Gallic Acid Dimer As a Double π–Hole Donor: Evidence from X‑ray, Theoretical Calculations, and Generalization from the Cambridge Structural Database

• Published in: Crystal growth & design 2019-07, Vol.19 (7), p.3989-3997
• Main Authors: Prohens, Rafel, de Sande, Dafne, Font-Bardia, Mercè, Franconetti, Antonio, González, José F, Frontera, Antonio
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.9b00387

In this work, we demonstrate that the centrosymmetric eight-membered supramolecular ring R 2 2(8) that is formed upon dimerization of benzoic acids has a marked tendency to establish π–hole interactions with electron-rich atoms. We have used the Cambridge Structural Database to demonstrate the preference of carboxylic acid dimers to form donor–acceptor interactions involving π–holes located at the C atoms above and below the molecular plane. Moreover, we have carried out DFT calculations (PBE0-D3/def2-TZVP) to investigate the geometric and energetic features of these interactions and how they are affected by the substituents of the aromatic ring. Finally, as an example we report the synthesis and X-ray characterization of a solvate of gallic acid with dioxane, where two molecules of dioxane are located above and below the eight-membered supramolecular ring, forming two symmetrically equivalent O···C π–hole interactions.