The combination of the redox-active mesogenic anion [Ni (Bdt)(BdtSQ)] (Bdt=1,2-benzenedithiolato; BdtSQ=1,2-dithia-semi-benzoquinonato) with alkyl-substituted ammonium cations afforded a series of redox-active ionic complexes of the type [NR ][Ni (Bdt)(BdtSQ)] [R=nC H (NC16 Ni) and C8,10 (NC8,10 Ni); C8,10=6-octylhexadecyl] or [NMe R ][Ni (Bdt)(BdtSQ)] [R=nC H (NMe C16 Ni) and C8,10 (NMe C8,10 Ni)]. X-ray crystallographic analyses of NMe C16 Ni and NC16 Ni revealed the formation of cation-dependent integrated ionic layers separated by interdigittated alkyl chains. Complexes NMe C16 Ni and NC16 Ni commonly form crystalline phases at room temperature, whereas complexes NMe C8,10 Ni and NC8,10 Ni, which contain branched alkyl chains, form a metastable mesophase and an amorphous phase at the same temperature, respectively. Furthermore, complexes NMe C16 Ni, NMe C8,10 Ni, and NC16 Ni commonly form a smectic A phase (SmA) at 375, 317, and 342 K, respectively. For the four complexes, well-defined cyclic voltammetry responses, derived from ligand-based oxidation and reduction, were observed in solution and the condensed phases, that is, upon casting these complexes on an indium-doped tin oxide working electrode. The present study demonstrates the tunability of the mesomorphism of ionic molecular assemblies composed of alkyl-substituted quaternary ammonium cations, while maintaining the well-defined redox responses of the anions even in the condensed phases.
