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TheoreticalInvestigationonMonomerandSolventSelectionforMolecularImprintingof †Copiah olnCommunityCollege,11Co ircle,Natchez,Mississippi39120,United‡DepartmentofChemistryandBiochemistry,JacksonStateUniversity,1400J.R.LynchStreet,Jackson,Mississippi39217,United::Theaimofthisworkistoserveasaguidelinefortheinitialselectionofmonomerandsolventforthesynthesisofthe poundbasedmolecularlyimprintedpolymers,MIPs.Reporteddataludeevaluationofsixsystemswiththeabilitytoformnoncovalentlybondedmonomer−temtecomplexes.Thesesystemsarerepresentedbythefollowingaliphaticandaromaticmolecules:acrolein,acrylonitrile,2,6bisacrylamide,4ethylenebenzoicacid,methylmethacrylate,and2vinylpyridine.Cavemodelsforselectedmonomersarealsopresentedandsupportedbybindingenergyysisundervariousconditions.Solventeffectsonmonomer−temtebindingenergyhavebeenstudiedforfoursolvents:acetone,acetonitrile,chloroform,andmethanol.Additionally,systemssuchas2,4dinitrotoluene(2,4DNT),2,6dinitrotoluene(2,6DNT),pentachlorophenol(PCP),and3,6dichloro2methoxybenzoicacid(Dicamba)havebeenusedtostudyselectivityofacroleinbasedMIPtowarddetection.Thedensityfunctionaltheory,DFT,methodhasbeenusedforallstructural,vibrationalfrequency,andsolventcalculations.numberofnecessarysearchsynthesesperformedfortheselectionofthebestcompoundforaparticularexperiment.Computationallybasedevaluationextractsthemostusefulsubstancesoutofthepoolofpossiblesystemsquicklyandcostimprinting,MI,isanexperimentaltechniqueforcreatingreceptorstructuresonapolymersurfacethatcanselectivelybindtomoleculesofinterest.MIhasabroadspectrumofextraction,3,4detection,5,6anddrugdelivery.7,8AspresentedinFigure1,themolecularimprintingprocess9canbedividedintoFigure1.MIPprocess:(A)selfassembly;(B)polymerization;(C)solventextraction.threemainstages.Duringthefirststage(monomerselfassembly)themoleculeofinterest,thetemte,issurroundedbymonomerspositionedtoinctwithfunctionalgroupsofthetemte.Thesecondstage(polymerization)occurswhenmonomerspolymerizewithcrosslinkingagentstoformacavearoundthetemte.Duringthefinal,third,stage(extraction),thetemteisremoved,byasolventextractionprocess,fromtheformed .Theemptypossessesthecharacter

ofthefunctionalgroups.TheformedMIPisreadytorebindthetemteforitsdetection,separation,orextraction.pounds,especially2,4,6trinitrotoluene,10,11arethegroupofhighlyenergeticmaterialsforwhichdetectionisindemandduetosecurity5,12aswellasenvironmental6reasons. causinganimmediatedanger,asanexplosivematerial,thissubstancec socontaminatesoilandgroundwater.6Hence,ithasbeenproposedtoapplytheMIPtechniqueforthedetectionandpossibleremovalofthethetheoreticalmodelfortheevaluationofthebindingenergiesbetweenthemonomerandtemteforbothDNT13and14specieshasbeendesigned.ThepresentedmodelallowsustopredictqualitativelyandtativelypossibleinteractionsintheMIPsystem.TheoreticaldatareportedinbothmanuscriptshavebeenverifiedbyexperimentalFTIRspectra.Theabovementionedmodelhasbeenutilizedinthecourseofthisworktoperformtheoreticalcalculationsofsixselectedaromaticandaliphaticmonomers,forselectionofthebestonefortheimprintingof .AspresentedinFigure2,studiedmonomersludeacrolein,acrylonitrile,2,6bisacrylamide,4ethylenebenzoicacid,methylmethacrylate,and2vinylpyridine.Theeffectsofthefourmostcommonsolventsacetonitrile,chloroform,andmethanol)onthe1:1monomer−temteandselectedcave−temtesystemshavealsobeenreported.Additionally,theselectivityofacroleinbasedMIPReceived:December26, January16,Published:January23,©2013AmericanChemical