東北大学 · 材料科学
和田坂正紀教授の研究室では、分子機能材料の設計と創出を柱とし、特に金属錯体や金属有機フレームワークを用いた新規機能性材料の開発を進めています。光誘導反応や低次元スピン・電子系の制御を核に、ナノスケールの金属酸化物・カーバイド、分子磁性体、および分子 heterostructure の構築を目指しています。特に、貴金属に依存しない触媒や、量子スピン特性を示す金属有機フレームワークの創出が、次世代エネルギー材料やスピントロニクスデバイスの基盤を提供する可能性を追求しています。
Figures are computed from collected data and may differ slightly.
Dehydrogenation of anhydrous methanol is of great importance, given its ubiquity as an intermediate for the production of a large number of industrial chemicals. Since dehydrogenation of methanol is an endothermic reaction, heterogeneous or homogeneous precious-metal-based catalysts and high temperatures are usually required for this reaction to proceed. Here we report the photochemical dehydrogenation of anhydrous methanol at room temperature catalysed by o-aminophenol (apH2), o-aminophenolate
The creation of low-dimensional heterostructures for intelligent devices is a challenging research topic; however, macro- and atomic-scale connections in one-dimensional (1D) electronic systems have not been achieved yet. Herein, we synthesize a heterostructure comprising a 1D Mott insulator [Ni(chxn)<sub>2</sub>Br]Br<sub>2</sub> (1; chxn = 1R-2R-diaminocyclohexane) and a 1D Peierls or charge-density-wave insulator [Pd(chxn)<sub>2</sub>Br]Br<sub>2</sub> (2) using stepwise electrochemical growth.
Halogen-bridged linear chain metal complexes (MX-Chains) are fascinating compounds that have a quasi-one-dimensional (1D) electronic system. In this study, we synthesized the first Ni-based MX-Chain compound having hydroxy groups, i.e., [Ni(dabdOH)<sub>2</sub>Br]Br<sub>2</sub>·[Ni(dabdOH<sub><i>x</i></sub>)<sub>2</sub>Br]<sub>0.5</sub>·(2-PrOH)<sub>0.25</sub>·(MeOH)<sub>0.25</sub> (<b>1</b>·solvent, <i>x</i> = ∼0.6, dabdOH = (2<i>S</i>,3<i>S</i>)-2,3-diaminobutane-1,4-diol). Single-crystal X-ray
Ultrasmall particles exhibit structures and/or properties that are different from those of the corresponding bulk materials; in this context especially ultrasmall precious-metal particles have been extensively investigated. In this study, we targeted the transition base-metal Mo and succeeded in systematically producing Mo oxycarbide/carbide particles with diameters of 1.7 ± 0.7, 1.4 ± 0.5, 1.3 ± 0.4, 1.2 ± 0.3, 1.0 ± 0.3, and 0.8 ± 0.2 nm on a carbon support using the carbothermal hydrogen redu
Abstract The combination of single‐ion magnets (SIMs) and metal–organic frameworks (MOFs) is expected to produce new quantum materials. The principal issue to be solved in this regard is the development of new strategies for the synthesis of SIM‐MOFs. This work demonstrates a new simple strategy for the synthesis of SIM‐MOFs where a diamagnetic MOF is used as the framework into which the SIM sites are doped. 1, 0.5, and 0.2 mol% of the Co(II) ions are doped into the Zn(II) sites of [CH 6 N 3 ][Z
With the aim of creating Cu(II) spin qubits in a rigid metal-organic framework (MOF), this work demonstrates a doping of 5 %, 2 %, 1 %, and 0.1 % mol of Cu(II) ions into a perovskite-type MOF [CH<sub>6</sub> N<sub>3</sub> ][Zn<sup>II</sup> (HCOO)<sub>3</sub> ]. The presence of dopant Cu(II) sites are confirmed with anisotropic g-factors (g<sub>x</sub> =2.07, g<sub>y</sub> =2.12, and g<sub>z</sub> =2.44) in the S=1/2 system by experimentally and theoretically. Magnetic dynamics indicate the occur
The controlled assembly of early transition metals remains a challenging research target, especially with respect to the generation of heterometallic molecules and nanomaterials. In this study, metal chlorides of the early 4d/5d-transition-metals, i.e., ZrCl<sub>4</sub>, NbCl<sub>5</sub>, MoCl<sub>5</sub>, HfCl<sub>4</sub>, TaCl<sub>5</sub>, and WCl<sub>6</sub>, were stoichiometrically introduced into a tetraphenylmethane-core dendritic-phenylazomethine generation 4 dendrimer in the presence of
