4-vinylpyridine: Theoretical insight into molecular imprinting complexes

Accepted Manuscript Quantum Investigation into Intermolecular Interactions between Bisphenol A and 2-Vinyl/4-vinylpyridine: Theoretical Insight into Molecular Imprinting Complexes Panpan Zhang, Xiuyan Ji, Hongxing Zhang, Baohui Xia PII: DOI: Reference:

S2210-271X(17)30138-X http://dx.doi.org/10.1016/j.comptc.2017.03.025 COMPTC 2452

To appear in:

Computational & Theoretical Chemistry

Received Date: Revised Date: Accepted Date:

16 January 2017 17 March 2017 20 March 2017

Please cite this article as: P. Zhang, X. Ji, H. Zhang, B. Xia, Quantum Investigation into Intermolecular Interactions between Bisphenol A and 2-Vinyl/4-vinylpyridine: Theoretical Insight into Molecular Imprinting Complexes, Computational & Theoretical Chemistry (2017), doi: http://dx.doi.org/10.1016/j.comptc.2017.03.025

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Quantum Investigation into Intermolecular Interactions between Bisphenol A and 2-Vinyl/4-vinylpyridine: Theoretical Insight into Molecular Imprinting Complexes

Panpan Zhanga, Xiuyan Jia, Hongxing Zhang b, Baohui Xiaa,* a

Colledge of Chemistry, Jilin University, Changchun, 130012, China

b

Institute of Theoretical Chemistry, Jilin University, Changchun, 130023, China,

*Corresponding author E-mail address: [email protected]

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ABSTRACT Molecular imprinting complexes of bisphenol A (BPA) templates with the isomeric functional monomers 2-vinylpyridine (2-Vpy, a) and 4-vinylpyridine (4-Vpy, b) in a molar ratio of 1:1 (1a, 1b) and 1:2 (2a, 2b) were investigated by quantum chemical calculations at the B3LYP/6-311++g(d,p) level. The optimized stable geometrical structures of the complexes revealed close contact between the N site of the functional monomer and the –OH group in BPA, with N…H(O) distances of 1.85-1.86 Å. Upon forming the imprinting complex, electrons migrated from N to –OH, and the strong O–H stretching vibration at 3453 cm-1 in isolated BPA was weakened and red-shifted by ca. 400 cm-1. The electron absorption spectra of the complexes, simulated using TD-B3LYP calculations, were a direct superposition of those of BPA and vinylpyridine. The evaluated N…H(O) interaction energies of 29-36 kJ/mol in all the complexes were equivalent to those of typical hydrogen bonding interactions. Calculation of the thermodynamic properties combined with solvent media analysis implied that mildly polar solvent at normal temperatures was thermodynamically favourable for preparing molecular imprinting complexes.

Key words: bisphenol A; vinylpyridine; molecular imprinting complex; theoretical investigation; intermolecular interaction.

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Quantum Investigation into Intermolecular Interactions between Bisphenol A and 2-Vinyl/4-vinylpyridine: Theoretical Insight into Molecular Imprinting Complexes

1. Introduction In recent years, endocrine-disrupting chemicals (EDCs) have attracted much attention because of their harmful effect on human health and wildlife. [1-3] Bisphenol A (BPA) is regarded as a representative EDC since it is widely used in the manufacture of polycarbonate epoxy resins and flame retardants and is an additive in plastics. [4-6] Many products can release BPA into the environment [7-9], such as baby bottles, reusable water bottles, food can walls, adhesives, artificial teeth and food packaging materials. Unfortunately, even very low doses of BPA have been demonstrated to do harm to wildlife and humans, leading to problems related to the breast, prostate, neurobehavioural systems and reproductive systems.[10-15] Much effort has been made to establish a simple, effective, and highly sensitive method for monitoring BPA. Traditional detecting methods for

BPA

include

high-performance

liquid

chromatography (HPLC), [

16 ]

gas

chromatography−tandem mass spectrometry (GC−MS/MS),[17] fluorescence analysis[18] and electrochemical detection (ED)[19]. However, these detection methods possess the drawbacks of low sensitivity and poor selectivity, are time consuming, and require professional operators and expensive instruments. It is still a challenge to explore new techniques to detect BPA in situ with high sensitivity, selectivity, and efficiency.

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The molecular imprinting technique is a method to prepare molecular imprinting polymers (MIPs) with highly specific recognition of a desired template molecule.[20-27] MIPs have high selectivity and can recognize the template molecule from a mixture that includes structurally analogous species. Thus, the molecular imprinting technique has been widely studied to offer a cost-effective, practical, and environmentally friendly method for separation and detection. [28-30] In recent years, the molecular imprinting technique has been applied to detect BPA due to its unique and remarkable detection abilities. Many studies have reported using fluorescent sensing strategies[31], photodegradation under UV light [32], and adsorption experiments[33] based on MIPs to recognize and detect BPA. Among those studies, typical small molecules, such as 2-vinylpyridine (2-Vpy), 4-vinylpyridine (4-Vpy)[ 34 , 35 ], methacrylic acid[36], and acrylamide[37], have been used as functional monomers to prepare the MIP system for BPA recognition. In contrast to the numerous experimental studies of the MIP technique for detecting BPA, the relevant theoretical research is sparse. Indeed, theoretical studies can avoid some disadvantages of experiments, such as environmental influences, time limits, and high costs. More importantly, theoretical research results can reveal the mechanism of MIPs formation and the relationship between the properties and structure of the MIP system. These results can afford valuable guidance for designing and preparing MIPs.[38-41]

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In this study, density functional theory (DFT) was adopted to simulate the imprinted preassembly complex of the target template BPA with the functional monomer 2-Vpy and 4-Vpy (both denoted Vpy for convenience), and the ratios of template to monomer in the simulations ranged from 1:1 (1a for the 2-Vpy complex and 1b for the 4-Vpy complex) to 1:2 (2a for the 2-Vpy complex and 2b for the 4-Vpy complex) (see Figure 1). 2-Vpy and 4-Vpy are isomeric in structure but can behave differently to some extent upon forming an imprinting system. A general theoretical approach involving structural, spectroscopic, and thermodynamic examination aims to study the interactions between BPA and 2-Vpy/4-Vpy, explore the nature of the interactions, and assess the performance of the two isomeric functional monomers. 2. Computational Details. In this work, all theoretical calculations were performed using the DFT approach[42]. González et al.

[43]

have surveyed the performance of density functional approaches on

hydrogen bonding systems and found that the B3LYP functional seems to be a good alternative to the much more expensive electron correlation methods, such as the MP2 method. Therefore, the B3LYP hybrid functional[44-49] with the standard 6-311++G(d,p) basis set[ 50 , 51 ] were utilized to carry out all the calculations. The fully optimized equilibrium geometry structures (for the isolated template BPA, functional monomers 2-Vpy and 4-Vpy, and all the complexes) were confirmed to be minima on the potential energy surface by vibrational frequency calculation.

