The Competition of σ-Hole···Cl– and π-Hole···Cl - ACS Publications

Article pubs.acs.org/JPCB

The Competition of σ‑Hole···Cl− and π‑Hole···Cl− Bonds between C6F5X (X = F, Cl, Br, I) and the Chloride Anion and Its Potential Application in Separation Science Xiao Qing Yan, Xiao Ran Zhao, Hui Wang, and Wei Jun Jin* College of Chemistry, Beijing Normal University, Beijing 100875, China S Supporting Information *

ABSTRACT: On the basis of the varying amplitude and patterns of the 19F NMR chemical shift of C6F5X (X = F, Cl, Br, I) in the presence of chloride anions, bonding models of C6F5X·Cl− complexes were tentatively established, and the relevant binding constants were obtained. Interaction models were also simulated using computational chemistry. The theoretical computations were found to be highly consistent with the results of the experiments. The results show that C6F5Br/C6F5I and Cl− were prone to forming C−I/Br···Cl− σhole bonding complexes with the 19F NMR signal shifting to higher fields, and the interaction strength of the C6F5I···Cl− σ-hole bond was larger than that of C6F5Br···Cl−; C6F6/C6F5Cl and Cl− formed π-hole···Cl− bonding complexes with the signal shifting to lower fields, and the interaction strength of C6F6 was larger than that of C6F5Cl. The binding constant of the C6F5I···Cl− σhole bonding complex is 38.0 M−1, which is nearly 165- to 345-fold larger than that of the other C6F5X·Cl− complexes. On the basis of the above results, solid phase extraction experiments were designed, and the results demonstrated the potential applicability of the C−I···Cl− σ-hole bond in separation science.

■

INTRODUCTION Over the past several decades, an important theme in supramolecular chemistry has been the development of hosts that exhibit anion recognition. A variety of reversible binding interactions are being explored to address this challenge. Among these interactions, there are two new ones, halogen bonds and anion−π interactions, which have garnered much attention in recent years. A halogen bond is the noncovalent interaction between covalently bonded halogen atoms (Lewis acids) and neutral or anionic Lewis bases,1,2 and it is also called a σ-hole bond.3−6 Some novel anion receptors with halogen bonding ability have been successfully synthesized.7−12 For halogenated aryl and heteroaryls, the presence of strong electron-withdrawing substituents, such as F, can lead to a reduction in the electron density of the aromatic ring and interact with Lewis bases.13−16 In this regard, because of its similarity with the σ-hole bond,3 the aromatic π system with a positive electrostatic surface potential region perpendicular to the aromatic molecular σ-framework is named a π-hole here, which closely resembles the term proposed by the Politzer group4−6 in the case of inorganic and nonconjugated molecules. Additionally, the interaction between the π-hole and the negative site is named a π-hole bond.17 The design and synthesis of selective anion receptors and channels based on the π-hole bond represent important advances in the field of supramolecular chemistry.18−26 When the two noncovalent interactions coexist, which one forms stronger complexes with the anion? For example, the existence of both σ-holes and π-holes gives haloperfluoroben© 2014 American Chemical Society

zenes, C6F5X (X = Cl, Br, I), the potential to form both halogen bonds and π-hole bonds.27 Therefore, for better understanding of the halogen and π-hole bonds, the competition between these interactions is explored herein.19F NMR-based methods are selected to probe the interaction between C6F5X and Cl− because of the high signal dispersion and sensitivity of 19F NMR techniques. Additionally, C6F6, which can only form πhole bonds, is chosen as a reference. By combining the experiments with theoretical computations, it can be observed that C6F5Br/C6F5I and Cl− are prone to forming C−I/Br···Cl− halogen bonds with the 19F NMR signal shifting to higher fields, while C6F6 or C6F5Cl and Cl− form π-hole···Cl− bonds with the signal shifting to lower fields. The results presented herein provide insight into the properties of halogen bonds and π-hole bonds and provide a theoretical reference for designing anion receptors or for the separation of C6F5X compounds.

■

MATERIALS AND METHODS Materials and Reagents. Iodopentafluorobenzene (C6F5I), bromopentafluorobenzene (C6F5Br), chloropentafluorobenzene (C6F5Cl), and hexafluorobenzene (C6F6) were purchased from ABCR Co. (Karlsruhe, Germany). Tetra-nbutylammonium chloride (Bu4N+Cl−) was supplied by TCI Co. (Tokyo, Japan), and acetonitrile was purchased from Tianjin Received: October 2, 2013 Revised: January 9, 2014 Published: January 9, 2014 1080

dx.doi.org/10.1021/jp4097869 | J. Phys. Chem. B 2014, 118, 1080−1087

The Journal of Physical Chemistry B

Article

Figure 1. 19F NMR spectra of C6F5X in the absence and presence of Cl− ([C6F5X] = 0.005 mol L−1, [Cl−] = 1.8 mol L−1) and the change in direction of the chemical shifts of haloperfluorbenzenes during its interaction with chloride (↑, the signals shift to lower fields; ↓, the signals shift to higher fields; additionally, the numbers next to the arrows are the variation values of the chemical shift).

