About the Editors xv
List of Contributors xvii
Foreword xxi
Acknowledgments xxiii
1 General Introduction to Spin States 1
Marcel Swart and Miquel Costas
1.1 Introduction 1
1.2 Experimental Chemistry: Reactivity, Synthesis and Spectroscopy 2
1.3 Computational Chemistry: Quantum Chemistry and Basis Sets 4
2 Application of Density Functional and Density Functional Based Ligand Field Theory to Spin States 7
Claude Daul, Matija Zlatar, Maja Gruden-Pavlovic and Marcel Swart
2.1 Introduction 7
2.2 What Is the Problem with Theory? 9
2.2.1 Density Functional Theory 9
2.2.2 LF Theory: Bridging the Gap Between Experimental and Computational Coordination Chemistry 11
2.3 Validation and Application Studies 15
2.3.1 Use of OPBE, SSB-D and S12g Density Functionals for Spin-State Splittings 17
2.3.2 Application of LF-DFT 21
2.4 Concluding Remarks 25
3 Ab Initio Wavefunction Approaches to Spin States 35
Carmen Sousa and Coen de Graaf
3.1 Introduction and Scope 35
3.2 Wavefunction-Based Methods for Spin States 35
3.2.1 Single Reference Methods 36
3.2.2 Multireference Methods 37
3.2.3 MR Perturbation Theory 39
3.2.4 Variational Approaches 40
3.2.5 Density Matrix Renormalization Group Theory 40
3.3 Spin Crossover 41
3.3.1 Choice of Active Space and Basis Set 41
3.3.2 The HS-LS Energy Difference 43
3.3.3 Light-Induced Excited Spin State Trapping (LIESST) 45
3.3.4 Spin Crossover in Other Metals 47
3.4 Magnetic Coupling 47
3.5 Spin States in Biochemical and Biomimetic Systems 50
3.6 Two-State Reactivity 52
3.7 Concluding Remarks 52
4 Experimental Techniques for Determining Spin States 59
Carole Duboc and Marcello Gennari
4.1 Introduction 59
4.2 Magnetic Measurements 61
4.2.1 g-Anisotropy and Zero-Field Splitting (zfs) 64
4.2.2 Unquenched Orbital Moment in the Ground State 64
4.2.3 Exchange Interactions 64
4.2.4 Spin Transitions and Spin Crossover 66
4.3 EPR Spectroscopy 66
4.4 Mossbauer Spectroscopy 70
4.5 X-ray Spectroscopic Techniques 74
4.6 NMR Spectroscopy 77
4.7 Other Techniques 80
4.A Appendix 81
4.A.1 Theoretical Background 81
4.A.2 List of Symbols 82
5 Molecular Discovery in Spin Crossover 85
Robert J. Deeth
5.1 Introduction 85
5.2 Theoretical Background 85
5.2.1 Spin Transition Curves 88
5.2.2 Light-Induced Excited Spin State Trapping 89
5.3 Thermal SCO Systems: Fe(II) 90
5.4 SCO in Non-d6 Systems 93
5.5 Computational Methods 95
5.6 Outlook 98
6 Multiple Spin-State Scenarios in Organometallic Reactivity 103
Wojciech I. Dzik, Wesley Bohmer and Bas de Bruin
6.1 Introduction 103
6.2 "Spin-Forbidden" Reactions and Two-State Reactivity 104
6.3 Spin-State Changes in Transition Metal Complexes 107
6.3.1 Influence of the Spin State on the Kinetics of Ligand Exchange 108
6.3.2 Stoichiometric Bond Making and Breaking Reactions 109
6.3.3 Spin-State Situations Involving Redox-Active Ligands 115
6.4 Spin-State Changes in Catalysis 119
6.4.1 Catalytic (Cyclo)oligomerizations 119
6.4.2 Phillips Cr(II)/SiO2 Catalyst 121
6.4.3 SNS-CrCl3 Catalyst 123
6.5 Concluding Remarks 125
7 Principles and Prospects of Spin-States Reactivity in Chemistry and Bioinorganic Chemistry 131
Dandamudi Usharani, Binju Wang, Dina A. Sharon and Sason Shaik
7.1 Introduction 131
7.2 Spin-States Reactivity 132
7.2.1 Two-State and Multi-State Reactivity 133
7.2.2 Origins of Spin-Selective Reactivity: Exchange-Enhanced Reactivity and Orbital Selection Rules 137
7.2.3 Considerations of Exchange-Enhanced Reactivity versus Orbital-Controlled Reactivity 140
7.2.4 Consideration of Spin-State Selectivity in H-Abstraction: The Power of EER 142
7.2.5 The Origins of Mechanistic Selection - Why Are C-H Hydroxylations Stepwise Processes? 146
7.3 Prospects of Two-State Reactivity and Multi-State Reactivity 148
