Resistance to unwanted photo-oxidation of multi-acene molecules

Article abstract of DOI:10.1021/acs.joc.0c01890

Although long acenes remain a key class of π- conjugated molecules for numerous applications, photoinduced oxidation upon exposure of the acene to light, often through sensitization of 1O2, is an important reaction requiring mitigation for most applications. In response to this ongoing challenge, this paper presents a series of four new diarylethynyl-substituted long acenes-three tetracenes and one anthradithiophene-in which the arylene pendants are either benzene, naphthalene, or anthracene. UV/vis and fluorescence spectroscopy reveals that the anthracene-substituted derivatives fluoresce poorly (φ < 0.01). Although all four long acenes react with 1O2 at expected rates when an external photosensitizer is included and show the expected changes in fluorescence to accompany these reactions, the anthracene-substituted derivatives resist direct photoinduced oxidation. Through a combination of mechanistic experiments, we conclude that rapid nonradiative decay of the anthracene-substituted derivatives, perhaps because of inter-arene torsions that emerge in theoretical geometry optimizations, makes these compounds poor photosensitizers for 1O2 or other reactive oxygen species. This discovery opens new design possibilities for extended acene structures with improved photochemical stability.

Full text of DOI:10.1021/acs.joc.0c01890

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Article
Resistance to unwanted photooxidation of multi-acene molecules
Yu Yan, Zachary A. Lamport, Ioannis Kymissis, and Samuel W. Thomas
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c01890 • Publication Date (Web): 07 Sep 2020
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Resistance to unwanted photooxidation of multi-acene molecules
Yu Yan,# Zachary A. Lamport,| Ioannis Kymissis,| Samuel W. Thomas III#*
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# Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, MA 02155, USA
| Department of Electrical Engineering, Columbia University, 500 W. 120th Street, New York, NY 10027 USA
ABSTRACT: Although long acenes remain a key class of p-conjugated molecules for numerous applications, photoinduced
oxidation upon exposure of the acene to light, often through sensitization of 1O2, is an important reaction requiring mitigation
for most applications. In response to this ongoing challenge, this paper presents a series of four new diarylethynyl-substituted
long acenes—three tetracenes and one anthradithiophene—in which the arylene pendants are either benzene, naphthalene,
or anthracene. UV/vis and fluorescence spectroscopy reveals that the anthracene-substituted derivatives fluoresce poorly (F
< 0.01). Although all four long acenes react with 1O2 at expected rates when an external photosensitizer is included, and show
the expected changes in fluorescence to accompany these reactions, the anthracene-substituted derivatives resist direct pho-
toinduced oxidation. Through a combination of mechanistic experiments, we conclude that rapid non-radiative decay of the
anthracene-substituted derivatives, perhaps due to inter-arene torsions that emerge in theoretical geometry optimizations,
make these compounds poor photosensitizers for 1O2 or other ROS. This discovery opens new design possibilities for extended
acene structures with improved photochemical stability.
cently, Briseno and co-workers described thiophene-sub-
stituted rubrene analogs with improved resistance to
photo-oxidation attributed to rapid non-radiative decay
that were unable to sensitize ROS.21 Finally, Linker identi-
fied the reduced barriers to endoperoxide cycloreversion
of ethynylated or pyridine-substituted acenes as an ap-
proach for recovering acenes after oxidation.22,23
INTRODUCTION
Acenes are a key class of organic molecules for a range of
optical and electronic applications.1-3 Pentacene,
bis(triisopropylsilylethynyl)pentacene, and rubrene are
examples of key benchmarking materials for organic field-
effect transistors due to their high charge-carrier mobility
in either thin films or a single-crystal devices. Their elec-
tronic structures also make acenes among the best mate-
rials for singlet fission applications in photovoltaics.4 In
addition, cycloaddition reactions, especially between an-
thracene moieties and reactive dieneophiles such as ma-
leimides, are important ligation reactions for materi-
als.5,6,7,8
Acene endoperoxidations have found important applica-
tion in responsive fluorophores. Dye-anthracene conju-
gates can undergo fluorescence “turn-on” upon cycloaddi-
tion due to elimination of electron transfer quenching.24,25
The commercially available probe Singlet Oxygen Sensor
Green (SOSG) is an example of this approach. Our group
has reported materials that contain the more reactive,
longer acenes for 1O2-responsive materials. These materi-
als operate by inhibiting energy transfer from a donor
chromophore to acenes, resulting in ratiometric fluores-
cent responses.26 We have employed this approach in
aqueous samples using conjugated polymer films,27 acrylic
For most applications of long acenes, such cycloadditions
can be problematic, as they destroy the conjugation of the
acene core and introduce bridgehead linkages. Although
acene-alkyne cycloadditions or [4+4] reactions can oc-
cur,9,10 chief among these problematic reactions is pho-
toinduced endoperoxidation of acenes through a reactive
oxygen species intermediate such as singlet oxygen or su-
peroxide.11,12 Typical endoperoxidation mechanisms in-
volve photosensitized formation of either 1O2, or superox-
ide oxidation of the acene.13 In many cases, the acene itself
acts as both the sensitizer and diene.14
polymers,28 and conjugated polymer nanoparticles.29,30
A
persistent challenge in 1O2-responsive fluorophores, how-
ever, is the proclivity of many chromophores, to sensitize
ROS themselves, increasing background signal.31 Several
probes address this challenge, including the dianionic Aar-
hus Sensor Green of Ogilby and coworkers,32 isobenzofu-
ran-based probes that do not produce 1O2,33 and chemilu-
minescent approaches that do not require photoexcita-
Numerous structural modifications have emerged that can
reduce the competitiveness of this oxidation.15 Examples
include: i) steric hinderance of the reactive acene core
with,16-18 ii) diethynylpentacenes that physically quench
1O2;19 iii) other directly attached pendants on pentacene,
such as thiol, thioether, or open-shell substituents.16,20 Re-
tion.34 These probes generally use slower O2 cycloaddi-
tion reactions than are available with longer acenes.
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Inspired by recent reports of multi-acene structures for spectra share some common features of diethynylacenes,
singlet fission35-37 and thin film transistors,38-41 we de-
scribe here a series of ethynylated long acenes with either
benzene, naphthalene, or anthracene conjugated pen-
dants. Although these molecules share the diethynylacene
cores with similar reactivity, the anthracene-substituted
acenes are highly stable to direct irradiation. This feature
addresses the problem of unwanted ROS sensitization. We
attribute this behavior to poor ROS sensitizing behavior,
due to rapid non-radiative deactivation.
such as an intense and sharp transition in the UV and
broad bands in the visible with some vibronic resolution.
As the lengths of the acene pendants increase from ben-
zene through anthracene, the onset of absorbance and lmax
of the lowest energy bands in the visible spectrum shifts
to lower energy, with anthracene-conjugated TET-3
showing lmax of 590 and 620 nm. In addition, TET-3 and
ADT-3 show distinct bands from 360-480 nm that resem-
ble isolated diethynylanthracene chromophores. As drop-
cast thin films (see Supporting Information), TET-1 and
TET-2 show spectra that, while broadened, are consistent
with those in solution. In contrast, the solid-state absorb-
ance of both TET-3 and ADT-3 stretch substantially to the
red, and in the case of TET-3, display a new intense band
at 720 nm. Preliminarily, we attribute this to a combina-
tion of increased planarization and intermolecular aggre-
gation. Although attempts to fabricate organic field-effect
transistors (OFETs) in a bottom-gate, bottom-contact ge-
ometry using TET-3 were successful,43 the tendency of
this molecule to form small needles upon deposition lim-
ited observed mobility to ~10-4 cm2/Vs.
