Interplay between anion-π and hydrogen bonding interactions

Interplay between Anion-p and Hydrogen

Bonding Interactions

DANIEL ESCUDERO, ANTONIO FRONTERA, DAVID QUINONERO, PERE M. DEYA

Departament de Quımica, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain

Received 29 February 2008; Accepted 17 April 2008DOI 10.1002/jcc.21031

Published online 28 May 2008 in Wiley InterScience (www.interscience.wiley.com).

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-p 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.

q 2008 Wiley Periodicals, Inc. J Comput Chem 30: 75–82, 2009

Key words: noncovalent interactions; hydrogen bonding; anion-p interactions; cooperativity; ab initio calculations

Introduction

Noncovalent interactions involving aromatic rings are key pro-

cesses in both chemical and biological recognition.1 Among

them, anion-p interactions2–6 have attracted considerable atten-

tion in the last 5 years.7 There is a great deal of experimental8–13

and theoretical14–17 work that evidence that the anion-p inter-

actions play a prominent role in several areas of chemistry, such

as molecular recognition18 and transmembrane anion trans-

port.19,20 Anion coordination is an important and challenging as-

pect of contemporary supramolecular chemistry. Recent investi-

gations have provided experimental evidence for the usefulness

of pyridine and diazines coordinated to Ag(I) in the design of

anion receptors by demonstrating the ability of these rings to

interact with anions through multiple anion-p interactions.21–25

The structural consistency displayed by these networks and the

uniform mode of anion binding demonstrate the potential use of

anion-p interaction in a structurally directing role.26

The anion-p interaction is dominated by electrostatic and

ion-induced polarization terms.27,28 The nature of the electro-

static term can be rationalized by means of the permanent quad-

rupole moment of the arene. The face-to-face interaction of the

benzene-hexafluorobenzene complex is favorable due to the

large and opposite permanent quadrupole moments of the two

molecules.29–31 The hydrogen bond interaction is mainly domi-

nated by electrostatic effects (dipole–dipole interactions).32

We have recently reported experimental33 and theoretical34,35

evidence of interesting synergistic effects between anion-p and

p–p interactions. We have demonstrated that there is a remark-

able interplay between the anion-p and p–p interaction in com-

plexes where both interactions coexist. This interplay can lead to

strong cooperativity effects. In this manuscript, we study how

the anion-p interaction is influenced if the arene participates in

hydrogen bonding interactions. We have selected three p-acidicaromatic rings, see Figure 1, that contain nitrogen atoms in the

structure which can participate in hydrogen bonding interactions

(r interactions). We have first computed the anion-r and anion-

p complexes 4–14 present in Figures 1 and 2. Since the aromatic

rings 1 (pyrazine) and 2 (pyridazino[4,5-d]pyridazine) can act as

hydrogen bond acceptors and the pyromellitic diimide 3 can act

as hydrogen bond donor, we have computed the anion-p-racceptorcomplexes 15–22 and the anion-p-rdonor complexes 23–24 pres-

ent in Figure 3, in order to study the interplay between the

anion-p and hydrogen bonding interactions. We have used the

Bader’s theory of ‘‘atoms-in-molecules’’ (AIM),36,37 which has

been widely used to characterize a great variety of interac-

tions,38–40 and analyze cooperativity effects in the complexes.

Compounds 2 and 3 are synthetically available; for instance

compound 225,41 has been prepared by inverse electron demand

Diels-Alder cycloaddition reactions of s-tetrazine. Its complexes

with Cu(II) and Ag(I) exhibit strong anion-p interactions. Com-

pound 3 is commercially available and the construction of

Additional Supporting Information may be found in the online version of

this article.

Contract/grant sponsor: DGICYT of Spain; contract/grant number:

CTQ2005-08989-01

Contract/grant sponsor: Govern Balear; contract/grant number: PROGE-

CIB-33A

Contract/grant sponsor: Fundacio Sa Nostra

Correspondence to: A. Frontera; e-mail: [email protected]

q 2008 Wiley Periodicals, Inc.

anion-receptors based on this binding unit is under investigation

in our laboratory.

