Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M4L6 supramolecular tetrahedron can encapsulate a variety of cationic guests with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated, and the C-H bond activation of aldehydes occurs with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.

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A chiral self-assembled M4L6 host assembly has been shown to be a suitable host for the supramolecular encapsulation of a series of guests in polar solvents, ranging from simple organic ammonium cations to more complex organometallic species. This molecular recognition process creates highly selective reactivity within the host cavity. In order to understand the factors driving the molecular recognition process, the standard thermodynamic parameters for encapsulation were determined for a series of protiated and fluorinated iridium guests in a variety of polar solvents using van't Hoff analysis. The encapsulation process for these guests exhibited enthalpy-entropy compensation effects. In solvents such as water and methanol, error analysis suggests a chemical origin for this behavior. In contrast, error analysis of this compensation behavior in polar aprotic solvents such as dimethyl sulfoxide reveals that this correlation is due to an artifact inherent in the intrinsic correlation between the enthalpy and entropy terms in the van't Hoff analysis. Guest encapsulation in polar protic solvents such as water appears to be driven by initial desolvation of the guest with concomitant rearrangement of the hydrogen bond networks in solution. This behavior shares common characteristics with other synthetic and natural host-guest and molecular recognition processes in aqueous solution, ranging from simple crown ether to complex enzyme-ligand interactions.

Interior design: A chiral supramolecular tetrahedral [Ga4L6]12− host (L=bis(bidentate) ligand) is shown to encapsulate a half‐sandwich iridium complex. This host–guest assembly reacts with aldehydes through CH bond activation, which occurs within the host interior. This activation occurs with high size and shape specificity as well as modest diastereoselectivity (d.r. 55:45–70:30) owing to the well‐defined shape of the host cavity.