Anion-π and lone pair-π interactions with s-tetrazine-based ligands

Most of traditional and contemporary interest in s-tetrazine derivatives focuses onto their redox properties, reactivity and energy density. In recent times, however, an increasing number of reports highlighted the possible usefulness of the s-tetrazine moiety as a binding site for anionic and electron rich species, according to the high and positive quadrupolar moment of this heterocycle and the consequent strength of anion-pi and lone pair-pi interactions. Herein, after giving a quick perspective on s-tetrazine properties and on how they foster these types of pi interactions, we present statistical and critical examination of the available structural data, doing justice to the debated topic of the existence and directionality of anion- and lone pair-pi interactions. Finally, available literature material concerning the usage of s-tetrazine as supramolecular binding site in solution, i.e. paving the way to applications such as molecular recognition and sensing, is presented and discussed. (C) 2019 Elsevier B.V. All rights reserved.