Theoretical Methods

The geometries of all complexes studied in this work were fully

optimized at the MP2/6-31þþG** level of theory using the Gaus-

sian-03 program.42 The binding energies were calculated with

correction for the basis set superposition error (BSSE) by using

the Boys-Bernardi counterpoise technique.43 The optimization of

the complexes 4–16, 19–24 has been performed imposing C2v

symmetry. For complexes 17–18 Cs symmetry was imposed dur-

ing the optimization. Frequency calculations indicate that all

hydrogen bonding complexes (4–8) are true minima. Fluoride

complexes have one or two imaginary frequencies apart from

complexes 9 and 11 that are true minima. Chloride complexes are

true minima apart from 14, 22, and 24 that have one imaginary

frequency. Other possible conformations of complexes have not

been considered because the ultimate aim of this study is to verify

the interplay between both non covalent interactions in the com-

plexes and to obtain an insight into the nature of the cooperativity.

Therefore we only concentrate on those complex geometries.

The AIM analysis has been performed by means of the

AIM2000 version 2.0 program44 using the MP2/6-31þþG**

wavefunction. Some basic concepts of Bader’s topology analysis

follow (see references 36 and 37 for a more comprehensive

treatment). The presence of a path linking two nuclei in an equi-

librium structure implies that the two atoms are bonded to one

another and it is characterized by the bond critical point, i.e. the

point of minimum electron charge density (q) along the bond

path, but maximum along the directions perpendicular to the

bond path. The curvature, the second derivative of q, is negativeat a maximum and positive at a minimum. The rank of a critical

point, denoted by x, is the number of nonzero curvatures. Its

signature, denoted by r, is the sum of their algebraic signs. The

critical point is labeled by giving the duo of values (x, r). Thecritical points of electron charge distribution for molecules at

energetically stable configurations are all rank 3 (x ¼ 3). For

instance, a bond critical point denoted as (3, 21) has two asso-

ciated curvatures of q, denoted as k1 and k2, negative and one

positive denoted as k3. In a bond with cylindrical symmetry, k1and k2 are of equal magnitude. However, if the density is prefer-

entially accumulated in a given plane along the bond path (for

example a bond with p character) k1 and k2 are not of equal

magnitude. The ellipticity, defined as e ¼ [k1/k2-1], provides a

measure of the extent at which the electron charge density is

accumulated in a given plane. For example, the ellipticity for

C��C bond in ethane is e ¼ 0.0 (symmetrical bond), in ethene is

e ¼ 0.45, in benzene is e ¼ 0.23. The remaining two stable criti-

cal points occur as a consequence of particular geometrical

arrangements of bond paths and they define the remaining ele-

Figure 1. Schematic representation of compounds 1–3 and their H-bonded complexes with water 4–8.

Figure 2. Schematic representation of binary complexes 9–14.

76 Escudero et al. • Vol. 30, No. 1 • Journal of Computational Chemistry

Journal of Computational Chemistry DOI 10.1002/jcc

ments of molecular structure, i.e., rings (3, þ1) and cages

(3, þ3).

The physical nature of the non covalent interactions has been

studied using the Molecular Interaction Potential with polariza-

tion (MIPp)45 method. The MIPp is a convenient tool for pre-

dicting binding properties. It has been successfully used for

rationalizing molecular interactions such as hydrogen bonding

and ion-p interactions and for predicting molecular reactiv-

ity.35,46,47 The MIPp partition scheme is an improved generaliza-

tion of the MEP where three terms contribute to the interaction

energy, (i) an electrostatic term identical to the MEP,48 (ii) a

classical dispersion-repulsion term,49 and (iii) a polarization

term derived from perturbational theory.50 Some basic concepts

of MIPp follow (see refs. 45 and 49 for a more comprehensive

treatment). The MEP can be understood as the interaction

energy between the molecular charge distribution and a classical

point charge. The formalism used to derive MEP remains valid

for any classical charge, therefore it can be generalized using

eq. (1) where QB is the classical point charge at RB. QB can

adopt any value, but it has a chemical meaning only when QB ¼1 (proton), / stands for the set of basis functions used for the

quantum mechanical molecule A, cli is the coefficient of atomic

orbital l in the molecular orbital i.

MEP ¼XA

ZAQB

RB � RAj j �Xocci

Xl

Xm

CliCmi /lQB

RB � rj j��

��/m

� �(1)

The MEP formalism permits the rigorous computation of the

electrostatic interaction between any classical particle and the

molecule. Nevertheless, nuclear repulsion and dispersion effects

are omitted. This can be resolved by the addition of a classical

dispersion–repulsion term, which leads to the definition of

MIP23 [eq. (2)], where C and D are empirical van der Waals

parameters.

MIP ¼ MEPþXA0B0

CA0B0

RB0 � RA0j j12 �DA0B0

RB0 � RA0j j6 !