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RESULTS AND DISCUSSION
Acene Design and Synthesis
Chart 1 shows the structures of the new acenes studied
in this work. All four structures comprise a long acene
core, either tetracene or anthradithiophene. Each of these
four molecules has an interior fused ring with two ar-
ylethynyl substituents that terminate with triisopropylsi-
lyl (TIPS) acetylenes. This group facilities solubility for
both synthesis and analysis. The key difference between
these structures are the lengths of the arene pendants,
which are either benzene (TET-1), naphthalene (TET-2),
or anthracene (TET-3 and ADT-3), on either side of the
long acene core. To compare to our previous work on sim-
pler analogs, we also include analogous data from control
compound DE-TET (Chart 2).42
Chart 1. Extended Acene Derivatives Described in this
Study.
Figure 1. UV/vis absorbance spectra of acenes in CH2Cl2 de-
scribed in this work.
As shown in Scheme S1 (SI), we relied on unsymmetrically
substituting the pendant acene (either benzene, naphtha-
lene, or anthracene) with an aryl iodide and a TIPS-
ethynylene by selective Sonogashira coupling of the para-
bromoiodide followed by lithium-bromide exchange and
quenching with I2. The resulting aryl iodides then under-
went Sonogashira coupling at elevated temperatures with
either diethynyltetracene or diethynylanthradithiophene,
each of which was prepared from the corresponding qui-
nones in an addition-reduction-desilylation procedure. All
four final compounds were at least moderately soluble;
ADT-3 resisted dissolution the most of the four, although
it was sufficiently soluble to enable characterization.
Electronic Absorbance Spectrophotometry and Density
Functional Theory
Figure 1 shows the UV/vis spectra of these molecules in
CH2Cl2 at low (10-5–10-6 M) concentration, while Table 1
summarizes their key spectroscopic parameters. These
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We calculated the molecular orbitals and optical transi-
1
tions of these molecules using density functional theory
(DFT) and time-dependent DFT with the B3LYP functional
and the 6-31G+(d,p) basis set. Geometry optimization at
this level of theory shows torsional angles of 32-35° for
TET-3 and ADT-3, similar to previously reported mole-
cules with three anthracenes connected through ethynyl
linkers.39 We attribute this twisting to steric interactions
between the C-H bonds on acene rings adjacent to the
ethynyl linkages—TET-2 (20-24° torsional angles) and
TET-1 (0° torsional angles) show improved planarity be-
tween arenes. Figure 2 shows the HOMO-2 through
LUMO+2 wavefunctions for TET-3. For all four molecules,
the lowest energy transition with non-zero oscillator
strength is HOMO-LUMO in nature, with the electronic
density for each mostly on the central long acenes, with
some occupancy along the entire p-conjugated system. As
an example, TET-3 shows two key electronic transitions
calculated to result from visible light with oscillator
strengths f > 0.2: i) 1.72 eV, purely HOMO to LUMO and ii)
2.91 eV, mostly HOMO-1 to LUMO+1, localized on the an-
thracene units.
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Figure 2. Molecular orbitals for TET-3 calculated at the
B3LYP/6-31G+(d,p) level. The torsional angles between the
acenes are 32-35°.
Table 1. Optical and reactivity characteristics of acenes studied in this work
ea, M-1cm-1
l
max(em), nm
FF
tav
6.3 ns
b
krel
lonset, nm
lmax, nm
TET-1
TET-2
TET-3
ADT-3
665
690
700
730
567*, 363, 293
581*, 403, 295
590*, 459, 262
612*, 466, 263
29,600
37,700
53,400
56,900
581
600
657
672
0.33
0.34
5.5
4.1
4.5
4.1
3.6 ns
< 0.001
-
< 0.003
-
a
Measured at the maximum of the longest wavelength band, indicated with an asterisk. b Disappearance of acene upon irradiation
of MB, relative to rate measured for 9,10-diphenylanthracene (DPA, krel = 1) under identical conditions.
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times faster than a similar 9,10-diarylanthracene. There-
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fore, neither the extended arylene-ethynylene linkers nor
the conjugated naphthalene or anthracene pendants no-
ticeably impact the intrinsic reactivity of these di-
ethynylacenes with 1O2. The evolution of the optical spec-
tra of these four acenes as they react are consistent with
oxidation of the long central acene moiety, although the
tetracenes retain broad absorbance between 400-500 nm.
We attribute this feature to retention of the fully conju-
gated arylene-ethynylene linker when the tetracene is ox-
idized across the unsubstituted 6 and 11 positions (vide
infra). In addition the structured absorbance of TET-3,
ADT-3 after oxidation indicates the persistence of the di-
ethynylanthracene side groups.
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Chart 2. Structure of diethynyltetracene DE-TET.
H3CO
OCH3
DE-TET
NMR spectroscopy of TET-3 upon photo-oxidation at
higher acene concentration (~ 1 mM) using MB as photo-
sensitizer provides further support for endoperoxide for-
mation (SI). Based on the chemical shifts of the singlets as-
sociated with the hydrogen atoms on the unsubstituted 6
and 11 positions of the tetracene, we approximate a 2:1
molar ratio of the 6,11-endoperoxide to the 5,12-endoper-
oxide; this preference for oxidation at the non-ethynylated
position of tetracene agrees with our previous work.45
Fluorescence Spectroscopy
Figure 3. Pseudo first-order kinetics analysis of disappear-
ance of acenes upon irradiation of MB. Rate constants relative
to DPA (krel) for the four acenes range between 4-6. The initial
absorbance spectrum of MB has been subtracted from each of
these spectra.
Trends in Photo-Oxidation Reactivity with an External
Photosensitizer
We began our investigation of the photochemical oxida-
tion of these acenes by irradiating methylene blue (MB) as
an external sensitizer selectively in CH2Cl2 using a 200W
Hg/Xe lamp and a 630 nm long-pass filter to irradiate MB
in the presence of each acene. We measure the concentra-
tion of the acene as a function of irradiation time using
UV/vis spectrophotometry. With constant light flux and
sensitizer absorbance, we assume a steady-state concen-
tration of 1O2 while irradiating, and therefore fit the result-
ing data to a pseudo first-order kinetic model. We also
monitored the disappearance of 9,10-diphenylanthracene
(DPA) in a separate experiment under identical conditions
as an external standard as it resembles the reactive an-
thracene unit in 1O2-sensitive fluorophores DPAX and Aar-
hus Sensor Green.32,44
Figure 4. Normalized fluorescence spectra of acenes in
CH2Cl2 described in this work. TET-3 and ADT-3 each
have quantum yields of fluorescence less than 0.003. Spec-
tra in the inset were acquired with wider slit widths (5 nm
bandpass) than those in the larger plot (2 nm bandpass).
