Researchers Database

Horii Yoji

    Faculty Division of Natural Sciences Research Group of Chemistry Assistant Professor
Last Updated :2021/07/07


Research Areas

  • Natural sciences, Bio-, chemical, and soft-matter physics

Published Papers

  • Cocrystals of Li+ encapsulated fullerenes and Tb(iii) double-decker single molecule magnet in a quasi-kagome lattice.

    Hikaru Iwami; Junfei Xing; Ryo Nakanishi; Yoji Horii; Keiichi Katoh; Brian K Breedlove; Kazuhiko Kawachi; Yasuhiko Kasama; Eunsang Kwon; Masahiro Yamashita

    Cocrystallization of a lithium ion encapsulated fullerene Li+@C60 with a terbium(iii) phthalocyaninato porphyrinato double-decker single-molecule magnet [Tb(Pc)(OEP)] is reported. The cocrystal, containing PF6- as a counter anion, packs in a quasi-kagome lattice, which leads to intermolecular ferromagnetic interactions as well as the modulation of the single-molecule magnet (SMM) properties., 28 Oct. 2020, Chemical communications (Cambridge, England), 56 (84), 12785 - 12788, True, doi;pubmed

    Scientific journal

  • Simultaneous Spin-Crossover Transition and Conductivity Switching in a Dinuclear Iron(II) Coordination Compound Based on 7,7 ',8,8 '-Tetracyano-p-quinodimethane

    Ishikawa Ryuta; Ueno Shuya; Nifuku Shoei; Horii Yoji; Iguchi Hiroaki; Miyazaki Yuji; Nakano Motohiro; Hayami Shinya; Kumagai Shohei; Katoh Keiichi; Li Zhao-Yang; Yamashita Masahiro; Kawata Satoshi

    10 Dec. 2019, CHEMISTRY-A EUROPEAN JOURNAL, doi;web_of_science

  • Detailed Analysis of the Crystal Structures and Magnetic Properties of a Dysprosium(III) Phthalocyaninato Sextuple-Decker Complex: Weak f-f Interactions Suppress Magnetic Relaxation

    Horii Yoji; Katoh Keiichi; Sugimoto Kunihisa; Nakanishi Ryo; Breedlove Brian K; Yamashita Masahiro

    26 Feb. 2019, CHEMISTRY-A EUROPEAN JOURNAL, 25 (12), 3098 - 3104, doi;web_of_science

  • Versatile coordination architectures of products generated by the in situ reaction of a doubly bis(2-pyridyl)pyrazolate bridged dinuclear copper(ii) complex with tetracyanoethylene

    Ryuta Ishikawa; Shunya Ueno; Yumi Hamatake; Yoji Horii; Yuji Miyazaki; Motohiro Nakano; Takeshi Noda; Mikoto Uematsu; Satoshi Kawata

    Reaction of doubly bpypz bridged Cu(ii) dinuclear complex and TCNE gave three versatile coordination assemblies with TCNE solvolysis derivatives, depending on reaction solvents.

    , Royal Society of Chemistry (RSC), 2019, CrystEngComm, 21 (12), 1886 - 1894, doi;web_of_science;url

    Scientific journal

  • Supramolecular Approach for Enhancing Single-Molecule Magnet Properties of Terbium(III)-Phthalocyaninato Double-Decker Complexes with Crown Moieties

    Yoji Horii; Shuhei Kishiue; Marko Damjanović; Keiichi Katoh; Brian K. Breedlove; Markus Enders; Masahiro Yamashita

