Guest‐Dependent Isomer Convergence of a Permanently Fluxional Coordination Cage

A fluxional bis-monodentate ligand, based on the archetypal shape-shifting molecule bullvalene, self-assembles with M2+ (M=Pd2+ or Pt2+) to produce a highly complex ensemble of permanently coordination cages. Metal-mediated self-assembly selects for an M2L4 architecture while maintaining ligand complexity. second level simplification is achieved guest-exchange; binding halides within cage mixture results in convergence species all four ligands present as “B isomer”. Within this confine, reaction graph bullvalene greatly restricted, but gives rise 38 possible diastereoisomers rapid exchange. X-ray crystallography reveals preference achiral form consisting both enantiomers. Through combination NMR spectroscopy and DFT calculations, we elucidate restricted isomerisation pathway assembly.