Electronic Absorption Spectra and Geometry of Organic Molecules

Electronic Absorption Spectra and Geometry of Organic Molecules: An Application of Molecular Orbital Theory focuses on electronic absorption spectra of organic compounds and molecules. The book begins with the discussions on molecular spectra, electronic absorption spectra of organic compounds, and practical measures of absorption intensity. The text also focuses on molecular orbital theory and group theory. Molecular state functions; fundamental postulates of quantum theory; representation of symmetry groups; and symmetry operations and symmetry groups are described. The book also discusses shape of absorption bands and geometry of excited electronic states; effect of environment on electronic absorption spectra; and the application of simple LCAO MO method to simple π systems. An evaluation of the parameters used in simple LCAO MO method is presented. The text notes the usefulness and restrictions of simple LCAO MO method in the interpretation of electronic absorption spectra. The correlation between results of simple MO calculation and spectral data in aromatic hydrocarbons, and correlation between results of simple MO calculation and spectral data in conjugated linear polyenes are discussed. The book also looks at MO methods and the relations between electronic absorption spectra and geometry of molecules, biphenyl, styrene, and related compounds. The text is a good source of data for researchers and chemistry students who want to study electronic absorption spectra.

Preface

Chapter 1. Introduction

1.1. Energy Levels of a Molecule and Molecular Spectra

1.2. Electronic Absorption Spectra of Organic Compounds

1.3. Wavelength, Wave Number, Energy, and Their Conversion Factors

1.4. Practical Measures of Absorption Intensity

Chapter 2. Molecular Orbital Theory

2.1. Fundamental Postulates of Quantum Theory

2.2. Molecular State Functions

2.3. The Method of Linear Combinations and the Variation Principle

2.4. The Perturbation Method

Chapter 3. Group Theory

3.1. Symmetry Operations and Symmetry Groups

3.2. Representations of Symmetry Groups

3.3. Character Tables for Point Groups and Symmetry Properties of Molecules

3.4. Symmetry Properties of Products of Functions

Chapter 4. Absorption Intensity and Selection Rules

4.1. Transition Probability

4.2. Total Probability of an Electronic Transition and Its Distribution among Vibrational Components

4.3. Selection Rules

Chapter 5. Shape of Absorption Bands and Geometry of Excited Electronic States

5.1. Shape of Absorption Bands

5.2. Influence of Temperature and Environment upon the Band Shape

5.3. Geometry of Molecules in Excited Electronic States

Chapter 6. Effect of Environment upon Electronic Absorption Spectra

6.1. Introduction

6.2. Solvent Effect

6.3. Absorption Spectra of Molecular Complexes

6.4. Absorption Spectra of Molecules in the Solid State

Chapter 7. Simple LCAO MO Method

7.1. Elements of Simple LCAO MO Method

7.2. The Pairing Property of π Orbitals of Alternant Hydrocarbons

7.3. Applications of Perturbation Theory in the Simple LCAO MO Method

Chapter 8. Application of Simple LCAO MO Method to Some Simple π Systems

8.1. Simplification of Secular Determinants by the Use of Group Theory

8.2. Application of Simple LCAO MO Method to Butadiene

8.3. Application of Simple LCAO MO Method to Some Aromatic Hydrocarbons

Chapter 9. Evaluation of Parameters Used in Simple LCAO MO Method

9.1. Introduction

9.2. Evaluation of Coulomb Parameters

9.3. Evaluation of Resonance Parameters

9.4. Supplementary Remarks

Chapter 10. Usefulness and Limitations of Simple LCAO MO Method in Interpretation of Electronic Absorption Spectra

10.1. General

10.2. Singlet-Triplet Splitting

10.3. Effects of Configuration Interaction

10.4. Correlation between Results of Simple MO Calculation and Spectral Data in Conjugated Linear Polyenes

10.5. Correlation between Results of Simple MO Calculation and Spectral Data in Aromatic Hydrocarbons

10.6. Effects of Replacement of Carbon π Centers by Heteroatom π Centers and of Introduction of Nonmesomeric Substituents on Spectra of Conjugated Hydrocarbons

