S.Özdemir Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 1174–1183
1181
Table 4
of the vibrations, 39 modes are stretching vibration, 38 are bending
modes of the vibrations and the remaining 37 modes are torsional
vibrational. This molecule has 36 CH vibrational modes.
The experimental and theoretical 1H and 13C NMR chemical shifts (with respect to
TMS) for the title molecule in the medium of DMSO (all values in ppm).
Atom (indices)
Experiment
Calculations
It is important to deal with the some fundamental vibrational
modes observed in the material studied in this work. For example,
the bands of the NAH stretching vibrations are observed at the
wavenumbers of 3876 cmÀ1, 3737 cmÀ1 and 3567 cmÀ1 while the
theoretical scaled values of NAH vibrations are predicted as
3528 cmÀ1, 3447 cmÀ1 and 3430 cmÀ1 by using DFT/B3LYP/6-
DFT/B3LYP/6-31G(d)
HF/6-31G(d)
H39 (a)
H40 (a)
H34 (b)
H37 (b)
H35 (c)
H36 (c)
H25 (d)
H6 (e)
H21 (e)
H7 (f)
H22 (f)
H8 (g)
H23 (g)
H14 (h)
H15 (h)
C28 (a)
C29 (b)
C33 (b)
C30 (c)
C32 (c)
C31 (d)
C26 (e)
C1 (f)
C16 (f)
C2 (g)
C17 (g)
C4 (i)
C19 (i)
C9 (j)
C12 (j)
C10 (k)
C11 (k)
C3 (h)
5.81
5.81
3.10
3.08
2.75
2.76
6.59
6.17
6.38
6.59
6.26
6.64
7.67
7.22
7.38
31G(d), respectively. They are also calculated as 3498 cmÀ1
3447 cmÀ1 and 3406 cmÀ1 via the HF/6-31G(d).
,
7.67
7.54
8.26
11.40
7.31
6.44
6.59
5.88
7.12
The CAH stretching vibrations of aromatic and heteroaromatic
structures are normally found in the region of 3000–3100 cmÀ1
[41]. They are observed at the 2780 cmÀ1 and 3067 cmÀ1. The scaled
streching CAH vibrations in the ranges of 3148–3059 cmÀ1 and
3009–3083 cmÀ1 are calculated by using DFT/B3LYP/6-31G(d) and
HF/6-31G(d) methods, respectively. From Table 3, the theoretically
calculated results scaled down corresponding with CAH stretching
vibrations show good agreement with the experimentally observed
vibrations.
In case of O@C stretching vibration, a very strong band at
1679 cmÀ1 in FT-IR spectra is attributed the O@C stretching vibra-
tion, which is in agreement with the scaled results at 1718 cmÀ1
(for DFT/6-31G(d)) and 1750 cmÀ1 (for HF/6-31G(d)).
7.31
6.66
7.11
6.97
6.59
6.83
6.97
6.60
6.85
7.21
6.88
6.92
7.21
6.61
6.98
6.50
6.03
6.21
6.50
6.18
6.13
152.92
112.81
112.81
129.60
129.60
118.03
165.82
127.28
127.28
124.43
124.43
132.67
132.67
132.10
132.10
106.61
106.61
123.39
123.39
136.59
99.98
100.57
114.60
118.82
106.36
152.36
116.05
118.56
111.47
111.81
124.98
125.15
116.54
118.05
97.95
93.53
108.79
113.66
152.01
106.37
107.70
130.01
134.17
112.92
163.88
127.85
129.75
121.60
120.68
132.67
132.41
126.39
126.84
105.48
104.22
123.19
126.84
There is one stretching vibration at 1611 cmÀ1 in the FT-IR spec-
trum, assigned to C@C stretching vibration. The value for C@C
stretching vibration is calculated at 1605 cmÀ1 and 1618 cmÀ1 by
using DFT/B3LYP/6-31G(d) and HF/6-31G(d) methods, respectively.
