Synthesis, spectral properties, crystal structure and theoretical calculations of a new geminal diamine: 2,2,2-Trichloro-N,N?-bis(2-nitrophenyl)-ethane-1,1-diamine

Article abstract of DOI:10.1016/j.molstruc.2021.129976

A new 2,2,2-trichloro-N,N?-bis(2-nitrophenyl)-ethane-1,1-diamine was synthesized by the reaction of 2-nitroaniline in DCM with the chloral formed by distillation of chloral hydrate over concentrated H₂SO₄. The structure of the title compound was identified by means of FT-IR, ¹H NMR, and ¹³C NMR spectroscopic techniques. The crystal structure of the title compound has also been examined by using X-ray crystallographic techniques and found to be crystallized in the monoclinic crystal system and space group P2₁/n with the unit cell parameters: a = 7.7075(12) ?, b = 7.7396(10) ?, c = 28.247(4) ?, β = 93.602(5)°, V = 1681.7(4) ?³, Dx = 1.602 Mg m ^{? 3}, and Z = 4 respectively. The calculated electronic structure properties of the title molecule such as HOMO-LUMO analysis, molecular electrostatic potential (MEP) map, and the Mulliken charge distributions were investigated by using the density functional theory (DFT) method. Theoretically calculated values exhibit the chemically hard, high kinetic stable and less reactive molecule.

Full text of DOI:10.1016/j.molstruc.2021.129976

Journal of Molecular Structure 1232 (2021) 129976
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstr
Synthesis, spectral properties, crystal structure and theoretical
calculations of a new geminal diamine:
2,2,2-Trichloro-N,N׳-bis(2-nitrophenyl)-ethane-1,1-diamine
Fatma Aydın a,∗, N Burcu Arslanb
a Department of Chemistry, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, 17100 Çanakkale, Turkey
b Department of Computer Education and Instructional Technology, Faculty of Education, Giresun University, 28200, Giresun, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
A new 2,2,2-trichloro-N,N׳-bis(2-nitrophenyl)-ethane-1,1-diamine was synthesized by the reaction of 2-
nitroaniline in DCM with the chloral formed by distillation of chloral hydrate over concentrated H2SO4.
The structure of the title compound was identified by means of FT-IR, 1H NMR, and 13 C NMR spectro-
scopic techniques. The crystal structure of the title compound has also been examined by using X-ray
crystallographic techniques and found to be crystallized in the monoclinic crystal system and space group
Received 3 July 2020
Revised 15 January 2021
Accepted 16 January 2021
Available online 3 February 2021
˚
˚
˚
P21/n with the unit cell parameters: a = 7.7075(12) A, b = 7.7396(10) A, c = 28.247(4) A, β = 93.602(5)°,
Keywords:
3
−
V = 1681.7(4) A , Dx = 1.602 Mg m 3, and Z = 4 respectively. The calculated electronic structure proper-
ties of the title molecule such as HOMO-LUMO analysis, molecular electrostatic potential (MEP) map, and
the Mulliken charge distributions were investigated by using the density functional theory (DFT) method.
Theoretically calculated values exhibit the chemically hard, high kinetic stable and less reactive molecule.
˚
Chloral hydrate
Geminal diamine
o-Nitroaniline
X-ray analysis
Global reactivity
© 2021 Elsevier B.V. All rights reserved.
1. Introduction
while those of aromatic aldehydes, having a conjugation system,
are more stable [9–11] .
Chloral, known as 2,2,2-trichloroacetaldehyde or 2,2,2-tri-
chloroethanal, is an organic compound with the formula Cl3CCHO,
which is a colorless oily liquid. Due to the presence of two func-
tional groups such as carbonyl and trichloromethyl and their mu-
tual activating effect, the chloral molecule has been used in a wide
variety of syntheses [1]. It is soluble in a wide range of solvents,
but it is very unstable in water and reacts with an equivalent of
water to form chloral hydrate. Chloral hydrate is a reagent and it
is used in industries to prepare organic compounds such as isatin,
DDT, etc. [2,3]. In medicine, it used for short-term treatment of in-
somnia and has anticonvulsant and muscle relaxant properties. It
was once used as a sedative and hypnotic substance in pharma-
ceutical drugs [4–7].
A geminal diamine compound contains two amino groups
bound to the same carbon atom. It usually acts as a reactive inter-
mediate product. Therefore, studies on the formation of substituted
geminal diamine derivatives are limited [12–16].
Herein,
a new gem–diamine compound named as 2,2,2-
trichloro-N,N׳-bis(2-nitrophenyl)-ethane-1,1-diamine (3) was syn-
thesized from a Schiff base obtained by the reaction of chloral
with 2-nitroaniline (Scheme 1) and its structure was characterized
by elemental analysis, FT-IR, 1H NMR and 13C NMR spectroscopic
techniques and structurally single crystal XRD method. Hydrogen
bond geometry of the molecule was determined by the X-ray tech-
nique. Additionally, optimized geometrical parameters, molecular
electrostatic potential (MEP), Mulliken charges, HOMO-LUMO en-
ergy gap and the global reactivity from the frontier orbitals of the
title molecule have been performed by using the density func-
tional theory (DFT) B3LYP method with the 6–311G(d,p) basis set.
