Diradicaloids

Cover
Half Title
Title Page
Copyright Page
Table of Contents
Preface
Chapter 1: Excitation Energies and Optical Properties of Open-Shell Singlet Diradicaloids
1.1: Introduction
1.2: Electronic Structures of Singlet Diradicaloids
1.2.1: VCI Model of Symmetric Diradicaloids
1.2.2: Diradical Character Dependences of Excitation Energies and Properties of Symmetric Diradicaloids by VCI Model
1.2.3: VCI Model of Asymmetric Diradicaloids
1.2.4: Diradical Character Dependences of Excitation Energies and Properties of Asymmetric Diradicaloids by VCI Model
1.2.5: Novel Definition of Diradical and Ionic Characters
1.2.5.1: Diradical and ionic characters and their densities for arbitrary states within thetwo-site model
1.2.5.2: Application to π-stacked dimer of phenalenyl-derivatives with varying intermonomer distance
1.2.6: Experimental Estimation of Diradical Character
1.3: BS Approach to Diradicaloids
1.3.1: Spin-Projected BS Approach to Diradical Character
1.3.2: Relationship between Diradical Character and Aromaticity
1.3.3: Estimation of Singlet Excitation Energies and ST Energy Gap for Diradicaloids
1.4: Functionalities of Singlet Diradicaloids
1.4.1: NLO Property
1.4.2: Singlet Fission
1.5: Summary
Chapter 2: Electronic Structure Characterization of Diradicaloids with Spin-Flip (SF) Methods
2.1: Introduction
2.2: Theory of SF Methods
2.2.1: SF Methods to Describe Diradicals
2.2.2: SF in CC and CI
2.2.3: SF in TDDFT
2.2.4: SF with Active Space
2.2.5: Characterization of Diradical Character
2.2.5.1: Singlet–triplet energy gap
2.2.5.2: Diradical index
2.2.5.3: Natural orbitals and occupation numbers
2.2.5.4: Density of unpaired electrons
2.2.5.5: Number of unpaired electrons
2.3: Application of SF Methods to the Study of Diradicaloids
2.3.1: Ethylene Torsion with SF-TDDFT
2.3.2: Radical Character of Triangulenes
2.3.3: Diradical Character of Linear Acenes and Zethrenes
2.3.4: Diradical Character of Fluorenofluorenes
2.3.5: Diradical Character of Cyclic Acenes and Carbon Nanobelts
2.3.6: Diradical Character in Nanographene Induced by Pressure
2.4: Summary
Chapter 3: Spectroscopy of Open-Shell Singlet Ground-State Diradicaloids: A Computational Perspective
3.1: Introduction
3.2: Cost-Effective Computational Approaches for Description of SE and DE States of Diradicaloids
3.2.1: Descriptors of Diradical Character
3.2.2: 2e-2o Model
3.2.3: TDUDFT
3.2.4: SF-TDDFT
3.2.5: DFT/MRCI
3.3: Results
3.3.1: Diradical Character from y0 and NFOD Descriptors
3.3.2: DE State from High-Level Computational Studies
3.3.3: Bright SE Excited State from DFT-Based Approaches
3.3.4: DE Excited State from DFT-Based Approaches
3.4: Concluding Remarks
Chapter 4: Vibrational Raman Spectroscopy of Diradicaloids: Revealing Their Physical Origin
4.1: Introduction to Vibrational Spectroscopy of Hydrocarbon Molecules
4.2: Fundamental Physics on the Raman Spectra of Poly-Conjugated Molecules and Diradicaloids
4.3: Tetracyano Quinoidal Oligothiophenes: The Oligomer Approach to Diradicaloid Molecules by Raman Spectroscopy
4.4: Tetracyano Oligoperylenes: Ground Electronic State Triplets Detected by Raman Spectroscopy
4.5: Planar Aromatic Oligorylenes Diradicaloids: Raman Spectra beyond Peierls Restrictions
4.6: Planar Zethrenes and Indenoacene Diradicaloids
4.7: Conclusions
Chapter 5: Phenalenyl- and Anthene-Based Diradicaloids
5.1: Introduction
5.2: Phenalenyl-Based Diradicaloids
5.2.1: Thermodynamic Stability of Phenalenyl Radical
5.2.2: Design and Synthesis of Bisphenalenyl Diradicaloid
5.2.3: Physical Properties of Bisphenalenyl Diradicaloid
5.2.4: Tuning of Diradical Character of Bisphenalenyl Diradicaloids
5.2.5: Non-linear Optical Property of Bisphenalenyl Diradicaloids
5.2.6: Cycloaddition Reactions of Bisphenalenyl Diradicaloid having o-Quinodimethane Scaffold
5.2.7: Electrocyclization of Bisphenalenyl Diradicaloid
5.2.8: Through-Space Conjugated Bisphenalenyl Diradicaloids
5.3: Anthene-Based Diradicaloids
5.3.1: Unique Electronic Properties of Graphene
5.3.2: Model System for Investigating Edge State
5.3.3: Synthesis of Anthenes
5.3.4: Molecular Structure of Anthenes
