Interplay between anion‐π and hydrogen bonding interactions

Abstract

The interplay between two important noncovalent interactions involving aromatic rings is studied by means of high level ab initio calculations. They demonstrate that synergistic effects are present in complexes where anion-pi and hydrogen bonding interactions coexist. These synergistic effects have been studied using the "atoms-in-molecules" theory and the Molecular Interaction Potential with polarization partition scheme. The present study examines how these two interactions mutually influence each other.

The intricacies of the stacking interaction in a pyrrole–pyrrole system

“…They play a key role in supramolecular chemistry which is defined as ''chemistry beyond the molecule'' and are without doubt the dominant type of interaction in maintaining the three-dimensional structure of large systems such as proteins, nucleic acids and other large molecules [1][2][3][4][5][6][7][8]. In these systems, NCI involving aromatic rings can be distinguished and those are for instance: p-stacking, cation/p, anion-p, C-H/p and N-H/p interactions [9][10][11][12][13][14]. The understanding of their nature together with their interplaying and dependencies between different types of NCI (for instance p-stacking vs N-H/p) is critical for harnessing their full potential in chemistry, especially when the precise control of the strength and geometry of intermolecular interactions is concerned, e.g.…”

Free-energy relationships for the interactions of tryptophan with phosphocholines

“…In a number of supramolecular systems, free energies for the formation of specific electrostatic interactions have been found to scale linearly with σ p . 46,47 Consequently, the inverted-U trends observed here would suggest that either the 50 formation of hydrogen bonds and cation-π interactions is cooperative in this system, or that other interactions influenced by the 5-substituent of the indole contribute to the free energy of binding. Table 1, which assume noncompetitive binding of 1a-h and water to 2.…”

“…Smoothing and derivative calculation were performed using 50 the R statistical graphics package (version 2.7.1). 43 Cluster analysis was conducted on a subset of the coordinates comprising the amino acid and lipid headgroup only, using the GROMOS clustering method, 32,44 with rms cut-offs in the range 0.10-0.14 nm, chosen such that the average rms 55 deviation per atom was <0.01 nm.…”

“…11,[14][15][16] More recently however, steric effects and dipole-dipole 45 contributions have been suggested to be more important than hydrogen bonding or cation-π interactions for determining the membrane partitioning and alignment of these and related indole derivatives. 10 Molecular dynamics simulations of mixed indole-lipid and tryptophan-lipid systems indicate a 50 preference for indole to localise at specific locations in relation to membranes, including the middle of the bilayer, proximal to the choline headgroup and in the region of the lipid carbonyl groups, with the latter being the preferred site. 17,18 This is supported by experimental work on model 55 helical transmembrane peptides bearing interfacial tryptophan residues, for which the presence of hydrogen bonding interactions with lipid carbonyl groups is notable.…”

“…50 However, the cation-π and hydrogen bond interaction energies in these systems are non-additive; the 65 formation of one leads to an interaction energy for the other that is more favorable by up to 5 kJ mol -1 , with a concomitant reduction in intermolecular distances. This free energy gain mostly comprises electrostatic rather than polarisation effects and is likely to be smaller for interactions with the ammonium 70 group of choline, which has a considerably more disperse charge than alkali metal cations.…”