Figure 3 summarizes the results of these experiments and
analyses, which shows that the four acenes all have similar
reactivities with 1O2. Relative to that of DPA, these acenes
react with rate constants (krel) of 4-6. This range is con-
sistent with the reactivity of the previously reported com-
pound from our group, DE-TET (Chart 2) which reacts ~5-
We also determined how the changes in chemical struc-
ture influence the fluorescence spectroscopy of these mol-
ecules in dilute organic solvent. Our previous work has
shown that most 5,12-diethynyltetracenes and analogous
diethynylanthradithiophenes have FF = 0.5-0.9 and
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max(emis) = 575-590 nm;26,42 additional phenyl substitu-
Direct Irradiation Reactivity
l
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tion on the 6 and 11 positions of tetracenes shifts emission
past 600 nm, with FF > 0.6.46 The maximum wavelength of
fluorescence for these four compounds (Figure 4) shifts
with increasing conjugation of the arene pendants, from
581 nm for TET-1, 600 nm for TET-2, and greater than
650 nm for both TET-3 and ADT-3. Notably, anthracene-
containing TET-3 and ADT-3 are very weakly fluorescent
(FF < 0.003). This observation is consistent with previ-
ously reported observations of weak fluorescence from
ethynyl-bridged multi-acene structures with either two
conjugated tetracenes or three conjugated anthra-
cenes.46,47 We attribute this quenching to rapid non-radia-
tive decay of the excited states of TET-3 and ADT-3 in-
duced by molecular motions, promoted by the steric hin-
drance between adjacent acenes in these molecules re-
flected in the geometry optimized structures. Alternative
explanations we considered are inconsistent with experi-
mental observations: intramolecular electron transfer is
unlikely due to the paucity of any solvatochromic effect
and the lack of donor-acceptor motifs, while intermolecu-
lar aggregation in solution is also unlikely as the shape of
absorbance spectra in solution do not vary between 40 µM
and 2 µM.
For many applications of acenes, preventing photooxida-
tion of acenes upon direct irradiation is crucial. Highly re-
active acenes such as pentacene and rubrene suffer from
self-sensitized oxidation, while physical quenching of 1O2
bestows TIPS-pentacene with slow inherent reactivity.
For fluorogenic sensing materials for O2, direct irradia-
tion of the fluorophore is necessary to measure lumines-
cent response; if the fluorophore itself generates O2 or
other ROS, false positives can occur. This drawback is a re-
ported characteristic of the commercially available Singlet
Oxygen Sensor Green (SOSG).31,32 Therefore, approaches
to preventing “self-sensitization” of ROS while preserving
their inherent reactivity is important for improving the
performance of responsive fluorophores.
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We therefore monitored the concentration of these four
acenes in CHCl3 in the absence of any external sensitizer,
while irradiating them directly at 546 nm (12 mW/cm2);
the initial absorbance of all samples was 0.45 at 546 nm.
As Figure 6 shows, fluorescent TET-1 and TET-2 degrade
rapidly, with half-lives of 8-12 minutes. In contrast,
quenched TET-3 and ADT-3 don not degrade after 20
minutes of irradiation. Our previous observation that the
rates of reactions with 1O2 for these four acenes are nearly
identical makes it unlikely that physical quenching of 1O2
by TET-3 or ADT-3 contributes to their persistence dur-
ing direct irradiation. Instead, consistent with the rapid
non-radiative relaxation of their excited states that we in-
fer from FF<0.003, we attribute their persistence 3 to
poor photosensitization of ROS. To further support this
conclusion, we compared the photosensitization perfor-
mance of TET-3 and our previously reported, highly fluo-
rescent diethynyltetracene DE-TET in the oxidation of a
diaryltetracene probe. As shown in the Supporting Infor-
mation, irradiation of DE-TET completely oxidized the
probe within three minutes, while irradiation of TET-3
under otherwise identical conditions led to only 50% oxi-
dation of the probe after thirty minutes of irradiation.
As shown in Figure 5, TET-1 (582 nm) and TET-2 (601
nm) show ratiometric responses to 1O2: initial acene fluo-
rescence decreases in intensity as the tetracene oxidizes,
while fluorescence from the endoperoxides emerge. In
contrast, the very weakly emissive TET-3 shows a “turn-
on” of fluorescence. Comparing the fluorescence of the
three mixtures of oxidized tetracenes, longer pendant
arenes yield bathochromically shifted final fluorescence:
TET-1 (benzene) at 425 nm, TET-2 (naphthalene) at 452
nm, and TET-3 (anthracene) at 537 nm. We attribute
these fluorescence spectra to the tetracenes oxidized
across the 6 and 11 positions, which retain a conjugated
chromophore along the entire molecule. In contrast, en-
doperoxidation of ADT-3 is more likely across the central
anthradithiophene ring, interrupting conjugation along
the arylene-ethynylene chromophore, yielding blue
shifted emission (478 nm).
Figure 6. Photochemical bleaching of acenes during direct
irradiation of each acene at 546 nm (12 mW/cm2) in aer-
ated CHCl3.
In conclusion, this work describes the synthesis, spectros-
copy, reactivity, and fluorescence response to photogen-
Figure 5. Fluorescent response of multi-chromophore acenes
to 1O2 generated through irradiation of MB in CH2Cl2.
1
erated O2 of four extended acenes. Our approaches for
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preparing these compounds are broadly applicable to oth- nyl)silane by immersion in a 60 mM solution in chloro-
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ers investigating multi-acene structures. Even though the
aromatic pendant groups did not alter the intrinsic reac-
form for 1 hour, followed by immersion in fresh chloro-
form and a thorough rinse with 2-propanol. A 0.25 wt%
solution of TET-3 in chlorobenzene was then prepared
and devices were formed using solvent-assisted crystalli-
zation,51 where the solution is drop-casted onto the pat-
terned substrate in a covered petri dish with 100 µL chlo-
robenzene dispensed around the substrate. This tech-
nique creates a solvent-rich atmosphere such that the
semiconductor solution evaporates more slowly, allowing
for the formation of larger crystallites.52 Electrical meas-
urements were then taken using two Keithley 2400
source-measure units in dark at ambient atmosphere.
1
tivity of these compounds with O2 substantially, the an-
thracene pendants yield rapid non-radiative decay, which
we attribute to steric interactions between the conjugated
acenes. TET-3 and ADT-3 are therefore poor sensitizers,
dramatically increasing their photochemical stability
upon direct irradiation. Given the importance of multi-
acene structures in a range of applications, we suspect
that these connections between structure and reactivity
will inform the work of others interested in the fundamen-
tal and applied aspects of acenes.
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Synthesis
EXPERIMENTAL SECTION
5,12-bis[2-(trimethylsilyl)ethynyl]tetracene. This reaction
was executed following a reported procedure.53 In a flame-
dried 2-neck round bottom flask, trimethylsilylacetylene
(0.71 mL, 490 mg, 5.0 mmol) was dissolved in 20 mL of
dry diethyl ether and cooled to 0°C in an ice-water bath. n-
Butyllithium (2.2 mL, 4.8 mmol, 2.2 M in hexanes) was
added dropwise. The colorless solution was allowed to
warm to room temperature and stirred for 1 h, at which
time napthacenequinone (520 mg, 2.0 mmol) was added
as a solid. The suspension was stirred overnight and then
neutralized with 1 M HCl (aq) and SnCl2•2H2O (1.0 g, 4.4
mmol) was added to the mixture. After stirring for 3 h, the
mixture was extracted using CH2Cl2 (3 x 10 mL), and the
combined organic layers were dried over MgSO4. The sol-
vent was removed in vacuo, and the residue was purified
through a plug of silica, eluted with hexanes to give 540
mg of the expected product ((65% yield) as a deep red
powder .
General Information. All synthetic manipulations were
performed under standard air-free conditions under an
atmosphere of argon gas with magnetic stirring unless
otherwise mentioned. Flash chromatography was per-
formed using silica gel (230−400 mesh) as the stationary
phase. NMR spectra were acquired on a 500 MHz spec-
trometer. Chemical shifts are reported relative to residual
protonated solvent (7.26 ppm for CHCl3 or 3.58 ppm for
THF). High-resolution mass spectra (HRMS) were ob-
tained using different ionization techniques and a peak-
matching protocol to determine the mass and error range
of the molecular ion.