(2)

The definition of MIPp is given by eq. (3), where polarization

effects are included at the second order perturbation level50; estands for the energy of virtual (j) and occupied (i) molecular

orbitals. It is worth noting that eq. (3) includes three important

contributions: first, the rigorous calculation of electrostatic

interactions between quantum mechanical and classical par-

ticles; second, the introduction of an empirical dispersion-repul-

sion term and third, the perturbative treatment of the polariza-

tion term.

MIPp ¼ MIPþXvirj

Xocci

1

ei � ej

3Xl

Xm

CliCmi /lQB

RB � rj j��

��/m

� �( )2

ð3Þ

In complexes where hydrogen bonding and anion-p interactions

coexist we have computed the genuine nonadditivity energies

(E-EA) using eqs. (4)–(6). Thus, the non-additivity energies are

computed by subtracting the binding energy of the sum of all

Figure 3. Schematic representation of multi-component complexes 15–24.

77Interplay between Anion-p and Hydrogen Bonding Interactions


pair interaction energies (EA) from the binding energy of the

complex (E). The eq. (4) has been used for complexes 17 and

18, the eq. (5) has been used for complexes 15, 16, 19, 20, 23,

and 24 and finally eq. (6) has been used for complexes 21 and

22:

Ternarysystem: E� EA ¼ Eabc � ðEab þ Eac þ EbcÞ (4)

Quaternary system: E� EA ¼ Eabcd � ðEab þ Eac þ Ead

þ Ebc þ Ebd þ EcdÞ ð5Þ

Senary system: E� EA ¼ Eabcdef � ðEab þ Eac þ Ead þ Eae þ Eaf

þ Ebc þ Ebd þ Ebe þ Ebf þ Ecd þ Ece þ Ecf þ Ede þ Edf þ EefÞð6Þ

Results and Discussion

In Table 1 we summarize the binding energies without and with

the basis set superposition error (BSSE) correction (E and EBSSE,

respectively) and equilibrium distances (Re and RHB) of com-

plexes 4–14 at the MP2/6-31þþG** level of theory. The ener-

getic features of the H-bonded complexes 4–8 depends upon the

acceptor/donor characteristic of the arene. In complexes 4–7 (H-

bond acceptors) each H-bond has an energetic contribution that

ranges 4–5 kcal/mol. In complex 8 (H-bond donor), each inter-

action is 6.2 kcal/mol. The binding energy of all anion-p com-

plexes 9–14 is negative, indicating a favorable interaction. It is

modest in pyrazine complexes 9 and 10 and large in complexes

11–14, in accord with the p-acidity of the arene.

The geometric and energetic results computed for the com-

plexes 15–24 are summarized in Table 2. Some very interesting

points can be extracted from the geometrical results. The equi-

librium distance (Re) of the anion-p interaction in the anion-p-racceptor complexes 15–22 shortens when compared to complexes

9–14, indicating that the presence of the r interaction strength-

ens the anion-p interaction. In addition, in the anion-p-racceptor

complexes 15–22 the equilibrium distance of the r interaction

(RHB) also shortens with respect to the H-bonding complexes 4–

6, indicating that the presence of the anion-p interaction

strengthens the H-bond interaction. It is worth mentioning that

in complexes 21 and 22, the equilibrium distance of the H-bond

interaction of the more distant water also shortens, indicating

that the presence of the anion-p interaction influences both the

nearby and the distant r-interactions. Finally, in the anion-p-rdonor complexes 23 and 24, a different behavior is observed.

The anion-p equilibrium distance is to some extent enlarged

with respect to the anion-p complexes 13 and 14 and the H-

bond distance is also enlarged with respect to complex 8, indi-

cating that both H-bonding and anion-p interactions are weak-

ened in the complexes 23 and 24.

We have included in Table 2 what we entitle synergistic

energies (Esyn), which is the difference between the binding

energy (BSSE corrected) of the complexes 15–24 and the bind-

ing energy of the related H-bonding (4–8) and anion-p (9–14)

complexes. For instance, in complex 17 (H2O��2��F2) we have

computed the synergistic energy by subtracting the interaction

energies of 2��F2 (complex 11) and H2O��2 (complex 5) from

the binding energy of 17. This value gives valuable information

regarding the interplay between both non covalent interactions

present in the complexes. It is worth mentioning that this term is

negative in the complexes 15–22 (anion-p-racceptor complexes).

