Fig. 8

A simplified energy landscape of the self-assembly of the cage. It is to be noted that the conversion of dinuclear intermediates ([Pd₂1₂Py*₅]⁴⁺ is shown as a typical structure) to the cage (right side) and to the sheet (left side) is not a single step but contains multiple reactions. Without a good template (NO₃⁻), an S-shaped conformation of the ditopic ligands 1 is preferred and the energy barrier for the formation of the (OTf⁻)@[Pd₂1₄]⁴⁺ cage (ΔG^‡_on) is higher than that for the sheet formation (ΔG^‡_off), which biases the self-assembly towards the off-pathway leading to the metastable sheet structure. In the presence of a good template (NO₃⁻), ΔG^‡_on is smaller than ΔG^‡_off, so the self-assembly takes place through the on-pathway to lead to the thermodynamically most stable (NO₃⁻)@[Pd₂1₄]⁴⁺ cage under kinetic control. If the self-assembly was controlled by the thermodynamic template effect, the product would be determined exclusively by the relative thermodynamic stability between the sheet and the (X⁻)@[Pd₂1₄]⁴⁺ cage