Photophysical studies of pi-conjugated oligomers and polymers that incorporate inorganic MLCT chromophores

271 Pages·2000·10.9 MB·English

by  Walters, Keith A.

PHOTOPHYSICALSTUDIESOFPI-CONJUGATEDOLIGOMERSAND
POLYMERSTHATPWCORPORATEINORGANICMLCTCHROMOPHORES
By
KEITHA.WALTERS
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2000
Tothebravewarriorinallofus.
ACKNOWLEDGMENTS
Whenyoureachthispointinyouracademiccareer,itishardtogothroughand
thankalltheindividualpeoplewhoguidedyoualongthelongpath. First,Imustthank
myparentsforgivingmethefreedomtoexplorethewonderfulworldoflifewithout
havingthescriptalreadywrittenforme. IalsoappreciatedtheirpatiencewhenIopted
outofmyinitialcareerchoice(medicalschool),decidedtojourneytoFloridafor
graduateschool,andbecameaMethodist!
Mydesirestobeateacher(asidefromtheteachingexperiencesofmyown
parents)comefromtwopeople. DavidStamey,ahistoryteacherinhighschool,madethe
commenttomeonedaythatIhadbetterbeateacherorhewould"huntmedown." At
thetimeIhadproblemsunderstandingthiscompliment,butIcandefinitelytellMr.
Stameytoputhisgunaway! Theinitialdesiretoteachwasplantedinhisclasses,butit
tookmyownexperiencesasateachingassistantatFurmantospawnitsfullfruition. My
undergraduateadvisor,mentor,andfriend,Dr.NoelA.P."crazyAustralian"
Kane-Maguire,hadabighandinopeningmyeyes(colorblindastheyare)totheworld
ofphotochemistry. Indeed,theentirechemistrydepartmentatFurmanshouldbethanked
fortheirwillingnesstoeducatewiththeintensityandzealtheypresenteddayafterday.
Iamfirmlyconvincedthatastudent'sexperienceingraduateschoollargelyrests
inthehandsofhisorhergraduateadvisor. Iamthankfultohavebeenblessedwithan
advisorthatmadeitanamazingexperience,Dr.KirkSchanze. Kirkwasalwayswilling
in
totreatmeasacolleagueratherthanasubordinate,andthatworkswondersonone's
creativityandinitiative. Ialwaysappreciatedhiswordsofencouragement,hisunique
ideastotrynext,andhispatiencetoletmetrysomethingsthatprobablywouldhave
neverworkedoutnomatterwhatIdid. Kirkgavemethefreedomtolearnandgrowas
myownmindevolved,andthatisprobablythebestgiftanyadvisorcangive.
ManypeopleinGainesvillehavemadeitaverygoodhomeforme. Myfellow
groupmembers(Joanne,Benjamin,Ed,Carla,Kevin,Yiting,Ben,Brian,Wang,Hai-
Feng)areallwonderfulcollaborators,willingtodiscussproblemsandabletosynthesize
thosedarnedcompoundsthateludeme! Ilookforwardtoseeingeachandeveryoneof
themprosperintheirownprofessionalandpersonallives. Thecollaborationswithinthe
department(especiallywithDr.DanTalhamandDr.AipingWufortheLBfilmwork)
arealwaystopnotch. OutsideofUF,myhandbellchoiratTrinity(Kathy,Keith[the
otherone!],Andrew,MarkandKristen,QuentaandDana,Connie,Judy,Susan,Cheryl,
Dori,Nick,Jackie,Anna,Neil,andRose)alwaysbroughtasmiletomyface,putasong
inmyheart,andremindedmethatotherthingsdogoonoutsideofachemistrylab.
IhavemanycollaboratorsoutsideofUFthathaveexpandedthegirthofmy
understandingandappreciationoftheworldofchemistry. TheseincludeDr.Stephan
GuillerezandLiseTrouilletatCEA-Grenoble,Dr.HansvanWilligenandDr.Alejandro
BussandriattheUniversityofMassachusettsatBoston,Dr.LindaPeteanuandLavanya
PremvardhanatCarnegieMellonUniversity,andDr.RobertPilatoandDr.KellyVan
HoutenattheUniversityofMaryland.
IV
Lastly,IthankGodforgivingmethegiftstodowhatIdoandtheinitiativeto
actuallyusethegiftsonceIdiscoverthem. WithHisblessing,Ipraythatmylifewill
continuetogrowandprosperbothinsideandoutsideofthechemistrylab.
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS
iii
LISTOFTABLES ix
LISTOFFIGURES xi
ABSTRACT xvi
tt-CONJUGATEDPOLYMERS
1
Introduction 1
Phenylenevinylene-andAryleneethynylene-BasedPolymers 1
Polythiophene-BasedPolymers 7
MLCT-Incorporated^-ConjugatedPolymers 12
Phenylenevinylene-andAryleneethynylene-BasedPolymers 12
Polythiophene-BasedPolymers 18
PreviousGroupWork 20
ScopeofThisWork 22
PHOTOTHERMALCHEMISTRY 24
Theory 25
Time-ResolvedThermalLensing 25
Thethermallenstheory 26
Asimplifiedcalculationmethod 29
Limitationsandinstrumentalconsiderations 32
Photoacoustic/Laser-InducedOptoacousticSpectroscopy 35
Earlyphotoacoustictechniques 37
Laser-inducedoptoacousticspectroscopy 38
Accountingforsolutionvolumechanges 41
InstrumentDesignandCalibrationStudies 43
Time-ResolvedThermalLensing 43
Apparatussetup 43
Calibrationstudies 45