    A TbIII-phthalocyaninato double-decker ([1]0) single-molecule magnet (SMM) having four 15-crown-5 moieties in one of the ligands was synthesized, and its dimerization and magnetic properties were studied in an attempt to utilize the supramolecular aggregation for enhancing the SMM properties. Aggregation of [1]0 to form [12K4]4+ in the presence of K+ ions was studied by using UV/Vis-NIR absorption and NMR spectroscopies. For the magnetic measurements, [1]0 and [12K4]4+ were dispersed in poly(methyl methacrylate) (PMMA). UV/Vis-NIR absorption measurements on the PMMA dispersed samples were used to track the formation of [12K4]4+. Direct current (DC) magnetic susceptibility measurements revealed that there were ferromagnetic Tb–Tb interactions in [12K4]4+, whereas there was no indication of ferromagnetic interactions in [1]0. Upon the formation of [12K4]4+ from [1]0 and K+ ions, the temperature at which the magnetic hysteresis occurred increased from 7 to 15 K. In addition, the area of magnetic hysteresis became larger for [12K4]4+, meaning that SMM properties of [12K4]4+ are superior to those of [1]0. Alternating current (AC) magnetic measurements were used to confirm this observation. Magnetic relaxation times at 2 K increased 1000-fold upon dimerization of [1]0 to [12K4]4+, demonstrating the effectiveness of using K+ ions to induce dimer formation for the improvement of the SMM properties., Wiley-VCH Verlag, 20 Mar. 2018, Chemistry - A European Journal, 24 (17), 4320 - 4327, doi;web_of_science

    Scientific journal

  • Changing Single-Molecule Magnet Properties of a Windmill-Like Distorted Terbium(III) α-Butoxy-Substituted Phthalocyaninato Double-Decker Complex by Protonation/Deprotonation

    Yoji Horii; Yusuke Horie; Keiichi Katoh; Brian K. Breedlove; Masahiro Yamashita

    Synthesis, structures, and magnetic properties of α-butoxy-substituted phthalocyaninato double-decker complexes Tb(α-obPc)2 (1-) (α-obPc: dianion of 1,4,8,11,15,18,22,25-octa(n-butoxy)phthalocyaninato) with protonated (1H), deprotonated (1[HDBU]), and diprotonated forms (1H2+) are discussed. X-ray analysis was used to confirm the position of the proton in 1H, and it was revealed that the protonation induced asymmetric distortion in 1H. In contrast, 1[HDBU] was distorted in a highly symmetric windmill-like fashion. 1H is arranged in a slipped column array in the crystal packing, whereas 1[HDBU] is arranged in a one-dimensional fashion, in which the magnetic easy axes of 1[HDBU] lie along the same line. From direct-current (dc) magnetic measurements, ferromagnetic Tb-Tb interactions occur in both 1H and 1[HDBU], and magnetic hysteresis was observed. However, the area of the magnetic hysteresis in 1[HDBU] is larger than that in 1H, meaning that magnetic relaxation time (τ) is longer in 1[HDBU]. In addition, the results of alternating-current magnetic measurements in a zero dc magnetic field indicate that τ of 1[HDBU] is longer as compared to 1H. In other words, protonation/deprotonation affects not only the molecular structures and crystal packing but also the single-molecule magnet properties., American Chemical Society, 16 Jan. 2018, Inorganic Chemistry, 57 (2), 565 - 574, doi;web_of_science

    Scientific journal

  • Elongation of magnetic relaxation times in a single-molecule magnet through intermetallic interactions: a clamshell-type dinuclear terbium(III)-phthalocynaninato quadruple-decker complex

    Yoji Horii; Keiichi Katoh; Brian K. Breedlove; Masahiro Yamashita

    A clamshell-type terbium(III)-phthalocyaninato quadruple-decker complex was synthesized. Magnetic measurements revealed that Tb-Tb interactions caused an increase in the magnetic relaxation time and enhanced the SMM properties., ROYAL SOC CHEMISTRY, Aug. 2017, CHEMICAL COMMUNICATIONS, 53 (61), 8561 - 8564, doi;web_of_science

    Scientific journal

  • Metal-Organic Framework of Lanthanoid Dinuclear Clusters Undergoes Slow Magnetic Relaxation

    Hikaru Iwami; Ryo Nakanishi; Yoji Horii; Keiichi Katoh; Brian K. Breedlove; Masahiro Yamashita

