Pd₁₂ML₂₄ (for n = 6, 8, 12) nanospheres by post-assembly modification of Pd₁₂L₂₄ spheres

In this contribution, we describe a post-assembly modification approach to selectively coordinate transition metals in Pd₁₂L₂₄ cuboctahedra. The herein reported approach involves the preparation of Pd₁₂L₂₄ nanospheres with protonated nitrogen donor ligands that are covalently linked at the interior. The so obtained Pd₁₂(LH⁺)₂₄ nanospheres are shown to be suitable for coordinative post-modification after deprotection by deprotonation. Selective formation of tetra-coordinated M^B in Pd₁₂M^B₆L₂₄, tri-coordinated M^B in Pd₁₂M^B₈L₂₄ nanospheres and two-coordinated M^B in Pd₁₂M^B₁₂L₂₄ nanospheres is achieved as a result of different nitrogen donor ligands. A combination of pulsed EPR spectroscopy (DEER) to measure Cu-Cu distances in the different spheres, NMR studies and computational investigations, support the presence of the complexes at precise locations of the Pd₁₂M^B₆L₂₄ nanosphere. The general post-assembly modification methodology can be extended using other transition metal precursors or supramolecular systems and can guide precise formation and investigation of novel transition metal-complex containing nanospheres with well-defined composition.