67

CHAPTER-II

Theoretical [HF/DFT] and experimental [FT-IR and FT-Raman] studies of

molecular structure and vibrational analysis of 2-Chloro 4-methylaniline

2.1. Introduction

Aniline is an aromatic amine and its derivatives are widely used in pharmaceutical

manufacturing, electro-optical, dye stuff and other commercial and industrial applications

[1]. Some of the para substituted derivates of aniline [2] are commonly used as local

anesthetics. The understanding of their structure, molecular properties as well as nature

of reaction mechanism, they are subjected to many experimental and theoretical studies.

Hence, the investigation on the structure and fundamental vibrations of aniline and its

derivatives are widely carried out. The inclusion of a substituent in aniline leads to the

variation of charge distribution in the molecule, and consequently affects the structural,

electronic and vibrational parameters. The electron donating methyl group interacts with

nearby π systems through hyper conjugation, while the NH2 shares its lone pair electrons

with the ring. Both the effects imply electron delocalization which is taken into account

in molecular orbital approach [3, 4].

Numerous investigations of the Raman and infrared spectra of aniline are reported

in many literatures [15-20]. Kohlraush et al [5] studied a series of monosubstituted

benzene derivatives and proposed an elaborate assignment, which mostly indicated the

characteristic of the phenyl group. Venkateswaran et al [6] also proposed a partial

vibrational assignment of some benzene derivatives on the basis of the Raman spectrum.

A study of the liquid infrared spectra of aniline and aniline-ND2 in the region 600-3600

cm-1

was made by Califano et al [7], who proposed a partial assignment of the C-NH2

modes [8]. Vibrational assignment based FT-IR in the vapour, liquid phases and the

68

Raman spectra in the liquid state have been reported for aniline [9]. The molecular

structure of aniline had also been reported in the gas phase using microwave

spectroscopy [10, 11] also from x-ray crystallography [12]. Vibrational analysis have

been reported theoretically using semi-empirical [13, 14], ab initio methods [13, 15, 16].

Extensive studies [17-22] on vibrational spectra of substituted aniline have been made on

the basis of vibrational mode and frequency assignments. Vibrational modes and

frequency analysis of m-methylaniline have been studied by Altun et al [17].

Assignments of some bands observed in the infrared spectrum of p-methylaniline were

given in literature [23-28]. The vibrational spectra of chloromethyl aniline [29]

and 2-chloro-6-methyl aniline [30] with polarized Raman and infrared spectra were

reported earlier.

Owing to less number of works with ab initio and DFT on this title molecule,

attempts have been made for the complete vibrational analysis of 2Cl4MA by combining

the experimental and theoretical information using Pulay’s Density Functional Theory

(DFT) based on scaled quantum chemical approach [31] and ab initio HF. It is expected

that both ab initio HF and DFT level of theories are reliable for predicting the vibrational

spectra of the title compound. So, in this present work, the vibrational wave numbers,

complete geometrical parameters, modes of vibrations, dipole moment, rotational

constants, electronic polarizability and other thermodynamic parameters of the title

molecule were investigated using HF and B3LYP calculations with 6-31G(d, p) and

6-31D++G(d, p) basis sets. Specific scale factors were used and employed in the

predicted frequencies.

69

2.2. Computational Details

The molecular structure optimization of the title compound and corresponding

vibrational harmonic frequencies were calculated using HF and the DFT with Beckee-3-

Lee-Yag-Parr (B3LYP) combined with 6-31G(d,p), 6-31++G(d,p) basis sets. Geometries

have been first optimized with full relaxation on the potential energy surfaces at HF/6-

31G (d, p), 6-31++G (d, p) basis sets. The geometry was then re-optimized at B3LYP

level using 6-31G (d, p), 6-31++G (d, p) basis sets.

By combining the results of Gaussian 03 package [32] and GAUSSVIEW [33]

program with symmetry considerations, along with the available related molecules,

vibrational frequency assignments were made with a high degree of accuracy. The FTIR

and FT Raman spectrum were recorded in the range of 3600 – 10 cm-1

in the solid phase.

2.3. Results and Discussion

2.3.1 Molecular Geometry

The molecular structure along with numbering of atoms of 2Cl4MA, obtained

from Gaussian 03 and GAUSSVIEW programs are as shown in the Figure 1. The global

minimum energy obtained by HF and DFT structure optimization using 6-31G (d, p) and

6-31++G(d,p) basis sets for the title molecule are -783.6857 a.u, -783.6947 a.u,

-786.5317 a.u. and -786.5462 a.u. respectively. The most optimized structural parameters

(bond length and bond angle) calculated by ab initio/HF, DFT/B3LYP with 6-31G (d, p)

and 6-31++G (d, p) basis sets are compared with the experimental data and presented in

Table 1.

