Polymorphism in Molecular Crystals

Polymorphism — the multiplicity of structures or forms — is a term used in many disciplines. In chemistry, it refers to the existence of more than one crystal structure for a particular chemical substance. The properties of a substance are determined by its composition and by its structure. In the last three decades there has been a sharp rise in the interest in polymorphic systems, as an intrinsically interesting phenomenon and as an increasingly important component in the development and marketing of a variety of materials based on organic molecules (e.g., pharmaceuticals, dyes, pigments, explosives, etc.). This book summarizes and brings up to date (as of 2002) the current knowledge and understanding of polymorphism of molecular crystals, and concentrates it in one comprehensive source. The opening chapter deals with nomenclature, a historical perspective of the phenomenon, and the industrial and commercial importance of polymorphism. This is followed by chapters covering fundamental concepts used in the description and study of polymorphism, thermodynamic and kinetic aspects of polymorph formation, the control of the polymorph obtained, analytical techniques for studying and characterizing polymorphs, conformational polymorphism, and the use of polymorphism to study structure-property relations in molecular crystals. Three individual chapters cover aspects of polymorphism in pharmaceuticals, dyes and pigments, and high energy materials. A final chapter covers some aspects of polymorphism and patents, another aspect of the subject of particular importance to the pharmaceutical industry.