Principles and Applications of ESR Spectroscopy

467 Pages·2011·11.377 MB·English

by  Anders Lund, Masaru Shiotani, Shigetaka Shimada (auth.)

Principles and Applications of ESR Spectroscopy
· ·
Anders Lund Masaru Shiotani
Shigetaka Shimada
Principles and Applications
of ESR Spectroscopy
123
Prof.AndersLund Prof.MasaruShiotani
DepartmentofPhysics,Chemistry GraduateSchoolofEngineering
andBiology,IFM HiroshimaUniversity
LinkopingUniversity 4-26-8Takamigaoka,Takaya
TheEmeritusAcademy,Linkoping Higashi-Hiroshima739-2115
University Japan
SE-58183,Linkoping [email protected]
Sweden
[email protected],[email protected]
Prof.ShigetakaShimada
GraduateSchoolofEngineering
NagoyaInstituteofTechnology
44-66Midorigaoka
Midori-Machi
Owari-Asahi488-0822
Japan
[email protected]
ISBN978-1-4020-5343-6 e-ISBN978-1-4020-5344-3
DOI10.1007/978-1-4020-5344-3
SpringerDordrechtHeidelbergLondonNewYork
©SpringerScience+BusinessMediaB.V.2011
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Preface
ESRorElectronSpinResonanceisaspectroscopicmethodforstudiesofparamag-
neticspecies.Speciesofthiskindareofinterestbothfromfundamentalviewpoints
and for a broad range of applications in materials and polymer sciences, physical
chemistry and chemical physics, bio-chemistry and medicine, catalysis and envi-
ronmentalsciences,radiationdosimetryandgeologicaldating,aswellasradiation
physics and chemistry. The magnetic properties, mainly attributed to the electron
spin,canbeemployedtodetermineboththestructure(atamolecularlevel)andthe
amount of paramagnetic species in a sample with the ESR method. This method
hasbeenpresentedfromdifferentviewpointsinthepast.Previousmonographson
ESR spectroscopy have focused on the technique as such, while the general text-
books in physics, chemistry or spectroscopy only briefly explain the applications,
whicharemainlypresentedinspecialistreviewsandintheoriginalliterature.The
presentbookisbasedupontheauthors’longexperienceofteachingthesubjectto
amixedaudience,withbackgroundsrangingfromphysicstobiology.Itaimsboth
at providing the principles of continuous wave and pulsed ESR techniques and to
illustratethepotentialofthemethodbyexamplesofapplications.Theprinciplesof
ESR,multi-resonanceandpulsedESRmethods,theanalysisofspectra,andmulti-
frequency and high field ESR techniques treated in the first four chapters are thus
followed by five chapters exemplifying recent applications in molecular science,
in catalysis and environmental science, in polymer science, in spin labeling and
moleculardynamics,andinquantitativeESR.
Theoretical derivations are in general left out, as they are presented repeatedly
inpreviousworks.Thenecessarytheoryisinsteadillustratedbypracticalexamples
fromtheliterature.CommonlyusedcomputercodestoevaluateexperimentalESR
dataaredescribedwithexamples.Internetaddressestodownloadthesoftwareare
given, whenever possible. Formulae employed in those programs are reproduced
in appendices, when the original literature references are not easily available. The
theory and the application parts are to a large extent independent of each other to
allow study of a special subject. For reasons of easy access of data and diagrams
several examples from the authors’ own work were employed to illustrate certain
applications. Exercises included in the theoretical part are mainly concerned with
spectrainterpretations,asthisisthekeyissueintheanalysisofexperimentaldata.
v
vi Preface
Ourintentionhasbeentoprepareatextbookwiththefollowingissuesinmind:
1. Thebook“PrinciplesandapplicationsofESRspectroscopy”isforstudentsand
scientistsplanningtousethemethodwithoutnecessarilybecomingexperts.The
bookprovidessufficientknowledgetoproperlyapplythetechniqueandtoavoid
mistakesintheplanningandperformanceofthemeasurements.
2. Thetheoreticalpartisadaptedforanon-specialistaudience.Derivationsofwell-
known formulae are left out. The non-specialist does not want the derivations,
while the physicist does not need them. The necessary theory is instead illus-
trated by practical examples from the literature. The potential of the method is
demonstratedwithapplicationsselectedfromtheauthors’wideexperience.
3. Commonly used software to evaluate experimental ESR data is described with
examples.Addressestodownloadthesoftwarearegiven.
