Molecular recognition of amino acid esters by porphyrinatozinc(II): observation of a new binding mode

Molecular recognition of amino acid ethyl esters (guest) by 5-(2-carboxylphenyl)-10,15,20-triphenylporphyrinatozinc(II) (host 1) was investigated using UV–Vis spectrophotometric titration method. The host–guest binding mode was studied by 1H NMR and it was found that the carbonyl group of the guest coordinates to the Zn atom of host 1 and the amino group of the guest forms hydrogen-bonding with the carboxyl group of host 1. This is a new type of binding mode which had not been observed for previous metalloporphyrin–amino acid ester recognition systems.