Faculty Profiles - SUZUKI Takayoshi

Papers - SUZUKI Takayoshi

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Iron(II) Complexes Having Dinuclear Mesocate or Octanuclear Bicapped Trigonal Prism Structures Dependent on the Rigidity of Bis(bidentate) Schiff Base Ligands Containing Imidazole Groups Reviewed

Tsubasa Tanaka, Yukinari Sunatsuki, Takayoshi Suzuki

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 93 ( 3 ) 427 - 437 2020.3

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

Dinuclear complex, [Fe-2(H2L1'(Me))(3)](ClO4)(4) (1Me, H(2)L1,(Me) = N,N'-(1,3 -phenylene)bis (1 -(5 -methyl-1H-imidazol-4-yl)methanimine)), and octanuclear complexes, [Fe-8(H2L2,H)(12)](ClO4)(16 )(2HClO: H2L2,H = N,N'-(1,3-phenylenebis(methylene))bis-(1-(1H-imidazol-4-yl)methanimine) and [Fe-2(H2L2'(Me))(12)](X)(16) (2MeX: H2L2,Me = N.N'-(1,3 -phenylene))bis-(methylene))bis- (1-(5-methyl-1H-imidazol-4-yl)methanimine), X = ClO4, BF4), were synthesized. It was revealed by X-ray analysis that 1Me has a dinuclear mesocate structure. On the other hand, 2HClO4 and 2MeX have novel octanuclear bicapped trigonal prism structures with six iron(II) sites having the meridional configuration on vertexes and two iron(II) sites having the facial one on the centers of each triangular base. Magnetic susceptibility studies indicated that these dinuclear and octanuclear complexes show gradual spin-crossover (SCO) behavior.

DOI： 10.1246/bcsj.20190360

Transition-metal(ii) complexes with a tripodal hexadentate ligand, 1,1,1-tris[2-aza-3-(imidazol-4-yl)prop-2-enyl]ethane, exhibiting incomplete total or absolute spontaneous resolution Reviewed

Misaki Matsushima, Koki Wada, Yuki Horino, Kazuma Takahara, Yukinari Sunatsuki, Takayoshi Suzuki

CrystEngComm 22 ( 3 ) 458 - 466 2020.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry ({RSC})

Crystal structures and crystallisation behaviours of a series of first-row transition-metal(II) complexes bearing 1,1,1-tris[2-aza-3-(imidazol-4-yl)prop-2-enyl]ethane (H3L), [M-II(H3L)]Cl(ClO4) (M = Mn, Fe, Co, Ni and Zn) were examined. These compounds crystallise in an orthorhombic crystal system with a non-enantiogenic (Sohncke) space group P2(1)2(1)2(1), resulting in spontaneous resolution of the chiral complex cations. Hydrogen bonds between the imidazole N-H atoms in the tripodal ligand and chloride anions give enantiomorphic crystals with a homochiral three-dimensional network structure. In order to verify the spontaneous resolution of these compounds, solid-state circular dichroism spectra of the resulting single crystals were measured (KBr disk method). Unexpectedly, the observed spectra indicated that imbalanced formation of the enantiomorphic crystals (i.e., left-handed Lambda-form vs. right-handed Delta-form complex cations) in all cases. Moreover, in the cases of Ni-II and Zn-II compounds, predominant enantiomorphic crystals formed by spontaneous resolution were always the same (in at least ten of our recrystallisation experiments). These observations suggest that there is a certain (but as yet unknown) factor that affects the predominant deposition of either enantiomorphic crystal when spontaneous resolution takes place from a solution of a racemic mixture in which rapid racemisation occurs.

DOI： 10.1039/c9ce01864f

Dinuclear lanthanoid(III) dithiocarbamato complexes bridged by (E)-N-benzylidenepicolinohydrazonate: Syntheses, crystal structures and spectroscopic properties Reviewed

