Iridium(III) in Optoelectronic and Photonics Applications, 2 Volume Set

Edited by Eli Zysman-Colman EaStCHEM School of Chemistry, University of St Andrews, UK

List of Contributors xv

Foreword xvii

Preface xix

VOLUME 1

1 Archetypal Iridium(III) Compounds for Optoelectronic and Photonic Applications: Photophysical Properties and Synthetic Methods 1
Joseph C. Deaton and Felix N. Castellano

1.1 Introduction 1

1.2 Iridium Complex Ion Dopants in Silver Halide Photographic Materials 1

1.3 Overview of the Photophysical Properties of C^N and C^C: Cyclometalated Ir(III) Complexes 2

1.4 Importance of Ir─C Bonds in the Archetypal Ir(III) Complexes for Optoelectronic and Photonic Applications 9

1.5 Tuning Emission Color 14

1.6 Absorbance and Photoluminescence of C^N Cyclometalated Ir(III) Complexes 17

1.7 SOC Mechanism: Radiative Decay Rates and ZFS 23

1.8 Non-Radiative Decay Rates 39

1.9 Synthetic Methods Targeting C^N Cyclometalated Ir(III) Compounds 42

1.10 Synthetic Methods for Cyclometalated Ir(III) Compounds Containing Carbenes 47

1.11 Conclusions 48

Acknowledgements 49

Abbreviations for Ligands in Ir(III) Complexes 49

References 50

2 Multinuclear Iridium Complexes 71
J. A. Gareth Williams

2.1 Introduction 71

2.2 Compounds Incorporating ‘Single Atom Bridges’: μ-Chloro, μ-Oxo and μ-Aza 72

2.2.1 μ-Chloro-Bridged Complexes 72

2.2.2 μ-Aza-Bridged Complexes 74

2.2.3 μ-Hydroxo-Bridged Complexes 76

2.3 Polyatomic Acyclic Bridges: Acetylides, Cyanides and Hydrazides 78

2.4 Compounds with Heterocyclic Bridges 82

2.4.1 Bis-(N^N)-Coordinating Ligands and Related Systems Incorporating At Least One N^N Unit 83

2.4.2 Bis-(N^C)-Coordinating Ligands 89

2.5 Multinuclear Complexes Featuring Conjugated Bridges between Iridium-Bound Polypyridyl or Arylpyridyl Ligands 93

2.5.1 Systems Incorporating C≡C or N=N Bridges with One or More [Ir(N^C)2(N^N)]+ Units 95

2.5.2 Multinuclear Complexes Incorporating Phenyl and Polyphenylene Bridges between the Ligands: ‘Supramolecular Assemblies’ 96

2.6 Concluding Remarks 104

Acknowledgements 104

References 104

3 Soft Materials and Soft Salts Based on Iridium Complexes 111
Etienne Baranoff and Yafei Wang

3.1 Introduction 111

3.2 Liquid Crystals 112

3.3 Gels 115

3.4 Micelles 116

3.5 Langmuir–Blodgett Films 118

3.6 Soft Salts 118

3.7 Conclusion 123

Acknowledgements 123

References 123

4 Porous Materials Based on Precious Metal Building Blocks for Solar Energy Applications 127
Daniel Micheroni and Wenbin Lin

