Tuning the Mesomorphism and Redox Response of Anionic‐Ligand‐Based Mixed‐Valent Nickel(II) Complexes by Alkyl‐Substituted Quaternary Ammonium Cations

Abstract

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.

A Ditopic Phosphane‐decorated Benzenedithiol as Scaffold for Di‐ and Trinuclear Complexes of Group‐10 Metals and Gold

“…The cyclic voltammograms of all three complexes showed oxidation waves (at peak potentials between 0.5 to 0.8 V vs. Fc/Fc + , Figure S3, Supporting Information) but no complementary reduction events, presumably because the oxidation products were consumed by follow‐up processes. Even if attempts to identifying the reaction products by spectro‐electrochemistry gave no conclusive results, these observations rule out that a reversible dithiolene redox chemistry involving oxidation of the benzenedithiolato to dithiosemiquinone and dithioquinone units takes place.…”

“…In view of the known ability of benzodithiolene derivatives to act as redox active ligands, we were also interested in studying the electron transfer behavior of the complexes prepared by cyclic voltammetry. Meaningful results were obtained for 4 , the trinuclear palladium complex 7 and the dinuclear nickel complex 8 .…”

Electrochemically Induced Mesomorphism Switching in a Chlorpromazine Hydrochloride Lyotropic Liquid Crystal

“…One of the characteristics of conformational change occurring in concert with electron transfer is sluggish electrode kinetics, since this can affect the reorganization energy for the heterogeneous electron transfer, as seen for the reduction of cyclooctatetraene ,, and some of its derivatives and nitrogen analogues, , wherein a nonplanar, “tub”-shaped neutral molecule affords a planar anion radical. ,− A second, more important, feature is due to the fact that any intermediate state does not last more than a few vibrations so that the observation is that there is a complete absence of an intermediate, even at the fastest, nanosecond timescales (corresponding to a few million volts per second scan rates) that can be explored voltammetrically. , Complications in the following conformation change resulting from heterogeneous electron transfer include ion pairing and potential inversions for two-electron transfers . In this article, following reports of electron transfer-induced mesomorphism in thermotropic liquid crystals based on ferrocene derivatives, − and in nickel­(II)-based mesogenic systems, we investigate whether the mechanism of electrochemically trigged conformational change can change as a result of close-packing monomers within a self-assembled, redox-active, liquid nanosystem (viz., lyotropic liquid crystal) based on chlorpromazine hydrochloride.…”