Abdallah Yakubu, Takayoshi Suzuki, Masakazu Kita

INORGANICA CHIMICA ACTA 498 119124 2019.12

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

(E)-N-Benzylidenepicolinohydrazide (Hbphz) was used to synthesize a series of hydrazonato-bridged homodinuclear Ln(2)(III) dithiocarbamato (RR'dtc(-)) complexes of the form [{Ln(RR' dtc)(2)}(2)(mu-bphz)(2)] {Ln= La, Pr, Nd, Sm or Eu; RR'= dimethyl-(Me-2) or pyrrolidine-(pyr)}. X-ray crystallographic studies revealed that these complexes possessed a common head-to-tail type dinuclear structural motif in which two hydrazonato ligands bridged two Ln(III) centers in the mu- 1 kappa N-2(py),O:2 kappa O-2,N(imine) mode and two RR'dtc ligands coordinated to each Ln(III) center. Interestingly, while the Sm-III and Eu-III complexes crystallized as simple 8:8-coordinate dinuclear molecules, the lighter Ln(III) (i.e. La-III, Pr-III and Nd-III) complexes afforded in some cases 9:9-coordinate molecules, where the ninth coordination site was occupied by a solvent ethanol or methanol molecule. Even for the lighter Ln(III) complexes, the complexes were solved in dichloromethane or chloroform as the 8:8-coordinate dimer, as revealed by H-1 NMR spectroscopy. In the UV-visible absorption and magnetic circular dichroism (MCD) spectra of the complexes, similar spectral patterns for ligand-centered and Laporte forbidden f-f transitions were observed. The MCD spectral studies demonstrated the characteristic magneto-optical behavior of the complexes.

DOI： 10.1016/j.ica.2019.119124

Homodinuclear lanthanoid(III) dithiocarbamato complexes bridged by 2,2′-bipyrimidine: Syntheses, structures and spectroscopic properties Reviewed

Abdallah Yakubu, Takayoshi Suzuki, Masakazu Kita

Polyhedron 171 515 - 522 2019.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier {BV}

Four new homodinuclear lanthanoid(III) dithiocarbamato (RR'dtc(-)) complexes bridged by 2,2'-bipyrimidine (bpm) of the form [{Ln(RR'dtc)(3)}(2)(mu-bpm)] {Ln = Nd or Eu; RR' = dimethyl- (Me-2) or pyrrolidine(pyr)} were prepared and their crystal structures and spectroscopic properties were characterized. The crystallographic studies revealed that all of the complexes possess a similar structural motif with an 8:8-coordination geometry, in which the bpm ligand bridges two Ln(III) centers in the kappa N-2(1,1') : kappa N-2(3,3') mode and three RR'dtc(-) ligands coordinate to each Ln(III) center. The complexes exhibit weak but relatively sharp f-f transition bands in the absorption and magnetic circular dichroism (MCD) spectra recorded in the visible region. The MCD spectral studies demonstrated the magneto-optical behavior of the complexes. The spectral features of the dithiocarbamato complexes were distinctly different from those of their beta-diketonato analogues, suggesting the coordination environment around the Ln(III) center influences the electronic structure and spectroscopic symmetry of the complexes in solution. (C) 2019 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.poly.2019.07.046

Tetra- and dinuclear manganese complexes of xanthene-bridged O,N,O-Schiff bases with 3-hydroxypropyl or 2-hydroxybenzyl groups: ligand substitution at a triply bridging site Reviewed

Rina Ogawa, Takayoshi Suzuki, Masakazu Hirotsu, Noriyuki Nishi, Yuu Shimizu, Yukinari Sunatsuki, Yoshio Teki, Isamu Kinoshita

Dalton Transactions 48 ( 36 ) 13622 - 13629 2019.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry ({RSC})

Complexation properties of U-shaped ligands, L-1 and L-2, which are Schiff bases of 5,5 '-(9,9-dimethylxanthene-4,5-diyl)bis(salicylaldehyde) (H(2)xansal) with 3-amino-1-propanol or 2-hydroxybenzylamine, respectively, were investigated to construct polynuclear manganese complexes. In these ligands, two O,N,O-Schiff bases are bridged by a xanthene backbone. The reactions of H4L1 or H4L2 with manganese salts afforded tetra- and dinuclear manganese complexes, including the tetramanganese(ii,ii,iii,iii) complex [Mn-4(L-1)(2)(mu-OAc)(2)] with a Mn4O6 core exhibiting an incomplete double-cubane structure. In the Mn4O6 core, phenolate and alkoxide O atoms bridge the manganese ions. Deprotonated 3-hydroxypropyl groups were crucial to the assembly of four manganese ions because the phenolate-bridged dimanganese(iii,iii) complex [Mn-2(H2L1)(2)](2+) was obtained in the absence of a base, and H4L2, which has 2-hydroxybenzyl groups instead of 3-hydroxypropyl groups in H4L1, afforded the cyclic dimanganese(iv,iv) complex [Mn-2(L-2)(2)]. We disclosed that [Mn-4(L-1)(2)(mu-OAc)(2)] was converted to the oxo-bridged tetramanganese(iii,iii,iii,iii) complex [Mn-4(L-1)(HL1)(mu(3)-O)(mu-OAc)(2)](+) by treating with NH4PF6 or NH4BF4: a triply bridging alkoxide was protonated and replaced by an oxide ligand. The cyclic voltammograms of [Mn-4(L-1)(HL1)(mu(3)-O)(mu-OAc)(2)](+) suggested that the reverse reaction forming [Mn-4(L-1)(2)(mu-OAc)(2)] occurred in the electrochemical processes and was assisted by protonation.

