198 Topics in Current Chemistry Editorial Board: A. de Meijere KN ...

58 A. Nangia · G.R. Desiraju
7 Supramolecular Interactions in Biological Systems . . . . . . . . . . 78
7.1 Weak Hydrogen Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . 78
7.2 Pattern Recognition in Drug-Enzyme Binding . . . . . . . . . . . . . 79
7.3 Pharmacophore Model . . . . . . . . . . . . . . . . . . . . . . . . . . 81
8 Polymorphism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
9 Comparison of Crystal Structures . . . . . . . . . . . . . . . . . . . . 87
10 “Absence” of Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
11 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
1
Introduction
Supramolecular chemistry is the chemistry of the intermolecular bond based
on the underlying theme of mutual recognition. Molecules recognise each
other through a complex combination of geometrical and chemical factors
and the complementary relationship between interacting molecules is characteristic
of the recognition process. Supramolecular chemistry has grown
around Lehn’s analogy that “supermolecules are to molecules and the intermolecular
bond what molecules are to atoms and the covalent bond” [1]. This
field has grown into two distinct branches – the study of supermolecules in
solution and the study of crystal, that is solid state, structures. The concepts
and principles of recognition and the nature of the interactions that mediate
supramolecular construction are nearly the same in solution and in the solid
state. However, distinctions in ethos in the early stages of development of these
two branches has led to studies of solution supermolecules being referred to
as molecular recognition and those in the solid state as crystal engineering [2].
Molecular recognition has been studied by physical and synthetic chemists
interested in understanding biological processes, biosynthetic mimics and
enzyme catalysis. Crystal engineering has been developed by structural
chemists and crystallographers to better understand non-covalent interactions
for the design of novel materials and solid state reactions. Crystal
engineering and molecular recognition are the supramolecular equivalents of
traditional organic synthesis, so that instead of building molecules with atoms
and covalent bonds, one builds supermolecules with molecules and non-covalent
interactions recognising certain repeating patterns of interactions, or
supramolecular synthons, that are the key elements of the synthetic exercise.
In this article, we attempt to show the importance of pattern recognition in
organic crystal chemistry and also the implications of such ideas in related
areas.