Excited State Structure Correlates with E ffi cient Photoconversion in Unidirectional Motors - Roy et al. - 2021 - Unknown

《Excited State Structure Correlates with E ffi cient Photoconversion in Unidirectional Motors - Roy et al. - 2021 - Unknown》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在學(xué)術(shù)論文-天天文庫(kù)。

pubs.acs.org/JPCLLetterExcitedStateStructureCorrelateswithE?cientPhotoconversioninUnidirectionalMotorsPalasRoy,AndyS.Sardjan,ArjenCnossen,WesleyR.Browne,BenL.Feringa,*andStephenR.Meech*CiteThis:J.Phys.Chem.Lett.2021,12,3367?3372ReadOnlineACCESSMetrics&MoreArticleRecommendations*s?SupportingInformationABSTRACT:Thedesignofunidirectionalphotomolecularmotorsdemandsacriticalunderstandingofanultrafastphotochemicalisomerization.Anintermediatedarkexcitedstatemediatesthereactionviaaconicalintersection(CI)withthegroundstate,butacorrelationbetweenmolecularstructureandphotoisomerizatione?ciencyhasremainedelusive.HerefemtosecondstimulatedRamanspectroscopycapturesvibrationalspectraofthedarkstateinasetofmolecularmotorsbearingdi?erentsubstituents.Adirectcorrelationbetweenisomerizationquantumyield,darkstatelifetime,andexcitedstatevibrationalspectrumisfound.Electronwithdrawingsubstituentsleadtoactivityinlowerfrequencymodes,whichwecorrelatewithapyramidalizationdistortionattheethylenicaxleoccurringwithin100fs.Thisstructureisnotformedwithanelectrondonatingsubstituent,wheretheaxleretainsdoublebondcharacter.Furtherstructuralreorganizationisobservedandassignedtoexcitedstatereorganizationandchargeredistributiononthesub-picosecondtimescale.Thecorrelationofthedarkstatestructurewithphotoconversionperformancesuggestsguidelinesfordevelopingnewmoree?cientmotorderivatives.Arti?cialunidirectionalphotochemicallydrivenmotorsarephotoisomerizationaroundthealkeneaxle,givingrisetoaapowerfultoolforgeneratingmechanicalenergyonametastablegroundstatewithayieldof5?20%depending1?4uponthesubstituent.13Thesecondstepisathermallymolecularscalebyabsorptionoflight.Theyhavebeenused2,14inawiderangeofapplicationsfromultrafastresponsiveactivatedhelixinversiontocompletea180°rotation.The5?8processisrepeatedwithasecondphotonabsorptionandmaterialstocatalysis.Thebasisoftheirfunctionisaphotochemicalcis?transisomerizationinastericallyover-thermalizationsteptodriveafullcyclerotation.Thus,thecrowdedalkene,whichfacilitatesunidirectionalrotationofthethermalstepisratelimiting,whilethephotochemicalstepmotor.9?12Secondgenerationmotorswitha“stator”?uorenedeterminesthequantumyield.ringlinkedtoa“rotor”moietythroughadoublebond“axle”ThephotochemicalstephasbeenstudiedtheoreticallyandDownloadedviaBUTLERUNIVonMay16,2021at08:58:11(UTC).(Figure1)havethefastestratesofrotation.9AschematicofshowntoinvolveultrafaststructuraldynamicsintheexcitedtheiroperationisshowninFigure1.The?rststepinvolvesstateleadingtoaconicalintersection(CI)withtheelectronicgroundstate,fromwhicheithertheisomerizedmetastable15,16productortheoriginalstatemaybegenerated.TheSeehttps://pubs.acs.org/sharingguidelinesforoptionsonhowtolegitimatelysharepublishedarticles.correspondingpotentialenergydiagramisshowninFigure1.However,exploitationofthesesecondgenerationmotorsmaybelimitedbytherelativelylowyieldofthephotochemicalisomerization.Thishaspromptedinvestigationsofthee?ectsofvariationinsubstituentandstructure,withtheaimof17?20maximizingphotoisomerizatione?ciency.Thedevelop-mentofpredictivemodelsforfuturesynthesescertainlyrequiresadetailedunderstandingofthee?ectsofsuchstructuralmodi?cationsonexcitedstatedynamics.Forexample,FilatovandOlivuccihaveshowntheoreticallythatReceived:March4,2021Figure1.Dynamicsofalight-drivenmolecularmotor.StructureofAccepted:March22,2021themolecularmotor,thestepsinitsphotoconversionmechanism,andPublished:March30,2021aschematicofthecorrespondingpotentialenergysurface.Thegroundandexcitedstatepotentialenergysurfacesintersectattheconicalintersection,CI(R=H,OMe,Cl,CN).?2021AmericanChemicalSocietyhttps://doi.org/10.1021/acs.jpclett.1c007103367J.Phys.Chem.Lett.2021,12,3367?3372

1TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLettersubstituentssigni?cantlymodifythepathwayofstructuralevolutionneartheCIsconnectinggroundandexcitedstates,21thusmodifyingthephotochemicalyield.Earlierexperimentalstudiesofexcitedstatedynamicsinsecondgenerationmotorsusedultrafast?uorescencespectros-copytoprobetheprimaryphotochemicalstep.ArelaxationoftheFranck?Condon(FC)brightstateoccursinabout100fspopulatinganintermediate“darkstate”ontheexcitedstate22surface.Extendingthosestudiestoaseriesofsubstitutedsecondgenerationmotorsshowedthattheenergeticsandlifetimeofthedarkstateareafunctionofthesubstituent,whichalsomodi?edthephotoconversione?ciency,withtheyieldincreasingwithincreasingsubstituentelectronwith-drawingcharacter(speci?cally,CN=0.2,Cl=0.15,H=0.14,13OMe=0.05).Theweakdependenceofbrightstatelifetimeonsolventviscosity,coupledwiththeresultsofcomputationalcalculations,suggestedpyramidalizationatanaxleCatomasanimportantcoordinateintheexcitedstatestructural13,15,16,22dynamics.However,directexperimentalevidencefortheroleofapyramidalizationcoordinateindarkstateformationanddecayhasnotbeenprovidedtodate.Herewereportastructure?functioncorrelationbetweenRamanspectraofthedarkexcitedstateandphotoconversione?ciencyinaseriesofsubstitutedmolecularmotors.Speci?cally,wehavemeasuredgroundandultrafastexcitedstateRamanspectrainfourderivativesofthe?uorenemolecularmotor9-(2-methyl-2,3-dihydro-1H-cyclopenta[a]-naphthalen-1-ylidene)-9H-?uorene,withsubstituents(?R):?H,electronwithdrawinggroups(?CNand?Cl),andelectrondonatinggroup(?OMe).We?ndremarkabledi?erencesindarkstatevibrationalspectraforthesefourmolecules,withspeci?cRamanactivemodesswappingtheirrelativeintensitiesasafunctionofsubstituent.WeassignthisFigure2.Experimental(redsolidlines)andcalculated(blackverticaltosubstituentcontrolofthedarkstatestructureinthefourlines)steady-stateo?-resonance(orpreresonance)Ramanofthefourderivatives.Furtherstructuralevolutioninthedarkstateisalsomotorderivativesinthesolidstate.Ramanat532nm,resonanceresolved.wavelengthca.400nm.Theregion650?1000cm?1isincreasedbyaSteady-StateMeasurements.Steady-stateabsorptionfactorof5toshowtheweakspectralfeaturesmoreclearly.Thepeaksintheregion1300?1400cm?1areconnectedbyreddottedlinestospectraforthefourmotorderivativesinmethanolareshowninSupportingInformation,FigureS1.Theabsorptionmaximashowsubstituentdependence.Thesymbolsrepresentυ-stretching,δforR=OMe,H,Cl,andCNderivativesareat402,387,391,-bending,φ-pyramidalization,A-ethylenicaxle,R-substitutedand402nmrespectively,correspondingtoaπ?π*transition.naphthylrotor,andS-?uorenestator.Quantumchemicalcalculationsrevealthatthistransitionis23localizedontheethylenicaxleofthemotor.Thus,theshownbyblackverticallinesinFigure2.Theexperimentalandobservedspectralshiftsindicatethattheperipheralsub-calculatedspectramatchquitewellforallthederivativesinthestituentsa?ecttheelectronicstructureatthecoreoftheregion650?1700cm?1.Themodesnear1580cm?1arisefrommolecule.symmetricstretchingoftheethylenicCCaxlecoupledtoInordertobetterunderstandthee?ectofsubstituentontheringbreathingmodes(υ(CC)),whilethe?ngerprintregiongroundstatestructure,werecordedsteady-stateRamanspectrafrom1100to1500cm?1isdominatedbystretching(υ(CC))undero?