DOI： 10.1039/c9dt03007g

Spin, Valence, and Structural Isomerism in the S3 State of the Oxygen-Evolving Complex of Photosystem II as a Manifestation of Multimetallic Cooperativity. Reviewed International journal

Hiroshi Isobe, Mitsuo Shoji, Takayoshi Suzuki, Jian-Ren Shen, Kizashi Yamaguchi

Journal of chemical theory and computation 15 ( 4 ) 2375 - 2391 2019.4

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

Photosynthetic water oxidation is catalyzed by a Mn4CaO5-cluster in photosystem II through an S-state cycle. Understanding the roles of heterogeneity in each S-state, as identified recently by the EPR spectroscopy, is very important to gain a complete description of the catalytic mechanism. We performed herein hybrid DFT calculations within the broken-symmetry formalism and associated analyses of Heisenberg spin models to study the electronic and spin structures of various isomeric structural motifs (hydroxo-oxo, oxyl-oxo, peroxo, and superoxo species) in the S3 state. Our extensive study reveals several factors that affect the spin ground state: (1) (formal) Mn oxidation state; (2) metal-ligand covalency; (3) coordination geometry; and (4) structural change of the Mn cluster induced by alternations in Mn···Mn distances. Some combination of these effects could selectively stabilize/destabilize some spin states. We found that the high spin state ( Stotal = 6) of the oxyl-oxo species can be causative for catalytic function, which manifests through mixing of the metal-ligand character in magnetic orbitals at relatively short O5···O6 distances (<2.0 Å) and long MnA···O5 distances (>2.0 Å). These results will serve as a basis to conceptually identify and rationalize the physicochemical synergisms that can be evoked by the unique "distorted chair" topology of the cluster through cooperative Jahn-Teller effects on multimetallic centers.

DOI： 10.1021/acs.jctc.8b01055

Syntheses and crystal structures of neodymium(III) and europium(III) complexes bearing dimethyl-, pyrrolidine-, or S-prolinol- dithiocarbamato ligands and their natural and magnetic circular dichroism spectra Reviewed

Yakubu, A., Suzuki, T., Kita, M.

Inorganica Chimica Acta 484 394 - 401 2019.1

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

A series of Nd-III and Eu-III complexes containing achiral or chiral dithiocarbamato (dtc) ligands, [Ln(Xdtc)(3)(NN)] {Ln = Nd or Eu; X = dimethyl- (Me-2), pyrrolidine- (pyr), or (S)-prolinol- (S-proOH); NN = 1,10-phenanthroline (phen) or 2,2'-bipyridine (bpy)}, were prepared and their crystal structures and spectroscopic properties, in particular the natural circular dichroism (CD) and magnetic circular dichroism (MCD), were investigated. The crystal structures of the complexes analyzed by the X-ray diffraction method showed an 8-coordinate geometry around the Ln III center with comparable structural parameters to one another and to the related complexes reported previously. These complexes exhibited similar spectral patterns in their absorption, natural CD and MCD spectra in solution. Weak but characteristic sharp f-f transition bands were observed in the absorption and MCD spectra, but no CD signals associated with these transitions were observed even in the S-proOHdtc complexes. The MCD spectral pattern of the Eu-III complexes revealed a local C-2v symmetry around the Ln(III) center in solution, in contrast to the aqua and the analogous beta-diketonato Eu-III complexes.