dx. |J.Phys.Chem.A2013,117,Figure2.Structuresoforganictowarddetectionofhasbeenstudiedusingacavemodelinctingwith2,4DNT,2,6DNT,PCP,andDicambamolecules,aspossiblecompetitors.Overall,thisworkaimstoprovideaguidelineforthemonomerandsolventselectionprocessforthemolecularimprintingofnitroaromaticcompounds,aswellasaninsightintoMIPselectivity.COMPUTATIONALThisstudyutilizespreviouslydeveloped1:1modelforimprinting,14whereinctswithasinglemonomermoleculethroughhydrogenbonding.Althoughthemonomercanformthreepossibleisomers(ortho,meta,andpara)withrespecttothemethylgroupof,themodelisbasedonthelowestenergyorthocomplex,AspresentedinFigure3,monomer(acrolein)inctswithmethylandtheorthonitrogroupofthemoleculethroughhydrogenbonds.Twocavemodelsmadeofthealiphaticandaromaticmonomers(underlinedinTable1)havebeendesignedto

studysolventeffectsonthebindingenergy.Thecaveinfirstsixdimersaroundthetemte.Figure4bshowsanemptyacroleincave.Thesecondcaveisbuiltfromeightaromatic2vinylpyridinemolecules,formingfourdimersaround,aspresentedinFigure4c.Figure4dshowsanempty2vinylpyridinecave.ThestudyontheselectivityofMIPtowardthemoleculehasbeenperformedusingapreviouslyoptimizedacroleave,reportedinFigure4b.ThegeometryofthecavehasbeenptomimictherealsolidstatepolymericstructureofformedMIP.Bindingenergiesoffourspecies,selectedduetotheirpresenceingroundwaterandsoilandstructuralsimilaritiesto,havebeencalculated.ThereportedinFigure5.Thedensityfunctionaltheory,15DFT,methodwiththeB3LYP16−18functionalhasbeenappliedtooptimizeallselectedspeciesandtheircomplexeswith2,4,6trinitrotolueneandtoperformsolventstudies.Nosymmetryconstraintswereimposedduringthegeometryoptimizationprocesses.Geometrysearchesforavarietyofpossibleconfigurationswereperformedtoobtaintheglobalminimum,whichhasbeenverifiedbyDFTvibrationalfrequencycalculations.ThestandardPoplebasisset,631G(d,p),wasusedinthisstudy.19Basissetsuperpositionerror,20,21BSSE,hasbeenludedincalculationsofthetotalbindingenergyof1:1complexesandtheircomponents.TheeffectofthesolventonthestudiedsystemswasmodeledbytheCPCMmodel.22CalculationspresentedinthisworkhavebeencarriedoututilizingtheGaussian0323suiteofprograms.RESULTSANDSix,themostpopular,monomersusedformolecularimprinting,MI,havebeenselectedforcomputationalstudyofmonomer−tem tecomplexformationoccurringduringimprintingof2,4,6 .Studyreportsbindingenergy,BE,hydrogenbondingdistancesandmonomer− BEaffectedbythepresenceofsolvent.Thisworkreferstopreviouslyreportedmodels13,14designedformodelingofmonomerselfassemblyprocessoccurringduringmolecularimprintingofselectednitrocoumpounds,wherethemosteffectivebindingsiteforthefunctionalmonomer(acrylicormethacrylicacid)involvesthemethylgroupandorthopositionednitrogroupofthenitroaromatic’smolecule.Asacontinuation,thisworkpresentssummaryofmonomer−temtebindingpropertiesforaliphatic(acrolein,acrylonitrile,methylmethacrylate),andaromatic(2,6bisacrylamide,4ethylenebenzoicacid,and2vinylpyridine)functionalmonomersinctingwith2,4,6.Bindingenergies,BE,andbindingdistancesforallsixstudiedcomplexes,calculatedinagasphase,andselectedcalculatedinthegasphase,decreasefrom7.03kcal/molfor2ethylenebenzoicacid to3.10kcal/molforthe2vinylpyridNTin ctingsystems.Gasphasecalculatedbindingenergieshavebeencorrectedbycounterpoisecorrectioncalculations.BSSElowersthevalueofBEforabout2.5kcal/mol,which,accordingtoGrabowski,24classifiesthemamongweakhydrogeninctions.Monomer−temteFigure3.1:1model ctingwithmonomer

