Hideki Yamochi

Japan Science and Technology Agency (JST), Edo, Tōkyō, Japan

Are you Hideki Yamochi?

Claim your profile

Publications (290)768.38 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The existence of a spin-disordered quantum state was predicted theoretically by Wannier in 1950 and Anderson in 1973. Various target materials had been considered before the discovery in 2003 of the first quantum spin liquid (QSL) system: a Mott insulator κ-(ET)2Cu2(CN)3, where ET is bis(ethylenedithio)tetrathiafulvalene. The family of dimer-type ET conductors κ-(ET)2X (where X = an anion) exhibits various conduction profiles ranging from insulators to metals to superconductors depending on the counter anion. In κ-(ET)2X, the anion molecules form characteristic patterns of anion openings, on each of which an ET dimer corresponding to a single spin site is positioned, namely a key-keyhole relation. The topological consideration of the crystal structure affords the information on both a spin geometry (t’/t) and electron correlation (U/W), where t and t’ are interdimer transfer interactions with an isosceles triangular geometry, and U and W are the on-site Coulomb repulsion energy and bandwidth, respectively. The QSL system κ-(ET)2Cu2(CN)3 is characterized by a spin lattice containing nearly equilateral triangles (t’/t = 1.09) with strong electron correlations (U/W = 0.93) at room temperature. The temperature dependences of t’/t and U/W are bases to understand the transport and magnetic behaviors of κ-(ET)2X. κ-(ET)2Cu2(CN)3 has a superconducting state next to the QSL state under pressure without passing through an antiferromagnetic state. Here, the design of QSL systems next to a superconducting state is discussed based on the crystal and the electronic structures and physical properties of κ-(ET)2X using the key-keyhole relation and temperature variant band parameters t, t’, U, and W.
    J. Mater. Chem. C. 12/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Radical anion salts of metal-containing and metal-free phthalocyanines [MPc(3−)].−, where M=CuII, NiII, H2, SnII, PbII, TiIVO, and VIVO (1–10) with tetraalkylammonium cations have been obtained as single crystals by phthalocyanine reduction with sodium fluorenone ketyl. Their formation is accompanied by the Pc ligand reduction and affects the molecular structure of metal phthalocyanine radical anions as well as their optical and magnetic properties. Radical anions are characterized by the alternation of short and long CNimine bonds in the Pc ligand owing to the disruption of its aromaticity. Salts 1–10 show new bands at 833–1041 nm in the NIR range, whereas the Q- and Soret bands are blue-shifted by 0.13–0.25 eV (38-92 nm) and 0.04–0.07 eV (4–13 nm), respectively. Radical anions with NiII, SnII, PbII, and TiIVO have S=1/2 spin state, whereas [CuIIPc(3−)].− and [VIVOPc(3−)].− containing paramagnetic CuII and VIVO have two S=1/2 spins per radical anion. Central metal atoms strongly affect EPR spectra of phthalocyanine radical anions. Instead of narrow EPR signals characteristic of metal-free phthalocyanine radical anions [H2Pc(3−)].− (linewidth of 0.08–0.24 mT), broad EPR signals are manifested (linewidth of 2–70 mT) with g-factors and linewidths that are strongly temperature-dependent. Salt 11 containing the [NaIPc(2−)]− anions as well as previously studied [FeIPc(2−)]− and [CoIPc(2−)]− anions that are formed without reduction of the Pc ligand do not show changes in molecular structure or optical and magnetic properties characteristic of [MPc(3−)].− in 1–10.
    Chemistry - A European Journal 11/2014; · 5.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Coordination nickel-bridged fullerene polymer [{Ni(Me3P)2}(μ-η(2),η(2)-C60)]∞ (1) has been obtained via reduction of a Ni(II)(Me3P)2Cl2 and C60 mixture. Each nickel atom is linked in the polymer with two fullerene units by η(2)-type Ni-C(C60) bonds of 2.087(8)-2.149(8) Å length. Nickel atoms are coordinated to the 6-6 bonds of C60 as well as two trimethylphosphine ligands to form a four-coordinated environment around the metal centers. Fullerene cages approach very close to each other in the polymer with a 9.693(3) Å interfullerene center-to-center distance, and two short interfullerene C-C contacts of 2.923(7) Å length are formed. Polymer chains are densely packed in a crystal with interfullerene center-to-center distances between fullerenes from neighboring polymer chains of 9.933(3) Å and multiple interfullerene C···C contacts. As a result, three-dimensional dense fullerene packing is formed in 1. According to optical and electron paramagnetic resonance spectra, fullerenes are neutral in 1 and nickel atoms have a zerovalent state with a diamagnetic d(10) electron configuration. The density functional theory calculations prove the diamagnetic state of the polymer with a singlet-triplet gap wider than 1.37 eV.
