Nickel-Dithiolene Ion-Pair Compounds Showing Thermotropic Liquid Crystal Behaviors and Alkyl Chain Length Dependent Electrochemical Properties

Nine ion-pair compounds [C_n-Apy]₂[Ni(mnt)₂] (C_n-Apy⁺ = 1-alkyl-4-aminopyridinium, n = 2-10, corresponding to compounds 1-9; mnt^2- = maleonitriledithiolate) were synthesized and characterized structurally. The hydrocarbon chain in the countercation adopts all trans-plane conformation when n < 7; otherwise, it adopts the mixed trans and gauche conformation. 1, 2, 8, and 9 show the layered packing structure of alternating anions and cations, whereas 3-6 display the mixed stacking structure of anions (A) and cations (C) in a … ACCA … manner. 3–9 exhibit the thermotropic liquid crystal behaviors. The redox couple of [Ni(mnt)₂]⁻/[Ni(mnt)₂]^2- in the solid state depend on the hydrocarbon chain length in the cation.[Supplemental materials are available for this article. Go to the publisher’s online edition of Soft Materials to view the free supplemental file.]