离子液体应用技术进展4

离子液体应用技术进展IonicLiquidApplicationTechnologyProgress王少君大连工业大学一、离子液体的多样化Diversifiedrangeofapplicationsofionicliquids(ILs)MaincationsandanionsdescribedinliteraturePropertiesofionicliquidsMeltingpoint;Volatility;Nonflammability;Thermalandchemicalstability;Conductivityandelectrochemicalwindow;ThechallengehereisstilltodesignILswithwideelectrochemicalwindowalongwithgoodelectricalconductivity.Density;Viscosity;ThedesignoflessviscousILsisstillachallengeformanyapplications.Polarity;Toxicityandbiodegradability;Surfacetension.Forindustrialimplementation,someILpropertiesmustbeinvestigatedunderrealprocessconditions.TypicalpolarityandvolatilitycharacteristicsofalternativesolventsAwideningrangeofionicliquidsavailableILswithtargetedproperties(decreaseviscosityanddensity).NewmethimazolebasedIlsExamplesofILswithtargetedfunctionsCost-effectiveILsTheseIlscancontainaweaklybasicanionandacationformedfromatertiaryamineandanexchangeableproton.‘‘Bio’’ILsProticILssynthesisedbydirectprotonation(X=[NTf2],[CF3SO3],[CF3CO2],[CH3SO3],[HCOO],[HSO4],[H2PO3]).Thecaseofproticbases(suchasdialkylamines)hasalsobeenstudiedN,N-dimethylethanolammoniumformateILsILsbaseddendrimerpolymersbaseJ.-F.Huang,…,J.Am.Chem.Soc.127(2005)12784(Multi)-functionalionicliquidsAcidandbasicILsMono-chargeddiaminebasedILswhichincorporateLewisbasicitysite(DABCOtype)onthecationwithboththermalstabilityandlowmeltingpointcanbeobtainedwhenassociatedwith[NTf2]anion.ExamplesofbasicILsChiralIlsExamplesofchiralILsHighlyorderedmesoporousfunctionalorganosilicasincorporatingchiralcamphorsulfon-amideentitiesweresynthesisedbyahydrolysis–polycondensationinvolvingchiralimidazoliumprecursorsandtetraethoxysilane(TEOS)ExampleofsilicasupportedCIL.Switchable-polaritysolvents(SPS)SwitchablePolaritySolvents(SPS).ILsatthefrontierbetweenorganicandinorganicmaterialsa.Inorganiccations.Two-stepsformationofAgbasedhydrophobicILs(L=olefinordiolefin)b.Deepeutecticsolvents(DES).Recently,somedeepeutecticmixtureswithpropertiessimilartothoseofILs,havebeendescribed.Thesemixturescansimplybeobtainedbymechanicallymixingtwodifferentcomponentswithnoemissionandmassefficiency.ExamplesofdeepeutecticsolventsLatestadvancesinthepreparationandpurificationofILs1.ThedifferentwaysofILspreparations(1)Metatheticexchangeofanion(pathA);(2)NeutralisationofbasewithBrφnstedacids(pathB)ordirectalkylationofalkylimidazole(pathC):(3)Thecarbonateroute(pathD):Adirectaccesstoanion-functionalisedILsconsistsintheone-stepring-openingreactionofsultones.DirectaccesstofunctionalisedILs.