determination of binding constants (Ka) according to Taylor’s method.28 (For details, see the Supporting Information.) Computational Methods. All calculations were carried out using the Gaussian 09 programs29 at the dispersion-corrected hybrid functional ωB97X-D.30 The basis set 6-311++G** was used for H, C, F, Cl, and Br atoms, and the basis set 6-311G** was used for the I atom.31 The ωB97X-D functional was selected for this study because it includes both long-range exchange and empirical dispersion corrections, which are important for the modeling of processes with weak interactions and localized anionic or strongly electron donating sites.32,33 Fully optimized calculations were performed in solution via the SMD solvent model.34 The binding energies (ΔE) of the complexes were obtained by subtracting the sum of the calculated energies of the isolated components from the calculated energy of the complex, ΔE = EAB − (EA + EB). Frequency calculations at the same level of theory have also been performed to identify all stationary points as minima (without imaginary frequencies). Natural bond orbital (NBO)35 analysis was employed through the use of the NBO program implemented in the Gaussian 09 package.29

Bodi Chemical Co. (Tianjin, China). Acetonitrile-D3 was purchased from Perkin Dabei Company (Beijing, China).The 40 μm BONDESIL-SAX with an ion exchange capacity of 0.85 mequiv g−1 was purchased from Angilent Co. (CA, America). The 40 μm silica gel Bond Elut-Si was provided by Agela (Tianjin, China). Spectral Measurements. The 19F NMR spectra were recorded using a Bruker Avance III 400 MHz NMR Spectrometer (Bruker Corporation, Billerica, MA, USA), and a sealed capillary tube containing CF3COOH (5 μL/mL) inserted into the sample solution was used as the external standard (δ = −76.86 ppm). UV absorption spectra were obtained in a 1 mm quartz cuvette using a TU-1901 spectrophotometer (Beijing Purkinje General Instrument Co., Beijing, China). Determination of Binding Constants by 19F NMR. The stock solutions of C6F5X (0.4 M) and Bu4N+Cl− (2.0 M) were prepared in acetonitrile. A series of solutions consisting of the two stock solutions was made in individual 1 mL volumetric flasks and then transferred to NMR tubes for analysis. Upon addition of Cl−, the changes in the 19F chemical shift of halopentafluorobenzene were observed and used in the 1081



Article

C6F6 and Cl− in solution was monitored using 19F NMR, it was observed that the chemical shifts of C6F6 moved to a lower field with an increase in Cl− concentration. Such a phenomenon can be ascribed to the π-hole···Cl− interaction between C6F6 and Cl−. For the C6F5X (X = Cl, Br, I) molecules, the existence of both σ-holes and π-holes allows them to form halogen bonds and π-hole bonds with Cl−. The ability of C6F5X (X = Cl, Br, I) to form halogen bonds decreases in the order of C6F5I > C6F5Br > C6F5Cl, while their ability to form π-hole bonds is reversed, i.e., C6F5Cl > C6F5Br > C6F5I. On the basis of the experimental data that showed a different changing direction of chemical shift of C6F5Cl with C6F5I and C6F5Br but following the same trend as C6F6, it is reasonable to deduce that C6F5Cl formed π-hole···Cl− bonds with Cl− rather than C−X···Cl− halogen bonds in solution. With the stronger electronwithdrawing ability of the Cl atom compared to Br and I, the π-hole of C6F5Cl is more positive than that of C6F5Br or C6F5I, resulting in the greater ability of C6F5Cl to form π-hole bonds rather than halogen bonds. On the basis of the above results, it can be concluded that C6F6/C6F5Cl and Cl− form π-hole···Cl− bonds, resulting in the NMR signal shift to a lower field, while C6F5Br/C6F5I and Cl− are prone to forming C−I/Br···Cl− halogen bonds, resulting in a shift to a higher field. The contrary effects of the halogen bond and π-hole bond on the chemical shift of the fluorine atom make the 19F NMR technique a perfect tool for studying the competition between the halogen bonds and π-hole bonds. Moreover, when the absolute values of the change in the chemical shift (|Δδ|) of different fluorine substituents in the haloperfluorbenzenes are plotted against the concentration of Cl−, as shown in Figure 3, it is found that |Δδ| of the para-F is the largest of all three of the haloperfluorbenzenes. This result differs from the result regarding the haloperfluoralkyls in which the shift in signal of the adjacent CF2 groups to the iodides is the largest.38 Additionally, for C6F5I, the |Δδ| of the ortho-F is larger than that of the meta-F, whereas, for C6F5Br and C6F5Cl, |Δδ| of the meta-F is larger than that of the ortho-F. Binding Constants for the Complexes of C6F5X (X = F, Cl, Br, and I) with Cl−. Using 19F NMR titrations, halogen bond association constants for a number of donor−acceptor pairs were determined.38−40 The results obtained using this method were in agreement with data obtained using other tools, including infrared, Raman spectroscopy, and calorimetric measurements. Likewise, this technique was used to determine binding constants (Ka) for halogen bonding interactions and πhole bonding interactions in this study. Titrations were performed to record the 19F NMR spectra of the halogen bond/π-hole bond donors in the presence of increasing concentrations of acceptor Cl−; the detailed processes are presented in the Supporting Information. Changes in the chemical shifts of the meta-F substituent were employed during the determinations of Ka. Changes in the chemical shift as a function of acceptor concentration were well modeled by 1:1 binding stoichiometry using curve-fitting methods. All of the experiments described herein were preformed in duplicate. Table 1 lists the Ka values of the C6F5X complexes with Cl−. The Ka value determination of the complexes was also attempted using UV spectroscopy and the Benesi−Hildebrand methodology41,42 (see Figure S1, Supporting Information); however, only the Ka value of the C6F5I···Cl− complex was obtained because no charge transfer bands were observed in the other complexes. The Ka of the C6F5I···Cl−

