Binding of Amino Acids into a Novel Multiresponsive Ferrocene Receptor Having an Ene Backbone

[reaction: see text] Receptor 1 featuring two open arms, multipoint binding sites, and unsaturated linkers on a ferrocene platform shows strong 1:1 binding to unprotected alpha-amino acids (UV-vis, fluorescence, CV, ITC, NMR, and ESI-MS). NMR and ESI-MS studies suggest an encapsulative binding mode involving the alpha,beta-unsaturated carbonyl residue (site for -NH3+, interaction A) and the terminal -OH groups (site for -COO-, interaction B).