ARTICLE pubs.acs.org/JPCA
Electronic Structure, Molecular Electrostatic Potentials, Vibrational Spectra in Substituted Calix[n]arenes (n = 4, 5) from Density Functional Theory Jayshree K. Khedkar, Rahul V. Pinjari, and Shridhar P. Gejji* Department of Chemistry, University of Pune, Pune 411007
bS Supporting Information ABSTRACT: Electronic structure, molecular electrostatic potential, and vibrational frequencies of para-substituted calix[n]arene CX[n]-R (n = 4, 5; R = H, NH2, t-Bu, CH2Cl, SO3H, NO2) and their thia analogs (S-CX[n]-R; with R = H and t-Bu) in which sulfur bridges two aromatic rings of CX[n] have been derived from the density functional theory. A rotation around CH2 groups connecting the phenol rings engenders four, namely, cone, partial cone, 1,2-alternate, and 1,3-alternate CX[n]-R conformers. Of these, the cone conformer comprising of large number of O1H1 3 3 3 O10 interactions turns out to be of lowest energy. Normal vibration analysis reveal the O1H1 stretching frequency of unsubstituted CX[n] shifts to higher wavenumber (blue shift) on substitution of electron-withdrawing (NO2 or SO3H) groups, while electron-donating substituents (NH2, t-Bu) engender a shift of O1H1 vibration in the opposite direction (red shift). The direction of frequency shifts have been analyzed using natural bond orbital analysis and molecular electrostatic potential (MESP) topography. Furthermore, calculated 1H NMR chemical shift (δH) in modified CX[n] hosts follow the order: H1 > H3/H5 > H7a > H7b. The δH values in CX[4] are in consonant with the observed 1H NMR spectra.
’ INTRODUCTION Calix[n]arenes (CX[n]) are macrocyclic compounds constructed by linking of a number of phenol residues connected via methylene groups at ortho positions (Scheme 1). A single-step condensation reaction between para-substituted phenols and formaldehyde yield these cyclic oligomers.15 CX[n] hosts with various cavity sizes have been designed, each of which has conformational isomers that vary in terms of orientation of their phenol groups and engender cone or partial cone or intermediate structures. The rotational barrier around methylene bridge governs interconversion between these conformers.3 Thus, CX[n] conformers endowed with different selectivity for inclusion of guest in the upper as well as lower cavity facilitate complexation3,6,7 with metal ions, anions, and neutral molecules as well.8,9 Changing the number of phenol residues alters the guest size appropriate for effective inclusion, for example, C60 fullerene can be accommodated within calix[8]arene host cavity because the cavity dimensions and the size of the guest complement to each other.1012 The versatility of calixarene framework has further been explored to synthesize array of functionalized hosts by modifying the groups of the upper (wide) and lower (narrow) rims.1315 Combining calix[n]arenes with other novel hosts such as crown ethers led to structures those possess novel architecture and complexation behavior with potential r 2011 American Chemical Society
Scheme 1
applications as sensors.1618 Interestingly, the CX[n] hosts or their derivatives further extend their use in a wide range of Received: June 10, 2011 Revised: August 19, 2011 Published: August 19, 2011 10624
dx.doi.org/10.1021/jp205441s | J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A applications such as catalyst,19 in enzyme mimetic,2022 ion carriers,23 analytical sensors,24,25 and in HPLC stationary phase.26,27 Moreover, CX[n] analogs in which methylene units are replaced by heteroatoms O, S, and NH led to novel hosts that are flexible and rendered with highly selective molecular recognition, hence, are of growing interest in supramolecular chemistry. The replacement of bridging methylene groups by sulfur atoms in CX[n] give thiacalix[4]arenes (S-CX[n]). Increased cavity size of S-CX[n] compared to CX[n], and incorporation of sulphide bridge to sulfoxide or sulfones2830 facilitate inclusion of transition metal ions31,32 and solvent molecules as well.33 To this end, selective modification of CX[n]
Figure 1. Atomic numbering scheme in calix[n]arene (CX[n]) monomer.
ARTICLE
framework has emerged with methods to devise hosts capable of binding to variety of guests.3436 CX[n] derivatives attached with chromophore reveal molecular recognition toward chiral guests accompanied with color change.3740 To understand selectivity underlying CX[n] or modified CX[n] host complexation UV/visible,4143 vibrational spectroscopy,44 NMR,45,46 and X-ray diffraction experiments have been carried out.47,48 It then was transparent that the nature of substituent(s), at the para-position of aromatic ring in the upper rim and at the phenolic OH in lower rim of CX[n] ligands has proven crucial in determining efficiency and selectivity toward cation extraction.4953 Shinkai and co-workers5458 have reported solubility of calixarene macrocycles in aqueous solutions can be enhanced with suitable substitution at the upper rim of pure CX[n]. Highly stable complexes between p-sulphanatocalix[n]arenes and viologens were characterized using NMR, isothermal titration calorimetry (ITC), and X-ray crystallography experiments and further explored in clinical treatment of viologen poisoning.59 Synthesis and structural analysis of S-CX[4] and p-tert-butyl-thiacalix[4]arene (S-CX[n]-t-Bu) have widely been investigated.60 NMR measurements on thiacalixarenes have shown that S-CX[n] hosts are more flexible and further increasing number of sulfur-bridge renders large flexibility to these hosts. Conformational analysis and vibrational spectra of calix[4]arene, thiacalix[4]arenes, and their tert-butyl derivatives revealed6163 that the intensity profile of normal vibrations therein are sensitive to orientation of phenol groups. A qualitative spectra-structure correlation, thus, can be explored for characterization of CX[4] conformers. Theoretical calculations using molecular mechanics,64 semiempirical65,66 to density functional theory67 are employed to understand structural and spectral features of CX[n] derivatives.
Figure 2. (a) Cone, (b) partial (M-1), (c) 1,2-alternate (D-1,2), and (d) 1,3-alternate (D-1,3) CX[4] conformers. 10625
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Table 1. Relative Stabilization Energies (in kJ mol1) of Calix[n]arene (n = 4, 5) Derivatives R X = CH2
X=S
CX[4]
CX[4]-M-1
CX[4]-D-1,2
CX[4]-D-1,3
CX[5]
CX[5]-M-1
CX[5]-D-1,2
CX[5]-D-1,3
H
0.0
38.4
50.9
65.7
0.0
37.9
18.1
63.9
NH2
0.0
37.4
51.3
66.4
0.0
36.5
64.4
62.7
t-Bu
0.0
38.3
50.6
64.6
0.0
38.7
19.7
65.2
CH2Cl
0.0
42.5
51.7
64.3
0.0
31.1
18.2
65.0
SO3H
0.0
26.1
36.9
54.3
0.0
23.4
17.7
12.0
NO2
0.0
35.2
46.7
60.1
0.0
35.9
51.6
60.1
H
0.0
38.0
55.6
51.1
0.0
1.7
3.9
8.5
t-Bu
0.0
38.0
55.4
55.6
0.0
0.6
7.7
21.3
Figure 3. Lowest energy (cone) conformers of CX[4] derivatives from B3LYP theory.