The standard thermodynamic functions: heat capacity (Cp), en-
tropy (S0) and enthalpy (ꢀH0) were calculated to investigate ther-
modynamical properties of the title compound.
Compounds known as Schiff bases are usually formed by the
condensation reaction of a carbonyl compound such as aldehyde or
ketone with a primary amine. Schiff bases, firstly reported by Hugo
=
Schiff in 1864, that contain an azomethine group (-HC N-) are also
=
identified as imines (>C NH-) [8]. Schiff bases of aliphatic alde-
hydes are relatively unstable and readily undergo polymerization,
∗
Corresponding author.
E-mail address: faydin@comu.edu.tr (F. Aydın).
https://doi.org/10.1016/j.molstruc.2021.129976
0022-2860/© 2021 Elsevier B.V. All rights reserved.

F. Aydın and N.B. Arslan
Journal of Molecular Structure 1232 (2021) 129976
Scheme 1. The synthesis of 2,2,2-trichloro-N,N׳-bis(2-nitrophenyl)-ethane-1,1-diamine.
2. Experimental details
2.1. Materials and measurements
All reagents for synthesis were commercially obtained and were
used without further purification. The 1H- and 13C NMR spectra
were recorded in deuterated chloroform (CDCl3) at 25 °C on a JEOL
NMR spectrometer operating at 400 and 100 MHz. Infrared absorp-
tion spectra were obtained by a Perkin Elmer BX II spectrometer
and reported in cm−1 units. The melting point was measured in
an Electro Thermal IA 9100 instrument using a capillary tube. Ele-
mental analysis was conducted on a LECO-932 CHNS analyzer.
2.2. Synthesis of
2,2,2-trichloro-N,N׳-bis(2-nitrophenyl)-ethane-1,1-diamine
Fig. 1. ORTEP drawing of the asymmetric unit for the 2,2,2-trichloro-N,N׳-bis(2-
nitrophenyl)ethane-1,1-diamine (3), Ellipsoids are displayed at the 30% probability
level.
The chloral (0.740 g, 5 mmol) obtained by distillation of chlo-
ral hydrate using a molecular sieve in the presence of concentrated
H2SO4 was dissolved in dichloromethane (15 mL) and added to 2-
nitroaniline (1.380 g, 10 mmol) in dichloromethane (15 mL). The
mixture was heated under reflux for 1 hour. The progress of the
reaction was monitored by T.L.C. (1:1, hexane:ethyl acetate). After
the completion of the reaction, the brilliant yellow precipitate of
the condensation product was filtered and washed with alcohol
(2 × 3 mL). The precipitate was dried in a vacuum desiccator and
purified by crystallization from THF. Yield 1.195 g (59.1%), mp. 118–
120 °C. Elemental analysis for C14 H11 Cl3N4O4: Calculated, (%): C:
41.45, H: 2.73, N: 13.81, Cl: 26.22, O: 15.78; Found, (%): C: 41.58,
H: 2.79, N: 13.74, Cl: 26.18, O: 15.71. FT-IR (ATR) ν 3337, 3335,
3175, 3097, 2971, 1609, 1577, 1490, 1443, 1417, 1341, 1299, 1268,
114.22 and 114.06 (d, J = 16.38 Hz), 100.98 (s), 74.01 and 73.86 (d,
J = 15.17 Hz).
2.3. Structure determination and refinement
Single crystal suitable for X-ray diffraction studies was obtained
by a slow evaporation technique using tetrahydrofuran as a solvent.
X-ray data was collected with a Bruker Smart Apex II CCD area de-
tector diffractometer with a graphite-monochromated MoKα radi-
˚
ation source (λ 0.71073 A) at 293°K. The structure was solved by
direct method using SHELXS97 [17] and all of the non-hydrogen
atoms were refined anisotropically by full-matrix least-squares on
F2 using SHELXL97 [18]. All H atoms were placed in their cal-
culated positions and included in the refinement using the rid-
ing model (Fig. 1). Crystal data and structure refinement param-
eters for the title compound are listed in Table 1. Diagrams for the
molecular structure and crystal packing are shown in Fig 2, Fig.S1a
and Fig. S1b. Unit cell packing details, such as geometric parame-
1152, 1038, 1226, 891, 838, 801, 734, 685 cm−1
;
1H NMR (400 MHz,
–
–
CDCl3) δ (ppm) 5.88 (t, J = 8.29 Hz, 1H, NH C H NH), 6.99 (d, 2H,
–
–
J = 8.50 Hz, -N H CH N H-), 6.87 (t, J = 7.71 Hz, 2H, CHar), 7.51 (t,
J = 7.79 Hz, 2H, CHar), 8.24 (dd, JHH = 8.49 and 1.42 Hz, 2H, CHar),
8.79 (d, J = 8.21 Hz, 2H, CHar); 13C NMR (100 MHz, CDCl3) δ (ppm),
142.13 (s), 136.66 and 136.55 (d, J = 0.10.6 Hz), 133.77 (s), 127.50
and 127.38 (d, J = 12.03 Hz), 118.55 and 118.42 (d, J = 13.57 Hz),
2

F. Aydın and N.B. Arslan
Journal of Molecular Structure 1232 (2021) 129976
Table 1
Crystal data and structure refinement parameters for the title compound.
