Carbamate-appended Zn-porphyrin: a neutral receptor for anions

A new neutral anion receptor that contains a unique combination of an immobilized Lewis acidic binding site and carbamate groups enabling additional hydrogen bonds with a coordinated anion guest has been developed. UV–vis titration binding studies revealed the free-base porphyrin 1 and ZnTPP to be poor complexing agents for anions. In contrast, the zinc metalloporphyrin receptor 2 strongly bound anionic guests and selectivity trends turned out to be dependent upon the anion basicity and geometrical complementarity between 2 and the guest.