Theoretical ab initio study of anion–π interactions in inorganic rings

Complexes of anions with several six-membered inorganic rings with more or less aromatic character have been optimized at the RI-MP2/aug-cc-pVDZ level of theory. The rings studied are hexazine (N6), boroxine (B3O3H3), borazine (B3N3H6), 1,3,5,2,4,6-triazatriborinine (B3N3) ring, and borthiin (B3S3H3). The anion–π complexes are energetically favorable and the interaction has been characterized by means of the Bader’s theory of ‘atoms-in-molecules’ and partitioning the energy using the SAPT method. Experimental evidence of the importance of this interaction in some inorganic rings has been obtained from the Cambridge Structural Database.