Solid Phase Extraction (SPE) Procedures. The SPE cartridges were prepared by packing 40 mg of the adsorbent SAX into each empty 1 mL SPE cartridge with upper and lower frits to avoid adsorbent loss. All of the steps were driven by gravity. The cartridges were preconditioned with 2 mL of MeOH and 3 mL of n-hexane prior to being loaded with the sample solutions. The corresponding effluents were monitored using UV spectroscopy.

■

RESULTS AND DISCUSSION F NMR of C6F5X (X = F, Cl, Br, and I) in the Presence of Varying Cl− Concentrations. The changes in the 19F NMR chemical shift (Δδ) of C6F5X were measured by incremental addition of Cl− at intervals of 0.2 mol·L−1 (from 0.2 to 1.8 mol·L−1) to a 0.005 mol·L−1 C6F5X solution. The experimental results indicated that there was no difference when using deuterated or non-deuterated acetonitrile as the solvent. Figure 1 shows the 19F NMR spectra of C6F5X in the absence and presence of Cl− along with the directions and values of the chemical shift change. Figure 2 shows the trends 19

Figure 2. The chemical shift change (Δδ) of para-F in haloperfluorbenzenes with incremental changes in Cl− concentration. Δδ = δobs − δD.

of chemical shift change in the para-fluorine substituents (paraF) to the −I/Br/Cl group in C6F5X with the increase in Cl− concentration. Additionally, ortho-F and meta-F have the same variation trends as para-F in each C6F5X complex. From Figures 1 and 2, it can be observed that the 19F chemical shifts of C6F5Br and C6F5I move in the opposite direction compared with those of C6F6 and C6F5Cl interacting with Cl−. As shown in Figure 2, the chemical shifts of C6F5Br and C6F5I move obviously to a higher field with the increase in Cl−, while the chemical shifts of C6F6 and C6F5Cl move to a slightly lower field. During the 1980s, through the use of theoretical computation, Kebarle et al.36 predicted that C6F6 could form a stable complex with Cl− in the gas phase and that ΔH was approximately −70.3 kJ·mol−1. Yamabe et al.37 further demonstrated that C6F6 and X− (X = Cl, Br, I) could form stable adducts in the gas phase with the halide perched above the arene centroid. Deyà et al.18 first used the term “anion−π interaction” to describe the interaction between C6F6 and anions. Although these theories supported the existence of the anion−π interaction, there are surprisingly few experimental examples involving halides and charge-neutral arenes in solution.15 As shown in Figure 2, when the interaction between 1082



Article

Figure 3. The absolute value of the 19F chemical shift change |Δδ| of the different substituent positions in haloperfluorbenzenes with increasing concentration of Cl−.

determined from these data that C6F6 has a greater ability than C6F5Cl to form π-hole···Cl− bonds. In addition, it is worth noting that the Ka value of the C6F5I···Cl− halogen bond is largest among the analogues tested herein. The large difference in binding constants between C6F5I and other C6F5X compounds should be significant in molecular recognition and separation science. Simulative Computation of the Interactions of C6F5X (X = F, Cl, Br, and I) with Cl− − Corrected Interaction Energy. The interaction types, stoichiometries, and binding constants of C6F5X·Cl− can easily be measured by the change in the chemical shift of C6F5X as the chloride anion concentration is varied; however, it is difficult to estimate the geometries of C6F5X·Cl− complexes in solution based on the experiments conducted. Moreover, the nature of the interaction could not be clearly explained based solely on experimental observations. To gain further insight into the experimental results and to obtain additional information about the competition between