TakingintoaccountafactthattheMIpolymerizationprocessoccursinasolution,itiscrucialtomimicsolventTable1.BondingPropertiesofStudiedMonomer−TemteComplexes luding:BindingEnergies,BE,CalculatedinaGasPhaseasWellasSelectedSolvents,andHydrogenBindingDistancesaBEinagasCOHCHOC≡NHCHOCHONHONOringHOHOCOCmethylCOHCHOCHOringNHCHOCHOaCalculationsperformedattheB3LYP/631G(d,p)leveloftheory.Energiesinkcal/mol,anglesinFigure5.Structuresofselectedorganicmoleculespresentinacetone,acetonitrile,ormethanolresultsindisintegrationofthecomplex(nomonomer−temteinctionisobserved).Hence,thosethreesolventsmaynotbethebestmediumforimprintingwith2,6bisacrylamideor4ethylenebenzoicFigure4.Cavemodelofencapsulatedinpolymerandemptycave(modelsforacroleinand2vinylpyridine).environmentomputationalstudies.Oneofthegoalsofthisworkistoprovidesolventysisforthepolymerizationprocess,andoverallhelpwithselectionofthebestsolventforimprintingof pounds.UsingtheCPCM22solvationmodelattheDFTleveloftheory,weattempttoinstigateandtemteduringselfassembly.Acetone,acetonitrile,chloroform,andmethanolhavebeenselectedforindividualstudyoftheirinfluenceonBE.AspresentedinTable1,introductionofsolventdramaticallychangesthevalueofBEwhencomparedtoonecalculatedinthegasphase.Themostspectaculareffectonbindingenergycanbeobservedfortheethylenebenzoicacid−systems,whereadditionof

Outofthreeinitiallyselectedaromaticfunctionalmonomersonly2vinylpyridinehasapotentialformolecularimprintingofnitrocoumpoundsinthepresenceofallfourstudiedsolvents.The2vinylpyrid NTcalculatedBEfora1:1ratio te)insolventsolutionamountsto0.56kcal/molforacetonitrileand2.36kcal/molforchloromonomer−inction,reportedinTable1showthefollowingtrends:Allfourstudiedsolventsaresuitableformolecularimprintingof poundtemte.InallcalculatedcasesthevalueofBEdecreasesintheorderacrolein>methylmethacrylate>acrylonitrileformonomer−temtecomplexes.about1.5kcal/mol)whencomparedtoBEsofstudiedaromaticsystems.Cavemodelsforimprinting,usingacroleinand2vinylpyridinemonomers,havebeendesignedtocreatemoreinFigure4.Inthefirstmodelthemoleculehasbeensurroundedbysixacroleindimersandinthesecondbyfourvinylpyridinedimers.Cave−temtebindingenergiesinagasphaseandsolventshavebeenreportedinTable2.TheysisTable2.BondingEnergies,BE,forStudiedCave−TemteComplexesCalculatedinaGasPhaseandSelectedSolventsaBEina BEin BEin BEin BEincavetemtegasphasemethanolacetonechloroformacetonitrileaCalculationswereperformedattheB3LYP/631G(d,p)leveloftheory.Energiesareinkcal/mol.ofcollecteddatashowsthatintroductionofthechloroformthefortheacroleinecaveand9.47kcal/molforthe2vinylpyridinecave.Introductionofothersolventslowerscave−temtebindingenergiesevenmoresignificantly.However,allcomputationallystudiedsolventsseemstobesuitableasamediumforthe imprintingwithacroleinand2Finally,theacroleavemodelhasbeenusedtostudytheselectivityofacrolinbasedMIPtowardthemolecule.AsacroleinbasedMIPisasolidstatepolymer,inourstudythegeometryoftheacroleavemodelhasbeenp.Nosymmetryconstraintshavebeenimposedonthefourspecieschosenfortheselectivitystudy.Thesepollutantshavebeenselectedduetotheirstructuralresemblancetoandallfourspeciesandtheacroleavehavebeencalculatedinagasphase.ThestudyindicatesthatbothDNTmoleculesbindtotheacrole avebutthebindingenergyissignificantlysmallerthanfor ,reportedas21.59kcal/mol.Bindingenergiesare10.98and3.73kcal/molfor2,4DNTand2,6DNT,respectively.PCPandDicambadonotbindtotheacroleave;performedcalculationsshowthattheyarestronglyrepelledbythecave.■Onthebasisoftheperformedcalculations,outofthesetoffourstudiedsolventsthemostuniversalsolventforMIPof,regardlessofthetypeofusedfunctionalmonomer,seemstobechloroform.Acetone,acetonitrile,andmethanolareproposedtobeusedforaliphaticmonomerimprintingorfortemteextractionofaromaticmonomers,withtheexceptionof2vinylpyridine.■AUTHOR446■Theauthorsdeclarenocompetingfinancial■ThisprojectissupportedbytheU.S.DepartmentofDefensethroughtheEngineer,ResearchandDevelopmentCenter(Vicksburg,MS),Contract#W912HZ10C0107,andTheMississippiCenterfor putingResearch(MCSR).

