Porphyrin clips derived from diphenylglycoluril. Synthesis, conformational analysis, and binding properties

With the aim to construct synthetic systems that function according to the principles of enzymes, molecular clips based on diphenylglycoluril were covalently attached to (metallo)porphyrins. Two different porphyrin clips, 1 and 2, were synthesized that differ in the length and position of the linker between the clip and the porphyrin. This resulted in a great difference in flexibility of the cavity molecules, which had remarkable consequences for their binding properties in organic solution. The physical properties of the free base and zinc porphyrin clips have been studied in detail with NMR techniques and by the host-guest binding of viologen, dihydroxybenzene, and pyridine derivatives.