    Lanthanoid metal-organic frameworks (Ln-MOFs) can adopt a variety of new structures due to the large coordination numbers of Ln metal ions, and Ln-MOFs are expected to show new luminescence and magnetic properties due to the localized f electrons. In particular, some Ln metal ions, such as Dy(III) and Tb(III) ions, work as isolated quantum magnets when they have magnetic anisotropy. In this work, using 4,4 0,4 ''-s-triazine-2,4,6-triyl-tribenzoic acid (H(3)TATB) as a ligand, two new Ln-MOFs, [Dy(TATB)(DMF)(2)] (1) and [Tb(TATB)(DMF)(2)] (2), were obtained. The Ln-MOFs contain Ln dinuclear clusters as secondary building units, and 1 underwent slow magnetic relaxation similar to single-molecule magnets., MDPI AG, Jan. 2017, MATERIALS, 10 (1), doi;web_of_science

    Scientific journal

  • How Ions Arrange in Solution: Detailed Insight from NMR Spectroscopy of Paramagnetic Ion Pairs

    Marko Damjanovic; Takaumi Morita; Yoji Horii; Keiichi Katoh; Masahiro Yamashita; Markus Enders

    Ion pairing between the paramagnetic anion [Tb(obPc)(2)](-) (obPc=2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato), which has a very large magnetic anisotropy, with various diamagnetic counterions [P(Ph)(4)](+) (1a), [As(Ph)(4)](+) (1b), bis(triphenylphosphine) iminium ([PPN](+), 1c) and tetra-n-butylammonium ([TBA](+), 1d) was studied by means of H-1, C-13, N-14, and P-31 NMR spectroscopy in solution at various temperatures. The influence of the paramagnetic anion on the NMR spectroscopy properties of the diamagnetic cations allowed a detailed insight into the distances and relative orientations of the paired ions. Isotropic tumbling models for the description of the quaternary cations are inaccurate, particularly for [TBA](+) with its flexible butyl chains. The effects of temperature and concentration were also assessed. The advantage of this technique is that relatively large distances and the orientation between molecules or ions in solution can be studied., WILEY-V C H VERLAG GMBH, Nov. 2016, CHEMPHYSCHEM, 17 (21), 3423 - 3429, doi;web_of_science

    Scientific journal

  • Weak Dy-III-Dy-III Interactions in Dy-III-Phthalocyaninato Multiple-Decker Single-Molecule Magnets Effectively Suppress Magnetic Relaxation

    Yoji Horii; Keiichi Katoh; Goulven Cosquer; Brian K. Breedlove; Masahiro Yamashita

    The Dy-III quintuple-decker complex DyCdCdDy and hetero quadruple-decker complex DyCdY were synthesized, and their magnetic properties were compared with those of the quadruple decker complex DyCdDy. Single-crystal X-ray analysis revealed that the coordination geometries around the Dy-III ions of DyCdCdDy, DyCdY, and DyCdDy were similar. dc (direct current) magnetic measurements indicated that DyCdCdDy had very weak ferromagnetic Dy-III-Dy-III interactions but DyCdY did not. From a comparison of the magnetic relaxation times (tau) of the three complexes, the tau values of DyCdCdDy and DyCdDy, which have weak Dy-III-Dy-III interactions, are longer than that of DyCdY. In other words, weak Dy-III-Dy-III interactions effectively suppress magnetic relaxation., AMER CHEMICAL SOC, Nov. 2016, INORGANIC CHEMISTRY, 55 (22), 11782 - 11790, doi;web_of_science

    Scientific journal

  • Field-Induced Single-Ion Magnetism Based on Spin-Phonon Relaxation in a Distorted Octahedral High-Spin Cobalt(II) Complex

    Ryuta Ishikawa; Yoji Horii; Ryo Nakanishi; Shunya Ueno; Brian K. Breedlove; Masahiro Yamashita; Satoshi Kawata

