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Theoretical investigations of the structures and electronic spectra of 8-hydroxylquinoline derivatives
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 464–468
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Theoretical investigations of the structures and electronic spectra of 8-hydroxylquinoline derivatives Pan Ning, Tiegang Ren, Yanxin Zhang, Jinglai Zhang ⇑ Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, China
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The ground state of the two groups
compounds were optimizated based on 6-31G (d) basis set of B3LYP method. UV absorption spectra are simulated through TD-DFT method with PCM model. Explained the red shift behavior in the electronic spectra of products. The reaction products of two sets of experiments are confirmed reasonably with theoretical calculations.
a r t i c l e
i n f o
Article history: Received 15 March 2013 Received in revised form 7 June 2013 Accepted 19 June 2013 Available online 1 July 2013 Keywords: B3LYP M06 8-Hydroxylquinoline Electronic spectra Red shift
a b s t r a c t The spectroscopic properties of 8-hydroxyquinoline derivatives are theoretically investigated by means of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The target molecules are divided into two groups: group (I): (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (A), together with corresponding potential reaction products of A with acetic acid, i.e., (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-yl acetate (AR1), and (E)-2(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)-8-hydroxyquinolinium (AR2); group (II): (E)-2-(2-(1(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (B), as well as potential reaction products of B with acetic acid, i.e., (E)-2-(2-(1-(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol4-yl)vinyl)quinolin-8-yl acetate (BR1), and (E)-2-(2-(1-(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl) vinyl)-8-hydroxyquinolinium (BR2). The geometries are optimized by B3LYP and M06 methods. The results indicate that product molecules tend to be effectively planar compared with reactants. Subsequently, UV absorption spectra are simulated through TD-DFT method with PCM model to further confirm the reasonable products of two reactions. AR2 and BR2 are identified as the target molecules through the experimental spectra for the real products. It is worth noting that the maximum absorption wavelengths of compounds AR2 and BR2 present prominent red shift compared the initial reactants A and B, respectively, which should be ascribed to the enhancive planarity of products that mentioned above and the decreased HOMO–LUMO energy gap. Geometric structures and optical properties for corresponding compounds are discussed in detail. Ó 2013 Elsevier B.V. All rights reserved.
Introduction As a family of very important quinoline compounds, 8-hydroxyquinoline derivatives have attracted considerable attention during ⇑ Corresponding author. Tel./fax: +86 378 3881589. E-mail address: [email protected] (J. Zhang). 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.06.063
the past three decades. This should be ascribed to their diverse spectrum of industrial applications and biological activities. They are not only used as substructures for synthesis of effective HIV1 integrase inhibitor or other bioactive compounds [1–4], but also have potential use in ion recognition for different metal ions [5– 11] and emission and electron conduction layers in organic light emitting devices [12].
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Previous experiments have reported that species and positions of substituent incorporated in the quinoline rings would make a difference in the bioactivities. Recently, a series of 8-hydroxyquinoline derivatives have synthesized by the author through incorporation of pyrazole group into different places. Interestingly, hyperchromicity was observed by the addition of acetic acid to two of the aforementioned derivatives (E)-2-(2-(3,5-dimethyl-1phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (A) and (E)-2-(2-(1(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (B). This noteworthy phenomenon addresses two questions: (i) Can (A) or (B) react with acetic acid? (ii) What causes the red-shift in the absorption bands? Because there is no definite experimental account for the two questions, we attempt to develop elucidation theoretically in this work. For clarity, a speculation is put forward that there exist two possible products in terms of reaction. (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-yl acetate (AR1) and (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)-8hydroxyquinolinium (AR2) are adopted as starting reactant A; (E)-2-(2-(1-(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)vinyl) quinolin-8-yl acetate (BR1), and (E)-2-(2-(1-(4-chlorophenyl)-3,5dimethyl-1H-pyrazol-4-yl)vinyl)-8-hydroxyquinoli-nium (BR2) are regarded as reactant B. Optimizations of the six above mentioned compounds are performed by the density functional theory (DFT) method. Next, time-dependent density functional theory (TDDFT) method is employed to obtain the absorption spectra with the DFT-optimized structures. We will demonstrate that the theoretical investigation can help us to identify the reasonable reaction products of compounds A and B in acetic acid, and elucidate spectroscopic properties of product molecules.
(TD-DFT) [20–22] with cc-pVDZ [23–25] basis set to obtain the absorption spectra. Considering that solvent effect plays an important role in spectroscopic properties of organic molecules, the polarized continuum model (PCM) [26,27] with methanol chosen from the available experiment has been employed to assess the solvent effects as implemented within the solvent reaction field using the optimized equilibrium structures in the gas phase. Applications of TD-DFT approaches in conjunction with PCM model for organic conjugated molecules have been reported and get considerable good results [28]. All theoretical calculations are carried out by using the Gaussian 09 [29] program package. Results and discussion Geometries and stabilities The schematic structures of compounds in group (I) and group (II) are depicted in Fig. S1 (see Supplementary information). Primary geometric parameters (selected bonds lengths, angles and dihedral angles) optimized by B3LYP and M06 methods with 631G(d) basis set are tabulated in Tables 1 and 2, respectively. As no experimental parameters for title compounds are available for direct comparison, two different functionals are selected to ensure the reliability of theoretical results. The maximum discrepancy between B3LYP and M06 calculations is within 0.02 Å for bond length and 2° for angle, which suggests that the selected DFT methods could reasonably describe the geometries. According to the primary geometric parameters in Table 1, no significant changes are examined in product AR1. While in terms of AR2, it is interested that the bond lengths connecting the quinoline ring and the pyrazole ring are averaged with the double bond C11AC12 elongated by 0.021 Å and C8AC11 and C12AC13 shortened by 0.036 and 0.031 Å, respectively. Another remarkable variation with dihedral angle C11AC12AC13AC18 being 173.92° at M06 optimizations expands the delocalization of the conjugated systems, which is expected to contribute to the average tendency of related bond lengths. The same behavior takes place in group (II) compounds as displayed in Table 2, which will not be discussed in detail any more. The absence of single crystal for X-ray diffraction data brings about the challenge to verify the structures of products, thus spectroscopic properties are needed to be investigated further.
