Triphenylamine/Tetracyanobutadiene-Based π-Conjugated Push–Pull Molecules End-Capped with Arene Platforms: Synthesis, Photophysics, and Photovoltaic Response

Article abstract of DOI:10.1002/chem.202002810

π-Conjugated push–pull molecules based on triphenylamine and 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) have been functionalized with different terminal arene units. In solution, these highly TCBD-twisted systems showed a strong internal charge transfer band

Full text of DOI:10.1002/chem.202002810

Accepted Article
Accepted Article
Title: Triphenylamine/Tetracyanobutadiene-based π-Conjugated Push-
Pull Molecules End-capped with Arene Platforms: Synthesis,
Photophysics, and Photovoltaic Response
Authors: Pablo Simón Marqués, José María Andrés Castán, Benedito
A. L. Raul, Giacomo Londi, Ivan Ramirez, Maxim S.
Pshenichnikov, David Beljonne, Karsten Walzer, Martin Blais,
Magali Allain, Clément Cabanetos, and Philippe Blanchard
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.202002810
Link to VoR: https://doi.org/10.1002/chem.202002810
01/2020

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
Triphenylamine/Tetracyanobutadiene-based -Conjugated Push-
Pull Molecules End-capped with Arene Platforms: Synthesis,
Photophysics, and Photovoltaic Response
Pablo Simón Marqués,†[a] José María Andrés Castán,[a] Benedito A. L. Raul,†[b] Giacomo Londi,†[c] Ivan
Ramirez,[d] Maxim S. Pshenichnikov,*[b] David Beljonne,*[c] Karsten Walzer,[d] Martin Blais,[a] Magali
Allain,[a] Clément Cabanetos[a] and Philippe Blanchard*[a]
[a]
[b]
[c]
P. Simón Marqués, J. M. Andrés Castán, M. Blais, M. Allain, Dr. C. Cabanetos, Dr. P. Blanchard
MOLTECH-Anjou
UMR CNRS 6200, UNIV Angers, SFR MATRIX
2 bd Lavoisier, 49045 ANGERS Cedex, France
E-mail: philippe.blanchard@univ-angers.fr
B. A. L. Raul, Prof. Dr. M. S. Pshenichnikov
Zernike Institute for Advanced Materials
University of Groningen
Nijenborgh 4, 9747 AG, Groningen, the Netherlands
E-mail: m.s.pchenitchnikov@rug.nl
G. Londi, Dr. D. Beljonne
Laboratory for Chemistry of Novel Materials
University of Mons
Place du Parc, 20, 7000 Mons, Belgium
E-mail: david.beljonne@umons.ac.be
Dr. I. Ramirez, Dr. K. Walzer
[d]
HELIATEK GmbH,
Treidlerstraße 3, 01139 Dresden, Germany
† These authors contributed equally to this work
Supporting information for this article is given via a link at the end of the document.
Abstract:
-Conjugated
push-pull
molecules
based
on
optics (NLO),[1],[2] organic light-emitting diodes (OLEDs),[3] bio-
imaging,[4] dye-sensitized solar cells (DSSCs)[5],[6] and organic
solar cells (OSCs).[6] In particular, related dipolar systems based
on arylamines as electron-donating D building block which
provide good hole-transporting properties,[7] have been
extensively investigated for the preparation of efficient donor
materials for organic photovoltaics (OPV).[6],[8] Depending on their
structure, this type of relatively simple molecules can combine
good solubility in common solvents and evaporability allowing the
fabrication of highly performing single-junction organic solar cells
(OSCs) either by solution-processing[9] or vacuum deposition.[10]
Recently, multi-junction OSCs based on arylamine-based D--A
push-pull molecules with power conversion efficiency (PCE)
exceeding 10% have been reported, highlighting the potential of
this class of molecular donors.[11]
Following the pioneer article of J. Roncali on the use of a
push-pull molecule for OPV,[12] namely the star-shaped
triphenylamine (TPA) compound TPA(T-DCV)3, some of us have
recently shown that the linear, simpler and more easily accessible
triphenylamine-thiophene-dicyanovinyl molecule, namely TPA-T-
DCV, exhibits comparable and even superior photovoltaic (PV)
properties when combined with C60 or its soluble analogue [6,6]-
phenyl-C61-butyric acid methyl ester (PC61BM) as acceptors
(Scheme 1).[13] Starting from TPA-T-DCV, minimal structural
changes of: i) the TPA unit aiming at improving the hole transport
properties,[14] ii) the -spacer toward extended electronic
delocalization[13d] and iii) the strength of the electron-withdrawing
group A,[13b] led to enhanced PV performance. Recently, the
substitution of the hydrogen atom of the DCV group by a phenyl
triphenylamine and 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) have
been functionalized with different terminal arene units. In solution,
these highly TCBD-twisted systems showed a strong internal charge
transfer band in the visible spectrum and no detectable
photoluminescence (PL). Photophysical and theoretical investigations
revealed very short singlet excited state deactivation time of ~ 10 ps
resulting from significant conformational changes of the TCBD-arene
moiety upon photoexcitation, opening a pathway for non-radiative
decay. The PL was recovered in vacuum-processed films or when the
molecules were dispersed in a PMMA matrix leading to a significant
increase of the excited state deactivation time. As shown by cyclic
voltammetry, these molecules can act as electron-donors compared
to C60. Hence, vacuum-processed planar heterojunction organic solar
cells were fabricated leading to a maximum power conversion
efficiency of ca. 1.9% which decreases with the increase of the arene
size.
Introduction
Small donor-acceptor conjugated push-pull molecules (D--A)
represent an outstanding class of materials due to their inherent
low-energy intramolecular charge-transfer (ICT) band in the
visible to the near infrared (NIR) region, with in some cases,
aggregation induced emission (AIE) or thermally-activated delay
fluorescence (TADF) properties. As a result, they have found
various electronic and optoelectronic applications in nonlinear
1
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
ring gave rise to the new thermally stable derivative TPA-T-DCV-
Ph that showed an unusual long exciton diffusion length (> 25 nm)
and was used in vacuum-processed bulk heterojunction (BHJ)
OSCs with C70 leading to a PCE higher than 5%.[15]
also been successfully used as non-fullerene acceptors (NFAs)
and combined with donor polymers in BHJ OSCs giving rise to
promising PCEs up to 7%.[26] Note that different molecules
combining TPA and TCBD have been also investigated for their
third-order nonlinear optical properties.[27]
In this work, new unsymmetrical TPA-derived D--A push-
pull molecules based on TCBD have been functionalized with a
terminal phenyl (Ph-1), a 2-naphthyl (Napht-1) or a 1-pyrenyl
(Pyr-1) unit (Scheme 2). The larger arene blocks are expected to
provide additional optical properties and develop -
intermolecular interactions in the solid state as already observed
in pyrene-functionalized TCBD derivatives[28] and small molecules
for efficient BHJ OSCs.[29] X-ray diffraction on single crystals has
given us some insights in the structure and intermolecular
interactions in the solid state of the titled compounds. Their
electrochemical and optical properties have been characterized
by cyclic voltammetry, steady state absorption, (time-resolved) PL
measurements, and ultrafast pump-probe experiments in various
environments. The latter results have been rationalized on the
basis of theoretical calculations and finally discussed with the PV
performance of these new molecular donors.
Scheme 1. Previously described DCV-based push-pull molecules as donors for
OPV.
