Thermochromic Magnetic Ionic Liquids from Cationic Nickel(II) Complexes Exhibiting Intramolecular Coordination Equilibrium.
Among the various thermochromic materials, liquid thermochromic materials are comparatively rare. To produce functional thermochromic liquids, we have designed ionic liquids based on cationic nickel complexes with ether side chains, [Ni(acac)(Me2NC2H4NR1R2)]Tf2N ([1]Tf2N: R1=C3H6OEt, R2=Me; [2]Tf2N: R1=C3H6OMe, R2=Me; [3]Tf2N: R1=R2=C3H6OMe), where acac=acetylacetonate and Tf2N=(F3CSO2)2N-. The side chains (R1, R2) can moderately coordinate to the metal center, enabling temperature-dependent coordination equilibria in the liquid state. [1]Tf2N is a liquid at room temperature. [2]Tf2N is obtained as a solid (Tm=352.7 K) but remains liquid at room temperature after melting. [3]Tf2N is a solid with a high melting point (Tm=422.3 K). These salts display thermochromism in the liquid state, appearing red at high temperatures and orange, light-blue, or bluish-green at lower temperatures, and exhibiting concomitant changes in their magnetic properties. This phenomenon is based on temperature-dependent equilibrium between a square-planar diamagnetic species and a paramagnetic species with intramolecular ether coordination.
Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Kobe, Hyogo, 657-8501, Japan.
Xue
X
Lan
Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Kobe, Hyogo, 657-8501, Japan.
Tomoyuki
http://orcid.org/0000-0002-3446-2145
T
Mochida
Department of Applied Chemistry, Faculty of Engineering, Tokyo University of Science, Yamaguchi, Sanyo-Onoda, Yamaguchi , 756-0884, Japan.
Yusuke
Y
Funasako
Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Kobe, Hyogo, 657-8501, Japan.
Kazuyuki
K
Takahashi
Center for Supports to Research and Education Activities, Kobe University, Kobe, Hyogo, 657-8501, Japan.
Takahiro
T
Sakurai
Department of Physics, Graduate School of Science, Kobe University, Kobe, Hyogo, 657-8501, Japan.|Molecular Photoscience Research Center, Kobe University, Kobe, Hyogo, 657-8501, Japan.
Hitoshi
H
Ohta
chelates; ionic liquids; magnetic properties; thermal properties; thermochromism