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Structures and Electronic Properties of HOCl···HCOCl Complexes
ACTA PHYSICO-CHIMICA SINICA Volume 24, Issue 9, September 2008 Online English edition of the Chinese language journal Cite this article as: Acta Phys. -Chim. Sin., 2008, 24(9): 1625−1630.
ARTICLE
Structures and Electronic Properties of HOCl···HCOCl Complexes Yanzhi Liu1,*,
Lihong He1,
Kun Yuan1,
Lingling Lü1,
Yunpu Wang2
1
College of Life Science and Chemistry, Tianshui Normal University, Tianshui 741000, Gansu Province, P. R. China;
2
College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. China
Abstract:
B3LYP/6-311++G** and MP2/6-311++G** calculations were used to analyze the interaction between hypochlorous
acid (HOCl) and formyl chloride (HCOCl). The results showed that there were four equilibrium geometries (S1, S2, S3, and S4) optimized at B3LYP/6-311++G** level, and all the equilibrium geometries were confirmed to be in stable states by analytical frequency calculations. Complexes S1 and S3 use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift hydrogen bond systems. However, the blue-shifted hydrogen bond (2C−3H···6O) coexists with 4Cl···5O interaction in structures S2. As for S4, it uses the 7Cl atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift halogen bond system. Interaction energies between monomers in the four complexes corrected with basis set superposition error (BSSE) and zero-point vibrational energy (ZPVE) lie in the range from −5.05 to −14.76 kJ·mol−1 at MP2/6-311++G** level. The natural bond orbital (NBO) and atoms in molecules (AIM) theories have also been applied to explain the structures and the properties of the complexes. Key Words:
Hypochlorous acid; Formyl chloride; Noncovalent interaction; NBO theory; AIM theory
From a fundamental point of view, the complexes formed by the noncovalent interactions are significant per se as they bridge the gap between the free molecular systems and the corresponding condensed phases. Also, in recent years, noncovalent intermolecular interaction has been implicated as an important type of interaction in many different types of physical systems and is especially of great interest within the fields of biochemistry[1−8], material science[9−14], and atmospheric chemistry[15−17]. The noncovalent interactions, especially hydrogen bond and halogen bond, play roles in a wide variety of biochemical phenomena such as protein-ligand complexation[18] and are responsible for many novel properties of materials[11,12]. As an illustrative example related to the significance of noncovalent systems in atmospheric chemistry, the proposed very accurate quantum mechanical procedures aiming to explain ozone layer depletion involve formation of certain intermolecular complexes[15,16]. Halogen-containing species, not only chlorofluorocarbons, but also hypochlorous acid (HOCl) and in particular, halogen monoxide radical (ClO,
BrO), are also involved in ozone degradation[19−21]. HOCl has been detected in the upper stratosphere by mass spectrometry in clusters with nitric and sulfuric acids and their anions[22,23]. Furthermore, formyl chloride, HCOCl, is a product of important atmospheric reactions[24,25]. To understand the details of the reactions occurring in atmospheric conditions, it is necessary to study the structure, stability, and other certain properties of the intermolecular complex taking part in these reactions. Although the title complexes of the present work are of interest in the field of atmospheric chemistry, so far studies of noncovalent complexes of HOCl are limited to a number of systems combining HOCl with SO3[17], X−(X=Cl, Br)[26,27], H2O[28], HOO radical[29], and O3[30]. Despite the potential importance of both HOCl and HCOCl, to our best knowledge, neither theoretical nor experimental study of their possible interaction is available in the literature. In the absence of experimental information, a theoretical analysis of the possible existence of such complexes and their properties appear to be in order. However, we have chosen the
Received: March 13, 2008; Revised: May 24, 2008. *Corresponding author. Email: [email protected]. The project was supported by the Natural Science Foundation of Gansu Province, China (07-08-12). Copyright © 2008, Chinese Chemical Society and College of Chemistry and Molecular Engineering, Peking University. Published by Elsevier BV. All rights reserved. Chinese edition available online at www.whxb.pku.edu.cn
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
HCOCl and HOCl systems (as opposed to HCOF, HCOBr, HOBr for example) due to the ability of density functional theory (DFT) and ab initio methods to accurately calculate structures and energies for chlorine containing compounds[24,31]. The present work reports the electronic structure, stabilities, and properties of the title complexes in detail.
1
Calculation details
The geometries of the isolated HOCl and HCOCl moieties and their complexes were fully optimized using both standard and counterpoise-corrected (CP) B3LYP/6-311++G** levels. This method and basis set adequately describes noncovalent interaction systems[32,33], so it is reliable for the purpose of our study. Harmonic vibrational frequency calculations confirmed the structures as a minimum or transition state and enabled the evaluation of zero-point vibrational energies (ZPVE). Counterpoise-corrected procedure was used to correct the interaction energy for basis set superposition error (BSSE). In the scheme of the CP method, the binding energy of two molecules (A and B) can be expressed as follows[34]: ∆ECP=EAB(AB)−[EAeq(A)+EBeq(B)]−[EA(AB)+EB(AB)]+ [EA(A)+EB(B)] where EAB(AB) is the total energy of the complex, EYeq(Y) (Y=A or B) is the total energy of monomer Y with equilibrium geometry but without extended basis sets, and EY(AB) and EY(Y) are the total energy of monomer Y based on the same geometry as that in the complex with and without extended basis sets. At the same time, ZPVE correction is also considered. Natural bond orbital (NBO)[35] analysis and atoms in molecules (AIM) theory analysis[36] are featured wholly through a series of intermolecular interactions under the HOCl···HCOCl system. Natural bond orbital analysis was preformed via NBO 5.0 program[37], and the other calculations were performed using Gaussian 03 program[38].
2
Results and discussion
2.1
Geometric configuration
All possible geometries obtained by standard and CP opti-
Fig.1
mization on the surface of HCOCl+HOCl are depicted in Fig.1. The results show that there are four equilibrium geometries at B3LYP/6-311++G** level. And all the equilibrium geometries were confirmed to be in stable states by frequency analysis. S1 and S3 complexes use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor. As for S2 and S4, S2 uses the 3H and 4Cl atoms of HCOCl as proton donors and the terminal 6O atom of HOCl as their same acceptor. However, S4 uses the 7Cl atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor. S1, S3 belong to conventional hydrogen bond complexes; S4 belongs to halogen bond noncovalent complex. And hydrogen bond (C−H···O) and O···Cl interaction coexist in S2. Noncovalent interaction between two electronegative atoms such as O and Cl predicted here in S2 structure is consistent with previous investigations that reported existence of O···Cl interaction[30,39]. Some of the key geometrical parameters optimized for these complexes using B3LYP/6-311++G** level are also displayed in Fig.1. By comparing the data, we can find that the 6O−5H distances in S1 and S3 or 6O−7Cl distance in S4 increase obviously after formation of complexes. For example, 6O−5H distances in S1 and S3 increase by 0.0007 and 0.0006 nm, respectively; 6O−7Cl distance in S4 increases by 0.0004 nm. As for 2C−3H in S2, its length decreases by 0.0001 nm. Bondi[40] reported that van der Waals radii of Cl and O atoms were 0.175 and 0.152 nm, respectively, and Taylor[41] reported that van der Waals radii of H atom was 0.109 nm. Here, 7Cl···1O in S4 is 0.2882 nm; 5H···1O in S1 and in S3 are 0.1948 and 0.1956 nm; 3H···6O and 4Cl···6O distances in S2 are 0.2273 and 0.3239 nm, respectively. It is clear that these noncovalent interaction distances are all less than the sum of the relevant atoms′ van der Waals radii, and this is a necessary condition for formation of the hydrogen or halogen bond[8]. Although the distances between noncovalent atoms in four complexes calculated under CP correction optimization method enlarged (in italics in Fig.1), a similar trend could still be obtained. Also, it can be observed that the distances between proton donors and
Partial bond parameters of the monomers and complexes optimized at B3LYP/6-311++G** and CP correction (in italics) levels The lengths of the bonds are in nm.