Crystal data
Chemical formula
Mr
C14H11Cl3N4O4
405.62
Crystal system, space group
Temperature (°K)
Monoclinic, P21/n
296
˚
a, b, c (A)
7.7075 (12), 7.7396 (10), 28.247 (4)
α, β, γ (°)
90, 93.602 (5), 90
3
˚
V (A )
1681.7 (4)
4
Z
Radiation type
Mo K
9895
α
No. of reflections for cell measurement
θ range (°) for cell measurement
3.0–27
μ (mm−1
)
0.57
Crystal shape
Block
Crystal size (mm)
0.17 × 0.14 × 0.11
Data collection
Diffractometer
Bruker APEX-II CCD
Multi-scan
Absorption correction
Tmin, Tmax
0.908, 0.939
65,820, 3324, 2931
0.057
No. of measured, independent and observed [I > 2σ(I)] reflections
Rint
−1
˚
(sin θ/λ)max (A
)
0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S
0.058, 0.120, 1.22
No. of reflections
3324
No. of parameters
H-atom treatment
227
H-atom parameters constrained
w = 1/[σ2(Fo2) + (0.0075P)2 + 4.1274P] where P = (Fo + 2Fc2)/3
2
(ꢀ/σ)max
< 0.001
−3
˚
ꢀρmax, ꢀρmin (e A
)
0.27, −0.31
the 6–311G(d,p) [21] basis set included in the Gaussian 09 program
[22]. The optimized molecular geometry parameters such as bond
length and bond angles by the B3LYP/6311G(d,p) level are listed in
Table S2.
For the molecular structure of the title compound optimized by
the B3LYP /6–311G(d,p) level, frontier molecular orbitals and elec-
trostatic potential were simulated. By using HOMO and LUMO en-
ergy values for the title compound, electron affinity (EA), ioniza-
tion potential (IP), energy gap, chemical potential (μ0), chemical
hardness (η), softness (ζ), electronegativity (χ) and electrophilicity
index (ω) were calculated using the equations [23,24], both equa-
tions and their values are listed in the Table 5.
3. Results and discussion
Fig. 2. Molecular packing along the b-axis; A partial view of the crystal packing of
–
title compound, showing the linear arrangement built from C H…. O weak inter-
Synthesis of the title compound (3) is confirmed from the spec-
troscopic characterization and the X-ray crystal structure of the
compound. The structure of the synthesized compound is defined
as a geminal diamine. As shown in Scheme 2, we can summarize
that the synthesis occurs with the cascade reactions. An imine has
formed in the first step of the reaction. In second step of the re-
action, 2-nitroaniline has reacted with obtained imine due to the
resonance effect of 2-nitropheyl moiety and the inductive effect of
trichloromethyl moiety and a geminal diamine has been obtained.
molecular interactions.
Table 2
Geometric parameters and symmetry operations for the inter-
molecular interactions (A˚, °).
•••
•••
•••
•••
D—H A
D—H
A
D—H
H
A
D
A
i
•••
•••
•••
•••
•••
•••
C1—H1
C7—H7
C8—H8
N2—H2
N1—H1
N2—H2
O1
0.98
0.93
0.93
0.86
0.86
0.86
2.54
2.91
2.45
1.96
1.95
2.62
3.519 (5)
3.830 (4)
3.293 (5)
2.606(4)
2.619(4)
3.025(3)
176
171
150
130
133
110
ii
Cl1
i
O1
O3
O2
3.1. Crystallographic results
Cl2
Symmetry codes:: (i) x − 1, y, z; (ii) −x, −y + 1, −z + 1.
X-ray investigation shows that the title compound indicates
a geminal diamine form. In the title gem–diamine (3), marked
structural differences in the molecule of the asymmetric unit are
observed (Fig. 1). Central fragments C9/C10/C11/C12/C13/C14 and
C3/C4/C5/C6/C7/C8 are almost planar with an r.m.s. deviation of
ters and symmetry operations for molecular interactions, are listed
in Table 2.
˚
−0.022 and 0.07 A, with atoms C11 and C4, respectively. Tor-
2.4. Computational studies
sion angles between two nitrophenyl amine groups are 77.8° on
C9/N2/C1/N1 and −138.8°on N2/C1/N1/C3 atomic chains.