Computational methods Two quantum mechanical models based on DFT, namely, B3LYP [13–16] and M06 [17], are utilized to optimize the equilibrium geometries of two reactants, i.e., A and B, and four possible products, i.e., AR1, AR2, BR1, and BR2 in the 1A electronic ground state. All geometry optimizations are performed without any symmetry constraints. 6-31G(d) [18,19] basis set is adopted in the geometry optimizations for all compounds. The computation of vibrational frequencies is undertaken at the same level to verify the nature of optimized stationary points. The nature of low-lying excited states is explored using time-dependent density functional theory
Table 1 Primary geometric parameters (bond lengths in Å, angles and dihedral angles in °) for compounds A, AR1 and AR2 in the ground state optimized at different levels of theory. Atom number
A
AR1
B3LYP C3AC4 C3AO14 C4AC5 C4AN7 N7AC8 C8AC11 C11AC12 C12AC13 N16AN17 N16AC19 O14AC3AC4 C3AC4AN7 N7AC8AC11 C9AC8AC11 C12AC13AC18 C6AC5AC4AN7 C8AC11AC12AC13 C11AC12AC13AC18 N17AN16AC19AC20
1.4342 1.3602 1.4307 1.3556 1.3313 1.4643 1.3526 1.4497 1.3688 1.4215 116.96 118.67 115.15 123.15 125.13 180.00 178.87 163.25 139.25
M06 1.4287 1.3500 1.4229 1.3507 1.3245 1.4582 1.3468 1.4445 1.3611 1.4159 116.91 118.59 115.38 122.62 125.80 179.73 178.08 159.44 141.10
B3LYP 1.4264 1.3878 1.4300 1.3563 1.3315 1.4635 1.3529 1.4487 1.3688 1.4221 119.08 119.02 115.30 123.00 125.18 179.04 178.96 163.10 138.79
AR2 M06 1.4213 1.3763 1.4211 1.3528 1.3253 1.4578 1.3474 1.4424 1.3613 1.4166 118.19 118.80 115.82 122.21 125.19 178.99 178.80 161.63 139.93
B3LYP 1.4121 1.3630 1.4140 1.3779 1.3576 1.4282 1.3733 1.4185 1.3795 1.4312 115.16 119.52 117.70 126.29 124.45 180.00 179.50 174.75 130.94
M06 1.4061 1.3532 1.4070 1.3745 1.3519 1.4222 1.3674 1.4136 1.3711 1.4260 115.22 119.49 117.43 126.33 125.04 179.96 179.87 173.92 132.22
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Table 2 Primary geometric parameters (bond lengths in Å, angles and dihedral angles in °) for compounds B, BR1 and BR2 in the ground state optimized at different levels of theory. Atom number
B
BR1
B3LYP C3AC4 C3AO14 C4AC5 C4AN7 N7AC8 C8AC11 C11AC12 C12AC13 N16AN17 N16AC19 C22ACl25 O14AC3AC4 C3AC4AN7 N7AC8AC11 C9AC8AC11 C12AC13AC18 C6AC5AC4AN7 C8AC11AC12AC13 C11AC12AC13AC18 N17AN16AC19AC20
M06
1.4342 1.3600 1.4308 1.3555 1.3310 1.4647 1.3522 1.4505 1.3691 1.4186 1.7578 116.96 118.67 115.08 123.17 125.22 179.98 178.82 161.80 140.76
BR2
B3LYP
1.4288 1.3500 1.4230 1.3515 1.3245 1.4589 1.3467 1.4440 1.3616 1.4134 1.7476 116.95 118.70 115.52 122.44 125.24 179.85 178.19 162.26 140.69
M06
1.4264 1.3876 1.4300 1.3564 1.3312 1.4641 1.3526 1.4494 1.3695 1.4190 1.7573 119.12 119.03 115.26 122.98 125.08 179.09 179.34 161.99 140.28
B3LYP
1.4208 1.3764 1.4209 1.3521 1.3249 1.4575 1.3469 1.4437 1.3617 1.4137 1.7468 118.14 118.77 115.35 122.65 125.58 179.15 179.48 160.35 141.05
M06
1.4122 1.3627 1.4142 1.3778 1.3572 1.4293 1.3725 1.4198 1.3794 1.4288 1.7474 115.18 119.54 117.68 126.29 124.43 179.98 179.60 174.63 131.80
1.4068 1.3529 1.4070 1.3752 1.3518 1.4238 1.3668 1.4142 1.3711 1.4239 1.7369 115.27 119.63 117.81 125.92 124.63 179.99 179.37 175.72 130.58
Table 3 Calculated absorption wavelength (k) and oscillator strength (f ) of compounds in group (I) and group (II) at different levels in methanol solvent, along with the available experimental values. Compounds
A
AR1
AR2
B
BR1
BR2
a b
PCM-TD-B3LYP
PCM-TD-M06
Exp.
k (nm)
f
ka (nm)
fa
kb (nm)
fb
k (nm)
e
363.10 315.46 281.54 252.31 366.90 324.16 247.57 421.86 327.61 284.49 253.46 363.89 316.23 290.29 252.21 366.61 303.69 250.79 422.88 327.21 288.95 257.90
1.0616 0.5116 0.0443 0.1416 1.0635 0.2064 0.3347 1.1870 0.4304 0.1272 0.1287 1.0934 0.5007 0.0390 0.2063 1.1356 0.2050 0.2708 1.2147 0.4487 0.0989 0.1087
358.64 310.45 272.21 247.43 360.27 297.42 243.42 414.55 319.25 274.94
1.0735 0.5237 0.0645 0.2222 1.1537 0.3220 0.2751 1.2624 0.3457 0.1363
355.05 308.10 270.11 245.70 356.63 295.99 241.90 411.70 317.29 273.12
1.0319 0.5121 0.0615 0.2368 1.1460 0.3267 0.2197 1.2393 0.3472 0.1426
336.5 304.0
0.6449 1.0221
252.5
0.7418
359.15 311.00 279.30 244.47 359.96 298.40 244.38 414.77 318.69 279.91 251.56
1.1086 0.5265 0.0585 0.3153 1.2225 0.3542 0.4410 1.2983 0.3650 0.1135 0.0967
355.94 308.71 277.23 243.14 357.33 297.17 242.92 410.15 316.10 278.97 249.89
1.1008 0.5156 0.0465 0.3262 1.2005 0.3538 0.2935 1.2827 0.3620 0.1133 0.1161
340.5 302.0
1.1800 1.9236
252.0
1.2651
396.0–401.0 305.0–322.5 255.0–266.0
396.5–401.0 306.0–321.5 256.5–265.0
TD-M06/cc-pVDZ//B3LYP/6-31G(d). TD-M06/cc-pVDZ//M06/6-31G(d).