    Inorganic Chemistry 11/2014; 53:11960-11965. · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A compound containing fullerene dimers bonded through two nickel atoms, {Ni(Ph3P)}2(μ2-η(2),η(2)-C60)2·2C6H4Cl2 (), has been obtained as single crystals. The fullerenes are neutral in , showing a zero-valent state of Ni. The nickel atoms are bonded in an η(2) coordination mode with Ni-C distances of 2.001(3)-2.037(3) Å and a close approach of the fullerenes with a 9.716 Å center-to-center distance. The DFT calculations showed a diamagnetic singlet ground state for this dimer.
    Dalton transactions (Cambridge, England : 2003). 10/2014;
  • Ken Onda, Hideki Yamochi, Shin-Ya Koshihara
    [Show abstract] [Hide abstract]
    ABSTRACT: Conspectus Phenomena that occur in nonequilibrium states created by photoexcitation differ qualitatively from those that occur at thermal equilibrium, and various physical theories developed for thermal equilibrium states can hardly be applied to such phenomena. Recently it has been realized that understanding phenomena in nonequilibrium states in solids is important for photoenergy usage and ultrafast computing. Consequently, much effort has been devoted to revealing such phenomena by developing various ultrafast observation techniques and theories applicable to nonequilibrium states. This Account describes our recent studies of diverse photoinduced dynamics in a strongly correlated organic solid using various ultrafast techniques. Solids in which the electronic behavior is affected by Coulomb interactions between electrons are designated as strongly correlated materials and are known to exhibit unique physical properties even at thermal equilibrium. Among them, many organic charge-transfer (CT) complexes have low dimensionality and flexibility in addition to strong correlations; thus, their physical properties change sensitively in response to changes in pressure or electric field. Photoexcitation is also expected to drastically change their physical properties and would be useful for ultrafast photoswitching devices. However, in nonequilibrium states, the complicated dynamics due to these characteristics prevents us from understanding and using these materials for photonic devices. The CT complex (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene) exhibits unique photoinduced dynamics due to strong electron-electron and electron-phonon interactions. We have performed detailed studies of the dynamics of this complex using transient electronic spectroscopy at the 10 and 100 fs time scales. These studies include transient vibrational spectroscopy, which is sensitive to the charges and structures of constituent molecules, and transient electron diffraction, which provides direct information on the crystal structure. Photoexcitation of the charge-ordered low-temperature phase of (EDO-TTF)2PF6 creates a new photoinduced phase over 40 fs via the Franck-Condon state, in which electrons and vibrations are coherently and strongly coupled. This new photoinduced phase is assigned to an insulator-like state in which the charge order differs from that of the initial state. In the photoinduced phase, translations of component molecules proceed before the rearrangements of intramolecular conformations. Subsequently, the charge order and structure gradually approach those of the high-temperature phase over 100 ps. This unusual two-step photoinduced phase transition presumably originates from steric effects due to the bent EDO-TTF as well as strong electron-lattice interactions.
    Accounts of Chemical Research 10/2014; · 24.35 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The compound containing fullerene dimers bonded through two nickel atoms {Ni(Ph3P)}2(gapta2-eta2,eta2-C60)2∙2C6H4Cl2 (1) has been obtained as single crystals. Fullerenes are neutral in 1 showing zero-valent state of Ni. Nickel atoms are bonded with the gapta2 coordination with Ni-C distances of 2.001(3)-2.037(3) Å and close approach of fullerenes with 9.716 Å center-to-center distance. The DFT calculations showed diamagnetic singlet ground state for this dimer.