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
Table 1 Complex S1 S2 S3 S4 a
Partial vibrational frequencies (cm−1) of the monomers (νc) and the complexes (νm) at B3LYP/6-311++G** level Vibrational mode
νm a
νca
∆νb
Approximate descriptionc,d
ν1
3776.2(79.4)
3651.8(522.8)
ν2
1226.4(37.7)
1312.1(59.1)
85.7
6O−5H rock in plane
ν1
3054.3(20.3)
3077.9(1.2)
23.6
2C−3H stretch
ν2
1328.3(32.2)
1315.5(48.7)
−12.8
ν1
3776.2(79.4)
3678.8(592.7)
−97.4
ν2
1226.4(37.7)
1298.7(52.6)
72.3
690.6(32.0)
−29.8
720.4(27.2)
ν1 −1
b
−124.4
6O−5H stretch
2C−3H rock in plane 6O−5H stretch 6O−5H rock in plane 6O−7Cl stretch
c
d
Infrared intensities (km·mol ) are in parentheses. ∆ν = νc−νm. Based on the calculated atomic displacements. For atomic number, see Fig.1.
acceptors in four complexes are in the order 5H···1O (in S1)<5H···1O (in S3)<3H···6O (in S2)<7Cl···1O (in S4). For the moment, the shorter the above distance, the more steady the complex. Further more, it should be noted that S1, S2, S3, and S4 all have planar configurations. 2.2 Vibrational frequencies, energies, and rotational constants The partial calculated frequencies of monomers and four complexes under B3LYP/6-311++G** level are listed in Table 1. It can be observed that the stretching frequencies of 6O−5H in S1 and S3 and 6O−7Cl in S4 have the red shifts. For example, compared with the monomer, 6O−5H stretching frequency decreases by 124.4 cm−1 in S1. However, the stretching frequencies of 2C−3H in S2 present a blue shift with 23.6 cm−1. Furthermore, we notice that the stretching vibrational intensities of the 6O−5H in S1 and S3 and 6O−7Cl in S4 are all enhanced after the formation of red shift hydrogen bond or halogen bond complex. In contrast, the stretching vibrational intensity of 2C−3H in S2 decreases obviously, which can be attributed to the polarizable ability of proton donor. Here, 6O−5H and 6O−7Cl are typical polar bonds and are easy to polarize, but 2C−3H bond is only with little polarity and is difficult to polarize. IR strength and electronic dipole at the corresponding vibration vector are correlative with square of displacement partial differentiation[42]. After formation of the complexes, the electronic dipoles of 6O−5H and 6O−7Cl bond increase but that of 2C−3H decreases. Thus, IR strengths of 6O−5H and 6O−7Cl increase, whereas that of 2C−3H decreases. In fact, the increase or decrease of stretching vibrational infrared intensity is regarded as a typical character in red shift or blue shift system[43]. Table 2 presents the total interaction energies (∆Etot) and the BSSE corrected interaction energies (∆ECP) for each complex. It can be observed that the interaction energies calculated using B3LYP method are higher (less negative) than those obtained using MP2 method. Because the interaction of the supermolecule is comprised of electrostatic force, dispersion force, and inductive effect, the dispersion force is not included in the B3LYP method (but B3LYP method has been proved reliable during the geometry optimization[27]); however,
we can get it from the MP2 method or the higher method[44]. Despite the basis set 6-311++G** that we chose is advantageous to the decrease of BSSE error, obviously, it is necessary to perform a CP correction. Both BSSE and ZPVE corrected interaction energies range between −5.05 and −14.76 kJ·mol−1 at MP2/6-311++G** level and −3.61 and −12.00 kJ·mol−1 at B3LYP/6-311++G** level. S1 and S3 are clearly the most strong bounds of the various complexes, with binding energies of –18.48 and −14.63 kJ·mol−1 after correction of BSSE at MP2/6-311++G** level. In contrast, the binding energies of S2 and S4 are only −11.19 and −7.06 kJ·mol−1 at the same computational level, respectively. Taking one with another, noncovalent interaction of halogen bond is obviously weaker than noncovalent interaction of hydrogen bond in the present study. According to the BSSE and ZPVE corrected interaction energies, which were calculated at MP2/6-311++G** level and listed in Table 2, we can conclude that the stabilities of the four complexes increase in the order of S4
Interaction energies in the four complexes
B3LYP/6-311++G**
MP2/6-3111++G**
∆Etot BSSE ∆ECP ∆ECP+ZPVE
∆Etot BSSE ∆ECP ∆ECP+ZPVE
S1
−19.20 2.30 −16.90 −12.00
−23.34 4.86 −18.48
−14.76
S2
−13.49 2.28 −11.21
−8.16
−19.30 8.11 −11.19
−8.69
S3
−17.91 1.98 −15.93 −11.25
−21.65 7.02 −14.63
−11.31
−12.32 5.26 −7.06
−5.05
S4
−7.74 1.83
−5.91
−3.61
∆Etot is the total interaction energy, ∆ECP is the interaction energy with BSSE correction, and ∆ECP+ZPVE is the interaction energy with both BSSE and ZPVE corrections. The energies are all in kJ·mol−1.
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
Table 3
HOMO energies (EHOMO), LUMO energies (ELUMO), and
Table 4
gap (∆ELUMO-HOMO) of the monomers and four complexes calculated
complexes calculated at B3LYP/6-311++G** level
at B3LYP/6-311++G** level
Compound
A
Species
ELUMO (a.u.)
EHOMO (a.u.)
∆ELUMO-HOMO (a.u.)
HOCl
609.728 (613.380)
HOCl
−0.1016
−0.3000
−
HCOCl
78.035
6.013
5.582
S1
10.366
0.779
0.725
S2
6.162
0.834
0.736
S3
9.213
0.752
0.696
27.274
0.658
0.643
HCOCl
−0.1015
−0.3149
−
S1
−0.0950
−0.2910
0.1960
S2
−0.1114
−0.3104
0.1990
S3
−0.0958
−0.2794
0.1836
S4
−0.0914
−0.2945
0.2031
S4
C 14.140 (14.725)
drogen bond and halogen bond, respectively. The interaction between filled orbitals in one subsystem and unfilled orbitals of another represents a deviation of the complex from its Lewis structure and can be used as a measure of the intermolecular delocalization, also called as hyperconjugation. The hyperconjugative interaction energy can be deduced from the second order perturbation approach[39]: σ* Fσ F2 =ησ ij E(2)=−ησ ∆E εσ * − εσ where Fij is the Fock matrix element between the i and j NBO orbitals, εσ and εσ* are the energies of σ and σ* orbitals, respectivey, and ησ is the population of the donor σ orbital. The interaction strength between monomers could be clarified according to second-order stabilization energy (E(2)) between proton donor and acceptor obtained from the NBO analysis. As NBO theory indicates, the larger the stabilization energy E(2), the stronger the interaction between donor and acceptor orbitals. In other words, the donor electrons are easier to transfer to the acceptor orbitals. In addition, the importance of the orbital hyperconjugation and electron density transfer (EDT) from electron donor orbital to electron acceptor orbital in noncovalent interaction systems are well known, which leads to an increase in population of electron acceptor antibonding orbital. This weakens the filled orbital bond and
NBO analysis
The analyses for the combining interaction between HCOCl and HOCl with the NBO method have been performed even at MP2/6-311++G** level. And the corresponding results are listed in Table 5. From the results of NBO analysis for the monomers, it can be suggested that the 5H and 7Cl atoms in HOCl carry significant amount (0.198e and 0.477e) of positive charge, whereas the 1O atom in HCOCl carries certain amount (−0.556e) of negative charge. Therefore, intermolecular interaction should take place in the 6O−5H···1O or 6O−7Cl···1O. This means that the noncovalent interaction involved in 6O−5H···1O and 6O−7Cl···1O can be defined as hyTable 5
B 14.475 (15.117)
Experimental values[30] are in parentheses.
