Whither Second-Sphere Coordination?

The properties of coordination complexes are dictated by both the metals and the ligands. The use of molecular receptors as second-sphere ligands enables significant modulation of the chemical and physical properties of coordination complexes. In this Mini-Review, we highlight recent advances in functional systems based on molecular receptors as second-sphere coordination ligands, as applied in molecular recognition, synthesis of mechanically interlocked molecules, separation of metals, catalysis, and biomolecular chemistry. These functional systems demonstrate that second-sphere coordination is an emerging and very promising strategy for addressing societal challenges in health, energy, and the environment.