Abstract
Quasi-One and quasi-two dimensional organic conductors consisting of TTF derivatives such as BEDT-TTF (bis-(ethylene-dithio)-tetra-thia-fulvalene) and TMTCF (C = S; TMTTF: tetra-methyl-tetra-thia-fulvalene, C = Se; TMTSF: tetra-methyl-tetra-selena-fulvalene) have been well investigated in condensed matter physics because of interest in the emerging electric and magnetic properties, such as the spin density wave, charge order, superconductivity, anti-ferromagnetism, and so on. To probe the electronic state, nuclear magnetic resonance (NMR) is one of the most powerful tools as the microscopic magnetometer. A number of 13C-NMR studies have been performed of the double-site central 13C=13C bond substituted molecules. However, problems with the coupled spin system of 13C=13C complicated the interpretation for observations on NMR. Therefore, single-site 13C-enriched molecules are desired. We summarize the problem of Pake doublet and the preparation of the single-site 13C-susbstituted BEDT-TTF and TMTCF molecules. We also demonstrate the superiority of 13C-NMR of the single-site 13C-susbstituted molecule utilizing the hyperfine coupling tensor.
Highlights
Organic conductors consisting of molecular donor and inorganic anion have been the subject of intense interest because of their low dimensionality, magnetism, and superconductivity [1,2,3,4]
Among them, (TMTCF)2X (C = S; TMTTF: tetra-methyl-tetra-thia-fulvalene, C = Se; TMTSF: tetra-methyl-tetra-selena-fulvalene) salts are known as quasi-one dimensional organic conductors, and, (BEDT-TTF)2X (BEDT-TTF: bis-(ethylene-dithio)-tetra-thia-fulvalene) salts are known as quasi-two dimensional organic conductors, where X− is a monovalent inorganic anion
We first summarize the problem of Pake doublet, we present the synthesis methods of single-site 13C-substituted molecules which avoid the Pake doublet problem, and demonstrate the superiority of 13C-nuclear magnetic resonance (NMR) of these molecular crystals
Summary
Organic conductors consisting of molecular donor and inorganic anion have been the subject of intense interest because of their low dimensionality, magnetism, and superconductivity [1,2,3,4]. Κ-(BEDT-TTF)2Cu(NCS) and κ-(BEDT-TTF)2Cu[N(CN)2]Br show superconductivity below 10.4 K and 11.6 K and κ-(BEDT-TTF)2[N(CN)2]Cl shows antiferromagnetic order below 27 K [15,16] These electronic properties in κ-(BEDT-TTF)2X are described in the phase diagram predicted by Kanoda et al, in which the physical properties can be controlled by temperature, physical pressure, and chemical substitution parameters. Κ-(BEDT-TTF)2X were performed from the viewpoint of the strongly-correlated electron system [17,18,19,20,21] Salt with another packing arrangement, α-(BEDT-TTF)2X and θ-(BEDT-TTF)2X, has been a topic of interest due to the metal-insulator (MI) transition and charge disproportionation by off-site coulomb interaction [22,23,24,25,26,27,28,29]. We first summarize the problem of Pake doublet, we present the synthesis methods of single-site 13C-substituted molecules which avoid the Pake doublet problem, and demonstrate the superiority of 13C-NMR of these molecular crystals
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