An expanded halogen bonding scale using astatine

As a non-covalent interaction, halogen bonding is now acknowledged to be useful in all fields where the control of intermolecular recognition plays a pivotal role. Halogen-bond basicity scales allow quantification of the halogen bonding of referential donors with organic functional groups from a thermodynamic point of view. Herein we present the pK(BAtI) basicity scale to provide the community an overview of halogen-bond acceptor strength towards astatine, the most potent halogen-bond donor element. This experimental scale is erected on the basis of complexation constants measured between astatine monoiodide (AtI) and sixteen selected Lewis bases. It spans over 6 log units and culminates with a value of 5.69 +/- 0.32 for N,N,N ',N '-tetramethylthiourea. On this scale, the carbon pi-bases are the weakest acceptors, the oxygen derivatives cover almost two-thirds of the scale, and sulphur bases exhibit the highest AtI basicity. Regarding the applications of At-211 in targeted radionuclide therapy, stronger labelling of carrier agents could be envisaged on the basis of the pK(BAtI) scale.

Automated summary

Halogen bonding is recognized as a valuable non-covalent interaction in various fields for intermolecular recognition control. The pK(BAtI) basicity scale quantifies the halogen bonding strength of astatine as the most potent halogen-bond donor element, with sulphur bases showing the highest AtI basicity. The scale can be used to enhance binding of carrier agents for targeted radionuclide therapy using At-211.