Controlling Molecular Organization by Using Phenyl Embraces of Multiple Trityl Groups.

Sixfold phenyl embraces are well-established aromatic interactions that are strong and directional. In addition, functional groups that are able to participate, such as triphenylmethyl (trityl), are easily incorporated in molecular structures. As a result, embraces offer a possible way to control molecular organization in materials. To test this notion, we used a hybrid organic-inorganic strategy to make compounds with multiple trityl groups. Trityl-substituted alkynylpyridines 3-5 react with Pd(II) to form square-planar 4:1 complexes with multiple divergent trityl groups poised to engage in embraces. The complexes were crystallized, and their structures were determined by X-ray diffraction. Surprisingly, few structures in this set of compounds were found to incorporate sixfold embraces. Our observations suggest that predictable molecular organization cannot normally be achieved using these embraces, which must compete with alternative aromatic interactions of similar energy.