Design,Synthesis,and Properties Of Benzimidazolium Geminal Dication Ionic Liquids

Ionic liquids(ILs) as “green solvents” have been used widely due to their unique physical and chemical properties.The most advantage of ILs is designability.Therefore,with the deep research of ILs,there has been a hot topic for designing more functional ILs.Compared with traditional ILs,dicationic ILs exhibited fascinating features in terms of thermostability and volatility.Physi-chemical properties can be altered by changing the chain length or adding ether group between the two cations,in which specific demand can be satisfied.What's more,Compared with traditional organic solvents,ILs possess fascinating feature such as negligible vapor pressure,nonvolatility,and environmental-friendliness.Meanwhile,the solubility to inorganic or organic compounds,polymer,and acidity or alkalinity can be controlled by designing different cations and anions,thus realizing extraction and separation for special materials.The design of functional ILs adjust dissolving capacity and liquid range effectively,which is applied widely in extraction and separation.In this work,two cations were connected by custom-made oligoethylene glycol with different molecular weight,and cations and anions were changed to design different germinal dicationic ionic liquids(DILs)with specific function.Furthermore,their thermodynamic and transport properties properties were studied,and they were also apply to the separation of dye.This work was supported financially by the National Natural Science Foundation(Nos.21173070,21303044,21573058).The major contents and conclusions of the present work are as follows:1.Geminal dicationic ionic liquids based on the combination of benzimidazolium cations with p-toluenesulfonate and hexafluorophosphate anion,have been synthesized,which consist of two head groups linked by oligoethylene glycol.The structure and physicochemical properties of the synthesized ionic liquids were characterized by nuclear magnetic resonance(MRI),differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).Experimental results indicate that the thermal decomposition temperature of the geminal dicationic ionic liquids are above 300 o C.They have good thermal stability.2.In this work,conductivities for ILs in ethanol solution were measured accurately at 298.15 K.The limiting conductivities(?0),the association constants(KA)and the critical aggregation concentration(CAC)were derived.The effect of alkoxy chain length on conductivities for ILs in ethanol was discussed,and some regular was obtained.Furthermore,the geminal DILs-solvent interactions in ethanol solution were discussed.3.The design of functional ILs adjust dissolving capacity and liquid range effectively,which is applied widely in extraction and separation.Therefore,we constructed liquid-liquid extraction system composed of DILs and water.The effect of ILs on extraction efficiency for rhodamine B were discussed in terms of concentration,temperature,and time.A two-step affinity extraction was used to extract rhodamine B,and the efficiency was up to 99%.