Earlier literatures [34, 35] have explained the changes in the frequency or bond

length of C-H bond on substitution due to change in the charge distribution on the carbon

70

atom of the benzene ring. The substituents may be either of the electron withdrawing

nature (Cl, F and Br…) or electron donating type (CH3, C2H5…). The Carbon atoms are

bonded to the hydrogen atoms with an σ bond in the benzene and the substitution of a

halogen for hydrogen reduces the electron density at the ring carbon atom. The ring

carbon atoms in substituted benzenes exert a larger attraction on the valence electron

cloud of the hydrogen atom resulting in an increase in the C-H force constant and a

decrease in the corresponding bond length. The reverse takes place in the case of

electron donating groups.

In this work, the optimized bond lengths of C-C in the ring in the case of HF, it

ranges from 1.3761 to 1.3989 Å whereas in B3LYP from 1.3894 to 1.4078 Å which are

in good agreement with the earlier experimental data (1.380 – 1.404 Å) of aniline. The

calculated C-CH3 bond length (1.51 Å) is found lower than the experimental value of p-

methylaniline (1.55 Å) which may be due to the electron donating nature [36]. As stated

in the earlier literature on benzene derivatives [37], the calculated C-Cl bond length of

1.77 Å (B3LYP) and 1.75 Å (HF) indicates a considerable increase in the bond length

when compared with C-H bond length. Bakiler et al. [38] calculated this bond length

1.746 Å for 3-chloropyridine and 1.784 Å for 2-chloropyrinde by using force field

calculations. Kurt et al [39] calculated C-Cl bond length as 1.767 Å (B3LYP) and 1.75 Å

(HF) in 3-chloro-4-methylaniline. The computed bond length was also found to be 1.735

- 1.744 Å for similar molecule [40, 41]. The C-N bond distance is 1.39 Å by

HF/B3LYP/6-31,6-31++ G(d,p) methods, which show just 0.01 Å lower than the

experimental value of 1.40 Å from the earlier literatures shown in Table 1, whereas

0.04 Å lower than the experimental value (1.43 Å) in the of 4-methyl aniline [46]. While

71

comparing the calculated bond length values of N-H with experimental data, it is clear

that the HF/6-31 G (d,p) and 6-31++G(d,p) bond lengths are slightly shorter due to the

neglect of electron correlation, while the B3LYP/6-31 G(d,p) and 6-31++ G(d,p) bond

lengths are closer to the experimental data due to slightly exaggerated electron correlation

effect. This reveals that bond lengths calculated by B3LYP method are more accurate.

2.3.2 Vibrational assignments

The maximum number of potentially active observable fundamentals of a non-

linear molecule which contains N atoms is equal to (3N-6), apart from three translational

and three rotational degrees of freedom [42]. Hence, 2Cl4MA molecule has 17 atoms

with 45 normal modes of vibrations. The molecule is considered under C1 point group

symmetry. For N-atomic molecule, 2N-3 of its vibrations is planar and N-3 is non-planar

[43]. Thus, with respect to the reflection on the symmetry plane, 31 of these modes

should be planar (A’) and 14 should be non planar (A”). The 45 normal modes of

vibrations are distributed amongst the symmetry species as

ΓVib = 31 A′ + 14 A

″.

The detailed vibrational analysis of fundamental modes with FTIR and FT Raman

experimental frequencies, unscaled and scaled vibrational frequencies using HF method

with 6-31G(d,p) and 6-31++G(d,p) basis sets, IR intensity, Raman activity,

depolarization ratio, reduced mass and force constant of 2Cl4MA are reported in the

Table 2 and 3 respectively. In Table 4 and 5, the values are further calculated using

B3LYP method with same basis sets is presented. For visual comparison, the

72

experimental spectra with calculated spectra of FTIR and FT Raman in solid phase using

HF/B3LYP methods are shown in the Figures 2-5 respectively.

In order to improve the calculated values in agreement with the experimental

values, it is necessary to scale down the calculated harmonic frequencies. Hence, the

vibrational frequencies calculated at B3LYP level are scaled by 0.9614 and 1.0013 where

as 0.914 and 0.9 for HF as recommended by Rahut et al [44]. Separate scaling factors of

0.885 and 0.94 were used with HF and B3LYP respectively for NH2 stretching vibrations.

2.3.3 C-H Vibrations

Normally, the C-H stretching vibrations are observed around 3100 – 3000 cm-1

in

aromatic molecules which is a ready identification of the benzene structure [45, 46]. This

must be due to one symmetric and two asymmetric stretches. One symmetric stretching is

observed at 3030 cm-1

in IR and two asymmetric stretching modes at 3070 and 3060 cm-1

in Raman. The C-H in plane bending vibrations usually occurs in the region 1430-990

cm-1

and is very useful for characterization purposes [47]. As stated in the earlier

literature [47], in this work, the peaks at 1270, 1240 and 1210 cm-1

occur due to the C-H

in-plane-bending vibrations. The substitution patterns on the ring can be judged from the

out of plane bending vibrations of the ring C-H bond in the region 900-675 cm-1

which

are highly informative [48]. The IR peaks at 890, 880 and 820 cm-1

confirms the C-H out

of plane bending vibrations. Though all the C-H vibrations are well within the expected

range, the in plane and the out of plane vibrations are shifted up to the top end of the

expected range which confirms that the substitutions favour the ring C-H vibrations.