    The six-coordinate mononuclear high-spin cobalt(II) complex [Co(bpy)(2)(ClAn)]EtOH (1; bpy = 2,2-bipyridine, ClAn(2-) = chloranilate) and its magnetically diluted analogue [Co0.1Zn0.9(bpy)(2)(ClAn)]EtOH (3), in which the Co-II centres of 1 are partially diluted with the magnetically inactive Zn-II centres of [Zn(bpy)(2)(ClAn)]EtOH (2) as a diamagnetic matrix, exhibited slow magnetic relaxation in applied direct-current (DC) magnetic fields. Fits of the DC magnetic data indicate that this new field-induced single-ion magnet possesses large positive axial and significant rhombic zero-field splittings. The results of temperature-dependent and DC-magnetic-field-dependent alternating-current magnetic measurements on 1 and 3, which is a field-induced single-ion magnet, agree with those from theoretical studies, and spin relaxation occurs through two-phonon Raman and direct spin-phonon bottleneck processes of Kramers ions., WILEY-V C H VERLAG GMBH, Jul. 2016, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, (20), 3233 - 3239, doi;web_of_science

    Scientific journal

  • alpha-Substituted Bis(octabutoxyphthalocyaninato)Terbium(III) Double-Decker Complexes: Preparation and Study of Protonation by NMR and DFT

    Marko Damjanovic; Yusuke Horie; Takaumi Morita; Yoji Horii; Keiichi Katoh; Masahiro Yamashita; Markus Enders

    Synthesis of the anionic, alpha-substituted, bis(phthalocyaninato)Tb-III complex [Tb(alpha-obPc)(2)](-) ([1](-)) (obPc = alpha-octabutoxyphthalocyaninato) leads to the isolation of its protonated form [1H](0). This complex was characterized by X-ray diffraction (XRD), mass spectroscopy (MS), infrared (IR) and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy. Crystal structure analysis did not allow localization of the additional proton, which is probably attached to the meso-N atom or isoindole-N atom of the phthalocyaninato ligand. [1H](0) can easily be deprotonated or protonated, giving the corresponding anionic and cationic complexes. The three compounds [1H](0), [1](-), and [1HH](+) were studied by a combination of paramagnetic NMR experiments (H-1, C-13, variable-temperature measurements, two-dimensional nuclear magnetic resonance and DFT calculations (done on Y-III analogues with octamethoxyphthalocyaninato ligands), for the purpose of elucidating the positions of the acidic protons and for understanding the structural changes of the coordination environment of the Tb ion induced by protonation., AMER CHEMICAL SOC, Dec. 2015, INORGANIC CHEMISTRY, 54 (24), 11986 - 11992, doi;web_of_science

    Scientific journal

  • Effects of f-f Interactions on the Single-Molecule Magnet Properties of Terbium(III)-Phthalocyaninato Quintuple-Decker Complexes

    Yoji Horii; Keiichi Katoh; Nobuhiro Yasuda; Brian K. Breedlove; Masahiro Yamashita

    Single-molecule magnet (SMM) properties of terbium(III)-phthalocyaninato quintuple-decker complex TbCdCdTb were studied and were compared with those of other multiple-decker complexes (triple-decker: TbTb, quadruple-decker: TbCdTb) to elucidate the relationship between magnetic dipole interactions and SMM properties. From X-ray crystallography performed with synchrotron radiation, the Tb-III-Tb-III distance in TbCdCdTb was determined to be 9.883 angstrom. From alternating current magnetic studies on TbCdCdTb, the activation energy for spin reversal (Delta) increased with an increase in the direct current magnetic field (H-dc). This behavior is similar to that of TbCdTb, although the increase in Delta for TbCdTb is smaller. On the other hand, for TbTb, which has shortest Tb-III-Tb-III distance, Delta did not depend on H-dc, indicating that there is a correlation between SMM properties and the strength of the Tb-III-Tb-III interactions. By comparing the Zeeman diagrams for multiple-decker complexes, we found that the Tb-III-Tb-III interactions affected the magnetic field regions where quantum tunnelling of the magnetization was active. The results obtained from Zeeman diagrams are consistent with the results obtained from the magnetic studies., AMER CHEMICAL SOC, Apr. 2015, INORGANIC CHEMISTRY, 54 (7), 3297 - 3305, doi;web_of_science

