Anion Recognition Based on a Combination of Double-Dentate

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Anion Recognition Based on Combination of Double-Dentate Hydrogen Bond and Double-Side Anion-# Noncovalent Interactions Yan-Zhi Liu, Kun Yuan, Liu Liu, Zhao Yuan, and Yuan-Cheng Zhu J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b12342 • Publication Date (Web): 06 Jan 2017 Downloaded from http://pubs.acs.org on January 7, 2017

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The Journal of Physical Chemistry

Anion Recognition Based on Combination of Double-Dentate Hydrogen

Bond

and

Double-Side

Anion-π

Noncovalent

Interactions Yan-Zhi Liu†,†, Kun Yuan†, §, *,†, Liu Liu†, Zhao Yuan‡,*, Yuan-Cheng Zhu†,* †

College of Chemical Engineering and Technology, Tianshui Normal University,

Tianshui, 741001, China ‡

Department of Chemical and Biomedical Engineering, Florida State University,

Tallahassee, 32306, USA §

Institute for Chemical Physics & Department of Chemistry, School of Mechanical

Engineering, Xi’an Jiaotong University, Xi’an 710049, China

ABSTRACT: Anion recognitions between common anions and a novel pincer-like receptor (N, N’-bis-(five-fluoro-benzoyl-oxyethyl)-urea, BFUR) were theoretically explored, particularly on geometric features of the BFUR@X (X = F-, Cl-, Br-, I-, CO32-, NO3- and SO42-) systems at a molecular level in this work. Complex structures show that two N-H groups as a claw and two -C6F5 rings on BFUR as a pair of tweezers simultaneously interact with captured anions through cooperative double-dentate hydrogen bond and double-side anion-π interactions. The binding energies and thermodynamic information indicate that the recognitions of the seven anions by BFUR in the vacuum are enthalpy-driven and entropy-opposed, which occur spontaneously. Although binding energy ΔEcp between F- and BFUR is relatively high (289.30 kJ·mol-1), ΔEcp, ΔG and ΔH of the recognition for CO32- and SO42- are much larger than the cases of F-, Cl-, Br-, I- and NO3-, suggesting BFUR an ideal selective anion receptor for CO32- and SO42-. Additionally, energy decomposition analysis based on localized molecular orbital energy decomposition analysis (LMO-EDA) was performed; electronic properties and behaviors of the present systems were further discussed according to calculations on frontier molecular orbital, UV-vis spectra, total electrostatic potential and visualized

1

ACS Paragon Plus Environment


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weak interaction regions. The present theoretical exploration of BFUR@X (X=F-, Cl-, Br-, I-, CO32-, NO3- and SO42-) systems is fundamentally crucial to establish anion recognition structure-property relationship upon combination of different noncovalent interactions, i.e. double-dentate hydrogen bond and double-side anion-π interactions.

1. INTRODUCTION Anion recognition has become a promising branch of supramolecular chemistry during the last two decades.1-6 The pioneering work of anion recognition and binding derived from the research on encapsulation of halide anions by protonated diazabicycloalkane ammonium ions, which was reported by Park and Simmons in 1968.7 In 1990s, it was found that anions play a crucial role in natural as well as in artificial systems,8 and their significance in different chemical and biological processes was recognized later in recent years.9,10 While design and synthesis of efficient and selective anion receptors is one of the most significant topics of supramolecular chemistry, the study of the recognition mechanism is also important.11-14 Many binding forces, such as electrostatic interaction, hydrogen bond, halogen bond, metal/Lewis acid coordination and anion-π interaction have been widely studied in anion recognition, in which hydrogen bond (HB) has been most intensively investigated. So far, a number of neutral hydrogen bond anion receptors have been designed and prepared based on amide and (thio)urea groups,15-17 as well as aromatic systems.18-26 The cooperation of multiple various noncovalent interactions has shown some promising

benefits

for

hydroxyl-functionalized 27

synthesized,

the

design

of

anion

receptors.

tetraoxacalix[2]arene[2]triazine

host

Very

recently,

molecule

a

was

and its infinite self-assembly based on cooperative anion-π, lone-pair

electron-π interactions and intermolecular hydrogen bond was constructed. In 2011, Taylor’s group successfully synthesized a series of urea-based anion receptors consisting of both -(CO)NH- and -C6H4-X (X = F, I) groups, whose anion selectivity can be modulated by cooperative combination of hydrogen and halogen bond interactions.28 One year later, Lu et al.29 theoretically investigated binding behaviors of these urea-based receptors (i.e. N, N’-bis-(benzoyl-oxyethyl)-urea and their derivatives) towards several anions (Cl-, Br-, I-, and NO3-) by using quantum chemical calculations at density 2


