Synthesis and characterization of dumbbell-like BTD-based derivatives to engineer organic building blocks in solid-state

Article abstract of DOI:10.1016/j.molstruc.2017.09.106

Four BTD-derivatives 4, 5, 7 and 8 were synthesized and characterized by using solution NMR, FTIR and HRMS. In this study, BTD-central cores were supported on trityl type fragments in order to evaluate the influence of these groups prone to aggregation through interdigitation in the consolidation of ordered solids. Structural variation, between compounds 4–5 and 7–8, was selected by introducing aromatic phenyl rings at positions C-4 and C-7 of the BTD central core in order to increase the stackable surface. Crystals of compounds 4 and 5 were obtained and solved in the C2/c and P2₁/c space groups, respectively. Both crystalline arrays are dominated by C[sbnd]H?π and π-stacking interactions, desirable features for the bottom-up construction of highly polarizable organic crystals. The featured compounds with a dumbbell-like structure could be useful as scaffolds for self-assembled crystalline materials such as solid organic semiconductors.

Full text of DOI:10.1016/j.molstruc.2017.09.106

Accepted Manuscript
Synthesis and characterization of dumbbell-like BTD-based derivatives to engineer
organic building blocks in solid-state
Ana Jiménez-Urias, Alejandra Zaavik Lugo-Aranda, Montserrat Miranda-Olvera,
Norberto Farfán, Rosa Santillan, Rafael Arcos-Ramos, María del Pilar Carreón-Castro
PII:
S0022-2860(17)31317-0
10.1016/j.molstruc.2017.09.106
MOLSTR 24355
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 14 July 2017
Revised Date: 26 September 2017
Accepted Date: 26 September 2017
Please cite this article as: A. Jiménez-Urias, A.Z. Lugo-Aranda, M. Miranda-Olvera, N. Farfán, R.
Santillan, R. Arcos-Ramos, Marí.del.Pilar. Carreón-Castro, Synthesis and characterization of dumbbell-
like BTD-based derivatives to engineer organic building blocks in solid-state, Journal of Molecular
Structure (2017), doi: 10.1016/j.molstruc.2017.09.106.
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ACCEPTED MANUSCRIPT
Synthesis and characterization of dumbbell-like BTD-based derivatives to
engineer organic building blocks in solid-state
Ana Jiménez-Urias,a Alejandra Zaavik Lugo-Aranda,b Montserrat Miranda-Olvera,a
Norberto Farfán,b Rosa Santillan,c Rafael Arcos-Ramos,a* María del Pilar Carreón-
Castroa*
a
Departamento de Química de Radiaciones y Radioquímica, Instituto de Ciencias
Nucleares, Universidad Nacional Autónoma de México, 04510 Ciudad de México, México.
b
Facultad de Química, Departamento de Química Orgánica, Universidad Nacional
Autónoma de México, 04510 Ciudad de México, México.
d
Departamento de Química, Centro de Investigación y de Estudios Avanzados del IPN,
Ciudad de México Apdo. Postal 14-740, 07000, México.
Corresponding authors:
Dra. María del Pilar Carreón-Castro, Dr. Rafael Arcos Ramos
Instituto de Ciencias Nucleares, Departamento de Química de Radiaciones y Radioquímica,
Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Ciudad de
México, México. E-mail: pilar@nucleares.unam.mx, rafael.arcos@nucleares.unam.mx

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Abstract
Four BTD-derivatives 4, 5, 7 and 8 were synthesized and characterized by using solution
NMR, FTIR and HRMS. In this study, BTD-central cores were supported on trityl type
fragments in order to evaluate the influence of these groups prone to aggregation through
interdigitation in the consolidation of ordered solids. Structural variation, between
compounds 4-5 and 7-8, was selected by introducing aromatic phenyl rings at positions C-4
and C-7 of the BTD central core in order to increase the stackable surface. Crystals of
compounds 4 and 5 were obtained and solved in the C2/c and P21/c space groups,
respectively. Both crystalline arrays are dominated by C-H···π and π-stacking interactions,
desirable features for the bottom-up construction of highly polarizable organic crystals. The
featured compounds with a dumbbell-like structure could be useful as scaffolds for self-
assembled crystalline materials such as solid organic semiconductors.
Keywords
BTD Derivatives; organic semiconductors; SXRD; molecular crystals; solid-state self-
assembly

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1. Introduction
Benzothiadiazole (BTD) derivatives have received much attention during the last decade
due to their biological (antiviral, antibacterial, fungicide and controlling plant growth) [1]
and remarkable photophysical properties (strong electron acceptor [2] and luminescent
behavior [3]). BTD-containing derivatives have been used in combination with different π-
extended compounds; in particular, 4,7-π-extended-BTD derivatives are promising
scaffolds due to their synthetic feasibility based on classical metal-mediated cross-coupling
methodologies [4]. The characteristic photophysical properties of BTD-derivatives have
allowed to applied them as fluorescent probes for cellular imaging as organic polymeric
dots [5], fluorescent two-photon absorption (TPA) dyes [6], electrogenerated
chemiluminescence derivatives [7], organic optoelectronic materials [8], mesoporous
COF’s [9], and MOF’s [10], also as electron-conducting pyrene-fused azaacenes [11].
In this sense, several organic chromophores supported on π-conjugated molecules have
been used in various organic electronics [12-17]. However, only a few molecular building
blocks have been explored in this area, among others we can found: quinoxalines,
benzimidazoles, BTD-derivatives, and certain types of polymers [18-21]. These building
blocks displayed some interesting capabilities such as high potential for reduction and
electronic affinity (EA); the HOMO/LUMO energy levels of π-conjugated molecules
depend on electron affinity and ionization potential (IP), which can be modulated by
chemical functionalization. Among their most relevant characteristics we can find its
reproducibility and synthetic versatility, facile processability and incorporation into thin-
films, enhanced solubility as well as self-assembly in the solid-state.