In this context, the “click”-type [2+2] cycloaddition–
retroelectrocyclization (CA-RE) reaction between an electron-rich
alkyne and electron-deficient olefin, such as tetracyanoethylene
(TCNE) leading to 1,1,4,4-tetracyanobuta-1,3-diene (TCBD)
derivatives,[16] has aroused our interest. This efficient reaction
performed in the absence of catalyst under mild conditions allows
the introduction of TCBD, a strong electron-accepting block (A),
which is particularly convenient for the synthesis of thermally
stable D--A push-pull conjugated molecules endowed with
interesting optical properties. As initially reported for NLO
applications,[17] the presence of TCBD in D--A push-pull
chromophores induces a non-planar conformation improving the
solubility and leading to an intense and low-energy ICT band in
the visible spectrum.[18] These results triggered the synthesis and
photophysical investigations of various electro- and photoactive
D-A multicomponent systems[19] while some devices for all-optical
switching have been fabricated.[20] On the other hand, as
expected for strongly-coupled donor–acceptor systems, the
photoluminescence (PL) of TCBD-based push-pull chromophores
is in general extremely weak, and in some cases even not
measurable in solution due to ultrafast (∼ 1 ps) radiationless
deactivation of the first singlet excited state.[21] This process can
compete with charge separation, which is expected at the
interface between the donor and acceptor materials in OSCs,
hence limiting the interest of TCBD derivatives for OPV. However,
while the self-assembly of a bis-TCBD derivative into vesicles or
nanotubes led to aggregation-induced emission properties as
early reported in 2008,[22] a very recent work on pyrene- and
perylene-functionalized TCBD derivatives shows that whereas PL
is not observed in solution, it is indeed detectable in the solid state,
with emission reaching the NIR region up to 1350 nm, which
opens interesting perspectives for bio-imaging.[23]
Scheme 2. Chemical structure of TPA-T-1, and the new phenyl (Ph-1), naphthyl
(Napht-1), pyrenyl (Pyr-1)-functionalized TCBD-based push-pull molecules.
Results and Discussion
Synthesis. The synthesis of the TCBD-based push-pull
molecules is based on the free alkyne compound 2 which can be
engaged
in
a
Sonogashira
coupling
with
various
monohalogenated arene derivatives affording aryl-end capped
alkynes 7 for subsequent CA-RE reaction with TCNE (Scheme 4).
As described in Scheme 3, compound 2 was prepared following
two different routes. First, a Suzuki coupling between the
commercial (4-(diphenylamino)phenyl)boronic acid and 2-
bromothiophene gave derivative 3 in good yields. As previously
reported,[24] the selective monobromination of 3 in the presence
of NBS led to 4 which was subjected to a Sonogashira coupling
with trimethylsilylacetylene. The silyl group of the intermediate
compound 5 was deprotected affording 2 in 93% yield. Thus
compound 2 was obtained in four steps in a 21% overall yield
starting from the triphenylamine-derived boronic acid.
A significantly optimized route to 2 was developed in two
steps in a 72% overall yield. After a Suzuki coupling between (4-
(diphenylamino)phenyl)boronic acid and 5-bromothiophene-2-
carbaldehyde,[30] the resulting aldehyde 6 was subjected to a
Seyferth-Gilbert homologation using the Ohira-Bestmann reagent
affording the desired free alkyne 2. In addition, this two-step
reaction sequence could be carried out on a gram scale.
Earlier, we described the synthesis and electronic
properties of symmetrical and unsymmetrical D--A--D
molecules using TCBD as the accepting central core and
oligothienyl-TPA chains as donor blocks, and reported for the first
time the use of a TCBD derivative, namely TPA-T-1, as donor
material for OPV leading to a PCE of ca. 1.1% (Scheme 2).[24]
Since then, other TCBD-derived push-pull molecular donors and
extended dicyanoquinodimethane (DCNQ) analogues have been
described in the literature for the fabrication of solution-processed
BHJ OSCs with PC61BM or PC71BM leading to PCEs between ca.
3% and 6%.[25] In addition, due to the strong electron-withdrawing
character of TCBD and DCNQ, different push-pull molecules have
2
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
Crystalline structure of Napht-1. Unlike Ph-1 and Pyr-1, single
crystals were successfully grown by slow evaporation of a solution
of Napht-1 in a mixture of chloroform and petroleum ether and
analyzed by X-ray diffraction. Napht-1 crystallizes in the cubic Fd-
3c space group with one independent molecule. The phenyl-
thiophene-dicyanovinyl (Ph-T-DCV) backbone adopts a quasi-
planar conformation with a slight curvature and a DCV unit
exhibiting a s-cis conformation relative to the neighboring
32]
thiophene ring as usually observed (Figure 1).[13b,
The two
outermost phenyl rings of the TPA unit are out of the
aforementioned plane, one of them showing two disordered
positions with a 65/35 occupancy rate.
Scheme 3. Optimization of the synthesis of 2.
The first attempts of coupling 2 and iodobenzene under
classical Sonogashira conditions in the presence of Cu(I) failed
affording essentially the dialkyne product resulting from a Glaser
homocoupling of 2. In order to prevent this undesired reaction, a
copper-free Sonogashira reaction was used.[31] After optimization,
the AsPh3/Pd2(dba)3 catalyst system in the presence of
diisopropylamine (DIPA) resulted in the highest yields. Thus,
Figure 1. Two different views showing the molecular structure of Napht-1
obtained from X-ray diffraction of a single crystal. Note that one of the external
phenyl ring of TPA adopts two disordered positions with a 65/35 occupancy rate.
More importantly, the TCBD moiety is highly twisted with a
significant dihedral angle of 77° between the two dicyanovinyl
groups (Figure 1, right), as already reported for other TCBD
derivatives,[16a] while the two planes defined by the naphthalene
unit and the phenyl-thiophene segment, respectively, are nearly
perpendicular (88°) (Figure S29).
compound
2
reacted with the commercially available
iodobenzene, 2-bromonaphthalene or 1-iodopyrene leading to
unsymmetrical alkyne derivatives Ph-7, Napht-7 or Pyr-7,
respectively, in moderate to good yields (Scheme 4). Subsequent
reaction with TCNE in refluxing dichloromethane gave the target
compounds Ph-1, Napht-1 and Pyr-1 in quantitative yields.
The examination of intermolecular interactions between one
selected molecule and their neighbors does not evidence -
interactions between two slipped planar naphthalene units.
However, short intermolecular distances can be found despite the
sterically hindered structure of Napht-1 resulting from the
presence of the twisted TCBD. For example, Figure 2 (left) shows
that the naphthyl plane of the molecule represented in red, adopts
a quasi-parallel (with a deviation angle of only 16°) face-to-face
arrangement with the thiophene ring of a neighboring molecule,
the intermolecular distance between the sulfur atom and the
naphthyl plan being of 3.52 Å. In addition, as shown in Figure 2
(right), the planes defined by the Ph-T-DCV backbone of the two
closest neighboring molecules are quasi parallel with a 5°
deviation only and separated by a short average distance of 3.27
Å, while the main axes of these two Ph-T-DCV backbones roughly
adopt a relative perpendicular orientation. Interestingly, the
intermolecular S···S distance of 3.51 Å between the sulfur atoms
of each thiophene ring of these two plans is smaller than the sum
of the van der Waals radium of two sulfur atoms (3.60 Å) in
agreement with the existence of S···S intermolecular interactions.
Scheme 4. Synthesis of target compounds Ph-1, Napht-1 and Pyr-1.
3
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
molecules (- 5.41 eV) suggesting that the HOMO orbital is mainly
located on the TPA-thiophene branch of the molecules. In addition,
although remaining compatible with a photoinduced electron
transfer to C60 (ELUMO = - 4.10 eV)[35] for photovoltaic applications,
the LUMO energy level of Pyr-1 is deeper (- 4.07 eV) than those
of Ph-1 and Napht-1 at - 3.98 eV (Figure 3, bottom).
Figure 2. Views showing the same selected molecule of Napht-1 in red and
one different neighboring molecule highlighting possible intermolecular
interactions between a naphthyl unit and thiophene ring (left) and two quasi
parallel plans defined by Ph-T-DCV segments perpendicularly oriented with a
short S···S intermolecular distance (3.51 Å) (right).
It is worth noting also that the unit cell of Napht-1 contains
192 molecules within a volume of 172515 Å3 (Figure S31), which
is a rare example of giant organic cubic cells.[33]
Electrochemical properties. The electrochemical properties of
Ph-1, Napht-1 and Pyr-1 were investigated by cyclic voltammetry
in CH2Cl2 in the presence of 0.1 M of Bu4NPF6 as supporting
electrolyte (Table 1). The cyclic voltammogram (CV) of each
compounds was recorded between - 1.20 V and + 0.70 V vs
Fc/Fc+ (Figure 3). Both molecules showed one reversible
oxidation peak at Epa = + 0.66 V which could be assigned to the
formation of a radical cation localized on the TPA-thiophene
branch as previously observed in the TPA-T-1 reference
compound (Epa = + 0.65 V).[24] When scanning toward negative
potentials, the CVs of Ph-1 and Napht-1 showed two successive
1
one-electron reversible reduction waves peaking at - 0.87 V (Epc
)
and - 1.15 V (Epc2) associated to the reduction of the acceptor
TCBD moiety. The first reduction wave of Pyr-1 was subjected to
1
a positive shift of Epc (- 0.77 V) suggesting a stronger electron-
accepting character of the pyrene unit. Thus, the replacement of
one strong electron-donating TPA-T segment in TPA-T-1 (Epc1 of
-
0.95 V) by benzene or extended polycyclic aromatic
hydrocarbons induces a positive shift of the first reduction
potential peak in agreement with the increased electron-
withdrawing character of the later.