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Considering the weak nature of the interaction, two kinds of energies, the stabilization energy (Esta) and interaction energy (Eint), were explored simultaneously. The interaction energy refers to the energy difference between the energy of the complex and the sum of the energies of the template molecule and functional monomers when frozen in the geometry of the corresponding complex, while the stabilization energy is the energy difference between the complex and its corresponding subsystems, all of which were computed at their respective optimized equilibrium conformations. Thus, the stabilization energies reflect how stable the complex should be. Indeed, in many cases these two kinds of energies in weak interaction systems are so similar in value that the two names are usually used interchangeably[ 52 - 54 ]. However, these two energies are significantly different in some systems. As an example, Boyd and Yáñez[55] reported their differences in H2Be···FCl···Base complexes, in which Base includes a wide set of N- and O-containing Lewis. From a classification viewpoint, the investigated target complexes belong to two-body or three-body weak interaction systems. Hankins et al.[56] proposed the formalism for the calculation of the many-body weak interaction energy, which has been adopted to compute the interaction energy[55,57,58]. In this work, the selected equations for the calculation of the stabilization energy Esta (Equation 1) and interaction energy Eint (Equation 2) were based on the Moskowitz’s formalism. Esta = EC(C)﹣EA(A)﹣nEB(B)

(1)

Eint = EC(C) - EA(C) - nEB(C)

(2)

n = 1 (in 1a, 1b), 2 (in 2a,2b); A = BPA, B = Vpy, C = complex

6

To correct the basis set superposition error (BSSE), the counterpoise strategy suggested by Boys and Bernardi[59] was employed during the calculation. Therefore, all energy terms, including those for the complex, BPA, and Vpy, in the above two equations were calculated with the complete basis sets of the corresponding complex, wherein EA(A), EB(B), and EC(C) were computed with the optimized stable conformation of BPA, Vpy, and the corresponding complex, respectively, while E A(C) and EB(C) were obtained in the frozen geometry of BPA and Vpy in the corresponding complex. Further characterization by the vibrational/electronic spectra and the electrostatic potential/charge were employed to evaluate the structure of the MIP complexes and the nature of the interaction between BPA and the functional monomer Vpy. All of the following discussions were based on results calculated in the gas phase. The electronic transition spectra of BPA, Vpy, and the corresponding complex were obtained with time-dependent DFT[60-62] at the B3LYP/6-311++G(d,p) level based on the respective equilibrium conformations. It should be noted that the solvent plays an important role in the formation of MIPs. Therefore, in addition to investigating the imprinting complexes in the gas phase, the effects of two solvents, methanol and toluene, on the imprinting system were assessed by adopting the polarized continuum model (PCM) [ 63 - 65 ]. Meanwhile, thermodynamic analysis was carried out on the complexes both in the gas phase and in solvent media. Thermodynamic data were obtained along with the frequency calculations.

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All calculations were performed using the Gaussian 09 program package[66], and the natural bond orbital (NBO)[ 67 ] calculation was performed using NBO 3.1 program implemented in the Gaussian 09 package. 3. Results and Discussions 3.1. Geometrical Structure Analysis The optimized geometries, along with the atom numbering scheme, of BPA and the 1:1 and 1:2 complexes are presented in Fig. 1, and some of the structural data are given in Table 1. Fig. 1 shows that isolated BPA exhibits C2 symmetry with the C2 axis passing through the 1C atom situated at the centre of the quasi-tetrahedron configuration and surrounded by two methyl and two hydroxyl-phenyl groups. The 1:1 complexes 1a and 1b have no symmetry, but the stable 1:2 complexes 2a and 2b have C2 symmetry with the C2 axis crossing the 1C atom in BPA and the two Vpy monomers localized on either side of BPA. The structure optimization results reveal that the template molecule closely approaches the functional monomer with a short N34…H33(O32) distance of ca. 1.85-1.86 Å (see Table 1). Therefore, MIP complexes were formed mainly due to this interaction. In the analysis of the structural data of isolated BPA, isolated Vpy, and the complexes, the following common features should be noted. First, all the optimized structural data for isolated BPA, 2-Vpy, and 4-Vpy are in the normal range with slightly acceptable deviations from those measured experimentally, due to the limits of the theoretical methodology. Second, compared with the isolated molecules, slight changes occurred in the structural data adjacent to the N…H(O) bond between the BPA and Vpy 8

fragments in the complexes, while those far from N…H(O) hardly vary. Third, The extent of structural variation in BPA and Vpy in all the complexes with the same functional monomer is very similar, for both the 1:1 or 1:2 ratio complex. Fourth, upon forming the molecular imprinting complexes, the geometric structure of BPA varies much more remarkably than that of Vpy. Variations of 0.01-0.02 Å are observed for bond distances, along with maximum variations of 2.3° in the bond angles, in the BPA fragments, while the structure of the Vpy fragment in the complexes only slightly changes, with variations of < 0.01 Å for the bond distances and < 1.5° for the bond angles. The most important structural characteristic in the complexes is the N …H(O) distance, which can indicate a weak interaction between BPA and Vpy. The calculated N34…H33(O32) lengths were 1.85-1.86 Å in all the complexes, which are shorter than the sum of the van der Waals radii of nitrogen and hydrogen (~2.74 Å)[68] but longer than the general N－H single bond distance (~1.009 Å)[68]. Recently, Gavezzotti[69] reported that the statistically typical N…H(O) hydrogen bond distance is ca. 1.826 Å. Therefore, the N…H(O) interaction in the imprinting complexes in this work should be attributed to hydrogen bond interactions, and the N34 …H33–O32 configurations in the complexes correspond to a typical hydrogen bond conformation with approximately linear configurations of ca. 169.3-172.9°. There is no prominent difference in the N…H(O) distances in the four complexes, but the 1:2 ratio complexes tend to show slightly longer N…H(O) distances (1.857 Å in 2a and 1.860 Å in 2b) than the 1:1 ratio complexes 9

(1.853 Å in 1a and 1.852 Å in 1b), possibly due to the arm-like balance action mode between BPA and Vpy in the 1:2 ratio complex. The obvious N…H(O) interaction in the complexes results in the structural variation of the adjacent moieties. In comparison with the isolated molecules, the O 32–H33 bond lengths in BPA in all the complexes are elongated by ca. 0.02 Å, and the H33-O32-C27 bond angles in BPA are further expanded to ca. 2.0°. Meanwhile, the N34–C35 and N34–C39 bonds in Vpy lengthen by 0.002 to 0.005 Å, which results from the attraction interaction of N with the hydrogen atom of –OH. On the other hand, the N34-C39-C44 and C39-C44-C45 bond angles are enlarged by 1.2-1.5° in the complexes compared with the isolated molecule, and the N34-C39-C44-C45 moiety in the 2-Vpy subunits in the complexes presents a ~7.0° torsion angle, compared with 0.0° in isolated 2-Vpy. Therefore, the N…H(O) interaction in the complexes should prevent steric hindrance from the ortho-vinyl group in 2-Vpy. 3.2. Electrostatic Potential and NBO Charge Analysis Fig. 2 depicts the electrostatic potential distribution of the isolated template, monomer, and complexes, respectively. It can be seen that BPA exhibits a large electropositive region on the hydrogen of the –OH group, while both 2-Vpy and 4-Vpy present strong electronegative character at the nitrogen site of the pyridyl group. Therefore, the diametrically opposite electronic properties of the H(O) and N sites can lead to an intense electrostatic attraction between BPA and Vpy. This is most likely the original driving force to form the MIP system. Fig. 2 also shows that the electronic 10