DOI： 10.1016/j.ica.2018.09.064

trans-Dichloridotetrakis(pyridine-κN)rhodium(III) chloride methanol tetrasolvate Reviewed

Takayoshi Suzuki, Misaki Tsujino, Yukinari Sunatsuki

IUCrData 3 ( 10 ) x181482 2018.10

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

Rina Ogawa, Yukinari Sunatsuki, Takayoshi Suzuki

European Journal of Inorganic Chemistry 2018 ( 16 ) 1733 - 1742 2018.4

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

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 MnII and CoII salts, the MII ion is oxidized by air to form a cationic complex with two mono-deprotonated ligands, [MIII(S-HLMe)2]X [M, X = Mn, ClO4 (S-1ClO4)
Co, ClO4 (S-3ClO4)
and Co, Cl (S-3Cl)], where (S-HLMe)– is coordinated to a MIII center in a tridentate κ3O,N,N′ mode with a mer configuration. In contrast, the NiII ion is not oxidized
only one of the ligands is deprotonated to form a similar monocationic complex, [NiII(S-HLMe)(S-H2LMe)]PF6 (S-6PF6), 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 NiII complexes of [Ni(HLMe)(H2LMe)](PF6 or Cl) (rac-6PF6 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

Field-induced single-molecule magnet behavior in ideal trigonal antiprismatic cobalt(II) complexes: precise geometrical control by a hydrogen-bonded rigid metalloligand

Mitsuhashi, R., Pedersen, K.S., Ueda, T., Suzuki, T., Bendix, J., Mikuriya, M.

Chemical Communications 54 ( 64 ) 8869 - 8872 2018

Hydrogen-bonding interactions and magnetic relaxation dynamics in tetracoordinated cobalt(II) single-ion magnets Reviewed

Ryoji Mitsuhashi, Satoshi Hosoya, Takayoshi Suzuki, Yukinari Sunatsuki, Hiroshi Sakiyama, Masahiro Mikuriya

Dalton Trans. 48 ( 2 ) 395 - 399 2018

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry ({RSC})

Three tetracoordinated cobalt(ii) complexes with a series of unsymmetrical bidentate ligands were synthesized and crystallographically characterized. Although their static magnetic properties are similar, their dynamic magnetic properties differ drastically depending indirectly on intermolecular hydrogen-bonding interactions.

DOI： 10.1039/C8DT04537B

Geometric isomerism and redox properties of ruthenium(II/III) complexes with 3-hydroxypicolinamide

Ryoji Mitsuhashi, Takayoshi Suzuki, Masahiro Mikuriya

Chemistry Letters 47 ( 4 ) 479 - 482 2018

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Society of Japan

Two geometric isomers of [RuCl2(PPh3)2(O-N)]-type complex were prepared and characterized by X-ray crystallography (PPh3 = triphenylphosphine, O-N = Hpia/pia-, Hpia = 3-hydroxypicolinamide). The electrochemical properties of the complexes upon protonation/deprotonation were investigated. The redox potential of the Ru center was remarkably shifted by isomerization. The UV-vis and electrochemical measurements suggested that slow isomerization from trans(P,Cl),trans(P,N) geometry to trans(P,P) geometry induced the oxidation and deprotonation of the complex.

DOI： 10.1246/cl.171166

Developing a Magnetic Circular Dichroism Apparatus Equipped with Neodymium Magnet for Students To Investigate the Electronic Structures of Transition Metals and Lanthanoids

Abdallah Yakubu, Takayoshi Suzuki, Masakazu Kita

JOURNAL OF CHEMICAL EDUCATION 94 ( 9 ) 1357 - 1362 2017.9

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

This paper describes the development of a simple magnetic circular dichroism (MCD) apparatus from a wood base and neodymium magnets and its configuration in the Faraday alignment. The applicability and effectiveness of the apparatus for MCD spectra measurements have been examined. The apparatus was used by undergraduate students to conduct MCD experiments on Ni2+, Nd3+, and Eu3+ ions in aqueous solutions. Absorption spectra of the sample solutions were also measured. The results of the MCD and absorption spectra of d-d and f-f transition were compared. The results indicate that the apparatus can be used to teach undergraduate students.

DOI： 10.1021/acs.jchemed.7b00106

Hydrogen-Bonded Supramolecular Structures of Cobalt(III) Complexes with Unsymmetrical Bidentate Ligands: mer/fac Interconversion Induced by Hydrogen-Bonding Interactions

