Anion-n Interactions

Keywords Anion-n interaction Charge transfer Electronic spectra Halogen n-bonding X-ray crystallography... 

In both structures anion-n interactions between one or two of the BfT counteranions and the electronically poor nitrogenated ring of the quinoxaline are observed in the solid state (Figure 3.9). 

Figure 3.11 Molecular view of the structure of complex 102 showing the alternating array of loops and the anion-n interactions. Distances are in A. 

Figure 3.12 Schematic views of the molecular structures of 114 (a) and 115 (b). The anion-n interactions found are indicated. Distances are in A.

Keywords Anion-n interactions Anion coordination Anion receptors Anions Host-guest systems Supramolecular chemistry... 

Fig. 13 Molecular structures of the anion receptors proposed by Mascal [13]. The anion is bound by a combination of three ion-pair reinforced hydrogen-bonding and two anion-n interactions...

Although several theoretical studies have proposed structures for novel receptors based on multiple anion-jt interactions, to date, and to the best of our knowledge, the experimental realization of such type of receptors and their anion-binding properties have not been reported. The few experimental studies that have attempted the experimental quantification of the anion-n interaction in solution have produced very different and even opposite results. 

Ballester provides an interesting account of anion - n interactions and their impact in host design. Over the past few years there has been mounting evidence that this type of interaction plays an important role in anion recognition. The chapter starts with a detailed overview of the theoretical aspects of anion - n interactions which is followed by a discussion of the existing... 

Schottel, B. L., Chifotides, H. T., Shatruk, M., Chouai, A., Perez, L. M., Bacsa, J., Dunbar, K. R. (2006). Anion-n Interactions as Controlling Elements in Self-Assembly Reactions of Ag(I) Complexes with n-Acidic Aromatic Rings. Journal of the American Chemical Society, 128(11), 5895-5912. 

Guha, S., Saha, S. (2010). Eluoride Ion Sensing by an Anion-n Interaction. Journal of the American Chemical Society, 132(50), 17674-17677. 

Another type of dimer is that which consists of two radical molecules stacked on each other in a n-n interaction. Such dimers have been observed e.g., with 9-ethylphenazyl radical, tetramethyl-p-phenylenediamine cation radical (167), 7,7,8,8-tetracyanoquinodimethane radical anion (168), methylviologen cation radical (169), and l-alkyl-4-carbomethoxypyridinyl radicals (170). Attempts have been reported (170, 171) to interpret the electronic spectra of dimers of this kind by MO calculations. 

Kestner, N. R. (1976), in Electron-Solvent and Anion-Solvent Interactions (Kevan, L., and Webster, B., eds.), p. 1, Elsevier, Amsterdam. 

Tetrachloro-5,6-diphenyl- and -5,6-di-n-propyl calicene were found to yield intensely colored radical anions when interacted with alkali metals (Na, K)291. As ESR-spectroscopic investigation showed an unpaired electron spin is located on three-ring carbons Cs/C6 and their substituents. 

Effect of Cs+, a structure-breaking type cation In acidic medium, the silica anions will interact preferentially with the smallest positively charged entities which appear to be the hydrated Cs+ ions. Consequently, a small number of nuclei (because silicate-Pr N interactions are less preferred), essentially Si-rich (becau -se silicate-Al(H20) + interactions are less favoured) and containing very little Na (because silicate-Na(H20)x+ interactions are... 

The structure of [H2dmbg] [CuClJ has been reported recently [42]. Not unexpectedly, the [H2dmbg]2+ cation, unlike the [Hdmbg]+ cation, acts as a discrete cation. Like the [Hdmbg]+ cation, however, it is non-planar without an intra-molecular N-H N contact. All seven N-H donor sites are utilised in cation-anion N-H Cl interactions to form a 3-D network structure. 

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