Inorganic ElectrochemistryTheory, Practice and Application2nd Edition

Piero Zanello and Fabrizia Fabrizi de Biani

Department of Chemistry, University of Siena, Siena, Italy

and

Carlo Nervi

Department of Chemistry, University of Torino, Torino, Italy

RSC Publishing

Contents

Part 1: Basic Aspects of Electrochemistry

Chapter 1 Fundamentals of Electrode Reactions 3

1.1 Electron-transfer Reactions 3

1.2 Fundamentals of Electron Transfers at an Electrode 6

1.2.1 Electrode/Solution System 6

1.2.2 Nature of Electrode Reactions 8

1.2.3 Current as a Measurement of the Rate of an

Electrode Reaction 9

1.2.4 Potential as a Measurement of the Energy of

the Electrons inside the Electrode 11

1.2.5 Biunique Relationship between Current and

Potential 12

1.3 Potential and Electrochemical Cells 12

1.4 Kinetic Aspects of Electrode Reactions 17

1.4.1 Electron Transfer 17

1.4.2 Mass Transport 28

1.4.3 Influence of Mass Transport on ChargeTransfer: Electrochemically 'Reversible' and

'Irreversible' Processes 35

1.5 Non-faradaic Processes: Capacitive Currents 36

1.6 Electrical Double Layer: A Deeper Examination 38

1.6.1 Kinetic Consequences of the Double LayerComposition on the Electron Transfer 39

References 41

Chapter 2 Voltammetric Techniques 42

2.1 Cyclic Voltammetry 42

2.1.1 Reversible (Nernstian) Processes 43

2.1.2 Irreversible Processes 51

Inorganic Electrochemistry: Theory, Practice and Application, 2 Edition

By Piero Zanello, Fabrizia Fabrizi de Biani and Carlo Nervi

© Piero Zanello, Carlo Nervi and Fabrizia Fabrizi de Biani, 2012

Published by the Royal Society of Chemistry, www.rsc.org

xi

xii Contents

2.1.3 Quasireversible Processes 53

2.1.4 Effect of Chemical Reactions Coupled to

Electron Transfers 58

2.1.5 Consecutive Electron-transfer Processes 85

2.1.6 Adsorption Processes 90

2.2 Electrochemical Techniques Complementary to Cyclic

Voltammetry 94

2.2.1 Pulsed Voltammetric Techniques 94

2.2.2 Mathematical Treatment of Voltammetric

Responses 99

2.2.3 Hydrodynamic Techniques 100

2.2.4 Controlled Potential Electrolysis 103

2.2.5 Chronoamperometry 107

References 108

Chapter 3 Software Able to Assist Electrochemistry 110

3.1 Digital Simulation of Voltammetric Responses 110

3.1.1 Mathematics and Electrochemistry 112

3.1.2 What Needs to done Before Starting a

Simulation? 112

3.1.3 Basics of Digital Simulation 114

3.1.4 Method of Explicit Finite Differences (EFD) 115

3.1.5 Analog vs. Digital Potentiostats 128

3.1.6 Overview of Electrochemical Simulators 129

3.1.7 A Practical Example 130

3.2 Computational Approaches to Redox Chemistry 136

3.2.1 Frontier Orbitals Approximation 137

3.2.2 Free Energy Cycle 141

3.2.3 Solvent Effects 147

3.2.4 Semiempirical Calculations vs. Ab Initio

Calculations 150

References 151

Part 2: Practical Aspects

Chapter 4 Basic Equipment for Electrochemical Measurements 155

4.1 Electrodes 155

4.1.1 Indicator Electrodes 155

4.1.2 Reference Electrodes 157

4.1.3 Auxiliary Electrodes 157

4.2 Electrochemical Cells 159

4.2.1 Cells for Cyclic Voltammetry and

Complementary Techniques 161

4.2.2 Cells for Controlled Potential Electrolysis 163

Contents xiii

4.3 Solutions for Electrochemical Studies: Solvents and

Supporting Electrolytes 164

References 169

Part 3: Applicative Aspects

Chapter 5 Electrochemical Behaviour of First Row Transition Metal

Sandwich Complexes: Metallocenes and Metallacarboranes 173

5.1 Metallocenes 173

5.1.1 Ferrocenes 174

5.1.2 Vanadocenes 218

5.1.3 Chromocenes 221

5.1.4 Manganocenes 223

5.1.5 Cobaltocenes 224

5.1.6 Nickelocenes 227

5.2 Metallacarboranes 231

5.2.1 Ferracarboranes 233

5.2.2 Chromacarboranes 235

5.2.3 Cobaltacarboranes 235

5.2.4 Nickelacarboranes 238

References 240

Chapter 6 Electrochemical Behaviour of Transition Metal Complexes 248

6.1 Vanadium Complexes 250

6.2 Chromium Complexes 259

6.3 Manganese Complexes 265

6.4 Iron Complexes 270

6.5 Cobalt Complexes 281

6.6 Nickel Complexes 291

6.7 Copper Complexes 300

6.8 Zinc Complexes 310

6.9 Intramolecular Electronic Communication

in Polynuclear Complexes 311

6.10 Redox Potential and Electronic Effects

of the Ligands 316

References 326

Chapter 7 Metal Complexes Containing Redox-active Ligands 335

7.1 Ferrocenes as Ligands in Metal Complexes 335

7.2 Fullerenes as Ligands in Metal Complexes 342

