How to Prepare Kinetically Stable Self-assembled Pt₁₂ L₂₄ Nanocages while Circumventing Kinetic Traps

Supramolecular coordination-based self-assembled nanostructures have been widely studied, and currently various applications are being explored. For several applications, the stability of the nanostructure is of key importance, and this strongly depends on the metal used in the self-assembly process. Herein, design strategies and synthetic protocols to access desirable kinetically stable Pt₁₂ L₂₄ nanospheres are reported, and it is demonstrated that these are stable under conditions under which the palladium counterparts decompose. Descriptors previously used for palladium nanospheres are insufficient for platinum analogues, as the stronger metal-ligand bond results in a mixture of kinetically trapped structures. We report that next to the dihedral angle, the rigidity of the ditopic ligand is also a key parameter for the controlled formation of Pt₁₂ L₂₄ nanospheres. Catalytic amounts of coordinating additives to labilise the platinum-pyridyl bond to some extent are needed to selectively form Pt₁₂ L₂₄ assemblies. The formed Pt₁₂ L₂₄ nanospheres were demonstrated to be stable in the presence of chloride, amines and acids, unlike the palladium analogues.