Ryoji Mitsuhashi, Takayoshi Suzuki, Satoshi Hosoya, Masahiro Mikuriya

CRYSTAL GROWTH & DESIGN 17 ( 1 ) 207 - 213 2017.1

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

Cobalt(III) complexes with three unsymmetrical bidentate ligands containing a noncoordinating N-H bond and a phenolate-O donor as hydrogen-bond donor and acceptor, respectively, were prepared and characterized. H-1 NMR spectroscopy indicated that all the tris-chelate Co(III) complexes prepared favor the mer configuration in solution. [Co(Hthp)(3)] and [Co(Himn)(3)] also possess the mer configuration in the crystals (Hthp(-) = 2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolate, Himn(-) = 2-(2-imidazolinyl)-phenolate). On the other hand, [Co(Himl(-))(3)] takes the fac configuration in the crystal (Himl(-) = 2-(2-irnidazolyl)-phenolate). 'these Co(III) complexes showed three types of characteristic supramolecular structures: ladder, distorted hexagonal sheet, and honeycomb sheet structure; constructed by intermolecular hydrogen bonds. Heating [Co(Himn)(3)] and [Co(Himl)(3)] in methanol selectively afforded precipitates of the fac isomer due to the low solubility of the hydrogen-bonded supramolecular structures. This mer to fac isomerization upon crystallization in methanol is presumably induced by the formation of highly ordered hydrogen-bond networks via the methanol molecule. The fac isomers remained intact in dimethyl sulfoxide (DMSO) for longer than a week at room temperature. Upon heating, however, fac to mer geometrical isomerization of both fac-[Co(Himn)(3)] and fac-[Co(Himl)(3)] was observed in DMSO. Thus, mer/fac interconversion was achieved by heating in two different solvents, due to the forrnation of a supramolecular assembly of hydrogen-bond networks.

DOI： 10.1021/acs.cgd.6601438

Effective cleaning of copper stained calcareous stone

Sanne Spile, Takayoshi Suzuki, Jesper Bendix, Kim Pilkjaer Simonsen

HERITAGE SCIENCE 4 ( 29 ) 1 - 6 2016.10

Language：English Publishing type：Research paper (scientific journal) Publisher：BIOMED CENTRAL LTD

Background: Light calcareous stone materials used in connection with cultural heritage objects, such as pedestals, or used as wall facings in connection with bronze statues or joints often show green staining due to the corrosion products from the bronze elements. The green stains alter the appearance of the monument and thus disrupt the original intention. Due to this, several cleaning methods, often involving ammonia, have been developed for removal of copper stains from stone surfaces. This paper describes a new, highly efficient method for cleaning copper stains from calcareous stone by introducing the chelating agent ethylenediamine in a poultice consisting of Laponite (R) RD, Arbocel (R) BC1000 and CMC.
Results: Cleaning experiments were performed on marble and on a calcareous sandstone plinth contaminated with natural copper corrosion products due to outdoor exposure of an untreated bronze statue. The cleaning results were evaluated by visual observations.
Conclusion: The chemical cleaning of copper stained calcareous stone surfaces has been investigated and a new method for removal of copper stains has been developed. A solution of 0.1 M ethylenediamine in a poultice consisting of Laponite (R) RD/Arbocel (R) BC1000/CMC has shown to be an effective, economical, and fast do-it-yourself method.

DOI： 10.1186/s40494-016-0102-5

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

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

INORGANICA CHIMICA ACTA 452 ( 1 ) 205 - 213 2016.10

Authorship：Lead author 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

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

Effective cleaning of rust stained marble

Sanne Spile, Takayoshi Suzuki, Jesper Bendix, Kim Pilkjaer Simonsen

HERITAGE SCIENCE 4 ( 12 ) 1 - 10 2016.5

Language：English Publishing type：Research paper (scientific journal) Publisher：BIOMED CENTRAL LTD

Background: Calcareous materials, like marble used in connection with cultural heritage objects such as statues and pedestals, or as wall facings on buildings, often show a brownish staining owing to contact with iron metal or iron-containing minerals in the stone. The discolouration alters the appearance of the stone, which is undesirable from an aesthetic point of view. Despite rust staining being a conspicuous phenomenon and numerous works that have dealt with the problem of removing rust stains, a simple and non-toxic method has so far been missing. This paper describes a highly efficient method for cleaning rust stains from marble by introducing the chelating amino acid cysteine in a Laponite poultice in combination with the strong reducing agent sodium dithionite.
Results: Cleaning experiments were performed on artificially discoloured samples of various types of Carrara Bianco marble and on naturally rust stained marble. To begin with, solutions of cysteine in combination with sodium dithionite and ammonium carbonate were tested by immersion of samples into the different solutions. Secondly, solutions of cysteine and sodium dithionite with and without buffering were used in a poultice consisting of Laponite (R) RD, Arbocel (R) BC1000 and CMC. The poultice was applied on three different marble types: Carrara Fabricotti, Carrara Vagli and Carrara La Piana. Thirdly, the optimized method was tested on original rust stained material of Greenlandic marble, which has been used as wall facing, and finally in situ in Copenhagen on a larger area of The Marble Church showing rust stains due to pyrite oxidation. The cleaning results were evaluated by visual observations, cross sections, and etching of the surface by testing on high gloss marble.
Conclusion: Cleaning of iron-discoloured marble surfaces has been investigated and a new method for removal of rust stained marble has been developed. A solution of 0.1 M cysteine and 0.1 M sodium dithionite in a poultice consisting of Laponite (R) RD/Arbocel (R) BC1000/CMC = 10:10:1 has shown to be a fast, simple, cheap, and non-toxic, do-it-yourself method.