Bernardino and Cabral predicted structure and energy rank order in calix[4]arene68 and thiocalix[4]arene69 conformers from the Hartree-Fock and density functional theory incorporating a variety of basis sets. Thus, partial cone or 1,2 and 1,3 alternate structures close-lying to the cone (lowest energy) conformer in S-CX[4] have been derived. With gradientcorrelated density functional calculations incorporating PerdewBurkeErnzerhof (PBE) exchange-correlation Furer obtained the equilibrium structure and vibrational frequencies of p-tert-butyl-thiacalix[4]arene.70 Soi et al.71 investigated dynamic behavior of several tetraalkoxycalix[4]arene derivatives. Further substituent dependence of the conformation was determined by X-ray crystallography and 1D as well as 2D dynamic NMR spectroscopy combined with force field and semiempirical calculations revealed partial cone conformer to be the preferred structure. Bernardino and Cabral further investigated binding of alkali metal ion to tetrahydoxy-calix[4]arenes72 using Hartree-Fock, second order MollerPlesset (MP2) theory and density functional theory. These calculations revealed smaller cations Li+ and Na+ bind to lower rim of
calix[4]arene, whereas larger ions K+, Rb+, or Cs+ interact with the upper rim of the cone conformer through cationπ interactions. Recent density functional calculations due to Venkataramanan and co-workers73 have shown that Li-doped p-tert-butyl calixarene can be explored for storage of hydrogen molecules owing to enhanced binding from the host. Quantum chemical investigations further demonstrated how doping by alkali cations improves hydrogen adsorption. It was further predicted that the curved calix[n]arene can adsorb up to five alkali atoms; one of which resides inside the cavity while the remaining ones attach to walls of the cavity. Thus, CX[4] was shown to be capable of adsorbing up to 30 H2 molecules with lowering of temperature.74 Conformational properties of calixarenes and their analogs are largely influenced by substituents at the p-positions.75 As pursuant to this, we obtain the electronic structure, energies, molecular electrostatic potentials, 1H NMR, and vibrational characteristics in CX[n] and S-CX[n] derivatives and discuss the effect of substitution on their conformational and spectral features. The computational method is outlined below. 10626
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Figure 4. Lowest energy (cone) conformers of CX[5] derivatives from B3LYP theory.
’ COMPUTATIONAL METHOD We employ the Gaussian 09 suite of programs76 to investigate energetics and conformational changes in CX[n], S-CX[n] (n = 4, 5), and their para-substituted derivatives. Geometry optimization of different conformers in each host were carried out within the premise of the density functional theory (DFT) using Becke’s three-parameter hybrid functional77 (B3) combined with the electron-correlation functional of Lee, Yang, and Parr78 (LYP). An internally stored 6-311G (d,p) basis set was used for all the calculations. The vibrational frequencies computed were all found to be real. This established that the optimized structures appear at least as local minima on the potential energy surface. The normal modes were assigned by visualizing displacements of atoms around their equilibrium (mean) positions using the locally written program UNIVIS2000.79 Natural bond orbital (NBO) analysis was subsequently carried out.80 The molecular electrostatic potential (MESP), V(r) is given by Z N ZA Fðr0 Þd3 r0 ð1Þ V ðrÞ ¼ jr r0 j A jr R A j
∑
Thus, the two terms comprising eq 1 represent the bare nuclear (VN) and electronic contributions (VE), respectively, to the total electrostatic potential V(r). The sign of V(r) at a given point represents whether the nuclear or electronic effects are dominant. Topological features of V(r) summarized by its critical points (CPs) accordingly, these CPs are classified in terms of an ordered pair denoted by (rank, signature). The (3, 3) CP represents the maxima and (3, +3) yield the minima near electronegative atom in the molecular system. Further, the remaining (3, 1) and (3, +1) CPs refer to saddle points in the electrostatic potentials. The set of CPs of a molecule are unique and hence their existence and nature offer a signature of
the molecular structure. The MESP exhibits rich topographical features, which has subsequently been mapped by examining eigenvalues of the Hessian matrix at the CPs (where the gradient V(r) vanishes). Thus, CPs of V(r) were located employing the program written in our laboratory.81 NMR chemical shifts (δ) were calculated by subtracting the nuclear magnetic shielding tensors of protons in CX[n] and S-CX[n] from those in the tetramethylsilane (TMS; as a reference) using the gauge-independent atomic orbital method (GIAO).82 Effect of solvation on the proton chemical shift (δH) values in CX[n] and S-CX[n] homologues were modeled through the self-consistent reaction field (SCRF) calculations incorporating the polarizable continuum model83 implemented in Gaussian 09.