73

2.3.4 C-C Vibrations

The bands in the region 1430 - 1650 cm-1

are usually assigned to CC stretching

modes [49-51]. As predicted in the earlier references, in this case, the prominent peaks at

1505, 1460 and 1440 cm-1

are due to strong ring C=C stretching vibrations whereas the

peaks at 1410, 1380 and 1320 cm-1

are assigned to the ring C-C stretching vibrations.

The C-C-C in plane and out of plane bending vibrations is observed at 540, 500 and 480

cm-1

and 440, 400 and 350 cm-1

respectively. Some bands of C-C stretching, all the in

and out-of-plane bending vibrations are lowered down. This may be due to the Cl and

NH2 substitutions with heavier mass in the ring.

The C-C stretching vibration associated with methyl group is observed at 1240

cm-1

and is mixed with the ring C-H bending vibration. When compared with ring C-C

stretching mode of vibration, it is found to be shifted down to the lower region, as there is

three H atoms attached to this bond. The corresponding in and out of plane bending

vibrations is observed at 200 and 100 cm-1

. These vibrations are found in the lowest

region.

2.3.5 Methyl group vibrations

For the assignments of methyl group frequencies, basically nine fundamentals can

be associated [58], namely, C-H stretch, C-H in-plane bends and C-H out of plane

bending vibrations. The C-H stretching of methyl group occurs at lower frequencies than

those of aromatic ring (3100-3000 cm-1

). The vibrations of methyl group in this molecule

are observed at 3000, 2930 and 2920 cm-1

. These assignments are within the typical range

as reported in earlier literatures [52-56]. The strong peaks are observed at 1095, 1050 and

74

1000 cm-1

in IR and at 880, 820 and 780cm-1

are assigned to C-H in-plane and out of

plane bending modes respectively, which are in good agreement with the value reported

by Durig et al [57]. The calculated values of methyl C-H stretching modes by B3LYP/6-

31++G (d, p) method also closely coincides with experimental values.

2.3.6 NH2 vibrations

The NH2 group gives rise to the six internal modes of vibrations such as the

asymmetric stretching (as), symmetric stretching (s), the symmetric planar deformation

or scissoring, the antisymmetric planar deformation or rocking, the symmetric non-planar

deformation or wagging and the anti-symmetric non-planar deformation or torsion. The

symmetric (s) and anti symmetric stretching (as) modes is easily assigned owing to their

characteristic magnitudes in tri-substituted benzenes. These modes satisfy the following

empirical relation, provided the two NH bonds are identical [68].

s = 345.5 + 0.876as

The NH2 stretching vibrations show the characteristic frequency shift caused by

the halogen substituent [59-61]. Based on the above literature the band observed at 3465

cm-1

in IR is assigned to NH2 asymmetric stretch and at 3380 cm-1

assigned to NH2

symmetric stretch. Bellamy and Mancy [62-63] suggested that NH2 scissoring mode lie in

the region 1590 – 1650 cm-1

. It is concluded from the above literature that the strong

band at 1630 cm-1

and medium band at 1600 cm-1

both in IR and Raman are assigned to

NH2 scissoring mode. In this study, the NH2 rocking mode is observed as weak intensity

band in IR at 930 and 900 cm-1

which is in good coherence with the literature [64]. From

75

these vibrational assignments, it is inferred that the NH2 vibrations are not affected by the

substitutions.

2.3.7 C-Cl vibrations

The vibrations belonging to the bond between the ring and the halogen atoms are

worth to discuss here, since mixing of the vibrations is possible due to the lowering of the

molecular symmetry and the presence of heavy atom on the periphery of molecule [65].

Mooney [66, 67] assigned vibrations of C-Cl in the frequency range 750-480 cm-1

. Based

on these literature values, a strong band is observed at 720 cm-1

is assigned to C-Cl

stretching vibration. The C-Cl in-plane bending vibration is observed around 300 cm-1

for

chloro derivatives [68]. In this work, C-Cl in plane bending vibration is found at 200 cm-1

and the corresponding out of plane bending is observed at 160 cm-1

. This decrease in

wave number may be due the coupled in-plane-bending effect of C-CH3. The deviation

for C-Cl bending vibrations towards lower range of spectrum may be due to the adjacent

substitutions.

2.3.8 C-N vibrations

The C-N stretching frequency is rather a difficult task, since there are problems in

identifying these frequencies from other vibrations [69]. The C-N stretching vibration is

usually assigned in the region 1386 – 1266 cm-1

[70] for aromatic amines. In the present

work, the C-N stretching is observed at 1300 cm-1

which is in line with the literature [71].

The bands with very strong intensity found at 250 and 110 cm-1

are assigned to C-N in-

plane and out-of-plane bending vibrations respectively. The observation of these bands

76

indicates that they are not much affected by other vibrations. The theoretically computed

frequencies by B3LYP/6-31++G (d, p) method also shows excellent agreement observed

values [72-73]. These vibrations are also observed only in Raman spectrum with very

strong intensity.