The molecular structure of the title compound was optimized
using DFT in the ground state by the B3LYP [19,20] method with
In the packing arrangement of the title compound, different
types of weak intermolecular interactions have appeared: C–H…O
3

F. Aydın and N.B. Arslan
Journal of Molecular Structure 1232 (2021) 129976
Scheme 2. A possible reaction mechanism for the title compound.
Table 3
and C–H…Cl weak intermolecular interactions as well as N–H…O
and N–H…Cl intramolecular interactions. The C1–H1…O1 weak
intermolecular interaction gives rise to C(7) chain and the C8–
H8…O1 interaction gives rise to C(6) chain, both chains propagate
along [100] direction. Since the chains have common atomic path-
way, an R21(7) ring motif also appears (Fig. 2 and Fig S1a). The in-
tramolecular hydrogen bond interaction between the N1–H1…O2
atoms constitutes a six-membered ring S(6) (Fig. S1b). Also, the
N2-H2…O3 and N2-H2…Cl2 intramolecular hydrogen bond inter-
actions in the compound create S(6) and S(5) motifs according to
graph set notation, respectively [25].
Comparison of the observed and simulated vibrational spec-
trum (cm−1) at the B3LYP/6–311G(d,p), (scaling factor for
simulated spectrum is 0.9619).
Assignments
Experimental
FT-IR
B3LYP/6 − 311G(d,p)
Scaled
freq.
3364
3362
3105
3079
2975
1493
1275
1144
1453
1094
1474
647
(cm−1
3337
3332
3105
3059
2971
1490
1268
1152
1417
1152
1443
685
)
ν
ν
N—H
N—H
s
as
ν C—H (bz-r)
ν C—H (bz-r)
ν C—H
ν C = C (bz-r)
δ C—H
The optimized parameters (bond length, bond angles and tor-
sion angles) of the title compound were obtained using the
DFT/B3LYP method with the 6–311G(d,p) basis set. The results are
listed in Table S2 and compared with the experimental data for the
title compound.
α C—H
ν C(bz-r)—N
ν N—CH
γ N—H
ω N—H
X-ray investigation shows that C1-N1 and C1-N2 bond lengths
ν
ν
ν
ν
N = O2
N = O2
ClC—CH
ClC—CH
1609
1341
838
1539
1329
978
as
s
˚
˚
in the title compound are 1.445 (4) A and 1.441 (4) A, respec-
˚
˚
tively. C3-N1 (1.364 (4) A) and C9-N2 (1.373 (5) A) bond lengths
are slightly shorter than the C1-N1 and C1-N2 bond lengths due
to resonance between the nitrogen atoms and 2-nitrophenyl rings.
as
s
734
766
Notes: Vibrational modes: ν, stretching; s, symmetric; as,
asymmetric; β in plane bending; α, scissoring; γ , rocking;
ω, wagging; δ, twisting; Abbreviations: benzene ring; bz-r,
benzene ring.
˚
Theoretical values of bond lengths are 1.443 and 1.437 A, respec-
tively (Table S1). In general, the calculated geometric parameters
are in good agreement with those obtained from the experimen-
tal results. As can be seen from Table S2, most of the optimized
bond distances were found to be slightly longer than the exper-
imental distances. The small differences may be due to fact that
the theoretical calculations belong to an isolated molecule with-
out any intermolecular interactions in the gaseous phase and the
experimental results belong to molecules in solid state.
spectively. The calculated wavenumbers at 3364 and 3362 cm−1
–
are assigned to N H stretching vibrations.
–
Additionally, the abnormal intensity ratio of ν (N H) band at
1577 cm−1 revealed that intra-molecular hydrogen bond interac-
tions might exist in this compound as observed in the X-ray anal-
ysis (Fig. 2).
–
3.2. Spectral studies
The C H stretching vibration for hetero-aromatic structures oc-
curs in the region of 3100 - 3000 cm−1, which is extended to 2800
Infrared spectroscopy has been extensively used for structural
determination and provides useful information about the func-
tional groups in the molecular structure under experimental and
theoretical studies [26]. Some important experimental (Fig. S2)
and calculated (unscaled) vibrational frequencies were collected
in Table 3. The vibrational frequencies for the optimized molecu-
lar structures are calculated with this method and then scaled by
0.9619.
cm−1 in some molecules and is usually overlapped by the stretch-
–
ing of aliphatic CH groups. The C H stretching vibrations of the
title compound are observed at 3105 and 3059 cm−1 in the FT-IR
spectrum, whereas the calculated wavenumbers at 3105 and 3079
cm−1 are assigned to the C H stretching vibration.
