were observed and the fine structures assigned to the F-4(9/2) -> H-6(15/2) transitions are partially observed. 1 and 2 showed an out-of phase signal with frequency-dependence in alternating current (ac) susceptibility under a dc bias field of 1000 Oe, indicative of field induced single ion magnet (SIM). The ac magnetic susceptibilities under 1000 Oe dc field of 2 showed the maximum peaks at the higher temperature than those of 1, indicating that the energy barrier of 2 is larger than that of 1. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2016.01.048

Binuclear tetra-acetate bridged Gd(III) complex [Gd-2(mu(2)-O2CMe)(4)(H2L)(2)] (ClO4)(2)center dot 2H(2)O center dot 2MeOH (H2L = bis(5-methylimidazol-4-yl-methylideneaminopropyl) methylamine): Synthesis, structure, and magnetic properties Reviewed

Makoto Ito, Daisuke Hamada, Hiromasa Ono, Naohide Matsumoto, Yukinari Sunatsuki, Nazzareno Re

INORGANICA CHIMICA ACTA 443 274 - 278 2016.3

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

A binuclear tetra-acetate bridged Gd-III complex [Gd-2(mu(2)-O2CMe)(4)(H2L)(2)](ClO4)(2)center dot 2H(2)O center dot 2MeOH was synthesized, where H2L = bis(5-methylimidazol-4-yl-methylideneaminopropyl)methylamine. The linear polydentate ligand H2L functions as a binding group to two Gd-III ions. Two Gd-III ions are bridged by two acetate in eta(1):eta(1):mu(2) fashion and other two in eta(2):eta(1):mu(2) fashion. The Gd-III center dot center dot center dot Gd-III distance of 3.920 (6) angstrom is shorter than 4.183(1) angstrom of the bis-acetate bridged Gd-III complex [{Gd-III(O2CMe)(3)(H2O)(2)}(2)]center dot 4H(2)O. A weak anti-ferromagnetic Gd-III-Gd-III interaction was observed. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2015.12.029

Synthesis, hydrogen-bonded 1D structure, and abrupt spin transition between high-spin (HS) and an ordered [HS-HS-HS-LS] of a mononuclear iron(III) complex [Fe-III(Him)(2)(4-MeOhapen)]CF3SO3 (Him = imidazole, 4-MeOhapen = N,N '-bis-(2-oxy-4-methoxyacetophenylidene)ethylenediamine) Reviewed

Kyohei Miyano, Takahiro Nishida, Hiromasa Ono, Daisuke Hamada, Takeshi Fujinami, Naohide Matsumoto, Yukinari Sunatsuki

INORGANICA CHIMICA ACTA 439 49 - 54 2016.1

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

A SCO iron(III) complex [Fe-III(Him)(2)(4MeOhapen)]CF3SO3 was synthesized, where Him = imidazole and 4-MeOhapen = N,N'-bis(2-oxy-4-methoxyacetophenylidene)ethylenediamine. Fe-III ion has an octahedral coordination geometry with N2O2 donor atoms of the equatorial tetradentate ligand (4-MeOhapen) and two nitrogen atoms of two imidazoles (Him) at the axial positions. The adjacent cations are bridged by CF3SO3 ion through NH center dot center dot center dot O hydrogen bonds between Him and CF3SO3 to give a one-dimensional chain structure {[Fe-III(Him)(2)(4MeO-hapen)]CF3SO3}(1 infinity). The magnetic susceptibility measurements showed that complex exhibits an abrupt spin transition between a single HS phase and a symmetry-breaking [HS-HS-HS-LS] phase and another transition around 80 K. The single-crystal X-ray analyses at 296 and 150 K revealed the structures at a single HS and [HS-HS-HS-LS] states. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2015.09.031

Abrupt Spin Transition and Chiral Hydrogen-Bonded One-Dimensional Structure of Iron(III) Complex [Fe-III(Him)(2)(hapen)]SbF6 (Him = imidazole, H(2)hapen = N, N '-bis(2-hydroxyacetophenylidene) ethylenediamine)