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In general, organic materials exhibit weak van der Waals interactions resulting in wide
valence-conduction band gaps, strong interactions between charge carriers and the lattice
due to low dielectric constants, high susceptibility to defects formation, and a strong
dependence on processes taking place at the interface with dielectrics. In order to
manipulate the self-assembly of organic molecules, and to modulate the photophysical
properties of molecular materials in different phases of condensed matter, it is necessary to
understand the molecular structure as well as intra- and intermolecular interactions that
govern their solid-state organization (single crystals, polycrystalline solids, amorphous
solids or thin films).
In recent years, dumbbell-like molecules have been used in the design, synthesis and
dynamic characterization of amphidynamic crystals; built with molecular components
which create an ordered rigid framework in combination with structural elements that are
able to experience fast internal rotational motion [22]; however, a common feature in this
systems is the appearance of interdigitation between molecular components via C-H···π
and π-stacking interactions [23], an interesting structural characteristic that that may be
applied in the development of organic semiconductors. Herein, we explore the self-
assembly of BTD derivatives with dumbbell-like molecular architectures, following
interdigitation strategy for the bottom-up construction of organized solids. The absorption
profiles of these in solution are relatively insensitive to the nature of the flanking groups
and the electronic excitations are described with the aid of time-dependant density
functional theory calculations (TDDFT).

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2. Materials and methods
2.1 Materials
Starting materials were purchased from commercial suppliers and used as received.
Reagent-grade solvents were fractional distilled prior to use. Tetrahydrofuran (THF) was
distilled from sodium-benzophenone in a continuous still under nitrogen atmosphere.
Sonogashira cross-coupling reactions were carried out under nitrogen atmosphere.
Analytical thin-layer chromatography (TLC) was performed using pre-coated TLC-sheets
ALUGRAM XtraSIL G/UV silica gel 60 with fluorescent indicator. Column
chromatography was performed using silica gel (230-400 mesh) as stationary phase.
Melting points were measured in a Barnstead Electrothermal 9300 apparatus and are
uncorrected. IR experiments were registered in a PerkinElmer Spectrum 400 spectrometer;
the signals are reported in wavenumber ν (cm-1). NMR experiments were recorded in
CDCl3 in a Varian MR-400 instrument. All the chemical shifts are reported in ppm with
respect to TMS using residual solvent as reference. The coupling constants are reported in
Hz. Signals multiplicities are reported as: single (s), doublet (d), doublet-doublet (dd),
triplet (t) and multiplet (m). High resolution mass spectra were obtained with an Agilent
G1969A spectrometer. Absorption studies were performed on a UV/VIS Lambda 35 Perkin
Elmer spectrophotometer. The spectroscopic data of BTD-derivatives were determined on
solutions prepared by dissolving crystalline compounds in CHCl3 and toluene. Stock
solutions (1 x 10-4 M) were prepared and diluted to appropriate concentrations for
determination of absorbance.

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2.2. Synthetic procedures
General synthetic procedure for Sonogashira cross-coupling reactions.
A solution of BTD core (1 mmol), trityl type derivative (2 mmol), Pd(PPh3)2Cl2 (6 %
mmol), CuI (10 % mmol), Et3N (1.5 mL) in THF (50 mL) was stirred and refluxed for 3 or
4.5 h under nitrogen atmosphere. After this time, the reaction mixture was cooled down to
room temperature, quenched with NH4Cl saturated and extracted with methylene chloride
(3 x 30 mL), the combined organic portions were dried over anhydrous Na2SO4 and
evaporated to dryness under vacuum. The crude products were purified by column
chromatography with silica gel as stationary phase and hexanes:ethyl acetate as eluent.
4,7-bis(3,3,3-triphenylprop-1-yn-1-yl)benzo[c][1,2,5]thiadiazole (4).
White crystalline solid (0.50 g, 75 %). Melting point: 251 – 252 °C. FTIR-ATR (ν, cm-1):
3050, 3014, 2188, 1588, 1486, 1442, 1336, 1176, 1044, 1030, 880, 840, 756, 694, 634, 540.
1H NMR [400 MHz, CDCl3] (δ, ppm): 7.69 (s, 1H, H-3), 7.49-7.45 (m, Hm, 6H), 7.39-7.34
13
(m, Ho, 6H), 7.33-7.26 (m, Hp, 3H). C NMR [100 MHz, CDCl3] (δ, ppm): 155.1 (C-1),
145.1 (Ci), 132.1 (C-3), 129.4 (Cm), 128.3 (Co), 127.1 (Cp), 117.5 (C-2), 103.8 (C-5), 81.6
(C-4), 58.6 (C-6). HRMS (ESI-TOF): Calculated for C48H33N2S, 669.2358. Found,
669.2356 [M++H+].
4,7-bis((triphenylsilyl)ethynyl)benzo[c][1,2,5]thiadiazole (5).
Yellow crystalline solid (0.56 g, 80 %). Melting point: 204 – 205 °C. FTIR-ATR (ν, cm-1):
2948, 2922, 2846, 2134, 2048, 1718, 1480, 1422, 1266, 1182, 1106, 1074, 958, 690, 494.
1H NMR [400 MHz, CDCl3] (δ, ppm): 7.84-7.80 (m, H-3, Ho, 7H), 7.51-7.42 (m, Hm, Hp,