Figure 3. Top: CVs of Ph-1, Napht-1 and Pyr-1,
1 mM in 0.10 M
Bu4NPF6/CH2Cl2, scan rate 100 mV s-1, Pt working electrode. Bottom: Energy
diagram showing the HOMO and LUMO energy values estimated from CV.
Table 1. Cyclic voltammetric data of Ph-1, Napht-1, Pyr-1 and reference TPA-
T-1 (Conditions: 1 mM in 0.10 M Bu4NPF6/CH2Cl2, scan rate 100 mV s-1, Pt
working electrode, potentials are expressed vs Fc/Fc+)
Optical properties. The optical properties of Ph-1, Napht-1 and
Pyr-1 have been analyzed by UV-vis spectroscopy in diluted
CH2Cl2 solution (ca. 1 × 10−5 M) and as thin-film on glass (Figure
4, Table 2). Their UV-vis spectra show three main absorption
bands, with maxima between 305 and 330 nm and between 350
and 450 nm, the last broad and intense one being centered at 571
nm for Ph-1 and Napht-1 and red-shifted to 580 nm for Pyr-1.
This latter low-energy broad and intense band can be assigned to
an internal charge transfer (ICT) from the electron-donating TPA
moiety to the electron-withdrawing TCBD group as observed in
TPA-T-1, although in this case the corresponding molecular
extinction  is higher due to the presence of two push-pull systems.
Theoretical calculations confirmed that the broad low-energy
band resulting from the combination of a HOMO  LUMO and a
HOMO  LUMO+1 transitions was associated with a strong ICT
character (see theoretical calculations section).
1
2
[a]
[b]
Compd
Epa
Epc
Epc
EHOMO
ELUMO
ΔEelec
(V)
(V)
(V)
(eV)
(eV)
(eV)
TPA-T-1[23]
Ph-1
0.65
0.66
0.66
0.66
- 0.95
- 0.87
- 0.87
- 0.77
- 1.11
- 1.15
- 1.15
- 1.15
- 5.35
- 5.41
- 5.41
- 5.41
- 3.95
- 3.98
- 3.98
- 4.07
1.40
1.43
1.43
1.33
Napht-1
Pyr-1
[a] EHOMO (eV) = - (Eox(onset) vs Fc/Fc+ + 4.8). [b] ELUMO (eV) = - (Ered(onset) vs Fc/Fc+
+ 4.8).[34]
The HOMO and LUMO energy levels were estimated from
the onsets of the first oxidation and reduction waves giving an
electrochemical gap ΔEelec of ca. 1.3-1.4 eV. The HOMO energy
level was not affected by the arene substitution for all target
4
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
In the case of Pyr-1, the presence of a shoulder at ca. 480
nm was attributed to an ICT from pyrene to the TCBD moiety in
agreement with theoretical calculations and as previously
reported for a TCBD-substituted pyrene exhibiting a similar
charge transfer band at 483 nm (Figure 4, top).[28a]
were estimated from the absorption edges at low energy reaching
the NIR region, respectively, values which are close to that of
TPA-T-1 (1.70 eV)[24] (Figure S33) and of interest for photovoltaic
conversion.
Additionally, temperature-dependent UV-vis measurements
between 10 and 70 °C were performed in chlorobenzene (ca. 1 ×
10−5 M) for Napht-1 (Figure 4, bottom) and Pyr-1 (Figure S34).
For both, the absence of new additional bands at low temperature
suggests no aggregation in solution, which may be prevented by
the non-planar twisted TCBD central unit, in agreement with X-ray
data. Nonetheless, the absorption maximum simply shifted
gradually to higher energy when raising the temperature. This
could be attributed to the gradual increase of the molecular
twisting of the TCBD unit already existing in the crystalline
structure. This thermally-induced conformational disorder
decreases the effective conjugation and moves the absorption
maximum to higher energies.
Table 2. UV-vis data of Ph-1, Napht-1, Pyr-1 and reference TPA-T-1 in CH2Cl2
(ca. 10-5 M) and as thin-films.
 (M-1 cm-1)
max (nm)
Film
Compd
Egopt (eV)

max (nm)
CH2Cl2
TPA-T-1[23]
Ph-1
569
384
303
571
391
305
571
391
336
580
401
307
592
391
306
595
403
310
598
400
343
606
411
312
1.70
1.70
1.71
1.65
4.7  104
1.3  104
2.6  104
1.7  104
5.0  103
1.5  104
3.3  104
1.5  104
2.7  104
3.3  104
2.2  104
3.7  104
Napht-1
Pyr-1
Photophysics. Steady state PL measurements showed the
absence of photoemission for Ph-1, Napht-1 and Pyr-1 (ca. 10-6
M) in dichloromethane, chloroform, toluene and hexane. Ultrafast
time-resolved photoluminescence (TRPL) measurements were
also performed with the excitation wavelength set at ~ 580 ± 10
nm to ensure optimal light absorption and the photoexcitation of
the lowest excited state. However, no PL was detected. In
agreement with previous photophysical investigations on other
TCBD derivatives,[21, 23] all these results strongly suggest very
short-lived singlet excited states in solution which are associated
with an ultrafast non-radiative deactivation for all the molecules.
Transient absorption. To uncover the lack of PL of the
compounds in solution, transient absorption (TA) measurements
using the pump-probe technique were carried out (see SI for
experimental details). The steady state and transient absorption
spectra in chloroform are shown in Figure 5. Ph-1, Napht-1 and
Pyr-1 exhibit similar UV-vis spectra to the ones previously
recorded in dichloromethane, albeit with a slightly bathochromic
shift of the absorption maximum of the lowest-energy bands up to
~ 580 nm (Figure 5a, Table 3). The excitation pump and probe
wavelengths were chosen in accordance with the region of
interest, i.e., a central wavelength of 590 nm with a full width at
half maximum (FWHM) bandwidth of 27 nm. Figures 5 b-d depict
the pump-probe transients consisting of an ingrowing and a
decaying components. The ingrowing exponent of ~ 0.7 ps is
assigned to vibrational relaxation at the excited state. The
subsequent mono-exponential decay is attributed to depopulation
of the excited state in ~ 10 ps. This short decay explains why it
was not possible to detect any signal with the TRPL setup with a
time resolution of 10 ps.
Figure 4. UV-vis spectra of Ph-1, Napht-1 and Pyr-1 ca. 10-5 M in CH2Cl2 (top)
and evolution of the UV-vis spectrum of Napht-1 ca. 10-5 M in chlorobenzene
with temperature (bottom).
The UV-vis spectra of Ph-1, Napht-1 and Pyr-1 spun cast
on glass-sheets from a chloroform solution, are slightly broaden
and ca. 25 nm red-shifted in agreement with the existence of
electronic intermolecular interactions in the solid state (Table 2,
Figure S32). Optical bandgaps (Egopt) of 1.70, 1.71 and 1.65 eV
5
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
poly(methyl methacrylate) (PMMA, Mw = 120000 g/mol) were
deposited on glass by solution process (see SI for more details).
PMMA matrix provides an environment that restrains molecular
conformational disorder (as in the neat films) but keeps the
molecules well apart (as in highly diluted solutions). In this
prospect, PMMA matrix is used as benchmark to interrelate
solution and neat film environments.[36] Interestingly, whereas PL
was not detected in solution as previously mentioned,
photoexcitation into the lowest energy absorption band of Ph-1,
Napht-1 and Pyr-1 either dispersed in PMMA matrices or as
evaporated neat thin-films, led to photoemission. Figure 6 (top
panel) shows the absorption spectra of molecules in chloroform
(ca. 10-5 M), in PMMA matrices, in neat thin films and their
respective steady state PL spectra (see also Table 3). The PL
spectra were obtained by time integrating the PL maps (Figure
S35) over (0-0.8) ns spectral range for the neat films and (0-1.8)
ns for the PMMA matrices.