-resonantconditionsat532nm(Figure2).Theandbending(δ(CH))modesofboththerotor(naphthyl)andstrongestRamanactivemodeinallfourderivativesisinthestator(?uorene)groups.Thecharacterofthemostprominentregionof1500?1600cm?1.The?ngerprintregion(1300?modesarelabeledinFigure2,andtheirnucleardisplacements1500cm?1)showssigni?cantvariation,withthesubstituentareillustratedinSupportingInformation,FigureS4.Thedependenceofmodesofthesamecharacterbeinghighlightedmodeswithasigni?cantsubstituentdependence(shownbybyreddottedlines.Thisvariationindicatesane?ectofthereddottedlines)areseentoarisefromringυ(CC)/δ(CH)substituentontheRamanactivemodesofthenaphthylunittomodesofthenaphthylrotorbearingthesubstituent.Thepeakwhichthesubstituentsareattached(seebelow).Theregionfrequenciesshiftdependingonthechangeinnaphthylring1100?1250cm?1isagainquitesimilarforallfourderivatives,conjugationwiththesubstituentgroup.Incontrast,themodeswhileactivityinlowfrequencymodes(<1000cm?1)isverynear1307and1450cm?1are?uorenestatorυ(CC)/δ(CH)weakinallcases,althoughthereismoderateintensityinamodesandareinsensitivetosubstitution.Thelow-frequencymodenear750cm?1.modesintheregion650?1000cm?1areveryweakintheGround-stateDFTcalculationsofRamanactivemodesgroundstate.However,themostprominentmodeinthe690?usingGaussian16wereusedtoassignthesespectra;calculated750cm?1regioncorrespondstoaxlepyramidalizationmotiondata(attherb3lyp/tzvplevel,frequencyscaledby0.98)arecoupledtoanHout-of-planebending(HOOP)(FigureS7).3368https://doi.org/10.1021/acs.jpclett.1c00710J.Phys.Chem.Lett.2021,12,3367?3372

2TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLetterExcitedStateDynamics.Thestructuralevolutionoftheobservedabroadpeakat720cm?1inthedarkstate,whichisfourmotorssubsequenttophotoexcitationisprobedbyveryweakfortheelectrondonatingOMesubstituentbutrecordingtransientabsorptionandtime-resolvedRamanstrongforelectronwithdrawingCN.Similarly,amodeat1170cm?1isabsentfortheOMesubstituentbutisenhancedinthespectrausingFSRS.Themotorswereexcitedusingafemtosecond“actinic”pumpat400nm.Transientabsorptionotherderivatives.Figure3bdepictsthechangeinrelativeintensityof720and1170cm?1modeswithrespecttothemeasurementsforallfourderivativesatdi?erentpump?probe1580cm?1mode.Thepeakintensityratioincreasesasthedelaysshowtwodistinctexcitedstateabsorption(ESA)features(seeSupportingInformation,FigureS2).Thesubstituentchangesfrom?OMethroughHandClto?CN,instantaneouslygeneratedESAnear620?800nmdecaysini.e.,asafunctionofincreasingelectronwithdrawingcharacter.Thebroadhighestfrequencymodeat1580cm?1inthe100?200fsconcomitantwiththeriseofESAnear550?620nm.ThisrepresentsevolutionoftheFCbright-statetoaexcitedstateisassignedtoethylenicCC+ringstretchingon24thebasisofthegroundstateDFTcalculation.Thismodeislongerlived(～ps)darkintermediateinallfourderivatives.Thedarkstateabsorptionisincreasinglyred-shiftedandmostintenseforthe?OMederivative,suggestingtheexcitedbecomesmoreintensewithincreasingelectronegativityofthestateretainsstrongdoublebondcharacter.Conversely,thissubstituent.Toprobethisdarkexcitedstatewithresonantmodeisveryweakinthe?CNderivative,suggestinganFSRS,thepicosecondRamanpumpwastunedinthe560?610excitedstategeometryinwhichtheethylenicdoublebondnmwindow,theresonantwavelengthbeingchosentoyieldacharacterisgreatlyreduced.Instead,intenseactivityin720and1170cm?1modesisobserved,whicharethemselvesweakinsimilarresonanceconditionsforallfourmotors(itismarkedbyverticaldasharrowsinSupportingInformation,FigureS2).the?OMederivative