This result is in agreement with the equilibrium distances Re and

RHB that are shorter in complexes 15–22 than in complexes 4–

14, indicating that both interactions strengthen. In contrast, in

the complexes 23 and 24, where the arene interacts with H2O as

an H-bond donor (anion-p-rdonor complexes), the synergistic

energy is positive, in agreement with the equilibrium distances

Re and RHB indicating that both interactions weaken. In some

cases the interplay between both interactions contribute to the

global stabilization of the system in 4–15 kcal/mol (complexes

15–22) and in others contribute in a destabilization of the system

in 6–8 kcal/mol (complexes 23 and 24), indicating that either

Table 1. Binding Energies Without and With the BSSE Correction

(E and EBSSE, kcal/mol, respectively), Number of Imaginary Frequencies

(NImag) and Equilibrium Distances (RHB/Re, A) at MP2/6-31þþG**

Level of Theory for Complexes 4–14.

Complex E EBSSE NImag RHB/Re

4 (1þ2H2O) 213.4 210.1 0 1.98

5 (2þ1H2O) 26.3 24.7 0 2.41

6 (2þ2H2O) 212.3 29.1 0 2.42

7 (2þ4H2O) 226.7 219.9 0 2.35 (1.92)a

8 (3þ2H2O) 217.2 212.4 0 1.88

9 (1þF2) 28.1 25.4 0 2.73

10 (1þCl2) 25.9 22.6 0 3.33

11 (2þF2) 224.6 220.8 0 2.33

12 (2þCl2) 218.8 212.8 0 3.02

13 (3þF2) 223.6 220.4 1 2.54

14 (3þCl2) 220.5 214.7 1 3.11

aThe value in parenthesis corresponds to the water–water H-bond

distance.

Table 2. Binding Energies Without and With the BSSE Correction

(E and EBSSE kcal/mol, Respectively), Synergistic Energies with BSSE

Correction (Esyn kcal/mol), Number of Imaginary Frequencies (NImag)

and Equilibrium Distances (RHB/Re, A) at the MP2/6-31þþG** Level

of Theory Computed for Complexes 15–24.

Complex E EBSSE Esyn NImag Re RHB

15 231.1 224.0 28.5 1 2.50 1.92

16 227.1 218.8 26.2 0 3.18 1.94

17 236.8 230.9 25.4 2 2.29 2.27

18 230.0 221.9 24.4 0 2.99 2.30

19 248.4 240.5 210.4 2 2.27 2.26

20 240.9 230.6 28.7 0 2.95 2.32

21 268.9 256.6 215.9 2 2.23 2.20 (1.87)a

22 260.4 245.9 213.2 1 2.92 2.23 (1.88)a

23 233.1 225.9 þ7.9 1 2.55 2.01

24 230.3 220.4 þ6.7 1 3.13 1.97

aThe values in parenthesis correspond to the water–water H-bond

distances.



the anion-p interaction has a very important influence upon the

H-bonding interaction or vice versa.

The AIM analysis is summarized in Table 3 and it gives

some helpful information regarding the strength of the non cova-

lent interactions involved in the complexes. It has been demon-

strated that the value of the electron charge density at the criti-

cal points (CP) that are generated in anion-p and H-bonded

complexes can be used as a measure of the bond

order.4,17,27,28,38 In Figure 4 we show the distribution of CPs in

complexes 16, 20, 22 and 24, as representative examples of

anion-p-rdonor (24) and the three types of anion-p-racceptor com-

plexes (16, 20 and 22). In complexes 9, 10, 15 and 16, two

bond CPs, two ring CPs and one cage CP describe the anion-pinteraction. The hydrogen bond interaction is described by one

bond CP, in complexes 15 and 16. In complexes 11, 12 and 17–

22, one bond CP describes the anion-p interaction. The hydro-

gen bonding interaction is described by one bond CP, and two

ring CPs (complexes 17–22) and one additional bond CP

describes the water-water hydrogen bond in complexes 21 and

22 (see Figure 4). Finally, in complexes 13, 14, 23 and 24, four

bond CPs, four ring CPs and one cage CP describe the anion-pinteraction. The hydrogen bonding interaction is described by

one bond CP, in complexes 23 and 24. In Table 3 we show the

values of the electron charge density (q) and its Laplacian

(!2q) computed at the bond critical points that characterize the

anion-p interaction (Ap) and H-bonding interaction (HB). The

values of the Laplacian of the charge density are positive, as is

common in closed-shell interactions. We also summarize the

variation of these values in the complexes 15–24 (both interac-

tion coexist) with respect to the complexes 4–14 (only one inter-

action apply). These values give information about the interplay

between the non covalent interaction involved in the complexes.

