Metal-Directed Self-assembly of Cavitand Frameworks

The self-assembly between bidentate cavitand ligands and mono/dinuclear metal precursors to give cavitand frameworks has been explored. For this purpose, two new cavitands bearing AB and AC phenylpyridyl moieties at the upper rim have been synthesized. A series of self-assembled molecular dimers featuring fac-Re(CO)(3)Br as metal corners have been prepared and characterized. Two possible dimeric structures (C-shaped and S-shaped) are possible when AB cavitand 2 is used in the self-assembly reaction; only one is obtained in the case of AC cavitand 3. In addition, the self-assembly of AB-dibridged cavitand 2 with dinuclear Pd/Pt metal precursors 5a and 5b has been studied. At this level of complexity, the self-assembly can lead to more than one structure. Several different final structures have been envisioned and their formation analyzed in silico and in solution. Out of the three possible cyclic structures (dimer, trimer, and tetramer), only the entropically favored dimer 6a (6b) is formed, as predicted from molecular modeling and demonstrated by PGSE NMR experiments.