’ RESULTS AND DISCUSSION Atomic numbering scheme and optimized geometry of CX monomer unit of CX[n] is shown in Figure 1. The CX[n] conformers and their derivatives have been generated by varying orientations of their phenol groups around CH2 and S. The conformers possessing (a) all of the phenols pointing to the same direction (cone structure), (b) with one phenol pointing in a different direction (partial cone), (c) two neighboring phenol groups pointing in a different direction (1,2 conformer), and (d) two opposing phenols pointing in different directions (1,3 conformer) have been optimized in the framework of B3LYP/6-311G(d,p) theory. The partial cone, 1,2 and 1,3 conformers are denoted by M-1, D-1,2, and D-1,3, respectively. B3LYP optimized geometries of CX[4] conformational isomers are displayed in Figure 2 as a prototype example. CX[n]-R with symmetrically oriented upper rim substituent (R = H, NH2, t-Bu, CH2Cl, SO3H, NO2) and S-CX[n]-R (R = H, t-Bu) have been investigated. Stabilization energies of CX[n] or S-CX[n] conformers and their substituted analogs (n = 4, 5) relative to their lowest energy 10627
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Table 2. B3LYP-Optimized Geometries (Bond Lengths in Å and Bond Angles in ) in CX[4] Derivatives CX[4]
CX[4]-NH2
CX[4]-t-Bu
CX[4]-CH2Cl
CX[4]-SO3H
CX[4]-NO2
S-CX[4]
S-CX[4]-t-Bu
O1H1
0.985
0.985
0.985
0.985
0.984
0.984
0.980
0.980
O1C1
1.376
1.385
1.381
1.376
1.372
1.372
1.353
1.354
C1C2
1.403
1.401
1.399
1.403
1.406
1.406
1.408
1.403
C2C70
1.524
1.524
1.526
1.524
1.524
1.524
1.804
1.804
C2C3
1.392
1.393
1.399
1.392
1.390
1.390
1.394
1.399
C3C4
1.396
1.399
1.395
1.396
1.391
1.389
1.391
1.395
C4C5
1.395
1.398
1.400
1.395
1.388
1.387
1.39
1.401
C5C6 C6C1
1.394 1.404
1.396 1.402
1.392 1.402
1.394 1.404
1.394 1.405
1.392 1.407
1.396 1.409
1.391 1.407
C6C7
1.526
1.526
1.524
1.526
1.526
1.526
1.804
1.805
C4H10
1.494
1.083
C4Ca
1.540
C4Na
1.494
1.539
1.404
1.475
C4Sa
1.782
H1O10
1.704
1.698
1.695
1.702
1.708
1.715
1.878
1.868
O1O1 O1O1*
2.655 3.756
2.660 3.762
2.653 3.753
2.655 3.756
2.656 3.757
2.660 3.763
2.766 3.912
2.761 3.904
C2C7C6
113.8
113.7
113.8
113.8
114.2
113.7 103.8
103.9
C7C6C1
122.4
122.1
121.2
122.4
122.6
122.5
120.5
120.5
C6C1O1
121.3
121.5
117.2
121.3
121.1
121.1
122.3
118.5
O1C1C2
116.9
117.4
121.6
116.9
116.5
116.6
118.3
122.8
C1C2C70
121.2
121.1
122.2
121.2
121.3
121.3
C1C2S70 C1C2C3
118.2
118.8
118.1
118.2
118.3
118.3
120.5 119.7
120.5 120.0
C2C3C4
121.7
121.6
122.8
121.7
119.8
119.7
120.9
122.3
C3C4C5
118.6
118.2
116.9
118.6
121.6
121.8
119.4
116.7
C4C5C6
122.0
121.9
122.7
122.0
120.2
120.1
120.9
122.5
C5C6C1
117.7
118.4
118.3
117.7
117.8
117.9
119.6
119.9
C2S7C6
cone conformer are given in Table 1. CX[4] conformers and their substituted analogs are displayed in Figure 3. Higher energy M-1, D-1,2, and D-1,3 conformers are shown in Figure 1S of the Supporting Information. CX[4] and S-CX[4] possess cone conformation in solid state and CCl4 solution3,4,7,62,84 and stabilized by hydrogen bonding network.62,85 DFT calculations due to Bernardino et al.68,69,72 concur with these observations. The relative stabilization energies in CX[n] conformers follow the rank order cone > M-1 > D-1,2 > D-1,3. The stability of these conformers has been attributed to interplay between number and strength of OH 3 3 3 O and OH 3 3 3 S interactions. It may as well be remarked here that the lower energy (cone) conformer possesses an array of four hydrogen bonded interactions (O1H1 3 3 3 O10 ) that renders stability to CX[4] and their substituted analogs. Both M-1 and D-1,2 conformers possess the same number of O1H1 3 3 3 O10 interactions, the longer hydrogen bond distances can be noticed for the latter. The higher energy D-1,3 conformers (5466 kJ mol1) of CX[4] derivatives are void of OH 3 3 3 O interactions. It should be remarked here S-CX[4] macrocycle possessing OH 3 3 3 S interactions as in D-1,3 engenders energy lowering of ∼5 kJ mol1 than D-1,2 conformer and, thus, alters energy rank order for CX[4]. These observations are consistent with those pointed out by Bernardino.69 The lowest energy CX[n]-t-Bu conformer possesses t-Bu substituents oriented in the opposite direction compared to a hydrogen bonding network that stems from phenoxy
groups at the bottom rim (cf., Figure 3). All the t-Bu groups on each monomer possess similar anticlockwise orientation except one CH3 group directing toward the cavity. These results concur with the conclusions drawn earlier by Venkataramanan et al.73 A comparison of selected bond angles in cone, M-1, D-1,2, and D-1,3 conformers in CX[4] and S-CX[4], as well as their substituted analogs, is presented in Table 1S of Supporting Information. The lowest energy cone conformer reveals — C6 C7C2, bridging two phenol rings ∼114. Flipping of one or two phenyl rings as in M-1 or D-1,2 conformers, respectively, engenders opening of the corresponding angle up to 7. The — C1O1H1 (110.6) in CX[4] vary less than 1 with electron-donating/withdrawing substituent. Relative energies of CX[5] and their substituted analogs are reported in Table 1. As may readily be noticed, the cone conformer (cf., Figure 4) turns out to be the lowest energy. The higher energy conformers relative to cone conformation are shown in Figure 2S of the Supporting Information. Lowering of energy of D-1,2 conformer over M-1 in R = CH2Cl or t-Bu analogs alters the energy rank order in case of CX[5]-SO3H. Thus, the interplay of number and strength of hydrogen bonded interactions engenders preference for M-1 over D-1,2 and D-1,3 conformers in S-CX[5] or S-CX[5]-t-Bu hosts and follow the energy rank order: cone > M-1 > D-1,2 > D-1,3. Interestingly, the S-CX[5]-t-Bu cone conformer has been merely ∼0.6 kJ mol1 lower in energy than M-1. The electron-withdrawing substituents 10628
