Chromic Phenomena Technological Applications of Colour Chemistry Second Edition Chromic Phenomena Technological Applications of Colour Chemistry Second Edition Peter Bamfield Consultant, Penarth, UK Michael G. Hutchings DyStar UK Ltd, Manchester, UK ISBN: 978 1 84755 868 8 A catalogue record for this book is available from the British Library r Peter Bamfield and Michael G. 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Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 0WF, UK Registered Charity Number 207890 For further information see our web site at www.rsc.org Preface to Second Edition It is almost a decade since the appearance of the first edition of ‘‘Chromic Phenomena’’ in 2001 when its stated aim was ‘‘to provide an overview of the many applications that colour chemistry, in its widest sense, has found in the last couple of decades’’. The rate of increase in such applications and under- pinning chemistry has accelerated to such an extent that a second edition has become fully justified. A recent issue of Chemical Communications (issue 24, 2009) is fairly typical. Amongst two feature articles and 38 communications, one of the feature articles and 15 comms – 40% of the total – are concerned in some way with aspects of colour in chemistry, spread across four of the five main themes of this book. To further emphasise this timeliness we recall the award of the 2008 Nobel Prize for Chemistry for studies into colour: the case of Green Fluorescent Protein. This was a fitting tribute not just to the individuals concerned, but to the core role that modern colour chemistry is playing through many aspects of today’s technology. This time the scale of the task of producing a new edition has benefited from re-establishing a collaboration between the two of us that started more than 30 years ago in ICI. Whilst maintaining the same five-chapter structure as in the first edition, a considerable amount of new material has been added to the areas previously covered. On top of that, introduction of new topics has resulted in almost doubling the size of the book. We have occasionally allowed ourselves to stray into the fringes of what is strictly physics, biology or medicine. We also include topics that we regard as ‘‘tomorrow’s technology’’ even if their com- mercialisation is not yet with us. And we also highlight a few others which some might simply regard as quirky: the lobster’s thermochromism during its cooking; the coloured materials that non-intuitively cool down when irradiated by a laser; and the male mosquito larvae with green fluorescent organs are three that spring to mind. Cutting edge research into the newer colour-producing materials such as metallic nanoparticles, quantum dots and photonic crystals is spread throughout the book. The impact of now cheap solid state lasers and their applications in multi-photon absorption processes in fields ranging from fluorescence imaging, optical data storage, photomedicine, lasers and nonlinear Chromic Phenomena: Technological Applications of Colour Chemistry, Second Edition By Peter Bamfield and Michael G. Hutchings r Peter Bamfield and Michael G. Hutchings 2010 Published by the Royal Society of Chemistry, www.rsc.org v vi Preface to Second Edition optics comprise another new theme throughout. Any remaining imbalance in the material included (and the corollary – the unavoidable omission of a mass of wonderful new science and technology) is also our responsibility. This sec- ond edition also benefits from the generous use of colour in many of the figures and formulae. We acknowledge innumerable stimulating discussions and collaborations with many, both in industry and academia, during our many years’ involve- ment with the colour industry in particular and chemistry more generally. We both fondly recall the fine examples of ‘‘Blackley Man’’ (some of them female) we worked with in the colours research group at ICI, who are too numerous to mention. Additionally, MGH acknowledges others in BASF, especially Jim Bullock and Manfred Patsch; his current colleagues in DyStar John Easton, Warren Ebenezer, Nigel Hall, Anthony Lawrence and Werner Russ; and recent collaborations with Harry Anderson (Oxford), Adrian Geisow (HP Research), Tony Gorman (Manchester), Anita Jones (Edinburgh) and Andrew Mills and John Parkinson (Strathclyde), plus an array of Ph.D. and M.Chem. students. All have contributed, sometimes indirectly and unwittingly, to his continuing education. We also thank Larry Dalton (Washington University) for providing a pre-publication article and valuable commentary, and Garry Rumbles (National Renewable Energy Laboratory, Colorado) for comment on his rhodamine dye upconversion experiment. But it is the intellectual interplay between the two of us over the last 18 months that has led to the new character of this second edition, as well as providing us with fresh personal perspectives on the fun that colour and chemistry continue to bring to us. Of course working on such a volume has required spending many hours alone in our offices peering at screens full of data and text, in the case of one of us during hours outside his full-time employment. It is through these periods that the support and understanding of our wives and families has been para- mount and immeasurably valued. Without it this book would not have appeared, and for that reason we dedicate it to Domini, and to Julie and Chris. Peter Bamfield Michael G. Hutchings peter.bamfi[email protected] [email protected] Preface to the First Edition The aim of this book is to provide an overview of the many applications that colour chemistry, in its widest sense, has found in the last couple of decades. Not only have there been developments in the traditional areas of colorants for textiles, paints and inks but also in an exciting variety of newer technolo- gies. Several of these are at the cutting edge of research, such as photo- dynamic therapy, electroluminescent displays, artificial photosynthesis, holographic data storage and photonics, and any report on the current posi- tion can only be interim. Most of the newer technologies are multi- disciplinary, where the active collaboration of chemists with physicists, biologists, biochemists, materials scientists, electronics engineers etc. is essen- tial if any progress is to be made. Covering as it does a very wide field, this book will provide an entry point for both new researchers and established ones who wish to broaden their horizons and accept the challenge of finding new applications for colour chemistry. During my more than four decades involvement in the colorants industry I have had many stimulating discussions and collaborations with innumerable colleagues to whom I am indebted. I would particularly like to mention Peter Austin, Gerald Booth, Peter Gregory, Paul Gordon, Colin Greenhalgh, Nigel Huges, Mike Hutchings, Brain Parton, Duncan Phillips, Ray Price, Peter Quan, Peter Tasker, Hunter Renfrew, Dennis Ridyard, John Schofield and John Taylor from my ICI/Zeneca days. Finally, but most of all, I wish to thank my wife Mary for her unstinting support during the books gestation period and particularly whilst I was pro- ducing the manuscripts. Peter Bamfield Chromic Phenomena: Technological Applications of Colour Chemistry, Second Edition By Peter Bamfield and Michael G. Hutchings r Peter Bamfield and Michael G. Hutchings 2010 Published by the Royal Society of Chemistry, www.rsc.org vii Contents Introduction 1 Chapter 1 Phenomena Involving a Stimulated Colour Change 9 1.1 Introduction 9 1.2 Photochromism 12 1.2.1 Main Chemical Classes 13 1.2.2 Spirobenzopyrans 14 1.2.3 Spironaphthoxazines 15 1.2.4 Benzo- and Naphthopyrans (Chromenes) 17 1.2.5 Fulgides 21 1.2.6 Diarylethenes 23 1.2.6.1 Gated Photochromism in Diarylethenes 27 1.2.7 Miscellaneous Photochromic Systems 28 1.2.7.1 Azobenzenes 28 1.2.7.2 Other Organic Photochromes 29 1.2.7.3 Inorganic Photochromes 31 1.2.7.4 Biological Photochromes 32 1.2.7.5 Polymers, Matrices and Amorphous Materials 33 1.2.8 Applications of Photochromic Materials 35 1.2.8.1 Applications in Ophthalmics 36 1.2.8.2 Novelty Items, Fashion, Cosmetics and Security 38 1.2.8.3 Optical Memories and Switches 39 1.2.8.4 Other Optical Applications 46 1.2.8.5 Biological and Bio-medical Applications 46 Chromic Phenomena: Technological Applications of Colour Chemistry, Second Edition By Peter Bamfield and Michael G. Hutchings r Peter Bamfield and Michael G. Hutchings 2010 Published by the Royal Society of Chemistry, www.rsc.org ix x Contents 1.3 Thermochromism 47 1.3.1 Inorganic and Organometallic Materials 48 1.3.2 Reversible Intrinsically Thermochromic