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Spin States in Biochemistry and Inorganic Chemistry

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It has long been recognized that metal spin states play a central role in the reactivity of important biomolecules, in industrial ... Lire la suite
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Description

It has long been recognized that metal spin states play a central role in the reactivity of important biomolecules, in industrial catalysis and in spin crossover compounds. As the fields of inorganic chemistry and catalysis move towards the use of cheap, non-toxic first row transition metals, it is essential to understand the important role of spin states in influencing molecular structure, bonding and reactivity.

Spin States in Biochemistry and Inorganic Chemistry provides a complete picture on the importance of spin states for reactivity in biochemistry and inorganic chemistry, presenting both theoretical and experimental perspectives. The successes and pitfalls of theoretical methods such as DFT, ligand-field theory and coupled cluster theory are discussed, and these methods are applied in studies throughout the book. Important spectroscopic techniques to determine spin states in transition metal complexes and proteins are explained, and the use of NMR for the analysis of spin densities is described.

Topics covered include:

DFT and ab initio wavefunction approaches to spin states
Experimental techniques for determining spin states
Molecular discovery in spin crossover
Multiple spin state scenarios in organometallic reactivity and gas phase reactions
Transition-metal complexes involving redox non-innocent ligands
Polynuclear iron sulfur clusters
Molecular magnetism
NMR analysis of spin densities
This book is a valuable reference for researchers working in bioinorganic and inorganic chemistry, computational chemistry, organometallic chemistry, catalysis, spin-crossover materials, materials science, biophysics and pharmaceutical chemistry.


Auteur

Prof. Dr. Marcel Swart, Universitat de Girona, Spain
Marcel Swart is ICREA Research Professor in the Institute of Computational Chemistry Catalysis at the Universitat de Girona, Spain. He is a computational/theoretical chemist working in the field of (bio)chemistry and biomedicine. He has published >100 papers in peer-reviewed scientific journals and has an h-index of 26. He was awarded the Young Scientist 2005 award by ICCMSE (International Conference of Computational Methods in Sciences and Engineering), and was selected as one of the promising young inorganic chemists of "The next generation" that were invited to contribute to a special issue of Inorganica Chimica Acta in 2007, and to a special issue of Polyhedron in 2010.
In 2012, he was awarded the MGMS Silver Jubilee Prize "for his development of new computational chemistry programs, design of new research tools and application to (bio)chemical systems that are highly relevant for society and science." In September 2012 he organized a CECAM/ESF Workshop on "Spin states in biochemistry and inorganic chemistry", highlighted in Nature Chem. 2013, 5, 7-9.

Prof. Dr. Miquel Costas, Universitat de Girona, Spain
Miquel Costas became Professor Titular at the University of Girona in 2003. He has published over 70 papers in international journals that have received over 3470 citations. His research interests involve the study of transition metal complexes involved in challenging oxidative transformations, including functionalization of C-H bonds and water oxidation. These systems commonly operate in multistate reactivity scenarios, implicating multiple spin states.



Échantillon de lecture
1
General Introduction to Spin States

Marcel Swart1,2 and Miquel Costas1

1Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Spain

2Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
1.1 Introduction

Spin is a fundamental property of all elements and molecules, which originates from their unpaired electrons. Spin states have a major role in defining the structure, reactivity, magnetic and spectroscopic properties of a molecule. Furthermore it is possible that more than one spin state is energetically accessible for a given molecule. In such cases, the molecule can accumulate multiple spectroscopic, magnetic and reactivity patterns arising from the different accessible spin states. The ground spin state of most organic molecules is a singlet, that is, they have a closed-shell electronic structure, and other states are energetically not accessible under standard conditions. Important exceptions are carbenes, which can exist as singlet and triplet spin states, and the molecule of dioxygen, whose triplet nature poses kinetic barriers to its thermodynamically favorable reaction with organic matter. The situation is completely reversed when transition metals are present, which makes that different spin states are accessible for the majority of transition metal complexes. This primarily results from the particular nature of d-orbitals of the metals (see Figure 1.1 ) that are close in energy and which can be occupied in different ways depending on the metal oxidation state, its ligands and its coordination geometry (see Figure 1.1 ). This picture can be further complicated when ligands are not redox innocent and can have a spin that can also engage in ferro or anti-ferromagnetic interactions with the spin of the metal center.

Figure 1.1 Transition metal d-orbitals shape (left) and orbital-level diagram (right).

Spin states play an important role [1, 2] in metalloenzymatic reactions (e.g. cytochrome P450cam), in metal-oxo complexes, in spin-crossover compounds and even in catalysis processes mediated by organometallic compounds where different reactions take place via different spin states [3, 4]. However, computational studies have shown that a correct description of the spin state is not trivial [1, 5, 6], and a combination of different density functionals (DFT) and/or ab initio methods may be needed. Experimental studies on biomimetic model complexes, enzymes or spin-crossover compounds have added to the complexity, making the spin state a challenging property that is poorly understood [1]. This was the origin for a CECAM/ESF Workshop organized in Zaragoza in September 2012 [7], leading subsequently to a COST Action (CM1305, ECOSTBio).
1.2 Experimental Chemistry: Reactivity, Synthesis and Spectroscopy

Spin states constitute a fundamental aspect of the electronic structure of molecules, and as such spin determines their electronic properties, magnetism and reactivity. Therefore, rationalization of the latter properties in paramagnetic molecules most often requires determination of their spin state. The most important spectroscopic techniques employed to determine spin states in transition metal complexes and proteins have been discussed in Chapter 4, and the use of nuclear magnetic resonance spectroscopy as a tool to shed information on the electronic structure of paramagnetic metal centers, especially those of metalloenzymes, is described in Chapter 16.

Compounds that can exist in multiple spin states open exciting possibilities in a number of fields. An interesting, widely explored case is transition metal centers in octahedral coordination environments with d-electron configurations d4 to d7, which can exist as high spin (HS) and low spin (LS) (see Chapters 5 and 12). Low

Contenu

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 HSLS 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 Mössbauer 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 Böhmer 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 SNSCrCl3 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 CH 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 Roithová

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 ...

Informations sur le produit

Titre: Spin States in Biochemistry and Inorganic Chemistry
Sous-titre: Influence on Structure and Reactivity
Auteur:
Code EAN: 9781118898284
ISBN: 978-1-118-89828-4
Protection contre la copie numérique: Adobe DRM
Format: eBook (epub)
Editeur: Wiley
Genre: Chimie anorganique
nombre de pages: 472
Parution: 22.09.2015
Année: 2015
Sous-titre: Englisch
Taille de fichier: 9.5 MB