With the aim to construct synthetic systems that function according to the
principles of enzymes, molecular clips based on diphenylglycoluril were cov
alently attached to (metallo)porphyrins. Two different porphyrin clips, 1 a
nd 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 t
he 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.