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Table 3. B3LYP-Optimized (Bond Lengths in Å and Bond Angles in ) in CX[5] Derivatives CX[5]
CX[5]-NH2
CX[5]-t-Bu
CX[5]-CH2Cl
CX[5]-SO3H
CX[5]-NO2
S-CX[5]
S-CX[5]-t-Bu
O1H1
0.982
0.982
0.982
0.982
0.981
0.981
0.976
0.976
O1C1
1.380
1.385
1.381
1.377
1.374
1.373
1.352
1.354
C1C2
1.402
1.400
1.402
1.403
1.406
1.405
1.408
1.403
C2C70
1.518
1.518
1.519
1.518
1.518
1.518
1.797
1.797
C2C3
1.395
1.393
1.392
1.392
1.390
1.39
1.394
1.397
C3C4
1.391
1.398
1.400
1.395
1.390
1.388
1.391
1.396
C4C5
1.389
1.396
1.394
1.394
1.387
1.386
1.390
1.399
C5C6 C6C1
1.397 1.403
1.396 1.401
1.400 1.398
1.395 1.403
1.394 1.404
1.392 1.406
1.396 1.409
1.393 1.408
C6C7
1.520
1.520
1.521
1.520
1.520
1.520
1.797
1.798
C4H10
1.084
1.083
C4Ca
1.539
C4Na
1.493
1.539
1.405
1.476
C4Sa
1.781
H1O10
1.794
1.787
1.789
1.792
1.794
1.797
2.168
2.130
O1O1 O1O1*
2.770 4.482
2.766 4.476
2.765 4.475
2.767 4.477
2.767 4.477
2.769 4.480
3.068 4.964
3.037 4.914
C2C7C6
117.4
117.2
117.5
117.4
117.7
117.2 106.7
106.7
C7C6C1
121.9
121.7
121.9
122.0
122.2
122.1
119.3
119.3
C6C1O1
121.6
122.0
122.0
121.7
121.5
121.5
122.4
122.7
O1C1C2
117.0
117.5
117.4
117.1
116.7
116.8
118.7
119.2
C1C2C70
121.0
120.9
121.0
121.0
121.0
121.0
C1C2S70 C1C2C3
118.4
119.1
118.6
118.4
118.5
118.6
120.0 119.8
120.0 120.2
C2C3C4
121.2
121.7
122.8
121.7
119.9
119.8
121.1
122.4
C3C4C5
119.2
117.8
116.6
118.2
121.2
121.5
119.1
116.4
C4C5C6
121.5
121.9
122.8
122.0
120.2
120.1
120.9
122.5
C5C6C1
118.1
118.7
118.4
118.1
118.1
118.2
119.9
120.1
C2S7C6
Table 4. MESP Minima (in kJ mol1) Near Portal Oxygens (x) in CX[4] and CX[5] Derivatives x R X = CH2
X=S
CX[4]
CX[5]
H
124.9
112.4
NH2
160.3
151.0 122.0
t-Bu
133.8
CH2Cl
85.8
71.2
NO2 SO3H
11.1 27.3
12.0 6.0
H
111.8
109.0
t-Bu
125.5
122.0
reveal relatively lesser destabilization for M-1, D-1,2, or D-1,3 conformers. From Table 2S of Supporting Information, — C1 O1H1 has been noticed to be nearly insensitive to nature of substituent, as also pointed out in the case of CX[4]. Selected geometrical parameters in CX[4], S-CX[4], and substituted analogs are compared in Table 2. The electronwithdrawing substituents (SO3H or NO2) predict shortening of C4C5 and C1O1 bonds, by 0.008 and 0.004 Å, respectively, compared to the unsubstituted CX[4]. The electron-donating
NH2 substitution on the other hand reveals elongation up to 0.009 Å for C1O1 bond. The longer O1H1 3 3 3 O10 hydrogen bonds can also be noticed for SO3H- or NO2-substituted CX[n]. The opposite oxygens on lower rim of S-CX[4] and S-CX[4]-tBu are separated by 3.912 and 3.904 Å, respectively, the separation being ∼0.11 Å large than those of CX[4] analogs and yield hosts with large cavity. The bond angles are nearly unchanged on para-substitution in CX[n]; — C3C4C5 shows the largest deviation of ∼3 in CX[4]-NO2 or CX[4]-SO3H. Similar conclusions may be drawn for CX[5] derivatives (cf., Table 3). As pointed out in the preceding section, MESP brings about the effective localization of electron-rich regions in a molecular system. The MESP minima near portal oxygens (O1) are displayed in Table 4. The electron-donating substituents engender minima with V = 160.9 and 133.8 kJ mol1 for CX[4]NH2 and CX[4]-t-Bu, respectively. Thus, electron-donating substituent renders electron-rich portal oxygens; the shallow minima with 11.1 kJ mol1 for CX[4]-NO2 and 27.1 kJ mol1 in CX[4]-SO3H hosts were identified. The thia analogs S-CX[4] and S-CX[4]-t-Bu also exhibit shallow minima near hydroxyl oxygens on the lower rim. MESP investigations in CX[5]-R derivatives led to similar inferences (cf., Table 4). The increasing number of phenol monomers in CX[4] yield shallow minima near CX[5] portals (112.4 kJ mol1) and hydroxyl oxygens on lower rim of CX[5], thus, turn out to be less electron-rich. 10629
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Figure 5. MESP (V = 183.8 to 236.3 kJ mol1) mapped on CX[4] derivatives.
An electrostatic potential mapping on molecular surface of the CX[4] and CX[5] derivatives, has been displayed in Figures 5 and 6, respectively. As may be inferred aromatic rings of CX[n] with electron-donating substituents possess large electron-rich regions than those for NO2 and SO3H (electron-withdrawing) substituents. From large negative potential (blue region) at lower rim, it may be inferred that interactions of cationic guest with hydroxyl oxygens are favored. Likewise, the bridging sulfur atoms
and hydroxyl oxygens in thia analogs emerge with large electronrich regions endowed with wider cavity and favors interaction with larger cations. The hydrogen bonding interactions can be gauged through electron density topography and the bcp in MED topography being the signature of hydrogen bond interactions. As suggested by Bader and co-workers86 the electron density at the bcp (Fbcp) provides a measure of corresponding bond strength. The Fbcp 10630
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Figure 6. MESP (V = 183.8 to 236.3 kJ mol1) mapped on CX[5] derivatives.