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functional theory (DFT-B3LYP) level. It was found that encapsulation of halogen atoms into urea-based framework results in disparate conformations of the receptors to better accommodate guest anions, leading to completely different binding behaviors. Moreover, binding affinity of anions was shown to be enhanced with introduction of iodine atoms into phenyl groups of the urea-based receptor. However, some multi-atom inorganic anions, such as SO42- and CO32-, were not taken into account of Lu’s work.29 In fact, anion recognition with noncovalent interactions is often very difficult by using theoretical methods. It requires careful consideration of proper theoretical methods. Since DFT-B3LYP is not suitable for describing such a noncovalent system at all due to its lack of long-range correction, new density functional theory (DFT) method should be employed in such a complicated system. In

our

previous

work,30,

31

a

novel

anion

receptor,

N-p-nitrophenyl-N’-(4-vinyl-2-five-fluoro-benzoic acid be nzyl ester)-phenyl-urea, was designed. It is found that the cooperation of double-dentate hydrogen bond and anion-π interactions is crucial for the nature of the geometries and recognition mechanism. Furthermore, a new geometric criterion of halide-anion-π contact was proposed based on the theoretical exploration for the fluorine substitution effects on the configuration and cooperative property of hydrogen bond and anion-π interactions, which is different from the criterion recommended by Frontera.32 In this work, we theoretically investigated the nature of interactions between some common anions (F-, Cl-, Br-, I-, SO42-, NO3- and CO32-) and a novel receptor, N, N’-bis-(five-fluoro-benzoyl-oxyethyl)-urea (BFUR, as seen in Scheme 128) at a molecular level by using a recently developed DFT method. The theoretical study in this work is essential for understanding the anion recognition mechanism via cooperation of double-dentate hydrogen bond and double-side anion-π interactions, and provides valuable information for further design and synthesis of fluorine-bearing phenyl-urea derivatives.

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Scheme 1. Chemical Structure of the Current Anion Receptor (BFUR).

2. COMPUTATIONAL METHODS The density functional of Grimme’s DFT-D333 were employed for the study of BFUR@X systems (X=F-, Cl-, Br-, I-, CO32-, NO3- and SO42-). DFT-D3 method provides an empirical dispersion correction for DFT.33, 34 The ability of this new density functional to predict and explain van der Waals distances is very encouraging since DFT can be used conveniently for supramolecular systems.35,36 All geometric configurations were optimized using B3LYP-D3 method under the basis sets: MIDIX,37 which is considered as a well-balanced and economical double-ζ basis set that gives reasonably good geometries and partial atomic charges, for I atom; and 6-311++G(d, p) for the other atoms. And the counterpoise method 38 was used during the geometric optimizations. No symmetry constraints were applied during optimizations. Harmonic frequency analyses were performed at the same level to confirm that these structures were local minima or transition state on the potential energy surfaces. The intermolecular interaction energies (ΔEintcp) with basis set superposition errors (BSSE) corrected were considered via the counterpoise method.38 Energy decomposition analyses were carried out with LMO-EDA method39 implemented in GAMESS-US 2014.40 Additionally, a visual study of intermolecular noncovalent interaction between host and guest was performed via calculating the reduced density gradient (RDG),41 derived from electron density (ρ(r)) and its first derivative (RDG(r)=1/(2(3π2)1/3)|‫׏‬ρ(r)|/ρ(r)4/3), as well as the second largest eigenvalue of Hessian matrix of electron density (λ2) functions by using Multiwfn program.42, 43 All other calculations were performed with Gaussian 09 program.44

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3. RESULTS AND DISCUSSION 3.1 Geometric Configurations. As mentioned above, recognitions of halide anions and three common oxygen-bearing anions (CO32-, NO3- and SO42-) by receptor BFUR occur through double-dentate hydrogen bond and double-side anion-π weak interactions. Two N-H groups on the urea structure are perfect donors of double-dentate hydrogen bonds. It is well known that anion-π interaction is defined as favorable noncovalent contact between an electron deficient (π-acidic) aromatic system and an anion.45 In the current system,

bis-(five-fluoro-benzoyl)

groups

are

considered

to

offer

electron-deficient-aromatic units.