Electronic absorbance spectra were acquired with a spec-
trophotometer in double-beam mode using a solvent-con-
taining cuvette for background subtraction spectra. Fluo-
rescence spectra were collected at a 90° angle from the in-
cident irradiation (75W Xe lamp) and corrected for both
fluctuations in the lamp intensity and the wavelength-de-
pendent sensitivity of the photomultiplier tube detector.
Fluorescence quantum yields were determined relative to
coumarin 6 in ethanol.48 Time-resolved fluorescence data
were collected using a time-correlated single-photon
counting instrument with a pulsed LED operating at 403
nm. Irradiation of methylene blue photosensitizer to gen-
erate 1O2 was performed with a 200 W Hg/Xe lamp
equipped with a condensing lens, water filter, and manual
shutter, with different long pass filters. Density functional
theory calculations were performed using the Gaussian 09
software package49, with optimized geometries and FMO
energies determined at the B3LYP/6-31G (d,p) level of
theory using a polarizable continuum solvent model for
CH2Cl2. The time-dependent results of these optimized ge-
ometries were calculated with the same functional and ba-
sis set, using the Tamm−Dancoff approximation.
1H NMR (500 MHz CDCl3): δ 9.20(s, 2H) 8.57-8.59 (dd , 2H),
8.08-8.10 (dd, 2H), 7.55-7.60 (dd, 2H), 7.47-7.49 (dd, 2 H),
0.54 (s, 18H). The chemical shifts are consistent with
those reported in the literature.53
5,12-diethynyltetracene.
5,12-bis[2-(trimethylsilyl)
ethynyl]tetracene (210 mg, 0.50 mmol) was dissolved in
10 mL CH2Cl2/methanol (1:1, v/v). To the solution, potas-
sium carbonate (210 mg, 1.5 mmol) was added. The sus-
pension was stirred at room temperature for 4 h. The sol-
vent was removed, and the residue was extracted with
CH2Cl2 (3 x 10 mL). The combined organic phase was se-
quentially washed with water and brine, and dried over
MgSO4. In syntheses of TET-1, TET-2, and TET-3, the
crude product was used immediately after removing the
solvent.
1H NMR (500 MHz CDCl3): δ 9.22 (s, 2H), 8.60-8.62 (dd,
2H), 8.08-8.10 (dd, 2H), 7.55-7.57 (dd, 2H), 7.48-7.50 (dd,
2H), 4.22 (s, 2H). 13C{1H} NMR (125 MHz CDCl3): δ 132.8,
130.4, 130.2, 128.5, 127.2, 126.9, 126.2, 125.9, 90.7, 80.7.
For fabrication of transistors, highly p-doped silicon was
used as the bottom-gate electrode, and 285 nm thermally
grown SiO2 served as the gate dielectric. Cr/Au (5
nm/40nm) source and drain electrodes were evaporated
through a shadow mask at 0.5 Å/s and functionalized with
the self-assembled monolayer (SAM) pentafluoroben-
zenethiol (PFBT) by vapor deposition at 70 °C for 2 hours.
This SAM serves to shift the electrode work function away
from the vacuum level, enhancing charge injection in p-
type organic semiconductors.50 To modify the surface en-
ergy and allow crystallites to form on the substrate, the
silicon oxide layer was functionalized with trichloro(phe-
Synthesis of TET-1
1-bromo-4-(2-triisopropyl)ethynyl-benzene.
Triiso-
propylsilylacetylene (0.22 mL, 180 mg, 1.0 mmol) of
triisopropylsilyl acetylene was dissolved in 30 mL
THF/triethylamine (2:1 v/v). The solution was deoxygen-
ated with argon gas for 1 h. To another flame-dried two-
neck round bottom flask, 1-iodo-4-bromobenzene (283
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mg 1.0 mmol), bis(triphenylphosphine)palladium(II) di-
1H NMR (500 MHz CDCl3): δ 8.40-8.41 (m, 1H), 8.24-8.26
(m, 1H), 7.72-7.73 (d, 1H), 7.62-7.65 (m, 2 H), 7.54-7.56 (d,
1 H), 1.19-1.20 (m, 21 H),
13C{1H} NMR (125 MHz CDCl3): δ 134.5, 132.8, 131.7,
130.9, 129.3, 127.7, 127.5, 126.8, 123.6, 121.3, 104.1, 97.3,
18.8 11.4.
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chloride (35 mg, 0.05 mmol), and copper (I) iodide (10 mg,
0.05 mmol) was added. Then, the degassed solution was
transferred to the flask containing solids via cannula. The
mixture was stirred overnight at room temperature. The
solvent was removed in vacuo. The resultant solid was pu-
rified by flash column chromatography (hexanes) to yield
the desired product as a colorless oil (320 mg, 95% yield).
1H NMR (500 MHz CDCl3): δ 7.42-7.44 (d, 2 H), 7.32-7.34
(d, 2 H), 1.09-1.12 (m, 21 H), The resonances are con-
sistent with those reported previously in the literature.54
1-iodo-4-(2-triisopropyl)ethynyl-naphthalene. In a flame
dried round bottom flask, 1-bromo-4-(2-triisopro-
pyl)ethynyl-naphthalene (1.25 g, 3.3 mmol) was dissolved
in 10 mL of dry THF. The solution was cooled to -78 °C us-
ing an acetone/dry ice bath. With a syringe, n-butylithium
solution (2.0 mL, 5.0 mmol, 2.5 M in hexanes) was added
dropwise. The solution was stirred at -78 °C for 1 h, and
then I2 (1.5 g, 6 mmol) was added as a solid. The reaction
was stirred overnight, and then quenched with aqueous
NaS2O3. The mixture was extracted with CH2Cl2 three
times, and the combined organic layers were dried over
MgSO4. Then, the solvent was removed in vacuo to yield
1.38 g yellow oil. This crude product was directly used in
the next step without further purification (96% yield).
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1-iodo-4-(2-triisopropyl)ethynyl-benzene. In a flame-dried
two-neck round bottom flask, 1-bromo-4-(2-triisopro-
pyl)ethynyl-benzene (870 mg, 2.6 mmol) was dissolved in
10 mL of dry diethyl ether. n-butyllithium (1.14 mL, 2.8
mmol, 2.5 M in hexanes) was added dropwise after cooling
the solution to -78 °C. The solution was stirred at -78 °C
for 1 h. I2 was added as a solid (857 mg, 3.4 mmol) and the
mixture was allowed to warm up to ambient temperature.
The reaction was then stirred for 8 h followed by quench-
ing with 10 mL saturated ammonium chloride solution.
The mixture was then extracted with CH2Cl2 and dried
over MgSO4. The crude product (870 mg, 87% yield) was
directly used after removing the solvent without any fur-
ther purification.
5,12-bis[((4-triisopropylethynyl)naphthyl)ethynyl]te-
tracene (TET-2). A round bottom flask was charged with
a solution of 1-iodo-4-(2-triisopropyl)ethynyl-naphtha-
lene (1.0 g, 2.3 mmol) dissolved in 14 mL of a tolu-
ene/diisopropylamine (4:3 v/v) mixture. The solution
was then deoxygenated by bubbling with argon for 1 h.
