Photophysical and photochemical properties of electronically ...
The Photophysical Properties of a Symmetrically ... · This project extends interest into the...
Transcript of The Photophysical Properties of a Symmetrically ... · This project extends interest into the...
![Page 1: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/1.jpg)
ThePhotophysicalPropertiesofaSymmetricallySubstituted2,5–
DiarylideneCyclopentanoneDye:(2E,5E)‐2,5‐bis(4‐
methoxycinnamylidene)‐cyclopentanone
AMajorQualifyingProjectReport
SubmittedtotheFacultyof
WORCESTERPOLYTECHNICINSTITUTE
Inpartialfulfillmentoftherequirementsforthe
DegreeofBachelorofScience
By:
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐KatarinaLopezApril28,2011
Approvedby:
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐Prof.RobertE.Connors,Ph.DProjectAdvisor
![Page 2: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/2.jpg)
2
TableofContents
Abstract ........................................................................................................................................................................ 5Acknowledgements ................................................................................................................................................. 6
Introduction................................................................................................................................................................ 7
ExperimentalProcedures .................................................................................................................................. 101.Synthesisof(2E,5E)‐2,5‐bis(4‐methoxycinnamylidene)‐cyclopentanone(2dbmxcp) 102.SpectrophotometricAnalysis–AbsorbanceandFluorescenceSpectra.............................. 143.FluorescenceQuantumYieldDetermination .................................................................................. 144.Fluorescencelifetimedetermination.................................................................................................. 15
ResultsandDiscussion........................................................................................................................................ 171.Introduction ................................................................................................................................................... 172.AbsorptionandFluorescenceProperties.......................................................................................... 183.QuantumChemicalCalculations ........................................................................................................... 32
Conclusions .............................................................................................................................................................. 34
References ................................................................................................................................................................ 35AppendixA:FluorescenceQuantumYieldCalculation......................................................................... 36
AppendixB:FluorescenceLifetimeSampleCalculation ...................................................................... 41
![Page 3: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/3.jpg)
3
ListofFigures
Figure1.GeneralStructureof2,5‐diarylidenecyclopentanones. ............................................8Figure2.Structureof(2E,5E)‐2,5‐bis(4‐methoxycinnamylidene)‐cyclopentanone
(2dbmxcp). ............................................................................................................................8Figure3.Jablonskidiagramshowingfluorescencewithsolventrelaxation10. ........................9Figure4.Reactionschemeforthesynthesisof2dbmxcp. .......................................................10Figure5:1HNMR2dbmxcpd2.5‐8.0ppm................................................................................11Figure6:1HNMR2dbmxcpd6.0‐8.05ppm .............................................................................12Figure7:1HNMR2dbmxcpd1.95‐4.05ppm ...........................................................................13Figure8.ChemicalStructureof2dbma .....................................................................................17Figure9.Absorbanceandemissionspectraof2dbmxcpinvarioussolvents. .......................19Figure10.Plotofmaximumabsorptionandfluorescentwavenumbersif2dbmxcpagainst
Δfinpolarprotic,polaraprotic,andnonpolarsolvents.Alcoholsarerepresentedasthecleardiamondandsquareshapes......................................................................................21
Figure11.Plotofmaximumabsorptionandfluorescentwavenumbersof2dbmxcpagainstET(30)invarioussolvents.Alcoholsarerepresentedascleardiamondandsquareshapes. .................................................................................................................................22
Figure12.Plotofmaximumabsorptionandfluorescentwavenumbersof2dbmaagainstΔfinvariousprotic,aprotic,andnonpolarsolvents.Alcoholsaredesignatedbytheredshapeddiamondsandsquares. ..........................................................................................22
Figure13.Plotofmaximumabsorptionandfluorescentwavenumbersof2dbmaagainstET(30)invarioustypesofsolvents.Alcoholsarerepresentedbytheredshapeddiamondsandsquares. .......................................................................................................23
Figure14.Plotofthefluorescencequantumyieldof2dbmxcpagainstνflinallsolvents. ....25Figure15.Solventcalculationsof2dbmxcpinTolueneandEthanol......................................27Figure16.Computedmolecularorbitalsof2dbmxcpand2dbma. .........................................29Figure17.Lippert‐MatagaPlotofStoke'sshift(Δν)againstΔfof2dbmxcpinallsolvents. .30Figure18.Lippert‐MatagaPlotofStoke'sshift(Δν)againstΔfof2dbmxcpinpolarprotic
andnonpolarsolvents. .......................................................................................................30Figure19.Lippert‐MatagaPlotofStoke'sshift(Δν)againstΔfof2dbmxcpinallsolvents.
Alcoholsaredesignatedastheredsquares. .....................................................................31Figure20.ComputedMolecularOrbitalsof2dbmxcp..............................................................32
![Page 4: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/4.jpg)
4
ListofTables
Table1.Spectroscopicandphotophysicalcharacteristicsof2dbmxcpinvarioussolvents. 20Table2.Spectroscopicandphotophysicalpropertiesofboth2dbmxcpand2dbmainMeOH
andEtOH. .............................................................................................................................27Table3.ComputedMolecularOrbitalCalculationsof2dbmxcp. ............................................32Table4.2dbmxcpTD‐DFTSpectralCalculationsinEthanolandToluene .............................33
![Page 5: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/5.jpg)
5
Abstract
Thisprojectextendsinterestintothephotophysicalpropertiesofsymmetrically
substituted2,5–diarylidenecyclopentanonedyes.Thefocusforthisresearchisonthe
compound(2E,5E)‐2,5‐bis(4‐methoxycinnamylidene)‐cyclopentanone(2dbmxcp).This
compoundwassynthesizedviaacrossedaldolcondensationreactionbetween
cyclopentanonewith(E)‐4–methoxycinnamaldehydeinthepresenceofNaOH.The
electronicabsorptionandfluorescencepropertieswereinvestigatedinavarietyof
nonpolar,polarprotic,andaproticsolvents.Solvatochromicshifts,specifically
bathochromic(red)shiftswereobservedinboththeabsorptionandfluorescencespectra
asaresultofsolventpolarity.Inadditiontothespectroscopicproperties,thephotophysical
propertieswerealsoinvestigated.Thisinvolvedcalculatingthefluorescencequantum
yields,andmeasuringthefluorescencelifetimeparameters.Thefluorescencequantum
yieldsof2dbmxcprangedfrom0.0012incarbontetrachloride,to0.17in2‐propanol.This
rangewasofparticularinterestbecauseahigherquantumyieldinalcoholsdiffersfrom
analogouscompounds.First‐orderradiativeandnonradiativeratesofdecaywere
determined.Quantumchemicalcalculationswereperformedon2dbmxcpattheDFT
B3LYP/6‐31G(d)leveloftheoryforgeometryoptimizationandTD‐DFTspectral
calculations.