Calculations based on B3LYP/6-31G(d) level of theory suggest that the lowest vibrational frequencies are 15.4075, 11.8047, and 17.5071 cm 1 for group (I) (A, AR1, and AR2, respectively) and 15.4204, 11.0031 and 17.6469 cm 1 for group (II) (B, BR1 and BR2, respectively). The absence of imaginary frequency indicates that the optimized structures of all the compounds in Fig. S1 are local minima on the potential energy surfaces (PES). Electronic spectra The absorption wavelengths (k) and oscillator strengths (f ) for the two groups of compounds computed using the TD-B3LYP and TD-M06 methods with cc-pVDZ basis set are given in Table 3. The experimental values are also listed for direct comparison.
The PCM model is used in the Gaussian calculations to simulate reasonable spectra with methanol as the solvent. The comparison of theoretical and experimental UV spectra of all title compounds can be seen in Fig. S2 (see Supplementary information). In combination of theoretical data in Table 3 and simulated UV absorption spectra in Fig. S2, it is easily found that spectroscopic properties of AR2 and BR2 reproduce the experimental spectra very well, while those of compounds AR1 and BR1 are unable to describe the observations in experiment. Consequently, we come to the conclusion that it is the hydrogen ion in acetic acid participates in the reaction with reactants A or B, which ultimately yields corresponding products AR2 or BR2. In addition, as is shown in Fig. S2, the absorption spectra of compounds A, AR2, B, and BR2 simulated by TD-M06 method
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Table 4 Calculated absorption wavelength (k), oscillator strength (f ), symmetry, and assignments for orbitals involved in the UV–vis absorption peaks at TD-M06 level, along with the available experimental values. Compounds
A
AR2
B
BR2
State
X1A 21A 41A 71A 111A X1A 21A 51A 81A X1A 21A 41A 61A 131A X1A 21A 51A 71A 131A
Transition
(89a)2(90a)2(91a)0 90a ? 91a 90a ? 92a 89a ? 92a 87a ? 91a (89a)2(90a)2(91a)0 90a ? 91a 90a ? 92a 86a ? 91a (97a)2(98a)2(99a)0 98a ? 99a 98a ? 100a 98a ? 101a 96a ? 101a (97a)2(98a)2(99a)0 98a ? 99a 98a ? 100a 97a ? 100a 96a ? 100a
Absorption
Exp.
k (nm)
f
k (nm)
e
355.05 308.10 270.11 245.70
1.0319 0.5121 0.0615 0.2368
336.5 304.0
0.6449 1.0221
252.5
0.7418
411.70 317.29 273.12
1.2393 0.3472 0.1426
396.0–401.0 305.0–322.5 255.0–266.0
355.94 308.71 277.23 243.14
1.1008 0.5156 0.0465 0.3262
340.5 302.0
1.1800 1.9236
252.0
1.2651
410.15 316.10 278.97 249.89
1.2827 0.3620 0.1133 0.1161
396.5–401.0 306.0–321.5 256.5–265.0
Fig. 1. The experimental and theoretical UV–vis spectra of compound (a) A, (b) AR2, (c) B, and (d) BR2 in methanol with calculated data at the TD-M06/cc-pVDZ level.
considering solvent effect is consistent with experimental absorption spectra better than the values obtained by TD-B3LYP method, and is independent of the ground-state geometries. Therefore, the following discussion about molecular orbitals and spectroscopy will be concentrated on the result obtained at TD-M06//M06 level as an example.
The frontier molecular orbitals To explore the absorption bands intrinsically, it is useful to examine the properties and composition of HOMO (the highest occupied molecular orbital) and LUMO (the lowest virtual molecular orbital), which determine the electronic excitation and transition characters. So the calculations for molecular orbitals are
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performed by M06 method with the ground-state geometries at the same level. For intuition, the contour plots for HOMO and LUMO orbitals involved in the electronic transitions of every species are displayed in Fig. S3. Visual inspection of their three-dimensional representations immediately reveal that all compounds presented large-scale of typically p-conjugated character as well as partial p orbital of oxygen atom for HOMOs; LUMOs are mainly constituted by p anti-bonding orbitals. According to the energy levels corresponding to homologous frontier orbitals, the HOMO–LUMO energy gap value e for product AR2 is decreased by 0.545 eV compared with that of reactant A (e = 3.673 and 4.218 eV for AR2 and A, respectively). Similarly, the e-value of compound BR2 is smaller than that of B. The decrement of e-value is speculated to be correlated with the aforementioned enhancive planarity of the product molecules, which in turn should be responsible for the increasing maximum absorption wavelength k of compounds AR2 and BR2. Absorption spectra In combination of the criteria of both the vertical excitation energies and oscillator strengths for dominant absorption bands, we make reasonable assignments of theoretical transitions to the bands observed in experiment. For clarity, the detailed data and simulated UV–vis spectra for four compounds A, AR2, B, and BR2 calculated at TD-M06/cc-pVDZ//M06/6-31G(d) level are shown in Table 4 and Fig. 1, respectively. The theoretical spectrum of compound A includes one intense absorption peak at 355.05 nm (f = 1.0319), one moderate peak at 308.10 nm (f = 0.5121), and one relative weak absorption band at 245.70 nm (f = 0.2368). The lowest-energy absorption arises from the