4.1 Introduction 127

4.2 The Luminescent Nature of MOFs and Their Use in Chemical Applications 129

4.3 Energy Transfer in Porous Materials 134

4.4 Porous Materials for Water Oxidation 136

4.5 Porous Materials for Proton Reduction 138

4.6 Porous Materials for CO2 Reduction 140

4.7 Conclusions and Outlook 141

References 141

5 Polymeric Architectures Containing Phosphorescent Iridium(III) Complexes 145
Andreas Winter and Ulrich S. Schubert

5.1 Introduction 145

5.2 Ir(III)-Containing Polymers: Classification, Design Principles, and Syntheses 146

5.2.1 Classification of Ir(III)-Containing Polymers 146

5.2.2 Design Principles for Metal-Containing Polymers 147

5.2.2.1 Decoration of Preformed Polymers with Ir(III) Complexes 149

5.2.2.2 Coordination of Ir(III) Precursor Complexes to Preformed Polymers 151

5.2.2.3 (Co)Polymerization of Ir(III)-Containing Monomers 157

5.2.2.4 Electropolymerization of Ir(III)-Containing Complexes 182

5.2.2.5 Synthetic Approaches Toward Ir(III)-Containing Polymers: The Roads Not Taken 186

5.3 Hyperbranched and Dendritic Architectures 187

5.3.1 Ir(III)-Containing Hyperbranched Polymers 187

5.3.2 Ir(III)-Containing Dendritic Systems 188

5.4 Concluding Remarks 191

References 192

6 Iridium(III) Complexes for OLED Application 205
Elena Longhi and Luisa De Cola

6.1 Introduction 205

6.2 Iridium Complexes 206

6.2.1 General Synthesis of Ir(III) Complexes 207

6.2.2 Luminescence of Iridium(III) Complexes 208

6.2.3 Emission Color Tuning in Iridium(III) Complexes 209

6.2.3.1 Influence of the (C^N) Ligand 210

6.2.3.2 Influence of the Ancillary Ligand 212

6.3 Organic Light-Emitting Diodes 216

6.3.1 Device Architecture and Fabrication 217

6.3.2 Device Lifetime 218

6.3.3 Device Efficiency 220

6.3.4 Phosphorescent Materials 221

6.3.5 Host Materials 222

6.4 Iridium(III) Complexes for PHOLED Application 227

6.4.1 Green Emitters 227

6.4.1.1 Role of the Ancillary Ligand 228

6.4.1.2 Modification of the Phenylpyridine Ring 229

6.4.1.3 Use of Different Tris-cyclometalated Motifs 230

6.4.2 Red Emitters 232

6.4.3 Blue Emitters 238

6.5 Conclusions and Perspectives 262

References 262

7 A Comprehensive Review of Luminescent Iridium Complexes Used in Light-Emitting Electrochemical Cells (LEECs) 275
Adam F. Henwood and Eli Zysman-Colman