.TherawFSRSdatawerebackgroundsubtractedandcorrectedTheoriginoftheenhancedlowfrequencymodesisforbaselineasdescribedintheSupportingInformation,andsuggestedbyearlierquantumchemicalcalculationsofthearepresentedinFigure3.excitedstatestructureofthe?uorene(H)motors,wheretheethyleniccarbononthe?uoreneringhaschangedfromsp2tosp3duetopyramidalizationdistortionuponformationofthe23,25darkstate.Notethatinallderivativesthepyramidalizationmodewascalculatedatca.750cm?1inthegroundstate(Figure2)althoughveryweak.Inthepresentcase,theCNderivativedisplaysanintenselow-frequencymodeat720cm?1andweakmodeat1580cm?1suggestingthattheelectronwithdrawingcharacterleadstoadarkstatestructurewherethepyramidalizationhasfavoredtheformationofsp3carbonattheethylenicaxle(labeledasansp3darkstate,S).Therefore,sp3thisstrong720cm?1modeisassignedtopyramidalizationsp3distortionattheaxlecarbon,andthismodebecomesincreasinglyprominentastheelectronwithdrawingcharacterofthesubstituentincreases.Whilenotpreviouslyreportedinmotormolecules,suchlowfrequencymodeshavebeenseeninotherphotochemicalisomerizationreactions,inphytochromes26?28andrhodopsins,forexample.Inthosecases,theHOOPactivitywasanimportantcoordinate,andwenotethatthecalculatedgroundstatepyramidalizationmodeforthemotormoleculesalsoincludessigni?cantHOOPdisplacements(FigureS7).Incontrast,inthe?OMederivativethe720cm?1modeisessentiallyabsent,andanintense1580cm?1modeisretained,suggestinganexcitedstategeometrywheretheethyleneaxlewithsp2charactercarbon(labeledassp2darkstate,Ssp2)isfavored,andthereislittledisplacementalongthepyramidalizationcoordinate.Boththe720and1580cm?1modesaremoderatelyintenseforthe?Hand?Clderivatives.Figure3.(a)FemtosecondstimulatedRamanspectraofthedark23Thissuggestsanintermediatestructurewherebothspandspexcitedstateofmolecularmotorsinmethanol,measuredat200fspump?probedelaytime.Asterisksrepresentsolventandinstrumentalgeometriesareaccessible,allowingestablishmentofarapidartifacts.Grayhighlightedareasrepresentregionsofinterest.(b)equilibriumbetweenSsp2andSsp3;thisoverallschemeisChangesofRamanintensityratio1170/1580cm?1and720/1580illustratedinFigure4.cm?1asthesidegroupsarevaried.ExcitedstateRamanspectrathusshowthatdarkexcitedstatestructuresaresubstituentdependent:theelectron-withdrawing?CNderivativehassigni?cantsp3axle(S)TheprocessedexcitedstateRamanspectrarecorded200fssp3afterexcitationarepresentedinFigure3a.TheRamanactivecharacter,whiletheelectron-donating?OMederivativehasconsiderablesp2axlecharacter,evenintheexcitedstate(S).modesintheexcitedstatearequitebroadcomparedtotheirsp2groundstatecounterparts,ane?ectpreviouslyassignedtoaThederivativeswithintermediatedonatingcharacter(?Hand24distributionofdarkstatestructures.Theprominenthigh?Cl)haveintermediatespectra,suggestingthatthetwofrequencymodesinR=OMetoHareclearlygreatlyexcitedstatestructuresinfastdynamicequilibriumcan“swing”suppressedwhenR=CN.Extendingthemeasurementstoonthetorsion-pyramidalizationcoordinate,asreportedinlowerwavenumber,wheregroundstateactivityisweak,wespin-restrictedDFTcalculationsofmotorexcitedstate3369https://doi.org/10.1021/acs.jpclett.1c00710J.Phys.Chem.Lett.2021,12,3367?3372

3TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLetterassignedtonaphthylringυ(CC)/δ(CH)modes(basedonourgroundstateDFTcalculation)andundergoaredshiftwithtimeasshownbytheblackverticaldottedline.ThepeakfrequencyforthismodeisplottedinFigure5bforallfourderivatives.Thefrequencyshiftsby5?10cm?1onasub-picosecondtimescaleforthe?CN,?Cl,and?Hderivatives,suggestingstructuralevolutionmodifyingspeci?callynaphthylringmodesintheexcitedstate.OtherRamanactivemodesdonotundergopeakshifts.Sincetorsionandpyramidalizationinethylenicisomerizationisassociatedwithchargeredistribution21,23,25,30(suddenpolarization)ontheethylenicbond,thered-shiftintheRamanspectramaybeexplainedbystabilizationofthisnewchargedistribution.Signi?cantly,transientRamanspectrarecordedforthe?OMederivativedonotshowashiftinpeakpositionforthismode(Figure5b).Thisisconsistentwith?OMemaintainingitsdoublebondSsp2characteroftheaxle.Theseobservationsarealsocorrelatedwithadynamicalpeakshiftofdarkstateelectronictransientabsorptionspectraona～1pstimescaleforthe?CN,?Cl,and?Hderivatives,whilenosigni?cantspectralshiftisobservedfor?OMe(seeSupportingInformation,FigureS3).Figure4.PhotophysicalmodelforthephotoconversionofsecondThedynamicsassociatedwiththetransientabsorptionandgenerationmolecularmotors.ThebrightstaterelaxestothedarkstateFSRSspectralshifts,andthenonsingleexponentialFSRS22inca.100fs.Di?erentpopulationsofSsp2andSsp3statesareamplitudedecay,aretabulatedinSupportingInformation.Theachieveddependingonthenatureofsubstituents,whichcontrolstheoverallnonsingleexponentialdarkstatedynamicshavebeennatureofthenuclearreorganizationcontributingtothereactionnotedpreviouslyforthe?Hderivativeandalsofor?rstcoordinate.Thestateformedwithincreasingelectronwithdrawing24,30character(Ssp2,Ssp2/Ssp3rapidequilibrium,Ssp3)in?uencesthegenerationmotors.Thepeakareadynamicsforthisnaphthylringmodeat1330?1375cm?1regionareplottedinprobabilityoftheproductiveisomerizationreaction.The0.5?1psrelaxationdynamicswithinthedarkstate(seebelow)areomittedforFigure5cforthefourderivatives.Thedecayisfasterfortheclarity.?OMederivativeandslowerforthe?CNderivative.Thistrendcorrelateswiththereportedlifetimefordarkstatesfrom29both?uorescenceupconversionandtransientabsorptiondynamics.Theseassignmentsarerepresentedonthemodel13measurements.Thus,theSsp2darkstateforthe?OMepotentialenergysurface(Figure4).Importantly,theobservedderivativehasashortlifetime(ca.200fs)andmainlydecaystostabilizationofSsp3correlateswithahigherconversiontheoriginalgroundstate.Incontrast,the?CNsubstitutede?ciencyforformationofthegroundstatemetastableproduct,whileSsp2characterleadstoalowyieldofproductformation.motorhasalong-lived(ca.10ps)Ssp3darkstate.TherelativelyTherefore,designingmoleculesthatpromoteformationofthelonglifetimeoftheSsp3statein?CNcouldbeattributedtothe23sp3axlecarbonstructuresintheexcitedstateshouldprovidealargerstructuralreorganizationrequiredtoreachtheCI.higheryieldofphotoisomerization.WenotetheshortlifetimeHowever,theCIaccessedfromthisdarkstatehasagreaterofSsp2contrastswiththelongerlifetimeoftheSsp3darkstateinprobabilityofformingthemetastableproduct.the?CNderivative.InprinciplethelongerSsp3lifetimeitselfInconclusion,wehaveshownthatthestructureofthedarkmayleadtohigherconversione?ciencyifacompetingexcitedstateofsecondgenerationmolecularmotorsvariesradiationlessprocessissuppressedforexample.However,thewiththenatureofthesubstituent.Moreelectronwithdrawingpresentvibrationalstructuredatasuggestthatitisthestructuresubstituents(?CN)leadtostrongeractivityinlowfrequencyofthedarkstate(andthereforetheinitialstructureinthemodes,assignedtoformationofansp3axlecarbon.Groundgroundstateafterinternalconversion)whichdeterminesthestateDFTcalculationssuggestthatthe720cm?1modecanbephotochemicalyield.Forexample,the?Clsubstituenthasaassignedtotheaxlepyramidalizationdistortioncoupledtoshortlifetimecomparedto?CNbutahigheryieldthanHOOPmotion.Fordecreasingelectronwithdrawingcharacter,?OMe.theintensityofthesemodesandhencethepopulationofSsp3Themainfeaturesofthedarkstatespectraareindependentdarkstatedecreases,and?nally,foranelectron-donatingofdelaytime(seeSupportingInformationFigureS5),but?OMederivative,theexcitedstateisseentobetrappedinansigni?canttemporalevolutionisobservedintheringmoderegion(1300?1400cm?1),whichwasalsoshowntobeSsp2state.Importantly,thisresultcorrelateswiththee?ciencyofphotoconversioninthesemotorsandalignswiththeresultssubstituentdependentingroundstatespectra(Figure2).Weofrecentexistinghighqualityquantumchemicalcalculations.haveplottedtheFSRSdataforthisregioninFigure5a.Thedataare?ttocharacterizetheevolutionbysumsoftwoorItwouldbeinstructiveifsuchcalculationscouldbeextendedthreeGaussianfunctions(shownbybluecurvesinearlyandtomodelthemeasuredexcitedstatevibrationalspectrum.Inaddition,weobserveda5?10cm?1peakshiftoftherotorlatedatasets)toresolveunderlyingpeakfrequenciesandareas;anadditionalGaussianfunctionisusedto?tthesolventbreathingmodesassignedtostabilizationofthechargeartefact(further?ttingdetailsaregiveninSupportingredistributionintheinitialdarkstatepriortointernalInformation).Thepeaksintherange1330?1375cm?1areconversionviaCIs.3370https://doi.org/10.1021/acs.jpclett.1c00710J.Phys.Chem.Lett.2021,12,3367?3372

4TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLetterFigure5.(a)FemtosecondstimulatedRamanspectraofthemolecularmotorsintheregion1300?1470cm?1shownatseveralpump?probedelaytimestodisplayspectralshifts(e.g.,relativetotheblackdottedline).Eachspectrum(redtraces)is?ttedbytwoorthreeGaussianfunctions(bluecurves)toprovidea?ttedspectrum(blacktraces).OneadditionalGaussianfunctionisusedto?tthesolventartefactsinthedatasets(marked*).(b)Thepeakfrequencyshiftforthe1330?1375cm?1modecorrespondingtonaphthylbreathing,and(c)theassociatedpeakareachangesasafunctionoftime,revealingpopulationdynamics.■EXPERIMENTALMETHODSBenL.Feringa?StratinghInstituteforChemistry,University13,20ofGroningen,9747AGGroningen,TheNetherlands;Thesynthesisofallderivativeswasreportedpreviously.orcid.org/0000-0003-0588-8435;Email:b.l.feringa@Thespectrometersfortransientabsorptionandfemtosecond24rug.nlstimulatedRamanweredescribedpreviously,andfurtherdetailsandsamplespreparationprotocolsareincludedintheAuthorsSupportingInformation.PalasRoy?SchoolofChemistry,UniversityofEastAnglia,NorwichNR47TJ,U.K.■ASSOCIATEDCONTENTAndyS.Sardjan?StratinghInstituteforChemistry,*s?SupportingInformationUniversityofGroningen,9747AGGroningen,TheTheSupportingInformationisavailablefreeofchargeatNetherlandshttps://pubs.acs.org/doi/10.1021/acs.jpclett.1c00710.ArjenCnossen?StratinghInstituteforChemistry,UniversityofGroningen,9747AGGroningen,TheNetherlandsSteadystateandtransientelectronicspectra;timeWesleyR.Browne?StratinghInstituteforChemistry,dependentexcitedstateRamanspectra;nucleardisplace-UniversityofGroningen,9747AGGroningen,ThementsassociatedwiththemostrelevantRamanactiveNetherlands;orcid.org/0000-0001-5063-6961groundstatevibrationalmodes,especiallythepyramidi-Completecontactinformationisavailableat:alization-likecoordinate;processingproceduresforhttps://pubs.acs.org/10.1021/acs.jpclett.1c00710FSRSspectra(PDF)Notes■AUTHORINFORMATIONTheauthorsdeclarenocompeting?nancialinterest.CorrespondingAuthorsStephenR.Meech?SchoolofChemistry,UniversityofEast■ACKNOWLEDGMENTSAnglia,NorwichNR47TJ,U.K.;orcid.org/0000-0001-FinancialsupportwasprovidedbyTheNetherlandsMinistry5561-2782;Email:s.meech@uea.ac.ukofEducation,CultureandScience(GravityProgram3371https://doi.org/10.1021/acs.jpclett.1c00710J.Phys.Chem.Lett.2021,12,3367?3372

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