![Page 6: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/6.jpg)
6
AcknowledgementsIwouldliketothankProfessorRobertE.Connorsforadvisingmeduringthecourseofthe
projectandfortheuseofhistime,laboratory,andequipment.Iwouldalsoliketothank
ChristopherZotoforallhisguidance,patience,andtime.
![Page 7: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/7.jpg)
7
Introduction
Conjugatedcompoundscontaincarbon‐carbondoublebondsina1,3–
conformation;aconjugatedsystemisdependentontheoverlapofpatomicorbitals.The
classoforganicconjugatedcompoundsthatareofinterestforthisstudyisthe2,5–
diarylidenecyclopentanonedyes.Thesehighlyconjugatedfluorescentdyeshavereceived
attentionfortheirlargescopeofapplications.Thesecompoundshavebeenutilizedas
photosensitizers3,fluorescentsolventpolarityprobes4,5,fluoroionophores6,andnonlinear
opticalmaterials7.
Arecentapplicationofthesefluorescentcompoundsisatechnologythathasbeen
developedbyConstellation3Dknownasthefluorescentmultilayerdisc(FMD).Thisisan
opticaldiscthatusesfluorescentcompoundsasdigitalreceptorsinsteadofthenormal
digitalreflectionusedintraditionalopticaldiscstostoredata.Fluorescentcompoundsare
filledintothepitsofanFMD,andlightisabletotravelthroughtheclearFMDdiscs
unimpeded.Thisenablesthedisctocarryuptoapproximately100datalayers,muchlarger
thanthetraditional2layersonanormaldisc.Asaresultoftheabilityofthefluorescent
compoundstoachievepossibleexcitationtohigherorderenergystates,theFMD
technologycanhavecapacitiesofuptoaterabytewhilemaintainingthesamephysicalsize
ofatraditionalopticaldisc8.
Previousresearchon2,5–diarylidenecyclopentanonessuggestthattheycould
drawattentionforfeasibleapplicationsinseveralnewtechnologies.Theresearch
conductedbyConnorsandUcak‐Astarlioglu1reporttheelectronicstructureand
spectroscopicpropertiesforasetofunsubstituted2,5–diarylidenecyclopentanonesina
varietyofsolvents;thegenericchemicalstructureofthedyeisshowninFigure1.The
researchhasaprimaryfocusthatinvolvesstudyingtheelectronicabsorptionand
fluorescencepropertiesofallthetransconfigurationsofunsubstituted2,5–diarylidene
cyclopentanones(R=H)withn=1,2,and31.
![Page 8: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/8.jpg)
8
Figure1.GeneralStructureof2,5‐diarylidenecyclopentanones.
Thisprojectservesasanextensionofpreviousresearch,anditinvolvesstudyinga
derivativewithmethoxysubstitutedgroups(‐OCH3)(thatserveaselectrondonating
groups)bondedattheparapositionsonthephenylrings.Thespectroscopicand
photophysicalspectroscopicpropertiesof(2E,5E)‐2,5‐bis(4‐methoxycinnamylidene)‐
cyclopentanone(2dbmxcp)havebeenstudiedinavarietyoffourteennonpolar,polar
aprotic,andproticsolvents.Thechemicalstructureof2dbmxcpisshownbelowinFigure2.
Investigationofthespectroscopiccharacteristicsof2dbmxcpprovidevaluableinsightinto
thesolvatochromicandphotophysicalpropertiesofthecompoundinvarioussolvent
systems.
Figure2.Structureof(2E,5E)‐2,5‐bis(4‐methoxycinnamylidene)‐cyclopentanone(2dbmxcp).
Solvatochromismistheabilityofasubstancetochangecolorwithrespecttosolvent
polarity2.Inabsorptionandfluorescencespectra,amoleculethatexhibitssolvatochromic
propertiesundergoeseitherbathochromic(red)shiftsorhypsochromic(blue)shifts
dependingonthesolventpolarity.Pastsolvatochromicresearchofanalogousdyesshowa
bathochromicshiftwhentestingfromnonpolartopolaraproticsolvents1.AJablonskistate
energy‐leveldiagramcanbeusedtoexplainthespectralshifts.Thisdiagram(Figure3)
illustratestheelectronicenergystatesofamoleculeandthetransitionsbetweenthem.
![Page 9: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/9.jpg)
9
Morespecifically,thediagramisusedtoshowtheradiativeprocessofabsorptionand
fluorescencewithnonradiativesolventrelaxation.Investigationofthesolvatochromic
propertiesof2dbmxcpshowthatthereisabathochromic(red)shiftasthesolventpolarity
increases.
Figure3.Jablonskidiagramshowingfluorescencewithsolventrelaxation10.
Theprimaryobjectiveforthisprojectistoinvestigateandanalyzethespectroscopic
andphotophysicalpropertiesof2dbmxcpinvarioussolvents,andexplainthetrends
observed.Examinationofthephotophysicalpropertiesinvolveexperimentallydetermining
theabsorptionandfluorescencespectra,fluorescencequantumyields(Фf),and
fluorescencelifetimes(τf).
