Faculty Profiles - SUNATSUKI Yukinari

Papers - SUNATSUKI Yukinari

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A Hydrogen Bond Motif Giving a Variety of Supramolecular Assembly Structures and Spin-Crossover Behaviors

Koshiro Nishi, Naohide Matsumoto, Seiichiro Iijima, Malcolm A. Halcrow, Yukinari Sunatsuki, Masaaki Kojima

INORGANIC CHEMISTRY 50 ( 22 ) 11303 - 11305 2011.11

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

fA series of spin-crossover (SCO) iron(II) compounds, fac-[Fe-II(HLR)(3)]Cl center dot PF6 [R = methyl (Me, 1), ethyl (Et, 2), n-propyl (n-Pr, 3), n-butyl (n-Bu, 4), and n-pentyl (n-Pen, 5)] were synthesized, where HLR denotes a series of [(2-methylimidazol-4-yl)methylidene]-monoallcylamines. The cations fac-[Fe-II(HLR)(3)](2+) and chloride anions associate through 3:3 imidazole center dot center dot center dot chloride hydrogen bonding. This hydrogen-bonding motif gives rise to a variety of assembly structures consisting of a one-dimensional ladder for 3 and 4, two kinds of two-dimensional networks for 1 and 2, and a cubane-like structure for S. The compounds exhibit various types of SCO transitions between high-spin (S = 2) and low-spin (S = 0) states as a result of their intermolecular interactions.

DOI： 10.1021/ic201993z

Chiral spin crossover iron(II) complex, fac-Lambda-[Fe-II(HLR)(3)](ClO4)(2)center dot EtOH (HLR=2-methylimidazol-4-yl-methylideneamino-R-(+)-1-methylphenyl)

Tomotaka Hashibe, Takeshi Fujinami, Daisuke Furusho, Naohide Matsumoto, Yukinari Sunatsuki

INORGANICA CHIMICA ACTA 375 ( 1 ) 338 - 342 2011.9

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

A chiral spin crossover iron(II) complex, fac-Lambda-[Fe-II(HLR)(3)](ClO4)(2)center dot EtOH was synthesized and its crystal structures in both the high-spin (HS) and low-spin (LS) states were determined, where HLR denotes 2-methylimidazol-4-yl-methylideneamino-R-(+)-1-methylphenyl. The complex assumes octahedral coordination geometry of N-6 donor atoms by three bidentate ligands HLR. The complex exists as the facial-Lambda-isomer of fac-Lambda-[Fe-II(HLR)(3)](2+) of the possible geometrical fac- and mer-isomers and the Delta- and Lambda-enantiomorphs. The X-ray structural analyses revealed that the R-form of the ligand (HLR) induces the fac-Lambda-isomer of fac-Lambda-[FeII(HLR)(3)](2+) and the S-form of the ligand (HLS) induces the fac-Delta-isomer of fac-Delta-[Fe(HLS)(3)](2+). The complex fac-Delta-[Fe-II(HLR)(3)](ClO4)(2)center dot EtOH shows a complete steep spin crossover between the HS and the LS states at T-1/2 = 195 K. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2011.05.032

Geometric Selectivity, Hydrogen-Bonding Interaction, and Solvatochromism of Bis{N-(aminoalkyl)salicylamidato(2-)}cobaltate(III)

Ryoji Mitsuhashi, Takayoshi Suzuki, Yukinari Sunatsuki, Masaaki Kojima

CHEMISTRY LETTERS 40 ( 7 ) 696 - 698 2011.7

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

Cobalt(HI) complexes with N-(aminoalkyl)salicylamide dianions, Ln(2-) (n = 1-4), have been prepared and their molecular and crystal structures have been determined. The geometric (mer- or fac-) selectivity of [Co(Ln)(2)](-) complexes was dependent on the number of the amine-amidato chelate ring member. Intermolecular homochiral hydrogen-bonds and solvatochromic behavior of the complexes were also observed.

