122

CHAPTER- VII

FT-IR and FT-Raman spectroscopic investigation on 2-Ethyl Pyridine using

HF and DFT (B3LYP and B3PW91) calculations

7.1. Introduction

Heterocyclic nitrogen containing compounds such as pyridine and its derivatives

are commonly present in synthetic and natural products [1-2]. The study of the

vibrational spectra of substituted pyridine mainly amino pyridine attracts the attention of

many spectroscopists due to their wide application in pharmacology and agro- chemistry.

Pyridine heterocyclic compounds and its derivatives are repeated moiety in many large

molecules with interesting photo physical, electrochemical and catalytic applications [3-

10]. They serve as good anesthetic agent and hence are used in the preparation of drugs

for certain brain disease. These pharmaceutically acceptable salts and the pre drugs are

used for the treatment (or) prevention of diabetic neuropathy [11-12]. The presence of

ethyl group in the molecule shows some difference in photo physical properties relative

to the pyridine. 2-Ethyl pyridine constitutes an important class of heterocyclic organic

compound. Investigations on the structure of these organic molecules have been a subject

of interest because of their peculiar photo physical properties and pharmaceutical

importance [13-15].

Adnan Saglam et al [16] has recorded the Fourier transform infrared and laser

Raman spectra of 4-Pyridine acid in the regions of 100- 4000 cm-1

. The optimized

molecular structures, vibrational frequencies and corresponding vibrational assignments

of the cis and trans conformers of 2-, 3- and 4-pyridine carboxaldehydes have been

123

calculated using ab initio Hartree–Fock (HF) and density functional theory (B3LYP)

methods with 6-311++G(d, p) basis set. The calculations were adapted to the CS

symmetries of all the molecules. The mean vibrational deviations between the vibrational

frequency values of the two conformers of all the compounds have been seen to increase

while the relative energies increase and it was concluded the more different the molecular

structure of the two conformers is the higher the relative energy between them, which

gives a bigger mean vibrational deviation.

Michalski et al [17] has studied the Synthesis of 2-phenylazo-5-nitro-6-methyl-

pyridine. Synthesis of 2-phenylazo-5-nitro-6-methyl-pyridine was described. Its X-ray

structure was reported and discussed in terms of the molecular conformation of the

compound. The crystal is triclinic, space group P-1, with the unit cell parameters

aZ6.372(1), bZ7.522(2), cZ12.495(2) A° , and aZ6.372(1), bZ89.62(3)8 and

gZ101.57(3)8. The pyridine and phenyl rings were planar deflected by torsional angle

JZ4.8 (3)8. The crystal structure was stabilized by non-classical hydrogen interaction of

the C–H/O type with C/O distance 3.307(5) A ° , H/O distance 2.481(3) A ° and C–H/O

angle equal to 147.8(3)8. These interactions in the crystal structure couple pairs of the

molecules related by an inversion centre. FT-IR, Raman and NMR spectra of this

compound have also been measured. The 6-31G (d,p) basis set with the B3LYP

functional has been used to discuss the structure and dynamics of the compound studied.

Literature survey reveals that no ab initio HF or DFT with 6-311G (d, p) basis

sets calculations have been reported 2-Ethyl Pyridine (2-EP) so far. Hence the present

124

work has been undertaken to carry out a complete vibrational analysis on this molecule,

based on both experimental and theoretical study.

7.2. Computational details

In the present work, the HF and some of the hybrid methods such as B3LYP and

B3PW91 are carried out using the basis sets 6-31G (d, p), 6-31+G (d, p), 6-311G(d, p)

and 6-311++G (d, p). All these calculations were performed using GAUSSIAN 03W

program package on Pentium IV processor in personal computer [18-21].

The calculated frequencies are scaled down by suitable factors in comparison with

the experimental frequencies. The scaling factors are 0.903 and 0.904 for HF and in

agreement with the literature [22-23]. In the case of B3LYP with 6-31G (d, p)

calculation, the scaling factors are 0.955, 0.971, 0.959, 0.939, 0.738 and 0.795; for 6-

311++G (d, p) basis sets, the scaling factors are 0.961, 0.969, 0.979, 0.939, 0.789 and

0.845. In the case of B3PW91/6-311G (d, p) calculation, the scaling factors are 0.954,

0.988, 0.849, 0.788, 0.709 and 1.04 and in good agreement with the literature [24].

7. 3 Results and Discussion

7.3.1 Molecular Geometry:

The most optimized geometry performed by HF and DFT of 2-Ethyl pyridine

molecule with atoms numbering is shown in Figure 7.1. The molecule consists of ethyl

group connected to a pyridine ring. The zero point vibrational energy as predicted by

HF/6-31+G (d, p), B3LYP/6-31G (d, p), B3LYP/6-311++G (d, p) and B3PW91/6-311G

(d, p) of the molecule is 70.90, 70.54, 66.18, 65.94 and 66.17 Kcal/mol respectively.

125

The structural parameters; bond lengths, bond angles and dihedral angles calculated using

different basis sets are presented in Table 7.1.

In comparison with the experimental values, it is observed that most of the

calculated bond length values are slightly larger than the experimental values. This may

be due to the fact that the calculations are performed for the isolated molecules (gaseous

phase) while the experimental spectra are recorded in solid phase. This is in accordance

with the earlier work [25]. Comparing bond angles and lengths of B3LYP/B3PW91 with

those of HF, as a whole the values of former are bigger than later. The calculated values

from B3LYP/B3PW91 correlate well with the experimental data. Although the

differences, calculated geometrical parameters represent a good approximation and they

are the bases for calculating other parameters, such as vibrational frequencies. Optimized

geometrical parameters, namely, bond lengths and bond angles at HF/6-31+G (d, p),

B3LYP/6-31+G (d, p), B3LYP/6-311++G (d, p) and B3PW91/6-311G (d, p) levels are

given in the Table 7.1. The comparative graphs of bond lengths, bond angles and dihedral

angles for three sets are presented in the Figures 7.6, 7.7 & 7.8.

