Elucidation of the electrochemical behavior of phenothiazine-based polyaromatic amines

Article abstract of DOI:10.1016/j.tet.2019.05.062

Polyarlylamines with discrete redox active groups in the polymer backbone represent a promising class of cathode materials for electrical energy storage applications. In this area, our group recently reported a set of phenothiazine-based polymers that exh

Full text of DOI:10.1016/j.tet.2019.05.062

Accepted Manuscript
Elucidation of the electrochemical behavior of phenothiazine-based polyaromatic
amines
Brian M. Peterson, Luxi Shen, Gerickson J. Lopez, Cara N. Gannett, Dong Ren,
Héctor D. Abruña, Brett P. Fors
PII:
S0040-4020(19)30624-6
https://doi.org/10.1016/j.tet.2019.05.062
TET 30383
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 24 April 2019
Revised Date: 24 May 2019
Accepted Date: 29 May 2019
Please cite this article as: Peterson BM, Shen L, Lopez GJ, Gannett CN, Ren D, Abruña HéD, Fors BP,
Elucidation of the electrochemical behavior of phenothiazine-based polyaromatic amines, Tetrahedron
(2019), doi: https://doi.org/10.1016/j.tet.2019.05.062.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Elucidation of the Electrochemical Behavior of Phenothiazine-
Based Polyaromatic Amines
Brian M. Peterson, Luxi Shen, Gerickson J. Lopez, Cara N. Gannett, Dong Ren, Héctor D.
Abruña,* Brett P. Fors*
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca,
New York 14853-1301, United States
*
Corresponding author. Department of Chemistry and Chemical Biology, Baker Laboratory,
Cornell University, Ithaca, New York 14853-1301, United States
E-mail addresses: hda1@cornell.edu (H. D. Abruña), bpf46@cornell.edu (B. P. Fors).
ABSTRACT: Polyarlylamines with discrete redox active groups in the polymer backbone represent a
promising class of cathode materials for electrical energy storage applications. In this area, our group
recently reported a set of phenothiazine-based polymers that exhibit both high capacities and power
densities. In order to rationally improve the properties of these electrode materials, a fundamental
understanding of their electrochemical properties is indispensable. Herein, we probe the electrochemical
behavior of our phenothiazine-based systems by synthesizing small molecule analogs using C–N cross-
coupling. Additionally, electropolymerization of a class of these small molecule phenothiazines yields thin
films that were then characterized with an electrochemical quartz crystal microbalance. Analysis of these
materials provides insights into the number of electrons accessed from each repeat unit in our polymer
backbone during electrochemical cycling, as well as counter ion transport dynamics.
1
. Introduction
Polymeric organic cathodes are promising alternatives to inorganic materials, owing to their high elemental
1–3
abundance and their ability to tolerate fast charge rates due to facile ion transport in amorphous materials. Many
polymerization methods used to synthesize organic cathodes afford materials with insulating backbones and excess
4
–6
mass that does not contribute to charge storage. This limits electron mobility to the current collector, hindering
charge-discharge rates, and decreases the energy density of the organic cathode. Polyanilines are one class of
materials that have the potential to overcome these limitations as they can be doped to achieve modest conductivity;
however, upon discharge a continuous voltage drop is observed. We reasoned that incorporation of discrete redox
active heterocycles into the polyaromatic amine backbone could circumvent the voltage drop and provide cathode
materials with high energy and power densities.
Phenothiazines and phenylenediamines are two classes of molecules that display reversible redox processes at
+
4,7-16
17,18
high voltages relative to Li/Li .
Using Buchwald-Hartwig C–N cross-coupling chemistry,
we envisioned that
we could efficiently incorporate these units into a polyamine backbone to provide a new class of cathode
1
9,20
materials.
Using this strategy, completely insoluble materials, P1 and P2, were obtained by cross-coupling
dialkylphenylene diamines (2 and 3) with 3,7-dibromo-10-methylphenothiazine (1) (Figure 1a) in a step growth
21
polymerization using a RuPhos-based Pd precatalyst that was developed by Buchwald and coworkers. The
polymers made from both phenylene diamine (P1) and benzidine (P2) showed multiple reversible redox couples.
