Guest-induced organization of an optimal receptor from a dynamic receptor library: spectroscopic screening.

Complexation of a cis-protected palladium ion and a family of exo-bidentate and -tridentate ligands results in the formation of an equilibrium mixture of numerous metal-linked receptors that are referred to as a dynamic receptor library. We found that a guest induced the selective formation of the optimal receptor of its own. Screening of the library by using difference NMR facilitates the search for new receptors because in difference NMR only receptors interacting with the guest can be observed. An unpredictable heterotopic receptor was discovered by this screening method. Interestingly, the new receptor thus found was assembled quantitatively only in the presence of its optimal guest.