Anion Symmetry and the Separability of Structural Parameters for Tetramethyltetraselenafulvalenium Salts, (TMTSF)2X

Empirical correlations of various structural parameters for a series of (TMTSF)₂X salts have been explored utilizing a van der Waals-like estimate for the radius of the counterion X. Included amongst the parameters studied are: (a) the lengths of the transverse cell constants c and b; (b) the interdonor Se .. Se contact distances; (c) the alternate separation between molecular centers of mass along the columnar stack of donors (a); and (d) the symmetry and strength of the anion coupling to its donor-dominated structural cavity. The notable result is that independent correlations are found for salts containing centrosymmetric and non-centrosymmetric anions.