Strong Ground- and Excited-State Charge Transfer in C3-Symmetric Truxene-Derived Phenothiazine-Tetracyanobutadine and Expanded Conjugates

Article abstract of DOI:10.1002/anie.201814388

The C₃-symmetric star-shaped phenothiazene-substituted truxene 1 was reacted with the electron acceptors tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). The cycloaddition–retroelectrocyclization reaction yields the conjugates 2 and 3. A combination of spectral, electrochemical, and photophysical investigations of 2 and 3 reveals that the functionalization of the triple bond has a pronounced effect on their ground and excited-state interactions. Specifically, the existence of strong ground-state interactions between phenothiazine and the electron-accepting groups results in charge-transfer states, while subsequent ultrafast charge separation yields electron transfer products. This is unprecedented not only in phenothiazine chemistry but also in tetracyanobutadiene- and dicyanoquinodimethane-derived donor–acceptor conjugates. Additionally, by manipulating spectroelectrochemical data, a spectrum of the charge-separated species is construed for the first time, and shown to be highly useful in interpreting the rather complex transient spectra.

Full text of DOI:10.1002/anie.201814388

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
International Edition Chemie
www.angewandte.org
Accepted Article
Title: Strong Ground and Excited State Charge Transfer in C3-
Symmetric Truxene Derived, Low-Band Gap, Phenothiazine-
Tetracyanobutadine (TCBD) and Expanded TCBD Conjugates
Authors: Rekha Sharma, Michael Thomas, Rajneesh Misra, and
Francis D'Souza
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: Angew. Chem. Int. Ed. 10.1002/anie.201814388
Angew. Chem. 10.1002/ange.201814388
Link to VoR: http://dx.doi.org/10.1002/anie.201814388
http://dx.doi.org/10.1002/ange.201814388

Angewandte Chemie International Edition
10.1002/anie.201814388
COMMUNICATION
Strong Ground and Excited State Charge Transfer in C -
3
Symmetric Truxene Derived, Low-Band Gap, Phenothiazine-
Tetracyanobutadine (TCBD) and Expanded TCBD Conjugates
Rekha Sharma,[a]‡ Michael B. Thomas,[b]‡ Rajneesh Misra[a]* and Francis D’Souza[b]*
Abstract: C
3
-symmetric, star shaped phenothiazene substituted
Specifically, the existence of strong ground state interactions between
phenothiazine and electron accepting TCBD or DCNQ resulting in
truxene 1, synthesized by the Pd-catalyzed Sonogashira cross-
coupling reaction, was reacted with electron acceptors
tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane
+
-
+
-
PTZ -TCBD
or PTZ -DCNQ
charge transfer states, and