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9H). 13C NMR [100 MHz, CDCl3] (δ, ppm): 154.7 (C-1), 135.9 (Co), 133.3 (C-3), 133.1
(Ci), 130.3 (Cp), 128.3 (Cm), 117.6 (C-2), 104.4 (C-5), 98.9 (C-4). HRMS (ESI-TOF):
Calculated for C46H32N2SSi2, 701.1897. Found, 701.1900 [M++H+].
4,7-bis(4-(3,3,3-triphenylprop-1-yn-1-yl)phenyl)benzo[c][1,2,5]thiadiazole (7).
Yellow crystalline solid (0.51 g, 63 %). Melting point: 270 – 272 °C. FTIR-ATR (ν, cm-1):
3044, 3006, 2270, 2232, 1588, 1482, 1442, 1172, 1064, 1002, 880, 846, 802, 752, 694, 636,
1
520. H NMR [400 MHz, CDCl3] (δ, ppm): 7.87 (d, J = 8.6 Hz, H-6, 2H), 7.79 (s, H-3,
1H), 7.70 (d, J = 8.6 Hz, H-5, 2H), 7.36-7.21 (m, Ho, m, p, 15H). 13C NMR [100 MHz,
CDCl3] (δ, ppm): 154.0 (C-1), 144.6 (Ci), 136.2 (C-4), 132.7 (C-3), 132.0 (C-5), 130.9 (C-
6), 129.4 (Cm), 128.3 (Co), 128.1 (C-7), 127.3 (Cp), 123.0 (C-2), 103.4 (C-9), 84.4 (C-8),
56.4 (C-10).
4,7-bis(4-((triphenylsilyl)ethynyl)phenyl)benzo[c][1,2,5]thiadiazole (8).
Yellow crystalline solid (0.58 g, 68 %). Melting point: 258 – 259 °C. FTIR-ATR (ν, cm-1):
1
3052, 2998, 2062, 1576, 1546, 1464, 1424, 1278, 1108, 1002, 878, 802, 688, 600, 500. H
NMR [400 MHz, CDCl3] (δ, ppm): 7.88 (d, J = 8.5 Hz, H-6, 2H), 7.80 (s, H-3, 1H), 7.71
(d, J = 8.5 Hz, H-5, 2H), 7.67 (dd, J = 7.9, 1.4 Hz, Ho, 6H), 7.50-7.38 (m, Hm, Hp, 9H). 3C
NMR [100 MHz, CDCl3] (δ, ppm): 153.8 (C-1), 136.1 (C-4), 135.6 (Co), 132.5 (C-3),
132.2 (Ci), 131.9 (C-5), 130.8 (C-6), 130.3 (Cp), 128.1 (Cm), 127.9 (C-7), 122.9 (C-2),
92.0 (C-9), 82.2 (C-8).

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2.3 Theoretical calculations
Density functional theory computations were performed using the Gaussian 09 program
[24] with the B3LYP functional and the triple-zeta quality basis set 6-311+G(d,p). The
polarizable continuum model was employed for implicit solvation with the dielectric
constant of chloroform.
2.4 Structural characterization.
Suitable crystals for SXRD experiments of BTD derivatives 4 and 5 were obtained during
slow evaporation of p-xylenes solutions in partially open glass vials. The XRD data were
collected on an Oxford Diffraction Xcalibur Atlas Gemini diffractometer with CCD area
detector (λCuKa = 1.54184 Å, monochromator: graphite) at 293 (2) K for 4, and on a Bruker
APEX-II CCD (λMoKa = 0.71073 Å, monochromator: graphite) at 293 (2) K for 5.
CrysAlisPro and CrysAlis RED [25] software packages were used for data collection and
data integration. All reflection data set was corrected for Lorentz and polarization effects.
The first structure solution was obtained using the SHELXS-97 programs and then the
SHELXL-97 program was applied for refinement and output data [26] by using OLEX2
software environment [27]. The programs Mercury [28] and ORTEP-3 [29] were used to
prepare artwork representations. Crystallographic data are summarized in Table S2. CCDC
1560958 (4) and 1560959 (5) contains the supplementary crystallographic data for this
paper, these data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif,
or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223
336033. See DOI: 10.1039/x0xx00000x

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3. Results and Discussion
3.1 Synthesis and characterization.
BTD central core 6 and trityl type derivative 2 were synthesized according reported
literature procedures in good yields [5b, 30]. BTD derivatives 4, 5, 7 and 8 were
synthesized using Sonogashira cross-coupling reactions mediated with Pd(0) catalyst under
basic conditions (Scheme 1) in moderate to good yields.
Scheme 1.
The presence of BTD-derivatives 4, 5, 7 and 8 was corroborated by solution NMR
experiments as shown in Figure S1. All the 1H NMR spectra showed a singlet between δ =
7.69-7.80, corresponding to the hydrogen atom (H-3) of the BTD central core; in addition,
trityl type molecules appeared as multiple signals in the aromatic region of the spectrum.