Figure 1. Configurations of the free BFUR and BFUR@anion systems and the definitions of double-dentate hydrogen bond parameters.

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Figure 1 shows the optimized geometric configurations of free BFUR and BFUR@X systems (X=F-, Cl-, Br- I-, CO32-, NO3- and SO42-). In the structure of free BFUR, two five-fluoro-benzoyl rings present “T” relative position in space, and intramolecular N-H…F hydrogen bond and C-F…π contact coexist. After formation of BFUR@X complexes, two five-fluoro-benzoyl rings are in pincer-like shape and deformation of receptor BFUR was observed, while the intramolecular N-H…F hydrogen bond and C-F…π are drastically destroyed due to strong BFUR-anion intermolecular interactions. Table 1 The double-dentate hydrogen bond geometric parameters of the BFUR and BFUR@X (X=F-, Cl-, Br- I-, CO32-, NO3- and SO42-) at B3LYP-D3/6-311++g(d, p) Systems BFUR

l1/Å

l2/Å

d1/Å

d2/Å

θ1/°

θ2/°

dpenetrationb/Å

1.012

1.009

–

–

–

–

–

-

1.037

1.035

1.720

1.743

156.53

154.07

1.179

-

1.024

1.024

2.317

2.298

159.56

158.96

1.003

-

1.023

1.023

2.517

2.452

160.15

161.76

1.115

-

1.017

1.018

2.837

2.714

157.40

162.35

0.954

BFUR@CO32-

1.062

1.073

1.668

1.565

177.73

169.21

1.104

-

1.021

1.021

1.940

1.930

176.39

167.62

0.785

2-

1.044

1.039

1.710

1.758

173.00

168.78

0.986

BFUR@F

BFUR@Cl

BFUR@Br a

BFUR@I

BFUR@NO3 BFUR@SO4 a

b

MIDIX basis set used for I atom. dpenetration, the average mutual penetration distance between anion

and H atom, is defined as dpenetration = ∑vdW-radii-1/2(d1+d2), where ∑vdW-radii is the sum of the van der Waals radii of H atom and halide-anion or O atom.

Table 1 lists double-dentate HB geometric parameters (as defined in Figure 1) of BFUR@X (X=F-, Cl-, Br- I-, CO32-, NO3- and SO42-). It is clearly seen that the bond length (l1, l2) of N-H (donor of HB) increased obviously after formation of the complexes, especially in the structures of BFUR@F-, BFUR@CO32- and BFUR@SO42-, which is the typical characteristic of strong HB interactions. Van der Waals radius is an important standard to investigate the structure of noncovalent systems. It is known that van der Waals radii of H, F-, Cl-, Br- and I- are 1.20, 1.71, 2.11, 2.3522 and 2.53 Å30, respectively. Here, the N-H…halide-anions distances, d1 and d2, are both distinctly shorter than the sum of the van der Waals radii of halide anions and H atom, indicating that the van der Waals surfaces of H atoms and halide-anions drastically penetrate into each other. The average mutual penetration distances of HB, dpenetration (as defined in the footnote of Table

6


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1) of four BFUR@X (X=F-, Cl-, Br- and I-) complexes are 1.179, 1.003, 1.115 and 0.954 Å, respectively, demonstrating that strong hydrogen bonds formed between halide-anions and N-H groups, among which N-H…F-…H-N is the strongest one. Although the van der Waals radii of these three oxygen-bearing anions (CO32-, NO3and SO42-) are unavailable, it is noted that d1 and d2 of the double-dentate HB in BFUR@X (X=CO32-, NO3- and SO42-) are also obviously shorter than the sum of the van der Waals radii of O (1.52 Å46) and H atoms (Here, the van der Waals radii of neutral O atom was used, while the O atom of X (X=CO32-, NO3- and SO42-) is not neutral in charge but in some degree of negative charge. Because van der Waals radius of Oδ- of X (X=CO32-, NO3- and SO42-) must be larger than that of the neutral O atom, both d1 and d2 should be distinctly shorter than sum of the van der Waals radii of Oδ- of X anions (X=CO32-, NO3- and SO42-) and H atom.), indicating the existence of strong N-H…O HB. The HB dpenetration in BFUR@CO32- and BFUR@SO42- are much greater than that in BFUR@NO3-, suggesting a relatively weak N-H…NO3-…H-N interaction. In addition, both d1/d2 and θ1/θ2 are not always equal, suggesting that two N-H…X- of the double-dentate hydrogen bonds in each complex are not utterly symmetrical.