Linköping,Sweden AndersLund
Higashi-Hiroshima,Japan MasaruShiotani
Owari-Asahi,Japan ShigetakaShimada
Contents
PartI Principles
1 PrinciplesofESR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Paramagnetism . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 WhichSubstancesAreParamagnetic? . . . . . . . . . . . 5
1.3 Resonance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 Relaxation–Saturation . . . . . . . . . . . . . . . . . . . 8
1.3.2 HyperfineStructure . . . . . . . . . . . . . . . . . . . . . 9
1.3.3 FineStructureorZero-FieldSplitting. . . . . . . . . . . . 11
1.3.4 QuenchingofOrbitalAngularMomentum . . . . . . . . . 12
1.4 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.5 SpinDistribution . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.5.1 IsotropicCoupling . . . . . . . . . . . . . . . . . . . . . 14
1.5.2 AnisotropicCoupling . . . . . . . . . . . . . . . . . . . . 15
1.5.3 AnExample . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.5.4 ComplexSpectra . . . . . . . . . . . . . . . . . . . . . . 16
1.5.5 Units,ConstantsandSymbolsinESR . . . . . . . . . . . 18
1.6 HistoricalandModernDevelopments . . . . . . . . . . . . . . . 18
1.6.1 HighFrequency . . . . . . . . . . . . . . . . . . . . . . . 19
1.6.2 ENDOR . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
1.6.3 Short-LivedRadicals . . . . . . . . . . . . . . . . . . . . 21
1.6.4 PulsedESR . . . . . . . . . . . . . . . . . . . . . . . . . 22
1.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2 Multi-ResonanceandPulsedESR . . . . . . . . . . . . . . . . . . . 29
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.2 ENDOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.2.1 ENDORinLiquids . . . . . . . . . . . . . . . . . . . . . 30
2.2.2 ENDORinSingleCrystals . . . . . . . . . . . . . . . . . 36
2.2.3 ENDORinDisorderedSolids . . . . . . . . . . . . . . . . 46
vii
viii Contents
2.3 PulsedESR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
2.3.1 PulsedESRinSolution . . . . . . . . . . . . . . . . . . . 50
2.3.2 PulsedESRinSolids . . . . . . . . . . . . . . . . . . . . 51
2.3.3 PulsedENDOR . . . . . . . . . . . . . . . . . . . . . . . 60
2.3.4 RelaxationTimes . . . . . . . . . . . . . . . . . . . . . . 62
2.4 DistanceMeasurements . . . . . . . . . . . . . . . . . . . . . . . 65
2.4.1 ThePoint-DipoleApproximation . . . . . . . . . . . . . . 65
2.4.2 Electron-ElectronDistances. . . . . . . . . . . . . . . . . 67
2.4.3 Electron-NucleusDistances . . . . . . . . . . . . . . . . . 68
2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3 AnalysisofSpectra. . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
3.2 Liquids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.2.1 HyperfineCouplings . . . . . . . . . . . . . . . . . . . . 80
3.2.2 EquivalentNuclei . . . . . . . . . . . . . . . . . . . . . . 81
3.2.3 InequivalentNuclei . . . . . . . . . . . . . . . . . . . . . 83
3.2.4 LargeHyperfineCouplings . . . . . . . . . . . . . . . . . 85
3.2.5 Multi-ComponentSpectra. . . . . . . . . . . . . . . . . . 87
3.2.6 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
3.2.7 Theg-Factor . . . . . . . . . . . . . . . . . . . . . . . . . 91
3.3 AnalysisofSingleCrystalSpectra . . . . . . . . . . . . . . . . . 92
3.3.1 TheSchonlandMethod . . . . . . . . . . . . . . . . . . . 93
3.3.2 Theg-Tensor . . . . . . . . . . . . . . . . . . . . . . . . 93
3.3.3 Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.3.4 TheHyperfineandNuclearQuadrupoleCouplingTensors. 95
3.3.5 TheZero-FieldSplittng . . . . . . . . . . . . . . . . . . . 98
3.3.6 CombinedZero-FieldandHyperfineCouplings . . . . . . 100
3.3.7 SoftwareforSingleCrystalAnalysis . . . . . . . . . . . . 101
3.4 AnalysisofPowderSpectra . . . . . . . . . . . . . . . . . . . . . 104
3.4.1 ESRPowderSpectra . . . . . . . . . . . . . . . . . . . . 105
3.4.2 ENDORPowderSpectra . . . . . . . . . . . . . . . . . . 120