transition HOMO (MO 90) ? LUMO (MO 91) and is related to the experimental peak at 336.5 nm. The moderate absorption peak at 308.10 nm, correlated to the 304.0 nm in the experimental UV– vis spectrum, is originated from transition HOMO (MO 90) to LUMO+1 (MO 92). The highest-energy absorption at 245.70 nm is derived from HOMO 3 to LUMO transition and corresponds to the observed peak at 252.5 nm. With the participation of acetic acid in the reaction with A, however, obvious red shift is examined with electronic absorption peaks located at 273.12, 317.29, and 411.70 nm for product AR2. As for compound B, the points in common with A are: (i) There also exists three observable absorption peaks lying at 355.94, 308.71, and 243.14 nm, respectively; (ii) After reaction, the absorption bands of product BR2, especially for the lowest-energy absorption, present prominent red shift. In terms of molecular orbital analysis, all the electronic transitions for two groups of compounds are basically originated from p ? p promotion accompanied by minor p ? p transition. By comprehensive consideration of geometric structures and electronic transitions, the spectroscopic changes corresponding to reactants and correlative products are supposed to be attributed to both the enlarged conjugated system caused by enhancive molecular planarity and the decreased HOMO–LUMO energy gap. Conclusions The structures and electronic spectra of two groups of pyrazole quinoline compounds in solution are investigated by using DFT and TD-DFT methods in this paper. For one thing, the TD-M06 simulated UV–vis spectra show fairly good performance as compared with the experimental observations. For another, the reaction products of two sets of experiments are confirmed reasonably with theoretical calculations. Furthermore, explanations for red shift
behavior in the electronic spectra of products are made based on structural changes and molecular orbitals involved in the electronic transitions. It is expected that our calculations help to understand the structural and optical properties of relevant systems in further experiments. Acknowledgments The authors gratefully thank the State Key Laboratory of Physical Chemistry of Solid Surfaces of Xiamen University for providing computational resources and the National Science Foundation of China (Grant No. 21003036) and Science Foundation of Henan University (Grant No. SBGJ090507) for financial supports. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2013.06.063. References [1] K. Mekouar, J.F. Mouscadet, D. Desmaële, F. Subra, H. Leh, D. Savouré, C. Auclair, J. d’Angelo, J. Med. Chem. 41 (1998) 2846–2857. [2] M. Ouali, C. Laboulais, H. Leh, D. Gill, D. Desmaële, K. Mekouar, F. Zouhiri, J. d’Angelo, C. Auclair, J.F. Mouscadet, M.L. Bret, J. Med. Chem. 43 (2000) 1949– 1957. [3] M.A. Rafiee, T. Partoee, Bull. Korean Chem. Soc. 32 (2011) 208–212. [4] J.F. Mouscadet, D. Desmaële, Molecules 15 (2010) 3048–3078. [5] X.H. Jiang, B.D. Wang, Z.Y. Yang, Y.C. Liu, T.R. Li, Z.C. Liu, Inorg. Chem. Commun. 14 (2011) 1224–1227. [6] Y.G. Zhao, Z.H. Lin, H.P. Liao, C.Y. Duan, Q.J. Meng, Inorg. Chem. Commun. 9 (2006) 966–968. [7] G.C. Ragos, M.A. Demertzis, P.B. Issopoulos, IL Farmaco 53 (1998) 611–616. [8] L. Shi, W. Song, Y. Li, D.W. Li, K.N. Swanick, Z.F. Ding, Y.T. Long, Talanta 84 (2011) 900–904. [9] J.M. Yu, P.A. Bentley, W. Wang, Tetrahedron Lett. 47 (2006) 2447–2449. [10] H. Wang, W.S. Wang, H.S. Zhang, Spectrochim. Acta Part A 57 (2001) 2403– 2407. [11] Y.F. Cheng, D.T. Zhao, M. Zhang, Z.Q. Liu, Y.F. Zhou, T.M. Shu, F.Y. Li, T. Yi, C.H. Huang, Tetrahedron Lett. 47 (2006) 6413–6416. [12] J.P. Wei, H.P. Zeng, D.F. Xu, J. Liu, Chin. J. Chem. 26 (2008) 1299–1304. [13] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785–789. [14] B. Miehlich, A. Savin, H. Stoll, H. Preuss, Chem. Phys. Lett. 157 (1989) 200–206. [15] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5652. [16] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J. Frich, J. Phys. Chem. 98 (1994) 11623–11627. [17] T. Yanai, D.P. Tew, N.C. Handy, Chem. Phys. Lett. 393 (2004) 51–57. [18] M.M. Francl, W.J. Pietro, W.J. Hehre, J.S. Binkley, M.S. Gordon, D.J. DeFrees, J.A. Pople, J. Chem. Phys. 77 (1982) 3654–3665. [19] P.C. Hariharan, J.A. Pople, Theor. Chim. Acta 28 (1973) 213–222. [20] R. Bauernschmitt, R. Ahlrichs, Chem. Phys. Lett. 256 (1996) 454–464. [21] M.E. Casida, C. Jamorski, K.C. Casida, D.R. Salahub, J. Chem. Phys. 108 (1998) 4439–4449. [22] R.E. Stratmann, G.E. Scuseria, M.J. Frisch, J. Chem. Phys. 109 (1998) 8218–8224. [23] T.H. Dunning Jr., J. Chem. Phys. 90 (1989) 1007–1023. [24] R.A. Kendall, T.H. Dunning Jr., R.J. Harrison, J. Chem. Phys. 96 (1992) 6796– 6806. [25] A.K. Wilson, D.E. Woon, K.A. Peterson, T.H. Dunning Jr., J. Chem. Phys. 110 (1999) 7667–7676. [26] Š. Miertus, E. Scrocco, J. Tomasi, Chem. Phys. 55 (1981) 117–129. [27] J. Tomasi, M. Persico, Chem. Rev. 94 (1994) 2027–2094. [28] E.A. Perpète, F. Maurel, D. Jacquemin, J. Phys. Chem. A 111 (2007) 5528–5535. [29] 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, Ö. Farkas, J.B. Foresman, J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian, Inc., Wallingford CT, 2009.