Chapter 11. Advanced MO Methods

11.1. Introduction

11.2. Matrix Elements of the Total π-Electronic Hamiltonian between Antisymmetrized Electron Configuration Functions

11.3. The Semiempirical LCAO ASMO CI Method (The Pariser-Parr Method)

11.4. The Semiempirical SCF LCAO MO Method (The Pople Method)

11.5. Application of the Pariser-Parr Method to Even Alternant Hydrocarbons

Chapter 12. Relations between Electronic Absorption Spectra and Geometry of Molecules. Biphenyl and Related Compounds

12.1. Introduction

12.2. Biphenyl

12.3. o-Substituted Biphenyls

12.4. o,o'-Bridged Biphenyls

12.5. Polyphenyls

Chapter 13. Styrene and Related Compounds

13.1. Styrene and Its Alkylated Derivatives

13.2. 1-Phenylcyclohexene and Its Derivatives

13.3. 1,1-Diphenylethylene and Its Methylated Derivatives

Chapter 14. Stilbene and Related Compounds

14.1. Stilbene

14.2. Sterically Hindered Stilbene Derivatives

14.3. Tetraphenylethylene and Related Compounds

14.4. The Influence of Environment on the Spectra of Stilbene and of Related Compounds

14.5. Vinylogs of Stilbene and of Tetraphenylethylene

14.6. Biphenylene Derivatives of Ethylene, Butadiene, and Hexatriene

Chapter 15. Relations of the Intensity and Shape of Conjugation Bands to the Geometry of Conjugated Systems

15.1. Intensity of Conjugation Bands

15.2. Shape of Conjugation Bands

Chapter 16. Conjugated Dienes and Polyenes

16.1. Conjugated Dienes

16.2. Conjugated Polyenes

Chapter 17. Polymethine Dyes

17.1. Spectra of Odd-Membered Conjugated Systems

17.2. Steric Effects in Spectra of Symmetrical Cyanines

17.3. Steric Effects in Spectra of Highly Unsymmetrical Cyanines

Chapter 18. Nonplanar Aromatic Systems

18.1. General

18.2. Correlation of the Direction of the Wavelength Shift with the π-Bond Order of the Mainly Twisted Bond

18.3. Effects of the Distortion of the Whole Aromatic System

Chapter 19. Simple Composite-Molecule Method and a Classification of π-π* Transitions

19.1. Introduction

19.2. Simple Composite-Molecule Method

19.3. Classification of π-π* Transitions in Composite Systems

19.4. Classification of Composite Conjugated Systems and Steric Effects on π-π* Transitions of Various Types

19.5. Treatment of the Effect of a Methyl Substituent on Absorption Bands by the Perturbation Method

19.6. Mixing of Electron Configurations Formed of Orbitals of Fragments in the One-Electron Approximation

Chapter 20. Advanced Composite-Molecule Method

20.1. Principle

20.2. Application

Chapter 21. Carbonyl Compounds

21.1. The Carbonyl Group

21.2. Effects of Substituents on the Absorption Bands of the Carbonyl Group

21.3. Conjugated Dicarbonyl Compounds (α,ß-Dicarbonyls)

21.4. Vinyl-Carbonyl and Phenyl-Carbonyl Compounds

21.5. The Steric Effect in the Spectra of Conjugated Carbonyl Compounds

Chapter 22. Nitrobenzene, Benzoic Acid, Aniline, and Related Compounds

22.1. Nitrobenzene and Related Compounds

22.2. Benzoic Acid and Related Compounds

22.3. Aniline and Related Compounds

22.4. Generalization of the Substituent Effects in the Spectra of Monosubstituted Benzenes—Weak and Strong Substituent Effects

22.5. Nitroanilines and Related Compounds

Chapter 23. Azobenzenes and Related Compounds

23.1. The Azo Group

23.2. Aliphatic Azo Compounds

23.3. Azobenzenes

23.4. Azobenzene Analogs and Derivatives

23.5. Azoxy Compounds

23.6. Hydrazo Compounds

23.7. Disulfides

Chapter 24. Interactions between Nonneighboring Atomic Orbitals

24.1. Introduction

24.2. Nonneighbor Interactions in Carbonyl Compounds

24.3. Nonneighbor Interactions in Unsaturated Hydrocarbons

Appendix. Notation for Electronic Spectral Bands

A.1. The Systems of Spectral Notation and Conventions Used in this Book

A.2. Some Other Systems of Spectral Notation

General References

Author Index

Subject Index