properties in area of N … H(O) become very weak after forming the complexes. Therefore, the complex systems are electronically stabilized. Natural bond orbital analysis is an essential tool for exploring intramolecular and intermolecular bonding interactions.[70,71] From the perspective of charge transport, the variation in the charge of BPA and Vpy when going from isolated molecules to fragments in a complex can reveal the microscopic mechanism involved in forming the MIP complex. Table 2 summarizes the NBO electronic charge data of isolated BPA, isolated Vpy, and the complexes. In general, the total electron numbers of BPA increase, while those of Vpy decrease after forming the composite system. Thus, Vpy acts as the electron donor, and BPA serves as the electron acceptor as they approach one another. It can be seen that a total of 0.0403 and 0.0444 electrons migrated from 2-Vpy and 4-Vpy to BPA, respectively, upon forming the 1:1 ratio complex, while in the formation of the 1:2 ratio complex, 0.0393 and 0.0429 electrons from 2-Vpy and 4-Vpy transferred to BPA, respectively. Notable changes in the electronic charge occurred on the N site in Vpy and the H(O) site in BPA. For example, the –OH group gained an additional 0.0442/0.0420 electrons in complex 1a/1b. At the same time, the N site in 2-Vpy/4-Vpy gave 0.0276/0.0283 electrons. In the 1:2 ratio complexes, each –OH moiety withdrew an extra 0.0433/0.0405 electrons, and the N atom donated 0.0270/0.0272 electrons to the 2a/2b complex. The electron transport from Vpy to BPA arises from the difference in the electronegativity of N and H(O), and the rearrangement of the electrons induces N…H–O hydrogen bonding. 11

It is worth mentioning that 4-Vpy can donate more electrons to BPA than 2-Vpy when forming both the 1:1 and 1:2 ratio complexes. For instance, BPA withdrew 0.0403 electrons from 2-Vpy and 0.0444 electrons from 4-Vpy when forming 1a and 1b, respectively. In particular, the N atom in the pyridyl group of 2-Vpy gave 0.0276 electrons to 1a, while the same atom in 4-Vpy provided 0.0283 electrons to 1b. As a result, 4-Vpy exhibits a stronger interaction with BPA than 2-Vpy (see Table 4). This signifies that 4-Vpy is a superior functional monomer to 2-Vpy. 3.3. Vibrational Proof The calculated typical stretching vibrational data for BPA and the complexes, after scaling with a factor of 0.9, are tabulated in Table 3. Meanwhile, the simulated vibrational spectra of BPA and -OH stretching in the complexes are displayed in Fig. 3 and Fig. 4, respectively. The simulated vibrational spectrum of BPA resembles the experimental spectrum[72], in which the sharp peak at 3453/3453 cm-1 is recognized as the intense asymmetrical/symmetrical stretching vibration of –OH, the multiple peaks at 2723-2792 cm-1 and 2831-2873 cm-1 belong to the C-H single bond stretching vibration of –CH3 and -C6H6, respectively, and the peak at 1152 cm-1 arises from the C–O stretching vibration. In comparing the vibrational data of isolated BPA and Vpy with those of the complexes, remarkable variations in the high-energy region can be seen, which are related to vibrations of the functional groups around the N and H(O) sites; however, no significant change can be found in the area not involved with the MIP interaction. For the 1:1 ratio complexes, the two identical –OH groups in isolated BPA 12

are subject to different chemical surroundings upon forming the complex: one is free as before, while the other interacts with the N of Vpy due to the weak N…H(O) interaction, which is termed as the imprinting group. This situation leads to the two –OH groups in the 1:1 complexes exhibiting different vibrational behaviours. The vibrational energy of the free –OH group (3453 cm-1 in 1a and 3452 cm-1 in 1b) is almost identical to that in isolated BPA, while that of the imprinting group is red-shifted to 3032 cm-1 in 1a and 3040 cm-1 in 1b. In contrast, there is only one kind of –OH group in the 1:2 ratio complexes, both are imprinting, the stretching vibration of which occurs at 3041/3044 cm-1 for 2a and 3053/3057 cm-1 for 2b, which are red-shifted in comparison with that in isolated BPA. The decrease in the vibrational energy of the imprinting –OH groups in all the complexes relative to the free groups results from the N…H–O interaction between BPA and Vpy. It should be mentioned that several weak and poorly differentiated vibrational modes seem to be related to N…H(O) stretching in the complex, such as the vibrations at 915, 948, 969, 1018, 1111 and 1443 cm-1 in 1a (see Table S1, Supporting Information), with very low intensity. Despite the weak strength and low intensity, these vibrations are related to N…H stretching, which is the reflection the weak N…H(O) interaction. Indeed, this is an unusual phenomenon for a weak intermolecular interaction system. The poor distinguishability and the weak strength of these modes precisely coincide with the fact that the N…H(O) interaction is weak and has a small magnitude. 3.4. Electronic Absorption Spectra 13

To probe the essence of the interaction between BPA and Vpy, the electronic absorptions of the complexes were inspected. Fig. 5/Fig. 6 shows the simulated electronic absorption spectra of BPA, 2-Vpy/4-Vpy, and corresponding complexes based on the calculated electron transition data. As shown in Figs. 5 and 6, isolated BPA and Vpy display absorptions in the ultraviolet region at < 330 nm. BPA possesses a sharp and intense absorption band with a maximum at 187 nm, accompanied by a broad tail band from 213 to 300 nm, while both 2-Vpy and 4-Vpy show three resoluble absorption bands in the range of 125 to 320 nm, along with a respective shoulder band ca. 270 nm for 2-Vpy and 140 nm for 4-Vpy. By contrast, the absorption intensities of Vpy are only one quarter of those of BPA. The fitted absorption spectra of the complexes with the same functional monomer in 1:1 and 1:2 ratios have identical profiles, but the 1:2 complexes 2a/2b have greater absorption intensities than the 1:1 complexes 1a/1b. When comprehensively examining the absorption spectra of the complexes, it can be seen that there are mainly three absorption bands covering the whole absorption range of BPA and Vpy. The higher energy bands at 125-170 nm result from Vpy, while the most intense bands centred at 190 nm result from the overlapping absorption bands of Vpy and BPA due to their almost identical absorption areas with different intensities. Meanwhile, the energy bands from 220 to 320 nm resemble the lower energy bands of Vpy with the tail band from BPA fully embedded. Hence, the absorption intensities of each complex are seemingly the sum of the corresponding fragments. No other absorption bands, except those of the BPA and Vpy themselves, can be seen over the entire wavelength range. 14

