Low temperature X-ray study of purely one-dimensional electronic system Me4X(CPDT-TCNQ)2(X=AS, N)

Isostructural anion radical salts Me2X(CPDT-TCNQ)2(X=N,P,As) have one-dimensional electronic structure, and show several type of metal-insulator transitions depending on X. The result of the polarized reflectance spectra shows that the compounds are probably purely one-dimensional electronic system. The results of X-ray photographs and crystal structure analyses indicate that the origins of the transitions are 4kF CDW accompanying a cation ordering in the Me2As, Me4P salts and by 2kF CDW in the Me4N salt.