the complexes, the values of ∆ELUMO-HOMO are in the order of S4>S2>S1>S3. The most stable complexes S1 and S3 have low ∆ELUMO-HOMO, which are 0.1960 and 0.1836 a.u., respectively. And as the most unstable complex S4 in the present study, the ∆ELUMO-HOMO is the highest (0.2031 a.u.). For the reason of completeness, the rotational constants for monomers and the complexes are also listed in Table 4 at B3LYP/6-311++G** computational level. The four complexes are asymmetric rotors and behave like prolate rotors, with A>B≈C. The calculated rotational constants for HOCl agree well with the experimental values[30]. 2.3
Rotational constants (in GHz) for monomers and four
NBO analysis of the monomers and the four complexes at MP2/6-311++G** level
Complexes
Monomers
S1
S2
S3
S4
E [n (1O)→σ (6O−5H)]/(kJ·mol )
−
E(2)[n1,2(6O)→σ*(2C−3H)]/(kJ·mol−1)
−
11.6, 18.9
−
15.5, 10.6
−
−
2.9, 5.8
−
E(2)[n2(4Cl)→σ*(6O−7Cl)]/(kJ·mol−1)
−
−
−
1.8
−
−
E(2)[n1,2(1O)→σ*(6O−7Cl)]/(kJ·mol−1)
−
−
−
−
2.4, 7.3
∆σ* a (6O−5H)/e
−
0.00856
−
0.00695
−
∆σ*(2C−3H)/e
−
−
−0.0037
−
−
∆σ*(6O−7Cl)/e
−
−
0.0021
−
0.00696
sp3.3, sp8.0
sp2.86, sp8.53
sp3.18, sp7.38
sp2.86, sp8.24
sp3.3, sp7.81
sp1.7, sp2.66
sp1.7, sp2.6
sp1.59, sp2.90
sp1.7, sp2.6
sp1.7, sp2.6
(2)
1,2
*
−1
spn(6O−5H or 7Cl) spn(2C−3H or 4Cl) b
∆{s(6O) in σ(6O−5H or 7Cl)} (%)
−
2.69, 3.52
0.76, 4.59
2.68, 3.49
0.06, 3.01
∆{s(2C) in σ(2C−3H or 4Cl)}c(%)
−
−0.37, 0.85
1.66, −1.67
−0.29, 0.73
−0.07, −0.27
a
change of natural population σ*; bchange of s-character of 6O hybrid orbital in σ(6O−5H or 7Cl) on the complexation; c
change of s-character of 2C hybrid orbital in σ(2C−3H or 4Cl) on the complexation
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
leads to its elongation and concomitant stretching frequency red shift. The above theory is applicable for HOCl···HCOCl system. In complex S1, the second-order stabilization energies (E(2)) of n1,2(1O)→σ*(6O−5H) are 11.6 and 18.9 kJ·mol−1, and natural population of σ*(6O−5H) increases by 0.00865e. 3D image of the interaction between n1,2(1O) and σ*(6O−5H) is given in Fig.2(a). In complex S3, similar to that of S1, there are high E(2) of n1,2(1O)→σ*(6O−5H), and an efficient overlap can be observed between the related orbitals (Fig.2(c)). As for complex S2 and S4, n1,2(6O)→σ*(2C−3H) and n1,2(1O)→ σ*(6O−7Cl) are the two main orbital interactions, respectively. Their E(2) values are relatively low, so the overlaps of the related orbitals are very small as shown in Fig.2(b,d). Different from red shift bonds, we can observe that the natural population of σ*(2C−3H) in S2 decreases by 0.0037e instead of increasing by some amounts; this shows that there has been electron density redistribution effect of HCOCl moiety in S2. Moreover, it can be observed from Table 5, s character of 2C in 2C−3H of HCOCl moiety increases after the formation of complex S2. Hence, we can conclude that the total of electron density redistribution and atom rehybridization effect exceed orbital hyperconjugation; thus, 2C−3H bond length decreases by 0.0001 nm, and its stretching frequency represents blue shift after the formation of complex. Further more, we observe that the total E(2) between natural bond orbitals in four complexes increases in the order of S4
Fig.2
orbitals in HOCl···HCOCl systems
presence of the hydrogen or halogen bond interactions in the four complexes. For example, in the hydrogen bond interaction (1O···5H) in complex S1, its ρ(r) is 0.0207 a.u., and its 2ρ(r) is 0.0929 a.u. (>0). This indicates that the charge density radiation at BCP and the hydrogen bond have more ionic property. As for halogen bond interaction in complex S4, the 2ρ(r) and ρ(r) of 1O···7Cl are similar to that of 1O···5H in S1. In addition, Lipkowski[48] pointed that the electron density and positive values of the Laplacian in hydrogen bond system should be in the range of 0.002−0.04 and 0.02−0.15 a.u.. Here, in hydrogen bond complexes of S1, S2, and S3, ρ(r) and 2ρ(r) all lie in the range of that suggested by Lipkowski. The value of ρ(r) is the measurement of the bond intensity. In general, the larger the ρ(r), the stronger is the bond. Here, the ρ(r) of hydrogen bond or halogen bond in the four complexes increases in the order of S4
AIM analysis
A topological analysis of the electron density was carried out using Bader′s theory of AIM[36]. This analysis has been applied to study the properties of a variety of interactions between atoms[45−47]. Especially, the properties of the electron density at bond critical points (BCP) for the binding interaction between HCOCl and HOCl were analyzed in present study. Table 6 lists the electron density (ρ(r)) at BCP and its Laplacian of electron density (2ρ(r)) and ellipticities (ε). λi (λ1, λ2, λ3) listed in Table 6 are the eigenvalues of the electron density Hessian matrix, and 2ρ(r)=λ1+λ2+λ3. From Table 6, we can observe that λ1<0, λ2<0, λ3>0 in each complex, according to Bader′s theory[36], they can be labeled as (3, −1) critical points, and christened BCP, which can indicate the Table 6
3D images of the main interactions between natural bond
Electron density topological properties at the intermolecular bond critical points of the four complexes calculated at MP2/6-311++G** level
a
a
Complex
Atom pair
ρ(r)
λ1
λ2
λ3
2ρ (r)
ε
Interaction distanceb
S1
1O···5H
0.0207
−0.0286
−0.0272
0.1490
0.0929
0.0500
0.1948
S2
6O···3H
0.0123
−0.0132
−0.0125
0.0741
0.0485
0.0560
0.2273
S2
6O···4Cl
0.0069
−0.0048
−0.0026
0.0373
0.0299
0.8454
0.3239
S3
1O···5H
0.0194
−0.0264
−0.0253
0.1428
0.0912
0.0423
0.1956
S4
1O···7Cl
0.0118
−0.0094
−0.0086
0.0676
0.0497
0.0934
0.2882
2
For atomic number, see Fig.1; ρ(r) is electron density of critical point; λi is Hessian eigenvalue; ρ(r) is density Laplacian; ε is ellipticity; ρ(r) and 2ρ(r) are in atom unit (a.u.); binteraction distance (nm) was calculated at B3LYP/6-311++G** level.