Thus, the absorption spectra of the complexes originate from the simple superposition of the spectra of isolated BPA and Vpy. This fact indicates that the interaction between BPA and Vpy is a non-bonding interaction, and no electron transition related to N…H(O) occurs. Hence, the assignment of the interaction between BPA and Vpy to intermolecular hydrogen bonding is reasonable. 3.5. Interaction Energy Table 4 presents the stabilization and interaction energies of all the MIP complexes combined with the basis set superposition error results. It can be seen that the calculated EBSSE is in the range of 2.6-6.0 kJ/mol and amounts to 9.0-10.5% and 7.1-7.6% of the absolute value of Esta/Eint for the 2-Vpy complex and 4-Vpy complex, respectively. Therefore, both the stabilization and interaction energy should be overestimated without the BSSE correction, and the BSSE correction is essential for modelling accurate template and functional monomer interactions. On the other hand, the differenced in the two calculated energies are within of 2.3-6.2 kJ/mol. Indeed, the difference is not big. This small discrepancy between the stabilization energy and the interaction energy is due to the slight deformation of the subunit in the complex. Furthermore, the stabilization energies of the 4-Vpy complexes are larger than those of the corresponding 2-Vpy complexes in both the 1:1 and 1:2 ratio. Thus, the MIP system from 4-Vpy should be more stabilized. Similarly, the calculated interaction energies for the 4-Vpy complex are higher than those for the 2-Vpy complex in both the 1:1 and 1:2 ratio. The calculated interaction 15

energy difference between 4-Vpy and 2-Vpy complexes in the 1:1/1:2 ratio is 3.4/6.1 kJ/mol. Therefore, it can be predicted that 4-Vpy can interact much more strongly with BPA than 2-Vpy as the functional monomer. On the other hand, since the interaction between BPA and Vpy is contained at the N and –OH sites, there should be another means to evaluate the N…H(O) interaction in order to determine the appropriate functional monomer. For simplicity, the interaction energy of the 1:1 ratio complex can be roughly regarded as the N…H(O) interaction energy, while the equivalent N…H(O) interaction energy in the 1:2 ratio complex can be taken as half of the total interaction energy of the complex. From the results listed in Table 4, the N…H(O) interaction energies are ca. 32 kJ/mol for the 2-Vpy complexes and are 35-36 kJ/mol for the 4-Vpy complexes. Therefore, solely considering the N…H(O) interaction, 4-Vpy is much more suitable than 2-Vpy as a functional monomer for producing a MIP complex with BPA. This difference should be due to the steric hindrance effect from the ortho-position vinyl group in 2-Vpy, which inhibits the most favourable linear orientation, producing a N 34… H33–O32 angle of ca. 169.0° in the 2-Vpy complex, while the N34…H33–O32 angle in the 4-Vpy complex is ca. 172.0°, which is much close to that in a linear configuration. It should be noted that the N…H(O) interaction energy slightly decreases when going from the 1:1 to the 1:2 ratio complex with the same functional monomer. Although the decrease magnitude is as small as ca. 0.7 kJ/mol, the descending trend is obvious. This result is in agreement with observation that the N…H(O) distance in the 1:2 complex is longer than that in the 1:1 complex. Therefore, it can be concluded that a high ratio 16

between BPA and Vpy can increase the total interaction energy in the complex but cannot enhance the interaction strength between the action sites. Such conclusion suggests that it is not necessary to use excess functional monomer in producing MIP systems. The magnitude of the calculated interaction energies of N…H(O) in the complexes are equivalent to those in classical hydrogen bonding systems, such as O…H–O[73,74] and N…H–O[75]. Therefore, the essence of the interaction between BPA and Vpy should be classified as a hydrogen bonding interaction. 3.6. Solvent Effect Assessment Due to the remarkable hydrogen-bonding characteristics displayed in MIPs, the solvent media can affect the interaction to some extent. In this work, a polarized continuum model was adopted to study the influence of solvent on the weak interaction. In this respect, two kinds of solvent, methanol and toluene, with different polarities were selected. Then, through comparison of certain properties of the complexes in the gas phase and in different solvent media, useful information concerning solvent effects can be obtained. Indeed, many properties of imprinting complexes can be affected by the media. However, only N … H(O) and O–H distances, the most important and characteristic geometrical features, and the interaction energies in different media relative to the imprinting interaction are investigated. The calculation results of the structural parameters are summarized in Table 5, and the interaction energies are summarized in Table 6. 17

As shown in Table 5, from the gas phase to toluene to methanol, the N34…H33(O) lengths shrink in sequence by ca. 0.025-0.033 Å in the 2-Vpy complexes and 0.043-0.047 Å in the 4-Vpy complexes, while the imprinting O32–H33 distances lengthen by 0.004-0.007 Å in all the complexes successively. The decreasing trend of the N34… H33(O) distance with the enhancement in solvent polarity is in line with the increasing trend of the imprinting O32–H33 distance. The stronger the N…H(O) hydrogen bond, the weaker the O–H bonding interaction, since both kinds of forces act on the active H simultaneously but in the opposite direction. This illustrates that the N…H(O) hydrogen bonding interaction is strengthened with increased solvent polarity. Furthermore, the much larger degree of variation in the N…H(O) distance in the 4-Vpy complexes in polar media indicates the positive influence of the solvent polarity on the N…H(O) interaction in the 4-Vpy complexes, compared with that in the 2-Vpy complexes. The results in Table 6 indicate that the polarity of the media can affect the interaction strength of the imprinting complexes. For each complex, the absolute value of the interaction energies enlarges with an increase in media polarity. It can be seen that there are 1.8/0.8 and 4.2/2.0 kJ/mol increases in the interaction energies of 1a and 2a when going from the gas phase to toluene to methanol. Meanwhile, the corresponding change is 2.9/2.2 and 6.9/4.9 kJ/mol for 1b and 2b, respectively. Therefore, polar media should work to reinforce the interaction between BPA and Vpy. Similar to the N…H(O) distance variation, the polarity of the media can enhance the interaction energies of the 4-Vpy complexes much more than those of the 2-Vpy complexes. For example, from 18

toluene to methanol, the interaction energies for 1b vary by 2.2 kJ/mol, but for 1a only 0.8 kJ/mol variations are seen in the same situation. Summarizing the above two points, high polarity media is a positive factor for preparing imprinting complexes. 3.7. Thermodynamic Properties Analysis of thermodynamic properties is helpful for understanding the formation of the complex from a macroscopic point of view. Calculated thermodynamic data, including the variation in enthalpy (ΔH°), free energy (ΔG°), and entropy (ΔS°), for the BPA + nVpy → complex (n = 1,2) reaction in the gas phase and in toluene/methanol media at 298.15 K are compiled in Table 7. Moreover, all the above properties with respect to temperature were also studied, and the results in the temperature range of 293.15 K to 313.15 K are listed in Table S2 (Supporting Information). All the calculated ΔH° values are negative, and the absolute values of ΔH° slightly increase with a decrease in temperature (see Table S2), which suggests that forming the imprinting complex is an exothermic process and the reaction temperature has little impact on the imprinting process. Therefore, it can be predicted that the temperature is not a strong factor in producing MIP systems. Indeed, MIP systems are usually prepared at moderate temperatures, for example, by being heated in a water bath at 50-60℃.[33,34] Furthermore, all the calculated ΔG° values are positive, implying that the preassembly complex cannot form spontaneously, and some intervention is essential to obtain the imprinting system. This agrees with practical solutions in the laboratory, such as 19