Takahiro Ueno, Kyohei Miyano, Daisuke Hamada, Hiromasa Ono, Takeshi Fujinami, Naohide Matsumoto, Yukinari Sunatsuki

MAGNETOCHEMISTRY 1 ( 1 ) 72 - 82 2015.12

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

Solvent-free spin crossover (SCO) iron(III) complex, [Fe-III(Him)(2)(hapen)] SbF6 (Him = imidazole, H(2)hapen = N,N'-bis(2-hydroxyacetophenylidene) ethylenediamine), is synthesized. The Fe-III ion has an octahedral coordination geometry, with N2O2 donor atoms of hapen and N-2 atoms of two imidazoles at the axial positions. The saturated five-membered chelate ring of hapen moiety assumes a gauche-type delta- or lambda-conformation to give chiral species of d-[Fe-III(Him)(2)(hapen)](+) or lambda-[Fe-III(Him)(2)(hapen)](+). One imidazole is hydrogen-bonded to phenoxo oxygen atom of hapen of the adjacent unit to give a hydrogen-bonded chiral one-dimensional structure, {delta-[Fe-III(Him) (2)(hapen)](+)}1 infinity or {lambda-[Fe-III(Him)(2)(hapen)](+)}1 infinity. The adjacent chains with the opposite chiralities are arrayed alternately. The temperature dependences of the magnetic susceptibilities revealed an abrupt one-step spin transition between high-spin (S = 5/ 2) and low-spin (S = 1/2) states at the spin transition temperature of T-1/2 = 105 K. The crystal structures were determined at 296 and 100 K, where the populations of HS:LS of high-and low-spin ratio are evaluated to be 1:0 and 0.3:0.7, respectively, based on magnetic measurements. During the spin transition from 296 K to100 K, the average Fe-N distance and O-Fe-O angle decrease to a regular octahedron by 0.16 angstrom and 13.4 degrees, respectively. The structural change in the coordination environment is transmitted to the adjacent spin crossover (SCO) sites along the chiral 1D chain through hydrogen-bonds. The abrupt SCO profile and the spin transition temperature for the isomorphous compounds [Fe-III(Him)(2)(hapen)]Y (Y = PF6, AsF6, SbF6) are ascribed to the chiral hydrogen-bonded 1D structure and chain-anion interaction.

DOI： 10.3390/magnetochemistry1010072

Scan Rate Dependent Spin Crossover Iron(II) Complex with Two Different Relaxations and Thermal Hysteresis fac-[Fe-II(HLn-Pr)(3)]Cl center dot PF6 (HLn-Pr=2-Methylimidazol-4-yl-methylideneamino-n-propyl)

Takeshi Fujinami, Koshiro Nishi, Daisuke Hamada, Keishiro Murakami, Naohide Matsumoto, Seiichiro Iijima, Masaaki Kojima, Yukinari Sunatsuki

INORGANIC CHEMISTRY 54 ( 15 ) 7291 - 7300 2015.8

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

Solvent-free spin crossover Fe-II complex fac-[Fe-II(HLn-Pr)(3)]Cl center dot PF6 was prepared, where HLn-Pr denotes 2-methylimidazol-4-yl-methylideneamino-n-propyl. The magnetic susceptibility measurements at scan rate of 0.5 K min(-1) showed two successive spin transition processes consisting of the first spin transition T-1 centered at 122 K (T-1 up arrow = 127.1 K, T-1 down arrow = 115.8 K) and the second spin transition T-2 centered at ca. 105 K (T-2 up arrow = 115.8 K, T-2 down arrow = 97.2 K). The magnetic susceptibility measurements at the scan rate of 2.0, 1.0, 0.5, 0.25, and 0.1 K min(-1) showed two scan speed dependent spin transitions, while the Mossbauer spectra detected only the first spin transition T-1. The crystal structures were determined at 160, 143, 120, 110, 95 K in the cooling mode, and 110, 120, and 130 K in the warming mode so as to follow the spin transition process of high-spin HS -> HS(T-1) -> HS(T-2) -> low-spin LS -> LS(T-2) -> LS(T-1) -> HS. The crystal structures at all temperatures have a triclinic space group P (1) over bar with Z = 2. The complex-cation has an octahedral N-6 coordination geometry with three bidentate ligands and assume a facial-isomer with Delta- and Lambda-enantimorphs. Three imidazole groups of fac-[Fe-II(HLn-Pr)(3)](2+) are hydrogen-bonded to three Cl- ions. The 3:3 NH(imidazole)center dot center dot center dot Cl- hydrogen-bonds form a stepwise ladder assembly structure, which is maintained during the spin transition process. The spin transition process is related to the structural changes of the FeN6 coordination environment, the order-disorder of PF6- anion, and the conformation change of n-propyl groups. The Fe-N bond distance in the HS state is longer by 0.2 angstrom than that in the LS state. Disorder of PF6- anion is not observed in the LS state but in the HS state. The conformational changes of n-propyl groups are found in the spin transition processes except for HS --> HS(T-1) -> HS(T-2).