■Jo,S.H.;Lee,S.Y.;Park,K.M.;Yi,S.C.;Kim,D.;Mun,S.J.Chromatogr.A2010,45,7100−7108.■Pap,T.;Horvath,V.;Tolokan,A.;Horvai,G.;Sellergen,B.J.Chromatogr.A2002,973,1−12.Purif.Technol.2004,38,173−179.Alizadeh,T.;Zare,M.;Ganjali,M.R.;Norouzi,P.;Tavana,Biosens.Bioelect.2010,25,Cormack,P.A.G.;Elorza,A.Z.J.Chromatogr.B2004,804,Politzer,P.;Murray,J.S.;Koppes,W.M.;Concha,M.C.;P.Cent.Eur.J.Energet.Mater.2009,6,Clarkson,J.;Smith,W.E.;Batcheldar,D.N.;Smith,D.A.;Coats,A.M.J.Mol.Struct.2003,648,203−214.Bunte,G.;Hurttlen,J.;Pontius,H.;Hartlieb,K.;Krause,Saloni,J.;Dasary,S.S.R.;Yerramilli,A.;Yu,H.;Hill,G.,Hill,G.,Jr.Polymer2011,52,1206−1216.Molecules;OxfordUniversityPress:NewYork,1994.Lee,C.;Yang,W.;Parr,R.G.Phys.Rev.B1988,37,Simon,S.;Duran,M.;Dannenberg,J.J.J.Chem.Phys.105,Boys,S.F.;Bernardi,F.Mol.Phys.1970,19,83,Frisch,M.J.;Trucks,G.W.;Schlegel,H.B.;Scuseria,G.E.;Robb,M.A.;Cheeseman,J.R.;etal.Gaussian03,revisionC02;Gaussian.:Pittsburgh,PA,2004.Grabowski,S.Annu.Rep.Prog.Chem.Sect.C2006,102,Copiah-LolnCommunityCollege,11Co-L ircle,Natchez,Mississippi39120,UnitedStatesDepartmentofChemistryandBiochemistry,JacksonStateUniversity,1400J.R.LynchStreet,Jackson,Mississippi39217,UnitedStates 丙烯醛、丙烯腈、2,6-双丙烯酰胺、4-亚乙基苯甲酸、甲基丙烯酸甲酯和2-乙烯基吡啶。还提出四种溶剂的模板结合能：丙酮、乙腈、氯仿和甲醇。此外，还有2,4-二硝基甲苯(2,4-DNT)、2,62,6-DNT(PCP)3,6-二氯-2Dicamba用于研究基于丙烯醛的MIP对检测的选择性。密度泛函理论（DFT）方法已用于所有结构、.MI1,23,4、5,67,819MIP2,4,6-三硝基甲苯,10,115,126因，需要对其进行检测。除了造成直接危险外，作为一种爆炸性物质，这种物质还会污染土壤和地下水。6因此，有人建议应用MIP技术来检测并尽可能去除环境中的及其衍生物。在型如图1所示。MIP过程：(A)自组装；(B)聚合；(C)溶剂萃取。MIPFT-IR香族和脂肪族单体进行理论计算，以选择最适合印迹的单体。如图2所示，研究的单体包括丙烯醛、丙烯腈、2,6-双丙烯酰胺、42-乙烯基吡啶。四种最常见溶剂（丙酮、乙腈、氯仿和甲醇）对1:1单体的影响。temte和选定的Cave.temteMIP：20111226：20131162013123物理化学杂志A》针对的检测进行了研究，使用洞穴模型与2,4-DNT、2,6-DNT、PCP和麦草畏分子（作为可能的竞争者）相互作用。总的来说，这项工作旨在为硝基芳香族化合物分子MIP2.发的印迹1:1模型，14其中通过氢键与单个单体分子相互作用。虽然单体相对于如图3所示，单体（丙烯醛）与甲基和对位相互作用。分子的邻硝基通过氢键连接。设计了两个由脂肪族和芳香族单体制成的洞穴模型（表1中下划线），用于研究溶剂对结合能的影响。.rst模型中的洞穴（图4a）由十二个丙烯醛分子组成，在模板周围形成六个二聚4b2-乙烯基吡啶分子构成，在周围形成四个二聚体，如图4c所示。图4d显示了一个空的2-乙烯基吡啶洞穴。MIP对分子的选择性研究是使用先前优化的丙烯醛洞进行的，如图4b所示。洞穴的几何形MIP由于它们存在于地下水和土壤中并且与结构相似而被选择的。2,4-DNT、2,6-DNT、PCP和麦草畏的结构如图5所示。密度泛函理论、15DFT、B3LYP16.182,4,6-三硝基何搜索以获得全局最小值，这已通过DFTPople19BSSE)1:1究系统的影响通过CPCM22Gaussian03233.结果和讨论六种最流行的用于分子印迹的单体，MI，已被选择用于2,4,6- 生的单体.模板复合物形成的计算研究。研究报告了结合能、BE、氢键距离和单体。BE受溶剂甲基丙烯酸甲酯）和芳香族（2,6-双丙烯酰胺、4-乙烯苯甲酸和2-乙烯基吡啶）功能单体与2、4,6-梯恩梯。表1报告了所有六种研究复合物在气相中计算的结合能、BE和结合距离以及所选溶剂。在气相中计算的BE的呈现值从2-的7.03kcal/mol降低对于2-乙烯基吡啶.相互作用系统，乙烯苯甲酸-至3.10kcal/mol。气相计算的结合能已通过平衡校正计算进行校正。BSSE使BE值降低约2.5kcal/mol，根据G