This solution was transferred by cannula into a flamed
dried round bottom flask containing compound 8 (280
mg, 1.0 mmol), Pd(PPh3)2Cl2 (35 mg, 0.05 mmol), and CuI
(10 mg, 0.05 mmol). The reaction was heated to 80 °C in
an oil bath and stirred for 20 h. The mixture was first pu-
rified by flash column chromatography (gradient elution
1:4 CH2Cl2/hexane to 100% CH2Cl2). Finally, 530 mg of
pure TET-2 was isolated by recrystallization from chloro-
form/methanol as a purple solid (60% yield).
1H NMR (500 MHz CDCl3): δ 9.39 (s, 2H), 8.76-8.80 (m, 4
H), 8.51-8.53 (m, 2 H), 8.08-8.10 (dd, 2 H), 7.99-8.00 (d,
2H), 7.81-7.83 (d, 2H), 7.71-7.76 (m, 6H), 7.62-7.64 (dd, 2
H), 7.49-7.51 (dd, 2 H), 1.24-1.28 (m, 42 H). 13C{1H} NMR
(125 MHz CDCl3): δ 133.0, 132.4, 132.3, 130.5, 130.1,
130.0, 128.6, 127.53, 127.50, 126.9, 126.8, 126.2, 122.3,
121.8, 118.6, 104.8, 101.8, 98.5, 93.7, 18.8, 11.5. HRMS
(MALDI, matrix: DCTB): m/z calcd for C64H64Si2 (M+)
888.4547, found 888.4537.
5,12-bis[((4-triisopropylethynyl)phenyl)ethynyl]tetracene
(TET-1). In a round bottom flask, 1-iodo-4-(2-triisopro-
pyl)ethynyl-benzene (670 mg, 1.7 mmol) was dissolved in
9 mL toluene/diisopropylamine (2:1 v/v). The solution
was deoxygenaged by bubbling with argon for 1 h. To an-
other flame dried two-neck round bottom flask equipped
with a condenser, 5,12-diethynyltetracene (180 mg, 0.63
mmol), Cl2Pd(PPh3)2 (30 mg, 0.04 mmol), and CuI (10 mg,
0.05 mmol) was added. The degassed solution was then
transferred to the flask via a syringe. The mixture was
then stirred at 80 °C in an oil bath for 36 h. The solvent
was removed in vacuo, and the residue was purified via
flash column chromatography (CH2Cl2/hexanes 1:1 v/v).
The crude product was recrystallized from CHCl3/MeOH
to yield TET-1 (150 mg, 30% yield) as a purple solid.
1H NMR (500 MHz CDCl3): δ 1.17-1.18 (m, 42 H), 7.49-7.51
(dd, 2 H), 7.58-7.59 (m, 6 H), 7.60 (d, 4H), 8.11-8.12 (dd,
2H), 8.64-8.65 (dd, 2H), 9.25 (s, 2H). 13C{1H} NMR (125
MHz CDCl3): δ 132.4, 132.2, 131.5, 129.9, 128.6, 127.4,
126.8, 126.2, 126.1, 123.9, 123.3, 118.3, 106.7, 103.2, 93.4,
89.0, 18.7, 11.4. HRMS (TOF, EI): m/z calcd for C56H60Si2
(M+) 788.4234, found 788.4212.
Synthesis of TET-3
9-iodo-10-bromo-anthracene. In a flame-dried round bot-
tom flask, 9,10-dibromoanthracene (1.0 g, 3.0 mmol) was
added to 30 mL of dry THF and cooled to -78 °C. To the
suspension, n-butyllithium (1.3 mL, 3.3 mmol, 2.5 M in
hexanes) was added dropwise. The resulting solution was
allowed to warm to room temperature and stirred for an-
other 3 hours. The flask was cooled to -78°C again fol-
lowed by the addition of 1.0 g of I2 (3.9 mmol). After stir-
ring at room temperature for 20 h, the solution was con-
centrated in vacuo to approximately 10% of its original
volume. Sodium thiosulfate aqueous solution (20 mL, 20%
w/v) was mixed into the residue, and the resulting precip-
Synthesis of TET-2
1-bromo-4-(2-triisopropyl)ethynyl-naphthalene. A flame-
dried round bottom flask was charged with 1-iodo-4-bro-
monaphthalene (1.2 g, 3.7 mmol) and 30 mL of degassed
THF/NEt3 (2:1 v/v). Pd(PPh3)2Cl2 (100 mg, 0.14 mmol)
and CuI (0.2 mmol, 40 mg) was added to the solution. With
a syringe, triisopropylsilylacetylene (0.82 mL, 3.7 mmol)
was added to the solution. The reaction was stirred over-
night before purification by elution through a plug of silica
with hexanes. After removing the solvent under vacuum,
1.25 g of the desired product was obtained as a pale-yel-
low oil. (88% yield).
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itate was collected by vacuum filtration to afford the de-
Page 8 of 11
1
2
sired product as needle-shaped yellow crystals (1.04 g,
91% yield)
Synthesis of ADT-3
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9
1H NMR (500 MHz CDCl3): δ 8.56-8.58 (m, 4 H), 7.61-7.63
(m, 4H). The chemical shifts are consistent with those re-
ported previously in the literature.55
Anthradithiophene-5,11-dione.
1,4-cyclohexanedione
(0.84 g, 7.5 mmol) was added to a solution of 2,3-thio-
phene dicarbaldehyde (2.1 g, 15 mmol) in 100 mL ethanol.
6 mL of 15% (w/v) KOH aqueous solution was then added
dropwise. The reaction was stirred at ambient tempera-
ture for four hours. The resulting precipitate was collected
by vacuum filtration and washed with ethanol to obtain
the product as a yellow solid. (2.4 g, 99% yield), which was
used directly without any purification.
9-bromo-10-(2-triisopropyl)ethynyl-anthracene. A flame-
dried round bottom flask was charged with a solution of
9-iodo-10-bromo-anthracene (1.04 g, 2.7 mmol) dissolved
in 30 mL of a degassed THF/ NEt3 (2:1, v/v) mixture.
Pd(PPh3)2Cl2 (98 mg, 0.14 mmol) and CuI (26 mg, 0.14
mmol) were added to the solution. With a syringe, triiso-
propylsilyl acetylene (0.61 mL, 2.7 mmol) was added to
the solution. The mixture was stirred overnight at ambient
temperature. The solvent was then removed in vacuo and
the residue was purified by flash column chromatography
(hexanes) to afford 1.10 g of the desired product as a pale
yellow oil (93% yield).
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5,11-bis[2-(trimethylsilyl)ethynyl]-anthradithiophene. In
a flame-dried round bottom flask, triisopropylsilylacety-
lene (1.1 mL, 5.0 mmol) was dissolved in 20 mL of dry di-
ethyl ether and cooled to 0 °C. A solution of n-BuLi (5
mmol, 2.0 mL 2.5 M in hexanes) was added dropwise. The
mixture was stirred at 0 °C for 30 minutes and stirred at
room temperature for another hour. Then, anthradithio-
phene-5,11-dione (640 mg, 2.0 mmol) was added as a
solid. The reaction was stirred at room temperature over-
night. The pH of the reaction was tuned to approximately
7 using a 0.1 M HCl aqueous solution, and then 1.0 g of
SnCl2·2H2O was added to the mixture. This mixture was
stirred in the dark for 3 hours. The mixture was extracted
with diethyl ether 3 times and the combined organic
phases were dried over MgSO4. The crude product was pu-
rified using column chromatography (hexanes) to obtain
the desired product (850 mg, 60% yield).