Quantumchemicalcalculationswereperformedon2dbmxcpattheDFTB3LYP/6‐
31G(d)leveloftheory.Theoreticalcalculationsconsistedofrunninggeometry
optimization,TD‐DFTspectralcalculation,andsolventcalculationsusingtheself‐
consistentreactionfieldpolarizablecontinuummodel(SCRFPCM).
![Page 10: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/10.jpg)
10
ExperimentalProcedures
1.Synthesisof(2E,5E)2,5bis(4methoxycinnamylidene)cyclopentanone(2dbmxcp)
2dbmxcpwassynthesizedpreviouslyandreadyfortestingatthestartofthe
project.Althoughthesynthesiswasnotconductedinthisproject,alookathowthe
moleculewassynthesizedprovidesvaluableinsighttothestructureandcompositionof
2dbmxcp.
Thecompound2dbmxcpwassynthesizedviaacrossedaldolcondensationreaction
betweencyclopentanone(1moleq)with(E)‐4‐methoxycinnamaldehyde(2moleq)inthe
presenceofNaOH(seeFigure4).Anorange‐coloredsolidprecipitatedoutofsolution.The
crudematerialwascollectedbyvacuumfiltrationandrecrystallizedfromtoluene,yielding
lustrousorangecrystals.1HNMRspectroscopywasusedforstructuralidentificationof
2dbmxcp.Both1HNMRinCDCl3andIRspectraldataarepresentedinFigures5‐7.Purity
wasconfirmedbyTLC(showingonespotupondevelopment).
Figure4.Reactionschemeforthesynthesisof2dbmxcp.
![Page 11: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/11.jpg)
11
1HNMRSpectraof2dbmxcp(forstructuralconfirmation)
Figure5:1HNMR2dbmxcpd2.5‐8.0ppm
![Page 12: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/12.jpg)
12
Figure6:1HNMR2dbmxcpd6.0‐8.05ppm
![Page 13: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/13.jpg)
13
Figure7:1HNMR2dbmxcpd1.95‐4.05ppm
![Page 14: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/14.jpg)
14
2.SpectrophotometricAnalysis–AbsorbanceandFluorescenceSpectraTheUV/VISabsorptionspectraweremeasuredwithaPerkinElmer®Lambda35
UV/VISspectrometer(2nmband‐pass).Thefluorescenceemissionspectrawerecollected
usingaPerkinElmer®LS50BluminescencespectrophotometerequippedwithanR928
phototubedetector.
3.FluorescenceQuantumYieldDeterminationThefluorescenceyieldofacompound(Φf)isdefinedastheratioofphotonsemitted
tothenumberofphotonsabsorbedbythecompound,andcanbecalculatedbythe
followingequation:
(Eq.1)
Inthisequation,Φsisthefluorescencequantumyieldoftheknownstandard
(obtainedfromliterature),Aistheabsorbancevalueatafixedwavelengthofexcitation,n
istherefractiveindexofthesolventsused,andDisthecalculatedareaunderthecorrected
emissionspectrum.Thesubscriptsreferstothestandard,andthesubscriptcreferstothe
compoundbeinginvestigated.
Thefluorescencequantumyieldsof2dbmxcpwerecalculatedbypreparingtwo
stocksolutionsofthecompoundandasolventwithamaximumabsorbanceof0.5.Two
stocksolutionsweremadeinorderfortheproceduretobeperformedtwicefor
reproducibility.Absorptionwasmeasuredusingsolventsofdifferingpolaritiesranging
frompolarprotic,polaraprotic,andnonpolarsolvents.Allofthesolventswere
commerciallyavailableandspectrophotometricgrade.Thesolventsusedwere:methanol,
ethanol,n‐butanol,1‐propanol,2‐propanol,chloroform,dimethylsulfoxide,acetonitrile,
acetone,ethylacetate,dichloromethane,toluene,benzene,andcarbontetrachloride.
Thestocksolutionswerethendilutedtenfoldandtheopticalabsorptionspectraof
boththestocksolutionsandthedilutedsolutionswerecollected.Thefluorescence
emissionspectrumofthetenfolddilutionswererecorded,fixingtheexcitationwavelength
![Page 15: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/15.jpg)
15
atλ=450nm.Absorptionandfluorescenceemissionspectrawereobtainedforallfourteen
standardstocksolutions,andfluoresceinin0.1MNaOH(Φf=0.95)9.Thediluted
fluoresceinsolutionwasre‐measuredforeachsolventinordertokeepthedataconsistent,
andtoaccountforinstrumentresponse.MicrosoftExcel®wasusedtoconvertspectraldata
fromwavelengthunitstowavenumbers.ThedatawasthenimportedintoMathcad®,which
wasusedtocorrectthefluorescenceemissionspectraandcomputethefluorescence
quantumyields.AppendixAillustratesanexampleofafluorescencequantumyieldcalculationfor2dbmxcpinchloroform.
Inordertocorrectthefluorescenceemissionspectraforinstrumentresponse,the
literatureemissionspectrumofN,N‐dimethylamino‐3‐nitrobenzene(N,N‐DMANB)was
comparedtotheexperimentalemissionspectrumofN,N‐DMANBmeasuredusingtheLS‐
50Bstatus.Scalefactorsweredeterminedevery50cm‐1between12,500and22,200cm‐1.9
4.Fluorescencelifetimedetermination
Thefluorescencelifetimeofacompound(τf)isdefinedastheinverseofthesumof
thefirst‐orderradiativeandnonradiativeratesofdecay:
τf=1/(kf+knr) (Eq.2)
whereknr=kic+kisc.Thefluorescencelifetimes(τf)of2dbmxcpweremeasuredinthe
followingfivesolvents:ethanol,1‐propanol,acetone,chloroform,andtoluene.