Laser-InducedOptoacousticSpectroscopy 48
Apparatussetup 48
Calibrationstudy-(b)Re'(CO)3(bzpy)+tripletenergies 50
Experimental 60
VI
((bb))RRee'((CCOO))33((bbzzppyy))++PShyonttohpehsyissics 6630
5-5'BIPHENYLOLIGOMERPHOTOPHYSICS 65
Introduction 65
Results 65
AbsorptionSpectra 67
EmissionSpectra 70
EmissionLifetimes 80
TransientAbsorptionSpectra 84
PhotothermalMeasurements 89
TransientAbsorptionQuenching/OligomerTripletEnergy 91
DecayRateCalculations 93
Excited-StateEnergyTransfer 96
Langmuir-BlodgettFilms 98
Electrochemistry 106
Discussion 106
OligomerLigandConformation 106
Electronicabsorptionspectra 108
Emissionspectra 109
Oligomertripletenergies 110
OligomerTemperatureDependenceandAggregation Ill
ExcitedStatePhotophysicsoftheRheniumComplexes 115
Experimental 122
OligomerandComplexSynthesis 122
PhotophysicalMeasurements 123
ElectrochemicalMeasurements 124
Langmuir-BlodgettFilmPreparation 125
5-5'MONOPHENYLOLIGOMERPHOTOPHYSICS 126
Introduction 126
Results 126
AbsorptionSpectra 128
EmissionSpectra 129
EmissionLifetimes 135
TransientAbsorptionSpectra 138
Electrochemistry 140
Discussion 140
Experimental 145
OligomerandComplexSynthesis 145
PhotophysicalMeasurements 146
ElectrochemicalMeasurements 146
vn
4,4'OLIGOMERPHOTOPHYSICS 147
Introduction 147
Results 147
AbsorptionSpectra 149
EmissionSpectra 151
EmissionLifetimes 157
TransientAbsorptionSpectra 161
PhotothermalMeasurements/TripletYields 165
DecayRateCalculations 167
Electrochemistry 169
ElectroabsorptionSpectroscopy 169
Discussion 172
Excited-StateEnergetics 172
HowDoestheSubstitutionPositionAlterthePhotophysics? 174
Semi-EmpiricalCalculations 177
MullikenTheoryCalculationof4-Re-lMLCTDipoleMoment 182
Experimental 189
OligomerandComplexSynthesis 189
PhotophysicalMeasurements 189
ElectrochemicalMeasurements 190
Semi-EmpiricalCalculations 190
THIOPHENEPHOTOPHYSICS 191
Introduction 191
Results 193
Electrochemistry 194
AbsorptionSpectra 197
EmissionSpectraandDecayKinetics 202
TransientAbsorptionSpectra 210
Discussion 218
Excited-StateEnergetics 218
ElectronTransferEnergetics 220
ImplicationsofthisWork 227
Experimental 229
ModelComplexandPolymerSynthesis 229
PhotophysicalMeasurements 229
ElectrochemicalMeasurements 230
CONCLUSIONS
231
REFERENCES
235
BIOGRAPHICALSKETCH
.251
vm
LISTOFTABLES
Table page
2-1. Emissiondatafor(b)Re'(CO)3(bzpy)+ 53
2-2. LIOASdatafor(b)Re'(CO)3(bzpy)+ 58
3-1. 5-Loligomerphotophysics 66
3-2. 5-Rerheniumcomplexphotophysics 67
3-3. Variabletemperatureemissiondecaytimesofthe5-Loligomers 81
3-4. Variabletemperatureemissiondecaytimesofthe5-Recomplexes 82
3-5. 5-LoligomerLIOASdata 89
3-6. 5-RecomplexLIOASdata 90
3-7. Tripletenergiesofthe5-Recomplexes 90
3-8. 5-LoligomerandPItripletquenchingstudyresults 91
3-9. TripletphotophysicsofPIand5-Loligomers 96
3-10.Decayratesofthe5-Loligomers 96
3-11.Fluorescenceintensityratiosformixedsamples 98
3-12.Surfacecoveragecalculationsformixed5-L-3/5-Ru-2LBfilms 104
4-1. 5-LPoligomerphotophysics 127
4-2. 5-RePrheniumcomplexphotophysics 128
4-3. Variabletemperatureemissiondecaytimesofthe5-LPoligomers 136
4-4. Variabletemperatureemissiondecaytimesofthe5-RePcomplexes 137
5-1. 4-Loligomerphotophysics 149
5-2. 4-Rerheniumcomplexphotophysics 149
IX
5-3. Variabletemperatureemissiondecaytimesofthe4-Loligomers 159
5-4. Variabletemperatureemissiondecaytimesofthe4-Recomplexes 160
5-5. 4-LoligomerLIOASdata 165
5-6. 4-RecomplexLIOASdata 165
5-7. 4-Loligomertripletyields 166
5-8. Tripletphotophysicsofthe4-Recomplexes 167
5-9. Decayratesofthe4-Loligomers 168
5-10.2-SA,3-SAand4-SAphotophysicaldata 175
5-11.Semi-empiricalcalculationsfor5-Mand4-M 178
5-12.Semi-empiricalcalculationsfor5-L-land4-L-1 180
5-13.Singletgroundstatemolecularorbitalsfor5-Mand4-M 186
5-14.Singletgroundstatemolecularorbitalsfor5-L-land4-L-l 187
5-15.Singletgroundstatemolecularorbitalsfor5-L-1Tand4-L-1T 188
6-1. Thiophenemodelcomplexphotophysics 194
6-2. Thiophenepolymerphotophysics 194
6-3. Electrochemistryofthiophenecomplexesandpolymers 197
6-4. Franck-Condonemissionbandshapefittingparametersformodelcomplexes 203
6-5. Electrontransferrateconstantsforthiophene-bipyridinemodelsandpolymers....221
6-6. Electrontransferfreeenergychangesforthiophene-bipyridinemodelsand
polymers 225