Carson J. Bruns is a Miller Research Fellow in the College of Chemistry at the University of California, Berkeley. He attended Luther College (2004–2008) where he earned degrees in chemistry, religion, and mathematics. He received a PhD in organic chemistry from Northwestern University (2008–2013), where he was a National Science Foundation (NSF) Graduate Research Fellow. Researching in the United States, Thailand, Korea, and Japan, he has co-authored more than 30 publications which have collectively been cited more than 1000 times. His research interests span all aspects of the mechanical bond, from fundamental science to applied chemical technologies.J. Fraser Stoddart is a Board of Trustees Professor of Chemistry at Northwestern University. By playing a major role in introducing the mechanical bond into molecules, he is one of the few contemporary chemists to have contributed to the opening up of an entirely new field of chemistry. He has pioneered the development of bistable mechanically interlocked molecules (MIMs) for use in molecular electronic devices and drug delivery vehicles. In 2016 he shared the Nobel Prize in Chemistry with Jean-Pierre Sauvage and Ben Feringa for the design and synthesis of molecular machines.

• Foreword ixPreface xiAcknowledgments xiiiAbout the Authors xivAbbreviations, Acronyms, and Symbols xvPart 1 Introducing Mechanical Bonds 11 An Introduction to the Mechanical Bond 3Conspectus 3Introduction 41.1 The Ubiquity of the Mechanical Bond 71.1.1 Mechanical Bonds in Nature 81.1.2 Mechanical Bonds in Art 101.1.3 Mechanical Bonds in Everyday Life 111.2 Representing Molecular Mechanical Bonds 131.2.1 A Historical Perspective 131.2.2 Perspective Stereoformulas 161.2.3 Depictions in Color 161.2.4 Solid-State Portrayals 171.2.5 Graphical Representations 181.2.6 Technomorphs 201.3 Aesthetics of Mechanical Bonds 211.3.1 Beauty in Diversity 211.3.2 Topological Beauty 211.3.3 Architectural Beauty 241.3.4 Simplicity and Elegance 281.3.5 Complexity and Emergence 301.3.6 Beautiful Machines with Mechanical Bonds 321.3.7 The Art of the Mechanical Bond 371.4 Evolution of Mechanostereochemistry 38References 42Part 2 Making Mechanical Bonds 552 The Fundamentals of Making Mechanical Bonds 57Conspectus 57Introduction 592.1 Statistical Synthesis 622.2 Directed Synthesis 652.2.1 Covalent Templates 652.2.2 Covalent-Directed Capture 692.2.3 The Möbius Approach 712.3 Template-Directed Synthesis 732.3.1 Solvophobic Forces 742.3.2 Transition Metals Templates 882.3.3 π-Donor/π-Acceptor Templates 1022.3.4 Hydrogen-Bonded Templates 1382.3.5 Halogen-Bonded Templates 1732.3.6 Anion-Binding Templates 1742.3.7 Ion-Pair Templates 1912.3.8 Other Cationic Templates 1952.3.9 Macrocyclic Arenes and Heteroarenes 1992.3.10 Radical-Pair Templates 2072.3.11 Homophilic Templates 2102.3.12 Biomolecular Templates 2112.4 Active Template Synthesis 2182.4.1 Active Copper Templates 2192.4.2 Active Zinc Templates 2252.4.3 Active Palladium Templates 2262.4.4 Active Nickel Templates 227Conclusions and Outlook 229References 2303 Making Mechanical Bonds Under Thermodynamic Control 269Conspectus 269Introduction 2713.1 Slippage 2713.1.1 Pseudorotaxane or Rotaxane? 2733.1.2 Slippage of π-Donor/π-Acceptor Rotaxanes 2753.1.3 Slippage of Hydrogen-Bonded Rotaxanes 2783.1.4 Slippage Driven by Hydrophobic Interactions 2833.1.5 Slippage of Anion-Binding Rotaxanes 2843.1.6 Triumphs and Tribulations of Slippage 2853.2 Self-Assembling Metallo-Organic MIMs 2853.2.1 MIMs Possessing Group 10 Elements 2853.2.2 MIMs Possessing Group 11 Elements 2923.2.3 MIMs Possessing Group 12 Elements 2973.2.4 MIMs Possessing Elements of Groups 7–9 2983.2.5 MIMs Possessing Alkaline Earth Elements 3023.3 Mechanical Bond Formation by Condensation 3033.3.1 Imines 3033.3.2 Hydrazones 3103.3.3 Boronic Esters and Boroxines 3123.4 Mechanical Bond Formation by Olefin Metathesis 3133.4.1 Ring-Closing Metathesis (RCM) 3143.4.2 Cross Metathesis (CM) 3233.5 Mechanical Bond Formation by Reversible Nucleophilic Reactions 3243.5.1 Disulfide Exchange 3243.5.2 Reversible Nucleophilic Substitutions 3283.5.3 Michael Additions 3303.6 Surface-Mounted MIMs 330Conclusions and Outlook 333References 333Part 3 Cultivating Mechanical Bonds 3474 Molecular Topologies and Architectures with Mechanical Bonds 349Conspectus 349Introduction 3514.1 Catenane Topologies 3524.1.1 Prime Links 3524.1.2 Composite Links 3614.1.3 Multi-Annulated Catenanes 3694.1.4 Covalently Bridged Catenanes 3864.2 Rotaxane Architectures 3924.2.1 [n]Rotaxanes 3924.2.2 Dendritic Rotaxanes 4164.2.3 Covalently Bridged Rotaxanes 4244.3 Other Architectures with Mechanical Bonds 4414.3.1 Catenarotaxanes 4414.3.2 Rotamacrocycles 4424.3.3 Ring-in-Ring Mechanomolecules 4424.3.4 Self-Threaded Macropolycyclics 4434.3.5 Suitanes 4444.3.6 Foldaxanes 4444.3.7 