Figure 2. Double-side anion-π structures and the definitions of the related geometry parameters of the BFUR@X (X=F-, Cl-, Br- I-, CO32-, NO3- and SO42-) systems (F atoms are omitted for clarity). 7



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The geometric structure of the double-side anion-π structures can be characterized by parameters of dc, dp and do, which are defined in Figure 2, and the corresponding geometric parameters are listed in Table 2. It is shown that all anions do not locate exactly above the center of aromatic ring in the anion-π contact and all structures of double-side anion-π are not symmetrical in the present system. These can be attributed to the balance and cooperation between double-dentate HB and double-side anion-π interactions. It can be seen that the values of α (α1 and α2, as defined in Figure 2 and listed in Table 2) in BFUR@F- are 26.90 and 45.94 °, which are apparently larger than those in BFUR@Br- and BFUR@I-, indicating that F- shifts away from the center of two aromatic rings more than Br- and I-. Moreover, dpenetration of double-side anion-π interaction in BFUR@F- is distinctly smaller than those in BFUR@Cl-, BFUR@Br- and BFUR@I-, suggesting a relative weak anion-π contact in BFUR@F-. Table 2 The double-side anion-π geometric parameters (defined as Figure 2 showing) of the BFUR and BFUR@X (X=F-, Cl-, Br- I-, CO32-, NO3- and SO42-) at B3LYP-D3/6-311++g(d, p)

BFUR@F-

dc2/Å

dp1/Å

dp2/Å

do1/Å

do2/Å

α1/°

α2/°

dpenetrationb/Å

3.05

3.48

2.72

2.42

1.38

2.50

26.90

45.94

0.15

-

3.68

3.32

3.11

3.27

1.97

0.57

32.30

9.96

0.32

-

3.48

3.78

3.43

3.31

0.59

2.15

9.72

34.64

0.42

BFUR@I-

BFUR@Cl

BFUR@Br a

dc1/Å

3.91

3.79

3.64

3.63

1.43

1.09

21.42

16.71

0.38

2-

2.81

3.22

2.74

2.75

0.62

1.68

12.82

31.35

0.21

-

3.04

3.37

3.02

3.05

0.35

1.43

6.58

25.17

0.02

BFUR@SO42-

2.90

2.89

2.84

2.77

0.59

0.82

11.68

16.57

0.33

BFUR@CO3

BFUR@NO3 a

b

MIDIX basis set used for I atom. dpenetration, the average mutual penetration distance between anion

and -C6F5 arene ring, is defined as dpenetration = ∑vdW-radii-1/2(dc1+dc2), where ∑vdW-radii is the sum of the van der Waals radii of C atom and halide-anions or O atoms (which are the nearest to the -C6F5 ring).

For the structures of double-side anion-π interactions in BFUR@X (X=CO32-, NO3and SO42-), O atoms involving in anion-π contact do not locate significantly far away from the center of aromatic ring according to the small corresponding values of α1 and α2,

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whereas dpenetration of double-side anion-π contact is much smaller than those in BFUR@X (X= Cl-, Br- and I-), especially, of which is only 0.02 Å in BFUR@NO3-, manifesting a relative weak anion-π interaction. Although the strengths and individual geometric parameters of double-side anion-π interactions in the present BFUR@X (X=F-, Cl-, Br- I-, CO32-, NO3- and SO42-) systems are quite different, they are all consistent with the geometric criterion of the anion-π contact proposed in our previous work,31 suggesting that the pincer-like double-side anion-π contact is cooperative to recognize these anions with double-dentate HB. 3.2 Energy and Its Decomposition. Binding energy and thermodynamic data are valid references to evaluate stability of BFUR@X (X=F-, Cl-, Br-, I-, CO32-, NO3- and SO42-) complexes. Table 3 lists BSSE corrected binding energies (ΔEcp), thermodynamic properties (ΔG, ΔH and ΔS) of the BFUR@X systems and deform energy (ΔEd) of BFUR. For the halide anion systems, the ΔEcp of BFUR@F- is much larger than those in BFUR@Cl-, BFUR@Br- and BFUR@I- by 89.20, 104.63 and 103.37 kJ·mol-1, respectively. The relative stability of four complexes increases in the order of BFUR@I≈BFUR@Br-< BFUR@Cl-

Anion Recognition Based on a Combination of Double-Dentate

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