3.4.3 ESEEMPowderSpectra . . . . . . . . . . . . . . . . . . 130
3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
4 Multi-FrequencyandHighFieldESR . . . . . . . . . . . . . . . . . 165
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
4.2 g-FactorResolution . . . . . . . . . . . . . . . . . . . . . . . . . 167
4.2.1 Resolution of Apparent Isotropic or Axially
Symmetricg-Tensor . . . . . . . . . . . . . . . . . . . . . 168
Contents ix
4.2.2 Resolutionofg-TensorinPresenceofHyperfine
Structure(hfs) . . . . . . . . . . . . . . . . . . . . . . . . 173
4.3 Zero-FieldSplitting(zfs) . . . . . . . . . . . . . . . . . . . . . . 175
4.3.1 Zero-FieldSplittinginPowderSpectra . . . . . . . . . . . 177
4.3.2 DeviationsfromFirstOrderAppearance . . . . . . . . . . 177
4.3.3 SignofZero-FieldSplitting . . . . . . . . . . . . . . . . . 182
4.4 HyperfineCouplings(hfc) . . . . . . . . . . . . . . . . . . . . . 185
4.4.1 TheDirectFieldEffect . . . . . . . . . . . . . . . . . . . 186
4.4.2 SignofAnisotropicHyperfineCouplings. . . . . . . . . . 190
4.5 MagneticallyCoupledSystems . . . . . . . . . . . . . . . . . . . 191
4.5.1 S=½Dimers . . . . . . . . . . . . . . . . . . . . . . . . 191
4.5.2 OtherCoupledSystems . . . . . . . . . . . . . . . . . . . 196
4.6 MultifrequencyENDORandESEEM . . . . . . . . . . . . . . . 196
4.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
PartII ApplicationsofESR
5 ApplicationstoMolecularScience . . . . . . . . . . . . . . . . . . . 211
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
5.2 RadicalAnions . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
5.2.1 PerfluorocycloalkaneRadicalAnions:Electron
Delocalization . . . . . . . . . . . . . . . . . . . . . . . . 215
5.2.2 PerfluoroalkeneRadicalAnions:StructuralDistortion . . . 221
5.2.3 AcetyleneRadicalAnions:Trans-BentStructure . . . . . . 224
5.3 RadicalCations . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
5.3.1 Jahn-TellerDistortionofT andD Molecules . . . . . . 231
d 3h
5.3.2 D-Labelled Methane Radical Cations: CH +,
4
CDH +,CD H +,CD H+andCD + . . . . . . . . . . . . 231
3 2 2 3 4
5.3.3 TrimethylenemethaneRadicalCation. . . . . . . . . . . . 234
5.4 HighResolutionESRSpectraandQuantumEffects . . . . . . . . 238
5.4.1 D-Labelled Methyl Radicals: Nuclear
Spin-RotationCouplings . . . . . . . . . . . . . . . . . . 238
5.4.2 HydrogenAtom–MethylRadicalPairs . . . . . . . . . . 245
5.4.3 HydrogenAtom–HydrogenMoleculeComplex. . . . . . 248
5.4.4 HydrogenMolecularComplexIonsofH D +
6-n n
inpara-H Matrix . . . . . . . . . . . . . . . . . . . . . . 253
2
5.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
6 ApplicationstoCatalysisandEnvironmentalScience . . . . . . . . 273
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
6.2 SurfaceProbing:NitricOxideInteractions
withMetalIonsinZeolites . . . . . . . . . . . . . . . . . . . . . 274
x Contents
6.2.1 NO-Na+ ComplexFormedinZeolites . . . . . . . . . . . 275
6.2.2 TripletStateof(NO) Bi-RadicalFormedinZeolite . . . . 281
2
6.2.3 OtherNitrogenOxidesasSpinProbes . . . . . . . . . . . 285
6.3 Cu(I)-NOComplexesFormedinZeolites . . . . . . . . . . . . . 286
6.3.1 MultifrequencyESRSpectra . . . . . . . . . . . . . . . . 286
6.3.2 PulsedENDORandHYSCOREStudies . . . . . . . . . . 289
6.4 MolecularMotionProbes:RadicalsinZeolites. . . . . . . . . . . 290
6.4.1 Structure and Dynamics of Et N+ and Pr N+
3 3
inAlPO -5 . . . . . . . . . . . . . . . . . . . . . . . . . 290
4
6.4.2 CageEffectsonStabilityandMolecularDynamics
ofAmineRadicalsinZeolites. . . . . . . . . . . . . . . . 293
6.5 TitaniumDioxide(TiO )SemiconductorPhotocatalysis . . . . . . 295
2
6.5.1 Nitrogen-DopedTiO . . . . . . . . . . . . . . . . . . . . 298
2
6.5.2 ReversiblePhotoinducedElectronTransferinTiO (Rutile) 304
2
6.5.3 ElectronTransferinMixedPhaseofAnataseandRutile . . 307
−
6.6 Superoxide(O )IonRadical . . . . . . . . . . . . . . . . . . . 309
2
6.6.1 g-ValuesofO – . . . . . . . . . . . . . . . . . . . . . . . 310