values in CX[4] and CX[5] derivatives in Table 5 points to relatively strong O1H1 3 3 3 O10 interactions in CX[4]. Stronger hydrogen bonding interactions with NH2 and t-Bu substituents are evident. Likewise S-CX[n] analogs reveal weak O1H1 3 3 3 O10 interactions than those comprising of methylene bridge. In the following we outline how substitution in CX[n] or modified CX[n] influence normal vibration frequencies in calculated
spectra. Harmonic vibrational frequencies of modified CX[n], scaled by a factor87 of 0.9682 are compared in Table 6. Vibrational spectra of CX[4] and its analogs in the 500 to 3500 cm1 region are displayed in Figure 7. As may readily be noticed, the O1H1 stretching vibration at the 3287 cm1 in CX[4] is upshifted (blue-shift) to 3310 cm1 in CX[4]-NO2 and 3303 cm1 in CX[4]-SO3H. Natural bond orbital analysis reveal decrease of 10631
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
electron density in antibonding O1H1 natural orbital from 0.0544 au to 0.0519 for CX[4]-NO2 and to 0.0529 au in the case of CX[4]-SO3H and, thus, support these inferences. As opposed to this, the frequency red shift of 13 cm1, accompanied by enhanced electron density in antibonding O1H1 natural orbital, can be noticed with electron-donating substituents as in CX[4]-NH2 and CX[4]-t-Bu. The direction of frequency shift can, thus, be rationalized through NBO analysis. A comparison of vibrational spectra of CX[5] and substituted CX[5] derivatives is presented in Figure 8. A graph of frequency of O1H1 stretching as a function of electron density residing in antibonding O1H1 natural orbitals in modified CX[4] (in blue) and CX[5] (as pink) displayed in Figure 9 turns out to be a straight line(s), with the correlation coefficient being 0.999. MESP investigations reveal shallow minima near portal oxygens for electron-withdrawing substituents (cf., Table 4). A frequency down shift of O1H1 stretching in CX[n]-R derivatives with electron-donating substituents is evident from deeper minima in MESP topography. Similar conclusions can be drawn for CX[5] derivatives; the O1H1 stretching appears at the higher wavenumber than their CX[4] counterparts. It may as well be remarked here that CH vibrations of aromatic ring with electron-withdrawing substituents on CX[n] reveal frequency shift from 3086 cm1 to 3112 cm1. A shift in the opposite direction for this vibration was predicted in case of CX[n]-NH2 and CX[n]-t-Bu. Likewise, a Table 5. Electron Density at the bcp of O1H1 3 3 3 O10 (Gbcp) in MED Topography of CX[4] and CX[5] Cone Conformers R X = CH2
X=S
CX[4]
CX[5]
H
0.0453
0.0353
NH2
0.0462
0.0360
t-Bu
0.0464
0.0358
CH2Cl
0.0454
0.0353
NO2
0.0439
0.0348
SO3H
0.0446
0.0351
H t-Bu
0.0291 0.0298
0.0147 0.0147
frequency down shift of ∼8 cm1 for CH vibration due to methylene protons was noticed in CX[n]-NO2 and CX[n]SO3H and the corresponding vibration in CX[n]-NH2 or CX[n]-t-Bu remain nearly unchanged compared to the unsubstituted analogs. The CO stretching (1247 cm1) in CX[4] appears at the lower wavenumber than that in CX[5] (1487 cm1). The vibrations due to CO (1243 cm1) and CdC (1606 cm1) stretchings invoking coupling from other internal coordinates as well, in CX[4]-t-Bu compare well with those in the experimental spectra.88 Selected normal vibration frequencies of S-CX[n] derivatives are given in Table 6. As may readily be noticed O1H1 stretching in S-CX[4] predicted at the higher wavenumber (3411 cm1) than CX[4]. This was attributed to transfer of electron density from bridging sulfur atom to benzene ring.61 B3LYP calculated wavenumbers of CdC stretching vibrations in CX[4] and in S-CX[4] are in consonant with the measured spectra. The CdC stretching results in two close lying vibrations at 1584 and 1577 cm1 in CX[4] and corresponds to a single band ∼1563 cm1 for S-CX[4]. The vibrations near 1597 and 1390 cm1 in the calculated spectra of CX[4] result from COH bending. These bands appear at lower wave numbers (1368 and 1341 cm1) in -S-CX[4] (cf., Table 3S) and match with those from experiment.61 It was further observed that δ(OH) vibration shifts to higher frequencies during hydrogen bond formation.61 The weaker hydrogen bonding in S-CX[4] was, thus, inferred. The Fbcp values of O1H1 3 3 3 O10 hydrogen bond in CX[4] and S-CX[4] displayed in Table 5 support these conclusions. The vibrational frequencies of CX[n]-R (R = H, NH2, t-Bu, CH2Cl, SO3H, NO2) and S-CX[n]-R (R = H and t-Bu) along with normal mode assignments are summarized in Tables 3S and 4S of the Supporting Information. As shown in Table 7, calculated 1H NMR chemical shifts (δH) of CX[4] derivatives in the gas phase, water, and chloroform follow the order: H1 > H3/H5 > H7a > H7b. Calculated δH values for unsubstituted CX[4], thus, concur with experimental data.89 The O1H1 3 3 3 O10 interactions engender deshielding of H1 protons, δH signals being nearly insensitive to solvation. The hydroxyl protons (H1) in CX[4]
Table 6. Selected Vibrational (ν = Stretch and δ = Bending) Frequencies of CX[4] and CX[5] Derivatives CX[4]-
CX[5 ]-
CX[4]-
CX[5]-
CX[4]-
CX[5]-
CX[5]
NH2
NH2
t-Bu
t-Bu
NO2
NO2
3290
3350
3275
3339
3274 (3165)a
3345
3310
3354
3287
3348
3334
3309
3353
ν (CH)
3086
3087
3052
3063
3112
3111
ν (CH2)
2954
2950
2955
2948
2962
2958
1585
1614
1577
1585
1230
1245
1259
1426
1423
1229
1244
1251
1408
1411
1478
1430
1410
1300
1264
assignment ν (O1H1)
CX[4]
3338
2949 ν (CdC) +
1584
1586
δ (CCH)
(1607)b 1577
1581
3052
3068 (3053)a
2950
2955
2949
S-
S-CX[5]-t-
CX[5]
S-CX[4]- t-Bu
Bu
3421
3490
3418
3489
3411
3486
1563 (1567)b
1554
S-CX[4]
3486
2947 1591 (1606)a
1589
1259
1242
1237
1241
1233
1240
1487
1432
(1593) b 1580 ν (CO) +
1247
ν(CC) +
1487
1208
1467
1244 (1243)a
δ (CCH)
1257 1253 a
Ref 88. b Ref 61. 10632
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Figure 7. Calculated infrared spectra (5003200 cm1) of CX[4] derivatives.
exhibit largely deshielded signals compared to those in CX[5]. Methylene protons directing toward cavity (H7a) are
deshielded more compared to those directing outside the cavity (H7b). 10633
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Figure 8. Calculated infrared spectra (5003200 cm1) of CX[5] derivatives.
10634
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A
ARTICLE
Figure 9. Graph of frequency of O1H1 stretching (ν) in cm1 as a function of electron density in antibonding O1H1 natural orbitals of modified CX[4] (blue) and CX[5] (pink) hosts.
