Coexisting Mixed-Ligated Coordination Architectures as Hosts for Supramolecular Matchmaking with Customized Guests

An ensemble of cis-Pd(tmeda)(NO3)2, L1·2PF6, L2, L3·3PF6, and L4 in a 5:1:1:1:1 ratio in a water medium resulted in a pair of coexisting mixed-ligated coordination architectures [Pd2(tmeda)2(L1)(L2)]6+, [1]6+, and [Pd3(tmeda)3(L3)(L4)]9+, [2]9+, exclusively. The ligands L12+ and L2 were bis-monodentate, whereas ligands L33+ and L4 were tris-monodentate. The 2-dimensional D-shaped, [1]6+, and 3-dimensional dome-shaped, [2]9+, were also prepared separately. Such architectures may interlock to form a corresponding 2-catenane or related interlocked structure, but the positive charge crafted in the ligand backbones inhibits interlocking. Although [1]6+ (host H) has an exposed cavity, [2]9+ (host H') possesses a confined cavity. Host H did not bind nonpolar aromatic guests because of the exposed cavity, whereas host H' could bind such guests, but of restricted size, because of the confinement. Both hosts are capable of binding polar (neutral or anionic) guests, but larger-sized polar guests are not accommodated by the confined cavity of H'. Building upon the guest-binding behavior, we demonstrated a supramolecular matchmaking phenomenon, where the coexisting self-assembled hosts H and H' picked the larger polar (anionic) guest G and smaller nonpolar guest G', respectively.