Figure 5. (a) Steady state absorption spectra of chloroform solutions of Ph-1
(red), Napht-1 (blue) and Pyr-1 (green). Transient absorption of Ph-1 (b),
Napht-1 (c) and Pyr-1 (d), the circles show the experimental data, while the
solid lines depict the exponential fittings with respective ingrowing and decaying
components. The pump and probe wavelengths for all the experiments was set
at 590 nm with FWHM of 27 nm.
Table 3. Steady state absorption and PL data for titled molecules in solution, in
PMMA matrix and as neat film.
Absorption max (nm)
Emission max (nm)
CHCl3
PMMA
Evap.
Film
598
CHCl3
PMMA
Evap.
Film
784
Photoluminescence dynamics of neat thin films or isolated
molecules in PMMA matrices. As a next step, photophysical
experiments were also performed in the solid state to assess the
singlet excited state lifetime, which is of interest for photovoltaic
conversion. Neat thin films of Ph-1, Napht-1 and Pyr-1 of 30 nm
on quartz were prepared by evaporation process under high
vacuum (ca. 10-6 mbar), while films of molecules dispersed in
Compd
Ph-1
577
579
587
562
566
569
no
no
no
653
660
665
Napht-1
Pyr-1
599
614
757
780
Figure 6. Top panel: absorption and PL spectra of (a) Ph-1, (b) Napht-1 and (c) Pyr-1. Steady state absorption spectra of molecules isolated in PMMA matrix
(gray), in chloroform (violet) and as neat thin film (pink) represented by solid lines and the corresponding time-integrated PL spectra for PMMA matrix (gray) and
neat thin film (violet) represented by circles. The excitation wavelength for the PL spectra was set at ~ 580 ± 10 nm. Bottom panel: Spectra-integrated (in 600-900
nm range) PL transients of (a) Ph-1, (b) Napht-1 and (c) Pyr-1 in PMMA matrices (gray circles) and neat films (pink circles) with their respective fitting (solid lines).
The dash black lines represent the mean lifetime as a 1/e fraction of the maximum. The corresponding times are shown next to the transients.
6
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
Compared to the diluted solutions in chloroform for which
the target molecules can be considered as isolated, the neat films
exhibit a 20-30 nm red shift of the absorption spectra due to
intermolecular interactions. Molecules dispersed in the polymer
polarizable environment. The typical dielectric constant of
chloroform ε = 4.7 was used to reproduce the surrounding
medium. Excited-state transition energies and oscillator strengths
were obtained with TDDFT calculations based on the Tamm-
Dancoff approximation (TDA).[41] In particular, we computed the
reorganization energy of Napht-1 going from the optimized
ground state to the fully relaxed (adiabatic) first excited state, as
described in Figure 7. Values of 0.48 eV and 0.50 eV were found
for S0 and S1 respectively, giving a total reorganization energy of
0.98 eV. Although the two potential energy surfaces involved are
pretty much symmetrical, this large reorganization energy is
ascribable to a remarkable molecular rearrangement occurring at
the excited state optimized geometry.
Figure 7 shows the optimized geometry of Napht-1 in its
excited state (in red) calculated starting from the optimized ground
state geometry (in blue) and without any constraint on the dihedral
angles of the molecule, thus mimicking the situation in a solvent.
By superimposing the nitrogen atom of the TPA unit, the
comparison clearly evidences the geometrical variations
occurring between both twisted ground and excited states. In
matrices show
a blue-shifted absorption and PL spectra
compared to those of the neat films suggesting the absence of
intermolecular interactions.[36a] The latter is confirmed by the lack
of dynamical PL mean energy shift compared to a larger shift in
the neat film (see Figure S36). Compared to chloroform solutions,
the absorption spectra of molecules dispersed in PMMA are even
more blue-shifted (by 13-18 nm) probably due to a difference of
medium polarity hence affecting the position of the ICT band.
The appearance of PL in the PMMA matrix with emission
maxima between 653 and 665 nm for Ph-1, Napht-1 and Pyr-1
may be explained by a motion restriction of the molecules within
the PMMA upon photoexcitation. This is also the case for neat
thin-films; however due to - intermolecular interactions, the PL
spectra are significantly shifted to lower energy, giving rise to
emission with maxima at ca. 760-780 nm.
Figure 6 (bottom panel) depicts the spectra-integrated PL
transients of the three molecules in PMMA matrices and neat films. particular, along with a minor rearrangement of the TPA unit, the
The neat films PL transients have a bi-exponential behavior. The
early times dynamics (< 0.1 ns) can be ascribed to a spectral
relaxation or excitonic traps as evidenced from the red shift of the
mean PL frequency (see SI for details), while the slowest
decaying exponents should be the actual singlet exciton lifetime
(see Table S3 for fitting parameters).[15, 37] The singlet exciton
average lifetimes in the neat films amount to 77 ps, 106 ps and
23 ps for Ph-1, Napht-1 and Pyr-1, respectively, which are higher
than the ones measured in solution, 7 ps, 9 ps and 12 ps,
respectively (Figure 5). In addition, Figure 6 (bottom panel) shows
that the singlet exciton mean lifetimes of molecules in the PMMA
matrices are significantly increased up to 870 ps, 660 ps and 810
ps for Ph-1, Napht-1 and Pyr-1, respectively. Accordingly, the
occurrence of PL of Ph-1, Napht-1 and Pyr-1 in neat films and in
the PMMA matrices is related to a progressive increase of singlet
exciton lifetime which is extremely short in chloroform, showing
also that restrained molecules in the solid state can recover their
PL. A similar solid-state PL enhancement has been previously
observed in other conjugated materials.[23, 38]
most considerable changes take place on the TCBD and the
naphthalene moieties. For instance, the initial dihedral angle of
79° between the two dicyanovinyl groups of the TCBD moiety in
the ground state (77° from X-ray data) is significantly affected in
the excited state leading to a smaller value of 39°. As a matter of
fact, the high reorganization energy found for Napht-1 can be
correlated to these significant geometrical changes upon
photoexcitation, which opens a possible efficient pathway for a
non-radiative decay, thus preventing the molecule to be
photoluminescent in solution.
To summarize, the combination of TRPL spectroscopy and
pump-probe measurements has allowed us to gain insights into
the excited state dynamics of novel TCBD-based push-pull
molecules. The TA measurements revealed extremely short
singlet excited state deactivation of ~ 10 ps in solution. Using
TRPL spectroscopy, we measured much longer excited state
deactivation in the neat films (up to ~ 100 ps) and even longer
times in the PMMA matrices (up to 870 ps). These altogether
reveal that the confinement of the molecules in the solid state
significantly limits the non-radiative losses in contrast to what is
observed in solution due to molecular rearrangement upon light
absorption, as discussed below.
Figure 7. Energetic diagram and expression of the reorganization energies S1
and S0 where E(Sm|Qn) stands for the energy of the state Sm at the geometry
for the state Qn. Right: geometry of optimized the ground state of Napht-1 (in
blue) and the fully relaxed excited state (in red), generated without any
constraint on the molecular soft degrees of freedom (i.e. torsion angles).
This
conformational
relaxation has
also some
consequences on the charge transfer (CT) nature of the excited
state and on the oscillator strength of the transition. In order to
quantify the former, we took advantage of the spatial overlap
metric S between hole and electron densities.[42] Indeed, the
vertical excited state transition (Figure 8, bottom) performed on
the ground-state structure shows a weaker intramolecular CT
state (higher S character of 0.69 with an oscillator strength of
1.33), with the hole and the electron density delocalized on the
Theoretical calculations. In order to shed some light on the
absence of photoemission properties of push-pull molecules Ph-
1, Napht-1 and Pyr-1 in solution, we performed a series of density
functional theory (DFT) and time-dependent (TD) DFT
calculations at the range-separated hybrid (RSH) ωB97X-D/6-
31G(d,p) level of theory,[39] including also a polarizable continuum
model (PCM)[40] to introduce dielectric screening effects of the
7
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
molecular backbone. On the other hand, the fully relaxed excited
state transition (Figure 8, top) turns out to yield a stronger twisted
intramolecular CT state (lower S character of 0.60 with an
oscillator strength of 0.76). The TCBD rearrangement upon
photoexcitation electronically decouples the TPA electron donor
group from the rest of the molecule, so that the electron density
resides mostly on the TCBD electron acceptor group.
