Theoretical and Crystallographic Study of the Dual σ/π Anion Binding Affinity of Quinolizinylium Cation

Benzoquinolizinylium salts are important compounds in the regulation of transmembrane conductance regulator channels. In this manuscript, the geometrical position (sigma/pi) of the counteranion in quinolizinylium salts has been studied by means of ab initio calculations at the RI-MP2(full)/6-31++G** level of theory. A search in the Cambridge Structural Database determines that the position of the anion depends upon its nature. Halogen anions prefer anion-sigma interactions, and BF4- and PF6- anions prefer anion-pi interactions. The dual sigma/pi binding affinity of title compound has been studied by means of ab initio and molecular interaction potential with polarization (MIPp) calculations and the Bader's theory of atoms-in-molecules.