2.3.8 Other molecular properties

Several calculated thermo dynamical parameters, rotational constants, rotational

temperature, dipole moment and polarizability of 2Cl4MA are presented in Table 6. The

Zero-Point Vibration Energies (ZPVE), entropy, Svib (T) and the molar capacity at

constant volume are also calculated. The variations in the ZPVEs seem to be

insignificant. The total energies are found to decrease with the increase of the basis set

dimension. The changes in the total entropy of 2Cl4MA at room temperature at different

basis sets are only marginal.

2.4. Conclusion

A detailed vibrational assignment and analysis is carried out for the molecule

2Cl4MA. The equilibrium geometries, harmonic vibrational frequencies, IR and Raman

spectra of 2Cl4MA are also determined and analyzed theoretically by ab initio-HF and

DFT (B3LYP) methods with 6-31G (d, p) and 6-31++G (d, p) basis sets. From the

analysis, the following observations are made.

1. The global minimum energy obtained by HF and DFT structure

optimization using 6-31G (d, p) and 6-31++G (d,p) basis sets for the

molecule are as -783.6857 a.u, -783.6947 a.u, -786.5317 a.u. and -

77

786.5462 a.u. respectively. It is found that the values are decreased with

higher basis sets.

2. From the calculated bond length values of N-H with experimental data, it

is clear that the HF/6-31G (d,p) and 6-31++G(d,p) bond lengths are

slightly shorter due to the neglect of electron correlation, while the

B3LYP/6-31G(d,p) and 6-31++G(d,p) bond lengths are closer to the

experimental data due to slightly exaggerated electron correlation effect.

This reveals that bond lengths calculated by B3LYP method are more

accurate.

3. All the C-H vibrations are well within the expected range, the in plane and

the out of plane vibrations are shifted up which confirms that the

substitutions favour the ring C-H vibrations.

4. Some bands of C-C stretching, all the in and out-of-plane bending

vibrations are lowered down. This may be due to the Cl and NH2

substitutions with heavier mass in the ring.

5. The calculated values of methyl C-H stretching modes by B3LYP/6-

31++G (d, p) method also closely coincides with experimental values and

most of the C-CH3 vibrations occur as coupled vibrations along with C-

NH2 and C-Cl vibrations.

6. The NH stretching vibrations are found to be not influenced by the other

substitutions in the molecule. The unaffected vibrations of NH2 reveal its

strong covalent, dipole and dispersion bond nature.

78

7. All the bands for C-Cl vibrations are of greater intensity which shows that

there exists a strong dipole moment for C-Cl bond.

The comparison of the simulated spectra provides important information about the

capability of the computational methods to describe the vibrational modes. The B3LYP

method with 6-31++G (d, p) basis set is found to have greater potential to predict both

vibrational parameter such as frequencies, intensities, Raman activities etc and the

structural parameters such as bond angles, bond lengths etc when compared to other

methods.

FIGURES

Table 2.1: Optimized geometrical parameters for 2Cl4MA computed at HF/6-31G (d, p), HF/6-31++G (d, p), B3LYP/6-31G

(d, p) and 6-31++G (d, p) basis sets

Parameters HF B3LYP

Experimental values 6-31G(d,p) 6-31++G(d,p) 6-31G(d,p) 6-31++G(d,p)

Bond length (A)

C1-C2 1.3877 1.3874 1.4057 1.4055 1.404(22)a, 1.397(19)b

C1-C6 1.3978 1.3989 1.407 1.4078 1.404(22)a, 1.397(19)b

C1-N10 1.3866 1.3883 1.3889 1.3909 1.398(22)a, 1.402(27)b

C2-C3 1.3865 1.3885 1.3918 1.394 1.380(23)a, 1.394(20)b

C2-Cl13 1.7519 1.7506 1.7685 1.7671

C3-C4 1.3817 1.3829 1.3978 1.3988 1.386(23)a,1.396(27)b

C3-H7 1.0747 1.0748 1.0854 1.0857 0.95(20)a

C4-C5 1.3935 1.3953 1.4015 1.4033 1.386(23)a,1.396(27)b

C4-C14 1.5108 1.5113 1.5106 1.5117

C5-C6 1.3761 1.3778 1.3894 1.3912 1.380(23)a, 1.394(20)b

C5-H8 1.0769 1.0768 1.087 1.0872 0.95(20)a, 1.083(27)b

C6-H9 1.0765 1.0764 1.0871 1.0873 1.03(19)a,1.084(20)b

N10-H11 0.9948 0.9953 1.0099 1.0099 1.07(22)a,1.001(26)b

N10-H12 0.9945 0.9951 1.0106 1.0107 1.07(21)a,1.004(26)b

C14-H15 1.0862 1.0861 1.0974 1.0975

C14-H16 1.0838 1.0839 1.0939 1.0942

C14-H17 1.0861 1.086 1.0947 1.0951

Bond angle ( 0

)