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For compounds 7 and 8, 1H NMR spectra displayed two doublets signals at ca. δ = 7.87 (H-
6) and 7.71 ppm (H-5), corresponding to the hydrogen’s of the extended phenyl rings. In
the case of 13C NMR experiments, all expected signals for each BTD derivative were
observed and assigned as depicted in Figure S2. The BTD carbon atoms were observed
between δ = 153-155 ppm (C-1), 117-123 ppm (C-2), and 132-133 ppm (C-3), confirming
the obtention of the featured compounds. FT-Infrared experiments were carried out by
using ATR technique as solid samples (Figure S3); in all the cases, the most relevant bands
are those derived from CAr-H stretching between 3000-2900 cm-1, as well as the bands
corresponding to substituted alkyne -C≡C- stretching in the range of 2260 to 2100 cm-1. For
the silylated BTD-derivatives 5 and 8, the stretch bands –Si-C- were observed between
850-650 cm-1.
3.2 UV-Vis Absorption studies and TDDFT electronic excitations
Absorption profiles of BTD-derivatives 4-5 and 7-8 are shown in Figure 1, relevant data is
summarized in Table S1. BTD derivatives 4-5 and 7-8 show the typical absorption band of
the BTD core around 390 nm in both solvents (there is no evidence of aggregate formation
in the selected solvents).

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1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
Chloroform
Toluene
0.6
BTD 8
BTD 4
BTD 5
BTD 7
BTD 8
BTD 4
BTD 5
BTD 7
0.4
0.2
0.0
300
350
400
450
500
550
300
350
400
450
500
550
Wavenumber (nm)
Wavenumber (nm)
Figure 1. Absorption profiles of BTD-derivatives 4-5 and 7-8.
Molecules in solution display absorption spectra where the features of the BTD core persist,
being remarkably insensitive to functionalization. We can ascribe this behavior to two main
factors: (i) the amphidynamic nature of these compounds lead to different regimes of
rotation between the central core and the bulky flanking groups, such difference may hinder
conjugation with the extended π-system of the lateral branches; and (ii) the phenyl rings of
the potentially more conjugated systems 7-8 are sterically hindered and thus π-overlap
suboptimal. However, conjugation can be present in the solid-state if rotation is suppressed
by densely packed environments. To estimate this hypothesis we carried out density
functional theory (DFT) computations of BTD derivatives 4-5 and 7-8.
Molecular geometries were optimized with the B3LYP functional and the 6-311+G(d,p)
basis set, using the polarizable continuum model for implicit salvation, with the dielectric
constant of CHCl3. On top of the optimized geometries, TDDFT calculations were applied
to estimate vertical excitation energies, with the same basis and salvation scheme used for

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optimization (Figure 2). The lowest 20 singlet states derived from the computation were
kept for inspection. The main features we observe in this study are: a) for all systems, the
main excitation is HOMO→LUMO+1 and the corresponding absorption profiles are
insensitive to the lateral groups in good agreement with experimental data, and b) for the
optimized structures, vertical excitation is predicted to shift slightly toward red as
conjugation increases. Their implementation of molecular semiconductors in optoelectronic
devices relies on the match between the working function of the chosen electrode with the
frontier orbital energies of the material. Thus, these parameters are of special significance
as they will impact the efficient injection of charges.
Figure 2. Main TDDFT excitations of BTD derivatives 4-5 and 7-8. Transition energies are
shown along with the orbitals involved with 0.04 isosurfaces. Computed at the TDDFT
B3LYP 6-311+G(d,p) in implicit chloroform.

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3.3 Structural analyses of BTD derivatives 4 and 5
The weak intermolecular interactions holding together make the hoping mechanism of
carrier transport dominant. Tailored self-assembly leading to controlled aggregation of pure
and dense solid is a desirable characteristic in the development of organic semiconducting
solids for organic electronics; by using BTD derivatives with dumbbell-like molecular
architectures it is possible to leverage the interdigitation of trityl-like groups to tailor
aggregation into compact, solvent-free organic solids with heterocyclic units such as
benzothiadiazole and its π-extended derivatives.
Molecular structure of BTD derivative 4 was solved in the monoclinic space group C 2/c
with Z = 8 and Z’ = 1 (Figure 3A). The measured angles (<C6-BTD centroid-C6’, 175.8 °)
and (<C6-C2-C2’-C6’, 93.6 °) confirmed that the 4,7-diethynylbenzo[
axle was slightly deviated from linearity. Aromatic trityl rings are partially eclipsed and
presented lower angles than those expected for a tetrahedron (< C -C6-BTD centroid, 105.3
°, 107.7 ° and 110.0 °), which is an indicative for the presence of phenyl embrace
interactions. Therefore, -stacking interactions established between adjacent aromatic trityl
rings [C-H··· , 2.85 and 2.90 Å] dominate the crystal packing of BTD derivative 4, these
interactions connected neighboring BTD molecules along the crystallographic bc plane
forming a 2D arrangement complemented by S··· [3.40 Å] (Figure 3B). The inclusion of a
c][1,2,5]thiadiazole
i
π
π
π
BTD central core favors a densely packed supramolecular self-assembly as shown in figure
3C, this molecular organization could enhance electron delocalization over different modes
and axles, a desirable characteristic to increase electron delocalization in organic
semiconductive materials [31].

