Experimental evidence for interactions between anions and electron-deficient aromatic rings

Abstract

This feature article summarizes our research aimed at using electron-deficient aromatic rings to bind anions in the context of complementary research in this active field. Particular attention is paid to the different types of interactions exhibited between anions and electron-deficient arenes in solution. The 120+ references cited in this article underscore the flurry of recent activity by numerous researchers in this field, which was relatively nascent when our efforts began in 2005. While the interaction of anions with electron-deficient aromatic rings has recently garnered much attention by supramolecular chemists, the observation of these interactions is not a recent discovery. Therefore, we begin with a historical perspective on early examples of anions interacting with electron-deficient arenes. An introduction to recent (and not so recent) computational investigations concerning anions and electron-deficient aromatic rings as well as a brief structural survey of crystalline examples of this interaction are provided. Finally, the limited solution-based observations of anions interacting with electron-deficient aromatic rings are summarized to introduce our current investigations in this area. We highlight three different systems from our lab where anion-arene interactions have been investigated. First, we show that tandem hydrogen bonds and anion-arene interactions augment halide binding in solution. Second, a crystallographic and computational study highlights the multiple types of interactions possible between anions and electron-deficient arenes. Third, we summarize the first example of a class of designed receptors that emphasize the different types of anion-arene interactions possible in solution.

Cation–π and Lone Pair–π Interactions Combined in One: The First Experimental Evidence of (H3O‐lp)+⋅⋅⋅π‐System Binding in a Crystal

“…[16] At the same time, recent investigations [16,19] on H 3 O + -and H 5 O 2 + -containing salts have shown that due to the formation of interionic H bonds the positive charge of these species is significantly reduced; this may appear sufficient to involve an oxonium cation into the lp-p binding. Although such interactions are well-known for neutral and negatively charged species, [1][2][3][4] those involving cations as the lp donors have-to the best of our knowledge-not been observed or even proposed yet in the literature.…”

Functional molecules and materials by π‐Interaction based quantum theoretical design

“…It is worth mentioning that the electrostatic term of anion-p interaction can also be described in terms of ESP as the quantitative predictor of anion-binding energies which are widely used to characterize p-acidity of aromatics and heterocycles. [68,69] For example, ESP maps (Fig. 6) for 1,3,5-trifluorobenzene (TFB), hexafluorobenzene (HFB) .…”

Dinuclear titanium complexes with methylphenylsilylene bridge between cyclopentadienyl rings. Synthesis, characterization and reactivity towards ethylene

“…This anion-p interaction is only present in the solid-stateits nonexistence in solution is proved by NMR spectroscopy (vide supra) suggestive of an unhindered rotation of both cyclopentadienyl rings around the Si-C Cp bonds. Since solid-state anion-p interactions can be either of electrostatic nature or of a weak r interaction [17][18][19], we have conducted some DFT studies on the target molecule.…”