Cation effect on structural and physical properties of purely one-dimensional electronic system [D](CPDT-TCNQ)(2) [D=Cation]

Structural and physical properties of purely one-dimensional (along the c-a xis) electronic system [D](CPDT-TCNQ)(2) were investigated. We synthesized isostructural anion radical salts using cyclic cations in order to reveal t he general concept for the cation displacement effect in the purely one-dim ensional system. At low temperature, we observed several types of satellite reflections in the X-ray diffraction measurement. The wave vectors are q = (1/2,1/2, 1/2) or (1/2,0,1/2) in the salts with the orientational order of the cation and q = (0,0,1/2) in the salts with the orientational disorder of the cation at room temperature.