DOI： 10.1246/cl.2011.696

Synthesis, Characterization, and Chiral Assembly Structure of a Self-Complementary Iron(III) Complex, [Fe-III(H2L5-Me)(HL5-Me)](ClO4)(2)center dot EtOH (H2L5-Me: N-[(5-Methylimidazol-4-yl)methylidene]histamine)

Hiroaki Hagiwara, Koshiro Nishi, Naohide Matsumoto, Yukinari Sunatsuki, Masaaki Kojima, Seiichiro Iijima

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 84 ( 3 ) 306 - 311 2011.3

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

A low-spin Fe-III complex, [Fe-III(H2L5-Me)(HL5-Me)](ClO4)(2)center dot EtOH, was prepared by the reaction of Fe-II(ClO4)(2)-6H(2)O and H2L5-Me in ethanol with 1:2 molar ratio and in air, where H2L5-Me: N-[(5-methylimidazol-4-yl)methylidene]histamine. Each complex molecule of [Fe(H2L5-Me)(HL5-Me)](2+) has both fully protonated ligand and mono-deprotonated ligand and acts as a chiral self-complementary building block to produce the homochiral imidazole-imidazolate-bridged zigzag-chain structure. The X-ray analysis confirmed that the adjacent chains with the same chirality are stacked in a crystal lattice to give a chiral crystal (conglomerate). Low-spin Fe-III was revealed by the magnetic susceptibility and Mossbauer measurements.

DOI： 10.1246/bcsj.20100299

Conformational effect of a spin crossover iron(II) complex: Bis[N-(2-methylimidazol-4-yl)methylidene-2-aminoethyl]propanediamineiron(II) perchlorate

Hiroaki Hagiwara, Akitsugu Kawano, Takeshi Fujinami, Naohide Matsumoto, Yukinari Sunatsuki, Masaaki Kojima, Hiroshi Miyamae

INORGANICA CHIMICA ACTA 367 ( 1 ) 141 - 150 2011.2

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

A iron(II) complex of the linear hexadentate N-6 ligand H2L2-3-2, [Fe(H2L2-3-2)](ClO4)(2), was synthesized and the spin crossover properties were investigated, where H2L2-3-2 denotes bis[N-(2-methylimidazol-4-yl)methylidene-2-aminoethyl]propanediamine. The complex showed a gradual and reversible one-step spin crossover (SCO) between the high-spin (S = 2) and low-spin (S = 0) states at T-1/2 = 208 K without hysteresis. The crystal structures were determined at 296 and 250 K (HS state), 230, 210, and 200 K (intermediate between the HS and LS states) and 150 and 110 K (LS state). The spin transition from 296 to 150 K accompanies with the conformation change of the chelate rings at the triamine moiety and the formation of the hydrogen bond network in the same space group of orthorhombic Pbcn (no. 60). However, in the LS state at 110 K, the space group changed from orthorhombic Pbcn at 150 K (Pcan when the same axial setting to 110 K was used) to monoclinic P2(1)/a (no. 14) at 110 K, although no spin transition and no change of assembly structure between 150 and 110 K were observed. It give us an idea that the space group transformation is mainly related to the conformational thermodynamic stability of the chelate rings at the triamine moiety and is not directly correlated with the spin transition. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ica.2010.12.016

Assembly Structures and Spin Crossover Properties of Facial and Meridional Isomers of Tris[benzyl(2-methylimidazol-4-ylmethylidene)amine]iron(II) Chloride Hexafluorophosphate

Daisuke Furusho, Koshiro Nishi, Tomotaka Hashibe, Takeshi Fujinami, Hiroaki Hagiwara, Naohide Matsumoto, Malcolm A. Halcrow, Seiichiro Iijima, Yukinari Sunatsuki, Masaaki Kojima

CHEMISTRY LETTERS 40 ( 1 ) 72 - 74 2011.1

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

Facial- and meridional-isomers of tris[benzyl(2-methylimidazol-4-ylmethylidene)amine]iron(II) chloride hexafluorophosphate with the formulas of fac-[Fe(HLMe-Benz)(3)]Cl center dot PF6 center dot EtOH center dot H2O (1) and mer-[Fe(HLMe-Benz)(3)]Cl center dot PF6 center dot 1.5H(2)O (2) were selectively crystallized in ethanol and methanol, respectively. All three imidazole groups in both the fac- and mer-[Fe(HLMe-Benz)(3)](2+) cations are hydrogen-bonded to neighboring Cl- ions and give the assembly structures. The compounds differ, however, in that 1 has a discrete cubane-like tetranuclear cluster, while 2 forms a two-dimensional (2D) network structure. The magnetic susceptibilities data revealed that 1 and 2 are spin crossover complexes.

