Determination of the hyperfine coupling tensor in organic conductors κ-(BEDT-TTF)2X (X=Cu[N(CN)2]Br, Cu(NCS)2) on central 13C sites

•Hyperfine coupling tensors of the most famous organic conductors are determined.•The tensor is highly dependent on the crystal structure and dimer arrangement.•The Korringa factors of κ-Br and NCS salts are determined quantitatively.

Although the organic superconductors κ-(BEDT-TTF)2X (X=Cu[N(CN)2]Br and Cu(NCS)2) have been studied by NMR spectroscopy, hyperfine coupling tensors are required to quantify NMR spectra. Angle dependences of NMR spectra were measured to determine hyperfine coupling tensors applicable to further NMR assessments of attractive physical phenomena on κ-salts. The tensors of κ-(BEDT-TTF)2X and β′-(BEDT-TTF)2ICl2 salts were compared to determine the hyperfine coupling mechanism in organic metals, with the results indicating that off-site dimer contribution should be considered. We also report the electron correlation of these salts and further application of the tensors.

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