Table 7. 1H NMR Chemical Shifts in CX[n] (n = 4, 5) Derivatives in Gas Phase and in Different Solvents H1
CX[n]
CX[n]-NH2
CX[5]-t-Bu
H3 /H5
H4
H7a
H7b
CX[4]
CX[5]
CX[4]
CX[5]
CX[4]
CX[5]
CX[4]
CX[5]
CX[4]
CX[5]
gas
10.2
9.4
7.2
7.5
6.9
7.0
4.3
4.1
3.4
3.5
water CHCl3
10.3 10.3
9.4 9.4
7.6 7.5
7.8 7.7
7.2 7.1
7.3 7.2
4.3 4.3
4.1 4.1
3.7 3.6
3.7 3.6
gas
9.8
8.9
6.4
6.6
4.1
4.0
3.1
3.2
water
9.8
8.9
6.8
7.0
4.0
3.9
3.3
3.4
CHCl3
9.8
8.9
6.6
7.0
4.1
3.9
3.2
3.4
gas
10.3
9.4
7.4
7.6
4.3
4.1
3.4
3.5
water
10.3
9.4
7.7
7.8
4.2
4.1
3.6
3.7
CHCl3
10.3
9.4
7.2
7.7
3.5
4.1
4.3
3.6
CX[n]-CH2Cl
gas water
10.2 10.3
9.4 9.5
7.2 7.5
7.5 7.9
4.2 4.2
4.1 4.1
3.4 3.6
3.5 3.7
CHCl3
10.3
9.4
7.5
7.7
4.2
4.1
3.6
3.7
CX[n]-SO3H
gas
10.2
9.4
7.7
7.9
4.1
3.9
3.5
3.6
water
10.4
9.7
8.0
8.1
4.3
4.1
3.8
3.8
CHCl3
10.3
9.5
7.8
8.0
4.2
4.0
3.7
3.8
gas
10.2
9.5
8.4
8.6
4.2
4.0
3.7
3.7
water
10.4
9.8
8.6
8.8
4.3
4.2
3.9
3.9
CHCl3 gas
10.3 9.8
9.7 8.5
8.5 7.8
8.7 7.4
4.3
4.1
3.8
3.9
6.8
7.8
water
9.8
8.5
8.0
7.8
7.0
8.2
7.1
8.0
CX[n]-NO2
S-CX[n]
S-CX[n]-t-Bu
CHCl3
9.8
8.5
8.0
7.7
gas
9.7
8.6
7.9
7.9
water
9.7
8.5
8.1
8.1
CHCl3
9.7
8.5
7.8
8.0
’ CONCLUSIONS Systematic investigations on electronic structure, charge distribution, and vibrational frequencies of substituted calix[n]arene
(CX[n]), n = 4, 5 have been presented. The characterization of molecular electron density and molecular electrostatic potentials in calixarenes and their derivatives should serve as the initial step 10635
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A toward understanding of molecular interactions between CX[n] macrocycles or related hosts and cationic or neutral guests. The following conclusions may be drawn. (i) The cone conformer turns out to be of lowest energy than partial cone or D-1,2 or D-1,3 conformers. The lowering of energy of this conformer stems from the strength as well as the number of O1H1 3 3 3 O10 interactions. The D-1,3 conformer in which O1H1 3 3 3 O10 interactions are absent is largely destabilized. X-ray diffraction experiments point to the cone conformer for CX[4] and S-CX[4]. (ii) The strength of hydrogen bond interactions can be gauged from MED topography. The mapping of MESP on the molecular surface of CX[n]-R qualitatively explains the affinity of these hosts toward different guests. (iii) Substitution of the electron-withdrawing group (NO2, SO3H) in CX[n] shifts the frequencies of the O1H1 and CH (aromatic ring) stretching vibration to a higher wavenumber (blue shift) while the electrondonating substituent results a frequency-shift in the opposite direction. (iv) The frequency shifts in normal vibrations are further rationalized using the natural bond orbital analysis and molecular electrostatic potential (MESP) topography. (v) An increase in monomer unit of CX[4] or replacement of methylene bridges with sulfur engenders an upshift of the OH stretching. (vi) Calculated NMR reveals the trend of δH values, H1 > H3/ H5 > H7a > H7b, for isolated CX[n] and modified CX[n] hosts, which is conserved in the presence of solvent. The δH signals for CX[4] agree with experimental 1H NMR.
’ ASSOCIATED CONTENT
bS
Supporting Information. B3LYP/6-311G(d, p) optimized geometries of CX[n]-R (R = H, NH2, t-Bu, CH2Cl, SO3H, NO2), and S-CX[n]-R (R = H and t-Bu). A comparison of selected bond angles in cone, M-1, D-1,2, and D-1,3 conformers in CX[n] and S-CX[n], as well as their substituted analogs. Vibrational frequencies data of CX[n]-R and S-CX[n]-R along with the assignments of these normal vibrations. This material is available free of charge via the Internet at http://pubs. acs.org.
’ AUTHOR INFORMATION Corresponding Author
*Fax: +91 20 225691728. E-mail:
[email protected].
’ ACKNOWLEDGMENT S.P.G. acknowledges support from the University Grants Commission (UGC), New Delhi, India [Research Project F34370/2008(SR)], and the University of Pune. J.K.K. thanks UGC for the award of fellowship. ’ REFERENCES (1) Takeshita, M.; Shinkai, S. Bull. Chem. Soc. Jpn. 1995, 68, 1088. (2) Shinkai, S. Tetrahedron 1993, 49, 8933. (3) Gutsche, C. D. Monographs in Supramolecular Chemistry; Vol. 1. Calixarenes; The Royal Society of Chemistry: Cambridge, U.K., 1989. (4) Gutsche, C. D. Monographs in Supramolecular Chemistry; Vol. 6. Calixarenes Revisited; The Royal Society of Chemistry: Cambridge, U.K.,1998. (5) Kunsagi-Mate, S.; Szabo, K.; Bitter, I.; Nagy, G.; Kollar, L. Tetrahedron Lett. 2004, 45, 1387. (6) Ni, X.-l.; Tomiyasu, H.; Shimizu, T.; Perez-Casas, C.; Xi, Z.; Yamato, T. J. Inclusion Phenom. Macrocyclic Chem. 2010, 68, 99.
