Halogenated diazabutadiene dyes: Synthesis, structures, supramolecular features, and theoretical studies

Article abstract of DOI:10.3390/molecules25215013

Novel halogenated aromatic dichlorodiazadienes were prepared via copper-mediated oxidative coupling between the corresponding hydrazones and CCl₄ . These rare azo-dyes were characterized using¹H and¹³C NMR techniques and X

Full text of DOI:10.3390/molecules25215013

molecules
Article
Halogenated Diazabutadiene Dyes: Synthesis,
Structures, Supramolecular Features,
and Theoretical Studies
Valentine G. Nenajdenko 1,
*
, Namiq G. Shikhaliyev 2, Abel M. Maharramov 2,
Khanim N. Bagirova 2, Gulnar T. Suleymanova 2, Alexander S. Novikov 3
,
Victor N. Khrustalev 4,5 and Alexander G. Tskhovrebov 4,6,
*
1
M. V. Lomonosov Moscow State University, 1, Leninskie Gory, 119991 Moscow, Russia
Department of Organic Chemistry, Baku State University, Z. Xalilov 23, Baku 1148, Azerbaijan;
namiqst@gmail.com (N.G.S.); amaharramov@bsu.edu.az (A.M.M.); stella_stand@icloud.com (K.N.B.);
gumusqiz91.sg@gmail.com (G.T.S.)
2
3
4
5
6
Saint Petersburg State University, Universitetskaya Nab. 7/9, 199034 Saint Petersburg, Russia;
a.s.novikov@spbu.ru
Peoples’ Friendship University of Russia, 6 Miklukho-Maklaya, 117198 Moscow, Russia;
vnkhrustalev@gmail.com
N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky Av.,
119334 Moscow, Russia
N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Kosygina 4,
119991 Moscow, Russia
*
Correspondence: nenajdenko@org.chem.msu.ru (V.G.N.); alexander.tskhovrebov@chph.ras.ru (A.G.T.)
ꢀꢁꢂꢀꢃꢄꢅꢆꢇ
Academic Editors: Ilya G. Shenderovich and Antonio Caballero
Received: 6 October 2020; Accepted: 26 October 2020; Published: 29 October 2020
ꢀꢁꢂꢃꢄꢅꢆ
Abstract: Novel halogenated aromatic dichlorodiazadienes were prepared via copper-mediated
oxidative coupling between the corresponding hydrazones and CCl4. These rare azo-dyes were
characterized using 1H and 13C NMR techniques and X-ray diffraction analysis for five halogenated
dichlorodiazadienes. Multiple non-covalent halogen···halogen interactions were detected in the solid
state and studied by DFT calculations and topological analysis of the electron density distribution
within the framework of Bader’s theory (QTAIM method). Theoretical studies demonstrated that
non-covalent halogen···halogen interactions play crucial role in self-assembly of highly polarizable
dichlorodiazadienes. Thus, halogen bonding can dictate a packing preference in the solid state for
this class of dichloro-substituted heterodienes, which could be a convenient tool for a fine tuning of
the properties of this novel class of dyes.
Keywords: non-covalent interactions; crystal engineering; halogen bonding; azo dyes; DFT; QTAIM
1. Introduction
Halogen bonding (XB) is one of the most intensively investigated areas in modern chemistry [1].
The field currently experiences a renaissance due to exploitation of such weak interactions for
a number of functional applications, such as catalysis, drug design, nonlinear optics, reactivity control,
and construction of functional supramolecular architectures [
interactions lies at the foundation of the design supramolecular materials and control of their
ultimate architectures [11 14]. XB has recently emerged as a powerful tool for the creation of such
materials due to its stability, directionality and reversibility [15 17]. In this context, halogen-halogen
interactions received particular attention and were intensively explored both experimentally and
2–10] Utilization of non-covalent
–
–
Molecules 2020, 25, 5013; doi:10.3390/molecules25215013
www.mdpi.com/journal/molecules

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theoretically [18–21]. Arguably, XB can be more beneficial than the hydrogen bonding in the construction
of functional materials and tuning their properties due to its higher directionality [10,22,23].
Recently, we discovered a novel class of azo-dyes, i.e., dichlorodiazadienes, which can be
easily prepared via unprecedented copper-catalyzed reaction between CCl4 with N-substituted
hydrazones (Scheme 1) [24]. Currently, very little is known about the chemistry and properties of these
dichloro-substituted heterodienes [25–31].