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Theoretical investigations of the structures and electronic spectra of 8-hydroxylquinoline derivatives Pan Ning, Tiegang Ren, Yanxin Zhang, Jinglai Zhang ⇑ Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, China
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The ground state of the two groups
compounds were optimizated based on 6-31G (d) basis set of B3LYP method. UV absorption spectra are simulated through TD-DFT method with PCM model. Explained the red shift behavior in the electronic spectra of products. The reaction products of two sets of experiments are confirmed reasonably with theoretical calculations.
a r t i c l e
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Article history: Received 15 March 2013 Received in revised form 7 June 2013 Accepted 19 June 2013 Available online 1 July 2013 Keywords: B3LYP M06 8-Hydroxylquinoline Electronic spectra Red shift
a b s t r a c t The spectroscopic properties of 8-hydroxyquinoline derivatives are theoretically investigated by means of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The target molecules are divided into two groups: group (I): (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (A), together with corresponding potential reaction products of A with acetic acid, i.e., (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-yl acetate (AR1), and (E)-2(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)-8-hydroxyquinolinium (AR2); group (II): (E)-2-(2-(1(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (B), as well as potential reaction products of B with acetic acid, i.e., (E)-2-(2-(1-(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol4-yl)vinyl)quinolin-8-yl acetate (BR1), and (E)-2-(2-(1-(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl) vinyl)-8-hydroxyquinolinium (BR2). The geometries are optimized by B3LYP and M06 methods. The results indicate that product molecules tend to be effectively planar compared with reactants. Subsequently, UV absorption spectra are simulated through TD-DFT method with PCM model to further confirm the reasonable products of two reactions. AR2 and BR2 are identified as the target molecules through the experimental spectra for the real products. It is worth noting that the maximum absorption wavelengths of compounds AR2 and BR2 present prominent red shift compared the initial reactants A and B, respectively, which should be ascribed to the enhancive planarity of products that mentioned above and the decreased HOMO–LUMO energy gap. Geometric structures and optical properties for corresponding compounds are discussed in detail. Ó 2013 Elsevier B.V. All rights reserved.
Introduction As a family of very important quinoline compounds, 8-hydroxyquinoline derivatives have attracted considerable attention during ⇑ Corresponding author. Tel./fax: +86 378 3881589. E-mail address: [email protected] (J. Zhang). 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.06.063
the past three decades. This should be ascribed to their diverse spectrum of industrial applications and biological activities. They are not only used as substructures for synthesis of effective HIV1 integrase inhibitor or other bioactive compounds [1–4], but also have potential use in ion recognition for different metal ions [5– 11] and emission and electron conduction layers in organic light emitting devices [12].
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Previous experiments have reported that species and positions of substituent incorporated in the quinoline rings would make a difference in the bioactivities. Recently, a series of 8-hydroxyquinoline derivatives have synthesized by the author through incorporation of pyrazole group into different places. Interestingly, hyperchromicity was observed by the addition of acetic acid to two of the aforementioned derivatives (E)-2-(2-(3,5-dimethyl-1phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (A) and (E)-2-(2-(1(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)vinyl)quinolin-8-ol (B). This noteworthy phenomenon addresses two questions: (i) Can (A) or (B) react with acetic acid? (ii) What causes the red-shift in the absorption bands? Because there is no definite experimental account for the two questions, we attempt to develop elucidation theoretically in this work. For clarity, a speculation is put forward that there exist two possible products in terms of reaction. (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)quinolin-8-yl acetate (AR1) and (E)-2-(2-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)vinyl)-8hydroxyquinolinium (AR2) are adopted as starting reactant A; (E)-2-(2-(1-(4-chlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)vinyl) quinolin-8-yl acetate (BR1), and (E)-2-(2-(1-(4-chlorophenyl)-3,5dimethyl-1H-pyrazol-4-yl)vinyl)-8-hydroxyquinoli-nium (BR2) are regarded as reactant B. Optimizations of the six above mentioned compounds are performed by the density functional theory (DFT) method. Next, time-dependent density functional theory (TDDFT) method is employed to obtain the absorption spectra with the DFT-optimized structures. We will demonstrate that the theoretical investigation can help us to identify the reasonable reaction products of compounds A and B in acetic acid, and elucidate spectroscopic properties of product molecules.
(TD-DFT) [20–22] with cc-pVDZ [23–25] basis set to obtain the absorption spectra. Considering that solvent effect plays an important role in spectroscopic properties of organic molecules, the polarized continuum model (PCM) [26,27] with methanol chosen from the available experiment has been employed to assess the solvent effects as implemented within the solvent reaction field using the optimized equilibrium structures in the gas phase. Applications of TD-DFT approaches in conjunction with PCM model for organic conjugated molecules have been reported and get considerable good results [28]. All theoretical calculations are carried out by using the Gaussian 09 [29] program package. Results and discussion Geometries and stabilities The schematic structures of compounds in group (I) and group (II) are depicted in Fig. S1 (see Supplementary information). Primary geometric parameters (selected bonds lengths, angles and dihedral angles) optimized by B3LYP and M06 methods with 631G(d) basis set are tabulated in Tables 1 and 2, respectively. As no experimental parameters for title compounds are available for direct comparison, two different functionals are selected to ensure the reliability of theoretical results. The maximum discrepancy between B3LYP and M06 calculations is within 0.02 Å for bond length and 2° for angle, which suggests that the selected DFT methods could reasonably describe the geometries. According to the primary geometric parameters in Table 1, no significant changes are examined in product AR1. While in terms of AR2, it is interested that the bond lengths connecting the quinoline ring and the pyrazole ring are averaged with the double bond C11AC12 elongated by 0.021 Å and C8AC11 and C12AC13 shortened by 0.036 and 0.031 Å, respectively. Another remarkable variation with dihedral angle C11AC12AC13AC18 being 173.92° at M06 optimizations expands the delocalization of the conjugated systems, which is expected to contribute to the average tendency of related bond lengths. The same behavior takes place in group (II) compounds as displayed in Table 2, which will not be discussed in detail any more. The absence of single crystal for X-ray diffraction data brings about the challenge to verify the structures of products, thus spectroscopic properties are needed to be investigated further.
