Self-assembly processes for the construction of supramolecular coordination compounds

In a 2002 viewpoint in Science, self-assembly was defined by Whitesides and coworkers as “the autonomous organization of components into patterns or structures without human intervention.”¹ Self-assembly is further defined as those processes that involve preexisting, distinct structures as building blocks and that the interactions between these building blocks should be reversible and controllable by the proper design of the components. On a molecular level, the components or structures are individual molecules, or different parts of one large, covalently-linked molecule. Noncovalent interactions provide the reversible driving force for many of these molecules to self-assemble into exemplary structures. Hydrogen bonding, p-p stacking, dipole-dipole interactions, and hydrophobic/hydrophilic interactions are all examples of the types of forces acting at the molecular level that can lead to individual molecules forming large and often complex structures, with DNA and proteins often serving as primary examples. Coordination-driven self-assembly refers to the use of metal-ligand bond formation to drive the self-assembly process. Metal-ligand bonding is in general weaker than the covalent bonding found in organic molecules^2,3 and thus the formation of these bonds is often reversible under standard reaction conditions. For coordination-driven self-assembly to occur, the molecules serving as building blocks, sometimes known as tectons, must meet two conditions: the first condition is that one of the molecular pieces must contain at least two Lewis-basic donor sites, while the other molecule must contain at least two Lewis-acid acceptor sites. The second is that the angle of the coordination vectors of the donor and acceptor sites to one....