Optimized structure yields fairly accurate bond length pairs for the bonds N1-C2

and N1-C6, C2-C3, C3-H8 and C4-H7 at all five levels of calculations. Bond lengths are

found decreasing in going from HF/6-31+G (d, p) to B3PW91/6-311G (d, p) to

B3LYP/6-311++G (d, p) to B3LYP/6-31G (d, p). According to the observed values [26],

the bond lengths N1-C2 and N1-C6 are almost equal (~1.340 Å) whereas in DFT

calculation, the bond length N1-C2 is 0.008 Å at B3LYP/6-311++G (d, p) level and

126

0.011 Å at B3PW91/6-311++G (d, p) level is greater than bond length N1-C6. This

increase in bond length is due to the substitutions and single (C-N) and double (C=N)

bonds in the ring. In accordance with the observed values, the bond lengths C2-C3 and

C5-C6 are equal (expt. 1.395 Å). The bond length C2-C3 (1.400 Å) calculated by

B3LYP/6-31G (d, p)) level is 0.05 Å lesser and C5-C6 (1.396Å) is 0.001 Å greater than

the experimental values [27-29]. This may be due to the substitution of CH2CH3 instead

of H. The bond lengths computed by B3LYP/6-311G (d, p) for the bonds C14-H15, C14-

H16 and C14-H17 are fairly accurate with experimental values [30]. The observed bond

length C11-C14 (~1.483 Å) [31] is 0.047 Å less than computed value (1.530 Å) by

B3LYP/6-311G (d, p).

Analogues to the bond length, order of the bond angle lie as C4-C5-C6<C2-N1-

C6<C3-C4-C5<C2-C3-C4<N1-C2-C3<N1-C6-C5. The pyridine ring appears to be a

little distorted with the decrease in bond angle N1-C2-C3 (121.65˚) than N1-C6-C5

(123.78˚) which is due to the substitution of ethyl group. The observed bottom ring angle

C2-N1-C6 (117.30˚) is 2.10 ˚ less than the top ring angle C3-C4-C5 (119.40˚) due to the

replacement of C by N in the ring. Also the ring carbon atom exerts a large attraction on

valence electron cloud of nitrogen which results in an increase in C-N force constant and

decrease in the corresponding bond length [32].

7.3.2. Vibrational assignments:

The title molecule belongs to CS point group of symmetry. The present molecule

has 17 atoms; hence there can be 45 normal modes of vibrations, of which 32 are in–

127

plane vibrations (A′ species) and 13 out–of–plane vibrations (A″ species). They can be

distributed as:

ΓVib = 32 A′ + 13A

″.

All the 45 fundamental vibrations are active in both Raman scattering and IR

absorption. The calculated and experimental frequency values, for different methods and

basis sets and the corresponding assignments are presented in the table 7.2. The

comparative graph of IR and Raman spectra are given in the figure 7.2 and 7.3.

7.3.3. Computed IR intensity and Raman activity analysis:

The computed IR intensities and Raman activities of the 2-EP for different modes

of vibrations with corresponding frequencies, calculated by different methods and basis

sets are given in the Table 7.3. The IR intensity values predicted by HF methods are

found to be larger when compared to hybrid methods whereas the Raman activity values

predicted by hybrid methods are found to be larger when compared to HF. The similar

effect was also observed in the earlier work [33].The comparison of IR intensity and

Raman activity among different methods and basis sets are graphically shown in figures

7.4 and 7.5 respectively.

7.3.4. Computed vibrational frequency analysis:

The standard deviation (SD) calculation made between experimental and

computed values (HF/DFT) for the title molecule is presented in the Table 7.4. According

to the SD, the frequency deviation decrease going from HF/6-31+G (d, p) to B3LYP/6-

31G (d, p) to B3LYP/6-311++G (d, p) to B3PW91/6-311G (d, p). The deviation ratio of

HF/6-31+G (d, p) to B3LYP/6-31G (d, p) is 1.90, HF/6-31+G (d, p) to B3LYP/6-311++G

128

(d, p) is 2.03 and HF/6-31+G (d, p) to B3PW91/6-311G (d, p) is 1.97. The comparative

graph of calculated vibrational frequencies by HF and DFT methods for the title molecule

are given in the Figure 7.9 and it is found that the frequencies are calculated by B3LYP

with 6-311++G (d, p) basis set is much closer to the experimental values than HF

method.

7.3.5 C-H Vibrations

The Carbon – Hydrogen stretching vibrations give rise to bands in the region

3000 – 3100 cm-1

in all aromatic compounds [35-36]. As 2-EP is a mono substituted

hetero aromatic molecule, it has four C-H moieties. The expected four stretching

vibrations are observed at 3070, 3060, 3040 and 3020 cm-1

. These assigned values are in

good agreement with B3LYP method as well as literature data.

The bands corresponding to the C-H in-plane and out-of-plane bending vibrations

normally occur in the region 1000 – 1300 cm-1

and 750 – 1000 cm-1

respectively [37-41].

The sharp bands are observed at 1380, 1330, 1290 and 1220 cm-1

for C-H in-plane

bending vibrations. The bands with medium intensity are found at 890, 880, 800 and 790

cm-1

are assigned to C-H out-of-plane bending vibrations. Except for the first two bands

in C-H in-plane bending vibrations all the assigned values are in well within the expected

range. The deviation of the bands is due to the interaction between the ring C-H and

substituted ethyl C-H group. The assigned frequencies are found to be well above the

expected range. This shows that, though the out-of-plane bending vibrations are not

129

influenced, the in-plane bending vibrations are clearly found influenced. This is naturally

due to the presence of ethyl group in the place of methyl group in the ring.

7.3.6. Ethyl group vibrations

Vibrational spectra studies on methyl pyridine show that asymmetric and

symmetric C-H stretching vibrations are observed between 2846 and 2960 cm-1

. However

in this case, the ethyl group is attached with the ring. This give rise to five bands

associated with ethyl C-H stretching vibrations. In 2-EP, the C-H stretching vibrations are

observed at 2990, 2970, 2940, 2890 and 2880 cm-1

sequentially. The C-H in-plane

bending vibrations are found at 1150, 1100 and 1060, 1040 and 990 cm-1

. Similarly, the

C-H out-of-plane bending vibrations for ethyl group are found at 780, 750, 740, 620 and

600 cm-1

. Except for two bands in the stretching mode, two in plane bending and one in

out of plane bending the above assignments are coherent with the literature data [42-

43].This may be naturally due to the presence of n in the ring. Last two bands of out of

plane bending are moved down to the expected range. This view indicates that the ethyl

group is slightly affected. The computed values by B3LYP/6-311++G (d, p) are in perfect

match with the experimental values.