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Figure 3. A) Crystalline structure with unit cell (thermal ellipsoids are drawn at 30 %
probability level for all atoms except hydrogen), B) π-interactions between adjacent BTD
molecules (phenyl embraces), and C) supramolecular arrangement found in BTD derivative
4 (hydrogen atoms were omitted for clarity purposes).
For BTD-derivative 5, the molecular structure was solved in the monoclinic space group P
21/c with Z = 4 and Z’ = 1 (Figure 4A). In comparison with BTD-derivative 4, introduction
of a silicon atom produced a larger distance between the BTD central core and trityl
fragments [C6-C2 4.11 Å for 4, and Si-C2 4.46 Å for 5]; as expected, this structural
modification was reflected in a more distorted 4,7-diethynylbenzo[c][1,2,5]thiadiazole axle,
as verified by the measured angles [<Si-BTD centroid-Si’, 176.3 ° and <Si-C2-C2’-Si’.
136.9 °] [32]. Analogously, the main interactions found in BTD-derivative 5 were C-H···π
[2.80 Å]) as well as complementary four phenyl embraces (4PE) between neighboring trityl
fragments [2.89 and 2.90 Å] (Figure 4B). These π-interactions produced that the BTD-

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derivative molecules being stacked in an antiparallel mode, creating a 2D layer
arrangement that grows along the crystallographic a axis. While the phenyl embraces
connect different 2D-layers (that are rotated 82 ° relative to the crystallographic c axis)
favoring a less dense supramolecular array as shown in Figure 4C.
Figure 4. A) Crystalline structure with unit cell (thermal ellipsoids are drawn at 30 %
probability level for all atoms except hydrogen), B) π-interactions (C-H···π and phenyl
embraces), and C) supramolecular arrangement found in BTD derivative 5 (hydrogen atoms
were omitted for clarity purposes).
3.4 Hirshfeld Surface Analysis of BTD derivatives 4-5.
An interesting approach to explore insights into crystal packing has been the so-called
Hirshfeld surface analysis; in brief, it provides a way to define the boundary of a molecule
within a crystal in terms of electron density. In this context, non-covalent intermolecular
interactions within a crystalline network can be analyzed and quantified by Hirshfeld

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Surface Analysis (HSA) deriving 2D fingerprintplots; surfaces were generated using
CrystalExplorer software based on experimental CIF data employing the BLYP 6-31G(d)
scheme [33-36].
Both BTD-derivatives 4 and 5 display different edge-to-face stacking due to diverse phenyl
embraces; particularly for compound 5, the inclusion of the silicon atoms favored the
appearance of these interactions. In general, is expected that increasing total stackable
surface through the covalent linkage of additional aromatic results could result in prevailing
extensive stacking as in compounds 7 and 8. Although no high quality single crystals for
BTD-derivatives 7 and 8 have been obtained, crystallization attempts with benzene yielded
weakly diffracting crystals that could not be further refined to acceptable publication
standards; therefore, consequences of increasing the stackable surface in a molecule could
not be evaluated in the solid state.
Hirshfeld surfaces were used to analyze the nature of contacts present in each BTD-
derivative; non-classical H-bonding interactions were distinguished for both compounds, in
the case of 4, S-π contacts were found; overall, near all contacts involve hydrogen atoms
which make 92.9 % (4) and 93.1 % (5) of the total Hirshfeld surfaces. Accordingly,
Hisrhfeld surfaces mapped over shape index indicate the presence of complementary
stacking interactions established by electron-deficient BTD rings as well as between
aromatic trityl fragments. Decomposed Hirshfeld 2D fingerprint plots show that H···H is
the main interaction in the crystal packing of BTD-derivatives 4 and 5 (figures 5-6),
supported by non-classical hydrogen-bonding interactions (C-H···π). Extensive stacking is
present in both crystals (estimated as the sum of the C---C, C---S, C---N and N---N
intermolecular contact areas: 7.1 % for 4, and 3.7 % for 5); nevertheless, the presence of the

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silicon atoms decrease the stacking percentage by increasing C-H···π interactions, this
behavior could affect the electronic properties of the studied derivatives.
Figure 5. Hirshfeld surfaces and decomposed 2D fingerprint plots of BTD-derivative 4.

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Figure 6. Hirshfeld surfaces and decomposed 2D fingerprint plots of BTD-derivative 5.
Conclusions
Four novel BTD-derivatives with dumbbell-like shape were synthesized in moderate to
good yields starting from readily available molecular units. Two unreported crystal
structures of BTD-derivatives 4 and 5 were obtained and described; both crystal packings
are dominated by cooperative phenyl embraces (C-H···π) and π-stacking interactions,
favoring interdigitation between BTD cores and aromatic trityl rings and producing highly
dense supramolecular arrangements, which confirms the applicability of the interdigitation
criterion for the self-assembly of organic solids.

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These systems could be useful as candidates for organic semiconductor materials with
extended electron delocalization; the studied BTD-derivatives possess desirable
characteristics for this purpose, such as synthetic accessibility, solution processability and
supramolecular self-assembly via H-bonding combined with π-stacking. These results open
the possibility to vary the molecular architecture introducing electron-donor or electron-
withdrawing groups at the BTD-central core, in order to fine-tune the semiconductor
character. Experimental work to explore electronic properties of these systems is currently
underway, trying to produce solution-processable organic semiconductor materials.
Acknowledgements
M. Carreón-Castro acknowledges to DGAPA-UNAM (PAPIIT IN-116716). N. Farfán
acknowledges to Faculty of Chemistry-UNAM (PAPIIT IN-216616). The authors would
like to express their gratitude to Marco Leyva-Ramírez for X-Ray Diffraction experiments.
A.J.U. and M.M.O. acknowledge to CONACYT for the granted scholarships (303614 and
335895, respectively).
References
[1] (a) P. Lewandowski, R. Kukawka, H. Popieszny, M. Smiglak, Bifunctional quaternary
ammonium salts based on benzo[1,2,3]thiadiazole-7-carboxylate as plant systemic acquired
resistance inducers, New J. Chem. 38 (2014) 1372-1375. (b) M. Smiglak, R. Kukawka, P.
Lewandowski, H. Popieszny, Cationic derivatives of the plant resistance inducer
benzo[1,2,3]thiadiazole-7-carbothioic acid S-methyl ester (BTH) as bifunctional ionic