DOI： 10.1246/cl.2011.72

1D and 2D assembly structures by imidazole center dot center dot center dot chloride hydrogen bonds of iron(II) complexes [Fe-II(HLn-Pr)(3)]Cl center dot Y (HLn-Pr=2-methylimidazol-4-yl-methylideneamino-n-propyl; Y = AsF6, BF4) and their spin states

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

DALTON TRANSACTIONS 40 ( 45 ) 12301 - 12309 2011

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

Two FeII complexes fac-[Fe-II(HLn-Pr)(3)]Cl center dot Y (Y = AsF6 (1) and BF4 (2)) were synthesized, where HLn-Pr is 2-methylimidazole-4-yl-methylideneamino-n-propyl. Each complex-cation has the same octahedral N-6 geometry coordinated by three bidentate ligands and assumes facial-isomerism, fac-[Fe-II(HLn-Pr)(3)](2+) with Delta- and K-enantiomorphs. Three imidazole groups per Delta- or K-fac-[Fe-II(HLn-Pr)(3)](2+) are hydrogen-bonded to three Cl- ions or, from the viewpoint of the Cl- ion, one Cl- ion is hydrogen-bonded to three neighbouring fac-[Fe-II(HLn-Pr)(3)](2+) cations. The 3 : 3 NH center dot center dot center dot Cl- hydrogen bonds between Delta- or K-fac-[Fe-II(HLn-Pr)(3)](2+) and Cl- generate two kinds of assembly structures. The directions of the 3 : 3 NH center dot center dot center dot Cl- hydrogen bonds and hence the resulting assembly structures are determined by the size of the anion Y, though Y is not involved into the network structure and just accommodated in the cavity. Compound 1 has a 1D ladder structure giving a larger cavity, in which the Delta- and K-fac-[Fe-II(HLn-Pr)(3)](2+) enantiomorphs are bridged by two NH center dot center dot center dot Cl- hydrogen bonds. Compound 2 has a 2D network structure with a net unit of a cyclic trimer of {fac-[Fe-II(HLn-Pr)(3)](2+) center dot center dot center dot Cl- } 3 giving a smaller cavity, in which Delta- or K-fac-[Fe-II(HLn-Pr)(3)](2+) species with the same chirality are linked by NH center dot center dot center dot Cl- hydrogen bonds to give a homochiral 2D network structure. Magnetic susceptibility and Mossbauer spectral measurements demonstrated that compound 1 showed an abrupt one-step spin crossover with 4.0 K thermal hysteresis of T-c down arrow = 125.5 K and T-c up arrow = 129.5 K and compound 2 showed no spin transition and stayed in the high-spin state over the 5-300 K temperature range.

DOI： 10.1039/c1dt11063b

A single tripodal ligand stabilizing three different oxidation states (II, III, and IV) of manganese

Yukinari Sunatsuki, Yukana Kishima, Tamami Kobayashi, Tomoka Yamaguchi, Takayoshi Suzuki, Masaaki Kojima, J. Krzystek, Markku R. Sundberg

CHEMICAL COMMUNICATIONS 47 ( 32 ) 9149 - 9151 2011

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

A series of mononuclear Mn-II, Mn-III, and Mn-IV complexes was prepared using a single tripodal ligand (H3L). Addition of a cation (NH4+, K+, Na+) to [(MnL)-L-III] showed a pronounced effect on the redox potentials. Different variants of Jahn-Teller distortion, axial elongation and compression, were observed in the Mn-III complexes.

DOI： 10.1039/c1cc12418h

Face-Sharing Heterotrinuclear M-II-Ln(III)-M-II (M = Mn, Fe, Co, Zn; Ln = La, Gd, Tb, Dy) Complexes: Synthesis, Structures, and Magnetic Properties

Tomoka Yamaguchi, Jean-Pierre Costes, Yukana Kishima, Masaaki Kojima, Yukinari Sunatsuki, Nicolas Brefuel, Jean-Pierre Tuchagues, Laure Vendier, Wolfgang Wernsdorfer

INORGANIC CHEMISTRY 49 ( 20 ) 9125 - 9135 2010.10

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

Trinuclear linear 3d-4f-3d complexes (3d = Mn-II, Fe-II, Co-II, Zn-II and 4f = La-III, Gd-III, Tb-III, Dy-III) were prepared by using a tripodal nonadentate Schiff base ligand, N,N',N ''-tris(2-hydroxy-3-methoxybenzilidene)-2-(aminomethyl)-2-methyl-1,3-propanediamine. The structural determinations showed that in these complexes two distorted trigonal prismatic transition metal complexes of identical chirality are assembled through 41 cations. The Mn and Fe entities crystallize in the chiral space group P2(1)2(1)2(1) as pure enantiomers; the cobalt complexes exhibit a less straightforward behavior. All Mn, Fe, and Co complexes experience M-II-Ln(III) ferromagnetic interactions. The Mn-Gd interaction is weak (0.08 cm(-1)) in comparison to the Fe-Gd (0.69 cm(-1)) and Co-Gd (0.52 cm(-1)) ones while the single ion zero field splitting (ZFS) term D is larger for the Fe complexes (5.7 cm(-1)) than for the cobalt ones. The cobalt complexes behave as single-molecules magnets (SMMs) with large magnetization hysteresis loops, as a consequence of the particularly slow magnetic relaxation characterizing these trinuclear molecules. Such large hysteresis loops, which are observed for the first time in Co-Ln complexes, confirm that quantum tunnelling of the magnetization does not operate in the Co-Gd-Co complex.