ARTICLE
(7) Vicens, J.; B€ohmer, V.; Calixarenes: a versatile class of macrocyclic compounds; Kluwer Academic Publishers: Dordrecht, Boston, 1991. (8) Furer, V. L.; Borisoglebskaya, E. I.; Zverev, V. V.; Kovalenko, V. I. Spectrochim. Acta, Part A 2005, 62, 483. (9) Gutsche, C. D. Calixarenes Revisited; The Royal Society of Chemistry: Cambridge, U.K., 1998. (10) Bourdelande, J. L.; Font, J.; Gonzalez-Moreno, R.; Nonell, S. J. Photochem. Photobiol., A 1998, 115 (1), 69. (11) Pan, G. B.; Liu, J.-M.; Zhang, H.-M.; Wan, L.-J.; Zheng, Q.-Y.; Bai, C. L. Angew. Chem., Int. Ed. 2003, 42, 2747. (12) Schlachter, I.; Howelef, U.; Iwanekb, W.; Urbaniakb, M.; Mattay, J. Tetrahedron 1999, 55, 14931. (13) Ikeda, S.; Shinkai, S. Chem. Rev. 1997, 97, 1713. (14) Bohmer, V. Angew. Chem., Int. Ed. 1995, 34, 713. (15) Suwattanamala, A.; Magalhaes, A. L.; Gomes, J. A. N. F. J. Mol. Struct.: THEOCHEM 2005, 729, 83. (16) Ludwig, R.; Dzung, N. T. K. Sensors 2002, 2, 397. (17) Kim, J. -S.; Lee, W. -K.; Ra, D.-Y.; Lee, Y. -I.; Choi, W. K.; Lee, K. W.; Won-Zin, Oh, W. -Z. Microchem. J. 1998, 59, 464. (18) Souchon, V.; Leray, I.; Valeur, B. Chem. Commun. 2006, 42, 24. (19) Harris, S. J.; McManus, M. Eur. Patent Appl., EP 1988, 24, 279. (20) Thallapally, P. K.; Lloyd, G. O.; Atwood, J. L.; Barbour, L. J. Angew. Chem. 2005, 44 (25), 3848. (21) Steed, J. W.; Juneja, R. K.; Burkhalter, R. S.; Atwood, J. L. J. Chem. Soc., Chem. Commun 1994, 2205. (22) Baldini, L.; Barcchini, C.; Cacciapaglia, R.; Casnati, A.; Mandolini, L.; Ungaro, R. Chem.—Eur. J. 2000, 6, 1322. (23) Visser, H. C.; Reinhoudt, D. N.; Jong, F. Chem. Soc. Rev. 1994, 94, 75. (24) Kremer, F. J. B.; Chiosis, G.; Engbersen, J. F. J.; Reinhoudt, D. N. J. Chem. Soc., Perkin Trans. 1994, 2, 677. (25) Diamond, D.; McKervey, M. A. Chem. Soc. Rev. 1996, 25, 15. (26) Li, L.-S.; Da, S.-L.; Feng, Y.-Q.; Liu, M. J. Liq. Chromatogr. 2004, 27 (14), 2167. (27) Purse, B. W.; Gissot, A.; Rebek, J., Jr. J. Am. Chem. Soc. 2005, 127 (32), 11222. (28) Iki, N.; Kumagai, H.; Morohashi, N.; Ejima, K.; Hasegawa, M.; Miyanari, S.; Miyano, S. Tetrahedron Lett. 1998, 39, 7559. (29) Mislin, G.; Graf, E.; Hosseini, M. W.; De Cian, A.; Fischer J. Chem. Commun. 1998, 1345. (30) Mislin, G.; Graf, E.; Hosseini, M. W.; De Cian, A.; Fischer, J. Tetrahedron Lett. 1999, 40, 1129. (31) Iki, N.; Morohashi, N.; Naruni, F.; Miyano, S. Bull. Chem. Soc. Jpn. 1998, 71, 1597. (32) Iki, N.; Narumi, F.; Fujimoto, T.; Morohasi, N.; Miyano, S. J. Chem. Soc., Perkin Trans. II 1998, 12, 2745. (33) Akdas, H.; Bringle, L.; Graf, E.; Hosseini, M. W.; Mislin, G.; Pansanel, J.; De Cian, A.; Fischer, J. Tetrahedron Lett. 1998, 39, 2311. (34) Vicens, J.; Bohmer, V. Calixarenes-A Versatile Class of Macrocyclic Compounds; Kluwer Academic Publishers: Dordrecht, 1991. (35) Brzezinski, B.; Bartl, F.; Zundel, G. J. Phys. Chem. B 1997, 101, 5611. (36) Mohammed-Ziegler, I.; Kubinyi, M.; Grofcsik, A.; Grun, A.; Bitter, I. J. Mol. Struct. 1999, 289, 480. (37) Gradya, T.; Joycea, T.; Smytha, M. R.; Harrisb, S. J.; Diamonda, D. Anal. Commun. 1998, 35, 123. (38) Balazs, B.; Toth, G.; Horvath, G.; Grun, A.; Csokai, V.; Toke, L.; Bitter, I. Eur. J. Org. Chem. 2001, 61, 271. (39) Kubinyi, M.; Mohammed-Ziegler, I.; Grofcsika, A.; Bitterb, I.; Jones, W. J J. Mol. Struct. 1997, 408/409, 543. (40) Ariga, K.; Kunitake, T. Supramolecular Chemistry Fundamentals and Applications Advanced Textbook; Springer-Verlag: Heidelberg, 2006. (41) Rouis, A.; Mlika, R.; Dridi, C.; Davenas, J.; Ben Ouada, H.; Halouani, H.; Bonnamour, I.; Jaffrezic, N. Mater. Sci. Eng., C 2006, 26 (23), 247. (42) Wasikiewicz, W.; Slaski, M.; Rokicki, G.; Bohmer, V.; Schmidt, C.; Paulus, E. F. New J. Chem. 2001, 25 (4), 581. 10636
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
The Journal of Physical Chemistry A (43) Zyryanov, G. V.; Rudkevich, D. M. J. Am. Chem. Soc. 2004, 126 (13), 4264. (44) Mohammed-Ziegler, I.; Grun, A. Spectrochim. Acta, Part A 2005, 62 (13), 506. (45) Molins, M. A.; Nieto, P. M.; Sanchez, C.; Prados, P.; Mendoza, J.; De.; Pons, M. J. Org. Chem. 1992, 57, 6924. (46) Benevelli, F.; Kolodziejski, W.; Wozniak, K.; Klinowski, J. Chem. Phys. Lett. 1999, 308, 65. (47) Kuzmicz, R.; Dobrzycki, L.; Wozniak, K.; Benevelli, F.; Klinowski, J.; Kolodziejski, W. Phys. Chem. Chem. Phys. 2002, 4, 2387. (48) Buscemi, S.; Pace, A.; Piccionello, A. P.; Pappalardo, S.; Garozo, D.; Pilati, T.; Gattuso, G.; Pappalardo, A.; Pisagatti, I.; Parisi, M. F. Tetrahedron Lett. 2006, 47, 9049. (49) Ungaro, R.; Pochini, A. Topics in Inclusion Science. In Calixarenes, A Versatile Class of Macrocyclic Compounds; Bohmer, V., Vicens, J., Eds.; Kluwer Academic Publishers: Dordrecht, 1990; p 127. (50) Arnaud-Neu, F.; Barboso, S.; Berny, F.; Casnati, A.; Muzet, N.; Pinalli, A.; Ungaro, R.; Schwing-Weill, M. -J.; Wipff, G. J. Chem. Soc., Perkin Trans. 