7.3.7 C-C vibrations:

The ring carbon–carbon stretching vibrations occur between the regions 1430 –

1625 cm-1

with variable intensity [44]. The bands between 1590 - 1650 cm-1

in pyridine

derivatives are usually assigned to C=C stretching modes [45]. In the present work, the

C=C stretching vibrations are observed at 1590 and 1580 cm-1

. The ring C-C stretching

130

vibrations normally occur in the region 1590-1430 cm-1

[46]. The C-C vibrations are

observed at 1480 and 1470 cm-1

sequentially. One band of C=C stretching vibration is

moved down to the expected range which is due to the substitution of ethyl group.

The C-C bonds present in the ethyl group give rise to two C-C stretching

vibrations and are observed at 1450 and 1430 cm-1

. When compared with ring C-C

vibrations, these vibrations are found to be well within the expected range. Though this

bond C-C is out of the ring, the corresponding vibrations are observed within the

literature range. The C-C-C in-plane and out-of-plane bending vibrations are observed

with the strong intensity at 570, 500 cm-1

and 390, 300 cm-1

respectively. According to

the literature [47-49], these vibrations are found to be shifted too below the expected

range. This is due to the suppression of ethyl group vibrations. The C-C in plane and out

of plane bending vibrations associated with ethyl group are observed at 290 and 150 cm-1

respectively which are also found to be deviated abruptly. This is mainly due to the C-C

bonds connected between the ring and ethyl group.

7.3.8. C-N vibrations

The existence of N in the ring give rise to a strong C=N stretching and C-N

stretching vibrations. The C=N and C-N stretching vibrations normally occur in the

region 1500 – 1600 cm-1

and 1266 – 1382 cm-1

respectively [50-53]. A strong band for

C=N stretching vibration is observed at 1560 cm-1

and C-N stretching vibration observed

at 1270 cm-1

for 2-EP. The C-N in plane and out of plane bending vibrations are observed

at 405 and 210 cm-1

. These assigned vibrational modes are apparently moved down due

to the ethyl group.

131

7.4. Conclusion:

A complete vibrational investigation on 2-Ethyl pyridine is performed by HF and

DFT (B3LYP and B3PW91) levels of theory. The observed and stimulated spectra have

shown a good frequency fit. The difference between theoretical and experimental wave

numbers within 10 cm–1

is confirmed by the qualitative agreement between the calculated

and observed frequencies. The global minimum energy between the different methods

shows the difference in optimizations between the same and the different sets. Various

quantum chemical calculations help us to identify the structural and symmetry properties

of the titled molecule. From the vibrational investigation, the following observations are

made;

1. In molecular geometry it is observed that, the bond lengths of all pairs

decrease in going from HF/6-31+G (d, p) to B3PW91/6-311G (d, p) to

B3LYP/6-311++G (d, p) to B3LYP/6-31G (d, p).

2. The pyridine ring appears to be a little distorted with the decrease in bond

angle N1-C2-C3 than N1-C6-C5 which is due to the substitution of ethyl

and methyl coupling.

3. The IR intensity values predicted by HF methods are found to be larger

when compared to hybrid methods whereas the Raman activity values

predicted by hybrid methods are found to be larger when compared to HF.

4. In computed frequency analysis, it is found that the frequencies are

calculated by B3LYP with 6-311++G (d, p) basis set is much closer to the

experimental values than HF method.

132

5. In C-H vibrations, except for the two bands in C-H in-plane bending

vibrations all the assigned values are well within the expected range. The

deviation of the bands is due to the interaction between the ring C-H and

substituted ethyl C-H group.

6. As the present molecule is mono substituted pyridine, the C-H vibrations

for ethyl group are not much affected. The computed values by B3LYP/6-

311++G (d, p) are in perfectly match with the experimental values.

7. One band of C=C stretching vibration is moved down to the expected

range which is due to the substitution of ethyl group.

8. In ethyl C-C vibrations, though this bond C-C is out of the ring, the

corresponding vibrations are observed within the literature range.

FIGURES

1

CHAPTER- IV

FT-IR and FT-Raman spectroscopic investigation on 2- Ethyl Pyridine using HF

and DFT (B3LYP and B3PW91) Calculations

4.1. Introduction

Heterocyclic nitrogen containing compounds, such as pyridine and its derivatives are

commonly present in synthetic and natural products [1-2]. The study of the vibrational spectra of

substituted pyridine mainly amino pyridine attracts the attention of many spectroscopists due to

their wide application in pharmacology and agro- chemistry. Pyridine heterocyclic compounds

and its derivatives are a repeated moiety in many large molecules with interesting photo

physical, electrochemical and catalytic applications [3-10]. They serve as good anesthetic agent

and hence are used in the preparation of drugs for certain brain disease. These pharmaceutically

acceptable sults and the pre drugs are used for the treatment (or) prevention of diabetic

neuropathy [11-12]. The methyl substitution on the CH2 group of title molecule shows some

difference in photo physical properties relative to the pyridine. 2-Ethyl pyridine constitutes an

important class of heterocyclic organic compound. Investigations on the structure of these

organic molecules have been a subject of great interest because of their peculiar photo physical

properties and pharmaceutical importance [13-15].

Adnan Sa˘glam et.al [16] have recorded the Fourier transform infrared and laser Raman

spectra of 4-Pyridine acid in the regions of 100- 4000 cm-1

, respectively. The optimized

molecular structures, vibrational frequencies and corresponding vibrational assignments of the

cis and trans conformers of 2-, 3- and 4-pyridine carboxaldehydes have been calculated using ab

initio Hartree–Fock (HF) and density functional theory (B3LYP) methods with 6-311++G(d, p)

basis set. The calculations were adapted to the CS symmetries of all the molecules. The mean

vibrational deviations between the vibrational frequency values of the two conformers of all the

2

compounds have been seen to increase while the relative energies increase and it was concluded

the more different the molecular structure of the two conformers is the higher the relative energy

is between them, and thus a bigger mean vibrational deviation.

