Contents

#### **Preface XI**

#### **Part 1 Small Molecules 1**


X Contents



Preface

transport.

properties and bulk material properties:

1. Molecular Structure - Single Molecules:

Single crystal X-ray crystallography is the most common and easily accessible way to determine the molecular structure of any crystalline material. This method provides two kinds of information which are needed for understanding both single molecule

Unambiguous and three-dimensional information about the structure of the molecular entities. The data useful here are the bond lengths, bond angles, and torsion angles. These details make this method not only useful for structural determination, confirmation, and analysis of three-dimensional geometry of the molecular entities, but also useful for the Structure-Activity Relationship studies, where the structural details are the basis for understanding the chemical reactivity and stability. These data

All the individual molecules have to come together to form the bulk crystal. How the molecules interact with each other in the crystal provides additional useful information. Various possible intermolecular interactions present in the crystalline bulk can be obtained from the X-ray studies, which are useful for the study of bulk properties as well. These can help explain the observed bulk properties and thereby enable us to make predictions of bulk properties based on structures. These interactions include H-bonding, pi-pi stacking, CH-pi interactions, halogen-halogen interactions, and other donor-acceptor interactions. If there is any phase separation in bipolar molecules, they can also be seen clearly. In addition to providing the details of the molecular arrangement in the bulk, we can also obtain the structure of the empty spaces (void spaces, channels or pores etc). These data are useful in widely varied fields, such as the design of pharmaceuticals, crystal engineering, zeolites for gas separation or catalysis, guest-host materials, sensors, organic magnets, and charge

Single crystal X-ray crystallography has moved a long way from the days I started my research career about a quarter of a century ago. In those days, it took about half a year to complete a structure, due to slow computers and serial data collection by the state-

are also useful for understanding most of the spectroscopic data of materials.

2. Intermolecular Interactions (Packing) - Bulk Material:

#### **Part 2 Macromolecules 283**

	- **Part 3 Complimentary Methods 365**