Scheme 1. Copper-catalyzed synthesis of dichlorodiazadienes.
Following our interest in construction of supramolecular architectures via non-covalent
interactions [32–39] and chemistry of novel diazadienes, we report now the synthesis of halogenated
dichlorodiazadienes to demonstrate that dichloro-substituted heterodiene fragment can behave as
a strong XB donor/acceptor, what can be used in the design of heterodiene azo-dyes and their
self-assembly in the solid state. Incorporation of a halogen atom(s) in the dichloro-dyes’ backbone
completely changes the way the colorants self-assemble in the crystal. Thus, we show that the XB
can dictate a packing preference in the solid state for this class of dichloro-substituted heterodienes.
In addition, we performed DFT calculations and topological analysis of the electron density distribution
within the formalism of Bader’s theory (QTAIM method), which support the presence of intermolecular
non-covalent interactions halogen···halogen (Hal···Hal) in the solid state.
2. Results and Discussion
The target halogenated azabutadienes 10
the corresponding hydrazones
solids (Scheme 2).
–
18 were synthesized by CuI-catalyzed reaction between
1–9 and CCl4 and isolated in up to 82% yield as red crystalline
Scheme 2. Copper-catalyzed synthesis of dichlorodiazadienes.
The structure of 10
analysis for 10 13
their solid-state structures. Dyes 10
crystals, suitable for analysis by single crystal X-ray crystallography. The structural investigations
confirmed the formation of azabutadienes. Overall, metrical parameters for 10 13 15, and 17 are
–
18 was confirmed by the 1H and 13C NMR spectroscopies and X-ray diffraction
1
,
–
15, and 17 (Figures 1–4). H NMR and 13C{1H} spectra (CDCl3) are consistent with
,
13–15, and 17 could be easily recrystallized to produce large red
,
–

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similar to those reported for similar azabutadienes [26
,
29
–31]. However, introduction of halogen atoms
in the dichloro-dyes’ backbone has a dramatic impact on its self-assembly in the crystal. In the crystal
packing of 10 (para-chloro substitution at the phenyl, attached the double C=C bond) dye molecules
form shifted columns (Figure 1) via
attractive interactions between the neighboring dye molecules (type 2 contacts) [23]. The dichloroalkene
acts as a donor of the halogen bond here (Figure 1).
π
-
π
interactions. The columns dimerize in the crystal via Cl···Cl
Figure 1. Ball-and-stick representation of 10 and its self-assembly via Cl···Cl bonding in the crystal.
Blue, green and grey spheres represent nitrogen, chlorine, carbon atoms, respectively. Hydrogen atoms
were omitted for clarity.
Figure 2. Ball-and-stick representations of 14 and 15 and their self-assembly via Cl···Hal bonding in
the crystal. Olive-green, blue, green, and grey spheres represent bromine, nitrogen, chlorine, and carbon
atoms, respectively. Hydrogen atoms were omitted for clarity.
Figure 3. Ball-and-stick representation of 17 and its supramolecular dimerization via Cl···Cl type 1
bonding in the crystal. Blue, green, and grey spheres represent nitrogen, chlorine, and carbon atoms,
respectively. Hydrogen atoms were omitted for clarity.

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Figure 4. Ball-and-stick representation of 13 and its self-assembly via Cl···Cl bonding in the crystal.
Blue, green, and grey and cyan spheres represent nitrogen, chlorine, carbon, and fluorine atoms,
respectively. Hydrogen atoms were omitted for clarity.
Functionalization of dichloro-dyes with another extra halogen atom (compounds 14 and 15) does
not prevent the formation of columns and supramolecular dimerization via Cl···Cl interactions in
the crystal (Figure 2). In addition to this, the columns in the crystal of 14 and 15 interact with another
neighboring columns via Cl···Hal (Hal=Cl(14), Br(15)) type 2 bonding forming 3D supramolecular
frameworks (Figure 2).
Introduction of one more halogen atom in the dichloro-dyes’ backbone completely changes its
self-assembly in the crystal. Remarkably, crystal packing of 17 features only one type of Hal···Hal
interaction between the chlorines of the p-cholorophenyl groups (Figure 3), which refer to repulsive
type 1 contacts. Halogen atoms, attached to the alkene or dichlorobenzene moieties do not form any
halogen bonding. Such a behavior is not very clear at the moment and requires additional studies.
One plausible explanation is insufficient nucleophilicity of halogens in 17 for the formation of type
2 contacts.