    Dalton Transactions 10/2014; 43:17920–17923. · 4.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: TTF derivatives decorated with four aryls through the sulfur bridges are employed to form the donor-acceptor type inclusion complexes with fullerenes. The key factor for the formation of inclusion complexes is the introduction of structural flexibility in TTF molecules along with the molecular size matching with fullerene. Crystallographic study indicates that the structures of the resulting complexes are stabilized by multidimensional intermolecular interaction network consisting of TTF cores, peripheral aryls, and fullerenes, which in turn gives rise to the electronic communication between the donor and acceptor as proved by the solid state absorption spectra. Moreover, the fullerene molecules form the two-dimensional sheet structure in the complexes.
    J. Mater. Chem. C. 07/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two salts containing fullerene C60 and indium(iii) bromide phthalocyanine (Pc) radical anions have been obtained as single crystals: (TBA(+))3(C60˙(-)){In(III)(Br)(Pc)˙(-)}(Br(-))·C6H4Cl2 (1) and (TEA(+))2(C60˙(-)){In(III)(Br)(Pc)˙(-)}·C6H4Cl2·C6H14 (2) where TBA(+) and TEA(+) are tetrabutyl- and tetraethylammonium cations, respectively. The presence of both radical anions is supported by spectra of and in the NIR and IR-ranges. The salts contain zigzag C60˙(-) chains with 10.136 and 10.383 Å center-to-center (ctc) distances in and a uniform ctc distance of 10.186 Å in . In 1, the C60˙(-) radical anions are dimerized in the 180-140 K range to form singly bonded (C60(-))2 dimers, whereas they remain monomeric in 2. Effective packing of planar In(Br)(Pc)˙(-) and spherical C60˙(-) is attained by introducing fullerene spheres between the phenylene substituents of Pc allowing the formation of multiple van der Waals contacts between them. The effective magnetic moment of at 300 K is 2.35μB, indicating a contribution of both C60˙(-) and In(Br)(Pc)˙(-) species having S = 1/2 spin state. There is strong antiferromagnetic coupling of spins between fullerenes in the chains and fullerenes and phthalocyanines in the monomeric phase of 1 with the Weiss temperature of -120 K in the 300-180 K range. The formation of diamagnetic (C60(-))2 dimers switches off magnetic coupling and magnetically isolates In(Br)(Pc)˙(-) (Weiss temperature is only -1 K in the 140-10 K range). Magnetic behavior of 2 is described by the Curie-Weiss law with weak ferromagnetic coupling of spins with Θ = +7.6 K in the 50-300 K range. Both salts manifest single Lorentzian EPR lines at room temperature with g = 1.9911 and a linewidth (ΔH) of 25.4 mT (1) and g = 1.9956 and ΔH = 7.5 mT (2) which can be attributed to both C60˙(-) and In(Br)(Pc)˙(-) species having strong exchange interaction. An asymmetric signal with the main component at g = 1.989-1.965 in the dimeric phase of 1 was attributed to the In(Br)(Pc)˙(-) radical anions.
    Dalton Transactions 07/2014; 43:13061-13069. · 4.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Fullerene salt {(Ph3P)3Au(+)}2(C60(•-))2(C60)·C6H4Cl2 (1) containing (Ph3P)3Au(+) cations with the C3v symmetry has been obtained as single crystals. Hexagonal corrugated fullerene layers formed in 1 alternate with the layers consisting of (Ph3P)3Au(+) and C6H4Cl2 along the c axis. According to IR spectra and peculiarities of the crystal structure, the charge on fullerenes in the layers is evaluated to be -1 for two and close to zero for one C60. These fullerenes have different cationic surroundings, and positively charged gold atoms approach closer to C60(•-). Charged and neutral fullerenes are closely packed within hexagonal layers with an interfullerene center-to-center distance of 10.02 Å and multiple short van der Waals C···C contacts. The distances between C60(•-) are essentially longer with an interfullerene center-to-center distance of 10.37 Å due to corrugation of the layers, and no van der Waals contacts are formed in this case. As a result, each C60(•-) has only three negatively charged fullerene neighbors with rather long interfullerene distances providing only weak antiferromagnetic interaction of spins in the fullerene layers with a Weiss temperature of -5 K.