2
6.6.2 17OLabelingStudy . . . . . . . . . . . . . . . . . . . . . 311
6.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
7 ApplicationstoPolymerScience . . . . . . . . . . . . . . . . . . . . 321
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
7.2 What Can We Obtain from the ESR Parameters
andTheirChangesinPolymerMaterials? . . . . . . . . . . . . . 322
7.3 PolymerizationMechanism . . . . . . . . . . . . . . . . . . . . . 325
7.3.1 RadicalPolymerizationintheLiquidState . . . . . . . . . 325
7.3.2 RadicalPolymerizationintheSolidState . . . . . . . . . 326
7.3.3 RadicalPolymerizationofMacro-Monomers . . . . . . . 327
7.4 Radiation Effects: Radiation Physics and Chemistry
ofPolymerMaterials . . . . . . . . . . . . . . . . . . . . . . . . 329
7.4.1 FreeRadicalsProducedbyIrradiationofPolymers
withIonizingRadiation . . . . . . . . . . . . . . . . . . . 329
7.4.2 DecayofFreeRadicalsProducedbyγ-Irradiation
ofPolymers . . . . . . . . . . . . . . . . . . . . . . . . . 335
7.4.3 Free Radical Pairs Produced by Irradiation of
PolymerswithIonizingRadiation . . . . . . . . . . . . . 339
7.4.4 Inhomogeneous Spur-Like Trapping of Free
RadicalsbyIrradiationofPolymerswithIonizing
Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . 340
7.5 MechanicalDestructionofSolidPolymers . . . . . . . . . . . . . 342
7.5.1 FreeRadicalsProducedbyMechanicalDestruction
ofSolidPolymers:Mechano-Radicals . . . . . . . . . . . 343
7.5.2 HighChemicalReactivityofMechano-Radicals . . . . . . 345
7.5.3 HighMolecularMobilityofMechano-Radicals . . . . . . 347
Contents xi
7.6 Auto-OxidationMechanismsofPolymerSystems . . . . . . . . . 349
7.6.1 ESRSpectrumofPeroxyRadicalsinPolymerMatrices . . 349
7.6.2 OxidationProcessesinIrradiatedPolymersand
ChemicalReactionsofPeroxyRadicals . . . . . . . . . . 352
7.6.3 Structure and Molecular Motion of Peroxy
RadicalsinPolymerMatrices . . . . . . . . . . . . . . . . 354
7.7 ConductingPolymers . . . . . . . . . . . . . . . . . . . . . . . . 360
7.7.1 Diffusive Motion of the Soliton in Pristine
PolyacetyleneDetectedbytheESRLineWidth . . . . . . 360
7.7.2 SpinDensityDistributionoftheSolitoninPristine
PolyacetyleneDetectedbyENDOR . . . . . . . . . . . . 363
7.7.3 Dyson’sTheoryofESRLineShapesinMetals. . . . . . . 367
7.7.4 ESR Spectra of Pristine and AsF Doped
5
Polyacetylene(PA) . . . . . . . . . . . . . . . . . . . . . 370
7.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
8 SpinLabelingandMolecularDynamics . . . . . . . . . . . . . . . . 379
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
8.2 MolecularMotioninSolidPolymers . . . . . . . . . . . . . . . . 380
8.2.1 CharacteristicsofESRforStudyingMolecular
MotioninSolidPolymers . . . . . . . . . . . . . . . . . . 380
8.2.2 Evaluation of Correlation Time for Molecular
MotionfromESRSpectra. . . . . . . . . . . . . . . . . . 380
8.2.3 Glass-RubberTransitionDetectedbytheSpin
LabelMethodforPolystyrene(PS):Molecular
WeightDependence . . . . . . . . . . . . . . . . . . . . . 382
8.2.4 Glass-RubberTransitionDetectedbytheSpin
LabelMethodforPolyethylene(PE):Crystallinity
Dependence . . . . . . . . . . . . . . . . . . . . . . . . . 386
8.2.5 Glass-RubberTransitionDetectedbytheSpin
ProbeMethod . . . . . . . . . . . . . . . . . . . . . . . . 388
8.2.6 Molecular Mobility of an Amorphous Chain
intheCrystallizationProcess . . . . . . . . . . . . . . . . 391
8.3 ApplicationsofSpinLabelingMethodtoBiopolymerSystems . . 393
8.3.1 StructureofBiologicalCellMembrane . . . . . . . . . . . 393
8.3.2 FluidityofBiologicalMembranesandtheOrder
ParameterofaLipidChain . . . . . . . . . . . . . . . . . 394
8.3.3 Dependence of Molecular Mobility of Lipid
BilayersonPositionoftheMethyleneGroup. . . . . . . . 396
8.3.4 Lateral Phase Separation in Phospholipid
MembranesCausedbyLateralDiffusionofLipidChains . 399
8.3.5 Lipid-ProteinInteractionsandRotationalDiffusion . . . . 403
8.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406