Cavitand Zn(II)-porphyrin capsules with high affinities for pyridines and N-methylimidazole

Covalent cavitand Zn(II)-porphyrins 17-20 were prepared via multistep syntheses. These host molecules show moderate to excellent binding affinities to N-methylimidazole and pyridine guests. The complexing behavior strongly depends on the spacer's length, number, and rigidity, in addition to the guest size. Cavitand capping and strapping of porphyrins strongly influence the complex formation and result in a 10-700-fold enhancement of the binding strength compared to tetraphenyl Zn(II)-porphyrin