Colour Chemistry 2nd edition Robert M Christie School of Textiles & Design, Heriot-Watt University, UK and Department of Chemistry, King Abdulaziz University, Saudi Arabia Email: [email protected] Print ISBN: 978-1-84973-328-1 A catalogue record for this book is available from the British Library r R M Christie 2015 All rights reserved Apart from fair dealing for the purposes of research for non-commercial purposes or for private study, criticism or review, as permitted under the Copyright, Designs and Patents Act 1988 and the Copyright and Related Rights Regulations 2003, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry or the copyright owner, or in the case of reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page. The RSC is not responsible for individual opinions expressed in this work. Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 0WF, UK Registered Charity Number 207890 Visit our website at www.rsc.org/books Preface I was pleased to receive the invitation from the RSC to write this second edition of Colour Chemistry following the success of the first edition published in 2001. I am also appreciative of the broadly positive reviews that the first edition received and of the favourable comments that I have received from a wide range of individuals. The initial approach to compiling this second edition involved tak- ing stock of the original content, while also assessing the extensive range of developments in colour chemistry that have taken place in the intervening years. While the chemistry of the traditional classes and applications of dyes and pigments is well-established, there have been significant developments in other areas, especially in topics related to functional dyes. The industry associated with the manufacture and application of dyes and pigments has continued to transfer substantially away from Europe and the USA towards the emerging economies in Asia, especially to China and India, and consequently many new developments are emerging from research undertaken in that region. Two important textbooks have been pub- lished in the last decade or so. I am honoured to pay a special tri- bute to the late Heinrich Zollinger, whose third edition of Color Chemistry appeared in 2003, and maintained the standard of detail, originality and excellence for which this eminent author was re- nowned. I also acknowledge the importance of Chromic Phenomena: Technological Applications of Colour Chemistry, by Peter Bamfield and Michael Hutchings, the second edition of which appeared in Colour Chemistry, 2nd edition By Robert M Christie r R M Christie 2015 Published by the Royal Society of Chemistry, www.rsc.org v vi Preface 2010. This excellent textbook, also published by the RSC, adopts an original approach to the subject, organising the topics according to the phenomena giving rise to colour. The experience and know- ledge of these authors from an industrial perspective is evident throughout their book. This second edition of Colour Chemistry adopts broadly the original philosophy and structure, retaining a relatively traditional approach to the subject. The content has been significantly revised and ex- panded throughout, especially to reflect newer developments. The book thus remains aimed at providing an insight into the chemistry of colour, with a particular focus on the most important colorants produced industrially. It is aimed at students or graduates who have knowledge of the principles of chemistry, to provide an illustration of how these principles are applied in producing the range of colours that are all around us. In addition, it is anticipated that professionals who are specialists in colour science, or have some involvement with the diverse range of coloured materials in an industrial or academic environment, will benefit from the overview of the subject that is provided. The opening chapter provides a historical perspective on how our understanding of colour chemistry has evolved, leading to the de- velopment of an innovative global industry. The second chapter provides a general introduction to the physical, chemical and, to a certain extent, biological principles which allow us to perceive col- ours. This chapter has been expanded in particular to provide a dis- cussion of the recent developments that have taken place in the use of computational methods used to model and predict the properties of colorants by calculation. Chapters 3–6 encompass the essential principles of the structural and synthetic chemistry associated with the most