–
The C–H of the methanetriyl group stretching vibration is gen-
erally observed in the range of 3000–2800 cm−1. The band ob-
served at 2971 cm−1 in FT-IR spectrum is assigned to a C1 H1
–
–
Generally, ν (N H) stretching vibrations are observed in the
symmetrical stretching vibration of the methanetriyl group. The
theoretically computed values by the B3LYP/6–311G(d,p) method
range of 3500–3300 cm−1 [27]. In the present study, the N H sym-
–
metric and asymmetric stretching vibrations of the title compound
are observed at 3337 and 3332 cm−1 in the FT-IR spectrum, re-
for the C H symmetrical stretching vibration is at 2975 cm−1. In
–
the higher wavenumber region of the spectra, differences between
4

F. Aydın and N.B. Arslan
Journal of Molecular Structure 1232 (2021) 129976
Table 4
Theoretical and experimental 1H and 13 C isotopic chemical shifts (with respect to TMS, all values in ppm) for the title compound.
Calculated chemical shifts(ppm) / B3LYP/6–311G(d,p)
Experimental (ppm)
(CDCl3)
Calculated chemical shifts
(ppm) (in gas phase)
Calculated chemical shifts
(ppm) (in CDCl3)
Calculated chemical shifts
(ppm) (in DMSO)
Atoms
C1
100.98
73.93
142.13
136.60
127.44
118.48
133.77
114.14
142.13
136.60
127.44
118.48
133.77
114.14
5.88
134.9758
149.3995
149.3995
148.0602
141.0406
140.9321
140.2721
139.8504
133.4607
77.1684
115.6265
116.7680
120.5944
133.0499
5.0415
135.1855
77.1222
149.8510
148.6036
143.1676
142.8978
141.148
140.7986
133.3723
116.9662
117.9896
121.7068
121.8781
133.0184
5.2534
135.4189
77.1528
150.1328
148.9331
144.2074
143.8327
141.5903
141.2711
133.2704
117.8165
118.8517
122.2114
122.4754
132.9270
5.3797
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C1-H1
N1-H1A
N2-H2
C5-H5
C6-H6
C7-H7
C8-H18
C11-H11
C12-H12
C13-H13
C14-H14
6.99
6.0689
6.2139
6.3021
6.99
6.0682
6.2145
6.3025
8.79
8.3536
8.3474
8.3318
8.24
8.4084
8.4018
8.3863
7.51
9.0424
8.955
8.9178
6.87
6.5830
6.7250
6.7760
8.79
7.1044
7.2985
7.3826
8.24
6.7066
6.8589
6.9143
7.51
7.0247
7.1909
7.2871
6.87
7.447
7.6535
7.7425
experimental and theoretical frequencies are seen due to anhar-
monicity. By considering Fig. 2 and Table 2, these differences can
be due to the weak intermolecular interaction (C1-H1…O1). Addi-
tionally, other vibration modes nearly coincide with FT-IR experi-
mentalvalues (Table 3).
mentally obtained in deuterated chloroform (CDCl3). To inves-
tigate NMR chemical shifts of the molecule, the GIAO (Gauge-
Independent Atomic Orbital) method was used [20]. 1H and 13C
chemical shift values were calculated using the DFT/B3LYP method
with the 6–311G(d,p) basis set.
The carbon-carbon stretching modes of the phenyl group are
expected in the range from 1650 to 1200 cm−1. In this respect, the
bands observed at 1490 cm−1 are assigned to a C = C stretching
vibration, that of the phenyl groups, where they affect to aromatic
conjugation. The band at 1493 cm−1 is calculated for the C = C
stretching.
To compute NMR chemical shifts of carbon and hydrogen atoms
within the compound, the molecular geometry of the compound
was optimized in the gas phase, chloroform, and dimethyl sulfox-
ide by using IEFPCM solvation model. The computed and measured
1H and 13C NMR chemical shift values were given in Table 4, Fig.
S3 and Fig. S4.
–
–
–
The mixing of several bands such as C N, C C, and N O stretch-
The N1-H1A and N2-H2 hydrogen atoms in the compound that
are around the neighborliness of electronegative N1 and N2 nitro-
gen atoms were observed as doublet peaks at δ 6.99 ppm for pro-
ton chemical shift of the spectrum, they were calculated at N1-
H1A δ 6.07 ppm and N2-H2 δ 6.06 ppm (in gas phase), δ 6.21
and 6.22 ppm and δ 6.30 and 6.30 ppm (in CDCl3 and DMSO–
d6 solvents), respectively in harmony with its experimental value.
In addition, C1-H1, for a hydrogen in the methanetriyl group of
the compound was observed at δ 5.88 ppm (exp.) as triplet peaks
and computed at δ 5.04 ppm (calc. in gas phase) and 5.25 and
5.37 ppm (calc. in CDCl3 and DMSO–d6 solvents), respectively.