    Inorganic Chemistry 06/2014; 53:6850−6855. · 4.79 Impact Factor
  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: (MDABCO+)(C60.−)(TPC) (1), in which MDABCO+ is N-methyldiazabicyclooctanium, TPC is triptycene, and both have threefold symmetry, is a rare example of a fullerene-based quasi-2D metal and contains closely packed hexagonal fullerene layers with interfullerene center-to-center distances of 10.07 Å at 300 K. Evidence for the metallic nature of 1 was obtained by optical and microwave conductivity measurements on single crystals. The metal is characterized by a nontypical Drude response and relatively large optical mass (m*/m0=6.7). The latter indicates a narrow-band nature, which is consistent with the calculated bandwidth of 0.10–0.15 eV. The coexistence of metallic and antiferromagnetic nonmetallic 2D layers was observed in 1 above 200–230 K. It was assumed that the nonmetallic layers undergo a transition to the metallic state below 200 K due to ordering of the fullerene and cationic sublattices. New layered complex (MQ+)(C60.−)(TPC) (2) with a hexagonal arrangement of C60.− was obtained by increasing the interfullerene distance with the bulkier N-methylquinuclidinium cations (MQ+) having threefold symmetry. The structure of 2 is characterized by increased interfullerene center-to-center distances in the layers (10.124, 10.155, and 10.177 Å at 250 K). Unit-cell doubling parallel to the 2D layer (along the b axis) was observed at low temperatures. In contrast to metallic 1, 2 exhibits a nonmetallic spin-frustrated state with an antiferromagnetic interaction of spins (the Weiss temperature is −27 K) and no magnetic ordering down to 1.9 K. It was supposed that the expanded interfullerene distances in the triangular arrangement decrease the bandwidth and suppress metallic conductivity in 2, and thus a Mott–Hubbard insulating state with antiferromagnetically frustrated spins results.
    Chemistry - A European Journal 05/2014; 20:7268–7277. · 5.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Iron hexadecachlorophthalocyanine (Cl16Pc) salts with a layered arrangement of phthalocyanine (Pc) macrocycles were obtained by the reduction of FeCl16Pc with sodium fluorenone ketyl in the presence of PPNCl [PPN+: bis(triphenylphosphine)iminium cation] and TBABr (TBA+: tetrabutylammonium cation). (PPN+)[{Fe(I)Cl16Pc}–]·0.78C6H4Cl2·0.22C6H14 (1) contains π–π stacking columns formed by dimerized {Fe(I)Cl16Pc}– anions. The side-by-side arrangement of neighboring columns results in the formation of a layered iron hexadecachlorophthalocyanine structure. (TBA+)3{[(FeCl16Pc)2]3–} (2) contains hexagonal layers formed by [(FeCl16Pc)2]3– dimers and separated by TBA+ cations. The dimers bear –3 charge and, according to optical and X-ray diffraction data, consist of a [Fe(I)(Cl16Pc)]– monoanion and a [Fe(0)(Cl16Pc)]2– dianion. These anions are bonded in the dimer by a Fe–Fe bond of 2.899(4) Å length. It was shown that the negative charge in both anions is localized on the iron atoms to form Fe(I) and Fe(0), respectively, and no electron transfer to the hexadecachlorophthalocyanine macrocycles is observed. Magnetic data indicate the presence of only one S = 1/2 spin per [(FeCl16Pc)2]3– dimer. This result is in agreement with the formation of iron(I) and iron(0) hexadecachlorophthalocyanine anions, which have the iron atoms in d7 and diamagnetic d8 electron configuration, respectively. The spins of the iron(I) atoms are arranged in a hexagonal manner and only weakly interact, which results in a Weiss temperature of –1 K because of the long distances between them (>18 Å). Previously studied anionic salts with a columnar arrangement of [Fe(I)(Cl16Pc)]– do not show EPR signals from FeI. In contrast, salt 2 shows an intense EPR signal with main components at g(per) = 2.249 and g∥ = 1.989, which are characteristic of Fe(I) with d7 electron configuration.
    Berichte der deutschen chemischen Gesellschaft 05/2014; · 2.97 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new salt, (MDABCO+)(C60.−) (1; MDABCO+=N-methyldiazabicyclooctanium cation), was obtained as single crystals. The crystal structure of 1 determined at 250 and 100 K showed 3D close packing of fullerenes with eight fullerene neighbors for each C60.−. These neighbors are located at 10.01–10.11 Å center-to-center distances (250 K) and van der Waals interfullerene C⋅⋅⋅C contacts are formed with four fullerene neighbors arranged in the bc plane. Fullerene ordering observed below 160 K is accompanied by the appearance of one and a half independent C60.− and trebling of the unit cell along the b axis. Fullerenes are packed closer to each other at 100 K. As a result, fullerenes are located in the three-dimensional packing at 9.91–10.12 Å center-to-center distances and 18 short interfullerene C⋅⋅⋅C contacts are formed for each C60.−. Although they are closed packed, fullerenes are not dimerized down to 1.9 K. Magnetic data indicate strong antiferromagnetic coupling of spins in the 70–300 K range with a Weiss temperature of Θ=−118 K. Magnetic susceptibility shows a round maximum at 46 K. Such behavior can be described well by the Heisenberg model for square two-dimensional antiferromagnetic coupling of spins with an exchange interaction of J/kB=−25.3 K. This magnetic coupling is one of the strongest observed for C60.− salts.
    Chemistry - An Asian Journal 04/2014; 9:1629-1635. · 4.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Compounds of the formula (EDO-TTF-Cl)2XF6 (EDO-TTF-Cl = 4-chloro-4′,5′-ethylenedioxytetrathiafulvalene, X = As, Sb) were prepared to examine the substituent size effect on the packing structure of the donor molecules. In these salts, a head-to-tail type donor stacking was observed. Although the AsF6 salt is a quasi-one-dimensional dimer Mott insulator, the SbF6 salt shows quasi-one-dimensional metallic behavior. Detailed crystal structure analyses revealed the correlation between the anion size and the intermolecular slipping among the donor molecules. The donor morphology, which plays an important role in the overlapping mode selectivity, is characterized by the magnitude and configuration of the out-of-plane substituent size.
    Berichte der deutschen chemischen Gesellschaft 04/2014; · 2.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The photoinduced phase formation in a strongly correlated crystal (EDO-TTF)2PF6 (EDO-TTF: 4,5-ethylenedioxytetrathiafulvalene) is investigated using a 12 fs laser pulse. The formation time is determined as 40 fs with observation of coherence of electron-phonon coupled excited states prior to formation. The temperature-independent dephasing time is determined as ̃22 fs up to 180 K and the frequency of phonon oscillation is ̃38 THz, corresponding to the intramolecular vibrations in EDO-TTF. The phase formation is coherently controlled by relative-phase-controlled two-pulse excitation.
    Physical Review B 03/2014; 89(16). · 3.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we obtained the first cation radical solid of a highly symmetric (D6h) polyaromatic hydrocarbon, coronene, by electrooxidation. The (coronene)3Mo6Cl14 salt, which is formed with an Oh-symmetric molybdenum cluster unit Mo6Cl142–, has an isotropic cubic structure with Pmm symmetry. The presence of two orientations for the coronene molecules related by an in-plane 90° rotation (merohedral disorder) allows for fourfold symmetry along the <100> direction. The disorder has dynamic features because 2H NMR spectroscopic studies revealed that the coronene molecules undergo an in-plane flipping motion. The observation of two motional sites with significantly different rotational rates (300 Hz and 5 MHz at 103 K) in an approximate 2:1 ratio appears to be consistent with the splitting of a Raman-active A1g mode, confirming a random charge-disproportionated state instead of a uniform partially-charged state. The slower- and faster-rotating species are assigned to charge-rich and charge-poor coronenes, respectively, with respect to C–H···Cl hydrogen bonds with neighboring Mo6Cl142– cluster units. The electrical conductivity of the salt is rather high but is well-described by a three-dimensional (3D) variable-range hopping mechanism, which is possibly associated with the random charge disproportionation. These results provide a significant step forward in developing an isotropic 3D π-conducting system composed of planar π-conjugated molecules.
