Quantitative Analysis of the Self-Assembly Process of a Pd₁₂ L₂₄ Coordination Sphere

The self-assembly process of a Pd₁₂ L₂₄ sphere was revealed by a quantitative approach (quantitative analysis of self-assembly process: QASAP) quantifying all the substrates, the products, and the observable intermediates, indicating that the Pd₁₂ L₂₄ sphere is produced through several pathways. Firstly, Pd_n L_2n (n=6, 8, and 9), which are perfectly closed structures smaller than the Pd₁₂ L₂₄ sphere, and a mixture of intermediates not observed by NMR (Int) were produced. Next, the sphere was assembled from intra-/intermolecular reaction of a certain class of Int (path A) and from the coordination of free pyridyl groups in Int to the Pd^II center of Pd_n L_2n (n=6, 8, and 9) (path B). While capping the free pyridyl groups in Int with Pd^II ions perfectly inhibited the sphere formation, the addition of free L to Int accelerated the formation of the sphere.