Thermochromic compound

Table 1. Some Typical Thermochromic Compounds and Their Transitions...

As an aid in laboratory investigations ether carboxylic acids have been used as chlorophyll solubilizers [234,235] and as dispersing agents for thermochromic compounds to be used as temperature indicators [236]. 

Although, in theory, intrinsically thermochromic compounds should be the materials of choice for many apphcations, in practice, with the major exception of thermotropic liquid crystals (see Chapter 5, section 5.2.2), they often require quite high temperatures to effect the change, and this has limited their use. Additionally, there is also a problem with synthesising compounds to cover the desired colour gamut across the visible spectrum. Consequently, indirect systems, in which the chro-mophoric material reacts to changes in its environment brought about by heat, have... 

J.C. Crano and R.J. Guglielmetti (Eds.), Organic Photochromic and Thermochromic Compounds, Volume 1, Main Photochromic Families, Plenum Press, New York, 1999. 

A compound that has one color at room temperature and a different color at a high temperature is known as a thermochromic compound. Zinc oxide is such a compound because it is white at low temperature but yellow at high temperature. The structure of ZnO is like that of the wurtzite form of ZnS shown in Figure 3.5. 

This survey of organic photochromic and thermochromic compounds focuses on the main families that are involved in existing commercial applications, such as variable optical transmission materials (ophthalmic glasses and lenses), or in potential uses such as optical storage (optical disks or memories). 

K. Kaftory, Photochromic and thermochromic compounds. I. Structures of(E) and (Z) isomers of 2-isopropylidene-3-[l-(2-methyl-5-phenyl)-3-thienylethylidene] succinic anhydride and the photoproduct 7,7a-dihydro-4,7,7,7a-tetramethyl-2-phenylbenzo[6]1hiophene 5,6-dicarboxylic anhydride (P), Acta Cryst., C40, 1015-1019 (1984). 

The first representative of a new group of photo- and thermochromic compounds in which the naphthalene fragment in spiroperimidine (1) is changed to a quinoline moiety has been obtained by coupling 2.6-di-fert-butyl-l, 4-bcnzo-... 

Since publication of the most recent Books, new areas have been explored and a large number of new results have been obtained and it seemed, therefore, timely to publish them. This was the endeavor of the chairmen of ISOP-93 and ISOP-96, Robert Guglielmetti and John Crano, respectively, who have acted as co-editors. R. Guglielmetti, a professor at the University of Marseilles is a recognized leader in the field and the late Dr. J. Crano, Associate Director of Research and Development for optical products at PPG since 1986, led research in the development of plastic ophthalmic eyewear. The efficient cooperation of a scholar and an industrial scientist has led to the Book entitled Organic Photochromic and Thermochromic Compounds in two volumes of about 400 pages each. 

This book, Organic Photochromic and Thermochromic Compounds, is the fourth major treatise on photochromism involving organic molecules and derived systems. The first such book was edited by G. H. Brown in the Weissberger series in 19711, the second was edited by H. Durr and H. Bouas-Laurent in the Elsevier series in 19902. 

The first volume deals with the synthesis and specific photochromic properties of the best-known classes and their field of application it contains 9 chapters. The aim of this new review, which is focused on organic photochromic compounds but also contains a brief survey on thermochromic compounds, is to give practical information involving selected series with the hope that this will lead to additional commercial applications for known photochromic families or to the discovery of new families. 

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