5.3.5: Magnetic Properties of Anthenes
5.3.6: Optical Properties of Anthenes
5.3.7: Mechanism of Diradical Character in Anthenes
5.3.8: Lateral Extension from Anthenes
5.3.9: Other Model Systems of Graphene
5.4: Summary
Chapter 6: Zethrenes and Related Molecules
6.1: Pioneers of Zethrene Chemistry
6.2: Modern Syntheses of Zethrenes and Discovery of Open-Shell Diradical Character
6.3: Extended Zethrenes-Based Diradicaloids
6.3.1: Vertically Extended Zethrenes
6.3.2: Laterally Extended Zethrenes
6.4: Zethrene Isomers and Analogs
6.5: Conclusion
Chapter 7: Extended para-Quinodimethanes and Quinones
7.1: Extended Para-Quinodimethanes
7.2: Extended Quinones
7.3: Quinoidal Oligothiophenes
7.4: Conclusion
Chapter 8: Fused Heteropolycyclic Compounds-Based Diradicaloids
8.1: Introduction
8.2: Quinoidal Acene and Heteroacene Analogs
8.2.1: General Synthetic Strategies
8.2.2: Extended Quinoidal Acene Analogs
8.2.3: Extended Quinoidal Heteroacene Analogs
8.3: Extended Aza-Acenes and Aza-Quinodimethanes
8.4: Non-Classical Acenes Capped with Thiophenes or Thiadiazoles
8.5: Summary
Chapter 9: Non-Benzenoid Polycyclic Hydrocarbon-Based Diradicaloids
9.1: Introduction
9.2: Five-Membered Ring-Containing Diradicaloids
9.2.1: Pentalene-Based Diradicaloids
9.2.2: Indacene-Based Diradicaloids
9.2.2.1: Indenofluorene and its π-extended homologues
9.2.2.2: Biphenalenyls
9.2.3: Curved Diradicaloids with Pentagons
9.2.4: Other Diradicaloids with Pentagons
9.3: Seven-Membered Ring-Containing Diradicaloids
9.4: Four- or Eight-Membered Ring-Containing Diradicaloids
9.5: Summary
Chapter 10: Photo-Responsive Diradicaloids
10.1: Introduction
10.2: Pentaarylbiimidazole
10.3: Phenoxyl-Imidazolyl Radical Complex
10.4: Bis(Phenoxyl-Imidazolyl Radical Complex)
10.5: Conclusion
Chapter 11: Porphyrinoid-Based Diradicaloids
11.1: Introduction—Porphyrinoid-Based Mono-Radicals
11.1.1: Electronic Flexibility and Radical-Stabilizing Ability of Porphyrinoids
11.1.2: Examples of Stable Porphyrinoid-Based Radicals
11.1.3: Spin Density Distribution Depending on Incorporated Radical Units
11.2: Classification of Porphyrinoid-Based Diradicaloids
11.3: Porphyrinoids Bearing Two Radical Units at Their Periphery (Type I)
11.3.1: Quinoidal Porphyrinoids
11.3.2: Diradicaloids Based on Porphyrin Dimers
11.3.3: Non-Kekulé Diradicals Based on Porphyrinoids
11.4: Porphyrinoid-Fused Diradicals and Diradicaloids (Type II)
11.4.1: Kekulé-Type Singlet Diradicaloids
11.4.2: Non-Kekulé Diradicals with High-Spin Ground States
11.5: Diradicaloids Based on Intrinsically Radical Porphyrinoids (Type III)
11.5.1: Corrole-Based Diradicaloids
11.5.2: Norcorroles: Strong Antiaromaticity and Singlet Diradical Characters
11.5.3: Diradicaloids Based on Core-Modified Expanded Porphyrins
11.6: Summary
Chapter 12: Heteroatom (N, P, B, S, etc.) Centered Monoradicals and Diradicals
12.1: Introduction
12.2: Group 13 Element-Centered Radicals
12.2.1: Boron-Centered Radical Anions
12.2.2: Gallium-Centered Radical Cation
12.3: Group 15 Element-Based Radicals
12.3.1: Nitrogen-Based Diradicals and Dications
12.3.1.1: Nitrogen analogs of Thiele’s hydrocarbon
12.3.1.2: Nitrogen analogs of Chichibabin’s hydrocarbon
12.3.1.3: Nitrogen analogs of Müller’s hydrocarbon
12.3.1.4: Other amine-based diradical dications
12.3.1.5: Nitrogen-based radical anions
12.3.2: Heavy Pnictogen-Centered Radical Ions
12.3.2.1: Heavy pnictogen-centered radical cations
12.3.2.2: Heavy pnictogen-centered radical anions
12.4: Group 16 Element-Based Radicals
12.5: Conclusion
Chapter 13: Polyradicaloids and 2D/3D Global Aromaticity
13.1: Introduction
13.2: Linear Polyradicaloids
13.3: 2D Macrocyclic Diradicaloids and Polyradicaloids
13.3.1 Expanded Porphyrinoids with Radical Character
13.3.2 Polycyclic Hydrocarbon-Based Macrocyclic Polyradicaloids Showing Hückel (Anti)Aromaticity
13.3.3 Macrocyclic Diradicaloids/Polyradicaloids Showing Baird Aromaticity
13.3.4 Global Antiaromaticity in Transition State of Macrocyclic Polyradicaloid
13.4: 3D Fully Conjugated Diradicaloid Cages and 3D Global Aromaticity
13.5: 2D CORFs
13.6: Conclusion
Index