二、离子液体结构与性能关系及理论基础Theoreticalbasisofionicliquidstructureandnature1.DFT研究氨基咪唑离子液体前驱体合成的SN2反应机理应用密度泛函理论(DFT)与广义梯度近似(GGA)相结合的方法进行研究,所有计算在MaterialStudioDMol3模块中完成。电子结构计算中采用自旋极化密度泛函进行全优化计算,电子交换相关作用采用GGA的PW91泛函形式,采用有效核势(ECP)来描述核电子的行为,以及包含极化函数的双精度数值基组(DNP)来描述价电子行为.自洽场收敛标准为2.72@10-4eV,采用Hirshfeld集局分布来分析电荷转移情况.几何构型优化中所有结构不加对称性限制,并通过共轭梯度法则获得最低能量结构.计算化学反应过渡态采用LST/QST方法.过渡态通过虚频振动分析判断其合理性.N-甲基咪唑与溴乙胺氢溴酸的分子构型N-甲基咪唑与溴乙胺氢溴酸的反应机理溴乙胺氢溴酸分子构型转变过程能量变化数据为键长/nmN(Ñ))CH3咪唑与两种构型溴乙胺氢溴酸相互作用的结构变化图(a)Path1;(b)Path2;数据为键长/nm不同N(Ñ)位取代基咪唑发生SN2反应时的计算结果N(Ñ))H(a)和N(Ñ))CF3(b)咪唑分别与溴乙胺氢溴酸构型Ò相互作用的结构变化数据为键长/nm结论结果表明,在一定温度下,溴乙胺氢溴酸盐先转化为一种能量较高的中间体,再与亲核试剂发生SN2亲核取代反应,该结论与实验结果吻合.亲核试剂中N(Ò)原子的电负性对该SN2亲核取代反应速率具有显著影响:CH3,H(给电子基团)为取代基时,前者的速率常数较后者大3.8倍,它们均比以CF3(吸电子基团)为取代基时的反应速率常数大上103个数量级。由此可知,可以通过在N(Ñ)位连接不同的取代基来调整N(Ò)原子的电负性从而控制反应的难易程度。张爱宏等，DFT研究～反应机理，武汉大学学报(理学版)，第56卷第3期，2010年6月pp302~3062.密度泛函论1-乙基3-甲基咪唑四氟硼酸盐离子液的结构和性质Structuresandatomiclabelingof1-buty-3-methylimidazoliumtetrafluoroborate([EMIM][BF4])ionpair.Optimizedstructuresof[EMIM]+,[BF4]-and[EMIM][BF4]Optimizedbondlengthof[EMIM]+,[BF4]-and[EMIM][BF4]d(nm)Optimizedbondlengthanddihedralangleof[EMIM]+,[BF4]-and[EMIM][BF4]Optimizedatomicchargesof[EMIM]+,[BF4]-and[EMIM][BF4]ThecomputedIRspectrafor[EMIM][BF4]attheB3LYP/6-31G(d)levelThecomputedIRspectrafor[EMIM]+attheB3LYP/6-31G(d)level结论先用Hyperchem软件构建分子3D模型并预优化,再用Gaussian03W程序中的密度泛函(DFT)法在B3LYP/631G(d)基组水平上计算[EMIM][BF4]的最优化构型。结果表明,[EMIM][BF4]中的原子与阳离子中部分原子具有相互作用而形成氢键,氢键弱相互作用性质可由优化的离子对结构数据和计算的红外谱图数据所证明。在[EMIM][BF4]离子对的形成过程中,存在电荷的转移,使红外谱有不同程度的红移,说明[BF4]-与[EMIM]+离子间有强烈的静电吸引作用。因此,[EMIM][BF4]离子液在氢键和静电吸引作用下形成的分子是这类离子液的结构特征。郑燕升，密度泛函论～结构和性质，算机与应用化学，第27卷第58期，2010年5月28日，pp699-702三、IL的应用(AppliedofIL)1.MultiphasicILsystemsTheIL-liquid/liquid-biphaseconcept(M=monomer,M-M=dimer,M-M-M=trimer).SomechallengesandopportunitiesofmultiphasicsystemsTheionicliquidcontainingtheCocatalystprecursorscanberecycledintothereactionsectionandreactivatedunderCO/H2pressureCo-catalysedhydroformylationofolefins.Anewconceptforcatalystrecycle(1:reaction,2:pressure/temperaturedecreasing,3:separationsection).UseofscCO2asthetransportvectorforsubstratesandproductsContinuousflowhomogeneouscatalysisusingasupercriticalfluid–ionicliquidbiphasicsystem(reproducedbypermissionoftheRoyalSocietyofChemistryP.B.Webb,T.E.Kunene,D.J.Cole-Hamilton,GreenChem.7(2005)373.ButitwasalsodiscoveredthathighreactionratescouldbeobtainedonlyforalkenesexhibitinggoodsolubilityinILsandunderveryhighpressure,tomakescCO2agoodsolventfortheproducts.ThesolubilityofalkenesinILsdependedconsider