ORGANIC REDOX SYSTEMS ORGANIC REDOX SYSTEMS Synthesis, Properties, and Applications Edited by ToHRU NISHINAGA Copyright © 2016 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per‐copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750‐8400, fax (978) 750‐4470, or on the web at www.copyright.com. 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Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762‐2974, outside the United States at (317) 572‐3993 or fax (317) 572‐4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com. Library of Congress Cataloging‐in‐Publication Data Organic redox systems : synthesis, properties, and applications / edited by Tohru Nishinaga. pages cm Includes bibliographical references and index. ISBN 978-1-118-85874-5 (cloth) 1. Oxidation-reduction reaction. I. Nishinaga, Tohru, editor. QD716.O95O74 2016 547′.23–dc23 2015030167 Cover image courtesy of Axel Kores/Getty Cover Illustration: Courtesy of Tohru Nishinaga and Takashi Kubo Set in 10/12pt Times by SPi Global, Pondicherry, India Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 1 2016 CONTENTS LIST OF CONTRIBUTORS xv PREFACE xix 1 Introduction: Basic Concepts and a Brief History of Organic Redox Systems 1 Tohru Nishinaga 1.1 Redox Reaction of Organic Molecules, 1 1.2 Redox Potential in Nonaqueous Solvents, 3 1.3 A Brief History of Organic Redox Compounds, 5 References, 10 2 Redox‐Mediated Reversible 힂‐Bond Formation/Cleavage 13 Takanori Suzuki, Hitomi Tamaoki, Jun‐ichi Nishida, Hiroki Higuchi, Tomohiro Iwai, Yusuke Ishigaki, Keisuke Hanada, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara and Takanori Fukushima 2.1 Dynamic Redox (“Dyrex”) Systems, 13 2.1.1 π ‐Electron Systems Exhibiting Drastic Structural Changes upon Electron Transfer, 13 2.1.2 Redox Switching of a σ‐Bond upon Electron Transfer, 16 2.1.3 Two Types of Dyrex Systems Exhibiting Redox Switching of a σ‐Bond, 17 2.2 Advanced Electrochromic Response of “Endo”‐Type Dyrex Systems Exhibiting Redox Switching of a σ‐Bond, 19 vi CONTENTS 2.2.1 Tetraaryldihydrophenanthrenes as Prototypes of “Endo”‐Dyrex Systems, 19 2.2.2 Tricolor Electrochromism with Hysteretic Color Change in Non‐C2‐Symmetric “Endo”‐Dyrex Pair, 20 2.2.3 Electrochromism with Chiroptical Output of Chiral “Endo”‐Dyrex Pair, 21 2.2.4 Multi‐Output Response System Based on Electrochromic “Endo”‐Dyrex Pair, 24 2.3 Advanced Electrochromic Response of “Exo”‐Type Dyrex Systems Exhibiting Redox Switching of a σ‐Bond, 26 2.3.1 Bis(diarylethenyl)biphenyls as Prototypes of “Exo”‐Dyrex Systems, 26 2.3.2 Electrochromism with Chiroptical Output of Chiral “Exo”‐Dyrex Systems, 26 2.3.3 Electrochromism of “Exo”‐Dyrex Systems in Aqueous Media, 28 2.4 Prospect: Redox Systems With Multiple Dyrex Units, 31 References, 33 3 Redox‐Controlled Intramolecular Motions Triggered by π‐Dimerization and Pimerization Processes 39 Christophe Kahlfuss, Eric Saint‐Aman and Christophe Bucher 3.1 Introduction, 39 3.2 Oligothiophenes, 40 3.3 Phenothiazine, 44 3.4 Naphthalene and Perylene Bisimides, 45 3.5 para‐Phenylenediamine, 47 3.6 Pyridinyl Radicals, 49 3.7 Viologen Derivatives, 50 3.8 Verdazyl, 60 3.9 Phenalenyl, 60 3.10 Porphyrins, 61 3.11 Benzenoid, 62 3.12 Cyclophane, 64 3.13 Tetrathiafulvalene, 68 3.14 Conclusion, 80 Acknowledgments, 80 References, 81 4 Tetrathiafulvalene: A Redox Unit for Functional Materials and a Building Block for Supramolecular Self‐Assembly 89 Masashi Hasegawa and Masahiko Iyoda 4.1 Introduction: Past and Present of TTF Chemistry, 89 4.2 Basic Redox Properties of TTF and Stacked TTF, 90 CONTENTS vii 4.2.1 Monomeric TTFs, 90 4.2.2 Interactions in Stacked TTF Dimer, 92 4.2.3 Interactions in Stacked TTF Oligomers, 97 4.2.4 Head‐to‐Tail TTF Dimer, 98 4.3 TTF as a Faithful Redox Active Unit in Functional Materials, 100 4.3.1 Electrochromic Materials, 100 4.3.2 Optically Active TTFs, 102 4.3.3 Uses as Positive Electrode Materials for Rechargeable