magnetic stirring during preparation. However, the ΔG° values of the process to produce complexes with 4-Vpy are smaller than those to produce complexes with 2-Vpy. As an example, the free energy change is 10.4 kJ/mol for producing 1a in the gas phase at 298.15 K, while the corresponding value to produce 1b is 5.85 kJ/mol. That is, it is easier to prepare complexes with 4-Vpy from the point of view of thermodynamics. This result verifies that the preferential choice of 4-Vpy, instead of 2-Vpy, as the functional monomer in experiments exactly agrees with the thermodynamics results. Another common feature observed from Table 7 is that all the calculated entropy variations in the imprinting process are negative. This coincides with the decrease in randomness after the formation of the imprinting system. In fact, the imprinting process is accompanied by a transformation from disordered to ordered due to the intermolecular interaction. It can also be noted that the absolute value of ΔS° for complexes with a 1:2 ratio is nearly twice that for 1:1 ratio complexes. This result is reasonable since the geometrical structures of the complexes with a 1:2 ratio are more rigid than those with a 1:1 ratio, resulting in well-organized imprinting complexes. Considering the solvent influence, when going from the gas phase to toluene to methanol, along with the increase in media polarity, the absolute values of ΔH° and ΔS° decrease, while those of ΔG° increase. This result seems to indicate that the solvent media, particularly when possessing high polarity, does not help the formation of the imprinting complex, and much effort is needed to overcome the higher free energy barrier in highly polar media. However, the use of solvent is unavoidable for producing MIP systems, and its positive actions are too important to be 20

omitted. The reasonable compromise is to select solvents with mild polarity, such as acetonitrile[76] and toluene[77], which are frequently adopted in experiment. 4. Conclusions In the present study, imprinting complexes between BPA and 2-Vpy/4-Vpy were investigated theoretically. The calculation results reveal the nature of the intermolecular hydrogen bonding in the imprinting complexes, which originates from electrons migrating from the N in the vinylpyridine fragment to the hydroxyl group of BPA. The results of the comprehensive investigation into solvent effects and the thermodynamic data indicate that solvent media with mild polarity and normal temperatures are suitable for producing imprinting complexes. Concerning the functional monomer, 4-Vpy should be superior to 2-Vpy in terms of both the microscopic structure and thermodynamics. These computational results provide substantial insight into the imprinting interaction between BPA and vinylpyridine which can be used as a reference in the study of other molecular imprinting systems.

Acknowledgments: This work was supported by the fund from Jilin Zhongshi Enviromental Engineering Development Co., Ltd (Grant. 2014220101000214).

21

Reference [1] J. Xu, L. Wang, Y.F. Zhu, Decontamination of Bisphenol A from Aqueous Solution by Graphene Adsorption. Langmuir 28 (2012) 8418−8425. [2] A.S. Stasinakis, C.I. Kordoutis, V.C. Tsiouma, G. Gatidou, N.S. Thomaidis, Removal of selected endocrine disrupters in activated sludge systems: Effect of sludge retention time on their sorption and biodegradation. Bioresour. Technol. 101 (2010) 2090−2095. [3] L.X. Chen, S.F. Xu, J.H. Li, Recent advances in molecular imprinting technology: current status, challenges and highlighted applications. Chem. Soc. Rev. 40 (2011) 2922−2942. [ 4 ] H.L. Wang, L. Toppare, J.E. Fernandez, Conducting polymer blends: polythiophene and polypyrrole blends with polystyrene and poly(bisphenol A carbonate). Macromolecules 23 (1990) 1053−1059. [5] A. Dondoni, C. Ghiglione, A. Marra, M. Scoponi, Synthesis and receptor properties of calix arene–bisphenol-A copolymers. Chem. Commun. (1997) 673−674. [6] C.A. Staples, P.B. Dome, G.M. Klecka, S.T. Oblock, L.R. Harris, A review of the environmental fate, effects, and exposures of bisphenol A. Chemosphere 36 (1998) 2149–2173. [7] R.C. Wang, D.J. Ren, S.Q. Xia, Y.L. Zhang, J.F. Zhao, Photocatalytic degradation of Bisphenol A (BPA) using immobilized TiO2 and UV illumination in a horizontal circulating bed photocatalytic reactor (HCBPR). J. Hazard. Mater. 169 (2009) 926−932. [8] S.L. Zheng, Z.M. Sun, Y. Park, G.A. Ayoko, R.L. Frost, Removal of bisphenol A from wastewater by Ca-montmorillonite modified with selected surfactants. Chem. Eng. J. 234 (2013) 416−422. [9] J.M. Zhao, Y.M. Li, C.J. Zhang, Q.L. Zeng, Q. Zhou, Sorption and degradation of bisphenol A by aerobic activated sludge. J. Hazard. Mater. 155 (2008) 305−311. [10] F.S. Vom-Saal, C. Hughes, An Extensive New Literature Concerning Low-Dose Effects of Bisphenol A Shows the Need for a New Risk Assessment. Environ. Health. Perspect. 113 (2005) 926–933. [11] C.A. Richter, L.S. Birnbaum, F. Farabollini, R.R. Newbold, B.S. Rubin, C.E. Talsness, J.G. Vandenbergh, D.R. Walser-Kuntz, F.S. Vom Saal, In vivo effects of bisphenol A in laboratory rodent studies. Reprod Toxicol 24 (2007) 199–224. [ 12 ] A.M. Soto, B.S. Rubin, C. Sonnenschein, Endocrine Disruption and the female, In: Endocrine-disrupting chemicals, Gore, A. Ed., Humana Press, Totowa, NJ, (2007). [13] L.N. Vandenberg, M.V. Maffini, C. Sonnenschein, B.S. Rubin, A.M. Soto, Bisphenol-A and the Great Divide: A Review of Controversies in the Field of Endocrine Disruption. Endocr. Rev. 30 (2009) 75–95. [14] E. Kandaraki, A. Chatzigeorgiou, S. Livadas, E. Palioura, F. Economou, M. Koutsilieris, S. Palimeri, D. Panidis, E. Diamanti-Kandarakis, Endocrine Disruptors and Polycystic Ovary Syndrome (PCOS): Elevated Serum Levels of Bisphenol A in Women with PCOS, J. Clin. Endocrinol. Metab. 96 (2011) 480–484. [15] S. Bae, J.H. Kim, Y.H. Lim, H.Y. Park, Y.C. Hong, Associations of Bisphenol A Exposure With Heart Rate Variability and Blood Pressure. Hypertension 60 (2012) 786–793.