Fluorescencelifetimesof2dbmxcpweremeasuredusingaPhotonTechnology
InternationalfluorescencelifetimespectrometerequippedwithaGL‐3300nitrogenlaser
andGL‐302dyelasercompartments.Inordertopreventfluorescencequenchingby
oxygen,thesolutionswereproperlydegassedbypurgingwithnitrogenpriortomeasuring
thefluorescencedecaycurves.FeliX32computersoftwarewasusedtogeneratethetime‐
dependentfluorescencedecayspectra.Thefluorescencedecayprofileoftheinstrument
responsefunction(IRF)wasgeneratedatthesamemaximumintensityasthedecaycurve
ofthecompoundbeinginvestigated.Ludox(Aldrich),acolloidalsuspensionofsilica,was
usedastheIRFtoscattertheexcitationbeam.Neutraldensityfilterswereusedtoadjust
![Page 16: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/16.jpg)
16
thefluorescenceintensityoftheIRFprofile.ThefluorescencedecayandIRFscatterdata
wereanalyzedusingacurve‐fittingprocedure.Thebest‐fitcurvesweredeterminedby
statisticallyanalyzinghowwellthefieldfitcurvefittedthedecaysamplecurve.Anexample
worksheetforthefluorescencelifetimedeterminationcanbefoundinAppendixB.
![Page 17: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/17.jpg)
17
ResultsandDiscussion
1.Introduction
Theelectronicabsorptionandfluorescencepropertiesof2dbmxcpwerestudiedina
varietyoffourteenpolarprotic,polaraprotic,andnonpolarsolvents.Experimentaldata
showthatthesolvatochromicpropertiesexhibitabathochromic(red)shiftincolorwhen
goingfromnonpolartopolarsolvents.ThisshiftinspectraisillustratedinFigure9.The
resultingsolutionsdifferedincolor,rangingfromlimegreen,tolightgreen,toyellow,and
thentoorangewithrespecttoanincreaseinsolventpolarity;illustratingthesolvent’s
influenceonlightabsorption.Theabsorptionandfluorescencepropertiesweremeasured,
andphotophysicalpropertieswereinvestigated,whichinvolvedmeasuringfluorescence
quantumyieldsandfluorescencelifetimesinvarioussolvents.Boththefirst‐order
radiativeandnonradiativeratesofdecaywerecalculatedfromthequantumyieldand
lifetimedatainethanol,1‐propanol,toluene,acetone,andchloroform.Finally,quantum
chemicalcalculationswereperformedon2dbmxcpattheDFTB3LYP/6‐31G(d)levelof
theory,whichinvolvedcarryingoutgeometryoptimizationinthegasphase,alongwithTD‐
DFTspectralcalculationsmodeledinthegasphase,andinethanolandtoluene
environments.
Inordertogainabetterunderstandingoftheexperimentalresultsand
characteristicsfoundfrom2dbmxcp,thissectionwilldoacomparisonstudywithan
analogouscompound,2,5‐bis(p‐dimethylaminocinnamylidene)‐cyclopentanone(2dbma).
2dbmaisalsoa2,5–diarylidenecyclopentanonedye,anditalsocontainselectron
donatinggroups(dimethylamino)substitutedonthearylmoieties.Figure8showsthe
chemicalstructureof2dbma.
Figure8.ChemicalStructureof2dbma
![Page 18: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/18.jpg)
18
2.AbsorptionandFluorescenceProperties
Theabsorptionandfluorescencespectraof2dbmxcpinsixsolventsareshownin
Figure9.Thisfigureillustratesthesolvatochromicpropertiesofthecompound,andshows
thatthecompoundundergoesbathochromicshiftswhengoingfromnonpolar,topolar
aproticandproticsolvents.Figure9showsthatthereisamorepronouncedredshiftinthe
fluorescencespectrathanthatintheabsorbtionspectra.2dbmxcpshiftsinthe
fluorescencespectrafrom518nminCCl4to620nminMeOH.Aninterestingexperimental
findingwasthatthecompoundhashighfluorescencequantumyieldinthepolarprotic
solvents,whichwasuncharacteristicofanalogousdyes.Typicallyfluorescencesignal
intensityislowerinpolarproticsolventsduetothequenchingofthecompoundinthe
solvent.
Thespectroscopicandphotophysicalcharacteristicsof2dbmxcparepresentedin
Table1.Alsoincludedinthetablearethesolventpolarityfunction(∆f)andtheempirical
scaleofsolventpolarity(ET(30))ofeachsolvent,whichareempiricalvaluesbasedon
literature2.Thesolventpolarityfunction(∆f)isdependentonboththedielectricconstant
(ε)andtherefractiveindex(n)ofthesolvent.Thisrelationshipisgivenby:
€
Δf =ε −12ε +1
−n2 −12n2 +1 (Eq.3)
TheET(30)empiricalsolventpolarityscaleisbasedonthechargetransfershiftofthefirst
maximumofabetaninedye2.
![Page 19: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/19.jpg)
19
Figure9.Absorbanceandemissionspectraof2dbmxcpinvarioussolvents.
![Page 20: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/20.jpg)
20
Table1.Spectroscopicandphotophysicalcharacteristicsof2dbmxcpinvarioussolvents.
Solvent νabs(cm‐1)
νflu(cm‐1) Δf* ET(30)*
(kcalmol‐1) ϕfτf(ns)
kf(s‐1)
knr(s‐1)
MeOH22831(438nm)
16119(620nm) 0.3093 55.4 0.15 ‐‐‐ ‐‐‐ ‐‐‐
EtOH22831(438nm)
16689(599nm) 0.2887 51.9 0.15 0.71 2.08x108 1.20x109
1‐PrOH22779(439nm)
16813(595nm) 0.2746 50.7 0.15 0.72 2.08x108 1.18x109
1‐BuOH22727(440nm)
18620(537nm) 0.2642 50.2 0.08 ‐‐‐ ‐‐‐ ‐‐‐
2‐PrOH23202(431nm)
17098(585nm) 0.2769 48.4 0.17 ‐‐‐ ‐‐‐ ‐‐‐
DMSO22779(439nm)
17392(575nm) 0.2637 45.1 0.16 ‐‐‐ ‐‐‐ ‐‐‐
ACN23419(427nm)
17558(570nm)
0.3054 45.6 0.07 ‐‐‐ ‐‐‐ ‐‐‐
Acetone23529(425nm)
17696(565nm) 0.2843 42.2 0.04 0.46 1.00x108 2.07x109
DCM23095(433nm)
18580(538nm) 0.2171 40.7 0.07 ‐‐‐ ‐‐‐ ‐‐‐
Chloroform22989(435nm)
18561(539nm) 0.1491 39.1 0.09 0.53 1.74x108 1.71x109
EtOAc23923(418nm)
18903(529nm) 0.1996 38.1 0.02 ‐‐‐ ‐‐‐ ‐‐‐
Benzene23641(423nm)
18979(527nm) 0.0031 34.3 0.005 ‐‐‐ ‐‐‐ ‐‐‐
Toluene23753(421nm)
18979(527nm) 0.0131 33.9 0.003 0.27 1.18x107 3.69x109
CCl423810(420nm)
19302(518nm) 0.0119 32.4 0.001 ‐‐‐ ‐‐‐ ‐‐‐
*2BothΔfandET(30)valuesweretakenfromSuppan,P.andGhonheim,N.,inSolvatochromism,TheRoyalSocietyofChemistry,Cambridge,1997.
