Rational design of metal-organic cages to increase the number of components via dihedral angle control

The general principles of discrete, large self-assemblies composed of numerous components are not unveiled and the artificial formation of such entities is a challenging topic. In metal-organic cages, design strategies for tuning the coordination directions in multitopic ligands by the bend and twist angles were previously developed to solve this problem. In this study, the importance of remote geometric communications between components is emphasized, realizing several types of metal-organic assemblies based on dihedral angle control in multitopic ligands although they have the same coordination directions. Self-assembly of a tritopic ligand with dihedral angles θ = 36° and a cis-protected Pd(II) ion afforded M9L6 and M12L8 cages as kinetic and thermodynamic products, respectively, whereas an M12L8 sheet was formed when θ = 90°. Geometric analyses of strains in the subcomponent rings revealed that remote geometric communications among neighboring multitopic ligands through coordination bonds are key for large assemblies.