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
would mainly represent σ property. Furthermore, all the intermolecular interactions present small values of the electron density and positive values of the Laplacian as an indication of closed shell interactions.
3
Conclusions
Theoretical calculations of the 1:1 complexes formed by HCOCl and HOCl have been carried out at B3LYP/ 6-311++G** and MP2/6-311++G** computational levels. Four stable configurations have been found at B3LYP/ 6-311++G** level. The theoretical analysis showed that the four complexes are composed by two red-shifted hydrogen bond (O−H···O) structures (S1 and S3), one co-exist of blueshifted hydrogen bond (C−H···O) and Cl···O interaction structure (S2), and one red-shifted halogen bond (O−Cl···O) structure (S4). According to the BSSE and ZPVE corrected interaction energies, which were calculated at MP2/6-311++G** level, it can be concluded that the stabilities of the four complexes increase in the order of S4
References 1 Lans, M. C.; Spiertz, C.; Brouwer, A.; Koeman, J. H. Eur. J. Pharmacol., 1994, 270: 129 2 Rablen, P. R.; Lockman, J. W.; Jorgensen, W. L. J. Phys. Chem. A, 1998, 102: 3782 3 Cai, Z. L.; Reimers, J. R. J. Phys. Chem. A, 2002, 106: 8769 4 Battistutta, R.; Mazzorana, M.; Sarno, S.; Kazimierczuk, Z.; Zanotti, G.; Pinna, L. A. Chem. Biol., 2005, 12: 1211 5 Himmel, D. M.; Das, K.; Clark, A. D.; Hughes, S. H.; Benjahad,
16 Calvert, J. G.; Lazrus, A.; Kok, G. L.; Heikes, B. G.; Walega, J. G.; Lind, J.; Cantrell, C. A. Nature, 1985, 317: 27 17 Solimannejad, M.; Pejov, L. J. Phys. Chem. A, 2005, 109: 825 18 Metrangolo, P.; Neukirch, H.; Pilati, T.; Resnati, G. Acc. Chem. Res., 2005, 38:386 19 Farman, J. C.; Gardiner, B. G.; Shanklin, J. D. Nature, 1985, 315: 207 20 Lehrer, E.; Hoenninger, G.; Platt, U. Atmos. Chem. Phys., 2004, 4: 2427 21 Aranda, A.; Le Bras, G.; La Verdet, G.; Poulet, G. Geophys. Res. Lett., 1997, 24: 2745 22 McCrumb, J. L.; Arnold, F. Nature, 1981, 294: 136 23 Schlager, H.; Arnold, F. Planet Space Sci., 1987, 35: 693 24 Drougas, E.; Kosmas, A. M.; JalbouA, F. T. J. Phys. Chem. A, 2004, 108: 5972 25 McGivern, W. S.; Kim, H.; Francisco, J. S.; North, S. W. J. Phys. Chem. A, 2004, 108: 7247 26 Francisco, J. S. Chem. Phys. Lett., 1996, 260: 485 27 Flowers, B. A.; Francisco, J. S. J. Phys. Chem. A, 2001, 105: 494 28 Ortiz-Repiso, M.; Escribano, R.; Gómez, P. C. J. Phys. Chem. A, 2000, 104: 600 29 Jalbout, A. F.; Li, X. H.; Solimannejad, M. Chem. Phys. Lett., 2006, 420: 204 30 Solimannejad, M.; Alkorta, I.; Elguero, J. Chem. Phys. Lett., 2007, 449: 23 31 Jalbout, A. F.; Nazari, F.; Turker, L. J. Mol. Struct. -Theochem, 2004, 671: 1 32 Su, M. D.; Chu, S. Y. J. Am. Chem. Soc., 1999, 121(17): 4229 33 King, B. F.; Weinhold, F. J. Chem. Phys., 1995, 103(1): 333
A.; Oumouch, S.; Guillemont, J.; Coupa, S.; Poncelet, A.; Csoka,
34 Liu, J. F.; Li, X. Y.; Zhu, Q. Int. J. Quantum Chem., 2004, 98: 33
I.;
35 Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev., 1988, 88:
Meyer, C.; Andries, K.; Nguyen, C. H.; Grierson, D. S.;
Arnold, E. J. Med. Chem., 2005, 48: 7582 6 Jiang, Y.; Alcaraz, A. A.; Chen, J. M.; Kobayashi, H.; Lu, Y. J.; Snyder, J. P. J. Med. Chem., 2006, 49: 1891 7 Trogdon, G.; Murray, J. S.; Concha, M. C.; Politzer, P. J. Mol. Model., 2007, 13: 313 8 Auffinger, P.; Hays, F. A.; Westhof, E.; Ho, P. S. Proc. Natl. Acad. Sci. USA, 2004, 101: 16789 9 Takeuchi, T.; Minato, Y. J.; Takase, M.; Shinmori, H. Tetrahedron Lett., 2005, 46: 9025 10 Xu, J. W.; Liu, X. M.; Ng, J. K. P.; Lin, T. T.; He, C. B. J. Mater. Chem., 2006, 16: 3540 11 Metrangolo, P.; Resnati, G.; Pilati, T.; Liantonio, R.; Meyer, F. J. Polym. Sci., Part A: Polym. Chem., 2007, 45: 1 12 Sourisseau, S.; Louvain, N.; Bi, W. H.; Mercier, N.; Rondeau, D.;
899 36 Bader, R. F. W. Atoms in molecules: a quantum theory. New York: Clarendon Press, 1990 37 Glendening, E. D.; Badenhoop, J. K.; Reed, A. E.; et al. Natural bond orbital program. Version 5.0. Madison, WI: Theoretical Chemistry Institute, University of Wisconsin, 2001 38 Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; et al. Gaussian 03, Revision B. 01. Pittsburgh, PA: Gaussian Inc., 2003 39 Kevin, E. R.; Pavel, H. J. Chem. Theory Comput., 2008, 4: 232 40 Bondi, A. J. Phys. Chem., 1964, 68: 441 41 Rowland, R. S.; Taylor, R. J. Phys. Chem., 1996, 100: 7384 42 Vorobyov, I.; Yappert, M. C.; DuPré, D. B. J. Phys. Chem. A, 2002, 106: 668 43 Hermansson, K. J. Phys. Chem. A, 2002, 106: 4695
Boucher, F.; Buzare, J. Y.; Legein, C. Chem. Mater., 2007, 19:
44 Rappe, A. K.; Bernstein, E. R. J. Phys. Chem. A, 2000, 104: 6117
600
45 Vila, A.; Vila, E.; Mosquera, R. A. Chem. Phys., 2006, 326: 401
13 Cariati, E.; Forni, A.; Biella, S.; Metrangolo, P.; Meyer, F.; Resnati, G.; Righetto, S.; Tordin, E.; Ugo, R. Chem. Commun., 2007: 2590 14 Politzer, P.; Murray, J. S.; Concha, M. C. J. Mol. Model., 2007, 13: 643 15 Sander, S. P.; Friedl, R. R.; Yung, Y. L. Science, 1989, 245: 1095
46 Popelier, P. L. A. J. Phys. Chem. A, 1998, 102: 1873 47 Zou, J. W.; Lu, Y. X.; Yu, Q. S.; Zhang, H. X.; Jiang, Y. J. Chin. J. Chem., 2006, 24: 1709 48 Lipkowski, P.; Grabowski, S. J.; Robinson, T. L.; Leszczynski, J. J. Phys. Chem. A, 2004, 108: 1086
ARTICLE
Structures and Electronic Properties of HOCl···HCOCl Complexes Yanzhi Liu1,*,
Lihong He1,
Kun Yuan1,
Lingling Lü1,
Yunpu Wang2
1
College of Life Science and Chemistry, Tianshui Normal University, Tianshui 741000, Gansu Province, P. R. China;
2
College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. China
Abstract:
B3LYP/6-311++G** and MP2/6-311++G** calculations were used to analyze the interaction between hypochlorous
acid (HOCl) and formyl chloride (HCOCl). The results showed that there were four equilibrium geometries (S1, S2, S3, and S4) optimized at B3LYP/6-311++G** level, and all the equilibrium geometries were confirmed to be in stable states by analytical frequency calculations. Complexes S1 and S3 use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift hydrogen bond systems. However, the blue-shifted hydrogen bond (2C−3H···6O) coexists with 4Cl···5O interaction in structures S2. As for S4, it uses the 7Cl atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift halogen bond system. Interaction energies between monomers in the four complexes corrected with basis set superposition error (BSSE) and zero-point vibrational energy (ZPVE) lie in the range from −5.05 to −14.76 kJ·mol−1 at MP2/6-311++G** level. The natural bond orbital (NBO) and atoms in molecules (AIM) theories have also been applied to explain the structures and the properties of the complexes. Key Words:
Hypochlorous acid; Formyl chloride; Noncovalent interaction; NBO theory; AIM theory