First, it is worth mentioning that the value of the charge density

and its Laplacian computed at the bond CPs is greater in com-

plexes 15–22 than in complexes 4–7 and 9–12, in agreement

with the computed synergistic energies and confirming that the

coexistence of anion-p and H-bonding interactions in these com-

plexes involve a strengthening of both. Second, the value of the

charge density and its Laplacian computed at the bond CPs is

smaller in complexes 23–24 than in complexes 8 and 13–14.

This is in agreement with the positive values obtained for syner-

gistic energy, which indicates that both interactions weaken. The

AIM analysis is in agreement with the lengthening/shortening of

the equilibrium distances of the complexes where both interac-

tions coexist with respect to the complexes where only one

interaction is present.

Table 3. Electron Charge Density (q, a.u.) and Its Laplacian (!2q, a.u.),Computed at the Bond Critical Point for Complexes 4–24 and Their

Variation Upon Formation of the Ternary and Quaternary Complexes

14–24.

Complex I 102 3 qa 10 3 !2qa 103 3 Dqa 102 3 D!2qa

4 HB 2.5327 0.7737 – –

5 HB 1.0894 0.3989 – –

6 HB 1.0608 0.3906 – –

7 HB 1.2343 0.4489

HB (2.3641)a (0.8426)a

8 HB 2.5984 0.9214 – –

9 Ap 0.8378 0.3714 – –

10 Ap 0.6464 0.1919 – –

11 Ap 2.8202 1.2324 – –

12 Ap 1.3800 0.4724 – –

13 Ap 0.1918 0.4911 – –

14 Ap 0.8676 0.2676 – –

15 Ap 1.2619 0.5318 4.241 1.604

HB 2.9702 0.8770 4.375 1.033

16 Ap 0.8361 0.2578 1.897 0.659

HB 2.8194 0.8422 2.867 0.685

17 Ap 2.9846 1.3168 1.644 0.844

HB 1.4587 0.5004 3.692 1.015

18 Ap 1.4665 0.5084 0.865 0.360

HB 1.3606 0.4741 2.712 0.755

19 Ap 3.2038 1.4288 3.836 1.964

HB 1.4286 0.4927 3.678 1.021

20 Ap 1.5575 0.5468 1.775 0.744

HB 1.3090 0.4595 2.482 0.689

21 Ap 3.3607 1.5097 5.405 2.773

HB 1.7067 0.5806 4.724 1.317

HB (2.6653)a (0.9613)a (3.012)a (1.117)a

22 Ap 1.6488 0.5855 2.688 1.131

HB 1.6009 0.5531 3.666 1.042

HB (2.5952)a (0.9335)a (2.311)a (0.909)a

23 Ap 1.1664 0.4825 20.302 20.086

HB 2.0952 0.6836 25.032 22.379

24 Ap 0.8244 0.2533 20.432 20.143

HB 2.2192 0.7393 23.792 21.821

I, interaction; HB, H-Bond; Ap, anion-p.aIn parenthesis we show the data for water–water bond CP.

Figure 4. Schematic representation of the location of bond (red),

ring (yellow) and cage (blue) CPs in complexes 16, 20, 22 and 24.



We have used the MIPp partition scheme to analyze the

physical nature of the anion-p interaction involved in the com-

plexes and to understand the bonding mechanism and the syner-

gistic energies. We have computed the MIPp of compouds 1–8

interacting with Cl- in order to analyze the anion-p interaction

in the absence (1–3) and presence (4–8) of H-bonding (see Ta-

ble 4). In compounds 1–2 the interaction is basically dominated

by polarization effects (Ep), since the electrostatic (Ee) and dis-

persion-repulsion contributions (Evw) are small. In compounds

4–7 interacting with Cl2 (favorable synergism) the Ee term con-

siderably increases and the Ep increases moderately in compari-

son with compounds 1–2 indicating that the synergism is due to

electrostatic effects. The increment of the electrostatic term is

remarkable in 7, indicating that the presence of additional hydro-

gen bonds between the water molecules has a considerable effect

on the ability of the ring to interact with anions. In contrast, in

compound 8 interacting with Cl2 the Ee term considerably

decreases and the Ep moderately increases with respect to com-

plex 3þCl2, indicating that the unfavorable synergism of this

complex is due to a diminution of the electrostatic interaction

when the arene participates in H-bonding.