7.1 Introduction 275

7.2 Device Fundamentals 278

7.3 Green Emitters 280

7.3.1 Archetypal Emitters 282

7.3.2 Pyrazoles 289

7.3.3 Imidazoles 292

7.3.4 Triazoles and Tetrazoles 293

7.3.5 Oxadiazoles 294

7.3.6 Thiophenes 296

7.3.7 Intramolecular π-Stacked Emitters 296

7.3.8 Supramolecular Emitters 300

7.4 Blue Emitters 301

7.4.1 [Ir(ppy)2(bpy)]+-Type Emitters 302

7.4.2 Pyrazoles 307

7.4.3 Imidazoles 312

7.4.4 Triazoles 313

7.4.5 Oxadiazoles 316

7.4.6 N-Heterocyclic Carbenes 320

7.4.7 Phosphines 322

7.5 Yellow Emitters 323

7.5.1 [Ir(ppy)2(bpy)]+-Type Emitters 324

7.5.2 Imidazole Emitters 327

7.5.3 Anionic Emitters 328

7.5.4 Intramolecularly π-Stacked Emitters 328

7.5.5 Multifunctional or Supramolecular Emitters 332

7.6 Orange-Red Emitters 334

7.6.1 [Ir(ppy)2(bpy)]+-Type Emitters 335

7.6.2 Emitters Bearing Five-Membered Heterocyclic Rings 340

7.6.3 Intramolecular π-Stacked Emitters 341

7.6.4 Multifunctional Emitters 345

7.7 Conclusions and Outlook 348

Acknowledgements 349

References 349

VOLUME 2

8 Electrochemiluminescence of Iridium Complexes 359
Sarah E. Laird and Conor F. Hogan

8.1 Background and Overview of Electrochemiluminescence 359

8.1.1 ECL from Metal Complexes 362

8.2 Iridium ECL 363

8.2.1 First Examples 363

8.2.2 Renewed Interest in Iridium ECL Stimulated by Progress in the Field of Light-Emitting Devices 364

8.2.3 Early Advances in Theoretical Understanding and Electrochemiluminophore Design 366

8.2.4 Modified Electrode Systems 370

8.2.5 ECL-Based Sensing Strategies 372

8.2.6 Issues Related to ECL of Iridium Complexes in Aqueous Media and Quenching by Oxygen 384

8.2.7 Tuning ECL Emission Colour and Redox Properties 386

8.2.8 Potential-Resolved Multicolour ECL 399

8.2.8.1 Miscellaneous ECL Systems Involving Iridium Complexes 405

8.2.9 Conclusion and Future Prospects 406

List of Ligand Abbreviations Used in Text 406

References 407

9 Strategic Applications of Luminescent Iridium(III) Complexes as Biomolecular Probes, Cellular Imaging Reagents, and Photodynamic Therapeutics 415
Karson Ka-Shun Tso and Kenneth Kam-Wing Lo

9.1 Introduction 415

9.2 General Cellular Staining Reagents 416

9.3 Hypoxia Sensing Probes 423

9.4 Molecular and Ion Intracellular Probes 427

9.4.1 Intracellular Probes for Sulfur-Containing Species 427

9.4.2 Intracellular Probes for Metal Ions 433

9.4.3 Intracellular Probes for Hypochlorous Acid and Hypochlorite 437

9.4.4 Intracellular Probes for Nitric Oxide 439

9.5 Organelle-Targeting Bioimaging Reagents 441

9.5.1 Nucleus 441

9.5.2 Nucleoli 443

9.5.3 Golgi Apparatus 445

9.5.4 Mitochondria 447

9.6 Functionalized Polypeptides for Bioimaging 450

9.7 Polymers and Nanoparticles for Bioimaging 454

9.8 Photocytotoxic Reagents and Photodynamic Therapeutics 458

9.9 Conclusion 466

Acknowledgements 466

Abbreviations 466

References 469

10 Iridium Complexes in the Development of Optical Sensors 479
Teresa Ramón-Márquez, Marta Marín-Suárez, Alberto Fernández-Gutiérrez and J. F. Fernández-Sánchez

