Interaction of Non-polarizable Cations with Azaborine Isomers and Their Mono-Substituted Derivatives: Position, Induction, and Non-Classical Effects Matter.

Progress in BN/CC isosterism has opened an overwhelming urge to find prospective applications of this class of materials. Herein, the interaction of three BN isosteres of benzene, i. e. 1,2-, 1,3-, 1,4-azaborines and their mono-substituted derivatives with Na and Mg cations has been surveyed in light of symmetry-adapted perturbation theory (SAPT) and interacting quantum atoms method (IQA). We have found that the orientation of the cations towards azaborines depends considerably on boron and nitrogen dispersion pattern. However, this tendency cannot be justified by electrostatics alone, without taking into account the induction as the major stabilizing factor, and Pauli repulsion, which effectively shapes the potential energy surface. Due to the significant role of induction, molecular electrostatic potentials (MEPs) can predict the interaction strength and anisotropy only if they are obtained from densities perturbed by the effective field of the cations. Through-bond and through-space effects of the substituents strongly depend on their position in the ring, where the through-bond effects are dominated by the inductive contribution. The importance of the induction energy even at short distances, and of the non-classical IQA component signify the multi-center covalency character of azaborine-cation interactions. Therefore, a pure classical view on the interaction between the cation and compounds standing on the organic/inorganic border is to a large extent misleading.