Finally, when dichloro-dyes are functionalized with the fluorine atom (13, para- substitution at
the phenyl, attached the double C=C bond, Figure 4), the situation with self-assembly in the crystal is
similar to the brominated or chlorinated analogs 14 and 15. The columns form 3D supramolecular
frameworks via Cl···Cl and Cl···F type 2 contacts. An interesting peculiarity of self-assembly of 13 in
the crystal is the formation of Cl···F type 1 contacts (Figure 4). Thus, the crystal structure of 13 features
a bifurcated XB and a remarkable combination of type 1 and 2 halogen contacts (Figure 4).
Inspection of the crystallographic data suggests the presence of multiple intermolecular
non-covalent interactions Hal···Hal in the crystals of 10
, 13–15, and 17. Indeed, the observed
distances Hal···Hal are shorter than the sum of Bondi’s vdW radii for the corresponding atoms [40].
Thus, in addition to structural analysis, a detailed computational studies were desired. In order
to understand the nature and quantify energies of various short halogen-halogen contacts the DFT
calculations followed by the topological analysis of the electron density distribution within the QTAIM
approach [41] were carried out at the
ωB97XD/6-311++G ** level of theory for model supramolecular
associates containing all types of these noncovalent interactions (see Computational details and Table S1
in the Supplementary Materials). Results of QTAIM analysis summarized in Table 1, the contour line
2
diagrams of the Laplacian of electron density distribution ∇ ρ(r), bond paths, and selected zero-flux
surfaces as well as visualization of electron localization function (ELF) analysis for selected short
halogen-halogen contacts shown in Figure 5 for illustrative purposes.

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2
Table 1. Values of the density of all electrons—
appropriate λ2 eigenvalues (with promolecular approximation), energy density—Hb, potential
energy density—V(r), and Lagrangian kinetic energy—G(r) (a.u.) at the bond critical points (3, 1),
15, and 17, and estimated energies
ρ(r), Laplacian of electron density—∇ ρ(r) and
−
corresponding to various short halogen-halogen contacts in 10
, 13–
for these interactions Eint (kcal/mol).
2
a
b
Halogen–Halogen Contact
ρ(r)
∇ ρ(r)
0.031
0.031
0.031
0.042
0.029
0.026
0.029
0.021
0.030
0.027
λ
Hb
V(r)
G(r)
Eint
Eint
2
10 Cl···Cl, 3.377 Å (96% from the sum
0.008
0.006
0.007
0.009
0.007
0.007
0.007
0.006
0.007
0.007
−
−
−
−
−
−
−
−
−
−
0.012 0.002
0.007 0.001
0.008 0.001
0.013 0.001
0.011 0.002
0.009 0.002
0.011 0.002
0.008 0.001
0.011 0.002
0.009 0.002
−
−
−
−
−
−
−
−
−
−
0.004 0.006
0.006 0.007
0.006 0.007
0.008 0.009
0.004 0.006
0.003 0.005
0.004 0.006
0.003 0.004
0.004 0.006
0.004 0.005
1.2
1.8
of Bondi’s vdW radii)
13
F
···F, 2.864 Å (97% from the sum of
≈2 *
≈2 *
2.5
1.2
0.9
1.2
0.9
1.2
1.2
≈2 *
≈2 *
2.7
1.8
1.5
1.8
1.2
1.8
1.5
Bondi’s vdW radii)
13
F
···F, 2.917 Å (99% from the sum of
Bondi’s vdW radii)
13 Cl···F, 2.963 Å (92% from the sum
of Bondi’s vdW radii)
13 Cl···Cl, 3.405 Å (97% from the sum
of Bondi’s vdW radii)
14 Cl···Cl, 3.463 Å (99% from the sum
of Bondi’s vdW radii)
14 Cl···Cl, 3.399 Å (97% from the sum
of Bondi’s vdW radii)
15 Cl···Br, 3.637 Å (102% from the
sum of Bondi’s vdW radii)
15 Cl···Cl, 3.394 Å (97% from the sum
of Bondi’s vdW radii)
17 Cl···Cl, 3.469 Å (99% from the sum
of Bondi’s vdW radii)
a
Eint = 0.49( V(r)) (this correlation between the interaction energy and the potential energy density of electrons at
−
the bond critical points (3, –1) was specifically developed for noncovalent interactions involving chlorine atoms)
b
[
42]. Eint = 0.47G(r) (this correlation between the interaction energy and the kinetic energy density of electrons at
the bond critical points (3, –1) was specifically developed for noncovalent interactions involving chlorine atoms)
42]. * There are no generally accepted specific correlations between the interaction energy and the potential or
[
kinetic energy densities of electrons at the bond critical points (3, –1) for F···F noncovalent interactions, but it is
clearly expected from values of V(r) and G(r) that strength of these contacts in 13 is approx. 2 kcal/mol.