The theoretical absorption spectra are in good agreement
with the experimental ones (Figure 5a). Table 4 shows the three
main electronic transitions for each compound (see also Figure
S40). In all cases, the calculated transition at around 650 nm is
assigned to a HOMO  LUMO contribution while the transition at
around 560 nm corresponds to a HOMO  LUMO+1. Figure 10
presents the electronic excitations related to Napht-1 depicted by
Natural Transition Orbitals (NTOs). The two electronic transitions
at 645 nm (HOMO  LUMO) and 563 nm (HOMO  LUMO+1)
for Napht-1 show a strong CT character from the TPA-T moiety
to TCBD, contributing both to the broad band observed
experimentally at max of 579 nm. The calculated peak at 372 nm
attributed to a HOMO-2  LUMO+1 transition for Napht-1
involves the concomitant charge transfer from TPA-T and the
naphthyl moiety to the TCBD acceptor. A similar behaviour is
observed for Ph-1 and Pyr-1 (Figures S41 and S42). In the case
of Pyr-1, the calculated electronic transition at 474 nm (Figures
S40 and S42), with a relatively high oscillator strength (f = 0.127),
exhibits a strong Pyrene  TCBD charge transfer character. We
associate that transition to the shoulder observed at ca. 480 nm
in the experimental absorption spectrum (Figure 5a).
As a proxy for solid-state effects, we calculated the
reorganization energy by performing a constrained relaxed
excited state optimization, i.e. freezing all the soft torsion angles
of the molecule. By doing that, smaller relaxation energy values
of 0.19 eV and 0.28 eV were found respectively for S and  ,
0
1
S
which could explain the recovery of fluorescence when such
molecules are embedded in a solid PMMA matrix. In addition, in
contrast to what obtained in the full conformational relaxation
scenario mimicking the situation in solution, there is almost no
significant structural variation between the ground state geometry
and the constrained relaxed excited state one (Figure S39),
neither in terms of CT character (S = 0.69 vs 0.72, respectively)
nor for the oscillator strength (1.33 vs 1.56, respectively).
Table 4. Main calculated electronic transitions of Ph-1, Napht-1, Pyr-1 in
chloroform and their orbital description, where H and L denote HOMO and
LUMO, respectively.
Compd
H-n  L+1
H  L+1
H  L
Ph-1
Napht-1
Pyr-1
370 nm (n = 1)
372 nm (n = 2)
371 nm (n = 2)
555 nm
563 nm
556 nm
648 nm
645 nm
656 nm
Figure 8. Hole and electron densities distribution, along with the charge transfer
character S computed in the full relaxed (top) and vertical (bottom) excited
state for Napht-1.
TDA-TDDFT calculations employing an optimally tuned
(OT) RSH ωB97X-D/6-31G(d,p) level of theory combined with
PCM (ε = 4.7) were also performed to investigate the optical
properties of the three TCBD-based molecules. The simulated
UV-vis spectra of Ph-1, Napht-1 and Pyr-1 in chloroform are
represented in Figure 9.
Figure 10. Electronic excitations related to Napht-1 depicted by Natural
Transition Orbitals (NTOs) for the three main transitions with oscillator strengths,
hole densities are shown on the left and electron densities on the right.
Figure 9. Calculated TDA-TDDFT absorption spectra of Ph-1, Napht-1 and
Pyr-1.
8
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
Thus
photophysical
experiments
combined
with
computational studies suggest that the ultra-short relaxation of
the singlet excited state of Ph-1, Napht-1 and Pyr-1 in solution
(ca. 10 ps) is related to significant geometrical changes occurring
at the TCBD-arene moiety upon photoexcitation causing the
molecules not to be emissive. This process is hindered in the solid
state, thereby leading to a recovery of PL with an enhancement
of the excited state deactivation time. Though the latter remains
relatively short for neat thin films with values ranging from ca. 20
up to 100 ps, they are high enough to facilitate exciton
dissociation at a donor/acceptor interface in organic solar cells.[43]
Photovoltaic performance. In order to evaluate the potential of
the titled compounds as electron donors for OPV, all vacuum-
processed planar heterojunction (PHJ) OSCs were fabricated
with the following configuration: ITO/C60 (15 nm)/Donor (6 or 10
nm, respectively)/BPAPF (10 nm)/BPAPF:NDP9 (45 nm, 9.5
wt%)/NDP9 (1 nm)/Al (100 nm). BPAPF (9,9-bis[4-(N,N-
bisbiphenyl-4-yl-amino)-phenyl]-9H-fluorene) and NDP9 (from
Novaled) were used as hole transporting material and p-dopant,
respectively. The photovoltaic parameters of these devices are
gathered in Table 5. The thickness of the donor Ph-1, Napht-1 or
Pyr-1 has been fixed at 6 or 10 nm to study its effect on the fill
factor (FF) and the current density (J), which gives a first insight
into recombination and charge transport behavior (Figure S43).
We found that for each compound, the PCE value slightly
decreased with the thickness of the donor layer owing to a
decrease of the short-circuit current density (Jsc) suggesting poor
hole transport properties of the twisted target compounds.
Comparison of the photovoltaic parameters of OSCs for the
different donors shows an increase of performance with the size
reduction of the cyclic aromatic hydrocarbons from pyrene (PCE
= 0.96%) to naphthalene (PCE = 1.23%) and benzene (PCE =
1.86%), the corresponding J vs V curves for a donor layer of 6 nm
being represented in Figure 11. Comparison of absorption spectra
of 30 nm-thick evaporated thin films of Ph-1, Napht-1 and Pyr-1
on quartz (Figure S44) suggests that the best PCE value for Ph-
1 mainly results from the higher absorption of Ph-1, leading to a
higher Jsc value corresponding to the slightly more intense
External Quantum Efficiency (EQE) spectra (Figure S43).
Figure 11. Comparison of the current density-voltage curves of vacuum-
processed PHJ OSCs prepared from Ph-1, Napht-1 and Pyr-1 (6 nm thickness)
under AM. 1.5 simulated solar illumination at 100 ± 2 mW cm-2.
Conventional bilayer OSCs of architecture ITO/PEDOT-
PSS/Donor/C60/Al were also prepared by spin-coating a solution
of each donor in chloroform (see SI). The same trend in terms of
photovoltaic performance was observed, the higher PCE of
0.95% for Ph-1 being associated to an open-circuit voltage (Voc)
of 0.62 V, a Jsc of 4.4 mA cm-2 and a FF of 34% (Figure S45 and
Table S4). For comparison, all vacuum-processed PHJ OSCs led
to better results as compared to OSCs fabricated by solution
process. In addition, much higher Voc values close to 1 V are
obtained for vacuum-processed devices as well as increased FF
values up to 57% probably resulting from the presence of
additional interfaces providing better collection of charges.
Thus, compared to Ph-1, the introduction of larger aromatic
platforms in Napht-1 and Pyr-1 appears detrimental for
photovoltaic performance of planar heterojunction OSCs with C60.
In addition to the aforementioned optical properties of thin-films,
several other hypotheses can be proposed to explain this
behavior. It is known that efficient charge generation is highly
dependent on the fullerene aggregate size and packing in bulk
heterojunctions between polymer donor and fullerene
acceptors.[44] However in the case of planar heterojunction OSCs
with a fixed evaporated layer of C60, the lower performance
obtained for Pyr-1 might be related to the lower energetic driving
force for charge transfer in agreement with the smaller difference
measured between its LUMO level and that of C60. On the other
hand, the shortest singlet exciton average lifetime measured for
Pyr-1 in neat film (23 ps) might induce a shorter exciton diffusion
length and hence a lower exciton dissociation rate. Indeed, even
the best photovoltaic performance obtained for Ph-1 remains
quite low compared to the PV performance reported for analogous
push-pull molecules with a DCV electron-withdrawing unit,[8d, 8e,
Table 5. Photovoltaic parameters of vacuum-processed PHJ OSCs
ITO/C60/Donor/BPAPF/BPAPF:NDP9/NDP9/Al prepared from Ph-1, Napht-1
and Pyr-1 and characterized under AM 1.5 simulated solar illumination at 100
mW cm-2 (+/- 2%).