Table 1. The Binding Constants of the Complexes of Haloperfluorbenzene with Cl− in Acetonitrile complexes −

C6F5I···Cl (halogen bond) C6F5Br···Cl−(halogen bond) C6F5Cl···Cl−(π-hole bond) C6F6···Cl−(π-hole bond)

Ka (mol−1·L)

R2

± ± ± ±

0.987 0.993 0.995 0.992

38.0 0.18 0.11 0.23

6.94 0.04 0.01 0.04

complex was determined to be 34.61 mol−1·L, which is in agreement with the value of 38.0 mol−1·L obtained by the 19F NMR. From Table 1, it can be observed that, for the halogen bond complexes, the Ka value of C6F5I·Cl− is larger than that of C6F5Br·Cl−, and for the π-hole bond complexes, the Ka value of C6F6·Cl− is larger than C6F5Cl·Cl−. The more positive σ-hole of iodine compared with bromine results in a stronger halogen bond in the C6F5I complex than in the C6F5Br complex. It was

Table 2. Calculated Geometric Parameters and Binding Energies (ΔE in kcal/mol) of the Complexes between Haloperfluorbenzenes and Cl− in the Solution (l) and Gas (g) Phases C−X···Cl− halogen bonding model donors C6F5I C6F5Br C6F5Cl C6F6

l g l g l g l g

π-hole···Cl− bonding model

dC−X (Å)

dX−Cl− (Å)

∠C−X···Cl−

ΔE

dC−X (Å)

do‑Cl− (Å)

∠C−o···Cl−

ΔE

2.108 2.179 1.882 1.911 1.724 1.724

3.277 2.865 3.403 2.901 3.586 3.020

180.0 180.0 179.7 180.0 175.1 180.0

−2.68 −22.30 −1.15 −14.77 −0.58 −8.79

2.091 2.088 1.878 1.877 1.724 1.725 1.329 1.331

3.752 3.284 3.726 3.261 3.643 3.245 3.612 3.244

96.8 86.4 83.4 88.9 96.5 90.6 81.0 89.8

−1.27 −13.70 −1.39 −13.68 −1.47 −13.86 −1.54 −14.20

1083



Article

Figure 4. The interaction models and geometries of the complexes formed between haloperfluorbenzenes and Cl− in the gas phase. Color code: C, gray; F, pale blue; Cl, green; Br, brown; I, purple. The small purple ball in the ring center refers to the π-hole center.

Figure 5. The highest occupied molecular orbitals (HOMOs) of the C−X···Cl− (upper) and π-hole···Cl− (lower) bonding complexes in the gas phase. Color code: C, gray; F, pale blue; Cl, green; Br, brown; I, purple.

than that of the π-hole···Cl− bonding model, and the chemical shifts of C6F5I moved to higher fields with the increase in the Cl− concentration. For the C6F5Cl···Cl− complex, the binding energy of the halogen bonding model is smaller than that of the π-hole···Cl− bonding model, and the chemical shifts of C6F5Cl moved to lower fields with the increase in the Cl − concentration. By combining the theoretical computation with the experimental results, it can be confirmed that the halogen bond is formed in the C6F5I···Cl−complex and the πhole bond is formed in the C6F5Cl···Cl− complex. Second, for C6F5Br, there is no significant difference in the binding energies between the C6F5Br···Cl− halogen bond and π-hole···Cl− bond. In the gas phase, the binding energy of the halogen bond is slightly larger than the π-hole bond, while the opposite is true for the solution phase. The computational result in the gas phase is consistent with the experimental result that C6F5Br forms halogen bonds with Cl−. The result indicates that both the halogen bonds and π-hole bonds are relatively simple in this study and that the complicated solvent model is not required for their computation. Taylor et al.28 observed in the investigation of the solvent effects on the halogen bond between Et3N and IC8H17 that the Lewis basic solvents, such as acetone, acetonitrile, and tetrahydrofuran, had a relatively minor effect on the interaction; however, the solvents that can serve as competitive hydrogen bond donors weaken the interaction significantly. Additionally, Wang et al.44 noted that the consideration of the solvation effect was not needed in the