Computational methods Two quantum mechanical models based on DFT, namely, B3LYP [13–16] and M06 [17], are utilized to optimize the equilibrium geometries of two reactants, i.e., A and B, and four possible products, i.e., AR1, AR2, BR1, and BR2 in the 1A electronic ground state. All geometry optimizations are performed without any symmetry constraints. 6-31G(d) [18,19] basis set is adopted in the geometry optimizations for all compounds. The computation of vibrational frequencies is undertaken at the same level to verify the nature of optimized stationary points. The nature of low-lying excited states is explored using time-dependent density functional theory
Table 1 Primary geometric parameters (bond lengths in Å, angles and dihedral angles in °) for compounds A, AR1 and AR2 in the ground state optimized at different levels of theory. Atom number
A
AR1
B3LYP C3AC4 C3AO14 C4AC5 C4AN7 N7AC8 C8AC11 C11AC12 C12AC13 N16AN17 N16AC19 O14AC3AC4 C3AC4AN7 N7AC8AC11 C9AC8AC11 C12AC13AC18 C6AC5AC4AN7 C8AC11AC12AC13 C11AC12AC13AC18 N17AN16AC19AC20
1.4342 1.3602 1.4307 1.3556 1.3313 1.4643 1.3526 1.4497 1.3688 1.4215 116.96 118.67 115.15 123.15 125.13 180.00 178.87 163.25 139.25
M06 1.4287 1.3500 1.4229 1.3507 1.3245 1.4582 1.3468 1.4445 1.3611 1.4159 116.91 118.59 115.38 122.62 125.80 179.73 178.08 159.44 141.10
B3LYP 1.4264 1.3878 1.4300 1.3563 1.3315 1.4635 1.3529 1.4487 1.3688 1.4221 119.08 119.02 115.30 123.00 125.18 179.04 178.96 163.10 138.79
AR2 M06 1.4213 1.3763 1.4211 1.3528 1.3253 1.4578 1.3474 1.4424 1.3613 1.4166 118.19 118.80 115.82 122.21 125.19 178.99 178.80 161.63 139.93
B3LYP 1.4121 1.3630 1.4140 1.3779 1.3576 1.4282 1.3733 1.4185 1.3795 1.4312 115.16 119.52 117.70 126.29 124.45 180.00 179.50 174.75 130.94
M06 1.4061 1.3532 1.4070 1.3745 1.3519 1.4222 1.3674 1.4136 1.3711 1.4260 115.22 119.49 117.43 126.33 125.04 179.96 179.87 173.92 132.22
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Table 2 Primary geometric parameters (bond lengths in Å, angles and dihedral angles in °) for compounds B, BR1 and BR2 in the ground state optimized at different levels of theory. Atom number
B
BR1
B3LYP C3AC4 C3AO14 C4AC5 C4AN7 N7AC8 C8AC11 C11AC12 C12AC13 N16AN17 N16AC19 C22ACl25 O14AC3AC4 C3AC4AN7 N7AC8AC11 C9AC8AC11 C12AC13AC18 C6AC5AC4AN7 C8AC11AC12AC13 C11AC12AC13AC18 N17AN16AC19AC20
M06
1.4342 1.3600 1.4308 1.3555 1.3310 1.4647 1.3522 1.4505 1.3691 1.4186 1.7578 116.96 118.67 115.08 123.17 125.22 179.98 178.82 161.80 140.76
BR2
B3LYP
1.4288 1.3500 1.4230 1.3515 1.3245 1.4589 1.3467 1.4440 1.3616 1.4134 1.7476 116.95 118.70 115.52 122.44 125.24 179.85 178.19 162.26 140.69
M06
1.4264 1.3876 1.4300 1.3564 1.3312 1.4641 1.3526 1.4494 1.3695 1.4190 1.7573 119.12 119.03 115.26 122.98 125.08 179.09 179.34 161.99 140.28
B3LYP
1.4208 1.3764 1.4209 1.3521 1.3249 1.4575 1.3469 1.4437 1.3617 1.4137 1.7468 118.14 118.77 115.35 122.65 125.58 179.15 179.48 160.35 141.05
M06
1.4122 1.3627 1.4142 1.3778 1.3572 1.4293 1.3725 1.4198 1.3794 1.4288 1.7474 115.18 119.54 117.68 126.29 124.43 179.98 179.60 174.63 131.80
1.4068 1.3529 1.4070 1.3752 1.3518 1.4238 1.3668 1.4142 1.3711 1.4239 1.7369 115.27 119.63 117.81 125.92 124.63 179.99 179.37 175.72 130.58
Table 3 Calculated absorption wavelength (k) and oscillator strength (f ) of compounds in group (I) and group (II) at different levels in methanol solvent, along with the available experimental values. Compounds
A
AR1
AR2
B
BR1
BR2
a b
PCM-TD-B3LYP
PCM-TD-M06
Exp.
k (nm)
f
ka (nm)
fa
kb (nm)
fb
k (nm)
e
363.10 315.46 281.54 252.31 366.90 324.16 247.57 421.86 327.61 284.49 253.46 363.89 316.23 290.29 252.21 366.61 303.69 250.79 422.88 327.21 288.95 257.90
1.0616 0.5116 0.0443 0.1416 1.0635 0.2064 0.3347 1.1870 0.4304 0.1272 0.1287 1.0934 0.5007 0.0390 0.2063 1.1356 0.2050 0.2708 1.2147 0.4487 0.0989 0.1087
358.64 310.45 272.21 247.43 360.27 297.42 243.42 414.55 319.25 274.94
1.0735 0.5237 0.0645 0.2222 1.1537 0.3220 0.2751 1.2624 0.3457 0.1363
355.05 308.10 270.11 245.70 356.63 295.99 241.90 411.70 317.29 273.12
1.0319 0.5121 0.0615 0.2368 1.1460 0.3267 0.2197 1.2393 0.3472 0.1426
336.5 304.0
0.6449 1.0221
252.5
0.7418
359.15 311.00 279.30 244.47 359.96 298.40 244.38 414.77 318.69 279.91 251.56
1.1086 0.5265 0.0585 0.3153 1.2225 0.3542 0.4410 1.2983 0.3650 0.1135 0.0967
355.94 308.71 277.23 243.14 357.33 297.17 242.92 410.15 316.10 278.97 249.89
1.1008 0.5156 0.0465 0.3262 1.2005 0.3538 0.2935 1.2827 0.3620 0.1133 0.1161
340.5 302.0
1.1800 1.9236
252.0
1.2651
396.0–401.0 305.0–322.5 255.0–266.0
396.5–401.0 306.0–321.5 256.5–265.0
TD-M06/cc-pVDZ//B3LYP/6-31G(d). TD-M06/cc-pVDZ//M06/6-31G(d).
