Organometallic Ionic Liquids Containing Sandwich Complexes: Molecular Design, Physical Properties, and Chemical Reactivities

Abstract

Ionic liquids (ILs) are salts with low melting points and are useful as electrolytes and solvents. We have developed ILs containing cationic metal complexes, which form a family of functional liquids that exhibit unique physical properties and chemical reactivities originating from metal complexes. Our study explores the liquid chemistry in the field of coordination chemistry, where solid‐state chemistry is currently the main focus. This review describes the molecular design, physical properties, and reactivities of organometallic ILs containing sandwich or half‐sandwich complexes. This paper mainly covers stimuli‐responsive ILs, whose magnetic properties, solvent polarities, colors, or structures change by the application of external fields, such as light, heat, and magnetic fields, or by reaction with coordinating molecules.

Controlling Ionic Conductivity in Organometallic Ionic Liquids through Light-Induced Coordination Polymer Formation and Thermal Reversion

“…In this context, we recently developed organometallic ILs possessing reversible light- and heat-modulated ionic conductivities to explore photocontrollable liquid electronic materials. − Employing ILs in device applications is advantageous, as they can be used in extremely small amounts as liquid films. Photoreactive IL 3-FSA (Figure a; FSA = (FSO 2 ) 2 N – ), containing a cationic Ru sandwich complex, undergoes cation photodissociation upon UV photoirradiation, and the reaction yields an amorphous coordination polymer where cyano groups bridge Ru ions, thereby reducing the ionic conductivity. , Heating reverses the photoproduct to its original IL, with the ionic conductivity exhibiting a reversible change.…”

Ionic liquids containing half-sandwich ruthenium complexes: in situ interconversions via photochemical and thermal ligand exchange

“…4–6 We have synthesized a variety of ILs containing cationic sandwich and half-sandwich complexes. 7,8 In particular, half-sandwich complexes are diverse in structure and reactivity, endowing ILs with various functionalities, such as catalytic activity, 9 ligand exchange, 10,11 and linkage isomerization, 12 though they are often irreversible. Development of reactive organometallic ILs leads to novel applications of organometallic compounds.…”