DOI： 10.1186/s40494-016-0081-6

Crystal structures of bis[2-(pyridin-2-yl)phenylk2N,C1]rhodium(III) complexes containing an acetonitrile or monodentate thyminate(1-) ligand

Mika Sakate, Haruka Hosoda, Takayoshi Suzuki

Acta Crystallographica Section E: Crystallographic Communications 72 543 - 547 2016.4

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

The crystal structures of bis[2-(pyridin-2-yl)phenyl]rhodium(III) complexes with the metal in an octahedral coordination containing chloride and acetonitrile ligands, namely (OC-6-42)-acetonitrilechloridobis[2-(pyridin-2- yl)phenyl-2N,C1]rhodium(III), [RhCl(C11H8N)2(CH3CN)] (1), thyminate(1-) and methanol, namely (OC-6-42)-methanol(5-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin- 1-ido-N1)bis[2-(pyridin-2-yl)phenyl-2N,C1]rhodium(III), [Rh(C11H8N)2(C5H5N2O2)(CH3OH)]CH3OH0.5H2O (2), and thyminate( 1-) and ethanol, namely (OC-6-42)-ethanol(5-methyl-2,4-dioxo- 1,2,3,4-tetrahydropyrimidin-1-ido-N1)bis[2-(pyridin-2-yl)phenyl-2N,C1]rhodium( III), [Rh(C11H8N)2(C5H5N2O2)(C2H5OH)]C2H5OH (3), are reported. The acetonitrile complex, 1, is isostructural with the IrIII analog. In complexes 2 and 3, the monodeprotonated thyminate (Hthym-) ligand coordinates to the RhIII atom through the N atom, and the resulting Rh-N(Hthym) bond lengths are relatively long [2.261 (2) and 2.252 (2) A ° for 2 and 3, respectively] as compared to the Rh-N bonds in the related thyminate complexes. In each of the crystals of 2 and 3, the complexes are linked via a pair of intermolecular N- H O hydrogen bonds between neighbouring Hthym- ligands, forming an inversion dimer. A strong intramolecular O-H O hydrogen bond between the thyminate(1-) and alcohol ligands in mutually cis positions to each other is also observed.

DOI： 10.1107/S2056989016004837

Circularly Polarized Luminescence of Chiral Pt(pppb)Cl (pppbH=1-pyridyl-3-(4,5-pinenopyridyl)benzene) Aggregate in the Excited State

Saori Tanaka, Kyohei Sato, Kyoko Ichida, Taichi Abe, Taro Tsubomura, Takayoshi Suzuki, Kazuteru Shinozaki

CHEMISTRY-AN ASIAN JOURNAL 11 ( 2 ) 265 - 273 2016.1

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

We prepared enantiomers of chiral Pt-II complexes, Pt(pppb)Cl and Pt(pppb)CN (pppbH=1-pyridyl-3-(4,5-pinenopyridyl)benzene), and measured their CPL (circularly polarized luminescence) spectra for excimer and trimer emission. The contribution of the pinene moiety to CPL was considerably low for the -* emission of the monomer but large for MMLCT (metal-metal-to-ligand charge-transfer) of the excimer and trimer which had a helical structure induced in a face-to-face stacking fashion. The trimer CPL for (+)-Pt(pppb)Cl was larger in intensity than that of excimer CPL; on the other hand, that for (+)-Pt(pppb)CN was opposite in sign compared with that of excimer CPL. We conclude that differences in the excited-state structure of the aggregate between Pt(pppb)Cl and Pt(pppb)CN account for the variation in the CPL spectra. By the aid of TD-DFT calculations it was predicted that the dihedral angle (Cl-Pt-Pt-Cl) was 50-60 degrees or 110-140 degrees for Pt(pppb)Cl aggregates and 160 degrees for Pt(pppb)CN aggregates.

DOI： 10.1002/asia.201500985

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