Lastly, we have also studied the mutual influence between

both interactions computing the genuine nonadditivity energies

for complexes 9–24, which are summarized in Table 5. As

aforementioned in the theoretical methods, the nonadditivity

energy (E 2 EA) is the difference between the binding energy

of the complex and the binding energy of the sum of all pair

interaction energies (denoted as EA), computed by pair-wise sin-

gle point calculations at the complex geometry. For instance, in

complex 17 (H2O��2��F2) we have computed the nonadditivity

energy by subtracting the sum of three pair interaction energies:

(i) 2��F2, (ii) H2O��2 and (iii) H2O��F2 from the binding

energy of 17. It is worth mentioning that this term is negative in

all complexes, including 23 and 24, in disagreement with the

Esyn energies. In the calculation of the synergistic energies, the

additional water-anion interaction present in the complexes is

not evaluated. To solve this matter, we have computed the syn-

ergistic energies taking into account the additional water-anion

interaction and we have summarized them in Table 5, denoted

as Esyn_w. This additional water-anion interaction has been cal-

culated at the complex geometry by performing a single point

calculation. It can be observed that the Esyn_w results are obvi-

ously smaller in absolute value than the Esyn ones. However, the

general trend is maintained, i.e., favorable synergism in com-

plexes 15–22 and unfavorable synergism in complexes 23 and

24. In Table 5 we have also summarized the other data that we

have used to evaluate the interplay between both interactions,

i.e., the variation of the equilibrium distances (DRe and DRHB)

and the electron charge densities (Dq(Ap) and Dq(HB), see Ta-

ble 5) with respect to the complexes where only one interaction

is present. It can be observed that three criteria (Esyn, geometri-

cal and AIM) coincide in the following reasoning. The simulta-

neous presence of hydrogen bonding and anion-p interactions in

the same complex reinforces both interactions if the arene acts

as a hydrogen bond acceptor and weakens both interactions if

the arene acts as a hydrogen bond donor. An additional argu-

ment that supports this conclusion can be extracted from the

MIPp partition scheme which demonstrates that the presence of

hydrogen bonding in the arene has a strong influence on the

electrostatic term. This term becomes more negative when the

arene participates in hydrogen bonding as an acceptor and it

becomes more positive if the arene participates in hydrogen

bonding as a donor. All this indicates that the evaluation of the

Table 4. Contributions to the Total Interaction Energy (kcal/mol),

Computed Using MIPp, of 1–8 Interacting With Cl2 at the Minimum.

Complex Ee Ep Evw Et

1þCl2 1.77 26.28 20.41 24.92

2þCl2 21.46 27.60 0.48 28.59

3þCl2 28.26 29.90 0.93 217.23

4þCl2 216.98 210.13 1.06 226.05

5þCl2 212.62 29.96 0.92 221.42

6þCl2 212.53 212.13 1.27 223.38

7þCl2 223.55 211.19 2.78 231.96

8þCl2 24.26 212.35 1.27 215.33

Table 5. Synergistic and Nonadditivity Energies with BSSE Correction (Esyn, Esyn_w and E-EA kcal/mol,

Respectively), Variation in the Equilibrium Distances (DRe, and DRHB, A) and variation of the Electron

Charge Density in Complexes 15-24 at the MP2/6-31þþG** Level of Theory.

Complex Esyn E-EA Esyn_w DRe DRHB 103 3 Dq(Ap) 103 3 Dq(HB)

15 28.5 26.1 21.4 20.23 20.06 4.24 4.37

16 26.2 24.7 22.6 20.15 20.04 1.90 2.87

17 25.4 22.6 21.4 20.04 20.14 1.64 3.69

18 24.4 22.5 21.1 20.03 20.11 0.86 2.71

19 210.4 25.9 22.8 20.06 20.16 3.84 3.69

20 28.7 25.4 21.4 20.07 20.10 1.78 1.48

21 215.9 215.3 25.7 20.10 20.15 (20.04)a 5.41 4.72 (3.01)a

22 213.2 214.3 24.6 20.10 20.12 (20.03)a 2.70 3.70 (2.31)a

23 þ7.9 21.4 þ2.9 0.01 0.13 20.30 25.03

24 þ6.7 21.4 þ1.5 0.02 0.09 20.43 23.79

aIn parenthesis we show the data for water–water interaction.



mutual influence of hydrogen bonding and anion-p non covalent

interactions using genuine non-additivity energies is not a good

choice, at least in the systems studied here. A likely explanation

is that the additivity energy of all ‘‘hypothetical’’ dimers is com-

puted using the geometry of the complex where both interactions

coexist. Therefore, in systems where the mutual influence of

both non covalent interactions has an important effect on the

equilibrium distances, each pair ‘‘anion-p’’ and ‘‘p-rdonor/acceptor’’is far from the ground state geometry and, consequently, the EA

term is influenced by this issue. This reasoning agrees with the

fact that the Esyn_w values are more positive than the E-EA val-

ues in all complexes.