The QTAIM analysis of 10, 13–15, and 17 demonstrates the presence of bond critical points (3, –1)
for all weak contacts presented in Table 1. The low magnitude of the electron density (0.006–0.009 a.u.),
positive values of the Laplacian of electron density (0.021–0.042 a.u.), and very close to zero positive
energy density (0.001–0.002 a.u.) in these bond critical points (3, –1) are typical for halogen-halogen
noncovalent interactions [
5,39
,43]. The balance between the potential and kinetic energy densities of
electrons at the bond critical points (3, –1) for studied weak contacts in 10
,
13–15, and 17 reveals that a
covalent contribution is absent in these interactions [44] (Table 1). The Laplacian of electron density is
typically decomposed into the sum of contributions along the three principal axes of maximal variation,
giving the three eigenvalues of the Hessian matrix (λ1
to distinguish bonding (attractive, λ2 < 0) weak interactions from non-bonding ones (repulsive, λ2
> 0) [45 46]. Thus, discussed noncovalent interactions in 10 13 15, and 17 are attractive (Table 1).
Overall, it follows from the results of theoretical calculations that all short halogen-halogen contacts
in 10 13 15, and 17 are very similar in terms of energies (their estimated strength per one contact
vary from 1 to 3 kcal/mol), which correlates well with very close values of minimal and maximal
, λ2 and λ3), and the sign of λ2 can be utilized
,
,
–
,
–
electrostatic surface potentials on halogen atoms in isolated molecules 10, 13–15, and 17 (Figure S1 in
the Supplementary Materials).

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2
Figure 5. Contour line diagrams of the Laplacian of electron density distribution ∇ ρ(r), bond paths,
and selected zero-flux surfaces (left) and visualization of electron localization function (ELF) analysis
(right) for intermolecular Cl···Br and Cl···Cl contacts in 15 (top); F···F (center) and Cl···F (bottom) contacts
in 13. Bond critical points (3,
critical points (3, +1)—in orange, cage critical points (3, +3)—in light green, length units—Å, bond
−
1) are shown in blue, nuclear critical points (3, 3)—in pale brown, ring
−
paths are shown as pale brown lines, and the color scale for the ELF maps is presented in a.u.
To understand what kind of interatomic contacts give the largest contributions in crystal packing,
we carried out the Hirshfeld surface analysis for all obtained X-ray structures 10, 13–15, and 17 (Table 2
and Figure 6). The Hirshfeld surface analysis for the X-ray structures 10 13 15, and 17 reveals that
,
–
in all cases crystal packing determined primarily by interatomic contacts involving chlorine and
hydrogen atoms.
Table 2. Main partial contributions of different interatomic contacts to the Hirshfeld surfaces of X-ray
structures 10, 13–15, and 17.
X-Ray Structure
Contributions of Different Interatomic Contacts to the Hirshfeld Surfaces
Cl-H 37.4%, H-H 21.0%, C-H 15.8%, C-C 7.9%, Cl-Cl 5.9%, N-H 5.8%, N-C 3.0%,
-Cl-C 2.9%, Cl-N 0.1%
Cl-H 32.6%, H-H 16.2%, C-H 14.6%, C-C 7.4%, Cl-Cl 6.1%, N-H 5.8%, Cl-F 4.1%,
N-C 3.1%, Cl-C 3.0%, F-H 2.8%, F-F 2.5%, F-C 1.7%
Cl-H 33.5%, H-H 17.1%, Cl-Cl 15.7%, C-H 12.6%, C-C 8.5%, N-H 5.2%, Cl-C 4.1%,
N-C 3.2%, N-N 0.1%
Cl-H 30.7%, H-H 15.7%, C-H 13.0%, C-C 8.1%, Cl-Cl 5.8%, Br-Cl 5.7%, N-H 5.2%,
Br-H 4.6%, Br-Br 3.8%, N-C 3.2%, Cl-C 2.2%, Br-C 1.8%, N-N 0.1%
Cl-H 44.6%, Cl-C 15.6%, H-H 10.5%, Cl-Cl 8.2%, C-H 8.1%, Cl-N 5.1%, C-C 4.4%,
N-C 1.9%, N-H 1.5%
10
13
14
15
17

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Figure 6. Visualization of Hirshfeld surfaces for X-ray structures 14, 15, and 17 (top), 13 and 10 (bottom).