important chemical classes of industrial dyes and pigments. Chapters 7–11 deal with the applications of dyes and pigments, and in particular the chemical principles underlying their technical per- formance, not only in traditional applications such as textiles, print- ing inks, coatings and plastics but also in an expanding range of high technology or functional applications. The chapter on functional dyes has been significantly re-written to reflect recent and current devel- opments in, for example, display technologies, solar energy con- version and biomedical applications. A new chapter introduces the chemistry of colour in cosmetics, with particular emphasis on hair dyes, which reflects the continuing growth of a sector of the colour industry that has thus far largely resisted the move from West to East. I express my gratitude to my co-author of this chapter, Olivier Morel, Preface vii for his contribution. The final chapter provides an account of the most important environmental issues associated with the manu- facture and use of colour, which the industry is increasingly required to acknowledge and address. R. M. Christie Contents Chapter 1 Colour: A Historical Perspective 1 1.1 Introduction 1 1.2 The Early History of Dyes and Pigments 2 1.3 The Era of the Synthetic Dye 6 1.4 Colour Chemistry in the Twentieth Century 13 1.5 Recent and Current Trends in Colour Chemistry 15 References 19 Chapter 2 The Physical and Chemical Basis of Colour 21 2.1 Introduction 21 2.2 Visible Light 22 2.3 The Eye 25 2.4 The Causes of Colour 27 2.5 The Interaction of Light with Objects 28 2.6 Fluorescence and Phosphorescence 33 2.7 Dyes and Pigments 35 2.8 Classification of Colorants 36 2.9 Colour and Molecular Structure 38 2.9.1 Valence-Bond Approach to Colour/Structure Relationships 40 2.9.2 Molecular Orbital Approach to Colour/Structure Relationships 50 2.9.3 Molecular Mechanics 62 2.9.4 QSAR and QSPR 64 Colour Chemistry, 2nd edition By Robert M Christie r R M Christie 2015 Published by the Royal Society of Chemistry, www.rsc.org ix x Contents 2.10 Colour in Inorganic Compounds 66 2.10.1 Colour in Metal Complexes (Coordination Compounds) 66 2.10.2 Colour from Charge Transfer Transitions in Inorganic Materials 67 2.10.3 Colour in Inorganic Semiconductors 67 References 68 Chapter 3 Azo Dyes and Pigments 72 3.1 Introduction 72 3.2 Isomerism in Azo Dyes and Pigments 73 3.3 Synthesis of Azo Dyes and Pigments 78 3.3.1 Diazotisation 79 3.3.2 Azo Coupling 84 3.4 Strategies for Azo Dye and Pigment Synthesis 87 3.4.1 Synthesis of Monoazo Dyes and Pigments 88 3.4.2 Synthesis of Disazo Dyes and Pigments 88 3.4.3 Synthesis of Dyes and Pigments containing more than two Azo Groups 92 3.5 Metal Complex Azo Dyes and Pigments 93 References 97 Chapter 4 Carbonyl Dyes and Pigments 99 4.1 Introduction 99 4.2 Anthraquinones 100 4.3 Indigoid Dyes and Pigments 105 4.4 Benzodifuranones 110 4.5 Fluorescent Carbonyl Dyes 111 4.6 Carbonyl Pigments 112 4.7 The Quinone–Hydroquinone Redox System 118 4.8 Synthesis of Carbonyl Colorants 119 4.8.1 Synthesis of Anthraquinones 119 4.8.2 Synthesis of Indigoid Colorants 125 4.8.3 Synthesis of Benzodifuranones and Coumarin Dyes 126 4.8.4 Synthesis of Carbonyl Pigments 126 References 131 Chapter 5 Phthalocyanines 133 5.1 Introduction 133 5.2 Structure and Properties of Phthalocyanines 134 5.3 Synthesis of Phthalocyanines 140 References 145 Contents xi Chapter 6 Miscellaneous Chemical Classes of Organic Dyes and Pigments 147 6.1 Introduction 147 6.2 Polyene and Polymethine Dyes 147 6.3 Arylcarbonium Ion Colorants 155 6.4 Dioxazines 161 6.5 Sulfur Dyes 162 6.6 Nitro Dyes 164 References 166 Chapter 7 Textile Dyes (excluding Reactive Dyes) 168 7.1 Introduction 168 7.2 Dyes for Protein Fibres 172 7.3 Dyes for Cellulosic Fibres 178 7.4 Dyes for Synthetic Fibres 184 References 191 Chapter 8 Reactive Dyes for Textile Fibres 194 8.1 Introduction 194 8.2 Fibre-Reactive Groups 197 8.2.1 Fibre-Reactive Groups Reacting by Nucleophilic Substitution 197 8.2.2 Fibre-Reactive Groups Reacting by Nucleophilic Addition 203 8.3 Polyfunctional Reactive Dyes 206 8.4 Chromogenic Groups 207 8.5 Synthesis of Reactive Dyes 209 References 211 Chapter 9 Pigments 212 9.1 Introduction 212 9.2 Inorganic Pigments 217 9.2.1 Titanium Dioxide and other White Pigments 218 9.2.2 Coloured Oxides and Oxide-hydroxides 221 9.2.3 Cadmium Sulfides, Lead Chromates and Related Pigments 223 9.2.4 Ultramarines 226 9.2.5 Prussian Blue 227 9.2.6 Carbon Black 227 xii Contents 9.3 Organic Pigments 229 9.3.1 Azo Pigments 230 9.3.2