A molecular-clip-based approach to cofacial zinc–porphyrin complexes

Abstract

We have synthesized molecular-clip-based cofacial zinc–porphyrin complexes. The complexes are shown to be new efficient receptors for the complexation of 1,4-diazabicyclo[2,2,2]octane, acridinium ions, 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA) and 1,2,4,5-benzenetetracarboxylic dianhydride (BTDA). Large binding constants ( K asso) in the range of 2.0 × 10 4–1.1 × 10 8 M −1 were obtained for the 1:1 complexes of molecular tweezers ( 3) and rectangle ( 8) by inserting the hosts between the two porphyrin rings. The values of K and the spectroscopic results suggest that 3 and 8 serve as effective building blocks to capture the hosts. Semi-empirical calculations show that the guests position themselves within the cleft of the bis-porphyrins.