![Page 21: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/21.jpg)
21
Theabsorptionandfluorescencecharacteristicswereplottedagainstboththe∆f
andtheET(30)empiricalsolventpolarityscales,asillustratedinFigures10and11.The
figuresshowthatsolvatochromicpropertiesareobserved,forboththe∆fandtheET(30),
havingboththeabsorptionandfluorescentwavenumbersdecreasingwithrespectto
solventpolarity.ThedecreaseismoreprevalentintheET(30)scale,whereasthe∆fFigure
showsonlyaveryslightdecrease,signifyingonlyminorsolvatochromism.
Figure10.Plotofmaximumabsorptionandfluorescentwavenumbersif2dbmxcpagainstΔfinpolarprotic,polaraprotic,andnonpolarsolvents.Alcoholsarerepresentedasthecleardiamondandsquareshapes.
Inthecaseof2dbma,thecompoundexhibitedstrongersolvatochromicproperties,
resultinginalinewithgreaterslope.Theobservedsolvatochromicpropertiesin2dbma
wereconsistentwithachargetransferelectronictransition.
y=‐0.2414x+2.373R²=0.4047
y=‐0.701x+1.9382R²=0.6137
0
0.5
1
1.5
2
2.5
3
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
(νab
s and
νfl)
/104
(cm
-1)
Δf
Absorption
Fluorescence
![Page 22: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/22.jpg)
22
Figure11.Plotofmaximumabsorptionandfluorescentwavenumbersof2dbmxcpagainstET(30)invarious
solvents.Alcoholsarerepresentedascleardiamondandsquareshapes.
Figure12.Plotofmaximumabsorptionandfluorescentwavenumbersof2dbmaagainstΔfinvariousprotic,
aprotic,andnonpolarsolvents.Alcoholsaredesignatedbytheredshapeddiamondsandsquares.
y=‐0.0047x+2.5296R²=0.64344
y=‐0.0123x+2.3276R²=0.77393
0
0.5
1
1.5
2
2.5
3
30 35 40 45 50 55 60 65
(νab
s and
νfl)
/104
(cm
-1)
ET(30) (kcal mol-1)
Absorbance
Fluorescence
![Page 23: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/23.jpg)
23
Figure13.Plotofmaximumabsorptionandfluorescentwavenumbersof2dbmaagainstET(30)invarious
typesofsolvents.Alcoholsarerepresentedbytheredshapeddiamondsandsquares.
Experimentalresultsfromthefluorescencelifetimes(τf)andfluorescencequantum
yields(Φf)showasolventdependenceforthe2dbmxcp.Anobservationthatwasmadeis
thatthelifetimesandquantumyieldschangedproportionallyfromonesolventtoanother.
Thealcoholshadthehighestquantumyieldsoutoftheentiresolventset,andwere
experimentallydetermined(outofthefivesolventstested)tohavethehighestlifetimes
values.ThelifetimevaluesarelistedinTable1,andtherangeoflifetimeswentfrom0.27
nsintolueneto0.72nsin1‐propanol.
TheΦfandτfparameterswereusedtocalculatethefirst‐orderradiative(kf)and
nonradiativedecayconstantsofthefirstexcitedsingletstateof2dbmxcp.Thefirst‐order
radiativedecayconstantcanbecalculatedbythefollowingequation:
(Eq.4)
![Page 24: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/24.jpg)
24
whereΦfisthefluorescencequantumyieldandτfisthefluorescencelifetimeofthe
decayingsample.Thefirstorder‐nonradiativedecayconstant(knr),canbecalculatedfrom
thefollowingequation:
€
knr =1Φ f
−1
k f (Eq.5)
Althoughonlyfivefluorescencelifetimesweremeasured,theknrappearedtogenerally
decreaseasthesolventpolarityincreased.AsshowninTable1,theknrwentfrom3.69x109
s‐1intolueneto1.20x109s‐1inethanol.Theenerygaplawisusedtopredictthe
exponentialdependenceofkic(internalconversion)onΔE,theenergygapbetweenS0and
S1.Thislawisexpressedbythefollowingequation:
€
kic = Ce−αΔE ,ΔE = ES1− ES0
(Eq.6)
whereCandαareconstants.Inaccordancewiththeenergygaplawofinternalconversion
forexcitedstates,knrisexpectedtoincreaseastheevergygapbetweenS0andS1decreases
duetovibrationaloverlapbetweentheS0andS1states.WhentheS0toS1energygap
increases,thevibrationaloverlapbetweentheenergylevelsofS0andS1decreases,thus
yieldingadecreaseintherateofinternalconversion.Essentially,thisequationstatesthat
askicincreasesasΔEdecreases,andthusΦfdecreases,assumingkiscandkfareconstant.
With2dbmathebehaviorofknrcanbeexplainedbytheenergygaplaw,butwith2dbmxcp,
thehigherquantumyieldsshowanti‐energygapbehavior.