10.1 Generalities of Optical Sensors 479

10.2 Ir(III) Used as Optical Probes 481

10.2.1 Optical Probes for the Detection of Gaseous Species 481

10.2.1.1 Oxygen 482

10.2.1.2 Other Gaseous Species 483

10.2.2 Optical Probes for the Detection of Ionic Species 485

10.2.2.1 Cations 485

10.2.2.2 pH 491

10.2.2.3 Anions 493

10.2.3 Optical Probes for the Detection of Biomolecules 498

10.2.3.1 Amino Acids and Proteins 498

10.2.3.2 Nucleotides and Nucleic Acids 506

10.2.4 Optical Probes for the Detection of Other Small Molecules 506

10.2.4.1 Explosives 506

10.2.4.2 Free Radicals 507

10.2.4.3 H2O2 508

10.2.4.4 Amines 508

10.2.4.5 Silver Salts 508

10.2.4.6 Hypochlorous Acid (HOCl) 508

10.3 Ir(III) Used in the Development of Sensing Phases 509

10.3.1 Sensing Phases for the Detection of Gases 509

10.3.1.1 Oxygen 509

10.3.1.2 Others Gases 516

10.3.2 Sensing Phases for the Detection of Ions 516

10.3.3 Sensing Phases for the Detection of Biomolecules 517

10.3.3.1 Glucose 518

10.3.3.2 BSA 520

10.3.3.3 Cysteine and Homocysteine 520

10.3.3.4 Heparin 520

10.3.3.5 Histone 521

10.3.4 Sensing Phases for Multiparametric Sensing 521

10.4 Conclusion and Future Challenges 522

Acronyms Used in the Names of the Complexes 525

References 528

11 Photoredox Catalysis of Iridium(III)-Based Photosensitizers 541
Timothy M. Monos and Corey R. J. Stephenson

11.1 Introduction 541

11.1.1 Photoredox Catalysis 541

11.1.2 Principles of Photoredox Catalysis 542

11.1.3 Iridium(III) Photocatalyst Design 542

11.1.4 Ir(III) Photocatalyst synthesis 545

11.2 Iridium-Based Photoredox Catalysis in Organic Synthesis 547

11.2.1 Net Oxidative Reactions 547

11.2.1.1 Amine Oxidation and Functionalization 547

11.2.1.2 Arene Oxidation 551

11.2.2 Net Reductive Reactions 551

11.2.2.1 Dehalogenation Reactions 551

11.2.2.2 Ketyl Radical Chemistry 553

11.2.3 Redox-Neutral Reactions 554

11.2.3.1 Atom Transfer Radical Addition 555

11.2.3.2 Radical-Based Arene Addition Reactions 561

11.2.3.3 Tandem Catalysis Methods 565

11.2.4 Amine Fragmentation 571

11.3 Conclusion 574

References 574

12 Solar Fuel Generation: Structural and Functional Evolution of Iridium Photosensitizers 583
Husain N. Kagalwala, Danielle N. Chirdon and Stefan Bernhard

12.1 Introduction 583

12.2 Fundamentals of [Ir(C^N)2(N^N)]+ Photosensitizers 585

12.2.1 Synthesis and Structure 585

12.2.2 Electronics: Photophysics and Electrochemistry 585

12.2.3 Complexes Made to Order 588

12.3 Application of [Ir(C^N)2(N^N)]+ in Photocatalytic Water Reduction 589

12.3.1 Initial Exploration 589

12.3.2 Systems with Non-precious Components 591

12.3.3 Strategies for Improved Efficiency 594

12.3.3.1 New C^N Ligands 594

12.3.3.2 New N^N Ligands 597

12.3.3.3 Orchestration 599

12.4 Alternative Iridium Structures 603

12.4.1 Tridentate Coordination 603

12.4.2 Tris-Cyclometalated Complexes 605

12.4.3 Dinuclear Iridium Complexes 606

12.5 Outlook 607

Acknowledgements 609

References 610

13 Iridium Complexes in Water Oxidation Catalysis 617
Ilaria Corbucci, Alceo Macchioni and Martin Albrecht

13.1 Introduction 617

13.2 Sacrificial Oxidants 619

13.2.1 Cerium(IV) Ammonium Nitrate 620

13.2.2 Sodium Periodate 620

13.3 Molecular Iridium Catalyst for Water Oxidation 621

13.3.1 Ir WOCs without Cp∗ 621

13.3.2 Ir WOCs with Cp∗ 624

13.3.3 Cp∗Ir WOCs Based on Carbene-Type Ligands 632

13.3.3.1 Cp∗Ir WOCs Bearing Normal Carbene-Type Ligands 633

13.3.3.2 Cp∗Ir WOCs Bearing Abnormal Carbene-Type Ligands 636

13.3.3.3 Comparison of Catalytic Activity of Cp∗Ir Bearing Mesoionic Imidazolylidene Ligand or the Mesoionic Triazolylidene Analogue 638

13.3.4 Heterogenized Molecular Iridium Catalyst for Water Oxidation 640

13.3.5 Iridium WOC as Photocatalyst for Water Oxidation under Visible Light Irradiation 645

13.4 Conclusions 647

Acknowledgements 648

Glossary of Terms and Abbreviations 648

References 649

14 Iridium Complexes as Photoactive Center for Light Harvesting and Solar Cell Applications 655
Etienne Baranoff and Prashant Kumar

14.1 Introduction 655

14.2 Photoinduced Electron Transfer in Multicomponent Arrays 656

14.2.1 Ir(tpy)2 Fragment (tpy = 2,2 :6 -2 -terpyridine) 656

14.2.2 Cyclometalated Iridium(III) 660

14.3 Iridium Complexes as Photoactive Center for Solar Cell Applications 665

14.3.1 Sensitizer for Dye-Sensitized Solar Cells 665

14.3.2 Iridium Complexes for Organic Photovoltaic Devices 673

14.4 Conclusions 676

References 677

Index 683