such as HF, LiH, and HCN. Two years later, Dougherty [16] and Besnard [17]
independently reported theoretical studies on interaction of water and hexafluorobenzene, the so-called lone-pair electron-π interaction. The binding energy
was predicted as being in the range of 1.5–4 kcal/mol, depending on the calculation
methods utilized. Inspired by the results of lone-pair electron-π interaction, in 2002
Deyà and coworkers [3] conducted theoretical calculations at HF/6-31++G** and
MP2/6-31++G** levels to demonstrate the energetically favored anion-π interaction based on hexafluorobenzene as the π receptors. By using Molecular Interaction Potential with Polarization (MIPp), they pointed out that the main
contributions to anion-π interaction are electrostatic and polarization components.
The minima for the complexes between anions and the π-cloud of the perfluoroaromatic derivatives were obtained with stabilization energy ranging from À8 to
À27 kcal/mol depending on the charge-negative species applied. In this report,
Deyà and coworkers termed the interaction between anion and π receptor as
“anion-π interaction.” Almost at the same time, Mascal [2] and Alkorta [4]
independently published their theoretical studies describing anion-π interactions.
In Mascal’s work, they reported a MP2/6-31+G* method for the interaction of
1,3,5-triazine and trifluoro-1,3,5-triazine with anions including fluoride, chloride,
and azide. Besides the non-covalent anion-π binding mode in which anion interacts
with the centroid of an electron-deficient aromatic ring, minima for both C-HÁ Á ÁX
À
hydrogen bonding and formation of reactive complexes derived from nucleophilic
attack on the triazine ring were also predicted. On the other hand,
Alkorta developed DFT (B3LYP/6-31++G**) and MP2 (MP2/6-31++G** and
MP2/6-311++G**) ab initio methods to evaluate the interaction of anions with
perfluorobenzene compounds. It is very interesting to note that although anion-π
interaction predicted by most of the calculations is attributed to the electrostatic
and polarization effects, different opinions have also appeared in literature. Kim
and coworkers [18], for example, have carried out high-level ab initio calculations
and used symmetry-adapted perturbation theory (SAPT) method to investigate the
nature of anion-π interactions. Except for electrostatic and induction energies, they
suggest that the contribution from dispersion energy is substantial for anion-π
interaction. Being different from most of the theoretical studies focusing the
typical non-covalent anion-π interaction mode, viz., the interaction of anion with
the centroid of electron-deficient aromatics, Hay and his coworkers [19] emphasized varied anion-π interaction motifs. On the basis of MP2/aug-cc-pVDZ calculations of the interactions of F
À
, Cl
À
, and Br
À with 1,2,4,5-tetracyanobenzene
(TCB), 1,3,5-tricyanobenzene, triazine, and hexafluorobenzene, they proposed
three distinct energetically favored complexes as depicted in Fig. 1. Recently,
Xu [20] set up a highly accurate extended ONIOM (XO) method based on
double-hybrid density functional XYG3/6-311++(d,p) level to understand the
anion-π nature in depth. They applied specific systems involving tetraoxacalix[2]
arene[2]triazine and four anions including SCN
À , NO 3
À , BF 4
À , and PF 6
À . With the
optimized structures, contribution and strength of anion-π and other non-covalent
interactions were systematically analyzed. This novel theoretical method provides
new angle on the study of anion-π interactions.
10 Application of Anion-π Interaction on Supramolecular Self-Assembly
255
independently reported theoretical studies on interaction of water and hexafluorobenzene, the so-called lone-pair electron-π interaction. The binding energy
was predicted as being in the range of 1.5–4 kcal/mol, depending on the calculation
methods utilized. Inspired by the results of lone-pair electron-π interaction, in 2002
Deyà and coworkers [3] conducted theoretical calculations at HF/6-31++G** and
MP2/6-31++G** levels to demonstrate the energetically favored anion-π interaction based on hexafluorobenzene as the π receptors. By using Molecular Interaction Potential with Polarization (MIPp), they pointed out that the main
contributions to anion-π interaction are electrostatic and polarization components.
The minima for the complexes between anions and the π-cloud of the perfluoroaromatic derivatives were obtained with stabilization energy ranging from À8 to
À27 kcal/mol depending on the charge-negative species applied. In this report,
Deyà and coworkers termed the interaction between anion and π receptor as
“anion-π interaction.” Almost at the same time, Mascal [2] and Alkorta [4]
independently published their theoretical studies describing anion-π interactions.
In Mascal’s work, they reported a MP2/6-31+G* method for the interaction of
1,3,5-triazine and trifluoro-1,3,5-triazine with anions including fluoride, chloride,
and azide. Besides the non-covalent anion-π binding mode in which anion interacts
with the centroid of an electron-deficient aromatic ring, minima for both C-HÁ Á ÁX
À
hydrogen bonding and formation of reactive complexes derived from nucleophilic
attack on the triazine ring were also predicted. On the other hand,
Alkorta developed DFT (B3LYP/6-31++G**) and MP2 (MP2/6-31++G** and
MP2/6-311++G**) ab initio methods to evaluate the interaction of anions with
perfluorobenzene compounds. It is very interesting to note that although anion-π
interaction predicted by most of the calculations is attributed to the electrostatic
and polarization effects, different opinions have also appeared in literature. Kim
and coworkers [18], for example, have carried out high-level ab initio calculations
and used symmetry-adapted perturbation theory (SAPT) method to investigate the
nature of anion-π interactions. Except for electrostatic and induction energies, they
suggest that the contribution from dispersion energy is substantial for anion-π
interaction. Being different from most of the theoretical studies focusing the
typical non-covalent anion-π interaction mode, viz., the interaction of anion with
the centroid of electron-deficient aromatics, Hay and his coworkers [19] emphasized varied anion-π interaction motifs. On the basis of MP2/aug-cc-pVDZ calculations of the interactions of F
À
, Cl
À
, and Br
À with 1,2,4,5-tetracyanobenzene
(TCB), 1,3,5-tricyanobenzene, triazine, and hexafluorobenzene, they proposed
three distinct energetically favored complexes as depicted in Fig. 1. Recently,
Xu [20] set up a highly accurate extended ONIOM (XO) method based on
double-hybrid density functional XYG3/6-311++(d,p) level to understand the
anion-π nature in depth. They applied specific systems involving tetraoxacalix[2]
arene[2]triazine and four anions including SCN
À , NO 3
À , BF 4
À , and PF 6
À . With the
optimized structures, contribution and strength of anion-π and other non-covalent
interactions were systematically analyzed. This novel theoretical method provides
new angle on the study of anion-π interactions.
10 Application of Anion-π Interaction on Supramolecular Self-Assembly
255