–1
Additionally, lithium half-cells that incorporated these polymers displayed specific capacities up to 150 mAhg and
could be discharged at 120 C while maintaining 81% of their capacity. These results demonstrated that main chain
polymers consisting of phenothiazine and phenylene diamine lead to materials with high capacities and high power
densities.
To improve these cathode materials we need a fundamental understanding of their electrochemical properties.
For both polymers P1 and P2, solid state cyclic voltammetry (CV) displayed three main oxidations (–0.1, 0.3 and
0
.9 V) and two smaller redox couples (0.6 – 0.9 V) (Figure 1b). The presence of the latter two redox couples was
1

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unexpected. Full characterization of these two polymers was difficult due to their insolubility and inhomogeneity in
chain lengths. In this manuscript, we synthesized and fully characterized small molecule analogs of these materials
to gain a better understanding of their electrochemical behavior. Specifically, we synthesized phenothiazine based
compounds that represents one and a half repeat units in the polymer backbone and fully characterize their redox
processes. Further, we synthesized a small molecule analog that could be electrochemically polymerized to give P2
on the surface of an electrode. We used such an approach to deposit films on the surface of a quartz crystal
microbalance. This enables us to accurately quantify the number of oxidation events that are occurring per repeat
a)
Me
N
Me
Me
N
Me
mNH
N
m
nH
i.
+
HN
Me
Br
S
N
Br
S
1
Br
Me
P1; m=1
P2; m=2
2
; m=1
; m=2
3
b)
Figure 1. a) Synthesis of P1 and P2; i. NaOtBu, RuPhos,
RuPhos Pd G2 precatalyst, toluene, 80 °C b) Slurry CV of P1
-1
(
pink) and P2 (green) in 1 M LiPF /MeCN at 20 mVs (scale
6
bar 25 µA).
unit on the polymer backbone, as well as characterize ionic transport and solvation dynamics.
2
. Results and Discussion
2
.1 Synthesis of Redox Active Small Molecule
To investigate the redox properties of these polyphenothiazines, we targeted C1, a small molecule analog of P1
22-26
that represents one and a half repeat units of the polymer backbone.
Using two consecutive C–N cross-coupling
reactions we were able to efficiently synthesize this molecule (Figure 2a). First, 4-bromo-N,N-dimethyl aniline (3)
was coupled with methyl amine using a catalyst system developed by Buchwald and coworkers to yield the
2
7,28
phenylene diamine 5.
A second cross-coupling between 1 with 5, using a RuPhos-based Pd catalyst, gives C1 in
The small molecule analog, C1, quickly oxidizes in air; therefore, C1 was kept under nitrogen and
electrochemical studies were conducted in deoxygenated solvents.
2
9,30
6
7% yield.
+
The CV of C1 shows five reversible redox couples between –0.5 and 1.1 V vs. Ag/Ag (Figures 2b and 2c). The
first four redox couples appear reversible, while the fifth oxidation is followed by adsorption onto the electrode. This
degree of redox activity is rarely observed in soluble organic molecules. As C1 is comprised of 1.5 repeat units of
2

ACCEPTED MANUSCRIPT
P1, four to five redox events were expected. The presence of five reversible redox events shows that the strucutural
units of P1 are indeed stable in a highly oxidized state.
The spectrochemical signature of C1 in each oxidation state was characterized in situ (Fig. 2d). We observed that
the neutral and monocationic states exhibit distinct electronic absorption spectra, while similar absorption behavior
was observed between the di- and tricationic states and between the tetra- and pentacationic states. In the UV region,
distinct sets of electronic absorptions were observed in the neutral state, distinguished by absorptions at 263 and 328
nm, and in the monocationic state, at 268 and 288 nm. In the 400–800 nm region, di- and tricationic states show
absorptions at 588 nm, while tetra- and pentacationic states exhibit absorptions at 817 nm.
Figure 2. a) Synthesis of C1; i. NaOtBu, BrettPhos, BrettPhos Pd G3 precatalyst, methylamine, tBuOH, 80
°
C; ii. NaOtBu, RuPhos, RuPhos Pd G2 precatalyst, dioxane, 80 °C; b) Oxidation of C1 to the
-1
pentacationic state; c) CV 0.5 mM C1 in 0.1 M TBAP in 1:1 MeCN/DCM at 20 mVs (scale bar 5 µA); d)
UV-Visible absorption spectra of C1 in each redox state; arrows indicate the major absorptions.
