配位化学.docx
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配位化学.docx
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配位化学
Two3-Dmetal-organicframeworksconstructedby2-methylor2-ethylimidazoledicarboxylates
NANCHEN,JUNZHANG,YONG-CHAOGAO,ZE-LIYANG,HUI-JIELU,GANGLI*
DepartmentofChemistry,ZhengzhouUniversity,Zhengzhou,Henan450052,P.R.China
Twopolymericframeworks,[Zn5(MIDC)2(HMIDC)2(phen)5]n
(1)(H3MIDC=2-methyl-1H-imidazole-4,5-dicarboxylicacid,phen=1,10-phenanthroline)and{[Ca2(HEIDC)2(H2O)]H2O}n
(2)(H3EIDC=2-ethyl-1H-imidazole-4,5-dicarboxylicacid)havebeensolvothermallysynthesizedandstructurallycharacterizedbysingle-crystalX-raydiffraction.Compound1exhibitsa3Dstructureconstructedfrom2Dlayermotifsjoinedby2-HMIDC2-or3-MIDC3-ligands.Compound2alsopresentsa3Dframework,whichisgeneratedfrom1DchainslinkedbyHEIDC2-ligandsbytwodifferentµ5-modes.Thethermalandsolid-statephotoluminescencepropertiesofthebothtwocomplexeshavebeendeterminedaswell.
Keywords:
Coordinationpolymer;Imidazoledicarboxylate;Crystalstructure;Properties
1.Introduction
Recently,metal-organicframeworks(MOFs)haveparticularlyattractedmuchattentionduetotheirinterestingstructuralfeaturesandgreatpotentialapplicationsas,magnetic,nonlinearopticalandfluorescentmaterials[1-15].Accordingtopreviousstudies,multifunctionalconnectorimidazole-4,5-dicarboxylicacid(H3IDC),hasbeenextensivelyinvestigatedincoordinationchemistry,whichshowsvariouscoordinationmodesunderhydro/solvothermalconditions[16-38].Promptedbytheseinterestingfindings,peoplehavesynthesizedseveralanalogueligandsofH3IDC,2-methyl-1H-imidazole-4,5-dicarboxylicacid(H3MIDC)or2-ethyl-1H-imidazole-4,5-dicarboxylicacid(H3EIDC)tobuildupdesiredcomplexes.Topredictthemethylandethylsubstituenteffectintheligands,H3MIDCandH3EIDC,theoptimizedgeometriesandthenaturalbondorbital(NBO)chargedistributionsofthefreeligandshavebeencalculatedbyus[39,40].Andthedatarevealthattheorganicligands,H3MIDCandH3EIDCinherittheoutstandingcoordinationproperties.However,uptodate,comparedwiththewell-studiedligandH3IDC,polymericframeworksbearingH3MIDCorH3EIDCarestilllimited[39-48].TheinterestingcoordinationfeaturesofH3MIDCandH3EIDChaveencouragedustoconstructmorenovelMOFs.
Herein,wereportthesolvothermalsynthesis,structuraldeterminationsoftwocoordinationpolymers,namely[Zn5(MIDC)2(HMIDC)2(phen)5]n
(1)(phen=1,10-phenanthroline)and{[Ca2(HEIDC)2(H2O)]H2O}n
(2).SinglecrystalX-raydiffractionsrevealthattwotothreehydrogenatomscanberemovedfromtheligandH3MIDCtocoordinatetometalionsin2-or3-modes(Scheme1aand1b),andthedoublydeprotonatedHEIDC2-couldassemblewithmetalionsintwodifferentµ5modes(Scheme1cand1d).Thethermalandsolid-statephotoluminescencepropertiesofpolymers1and2havebeendeterminedaswell.
Scheme1CoordinationmodesofMIDC3-,HMIDC2-orHEIDC2-anions
2.Experimental
2.1.Materialsandphysicaltechniques
Allchemicalswereofreagentgradequalityobtainedfromcommercialsourcesandusedwithoutfurtherpurification.TheorganicligandsH3MIDCandH3EIDCwerepreparedaccordingtotheliteratureprocedure[49].