![Page 25: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/25.jpg)
25
Thefluorescencequantumyieldswereplottedagainstthemaximumfluorescent
wavenumbers(νfl)inavarietyofpolarprotic,polaraprotic,andnonpolarsolvnets,shown
inFigure14.
Figure14.Plotofthefluorescencequantumyieldof2dbmxcpagainstνflinallsolvents.
Figure14illustratesthatthequantumyieldsincreaseforsolventswiththestrongest
polarity.Thisisalsotrueforthefluorecencelifetimes,thesovlentswiththelargerpolarity
wereexperimentallyproventohavelongerfluorscencelifetimes.
Both2dbmxcpand2dbmageneratedsimilarquantumyieldsinthehigh
wavenumbersregions,althoughtheydidnothavethesamequantumyieldsinthealcohols,
2dbmxcpgeneratedhigherquantumyieldsinthealcoholsthan2dbma.
For2dbmatheplotofthefluorescencequantumyieldagainstνflillustratesaparabolic
relationship.Itisobservedthatthequantumyieldreachesamaximumforsolventsof
0.0000
0.0200
0.0400
0.0600
0.0800
0.1000
0.1200
0.1400
0.1600
0.1800
0.2000
12000 14000 16000 18000 20000
Φf
νfl (cm-1)
2‐PrOH
DMSOMeOHEtOH 1‐PrOH
ACN1‐BuOHDCM
Acetone
EtOAc
CCl4Benzene
Toluene
Chloroform
![Page 26: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/26.jpg)
26
moderatepolarity,andthisobservationisconsistentwiththeinterpretationofthetrendin
knr.Rearrangmentofequations4and5withτf=1/(kf+knr),yieldsanexpressionforthe
fluorescencequantumyieldofanelectronicsystem:
€
Φ f =k f
k f + knr (Eq.7)
€
Φ f =k f
k f + kic + kisc
whereknr=kic+kisc.For2dbma,thequantumyieldislowatlowνflvalues.Whenthe
polarityofthesolventincreasesΦfincreasesduetothedecreasingrateinintersystem
crossing.Whentheνflincreasesinmorepolarsolvents,therateofinternalconverstion
increasesandproceedstodominateoverthecompetingdecreasingrateofintersystem
crossing,resultinginalowerquantumyield,andthusaparabolictrendwhenplottingΦf
vs.νfl.For2dbma,thistrendissupportedbytheenergygaplaw.
With2dbmxcp,thefluorescencequantumyieldagainstνfldoesnotillustratea
parabolicrelationship,asseeninFigure14.Inthiscasetherateofinternalconversion
doesnotproceedtodominateoverthecompetingrateofinterststemcrossinginmore
polarsolvents.Duetothisanti‐energygapbehavior,theplotofΦfvs.νflonlyillustratesthe
decreasingtrendinkisc,andthushigherquantumyieldsareobservedinthemorepolar
solvents.Thisexplanationillustratesthatthequantumyielddependsonthecompitition
betweenkf,kic,andkisc.
Acomparisonof2dbmaand2dbmxcpinsolventsofhighpolaritysuchasethanol
andmethanolcanbeusedtosupporttheexplanationoftheobservedhigherquantum
yieldsseenin2dbmxcp,andalsohelpinexplainingtheobservedanti‐energygaplaw
behavior.
In2dbmxcp,theνflinbothMeOHandEtOHissignificantlylargerthan2dbma,as
seeninTable2.ThismeansthattheenergygapbetweentheS0andS1statesislarger
whichmeansthattheΔEislarger.Whenusingtheenerygaplawequation,havingalarger
ΔEyieldsalessdominantrateofkic,andthusalargerquantumyield.Since2dbmahad
![Page 27: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/27.jpg)
27
smallerνflinbothMeOHandEtOH,thisleadstoasmallerΔE,largerkic,andthusasmaller
quantumyield.
Table2.Spectroscopicandphotophysicalpropertiesofboth2dbmxcpand2dbmainMeOHandEtOH.
2dbmxcp(vfl,cm‐1) 2dbma(vfl,cm
‐1)MeOH:16119(620nm) MeOH:13605(735nm)EtOH:16689(599nm) EtOH:13445(744nm)
Thesolventcalculationscomputationallyconductedinethanolandtoluenehelp
explainthelowquantumyieldandhighknrobservedfor2dbmxcpintoluene.Thisbehavior
canbeattributedtothelocationofthe(n,π*)orbitaltypeanditsinfluenceonintersystem
crossing.AsshowninFigure15,thekiscfor(π,π*)(n,π*)issignificantlylargerthanthe
kiscfor(π,π*)(π,π*).ThisisdeterminedbyElSayed’srule12,whichstatesthattherateof
intersystemcrossingisfasterandmoreefficientbetweentwodifferentorbitaltypesthan
twoofthesameorbitaltype.Theoveralleffectisthatkiscandknrdecreaseassolvent
polarityincreases,whichisworkinginoppositionofthetrendobservedinkiccausedbythe
energygaplaw.Thuswithmorepolarsolvents,suchasethanol,slowkiscoccurswhich
resultsinalargerquantumyield.
Figure15.Solventcalculationsof2dbmxcpinTolueneandEthanol.
!"#$%&%''
!