Donor
d (nm)[a]
Voc (V)
Jsc (mA cm-2)
FF (%)
PCE (%)
Ph-1
6
10
6
0.99
0.99
0.98
0.96
0.97
0.96
3.3
3.0
2.3
2.1
2.1
1.8
57
55
55
54
47
46
1.86
1.63
1.23
1.09
0.96
0.74
Napht-1
Pyr-1
10
6
9],[10b,10c,11],[13a],[15]
one possible reason can stem from the
significantly longer singlet excited state lifetimes of the later
derivatives and hence their higher diffusion lengths.[15] As a
consequence, TCBD-based push-pull molecules can be used as
donor materials in OSCs, however their relative short singlet
excited state lifetimes in the solid state, seems to limit their
photovoltaic performance.
10
[a] Thickness.
9
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
Conclusion
of Angers. M. B. thanks the University of Angers for his contract
as Engineer. Dr. B. Kriete is thanked for his help with TA
experiments. Computational resources in Mons were provided by
the Consortium des ꢀquipements de Calcul Intensif (CꢀCI),
funded by the Fonds de la Recherche Scientifiques de Belgique
(F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1
A series of D--A push-pull -conjugated molecules based on
triphenylamine as electron-donating group D, a thiophene -
spacer and tetracyanobutadiene (TCBD) as electron-withdrawing
group A, end-capped with arene platforms of increasing size from
a phenyl, a 2-naphthyl or a 1-pyrenyl substituent, was synthesized
in few steps and in good yields. The synthesis was optimized
thanks to the use of an efficient Seyferth-Gilbert homologation of
a conjugated aldehyde affording a free conjugated alkyne
supercomputer
of
the
Fedꢁration
Wallonie-Bruxelles,
infrastructure funded by the Walloon Region under Grant
Agreement No. 1117545. D.B. is a FNRS Research Director.
derivative, which was subject to
Sonogashira reaction with halogenoarenes in order to avoid
Glaser homocouplings. Finally, [2+2] cycloaddition–
a selective copper-free
Conflict of interest
a
retroelectrocyclization reaction between the unsymmetrical
electron-rich alkynes and tetracyanoethylene quantitatively led to
the target molecules Ph-1, Napht-1 and Pyr-1.
The authors declare no conflict of interest
Keywords: computational chemistry • donor-acceptor systems •
organic solar cells • photophysics • tetracyanobutadiene
As shown by X-ray diffraction analysis of single crystals of
Napht-1, the highly twisted TCBD moiety limits - intermolecular
interactions although short S···S intermolecular distances have
been observed. While the target molecules show typical
electrochemical oxidation behavior of triphenylamine derivatives,
they can also be reversibly reduced at accessible negative
potentials in agreement with the strong electron-withdrawing
character of TCBD, which is exalted when it is conjugated with the
pyrene unit. They also exhibit good absorption in the visible range
due to their inherent ICT band. Moreover, they present frontier
orbitals compatible with their use as donor materials for organic
solar cells in combination with C60.
Photophysical experiments showed that the molecules
exhibited extremely fast depopulation of their singlet excited state
in solution (∼ 10 ps), preventing them to be photoemissive. As
supported by theoretical calculations, these values can be
explained by the high reorganization energy of the molecules
upon photoexcitation associated with significant conformational
changes of the TCBD-arene moiety. Interestingly, the singlet
excited state deactivation time decay for all the compounds
progressively increases (by two orders of magnitude) from the
solution to the neat thin films and then in the PMMA matrices,
respectively, leading to a recovery of PL. This behavior results
from a restriction of structural disorder, which is of interest for
photovoltaic conversion. Hence, we prepared all vacuum-
processed planar heterojunction organic solar cells with a power
conversion efficiency of ca. 1.9% for Ph-1 whereas a decrease of
photovoltaic performance was observed with the increase of the
arene size.
[1]
[2]
L. R. Dalton, P. A. Sullivan, D. H. Bale, Chem. Rev. 2010, 110, 25-55.
a) J. M. Raimundo, P. Blanchard, N. Gallego-Planas, N. Mercier, I.
Ledoux-Rak, R. Hierle, J. Roncali, J. Org. Chem. 2002, 67, 205-218; b)
J. D. Luo, X. H. Zhou, A. K. Y. Jen, J. Mater. Chem. 2009, 19, 7410-
7424; c) C. Cabanetos, W. Bentoumi, V. Silvestre, E. Blart, Y. Pellegrin,
V. Montembault, A. Barsella, K. Dorkenoo, Y. Bretonnière, C. Andraud,
L. Mager, L. Fontaine, F. Odobel, Chem. Mater. 2012, 24, 1143-1157; d)
A. B. Marco, N. Martinez de Baroja, S. Franco, J. Garin, J. Orduna, B.
Villacampa, A. Revuelto, R. Andreu, Chem. Asian J. 2015, 10, 188-197.
a) C.-T. Chen, Chem. Mater. 2004, 16, 4389-4400; b) H. Uoyama, K.
Goushi, K. Shizu, H. Nomura, C. Adachi, Nature 2012, 492, 234-238; c)
L. Yao, S. Zhang, R. Wang, W. Li, F. Shen, B. Yang, Y. Ma, Angew.
Chem. Int. Ed. Engl. 2014, 53, 2119-2123; Angew. Chem. 2014, 126,
2151-2155; d) D. H. Kim, A. D'Aléo, X. K. Chen, A. D. S. Sandanayaka,
D. D. Yao, L. Zhao, T. Komino, E. Zaborova, G. Canard, Y. Tsuchiya, E.
Choi, J. W. Wu, F. Fages, J. L. Brédas, J. C. Ribierre, C. Adachi, Nat.
Photonics 2018, 12, 98-106; e) Y. C. Liu, C. S. Li, Z. J. Ren, S. K. Yan,
M. R. Bryce, Nat. Rev. Mater. 2018, 3, 18020; f) W. W. H. Lee, Z. Zhao,
Y. Cai, Z. Xu, Y. Yu, Y. Xiong, R. T. K. Kwok, Y. Chen, N. L. C. Leung,
D. Ma, J. W. Y. Lam, A. Qin, B. Z. Tang, Chem. Sci. 2018, 9, 6118-6125;
g) W. Zeng, T. Zhou, W. Ning, C. Zhong, J. He, S. Gong, G. Xie, C. Yang,
Adv. Mater. 2019, 31, 1901404.
[3]
[4]
a) E. Genin, Z. Gao, J. A. Varela, J. Daniel, T. Bsaibess, I. Gosse, L.
Groc, L. Cognet, M. Blanchard-Desce, Adv. Mater. 2014, 26, 2258-2261;
b) E. Campioli, D. M. Nikolaidou, V. Hugues, M. Campanini, L. Nasi, M.
Blanchard-Desce, F. Terenziani, J. Mater. Chem. C 2015, 3, 7483-7491;
c) X. Yan, M. Remond, Z. Zheng, E. Hoibian, C. Soulage, S. Chambert,
C. Andraud, B. Van der Sanden, F. Ganachaud, Y. Bretonnière, J.
Bernard, ACS Appl. Mater. Interfaces 2018, 10, 25154-25165; d) M.
Remond, Z. Zheng, E. Jeanneau, C. Andraud, Y. Bretonnière, S. Redon,
J. Org. Chem. 2019, 84, 9965-9974; e) A. H. Ashoka, P. Ashokkumar, Y.
P. Kovtun, A. S. Klymchenko, J. Phys. Chem. Lett. 2019, 10, 2414-2421.
B. E. Hardin, H. J. Snaith, M. D. McGehee, Nat. Photonics 2012, 6, 162-
169.
Our findings not only disentangle the underlying factors
behind the lack of photoemission in solution, but also offer
structural, photophysical and theoretical insights into these TCBD
push-pull molecules for potential use in organic semiconductors
devices. For instance, the design of more -extended TCBD-
based conjugated systems with reduced conformational changes
upon photoexcitation could be of interest for novel donor or non-
fullerene acceptor materials for organic photovoltaics.