1H NMR (500 MHz CDCl3): δ 8.54-8.68 (m, 4H), 7.60-7.64
(m, 4H), 1.25-1.30 (m, 21 H). The resonances are con-
sistent with those reported previously.56
9-iodo-10-(2-triisopropyl)ethynyl-anthracene. In a flame-
dried round bottom flask, 9-bromo-10-(2-triisopro-
pyl)ethynyl-anthracene (600 mg, 1.4 mmol) was dissolved
in 10 mL of dry diethyl ether. The solution was then cooled
to -78°C. n-butyllithium (1.1 mL, 2.1 mmol, 2.2 M in hex-
anes) was added dropwise to the solution. The mixture
was stirred for 1 h at -78°C, after which solid I2 (630 mg,
2.5 mmol) was added to the mixture, and the reaction was
allowed to warm to room temperature and stirred over-
night. After quenching by adding sodium thiosulfate aque-
ous solution (20% w/v), the mixture was extracted with
diethyl ether three times. The combined organic layers
were dried over MgSO4 and the solvent was removed un-
der vacuum to afford the desired product as a red oil, (626
mg, 93% yield) which was used for the next step without
further purification.
1H NMR (300 MHz, CDCl3): δ 9.20 (s, 2H), 9.16 (s, 2H), 7.55-
7.56 (d, 2H), 7.43-7.44 (d, 2H), 1.32-1.38 (m, 42H), These
resonances are consistent with those reported in the liter-
ature.10
5,11-diethynylanthradithiophene. In a round bottom flask,
5,11-bis[2-(trimethylsilyl)ethynyl]-anthradithiophene
(130 mg 0.20 mmol) was dissolved in 5 mL of THF and
cooled to -78 °C. 2.0 mL of TBAF solution (1 M in THF) was
added dropwise. In the dark, the reaction was stirred for
5 min at -78 °C and stirred for another hour at room tem-
perature. After quenching the reaction with 10 mL of wa-
ter, the precipitate was filtered and washed with water
and cold methanol to afford the desired product as a red
solid. (340 mg, 83% yield)
1H NMR (300 MHz CDCl3): δ = 9.19 (s, 2H), 9.12 (s, 2H),
7.56-7.58 (d, 2H), 7.48-7.49 (d, 2H). 4.24-4.29 (m, 2H). The
solubility of this compound is very low in solvents for
NMR spectroscopy. Thus, the 13C NMR spectrum could not
be obtained with high quality.
5,12-bis[((10-triisopropylethynyl)anthracenyl)ethynyl]te-
tracene (TET-3). A round bottom flask was charged with
9-iodo-10-(2-triisopropyl)ethynyl-anthracene (490 mg,
1.0 mmol) dissolved in 5 mL of a toluene/diisopropyla-
mine mixture (3:2 v/v). The solution was then deoxygen-
ated by bubbling with argon for 1 h. To a flame-dried
round bottom flask, compound 8 (130 mg, 0.5 mmol),
Pd(PPh3)2Cl2 (14 mg, 0.02 mmol) and CuI (10 mg, 0.05
mmol) were added as solids. The degassed solution was
transferred into the flask containing solids using a can-
nula.. After stirring in the dark for 24 hours at 80 °C in an
oil bath, the solvent was removed in vacuo. The residue
was passed through a plug of silica with CH2Cl2 to remove
highly polar impurities. The product was then recrystal-
lized from acetone to yield 140 mg of TET-3 as a blue solid
(28% yield).
1H NMR (500 MHz THF-d8): δ 9.48 (s, 2H), 8.99-9.01 (dd,
4H), 8.84-8.86 (dd, 2H), 8.70-8.72 (dd, 4H), 8.05-8.07 (dd,
2H), 7.66-7.71 (m, 10 H), 7.49-7.51 (dd, 2 H), 1.34-1.35 (m,
42 H). 13C{1H} NMR (125 MHz THF-d8): δ 11.6, 18.4,
100.4,100.8, 103.7, 105.0, 118.6, 118.8, 126.1, 126.3,
127.0, 127.07, 127.10, 127.14, 127.3, 128.4, 129.8, 132.1,
132.3, 132.4, 132.5. HRMS (MALDI matrix: DCTB): m/z
calcd for C72H68Si2 (M+) 988.4860, found 988.4817.
5,11-Bis[((10-triisopropylethynyl)anthracenyl)ethynyl]an-
thradithiophene (ADT-3). In a round bottom flask, 9-iodo-
10-(2-triisopropyl)ethynyl-anthracene (1.20 g, 2.5 mmol)
was dissolved in 15 mL of THF/diisopropylamine (2:1
v/v). The solution was then deoxygenated by bubbling
with argon gas for 1 h. In another flame-dried flask, of
5,11-diethynylanthradithiophene (340 mg, 1.0 mmol),
Pd(PPh3)2Cl2 (35 mg, 0.05 mmol), and CuI (10 mg, 0.05
mmol) were added as solids. The degassed solution was
then added to the flask with solids using a cannula. The
reaction was stirred at 80 °C in an oil bath for 24 hours.
After removal of solvent in vacuo, the residue was passed
through a plug of silica with CH2Cl2 eluent. The product
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The Journal of Organic Chemistry
an Efficient Route to Single-Chain Nanoparticle Fabrication.
was recrystallized from acetone twice and then chloro-
form/methanol twice to yield ADT-3 as a dark green solid.
(250 mg, 25% yield).
Macromol. Rapid Commun. 2014, 35, 249-253.
9. Purushothaman, B.; Parkin, S. R.; Anthony, J. E. Synthesis
and Stability of Soluble Hexacenes. Org. Lett. 2010, 12, 2060-
2063.
10. Payne, M. M.; Odom, S. A.; Parkin, S. R.; Anthony, J. E. Stable,
Crystalline Acenedithiophenes with up to Seven Linearly Fused
Rings. Org. Lett. 2004, 6, 3325-3328.
11. Aubry, J.-M.; Pierlot, C.; Rigaudy, J.; Schmidt, R. Reversible
Binding of Oxygen to Aromatic Compounds. Acc. Chem. Res. 2003,
36, 668-675.
1
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5
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8
1H NMR (500 MHz THF-d8): δ 9.00-9.07 (m, 4H), 8.73-8.74
(m, 4H), 8.58-8.60 (m, 4H), 7.60 (m, 2H), 7.56 (m, 4H), 7.25
(m, 4 H), 6.92 (m, 2 H), 1.38-1.4 (m, 42 H). HRMS (MALDI
matrix: DCTB): m/z calcd for C72H66S2Si2 (M+) 1050.4144,
found 1050.4104. The product is a mixture of slightly sol-
uble trans-/cis- isomers, so the multiplicity of signals can-
not be distinguished. However, the structure can be con-
firmed by the HRMS and 2D-NMR. In addition, the solubil-
ity of ADT-3 is very low in solvents for NMR spectroscopy.
Thus, the 13C NMR spectrum cannot be obtained with high
quality.
9
12. Maliakal, A.; Raghavachari, K.; Katz, H.; Chandross, E.;
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Siegrist, T. Photochemical Stability of Pentacene and
a
Substituted Pentacene in Solution and in Thin Films. Chem. Mater.
2004, 16, 4980-4986.
13. Reddy, A. R.; Bendikov, M. Diels–Alder Reaction of Acenes
with Singlet and Triplet Oxygen – Theoretical Study of Two-State
Reactivity. Chem. Commun. 2006, 1179-1181.
ASSOCIATED CONTENT
14. Liu, K.; Lalancette, R. A.; Jäkle, F. Tuning the Structure and
Electronic Properties of B–N Fused Dipyridylanthracene and
Implications on the Self-Sensitized Reactivity with Singlet
Oxygen. J. Am. Chem. Soc. 2019, 141, 7453-7462.