C2-C1-C6 116.6298 116.7008 116.4021 116.5016 122a

C2-C1-N10 122.8212 122.7953 122.3072 122.3032

C6-C1-N10 120.5033 120.4499 121.2427 121.1451 124a

C1-C2-C3 121.9145 121.8873 122.1637 122.099 119a

C1-C2-Cl13 119.6954 119.7156 119.9596 119.0369

C3-C2-Cl13 118.39 118.3969 118.8731 118.8613

C2-C3-C4 121.1434 121.168 120.9227 120.9665 117a

C2-C3-H7 118.4705 118.4583 118.7514 118.725

C4-C3-H7 120.386 120.3736 120.3254 120.308

C3-C4-C5 117.3026 117.2772 117.4347 117.4063

C3-C4-C14 121.584 121.6162 121.1075 121.1565

C5-C4-C14 121.1134 121.1065 121.4484 121.4276

C4-C5-C6 121.5629 121.5413 121.5684 121.5401

C4-C5-H8 119.5741 119.6148 119.4911 119.5493

C6-C5-H8 118.8629 118.8437 118.9404 118.9106

C1-C6-C5 121.4468 121.4252 121.507 121.4851 117a

C1-C6-H9 118.7027 118.7812 118.5652 118.6669

C5-C6-H9 119.8488 119.7919 119.9276 119.8477

C1-N10-H11 114.6218 114.8237 115.071 115.8309

C1-N10-H12 115.6332 115.8311 115.3518 116.1626

H11-N10-H12 112.4557 112.4542 112.9978 113.4752

C4-C14-H15 111.2621 111.1948 111.5555 111.4208

C4-C14-H16 111.1884 111.0992 111.4631 111.4027

C4-C14-H17 111.281 111.2012 111.3622 111.3241

H15-C14-H16 107.705 107.7572 107.2827 107.401 119a

H15-C14-H17 107.4974 107.6421 107.1438 107.2708

H16-C14-H17 107.7235 107.7774 107.8062 107.8102

Table 2.2Experimental and calculated HF/6-31G (d,p) level vibrational frequencies (cm-1), IR Intensity (KM Mol-1),

Raman Activity (A04

amu-1), of 2Cl4MA

S.

No

Symmetry

Species

Experimental

Frequency

HF/6-31G(d,p) IR

Intensity

Raman

Activity

Vibrational Assignments

FT-IR FT-

Raman

Unscaled Scaleda Abs Rel Abs Rel

1 A’ 3465s - 3930 3478 27 12 48 27 (N-H) υ

2 A’ 3380s - 3818 3379 33 14 125 70 (N-H) υ

3 A’ - 3070s 3369 3079 4 2 76 43 (C-H) υ

4 A’ - 3060s 3352 3064 25 11 140 78 (C-H) υ

5 A’ 3030m - 3332 3046 13 6 58 32 (C-H) υ

6 A’ - 3000m 3264 2983 24 11 62 34 (CH3) (C-H) υ

7 A’ - 2930m 3236 2957 34 15 103 58 (CH3) (C-H) υ

8 A’ 2920m - 3181 2908 49 22 179 100 (CH3) (C-H) υ

9 A’ 1630s 1630s 1829 1646 99 44 54 30 (N-H) δ

10 A’ 1600m 1600m 1802 1621 40 18 6 4 (N-H) δ

11 A’ 1505s - 1769 1592 8 3 4 2 (C=C) υ

12 A’ 1460m - 1677 1510 113 50 3 1 (C=C) υ

13 A’ - 1440w 1628 1465 16 7 15 8 (C=C) υ

14 A’ - 1410w 1614 1452 4 2 20 11 (C-C) υ

15 A’ - 1380s 1561 1405 10 4 2 1 (C-C) υ

16 A” 1320w - 1552 1397 6 3 20 11 (C-C) υ

17 A’ 1300s 1300s 1443 1299 20 9 2 1 (C-N) υ

18 A’ 1270m - 1407 1266 36 16 12 6 (C-H) δ

19 A’ - 1240s 1332 1199 17 7 5 3 (C-H) δ(C-C) υ

20 A’ 1210s 1210s 1319 1187 2 1 2 1 (C-H) δ

21 A’ 1150s - 1235 1111 17 7 4 2 (C-H) δ

22 A’ 1095w - 1196 1076 33 15 3 2 (C-H) δ

23 A’ 1050s - 1167 1050 3 1 0 0 (C-H) δ

24 A’ 1000m - 1145 1031 12 5 2 1 (C-H) δ

25 A’ 930w - 1084 976 29 13 6 3 (N-H) γ

26 A” - 900s 1080 972 2 1 1 0 (N-H) γ

27 A’ 890w - 1007 907 4 ss 3 1 (C-H) γ 28 A” 880w - 961 865 14 6 16 9 (C-H) γ 29 A” 820s - 920 828 52 23 3 1 (C-H) γ 30 A’ - 780s 836 752 12 6 3 2 (C-H) γ 31 A” 720s - 800 720 14 6 2 1 (C-Cl) υ

32 A’ 695s 695s 748 673 13 6 9 5 (C-H) γ 33 A” 570s - 650 585 225 100 4 2 (C-H) γ 34 A” - 540w 605 545 125 56 2 1 (CCC) δ 35 A’ - 500s 533 479 2 1 6 3 (CCC) δ 36 A’ - 480s 510 459 3 1 10 6 (CCC) δ 37 A” 440m - 496 446 14 6 0 0 (CCC) γ 38 A” - 400s 433 390 1 0 4 2 (CCC) γ 39 A” - 350s 367 331 4 2 2 1 (CCC) γ

