Coupling between molecular chains and anions in (TMTTF)2X salts

Upon cooling the (TMTTF)₂X salts undergo transitions to various ordered states in the charge and spin degrees of freedom; these different ground states depend on the anions X. It turns out that the anions are not simple spacers between the TMTTF stacks, but their symmetry and size play an important role as well as the dipole moment and polarizability. Here we discuss the coupling between TMTTF-molecules and anions with different symmetries.