    Scientific journal

  • Effect of f-f interactions on quantum tunnelling of the magnetization: mono- and dinuclear Dy(III) phthalocyaninato triple-decker single-molecule magnets with the same octacoordination environment

    Keiichi Katoh; Rina Asano; Akira Miura; Yoji Horii; Takaumi Morita; Brian K. Breedlove; Masahiro Yamashita

    The single-molecule magnet (SMM) behaviour of dinuclear Ln(III)-Pc triple-decker complexes (Dy(III)-Y(III): 1 and Dy(III)-Dy(III): 2) with the same octacoordination environment and slow magnetic relaxation behaviour were explained using X-ray crystallography and static and dynamic susceptibility measurements. In particular, interactions among the 4f electrons of dinuclear Dy(III)-Pc triple-decker type SMMs have never been discussed on the basis of the same octacoordination environment. Our results clearly show that the Dy(III) ion sites of 1 and 2 are equivalent, consistent with the crystal structure. 2 Exhibited ferromagnetic interaction between Dy(III) ions. This is clear evidence that the magnetic relaxation mechanism depends heavily on the dipole-dipole (f-f) interactions between the Dy(III) ions in the dinuclear systems. For both 1 and 2, quantum tunnelling of the magnetization (QTM) was observed. However, the magnetic relaxation time (tau) for 2 was one order of magnitude greater than that for 1, and single-component magnetic relaxation behaviour was explained. In other words, it is possible to use f-f interactions to increase tau by one order of magnitude., ROYAL SOC CHEMISTRY, 2014, DALTON TRANSACTIONS, 43 (21), 7716 - 7725, doi;web_of_science

    Scientific journal

  • Multiple-decker phthalocyaninato dinuclear lanthanoid(III) single-molecule magnets with dual-magnetic relaxation processes

    Keiichi Katoh; Yoji Horii; Nobuhiro Yasuda; Wolfgang Wernsdorfer; Koshiro Toriumi; Brian K. Breedlove; Masahiro Yamashita

    The SMM behaviour of dinuclear Ln(III)-Pc multiple-decker complexes (Ln = Tb3+ and Dy3+) with energy barriers and slow-relaxation behaviour were explained by using X-ray crystallography and static and dynamic susceptibility measurements. In particular, interactions among the 4f electrons of several dinuclear Ln(III)-Pc type SMMs have never been discussed on the basis of the crystal structure. For dinuclear Tb(III)-Pc complexes, a dual magnetic relaxation process was observed. The relaxation processes are due to the anisotropic centres. Our results clearly show that the two Tb3+ ion sites are equivalent and are consistent with the crystal structure. On the other hand, the mononuclear Tb(III)-Pc complex exhibited only a single magnetic relaxation process. This is clear evidence that the magnetic relaxation mechanism depends heavily on the dipole-dipole (f-f) interactions between the Tb3+ ions in the dinuclear systems. Furthermore, the SMM behaviour of dinuclear Dy(III)-Pc type SMMs with smaller energy barriers compared with that of Tb(III)-Pc and slow-relaxation behaviour was explained. Dinuclear Dy(III)-Pc SMMs exhibited single-component magnetic relaxation behaviour. The results indicate that the magnetic relaxation properties of dinuclear Ln(III)-Pc multiple-decker complexes are affected by the local molecular symmetry and are extremely sensitive to tiny distortions in the coordination geometry. In other words, the spatial arrangement of the Ln(3+) ions (f-f interactions) in the crystal is important. Our work shows that the SMM properties can be fine-tuned by introducing weak intermolecular magnetic interactions in a controlled SMM spatial arrangement., ROYAL SOC CHEMISTRY, 2012, DALTON TRANSACTIONS, 41 (44), 13582 - 13600, doi;web_of_science

    Scientific journal

  • Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple-Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy.

