Studies on the Novel Calix [4] pyrrole and Its High Selectivity for p‐Nitrophenol

Synthesis of novel neutral molecule receptor calix [4] pyrrole (2) from pyrrole and tropinone has been described and its ability of binding neutral molecules was tested. Spectroscopic titrations indicate that receptor 2 shows the highest selectivity for p‐nitrophenol among m,o,p‐nitrophenols due to the coincidence between the host's binding sites and the guest's geometry.