IRSpectrawererecordedonaNicoletNEXUS470-FTIRspectrophotometerasKBrpelletsinthe400-4000cm-1region.Elementalanalysis(C,HandN)wascarriedoutonaFLASHEA1112ElementalAnalyzer.TG-DSCmeasurementwasperformedbyheatingthecrystallinesamplefrom20to850Catarateof10Cmin-1inaironaNetzschSTA409PCdifferentialthermalanalyzer.FluorescencespectraofthetwocomplexeswerecharacterizedatroomtemperaturebyaF-4500fluorescencespectrophotometer(240nm/min).
2.2.Synthesisofcrystalline[Zn5(MIDC)2(HMIDC)2(phen)5]n
(1)
AmixtureofH3MIDC(34.0mg,0.2mmol),Zn(OAc)2(43.9mg;0.2mmol),phen(39.6mg,0.2mmol),Et3N(0.056mL,0.4mmol)andEtOH/H2O(4:
3,7mL)wassealedin25mLTeflon-linedbombandheatedat160°Cfor96h.Thereactionmixturewasthenallowedtocooltoroomtemperatureatarateof10°C/h.Colorlessblock-shapecrystalsof1werecollected,washedwithdeionizedwateranddriedinair.Crystalsof1arestableintheair.Yield:
68%(basedonZn).Anal.CalcdforC84H54N18O16Zn5:
C,53.10;H,2.84;N,13.28.Found:
C,52.82;H,2.93;N,13.04.IR(cm-1,KBr):
3416(m),3059(w),1572(s),1544(s),1426(s),1342(m),1287(w),1253(m),1121(m),962(w),856(m),726(s),638(w),422(w).
2.3.Synthesisofcrystalline{[Ca2(HEIDC)2(H2O)]H2O}n
(2)
AmixtureofH3EIDC(36.8mg,0.2mmol),Ca(NO3)24H2O(23.6mg,0.1mmol),Et3N(0.056mL,0.4mmol)andEtOH/H2O(4:
3,7mL)wassealedin25mLTeflon-linedbomb,whichwasheatedto160°Cfor96h.Afterthemixturewascooledtoroomtemperatureatarateof10°C/h,pinkstrip-shapecrystalsof2wereobtained,washedwithdeionizedwater,anddriedinair.Crystalsof2arestableintheair.Yield:
65%(basedonCa).Anal.CalcdforC14N4O10H16Ca2:
C,34.99;H,3.36;N,11.66%.Found:
C,35.15;H,3.23;N,11.98%.IR(cm-1,KBr):
3422(m),2988(w),1600(s),1523(s),1384(s),1238(m),1113(m),867(m),792(s),611(w),447(w).
2.4.X-raycrystallography
Crystaldataandexperimentaldetailsforpolymers1and2arecontainedinTable1.AllmeasurementsweremadeonaBrukersmart1000CCDimagingplateareadetectorwithagraphite-monochromatedMo-Kradiation(=0.71073Å).Colorlessblock-shapecrystalsof1(0.320.210.20mm3)andstrip-shapesinglecrystalsof2(0.310.300.28mm3)wereselectedandmountedonaglassfiber.Alldatawerecollectedatatemperatureof296
(2)Kusingthe-2scantechniqueandcorrectedforLorenz-polarizationeffects.Acorrectionforsecondaryextinctionwasapplied.ThetwostructuresweresolvedbydirectmethodsandexpandedusingtheFouriertechnique.Thenon-hydrogenatomswererefinedwithanisotropicthermalparameters.Hydrogenatomswereincludedbutnotrefined.Thefinalcycleoffull-matrixleastsquaresrefinementwasbasedon7814observedreflectionsand558variableparametersfor1,and3399observedreflectionsand282variableparametersfor2.AllcalculationswereperformedusingtheSHELX-97crystallographicsoftwarepackage[50].SelectedbondlengthsandangelsarelistedinTable2.