22

[ 16 ] M. Rezaee, Y. Yamini, S. Shariati, A. Esrafili, M. Shamsipur, Dispersive liquid–liquid microextraction combined with high-performance liquid chromatography-UV detection as a very simple, rapid and sensitive method for the determination of bisphenol A in water samples. J. Chromatorgr. A. 1216 (2009) 1511–1514. [17] M.J. Gómez, A. Agüera, M. Mezcua, J. Hurtado, F. Mocholí, A.R. Fernández-Alba, Simultaneous analysis of neutral and acidic pharmaceuticals as well as related compounds by gas chromatography–tandem mass spectrometry in wastewater. Talanta 73 (2007) 314–320. [18] A. García-Prieto, M.L. Lunar, S. Rubio, D. Pérez-Bendito, Determination of urinary bisphenol A by coacervative microextraction and liquid chromatography–fluorescence detection. Anal. Chim. Acta 630 (2008) 19–27. [19] K. Inoue, K. Kato, Y. Yoshimura, T. Makino, H. Nakazawa, Determination of bisphenol A in human serum by high-performance liquid chromatography with multi-electrode electrochemical detection. J. Chromatogr. B. 749 (2000) 17–23. [20] B. Sellergren, Molecularly Imprinted Polymers: Man-made Mimics of Antibodies and Their Applications in Analytical Chemistry, Ed., Elsevier, Amsterdam, 23 (2000). [21] K.J. Shea, M.J. Roberts, M. Yan, Molecularly Imprinted Materials-sensors and Other DeVices, Eds., Materials Research Society: Warrendale, PA, (2002). [22] M. Yan, O. Ramstrom, Molecularly Imprinted Materials: Science and Technology, Eds., Marcel Dekker, New York, (2005). [23] M. Komiyama, Molecular Imprinting: From Fundamentals to Applications, Ed., Wiley-VCH, Weinheim, (2002). [24] K. Haupt, K. Mosbach, Molecularly Imprinted Polymers and Their Use in Biomimetic Sensors. Chem. Rev. 100 (2000) 2495–2504. [25] G. Wulff, Enzyme-like Catalysis by Molecularly Imprinted Polymers. Chem. Rev. 102 (2002) 1–28. [26] C. Alexander, H.S. Andersson, L.I. Andersson, R.J. Ansell, N. Kirsch, I.A. Nicholls, J. O’Mahony, M.J. Whitcombe, Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003. J. Mol. Recognit. 19 (2006) 106–180. [27] H.S. Byun, D.S. Yang, S.H. Cho, Synthesis and characterization of high selective molecularly imprinted polymers for bisphenol A and 2,4-dichlorophenoxyacetic acid by using supercritical fluid technology. Polymer 54 (2013) 589–595. [ 28 ] V. Pichon, F. Chapuis-Hugon, Role of molecularly imprinted polymers for selective determination of environmental pollutants—A review. Anal. Chim. Acta. 622 (2008) 48–61. [29] T. Kubo, K. Hosoya, K. Otsuka, Molecularly Imprinted Adsorbents for Selective Separation and/or Concentration of Environmental Pollutants. Anal. Sci. 30 (2014) 97–104. [30] X.T. Shen, C.G. Xu, L. Ye, Molecularly Imprinted Polymers for Clean Water: Analysis and Purification. Ind. Eng. Chem. Res. 52 (2013) 13890–13899. [ 31 ] X.Q. Wu, Z. Zhang, J.H. Li, H.Y. You, Y.B. Li, L.X. Chen, Molecularly imprinted polymers-coated gold nanoclusters for fluorescent detection of bisphenol A. Sensor. Actuat. B 211 (2015) 507–514.

23

[ 32 ] Y.B. Zhou, X.C. Gu, R.Z. Zhang, J. Lu, Influences of Various Cyclodextrins on the Photodegradation of Phenol and Bisphenol A under UV Light. Ind. Eng. Chem. Res. 54 (2015) 426−433. [33] F.F. Duan, C.Q. Chen, L. Chen, Y.J. Sun, Y.W. Wang, Y.Z. Yang, X.G. Liu, Y. Qin, Preparation and Evaluation of Water-Compatible Surface Molecularly Imprinted Polymers for Selective Adsorption of Bisphenol A from Aqueous Solution. Ind. Eng. Chem. Res. 53 (2014) 14291−14300. [ 34 ] X.H. Jiang, W.J. Ding, C.L. Luan, Molecularly imprinted polymers for the selective determination of trace bisphenol A in river water by electrochemiluminescence. Can. J. Chem. 91 (2013) 656–661. [35] A. Lasagabáster-Latorre, M.C. Cela-Pérez, S. Fernández-Fernández, J.M. López-Vilariño, M.V. González-Rodríguez, M.J. Abad, L.F. Barral-Losada, Insight into BPA－4-vinylpyridine interactions in molecularly imprinted polymers using complementary spectroscopy techniques. Mater. Chem. Phys. 141 (2013) 461–476. [36] H. Sanbe, J. Haginaka, Uniformly sized molecularly imprinted polymers for bisphenol A and β-estradiol: retention and molecular recognition properties in hydro-organic mobile phases. J. Pharm. Biomed. Anal. 30 (2002) 1835–1844. [37] R.M. Liu, F. Feng, G.L. Chen, Z.M. Liu, Z.G. Xu, Barbell-shaped stir bar sorptive extraction using dummy template molecularly imprinted polymer coatings for analysis of bisphenol A in water. Anal. Bioanal. Chem. 408 (2016) 5329–5335. [38] D. Pavel, J. Lagowski, Computationally designed monomers and polymers for molecular imprinting of theophylline and its derivatives. Part I. Polymer 46 (2005) 7528–7542. [39] D. Pavel, J. Lagowski, Computationally designed monomers and polymers for molecular imprinting of theophylline—part II. Polymer 46 (2005) 7543–7556. [40] D. Pavel, J. Lagowski, C.J. Lepage, Computationally designed monomers for molecular imprinting of chemical warfare agents—Part V. Polymer 47 (2006) 8389–8399. [41] J. Saloni, P. Lipkowski, S.S.R. Dasary, Y. Anjaneyulu, H.T. Yu, G.H. Jr., Theoretical study of molecular interactions of TNT, acrylic acid, and ethylene glycol dimethacrylate─Elements of molecularly imprinted polymer modeling process. Polymer 52 (2011) 1206–1216. [42] E. Runge, E.K.U. Gross, Density-Functional Theory for Time-Dependent Systems. Phys. Rev. Lett. 52 (1984) 997–1000. [43] L. González, O. Mó, M. Yáñez, J. Elguero, Cooperative effects in water trimers. The performance of density functional approaches. J. Mol. Struct.: Theochem. 371 (1996) 1–10. [44] S.L. Mayo, B.D. Olafson, W.A. Goddard, DREIDING: a generic force field for molecular simulations. J. Phys. Chem. 94 (1990) 8897–8909. [45] G.A. Petersson, A. Bennett, T.G. Tensfeldt, M.A. Al-Laham, W.A. Shirley, J. Mantzaris, A complete basis set model chemistry. I. The total energies of closed‐ shell atoms and hydrides of the first‐ row elements. J. Chem. Phys. 89 (1988) 2193–2218. [46] G.A. Petersson, M.A. Al-Laham, A complete basis set model chemistry. II. Open‐ shell systems and the total energies of the first‐ row atoms. J. Chem. Phys. 94 (1991) 6081–6090.