[5]
[6]
[7]
[8]
T. D. Kim, K. S. Lee, Macromol. Rapid Commun. 2015, 36, 943-958.
Y. Shirota, H. Kageyama, Chem. Rev. 2007, 107, 953-1010.
a) J. Roncali, P. Leriche, P. Blanchard, Adv. Mater. 2014, 26, 3821-3838;
b) V. Malytskyi, J.-J. Simon, L. Patrone, J.-M. Raimundo, RSC Adv. 2015,
5, 354-397; c) J. Wang, K. Liu, L. Ma, X. Zhan, Chem. Rev. 2016, 116,
14675-14725; d) P. Blanchard, C. Malacrida, C. Cabanetos, J. Roncali,
S. Ludwigs, Polym. Int. 2019, 68, 589-606; e) C. Cabanetos, P.
Blanchard, J. Roncali, Chem. Rec. 2019, 19, 1123-1130.
Acknowledgments
P. S. M., J. M. A. C., B. A. L. R, G. L. and I. R. acknowledge the
European Union’s Horizon 2020 research and innovation program
under Marie Sklodowska Curie Grant agreement No. 722651
(SEPOMO). The authors thank the MATRIX SFR of the University
[9]
a) N. Cho, S. Paek, J. Jeon, K. Song, G. D. Sharma, J. Ko, J. Mater.
Chem. A 2014, 2, 12368-12379; b) J. Min, Y. N. Luponosov, D. Baran,
S. N. Chvalun, M. A. Shcherbina, A. V. Bakirov, P. V. Dmitryakov, S. M.
10
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
Peregudova, N. Kausch-Busies, S. A. Ponomarenko, T. Ameri, C. J.
Brabec, J. Mater. Chem. A 2014, 2, 16135-16147; c) A. Mishra, C.
Wetzel, R. Singhal, P. Bäuerle, G. D. Sharma, J. Phys. Chem. C 2018,
122, 11262-11269.
[23] A. T. Bui, C. Philippe, M. Beau, N. Richy, M. Cordier, T. Roisnel, L.
Lemiegre, O. Mongin, F. Paul, Y. Trolez, Chem. Commun. 2020, 56,
3571-3574.
[24] A. Leliège, P. Blanchard, T. Rousseau, J. Roncali, Org. Lett. 2011, 13,
3098-3101.
[10] a) V. Steinmann, N. M. Kronenberg, M. R. Lenze, S. M. Graf, D. Hertel,
K. Meerholz, H. Burckstummer, E. V. Tulyakova, F. Würthner, Adv.
Energy Mater. 2011, 1, 888-893; b) S. W. Chiu, L. Y. Lin, H. W. Lin, Y. H.
Chen, Z. Y. Huang, Y. T. Lin, F. Lin, Y. H. Liu, K. T. Wong, Chem.
Commun. 2012, 48, 1857-1859; c) Y. H. Chen, L. Y. Lin, C. W. Lu, F. Lin,
Z. Y. Huang, H. W. Lin, P. H. Wang, Y. H. Liu, K. T. Wong, J. Wen, D. J.
Miller, S. B. Darling, J. Am. Chem. Soc. 2012, 134, 13616-13623; d) X.
Z. Che, C.-L. Chung, C.-C. Hsu, F. Liu, K.-T. Wong, S. R. Forrest, Adv.
Energy Mater. 2018, 8, 1703603.
[25] a) P. Gautam, R. Misra, E. N. Koukaras, A. Sharma, G. D. Sharma, Org.
Electron. 2015, 27, 72-83; b) P. Gautam, R. Misra, S. A. Siddiqui, G. D.
Sharma, Org. Electron. 2015, 19, 76-82; c) P. Gautam, R. Misra, S. A.
Siddiqui, G. D. Sharma, ACS Appl. Mater. Interfaces 2015, 7, 10283-
10292; d) P. Gautam, R. Misra, G. D. Sharma, Phys. Chem. Chem. Phys.
2016, 18, 7235-7241; e) A. A. Raheem, S. Kamaraj, V. Sannasi, C.
Praveen, Org. Chem. Front. 2018, 5, 777-787.
[26] a) Y. Patil, R. Misra, M. L. Keshtov, G. D. Sharma, J. Phys. Chem. C
2016, 120, 6324-6335; b) P. Srinivasa Rao, A. Gupta, S. V. Bhosale, A.
Bilic, W. Xiang, R. A. Evans, S. V. Bhosale, Dyes Pigm. 2017, 146, 502-
511; c) Y. Patil, R. Misra, R. Singhal, G. D. Sharma, J. Mater. Chem. A
2017, 5, 13625-13633; d) Y. Patil, R. Misra, M. L. Keshtov, G. D. Sharma,
J Mater. Chem. A 2017, 5, 3311-3319; e) P. Gautam, R. Sharma, R.
Misra, M. L. Keshtov, S. A. Kuklin, G. D. Sharma, Chem. Sci. 2017, 8,
2017-2024; f) Y. Patil, R. Misra, Chem. Asian J. 2018, 13, 220-229.
[27] Z. Pokladek, N. Ripoche, M. Betou, Y. Trolez, O. Mongin, J. Olesiak-
Banska, K. Matczyszyn, M. Samoc, M. G. Humphrey, M. Blanchard-
Desce, F. Paul, Chem. Eur. J. 2016, 22, 10155-10167.
[11] a) X. Z. Che, X. Xiao, J. D. Zimmerman, D. J. Fan, S. R. Forrest, Adv.
Energy Mater. 2014, 4, 1400568; b) X. Z. Che, Y. X. Li, Y. Qu, S. R.
Forrest, Nat. Energy 2018, 3, 422-427.
[12] S. Roquet, A. Cravino, P. Leriche, O. Alévêque, P. Frère, J. Roncali, J.
Am. Chem. Soc. 2006, 128, 3459-3466.
[13] a) A. Leliège, C. H. Le Régent, M. Allain, P. Blanchard, J. Roncali, Chem.
Commun. 2012, 48, 8907-8909; b) A. Leliège, J. Grolleau, M. Allain, P.
Blanchard, D. Demeter, T. Rousseau, J. Roncali, Chem. Eur. J. 2013, 19,
9948-9960; c) J. W. Choi, C. H. Kim, J. Pison, A. Oyedele, D. Tondelier,
A. Leliège, E. Kirchner, P. Blanchard, J. Roncali, B. Geffroy, RSC Adv.
2014, 4, 5236-5242; d) A. Labrunie, Y. Jiang, F. Baert, A. Leliège, J.
Roncali, C. Cabanetos, P. Blanchard, RSC Adv. 2015, 5, 102550-102554.
[14] a) Y. Jiang, C. Cabanetos, M. Allain, P. Liu, J. Roncali, J. Mater. Chem.
C 2015, 3, 5145-5151; b) S. Mohamed, D. Demeter, J. A. Laffitte, P.
Blanchard, J. Roncali, Sci. Rep. 2015, 5, 9031; c) Y. Jiang, C. Cabanetos,
S. Jungsuttiwong, D. Alberga, C. Adamo, J. Roncali, ChemistrySelect
2017, 2, 6296-6303.
[28] a) B. Dhokale, T. Jadhav, S. M. Mobin, R. Misra, RSC Adv. 2015, 5,
57692-57699; b) W. Jiang, Y. Shen, Y. Ge, C. Zhou, Y. Wen, H. Liu, H.
Liu, S. Zhang, P. Lu, B. Yang, J. Mater. Chem. C 2020, 8, 3367-3373.
[29] O. P. Lee, A. T. Yiu, P. M. Beaujuge, C. H. Woo, T. W. Holcombe, J. E.
Millstone, J. D. Douglas, M. S. Chen, J. M. Fréchet, Adv. Mater. 2011,
23, 5359-5363.
[30] A. Labrunie, J. Gorenflot, M. Babics, O. Alévêque, S. Dabos-Seignon, A.
H. Balawi, Z. Kan, M. Wohlfahrt, E. Levillain, P. Hudhomme, P. M.
Beaujuge, F. Laquai, C. Cabanetos, P. Blanchard, Chem. Mater. 2018,
30, 3474-3485.
[15] O. V. Kozlov, Y. N. Luponosov, A. N. Solodukhin, B. Flament, O.
Douheret, P. Viville, D. Beljonne, R. Lazzaroni, J. Cornil, S. A.