40 A” 300s 300s 322 290 9 4 1 1 (C-Cl) δ

41 A” - 250s 286 257 18 8 1 0 (C-NH2) δ 42 A” 200m - 248 223 1 0 1 1 (C-CH3) δ

43 A” 160m - 199 179 2 1 2 1 (C-Cl) γ 44 A” - 110w 148 133 3 1 1 1 (C-NH2) γ

45 A” 100w - 35 31 0 0 0 0 (C-CH3) γ

w – weak, m – medium, s – strong, - stretching, s - symmetric stretching, as- asymmetric stretching, - in-plane-bending,- out-of-plane

bending, - rocking,wagging, t- twisting, torsion, sci – scissoring, sym – symmetric, asym – asymmetric, d- deformation

Table 2.3Experimental and calculated HF/6-31++G (d, p) level vibrational frequencies (cm-1), IR Intensity (KM Mol-1),

Raman Activity (A04

amu-1), of 2Cl4MA

S.No

Symmetry

Species

Experimental

Frequency

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

Intensity

Raman

Activity

Vibrational

Assignments FT-IR FT-

Raman

Unscaled Scaleda Abs Rel Abs Rel

1 A’ 3465s - 3925 3474 32 18 39 18 (N-H) υ

2 A’ 3380s - 3814 3376 34 19 129 61 (N-H) υ

3 A’ - 3070s 3369 3079 4 2 77 36 (C-H) υ

4 A’ - 3060s 3353 3065 22 12 141 66 (C-H) υ

5 A’ 3030m - 3333 3047 13 7 59 28 (C-H) υ

6 A’ - 3000m 3260 2980 25 14 63 30 (CH3) (C-H) υ

7 A’ - 2930m 3233 2955 27 15 95 45 (CH3) (C-H) υ

8 A’ 2920m - 3180 2907 52 29 213 100 (CH3) (C-H) υ

9 A’ 1630s 1630s 1822 1640 119 67 46 21 (N-H) δ

10 A’ 1600m 1600m 1791 1612 24 14 11 5 (N-H) δ

11 A’ 1505s - 1762 1586 9 5 4 2 (C=C) υ

12 A’ 1460m - 1670 1503 117 66 3 1 (C=C) υ

13 A’ - 1440w 1622 1460 18 10 9 4 (C=C) υ

14 A’ - 1410w 1608 1448 6 3 12 6 (C-C) υ

15 A’ - 1380s 1553 1398 8 5 2 1 (C-C) υ

16 A” 1320w - 1548 1393 6 3 15 7 (C-C) υ

17 A’ 1300s 1300s 1439 1295 18 10 2 1 (C-N) υ

18 A’ 1270m - 1400 1260 44 25 20 9 (C-H) δ

19 A’ - 1240s 1330 1197 18 10 6 3 (C-H) δ(C-C) υ

20 A’ 1210s 1210s 1316 1184 1 1 3 1 (C-H) δ

21 A’ 1150s - 1232 1109 17 10 4 2 (C-H) δ

22 A’ 1095w - 1194 1074 33 18 2 1 (C-H) δ

23 A’ 1050s - 1166 1050 2 1 0 0 (C-H) δ 24 A’ 1000m - 1143 1029 11 6 2 1 (C-H) δ

25 A’ 930w - 1083 974 25 14 5 2 (N-H) γ

26 A” - 900s 1082 974 2 1 0 0 (N-H) γ

27 A’ 890w - 1007 906 6 3 0 0 (C-H) γ 28 A” 880w - 958 862 14 8 23 11 (C-H) γ 29 A” 820s - 919 827 59 33 0 0 (C-H) γ 30 A’ - 780s 833 750 12 7 4 2 (C-H) γ 31 A” 720s - 811 730 7 4 3 2 (C-Cl) υ

32 A’ 695s 695s 746 672 12 7 10 5 (C-H) γ 33 A” 570s - 652 587 178 100 2 1 (C-H) γ 34 A” - 540w 608 548 131 74 2 1 (CCC) δ 35 A’ - 500s 532 479 2 1 6 3 (CCC) δ 36 A’ - 480s 509 458 2 1 12 6 (CCC) δ 37 A” 440m - 496 446 17 9 0 0 (CCC) γ 38 A” - 400s 433 390 1 0 5 2 (CCC) γ 39 A” - 350s 366 329 4 2 2 1 (CCC) γ

40 A” 300s 300s 321 288 8 5 1 0 (C-Cl) δ

41 A’ - 250s 290 261 18 10 0 0 (C-NH2) δ 42 A’ 200m - 248 223 1 0 1 1 (C-CH3) δ

43 A” 160m - 199 179 3 1 1 0 (C-Cl) γ 44 A” - 110w 147 132 3 2 1 0 (C-NH2) γ

45 A” 100w - 36 32 0 0 0 0 (C-CH3) γ

w – weak, m – medium, s – strong, - stretching, s - symmetric stretching, as- asymmetric stretching, - in-plane-bending,- out-of-plane

bending,- rocking,wagging, t- twisting, torsion, sci – scissoring, sym – symmetric, asym – asymmetric, d- deformation.