Calculations based on B3LYP/6-31G(d) level of theory suggest that the lowest vibrational frequencies are 15.4075, 11.8047, and 17.5071 cm 1 for group (I) (A, AR1, and AR2, respectively) and 15.4204, 11.0031 and 17.6469 cm 1 for group (II) (B, BR1 and BR2, respectively). The absence of imaginary frequency indicates that the optimized structures of all the compounds in Fig. S1 are local minima on the potential energy surfaces (PES). Electronic spectra The absorption wavelengths (k) and oscillator strengths (f ) for the two groups of compounds computed using the TD-B3LYP and TD-M06 methods with cc-pVDZ basis set are given in Table 3. The experimental values are also listed for direct comparison.
The PCM model is used in the Gaussian calculations to simulate reasonable spectra with methanol as the solvent. The comparison of theoretical and experimental UV spectra of all title compounds can be seen in Fig. S2 (see Supplementary information). In combination of theoretical data in Table 3 and simulated UV absorption spectra in Fig. S2, it is easily found that spectroscopic properties of AR2 and BR2 reproduce the experimental spectra very well, while those of compounds AR1 and BR1 are unable to describe the observations in experiment. Consequently, we come to the conclusion that it is the hydrogen ion in acetic acid participates in the reaction with reactants A or B, which ultimately yields corresponding products AR2 or BR2. In addition, as is shown in Fig. S2, the absorption spectra of compounds A, AR2, B, and BR2 simulated by TD-M06 method
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Table 4 Calculated absorption wavelength (k), oscillator strength (f ), symmetry, and assignments for orbitals involved in the UV–vis absorption peaks at TD-M06 level, along with the available experimental values. Compounds
A
AR2
B
BR2
State
X1A 21A 41A 71A 111A X1A 21A 51A 81A X1A 21A 41A 61A 131A X1A 21A 51A 71A 131A
Transition
(89a)2(90a)2(91a)0 90a ? 91a 90a ? 92a 89a ? 92a 87a ? 91a (89a)2(90a)2(91a)0 90a ? 91a 90a ? 92a 86a ? 91a (97a)2(98a)2(99a)0 98a ? 99a 98a ? 100a 98a ? 101a 96a ? 101a (97a)2(98a)2(99a)0 98a ? 99a 98a ? 100a 97a ? 100a 96a ? 100a
Absorption
Exp.
k (nm)
f
k (nm)
e
355.05 308.10 270.11 245.70
1.0319 0.5121 0.0615 0.2368
336.5 304.0
0.6449 1.0221
252.5
0.7418
411.70 317.29 273.12
1.2393 0.3472 0.1426
396.0–401.0 305.0–322.5 255.0–266.0
355.94 308.71 277.23 243.14
1.1008 0.5156 0.0465 0.3262
340.5 302.0
1.1800 1.9236
252.0
1.2651
410.15 316.10 278.97 249.89
1.2827 0.3620 0.1133 0.1161
396.5–401.0 306.0–321.5 256.5–265.0
Fig. 1. The experimental and theoretical UV–vis spectra of compound (a) A, (b) AR2, (c) B, and (d) BR2 in methanol with calculated data at the TD-M06/cc-pVDZ level.
considering solvent effect is consistent with experimental absorption spectra better than the values obtained by TD-B3LYP method, and is independent of the ground-state geometries. Therefore, the following discussion about molecular orbitals and spectroscopy will be concentrated on the result obtained at TD-M06//M06 level as an example.
The frontier molecular orbitals To explore the absorption bands intrinsically, it is useful to examine the properties and composition of HOMO (the highest occupied molecular orbital) and LUMO (the lowest virtual molecular orbital), which determine the electronic excitation and transition characters. So the calculations for molecular orbitals are
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performed by M06 method with the ground-state geometries at the same level. For intuition, the contour plots for HOMO and LUMO orbitals involved in the electronic transitions of every species are displayed in Fig. S3. Visual inspection of their three-dimensional representations immediately reveal that all compounds presented large-scale of typically p-conjugated character as well as partial p orbital of oxygen atom for HOMOs; LUMOs are mainly constituted by p anti-bonding orbitals. According to the energy levels corresponding to homologous frontier orbitals, the HOMO–LUMO energy gap value e for product AR2 is decreased by 0.545 eV compared with that of reactant A (e = 3.673 and 4.218 eV for AR2 and A, respectively). Similarly, the e-value of compound BR2 is smaller than that of B. The decrement of e-value is speculated to be correlated with the aforementioned enhancive planarity of the product molecules, which in turn should be responsible for the increasing maximum absorption wavelength k of compounds AR2 and BR2. Absorption spectra In combination of the criteria of both the vertical excitation energies and oscillator strengths for dominant absorption bands, we make reasonable assignments of theoretical transitions to the bands observed in experiment. For clarity, the detailed data and simulated UV–vis spectra for four compounds A, AR2, B, and BR2 calculated at TD-M06/cc-pVDZ//M06/6-31G(d) level are shown in Table 4 and Fig. 1, respectively. The theoretical spectrum of compound A includes one intense absorption peak at 355.05 nm (f = 1.0319), one moderate peak at 308.10 nm (f = 0.5121), and one relative weak absorption band at 245.70 nm (f = 0.2368). The lowest-energy absorption arises from the