Ionic Liquids of Cationic Sandwich Complexes

Abstract

Simple cationic sandwich complexes that contained alkyl- or halogen substituents provided ionic liquids (ILs) with the bis(perfluoroalkanesulfonyl)imide anion. Ferrocenium- and cobaltocenium ILs [M(C(5)H(4)R(1))(C(5)H(4)R(2))][Tf(2)N] (M=Fe, Co) and arene-ferrocenium ILs [Fe(C(5)H(4)R(1))(C(6)H(5)R(2))][Tf(2)N] were prepared and their physical properties were investigated. A detailed comparison of their thermal properties revealed the effects of molecular symmetry and substituents on their melting points. Their viscosity increased on increasing the length of the substituent on the cation and the perfluoroalkyl chain length on the anion. Upon cooling, ILs with low viscosities exhibited crystallization, whereas those with higher viscosities tended to exhibit glass transitions. Most of these salts showed phase transitions in the solid state. A magnetic-switching phenomenon was observed for the paramagnetic ferrocenium IL, which was associated with a liquid/solid transformation, based on the magnetic anisotropy of the ferrocenium cation. (57)Fe Mössbauer spectroscopy was applied to [Fe(C(5)H(4)nBu)(2)][Tf(2)N] to investigate the vibrational behavior of the iron atom in the crystal and glassy states of the ferrocenium IL.

Synthesis and characterization of an electroactive ionic liquid based on the ferrocenylsulfonyl(trifluoromethylsulfonyl)imide anion

“…However, there are very few reports on electroactive ILs and there is a very narrow array of available structures and given that the design of a new RIL is hindered by a lack of knowledge of their structure-properties relationships [18][19][20][21][22][23][24]. In addition, the current library of RILs almost exclusively contains structures based on the modification of alkylimidazoliums, with some exceptions from reports on ferrocene-functionalized phosphonium IL [14,25] and metallocenium ILs [26,27]. Our group reported on the development of RIL as redox additive in electrolytes for lithium-ion batteries to protect the cathode against overcharging [28,29].…”

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

“…[8] However, little has been reported on the anion chain dependence of the thermal properties and structures of the ionic liquids with bis(perfluoroalkylsulfonyl)amide anions. [3a, 9, 10] Recently, we reported that alkyl metallocenium salts with bis(perfluoroalkylsulfonyl)amide anions become ionic liquids, [11] whereas the corresponding cobaltocenium salts are solids at room temperature.…”

Effects of substituent branching and chirality on the physical properties of ionic liquids based on cationic ruthenium sandwich complexes

“…For rac- [1][PF 6 ], the origin of the high T g /T m ratio is discussed in the following section. 17 6 ] exhibits a phase transition at 70.1 1C (DS = 18.8 J mol À1 K À1 ). Ionic liquids based on cationic sandwich complexes often undergo phase transitions in the solid state.…”

“…Therefore, the effects of molecular structure, such as the length of alkyl substituents, on the physical properties of ionic liquids have been extensively investigated. [17][18][19][20][21] We examine herein how substituent branching and chirality affect the thermal properties of organometallic ionic liquids. [4][5][6][7][8][9][10][11] Although most ionic liquids contain organic cations such as imidazolium cations, various metal-containing ionic liquids that exhibit intriguing functionalities have recently been developed.…”