()*+&"#'
!"##$%& '!&(n,!*)
!"()$%& '!(n,!*)
!"*($%& '+&(!,!*)
!"**$%&
+"#,$%&
+"-.$%&
(n,!*)
(!,!*)
(!,!*)
/.&
/!&
/+&
!"*-$%&
/.&
/!&
/+&
(n,!*)
(!,!*)
(!,!*)
',&',&
!"--$%&
+"#.$%&
+"-+$%&
!0&1&,",,.& !0&1&,"+*&
,-'
,.-'
,.-'
,-'
,.-'
23456&7849&1&:3;<$&
':=>6&7849&1&4?3::&'+&(!,!*)
![Page 28: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/28.jpg)
28
Lippert‐MatagaPlotswerecreatedfor2dbmxcpfromthespectroscopicdataandare
showninFigures17,18,and19.Figure17wasconstructedwithallofthesolvents,
whereasFigure18hasjustthepolarandnonpolarsolvents,whichyieldedalargerR2
value.Lippert‐MatagaplotsareusedtodirectlyrelatetheStoke’sshiftforamoleculein
differentsolventstothesolventpolarityfunction.TheStokesshift(Δν),istheenergy
differenceinwavenumbersbetweentheabsorptionandfluorescencemaxima,related
linearlytoΔfbytheLippert‐Matagaequation11:
€
Δν =2Δµ2
hca3Δf + Δν 0 (Eq.8)
where∆µ=µe‐µgisthedifferencebetweentheexcited‐stateandground‐statedipole
moments,hisPlank’sconstant(6.626x10‐34J),cisthespeedoflightinavacuum
(2.998x108ms‐1)andaistheOnsagercavityradiusforthesphericalinteractionofthe
dipoleinasolvent.
Lippert‐Matagaplotscreatealinearrelationshipbetweenthestokesshift(Δν)and
Δf,yieldingastraightlinewithaslopethatisequalto2Δμ2/hca3.Bothaandμgare
calculatedcomputationally,andareputintotheequationtocalculatetheexcitedstate
dipolemoment.ComputedresultsyieldanOnsagercavityradiusequalto5.86Åanda
groundstatedipolemoment(µg)of2.04D.UtilizingtheLippert‐Matagacalculation
method,theexcitedstatedipolemomentsof2dbmxcpwerecalculatedtobe10.3D(all
solvents),and11.62D(non‐alcohols).
2dbmxcpyieldsasmallerdipolemomentcontraryto2dbma,whichgivesan
excited‐statedipolemomentof22.23D.Theelectronicdistributionisinternallytransferred
toalargerdegreefor2dbmathan2dbmxcpingoingfromthegroundstatetotheexcited
singletstate.Thisobservationistakenfromcomputingthemolecularorbitalsandthe∆µ
magnitudebetweenthegroundandexcitedstates.Soconceptually,itappearsthat
2dbmxcpwouldhaveasmallerchargetransfer,duetothesmallincreaseindipolemoment.
![Page 29: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/29.jpg)
29
Additionally,lookingatthecomputedmolecularorbitalsof2dbmxcpincomparison
to2dbmashowsthatthereisaclearchargetransferfromthehomotothelumostagein
2dbma.With2dbmxcp,thechargeistransferredtoalesserdegree,asshowninFigure16.
AccordingtoresearchconductedbyMorimoito13,fluorescenceofanexcitedmoleculewith
asmallerchargetransfercannotbequenchedwellbyanalcoholbecauseoftheweak
interactiononthecarbonyloxygen,whichisconsistentwiththeresultsreportedhere.
Figure16.Computedmolecularorbitalsof2dbmxcpand2dbma.
TheLippert‐Matagacalculationcanbereasonedinamorequantitativewayby
calculatingtheunit‐chargeseparation.AccordingtoLacowicz9,4.8Distheelectronicdipole
momentthatresultsfromachargeseparationofoneunitchargeby1angstromoflength.
Withthatinformation,ifthe11.62D(non‐alcohols)calculationisused,itiscomparableto
aunit‐chargeseparationof2.4angstroms.For2dbma,thedipolemomentof22.23Dis
comparabletoaunitchargeseparationof4.6angstroms.
S1 (!,!*) S1 (CT, !,!*)
!"#$%&'( !"#$)(
![Page 30: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/30.jpg)
30
Figure17.Lippert‐MatagaPlotofStoke'sshift(Δν)againstΔfof2dbmxcpinallsolvents.
Figure18.Lippert‐MatagaPlotofStoke'sshift(Δν)againstΔfof2dbmxcpinpolarproticandnonpolarsolvents.
y=4596.4x+4347.8R²=0.41668
0
1000
2000
3000
4000
5000
6000
7000
8000
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Δν
(cm
-1)
Δf
y=3384.2x+4454.4R²=0.53919
0
1000
2000
3000
4000
5000
6000
7000
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Δν
(cm
-1)
Δf
![Page 31: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/31.jpg)
31
Figure19.Lippert‐MatagaPlotofStoke'sshift(Δν)againstΔfof2dbmxcpinallsolvents.Alcoholsare
designatedastheredsquares.
y=3384.2x+4454.4R²=0.53919
y=46006x‐7201.5R²=0.6376
0
1000
2000
3000
4000
5000
6000
7000
8000
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
∆ υ
(cm‐1)
∆f
PolarProticandNonpolarPolarAprotic
![Page 32: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/32.jpg)
32
3.QuantumChemicalCalculations DFTB3LYP/6‐31G(d)geometryoptimizationaswellasTD‐DFTspectralcalculations
wereperformedon2dbmxcp.MolecularorbitalsofthiscompoundareshowninFigure20.
CalculationsshowthattheS0→S1transitionwasfoundtobe(π,π*)andtheS0→S2
transitionwaspredictedtobe(n,π*)Electrondensityisdistributedevenlyacrossthe
conjugatedπsysteminthecomputedHOMO,butgetstransferredtoaminordegree
closertothecarbonylcenterinthecomputedLUMOasillustratedinFigure20.Table3
showsthemolecularorbitalcalculationsof2dbmxcpaswellasthecorresponding
oscillatorstrengths(f)foreachtransition.Table4showstheTD‐DFTspectralcalculations
attheB3LYP/6‐31G(d)leveloftheoryinethanolandToluene.
Table3.ComputedMolecularOrbitalCalculationsof2dbmxcp.
Figure20.ComputedMolecularOrbitalsof2dbmxcp.