transition HOMO (MO 90) ? LUMO (MO 91) and is related to the experimental peak at 336.5 nm. The moderate absorption peak at 308.10 nm, correlated to the 304.0 nm in the experimental UV– vis spectrum, is originated from transition HOMO (MO 90) to LUMO+1 (MO 92). The highest-energy absorption at 245.70 nm is derived from HOMO 3 to LUMO transition and corresponds to the observed peak at 252.5 nm. With the participation of acetic acid in the reaction with A, however, obvious red shift is examined with electronic absorption peaks located at 273.12, 317.29, and 411.70 nm for product AR2. As for compound B, the points in common with A are: (i) There also exists three observable absorption peaks lying at 355.94, 308.71, and 243.14 nm, respectively; (ii) After reaction, the absorption bands of product BR2, especially for the lowest-energy absorption, present prominent red shift. In terms of molecular orbital analysis, all the electronic transitions for two groups of compounds are basically originated from p ? p promotion accompanied by minor p ? p transition. By comprehensive consideration of geometric structures and electronic transitions, the spectroscopic changes corresponding to reactants and correlative products are supposed to be attributed to both the enlarged conjugated system caused by enhancive molecular planarity and the decreased HOMO–LUMO energy gap. Conclusions The structures and electronic spectra of two groups of pyrazole quinoline compounds in solution are investigated by using DFT and TD-DFT methods in this paper. For one thing, the TD-M06 simulated UV–vis spectra show fairly good performance as compared with the experimental observations. For another, the reaction products of two sets of experiments are confirmed reasonably with theoretical calculations. Furthermore, explanations for red shift
behavior in the electronic spectra of products are made based on structural changes and molecular orbitals involved in the electronic transitions. It is expected that our calculations help to understand the structural and optical properties of relevant systems in further experiments. Acknowledgments The authors gratefully thank the State Key Laboratory of Physical Chemistry of Solid Surfaces of Xiamen University for providing computational resources and the National Science Foundation of China (Grant No. 21003036) and Science Foundation of Henan University (Grant No. SBGJ090507) for financial supports. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2013.06.063. References [1] K. Mekouar, J.F. Mouscadet, D. Desmaële, F. Subra, H. Leh, D. Savouré, C. Auclair, J. d’Angelo, J. Med. Chem. 41 (1998) 2846–2857. [2] M. Ouali, C. Laboulais, H. Leh, D. Gill, D. Desmaële, K. Mekouar, F. Zouhiri, J. d’Angelo, C. Auclair, J.F. Mouscadet, M.L. Bret, J. Med. Chem. 43 (2000) 1949– 1957. [3] M.A. Rafiee, T. Partoee, Bull. Korean Chem. Soc. 32 (2011) 208–212. [4] J.F. Mouscadet, D. Desmaële, Molecules 15 (2010) 3048–3078. [5] X.H. Jiang, B.D. Wang, Z.Y. Yang, Y.C. Liu, T.R. Li, Z.C. Liu, Inorg. Chem. Commun. 14 (2011) 1224–1227. [6] Y.G. Zhao, Z.H. Lin, H.P. Liao, C.Y. Duan, Q.J. Meng, Inorg. Chem. Commun. 9 (2006) 966–968. [7] G.C. Ragos, M.A. Demertzis, P.B. Issopoulos, IL Farmaco 53 (1998) 611–616. [8] L. Shi, W. Song, Y. Li, D.W. Li, K.N. Swanick, Z.F. Ding, Y.T. Long, Talanta 84 (2011) 900–904. [9] J.M. Yu, P.A. Bentley, W. Wang, Tetrahedron Lett. 47 (2006) 2447–2449. [10] H. Wang, W.S. Wang, H.S. Zhang, Spectrochim. Acta Part A 57 (2001) 2403– 2407. [11] Y.F. Cheng, D.T. Zhao, M. Zhang, Z.Q. Liu, Y.F. Zhou, T.M. Shu, F.Y. Li, T. Yi, C.H. Huang, Tetrahedron Lett. 47 (2006) 6413–6416. [12] J.P. Wei, H.P. Zeng, D.F. Xu, J. Liu, Chin. J. Chem. 26 (2008) 1299–1304. [13] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785–789. [14] B. Miehlich, A. Savin, H. Stoll, H. Preuss, Chem. Phys. Lett. 157 (1989) 200–206. [15] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5652. [16] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J. Frich, J. Phys. Chem. 98 (1994) 11623–11627. [17] T. Yanai, D.P. Tew, N.C. Handy, Chem. Phys. Lett. 393 (2004) 51–57. [18] M.M. Francl, W.J. Pietro, W.J. Hehre, J.S. Binkley, M.S. Gordon, D.J. DeFrees, J.A. Pople, J. Chem. Phys. 77 (1982) 3654–3665. [19] P.C. Hariharan, J.A. Pople, Theor. Chim. Acta 28 (1973) 213–222. [20] R. Bauernschmitt, R. Ahlrichs, Chem. Phys. Lett. 256 (1996) 454–464. [21] M.E. Casida, C. Jamorski, K.C. Casida, D.R. Salahub, J. Chem. Phys. 108 (1998) 4439–4449. [22] R.E. Stratmann, G.E. Scuseria, M.J. Frisch, J. Chem. Phys. 109 (1998) 8218–8224. [23] T.H. Dunning Jr., J. Chem. Phys. 90 (1989) 1007–1023. [24] R.A. Kendall, T.H. Dunning Jr., R.J. Harrison, J. Chem. Phys. 96 (1992) 6796– 6806. [25] A.K. Wilson, D.E. Woon, K.A. Peterson, T.H. Dunning Jr., J. Chem. Phys. 110 (1999) 7667–7676. [26] Š. Miertus, E. Scrocco, J. Tomasi, Chem. Phys. 55 (1981) 117–129. [27] J. Tomasi, M. Persico, Chem. Rev. 94 (1994) 2027–2094. [28] E.A. Perpète, F. Maurel, D. Jacquemin, J. Phys. Chem. A 111 (2007) 5528–5535. [29] 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, Ö. Farkas, J.B. Foresman, J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian, Inc., Wallingford CT, 2009.