DOI： 10.1021/ic100460w

Structures and spin states of mono- and dinuclear iron(II) complexes of imidazole-4-carbaldehyde azine and its derivatives

Yukinari Sunatsuki, Ryohei Kawamoto, Kunihiro Fujita, Hisashi Maruyama, Takayoshi Suzuki, Hiroyuki Ishida, Masaaki Kojima, Seiichiro Iijima, Naohide Matsumoto

COORDINATION CHEMISTRY REVIEWS 254 ( 15-16 ) 1871 - 1881 2010.8

Language：English Publisher：ELSEVIER SCIENCE SA

Mononuclear [Fe(H2LR)(2)]X-2 (R = H, 2-Me, 5-Me, 2-Et-5-Me; X = ClO4, BF4) and dinuclear [Fe-2(H2LR)(3)]X-4 complexes containing imidazole-4-carbaldehyde azine (H2LH) and its derivatives prepared by condensation of 4-formylimidazole, 2-methyl- or 5-methyl-4-formylimidazole, or 2-ethy1-4-methy15-formylimidazole, with hydrazine in a 2:1 mole ratio in methanol, were prepared and their magnetostructural relationships were studied. In the mononuclear complexes, H2LR acts as an unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom, while in the dinuclear complexes, H2LR acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate structure. At room temperature, [Fe-2(H2LH)(3)](ClO4)(4) and [Fe-2(H2L2-me)(3)](ClO4)(4) were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L2-Me with electron-donating methyl groups being stronger than H2LH, with the order of the ligand field strengths being H2L2-me > H2LH. However, in the mononuclear [Fe(H2LH)(2)](ClO4)(2) and [Fe(H2L2-Me)(2)](ClO4)(2) complexes, a different order of ligand field strengths, H2LH > H2L2-Me, was observed because [Fe(H2O)(2)](ClO4)(2) was in the LS state while Fe(H2L2-me)(2)](ClO4)(2) was in the HS state at room temperature. X-ray structural studies revealed that the interligand steric repulsion between a methyl group of an H2L2-Me ligand and the other ligand in Fe(H2L2-Me)(2)](ClO4)(2) is responsible for the observed change in the spin state. The same is true for [Fe(H2L2-Et-5-Me)2](ClO4)(2), while [Fe(H2L5-Me)2](ClO4)(2) does not involve such a steric congestion and stays in the LS state over the temperature range 5-300K. Two kinds of crystals (polymorphs) were isolated for [Fe-2(H2LH)(3)](BF4)(4) and [Fe-2(H2L2-Et-5-Me)(3)](ClO4)(4), and they exhibited different magnetic behaviors. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ccr.2009.11.016

One-Dimensional Spin-Crossover Iron(II) Complexes Bridged by Intermolecular Imidazole-Pyridine NH center dot center dot center dot N Hydrogen Bonds, [Fe(HLMe)(3)]X-2 (HLMe = (2-Methylimidazol-4-yl-methylideneamino-2-ethylpyridine; X = PF6, ClO4, BF4)

Koshiro Nishi, Shinobu Arata, Naohide Matsumoto, Seiichiro Iijima, Yukinari Sunatsuki, Hiroyuki Ishida, Masaaki Kojima