2.2 Electropolymerization of Thin-Film P2-TF
When analyzing P1 in a Li half-cell, we observed good agreement between theoretical and experimental capacity,
if only two electrons are exchanged during charge and discharge. To further support our observation that we could
efficiently access the first two redox couples of our polymers in the Li half-cells, we set out to quantitatively
determine the number of electrons involved in each redox event for our materials. We hypothesized that we could
electropolymerize a thin film of P2 on a quartz crystal microbalance electrode, which would allow us to accurately
quantify the number of counterions transported in and out of the film when oxidized and reduced. This experiment
would give us evidence for the number of electrons accessed from each repeat unit during cycling.
We proposed that we could deposit P2 as a thin film (P2-TF) on an electrode surface through the electrochemical
oxidative step growth polymerization of monomer C2 (Figure 3b), based on the fact that the electrochemical
3

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14,31
dimerization of anilines to benzidine is a well-studied and highly efficient reaction.
To test our strategy, we
synthesized monomer C2 in 71% yield by coupling N-methylaniline with 1 (Figure 3a). C2 exhibited two highly
reversible redox couples at 0.0 and 0.3 V (Figures 3b and 3c) and efficiently polymerized into a thin film upon a
third oxidation at 1.3 V, which can be observed by an increase in current in subsequent cycles. In dichloromethane
(
DCM), adsorptive behavior is observed at high concentration, and deposition on the electrode can be monitored
during sequential scans (Figure 3d). The coupling reaction can also be monitored spectroscopically (Figure 3e). The
+
+
neutral, 1 and 2 states of the monomer can be clearly seen as the potential of the electrode is swept from–0.4 to
3
+
1
.2 V. The coupled species between two tricationic C2 species (C2 ) is observed when sweeping the potential in
a)
b)
c)
d)
b)
c)
e)
Figure 3. a) Synthesis of C2; i. NaOtBu, RuPhos, RuPhos Pd G2 precatalyst, dioxane, 80 °C b) Mechanism of
the electropolymerization of C2 and redox states of P2-TF; c) CV profile of C2 at 0.5 mM in 0.1 M TBAP in
MeCN (scale bar 10 µA); small window (red) vs. full window (black); d) Electropolymerization of C2 at 10
-1
mM in 1 M TBAP in DCM at 50 mVs on a glassy carbon electrode (scale bar 20 µA); first scan (red) and
subsequent scans (black); e) UV-Vis spectra of C2 in electrolyte solution during potential sweeping from –0.4
to 1.2 V.
the reverse direction between 1.2 and 0.8 V, which is followed by polymer deposition on the electrode surface.
3
+
Sweeping the potential to more negative values, any uncoupled C2 is reduced to the dication state, which can be
observed between 0.8 to 0.2 V. Once the potential of electrode is swept past 0.2 V, the characteristic spectral peak of
2
+
+
C2 at approximately 850 nm recedes. Continuing to sweep between 0.2 and –0.4 V, the spectral signature of the 1
oxidation state is observed before being reduced to neutral C2 at –0.2 V.
4

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2
.3 Electrochemical Quartz Crystal Microbalance
With efficient conditions for the electrochemical formation of P2-TF, we set out to deposit a thin film on a quartz
crystal microbalance electrode to perform electrochemical quartz crystal microbalance (EQCM) analysis during
32
cycling. EQCM enables monitoring of the mass changes associated with ion movement and viscoelastic changes in
3
3-35
a thin-film during electrochemical processes.
Numerous studies have employed this method to elucidate
transport dynamics in thin-film materials. To probe the redox mechanisms of P2-TF we employed EQCM to
monitor the anion flux into the film as the polymer was oxidized in electrolyte solution. This enables us to determine
the approximate number of electrons exchanged per repeat unit in P2-TF, and by extension P1, and P2.
