Coordination-Driven Self-assembly of Cyclopentadienyl-Capped Heterometallic Zr–Pd Cages

A series of heterometallic Zr3Pd3-trigonal bipyramidal compounds (1-4) was synthesized by two-component coordination-driven self-assembly of cis-protected palladium(II) 90° acceptors with trinuclear carboxylate-bridged zirconocene-based tripodal metallo-ligands. To avoid multiple product formation using two different metal acceptors, we chose trinuclear Zr(IV) metallo-ligands as donors. All the compounds were characterized by NMR and single crystal X-ray diffraction. Among the compounds, the water-soluble compound 2 is capable to encapsulate aromatic guests such as naphthalene and 2-naphthaldehyde. The encapsulation of the guests was confirmed by NMR and UV-vis spectrometry. The binding constants as well as corresponding Gibbs free energy changes were calculated separately from the 1H NMR titration of compound 2 with guests (naphthalene/2-naphthaldehyde).