INORGANIC CHEMISTRY 49 ( 4 ) 1517 - 1523 2010.2

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

2-Methylimidazol-4-yl-methylideneamino-2-ethylpyddine (abbreviated as HLMe) is the 1:1 condensation product of 2-methyl-4-formylimidazole and 2-aminoethylpyridine and functions as a bidentate ligand to the iron(II) ion to produce the 3:1 complexes together with anions, [Fe(HLMe)(3)]X-2 (X = PF6 (1), ClO4 (2), BF4 (3)). The magnetic susceptibilities, differential scanning calorimetric measurements, and Mossbauer spectral measurements demonstrated that complexes 1, 2, and 3 showed a steep one-step spin crossover (SCO) between the high-spin (HS, S=2) and low-spin (LS, S = 0) states with small thermal hysteresis. Three complexes have an isomorphous structure and are crystallized in the same monoclinic space group, C2/c, both in the HS and LS states. The iron(II) ion has the octahedral coordination geometry of a facial isomer with N-6 donor atoms of three bidentate ligands, in which an imidazole and an imine nitrogen atom per ligand participate in the formation of the coordination bond, but the pyridine nitrogen is free from coordination. The complex cation fac-[Fe(HLMe)(3)](2+) is a chiral species with a Delta or Lambda isomer, and the adjacent Delta and Lambda isomers are linked alternately by an intermolecular imidazole-pyridine NH center dot center dot center dot N hydrogen bond to produce an achiral 1D chain. The two remaining imidazole moieties per complex are hydrogen-bonded to the anions that occupy the space among the chains. The SCO profile becomes steeper with the decrease of the anion size (73.0 angstrom(3) for PF6-, 54.4 angstrom(3) for ClO4-, and 53.4 angstrom(3) for BF4-). The SCO transition temperature T-1/2 of the PF6 (1), ClO4 (2), and BF4 (3) salts estimated from the magnetic susceptibility measurements are (T-down arrow = 151.8 K, T-up arrow = 155.3 K), (T-down arrow = 184.5 K, T-up arrow = 186.0 K), and (T-down arrow = 146.4 K, T-up arrow = 148.2 K), respectively, indicating that the T-1/2 value is not in accord with the anion size.

DOI： 10.1021/ic9017344

Homochiral column structure of rac- and Lambda-[M-III(tn)(3)]P3O9 (M = Co, Cr; tn=1,3-diaminopropane; P3O9 = cyclotriphosphate(3-)) produced by multiple hydrogen bonds

Yukinari Sunatsuki, Sho Miyahara, Takayoshi Suzuki, Masaaki Kojima, Toshio Nakashima, Naohide Matsumoto, Frode Galsbol

NEW JOURNAL OF CHEMISTRY 34 ( 12 ) 2777 - 2784 2010

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

The crystal structures of rac- and Lambda-[M-III(tn)(3)]P3O9 center dot nH(2)O (M = Co, Cr; tn = 1,3-diaminopropane = trimethylenediamine; P3O9 = cyclotriphosphate(3-))were determined by single-crystal X-ray analyses. In rac-[Co(tn)(3)]P3O9 center dot 7.3H(2)O, the [Co(tn)(3)](3+) cations with the same absolute configuration (Delta or Lambda) and the P3O93- anions are alternately arrayed and connected by multiple NH center dot center dot center dot O hydrogen bonds to form a homochiral columnar structure. Adjacent homochiral columns with opposite chirality are connected by intercolumn hydrogen bonds to form a racemic pair of columns. The crystal structure of rac-[Cr(tn)(3)]P3O9 center dot 7.5H(2)O is similar to that of the Co complex; however, there exist two types of racemic pairs of columns. In the crystal of Lambda-[Co(tn)(3)]P3O9 center dot 2.5H(2)O, a pair of columns consisting of alternately stacked Lambda-[Co(tn)(3)](3+) cations and P3O93- anions are linked by hydrogen bonds. Neighboring column pairs are further linked by hydrogen bonds to form a three-dimensional (3-D) sheet structure. The crystal structure of Lambda-[Cr(tn)(3)]P3O9 center dot 2.5H(2)O is isomorphous with the Co complex. The circular dichroism (CD) spectra of aqueous solutions of Lambda-[M(tn)(3)]Br-3 (M = Co, Cr) change when P3O93- is added, and the changes were explained by ion pair formation through hydrogen bonds.

DOI： 10.1039/c0nj00270d

Mononuclear Bis(tridentate)-Type and Dinuclear Triple Helicate Iron(II) Complexes Containing 2-Ethyl-5-methylimidazole-4-carbaldehyde Azine

Yukinari Sunatsuki, Hisashi Maruyama, Kunihiro Fujita, Takayoshi Suzuki, Masaaki Kojima, Naohide Matsumoto

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 82 ( 12 ) 1497 - 1505 2009.12

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

Mononuclear [Fe(H2L2-Et-5-Me)(2)](2+) and dinuclear [Fe-2(H2L2-Et-5-Me)(3)](4+) complexes, where H2L2-Et-5-Me denotes 2-ethyl-5-methylimidazole-4-carbaldehyde azine, were prepared and isolated as the perchlorate salts, and their structures and magnetic properties were studied. In file mononuclear complex, the ligand acts as ail unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom. The complex was in the HS state above 50 K. In the dinuclear complex, each ligand acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate structure. Two types of crystals, plates and blocks, were isolated for the dinuclear complex. The plate crystals exhibited a sharp spin transition, [LS-HS] <-> [HS-HS], with no [LS-LS] state being observed. The block crystals remained in the [HS-HS] state above 50 K.