The EQCM experiment was divided into two parts: electropolymerization and film cycling (Figure 4a). Polymer
film mass was established by the frequency change of the QCM electrode in solution, before and after
electropolymerization. Frequency and mass changes are minimal during the first two redox couples. However, when
the potential of the gold electrode was scanned to 1.10 V, a sudden and large decrease in frequency, and increase in
mass, associated with film deposition were observed, as seen in Figure 4a through 1250 seconds. Typically, twenty
cycles of electropolymerization yielded a film-thickness of 40 – 50 nm, as measured by contact profilometry. This
-2
yielded a mass loading in the range of a few µg cm .
a)
c)
Me
N
Me
N
S
N
3
N
S
N
N
Me
Me
Cross-linker, C3
b)
d)
Figure 4. a) Frequency and mass changes during electropolymerization of C2 on a QCM Au electrode.
Inset shows the CV profile during the electropolymerization, polymerization was achieved by cycling
between 0.7 – 1.15 V to accelerate film deposition (10 mM C2 in 1 M TBAP/DCM, scale bar: 500 µA); b)
The simultaneous change in frequency and mass during cycling of P2-TF in fresh electrolyte, 0.1 M
–
1
TBAP/MeCN at 20 mVs ; c) Chemical structure of cross-linker C3; d) The number of electrons
exchanged during film cycling as a function of the amount of C3 present during electropolymerization.
Upon completion of electropolymerization, P2-TF was subjected to cycling in blank electrolyte solution
containing no monomer. During film cycling, frequency and mass changes are attributed to anion movement into
and out of the polymer film, between 1250 and 2500 seconds in Figure 4a. Upon cycling the potential of the
electrode between –0.6 to 0.8 V the frequency decreased, corresponding to an increase in mass, which was attributed
5

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to an influx of charge compensating perchlorate ions into the polymer film (Figure 4b). During the reverse scan, an
increase in frequency, corresponding to a decrease in mass, is observed as anions diffuse out of P2-TF.
Simultaneous resistance measurements indicate no significant changes in the viscoelastic properties during potential
cycling. This confirms the rigid film nature of the P2-TF, and allows for the direct application of the Sauerbrey
equation, which correlates frequency changes to a change in mass on the QCM electrode.
Only the first two redox couples near 0.0 and 0.3 V could be studied, since the electrochemical stability of the
+
gold electrode of the QCM does not allow potential sweeps beyond 0.8 V vs. Ag/Ag When the thin film is oxidized
.
to the dication, approximately 0.8 counterions diffuse into the thin film, which is in contrast to our expectation that
two counterions would be brought in during cycling to account for the two redox couples in the CV (Figure 4d).
We hypothesized that this discrepancy in the capacity of our Li half-cells and EQCM studies could be explained
by two scenarios: the film is not fully accessed by ions, leading to an underestimation of anions transported in, or a
portion of the film was dissolving away while the electrode was washed. Film cycling in the presence of ferrocene,
as a redox shuttle, could aid in unclogging any electronically or ionically isolated portions of film. However, no sign
of unclogging or improvement of film accessibility was observed (Figure S11). Therefore, we hypothesized that if
the film was indeed washing away when rinsed with acetone after the film was deposited, incorporation of a cross-
linker could improve the polymer’s adherence to the gold electrode (Figure 4c). It is important to mention that we
observed similar behavior in our Li half-cells. The linear polymer of P1 showed significant capacity fade after
every charging cycle due to dissolution of the active material. In our initial coin cell study we demonstrated that
cross-linking of the polymer film mitigated dissolution of the polymers.
Electropolymerization of C2 with varying amounts of cross-linker C3 to cross-link the thin film in the EQCM
experiment could prevent dissolution of the thin film during washing. No difference was observed during
electropolymerization or film cycling, as the addition of the cross-linker did not alter the polymer’s redox activity
(
only a butyl-chain differentiates the cross-linker from the monomer, as shown in Fig 4c). With incremental addition
of cross-linker C3 to the electropolymerization solution, the number of electrons exchanged increased to 2.17 per
repeating unit at 10 mol% C3. At higher loadings of C3 (20 mol%), a decrease in electrons exchanged per repeat
unit was observed. This decrease at higher cross-linker content is likely due to transport limitations arising from the
highly cross-linked network (Figure 4d). These experiments are in good agreement with our coin cell studies where
we found that the optimal cathode material contained 10% cross-linker. Moreover, these results suggest that two
electrons are exchanged per repeat unit during potential sweeps through the first two redox couples. This is in
–1
excellent agreement with our previous study which showed an experimental capacity of 150 mAh g in agreement
–1
with the theoretical capacity for two electron energy storage in P1 (152 mAh g ).