    Berichte der deutschen chemischen Gesellschaft 03/2014; · 2.97 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two mononuclear coordination complexes of fullerene C60 with cobalt, Co(η(2)-C60)(dppe)(C6H5CN)·C6H4Cl2 (1) and Co(η(2)-C60)(dppf)(C6H5CN)·C6H4Cl2 (2) (dppe is 1,2-bis(diphenylphosphino)ethane and dppf is 1,1'-bis(diphenylphosphino)ferrocene) have been obtained by sodium fluorenone reduction of the Co(dppe)Cl2 or Co(dppf)Br2 and C60 mixtures. The IR and visible-NIR spectra of 1 and 2 indicate the neutral state of fullerenes. Therefore, cobalt atoms formally have the zerovalent state. Cobalt coordinates to the 6-6 bond of C60 by η(2)-type coordination with Co-C bond lengths in the 2.008(3)-2.060(3) Å range. Diphosphine and benzonitrile ligands additionally coordinate to cobalt to form a distorted square-pyramidal environment for the cobalt atoms. Complexes 1 and 2 are rare examples of fullerene coordination complexes with paramagnetic metal centers. Both complexes manifest intense asymmetric EPR signals attributed to zerovalent cobalt atoms, which can be fitted by three components with g = 2.261-2.124 (1) and g = 2.258-2.092 (2). Effective magnetic moments of 1 and 2 indicate the low-spin (S = 1/2) state of Co(0). In accordance with EPR spectra, DFT calculations show that the spin density is localized mainly on the central cobalt atoms and only slightly delocalized into C60, benzonitrile, dppe, or dppf ligands.
    Inorganic Chemistry 11/2013; · 4.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ionic compounds containing iron(I) hexadecachlorophthalocyanine anions have been obtained for the first time as single crystals: (PPN+){[Fe(I)Cl16Pc-(−2)]−} (1), (Ph3MeP+)2{[Fe(I)Cl16Pc(−2)]−}(Br−)·C6H4Cl2 (2), and (PPN+)2[Fe-(I, II)Cl16Pc(−2)]3(2−)·4C6H4Cl2 (3), where PPN+ is the cation of bis- (triphenylphosphoranylidene)ammonium and Ph3MeP+ is the triphenylmethylphosphonium cation. The [Fe(I)Cl16Pc(−2)]− anions form closely packed π−π stacking columns in 1−3. Salts 1 and 2 with integer −1 charge on iron phthalocyanines have uniform and weakly dimerized columns, respectively. Salt 3 has two cations per three iron phthalocyanine molecules which are arranged in trimers within the columns. Different shift of phthalocyanines at the same interplanar distances of 3.33−3.38 Å provides essentially shorter Fe···Fe distances in 3 (3.62−3.84 Å) than those in 1 and 2 (5.07−5.45 Å). Calculations show a strong LUMO−LUMO overlapping between [Fe(I)Cl16Pc(−2)]− in 1−3 with the overlap integrals of 4.1−7.6 × 10−3. Weak signals attributed to the [Fe(II)Cl16Pc(−3)]− species with the delocalization of electron on the phthalocyanine macrocycles are observed in the EPR spectra of 1−3. The content of this admixture is less than 1% in all salts. Nevertheless, static magnetic susceptibility measurements for 3 detected significant magnetization. The effective magnetic moment is 4.05 μB per formula unit at 300 K. It can originate from the spins localized on the iron atoms of [Fe(I)Cl16Pc(−2)]−. The Weiss temperature of −53 K in the 60−300 K range indicates a strong antiferromagnetic interaction of spins which results in the decreases of magnetic moment of 3 with temperature below 220 K down to 2.72 μB at 6 K. Optical spectra of 1−3 show bands ascribed to [Fe(I)Cl16Pc(−2)]− at 339−349, 538−548, 685−691, and 805−821 nm. The bands in the NIR range at 1740−1810 nm were attributed to charge transfer excitations within phthalocyanine columns associated with the unpaired electrons on the iron atoms.