Assembling conductive or magnetic heterostructures by bulk inorganic materials is important for making functional electronic or spintronic devices, such as semiconductive p-doped and n-doped silicon for P-N junction diodes, alternating ferromagnetic and nonmagnetic conductive layers used in giant magnetoresistance (GMR). Nonetheless, there have been few demonstrations of conductive or magnetic heterostructures made by discrete molecules. It is of fundamental interest to prepare and investigate h
Ohmic contacts are of critical importance to improve the performance of semiconductor devices as well as those of low-dimensional materials. Halogen-bridged metal complexes (MX-Chains) are fascinating quasi-one-dimensional (1D) electronic materials. However, reports on the electrical characteristics of MX-Chains remain elusive. Herein, we report the electrical characteristics of single crystals of [Ni(chxn)<sub>2</sub> Br]Br<sub>2</sub> (chxn: (1R,2R)-(-)-1,2-cyclohexanediamine), which is a 1D M
In the last decade, S = 1/2 systems of Cu(II) complexes and Cu(II) ions in the solid state have been found to exhibit slow magnetic relaxations. The mechanism driving this magnetic behavior is different from that of high spin single-molecule magnets and that of bulk/nanoparticle magnets. This behavior is related to spin qubits and is considered to be a new type of quantum magnetism. This review focuses on the magnetic relaxation (τ), spin-lattice relaxation (T1), and spin-spin relaxation (T2 or
Carbothermal hydrogen reduction (CHR) is a unique dry chemical process used to fabricate metals and carbides on carbon supports. In this study, a stepwise CHR of WCl<sub>6</sub> on a graphite support is demonstrated for the first time. Powder X-ray diffraction studies revealed that, at 773 K, metallic tungsten nanoparticles are produced, whereas, at 1073 K, the metastable W<sub>2</sub>C phase is generated rather than the thermodynamically stable WC phase. X-ray photoelectron spectroscopy and X-r
Abstract Bulk tungsten oxides exhibit a wide range of oxidation states, whereas the oxidation states available in molecular oxides such as polyoxometalates (POMs) is limited. In this paper, tungsten oxide clusters with diameters of 1.2±0.4 ( W 60 O x /C ), 1.1±0.4 ( W 28 O x /C ), and 0.9±0.3 nm ( W 12 O x /C ) were produced in a size‐selective manner on graphitic carbon by using a phenyl‐azomethine‐type dendrimer as a template and applying hydrogen reduction after fixing the dendrimers on a sup
Molybdenum oxycarbide clusters are novel nanomaterials that exhibit attractive catalytic activity; however, the methods for their production are currently very restrictive. This work represents a new strategy for the creation of near-subnanometer size molybdenum oxycarbide clusters on multilayer graphene. To adsorb Mo-based polyoxometalates of the type [PMo<sub>12</sub> O<sub>40</sub> ]<sup>3-</sup> as a precursor for Mo oxycarbide clusters, the novel tripodal-phenyl cation N,N,N-tri(4-phenylbut
Abstract Citric acid (citH 4 ) is a ubiquitous product in nature with an interesting chemistry owing to its three carboxy and one hydroxy groups, which can be deprotonated in a stepwise manner into six kinds of citrate anions involving two protonation isomers. Deprotonated citrates easily coordinate to late‐3d‐metal ions (Mn, Fe, Co, Ni, Cu, and Zn), affording complexes including mono‐, di‐, tri‐, tetra‐, hexa‐, hepta‐, octa‐, nona‐, and 21‐nuclear complexes with a variety of structures. Magneti
Abstract Multi-metallic inorganic alloy materials have attracted great attention recently. Additionally, molecule-based materials have wide designability in terms of their structures and electronic states. These are two different ideas. Here, we report the mixing of Pd(III) and Au(III) ions into a bromide-bridged molecular chain compound [Ni(chxn)2Br]Br2 (chxn: 1R,2R-diaminocyclohexane) to form an average formula of [Ni0.853Pd0.142Au0.005(chxn)2Br]Br2, which was synthesized by an electrochemical
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