3. Materials and Methods
General remarks. Unless stated otherwise, all the reagents used in this study were obtained
from the commercial sources (Aldrich, TCI-Europe, Strem, ABCR). NMR spectra were recorded
on a Bruker Avance 300 (1H: 300 MHz, Karlsruhe, Germany); chemical shifts (
δ) are given in
ppm relative to TMS, coupling constants (J) in Hz. The solvent signals were used as references
(CDCl3: δC = 77.16 ppm; residual CHCl3 in CDCl3: δH = 7.26 ppm; CD2Cl2: δC = 53.84 ppm; residual
CHDCl2 in CD2Cl2: δH = 5.32 ppm); 1H and 13C assignments were established using NOESY, HSQC,
and HMBC experiments; numbering schemes as shown in the Inserts. IR: Perkin-Elmer Spectrum One
spectrometer (Waltham, MA, USA.), wavenumbers (v
˜
) in cm−1. Mass-spectra were obtained on a Bruker
micrOTOF spectrometer equipped with electrospray ionization (ESI) source (Bremen, Germany);
MeOH, CH2Cl2, or MeOH/CH2Cl2 mixture was used as a solvent. Thermogravimetric analysis
(TGA) and differential thermal analysis were determined using a Netzsch TG 209F1 Libra apparatus
(Selb, Germany). Solvents were purified by distillation over the indicated drying agents and were
transferred under Ar: Et2O (Mg/anthracene), CH2Cl2 (CaH2), hexane (Na/K). Flash chromatography:
Merck Geduran® Si 60 (Darmstadt, Germany) (40–63 µm).
The single point calculations based on the experimental X-ray geometries of 10
been carried out at the DFT level of theory using the dispersion-corrected hybrid functional
,
13
–
15, and 17 have
B97XD [47
ω
]
with the help of Gaussian-09 program package ([M. J. Frisch et al., Gaussian-09, Revision C.01, Gaussian,
Inc., Wallingford CT, USA, 2010.], full citation for this program is given in the SI). The 6-311++G **
basis sets [48–51] were used for all atoms. The topological analysis of the electron density distribution
with the help of the atoms in molecules (QTAIM) method developed by Bader [41] has been performed
by using the Multiwfn program (version 3.6, Beijing, China) [52]. The Cartesian atomic coordinates for

Molecules 2020, 25, 5013
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model supramolecular associates are presented in Table S1, Supporting Information. The Hirshfeld
surfaces analysis has been performed by using the CrystalExplorer program (version 17.5, Perth,
Australia) [53]. The normalized contact distances (dnorm) [54] based on Bondi’s van der Waals radii [40
were mapped into the Hirshfeld surfaces.
]
3.1. Crystal Structure Determination
X-ray diffraction data for 10
the Kurchatov Synchrotron Radiation Source. All datasets were collected at 100 K. In total, 720 frames
were collected with an oscillation range of 1.0 in the scanning mode using two different orientations
for each crystal. The semi-empirical correction for absorption was applied using the Scala program [55
The data were indexed and integrated using the utility iMOSFLM from the CCP4 software suite [56 57].
, 13–15, and 17 were collected at the ‘RSA’ beamline (λ = 0.80246 Å) of
ϕ
].
,
For details, see Table S1. The structures were solved by intrinsic phasing modification of direct
methods [58] and refined by a full-matrix least-squares technique on F2 with anisotropic displacement
parameters for all non-hydrogen atoms. The hydrogen atoms were placed in calculated positions and
refined within the riding model with fixed isotropic displacement parameters [Uiso(H) = 1.5Ueq(C)
for the methyl groups and 1.2Ueq(C) for the other groups]. All calculations were carried out using
the SHELXTL program [59,60].
Crystallographic data for 10, 13–15, and 17 have been deposited with the Cambridge
Crystallographic Data Center, CCDC 2035010-2035014, respectively. Copies of this information
may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(fax: +44-1223-336033; e-mail: edeposit@ccdc.cam.ac.uk or www.ccdc.cam.ac.uk).