the halogen bonds and π-hole bonds, the ωB97X-D of dispersion-corrected density functional theory was used to simulate the geometries and interaction energies of the complexes in the gas phase and solution phase via the SMD solvent model. The seven interaction models that were constructed for computation are as follows: the π-hole···Cl− bond model for C6F6 and both the C−X···Cl− halogen bond and π-hole···Cl− bond models for C6F5I, C6F5Br, and C6F5Cl. The calculated geometric parameters and binding energies are listed in Table 2, while Figure 4 shows the geometric structures of the complexes. It was recently reported that the pure and some hybrid functionals largely overestimate the interaction energy of the halogen bonding complexes involving anions and that the use of dispersion correction may further contribute to the overestimation of the interaction energy. However, the M06-2X method can offer good results for anionic complexes.43 Therefore, the M06-2X and MP2 methods were used to verify the reliability of the ωB97X-D method. The corresponding calculated results are presented in Tables S1 and S2 (Supporting Information), which indicate that the ωB97X-D method is a reliable fuctional for the study of our interaction systems. First, from the data in Table 2, it can be concluded that, for C6F5I and C6F5Cl complexes, the values of the binding energies in both the gas and solution phases correlate well with the changes in the chemical shift. For the C6F5I···Cl− complex, the binding energy of the halogen bonding model is much larger 1084



Article

competition between halogen bonds and lone-pair···π-hole interactions. Therefore, it is reasonable that the acetonitrile solvent has a minimal effect on the halogen bond between C6F5Br and Cl−. In addition, for C6F5Br, acceptors influence the competition between the halogen bond and the π-hole bond. Here, the C6F5Br···Cl− halogen bond is preferential, but in the case where deuterobenzene is used as an acceptor, the πhole···π bond is preferential for the C6F5Br···C6D6 complex.27 Finally, the binding energy of the C6F5I···Cl− halogen bond is much greater than that of the C6F5Br···Cl− halogen bond, and the bonding energy of the π-hole···Cl− in C6F6 is greater than that in C6F5Cl. Moreover, the halogen bonding energy of C6F5I···Cl− is much greater than all other bonding models. The variation trend of the binding energies is consistent with that of the experimental Ka values. Natural Bond Orbital Analysis. The natural bond orbital (NBO) theory is valuable for understanding molecular complex formation. Figure 5 directly shows that the lone-pair electron of Cl− delocalizes to the iodine atom in the C6F5I···Cl− halogen bonding complex, while there are weak delocalizations of lonepair electrons in other C6F5X complexes. The strong effect of delocalization at the ground state is believed to be the reason that only the charge transfer band of the C6F5I···Cl− complex can be observed in solution (Figure S1, Supporting Information).45 The second-order perturbation stabilization energy (E2) reflects the delocalization degree of the electron or charge from the bonding orbital to the antibonding or unoccupied orbital. The calculated E2 for the halogen bond complexes of C6F5X with Cl− is 14.7 kcal mol−1 for C6F5I and 10.4 kcal mol−1 for C6F5Br, while the E2 corresponding to the π-hole bond complexes of C6F5Cl/C6F6 with Cl− are only 0.30 and 0.11 kcal mol−1, respectively. There is minimal contribution of the charge transfer interaction to the π-hole bond complexes, while the electrostatic forces and ion-induced polarization are the main energetic contributors to the π-hole···Cl− bonding complexes.46,47 The Potential Application of the Strong C6F5I···Cl− Halogen Bond in the Field of Separation. The binding constant of the C6F5I···Cl− halogen bond is 38.0 mol−1·L, which is the largest among the analogous complexes tested herein. Such a large difference in binding constants between C6F5I and the other C6F5X compounds is significant in separation science. Therefore, possible application of this property in solid phase extraction techniques was preliminarily tested. To utilize the C6F5I···Cl− halogen bond interaction, the SAX sorbent,48 a chloride ion bonded silica gel, was selected as the sorbent to extract C6F5I. The n-hexane solutions of the samples (3 mmol L−1, 1 mL) were passed through the cartridges packed with 40 mg of the sorbent material, and the corresponding effluents were monitored by UV spectroscopy. The corresponding UV absorption spectra are shown in Figure S3 (Supporting Information). No analytes were detected in the n-hexane effluents of C6F5I, indicating that the SAX sorbent had good adsorption abilities for C6F5I. By calculating the ratio of the concentration of the sample in solution before and after passing through the cartridge, the retention ratio of the tested sample was obtained. As shown in Figure 6, the SAX sorbent has a strong adsorption affinity toward C6F5I, with a retention ratio as high as 95.29%, and shows weak affinity toward C6F6, C6F5Br, C6F5Cl, C6H5Br, C6H5Cl, and C6H5I, allowing the C6F5I compound to be extracted selectively. The same adsorption experiments were also performed using silica gel,

Figure 6. Retention ratio of the SAX sorbent for halogenated benzenes and halopentafluorobenzenes.