Batteries, 108 4.4 Electroconducting Properties of TTF Derivatives Based on Supramolecular Self‐Assembly, 112 4.4.1 Redox‐Active Nanostructure Formation in the Solid State, 113 4.4.2 Conducting Nanostructure Formation, 115 4.4.3 Conducting Nanofibers by Iodine Doping, 116 4.4.4 Conducting Nanofibers Based on Cation Radicals, 120 4.4.5 Conducting Nanowires of Neutral TTF Derivatives, 123 4.5 Summary and Outlook, 124 References, 125 5 Robust Aromatic Cation Radicals as Redox Tunable Oxidants 131 Marat R. Talipov and Rajendra Rathore 5.1 Introduction, 131 5.2 Designing Molecules for the Formation of Stable Cation Radicals (CRs)—A Case Study, 135 5.2.1 Exploring the Cause of Exceptional Stability of THE‐Orange+·, 137 5.3 Methods of Preparative Isolation of Aromatic Cation Radicals, 142 5.3.1 Nitrosonium (NO+) Salts, 143 5.3.2 Antimony Pentachloride (SbCl5), 144 5.3.3 Triethyloxonium Hexachloroantimonate + – (Et3O SbCl6 ), 148 5.3.4 DDQ and HBF4‐Ether Complex, 149 5.4 Quantitative Oxidation of Electron Donors Using THE-Orange+· – SbCl6 as One‐Electron Oxidant, 150 5.4.1 Analysis of Two‐Electron Oxidation Processes Using MF/D Plots, 157 5.5 Readily Available Electron Donors for the Redox‐Tunable Aromatic Oxidants, 164 5.5.1 Triptycene Based Electron Donors, 164 5.5.2 Tetrabenzodifurans, 166 5.5.3 Polyaromatic Hydrocarbons, 168 5.5.4 Multi‐Electron Redox Systems, 168 5.6 Conclusion, 171 References, 173 viii CONTENTS 6 Air‐Stable Redox‐Active Neutral Radicals: Topological Symmetry Control of Electronic‐Spin, Multicentered Chemical Bonding, and Organic Battery Application 177 Shinsuke Nishida and Yasushi Morita 6.1 Introduction, 177 6.2 Open‐Shell Graphene Fragment: Design and Synthesis of Air‐Stable Carbon‐Centered Neutral Radicals Based on Fused‐Polycyclic π‐System, 179 6.3 Topological Symmetry Control of Electronic‐Spin Density Distribution by Redox and other External Stimuli, 181 6.3.1 Redox‐Based Spin Diversity of Oxophenalenoxyl Sytems, 181 6.3.2 Spin‐Center Transfer and Solvato‐/Thermochromism of Tetrathiafulvalene‐Substituted 6‐Oxophenalenoxyl Neutral Radical, 183 6.4 Control of Electronic‐Spin Structure and Optical Properties of Multicentered C─C Bonds, 184 6.4.1 Strong SOMO–SOMO Interaction within π‐Dimeric Structure of Phenalenyl Derivatives, 184 6.4.2 Thermochromism Induced by Thermal Equilibrium of π‐Dimeric Structure and σ‐Dimeric Structure, 188 6.4.3 Weak SOMO–SOMO Interactions by Molecular Modification of Phenalenyl System, 190 6.4.4 Multidimensional Spin–Spin Interaction and π‐Staked Radical Polymer, 193 6.5 Rechargeable Batteries Using Organic Electrode‐Active Materials, 195 6.5.1 Closed‐Shell Organic Molecules as Electrode‐Active Materials, 196 6.5.2 Closed‐Shell Organic Polymers, 214 6.5.3 Stable Organic Neutral Radicals, 218 6.5.4 Stable Organic Neutral Radical Polymers, 220 6.6 Molecular Spin Batteries: Design Criteria and Performance of High Capacity Organic Rechargeable Battery Materials, 223 6.6.1 Molecular Crystalline Secondary Batteries, 223 6.6.2 Trioxotriangulene Neutral Radical (TOT) Derivatives, 224 6.6.3 Molecular Spin Batteries, 227 6.7 Conclusion, 229 Acknowledgement, 231 References, 231 7 Triarylamine‐Based Organic Mixed‐Valence Compounds: The Role of the Bridge 245 Christoph Lambert 7.1 Introduction, 245 7.2 The MV Concept, 246 CONTENTS ix 7.3 The Redox Center, 250 7.4 The Bridge, 251 7.5 The Length of the Bridge, 254 7.6 Changing the Connectivity, 256 7.7 Twisting the Bridge, 258 7.8 Saturated vs Unsaturated Bridge, 258 7.9 Meta vs Para Conjugation, 260 7.10 Switching the Bridge, 262 7.11 Metal Atoms as the Bridge, 263 7.12 And Finally: Without a Bridge, 264 Acknowledgment, 265 References, 265 8 Magnetic Properties of Multiradicals Based on Triarylamine Radical Cations 269 Shuichi Suzuki and Keiji Okada 8.1 Introduction, 269 8.2 Triarylamine Radical Cations as Synthetic Reagents for Preparation of Donor Radical Cations