24

[47] C. Lee, W.T. Yang, R.G. Parr, Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B 37 (1998) 785–789. [48] A.D. Becke, Density‐ functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98 (1993) 5648–5652. [49] R.G. Parr, W. Yang, Density Functional Theory of Atoms and Molecules. Oxford, New York, (1989). [50] M.E. Casida, in: D.P. Chong (Eds.), Recent Developments in Density Functional Theory. vol. 1, World Scientific, Singapore, (1995) 155–192. [ 51 ] M.E. Casida, K.C. Casida, D.R. Salahub, Excited-state potential energy curves from time-dependent density-functional theory: A cross section of formaldehyde's 1A1 manifold. Int. J. Quantum Chem. 70 (1998) 933–941. [52] G.M. Zhao, Y.C. Liu, W.J. Shi, T. Chai, F.D. Ren, A B3LYP and MP2(full) theoretical investigation into cooperativity effects, aromaticity and thermodynamic properties in the Na + … benzonitrile…H2O ternary complex. J. Mol. Model. 20 (2014) 2341–2353. [53] H.X. Liu, R.L. Man, Z.X. Wang, P.G. Yi, J.J. Liu, Theoretical investigation on the interplay of hydrogen bond and halogen bond in HX…(BrCl)n (X=F, Cl, Br and n = 1, 2) complexes. J. Theor. Comput. Chem. 13 (2014) 1450001–1450022. [54] O. Mó, M. Yáñez, J. Elguero, Cooperative effects in the cyclic trimer of methanol. An ab initio molecular orbital study. J. Mol. Struct.: Theochem 314 (1994) 73-81. [55] L. Albrecht, R.J. Boyd, O. M , M. ez, Changing Weak Halogen Bonds into Strong Ones through Cooperativity with Beryllium Bonds. J. Phys. Chem. A 118 (2014) 4205−4213. [56] D. Hankins, J.W. Moskowitz, F.H. Stillinger, Water Molecule Interactions. J. Chem. Phys. 53 (1970) 4544−4554. [57] S. Salehzadeh, F. Maleki, New Equation for Calculating Total Interaction Energy in One Noncyclic ABC Triad and New Insights into Cooperativity of Noncovalent Bonds. J. Comput. Chem. 37 (2016) 2799–2807. [58] S.S. Xantheas, Ab Initio Studies of Cyclic Water Clusters (H 2O)n, n=1−6. II. Analysis of Many-Body Interactions. J. Chem. Phys. 100 (1994) 7523−7534. [59] S.F. Boys, F. Bernardi, The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors. Mol. Phys. 19 (1970) 553–566. [60] T. Helgaker, P. Jørgensen, An electronic Hamiltonian for origin independent calculations of magnetic properties. J. Chem. Phys. 95 (1991) 2595–2601. [61] K.L. Bak, P. Jørgensen, T. Helgaker, K. Ruud, H.J.A. Jensen, Gauge-origin independent multiconfigurational self-consistent-field theory for vibrational circular dichroism. J. Chem. Phys. 98 (1993) 8873–8887. [ 62 ] J. Autschbach, T. Ziegler, S.J.A. Gisbergen, E.J. Baerends, Chiroptical properties from time-dependent density functional theory. I. Circular dichroism spectra of organic molecules. J. Chem. Phys. 116 (2002) 6930–6940.

25

[63] E. Cancès, B. Mennucci, J. Tomasi, A new integral equation formalism for the polarizable continuum model: Theoretical background and applications to isotropic and anisotropic dielectrics. J. Chem. Phys. 107 (1997) 3032–3041. [64] M. Cossi, V. Barone, B. Mennucci, J. Tomasi, Ab initio study of ionic solutions by a polarizable continuum dielectric model. Chem. Phys. Lett. 286 (1998) 253–260. [65] B. Mennucci, J. Tomasi, Continuum solvation models: A new approach to the problem of solute’s charge distribution and cavity boundaries. J. Chem. Phys. 106 (1997) 5151–5158. [66] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox,Gaussian 09, Revision A.02, Gaussian, Inc., Wallingford CT, (2009). [67] N. Davidson, Statistical mechanics, New York: McGraw-Hill, (1962). [68] R.S. Rowland, R. Taylor, Intermolecular Nonbonded Contact Distances in Organic Crystal Structures: Comparison with Distances Expected from van der Waals Radii. J. Phys. Chem. 100 (1996) 7384–7391. [69] A. Gavezzotti, Comparing the strength of covalent bonds, intermolecular hydrogen bonds and other intermolecular interactions for organic molecules: X-ray diffraction data and quantum chemical Calculations. New J. Chem. 40 (2016) 6848–6853. [70] Z.F. Li, H.Y. Li, Y.Z. Liu, X.N. Shi, H.A. Tang, Weak interaction between CH 3SO and HOCl: Hydrogen bond, chlorine bond and oxygen bond. Chinese Sci Bull 54 (2009) 3014–3022. [71] N.J. Jasmine, P.T. Muthiah, C. Arunagiri, A. Subashini. Vibrational spectra (experimental and theoretical), molecular structure, natural bond orbital, HOMO–LUMO energy, Mulliken charge and thermodynamic analysis of N’-hydroxy-pyrimidine-2-carboximidamide by DFT approach. Mol. Biomol. Spectrosc. 144 (2015) 215–225. [72] R. Ullah, H. Li, .M. Zhu, Terahertz and FTIR spectroscopy of ‘Bisphenol A’. J. Mol. Struct. 1059 (2014) 255–259. [73] J.J. Hao, S.S. Li, X.N. Jiang, X.L. Li, C.S. Wang, Rapid evaluation of the interaction energies for O–H…O hydrogen-bonded complexes. Theor. Chem. Acc. 133 (2014) 1516–1527. [74] P. Schuster, LCAO-MO Studies on Hydrogen Bonding: The Interaction between Carbonyl and Hydroxyl Groups. Int. J. Quantum Chem. 3 (1969) 851–871. [75] D. Kaur, S. Khanna, Intermolecular hydrogen bonding interactions of furan, isoxazole and oxazole with water. Comput. Theor. Chem. 963 (2011) 71–75.

26

[76] Z.C. Zhang, Z.Q. Cheng, C.F. Zhang, H.Y. Wang, J.F. Li, Precipitation Polymerization of Molecularly Imprinted Polymers for Recognition of Melamine Molecule. J. Appl. Polym. Sci. 123 (2012) 962–967. [77] L.Q. Wu, K.C. Zhu, M.P. Zhao, Y.Z. Li, Theoretical and experimental study of nicotinamide molecularly imprinted polymers with different porogens. Anal. Chim. Acta. 549 (2005) 39–44.

27

Fig. 1. The optimized geometry structure with atom numbering scheme of BPA, 1:1 complex 1a and 1b, 1:2 complex 2a and 2b.

Fig. 2. Electrostatic potential distributions of BPA, 2-Vpy, 4-Vpy, 1:1 complex 1a and 1b, 1:2 complex 2a and 2b.

Fig. 3. The modeled vibration spectrum of BPA.

Fig. 4. The calculated -OH stretching vibrations of BPA and all complexes. .

Fig. 5. The modeled electronic absorption spectra of BPA, 2-Vpy, and corresponding complexes.

Fig. 6. The modeled electronic absorption spectra of BPA, 4-Vpy, and corresponding complexes.

