The Definition of a Molecular Template

In this chapter, we will show how the concept of template-directed organic synthesis has expanded so that now metal-ligand binding, hydrogen bonding, n-n interactions, and covalent bonding can all be exploited to allow the synthesis of molecules with a remarkable degree of control. Several detailed reviews of molecular templates have been published [14-20]. This chapter explores the definition and classification of molecular templates and discusses how their performance can be quantified and optimized. 

The word template is used widely in chemistry, biochemistry, and materials science its use has spread dramatically since the 1960s, particularly since 1990. What do we mean by a template in the context of organic synthesis Busch gave the following definition [21]  

A chemical template organizes an assembly of atoms with respect to one or more geometric loci, in order to achieve a particular linking of atoms. 

The use of templates (both molecular and supramolecular) has also become a popular synthetic strategy in materials science. For example, organic cations template the formation of zeolites [22], surfactant mesophases template the synthesis of mesoporous solids 

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The question of the definition of a molecular template is therefore an important one, and one which needs consideration in any particular area in which templates might be used. 

This chapter illustrates how templates have been used to aid organic synthesis and attempts to refine and expand the definition of a molecular template. The later chapters in this book demonstrate that templates are emerging as powerful tools in many areas of molecular construction. We have highlighted the key parameters required to evaluate template effects quantitatively. We hope this will encourage pioneers in the field to calibrate new systems, so that we can gauge their progress as they escalate to higher levels of efficiency and sophistication. 

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