Table 2.4; Experimental and calculated B3LPY/6- 31(d,p)level vibrational frequencies (cm-1), IR Intensity (KM Mol-1),

Raman Activity (A04

amu-1), of 2Cl4MA

S.No

Symmetry

Species

Experimental

Frequency

B3LYP/6-

31G(d,p)

IR

Intensity

Raman

Activity

Vibrational Assignments

FT-IR FT-

Raman

Unscaled Scaleda Abs Rel Abs Rel

1 A’ 3465s - 3687 3466 20 10 55 61 (N-H) υ

2 A’ 3380s - 3576 3361 25 13 169 26 (N-H) υ

3 A’ - 3070s 3202 3078 3 2 84 27 (C-H) υ

4 A’ - 3060s 3188 3065 21 11 145 41 (C-H) υ

5 A’ 3030m - 3171 3048 12 6 62 100 (C-H) υ

6 A’ - 3000m 3122 3002 16 8 64 27 (CH3) (C-H) υ

7 A’ - 2930m 3093 2974 22 11 98 2 (CH3) (C-H) υ

8 A’ 2920m - 3035 2917 42 21 238 2 (CH3) (C-H) υ

9 A’ 1630s 1630s 1681 1616 92 47 64 1 (N-H) δ

10 A’ 1600m 1600m 1649 1585 42 22 5 6 (N-H) δ

11 A’ 1505s - 1617 1554 5 2 4 10 (C=C) υ

12 A’ 1460m - 1552 1492 108 55 3 1 (C=C) υ

13 A’ - 1440w 1511 1452 13 7 15 17 (C=C) υ

14 A’ - 1410w 1501 1443 5 2 23 2 (C-C) υ

15 A’ - 1380s 1450 1394 4 2 2 3 (C-C) υ

16 A” 1320w - 1430 1374 2 1 41 2 (C-C) υ

17 A’ 1300s 1300s 1359 1306 13 6 4 4 (C-N) υ

18 A’ 1270m - 1341 1289 43 22 8 1 (C-H) δ

19 A’ - 1240s 1300 1250 7 3 4 2 (C-H) δ(C-C) υ

20 A’ 1210s 1210s 1237 1189 10 5 9 1 (C-H) δ

21 A’ 1150s - 1186 1141 9 5 2 1 (C-H) δ

22 A’ 1095w - 1105 1063 11 6 4 1 (C-H) δ

23 A’ 1050s - 1065 1024 8 4 3 1 (C-H) δ

24 A’ 1000m - 1059 1018 17 9 1 8 (C-H) δ

25 A’ 930w - 1018 979 13 7 2 1 (N-H) γ

26 A” - 900s 944 907 0 0 1 1 (N-H) γ

27 A’ 890w - 897 898 17 9 20 2 (C-H) γ

28 A” 880w - 887 888 6 3 4 0 (C-H) γ

29 A” 820s - 822 823 33 17 3 3 (C-H) γ

30 A’ - 780s 783 784 11 5 4 1 (C-H) γ

31 A” 720s - 715 715 7 4 1 2 (C-Cl) υ

32 A’ 695s 695s 697 698 11 6 8 2 (C-H) γ

33 A” 570s - 582 583 139 71 3 4 (C-H) γ

34 A” - 540w 551 552 196 100 4 0 (CCC) δ

35 A’ - 500s 492 493 3 2 5 2 (CCC) δ

36 A’ - 480s 478 478 5 2 10 0 (CCC) δ

37 A” 440m - 445 445 10 5 0 0 (CCC) γ

38 A” - 400s 401 401 1 0 4 0 (CCC) γ

39 A” - 350s 343 343 7 4 1 1 (CCC) γ

40 A” 300s 300s 320 321 19 10 1 1 (C-Cl) δ

41 A’ - 250s 298 298 2 1 1 1 (C-NH2) δ

42 A’ 200m - 233 233 0 0 2 0 (C-CH3) δ

43 A” 160m - 182 182 2 1 2 0 (C-Cl) γ

44 A” - 110w 136 136 3 1 1 0 (C-NH2) γ

45 A” 100w - 45 45 0 0 0 0 (C-CH3) γ a

w– weak, m – medium, s – strong, - stretching, s - symmetric stretching, as- asymmetric stretching, - in-plane-bending,

- out-of-plane bending, - rocking,wagging, t- twisting, torsion, sci – scissoring, sym – symmetric, asym – asymmetric, d- deformation

Table 2.5; Experimental and calculated B3LYP/6- 31++ G (d, p) level vibrational frequencies (cm-1),

IR Intensity (KM Mol-1), Raman Activity (A04

amu-1) of 2Cl4MA

S.