From a fundamental point of view, the complexes formed by the noncovalent interactions are significant per se as they bridge the gap between the free molecular systems and the corresponding condensed phases. Also, in recent years, noncovalent intermolecular interaction has been implicated as an important type of interaction in many different types of physical systems and is especially of great interest within the fields of biochemistry[1−8], material science[9−14], and atmospheric chemistry[15−17]. The noncovalent interactions, especially hydrogen bond and halogen bond, play roles in a wide variety of biochemical phenomena such as protein-ligand complexation[18] and are responsible for many novel properties of materials[11,12]. As an illustrative example related to the significance of noncovalent systems in atmospheric chemistry, the proposed very accurate quantum mechanical procedures aiming to explain ozone layer depletion involve formation of certain intermolecular complexes[15,16]. Halogen-containing species, not only chlorofluorocarbons, but also hypochlorous acid (HOCl) and in particular, halogen monoxide radical (ClO,
BrO), are also involved in ozone degradation[19−21]. HOCl has been detected in the upper stratosphere by mass spectrometry in clusters with nitric and sulfuric acids and their anions[22,23]. Furthermore, formyl chloride, HCOCl, is a product of important atmospheric reactions[24,25]. To understand the details of the reactions occurring in atmospheric conditions, it is necessary to study the structure, stability, and other certain properties of the intermolecular complex taking part in these reactions. Although the title complexes of the present work are of interest in the field of atmospheric chemistry, so far studies of noncovalent complexes of HOCl are limited to a number of systems combining HOCl with SO3[17], X−(X=Cl, Br)[26,27], H2O[28], HOO radical[29], and O3[30]. Despite the potential importance of both HOCl and HCOCl, to our best knowledge, neither theoretical nor experimental study of their possible interaction is available in the literature. In the absence of experimental information, a theoretical analysis of the possible existence of such complexes and their properties appear to be in order. However, we have chosen the
Received: March 13, 2008; Revised: May 24, 2008. *Corresponding author. Email: [email protected]. The project was supported by the Natural Science Foundation of Gansu Province, China (07-08-12). Copyright © 2008, Chinese Chemical Society and College of Chemistry and Molecular Engineering, Peking University. Published by Elsevier BV. All rights reserved. Chinese edition available online at www.whxb.pku.edu.cn
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
HCOCl and HOCl systems (as opposed to HCOF, HCOBr, HOBr for example) due to the ability of density functional theory (DFT) and ab initio methods to accurately calculate structures and energies for chlorine containing compounds[24,31]. The present work reports the electronic structure, stabilities, and properties of the title complexes in detail.
1
Calculation details
The geometries of the isolated HOCl and HCOCl moieties and their complexes were fully optimized using both standard and counterpoise-corrected (CP) B3LYP/6-311++G** levels. This method and basis set adequately describes noncovalent interaction systems[32,33], so it is reliable for the purpose of our study. Harmonic vibrational frequency calculations confirmed the structures as a minimum or transition state and enabled the evaluation of zero-point vibrational energies (ZPVE). Counterpoise-corrected procedure was used to correct the interaction energy for basis set superposition error (BSSE). In the scheme of the CP method, the binding energy of two molecules (A and B) can be expressed as follows[34]: ∆ECP=EAB(AB)−[EAeq(A)+EBeq(B)]−[EA(AB)+EB(AB)]+ [EA(A)+EB(B)] where EAB(AB) is the total energy of the complex, EYeq(Y) (Y=A or B) is the total energy of monomer Y with equilibrium geometry but without extended basis sets, and EY(AB) and EY(Y) are the total energy of monomer Y based on the same geometry as that in the complex with and without extended basis sets. At the same time, ZPVE correction is also considered. Natural bond orbital (NBO)[35] analysis and atoms in molecules (AIM) theory analysis[36] are featured wholly through a series of intermolecular interactions under the HOCl···HCOCl system. Natural bond orbital analysis was preformed via NBO 5.0 program[37], and the other calculations were performed using Gaussian 03 program[38].
2
Results and discussion
2.1
Geometric configuration
All possible geometries obtained by standard and CP opti-
Fig.1
mization on the surface of HCOCl+HOCl are depicted in Fig.1. The results show that there are four equilibrium geometries at B3LYP/6-311++G** level. And all the equilibrium geometries were confirmed to be in stable states by frequency analysis. S1 and S3 complexes use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor. As for S2 and S4, S2 uses the 3H and 4Cl atoms of HCOCl as proton donors and the terminal 6O atom of HOCl as their same acceptor. However, S4 uses the 7Cl atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor. S1, S3 belong to conventional hydrogen bond complexes; S4 belongs to halogen bond noncovalent complex. And hydrogen bond (C−H···O) and O···Cl interaction coexist in S2. Noncovalent interaction between two electronegative atoms such as O and Cl predicted here in S2 structure is consistent with previous investigations that reported existence of O···Cl interaction[30,39]. Some of the key geometrical parameters optimized for these complexes using B3LYP/6-311++G** level are also displayed in Fig.1. By comparing the data, we can find that the 6O−5H distances in S1 and S3 or 6O−7Cl distance in S4 increase obviously after formation of complexes. For example, 6O−5H distances in S1 and S3 increase by 0.0007 and 0.0006 nm, respectively; 6O−7Cl distance in S4 increases by 0.0004 nm. As for 2C−3H in S2, its length decreases by 0.0001 nm. Bondi[40] reported that van der Waals radii of Cl and O atoms were 0.175 and 0.152 nm, respectively, and Taylor[41] reported that van der Waals radii of H atom was 0.109 nm. Here, 7Cl···1O in S4 is 0.2882 nm; 5H···1O in S1 and in S3 are 0.1948 and 0.1956 nm; 3H···6O and 4Cl···6O distances in S2 are 0.2273 and 0.3239 nm, respectively. It is clear that these noncovalent interaction distances are all less than the sum of the relevant atoms′ van der Waals radii, and this is a necessary condition for formation of the hydrogen or halogen bond[8]. Although the distances between noncovalent atoms in four complexes calculated under CP correction optimization method enlarged (in italics in Fig.1), a similar trend could still be obtained. Also, it can be observed that the distances between proton donors and
Partial bond parameters of the monomers and complexes optimized at B3LYP/6-311++G** and CP correction (in italics) levels The lengths of the bonds are in nm.