3.2. Synthetic Part
Schiff bases 1–9 were synthesized according to the reported method [20,21]. A mixture of
(2-nitrophenyl)hydrazine (10.2 mmol), CH3COONa (0.82 g) and a corresponding 4-substituted
aldehyde (10 mmol) were refluxed with stirring in ethanol (50 mL) for 2 h. The reaction mixture
was cooled to room temperature and water (50 mL) was added to give a precipitate of crude
product, which was filtered off, washed with diluted ethanol (1:1 with water) and dried in vacuo.
1. White solid (69%), mp 118 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.46 (s, 1H, NH), 7.85 (s, 1H, CH), 7.66 (d, J = 8.4 Hz, 2H, arom),
7.43 (d, J = 8.4 Hz, 2H, arom), 7.23 (t, J = 7.7 Hz, 2H, arom),
7.09 (d, J = 7.9 Hz, 2H, arom), 6.76 (t, J = 7.2 Hz, 1H, arom).
13C NMR (75 MHz, DMSO-d6) δ 145.5, 135.4, 135.2, 132.5, 129.5,
129.1, 127.5, 119.41, 112.5.
2. White solid (92%), mp 151 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.33 (s, 1H, NH), 7.80 (s, 1H, CH), 7.66 (s, 1H, arom),
7.42 (d, J = 8.4 Hz, 2H, arom), 7.00 (q, J = 8.4 Hz, 5H, arom),
2.09 (s, 3H, CH3). 13C NMR (75 MHz, DMSO-d6)
δ 138.6, 130.8, 130.1,
127.7, 125.4, 124.5, 123.3, 122.8, 107.92, 16.1.
3. White solid (87%), mp 141 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.24 (s, 1H, NH), 7.78 (s, 1H, CH), 7.63 (d, J = 8.5 Hz, 2H, arom),
7.41 (d, J = 8.5 Hz, 2H, arom), 7.01 (d, J = 8.9 Hz, 2H, arom),
6.84 (d, J = 8.9 Hz, 2H, arom), 3.69 (s, 3H, OCH3). 13C NMR
(75 MHz, DMSO-d6) δ 153.2, 139.5, 135.5, 134.2, 132.1, 129.0, 127.3,
115.0, 113.5, 55.7.

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4. White solid (77%), mp 135 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 7.02 (d, 2H, J = 6.0 Hz), 7.22 (t, 2H, J = 9.1 Hz),
7.37 (d, 2H, J = 9.1 Hz), 7.68–7.73(m, 2H), 7.87(s, 1H), 10.49 (s, 1H).
13C NMR (75 MHz, DMSO-d6) δ 114.3, 115.9, 116.2, 128.0, 132.1,
132,63, 136,7, 145.0, 109.9.
5. White solid (76%), mp 153 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.58 (s, 1H, NH), 7.85 (s, 1H, CH), 7.67 (d, J = 8.3 Hz, 2H, arom),
7.48–7.38 (m, 2H, arom), 7.25 (d, J = 8.7 Hz, 2H, arom),
7.07 (d, J = 8.7 Hz, 2H, arom). 13C NMR (75 MHz, DMSO-d6)
δ 144.4,
136.3, 135.0, 132.8, 129.3, 129.1, 127.7, 122.6, 113.9.
6. White solid (94%), mp 131 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.59 (s, 1H, NH), 7.85 (s, 1H, CH), 7.67 (d, J = 8.5 Hz, 2H, arom),
7.43 (d, J = 8.5 Hz, 2H, arom), 7.37 (d, J = 8.8 Hz, 2H, arom),
7.03 (d, J = 8.8 Hz, 2H, arom). 13C NMR (75 MHz, DMSO-d6)
δ 144.8,
136.4, 134.9, 132.8, 132.2, 129.1, 127.7, 114.4, 110.2, 39.9.
7. White solid (72%), mp 119 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.30 (s, 1H, NH), 7.81 (s, 1H, CH), 7.65 (d, J = 8.5 Hz, 2H, arom),
7.42 (d, J = 8.5 Hz, 2H, arom), 6.69 (s, 2H, arom), 6.41 (s, 1H, arom),
2.22 (s, 6H, CH3). 13C NMR (75 MHz, DMSO-d6)
δ 145.3, 138.5, 135.3,
135.0, 132.3, 129.1, 127.5, 121.3, 110.3, 21.7.