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liquids, Tetrahedron Lett. 55 (2014) 3565-3568. (c) M. Takeshita, M. Okuda, S. Okuda, A.
Hyodo, K. Hamano, N. Furuya, K. Tsuchiya, Induction of antiviral responses by
acibenzolar-s-methyl against cucurbit chlorotic yellows virus in Melon, Phytopathology
103 (2013) 960-965. (d) A.P. Piccionello, A. Guarcello, Bioactive compounds containing
benzooxadiazole, benzothiadiazole, benxotriazole, Curr. Bioact. Compd. 6 (2010) 266-283.
(e) T. Balasankar, M. Gopalakrishnan, S. Nagarajan, Synthesis and antibacterial activity of
some 5-(4-biphenylyl)-7-aryl[3,4-d] [1,2,3]-benzothiadiazoles, Eur. J. Med. Chem. 40
(2005) 728-731.
[2] (a) P. Zhou, Z.G. Zhou, Y. Li, X. Chen, J. Qin, Thiophene-Fused Benzothiadiazole: A
Strong Electron-Acceptor Unit to Build D–A Copolymer for Highly Efficient Polymer
Solar Cells, Chem. Mater. 26 (2014) 3495-3501. (b) W.W. Wong, J. Subbiah, S.R.
Puniredd, W. Pisula, D.J. Jones, A.B. Holmes, Benzotriazole-based donor–acceptor
conjugated polymers with a broad absorption in the visible range, Polym. Chem. 5 (2014)
1258-1263.
[3] (a) J.Y. Chen, Y.C. Chiu, C.C. Shih, W.C. Wu, W.C. Chen, Electrospun nanofibers with
dual plasmonic-enhanced luminescent solar concentrator effects for high-performance
organic photovoltaic cells, J. Mater. Chem. A 3 (2015) 15039-15048. (b) Z. Wang, Q. Liu,
T. Chen, Y. Wang, J. Yuan, C. Zheng, R. Chen, W. Huan, Molecular rearrangement at
charged states: Intrinsic effects upon photo and electroluminescence, Dyes and pigments
113 (2015) 529-535.
[4] (a) T.O. Lopes, D.A. da Silva Filho, A.A. Lapis, H.C. de Oliveira, B.A. Neto, Designed
non-symmetrical 4,7-pi-extended-2,1,3-benzothiadiazole derivatives: Synthesis guided by

ACCEPTED MANUSCRIPT
DFT predictions, J. Phys. Org. Chem. 27 (2014) 303-309. (b) P.M. Beaujuge, H.N. Tsao,
M.R. Hansen, C.M. Amb, C. Risko, J. Subbiah, K.R. Choundhury, A. Mavrinskiy, W.
Pisula, J.L. Bredas. F. So, K. Müllen, J.R. Reynolds, Synthetic Principles Directing Charge
Transport in Low-Band-Gap Dithienosilole–Benzothiadiazole Copolymers, J. Am. Chem.
Soc. 134 (2012) 8944-8957.
[5] (a) B.A. Neto, P.H. Carvalho, J.R. Correa, Benzothiadiazole Derivatives as
Fluorescence Imaging Probes: Beyond Classical Scaffolds, Acc. Chem. Res. 48 (2015)
1560-1569. (b) W. Qin, K.Li, G. Feng, M. Li, Z. Yang, B. Liu, B.Z. Tang, Bright and
Photostable Organic Fluorescent Dots with Aggregation-Induced Emission Characteristics
for Noninvasive Long-Term Cell Imaging, Adv. Funct. Mater. 24 (2014) 635-643. (c) Y.
Zhang, T. Yu, M.E. Gallina, W. Sun, Y. Rong, D.T. Chiu, Highly luminescent, fluorinated
semiconducting polymer dots for cellular imaging and analysis, Chem. Commun. 49 (2013)
8256-8258.
[6] T. Ishi-I, N. Nakamura, T. Mine, S. Imamura, M. Shigeiwa, H. Gorohmaru, S. Maeda,
Fluorescent Two-photon Absorption Benzothiadiazole Dyes Having Photoreleasing
Quenchers, Chem. Lett. 38 (2009) 1042-1043.
[7] K.M. Omer, S.Y. Ku, K.T. Wong, A.J. Bard, Green Electrogenerated
Chemiluminescence of Highly Fluorescent Benzothiadiazole and Fluorene Derivatives, J.
Am. Chem. Soc. 131 (2009) 10733-10741.
[8] J. Zhang, W. Chen, A.J. Rojas, E.V. Jucov, T.V. Timofeeva, T.C. Parker, S. Varlow,
S.R. Marder, Controllable Direct Arylation: Fast Route to Symmetrical and Unsymmetrical

