Remarkable Stabilization of M12L24 Spherical Frameworks through the Cooperation of 48 Pd(II)−Pyridine Interactions

Kinetic studies on the ligand exchange of self-assembled M(12)L(24) spherical complexes demonstrate that the multicomponent self-assembly roughly undergoes three stages. Initially, (i) there are very rapid equilibrations (ms(-1)) among the many components; (ii) as more stable structures are formed, the system equilibrates quickly (s(-1) to min(-1)) among the completed and uncompleted self-assemblies; misassembled structures are presumably corrected at this stage; and finally (iii) very slow equilibration (hours to days) at the final stage after the self-assembly completes, producing the kinetic stability of the whole. The half-lives of the ligand exchange processes in the M(12)L(24) complexes are much longer than those for comparable monodentate Pd(II)-pyridine complexes by a factor of approximately 10(5), suggesting that, once formed, the 36-component molecular spheres behave like covalent componds.