3
. Conclusion
This study provides a thorough and comprehensive analysis of the electrochemical and spectrochemical behavior
of two charge storing polymers synthesized by palladium-catalyzed C–N cross-coupling reactions. The investigation
of the small molecule analog C1, provided confidence that the charge storing units in P1 are stable in all accessible
oxidation states. Analysis of the core structure of P2 in a thin film provided evidence that nearly quantitative
oxidation of the first two redox couples contributes to the experimental capacity observed in these phenothiazine
based polyaromatic amines. The electropolymerization of cross-linked P2-TF was analyzed by EQCM and cycling
the potential between the first two redox processes showed that 2.18 electrons are accessed per repeat unit. Through
the analysis of small molecule and thin film analogs, the spectrochemical and electrochemical properties of a series
of redox active polymer cathode materials were probed.
4
. Experimental
4
.1 General Methods
Toluene, DCM, and THF were purchased from J.T. Baker and were purified by vigorous purging with argon for 2
h, followed by passing through two packed columns of neutral alumina under argon pressure. BrettPhos (96%),
BrettPhos Pd G3 (95%), RuPhos (95%), RuPhos Pd G2, sodium tert-butoxide (NaOtBu), potassium tert-butoxide
(
KOtBu), anhydrous hydrazine, 4-bromo-N,N’-dimethylaniline (97%), and methylaniline were purchased from
Sigma Aldrich and used as received. 1,4-dibromobutane (99%), phenothiazine (98%+), iodomethane (99.5%), and
methylamine (2 M in THF) were purchased from Alfa Aesar and used as received. Anhydrous magnesium sulfate
6

ACCEPTED MANUSCRIPT
(
MgSO ) was purchased from EMD Chemicals. N-Bromosuccinimide was purchased from Oakwood Chemicals and
4
recrystallized from DI water before use as a brominating agent. Sodium sulfite (Na SO ) was purchased from
2
3
Fischer Scientific and used as received. Tetrabutylammonium perchlorate (TBAP) was purchased from TCI
>98%), and recrystallized from ethyl acetate (EtOAc) three times to obtain white crystal. Acetonitrile (MeCN) was
(
purchased from Fisher (ACS grade) dried over activated 4 Å molecular sieves. 1-Methyl-2-pyrrolidinone (NMP,
anhydrous, 99.5%) was purchased from Sigma Aldrich and used as received.
Nuclear magnetic resonance (NMR) spectra were recorded on a Mercury 300 MHz, a Varian 400 MHz or a
Bruker 500 MHz. Cyclic voltammetric analysis on glassy carbon electrodes were performed on a Hokuto Denko
HABF1050m potentiostat/galvanostat controlled by LabView program. UV-vis spectroscopy experiments were
carried out using an Agilent/HP 8453 UV-visible spectroscopy system. Frequency, mass, and resistance data were
measured on a Model QCM 200 Quartz Crystal Microbalance Digital Controller from Stanford Research Systems
and processed by a SRS LabVIEW program. The temperature of the electrochemical system was controlled by a
Fisher Scientific thermostat (Model No. 9101). 5 MHz AT-cut quartz crystals sputtered with gold were obtained
2
from Maxtek, with a front electrode area of 1.37 cm and used for EQCM experiments. Polymer P1, P2 and small
molecules 10-methylphenothiazine, 3,7-dibromo-10-methylphenothiazine (1), N,N’-dimethyl-p-phenylenediamine
(
2), N,N’-dimethylbenzidine (3) , 1,4-bis(3,7-dibromo-10H-phenothiazin-10-yl)butane were synthesized by literature
21
procedures.
