Energy matters!

Abstract

The delicate balance between a variety of energetic factors in molecules and crystal structures is reflected in the molecular and intermolecular geometry determined by X-ray diffraction methods. This balance is most clearly observed in the energetically soft parameters: torsion angles that define conformation and the distances and angles that define intermolecular interactions and molecular aggregation in the crystalline state. This review stresses the importance of the geometry–energy relationship as an aid to our interpretation of individual crystal structures, and discusses the transferability of systematic information derived from crystal structures to other phases and to other application domains, such as drug discovery and materials development. Alloxan structure 187 Benzophenone conformations 173, 174 Biphenyl conformations 174–176 Cambridge Structural Database 170, 190 Cluster analysis 171, 177 Conformational analysis 170, 171 Conformational diversity 177 Conformational preferences 170–173, 177 Crystal Packing 173, 187 CSD software system 170–181, 183–187, 189 Cyclobutane 175, 176 Drug development 179, 184, 190 Drug discovery 173, 176, 178, 179, 190 Ethyl esters 173, 174 Geometry-energy relationships 170 Hydrogen bond competition 179, 181–183, 187 Hydrogen bond linearity 184 Hydrogen bond prediction 181, 185, 190 Hydrogen bonding 180 IMPT program 180–183, 187 Interaction energy 180–183 Intermolecular interactions 170, 172, 173, 177, 179, 186, 187 IsoStar knowledge base 187–189 Mogul knowledge base 178 Polymorph screening 184 Principal components analysis 171 Ring conformations 171 Structure correlation 170, 175, 185, 189, 190