DOI： 10.1021/acs.inorgchem.5b00701

Syntheses, hydrogen-bonded assembly structures, and spin crossover properties of [Fe-III(Him)(2)(n-MeOhapen)]PF6 (Him = imidazole and n-MeOhapen = N,N '-bis(n-methoxy-2-oxyacetophenylidene)ethylenediamine); n=4, 5, 6)

Takeshi Fujinami, Mizuki Ikeda, Masataka Koike, Naohide Matsumoto, Tomohiro Oishi, Yukinari Sunatsuki

INORGANICA CHIMICA ACTA 432 89 - 95 2015.6

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

Three iron(III) complexes, [Fe-III(Him)(2)(n-MeOhapen)]PF6 (1: n = 4, 2: n = 5, 3: n = 6), where Him = imidazole and n-MeOhapen = N,N'-bis(n-methoxy-2-oxyacetophenylidene)ethylenediamine, were synthesized. Each Fe-III ion was coordinated by N4O2 donor atoms of equatorial n-MeOhapen and two axial Him. The saturated FeC2N2 chelate ring involving the ethylenediamine moiety adopted a gauche conformation and the two phenylidene planes of [Fe-III(Him)(2)(n-MeOhapen)](+) were oriented opposite to the FeO2N2 coordination plane. Two adjacent [Fe-III(Him)(2)(4-MeOhapen)](+) cations in 1 were connected via PF6 ions by hydrogen bonds between the imidazole group and PF6 to give a one-dimensional chain. Two adjacent cations in 2 were connected via hydrogen bonds between the phenylidene oxygen and imidazole atoms to form a cyclic dimer structure. Two EtOH molecules were involved in a hydrogen-bonded cyclic dimer structure in 3. Compounds 1 and 2 showed spin crossover behavior, but 3 showed incomplete spin crossover. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2015.03.034

Synthesis, structure, and spin equilibrium properties of [(FeX2L)-X-III]BPh4 center dot solvents ( X=1-methylimidazole and imidazole; L = N, N'-bis(3-ethoxycarbonylsalicylidene) ethylenediamine)

Takeshi Fujinami, Daisuke Hamada, Naohide Matsumoto, Yukinari Sunatsuki, Ryo Irie

INORGANICA CHIMICA ACTA 430 239 - 244 2015.5

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

Two iron(III) complexes [(FeX2L)-X-III]BPh4 center dot solvents (X = 1-Meim (1), Him (2)) were synthesized and the crystal structures were determined, where H2L = N, N'-bis(3-ethoxycarbonylsalicylidene) ethylenediamine, 1-Meim = 1-methylimidazole, Him = imidazole, BPh4 = tetraphenylborate. Fe-III ion has an octahedral coordination environment by N2O2 donor atoms of equatorial L-2 and N-2 donor atoms of axial imidazoles. Complex 1 is described as isolated molecule, while complex 2 has a hydrogen-bonded cyclic dimer structure constructed by hydrogen-bond between imidazole group and ethoxycarbonyl oxygen via ethanol. Complex 1 is in a high-spin (S = 5/2) state over the whole temperature region 5-300 K, while complex 2 showed a gradual complete spin equilibrium between high and low-spin states at T-1/2 = 192 K. (C) 2015 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.ica.2015.03.008