7.3.1 Probing Spin-State Reactivity 148
7.3.2 Are Spin Inversion Probabilities Useful for Analyzing TSR? 150
7.4 Concluding Remarks 151
8 Multiple Spin-State Scenarios in Gas-Phase Reactions 157
Jana Roithova
8.1 Introduction 157
8.2 Experimental Methods for the Investigation of Metal-Ion Reactions 158
8.3 Multiple State Reactivity: Reactions of Metal Cations with Methane 160
8.4 Effect of the Oxidation State: Reactions of Metal Hydride Cations with Methane 163
8.5 Two-State Reactivity: Reactions of Metal Oxide Cations 164
8.6 Effect of Ligands 171
8.7 Effect of Noninnocent Ligands 174
8.8 Concluding Remarks 177
9 Catalytic Function and Mechanism of Heme and Nonheme Iron(IV)-Oxo Complexes in Nature 185
Matthew G. Quesne, Abayomi S. Faponle, David P. Goldberg and Sam P. de Visser
9.1 Introduction 185
9.2 Cytochrome P450 Enzymes 186
9.2.1 Importance of Cytochrome P450 Enzymes 187
9.2.2 P450 Activation of Long-Chain Fatty Acids 188
9.2.3 Heme Monooxygenases and Peroxygenases 188
9.2.4 Catalytic Cycle of Cytochrome P450 Enzymes 188
9.3 Nonheme Iron Dioxygenases 190
9.3.1 Cysteine Dioxygenase 191
9.3.2 AlkB Repair Enzymes 192
9.3.3 Nonheme Iron Halogenases 194
9.4 Conclusions 197
9.5 Acknowledgments 197
10 Terminal Metal-Oxo Species with Unusual Spin States 203
Sarah A. Cook, David C. Lacy and Andy S. Borovik
10.1 Introduction 203
10.2 Bonding 204
10.2.1 Bonding Considerations: Tetragonal Symmetry 204
10.2.2 Bonding Considerations: Trigonal Symmetry 205
10.2.3 Methods of Characterization 206
10.3 Case Studies 206
10.3.1 Iron-Oxo Chemistry 206
10.3.2 Manganese-Oxo Chemistry 212
10.3.3 Cautionary Tales: Late Transition Metal Oxido Complexes 217
10.3.4 Effects of Redox Inactive Metal Ions 217
10.3.5 Metal-Oxyl Complexes 218
10.4 Reactivity 218
10.4.1 General Concepts: Proton versus Electron Transfer 218
10.4.2 Spin State and Reactivity 220
10.5 Summary 220
11 Multiple Spin Scenarios in Transition-Metal Complexes Involving Redox Non-Innocent Ligands 229
Florian Heims and Kallol Ray
11.1 Introduction 229
11.2 Survey of Non-Innocent Ligands 231
11.3 Identification of Non-Innocent Ligands 232
11.3.1 X-ray Crystallography 232
11.3.2 EPR Spectroscopy 234
11.3.3 Mossbauer Spectroscopy 235
11.3.4 XAS Spectroscopy 236
11.4 Selected Examples of Biological and Chemical Systems Involving Non-Innocent Ligands 237
11.4.1 Copper-Radical Interaction 237
11.4.2 Iron-Radical Interaction 246
11.5 Concluding Remarks 252
12 Molecular Magnetism 263
Guillem Aromi, Patrick Gamez and Olivier Roubeau
12.1 Introduction 263
12.2 Molecular Magnetism: Motivations, Early Achievements and Foundations 264
12.3 Molecular Nanomagnets (MNM) 265
12.3.1 Single-Molecule Magnets 266
12.3.2 Single-Chain Magnets (SCM) 268
12.3.3 Single-Ion Magnets (SIM) 271
12.4 Switchable Systems 273
12.4.1 Spin Crossover (SCO) 273
12.4.2 Valence Tautomerism (VT) 273
12.4.3 Charge Transfer (CT) 275
12.4.4 Light-Driven Ligand-Induced Spin Change (LD-LISC) 276
12.4.5 Photoswitching (PS) Through Intermetallic CT 277
12.5 Molecular-Based Magnetic Refrigerants 278
12.5.1 The Magneto-Caloric Effect, Its Experimental Determination and Key Parameters 278
12.5.2 Molecular to Extended Framework Coolers Towards Applications 280
12.6 Quantum Manipulation of the Electronic Spin for Quantum Computing 282
12.6.1 Organic Radicals 283
12.6.2 Transition Metal Clusters 284
12.6.3 Lanthanides as Realization of Qubits 285
12.6.4 Engineering of Molecular Quantum Gates with Lanthanide Qubits 285
12.7 Perspectives Toward Applications and Concluding Remarks 287
13 Electronic Structure, Bonding, Spin Coupling, and Energetics of Polynuclear Iron-Sulfur Clusters - A Broken Symmetry Density Functional Theory Perspective 297