No

Symmetry

Species

Experimental

Frequency

B3LYP/631++G(d,p) IR

Intensity

Raman

Activity

Vibrational

Assignments FT-IR FT-

Raman

Unscaled Scaleda Abs Rel Abs Rel

1 A’ 3465s - 3692 3471 28 10 47 15 (N-H) υ

2 A’ 3380s - 3580 3365 27 10 187 61 (N-H) υ

3 A’ - 3070s 3199 3076 3 1 94 31 (C-H) υ

4 A’ - 3060s 3187 3064 20 7 160 52 (C-H) υ

5 A’ 3030m - 3170 3048 13 5 68 22 (C-H) υ

6 A’ - 3000m 3116 2995 17 6 69 23 (CH3) (C-H) υ

7 A’ - 2930m 3087 2968 20 8 104 34 (CH3) (C-H) υ

8 A’ 2920m - 3030 2913 47 17 307 100 (CH3) (C-H) υ

9 A’ 1630s 1630s 1671 1607 112 42 60 19 (N-H) δ

10 A’ 1600m 1600m 1645 1581 34 12 8 3 (N-H) δ

11 A’ 1505s - 1609 1547 6 2 4 1 (C=C) υ

12 A’ 1460m - 1543 1483 123 46 2 1 (C=C) υ

13 A’ - 1440w 1501 1443 16 6 8 3 (C=C) υ

14 A’ - 1410w 1492 1435 7 3 13 4 (C-C) υ

15 A’ - 1380s 1440 1385 5 2 2 1 (C-C) υ

16 A” 1320w - 1423 1368 0 0 31 10 (C-C) υ

17 A’ 1300s 1300s 1353 1301 12 5 6 2 (C-N) υ

18 A’ 1270m - 1331 1279 51 19 12 4 (C-H) δ

19 A’ - 1240s 1293 1243 11 4 8 3 (C-H) δ(C-C) υ

20 A’ 1210s 1210s 1232 1185 11 4 11 4 (C-H) δ

21 A’ 1150s - 1182 1136 10 4 2 1 (C-H) δ

22 A’ 1095w - 1097 1055 14 5 3 1 (C-H) δ

23 A’ 1050s - 1063 1022 7 3 3 1 (C-H) δ 24 A’ 1000m - 1056 1015 14 5 1 0 (C-H) δ

25 A’ 930w - 1014 974 12 4 1 0 (N-H) γ

26 A” - 900s 950 951 1 0 0 0 (N-H) γ

27 A’ 890w - 894 895 17 6 27 9 (C-H) γ 28 A” 880w - 885 886 8 3 1 0 (C-H) γ 29 A” 820s - 822 823 40 15 0 0 (C-H) γ 30 A’ - 780s 780 781 13 5 5 2 (C-H) γ 31 A” 720s - 719 720 1 0 2 1 (C-Cl) υ

32 A’ 695s 695s 692 693 10 4 9 3 (C-H) γ 33 A” 570s - 573 574 23 8 1 0 (C-H) γ 34 A” - 540w 534 535 269 100 3 1 (CCC) δ 35 A’ - 500s 490 491 6 2 6 2 (CCC) δ 36 A’ - 480s 477 477 5 2 11 4 (CCC) δ 37 A” 440m - 445 446 16 6 0 0 (CCC) γ 38 A” - 400s 401 401 1 0 4 1 (CCC) γ 39 A” - 350s 343 344 7 3 1 0 (CCC) γ

40 A” 300s 300s 318 319 18 7 1 0 (C-Cl) δ

41 A’ - 250s 297 297 3 1 1 0 (C-NH2) δ 42 A’ 200m - 232 233 0 0 2 1 (C-CH3) δ

43 A” 160m - 181 182 2 1 1 0 (C-Cl) γ 44 A” - 110w 134 135 3 1 1 0 (C-NH2) γ

45 A” 100w - 43 43 0 0 1 0 (C-CH3) γ a

w – weak, m – medium, s – strong, - stretching, s - symmetric stretching, as- asymmetric stretching, - in-plane-bending,

- out-of-plane bending,- rocking,wagging, t- twisting, torsion, sci – scissoring, sym – symmetric, asym – asymmetric, d- deformation.

Table 2.6; Computed Zero point vibrational energy (kcal mol-1), rotational constants (GHz),

rotational temperature (Kelvin), thermal energy (kcal mol-1), molar capacity at constant volume (cal mol-1 Kelvin-1),

entropy (cal mol-1Kelvin-1), dipole moment, μ (Debyes) and averaged electronic dipole polarizability, α (au).

Parameter HF B3LYP

Basis set 6-31 G(d,p) 6-31++ G(d,p) 6 6-31 G(d,p) 6-31++ G(d,p) 6

Zero Point

Vibrational

Energy 90.67384 90.55675 84.88886 84.66056

Rotational

Constants 2.27686 2.27558 2.25646 2.25362

Rotational

Temperatures 1.07912 1.07782 1.06261 1.06122

Energy 0.73587 0.73513 0.72612 0.72514

Molar capacity

at constant

volume 0.10927 0.10921 0.10829 0.10816

Entropy 0.05179 0.05173 0.051 0.05093

Dipole

moment 0.03532 0.03528 0.03485 0.0348

Polarisability 95.905 95.786 90.404 90.197