ACCEPTED MANUSCRIPT
4,7-Diaryl-5,6-difluoro-2,1,3-benzothiadiazole Derivatives for Organic Optoelectronic
Materials, J. Am. Chem. Soc. 135 (2013) 16376-16379.
[9] M. Dogru, A. Sonnauer, S. Zimdars, M. Doblinger, P. Knochel, T. Bein, Facile
synthesis of a mesoporous benzothiadiazole-COF based on a transesterification process,
CrystEngComm 15 (2013) 1500-1502.
[10] C. Song, Y. He, B. Li, Y. Ling, H. Wang, Y. Feng, R. Krishna, B. Chen, Enhanced
CO2 sorption and selectivity by functionalization of a NbO-type metal–organic framework
with polarized benzothiadiazole moieties, Chem. Commun. 50 (2014) 12105-12108.
[11] (a) A.B. Marco, D. Cortizo-Lacalle, C. Gozalvez, M. Olano, A. Atxabal, X. Sun, M.
Melle-Franco, L.E. Hueso, A. Mateo-Alonso, An electron-conducting pyrene-fused
phenazinothiadiazole, Chem. Commun. 51 (2015) 10754-10757. (b) S. Choudhary, C.
Gozalvez, A. Higelin, I. Krossing, M. Melle-Franco, A. Mateo-Alonso,
Hexaazatrinaphthylenes with Different Twists, Chem. Eur. J. 20 (2014) 1525-1528. (c) S.
More, S. Choudhary, A. Higelin, I. Krossing, M. Melle-Franco, A. Mateo-Alonso, Twisted
pyrene-fused azaacenes, Chem. Commun. 50 (2014) 1976-1979.
[12] M.T. Lee, C.K. Yen, W.P. Yang, H.H. Chen, C.H. Liao, C.H. Tsai, C.H. Chen,
Efficient Green Coumarin Dopants for Organic Light-Emitting Devices, Org. Lett. 6 (2004)
1241-1244.
[13] S.A. Odom, S.R. Parkin, J.E. Anthony, Tetracene Derivatives as Potential Red
Emitters for Organic LEDs, Org. Lett. 5 (2003) 4245-4248.

ACCEPTED MANUSCRIPT
[14] W.J. Shen, R. Dodda, C.C. Wu, F.I. Wu, T.H. Liu, H.H. Chen, C.H. Chen, C.F. Shu,
Spirobifluorene-Linked Bisanthracene:ꢀ An Efficient Blue Emitter with Pronounced
Thermal Stability, Chem. Mater. 16 (2004) 930-934.
[15] M. Akhtaruzzaman, M. Tomira, J. Nishida, Y. Yamashita, Synthesis and
Characterization of Novel Dipyridylbenzothiadiazole and Bisbenzothiadiazole Derivatives,
J. Org. Chem. 69 (2004) 2953-2958.
[16] S.S. Sun, A.J. Lees, Self-Assembly Triangular and Square Rhenium(I) Tricarbonyl
Complexes:ꢀ
A
Comprehensive Study of Their Preparation, Electrochemistry,
Photophysics, Photochemistry, and Host−Guest Properties, J. Am. Chem. Soc. 122 (2002)
8956-8967.
[17] Q. Hou, Q. Zhou, Y. Zhang, W. Yang, T. Yang, Y. Cao, Synthesis and
Electroluminescent Properties of High-Efficiency Saturated Red Emitter Based on
Copolymers from Fluorene and 4,7-Di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole,
Macromolecules 37 (2004) 6299-6305.
[18] C.J. Tonzola, M.M. Alam, W. Kaminsky, S.A. Jenekhe, New n-Type Organic
Semiconductors:ꢀ Synthesis, Single Crystal Structures, Cyclic Voltammetry, Photophysics,
Electron Transport, and Electroluminescence of a Series of Diphenylanthrazolines, J. Am.
Chem. Soc. 125 (2003) 13548-13558.
[19] Y. Cui, X. Zhang, S.A. Jenekhe, Thiophene-Linked Polyphenylquinoxaline:ꢀ A New
Electron Transport Conjugated Polymer for Electroluminescent Devices, Macromolecules
32 (1999) 3824-3826.

ACCEPTED MANUSCRIPT
[20] D.Y. Kim, S.K. Lee, J.L. Kim, H. Lee, H.N. Cho, S.I. Hong, C.Y. Kim, Improved
efficiency of polymer LEDs using electron transporting layer, Synth. Met. 12 (2001) 1707-
1708.
[21] Z.Q. Gao, C.S. Lee, I. Bello, S.T. Lee, S.K. Wu, Z.L. Yan, X.H. Zhang, Blue organic
electroluminescence of 1,3,5-triaryl-2-pyrazoline, Synth. Met. 105 (1999) 141-144.
[22] (a) R. Arcos-Ramos, B. Rodríguez-Molina, M. Romero, J.M. Mendez-Stivalet, M.E.
Ochoa, P.I. Ramírez-Montés, R. Santillan, M.A. Garcia-Garibay, N. Farfán, Synthesis and
Evaluation of Molecular Rotors with Large and Bulky tert-Butyldiphenylsilyloxy-
Substituted Trityl Stators, J. Org. Chem. 77 (2012) 6887-6894. (b) B. Rodríguez-Molina,
M.E. Ochoa, N. Farfán, R. Santillan, M.A. Garcia-Garibay, Synthesis, characterization and
rotational dynamics of crystalline molecular compasses with N-heterocyclic rotators, J.
Org. Chem. 74 (2009) 8554—8565.
[23] R. Arcos-Ramos, B. Rodríguez-Molina, E. González-Rodríguez, P.I. Ramírez-Montés,
M.E. Ochoa, R. Santillan, N. Farfán, M.A. Garcia-Garibay, Crystalline arrays of molecular
rotors with TIPS-trityl and phenolic-trityl stators using phenylene, 1,2-difluorophenylene
and pyridine rotators, RSC Adv. 5 (2015) 55201-55208.
[24] Gaussian 09, Revision D.01, MJ Frisch, GW Trucks, HB Schlegel, GE Scuseria, MA
Robb, JR Cheeseman, G. Sacalmani, V. Barone, B. Menucci, GA Petersson, H. Nakatsuji,
M. Caricato, X. Li, HP Hratchian, AF Izmaylov, J. Bloino, G. Zheng, JL Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, T. Vreven, JA Montgomery, JE Peralta, F. Ogliaro, M. Bearpak, JJ Heyd,
E. Brothers, KN Kudin, VN Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A.

