Synthesis and photophysics of mono-disperse phenylene ethynylene oligomers that feature Ru(II), Os(II), and Re(l) polypyridine complexes

261 Pages·2001·9.9 MB·English

by  Li, Yiting, 1972-

SYNTHESISANDPHOTOPHYSICSOFMONO-DIPERSEPHENYLENE
ETHYNYLENEOLIGOMERSTHATFEATURERu(E),Os(n)ANDRe(I)
POLYPYRIDINECOMPLEXES
By
YITINGLI
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2001
Copyright2001
by
YitingLi
Dedicatedtomyfamilyfortheirloveandsupport
ACKNOWLEDGMENTS
Iamgratefultothechairmanofmycommittee,Dr.KirkS.Schanze,who
introducedthisareaofresearchtome.Iwouldalsoliketothankhimforhisguidance,
bothprofessionallyandpersonally,andalsoforhistremendousencouragement,advice
andsupportduringmydoctoralwork.
Iwouldalsoliketothanktheothermembersofmycommittee.Dr.WilliamR.
Dolbier,Dr.KennethB.Wagener,Dr.DavidE.Richardson,andDr.BruceF.Carroll,
fortheirvaluedadvice,expertise,andsupportwhichhelpedinthedevelopmentofthis
researchproject.
IwouldalsoliketothankDr.YibingShenandDr.YingshengWangforalltheir
helpandcontinuedfriendship.
IwouldalsoliketothankDr.ShujunJiangandDr.YaoLiufortheirhelpinmy
work.
Iwouldalsoliketothankallmembers(orformermembers)oftheSchanze
Group,ShengxiaLiu,KevinLey,KeithWalters,EdWhittle,ChunyanTan,Eric
Silverman,KsenijaGlusac,andBenjaminHarrison.
Last,butnotleast,Iwouldliketothankmyhusband,TianhongJiang,forhis
love,supportandunderstandingduringthemosttryingyearsofmylifeandtomyfamily
inPennsylvania,Minnesota,andChinafortheirloveandsupport.
IV
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS iv
ABSTRACT ix
CHAPTERS
1 INTRODUCTION 1
SonogashiraCu-Pd-CatalyzedAlkyneCouplingReactionandSynthesis
ofPPEPolymers 1
ChoiceofHalide 4
SubstituentsontheHaloarene 5
Catalyst 5
Solvents 5
TransitionMetal-Containing7i-ConjugatedOligomersandPolymers 6
PhotophysicsofPPEPolymers 16
PhotophysicsofMetalCoordinationComplexes 18
PreviousGroupWorkandObjectofPresentStudy 25
2 SYNTHESISANDPHOTOPHYSICSOFPHENYLENEETHYNYLENE
OLIGOMERSTHATCONTAINTHE Ru(bpy)2^^CHROMOPHORE 27
Introduction 27
Synthesis 29
Results 39
AbsorptionSpectra 39
EmissionSpectra 40
EmissionDecays 46
EmissionSpectraFitting 53
TransientAbsorption 59
Electrochemistry 61
ExcitedStateElectronTransferQuenching 64
Discussion 20
UV-VisibleAbsorptionSpectra 70
PhotophysicsoftheMetal-OrganicOligomers 73
ddStates 75
EnergyGapCorrelation 77
V
NatureoftheLowestExcitedStates 80
Experimental 84
PhotophysicalMeasurements 84
UV-VisibleSpectra 85
Steady-stateEmissionSpectra 85
EmissionLifetimes 85
TransientAbsorptionSpectroscopy 85
EmissionQuantumYield 86
QuenchingExperiments 86
ElectrochemicalMeasurements 87
GeneralSynthetic 87
Synthesis 88
3 SYNTHESISANDPHOTOPHYSICSOF5,5’-BIPHENYLOLIGOMERSTHAT
CONTAINOs“(bpy)2ANDRu“(R-bpy)2CHROMOPHORES 107
Introduction 107
HO
Synthesis
Results 110
HO
Electrochemistry
AbsorptionSpectraof(L)Ru”(R-bpy)2 121
EmissionSpectraof(L)Ru*'(R-bpy)2 123
EmissionLifetimesof(L)Ru*^(R-bpy)2 129
TransientAbsorptionSpectraof(L)Ru**(R-bpy)2 133
AbsorptionSpectraof(L)Os“(bpy)2 135
EmissionSpectraof(L)Os’*(bpy)2 120
TransientAbsorptionSpectraof(L)Os"(bpy)2 140
Spectroelectrochernistry 140
Discussion 140
Excited-StateEnergeticsandInterconversionin(L)Ru*^(R-bpy)2Complexes...146
EnergyGapCorrelation 152
Excited-StateEnergeticsandhiterconversionin(L)Os^’(bpy)2Complexes 153
Experimental 105
PhotophysicalMeasurements 155
EmissionQuantumYield 156
ElectrochemicalMeasurements 156
SpectroelectrochemicalMeasurements 156
GeneralSynthetic 102
Synthesis 102
4 SYNTHESISANDPHOTOPHYSICSOF5,5’-BIPHENYLOLIGOMERSTHAT
CONTAINRe(CO>3MOIETY 106
