Time scale of electronic and molecular motions in the conducting radical cation salt diperylene hexafluorophosphate

Frequency and temperature dependence of nuclear spin lattice relaxation is used for the derivation of motional time scales in the quasi-one-dimensional conductor diperylene hexafluorophosphate (incorporating tetrahydrofurane (THF) solvent molecules). Freezing in of reorientational motion of the THF molecules at the stack-rotation phase transition Tr ≈ 153 K is proved by the use of perdeuterated solvent. Slowing down of hexafluorophosphate rotational motion is reflected by 19F and 1H relaxation in the 100 K range. The time constant describing termination of the diffusive decay of the conduction-electron spin correlation is estimated from frequency-dependent proton spin relaxation including rotating-frame data.