| 研究領域 | π造形科学: 電子と構造のダイナミズム制御による新機能創出 |
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| 研究課題/領域番号 |
17H05139
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| 研究機関 | 大阪府立大学 |
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研究代表者 |
プラシデス コスマス 大阪府立大学, 工学(系)研究科(研究院), 教授 (90719006)
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| 研究期間 (年度) |
2017-04-01 – 2019-03-31
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| キーワード | Superconductivity / Spin liquids / Polyaromatic hydrocarbon / Quantum magnetism / Fullerenes / pi-electron systems |
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| 研究実績の概要 |
We succeeded in preparing reproducibly and structurally characterizing the first generation of phase-pure highly-crystalline metal-doped PAHs, which emerge as candidates of new exotic electronic states of matter, including three-dimensional quantum spin liquids arising purely from carbon pi-electrons for the first time. This was achieved by devising entirely new chemical approaches to produce for the first time intercalated PAHs with controlled oxidation states. The new synthetic routes allowed the isolation of unique materials, including the isolation of a S = 1/2 quantum spin-liquid state arising for the first time purely from pi-electrons. These results provide the seeds of new ideas to transform thinking about the scientific area of quantum magnetism in molecular systems and open a new branch of molecular science in the same way that, 10 years ago, the discovery of the Cs3C60 superconductor led to the renaissance of fullerene superconductivity.
Finally, we developed the synthesis of the first unsolvated alkali metal rubrene phase and reported its crystal structure. The crystal chemistry of the potassium rubrene phase contrasts with that of earlier structures in a way that can be directly related to the molecular structure of rubrene. The presence of the phenyl groups together with the linear tetracene core controls the interactions between the potassium cations and the hydrocarbon, taking the first step towards structure-composition relationships in this class of materials.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
Our project has been tremendously successful until now. In the last year we succeeded in preparing pure materials through the development of appropriate chemistries. The four reported solvent-free alkali metal PAH crystal structures are the only ones existent in the literature to date and give only a first glimpse of the rich chemical, structural and electronic diversity of these materials; they comprise four distinct anionic PAH species and three new packing motifs and harbour a S = 1/2 quantum spin-liquid arising purely from pi-electrons. This highlights the need for increased understanding of the complex synthetic chemistry of alkali metals with unsaturated hydrocarbons as the essential pre-requisite to defining the accessible physical properties in these phases.
However, in July 2018, we also successfully synthesized a new unexpected key member of the new family of pi-electron quantum magnets. Moreover, in the course of structural analysis we discovered that the synthesized sample crystallized with an unexpected new structure. This result is of extremely important significance for the future development of electronic functional materials based on pi-electron networks. As we have to further optimize the newly developed synthetic conditions to obtain high purity samples reproducibly so that the new structural motifs can be authenticated, we need to do additional synthesis, structural analysis, evaluation of physical properties, and data analysis and therefore our work will spill-over into the next year.
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| 今後の研究の推進方策 |
We are currently tackling more complex materials both synthetically and electronically. Emphasis is now placed towards tackling the new frontier of multi-component hybrid pi-figuration fullerene/polyaromatic hydrocarbon (PAH) molecular materials. C60 adopts an isotropic 3D crystal structure and co-crystallizes with planar pi-electron PAHs via favorable supramolecular pi-pi interactions. This synergy can be used to isolate crystalline co-adducts of C60 and PAHs with layered 2D structures. Condensed-matter systems that are both low-dimensional and strongly interacting exhibit unusual electronic properties distinct from those of their 3D analogues. The new chemistry will be applied to various PAH materials to discover new magnets and superconductors. The properties will be controlled by molecular size and shape (planar vs curved), frontier orbitals (degeneracy), and number of electrons transferred (doping level). We will combine high-symmetry molecular acceptors possessing high pi-orbital degeneracies. The triple C60 LUMO degeneracy is key ingredient responsible for the high Tc of fullerides. For example, combination of C60 with coronene acceptor which has a doubly-degenerate LUMO is an excellent candidate to produce new high-Tc molecular superconductors, surpassing our current record of 38 K, upon metal intercalation. Such hybrid pi-electron materials with complementary electronic structure are not possible in single-component solids.
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