Hydrogen-bonded 2D network structure and abrupt spin transition with thermal hysteresis of iron(III) complexes [Fe-III(Him)(2) (3-MeOsalen)]center dot H2OEtOH center dot X (Him = imidazole, 3-MeOsalen = N,N '-bis (3-methoxysalicylidene)ethylenediaminato, and X = PF6, AsF6, SbF6)

Keita Hanahara, Hiromasa Ono, Takeshi Fujinami, Naohide Matsumoto, Yukinari Sunatsuki

INORGANICA CHIMICA ACTA 429 93 - 98 2015.4

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

Spin crossover (SCO) iron(III) complexes exhibiting thermal hysteresis, [Fe-III(Him)(2)(3-MeOsalen)]center dot H2O center dot EtOH center dot X (Him = imidazole, 3-MeOsalen = N, N'-bis(3-methoxysalicylidene) ethylenediaminato, and X = PF6, AsF6, SbF6), were synthesized in ethanol. The FeIII ion has an octahedral coordination geometry with N2O2 donor atoms of the planar tetradentate ligand (3-MeOsalen) and two nitrogen atoms of two imidazoles at the axial positions. Through H2O and EtOH the complex-cations are assembled into a hydrogen-bonded 2D network structure and the anion X is accommodated in the void of the 2D network. The temperature dependences of the magnetic susceptibilities revealed an abrupt and two-step spin transition with thermal hysteresis for the PF6 and AsF6 salts. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2015.01.047

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

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

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

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

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

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

Crystal Field Splitting of the Ground State of Terbium(III) and Dysprosium(III) Complexes with a Triimidazolyl Tripod Ligand and an Acetate Determined by Magnetic Analysis and Luminescence

Seira Shintoyo, Keishiro Murakami, Takeshi Fujinami, Naohide Matsumoto, Naotaka Mochida, Takayuki Ishida, Yukinari Sunatsuki, Masayuki Watanabe, Masanobu Tsuchimoto, Jerzy Mrozinski, Cecilia Coletti, Nazzareno Re

INORGANIC CHEMISTRY 53 ( 19 ) 10359 - 10369 2014.10

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

Terbium(III) and dysprosium(III) complexes with a tripodal N-7 ligand containing three imidazoles (H3L) and a bidentate acetate ion (OAc-), [Ln(III)(H3L)(OAc)](ClO4)(2)center dot MeOH center dot H2O (Ln = Tb, 1; Ln = Dy, 2), were synthesized and studied, where H3L = tris[2-(((imidazol-4-yl)methylidene)amino)ethyl]amine. The Tb-III and Dy-III complexes have an isomorphous structure, and each Tb-III or Dy-III ion is coordinated by the tripodal N-7 and the bidentate acetate ligands, resulting in a nonacoordinated capped-square-antiprismatic geometry. The magnetic data, including temperature dependence of the magnetic susceptibilities and field dependence of the magnetization, were analyzed by a spin Hamiltonian, including the crystal field effect on the Tb-III ion (4f(8), J = 6, S = 3, L = 3, g(J) = 3/2, F-7(6)) and the Dy-III ion (4f(9),J = 15/2, S = 5/2, L = 5, g(J) = 4/3, H-6(15/2)). The Stark splittings of the ground states F-7(6) of the Tb-III ion and H-6(15/2) of the Dy-III ion were evaluated from the magnetic analyses, and the energy diagram patterns indicated an easy axis (Ising type) anisotropy for both complexes, which is more pronounced for 2. The solid-state emission spectra of both complexes displayed sharp bands corresponding to the f-f transitions, and the fine structures assignable to the D-5(4) -> F-7(6) transition for 1 and the F-6(9/2) -> H-6(15/2) transition for 2 were related to the energy diagram patterns from the magnetic analyses. 1 and 2 showed an out-of-phase signal with frequency dependence in alternating current (ac) susceptibility under a dc bias field of 1000 Oe, indicative of a field-induced SIM.

