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

Abstract

In this work, we demonstrate that the centrosymmetric eight-membered supramolecular ring R2 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.

π-Hole bonding in a new co-crystal hydrate of gallic acid and pyrazine: static and dynamic charge density analysis

“…The carboxyl C atom displays the characteristics of -holes with electropositive regions above and below the molecular plane. The double -hole characteristics of the acid dimer in a solvate of gallic acid with dioxane were recently addressed (Prohens et al, 2019). In the same study, a detailed Cambridge Structural Database (CSD) analysis on aromatic carboxylic acid dimers was performed and it was demonstrated that the centrosymmetric hydrogenbonded carboxylic dimer is well suited to form -hole interactions (Prohens et al, 2019).…”

“…The double -hole characteristics of the acid dimer in a solvate of gallic acid with dioxane were recently addressed (Prohens et al, 2019). In the same study, a detailed Cambridge Structural Database (CSD) analysis on aromatic carboxylic acid dimers was performed and it was demonstrated that the centrosymmetric hydrogenbonded carboxylic dimer is well suited to form -hole interactions (Prohens et al, 2019). The analysis also showed that in 232 out of 497 investigated structures the carboxylic acid dimers participate in two symmetrically-related -hole interactions, above and below the molecular plane.…”

Competition between Intra and Intermolecular Triel Bonds. Complexes between Naphthalene Derivatives and Neutral or Anionic Lewis Bases

“…There are also exceptional cases wherein a tetravalent Tr atom can generate a σ-hole [57]. This TrB has generated sufficient interest so as to be the focus of a number of prior quantum chemical studies [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73]. Our own earlier study of the TrB [73] in complexes of TrR 3 (Tr = B, Al, Ga; R = H, F, Cl, Br, CH 3 ) with pyrazine provides some information about the influence of various substituents on the energy, geometry, and properties of this interaction.…”

Relevant π-hole tetrel bonding interactions in ethyl 2-triazolyl-2-oxoacetate derivatives: Hirshfeld surface analysis and DFT calculations

“…Moreover, the relevance of n → π* interactions in proteins from a lone pair of electrons (n) to the antibonding orbital (pi*) of carbonyl group has been demonstrated 21 . In addition, significant π-hole interaction have been described an studied in benzoic acid dimers 22 , nitro derivatives [23][24][25][26][27] , and acyl carbon containing molecules [28][29][30] .…”