DOI： 10.1246/bcsj.82.1497

Structures and Spin States of Bis(tridentate)-Type Mononuclear and Triple Helicate Dinuclear lron(II) Complexes of Imidazole-4-carbaldehyde azine

Yukinari Sunatsuki, Ryohei Kawamoto, Kunihiro Fujita, Hisashi Maruyama, Takayoshi Suzuki, Hiroyuki Ishida, Masaaki Kojima, Seiichiro Iijima, Naohide Matsumoto

INORGANIC CHEMISTRY 48 ( 18 ) 8784 - 8795 2009.9

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

Mononuclear [Fe(H2LR)(2)](2+) and dinuclear [Fe(H2LR)(3)](4+) (R = H, 2-Me, 5-Me) complexes containing the new imidazole-4-carbaldehyde azine ligand (H2LH) and its derivatives (H2L2-Me and H2L5-Me) prepared from the condensation reaction of 4-formylimidazole or 2-methyl- or 5-methyl-4-formylimidazole with hydrazine (2:1) were prepared, and their magnetostructural relationships were studied. In the mononuclear complexes, H2LR acts as an unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom, while in the dinuclear complexes, H2LR acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate. At room temperature, [Fe-2(H2LH)(3)](CIO4)(4) and [Fe-2(H2L2-Me)(3)](CIO4)(4) were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L2-Me with electron-donating methyl groups being stronger than H2LH, with the order of the ligand field strengths being H2L2-M (e)> H2LH, However, in the mononuclearjFe(H2LH)(2)](CIO4)(2) and [Fe(H2L2-Me)(2)](CIO4)(2) complexes, a different order of Iigand field strengths, H2LH > H2L2-Me, was observed because [Fe(H2LH)(2)] (CIO4)(2) was in the LS state while [Fe(H2L2-Me)(2)](CIO4)(2) was in the HS state at room temperature. X-ray structural studies revealed that the interligand steric repulsion between a methyl group of an H2L2-Me ligand and the other ligand in [Fe(H2L2-Me)(2)](CIO4)(2) is responsible for the observed change in the spin state. Two kinds of crystals, needles and blocks, were isolated for [Fe2(H2LH)(3)](BF4)(4), and both exhibited a sharp spin transition, [LS-HS] <-> [HS-HS], The spin transition of the block crystals is more abrupt with a hysteresis, T-c up arrow = 190 K and T-c down arrow = 183 K with Delta T= 7 K.

DOI： 10.1021/ic900977m

Synthesis and characterization of 8-quinolinolato vanadium(IV) complexes

Kentaro Takano, Yukinari Sunatsuki, Masaaki Kojima, Isamu Kinoshita, Takashi Shibahara

INORGANICA CHIMICA ACTA 362 ( 9 ) 3201 - 3207 2009.7

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

Reaction of vanadium(III) chloride with 8-quinolinol (Hqn) gave a mononuclear vanadium(IV) complex, [VOCl2(H2O)(2)] 1) center dot 2H(2)qn center dot 2Cl center dot CH3CN, and three dinuclear vanadium(IV) complexes: [V2O2Cl2 (qn)(2)(H2O)(2)] (2) center dot Hqn, [V2O2Cl2(qn)(2)(C3H7OH)(2)] (3), and [V2O2Cl2(qn)(2)(C4H9OH)(2)] (4). Reaction of vanadium(III) chloride with 5-chloro-8-quinolinol (HClqn) gave four dinuclear vanadium(IV) complexes: [V2O2Cl2(Clqn)(2)(H2O)(2)] (5) center dot 2HClqn, [V2O2Cl2(Clqn)(2)(C3H7OH)(2)] (6), [V2O2Cl2(Clqn)(2)(C6H5CH2OH)(2)] (7), and [V2O2Cl2(Clqn)(2)(C4H9OH)(2)] (8) center dot 2C(4)H(9)OH. Reaction of vanadium(III) chloride with 5-fluoro-8-quinolinol (HFqn) gave two dinuclear vanadium(IV) complexes: [V2O2Cl2(Fqn)(2)(H2O)(2)] (9) center dot HFqn center dot 2H(2)O and V2O2Cl2(Fqn)(2)(C3H7OH)(2)] (10). X-ray structures of 1 center dot 2H(2)qn center dot 2Cl center dot CH3CN, 3, 4, 6, 7, 8 center dot 2 t-BuOH, and 10 have been determined. As to the mononuclear species 1 center dot 2H2qn center dot 2Cl center dot CH3CN, coordination of Hqn to vanadium does not occur, but protonation to Hqn occurs to give H(2)qn(+), which links 1's through hydrogen bonding, while each of the dinuclear species has a terminal and a bridging qn (or Clqn, Fqn) ligand, giving rise to a (V-O)(2) ring. Magnetic measurements of 3, 4, 6, 7, and 10 in solid form show very weak antiferromagnetic behavior, and the effective magnetic moments are close to spin only value (2.44) of d(1)-d(1) system, while ESR of 3 in THF shows dissociation to monomeric species. Change from mononuclear, 1, to dinuclear, 2, species was followed by the change of electronic spectrum. (C) 2009 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.ica.2009.02.025

