Templation effects on formation of a hemicarceplex

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Abstract
We have shown previously that the reaction to form carceplex 3•guest has dramatic templation requirements where the best template molecule studied is one million times more effective at bridging the two bowl-shaped precursors than the poorest template. Here, we investigate the template requirements for the formation of hemicarceplex 4•guest which is similar to carceplex 3•guest in cavity size and shape. The two compounds differ in that 4•guest lacks one of the four inter-bowl methylene bridges and thus has a portal and reduced symmetry relative to carceplex 3•guest (C2v vs D4h). Thus, the template requirements for hemicarceplex 4•guest are more stringent because the two bowls can, in principle, misalign. We have found that despite these differences, the same template effect holds. We conclude that the same forces are at play in each reaction. These forces include 1) favorable van der Waals interactions between the template molecule and the forming cavity of the carceplex or hemicarceplex 2) unfavorable steric strain being imparted to the complex and 3) hydrogen bonds between the bowls. We also demonstrate the utility of matrix-assisted laser desorption ionization (MALDI) as a mild mass spectrometric technique for non-volatile organic compounds and complexes.