to which no Cl− bonded. The silica gel had no adsorptivity for any of the above substances. This result further demonstrates that the adsorption of the C6F5I by the SAX sorbent is based on the halogen bond with Cl− rather than the silica matrix. This indicates that halogen bonds have a potential application in the solid phase extraction and chromatographic separation of haloperfluorinated benzenes.48

■

CONCLUSIONS The competition between halogen/σ-hole bonds and π-hole bonds in solution was investigated using 19F NMR spectroscopy and computational chemistry. The results of the experiments and the theoretical computation were highly consistent, both indicating that C6F5Br or C6F5I and Cl− formed halogen/σ-hole bonds with the 19F NMR signal shifting to higher fields, and the interaction strength of the C6F5I···Cl− halogen/σ-hole bond is much larger than that in C6F5Br···Cl−; C6F6 or C6F5Cl and Cl− were shown to form π-hole···Cl− bonds with the signal shifting to lower fields, while the interaction strength of C6F6 was found to be larger than that of C6F5Cl. It was also noted that, unlike haloperfluoralkyls, the change in the chemical shift of the para-F was most sensitive for Cl− in haloperfluorbenzene. In addition, through solid phase extraction experiments, it was proven that the C6F5I compound could be selectively extracted from solution by the SAX sorbents through the C6F5I···Cl− halogen/σ-hole bond. This is consistent with the results of the 19F NMR titration experiments, which showed that the binding constant of the C6F5I···Cl− halogen/σ-hole bonding complex is much larger than that of the other complexes. The results presented herein provide insight into the properties of the halogen/σ-hole bonds and π-hole bonds. The phenomenon that C6F5X compounds present different interaction models and strengths toward Cl− because of different halogen substituents provides significant references for designing and synthesizing host molecules for anion recognition, along with separation techniques.

■

ASSOCIATED CONTENT

S Supporting Information *

The measurement of the binding constant Ka of the halogen bonding complex C6F5X·Cl− (X = F, Cl, Br, and I) by 19F NMR and Benesi−Hildebrand methodology; simulative calculation on the interactions of C6F5X with Cl− using the MP2 method and the M06-2X method; and UV absorption spectra of halogenated benzenes in n-hexane before and after going 1085



Article

bonding, π-hole···π bonding and other assisting interactions. CrystEngComm 2013, 15, 2722−2730. (18) Quiñonero, D.; Garau, C.; Rotger, C.; Frontera, A.; Ballester, P.; Costa, A.; Deyà, P. M. Anion−π Interactions: Do They Exist? Angew. Chem., Int. Ed. 2002, 41, 3389−3392. (19) Mooibroek, T. J.; Gamez, P.; Reedijk, J. Lone pair-π interactions: a new supramolecular bond? CrystEngComm 2008, 10, 1501−1515. (20) Chen, Y.; Wang, D. X.; Huang, Z. T.; Wang, M. X. Ion pair receptors based on anion-π interaction. Chem. Commun. 2011, 47, 8112−8114. (21) Watt, M. M.; Collins, M. S.; Johnson, D. W. Ion-π interactions in ligand design for anions and main group cations. Acc. Chem. Res. 2013, 46, 955−966. (22) Mareda, J.; Matile, S. Anion-π Slides for Transmembrane Transport. Chem.Eur. J. 2009, 15, 28−37. (23) Gorteau, V.; Bollot, G.; Mareda, J.; Perez-Velasco, A.; Matile, S. Rigid oligonaphthalenediimide rods as transmembrane anion-π slides. J. Am. Chem. Soc. 2006, 128, 14788−14789. (24) Perez-Velasco, A.; Gorteau, V.; Matile, S. Rigid Oligoperylenediimide Rods: Anion-π Slides with Photosynthetic Activity. Angew. Chem. 2008, 120, 935−937. (25) Dawson, R. E.; Hennig, A.; Weimann, D. P.; Emery, D.; Ravikumar, V.; Montenegro, J.; Takeuchi, T.; Gabutti, S.; Mayor, M.; Mareda, J.; Schalley, C. A.; Matile, S. Experimental evidence for the functional relevance of anion-π interactions. Nat. Chem. 2010, 2, 533− 538. (26) Sakai, N.; Mareda, J.; Vauthey, E.; Matile, S. Core-substituted naphthalenediimides. Chem. Commun. 2010, 46, 4225−4237. (27) Zhang, Y.; Ji, B. M.; Tian, A. M.; Wang, W. Z. Communication: Competition between π-π interaction and halogen bond in solution: A combined 13C NMR and density functional theory study. J. Chem. Phys. 2012, 136, 141101−141104. (28) Sarwar, M. G.; Dragisic, B.; L. Salsberg, J.; Gouliaras, C.; Taylor, M. S. Thermodynamics of halogen bonding in solution: substituent, structural, and solvent effects. J. Am. Chem. Soc. 2010, 132, 1646− 1653. (29) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; 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.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö .; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, revision A.02; Gaussian, Inc.: Wallingford, CT, 2009. (30) Chai, J. -D.; Head-Gordon, M. Long-range corrected hybrid density functionals with damped atom−atom dispersion corrections. Phys. Chem. Chem. Phys. 2008, 10, 6615−6620. (31) Obtained from https://bse.pnl.gov/bse/portal. (32) Jensen, F. Describing Anions by Density Functional Theory: Fractional Electron Affinity. J. Chem. Theory Comput. 2010, 6, 2726− 2735. (33) Thanthiriwatte, K. S.; Hohenstein, E. G.; Burns, L. A.; Sherrill, C. D. Assessment of the Performance of DFT and DFT-D Methods for Describing Distance Dependence of Hydrogen-Bonded Interactions. J. Chem. Theory Comput. 2011, 7, 88−96. (34) Marenich, A. V.; Cramer, C. J.; Truhlar, D. G. Universal solvation model based on solute electron density and on a continuum model of the solvent defined by the bulk dielectric constant and atomic surface tensions. J. Phys. Chem. B 2009, 113, 6378−6396.

