- Covers bond formation and cleavage, supramolecular systems, molecular design, and synthesis and properties
- Addresses preparative methods, unique structural features, physical properties, and material applications of redox active p-conjugated systems
- Offers a useful guide for both academic and industrial chemists involved with organic electronic materials
- Focuses on the transition-metal-free redox systems composed of organic and organo main group compounds
Tohru Nishinaga, PhD, is an Associate Professor of Chemistry at Tokyo Metropolitan University. His current research interest is the design, synthesis and application of pi-electron systems with novel electronic properties. Dr. Nishinaga has published over 80 scientific papers and 10 book chapters.
Autorentext
Tohru Nishinaga, PhD, is an Associate Professor of Chemistry at Tokyo Metropolitan University. His current research interest is the design, synthesis and application of pi-electron systems with novel electronic properties. Dr. Nishinaga has published over 80 scientific papers and 10 book chapters.
Leseprobe
1
INTRODUCTION: BASIC CONCEPTS AND A BRIEF HISTORY OF ORGANIC REDOX SYSTEMS
Tohru Nishinaga
Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
1.1 REDOX REACTION OF ORGANIC MOLECULES
Redox is a portmanteau word of "reduction" and "oxidation." Originally, oxidation meant a chemical reaction in which oxygen combines with another substance, after Antoine Lavoisier, late in the eighteenth century, called a product of the reaction an oxide [1]. The term "reduction" had been used long before the introduction of the term "oxidation" in the smelting to produce iron from ore and coke [1]. In the contemporary definition recommended by IUPAC [2], oxidation is a reaction that satisfies criteria 1 "the complete, net removal of one or more electrons from a molecular entity" and 2 "an increase in the oxidation number of any atom within any substrate" and meets in many cases criterion 3 "gain of oxygen and/or loss of hydrogen of an organic substrate." Conversely, reduction is the reverse process of oxidation.
For transition metals, a direct one-electron transfer related to the aforementioned criterion 1 is common due to their relatively lower ionization energy in comparison with main group elements [3] and low reactivity of the unpaired d-electrons. In contrast, the mechanisms of common organic redox reactions do not involve a direct one-electron transfer [4], and reactions based on the criterion 3 are typical. For example, oxidation of primary alcohol (RCH2OH) to aldehyde (RHC _ O) with Cr(VI)O3 proceeds via chromic ester intermediate (RCH2O3Cr(VI)OH), and proton and HOCr(IV)O2_ are eliminated from the intermediate [5] ( Scheme 1.1 a). In this reaction, the total number of electrons in the outer shell decreases from 14 at the C _ O moiety to 12 at the C _ O moiety, that is, two-electron oxidation, while the formal oxidation number of Cr changes from +6 to +4, that is, two-electron reduction. Similarly, reduction of carbonyl group to alcohol with NaBH4 in ethanol formally proceeds via nucleophilic attack of a pair of electrons in hydride to electron-deficient carbonyl carbon [5] ( Scheme 1.1 b). Thus, formally, a pair of two electrons moves together in typical organic redox reactions as known in other organic reactions such as substitutions.
SCHEME 1.1 (a) Oxidation of alcohol to aldehyde with Cr(VI) and (b) hydride reduction of aldehyde to alcohol.
On the other hand, one-electron oxidation or reduction of a neutral or ionic molecule ( Scheme 1.2 ) gives generally highly reactive ion radicals or radicals, and follow-up reactions such as radical coupling and deprotonation are prone to take place [6]. Nevertheless, some organic molecules give persistent species after one-electron transfer at ambient temperature [7, 8]. Simple _-extension and substituents of resonance electron donating R2N _ , RO _ , RS _ or withdrawing N_C _ , C _ O groups cause delocalization of spin and charge density, which reduces the reactivity of the reactive center. As the other thermodynamic stabilization, aromatization after electron transfer plays an important role for certain molecules. An appropriate steric protection is also an effective strategy for protecting a reactive radical center [9]. As a result of these effects, they can be reversibly regenerated by the reverse electron transfer. This book deals with organic _-electron systems and related organo main group compounds that show such reversible one-electron transfer.
SCHEME 1.2 One-electron oxidation and reduction of neutral and ionic molecules.
1.2 REDOX POTENTIAL IN NONAQUEOUS SOLVENTS
Redox potential is the important measure for redox systems, by wh
Inhalt
LIST OF CONTRIBUTO RS 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 𝞂?\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 ?\Electron Systems Exhibiting Drastic Structural Changes upon Electron Transfer, 13
2.1.2 Redox Switching of a ?\Bond upon Electron Transfer, 16
2.1.3 Two Types of Dyrex Systems Exhibiting Redox Switching of a ?\Bond, 17
2.2 Advanced Electrochromic Response of Endo?\Type Dyrex Systems Exhibiting Redox Switching of a ?\Bond, 19
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 ?\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 ?\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 …