The mainly carbon–carbon vibrations modes named as stretch-
ing, in-plane-bending, out-of plane bending and torsion occur in
the region of 1611–453 cmÀ1. The vibrational data calculated from
DFT and HF methods with the basis set of 6-31G(d) are compatible
with the corresponding observed values of the FT-IR. The other
observed vibrations of the title molecule are also given in Table 3.
It is to say that it is difficult to assign all bands due to the complex-
ity of the vibration bands. Therefore, it is shown that only charac-
teristic vibration bands can be identified.
C18 (h)
Labels of the atoms in this Table are given according to Fig. 1(a) used in the
assignment of the chemical shifts.
The correlation graphs of the calculated versus experimental
vibrational frequencies for the title molecule are given in Fig. 3(a)
and (b) predicted from DFT and HF levels, respectively. Linear
regression is carried out by using the linear equation of y = A + Bx,
where A and B are fit constants. The correlation between the exper-
imental and the calculated frequencies after scaling are linear as
shown in Fig. 3(a) and (b). The equalities; y = 18.74 + 1.01x
(R2 = 0.9944) and y = 6.36 + 1.03 x (R2 = 0.9949) are obtained by
using the methods of DFT/B3LYP and HF, respectively. It can be con-
cluded that the frequency values obtained from the methods of DFT/
B3LYP and HF are consistent with the experimental data since the
slope and the intercept values in the case of both methods go to
unity and zero, respectively, as shown in Fig. 3.
set are presented in Table 2. In order to define the molecular struc-
ture of the title molecule 43 bond lengths, 68 bond angles and 129
dihedral angles are necessary. These bond lengths, bond angles and
dihedral angles are given in Table 2.
Rotational disorder around interannular single bonds in
molecule as seen in Fig. 1(b) contributes to the delocalization of
p-electrons along the conjugated backbone and hence to decrease
band gap.
Analysis of vibrational spectra
Vibrational spectroscopy is one of the most useful tools for
characterization of the chemical compounds in terms of both
experimental studies and theoretical calculations. In this present
study, we have performed a frequency calculation analysis to
obtain the spectroscopic signature of the title molecule. The exper-
imental FT-IR spectra of the title molecule and their corresponding
theoretical calculations of FT-IR spectra computed from DFT/B3LYP
and HF methods with basis set of 6-31G(d) are plotted in Fig. 2(a)–
(c), respectively. Some specific and important vibrational modes of
the theoretical data computed from DFT and HF methods are given
in Table 3 along with the assignment of fundamental vibration
modes. The experimental results are also given in Table 3 to
compare them with the corresponding theoretical results. All the
theoretical vibrational wavenumbers, IR intensity calculations
predicted from DFT/B3LYP/6-31G(d) and HF/6-31G(d) and assign-
ments of IR vibration modes of the title molecule are provided in
Table S1 as a Supplementary material. Of the 114 normal modes
NMR spectra
The characterization of the title molecule is further clarified by
the use of 1H and 13C NMR spectroscopy. The 1H and 13C NMR spec-
tra of the title molecule are recorded in the medium of dimethyl-
sulfoxide (DMSO). The experimentally observed 1H and 13C NMR
spectra of title molecule (with respect to TMS, and in DMSO solu-
tion) are shown in Fig. 4(a) and (b), respectively. 1H NMR
(400 MHz, 25 °C, in DMSO-d6 = 11.40d (s; 1Hd=25, ANHA), 7.67d
(d; 2Hc=35,36), 7.31d (d; 2He=6,21), 7.21d (d; 2Hg=8,23), 6.97d (t;
2Hf=7,22), 6.59d (d; 2Hb=34,37), 6.50d (s; 2Hh=14,15) 5,81d (br. s;
2Ha=39,40, ANH2). In the 1H NMR spectra of HKCN the resonance
of the NH proton appears as a singlet at 11.40 ppm. The broad
absorption peak appeared at 5.81 ppm is assigned to the NH2
protons of benzene ring. The signal of the aromatic atoms of the
Kart, Sevgi ?zdemir
