A key to understanding ionic mixed stacked organic solids: Tetrathiafulvalene-bromanil (TTF-BA)

An extensive series of structural, optical, vibrational and magnetic susceptibility measurements are reported for the charge transfer complex tetrathiafulvalene-bromanil (TTF-BA). The complex is shown to be an ionic mixed stack solid at all temperatures, with a phase transition around 50 K to a nonmagnetic state. The origin of this nonmagnetic state in other ionic charge transfer crystals has been the matter of considerable debate. In TTF-BA, it is shown to be associated with a distortion of the stacks. © 1985.