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
Table 1 Complex S1 S2 S3 S4 a
Partial vibrational frequencies (cm−1) of the monomers (νc) and the complexes (νm) at B3LYP/6-311++G** level Vibrational mode
νm a
νca
∆νb
Approximate descriptionc,d
ν1
3776.2(79.4)
3651.8(522.8)
ν2
1226.4(37.7)
1312.1(59.1)
85.7
6O−5H rock in plane
ν1
3054.3(20.3)
3077.9(1.2)
23.6
2C−3H stretch
ν2
1328.3(32.2)
1315.5(48.7)
−12.8
ν1
3776.2(79.4)
3678.8(592.7)
−97.4
ν2
1226.4(37.7)
1298.7(52.6)
72.3
690.6(32.0)
−29.8
720.4(27.2)
ν1 −1
b
−124.4
6O−5H stretch
2C−3H rock in plane 6O−5H stretch 6O−5H rock in plane 6O−7Cl stretch
c
d
Infrared intensities (km·mol ) are in parentheses. ∆ν = νc−νm. Based on the calculated atomic displacements. For atomic number, see Fig.1.
acceptors in four complexes are in the order 5H···1O (in S1)<5H···1O (in S3)<3H···6O (in S2)<7Cl···1O (in S4). For the moment, the shorter the above distance, the more steady the complex. Further more, it should be noted that S1, S2, S3, and S4 all have planar configurations. 2.2 Vibrational frequencies, energies, and rotational constants The partial calculated frequencies of monomers and four complexes under B3LYP/6-311++G** level are listed in Table 1. It can be observed that the stretching frequencies of 6O−5H in S1 and S3 and 6O−7Cl in S4 have the red shifts. For example, compared with the monomer, 6O−5H stretching frequency decreases by 124.4 cm−1 in S1. However, the stretching frequencies of 2C−3H in S2 present a blue shift with 23.6 cm−1. Furthermore, we notice that the stretching vibrational intensities of the 6O−5H in S1 and S3 and 6O−7Cl in S4 are all enhanced after the formation of red shift hydrogen bond or halogen bond complex. In contrast, the stretching vibrational intensity of 2C−3H in S2 decreases obviously, which can be attributed to the polarizable ability of proton donor. Here, 6O−5H and 6O−7Cl are typical polar bonds and are easy to polarize, but 2C−3H bond is only with little polarity and is difficult to polarize. IR strength and electronic dipole at the corresponding vibration vector are correlative with square of displacement partial differentiation[42]. After formation of the complexes, the electronic dipoles of 6O−5H and 6O−7Cl bond increase but that of 2C−3H decreases. Thus, IR strengths of 6O−5H and 6O−7Cl increase, whereas that of 2C−3H decreases. In fact, the increase or decrease of stretching vibrational infrared intensity is regarded as a typical character in red shift or blue shift system[43]. Table 2 presents the total interaction energies (∆Etot) and the BSSE corrected interaction energies (∆ECP) for each complex. It can be observed that the interaction energies calculated using B3LYP method are higher (less negative) than those obtained using MP2 method. Because the interaction of the supermolecule is comprised of electrostatic force, dispersion force, and inductive effect, the dispersion force is not included in the B3LYP method (but B3LYP method has been proved reliable during the geometry optimization[27]); however,
we can get it from the MP2 method or the higher method[44]. Despite the basis set 6-311++G** that we chose is advantageous to the decrease of BSSE error, obviously, it is necessary to perform a CP correction. Both BSSE and ZPVE corrected interaction energies range between −5.05 and −14.76 kJ·mol−1 at MP2/6-311++G** level and −3.61 and −12.00 kJ·mol−1 at B3LYP/6-311++G** level. S1 and S3 are clearly the most strong bounds of the various complexes, with binding energies of –18.48 and −14.63 kJ·mol−1 after correction of BSSE at MP2/6-311++G** level. In contrast, the binding energies of S2 and S4 are only −11.19 and −7.06 kJ·mol−1 at the same computational level, respectively. Taking one with another, noncovalent interaction of halogen bond is obviously weaker than noncovalent interaction of hydrogen bond in the present study. According to the BSSE and ZPVE corrected interaction energies, which were calculated at MP2/6-311++G** level and listed in Table 2, we can conclude that the stabilities of the four complexes increase in the order of S4
Interaction energies in the four complexes
B3LYP/6-311++G**
MP2/6-3111++G**
∆Etot BSSE ∆ECP ∆ECP+ZPVE
∆Etot BSSE ∆ECP ∆ECP+ZPVE
S1
−19.20 2.30 −16.90 −12.00
−23.34 4.86 −18.48
−14.76
S2
−13.49 2.28 −11.21
−8.16
−19.30 8.11 −11.19
−8.69
S3
−17.91 1.98 −15.93 −11.25
−21.65 7.02 −14.63
−11.31
−12.32 5.26 −7.06
−5.05
S4
−7.74 1.83
−5.91
−3.61
∆Etot is the total interaction energy, ∆ECP is the interaction energy with BSSE correction, and ∆ECP+ZPVE is the interaction energy with both BSSE and ZPVE corrections. The energies are all in kJ·mol−1.
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
Table 3
HOMO energies (EHOMO), LUMO energies (ELUMO), and
Table 4
gap (∆ELUMO-HOMO) of the monomers and four complexes calculated
complexes calculated at B3LYP/6-311++G** level
at B3LYP/6-311++G** level
Compound
A
Species
ELUMO (a.u.)
EHOMO (a.u.)
∆ELUMO-HOMO (a.u.)
HOCl
609.728 (613.380)
HOCl
−0.1016
−0.3000
−
HCOCl
78.035
6.013
5.582
S1
10.366
0.779
0.725
S2
6.162
0.834
0.736
S3
9.213
0.752
0.696
27.274
0.658
0.643
HCOCl
−0.1015
−0.3149
−
S1
−0.0950
−0.2910
0.1960
S2
−0.1114
−0.3104
0.1990
S3
−0.0958
−0.2794
0.1836
S4
−0.0914
−0.2945
0.2031
S4
C 14.140 (14.725)
drogen bond and halogen bond, respectively. The interaction between filled orbitals in one subsystem and unfilled orbitals of another represents a deviation of the complex from its Lewis structure and can be used as a measure of the intermolecular delocalization, also called as hyperconjugation. The hyperconjugative interaction energy can be deduced from the second order perturbation approach[39]: σ* Fσ F2 =ησ ij E(2)=−ησ ∆E εσ * − εσ where Fij is the Fock matrix element between the i and j NBO orbitals, εσ and εσ* are the energies of σ and σ* orbitals, respectivey, and ησ is the population of the donor σ orbital. The interaction strength between monomers could be clarified according to second-order stabilization energy (E(2)) between proton donor and acceptor obtained from the NBO analysis. As NBO theory indicates, the larger the stabilization energy E(2), the stronger the interaction between donor and acceptor orbitals. In other words, the donor electrons are easier to transfer to the acceptor orbitals. In addition, the importance of the orbital hyperconjugation and electron density transfer (EDT) from electron donor orbital to electron acceptor orbital in noncovalent interaction systems are well known, which leads to an increase in population of electron acceptor antibonding orbital. This weakens the filled orbital bond and
NBO analysis
The analyses for the combining interaction between HCOCl and HOCl with the NBO method have been performed even at MP2/6-311++G** level. And the corresponding results are listed in Table 5. From the results of NBO analysis for the monomers, it can be suggested that the 5H and 7Cl atoms in HOCl carry significant amount (0.198e and 0.477e) of positive charge, whereas the 1O atom in HCOCl carries certain amount (−0.556e) of negative charge. Therefore, intermolecular interaction should take place in the 6O−5H···1O or 6O−7Cl···1O. This means that the noncovalent interaction involved in 6O−5H···1O and 6O−7Cl···1O can be defined as hyTable 5
B 14.475 (15.117)
Experimental values[30] are in parentheses.