Synthesis, structures, and magnetic properties of face-sharing heterodinuclear Ni(II)-Ln(III) (Ln = Eu, Gd, Tb, Dy) complexes

Tomoka Yamaguchi, Yukinari Sunatsuki, Hiroyuki Ishida, Masaaki Kojima, Haruo Akashi, Nazzareno Re, Naohide Matsumoto, Andrzej Pochaba, Jerzy Mrozinski

INORGANIC CHEMISTRY 47 ( 13 ) 5736 - 5745 2008.7

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

Heterodinuclear [((NiL)-L-II)Ln(III)(hfac)(2)(EtOH)] (H3L = 1,1,1-tris[(salicylideneamino)methyl]ethane; Ln = Eu, Gd, Tb, and Dy; hfac = hexafluoroacetylacetonate) complexes (1 . Ln) were prepared by treating [Ni(H1.5L)]Cl-0.5 (1) with (Ln(hfaC)(3)(H2O)(2)] and triethylamine in ethanol (1:11). All 1 . Ln complexes (1 . Eu, 1 . Gd, 1 . Tb, and 1 . Dy) crystallized in the triclinic space group P (1) over bar (No. 2) with Z = 2 with very similar structures. Each complex is a face-sharing dinuclear molecule. The Ni-II ion is coordinated by the L3- ligand in a N3O3 coordination sphere, and the three phenolate oxygen atoms coordinate to an Ln(III) ion as bridging atoms. The Ln(III) ion is eight-coordinate, with four oxygen atoms of two hfac-'s, three phenolate oxygen atoms of L3-, and one ethanol oxygen atom coordinated. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements showed a ferromagnetic interaction between Ni-II and Gd-III in 1 . Gd. The Ni-II-Ln(III) magnetic interactions in 1 . Eu, 1 . Tb, and 1 . Dy were evaluated by comparing their magnetic susceptibilities with those of the isostructural Zn-II-Ln(III) complexes, [(ZnL)Ln(hfac)(2)(EtOH)] (2 . Ln) containing a diamagnetic Zn-II ion. A ferromagnetic interaction was indicated in 1 . Tb and 1 . Dy, while the interaction between Ni-II and Eu-III was negligible in 1 . Eu. The magnetic behaviors of 1 . Dy and 2 . Dy were analyzed theoretically to give insight into the sublevel structures of the Dy-III ion and its coupling with Ni-II. Frequency dependence in the ac susceptibility signals was observed in 1 . Dy.

DOI： 10.1021/ic8000575

Mono- and trinuclear Cu-II complexes with tripodal ligands

Yukinari Sunatsuki, Tamami Kobayashi, Kenji Harada, Tomoka Yamaguchi, Matsuo Nonoyama, Masaaki Kojima

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 81 ( 6 ) 716 - 725 2008.6

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

Mononuclear [Cu(HL)] (1) and trinuclear [Cu-3(L)(2)] (3) complexes were synthesized, where H3L (1,1,1-tris[(salicylideneamino)methyl] ethane) is a tripodal ligand obtained by condensation of 1,1,1-tris(aminomethyl)ethane and salicylaldehyde in a 1:3 mole ratio. Another mononuclear complex [Cu(HL')] (2), where one of the three arms was disconnected probably due to thermal hydrolysis, was also obtained. The crystal structures, electronic spectra, and electrochemical and magnetic properties of the complexes were studied. In 1, one of the arms of H3L is not coordinated to the metal atom, and the ligand serves as a tetradentate N2O2 ligand, the complex assuming a slightly distorted square-planar structure. In the trinuclear complex, an imine nitrogen atom and a phenolate oxygen atom of one arm of each terminal unit coordinate to the central Cu-II ion to form a linear trinuclear complex. The coordination geometry about each Cu is square planar. All of the complexes involve pi-pi stacking interactions between the molecules in the crystal structures, which are responsible for weak magnetic interactions. An electrochemical study of 3 in DMSO showed that the central Cu-II is more easily reduced to Cu-I than the terminal Cu ions. The mononuclear complexes, 1 and 2, show a quasi-reversible Cu-II/I couple almost at the same position as that of the terminal Cu ions of 3.