15. Shi, X.; Chi, C. Different Strategies for the Stabilization of
Acenes and Acene Analogues. Chem. Record 2016, 16, 1690-
1700.
16. Kaur, I.; Jia, W.; Kopreski, R. P.; Selvarasah, S.; Dokmeci, M.
R.; Pramanik, C.; McGruer, N. E.; Miller, G. P. Substituent Effects in
Pentacenes: Gaining Control over HOMO−LUMO Gaps and
Photooxidative Resistances. J. Am. Chem. Soc. 2008, 130, 16274-
16286.
17. Zhang, J.; Pawle, R. H.; Haas, T. E.; Thomas Iii, S. W.
Combining Electronic and Steric Effects for Highly Stable
Unsymmetric Pentacenes. Chem. Eur. J. 2014, 20, 5880-5884.
18. Baral, R. N.; Thomas, S. W. Steric and Electronic
Substituent Effects Influencing Regioselectivity of Tetracene
Endoperoxidation. J. Org. Chem. 2015, 80, 11086-11091.
19. Fudickar, W.; Linker, T. Why Triple Bonds Protect Acenes
from Oxidation and Decomposition. J. Am Chem. Soc. 2012, 134,
15071-15082.
20. Shimizu, A.; Ito, A.; Teki, Y. Photostability Enhancement of
the Pentacene Derivative Having Two Nitronyl Nitroxide Radical
Substituents. Chem. Commun. 2016, 52, 2889-2892.
21. Ly, J.; Martin, K.; Thomas, S.; Yamashita, M.; Yu, B.; Pointer,
C. A.; Yamada, H.; Carter, K. R.; Parkin, S.; Zhang, L.; Bredas, J.-L.;
Young, E. R.; Briseno, A. L. Short Excited-State Lifetimes Enable
Photo-Oxidatively Stable Rubrene Derivatives. J. Phys. Chem. A
2019, 123, 7558-7566.
22. Fudickar, W.; Linker, T. Release of Singlet Oxygen from
Aromatic Endoperoxides by Chemical Triggers. Angew. Chem. Int.
Ed. 2018, 57, 12971-12975.
23. Fudickar, W.; Linker, T. Reversible Photooxygenation of
Alkynylanthracenes: Chemical Generation of Singlet Oxygen
under Very Mild Conditions. Chem. Eur. J. 2011, 17, 13661-
13664.
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website.
NMR spectra of new compounds, spectroscopic and reactivity
experiments. (PDF)
AUTHOR INFORMATION
Corresponding Author
* sam.thomas@tufts.edu
ACKNOWLEDGMENT
This work was supported by the National Science Foundation
(CHE-1609146). Z. L. thanks Corning and the NSF under STTR
1914013 for financial support.
REFERENCES
1. Anthony, J. E. The Larger Acenes: Versatile Organic
Semiconductors. Angew. Chem. Int. Ed. 2008, 47, 452-483.
2. Wang, C.; Dong, H.; Hu, W.; Liu, Y.; Zhu, D. Semiconducting
p-Conjugated Systems in Field-Effect Transistors: A Material
Odyssey of Organic Electronics. Chem. Rev. 2012, 112, 2208-
2267.
3. Wang, C.; Dong, H.; Jiang, L.; Hu, W. Organic Semiconductor
Crystals. Chem. Soc. Rev. 2018, 47, 422-500.
4. Zimmerman, P. M.; Bell, F.; Casanova, D.; Head-Gordon, M.
Mechanism for Singlet Fission in Pentacene and Tetracene: From
Single Exciton to Two Triplets. J. Am. Chem. So. 2011, 133, 19944-
19952.
5. Van Damme, J.; Du Prez, F. Anthracene-Containing Polymers
toward High-End Applications. Prog. Polym. Sci. 2018, 82, 92-
119.
6. Tasdelen, M. A. Diels–Alder “Click” Reactions: Recent
Applications in Polymer and Material Science. Polym. Chem.
2011, 2, 2133-2145.
7. Kabb, C. P.; O'Bryan, C. S.; Morley, C. D.; Angelini, T. E.;
Sumerlin, B. S. Anthracene-Based Mechanophores for
Compression-Activated Fluorescence in Polymeric Networks.
Chem. Sci. 2019, 10, 7702-7708.
24. Tanaka, K.; Miura, T.; Umezawa, N.; Urano, Y.; Kikuchi, K.;
Higuchi, T.; Nagano, T. Rational Design of Fluorescein-Based
Fluorescence Probes. Mechanism-Based Design of a Maximum
Fluorescence Probe for Singlet Oxygen. J. Am. Chem. Soc. 2001,
123, 2530-2536.
25. You, Y. Chemical Tools for the Generation and Detection of
Singlet Oxygen. Org. Biomol. Chem. 2018, 16, 4044-4060.
26. Altınok, E.; Smith, Z. C.; Thomas, S. W. Two-Dimensional,
Acene-Containing Conjugated Polymers That Show Ratiometric
Fluorescent Response to Singlet Oxygen. Macromolecules 2015,
48, 6825-6831.
27. Koylu, D.; Sarrafpour, S.; Zhang, J.; Ramjattan, S.; Panzer, M.
J.; Thomas, S. W. Acene-Doped Polymer Films: Singlet Oxygen
Dosimetry and Protein Sensing. Chem. Commun. 2012, 48, 9489-
9491.
8. Frank, P. G.; Tuten, B. T.; Prasher, A.; Chao, D.; Berda, E. B.
Intra-Chain Photodimerization of Pendant Anthracene Units as
9
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 10 of 11
28. Altinok, E.; Frausto, F.; Thomas, S. W. Water-Soluble
Fluorescent Polymers That Respond to Singlet Oxygen. J. Polym.
46. Barlier, V. S.; Schlenker, C. W.; Chin, S. W.; Thompson, M. E.
Acetylide-Bridged Tetracene Dimers. Chem. Commun. 2011, 47,
1
2
3
4
5
6
7
8
Sci. A Polym. Chem. 2016, 54, 2526-2535.
3754-3756.
29. Frausto, F.; Thomas, S. W. Tuning the Key Properties of
Singlet Oxygen-Responsive Acene-Doped Conjugated Polymer
Nanoparticles. ChemPhotoChem 2018, 2, 632-639.
47. Toyota, S.; Karashima, S.; Iwanaga, T. Synthesis and
Properties of Extended p-Conjugated Compounds with 9,10-
Bis(Phenylethynyl)Anthracene Units. Bull. Chem. Soc. Japan
2015, 88, 192-199.
30. Frausto, F.; Thomas, S. W. Ratiometric Singlet Oxygen
Detection in Water Using Acene-Doped Conjugated Polymer
Nanoparticles. ACS Appl. Mater. Interf. 2017, 9, 15768-15775.
31. Kim, S.; Fujitsuka, M.; Majima, T. Photochemistry of Singlet
Oxygen Sensor Green. J. Phys. Chem. B 2013, 117, 13985-13992.
32. Pedersen, S. K.; Holmehave, J.; Blaikie, F. H.; Gollmer, A.;
Breitenbach, T.; Jensen, H. H.; Ogilby, P. R. Aarhus Sensor Green:
A Fluorescent Probe for Singlet Oxygen. J. Org. Chem. 2014, 79,
3079-3087.
33. Song, D.; Cho, S.; Han, Y.; You, Y.; Nam, W. Ratiometric
Fluorescent Probes for Detection of Intracellular Singlet Oxygen.
Org. Lett. 2013, 15, 3582-3585.
