Synthesis Of Functionalized Ionic Liquids And Their Catalytic Applications In Non-aqueous Media

Non-aqueous solvents include organic solvents and ionic liquids(ILs).Great quantities of products have been made with the aid of conventional organic solvents,which are volatile resulting in environment pollution.It is a solvent revolution for the arrival of ILs,which is composed of organic cation and inorganic or inorganic anion.ILs have so limited vapor pressure that they are called 'green solvent' with no emission to the air.The cation and anion can be modified to have specific chemical and physical properties and the resulting ILs are called 'task-specific ionic liquids',which are of significance in many fields recently.The objectives of this dissertation are synthesis of ionic-liquid buffers and their application to the non-aqueous catalysis to shed light on the pH effect of metal complex catalysts and biocatalysts.The main results are as follows,1.Ionic-liquid buffer[BMIM][HP],[OMIM][HP],and[BMIM][HT]with buffer characteristic were successfully synthesized by neutralization method.The composition of the ionic-liquid buffers characterized by NMR and ESI-MS is consistent with the formula.Ionic-liquid buffers are miscible with polar organic solvent and common ionic liquids and have high buffer capacity,low dilution value,and high thermal stability.[BMIM][HP],[OMIM][HP], and[BMIM][HT]are potential primary buffer standards for non-aqueous solution.2.pH control in non-aqueous catalysisIonic-liquid buffers were used to control pH of non-aqueous media and the effect of pH on catalytic activity was investigated in homogenous and biphasic system.In DMF and ionic liquid[BMIM][BF₄],ionic-liquid buffer[BMIM][HP]can control the pH of the media and a strong pH effect was observed on hydrogenation of olefin catalyzed by [RuCl₂(PPh₃)₃].NMR characterization showed that[RuHCl(PPh₃)₃]is the active catalytic species for hydrogenation of olefin in non-aqueous media,and that[RuHCl(PPh₃)₃]is the predominant active catalytic species in acidic conditions while[RuHCl(PPh₃)₃ can not be detected in basic conditions.In enzyme-benign organic solvents and enzyme-benign ionic liquids,EDTA-based ionic-liquid buffers can control the pH of the media and transesterification catalyzed by Candida Antarctica Lipase B(CALB) showed obvious pH dependence.3.Solvation stabilization and electrostatic stabilization of macromolecular catalysts in ILMore polar ionic liquid[C₂OHMIM][BF₄]was used to dissolve negatively charged dendrimers,which are templates as dendrimer-encapsulated palladium nanoparticles (Pd-DENs) catalyst.[C₂OHMIM][BF₄]showed strong power to solvate the Pd-DENs resulting in solvation stabilization.And the charges on the periphery of dendrimers have strong repulse forces to resist the aggregation of Pd-DENs.It is the electrostatic stabilization together with solvation stabilization that makes Pd-DENs long-life recycling.Ionic liquid[C₂OHMIM][BF₄]can dissolve CALB.CALB showed high activity of transesterification in dissolved form in buffered IL and maintained its efficiency during recycling.4.Characterization of DENs by CECapillary electrophoresis(CE) was used for the first time to characterize Pd-DENs.CE data showed that Pd nanoparticles resided in the internal of dendrimers,and that Pd did not averagely distribute into every dendrimers,which is the main cause for the phenomena of observed particle size(HRTEM) bigger than expected.5.Enzymatic catalysis on dielectric constant of mediaEnzyme deactivates in solvents like alcohol,DMSO,and DMF,which is because of the impact of the media on the ionization of amino acid residues.In water,the carboxyl groups of the catalytic triads can ionize into solvated carboxylate,which is one of the active sites of the enzyme.In solvents like alcohol,DMSO,and DMF,however,the carboxyl groups ionize into solvated carboxylate and ion pairs.Formation of ion pairs would lead to lower enzymatic activity or complete deactivation.The enzyme molecules are charged and most of the negative charges distribute on the periphery of the enzyme molecules.In aqueous solution,the repulsive force from the like-sign charges equals to the attractive force of van der Waal among the molecules, maintaining the active configuration of the enzyme.If the enzyme is dissolved in media which dielectric constant is greater than water,the repulsive force from like-sign charges decreases,resulting in the contraction of configuration of the enzyme molecules. Consequently,the amino residues of the triad change their spatial locations and this configuration changes make the enzyme deactivate.On the contrary,if the enzyme is dissolved in media which dielectric constant is less than water,the repulsive force from like-sign charges increases,resulting in the unfolding of the enzyme molecules.Consequently, the amino residues of the triad change their spatial locations and this configuration changes make the enzyme deactivate.Solvents with high dielectric constant were synthesized and characterized.CALB can be dissolved in these solvents and showed high activity of transesterification in dissolved form.