4
.2.1 N,N,N’-Trimethyl-p-phenylenediamine (5)
-Bromo-N,N-dimethylaniline (600 mg, 3 mmol, 1 equiv), NaOtBu (432.5 mg, 4.5 mmol, 1.5 equiv), BrettPhos
16.1 mg, 0.03 mmol, 0.01 equiv), BrettPhos Pd G3 ( 27.21 mg, 0.03 mmol, 0.01 equiv), and a magnetic stir bar
4
(
were charged to a flame dried, 20 mL reaction tube and sealed with a Teflon cap. A nitrogen atmosphere was
established and methylamine (2M in THF) (3 mL, 6 mmol, 2 equiv) and tert-butanol (6 mL) were added. The
reaction was stirred at 80 °C for 7 hours. The reaction mixture was extracted into ethyl acetate (EtOAc) and washed
with water. The organic layer was dried with MgSO4 and concentrated. Purification by silica column
1
chromatography (4:6 EtOAc:Hexanes) yielded 346 mg (77% yield) of the desired product. H NMR (CDCl
3
, 500
13
MHz): δ 6.77 (d, 2H), 6.62 (d, 2H), 2.83 (s, 6H), 2.81 (s, 3H). C NMR (CDCl
3
, 126 MHz): δ 144.15, 142.06,
15.99, 113.89, 42.36, 31.74. IR (ATR, cm ): 3397, 3022, 2941, 2873, 2799, 1520, 1476, 1447, 1304, 815.
–1
1
1
1'
1
4
4
4
.2.2 N ,N -(10-methyl-10H-phenothiazine-3,7-diyl)bis(N ,N ,N -trimethylbenzene-1,4-diamine) (C1)
,7-Dibromo-N-methylphenothiazine (93 mg, 0.25 mmol, 1 equiv), N, N, N’-trimethyl-1,4-diaminobenzene (115
3
mg, 0.75 mmol, 3 equiv), NaOtBu (75 mg, 0.75 mmol, 3 equiv), RuPhos (2.3 mg, 2.5 µmol, 0.01 equiv), RuPhos Pd
G2 (3.8 mg, 2.5 µmol, 0.01 equiv), and a magnetic stir bar were charged to a flame dried, 20 mL reaction tube and
sealed with a Teflon cap. A nitrogen atmosphere was established and dioxane (2 mL) was added via syringe. The
reaction was stirred at 80 °C for 16 hours. After cooling, the reaction was diluted with EtOAc and washed with DI
water. The organic layer was dried with MgSO and concentrated. Purification by silica column chromatography
4
(
2:3 EtOAc:Hexanes) yielded 80 mg (63%) of the desired product. Hydrazine was added to NMR to prevent
1
oxidation of product. H NMR (500 MHz, CDCl ) δ 6.95 (d, J = 8.9 Hz, 4H), 6.71 (d, J = 8.9 Hz, 4H), 6.68 (t, J =
3
13
1
1
1
5
.5 Hz, 2H), 6.64 (d, J = 1.6 Hz, 4H), 3.27 (s, 3H), 3.16 (s, 6H), 2.91 (s, 12H). C NMR (126 MHz, CDCl ) δ 147.1,
3
45.6, 139.8, 138.9, 124.4, 124.0, 116.3, 116.1, 114.0, 113.9, 41.2, 40.9, 35.1; IR (ATR, cm ): 2933, 2821, 2781,
515, 1485, 1450, 1326, 1259, 820; HRMS (DART): m/z calc’d for (M+H) [C31
–
1
+
+
H
36
N
5
S] : 510.2691, found
10.2693.
4
.2.3 N3,N7-10-trimethyl-N3,N7-diphenyl-10H-phenothiazine-3,7-diamine (C2)
1
(743 mg, 2mmol, 1 equiv), RuPhos ligand (9.7 mg, 0. 02 mmol, 0.01 equiv), RuPhos Pd G2 precatalyst (15.5
mg, 0.02 mmol, 0.01 equiv), NaOtBu (575 mg, 6 mmol, 3 equiv), and a magnetic stir bar were charged to a flame
dried, 20 mL reaction tube and sealed with a Teflon cap. A nitrogen atmosphere was established and N-
Methylaniline (0.44 mL, 4 mmol, 2 equiv) and dioxane (2 mL) were added via syringe. The reaction was stirred at
7

ACCEPTED MANUSCRIPT
8
0 °C for 16 hrs. After cooling, the reaction was diluted with DCM and washed with DI water three times. The
organic layer was dried with MgSO4 and concentrated. Purification by silica column chromatography (1:1
1
DCM:Hexanes) yielded 562 mg (66% yield) of the desired product. H NMR (500 MHz, C D ) δ 7.14 (m, 4H), 6.95
6
6
(
d, J = 2.5 Hz, 4H), 6.84 (d, J = 8.3 Hz, 4H), 6.83 – 6.78 (m, 4H), 6.33 (d, J = 8.6 Hz, 2H), 2.87 (s, 6H), 2.74 (s,
1
3
3
H); C NMR (125 MHz, C D ) δ 149.9, 144.5, 142.2, 129.4, 125.0, 123.2, 123.1, 119.8, 117.6, 114.7, 40.2, 35.0;
6 6
+
+
HRMS (DART): m/z calc’d for (M+H) [C H N S] : 424.1847, found 424.1845.