Introduction 100
Synthesis 109
Results 122
vi
Electrochemistry 177
AbsorptionSpectra 180
EmissionSpectra 181
EmissionLifetimes 185
TransientAbsorptionSpectraof[(2)Re’(CO)3(X)] 187
Discussion 190
ExcitedStateEnergeticsof[(2)Re'(CO)3(X)]Complexes 190
PhotophysicsofRe-2-Py 193
PhotophysicsofRe-2-bpy-Re-2 194
PhotophysicsofRe-2-MQ 194
Experimental 199
PhotophysicalMeasurements 199
ElectrochemicalMeasurements 199
GeneralSynthetic 199
Synthesis 200
5 SYNTHESISANDPHOTOPHYSICSOFPHENYLENEETHYNYLENE
VINYLENEOLIGOMERSTHATCONTAINTHE
Ru(bpy)2^^CHROMOPHORE 207
Introduction 207
Synthesis 208
Results 209
Electrochemistry 209
AbsorptionSpectra 211
EmissionSpectra 212
EmissionLifetime 216
TransientAbsorptionSpectra 220
Discussion 221
PhotophysicsofOligomerV-2 221
PhotophysicsofRu-V-2 221
Experimental 223
PhotophysicalMeasurements 223
EmissionQuantumYield 224
ElectrochemicalMeasurements 224
GeneralSynthetic 224
Synthesis 224
6 CONCLUSION 227
APPENDIECS
A SPECTRALFITTINGDIAGRAMOF(L)Ru"(bpy)COMPLEXES 229
B TPRRAENSSEINECNETOAFBPSQO^R^PATNIDONDDMIAFFERENCESPECTRAOF(L)Ru“(bpy)2INTHE233
Vll
C EMISSIONLIFETIMEDATAOF(L)Ru“(R-bpy)2IN4;1(v/v)EtOH/MeOHFROM
80KTO298K 235
REFERENCES 238
BIOGRAPHICALSKETCH 249
Vlll
AbstractofDissertationPresentedtotheGraduateSchool
oftheUniversityofFloridainPartialFulfillmentofthe
RequirementsfortheDegreeofDoctorofPhilosophy
SYNTHESISANDPHOTOPHYSICSOFMONO-DIPERSEPHENYLENE
ETHYNYLENEOLIGOMERSTHATFEATURERu(II),Os(II)ANDRe(I)
POLYPYRIDINECOMPLEXES
By
YitingLi
August,2001
Chairman: KirkS.Schanze
MajorDepartment: Chemistry
Therehasbeenasurgeofinterestconcerningthesynthesisandpropertiesoftt-
conjugatedpolymersthatcontaintransitionmetalcomplexes.Theintegrationof
transitionmetalchromophoreswithmetal-to-ligandchargetransfer(MLCT)excited
statesintothepolymerspermitseasyvariationoftheiropticalpropertiesbychanging
ligandsorthemetalchromophore.However,theirphotophysicalpropertieswerenotthe
majorfocusofthereportedresearch.Withthisinmind,thesynthesisandphotophysicsof
twodifferenttypesofmetal-organicpolymersandoligomersarepresented.
First,aseriesofmassexactPPE-typearyleneethynyleneoligomerswiththe
Ru*’(bpy)2chromophoreincorporatedviaa2,2’-bipyridylunitweresynthesized.Organic-
basedfluorescenceisquenched,andisreplacedbyanMLCT-basedemission.
Photoluminescenceandtransientabsorptionphotophysicsaredominatedby^MLCT
excitedstate.Buttheenergylevelsof^MLCTand^71,71*excitedstatesareverycloseand
IX
thereisequilibriumbetweenthesetwomanifolds.Togainafurtherunderstandingofthe
interactionbetweenthePPEbackboneandthemetalcenter,electronwithdrawing
substituentswereintroducedintothebipyridinegrouponRu”(bpy)2chromophore.The
observedMLCTemissionquenchingisattributedtothepresenceofaligand-to-ligand
charge-transferstateintheexcitedstatemanifold.AlsothePPEoligomerscontaining
differentmetalcenters,Os"(bpy)2andRe(CO)3(MQ^),weresynthesized.By
incorporationoflowoxidationpotentialosmiummetal,theMLCTstateisseparatedfrom
^7r,7c*statesandthe“unperturbed”MLCTemissionisobserved.TheMLCTstategives
risetoaluminescenceandlifetimethataretypicalfortheOs(bpy)3chromophore.The
introductionofRe(CO)3(MQ^)chromophoreintothePPEbackboneshiftstheMLCT
statetohigherenergy.Andthe^n,n*statebecomesdominantatphotoluminescenceand
transientabsorptionspectra.
Second,amassexactPPVE-typearyleneethynylenevinyleneoligomerthat
incorporatesRu(bpy)2chromophoreissynthesized.Theintroductionofvinylenebond
intoPPEbackbonedecreasestheenergylevelof^7r,7t*stateandthephotoluminescence
andtransientabsorptionaredominatedby n,n*phosphorescence.
X