J. Michalski et.al [17] have studied the Synthesis of 2-phenylazo-5-nitro-6-methyl-

pyridine. Synthesis of 2-phenylazo-5-nitro-6-methyl-pyridine was described. Its X-ray structure

was reported and discussed in terms of the molecular conformation of the compound. The crystal

is triclinic, space group P-1, with the unit cell parameters aZ6.372(1), bZ7.522(2), cZ12.495(2)

A° , and aZ6.372(1), bZ89.62(3)8 and gZ101.57(3)8. The pyridine and phenyl rings were planar

deflected by torsional angle JZ4.8(3)8. The crystal structure was stabilised by non-classical

hydrogen interaction of the C–H/O type with C/O distance 3.307(5) A ° , H/O distance 2.481(3)

A ° and C–H/O angle equal to 147.8(3)8. These interactions in the crystal structure couple pairs

of the molecules related by an inversion centre. FT-IR, Raman and NMR spectra of this

compound have also been measured. The 6-31G(d,p) basis set with the B3LYP functional has

been used to discuss the structure and dynamics of the compound studied.

Literature survey reveals that to the best of our knowledge no ab initio HF/DFT with 6-

311G (d, p) basis sets calculations of 2-EP have been reported so far. Hence the present work has

been undertaken to carry out a complete vibrational analysis on these molecules, based on both

experimental and theoretical study.

3

4.3. Computational details

In the present work, the HF and some of the hybrid methods such as B3LYP and

B3PW91 were carried out using the basis sets 6-31G (d, p), 6-31+G (d, p), 6-311G(d, p) and 6-

311++G (d, p). All these calculations were performed using GAUSSIAN 03W program package

on Pentium IV processor in personal computer [18-21].

The calculated frequencies are scaled down by suitable factors in comparison with the

experimental frequencies. The scaling factors are 0.903 and 0.904 for HF and in agreement with

the literature [22-23]. In the case of B3LYP with 6-31G (d, p) calculation, the scaling factors

are0.955, 0.971, 0.959, 0.939, 0.738 and 0.795; for 6-311++G (d, p)basis sets, the scaling factors

are0.961, 0.969, 0.979, 0.939, 0.789 and 0.845. In the case of B3PW91/6-311G (d, p)

calculation, the scaling factors are 0.954, 0.988, 0.849, 0.788, 0.709 and 1.04 and in good

agreement with the literature [24].

4. Results and Discussion

4.1 Molecular Geometry:

The most optimized geometries are performed by HF and DFT of 2-Ethyl pyridine

molecule with atoms numbering are shown in figure 4.1. The molecule consists of amino group

connected to a pyridine ring. The zero point vibrational energy of the molecule is 70.90, 70.54,

66.18, 65.94 and 66.17 Kcal/mol respectively as predicted by HF/6-31+G (d, p), B3LYP/6-31G

(d, p), B3LYP/6-311++G (d, p) and B3PW91/6-311G (d, p). The structural parameters; bond

lengths, bond angles and dihedral angles calculated using different basis sets are presented in

Table 4.1.

4

In comparison with the experimental values, it is observed that most of the calculated

bond length values are slightly larger than the experimental values. This may be due to the fact

that the calculations are performed for the isolated molecules (gaseous phase) while the

experimental spectra are recorded in solid phase. This is in accordance with the earlier work

[25]. Comparing bond angles and lengths of B3LYP/B3PW91 with those of HF, as a whole the

formers are bigger than later and the B3LYP/B3PW91 calculated values correlates well

compared with the experimental data. Although the differences, calculated geometrical

parameters represent a good approximation and they are the bases for calculating other

parameters, such as vibrational frequencies. Optimized geometrical parameters, namely, bond

lengths and bond angles at HF/6-31+G (d, p), B3LYP/6-31+G (d, p), B3LYP/6-311++G (d, p)

and B3PW91/6-311G (d, p) levels are given in the Table 4.1. The comparative graphs of bond

lengths, bond angles and dihedral angles for three sets are presented in the Figures 6, 7 & 8.

Optimized structure yields fairly accurate bond length pairs for the bonds N1-C2 and N1-

C6, C2-C3, C3-H8 and C4-H7 at all five levels of calculations. Bond lengths of all pairs decrease

in going from HF/6-31+G (d, p) to B3PW91/6-311G (d, p) to B3LYP/6-311++G (d, p) to

B3LYP/6-31G (d, p). According to the observed values [26], the bond lengths N1-C2 and N1-C6

are almost equal (~1.340 Å) whereas in DFT calculation, the bond length N1-C2 is 0.008 Å at

B3LYP/6-311++G (d, p) level and 0.011 Å at B3PW91/6-311++G (d, p) level is greater than

bond length N1-C6. This increase in bond length is due to the substitutions and single (C-N) and

double (C=N) bonds in the ring. In accordance with the observed values, the bond lengths C2-

C3 and C5-C6 are equal (expt. 1.395 Å). The bond length C2-C3 (1.400 Å) calculated by

B3LYP/6-31G (d, p)) level is 0.05 Å lesser and C5-C6 (1.396Å) is 0.001 Å greater than the

5

experimental values [27-29]. This may be due to the substitution of CH2CH3 instead of H. The

bond lengths computed by B3LYP/6-311G (d, p) for the bonds C14-H15, C14-H16 and C14-

H17 are fairly accurate with experimental values [30]. The observed bond length C11-C14

(~1.483 Å) [31] is 0.047 Å less than computed value (1.530 Å) by B3LYP/6-311G (d, p).

Analogues to the bond length, order of the bond angle lie as C4-C5-C6<C2-N1-C6<C3-

C4-C5<C2-C3-C4<N1-C2-C3<N1-C6-C5. The pyridine ring appears to be a little distorted with

the decrease in bond angle N1-C2-C3 (121.65˚) than N1-C6-C5 (123.78˚) which is due to the

substitution of ethyl and methyl coupling. The observed bottom ring angle C2-N1-C6 (117.30˚)

is 2.10 ˚ less than the top ring angle C3-C4-C5 (119.40˚) due to the replacement of C by N in the

ring. Also the ring carbon atom exerts a large attraction on valence electron cloud of nitrogen

resulting in an increase in C-N force constant and decrease in the corresponding bond length

[32].

4.2. Vibrational assignments:

The title molecule belongs to CS point group of symmetry and the optimized geometrical

parameters are calculated according to labeling of atoms. The present molecule has 17 atoms;

hence there can be 45 normal modes of vibrations, of which 32 are in–plane vibrations (A′

species) and 13 out–of–plane vibrations (A″ species). They can be distributed as:

ΓVib = 32 A′ + 13A

″.

All the 45 fundamental vibrations are active in both Raman scattering and IR absorption.

The calculated and experimental frequency values, for different methods and basis sets and the

6

corresponding assignments are presented in the table 4.2.The comparative graph of IR and

Raman spectra are given in the figure 4.2 and 4.3.