HOMOLUMO S1(π,π*)λ=449.72nm f=1.9045
HOMO‐2LUMO S2(n,π*)λ=445.41nm f=0.0000
![Page 33: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/33.jpg)
33
Table4.2dbmxcpTD‐DFTSpectralCalculationsinEthanolandToluene
LevelofTheory:DFTB3LYP/6‐31G(d)
Solvent MolecularOrbitalCalculations Experimentalλmax
PercentError(%)
DipoleMoment(µg)
EtOH HOMOLUMO S1(π,π*) λ=483.76nm f=2.1424 9.45 HOMO‐2LUMO S2(n,π*) λ=417.49nm f=0.0050
438nm
4.91
2.78D
Toluene HOMOLUMO S1(π,π*) λ=478.89nm f=2.1470 12.08 HOMO‐2LUMO S2(n,π*) λ=430.84nm f=0.0004
421nm
2.28
2.38D
![Page 34: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/34.jpg)
34
Conclusions
Theexperimentalresultsgeneratedfromthemeasuredphotophysicaland
spectroscopicpropertiesindicatethat2dbmxcpexhibitssolvatochromicpropertieswhen
testedfromnonpolartopolarprotictopolaraproticsolvents.2dbmxcpshows
bathochromic(red)shifts,andlessred‐shiftingoccurredinthealcoholswhencomparedto
ananalogouscompound2dbma,signifyinglesssolvatochromism.Thespectroscopic
characteristicsshowalinearcorrelationinboththeΔfandET(30)scale.2dbmxcp
generatedhigherquantumyieldsinthealcoholsthan2dbma.Thiscanbeattributedto
lowersolvatochromism,higher∆E,andlowerkic.Thesefactorscombinedwillproduce
higherquantumyields.Whenanalyzingthecalculatedmolecularorbital’sof2dbmxcpand
2dbma,therewasaclearindicationthattherewasasmallerchargetransferin2dbmxcp
than2dbmawhentransitioningfromthehomotothelumo.Thequantumchemical
calculationsof2dbmxcpindicatedthatS1is(π,π*)andS2is(n,π*).Additionallyitwas
determinedthatthequantumyieldsandfluorescencelifetimesvaryuponthenatureofthe
solvent.Themostpolarsolventsexhibitedthelargestquantumyieldsandlongestlifetimes.
![Page 35: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/35.jpg)
35
References
1. Connors,R.E.;Ucak‐Astarlioglu,M.G.J.Phys.Chem.A2003,107,7684.2. Suppan,P.;Ghonheim,N.Solvatochromism;RoyalSocietyofChemistry:Cambridge,
19973. Barnabus,M.V.;Liu,A.;Trifunac,A.D.;Krongauz,V.V.;Chang,C.T.J.Phys.Chem.1992,
96,212.4. Pivovarenko,V.G.;Klueva,A.V.;Doroshenko,A.O;Demchenko,A.P.Chem.Phys.Lett
2000,325,389.5. Das,P.K.;Pramanik,R.;Banerjee,D.;Bagchi,S.Spectrochim.Acta.A.2000,56,2763.6. Doroshenko,A.O.;Grigorovich,A.V.;Posokhov,E.A.;Pivovarenko,V.G.;Demchenko,
A.P.Mol.Eng.1999,8,1997. Kawamata,J.;Inoue,K.;Inabe,T.Bull.Chem.Soc.Jpn.1998,71,2777.8. Walker,E.P.;WenyiFeng;YiZhang;HaichuanZhang;McCormick,F.B.;Esener,
S.;Call/RecallInc.,SanDiego,CA.3DParallelreadoutina3Dmultilayeropticaldatastoragesystem.OpticalMemoryandOpticalDataStorageTopicalMeetingg,2002.InternationalSymposium.p.147‐149
9. Lakowicz,J.R.PrinciplesofFluorescenceSpectroscopy,2nded.;Springer:NewYork,2004.
10. “Epi‐FluorescencewiththeZeissUniversal.”UniversityofVictoria–Web.UVic.ca.21Sept.2005.Web.25Mar2011.http://web.uvic.ca/ail/techniques/epi‐fluorescence.html.
11. Nad,S.;Pal,H.J.Phys.Chem.A2001,105,109712. El‐Sayed,M.A.J.Chem.Phys.1963,38,2864.13. Morimoto,A.,Yatsuhashi,T.,Shimada,T.,Biczok,L.,Tryk,D.andInoue,H.
RadiationlessDeactivationofanIntramolecularChargeTransferExcitedStatethroughHydrogenBonding:EffectofMolecularStructureandHard–SoftAnionicCharacterintheExcitedState.J.Phys.Chem.A2001,105,10488‐10496.
![Page 36: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/36.jpg)
36
AppendixA:FluorescenceQuantumYieldCalculation
![Page 37: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/37.jpg)
37
![Page 38: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/38.jpg)
38
![Page 39: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/39.jpg)
39
![Page 40: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/40.jpg)
40
![Page 41: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/41.jpg)
41
AppendixB:FluorescenceLifetimeSampleCalculationFluorescencelifetimecalculationof2dbmxcpinEthanol2dbmxcpinEthanol(sample1)*************************************************AnalysisFunction: SatApr022011at14:26******one‐to‐fourexponentials***********InputValues*****Decaycurve :A1430:578_s1IRFcurve :normalize(A1430:430_irfs2)StartTime :40.91EndTime :55.06OffsetwillbecalculatedShiftwillbecalculatedPre‐exp.1 :1Lifetime1 :1*****Statistics*****Jobdoneafter4iterationsin0.063sec.Fittedcurve :FLDFit(2)Residuals :FLDResiduals(2)Autocorrelation :FLDAutocorrelation(2)DeconvolvedFit :FLDDeconvoluted(2)Chi2 :2.419DurbinWatson :0.5903Z :‐0.1885Pre‐exp.1 :1.94 ±2.365e‐002(100 ±1.219%)Lifetime1 :0.6975 ±7.571e‐003F1 :1Tau‐av1 :0.6975Tau‐av2 :0.6975
![Page 42: The Photophysical Properties of a Symmetrically ... · This project extends interest into the photophysical properties of symmetrically substituted 2,5 – diarylidene cyclopentanone](https://reader033.fdocuments.in/reader033/viewer/2022041616/5e3b691fd4df2f2edc7c15fb/html5/thumbnails/42.jpg)
42
Offset :16.63Shift :‐0.184*************************************************