Table 1 Optimized Geometrical Parameters of BPA and Complexes at B3LYP / 6-311++G (d,p) Level Bond length /Å BPA

2-Vpy

4-Vpy

1a

2a

1b

2b

O32-H33 C27-O32 C25-C27 N34-C35 N34-C39

0.963 1.371 1.391 1.330 1.346

N34-C35 N34-C39

1.339 1.335

O32-H33 O20-H21 C27-O32 C25-C27 N34-C35 N34-C39 N34…H33 O32-H33 C27-O32 C25-C27 N34-C35 N34-C39 N34…H33

0.985 0.963 1.360 1.396 1.335 1.349 1.853 0.985 1.361 1.396 1.335 1.349 1.857

O32-H33 O20-H21 C27-O32 C25-C27 N34-C35 N34-C39 N34…H33 O32-H33 C27-O32 C25-C27 N34-C35 N34-C39 N34…H33

0.985 0.963 1.357 1.397 1.341 1.337 1.852 0.984 1.359 1.396 1.341 1.337 1.860

Bond angle /deg H33-O32-C27 O32-C27-C25

109.6 123.0

N34-C35-H40 C35-N34-C39 N34-C39-C44 C39-C44-C45 N34-C35-H40 N34-C39-H43 C35-N34-C39 H33-O32-C27 O32-C27-C25 N34-C35-H40 C35-N34-C39 N34-C39-C44 C39-C44-C45 N34…H33-O32 H33-O32-C27 O32-C27-C25 N34-C35-H40 C35-N34-C39 N34-C39-C44 C39-C44-C45 N34…H33-O32 H33-O32-C27 O32-C27-C25 N34-C35-H40 N34-C39-H43 C35-N34-C39 N34…H33-O32

116.0 118.4 118.4 124.8 116.0 116.2 116.7 111.9 123.4 115.9 118.9 119.7 126.3 169.8 111.9 123.4 115.8 118.9 119.6 126.2 169.3 111.8 123.5 116.0 116.2 117.4 172.9

H33-O32-C27 O32-C27-C25 N34-C35-H40 N34-C39-H43 C35-N34-C39 N34…H33-O32

111.7 123.4 116.0 116.2 117.4 172.4

Table 2 The Electronic Charge Data from NBO Analysis q{LP(N34)}

BPA

2-Vpy

4-Vpy

1a

2a

1b

2b

－

1.9160

1.9182

1.8884

1.8890

1.8899

1.8910

－

56.0000

56.0000

55.9597

55.9607

55.9556

55.9571

q{LP(N49} q{Vpy}a

1.8890

q{Vpy}b

55.9606 *

q {O32-H33 }

0.0073

－

－

0.0515

*

q {O20-H21 }

0.0492

0.0506

0.0478 0.0478

122.0000

－

－

122.0403

122.0787

122.0444

122.0858

Δq{LP(N34)}

－

－

－

-0.0276

-0.0270

-0.0283

-0.0272

－

－

－

0.0442

Δq{LP(N49)}

-0.0270

*

Δq {O20-H21 } a

q{Vpy} →q{BPA}

0.0433

-0.0272 0.0420

0.0433 －

－

－

b

q{Vpy} →q{BPA} b

0.0505

55.9571

q{BPA}

Δq {O32-H33*}

a

1.8910

The Vpy located on the left side of the BPA The Vpy located on the right side of the BPA

0.0403

0.0393 0.0394

0.0406 0.0405

0.0444

0.0429 0.0429

Table 3 The Calculated Typical Stretching Vibration Data with the Scaling Factor of 0.90 for BPA, Vpy and Complexes in Gas Phase Vibrational assignments νO-Ha νO-Hb νC-H ( methyl )

BPA

2-Vpy

4-Vpy

1a

2a

1b

2b

3453/3453

-

-

3453

-

3452

-

-

-

-

3032

3041/3044

3040

3053/3057

2723-2792

-

-

2721-2792

2720-2790

2721-2793

2720-2791

-

-

1149

1167

1149

1170

1168

1167

1172

1170

νC15-O20

1152

νC27-O32

1152

νC-H ( phenyl )

2831-2873

2828-2874

2832-2868

2840-2880

2840-2880

2845-2876

2845-2876

νC-H（vinyl）

-

2825 /2834

2822 /2831

2828 /2838

2828 /2838

2827 /2832

2826/ 2832

νC=C（vinyl）

-

1517

1518

1520

1520

1520

1520

νC  N

-

1462

1430

1442

1443

1430

1430

a b

free –OH group. imprinting –OH group.

Table 4 The Calculated Stablization Energies (Esta) and Interaction Energies (Eint) along with BSSE Values for All the Complexesa Complex

Stablization

Interaction

EBSSE

Esta

EBSSE

Eint

EN…H(O)

3.1 6.0 2.6 5.0

-29.5 -58.3 -34.0 -66.5

3.0 5.8 2.6 5.0

-32.9 -64.5 -36.3 -70.6

-32.9 -32.3 -36.3 -35.3

1a 2a 1b 2b a

All values are in kJ/mol.

Table 5 The Characteristic Geometrical Parameters of Complexes in Different Media Bond length (Å) N34…H33(O)

O32－H33a a

Media

1a

2a

1b

2b

gas toluene methanol gas

1.853 1.828 1.798 0.985

1.857 1.830 1.797 0.985

1.852 1.809 1.766 0.985

1.860 1.813 1.768 0.984

toluene

0.989

0.989

0.991

0.990

methanol

0.994

0.994

0.998

0.997

imprinting –OH group

Table 6 The Calculated Interaction Energies (Eint) Corrected for BSSE in Different Media Media

Eint (kJ/mol) 1a

2a

1b

2b

gas

-32.9

-64.5

-36.3

-70.6

toluene

-34.7

-68.7

-39.2

-77.7

methanol

-35.5

-70.7

-41.4

-82.6

Table 7 Thermodynamic Properties of Complexes in Different Media at 298.15 K methanol Complex 1a 2a 1b 2b

toluene

gas

ΔH°

ΔG°

ΔSo

ΔH°

ΔG°

ΔSo

ΔH°

ΔG°

ΔSo

(kJ/mol)

(kJ/mol)

(J/mol·K)

(kJ/mol)

(kJ/mol)

(J/mol·K)

(kJ/mol)

(kJ/mol)

(J/mol·K)

-20.41

13.82

-114.81

-23.98

12.24

-121.48

-26.03

10.40

-122.21

-39.70

38.06

-260.80

-46.94

30.99

-261.37

-50.63

28.01

-263.76

-26.13

11.83

-127.34

-29.09

5.69

-116.67

-30.00

5.85

-120.26

-51.37

24.52

-254.56

-56.45

14.00

-236.33

-57.98

12.80

-237.39

Graphical Abstract:

Highlights • The molecular imprinting complexes from bisphenol A were theoretically investigated. • N…H(O) interaction caused the complexation between bisphenol A and vinylpyridine. • 4-Vinylpyridine is superior as functional monomer to 2-vinylpyridine. • The impact of solvent polarity and temperature on preparing complex was evaluated.

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