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-p and lone pair-p interactions. Herein, after giving a quick perspective on s-tetrazine properties and on how they foster these types of p 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-p 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.