8. White solid (88%), mp 114 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.16 (s, 1H, NH), 8.28 (s, 1H, CH), 7.69 (d, J = 8.7 Hz, 2H, arom),
7.56 (d, J = 8.7 Hz, 1H, arom), 7.51–7.43 (m, 3H, arom),
7.35–7.17 (m, 1H, arom). 13C NMR (75 MHz, DMSO-d6) δ 162.3,
140.9, 140.1, 134.6, 133.4, 129.2, 129.0, 128.5, 128.1, 122.8, 117.1, 115.5.
9. White solid (92%), mp 112 ◦C. 1H NMR (300 MHz, DMSO-d6)
δ 10.74 (s, 1H, NH), 7.90 (d, J = 14.3 Hz, 1H), 7.69 (d, J = 8.3 Hz, 2H,
arom), 7.44 (q, J = 8.3, 7.5 Hz, 3H, arom), 7.26 (s, 1H, CH),
7.00 (d, J = 8.4 Hz, 1H, arom). 13C NMR (75 MHz, DMSO-d6)
δ 145.6,
137.6, 134.6, 133.2, 132.1, 131.5, 131.3, 130.2, 129.8, 129.1, 128.0, 120.1,
113.3, 112.8.
3.3. Synthesis of Dichlorodiazadiens
A
twenty-milliliter screw neck vial was charged with DMSO (10 mL), 1–9 (1 mmol),
tetramethylethylenediamine (TMEDA) (295 mg, 2.5 mmol), CuCl (2 mg, 0.02 mmol), and CCl4 (20 mmol,
10 equiv). After 3 h (until TLC analysis showed complete consumption of corresponding Schiff base) reaction
mixture was poured into ~0.01 M solution of HCl (100 mL, ~pH = 2), and extracted with dichloromethane
(3
×
20 mL). The combined organic phase was washed with water (3
×
50 mL), brine (30 mL), dried over anhydrous
Na2SO4 and concentrated in vacuo. The residue was purified by column chromatography on silica gel using
appropriate mixtures of hexane and dichloromethane (3/1–1/1).

Molecules 2020, 25, 5013
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10. Red solid (73%), mp 85 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.71–7.60 (m, 2H, arom), 7.35 (dd, J = 7.6, 3.8 Hz, 4H, arom),
7.28 (s, 1H, arom), 7.03 (d, J = 8.3 Hz, 2H, arom). 13C NMR
(75 MHz, CDCl3) δ 134.6, 131.7, 131.3, 130.7, 129.4, 129.0, 128.4, 127.1,
126.2, 123.1.
11. Red solid (79%), mp 90 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.69 (d, J = 8.2 Hz, 2H, arom), 7.42 (d, J = 8.3 Hz, 2H, arom),
7.26 (d, J = 8.2 Hz, 2H, arom), 7.13 (d, J = 8.3 Hz, 2H, arom),
2.42 (s, 3H, CH3). 13C NMR (75 MHz, CDCl3) δ 162.3, 151.2, 150.9,
142.5, 134.7, 131.4, 131.0, 129.7, 128.4, 123.2, 21.5.
Crystals, suitable for X-ray analysis, were obtained by the slow
evaporation of saturated hexane/EtOAc (5/1) solution.
12. Red solid (72%), mp 96 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.78 (d, J = 9.0 Hz, 2H, arom), 7.42 (d, J = 8.4 Hz, 2H, arom),
7.13 (d, J = 8.4 Hz, 2H, arom), 6.95 (d, J = 9.0 Hz, 2H, arom),
3.88 (s, 3H, OCH3). 13C NMR (75 MHz, CDCl3) δ 162.7, 162.3, 151.1,
147.2, 134.6, 131.4, 131.2, 128.4, 125.3, 114.2, 55.6.
13. Red solid (68%), mp 77 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.81 (dd, J = 8.6, 5.4 Hz, 2H), 7.43 (d, J = 8.3 Hz, 2H),
7.14 (t, J = 8.8 Hz, 4H). 13C NMR (75 MHz, CDCl3) δ 167.6, 166.4,
151.1, 149.3, 134.8, 131.4, 130.8, 129.6, 128.5, 125.4, 116.2, 115.9.
Crystals, suitable for X-ray analysis, were obtained by the slow
evaporation of saturated hexane/EtOAc (5/1) solution.
14. Red solid (67%), mp 94 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.73 (d, J = 8.6 Hz, 1H), 7.43 (d, J = 8.4 Hz, 2H),
7.12 (d, J = 8.4 Hz, 1H). 13C NMR (75 MHz, CDCl3) δ 162.3, 151.1,
137.7, 136.5, 134.9, 131.4, 130.6, 129.3, 128.5, 124.4.