4.2.1. Computed IR Intensity and Raman Activity Analysis:

The computed IR intensities and Raman activities of the 2-EP for different modes of

vibrations with corresponding frequencies, calculated by different methods and basis sets are

given in the Table 4.3. The IR intensity values predicted by HF methods are found to be larger

when compared to hybrid methods whereas the Raman activity values predicted by hybrid

methods are found to be larger when compared to HF. The similar effect was also observed in

the earlier work [33].The comparison of IR intensity and Raman activity among different

methods and basis sets are graphically shown in figures 4.4 and 4.5 respectively.

4.2.2. Computed Vibrational frequency Analysis:

The standard deviation (SD) calculation made between experimental and computed

(HF/DFT) for the title molecule is presented in the Table 4.4. According to the SD, the frequency

deviation decrease is going from HF/6-31+G (d, p) to B3LYP/6-31G (d, p) to B3LYP/6-311++G

(d, p) to B3PW91/6-311G (d, p). The deviation ratio of HF/6-31+G (d, p) to B3LYP/6-31G (d, p)

is 1.90, HF/6-31+G (d, p) to B3LYP/6-311++G (d, p) is 2.03 and HF/6-31+G (d, p) to

B3PW91/6-311G (d, p) is 1.97. The comparative graph of calculated vibrational frequencies by

HF and DFT methods for the title molecule are given in the Figure 4.9 and it is found that the

frequencies are calculated by B3LYP with 6-311++G (d, p) basis set is much closer to the

experimental values than HF method.

7

4.2.3. C-H Vibrations

The Carbon – Hydrogen stretching vibrations give rise to bands in the region 3000 –

3100 cm-1

in all aromatic compounds [35-36]. As 2-EP is a mono substituted hetero aromatic

molecule, it has four C-H moieties. The expected four stretching vibrations are observed at 3070,

3060, 3040 and 3020 cm-1

. These assigned values are in good agreement with B3LYP method as

well as literature data. The bands corresponding to the C-H in-plane and out-of-plane bending

vibrations normally occur in the region 1000 – 1300 cm-1

and 750 – 1000 cm-1

respectively [37-

41]. The sharp bands are observed at 1330, 1290, 1270 and 1230 cm-1

for C-H in-plane bending

vibrations. The bands with medium intensity are found at 890, 880, 800 and 780 cm-1

are

assigned to C-H out-of-plane bending vibrations. Except for the first band in C-H in-plane

bending vibrations all the assigned values are in well within the expected range. The deviation of

first band is due to the interaction between the ring C-H and substituted ethyl C-H group. The

assigned frequencies are found to be well above the expected range. This shows that, though the

out-of-plane bending vibrations are not influenced, the in-plane bending vibrations are clearly

found influenced. This is naturally due to the interaction of ring C-H and substituted ethyl C-H

group vibrations as expected.

4.2.4. Methyl and ethyl group vibrations

Vibrational spectra studies on Methyl pyridine shows that asymmetric and symmetric C-

H stretching vibrations are observed between 2846 and 2960 cm-1

. However in this case, the

methyl group is attached with CH2 in the ring. This give rise to five bands associated with ethyl

and methyl C-H stretching vibrations. In 2-EP, the C-H stretching vibrations corresponding to

methyl group are observed at 2990, 2970 and 2940 cm-1

and corresponding to ethyl group are

8

found at 2890 and 2880 cm-1

sequentially. The C-H in-plane bending vibrations of methyl group

are found at 1150, 1100 and 1060 cm-1

and of ethyl group are found at 1040 and 990 cm-1

. The

C-H out-of-plane bending vibrations for methyl group are assigned at 780, 750 and 740 cm-1

.

The above assignments are coherent with the literature data [42-43]. As the molecule is mono

substituted pyridine, the C-H vibrations for ethyl and methyl groups are not much affected. The

computed values by B3LYP/6-311++G (d, p) are in perfectly match with the experimental

values.

4.2.5. C-C vibrations:

The ring carbon–carbon stretching vibrations occur between the regions 1430 – 1625

cm-1

with variable intensity [44]. In the present work, the C=C stretching vibrations are observed

at 1590 and 1580 cm-1

and C-C vibrations are observed at 1480 and 1470 cm-1

sequentially.

Though the 2-EP is a pyridine ring, the C-C stretching vibrations are not shifted from the

expected range [45]. The C-C-C in-plane and out-of-plane bending vibrations are observed with

the strong intensity at 620 and 500 cm-1

respectively. These assignments are also supported by

the literature [46-49]. The observed values of C=C vibrations are well within the expected range,

however the C-C vibrations are shifted down slightly which is due to the interruption of C=N

vibrations.

4.2.6. C-N vibrations

The existence of N in the ring give rise to a strong C=N stretching and C-N stretching

vibrations. The C=N and C-N stretching vibrations normally occur in the region 1500 – 1600

cm-1

and 1266 – 1382 cm-1

respectively [50-52]. A strong band for C=N stretching vibration is

observed at 1560 cm-1

and C-N stretching vibration observed at 1270 cm-1

for 2-EP. The

9

associated C=N in-plane bending vibration is shifted up by 30 cm-1

from C-N (570 cm-1

) in-plane

bending vibration. These assigned vibrational values also supported by the literature [53].

4.2.7. C- CH3 vibrations:

The asymmetric deformation of CH3 group is usually observed at around 1450 cm-1

for

methyl substituted molecules [54]. In the present compound, the CH3 deformations are observed

at 1450 and 1430 cm-1

. These assigned values are well within the expected range. Though it is

connected next to ethyl group with the ring, the C-CH2CH3 stretching vibration is observed at

1380 cm-1

. According to the literature [55-56], this absorption overlaps with C-C ring stretching

vibrations. The C-CH2 in- plane bending vibrations and C-CH2 out-of-plane bending vibrations

observed at 405 and 300 cm-1

. The CH3 and CH2 twisting vibrations are observed at 210 and 150

cm-1

which are also supported by the literature values [57-59]. Though the methyl group is

attached with the CH2, the vibrations of methyl group remain unaffected.

5. Conclusion:

A complete vibrational investigation on 2-Ethyl pyridine is performed by HF and DFT

(B3LYP and B3PW91) levels of theory. The observed and stimulated spectra have shown a good

frequency fit. The difference between theoretical and experimental wave numbers within 10

cm–1

is confirmed by the qualitative agreement between the calculated and observed frequencies.