    Crystal Growth & Design 11/2013; 13:4930−4939. · 4.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new salt, (PPN(+) )2 (C70 (2-) )⋅2 C6 H4 Cl2 (1), which contains C70 (2-) dianions, has been obtained as single crystals (PPN(+) =bis(triphenylphosphine)iminium cation). The C70 (2-) dianions form polymeric zigzag (C70 (2-) )n chains, in which the fullerene units are bonded through single CC bonds of length 1.581(5)-1.586(6) Å. The distance between the centers of neighboring C70 (2-) units is 10.441 Å. The optical and magnetic properties of (C70 (2-) )n have also been studied. Decreasing the symmetry of C70 in the polymer activate about 20 new IR bands in addition to the 10 IR-active bands of the starting C70 . The polymeric structure shows absorptions in the visible and NIR regions, with three main bands at 890, 1200, and 1550 nm, instead of one band of isolated C70 (2-) dianions at 1165-1184 nm. We concluded that the (C70 (2-) )n polymer was diamagnetic, with a negative molar magnetic susceptibility of -3.82×10(-4) emu mol(-1) per C70 (2-) dianion. The polymer is EPR silent and a weak narrow EPR signal in salt 1 is due to impurities, which only constitute 0.84 % of spin S=1/2 of the total amount of fullerene C70 .
    Chemistry - An Asian Journal 08/2013; · 4.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Protonated species of the nucleobase cytosine (C), namely the monoprotonated CH(+) and the hemiprotonated CHC(+) , were used to obtain four charge-transfer complexes of [Ni(dmit)2 ] (dmit: 1,3-dithiole-2-thione-4,5-dithiolate). Diffusion methods afforded two semiconducting [Ni(dmit)2 ](-) salts; (CH)[Ni(dmit)2 ](CH3 CN) (1) and (CHC)[Ni(dmit)2 ] (2). In salt 1, the [Ni(dmit)2 ](-) ions with a S=1/2 spin construct a uniform one-dimensional array along the molecular long axis, and the significant intermolecular interaction along the face-to-face direction results in a spin-singlet ground state. In contrast, salt 2 exhibits the Mott insulating behavior associated with uniform 1D arrays of [Ni(dmit)2 ](-) , which assemble a two-dimensional layer that is sandwiched between the layers of hydrogen-bonded CHC(+) ribbons. Multiple hydrogen bonds between CHC(+) and [Ni(dmit)2 ](-) seem to result in the absence of structural phase transition down to 0.5 K. Electrooxidation of [Ni(dmit)2 ](-) afforded the polymorphs of the [Ni(dmit)2 ](0.5-) salts, (CHC(+) )[{Ni(dmit)2 }(0.5-) ]2 (3 and 4), which are the first mixed-valence salts of nucleobase cations with metal complex anions. Similar to 2, salt 3 contains CHC(+) ribbons that are sandwiched between the 2D [Ni(dmit)2 ](0.5-) layers. In the layer, the [Ni(dmit)2 ](0.5-) ions form dimers with a S=1/2 spin and the narrow electronic bandwidth causes a semiconducting behavior. In salt 4, the CHC(+) units form an unprecedented corrugated 2D sheet, which is sandwiched between the 2D [Ni(dmit)2 ](0.5-) layers that involve ring-over-atom and spanning overlaps. In contrast to 3, salt 4 exhibits metallic behavior down to 1.8 K, associated with a wide bandwidth and a 2D Fermi surface. The ability of hydrogen-bonded CHC(+) sheets as a template for the anion radical arrangements is demonstrated.
    Chemistry - A European Journal 07/2013; · 5.93 Impact Factor

Publication Stats

2k Citations
768.38 Total Impact Points

Institutions

  • 2014
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan
  • 1991–2014
    • Kyoto University
      • Division of Chemistry
      Kioto, Kyōto, Japan
    • University of California, Santa Barbara
      Santa Barbara, California, United States
  • 2013
    • Russian Academy of Sciences
      • Institute of the Problems of Chemical Physics
      Moskva, Moscow, Russia
    • Meijo University
      • Faculty of Agriculture
      Nagoya-shi, Aichi-ken, Japan
  • 1986–2010
    • Osaka University
      • • Department of Macromolecular Science
      • • Department of Chemistry
      • • Institute for Protein Research
      Suika, Ōsaka, Japan
  • 2005
    • Tokyo Institute of Technology
      • Department of Materials Science and Engineering
      Tokyo, Tokyo-to, Japan
  • 1994
    • Tokyo University of Science
      • Department of Applied Physics
      Edo, Tōkyō, Japan
  • 1988–1991
    • The University of Tokyo
      • Institute for Solid State Physics
      Tokyo, Tokyo-to, Japan
    • Tohoku University
      Japan
  • 1987–1988
    • Nagoya University
      • Department of Chemistry
      Nagoya-shi, Aichi-ken, Japan