through the SAX-packed SPE cartridges. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone/Fax: +86-10-58802146. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors thank the Natural Science Foundation of China (No. 90922023) and Research Fund for the Doctoral Program of Higher Education of China (No. 20110003110011) for the support.

■

REFERENCES

(1) Legon, A. C. Prereactive Complexes of Dihalogens XY with Lewis Bases B in the Gas Phase: A Systematic Case for the Halogen Analogue B···XY of the Hydrogen Bond B···HX. Angew. Chem., Int. Ed. 1999, 38, 2686−2714. (2) Fourmigué, M. Halogen bonding: Recent advances. Curr. Opin. Solid State Mater. Sci. 2009, 13, 36−45. (3) Clark, T.; Hennemann, M.; Murray, J. S.; Politzer, P. Halogen bonding: the σ-hole. J. Mol. Model. 2007, 13, 291−296. (4) Politzer, P.; Murray, J. S.; Clark, T. Halogen bonding: an electrostatically-driven highly directional noncovalent interaction. Phys. Chem. Chem. Phys. 2010, 12, 7748−7757. (5) Politzer, P.; Murray, J. S.; Clark, T. Halogen bonding and other σhole interactions: a perspective. Phys. Chem. Chem. Phys. 2013, 15, 11178−11189. (6) Murray, J. S.; Lane, P.; Clark, T.; Riley, K. E.; Politzer, P. σ-Holes, π-holes and electrostatically-driven interactions. J. Mol. Model. 2012, 18, 541−548. (7) Serpell, C. J.; Kilah, N. L.; Costa, P. J.; Félix, V.; Beer, P. D. Halogen bond anion templated assembly of an imidazolium pseudorotaxane. Angew. Chem., Int. Ed. 2010, 49, 5322−5326. (8) Kilah, N. L.; Wise, M. D.; Serpell, C. J.; Thompson, A. L.; White, N. G.; Christensen, K. E.; Beer, P. D. Enhancement of anion recognition exhibited by a halogen-bonding rotaxane host system. J. Am. Chem. Soc. 2010, 132, 11893−11895. (9) Caballero, A.; White, N. G.; Beer, P. D. A Bidentate HalogenBonding Bromoimidazoliophane Receptor for Bromide Ion Recognition in Aqueous Media. Angew. Chem., Int. Ed. 2011, 50, 1845−1848. (10) Sarwar, M. G.; Dragisic, B.; Sagoo, S.; Taylor, M. S. A Tridentate Halogen-Bonding Receptor for Tight Binding of Halide Anions. Angew. Chem., Int. Ed. 2010, 49, 1674−1677. (11) Chudzinski, M. G.; McClary, C. A.; Taylor, M. S. Anion receptors composed of hydrogen-and halogen-bond donor groups: modulating selectivity with combinations of distinct noncovalent interactions. J. Am. Chem. Soc. 2011, 133, 10559−10567. (12) Mele, A.; Metrangolo, P.; Neukirch, H.; Pilati, T.; Resnati, G. A halogen-bonding-based heteroditopic receptor for alkali metal halides. J. Am. Chem. Soc. 2005, 127, 14972−14973. (13) Egli, M.; Sarkhel, S. Lone pair-aromatic interactions: To stabilize or not to stabilize. Acc. Chem. Res. 2007, 40, 197−205. (14) Ran, J.; Hobza, P. On the Nature of Bonding in Lone Pair···πElectron Complexes: CCSD (T)/Complete Basis Set Limit Calculations. J. Chem. Theory Comput. 2009, 5, 1180−1185. (15) Hay, B. P.; Bryantsev, V. S. Anion-arene adducts: C-H hydrogen bonding, anion−π interaction, and carbon bonding motifs. Chem. Commun. 2008, 2417−2428. (16) Frontera, A.; Gamez, P.; Mascal, M.; Mooibroek, T. J.; Reedijk, J. Putting Anion-π Interactions Into Perspective. Angew. Chem., Int. Ed. 2011, 50, 9564−9583. (17) Pang, X.; Wang, H.; Zhao, X. R.; Jin, W. J. Co-crystallization turned on the phosphorescence of phenanthrene by C-Br···π halogen 1086