Conclusion

In summary, the results reported in this manuscript stress the

importance of non covalent interactions involving aromatic sys-

tems and the interplay among them, that can lead to synergistic

effects. Because of the presence of a great number of aromatic

rings containing heteroatoms in biological systems, this effect

can be important and might help to understand some biological

processes where the interplay between both interactions exist. It

also should be taken into account in supramolecular chemistry

and crystal engineering fields.

Acknowledgments

The authors thank the Centre de Supercomputacio de Catalunya

(CESCA) for computational facilities.

References

1. Meyer, E. A.; Castellano, R. K.; Diederich F. Angew Chem Int Ed

2003, 42, 1210.

2. Mascal, M.; Armstrong, A.; Bartberger, M. J Am Chem Soc 2002,

124, 6274.

3. Alkorta, I.; Rozas, I.; Elguero, J. J Am Chem Soc 2002, 124, 8593.

4. Quinonero, D.; Garau, C.; Rotger, C.; Frontera, A.; Ballester, P.;

Costa, A.; Deya, P. M. Angew Chem Int Ed 2002, 41, 3389.

5. Mooibroek, T. J.; Black, C. A.; Gamez, P.; Reedijk J. Cryst Growth

Des 2008, 8. DOI: 10.1021/cg7009435.

6. Schottel, B. L.; Chifotides, H. T.; Dunbar, K. R. Chem Soc Rev

2008, 37, 68.

7. Gamez, P.; Mooibroek, T. J.; Teat, S. J.; Reedijk, J. Acc Chem Res

2007, 40, 435.

8. Demeshko, S.; Dechert, S.; Meyer, F. J Am Chem Soc 2004, 126,

4508.

9. Schottel, B. L.; Bacsa, J.; Dunbar, K. R. Chem Commun 2005, 46.

10. Rosokha, Y. S.; Lindeman, S. V.; Rosokha, S. V.; Kochi, J. K.

Angew Chem Int Ed 2004, 43, 4650.

11. de Hoog, P.; Gamez, P.; Mutikainen, I.; Turpeinen, U.; Reedijk, J.

Angew Chem Int Ed 2004, 43, 5815.

12. Frontera, A.; Saczewski, F.; Gdaniec, M.; Dziemidowicz-Borys, E.;

Kurland, A.; Deya, P. M.; Quinonero, D.; Garau, C. Chem Eur J

2005, 11, 6560.

13. Garcia-Raso, A.; Alberti, F. M.; Fiol, J. J.; Tasada, A.; Barcelo-

Oliver, M.; Molins, E.; Escudero, D.; Frontera, A.; Quinonero, D.;

Deya, P. M. Eur J Org Chem 2007, 5821.

14. Berryman, O. B.; Bryantsev, V. S.; Stay, D. P.; Johnson, D. W.;

Hay, B. P. J Am Chem Soc 2007, 129, 48.

15. Mascal, M. Angew Chem Int Ed 2006, 45, 2890–2893.

16. Escudero, D.; Frontera, A.; Quinonero, D.; Ballester, P.; Costa, A.;

Deya, P. M. J Chem Theory Comput 2007, 3, 2098; and references

cited therein.

17. Estarellas, C.; Quinonero, D.; Frontera, A.; Ballester, P.; Morey, J.;

Costa, A.; Deya, P. M. J Phys Chem A 2008, 112, 1622.

18. Mascal, M.; Yakovlev, I.; Nikitin, E. B.; Fettinger, J. C. Angew

Chem Int Ed 2007, 46, 872.

19. Gorteau, V.; Bollot, G.; Mareda, J.; Perez-Velasco, A.; Matile, S.

J Am Chem Soc 2006, 128, 14788.

20. Gorteau, V.; Bollot, G.; Mareda, J.; Matile, S. Org Biomol Chem

2007, 5, 3000.

