Synthesis of Oxygen‐Containing Spirobipyrrolidinium Salts for High Conductivity Room Temperature Ionic Liquids

Abstract

Synthesis of ionic liquids (IL) based on oxygen‐containing spirobipyrrolidinium salts with BF4, BF3C2F5, and NTf2 as counterions was undertaken. Their physical and electrochemical properties were evaluated for suitability for Room Temperature Ionic Liquids (RTIL) application. Reduction in melting point occurred upon exchange of C(2) by an O‐atom of spirobipyrrolidinium, without sacrificing the electrochemical stability; while introduction of alkyl groups between the N‐ and O‐atoms led to incorporation of asymmetry, and hence reduced the melting points, and viscosity.

Crystal structures and quantitative structure–property relationships of spirobipyrrolidinium and the oxygen-containing derivatives

“…Reaction of chlorides of SBP, SBO, and OP with HBF 4 led to formation of corresponding BF 4 salts, basically, an ion exchange process [1,2]. BF 3 C 2 F 5 salt was synthesized using reaction of 2MOP BF 4 with KBF 3 C 2 F 5 .…”

“…In an earlier publication, we had reported excellent properties of SBP BF 4 salt (1,1 0 -spirobipyrrolidinium (SBP, 5-azoniaspiro [4.4]nonane)), and its oxygenated derivatives for electric double layer capacitor applications [1,2]. Their superior chemical and electrochemical robustness, high solubility range, wide voltage window, and conductivity make them especially suitable for electrical energy storage applications, including supercapacitors [3][4][5][6][7][8].…”

“…Their superior chemical and electrochemical robustness, high solubility range, wide voltage window, and conductivity make them especially suitable for electrical energy storage applications, including supercapacitors [3][4][5][6][7][8]. We have been investigating SBP-based oxygen-containing spiroammonium salts for preparation of room temperature ionic liquids (RTILs) without sacrificing other preferable properties [1,2]. Introduction of oxygen atoms to aliphatic ammonium cations frequently lead to formation of low melting point and less viscous salts [9][10][11][12][13] is widely reported.…”

Task-Specific Ionic Liquids for Electrochemical Applications

“…At a working voltage of ~2.5 V, the EDLC exhibited a higher capacity above room temperature and a better charge-discharge cycle durability at 100 °C than a conventional EDLC using an organic liquid electrolyte such as [Et 4 N][BF 4 ] in propylene carbonate. Higashiya et al [ 82 ] prepared oxygen-containing spirobipyrrolidinium salts (Scheme 8.3 ) for potential applications as electrolytes in EDLCs. This group observed that introducing an oxygen atom (and alkyl groups to break the symmetry) to the spirobipyrrolidinium ring led to a reduction in melting points and viscosities of the resulting ILs.…”

Preparation of spiro-type quaternary ammonium salt via economical and efficient synthetic route as electrolyte for electric double-layer capacitor

“…Synthesis of SBP-BF 4 was attempted by HIGASHIYA et al [7] using pyrrolidine, 1,4-dibromobutane, K 2 CO 3 , and KBF 4 in AN. HIGONO et al [8] reported that spiro-(1,1′)-bipyrrolidinium chloride (SBP-Cl) was synthesized by reacting pyrrolidine with 1,4-dichlorobutane and neutralized with addition of an equivalent amount of HBF 4 , thereby obtaining SBP-BF 4 [9].…”