Braided and Interwoven Polymer Entanglements 444Conclusions and Outlook 444References 4455 The Stereochemistry of the Mechanical Bond 471Conspectus 471Introduction 4725.1 Dynamic Mechanostereoisomerism 4735.1.1 Translation and Circumrotation 4745.1.2 Pirouetting 5025.1.3 Rocking 5125.1.4 Robust Dynamics 5135.2 Static Mechanostereoisomerism 5155.2.1 Orientational Mechanostereoisomers 5155.2.2 Sequence Mechanostereoisomers 5205.2.3 Mechanically Chiral Mechanostereoisomers 5225.2.4 Topological Stereoisomerism 531Concluding Remarks 540References 5416 Molecular Switches and Machines with Mechanical Bonds 555Conspectus 555Introduction 5586.1 Redox-Driven Switches 5606.1.1 Redox-Switchable Donor-Acceptor (D-A) MIMs 5606.1.2 Redox Switching of Metallo-Mechanomolecules 5666.1.3 Redox Switching of Hydrogen-Bonded MIMs 5726.1.4 Aqueous Redox Switching 5736.2 Photo-Driven Switches 5746.2.1 Switching Driven by Photoinduced Electron Transfer 5746.2.2 Switching Driven by Photoisomerization 5776.2.3 Switching in a Dissociative Excited State 5806.2.4 Switching Driven by Photochemical Reactions 5806.3 Acid/Base-Driven Switches 5816.3.1 pH Switching Driven by Hydrophobic Effects 5816.3.2 pH Switching Driven by Electrostatic Repulsion 5836.3.3 pH Switching Driven by Hydrogen Bonding 5846.3.4 pH Switching Driven by Metal Chelation 5886.4 Cation-Triggered Switches 5916.4.1 Switching with Transition Metal Cations 5916.4.2 Switching with Alkali Metal Cations 5946.4.3 Switching with Alkaline Earth Metal Cations 5976.5 Anion-Triggered Switches 5986.5.1 Switches Driven by Anion Solvation Effects 5986.5.2 Switching Through Second-Sphere Interactions 6006.5.3 Switches Driven by Anion Binding 6006.6 Switches Driven by Molecular Recognition 6046.6.1 Switches Driven by Neutral Small Molecules 6046.6.2 Switches Driven by DNA Strand Displacement 6066.7 Switches Driven by Covalent Reactions 6076.7.1 Switches Driven by Acylations of Amines 6076.7.2 Switches Driven by Reactions of Pyridines 6096.7.3 Switches Driven by Protection of Aldehydes 6106.7.4 Switches Driven by Diels-Alder Reactions 6106.7.5 Switches Driven by (De)Hydrogenation 6106.7.6 Switches Driven by the Mitsunobu Reaction 6106.8 Solvent-Driven Switches 6116.8.1 Switching Driven by Hydrogen Bond Disruption 6126.8.2 Switching Driven by Solvation Effects 6156.9 Thermally Driven Switches 6166.9.1 Switching Driven by Entropic Effects 6166.9.2 Switching Driven by Thermal Decomposition 6216.10 Pressure-Driven Switches 6226.11 Switches Driven by Electric Fields 6236.12 Switches Driven by Mechanical Force 6246.13 Beyond Translation and Circumrotation 6276.13.1 Expansion and Contraction: Molecular Muscles with Mechanical Bonds 6276.13.2 Ultramacrocyclic Constriction/Dilation 6396.13.3 Motions of Branched Rotaxanes 6436.13.4 The Gemini Co-Conformation 6456.13.5 Rotaxane Flapping 6466.13.6 Collapsing Mechanomolecules 6476.13.7 Mechanically Constrained Inflation/Deflation 6476.13.8 Folding/Unfolding in Mechanomolecules 6476.13.9 Stepwise Motion in Pseudocatenanes 6496.13.10 Molecular Pulleys 6496.13.11 Multicomponent Pirouetting and Translation 6496.13.12 Molecular Conveyor Belts 6526.14 Condensed-Phase Switching 6526.14.1 Condensed-Phase Redox Switches 6526.14.2 Condensed-Phase Photoswitches 6666.14.3 Condensed-Phase Chemical Switches 6676.15 Mechanomolecular Motors and Machines 6696.15.1 Systems-Coupled Functional Switches 6706.15.2 Brownian Ratchets with Mechanical Bonds 6946.15.3 Mechanically Bonded Molecular Assemblers 706Conclusions and Outlook 708References 709Appendix A: Glossary of Terminology 734Appendix B: Cover Art Gallery 742Index 753

"This book will serve very well to inform any chemist or chemistry student curious as to the workings of molecular topology and the molecular machines that depend upon it, and should be read by anyone seeking to enter these fields. The writing is elegant and at times playful-thoroughly enjoyable to read. This book will certainly occupy pride of place in my research group' library."Angewandte Chemie International Edition, 8th December 2016"The book contains numerous schemes and illustrations of high quality. These facilitate the visualization of the molecular structures and of the chemical and dynamical processes. Each chapter contains approximately 500 to 1500 references and the book presents a total of 3400 unique references which corresponds to the main publications in this research domain. Undoubtedly, the book will be a most useful tool for all researchers interested in mechanically interlocked molecules ... One can anticipate, I believe, that The Nature of the Mechanical Bond will open new horizons for generations of readers and will stimulate the creativity of many architects of matter who wish to design more and more fascinating molecular systems."Acta Cryst, November 2017