34. Hananya, N.; Green, O.; Blau, R.; Satchi-Fainaro, R.; Shabat,
D. A Highly Efficient Chemiluminescence Probe for the Detection
of Singlet Oxygen in Living Cells. Angew. Chem. Int. Ed. 2017, 56,
11793-11796.
35. Fuemmeler, E. G.; Sanders, S. N.; Pun, A. B.; Kumarasamy,
E.; Zeng, T.; Miyata, K.; Steigerwald, M. L.; Zhu, X. Y.; Sfeir, M. Y.;
Campos, L. M.; Ananth, N. A Direct Mechanism of Ultrafast
Intramolecular Singlet Fission in Pentacene Dimers. ACS Central
Sci. 2016, 2, 316-324.
36. Korovina, N. V.; Das, S.; Nett, Z.; Feng, X.; Joy, J.; Haiges, R.;
Krylov, A. I.; Bradforth, S. E.; Thompson, M. E. Singlet Fission in a
Covalently Linked Cofacial Alkynyltetracene Dimer. J. Am. Chem.
Soc. 2016, 138, 617-627.
37. Korovina, N. V.; Joy, J.; Feng, X.; Feltenberger, C.; Krylov, A.
I.; Bradforth, S. E.; Thompson, M. E. Linker-Dependent Singlet
Fission in Tetracene Dimers. J. Am. Chem. Soc. 2018, 140, 10179-
10190.
38. Dell'Aquila, A.; Marinelli, F.; Tey, J.; Keg, P.; Lam, Y.-M.;
Kapitanchuk, O. L.; Mastrorilli, P.; Nobile, C. F.; Cosma, P.;
Marchenko, A.; Fichou, D.; Mhaisalkar, S. G.; Suranna, G. P.; Torsi,
48. Drexhage, K. H. Fluorescence Efficiency of Laser Dyes. J.
Res. Natl. Bur. Stand. Sect. A Phys. Chem. 1976, 80A, 421-428.
49. Gaussian 09, Revision D.01, M. J. Frisch, G. W. Trucks, H. B.
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani,
V. Barone, G. A. Petersson, H. Nakatsuji, X. Li, M. Caricato, A.
Marenich, J. Bloino, B. G. Janesko, R. Gomperts, B. Mennucci, H. P.
Hratchian, J. V. Ortiz, A. F. Izmaylov, J. L. Sonnenberg, D. Williams-
Young, F. Ding, F. Lipparini, F. Egidi, J. Goings, B. Peng, A. Petrone,
T. Henderson, D. Ranasinghe, V. G. Zakrzewski, J. Gao, N. Rega, G.
Zheng, W. Liang, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J.
Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T.
Vreven, K. Throssell, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro,
M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov,
T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J.
C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, J. M. Millam, M. Klene,
C. Adamo, R. Cammi, J. W. Ochterski, R. L. Martin, K. Morokuma,
O. Farkas, J. B. Foresman, and D. J. Fox, Gaussian, Inc., Wallingford
CT, 2016
50. deꢀBoer, B.; Hadipour, A.; Mandoc, M. M.;
vanꢀWoudenbergh, T.; Blom, P. W. M. Tuning of Metal Work
Functions with Self-Assembled Monolayers. Adv. Mater. 2005,
17, 621-625.
51. Goetz, K. P.; Li, Z.; Ward, J. W.; Bougher, C.; Rivnay, J.; Smith,
J.; Conrad, B. R.; Parkin, S. R.; Anthopoulos, T. D.; Salleo, A.;
Anthony, J. E.; Jurchescu, O. D. Effect of Acene Length on
Electronic Properties in 5-, 6-, and 7-Ringed Heteroacenes. Adv.
Mater. 2011, 23, 3698-3703.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
52. Chen, J.; Martin, D. C.; Anthony, J. E. Morphology and
Molecular Orientation of Thin-Film Bis(triisopropylsilylethynyl)
Pentacene. J. Mater. Res. 2007, 22, 1701-1709.
L. 9,10-Ter-Anthrylene-Ethynylene:
Architecture for Solution Processed Anthracene-Based Thin Film
Transistors. J. Mater. Chem. 2008, 18, 786-791.
A
New Molecular
53. Iwanaga, T.; Yamamoto, Y.; Nishioka, K.; Toyota, S. Efficient
Synthesis and Electronic Spectra of Unsymmetrical 5,12-
Diethynyltetracene Derivatives. Synthesis 2015, 47, 3997–4007.
54. Urushibara, K.; Yamada, T.; Yokoyama, A.; Mori, H.; Masu,
H.; Azumaya, I.; Kagechika, H.; Yokozawa, T.; Tanatani, A.
Development of Helical Aromatic Amide Foldamers with a
Diphenylacetylene Backbone. J. Org. Chem. 2020, 85, 2019–2039.
55. Nesterov, E. E.; Zhu, Z.; Swager, T. M. Conjugation
Enhancement of Intramolecular Exciton Migration in Poly(p-
phenylene ethynylene)s. J. Am. Chem. Soc. 2005, 127, 10083–
10088.
39. Keg, P.; Dell'Aquila, A.; Marinelli, F.; Kapitanchuk, O. L.;
Fichou, D.; Mastrorilli, P.; Romanazzi, G.; Suranna, G. P.; Torsi, L.;
Lam, Y. M.; Mhaisalkar, S. G. Solution Processable Ter-
Anthrylene-Ethynylenes Semiconductors: Thin Film Transistor
Properties and STM Study on Hopg and Au(111). J. Mater. Chem.
2010, 20, 2448-2456.
40. Romanazzi, G.; Dell'Aquila, A.; Suranna, G. P.; Marinelli, F.;
Cotrone, S.; Altamura, D.; Giannini, C.; Torsi, L.; Mastrorilli, P.
Solution Processed Ter-Anthrylene-Ethynylenes for Annealing-
56. De Montigny, F.; Argouarch, G.; Lapinte, C. New Route to
Unsymmetrical
Derivatives. Synthesis 2006, 293–298.
Activated Organic Field-Effect Transistors:
Performance Correlation Study. J. Mater. Chem. 2011, 21, 15186-
15189.
A Structure–
9,10-Disubstituted
Ethynylanthracene
41. Kawano, K.; Hayashi, H.; Yoshimoto, S.; Aratani, N.; Suzuki,
M.; Yoshinobu, J.; Yamada, H. An Ethynylene-Bridged Pentacene
Dimer: Two-Step Synthesis and Charge-Transport Properties.
Chem. Eur. J. 2018, 24, 14916-14920.
42. Zhang, J.; Smith, Z. C.; Thomas, S. W. Electronic Effects of
Ring Fusion and Alkyne Substitution on Acene Properties and
Reactivity. J. Org. Chem. 2014, 79, 10081-10093.
43. Lamport, Z. A.; Haneef, H. F.; Anand, S.; Waldrip, M.;
Jurchescu, O. D. Tutorial: Organic Field-Effect Transistors:
Materials, Structure and Operation. J. Appl. Phys. 2018, 124,
071101.
44. Umezawa, N.; Tanaka, K.; Urano, Y.; Kikuchi, K.; Higuchi, T.;
Nagano, T. Novel Fluorescent Probes for Singlet Oxygen. Angew.
Chem. Int. Ed. 1999, 38, 2899-2901.
45. Zhang, J.; Sarrafpour, S.; Haas, T. E.; Müller, P.; Thomas, S.
W. Structure, Photophysics, and Photooxidation of Crowded
Diethynyltetracenes. J. Mater. Chem. 2012, 22, 6182-6189.
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