3.Resultsanddiscussion
3.1.Synthesis
Accordingtothepreviousstudy[41,47],thecrystals,[Zn(H2MIDC)2(H2O)2](0D),{[Zn3(MIDC)2(H2O)2(DMF)2]·0.5H2O}(2D)and[Ca(H2O)2(H2EIDC)2](2D)havebeensuccessfullyobtained.Byanalyzingthemethodsadopted,wetriedtosynthesiscrystalsbysolvothermalmethodusingmixedsolventofethanolandwater.Tooursurprise,the3-Dploymers1and2canbegot.Sowecanconcludethatthemixedsolventaremoresuitableforthegrowthofcrystalswithhigh-dimensionalcomplicatedstructures.Itistobepointedoutthatthefactorsgoverningthereactionandformationofthehydrothermalorsolvothermalproductarecomplicated.Forexample,sameimidazoledicarboxylateligandandsamemetalionwereusedbyJ.-F.Songandcoworkers[41]andbyusinthisworkindifferentsolventsandwithorwithoutauxiliaryligand,phen.ThreedifferentZn(II)productswereobtained.ThecasesinCa(II)-H3EIDCreactionsystemreportedbyD.-M.Tianandcoworkers[47]andbyusherearealsocomplicated.Sowecouldnotgivetheeffectofmetalcenterandauxiliaryligandsonfinalstructure.ButwecanfindthattheligandsH3MIDCorH3EIDCshowstrongcoordinationabilitiesandvariouscoordinationmodesfromthestructuraldataofthe3Dploymers1and2.
Atthesametime,thefinalpHvaluesofthesolutionsarealsoacrucialfactorfortheformationofcrystallineproducts.WeusedEt3Ntoneutralizetheprotonscontainedincarboxylgroupsothattheycancoordinatewithmetalionseasily.ItisfoundthatthepHvalueofsolutioncanbeperfectlycontrolledbyEt3Nat7-8,whichissuitableforthegrowthofcrystal.
3.2.Crystalstructureofcrystalline[Zn5(MIDC)2(HMIDC)2(phen)5]n
(1)
Single-crystalX-rayanalysisrevealsthat1possessesa3DnetworkandcrystallizesintheorthorhombicspacegroupFdd2.
AsshowninFigure1a,therearethreecrystallographicallyuniqueZn(II)centersintheasymmetricunit.AlltheZn(II)ionsareinsixcoordinatedenvironmentsandshowslightlydistortedoctahedralgeometries:
forZn
(1),threecarboxylatooxygenatoms(O1,O2A,O3A)andonenitrogenatom(N1)arefromtwoindividual3-MIDC3-,anothertwonitrogenatoms(N3,N4)comefromonephen,whichformtwofive-memberedchelatingringsandoneseven-memberedring.Itisworthmentioningthatoxygenatoms(O1,O2)from3-MIDC3-ligandslinkneighboringZn1(II)ionstoforma1-Dzigzagchaincomposedoffusedfive-memberedringsalongb-axisasshowninFigure1b,andauxiliaryligandphenarrangedregularlyinthesidechain.ThenearestZn1Zn1distanceis5.9402(9)Åinthechain,respectively;forZn(3),twocarboxylatooxygenatoms(O4,O5)andtwonitrogenatoms(N2,N5)arefrom3-MIDC3-and2-HMIDC2-units,andanothertwonitrogenatoms(N8,N9)comefromonephen,thenthreefive-memberedchelatingringswereobtained;Zn(9)hasthesamecoordinationenvironmentwithZn(3).TheZn-Obondlengthsvaryfrom2.038(6)-2.226(6)ÅandtheZn-Nbondlengthsareintherangeof2.231
(2)-2.269
(2)Å.ThebondanglesaroundeachZn(II)ionvaryfrom74.4
(2)to177.56(18).
Interestingly,doublydeprotonatedHMIDC2-andtriplydeprotonatedMIDC3-coexistin1,andtheyadopttwotypesofcoordinationmodes(Schemes1aand1b),namely2-kN,O:
kN,Oand3-kN,O:
kO:
kN,O.EachMIDC3-anionbridgesthreeZn(II)ionsinN,O-chelating,O,O-chelatingandN,O-chelatingmodes.EveryHMIDC2-bridgestwoZn(II)ionsinN,O-chelatingandN,O-chelatingcoordin
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