The global minimum energy between the different methods shows the difference in

optimizations between the same and the different sets. Various quantum chemical calculations

help us to identify the structural and symmetry properties of the titled molecule. From the

vibrational investigation, the following observations are made;

10

1. In molecular geometry it is observed that, the bond lengths of all pairs decrease in

going from HF/6-31+G (d, p) to B3PW91/6-311G (d, p) to B3LYP/6-311++G (d,

p) to B3LYP/6-31G (d, p).

2. The pyridine ring appears to be a little distorted with the decrease in bond angle

N1-C2-C3 than N1-C6-C5 which is due to the substitution of ethyl and methyl

coupling.

3. The IR intensity values predicted by HF methods are found to be larger when

compared to hybrid methods whereas the Raman activity values predicted by

hybrid methods are found to be larger when compared to HF.

4. In computed frequency analysis, it is found that the frequencies are calculated by

B3LYP with 6-311++G (d, p) basis set is much closer to the experimental values

than HF method.

5. In C-H vibrations, except for the first band in C-H in-plane bending vibrations all

the assigned values are in well within the expected range. The deviation of first

band is due to the interaction between the ring C-H and substituted ethyl C-H

group.

6. As the present molecule is mono substituted pyridine, the C-H vibrations for ethyl

and methyl groups are not much affected. The computed values by B3LYP/6-

311++G (d, p) are in perfectly match with the experimental values.

7. The observed values of C=C vibrations are well within the expected range,

however the C-C vibrations are shifted down slightly which is due to the

interruption of C=N vibrations.

11

8. In C-CH3 vibrations, though the methyl group is attached with the CH2, the

vibrations of methyl group remain unaffected.

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Table 7.1: Optimized geometrical parameters for 2-Ethyl pyridine computed at HF/6-31+G (d, p), B3LYP/6-31G (d, p) and 6-311++G (d,

p) and B3PW91/6-311G (d, p) basis sets

Geometrical

Parameters

Methods

HF/6-31+G(d, p) B3lyp/6-

31G(d, p)

B3lyp/6-

311++G(d, p)

B3PW91/6-

311G(d, p)

Experimental

Value

Bong length(Å)

N1 - C2 1.328 1.346 1.342 1.340 1.341

N1 - C6 1.316 1.335 1.334 1.329 1.340

C2 – C3 1.388 1.400 1.398 1.395 1.395

C2 – C11 1.514 1.517 1.515 1.509 -

C3 - C4 1.385 1.394 1.391 1.390 1.374

C3 – H8 1.072 1.084 1.082 1.083 1.081

C4 - C5 1.380 1.391 1.390 1.387 1.394

C4 – H7 1.076 1.086 1.084 1.085 1.081

C5 - C6 1.385 1.396 1.392 1.391 1.395

C5 – H9 1.074 1.085 1.083 1.084 1.081

C6 – H10 1.077 1.089 1.087 1.088 1.081

C11 –H12 1.086 1.097 1.097 1.096 1.071

C11 - H13 1.086 1.096 1.093 1.095 -

C11 - C14 1.526 1.529 1.530 1.522 1.483

C14 - H15 1.084 1.093 1.092 1.092 1.090

C14 - H16 1.085 1.095 1.093 1.094 1.090

C14 - H17 1.087 1.095 1.093 1.094 1.090

Bong Angle(˚)

