Self-assembly of giant supramolecular cubes with terpyridine ligands as vertices and metals on edges

Abstract

Self-assembly of three-dimensional (3-D) architecture using terpyridine (tpy)-based building blocks is challenging and seldom addressed due the fixed geometry (around 180°) of tpy-M(II)-tpy (M = Ru, Fe, Zn, and Cd) connectivity. Here we describe the self-assembly of 3-D giant metallo-supramolecular cubes using three-armed terpyridine ligands constructed on adamantane with molecular weight up to 18 k and edge length at ∼4.9 nm, which is significantly larger than the sizes of previous metallo-supramolecular cubes. Instead of using metal center as vertices in the commonly used synthetic strategy of 3-D molecular coordination ensembles, these cages [M₁₂L₈] bear 8 ligands as vertices with 12 metal ions on the edges. With a suitable edge length, the giant cubes appear to be the sole product after self-assembly from a variety of possible architectures. The 3-D metallo-supramolecules were characterized and supported by NMR, DOSY, ESI-MS, travelling wave ion mobility-MS and AFM.