Molecular structure as a blueprint for supramolecular structure chemistry in confined spaces.

C hemistry is an ever expanding ‘‘universe’’ at the microscopic level requiring mastery of the invisible at ever increasing levels of complexity. Starting with atoms, assemblies of a single nucleus and orbiting electrons, the chemist has learned to understand atomic structure through mastery of the principles of electronic configurations. Proceeding to molecules, assemblies of two or more atoms, the chemist has learned to understand molecular structure through mastery of the principles of the covalent bond. It is quite natural that the next level of complexity will be supermolecules, assemblies of two or more molecules, whose structure will be understood through mastery of the principles of the intermolecular bond, which are at the heart of supramolecular chemistry. We shall see that the principles of weak intermolecular ‘‘bonds,’’ while perhaps a bit nonintuitive, obeys the same rules of chemistry as the strong intramolecular covalent bonds. Chemists (and nature) have used 100 atoms on which they have designed the assembly of millions of molecules by using the concept of the covalent bond between atoms. The number of supramolecular systems that can be assembled is stunning and infinite. A holy grail of supramolecular chemistry is to put the ‘‘syntheses’’ of suprmolecular systems based on intermolecular bonds on the same level of understanding as the current state of the syntheses of molecular systems based on covalent bonds.