Expanding the Electrochemical Window: New Tunable Aryl Alkyl Ionic Liquids (TAAILs) with Dicyanamide Anions

Abstract

As et of new tunable aryl alkyl ionic liquids (TAAILs) based on the 1-aryl-3-alkyli midazolium motif has been synthesized, in which the following variables were systematically changed:a lkyl chain length, aryl substitution (group and position), and counter ion. TAAILs with dicyanamide (DCA) and bis(trifluoromethylsulfonyl)imide (N(SO 2 CF 3 ) 2 ,N Tf 2 )a nions showed remarkable differences of their physical properties:N Tf 2 ionic liquidsw ere found to have high decomposition temperatures andv iscositiesw ell below those of the DCA TAAILs. In contrast, the dicyanamide anion increased the electrochemical stabilityl eadingt o TAAILs with an extremely wide electrochemical window of up to 7.17 V. Additionally,b oth classes of TAAILs extract transition metalsf rom aqueous solutions:T AAILs with the DCA anion extract both platinum andc opperw hile TAAILs with the NTf 2 anion are selective towards platinum. Thisd emonstratest hat minor changes of the molecular structure lead to TAAILs with drastically changed physicochemical properties.

Synthesis and Physical Properties of Tunable Aryl Alkyl Ionic Liquids (TAAILs)

“… [44] In order to increase the EWs of TAAILs, the use of the dicyanamide anion [45] has been proven to be beneficial. [28] …”

“… [23] In 2009, 1‐aryl‐3‐alkyl‐imidazolium based ILs which we named tunable aryl alkyl ionic liquids (TAAILs) were introduced by our group. [24] Since then, their application in transition metal catalysis,[ 25 , 26 ] metal extraction[ 27 , 28 ] and for the synthesis of metal nano particles has been reported. [29] This new structural motive allows for the modification not only of its anion and alkyl substitution of the cation, but also by the aryl substitution giving rise to additional ways of controlling the physical and chemical properties of an ionic liquid.…”

Tetrakis(pentafluoroethyl)gallate, [Ga(C2F5)4]−, Ionic Liquids

“…The viscosities of the substituted TAAILs depicted in Figure 4 are following the same pattern in terms of the alkyl chain length, however, they show higher viscosities at all. The 4-OMe substituted ILs (12)(13)(14) exhibits the highest viscosities between 162-91 cP followed by 2-Me (7-10) at 139-77 cP and 2,4-F (15-18) at 126-67 cP. Following the Vogel-Fulcher-Tammann equation, viscosities decrease exponentially at higher temperatures and reach less than 50 cP at 60°C.…”

“… [12] Recently, the effect of different anions in TAAILs was reported. The combination with a dicyanamide anion [N(CN) 2 ] − results in very wide electrochemical windows, [13] while TAAILs with palladate anions gave access to catalytically active ionic liquids. [14] Weakly coordinating anions are well suited for ionic liquids, since positive effects were achieved by reduced ion interactions.…”

Ionic liquid decoration for the hole transport improvement of PEDOT

“…S6 in ESI †), while it likely manifests a high degree of From a realistic perspective, the theoretically designed cation should be easily synthesized. As shown in Scheme 1, two synthetic pathways (a) and (b) are proposed where path (a) is accessible by a two-step synthesis starting from commercially available aniline derivates 63 and path (b) is completed via 4-bromoanisole based on the reported routines in ref. 64.…”