DOI： 10.1021/ic501453h

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

Synthesis, Structure, Luminescence, and Magnetic Properties of a Single-Ion Magnet "mer"-[Tris(N-[(imidazol-4-yl)-methylidene]-DL-phenylalaninato)terbium(III) and Related "fac"-DL-Alaninato Derivative

Suguru Yamauchi, Takeshi Fujinami, Naohide Matsumoto, Naotaka Mochida, Takayuki Ishida, Yukinari Sunatsuki, Masayuki Watanabe, Masanobu Tsuchimoto, Cecilia Coletti, Nazzareno Re

INORGANIC CHEMISTRY 53 ( 12 ) 5961 - 5971 2014.6

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

Two Tb-III complexes with the same N6O3 donor atoms but different coordination geometries, "fac"- [Tb-III(HLDL-ala)(3)]center dot 7H(2)O (1) and "mer"- [Tb-III(HLDL-phe)(3 center dot)7H(2)O (2), were synthesized, where H2LDL-ala and H2L2DL-phe are N-imidazol-4-yl)methylidene-DL-alanine and -DL-phenylalanine, respectively. Each Tb-III ion is coordinated by three electronically mononegative NNO tridentate ligands to form a coordination geometry of a tricapped trigonal prism. Compound 1 consists of enantiomers "fac"-[Tb-III(HLD-ala)(3)] and "fac"-[Tb-III(HLL-ala)(3)], while 2 consists of "mer"-[Tb-III(HLD-phe)(2)(HLD-Phe)(HLL-Phe)(2)]. Magnetic data were analyzed by a spin Hamiltonian including the crystal field effect on the Tb-III ion (4f(8), J = 6, S = 3, L = 3, gi = 3/2, F-7(6)). The Stark splitting of the ground state 7F6 was evaluated from magnetic analysis, and the energy diagram pattern indicated easyplane and easy-axis (Ising type) magnetic anisotropies for 1 and 2, respectively. Highly efficient luminescences with phi = 0.50 and 0.61 for 1 and 2, respectively, were observed, and the luminescence fine structure due to the D-5(4) -> F-7(6) transition is in good accordance with the energy diagram determined from magnetic analysis. The energy diagram of 1 shows an approximate single-well potential curve, whereas that of 2 shows a double- or quadruple-well potential within the F-7(6) multiplets. Complex 2 displayed an onset of the out-of-phase signal in alternating current (ac) susceptibility at a direct current bias field of 1000 Oe on cooling down to 1.9 K. A slight frequency dependence was recorded around 2 K. On the other hand, 1 did not show any meaningful out-of-phase ac susceptibility. Pulsed-field magnetizations of 1 and 2 were measured below 1.6 K, and only 2 exhibited magnetic hysteresis. This finding agrees well with the energy diagram pattern from crystal field calculation on 1 and 2. DFT calculation allowed us to estimate the negative charge distribution around the Tb-III ion, giving a rationale to the different magnetic anisotropies of 1 and 2.

DOI： 10.1021/ic5001599

Synthesis, Structure, and Magnetic Property of a New Mononuclear Iron(II) Spin Crossover Complex with a Tripodal Ligand Containing Three 1,2,3-Triazole Groups

Hiroaki Hagiwara, Ryo Minoura, Shohei Okada, Yukinari Sunatsuki

CHEMISTRY LETTERS 43 ( 6 ) 950 - 952 2014.6

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

A novel mononuclear iron(II) complex of a 1,2,3-triazole-containing ligand, [(FeLPh)-L-II](NTf2)(2) [L-Ph: tris(2-{[(1-phenyl-1,2,3-triazol-4-yl)methylidene]amino}ethyl)amine and NTf2: bis(trifluoromethanesulfonyl)imide], was synthesized. The complex shows a gradual one-step spin crossover at around room temperature with T-1/2 = 280 K. The complex cations, [(FeLPh)-L-II](2+), are linked via CH/pi and pi-pi interactions forming a two-dimensional layer. The cationic layers are linked together by NTf2- ions via CH center dot center dot center dot X (X = N, O, and F) hydrogen-bonding interactions to form an extended three-dimensional structure.

DOI： 10.1246/cl.140133

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