Aromatic ring hydrogens of sp2 hybridization give resonance
signals at the interval of δ 6.5–8.5 ppm [30]. Eleven protons (H5,
H6, H7, H8 in phenyl and H11, H12, H13, and H14 in other phenyl)
within the aromatic groups of the compound were recorded as sig-
nals in the resonance region of δ 6.87–8.79 ppm. The C5-H5 and
C11-H11 hydrogen atoms were reported as greater chemical shift
signal than other ring hydrogens at 8.79 ppm (exp.) as doublet
peak and δ 8.35 ppm (calc. in gas phase) and 8.34 and 8.33 ppm
(calc. in CDCl3 and DMSO–d6 solvents) due to the mesomeric ef-
fect of amino groups and the powerful electron withdrawing effect
of the nitro group, respectively. The other aromatic hydrogens were
calculated at the interval of δ 8.40–6.58 ppm (in gas phase), 8.40–
6.85 and 8.38–6.91 ppm (in CDCl3 and DMSO–d6 solvents), respec-
tively, according to the DFT/6–311G(d,p) method and they are in a
good harmony with the experimental values (Scheme 3).
ing vibrations are possible in the same region. The assignment of
–
C N stretching frequency is a rather difficult task. In the present
study, the bands observed at 1417 and 1152 cm−1 in FT-IR spec-
–
trum are attributed to Cbz-N and N CH stretching vibrations. Their
calculated values are at 1453 and 1094 cm−1
The characteristic asymmetric and symmetric frequencies of ni-
tro compounds are observed at 1540–1614 and 1320–1390 cm−1
.
,
respectively [28]. The intramolecular interaction has little effect
on the NO2 asymmetric stretching vibrations. Thus, the bands at
1609 and 1341 cm−1 are assigned to the asymmetric and symmet-
ric stretching modes of -NO2 in the compound. The calculated fre-
quencies for these modes of NO2 are 1539 and 1329 cm−1, respec-
tively.
The CCl3 group possesses many normal modes of vibration as in
the case of methyl group. However, different halogen atoms have
considerably lowered the wavenumber values [29]. It can be clas-
sified as the absorption regions of stretching, bending, rocking etc.
The asymmetric and symmetric stretching modes of CCl3 group
were calculated at 978 and 893 cm−1 and the corresponding ex-
perimental peaks were observed as weak bands at 838 and 734
cm−1 in FT-IR spectra, respectively.
3.3. 1H and 13 C NMR chemical shift analyses
The 1H and 13C NMR chemical shift records for 2,2,2-
trichloro-N,N׳-bis(2-nitrophenyl)-ethane-1,1-diamine were experi-
5

F. Aydın and N.B. Arslan
Journal of Molecular Structure 1232 (2021) 129976
part in chemical reaction and give information about the reactivity
or stability of specific regions of the molecule. The frontier molec-
ular orbitals of the title compound were calculated by using the
B3LYP/6–311G(d,p) level of theory.
The distribution of HOMO, HOMO-1 and LUMO, LUMO+1 ener-
gies for the compound are shown in Fig. 3.
The ionization potential (I) and electron affinity (A) can be ex-
pressed as follows in terms of HOMO and LUMO orbital energy
[32],
I = −EHOMO and A = −ELU MO
In addition, theoretical reactivities such as chemical hardness
(η), chemical softness (ζ), nucleophilicity (ε), chemical potential
(μ), electrophilicity index (ω), electronegativity (χ) and energy
band gap (ꢀE) were calculated by using the following defined for-
mulas in gas phase, Table 5, [33].
Scheme 3. 1H and 13 C NMR chemical shifts of the title compound.
Table 5
orbital energies, HOMO-LUMO energy gap, ionization potential (I),
Electron affinity (A), chemical potential (μ), chemical hardness (η),
absolute softness (ζ), absolute electronegativity (χ), chemical poten-
tial (μ), and electrophilicity index (ω) of title compound for ground
state geometries in the gas phase at the B3LYP/6–311G(d,p) level.
Based on the results in Table 6, the HOMO and LUMO energies
for the compound are −6.705 and −2.698 eV, respectively, and the
energy gap value of title compound is found to be 4.007 eV. A
small gap implies low stability and a large gap implies high sta-
bility. A molecule with a large HOMO-LUMO gap is less polariz-
ability and is generally associated with a low chemical reactivity.
The chemical hardness (ƞ), softness (σ), and chemical potential
(μ) of the title compound were calcalated to be 2.003, 0.499 and
−4.702 eV. It should be noted that the electro-negativity provides
information about the electron accepting capability of a molecule
while nucleophilicity is a measure of Lewis basicity [34]. Calculated
electro-negativity (χ) and nucleophilicity (ε) values for this com-
pound are 4.702 and 0.181 eV, respectively. Hence, these values in-
dicate that the title compound is a chemically hard, high kinetic
stable, and less reactive molecule.
Parameters B3LYP/6–311G(d,p)
(eV)
Kcal/mol
Electronic Energy (a.u.)
EHOMO
−2440,521
- 6.705
- 2.698
+6.705
+2.698
+4.007
2.003
154.61
62.21
154.61
62.21
92.40
46.18
11.50
4.17
ELUMO
Ionization energy, I= -EHOMO
Electron affinity, A= -ELUMO
Energy band gap, [ꢀE=EHOMO-ELUMO
Chemical hardness, η = (I-A) / 2
Chemical softness, ζ = 1/2η
Nucleophilicity, ε = 1/ω
Proton affinity Pı
]
0.499
0.181
−4.702
−4.007
5.518
108.42
92.40
127.24
108.42
Chemical potential, μ = - (I + A) / 2
Electrophilicity index, ω = μ²/2 η
Electronegativity, χ = (I + A) / 2
Dipol moment (Debye)
4.702
7.891
3.5. Molecular Electrostatic Potential (MEP)
The structure of the compound was confirmed by the presence
of eight peaks in the 13C NMR spectrum. In the 13C NMR spec-
trum, the methanetriyl carbon connected with diamine (C1) has
a sp3 hybrid, but it was located at δ 100.98 ppm because of the
geminal diamine and trichloromethyl group. The chemical shift of
carbon, C1 was calculated as δ 134.97 ppm (in gas phase), 135.18
and 135.41 ppm (in CDCl3 and DMSO–d6 solvents), respectively.
The 13C NMR signal of the trichloromethyl group (C2) appeared
at δ 73.93 ppm due to effect of the attached electron-withdrawing
chloride atoms. Likewise, the calculated chemical shift values for
C2 atom, known carbon of trichloromethyl were calculated at δ
149.39 ppm (in gas phase) and 77.12, 77.15 ppm (in CDCl3 and
DMSO–d6 solvents), respectively. The carbon atoms in groups are
shielded by their own three chlorine atoms and therefore they give
a resonance signal in high field [31].
The molecular electrostatic potential (MEP) surface analysis is
an important property that can be successfully used to explain the
electrostatic interactions. Furthermore, MEP is useful for mapping
sites for nucleophilic reactions and electrophilic attacks by show-
ing electron density [35]. To predict the reactive sites of the in-
vestigated title compound, MEP was calculated using DFT at the
B3LYP/6–311G(d,p) basis set in the gas phase, as shown in Fig. 4.
In the color scheme adopted, red indicates an electron-rich region
with a partially negative charge and blue an electron-deficient re-
gion with partially positive charge, light blue indicates a slightly
electron-deficient, yellow a slightly electron-rich region and green
a neutral region [36]. Negative regions of the MEP (red color)
are related to electrophilic reactivity, while positive regions (blue
color) explain the nucleophilic attacks.
Twelve aromatic carbons were observed in the region of
δ 142.13–114.14 ppm as expected. The highest chemical shifts
142.13 ppm were belonging to the amino-bound carbons C3 and C9
as doublets. These carbons were found as δ 134.97 (in gas phase),
135.18 and 135.41 ppm (in CDCl3 and DMSO–d6 solvents) by theo-
retical calculations, respectively.
In Fig. 4, it appears that the negative region is mainly around
the nitro groups (red) [37]. Amine sites, which could be easily at-
tributed to the lone pair electrons on nitrogen atoms are electron-
rich and hence could be reactive atomic sites. Positive regions are
mainly distributed around some hydrogen atoms (blue). Besides,
the most positive region (0.351 a.u.) is the carbon (C2) connected
with chloride atoms. The positive region (blue) is over the C1-H
group, while the delocalization of electrons from N1 and N2 to
the nitrophenyl rings is confirmed by the yellowish color. In addi-
tion to these, MEP is related to the electron density on atoms in a
molecule and is a very useful descriptor in understanding sites for
hydrogen bonding interactions [38]. Regions of positive and nega-
tive MEP on the surface of hydrogen bond donors and acceptors
are influenced by the formation of intramolecular contacts with
the molecules. In the compound, the C6 and C8 carbons are meta
position atoms with respect to nitro group, and ortho and para po-
sition atoms with respect to amino group. The C6 and C8 carbons
became less positive due to the electron withdrawing of the nitro
Other aromatic carbons were observed at 136.60, 133.77, 127.44,
118.48 and 114.14 ppm in the spectrum (Scheme 3 and Fig. S4).
These carbons were calculated similarly to the experimental val-
ues (Table 5). Besides the change in chemical shift values of car-
bon atoms depending on the substrate concentration and relax-
ation time, approaches in the theoretical calculation can also be
different, so the correlation is not sometimes perfect.
3.4. Frontier Molecular Orbitals (FMOs) analysis and global reactivity
The frontier orbitals, HOMO and LUMO are the most important
orbitals in a molecule. These orbitals are the main orbitals taking
6

F. Aydın and N.B. Arslan
Journal of Molecular Structure 1232 (2021) 129976
Fig. 3. Highest occupied molecular orbitals (HOMO and HOMO-1) and the lowest unoccupied molecular orbitals (LUMO and LUMO+1) of the title compound.