27
26
3
3
7
3
7
4
.1.10 10,10'-(butane-1,4-diyl)bis(N ,N -dimethyl-N ,N -diphenyl-10H-phenothiazine-3,7-diamine) (C3)
1
,4-bis(3,7-dibromo-10H-phenothiazin-10-yl)butane (115 mg, 0.15 mmol, 1 equiv), NaOtBu (96.1 mg, 1 mmol, 6.6
equiv), RuPhos (1.4 mg, 0.003 mmol, 0.02 equiv), RuPhos Pd G2 (2.3 mg, 0.003 mmol, 0.02 equiv), and a magnetic
stir bar were charged to a flame dried, 20 mL reaction tube and sealed with a Teflon cap. A nitrogen atmosphere
was established and methylaniline (0.1 mL, 0.9 mmol, 6 equiv) and dioxane (1 mL) were added via syringe. The
reaction was stirred at 80 °C overnight. The reaction was quenched with Na
Product was extracted into DCM and dried with MgSO The organic layer was concentrated and dried under
vacuo. The product was isolated by recrystallization from benzene yielding 78 mg (59% yield) of light green
2 3
SO and stirred for 30 minutes.
4
.
1
6 6
powder. H NMR (500 MHz, C D ) δ 7.11 (dd, J = 8.7, 7.2 Hz, 8H), 6.97 (d, J = 2.5 Hz, 4H), 6.87 – 6.77 (m, 16H),
1
3
6
1
1
.46 (d, J = 8.7 Hz, 4H), 3.39 (m, 4H), 2.86 (s, 12H), 1.71 (m, 4H); C NMR (125 MHz, C
6
D
6
) δ 149.4, 144.3,
–1
41.0, 129.1, 126.4, 122.6, 122.4, 119.7, 117.7, 116.0, 46.4, 39.9, 24.0; IR (ATR, cm ): 3053, 2919, 2848, 2805,
593, 1493, 1455, 1250, 1153, 1129, 1088, 748; HRMS (DART): m/z calc’d for (M+H) [C H N S ] : 873.3773,
56 53 6 2
+
+
found 873.3787.
Dedication
In honor of Prof. Stephen L Buchwald for his mentorship and leadership in the field of organic chemistry.
Acknowledgements
This work was primarily funded by a grant to the Cornell Center for Materials Research from the NSF MRSEC
program (DMR-1719875). B.P.F. thanks 3M for a Non-Tenured Faculty Award and the Sloan Foundation for the
Sloan Research Fellowship.
Supplementary Information
Supplementary data related to this article can be found at
References
[
[
[
[
[
[
[
[
1] Q. Zhao, C. Guo, Y. Lu, L. Liu, J. Liang, J. Chen. Ind. Eng. Chem. Res. 55 (2016) 5795.
2] T. B. Schon, B. T. McAllister, P.-F. Li, D. S. Seferos, Chem. Soc. Rev. 45 (2016) 6345.
3] P. Novák. K. Müller, K. S. V. Santhanam, O. Haas, Chem. Rev. 97 (1997) 207.
4] S. Conte, G. G. Rodriguez-Calero, S. E. Burkhardt, M. A. Lowe, H. D. Abruña, RSC Adv. 3 (2013) 1957.
5] Y. Liang, Z. Tao, J. Chen, Adv. Energy Mater. 2 (2012) 742.
6] S. Muench, A. Wild, C. Friebe, B. Häupler, T. Janoschka, U. S. Schubert, Chem. Rev. 116 (2016) 9438.
7] A. A. Golriz, T. Suga, H Nishide, R. Berger, J. S. Gutmann, RSC Adv. 5 (2015) 22947
8] M. Kolek, F. Otteny, P. Schmidt, C. Mück-Lichtenfeld, C. Einholz, J. Becking, E. Schleicher, M. Winter, P.
