Kinetically Controlled Fast Crystallization of M_(12)L_8Poly-[n]-catenanes Using the 2,4,6-Tris(4-pyridyl)benzene Ligand and ZnCl_2 in an Aromatic Environment

摘要

Kinetic control in the presence of six aromatic solvents has been successfully applied in the synthesis of a poly-[n]-catenane composed of interlocked M_(12)L_8 icosahedral nanometric cages (i.e., internal voids of 2500 A~3). When the exotridentate tris-pyridyl benzene ligand and ZnCl_2 with appropriate templating molecules because of good ligand aromatic interactions are used, the metal-organic cages can be synthesized very fast, homogeneously, and in large quantities as microcrystalline materials. Synchrotron single-crystal X-ray data (100 K) allowed the resolution of nitrobenzene guest molecules at the internal walls of the M_(12)L_8 nanocages, whereas in the central part of the cages the solvent is highly disordered. The guest release occurs in two steps with the disordered nitrobenzene guests released in the first step (lower temperatures) because of the absence of strong cage-guest interactions. Density functional theory calculations provided a rationalization of these outcomes and, in particular, solid-state approaches, showed theoretical evidence of the kinetic nature in the formation of the poly-[n]-catenane by the analysis of the packing energy in terms of monomeric and dimeric cages.