the complexes, the values of ∆ELUMO-HOMO are in the order of S4>S2>S1>S3. The most stable complexes S1 and S3 have low ∆ELUMO-HOMO, which are 0.1960 and 0.1836 a.u., respectively. And as the most unstable complex S4 in the present study, the ∆ELUMO-HOMO is the highest (0.2031 a.u.). For the reason of completeness, the rotational constants for monomers and the complexes are also listed in Table 4 at B3LYP/6-311++G** computational level. The four complexes are asymmetric rotors and behave like prolate rotors, with A>B≈C. The calculated rotational constants for HOCl agree well with the experimental values[30]. 2.3
Rotational constants (in GHz) for monomers and four
NBO analysis of the monomers and the four complexes at MP2/6-311++G** level
Complexes
Monomers
S1
S2
S3
S4
E [n (1O)→σ (6O−5H)]/(kJ·mol )
−
E(2)[n1,2(6O)→σ*(2C−3H)]/(kJ·mol−1)
−
11.6, 18.9
−
15.5, 10.6
−
−
2.9, 5.8
−
E(2)[n2(4Cl)→σ*(6O−7Cl)]/(kJ·mol−1)
−
−
−
1.8
−
−
E(2)[n1,2(1O)→σ*(6O−7Cl)]/(kJ·mol−1)
−
−
−
−
2.4, 7.3
∆σ* a (6O−5H)/e
−
0.00856
−
0.00695
−
∆σ*(2C−3H)/e
−
−
−0.0037
−
−
∆σ*(6O−7Cl)/e
−
−
0.0021
−
0.00696
sp3.3, sp8.0
sp2.86, sp8.53
sp3.18, sp7.38
sp2.86, sp8.24
sp3.3, sp7.81
sp1.7, sp2.66
sp1.7, sp2.6
sp1.59, sp2.90
sp1.7, sp2.6
sp1.7, sp2.6
(2)
1,2
*
−1
spn(6O−5H or 7Cl) spn(2C−3H or 4Cl) b
∆{s(6O) in σ(6O−5H or 7Cl)} (%)
−
2.69, 3.52
0.76, 4.59
2.68, 3.49
0.06, 3.01
∆{s(2C) in σ(2C−3H or 4Cl)}c(%)
−
−0.37, 0.85
1.66, −1.67
−0.29, 0.73
−0.07, −0.27
a
change of natural population σ*; bchange of s-character of 6O hybrid orbital in σ(6O−5H or 7Cl) on the complexation; c
change of s-character of 2C hybrid orbital in σ(2C−3H or 4Cl) on the complexation
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
leads to its elongation and concomitant stretching frequency red shift. The above theory is applicable for HOCl···HCOCl system. In complex S1, the second-order stabilization energies (E(2)) of n1,2(1O)→σ*(6O−5H) are 11.6 and 18.9 kJ·mol−1, and natural population of σ*(6O−5H) increases by 0.00865e. 3D image of the interaction between n1,2(1O) and σ*(6O−5H) is given in Fig.2(a). In complex S3, similar to that of S1, there are high E(2) of n1,2(1O)→σ*(6O−5H), and an efficient overlap can be observed between the related orbitals (Fig.2(c)). As for complex S2 and S4, n1,2(6O)→σ*(2C−3H) and n1,2(1O)→ σ*(6O−7Cl) are the two main orbital interactions, respectively. Their E(2) values are relatively low, so the overlaps of the related orbitals are very small as shown in Fig.2(b,d). Different from red shift bonds, we can observe that the natural population of σ*(2C−3H) in S2 decreases by 0.0037e instead of increasing by some amounts; this shows that there has been electron density redistribution effect of HCOCl moiety in S2. Moreover, it can be observed from Table 5, s character of 2C in 2C−3H of HCOCl moiety increases after the formation of complex S2. Hence, we can conclude that the total of electron density redistribution and atom rehybridization effect exceed orbital hyperconjugation; thus, 2C−3H bond length decreases by 0.0001 nm, and its stretching frequency represents blue shift after the formation of complex. Further more, we observe that the total E(2) between natural bond orbitals in four complexes increases in the order of S4
Fig.2
orbitals in HOCl···HCOCl systems
presence of the hydrogen or halogen bond interactions in the four complexes. For example, in the hydrogen bond interaction (1O···5H) in complex S1, its ρ(r) is 0.0207 a.u., and its 2ρ(r) is 0.0929 a.u. (>0). This indicates that the charge density radiation at BCP and the hydrogen bond have more ionic property. As for halogen bond interaction in complex S4, the 2ρ(r) and ρ(r) of 1O···7Cl are similar to that of 1O···5H in S1. In addition, Lipkowski[48] pointed that the electron density and positive values of the Laplacian in hydrogen bond system should be in the range of 0.002−0.04 and 0.02−0.15 a.u.. Here, in hydrogen bond complexes of S1, S2, and S3, ρ(r) and 2ρ(r) all lie in the range of that suggested by Lipkowski. The value of ρ(r) is the measurement of the bond intensity. In general, the larger the ρ(r), the stronger is the bond. Here, the ρ(r) of hydrogen bond or halogen bond in the four complexes increases in the order of S4
AIM analysis
A topological analysis of the electron density was carried out using Bader′s theory of AIM[36]. This analysis has been applied to study the properties of a variety of interactions between atoms[45−47]. Especially, the properties of the electron density at bond critical points (BCP) for the binding interaction between HCOCl and HOCl were analyzed in present study. Table 6 lists the electron density (ρ(r)) at BCP and its Laplacian of electron density (2ρ(r)) and ellipticities (ε). λi (λ1, λ2, λ3) listed in Table 6 are the eigenvalues of the electron density Hessian matrix, and 2ρ(r)=λ1+λ2+λ3. From Table 6, we can observe that λ1<0, λ2<0, λ3>0 in each complex, according to Bader′s theory[36], they can be labeled as (3, −1) critical points, and christened BCP, which can indicate the Table 6
3D images of the main interactions between natural bond
Electron density topological properties at the intermolecular bond critical points of the four complexes calculated at MP2/6-311++G** level
a
a
Complex
Atom pair
ρ(r)
λ1
λ2
λ3
2ρ (r)
ε
Interaction distanceb
S1
1O···5H
0.0207
−0.0286
−0.0272
0.1490
0.0929
0.0500
0.1948
S2
6O···3H
0.0123
−0.0132
−0.0125
0.0741
0.0485
0.0560
0.2273
S2
6O···4Cl
0.0069
−0.0048
−0.0026
0.0373
0.0299
0.8454
0.3239
S3
1O···5H
0.0194
−0.0264
−0.0253
0.1428
0.0912
0.0423
0.1956
S4
1O···7Cl
0.0118
−0.0094
−0.0086
0.0676
0.0497
0.0934
0.2882
2
For atomic number, see Fig.1; ρ(r) is electron density of critical point; λi is Hessian eigenvalue; ρ(r) is density Laplacian; ε is ellipticity; ρ(r) and 2ρ(r) are in atom unit (a.u.); binteraction distance (nm) was calculated at B3LYP/6-311++G** level.
