Locally resolved isotropic and anisotropicC13Knight shifts in the organic conductor (fluoranthenyl)

Abstract

C Knight-shift tensors including both the isotropic and anisotropic parts of the organic conductors (fluoranthenyl)&X with X = AsF6 or PF6 have been obtained by NMR experiments on powdered samples and on single crystals. It is found that the anisotropic part of the Knight shift yields a more direct access to the local p, spin-density distribution of the conduction-electron band than the isotropic part.

What does NMR tell us about the electronic state of high-T c superconductors?

“…Whereas the on-site hyperfine interaction tensor A is anisotropic, reflecting the symmetry of the dx2_y2-orbital , the transferred hyperfine interaction tensor Bis expected to be isotropic. I should remark that this is in accord with the so-called the Karplus-Fraenkel relation [43] in organic radicals and which has been extensively employed in organic solids [44]. Along these lines the hyperfine interaction Hamiltonian for the different nuclear sites in the unit cell can be expressed as:…”

Temperature dependent locally resolved 13C Knight shifts in the organic conductor TTF[Ni(dmit)2]2

“…To our knowledge, this is the first observation of such a different temperature behaviour of the local Knight shifts for the same molecule in an organic conductor. Temperature dependent Knight shifts have been reported for (TMTSF)2PF6 [15], (TMTSF)2Re04 [16] and (FA)2AsF6 [17]. In these cases, however, they decrease at low temperatures for all carbon sites of the cation radical.…”

1H-Overhauser Shift in Radical Cation Salts

“…The analysis will be explained in details for FA,PF6 where a precise crystal structure4 and local resolved spin densities are available. 20 We will further concentrate on a 11 B,, which simplifies the discussion. For a (1 B, all C-H bonds are perpendicular to the static field.…”