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What is Molecular Self-Assembly?

Molecular self-assembly occurs when many molecules spontaneously associate together into one discrete functional structure, using non-covalent forces. This is a remarkable phenomenon, because it makes a very complex structure from its components in one step, merely by mixing these components! This is in contrast with conventional covalent synthesis, which would require a long sequence of synthetic steps to create the final structure.

Covalent Synthesis:

Molecular Self-Assembly:

There are some important requirements for successful self-assembly: (1) the individual molecules must have complementary functional groups, so that they can bind to each other, using hydrogen bonds, electrostatic interactions, or metal coordination;
(2) these functional groups must be in the correct geometry, so that the association of the individual molecules results in a closed structure. For example, the two functionalities 4,6-diaminopyridine (red) and cyclic imide (blue) are complementary, and can undergo hydrogen-bonded association.

By including two diaminopyridine binding units in one molecule (red) and two imide units in the other molecule (blue), more than two molecules can come together. Finally, by placing the two units on each molecule so that they are at 120o angles, the two molecular components can undergo self-assembly into a hexameric structure, containing 3 molecules of each of the two components. This self-assembly process occurs in one step, under mild conditions. (1.)

Molecular self-assembly represents a highly economical method to generate quite complex supramolecular structures, and this strategy has permeated a large number of fields, from biological chemistry to materials science and nanotechnology.

1. J.-M. Lehn, Angew. Chem. Int. Ed. Engl. 1990, 29, 1304; G. M. Whitesides, J. P. Mathias, C. T. Seto, Science 1991, 254, 1312; J. Lindsey, New J. Chem. 1991, 15, 153.