C2- N1- C6 119.02 118.34 118.50 118.44 117.30

N1 -C2-C3 121.60 121.77 121.65 121.77 123.60

N1-C2-C11 114.72 114.87 115.33 114.95 -

C3-C2-C11 123.66 123.34 123.00 123.26 -

C2-C3-C4 118.96 119.23 119.29 119.21 118.50

C2-C3-H8 120.86 120.57 120.53 120.57 -

C4-C3-H8 120.17 120.18 120.16 120.20 -

C3-C4-C5 119.18 118.98 118.99 118.96 119.40

C3-C4-H7 120.16 120.26 120.30 120.29 -

C5-C4-H7 120.65 120.74 120.70 120.73 -

C4-C5-C6 117.48 117.76 117.77 117.75 118.10

C4-C5-H9 121.82 121.64 121.59 121.64 121.0

C6-C5-H9 120.68 120.59 120.62 120.60 -

N1-C6-C5 123.72 123.88 123.78 123.85 123.30

N1-C6-H10 116.07 115.92 115.82 115.86 -

C5-C6-H10 120.19 120.18 120.38 120.28 -

C2-C11-H12 107.23 107.45 107.74 107.17 -

C2-C11-H13 107.23 107.21 106.78 106.94 -

C2-C11-C14 116.64 116.60 116.39 116.70 -

H12-C11-H13 105.65 105.00 105.44 105.02 -

H12-C11-C14 109.74 109.84 109.42 110.04 -

H13-C11- C14 109.74 110.05 110.46 110.26 -

C11-C14-H15 109.89 110.26 110.14 110.26 -

C11-C14-H16 111.79 111.83 112.14 111.94 -

C11-C14-H17 111.79 111.69 111.44 111.72 -

H15-C14-H16 107.54 107.38 107.20 107.30 -

H15-C14-H17 107.54 107.54 107.80 107.47 -

H16-C14-H17 108.08 107.84 107.90 107.92 -

Dihedral Angle(˚) -

C6-N1-C2-C3 0.00 0.02 0.31 0.04 -

C6- C1- C2- C11 -179.99 -179.74 178.68 -179.73 -

C2-N1-C6-C5 -0.00 -0.01 -0.18 -0.023 -

C2-C1-C6-H10 -179.99 -179.95 179.96 -179.95 -

C1-C2-C3- C4 -0.00 -0.02 -0.24 -0.04 -

C1-C2-C3- H8 179.99 179.93 179.63 179.91 -

C11-C2-C3-C4 179.99 179.72 178.68 179.72 -

C11-C2-C3-H8 -0.00 -0.31 -1.43 -0.31 -

N1-C2-C11-H12 56.56 60.66 79.54 60.73 -

N1-C2-C11-H13 -56.50 -51.76 -33.31 -51.46 -

N1-C2-C11-C14 -179.97 -175.58 -157.18 -175.41 -

C3-C2-C11-H12 -123.43 -119.10 -99.44 -119.04 -

C3-C2-C11-H13 123.49 128.46 147.69 128.75 -

C3-C2-C11-C14 0.02 4.64 23.82 4.80 -

C2-C3-C4-C5 0.00 0.01 0.03 0.02 -

C2-C3-C4-H7 -179.99 179.98 179.92 179.99 -

H8-C3-C4-C5 -179.99 -179.94 -179.84 -179.93 -

H8-C3-C4-H7 0.00 0.02 0.04 0.02 -

C3-C4-C5-C6 -0.00 -0.00 0.09 -0.00 -

C3-C4-C5-H9 179.99 179.93 179.82 179.93 -

H7-C4-C5- C6 179.99 -179.97 -179.80 -179.97 -

H7-C4-C5-H9 -0.00 -0.03 -0.06 -0.03 -

C4-C5-C6-N1 0.00 0.00 -0.01 0.00 -

C4-C5-C6-H10 179.99 179.93 179.74 179.92 -

H9-C5-C6-N1 -179.99 -179.93 -179.75 -179.93 -

H9-C5-C6-H10 -0.00 -0.00 0.01 -0.01 -

C2-C11-C14-H15 -179.99 178.78 175.60 178.76 -

C2-C11-C14-H16 -60.66 -61.76 -65.08 -61.85 -

C2-C11-C14-H17 60.66 59.25 56.00 59.32 -

H12-C11-C14-H15 -57.84 -58.70 -61.99 -58.86 -

C12-C11-C14-H16 61.49 60.74 57.30 60.51 -

H13-C11-C14-H16 -177.17 -178.23 178.39 -178.30 -

H13-C11-C14-H17 57.84 56.42 53.65 56.52 -

H13-C11-C14-H16 177.17 175.87 172.96 175.90 -

H13-C11-C14-H17 -61.49 -63.09 -65.94 -62.91 -

Table 7.2: Observed and HF /6-31+G (d, p), B3LYP/6-31G (d, p), B3LYP/6-311+G (d, p) and B3PW91/6-311++G (d, p) level

calculated vibrational frequencies of 2-Ethyl Pyridine

Sl.

No.

Symmetry

species

CS

Observed

fundamentals

(cm-1

)

Calculated Frequencies (cm-1

)

Vibrational

assignments FTIR

FT

Raman

HF/6-31+G(d, p) B3LYP/6-31G

(d, p)

B3LYP/6-311++

G(d, p)

B3PW91/6-311G(d,

p)

Unscaled Scaled Unscaled Scaled Unscaled Scaled Unscaled Scaled

1 A´ - 3070 3392 3066 3217 3075 3195 3073 3208 3063 (C-H) υ

2 A´ 3060 3060 3377 3053 3208 3066 3188 3066 3201 3056 (C-H) υ

3 A´ - 3040 3348 3027 3185 3044 3165 3044 3179 3035 (C-H) υ

4 A´ 3020 3020 3335 3015 3156 3017 3137 3017 3149 3007 (C-H) υ

5 A´ 2990 2990 3254 2941 3119 2981 3092 2974 3113 2972 (C-H) υ

6 A´ 2970 2970 3253 2941 3112 2975 3090 2972 3106 2966 (C-H) υ

7 A´ 2940 2940 3224 2915 3070 2934 3065 2948 3068 2929 (C-H) υ

8 A´ 2890 2890 3197 2890 3044 2891 3025 2910 3039 2902 (C-H) υ

9 A´ 2880 2880 3183 2877 3041 2888 3011 2896 3035 2898 (C-H) υ

10 A´ 1590 1590 1804 1631 1646 1600 1632 1583 1646 1571 (C=C) υ

11 A´ 1580 1580 1780 1609 1629 1583 1614 1565 1628 1554 (C=C) υ

12 A´ 1560 - 1654 1495 1522 1479 1510 1555 1509 1580 (C=N) υ

13 A″ 1480 - 1636 1479 1516 1473 1507 1476 1501 1484 (C-C) υ

14 A″ 1470 - 1629 1473 1514 1471 1500 1470 1496 1479 (C-C) υ

15 A″ 1450 1450 1607 1453 1487 1445 1481 1451 1472 1455 (C-C) υ

16 A´ 1430 - 1596 1443 1470 1428 1462 1432 1456 1439 (C-C) υ

17 A´ 1380 - 1551 1402 1427 1387 1415 1386 1407 1391 (C-H) δ

18 A´ - 1330 1498 1354 1377 1338 1371 1343 1368 1325 (C-H) δ

19 A´ 1290 1290 1428 1291 1320 1285 1315 1288 1320 1279 (C-H) δ

20 A´ 1270 - 1402 1267 1312 1259 1297 1271 1307 1266 (C-N) υ

21 A´ 1220 1220 1355 1225 1290 1238 1278 1229 1282 1283 (C-H) δ

υ- Stretching; α– Deformation; δ-In plane bending; γ- Out plane bending; τ- Twisting:

22 A´ 1150 1150 1313 1187 1241 1166 1237 1162 1241 1149 (C-H) δ

23 A´ 1100 1100 1217 1100 1182 1111 1177 1106 1174 1087 (C-H) δ

24 A´ 1060 - 1210 1094 1131 1063 1128 1060 1126 1042 (C-H) δ

25 A´ 1040 1040 1192 1077 1109 1042 1102 1035 1100 101 (C-H) ) δ

26 A´ 990 990 1155 1044 1079 992 1072 1007 1078 998 (C-H) ) δ

27 A″ 890 1141 1031 1072 986 1065 894 1071 910 (C-H) γ

28 A″ 880 880 1129 1021 1008 802 1011 850 1011 859 (C-H) γ

29 A″ 800 - 1100 994 1006 800 1010 797 1010 797 (C-H) γ

30 A″ 790 - 1090 985 995 792 991 782 995 786 (C-H) γ

31 A″ 780 780 1058 957 976 776 980 774 980 774 (C-H) γ

32 A″ 750 - 996 900 905 720 906 766 905 769 (C-H) γ

33 A″ 740 - 884 799 813 647 815 706 812 755 (C-H) γ

34 A″ 620 - 845 764 791 629 789 623 792 625 (C-H) γ

35 A´ 600 - 844 763 765 608 764 603 764 603 (C-H) γ

36 A´ 570 570 779 704 721 573 733 579 721 569 (CCC) δ

37 A´ 500 500 685 619 638 507 640 505 635 501 (CCC) δ

38 A´ 405 405 595 538 555 410 563 444 555 394 (C-N) δ

39 A´ - 390 528 477 480 355 486 383 479 378 (CCC) γ

40 A´ - 300 460 416 425 314 417 329 426 302 (CCC) γ

41 A″ 290 290 453 410 416 307 415 327 412 292 (C-C) δ

42 A″ 210 - 311 281 281 207 267 224 276 218 (C-N) τ

43 A″ 150 150 239 216 221 163 235 185 217 171 (C-C) γ

Table 7.3: Comparative values of IR intensity and Raman Activity between HF /6-31+G (d, p), B3LYP/6-31G (d, p), B3LYP/6-

311++G (d, p) and B3PW91/6-311G (d, p) of 2-Ethyl pyridine

Sl.

