Molecular building-blocks for anion–π interactions

Theoretical calculations are performed to design a set of π molecules, significant for anion-π interactions. Quadrupole moments are reported at several levels of calculation. Trends from MP2 calculations are reproduced from DFT calculations, although actual values are different. Binding energies towards a chloride anion have been evaluated for the considered molecules and they roughly correlate with the quadrupole moment of the molecules, although other effects, such as structural flexibility, play a role. Imide moieties that decorate the π molecules provide privileged binding sites for anions; however, similar binding energies are obtained for the interaction between a chloride and benzenediimide, naphthalenediimide and perylenediimide, although quadrupole moments vary by a factor of two. The naphthalenediimide and the benzenetriimide emerge as valuable building blocks to construct extended molecular architectures with either <i>C</i>₂ or <i>C</i>₃ symmetry, for improved anion-π interactions and anion recognition.