Decamethyl- and octamethyl-ferrocenium salts of F1- and F2-TCNQ: Effects of fluorine substitution on the crystal structures and magnetic interactions

Decamethyl- and octamethyl-ferrocenium salts of FnTCNQ (n = 1, 2) were prepared and their crystal structures characterized. The 2,5-F2TCNQ salts [Fe(C5Me5)2](2,5-F2TCNQ) (1) and [Fe(C5Me4H)2](2,5-F2TCNQ) (2) exhibit one-dimensional …[D]+[A]−[D]+[A]−… mixed-stack structures, while the salts with polar acceptors [Fe(C5Me5)2][A] (A = F1TCNQ (3), 2,3-F2TCNQ (4), 2,6-F2TCNQ (5)) and [Fe(C5Me4H)2][A] (A = 2,3-F2TCNQ (6), 2,6-F2TCNQ (7)) consist of [D]+[A2]2−[D]+ units involving a diamagnetic dimer of the acceptors. These salts are isomorphous to the corresponding TCNQ salts. 1 and 2 exhibit small ferromagnetic interactions at low temperatures. 1 undergoes an antiferromagnetic phase transition at TN = 3.9 K, which is higher than TN = 2.1 K of the metamagnetic polymorph of [Fe(C5Me5)2](TCNQ).