Halogen bonding as a key interaction in the self-assembly of iodinated diphenylalanine peptides
Pizzi, A.a, Catalano, L.a, Demitri, N.b, Dichiarante, V.a, Terraneo, G.a, Metrangolo, P.a
a Department of Chemistry, Materials, and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milano, Via Luigi Mancinelli 7, 20131, Italy
b Elettra-Sincrotrone Trieste, S.S. 14 Km 163.5 in Area Science Park, 34149 Basovizza, Trieste, Italy
The diphenylalanine peptide FF (H2N-Phe-Phe-COOH) is a simple building-block that has been extensively studied for multiple purposes. Among the many possible mutations finalized to tailor specific functions and properties of FF-based materials, halogenation was marginally considered despite the huge changes it confers to molecular self-assembly. Here, we report a detailed study on the role of halogenation, specifically iodination, in the aggregation behavior of iodine-modified FF dipeptides. Single-crystal X-ray structures of mono-iodinated—F(I)F—and bis-iodinated—F(I)F(I)—diphenylalanine reveal that halogen atoms exert a key role in the packing features of these compounds. Specifically, halogen bonding provides additional stability to the dry interfaces formed by the aromatic rings, providing a contribution in the solid-state packing of these dipeptides. The structural evidence of halogen bonding as crucial noncovalent interaction confirms the great potential of halogenation as supramolecular tool for peptide-based systems.