Beiker, B. Esser, Energy Environ. Sci. 10 (2017) 2334.
[
[
9] T. Godet-Bar, J.-C. Lepretre, O. Le Bacq, J.-Y. Sanchez, A. Deronzier, A. Pasturel, Phys. Chem. Chem. Phys. 17
(
2015) 25283.
10] J. A. Kowalski, M. D. Casselman, A. P. Kaur, J. D. Milshtein, C. F. Elliot, S. Modekrutti, N. H. Attanayake, N.
Zhang, S. R Parkin, C. Risko, F. R. Brushett, S. A. Odom, J. Mater. Chem. A. 5 (2017) 24371.
11] X. Kong, A. P. Kulkarni, S. A. Jenekhe, Macromolecules 36 (2003) 8992.
[
[
12] A. A. Golriz, T. Kaule, M. B. Untch, K. Kolman, R. Berger, J. S. Gutmann, ACS Appl. Mater. Interfaces 5
(
2013) 2485.
[
[
13] F. Fungo, S. A. Jenekhe, A. J. Bard, Chem. Mater. 15 (2003) 1264.
14] T.-T. Truong, G. W. Coates, H. D. Abruña, Chem. Commun. 51 (2015) 14674
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ACCEPTED MANUSCRIPT
[
[
[
[
[
[
[
15] H. Yang, D. O. Wipf, A. J. Bard, J. Electroanal. Chem. 331 (1992) 913.
16] T. Mizoguchi, R. N. Adams, J. Am. Chem. Soc. 84 (1962) 2058.
17] P. Ruiz-Castillo, S. L. Buchwald, Chem. Rev. 116 (2016) 12564.
18] J. F. Hartwig, Synlett, 0 (2006) 1283.
19] R. A. Singer, J. P. Sadighi, S. L. Buchwald, J. Am. Chem. Soc. 120 (1998) 213.
20] X.-X. Zhang, J. P. Sadighi, T. W. Mackewitz, S. L. Buchwald, J. Am. Chem. Soc. 122 (2000) 7606.
21] B. M. Peterson, D. Ren, L. Shen, Y.-C. M. Wu, B. Ulgut, G. W. Coates, H. D. Abruña, B. P. Fors. ACS Appl.
Energy Mater. 1 (2018) 3560.
[
[
[
[
[
22] H. Etori, T. Kanbara, T. Yamamoto, Chem. Lett. 23 (1994) 461.
23] P. Nguyen, P. Gómez-Elipe, I. Manners, Chem. Rev. 99 (1999) 1515.
24]K. Naka, T. Uemura, Y. Chujo, Macromolecules 33 (2000) 6965.
25] R. Rulkens, A. J. Lough, I. Manners, J. Am. Chem. Soc. 116 (1994) 797.
26] R. Rulkens, A. J. Lough, I. Manners, S. R. Lovelace, C. Grant, W. E. Geiger, J. Am. Chem. Soc. 118 (1996)
1
2683.
[
[
[
[
[
[
[
[
[
27] B. P. Fors, D. A. Watson, M. R. Briscoe, S. L. Buchwald, J. Am. Chem. Soc. 130 (2008) 13552.
28] N. C. Bruno, M. T. Trudge, S. L. Buchwald, Chem. Sci. 4 (2013) 916.
29] D. Maiti, B. P. Fors, J. L. Henderson, Y. Nakamura, S. L. Buchwald, Chem. Sci. 2 (2011) 57.
30] T. Kinzel, Y. Zhang, S. L. Buchwald, J. Am. Chem. Soc. 132 (2010) 14073.
31] D. Wei, C. Kvarnström, T. Lindfors, L. Kronberg, R. Sjöholm, A. Ivaska, Synth. Met. 156 (2006) 541.
32] D. A. Buttry, M. D. Ward, Chem. Rev. 92 (1992) 1355.
33] R. Borjas, D. A. Buttry, Chem. Mater. 3 (1991) 872.
34] A. R. Hillman, D. C. Loveday, S. Bruckenstein, Langmuir 7 (1991) 191.
35] J. John, K. M. Hugar, J. Rivera-Meléndez, H. A. Kostalik, E. D. Rus, H. Wang, G. W. Coates, H. D. Abruña, J.
Am. Chem. Soc. 136 (2014) 5309.
9