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

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 i...

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Veröffentlicht in:Journal of the American Chemical Society 2014-08, Vol.136 (34), p.12184-12192
Hauptverfasser: Ueda, Akira, Yamada, Shota, Isono, Takayuki, Kamo, Hiromichi, Nakao, Akiko, Kumai, Reiji, Nakao, Hironori, Murakami, Youichi, Yamamoto, Kaoru, Nishio, Yutaka, Mori, Hatsumi
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Sprache:eng
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Zusammenfassung: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, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-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···D···O]−1-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1̅). 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 π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja507132m