Fig. 4. Molecular electrostatic potential (MEP) mapped on the electron density sur-
face calculated by the DFT/B3LYP method of the title compound.
group and the donation of electrons by the amino group. There-
fore, C5-H5 and C7-H7 regions have more positive and they appear
in partial blue on the MEP map. Also, the C1-H1 region appears
in partial blue due to the inductive effect of the trichloromethyl
moiety. This state provides an explanation for inter-molecular in-
teractions of C1-H1…O1 and C7-H7…Cl1 in the crystal structure
[39–41].
3.6. Mulliken charge distributions
Dipole moment, molecular polarizability, and bond properties
are affected by atomic charge, therefore, the Mulliken atomic
charge calculation has an important role in quantum chemistry
[42]. The Mulliken charge distributions of the molecule are per-
formed using the DFT/B3LYP calculation method with the 6–
311G(d,p) basis set for the studied compounds. Graphical reorien-
tations of Mulliken charge distribution of compound are shown in
Fig. 5 and Table S3. As can be seen in Fig. 5, all oxygen atoms have
Fig. 5. The Mulliken atomic charge distribution of the title compound in the gas
a net negative charge, and all hydrogen atoms have a net positive
phase.
charge. Naturally, while the nitrogen atoms of the nitro group (N3,
N4) have positive charges (0.1655 and 0.1614), the nitrogen atoms
7

F. Aydın and N.B. Arslan
Journal of Molecular Structure 1232 (2021) 129976
together, which results in differences between the calculated and
experimental values for the bond parameters.
By clarifying the structure of the newly synthesized title com-
pound, the Schiff base formed from chloral is considered as an un-
stable and reactive intermediate. It has been confirmed that the
carbonyl group of chloral is highly reactive and susceptible to nu-
cleophile attack. The 1H NMR and 13C NMR spectra clearly con-
firm the molecular structure. In addition, the HOMO-LUMO analy-
sis, and the regions of the MEP and Mulliken’s atomic net charges
were calculated by the density functional theory (DFT) method us-
ing optimized geometry at the B3LYP/6–311G(d,p) level to investi-
gate the reactive sites of the title compound. As can be seen from
the MEP map of the molecule, the negative region is mainly local-
ized over the oxygen atom of the nitro moiety. When the max-
imum positive region is examined, it is localized on the carbon
atom between trichloromethyl and geminal diamine. The chemi-
cal reactivity parameters and the thermodynamic properties have
been examined for the molecule. The calculated HOMO-LUMO gap
energy is 4.007 eV, pointing to a hard molecule as a new gem-
inal diamine compound. Despite the little differences, an accept-
able correlation between the computational and experimental re-
sults were found.
Fig. 6. Calculated thermodynamic properties and temperatures for the title com-
pound.
of the diamine moiety (N1, N2) have negative charges (−0.1421 and
−0.1661).
The C2 (−0.3904) carbon atom to which three chloride atoms
are attached is the most electronegative among all carbon atoms
due to the electronegativity effect of the chloride atoms. On the
other hand, the carbon atom C1 (0.2723) attached with two nitro-
gen atoms is more electropositive than other carbon atoms (C3, C4
and C9, C10) in the compound (0.2343, 0.1197 and 0.2352, 0.1341,
respectively) due to the mesomeric effect of the nitrogen atoms.
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work “Synthesis, spectral properties, crystal struc-
ture and theoretical calculations of a new geminal diamine: 2,2,2-
Trichloro-N, N׳-bis(2-nitrophenyl) ethane-1,1-diamine” reported in
this paper.
3.7. Thermodynamic properties
Thermodynamic parameters provide helpful information for un-
derstanding the chemical processes. Thermodynamic properties
such as heat capacity at constant pressure (Cp), entropy (S), en-
thalpy (ꢀH) for the title compound were also calculated by the
DFT method using the B3LYP/6–311G(d,p) basis set and were de-
picted in Table S3.
CRediT authorship contribution statement
Fatma Aydın: Methodology, Conceptualization, Data curation,
Writing - original draft, Writing - review & editing. N Burcu Ar-
slan: Formal analysis, Visualization.
Acknowledgments
As seen from Table S4, the standard thermodynamic functions
increase with increase in temperature from 100 to 1000 K, since
the molecular vibrational intensities increase with temperature
[43]. These observed relations of the thermodynamic functions
with temperature were fitted by quadratic formulas and the cor-
responding fitting factors (R2) for these thermodynamic properties
are 0.99776, 0.99901 and 0.99908, respectively. The temperature
dependence correlation graphs are shown in Fig. 6.
This work was supported by the Scientific Research Coordina-
tion Unit of Çanakkale Onsekiz Mart University, [Project No: FYL-
2016–672].
Supplementary materials
ꢀ
ꢁ
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.2021.129976.
C◦p.m = 6.2610 + 0.2417T − 1.2345x10−4T2 R2 = 0.99776
ꢀ
ꢁ
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S◦m = 60.6919 + 0.2872 T − −8.5930x10−5T2 R2 = 0.99901
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