Yanzhi Liu et al. / Acta Physico-Chimica Sinica, 2008, 24(9): 1625−1630
would mainly represent σ property. Furthermore, all the intermolecular interactions present small values of the electron density and positive values of the Laplacian as an indication of closed shell interactions.
3
Conclusions
Theoretical calculations of the 1:1 complexes formed by HCOCl and HOCl have been carried out at B3LYP/ 6-311++G** and MP2/6-311++G** computational levels. Four stable configurations have been found at B3LYP/ 6-311++G** level. The theoretical analysis showed that the four complexes are composed by two red-shifted hydrogen bond (O−H···O) structures (S1 and S3), one co-exist of blueshifted hydrogen bond (C−H···O) and Cl···O interaction structure (S2), and one red-shifted halogen bond (O−Cl···O) structure (S4). According to the BSSE and ZPVE corrected interaction energies, which were calculated at MP2/6-311++G** level, it can be concluded that the stabilities of the four complexes increase in the order of S4
References 1 Lans, M. C.; Spiertz, C.; Brouwer, A.; Koeman, J. H. Eur. J. Pharmacol., 1994, 270: 129 2 Rablen, P. R.; Lockman, J. W.; Jorgensen, W. L. J. Phys. Chem. A, 1998, 102: 3782 3 Cai, Z. L.; Reimers, J. R. J. Phys. Chem. A, 2002, 106: 8769 4 Battistutta, R.; Mazzorana, M.; Sarno, S.; Kazimierczuk, Z.; Zanotti, G.; Pinna, L. A. Chem. Biol., 2005, 12: 1211 5 Himmel, D. M.; Das, K.; Clark, A. D.; Hughes, S. H.; Benjahad,
16 Calvert, J. G.; Lazrus, A.; Kok, G. L.; Heikes, B. G.; Walega, J. G.; Lind, J.; Cantrell, C. A. Nature, 1985, 317: 27 17 Solimannejad, M.; Pejov, L. J. Phys. Chem. A, 2005, 109: 825 18 Metrangolo, P.; Neukirch, H.; Pilati, T.; Resnati, G. Acc. Chem. Res., 2005, 38:386 19 Farman, J. C.; Gardiner, B. G.; Shanklin, J. D. Nature, 1985, 315: 207 20 Lehrer, E.; Hoenninger, G.; Platt, U. Atmos. Chem. Phys., 2004, 4: 2427 21 Aranda, A.; Le Bras, G.; La Verdet, G.; Poulet, G. Geophys. Res. Lett., 1997, 24: 2745 22 McCrumb, J. L.; Arnold, F. Nature, 1981, 294: 136 23 Schlager, H.; Arnold, F. Planet Space Sci., 1987, 35: 693 24 Drougas, E.; Kosmas, A. M.; JalbouA, F. T. J. Phys. Chem. A, 2004, 108: 5972 25 McGivern, W. S.; Kim, H.; Francisco, J. S.; North, S. W. J. Phys. Chem. A, 2004, 108: 7247 26 Francisco, J. S. Chem. Phys. Lett., 1996, 260: 485 27 Flowers, B. A.; Francisco, J. S. J. Phys. Chem. A, 2001, 105: 494 28 Ortiz-Repiso, M.; Escribano, R.; Gómez, P. C. J. Phys. Chem. A, 2000, 104: 600 29 Jalbout, A. F.; Li, X. H.; Solimannejad, M. Chem. Phys. Lett., 2006, 420: 204 30 Solimannejad, M.; Alkorta, I.; Elguero, J. Chem. Phys. Lett., 2007, 449: 23 31 Jalbout, A. F.; Nazari, F.; Turker, L. J. Mol. Struct. -Theochem, 2004, 671: 1 32 Su, M. D.; Chu, S. Y. J. Am. Chem. Soc., 1999, 121(17): 4229 33 King, B. F.; Weinhold, F. J. Chem. Phys., 1995, 103(1): 333
A.; Oumouch, S.; Guillemont, J.; Coupa, S.; Poncelet, A.; Csoka,
34 Liu, J. F.; Li, X. Y.; Zhu, Q. Int. J. Quantum Chem., 2004, 98: 33
I.;
35 Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev., 1988, 88:
Meyer, C.; Andries, K.; Nguyen, C. H.; Grierson, D. S.;
Arnold, E. J. Med. Chem., 2005, 48: 7582 6 Jiang, Y.; Alcaraz, A. A.; Chen, J. M.; Kobayashi, H.; Lu, Y. J.; Snyder, J. P. J. Med. Chem., 2006, 49: 1891 7 Trogdon, G.; Murray, J. S.; Concha, M. C.; Politzer, P. J. Mol. Model., 2007, 13: 313 8 Auffinger, P.; Hays, F. A.; Westhof, E.; Ho, P. S. Proc. Natl. Acad. Sci. USA, 2004, 101: 16789 9 Takeuchi, T.; Minato, Y. J.; Takase, M.; Shinmori, H. Tetrahedron Lett., 2005, 46: 9025 10 Xu, J. W.; Liu, X. M.; Ng, J. K. P.; Lin, T. T.; He, C. B. J. Mater. Chem., 2006, 16: 3540 11 Metrangolo, P.; Resnati, G.; Pilati, T.; Liantonio, R.; Meyer, F. J. Polym. Sci., Part A: Polym. Chem., 2007, 45: 1 12 Sourisseau, S.; Louvain, N.; Bi, W. H.; Mercier, N.; Rondeau, D.;
899 36 Bader, R. F. W. Atoms in molecules: a quantum theory. New York: Clarendon Press, 1990 37 Glendening, E. D.; Badenhoop, J. K.; Reed, A. E.; et al. Natural bond orbital program. Version 5.0. Madison, WI: Theoretical Chemistry Institute, University of Wisconsin, 2001 38 Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; et al. Gaussian 03, Revision B. 01. Pittsburgh, PA: Gaussian Inc., 2003 39 Kevin, E. R.; Pavel, H. J. Chem. Theory Comput., 2008, 4: 232 40 Bondi, A. J. Phys. Chem., 1964, 68: 441 41 Rowland, R. S.; Taylor, R. J. Phys. Chem., 1996, 100: 7384 42 Vorobyov, I.; Yappert, M. C.; DuPré, D. B. J. Phys. Chem. A, 2002, 106: 668 43 Hermansson, K. J. Phys. Chem. A, 2002, 106: 4695
Boucher, F.; Buzare, J. Y.; Legein, C. Chem. Mater., 2007, 19:
44 Rappe, A. K.; Bernstein, E. R. J. Phys. Chem. A, 2000, 104: 6117
600
45 Vila, A.; Vila, E.; Mosquera, R. A. Chem. Phys., 2006, 326: 401
13 Cariati, E.; Forni, A.; Biella, S.; Metrangolo, P.; Meyer, F.; Resnati, G.; Righetto, S.; Tordin, E.; Ugo, R. Chem. Commun., 2007: 2590 14 Politzer, P.; Murray, J. S.; Concha, M. C. J. Mol. Model., 2007, 13: 643 15 Sander, S. P.; Friedl, R. R.; Yung, Y. L. Science, 1989, 245: 1095
46 Popelier, P. L. A. J. Phys. Chem. A, 1998, 102: 1873 47 Zou, J. W.; Lu, Y. X.; Yu, Q. S.; Zhang, H. X.; Jiang, Y. J. Chin. J. Chem., 2006, 24: 1709 48 Lipkowski, P.; Grabowski, S. J.; Robinson, T. L.; Leszczynski, J. J. Phys. Chem. A, 2004, 108: 1086