Principles and Applications of Photochemistry

A modern introduction to photochemistry covering the principles and applications of this topic from both a physical chemistry and organic chemistry angle. Coverage ranges from subjects such as lasers, the atmosphere, biochemistry, medicine and industry and also includes the latest developments in relation to photochemical molecular machines, photodynamic therapy applied to cancer, photochromatic imaging, and photostabilizers. Little in the way of prior knowledge is assumed, and the reader is aided by numerous worked examples, learning objectives, chapter summaries and problems.

Auteur

Brian Wardle is the author of Principles and Applications of *Photochemistry, published by Wiley.

Texte du rabat
Based on a course given by the author, this text provides an introduction to the principles and applications of photochemistry. Covering both principles and applications, the 12 chapters are organised in the following way:

• General introduction to the concepts of light and matter and their interaction resulting in electronically excited states
• Processes involving physical deactivation of the electronically excited states
• An overview of the chemical properties of excited states
• Photochemical reactions of Alkenes and Carbonyl Compounds
• Techniques used in photochemical reactions
• The outstanding progress that has been made in recent years Throughout Principles and Applications of Photochemistry, the reader's understanding is enhanced with learning objectives, worked examples and chapter summaries. Written at a level suitable for undergraduates, this book is ideal for students in chemistry, physics and related topics, as well as serving more experienced researchers needing an introduction to this subject area.

Contenu

Preface xiii

1 Introductory Concepts 1

Aims and Objectives 1

1.1 The Quantum Nature of Matter and Light 2

1.2 Modelling Atoms: Atomic Orbitals 6

1.3 Modelling Molecules: Molecular Orbitals 9

1.4 Modelling Molecules: Electronic States 13

1.5 Light Sources Used in Photochemistry 16

1.6 Efficiency of Photochemical Processes: Quantum Yield 25

2 Light Absorption and Electronically-excited States 29

Aims and Objectives 29

2.1 Introduction 29

2.2 The BeerLambert Law 30

2.3 The Physical Basis of Light Absorption by Molecules 32

2.4 Absorption of Light by Organic Molecules 35

2.5 Linearly-conjugated Molecules 39

2.6 Some Selection Rules 42

2.7 Absorption of Light by Inorganic Complexes 43

3 The Physical Deactivation of Excited States 47

Aims and Objectives 47

3.1 Introduction 47

3.2 Jablonski Diagrams 49

3.3 Excited-state Lifetimes 53

4 Radiative Processes of Excited States 59

Aims and Objectives 59

4.1 Introduction 60

4.2 Fluorescence and Fluorescence Spectra 61

4.3 An Exception to Kasha's Rule 63

4.4 Fluorescence Quantum Yield 64

4.5 Factors Contributing to Fluorescence Behaviour 65

4.6 Molecular Fluorescence in Analytical Chemistry 67

4.7 Phosphorescence 70

4.8 Delayed Fluorescence 73

4.9 Lanthanide Luminescence 74

5 Intramolecular Radiationless Transitions of Excited States 77

Aims and Objectives 77

5.1 Introduction 77

5.2 The Energy Gap Law 79

5.3 The FranckCondon Factor 79

5.4 Heavy Atom Effects on Intersystem Crossing 82

5.5 El-Sayed's Selection Rules for Intersystem Crosssing 83

6 Intermolecular Physical Processes of Excited States 87

Aims and Objectives 87

6.1 Quenching Processes 88

6.2 Excimers 90

6.3 Exciplexes 93

6.4 Intermolecular Electronic Energy Transfer 96

6.5 The Trivial or Radiative Mechanism of Energy Transfer 97

6.6 Long-range DipoleDipole (Coulombic) Energy Transfer 98

6.7 Short-range Electron-exchange Energy Transfer 105

6.8 Photoinduced Electron Transfer (PET) 110

7 Some Aspects of the Chemical Properties of Excited States 119

Aims and Objectives 119

7.1 The Pathway of Photochemical Reactions 120

7.2 Differences between Photochemical and Thermal Reactions 124

7.3 Photolysis 127

7.4 An Introduction to the Chemistry of Carbon-centred Radicals 133

7.5 Photochemistry of the Complexes and Organometallic Compounds of d-block Elements 135

8 The Photochemistry of Alkenes 145

Aims and Objectives 145

8.1 Excited States of Alkenes 146

8.2 Geometrical Isomerisation by Direct Irradiation of C=C Compounds 147

8.3 Photosensitised Geometrical Isomerisation of C=C Compounds 149

8.4 Concerted Photoreactions 151

8.5 Photocycloaddition Reactions 157

8.6 Photoaddition Reactions 159

9 The Photochemistry of Carbonyl Compounds 161

Aims and Objectives 161

9.1 Excited States of Carbonyl Compounds 162

9.2 -cleavage Reactions 163

9.3 Intermolecular Hydrogen-abstraction Reactions 166

9.4 Intramolecular Hydrogen-abstraction Reactions 167

9.5 Photocyloaddition Reactions 168

9.6 The Role of Carbonyl Compounds in Polymer Chemistry 169

10 Investigating Some Aspects of Photochemical Reaction Mechanisms 173

Aims and Objectives 173

10.1 Introduction 174

10.2 Information from Electronic Spectra 174

10.3 Triplet-quenching Studies 176

10.4 Sensitisation 180

10.5 Flash Photolysis Studies 182

10.6 Low-temperature Studies 195

Further Reading 196

11 Semiconductor Photochemistry 197

Aims and Objectives 197 &l...