Polymorphism in Molecular Crystals

Joel Bernstein, Clarendon Press, Oxford, May, 2002, Hardcover, ISBN 019 850605 8.

The latest Oxford Science Publication in the IUCr series of Monographs on Crystallography. The book has 410 pages plus 14 pages of Contents and Author's Preface and over 200 line-drawn figures and schemes. The scientific community has been presented with a long-awaited book on polymorphism. It comes from a world-renowned expert in this field, Joel Bernstein (Ben-Gurion U., Beer Sheva). His three-decade long scientific interest in polymorphs has been marked by many well known achievements such as descriptions of conformational, disappearing or concommitant polymorphs and jumping crystals, as well as development of graph descriptors for hydrogen-bonded patterns commonly used for comparisons of molecular aggregation, particularly in polymorphs.

Personally, I was already excited by the titles of sections and subsections in the Contents. Then I 'swallowed' all the chapters one by one in a few days. The scope and purpose of the book are outlined in the Introduction. Obviously he had to make choices from the thousands of substances referred to as polymorphs in literature, to which related subjects should be included and, even more importantly, which of many definitions of polymorphism to accept. His decision to take the least restrictive approach of supramolecular isomorphism was a good one. Although written by a chemical crystallographer mainly for chemists, crystallographers, material scientists and pharmacists, the book will also appeal to specialists in related sciences. It is written in an easy style that takes us back to the first observations of polymorphism and follows its history up to the present.

Over the last decades the subject has constantly become more of a concern to the scientific community. Any scientist involved in crystallography, materials sciences, solid-state physics, chemistry or pharmacology, must be aware of the possible polymorphic modifications of any given substance. No type of compound is exempt, polymorphs occur among small-molecules, medicinal drugs, pigments, explosives, fats, charge-transfer complexes, inclusion compounds, polymers and proteins. The different properties of polymorphs make the subject ideal for studying structure-property relationships, and essential, or even obligatory, for technological applications in chemistry-related industries. Polymorphs may differ in color, therapeutic activity, thermal or electric conductivity. Even fats in chocolate may melt and taste differently. Bernstein's book is a rich and comprehensive compilation and illustration of the structural variety of polymorphs and their properties.

There is also a chapter on legal issues related to polymorphs in industry, and litigations over the patent protection of medicinal drugs. The book can be recommended for all researchers working on organic materials, or any materials indeed. It will be of interest to academic lecturers, who will find additional illustrations for their lectures, and to undergraduates studying structural or materials sciences. The huge list of about 1500 references to scientific articles, conveniently cited with their titles, guides the reader to original and complementary sources. Page numbers added to references, direct one back to where they are cited. The Index (10 pages), also facilitates reading and quick location of a subject of interest. Today's instrumentation and powerful computers make it possible to rapidly perform structural analyses at various temperatures and even to do charge density studies of proteins. Powder diffraction experiments resolve two or more phases of increasingly complex substances, while theoretical predictions of the crystal structures become more efficient. With these facilities at hand, appropriate education and awareness of polymorphism is crucial. Today's knowledge of the field of polymorphism appears as the tip of an iceberg, and Bernstein decleares that one purpose of his book is to be a platform for future research. 'Be wary of the polymorph, that slyly lies in wait' in your laboratory, and its scientific and economic implications!