7.2.1 Exohedral Metallafullerenes 346

7.2.2 Endohedral Metallafullerenes 355

xiv Contents

7.3 Dioxolenes and their Imino Analogues as Ligands in

Metal Complexes 360

7.4 Dithiolene Ligands in Metal Complexes 371

7.5 Porphyrins and Tetraazaporphyrins as Ligandsin Metal Complexes 377

7.6 Less Well-known Redox-active Ligands in Metal

Complexes 384

References 391

Chapter 8 Electrochemistry and Molecular Reorganizations 402

8.1 Geometrical Isomers 402

8.2 Redox-induced Geometrical

Isomerizations 406

References 418

Chapter 9 Reactivity of Transition Metal Complexes with Small

Molecules 420

9.1 Reactivity of Transition Metal Complexeswith Dioxygen 420

9.1.1 Metal Complexes that React Irreversibly with

Dioxygen 421

9.1.2 Metal Complexes that React Reversibly with

Dioxygen 423

9.1.3 Hemoprotein-like Metal Complexes 427

9.1.4 Hemocyanin-like Metal Complexes 438

9.1.5 Hemerythrin-like Metal Complexes 439

9.2 Reactivity of Transition Metal Complexes with

Dinitrogen 440

9.2.1 Metal Complexes with Terminal Coordination

to One Dinitrogen Molecule 443

9.2.2 Metal Complexes with Bridging Coordination

to One Dinitrogen Molecule 445

9.2.3 Metal Complexes with Terminal Coordination

to Two Dinitrogen Molecules 450

9.3 Reactivity of Transition Metal Complexes with

Dihydrogen 451

9.4 Reactivity of Transition Metal Complexes with

Nitric Oxide 460

9.4.1 Iron Nitrosyl Derivatives 461

9.4.2 Ruthenium Nitrosyl Derivatives 468

9.4.3 Osmium Nitrosyl Derivatives 471

References 473

Contents xv

Chapter 10 Transition Metal Clusters 481

10.1 Metal-Sulfur Clusters 481

10.1.1 M3S„(n = 2, 4) 481

10.1.2 M4S„(h = 3-6) 486

10.1.3 M6S„(w = 6, 8, 9) 490

10.1.4 M9S9 494

10.1.5 M,5S15 494

10.2 Homoleptic Metal-Carbonyl Clusters 494

10.2.1 M3(CO),2, [M3(CO)„]2- (M = Fe, Ru, Os) 495

10.2.2 [Fe4(CO)i3]2", M4(CO)12(M= Co,Rh, Ir) 497

10.2.3 [M5(CO)15]"" (M = Os, n = 2; M= Rh, n = 1) 498

10.2.4 From [M6(CO)i5]2" to [M^CO)^]2"(M = Co, Ru, Rh, Os, Ir, Pt) 498

10.3 Carbonyl Clusters with Interstitial Atoms 501

10.3.1 [Fe4(CO)i2N]-, [Fe4(CO)12C]2- 502

10.3.2 [Fe5(CO)14N]', [Fe5(CO)14C]2- 505

10.3.3 [Fe6(CO)15N]3-, [Fe6(CO)16C]2-[Os6(CO)18P]- 506

10.3.4 [Co10(CO)22P]3- [Co10N2(CO)19]^,[ConCCO)^),]4- 507

10.3.5 [Ni32(CO)36(C)6]6- 509

10.4 Thiolate-protected Gold Nanoclusters 510

References 512

Chapter 11 'Direct' Electrochemistry of Redox-active Proteins 519

11.1 Introduction 519

11.2 Electrochemistry of Cytochromes 522

11.3 Electrochemistry of Iron-Sulfur Proteins 535

11.4 Electrochemistry of Copper Proteins 546

11.4.1 Electrochemistry of'Type 1' Blue CopperProteins 547

11.4.2 Electrochemistry of 'Type 2' Copper Proteins 552

11.4.3 Electrochemistry of 'Type 3' Copper Proteins 553

11.4.4 Electrochemistry of Multi-copperBlue Oxidases 554

References 559

Chapter 12 Single-molecule Electronics: From Molecular Metal Wires

to Molecular Motors 564

12.1 Molecular Metal Wires 564

12.1.1 Platinum Blues 566

12.1.2 Chloride-bridged Triruthenium

Complexes 568

xvi Contents

12.1.3 Oligo-oc-pyridylamides and Related

Derivatives as Bridging Ligands in

Polynuclear Linear Complexes 570

12.1.4 Other Polynuclear Linear Complexes 587

12.2 Electrochemically Triggered Molecular Motion 589

12.2.1 Rotaxanes 590

12.2.2 Catenanes 595

References 600

Chapter 13 Spectroelectrochemistry 606

13.1 Basics of Spectroelectrochemical Methods 606

13.1.1 Transmission and Reflectance Spectroscopies 607

13.2 Absorption Spectroscopic Techniques Coupled with

Electrochemistry 620

13.2.1 UV-Vis-NIR Spectroelectrochemistry 620

13.2.2 IR Spectroelectrochemistry 627

13.2.3 Circular Dichroism Spectroelectrochemistry 633

13.2.4 X-Ray Absorption: XANES and EXAFS

Spectroelectrochemistry 634

13.2.5 Other Spectroelectrochemical Techniques 636

13.3 Applications 644

13.3.1 Organic and Inorganic Spectroelectro¬chemistry 644

13.3.2 Biological Systems 647

13.3.3 Reaction Kinetics and Mechanisms 649

13.3.4 Analytical Applications 650

13.4 Conclusion 651

References 651

Chapter 14 An Introduction to Electrogenerated Chemiluminescence 657

14.1 Basics of ECL 658

14.1.1 Annihilation 658

14.1.2 Co-reactants 662

References 667

Appendices 668

Physical Constants 668

SI Base Units 668

Derived SI Units 669

SI Prefixes 669

Conversion Factors 669

Subject Index 671