2 1999, 1727. (51) Fanni, S.; Arnaud-Neu, F.; McKervey, M. A.; Schwing-Weill, M. J.; Ziat, K. Tetrahedron Lett. 1996, 37, 7975. (52) Havlicek, J.; Kratky, R.; Ruzickova, M.; Lhotak, P.; Stibor, I. J. Mol. Struct. 2001, 301, 563. (53) Ikeda, A.; Shinkai, S. Chem. Rev. 1997, 97, 1713. (54) Shinkai, S.; Mori, S.; Tsubaki, T.; Sone, T.; Manabe, O. Tetrahedron Lett. 1984, 25, 5315. (55) Shinkai, S.; Mori, S.; Koreishi, K.; Tsubaki, T.; Manabe, O. J. Am. Chem. Soc. 1986, 108, 2409. (56) Shinkai, S.; Araki, K.; Tsubaki, T.; Arimura, T.; Manabe, O. J. Chem. Soc., Perkin Trans. 1 1987, 2297. (57) Shinkai, S.; Mori, S.; Araki, T.; Manabe, O. Bull. Chem. Soc. Jpn. 1987, 60, 3679. (58) Shinkai, S.; Araki, K.; Matsuda, T.; Nishiyama, N.; Ikeda, H.; Takasu, I.; Iwamoto, M. J. Am. Chem. Soc. 1990, 112, 9053. (59) Guo, D. S.; Wang, L. H.; Liu, Y. J. Org. Chem. 2007, 72, 7775. (60) Sone, T.; Ohba, Y.; Moriya, K.; Kumada, H.; Ito, K. Tetrahedron 1997, 53, 10689. (61) Furer, V. L.; Borisoglebskaya, E. I.; Kovalenko, V. I. Spectrochim. Acta, A 2005, 61 (12), 355. (62) Katsyuba, S.; Kovalenko, V.; Chernova, A.; Vandyukova, E.; Zverev, V.; Shagidullin, R.; Antipin, I.; Solovieva, S.; Stoikov, I.; Konovalov, A. Org. Biomol. Chem. 2005, 3 (14), 2558. (63) Furer, V. L.; Borisoglebskaya, E. I.; Zverev, V. V.; Kovalenko, V. I. Spectrochim. Acta, Part A 2005, 62 (13), 483. (64) Biali, S. E.; Bohmer, V.; Brenn, J.; Frings, M.; Thondorf, I.; Vogt, W.; Wohnert, J. J. Org. Chem. 1997, 62, 8350. (65) Morley, J. O.; Naji, M. J. Phys. Chem. A 1997, 101, 2681. (66) Bhattacharya, S.; Nayak, S. K.; Semwal, A.; Banerjee, M. Spectrochim. Acta, Part A 2005, 61 (4), 595. (67) Aleman, C.; Casanovas, J. J. Phys. Chem. A 2005, 109 (35), 8049. (68) Bernardino, R. J.; Cabral, B. J. C. J. Phys. Chem. A 1999, 103, 9080. (69) Bernardino, R. J.; Cabral, B. J. C. J. Mol. Struct.: THEOCHEM 2001, 549, 253. (70) Furer, V. L.; Borisoglebskaya, E. I.; Zverev, V. V.; Kovalenko, V. I. Spectrochim. Acta, Part A 2006, 63, 207. (71) Soi, W.; Bauer, H.; Mauser, C.; Moll, F.; Hampel, A.; Hirsch, A. J. Chem. Soc., Perkin Trans. 2 1998, 1471. (72) Bernardino, R. J.; Cabral, B. J. C. Supramol. Chem. 2002, 14, 57. (73) Venkataramanan, N. S.; Sahara, R.; Mizuseki, H.; Kawazoe, Y. J. Phys. Chem. C 2008, 112, 19676. (74) Venkataramanan, N. S.; Sahara, R.; Mizuseki, H.; Kawazoe, Y. Comput. Mater. Sci. 2010, 49, S263. (75) Asfari, Z.; B€ohmer, V.; Harrowfield, J. M.; Vicens, J. Calixarenes 2001; Kluwer Academic Publishers: Dordrecht, 2001. (76) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,M. A.; Cheeseman, J. R. G.; Calmani, V.; Barone, B.; Mennucci,
ARTICLE
G. A.;Petersson, H.; Nakatsuji, M.; Caricato, Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A.; Peralta, J. E. F., Jr.; Ogliaro, M.; Bearpark, J. J.; Heyd, E.; Brothers, K. N.; Kudin, V. N.; Staroverov, R.; Kobayashi, J.; Normand, K.; Raghavachari, A.; Rendell, J. C.; Burant, S. S.; Iyengar, J.; Tomasi, M.; Cossi, N.; Rega, J. M.; Millam, M.; Klene, J. E.; Knox, J. B.; Cross, V.; Bakken, C.; Adamo, J.; Jaramillo, R.;Gomperts, R. E.; Stratmann, O.; Yazyev, A. J.; Austin, R.; Cammi, C.; Pomelli, J. W.; Ochterski, R. L.; Martin, K.; Morokuma, V. G.; Zakrzewski, G. A.; Voth, P.; Salvador, J. J.; Dannenberg, S.; Dapprich, A. D.; Daniels, O.; Farkas, J. B.; Foresman, J. V.; Ortiz, J.; Cioslowski Fox, D. J. Gaussian 09; Gaussian, Inc.: Wallingford, CT, 2009. (77) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (78) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (79) Limaye, A. C.; Gadre, S. R. Curr. Sci. 2001, 80, 1298. (80) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899. (81) Balanarayan, P.; Gadre, S. R. J. Chem. Phys 2003, 119, 5037. (82) Wolinski, K.; Hilton, J. F.; Pulay, P. J. Am. Chem. Soc. 1990, 112, 8251. (83) Miertus, S.; Scrocco, E.; Tomasi, M. J. Chem. Phys. 1981, 55, 117. (84) Kovalenko, V. I.; Chernova, A. V.; Borisoglebskaya, E. I.; Syuba, S. A.; Zverev, V. V.; Shagidullin, R. R.; Antipin, I. S.; Solovieva, S. E.; Stoikov, I. I.; Konovalov, A. I. Russ. Chem. Bull., Int. Ed. 2002, 51, 825. (85) Groenen, L. C.; Steinwender, E.; Lutz, B. T. G.; Vander Maas, J. H.; Reinhoudt, D. N. J. Chem. Soc., Perkin Trans. 2 1992, 1893. (86) Bader, R. F. W. Atoms in Molecules: A Quantum Theory; Oxford University Press: Oxford, U.K., 1990. (87) Merrick, J. P.; Moran, D.; Radom, L. J. Phys. Chem. A 2007, 111, 11683. (88) Amiri, A.; Babaeie, F.; Monajjemi, M. Phys. Chem. Liq. 2008, 46 (4), 379. (89) Kara, I.; Kart, H. H.; Kolsuz, N.; Karakus, O. O.; Deligo, H. Struct. Chem. 2009, 20, 113.
10637
dx.doi.org/10.1021/jp205441s |J. Phys. Chem. A 2011, 115, 10624–10637
