Four faces of the interaction between ions and aromatic rings

Dóra Papp, Petra Rovó, Imre Jákli, A. Császár, A. Perczel

Research output: Contribution to journalArticle

5 Citations (Scopus)


Non-covalent interactions between ions and aromatic rings play an important role in the stabilization of macromolecular complexes; of particular interest are peptides and proteins containing aromatic side chains (Phe, Trp, and Tyr) interacting with negatively (Asp and Glu) and positively (Arg and Lys) charged amino acid residues. The structures of the ion–aromatic-ring complexes are the result of an interaction between the large quadrupole moment of the ring and the charge of the ion. Four attractive interaction types are proposed to be distinguished based on the position of the ion with respect to the plane of the ring: perpendicular cation–π (CP), co-planar cation–π (CP), perpendicular anion–π (AP), and co-planar anion–π (AP). To understand more than the basic features of these four interaction types, a systematic, high-level quantum chemical study is performed, using the X + C6H6, M+ + C6H6, X + C6F6, and M+ + C6F6 model systems with X = H, F, Cl, HCOO, CH3COO and M+ = H+, Li+, Na+, NH+ 4, CH3 NH+ 3, whereby C6H6 and C6F6 represent an electron-rich and an electron-deficient π system, respectively. Benchmark-quality interaction energies with small uncertainties, obtained via the so-called focal-point analysis (FPA) technique, are reported for the four interaction types. The computations reveal that the interactions lead to significant stabilization, and that the interaction energy order, given in kcal mol−1 in parentheses, is CP (23–37) > AP (14–21) > CP (9–22) > AP (6–16). A natural bond orbital analysis performed leads to a deeper qualitative understanding of the four interaction types. To facilitate the future quantum chemical characterization of ion–aromatic-ring interactions in large biomolecules, the performance of three density functional theory methods, B3LYP, BHandHLYP, and M06-2X, is tested against the FPA benchmarks, with the result that the M06-2X functional performs best.

Original languageEnglish
Pages (from-to)1762-1773
Number of pages12
JournalJournal of Computational Chemistry
Issue number20
Publication statusPublished - Jul 30 2017


  • focal-point analysis of interaction energies
  • ion–aromatic-ring interaction
  • natural bond orbital analysis
  • non-covalent interaction

ASJC Scopus subject areas

  • Chemistry(all)
  • Computational Mathematics

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