No.

Symmetry

species

Cs

Observed

fundamentals (cm-1

)

Calculated Frequencies (cm-1

)

FTIR

FT

Raman

HF/6-31+G(d, p) B3LYP/6-31G(d, p) B3LYP/6-311++G

(d, p) B3PW91/6-311G(d, p)

IR

Intensity

Raman

Activity

IR

Intensity

Raman

Activity

IR

Intensity

Raman

Activity

IR

Intensity

Raman

Activity

1 A’ - 3070 7.71 112.28 8.38 152.46 8.89 209.70 6.90 196.70

2 A’ 3060 3060 26.31 131.35 23.51 116.30 23.39 84.47 19.59 85.97

3 A’ - 3040 19.46 80.18 9.27 83.11 8.02 87.90 7.25 83.84

4 A’ 3020 3020 23.60 97.55 28.25 116.93 25.60 126.00 24.32 122.30

5 A’ 2990 2990 51.86 112.98 33.68 109.69 38.97 123.44 31.95 116.87

6 A’ 2970 2970 62.77 12.91 38.40 23.53 41.20 18.48 36.60 22.31

7 A’ 2940 2940 1.91 116.41 5.82 101.89 1.31 98.02 2.92 108.10

8 A’ 2890 2890 15.01 135.29 27.15 42.47 25.49 123.30 18.35 87.81

9 A’ 2880 2880 29.62 91.56 7.73 202.59 15.42 171.71 15.65 200.68

10 A’ 1590 1590 83.48 20.07 54.33 21.66 54.09 21.98 60.30 21.49

11 A’ 1580 1580 40.40 7.79 18.17 7.17 19.43 6.26 20.08 5.48

12 A’ 1560 - 30.71 0.39 8.73 10.50 7.49 8.82 37.61 1.25

13 A’’ 1480 - 1.26 8.69 21.01 4.72 28.79 4.38 2.28 6.73

14 A’’ 1470 - 5.17 21.50 7.63 17.71 9.49 6.87 8.18 12.08

15 A’’ 1450 1450 15.63 8.82 8.06 12.38 8.30 10.15 15.10 3.34

16 A’ 1430 - 24.71 6.89 25.42 8.24 25.29 5.24 24.31 11.58

17 A’ 1380 - 4.87 2.62 2.96 4.26 4.13 1.62 6.82 2.24

18 A’ 1330 18.67 3.77 11.48 8.40 6.10 5.23 6.14 5.76

19 A’ 1290 1290 1.61 3.76 1.16 3.10 0.57 4.95 1.19 1.58

20 A’ 1270 - 0.05 8.71 0.74 4.72 0.93 4.04 1.13 5.24

21 A’ 1220 1220 6.15 2.68 0.21 8.66 2.08 3.41 0.15 4.48

22 A’ 1150 1150 0.87 6.48 8.36 6.35 5.08 9.12 6.13 7.75

23 A’ 1100 1100 0.05 5.20 1.70 4.79 2.39 2.68 2.14 2.99

24 A’ 1060 - 1.10 0.21 0.46 6.19 0.44 4.18 1.03 4.58

25 A’ 1040 1040 9.03 0.77 0.60 0.40 2.32 0.56 0.47 0.21

26 A’ 990 990 6.84 16.33 5.88 16.68 6.47 18.01 7.17 15.48

27 A’ 890 5.62 0.26 0.34 0.44 2.47 0.64 0.15 2.90

28 A’’ 880 880 0.44 0.30 6.63 14.70 0.65 1.55 0.10 0.32

29 A’’ 800 - 0.00 1.48 0.02 0.21 6.07 13.52 5.42 16.42

30 A’’ 790 - 6.19 17.11 1.92 4.16 2.28 5.31 3.83 2.77

31 A’’ 780 780 2.69 3.53 0.04 2.15 0.20 0.36 0.22 0.37

32 A’’ 750 - 0.74 1.18 0.39 2.74 0.39 0.32 0.37 0.13

33 A’’ 740 - 32.57 0.17 22.57 0.14 22.54 0.48 28.48 0.32

34 A’’ 620 - 0.77 11.80 2.32 9.25 2.31 9.77 2.85 9.57

35 A’ 600 - 14.00 1.54 12.07 2.30 23.73 0.77 22.12 0.54

36 A’ 570 570 9.88 0.05 4.36 0.24 7.30 0.19 7.24 0.22

37 A’ 500 500 2.92 4.65 2.40 4.44 2.16 4.33 2.13 4.44

38 A’’ 405 405 1.74 4.10 0.84 3.04 1.93 2.69 0.72 2.82

39 A’ - 390 3.67 0.33 2.54 0.47 3.99 1.66 4.87 0.27

40 A’ - 300 3.74 0.55 3.32 3.27 3.17 1.49 3.62 3.32

41 A’’ 290 290 3.61 3.73 3.35 0.68 3.78 1.48 3.55 0.49

42 A’’ 210 - 0.59 0.27 0.52 0.30 0.43 0.29 0.44 0.19

43 A’’ 150 150 1.22 0.10 1.05 0.12 1.43 0.36 1.15 0.17

Table 7.4: Standard Deviation of frequencies by HF/DFT (B3LYP/B3PW91) at 6-31G (d, p), 6-31+G (d, p), 6-31++G (d, p), 6-

311G (d, p) and 6-311++G (d, p) basis sets

S.No. Basic set levels Total

values Average

Standard

Deviation

Deviation

ratio

Experimental 58915 1370.1

1 HF/6-31+(d, p) 67727 1575.0 144.90 1.90

2 B3LYP/6-31(d, p) 63472 1476.0 76.18

3 B3LYP/6-311++(d, p) 63153 1468.6 71.33 2.03

4 B3PW91/6-311(d, p) 63270 1471.3 73.29 1.97