Hydrogen-Bond-Dynamics-Based Switching of Conductivity and Magnetism: A Phase Transition Caused by Deuterium and Electron Transfer in a Hydrogen-Bonded Purely Organic Conductor Crystal

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• 作者：Akira Ueda ; Shota Yamada ; Takayuki Isono ; Hiromichi Kamo ; Akiko Nakao ; Reiji Kumai ; Hironori Nakao ; Youichi Murakami ; Kaoru Yamamoto ; Yutaka Nishio ; Hatsumi Mori
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：August 27, 2014
• 年：2014
• 卷：136
• 期：34
• 页码：12184-12192
• 全文大小：604K
• ISSN：1520-5126

文摘

A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, 魏-D₃(Cat-EDT-TTF)₂ (abbreviated as 魏-D). This novel crystal 魏-D, a deuterated analogue of 魏-H₃(Cat-EDT-TTF)₂ (abbreviated as 魏-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O路路路D路路路O]^鈭?-type strong H-bond. Although the deuterated and parent hydrogen systems, 魏-D and 魏-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only 魏-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1虆). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF 蟺-systems, proving that the H-bonded deuterium dynamics and the conducting TTF 蟺-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in 魏-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve.