Anion-pi interactions in [S4N3]+ rings

Abstract

[eng] In 1996 J. Derek Woollins reported ''p-facial'' interactions between the chloride anion and the seven-membered aromatic [S4N3]+ and inorganic ring (Polyhedron, 1996, 15, 4603-4605). In spite of this manuscript has not been highlighted before (only 5 citations so far), it can be considered as a pioneering work in the field of noncovalent interactions involving anions, since unprecedented anion-p contacts were described as ''p-facial'' interactions. In this manuscript several complexes of [S4N3]+ with anions were optimized at the BP86-D3/def2-TZVPD level of theory and compared to X-ray structures retrieved from the CSD. We have evaluated the interaction energies between the chloride and nitrate anions and the [S4N3]+ ring. The anion-p complexes are energetically favourable and the complexation has been characterized by means of Bader's theory of ''atoms in molecules''. Moreover, the p-orbitals of the [S4N3]+ ring have been computed and the aromaticity of the 10-p electron seven membered ring was analysed.