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Tuning the Mesomorphism and Redox Response of Anionic‐Ligand‐Based Mixed‐Valent Nickel(II) Complexes by Alkyl‐Substituted Quaternary Ammonium Cations
Author(s) -
Nakamura Yuichi,
Matsumoto Takeshi,
Sakazume Yasutaka,
Murata Junnosuke,
Chang HoChol
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201706006
Subject(s) - chemistry , alkyl , nickel , redox , ligand (biochemistry) , mesophase , cyclic voltammetry , ionic bonding , crystallography , mesogen , inorganic chemistry , phase (matter) , electrochemistry , ion , organic chemistry , electrode , liquid crystalline , biochemistry , receptor
The combination of the redox‐active mesogenic anion [Ni II (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 4 ][Ni II (Bdt)(BdtSQ)] [R= n C 16 H 33 (NC16 4 Ni) and C8,10 (NC8,10 4 Ni); C8,10=6‐octylhexadecyl] or [NMe 2 R 2 ][Ni II (Bdt)(BdtSQ)] [R= n C 16 H 33 (NMe 2 C16 2 Ni) and C8,10 (NMe 2 C8,10 2 Ni)]. X‐ray crystallographic analyses of NMe 2 C16 2 Ni and NC16 4 Ni revealed the formation of cation‐dependent integrated ionic layers separated by interdigittated alkyl chains. Complexes NMe 2 C16 2 Ni and NC16 4 Ni commonly form crystalline phases at room temperature, whereas complexes NMe 2 C8,10 2 Ni and NC8,10 4 Ni, which contain branched alkyl chains, form a metastable mesophase and an amorphous phase at the same temperature, respectively. Furthermore, complexes NMe 2 C16 2 Ni, NMe 2 C8,10 2 Ni, and NC16 4 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.