Anion−Aromatic Bonding:  A Case for Anion Recognition by π-Acidic Rings

Abstract

The basis for unprecedented noncovalent bonding between anions and the aryl centroid of electron-deficient aromatic rings has been demonstrated by an ab initio study of the interaction between 1,3,5-triazine and the fluoride, chloride, and azide ion at the MP2 level of theory. Minima are also located corresponding to C[bond]H...X(-) hydrogen bonding, reactive complexes for nucleophilic attack on the triazine ring, and pi-stacking interactions (with azide). Trifluoro-1,3,5-triazine also participates in aryl centroid complexation and forms nucleophilic reactive complexes with anions. This novel mode of bonding suggests the development of new cyclophane-type receptors for the recognition of anions.

The World of Non-Covalent Interactions: 2006

“…Although cation...conjugated systems are more common than analogue interactions with anions, anion recognition by π-acidic rings might be important, and not only in chemistry 265 . Interactions between (fluorinated) 1,3,5-triazine and small anions were studied at the MP2 level of theory.…”

Enolate chemistry with anion–π interactions

“…Pertinent anion transport experiments have identified anion-p interactions 1,4 and halogen bonds 5,6 as promising candidates to contribute to the acceleration of transformations with anionic transition states. Anion-p interactions [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] are particularly intriguing because the complementary cation-p interactions are essential in biocatalysis 25,26 and are increasingly used in organocatalysis 25,27,28 . In sharp contrast, anion-p interactions are essentially unexplored in catalysis 23,24 .…”

“…To attract anions, the negative quadrupole moment of p-basic aromatics has to be inverted. This is possible with the introduction of strongly electron-withdrawing substituents 1,4,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] . Popular examples are hexafluorobenzene or 2,4,6-trinitrotoluene.…”

“…The possibility to bind anions on the surface of p-acidic aromatics has fascinated theoreticians and crystal engineers since about a decade [7][8][9] . However, it was not easy to confirm their functional relevance in solution 4,10,14,16 .…”

Synthesis, Crystal Structure and Application of New Cobalt(II) Complex [Co(bpy)2NO3]·NO3·5H2O as Sensitizer in Dye-Sensitized Solar Cells

“…In search of new materials for application in smart electronic devices, systems having π-conjugated molecules have drawn special attention and thus have been applied as building blocks to develop new classes of such electronic materials [6,7]. Although, coordination bonding and hydrogen bonding interactions act as important driving forces in crystal engineering, several other types of forces, such as π-π stacking and other such electrostatic interactions also have gained significant importance in constructing extended networks [8][9][10]. Moreover, these complexes show good panchromatic behaviour owing to the enhanced absorption over a broad range due to their large conjugated structure and as well as for the capacity of producing strong charge transfer bands with high molar extinction coefficient; they are preferred as potential photosensitizer dye in DSSC [11][12][13][14].…”