Kathrin H. Hopmann, Vladimir Pelmenschikov, Wen-Ge Han Du and Louis Noodleman
13.1 Introduction 297
13.2 Iron-Sulfur Coordination: Geometric and Electronic Structure 298
13.3 Spin Polarization Splitting and the Inverted Level Scheme 300
13.4 Spin Coupling and the Broken Symmetry Method 300
13.5 Electron Localization and Delocalization 301
13.6 Polynuclear Systems - Competing Heisenberg Interactions and Spin-Dependent Delocalization 303
13.7 Preamble to Three Major Topics: Iron-Sulfur-Nitrosyls, Adenosine-5'-Phosphosulfate Reductase, and the Proximal Cluster of Membrane-Bound [NiFe]-Hydrogenase 303
13.7.1 Nonheme Iron Nitrosyl Complexes 303
13.7.2 Adenosine-5'-Phosphosulfate Reductase 310
13.7.3 Proximal Cluster of O2-Tolerant Membrane-Bound [NiFe]-Hydrogenase in Three Redox States 315
13.8 Concluding Remarks 318
13.9 Acknowledgments 319
14 Environment Effects on Spin States, Properties, and Dynamics from Multi-level QM/MM Studies 327
Alexander Petrenko and Matthias Stein
14.1 Introduction 327
14.1.1 Environmental Effects 328
14.1.2 Hybrid QM/MM Embedding Schemes 329
14.2 The Quantum Spin Hamiltonian - Linking Theory and Experiment 332
14.3 The Solvent as an Environment 335
14.3.1 Fourier Transform Infrared Spectroscopy 336
14.3.2 Nuclear Magnetic Resonance 336
14.3.3 Electron Paramagnetic Resonance 336
14.4 Effect of Different Levels of QM and MM Treatment 338
14.4.1 Convergence and Caveats at the QM Level 338
14.4.2 Accuracy of the MM Part 341
14.4.3 QM versus QM/MM Methods 341
14.5 Illustrative Bioinorganic Examples 343
14.5.1 Cytochrome P450 343
14.5.2 Hydrogenase Enzymes 349
14.5.3 Photosystem II and the Effect of QM Size 354
14.6 From Static Spin-State Properties to Dynamics and Kinetics of Electron Transfer 357
14.7 Final Remarks and Conclusions 359
14.8 Acknowledgments 362
15 High-Spin and Low-Spin States in {FeNO}7, FeIV=O, and FeIII-OOH Complexes and Their Correlations to Reactivity 369
Edward I. Solomon, Kyle D. Sutherlin and Martin Srnec
15.1 Introduction 369
15.2 High- and Low-Spin {FeNO}7 Complexes: Correlations to O2 Activation 372
15.2.1 Spectroscopic Definition of the Electronic Structure of High-Spin {FeNO}7 372
15.2.2 Computational Studies of S = 3/2 {FeNO}7 Complexes and Related {FeO2}8 Complexes 375
15.2.3 Extension to IPNS and HPPD: Implications for Reactivity 377
15.2.4 Correlation to {FeNO}7 S = 1/2 385
15.3 Low-Spin (S = 1) and High-Spin (S = 2) FeIV=O Complexes 386
15.3.1 FeIV=O S = 1 Complexes: ?* FMO 386
15.3.2 FeIV=O S = 2 Sites: ?* and ?* FMOs 390
15.3.3 Contributions of FMOs to Reactivity 392
15.4 Low-Spin (S = 1/2) and High-Spin (S = 5/2) FeIII-OOH Complexes 396
15.4.1 Spin State Dependence of O-O Bond Homolysis 396
15.4.2 FeIII-OOH S = 1/2 Reactivity: ABLM 398
15.4.3 FeIII-OOH Spin State-Dependent Reactivity: FMOs 399
15.5 Concluding Remarks 401
15.6 Acknowledgments 402
16 NMR Analysis of Spin Densities 409
Kara L. Bren
16.1 Introduction and Scope 409
16.2 Spin Density Distribution in Transition Metal Complexes 410
16.3 NMR of Paramagnetic Molecules 412
16.3.1 Chemical Shifts 413
16.3.2 Relaxation Rates 414
16.4 Analysis of Spin Densities by NMR 416
16.4.1 Factoring Contributions to Hyperfine Shifts 416
16.4.2 Relaxation Properties and Spin Density 418
16.4.3 DFT Approaches to Analyzing Hyperfine Shifts 419
16.4.4 Natural Bond Orbital Analysis 420
16.4.5 Application and Practicalities 421
16.5 Probing Spin Densities in Paramagnetic Metalloproteins 422
16.5.1 Heme Proteins 422
16.5.2 Iron-Sulfur Proteins 425
16.5.3 Copper Proteins 427
16.6 Conclusions and Outlook 429
17 Summary and Outlook 435
Miquel Costas and Marcel Swart
17.1 Summary 435
17.2 Outlook 436
Index 439