21. Schottel, B. L.; Chifotides, H. T.; Shatruk, M.; Chouai, A.; Perez,

L. M.; Bacsa, J.; Dunbar, K. R. J Am Chem Soc 2006, 128,

5895.

22. Reger, D. L.; Wayson, R. P.; Smith, M. D. Inorg Chem 2006, 45,

10077.

23. Zhou, X.-P.; Zhang, X.; Lin, S.-H.; Li, D. Cryst Growth Des 2007,

7, 485.

24. Steel, J.; Sumbly, C. J. Dalton Trans 2003, 4505.

25. Domasevitch, K. V.; Solntsev, P. V.; Gural’skiy, I. A.; Krautscheid,

H.; Rusanov, E. B.; Chernega, A. N.; Howard J. A. K. Dalton Trans

2007, 3893.

26. Black, C. A.; Hanton, L. R.,; Spicer, M. D. Chem Commun 2007,

3171.

27. Garau, C.; Frontera, A.; Quinonero, D.; Ballester, P.; Costa, A.;

Deya, P. M. ChemPhysChem 2003, 4, 1344.

28. Garau, C.; Frontera, A.; Quinonero, D.; Ballester, P.; Costa, A.;

Deya, P. M. J Phys Chem A 2004, 108, 9423.

29. Williams, J. H.; Cockcroft, J. K.; Fitch, A. N. Angew Chem Int Ed

Engl 1992, 31, 1655.

30. Williams, J. H. Acc Chem Res 1993, 26, 593.

31. Adams, H.; Carver, F. J.; Hunter, C. A.; Morales, J. C.; Seward, E.

M. Angew Chem Int Ed Engl 1996, 35, 1542.

32. Jeffrey,G. A. An Introduction to Hydrogen Bonding (Topics in Phys-

ical Chemistry); Oxford University Press: USA, 1997.

33. Garcia-Raso, A.; Alberti, F. M.; Fiol, J. J.; Tasada, A.; Barcelo-

Oliver, M.; Molins, E.; Escudero, D.; Frontera, A.; Quinonero, D.;

Deya, P. M. Inorg Chem 2007, 46, 10724.

34. Frontera, A.; Quinonero, D.; Costa, A.; Ballester, P.; Deya, P. M.

New J Chem 2007, 31, 556.

35. Quinonero, D.; Frontera, A.; Garau, C.; Ballester, P.; Costa, A.;

Deya, P. M. ChemPhysChem 2006, 7, 2487–2491.

36. Bader, R. F. W. Chem Rev 1991, 91, 893.

37. Bader, R. F. W. Atoms in Molecules: A Quantum Theory; Claren-

don: Oxford, 1990.

38. Cheeseman, J. R.; Carrol, M. T.; Bader R. F. W. Chem Phys Lett

1998, 143, 450.

39. Koch, U.; Popelier, P. L. A. J Phys Chem 1995, 99, 9747.

40. Cubero, E.; Orozco, M.; Luque, F. J. J Phys Chem A 1999, 103,

315.

41. Gural’skiy, I. A.; Solntsev, P. V.; Krautscheid, H.; Domasevitch, K.

V. Chem Commun 2006, 4808.

42. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,

M. A.; Cheeseman, J. R.; Montgomery, Jr.,J. A.; Vreven, T.; Kudin,

K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Bar-

one, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson,

G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;

Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.;

Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J.

B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann,



R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J.

W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannen-

berg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M.

C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Fores-

man, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslow-

ski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi,

I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;

Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,

W.; Wong, M. W.; Gonzalez, C.; and Pople, J. A. Gaussian 03, Revi-

sion C. 02, Gaussian: Wallingford, CT, 2004.

43. Boys, S. B.; Bernardy, F. Mol Phys 1970, 19, 553.

44. Biegler-Konig, F.; Schonbohm, J. AIM2000, version 2.0; University

of Applied Sciences: Bielefeld, Germany, 2002.

45. Luque, F. J.; Orozco, M. J Comput Chem 1998, 19, 866.

46. Hernandez, B.; Orozco, M.; Luque, F. J. J Comput-Aided Mol Des

1997, 11, 153.

47. Luque, F. J.; Orozco, M. J Chem Soc Perkin Trans 2 1993, 683.

48. Scrocco, E.; Tomasi, J. Top Curr Chem 1973, 42, 95.

49. Orozco, M.; Luque, F. J. J Comput Chem 1993, 14, 587.

50. Francl, M. M. J Phys Chem 1985, 89, 428.



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Interplay between anion-π and hydrogen bonding interactions