Article

(35) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Intermolecular Interactions from a Natural Bond Orbital, Donor-Acceptor Viewpoint. Chem. Rev. 1988, 88, 899−926. (36) Chowdhury, S.; Kebarle, P. Role of binding energies in A−•B and A•B− complexes in the kinetics of gas phase electron transfer reactions: A−+B= A+B− involving perfluoro compounds: SF6, C6F11CF3, C6F6. J. Chem. Phys. 1986, 85, 4989−4994. (37) Hiraoka, K.; Mizuse, S.; Yamabe, S. High-symmetric structure of the gas-phase cluster ions X−···C6F6 (X= Cl, Br, and I). J. Phys. Chem. 1987, 91, 5294−5297. (38) Metrangolo, P.; Panzeri, W.; Recupero, F.; Resnati, G. Perfluorocarbon-hydrocarbon self-assembly: Part 16. 19F NMR study of the halogen bonding between halo-perfluorocarbons and heteroatom containing hydrocarbons. J. Fluorine Chem. 2002, 114, 27−33. (39) Libri, S.; Jasim, N. A.; Perutz, R. N.; Brammer, L. Metal fluorides form strong hydrogen bonds and halogen bonds: measuring interaction enthalpies and entropies in solution. J. Am. Chem. Soc. 2008, 130, 7842−7844. (40) Cabot, R.; Hunter, C. Non-covalent interactions between iodoperfluorocarbons and hydrogen bond acceptors. Chem. Commun. 2009, 2005−2007. (41) Blackstock, S. C.; Lorand, J. P.; Kochi, J. K. Charge-transfer interactions of amines with tetrahalomethanes. X-ray crystal structures of the donor-acceptor complexes of quinuclidine and diazabicyclo [2.2.2] octane with carbon tetrabromide. J. Org. Chem. 1987, 52, 1451−1460. (42) Benesi, H. A.; Hildebrand, J. A Spectrophotometric Investigation of the Interaction of Iodine with Aromatic Hydrocarbons. J. Am. Chem. Soc. 1949, 71, 2703−2707. (43) Bauzá, A.; Alkorta, I.; Frontera, A.; Elguero, J. On the reliability of pure and hybrid DFT methods for the evaluation of halogen, chalcogen, and pnicogen bonds involving anionic and neutral electron donors. J. Chem. Theory Comput. 2013, 9, 5201−5210. (44) Ma, N.; Zhang, Y.; Ji, B. M.; Tian, A.; Wang, W. Z. Structural Competition between Halogen Bonds and Lone-Pair···π Interactions in Solution. ChemPhysChem 2012, 13, 1411−1414. (45) About the halogen bond/σ-hole bond, we strongly agree with Politzer’s opinions that σ-hole bond can be understood in terms of electrostatics/polarization and dispersion. The formation of halogen bonded complexes and their experimentally determined properties can be fully explained on the basis of electrostatics/polarization and dispersion. (see Politzer, P.; Murray, J. S. Halogen Bonding: An Interim Discussion. ChemPhysChem 2013, 14, 278−294. (46) Garau, C.; Frontera, A.; Quiñonero, D.; Ballester, P.; Costa, A.; Deyà, P. M. A topological analysis of the electron density in anion-π interactions. ChemPhysChem 2003, 4, 1344−1348. (47) Quiñonero, D.; Garau, C.; Frontera, A.; Ballester, P.; Costa, A.; Deyà, P. M. Counterintuitive interaction of anions with benzene derivatives. Chem. Phys. Lett. 2002, 359, 486−492. (48) Yan, X. Q.; Shen, Q. J.; Zhao, X. R.; Gao, H. Y.; Pang, X.; Jin, W. J. Halogen bonding: A new retention mechanism for the solid phase extraction of perfluorinated iodoalkanes. Anal. Chim. Acta 2012, 753, 48−56.

1087


The Competition of σ-Hole···Cl– and π-Hole···Cl - ACS Publications

Recommend Documents