    Yoji Horii; Marko Damjanović; M R Ajayakumar; Keiichi Katoh; Yasutaka Kitagawa; Liviu Chibotaru; Liviu Ungur; Marta Mas-Torrent; Wolfgang Wernsdorfer; Brian K Breedlove; Markus Enders; Jaume Veciana; Masahiro Yamashita

    Presented here is a comprehensive study of highly oxidized multiple-decker complexes composed of TbIII and CdII ions and two to five phthalocyaninato ligands, which are stabilized by electron-donating n-butoxy groups. From X-ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl-shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic 1 H NMR studies on the resulting series of triple, quadruple and quintuple-decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple-decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single-molecule magnet properties, which are controlled by the multi-step redox induced structural changes., 14 Jul. 2020, Chemistry (Weinheim an der Bergstrasse, Germany), 26 (39), 8621 - 8630, True, doi;pubmed;pmc

    Scientific journal

  • Coexistence of Spin-Lattice Relaxation and Phonon-Bottleneck Processes in GdIII -Phthlocyaninato Triple-Decker Complexes under Highly Diluted Conditions.

    Yoji Horii; Keiichi Katoh; Yuji Miyazaki; Marko Damjanović; Tetsu Sato; Liviu Ungur; Liviu F Chibotaru; Brian K Breedlove; Motohiro Nakano; Wolfgang Wernsdorfer; Masahiro Yamashita

    Gd3+ complexes have been shown to undergo unusual slow magnetic relaxation processes similar to those of single-molecule magnets (SMMs), even though Gd3+ does not exhibit strong magnetic anisotropy. To reveal the origin of the slow magnetic relaxation of Gd3+ complexes, we have investigated the magnetic properties and heat capacities of two Gd3+ -phthalocyaninato triple-decker complexes, one of which has intramolecular Gd3+ -Gd3+ interactions and the other does not. It was found that the Gd3+ -Gd3+ interactions accelerate the magnetic relaxation processes. In addition, magnetically diluted samples, prepared by doping a small amount of the Gd3+ complexes into a large amount of diamagnetic Y3+ complexes, underwent dual magnetic relaxation processes. A detailed dynamic magnetic analysis revealed that the coexistence of spin-lattice relaxation and phonon-bottleneck processes is the origin of the dual magnetic relaxation processes., 26 Jun. 2020, Chemistry (Weinheim an der Bergstrasse, Germany), 26 (36), 8076 - 8082, True, doi;pubmed

    Scientific journal

  • Solid-State Spin Equilibrium of Ni(cyclam)2 Complex: Magnetostructural Correlations in Two Polymorphs.

    Yoji Horii; Yuki Kanegae; Kiyonori Takahashi; Akira Fuyuhiro; Mariko Noguchi; Hal Suzuki; Motohiro Nakano

    Two crystal polymorphs of Ni(cyclam)I2 (cyclam = 1,4,8,11-tetraazacyclotetradecane) were synthesized, and their magnetic properties were investigated. Temperature-dependent X-ray structural analysis and magnetic measurements revealed gradual spin transition in molecular-crystal polymorph trans-[Ni(cyclam)I2] (1a), whereas the zigzag-chain polymorph catena-[Ni(cyclam)(μ-I)]I (1b) did not show an obvious spin transition. The entropy difference between high- and low-spin states of 1a estimated by assuming the spin-equilibrium model is much smaller than those in typical iron(II)-based spin-crossover (SCO) complexes, suggesting that the normal mode softening is less remarkable in 1a. In this system, it is clearly evidenced that the interaction mode responsible to the spin equilibrium in octahedral nickel(II) complexes is highly anistropic, i.e., z-elongation and x,y-shortening of the coordination octahedron., 20 Apr. 2020, Inorganic chemistry, 59 (8), 5418 - 5423, True, doi;pubmed

    Scientific journal


  • Suppression of Quantum Tunneling Effect by Dimerization of Single-Molecule Magnets

    堀井洋司; 堀井洋司

    2020, 熱測定, 47 (3), j_global

  • 進化を続ける次世代型ナノ分子磁石-高温動作する単分子磁石を目指して!!

    堀井洋司; 加藤恵一; 山下正廣

    2014, 月刊化学, (1), 45 - 50

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