Crystals, suitable for X-ray analysis, were obtained by the slow
evaporation of saturated hexane/EtOAc (5/1) solution.
15. Red solid (70%), mp 105 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.69–7.56 (m, 4H, arom), 7.49–7.39 (m, 2H, arom),
7.12 (d, J = 8.4 Hz, 2H, arom). 13C NMR (75 MHz, CDCl3) δ 151.4,
134.9, 132.3, 131.4, 130.6, 129.8, 128.5, 127.4, 126.3, 124.6.
Crystals, suitable for X-ray analysis, were obtained by the slow
evaporation of saturated hexane/EtOAc (5/1) solution.

Molecules 2020, 25, 5013
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16. Red solid (82%), mp 145 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.44 (d, J = 7.7 Hz, 4H, arom), 7.15 (d, J = 7.7 Hz, 3H, arom),
2.40 (s, 6H, CH3). 13C NMR (75 MHz, CDCl3) δ 157.7, 148.3, 146.7,
134.2, 130.2, 129.0, 126.8, 126.5, 123.9, 116.5, 16.6.
17. Red solid (66%), mp 115 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.89 (s, 1H, arom), 7.68–7.61 (m, 1H, arom),
7.54 (d, J = 8.6 Hz, 1H, arom), 7.44 (d, J = 8.3 Hz, 2H, arom),
7.11 (d, J = 8.3 Hz, 2H, arom). 13C NMR (75 MHz, CDCl3) δ 151.5,
151.4, 135.7, 135.0, 133.5, 131.3, 130.8, 130.4, 129.8, 128.6, 124.5, 122.7.
Crystals, suitable for X-ray analysis, were obtained by the slow
evaporation of saturated hexane/EtOAc (5/1) solution.
18. Red solid (71%), mp 121 ◦C. 1H NMR (300 MHz, CDCl3)
δ 7.57 (d, J = 8.7 Hz, 1H, arom), 7.46 (d, J = 2.0 Hz, 1H, arom),
7.37 (d, J = 8.4 Hz, 2H, arom), 7.24 (d, J = 2.3 Hz, 1H, arom),
7.12 (d, J = 8.4 Hz, 2H, arom).
4. Conclusions
In summary,
9 novel halogenated dichlorodiazadienes were prepared and fully characterized, while for 5 of
them single crystal structures were determined. Solid state structures contained multiple Hal···Hal interactions,
which were studied by DFT calculations and topological analysis of the electron density distribution within
the framework of Bader’s theory (QTAIM method). Calculations showed that the Hal···Hal interactions dictate
a packing preference for this newly discovered class of dyes. These results further demonstrate the potential of
Hal···Hal bonding in supramolecular engineering and crucial role in the stabilization of the intermolecular networks
of dichlorodiazadienes. Further studies into photophysical properties of halogenated dichlorodiazadienes and
their applications from our laboratory are underway and will be reported in due course.
Supplementary Materials: Figure S1. Visualization of electrostatic surface potentials for 10, 13–15 and 17
with selected Vs,min/Vs,max values (in kcal/mol). Table S1: Crystal data and structure refinement for 10
,
2
13
–
15 and 17, Table S2. Values of the density of all electrons—
ρ
(r), Laplacian of electron density—∇ ρ(r)
and appropriate λ2 eigenvalues (with promolecular approximation), energy density—Hb, potential energy
density—V(r), and Lagrangian kinetic energy—G(r) (a.u.) at the bond critical points (3, –1), corresponding to
Cl···F halogen-halogen contacts in 13, Table S3. Cartesian atomic coordinates for model supramolecular associates.
Author Contributions: Conceptualization, V.G.N. and A.G.T.; writing—review and editing; writing—original
draft preparation, V.G.N., A.G.T., A.S.N.; V.G.N. and A.G.T.; software, A.S.N.; investigation, N.G.S.; A.M.M.;
K.N.B.; G.T.S.; supervision, V.N.K. All authors have read and agreed to the published version of the manuscript.
Funding: This work was performed under the support of the FRCCP RAS State task AAAA-A19-119012990175-9.
A.S.N. is grateful to Russian Science Foundation for the support of his theoretical studies (project No. 19-73-00001).
WeacknowledgetheRUDNUniversityProgram5-100. V.G.N. isgratefultoRFBRforthesupport (grant N 18-03-00791).
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds 1–18 are available from the authors.
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