Ponomarenko, M. S. Pshenichnikov, Org. Electron. 2018, 53, 185-190.
[16] a) S. Kato, F. Diederich, Chem. Commun. 2010, 46, 1994-2006; b) T.
Michinobu, F. Diederich, Angew. Chem. Int. Ed. Engl. 2018, 57, 3552-
3577; Angew. Chem. 2018, 130, 3612-3638.
[31] a) H. Huang, H. Liu, H. Jiang, K. Chen, J. Org. Chem. 2008, 73, 6037-
6040; b) M. E. Ragoussi, G. de la Torre, T. Torres, Eur. J. Org. Chem.
2013, 14, 2832-2840; c) R. Chinchilla, C. Najera, Chem. Rev. 2007, 107,
874-922.
[17] a) X. M. Wu, J. Y. Wu, Y. Q. Liu, A. K. Y. Jen, J. Am. Chem. Soc. 1999,
121, 472-473; b) C. Cai, I. Liakatas, M.-S. Wong, M. Bösch, C. Bosshard,
P. Günter, S. Concilio, N. Tirelli, U. W. Suter, Org. Lett. 1999, 1, 1847-
1849; c) T. Michinobu, J. C. May, J. H. Lim, C. Boudon, J. P. Gisselbrecht,
P. Seiler, M. Gross, I. Biaggio, F. Diederich, Chem. Commun. 2005, 737-
739.
[32] a) R. Fitzner, E. Reinold, A. Mishra, E. Mena-Osteritz, H. Ziehlke, C.
Korner, K. Leo, M. Riede, M. Weil, O. Tsaryova, A. Weiss, C. Uhrich, M.
Pfeiffer, P. Bäuerle, Adv. Funct. Mater. 2011, 21, 897-910; b) R. Fitzner,
C. Elschner, M. Weil, C. Uhrich, C. Korner, M. Riede, K. Leo, M. Pfeiffer,
E. Reinold, E. Mena-Osteritz, P. Bäuerle, Adv. Mater. 2012, 24, 675-680.
[33] a) D. Cortizo-Lacalle, A. Pertegas, L. Martinez-Sarti, M. Melle-Franco, H.
J. Bolink, A. Mateo-Alonso, J. Mater. Chem. C 2015, 3, 9170-9174; b) J.
Li, S. Chen, P. Zhang, Z. Wang, G. Long, R. Ganguly, Y. Li, Q. Zhang,
Chem. Asian J. 2016, 11, 136-140.
[18] S. Kato, M. Kivala, W. B. Schweizer, C. Boudon, J. P. Gisselbrecht, F.
Diederich, Chem. Eur. J. 2009, 15, 8687-8691.
[19] a) S. Niu, G. Ulrich, P. Retailleau, R. Ziessel, Org. Lett. 2011, 13, 4996-
4999; b) P. Gautam, R. Misra, M. B. Thomas, F. D'Souza, Chem. Eur. J.
2017, 23, 9192-9200; c) R. Garcia, M. A. Herranz, M. R. Torres, P. A.
Bouit, J. L. Delgado, J. Calbo, P. M. Viruela, E. Orti, N. Martin, J. Org.
Chem. 2012, 77, 10707-10717; d) F. Tancini, F. Monti, K. Howes, A.
Belbakra, A. Listorti, W. B. Schweizer, P. Reutenauer, J. L. Alonso-
Gomez, C. Chiorboli, L. M. Urner, J. P. Gisselbrecht, C. Boudon, N.
Armaroli, F. Diederich, Chem. Eur. J. 2014, 20, 202-216; e) C. Dengiz,
B. Breiten, J. P. Gisselbrecht, C. Boudon, N. Trapp, W. B. Schweizer, F.
Diederich, J. Org. Chem. 2015, 80, 882-896; f) M. Sekita, B. Ballesteros,
F. Diederich, D. M. Guldi, G. Bottari, T. Torres, Angew. Chem. Int. Ed.
Engl. 2016, 55, 5560-5564; Angew. Chem. 2016, 128, 5650-5654; g) K.
A. Winterfeld, G. Lavarda, J. Guilleme, M. Sekita, D. M. Guldi, T. Torres,
G. Bottari, J. Am. Chem. Soc. 2017, 139, 5520-5529; h) T. Shoji, S. Ito,
Chem. Eur. J. 2017, 23, 16696-16709; i) R. Garcia, J. Calbo, R. Viruela,
M. A. Herranz, E. Orti, N. Martin, ChemPlusChem 2018, 83, 300-307; j)
P. Srinivasa Rao, A. L. Puyad, S. V. Bhosale, S. V. Bhosale, Int. J. Mol.
Sci. 2019, 20, 1621.
[34] C. M. Cardona, W. Li, A. E. Kaifer, D. Stockdale, G. C. Bazan, Adv. Mater.
2011, 23, 2367-2371.
[35] Q. Xie, E. Perez-Cordero, L. Echegoyen, J. Am. Chem. Soc. 1992, 114,
3978-3980.
[36] a) E. Salamatova, O. V. Kozlov, Y. N. Luponosov, A. N. Solodukhin, V.
Y. Toropynina, S. A. Ponomarenko, M. S. Pshenichnikov, Proc. SPIE
2016, 9923, 99230K; b) O. V. Kozlov, Y. N. Luponosov, A. N. Solodukhin,
B. Flament, Y. Olivier, R. Lazzaroni, J. Cornil, S. A. Ponomarenko, M. S.
Pshenichnikov, Adv. Opt. Mater. 2017, 5, 1700024.
[37] O. V. Mikhnenko, M. Kuik, J. Lin, N. van der Kaap, T. Q. Nguyen, P. W.
Blom, Adv. Mater. 2014, 26, 1912-1917.
[38] J. Shi, L. E. Aguilar Suarez, S.-J. Yoon, S. Varghese, C. Serpa, S. Y.
Park, L. Lüer, D. Roca-Sanjuán, B. Milián-Medina, J. Gierschner, J. Phys.
Chem. C 2017, 121, 23166-23183.
[39] Y. S. Lin, G. D. Li, S. P. Mao, J. D. Chai, J. Chem. Theory Comput. 2013,
9, 263-272.
[20] C. Koos, P. Vorreau, T. Vallaitis, P. Dumon, W. Bogaerts, R. Baets, B.
Esembeson, I. Biaggio, T. Michinobu, F. Diederich, W. Freude, J.
Leuthold, Nat. Photonics 2009, 3, 216-219.
[40] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 2005, 105, 2999-3093.
[41] S. Hirata, M. Head-Gordon, Chem. Phys. Lett. 1999, 314, 291-299.
[42] G. Londi, R. Dilmurat, G. D'Avino, V. Lemaur, Y. Olivier, D. Beljonne,
Phys. Chem. Chem. Phys. 2019, 21, 25023-25034.
[21] F. Monti, A. Venturini, A. Nenov, F. Tancini, A. D. Finke, F. Diederich, N.
Armaroli, J. Phys. Chem. A 2015, 119, 10677-10683.
[43] a) N. S. Sariciftci, L. Smilowitz, A. J. Heeger, F. Wudl, Science 1992, 258,
1474-1476; b) I. A. Howard, F. Laquai, Macromol. Chem. Phys. 2010,
211, 2063-2070.
[22] J. Xu, X. Liu, J. Lv, M. Zhu, C. Huang, W. Zhou, X. Yin, H. Liu, Y. Li, J.
Ye, Langmuir 2008, 24, 4231-4237.
11
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
[44] A. C. Jakowetz, M. L. Bohm, J. Zhang, A. Sadhanala, S. Huettner, A. A.
Bakulin, A. Rao, R. H. Friend, J. Am. Chem. Soc. 2016, 138, 11672-
11679.
12
This article is protected by copyright. All rights reserved.

10.1002/chem.202002810
Chemistry - A European Journal
FULL PAPER
Entry for the Table of Contents
Whereas D--A push-pull molecules based on triphenylamine and 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) functionalized with
terminal arene units, strongly absorb in the visible spectrum, they do not show detectable photoluminescence in solution in
agreement with their very short singlet excited state deactivation time. The latter significantly increases in the solid state making
TCBD derivatives potential candidates for photovoltaic application.
13
This article is protected by copyright. All rights reserved.