ACCEPTED MANUSCRIPT
Rendell, JC Burant, SS Iyengar, J. Tomasi, M. Cossi, N. Rega, JM Millam, M. Klene, JE
Knox, JB Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, RE Stratmann, O.
Yazyev, AJ Austin, R. Cammi, C. Pomelli, JW Ochterski, RL Martin, K. Morokuma, VG
Zakrzewsli, GA Voth, P. Salvador, JJ Dannenberg, S. Dapprich, AD Daniels, Ö. Farkas, JB
Foresman, JV Ortiz, J Ciolowski, J. Fox, Gaussian, Inc., Wallingford CT, 2009.
[25] Oxford Diffraction (2009). CrysAlis PRO and CrysAlis RED. Agilent Technologies,
Yarton, England. Software system, version 1.171.33.31, Oxford Diffraction Ltd.,
Abingdon, England.
[26] G.M. Sheldrick, A short history of SHELX, Acta Cryst. Sect. A: Found. Crystallogr.
64 (2008) 122.
[27] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, OLEX2: a
complete structure solution, refinement and analysis program, J. Appl. Cryst. 42 (2009)
339.
[28] C.F. Macrae, P.R. Edington, P. McCabe, E. Pidcock, G.P. Shields, R. Taylor, M.
Towler, J. van de Streek, Mercury: visualization and analysis of crystal structures, J. Appl.
Cryst. 39 (2006) 453-457.
[29] L.J. Farrugia, ORTEP-3 for Windows-a version of ORTEP-III with a graphical user
interface (GUI), J. Appl. Cryst. 30 (1997) 565.
[30] S.D. Karlen, R. Ortiz, O.L. Chapman and M.A. Garcia-Garibay, Effects of Rotational
Symmetry Order on the Solid State Dynamics of Phenylene and Diamantane Rotators, J.
Am. Chem. Soc. 127 (2005) 6554-6555.

ACCEPTED MANUSCRIPT
[31] (a) M. Maldonado-Domínguez, R. Arcos-Ramos, M. Romero, N. Farfán, R. Santillan,
P.G. Lacroix, I. Malfant, The amide bridge in donoreacceptor systems: delocalization
depends on pushepull stress, New J. Chem. 38 (2014) 260-268. (b) H. Moon, R. Zeis, E.J.
Borkent, C. Besnard, A.J. Lovinger, T. Siegrist, C. Kloc, Z.N. Bao, Synthesis, crystal
structure, and transistor performance of tetracene derivatives, J. Am. Chem. Soc. 126
(2004) 15322-15323. (c) J.E. de la Cerda-Pedro, R. Arcos-Ramos, M. Maldonado-
Domínguez, S. Rojas- Lima, M. Romero-Ávila, M.P. Carreón-Castro, R. Santillan, N.
Farfán, H. López-Ruíz, Engineering organic semiconducting solids. Multicomponent access
to crystalline 3-(4-aryl-1,2,3-triazolyl)coumarins, CrystEngComm 18 (2016) 5562-5571.
[32] S.D. Karlen, H. Reyes, R.E. Taylor, S.I. Khan, M.F. Hawthorne, M.A. Garcia-Garibay,
Symmetry and dynamics of molecular rotors in amphidynamic molecular crystals, Proc.
Natl. Acad. Sci. USA 107 (2010) 14973-14977.
[33] M.A. Spackman and D. Jayalitaka, Hirshfeld surface analysis, CrystEngComm, 11
(2009) 19-32.
[34] F.L. Hirshfeld, Bonded-atom fragments for describing molecular charge densities,
Theor. Chim. Acta, 44 (1977) 129-138.
[35] M.A. Spackman, J.J. McKinnon, Fingerprinting intermolecular interactions in
molecular crystals, CrystEngComm, 2002, 4, 378-392.
[36] Crystal Explorer (Version 3.1) S.K. Wolff, D.J. Grimwood, J.J. McKinnon, M.J.
Turner, D. Jayatilaka, M. Spackman, University of Western Australia, 2012.

ACCEPTED MANUSCRIPT
Highlights
Four novel BTD-based organic building blocks were synthesized and characterized.
BTD-derivatives are synthetically accessible and solution processable.
Crystal structures 4 and 5 were solved in the C2/c and P21/c space groups.
Self-assembly is directed by non-classical H-bonding and π-stacking.
Interdigitation between BTD-based dumbbell-like molecules was found.