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

Isostructural anion radical salts Me4X(CPDT-TCNQ)(2)(X=N,P,As) have one-dim ensional electronic structure, and show several type of metal-insulator tra nsitions depending on X. The result of the polarized reflectance spectra sh ows that the compounds are probably purely one-dimensional electronic syste m. The results of X-ray photographs and crystal structure analyses indicate that the origins of the transitions are 4k(F) CDW accompanying a cation or dering in the Me4As, Me4P salts and by 2k(F) CDW in the Me4N salt.