DOI： 10.1246/bcsj.81.716

Synthesis, structures, and magnetic properties of doubly face-sharing heterotrinuclear Ni-II-Ln(III)-Ni-II (Ln = Eu, Gd, Tb, and Dy) complexes

Tomoka Yamaguchi, Yukinari Sunatsuki, Hiroyuki Ishida, Masaaki Kojima, Haruo Akashi, Nazzareno Re, Naohide Matsmuoto, Andrzej Pochaba, Jerzy Mrozinski

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 81 ( 5 ) 598 - 605 2008.5

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

Heterotrinuclear [((NiL)-L-II)(2)Ln(III)(NO3)] complexes (where H3L = 1,1,1-tris[(salicylideneamino)methyl] ethane and Ln = Gd (1), Eu (2), Tb (3), and Dy (4)) were prepared by treating [Ni(H1.5L)]Cl-0.5 with Ln(NO3)(3)center dot 6H(2)O in the presence of triethylamine. Complexes 1 center dot 2CH(3)OH, 3 center dot 2CH(3)OH, and 4 center dot C2H5OH center dot 0.5H(2)O crystallized in the triclinic space group, P (1) over bar (No. 2), with Z = 2, while 2 center dot CH3OH center dot 0.5H(2)O crystallized in the tetragonal space group, I4(1)/a (No. 88), with Z = 8. All the complexes had very similar structures. Each complex was a doubly face-sharing trinuclear molecule. The Ni-II ion is coordinated by the L3- ligand in an N3O3 coordination sphere, and the three phenolate oxygen atoms coordinate to an Ln(III) ion as bridging atoms. The Ln(III) ion is eight coordinate with six phenolate oxygen atoms of the two L3- ligands and two oxygen atoms of NO3-. Coordination of the NO3- group entails a bending of the Ni center dot center dot center dot Ln center dot center dot center dot Ni angle (ca. 140 degrees). All the complexes involve pi-pi and CH-pi interactions between the neighboring molecules to form a three-dimensional structure. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements on 1 showed a ferromagnetic interaction between the Ni-II and Gd-III atoms. A ferromagnetic interaction was also suggested for Ni-II-Tb-III (3) and Ni-II-Dy-III (4).

DOI： 10.1246/bcsj.81.598

Mononuclear nickel(II) and zinc(II) complexes with deprotonated forms of the tripodal hexadentate ligand 1,3-bis(2-hydroxybenzylidene)-2-(2-hydroxybenzylideneaminomethyl)-2-methylpropane-1,3-diamine

Tomoka Yamaguchi, Yukinari Sunatsuki, Hiroyuki Ishida

ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 64 M156 - M160 2008.4

Cobalt(III) complexes of a tripodal ligand containing three imidazole groups: Properties and structures of racemic and optically active species

Hirofumi Nakamura, Megumi Fujii, Yukinari Sunatsuki, Masaaki Kojima, Naohide Matsumoto

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY ( 8 ) 1258 - 1267 2008.3

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

The complex [Co(H3L)](ClO4)(3)center dot H2O (1), where H3L (tris[2-(4-imidazoylmethylideneamino) ethyl] amine) is a tripodal ligand obtained by condensation of tris(2-aminoethyl)amine and 4-formylimidazole in a 1:3 molar ratio, was synthesized and optically resolved by fractional crystallization of the dia-stereomeric salt with [Sb-2{(R,R)-tart)(2)](2-) [(R,R)-tart = (2R,3R)-tartrate(4-) ion]. From the less soluble part, Lambda-[Co(H2L)][Sb-2- (R, R) -tart)(2)]center dot 4H(2)O (2) was isolated. Starting from 2, two optically active complexes, Lambda-[Co(H3L)]ClO4)(3)center dot 1.5H(2)O (Lambda-1) and Lambda-[Co(L)] (Lambda-3), were obtained. The crystal structures of these complexes are compared with those of the racemic structures. A-I shows an unusually strong circular dichroism (lambda = 488 nm, Delta epsilon = -7.74 M-1 cm(-1)) in the first d-d absorption band region. The effects of deprotonation-reprotonation of the uncoordinated imidazole NH groups of Lambda-[Co(H3L)](3+) on the UV/Vis and CD spectra and on the cyclic voltammograms were studied in methanol. Although the deprotonation-reprotonation reactions are reversible, the redox couple for the completely deprotonated species [CoIII/II(L)](0/-) is not observed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

DOI： 10.1002/ejic.200700950

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