+
-
subsequent ultrafast charge separation resulting in PTZ -TCBD or

+
-
(TCNQ) which undergo, cycloaddition-retroelectrocyclization reaction
PTZ -DCNQ electron transfer products is unequalled not only in
phenothiazine chemistry but also in TCBD and DCNQ-derived donor-
acceptor conjugates. Additionally, for the first time, by manipulating
spectroelectrochemical data, spectrum of the charge-separated
species is construed, and shown to be highly useful in interpreting the
rather complex transient spectra.
to yield tetracyanobutadine (TCBD) and cyclohexa–2,5–diene–1,4–
ylidene–expanded TCBD bearing conjugates 2 and 3. A combination
of spectral, electrochemical, and photophysical investigations of 2 and
3
reveal that the functionalization of the triple bond by TCBD and
expanded TCBD (abbreviated as DCNQ = dicyanoquinodimethane)
has a pronounced effect on their ground and excited‐state interactions.
unique optoelectronic properties and are useful in various applications
including dye sensitized solar cells and organic photovoltaics, and
[
6]
light-emitting diodes.
Ground and excited state charge transfer (CT) interactions in donor-
acceptor (D-A) systems has been one of the most widely studied
topics by the scientific community over the last two decades as its
significance is palpable in solar energy conversion, and building
TCNE and TCNQ are powerful electron acceptors and
undergo [2+2] cycloaddition–retroelectrocyclization reaction.[
Many groups have explored their D-A properties; e.g., Shoji et al.
have explored donor–acceptor based TCBD and DCNQ
7]
[
1-2]
molecular optoelectronic switches and wires.
Among these, -
[
8]
molecules as redox active chromophores. Research teams of
Diederich, Torres, and Guldi have also reported phthalocyanine-
conjugated D-A systems are appealing because of their applications
in the field of non-linear optics, and electroluminescent devices. The
photonic properties of -conjugated D-A systems can be tuned by
altering the strength of the donor or acceptor units, and by varying the
connecting -linker. Porphyrins and phthalocyanines have been
traditionally used as building blocks in
[9]
TCBD and subphthalocyanine-TCBD D-A systems. Our groups
have reported a variety of TCBD functionalized chromophores for
optoelectronic applications.[10]
the construction of such light-powered
ensembles due to their easily modifiable
[
3]
spectral
Recently, other photosensitizers such as
BF -chealted dipyrromethene, corrole,
phenothiazine (PTZ) etc., have also
and
redox
properties.
2
[
4]
been employed. Among these, PTZ
deserved special mention as it is a well-
known heterocyclic compound with
electron-rich sulphur and nitrogen
heteroatoms, exhibiting
a
butterfly
shaped nonplanar geometry, high
Chart 1. Structure of truxene derived strongly interacting Phenothiazine-TCBD
electron-donating ability, as well as good thermal and electrochemical
[
5]
and Phenothiazine-DCNQ D-A hybrids.
stability. Consequently, phenothiazine containing systems exhibit
3
The star-shaped truxene is a planar C -symmetric, fused
fluorene trimer, which provides easy functionalization, high
[
[
a] Department of Chemistry, Indian Institute of Technology, Indore
53552, India. E-mail: rajneeshmisra@iiti.ac.in
b] Department of Chemistry, University of North Texas, 1155 Union
Circle, #305070, Denton, TX 76203-5017, USA, E-mail:
Francis.DSouza@UNT.edu
thermal and chemical stability.[11] The -surface and multi-reactive
4
sites offer -extension leading diverse functionalization.[12] Pei et
al. have devoted considerable synthetic effort on various star
shaped -conjugated truxene based molecular systems, useful
‡
Equal contribution
[13]
for optoelectronic applications.

Supporting information for this article, additional spectral and
1
13
3
Due to planar C -symmetry and diverse functionalization,
truxene stands out to be a scaffold to build multi-modular D-A
systems for appealing photonic applications, especially when they
femtosecond spectra, H and C NMR and MALDI-mass of
synthesized compounds.
1
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201814388
COMMUNICATION
are used to decorate powerful electron acceptors like TCNE and
TCNQ. This has been accomplished here wherein truxene is
utilized as a scaffold to build star-shaped D-A systems decorated
with three PTZ-TCBD or PTZ-DCNQ entities, 2 and 3 (Chart 1).
(see Figure S1 for absorption and fluorescence spectrum of PTZ).
Truxene peaks in 1 were hidden under the strong 342 nm peak of
PTZ. Interestingly, for the D-A conjugate 2 bearing three entities
of PTZ-TCBD, peaks at 345, 432, and 552 nm were observed.
The broad 552 nm peak had absorption coverage up to 800 nm.
Even more drastic changes for conjugate 3 was observed, that is,
peaks at 388, 463, and 702 nm were observed in which the broad
702 nm peak stretched until 900 nm covering the near-IR (NIR)
region. The broad absorption features of the new NIR band is
attributable to CT absorption resulting from ground state
interactions between the electron donating PTZ and the electron
+
-
+
-
Strong intramolecular PTZ -TCBD or PTZ -DCNQ type CT
interactions covering the visible-near IR region of the spectrum in
these low-band gap conjugates have been observed. Further, for
the first time, by manipulating spectroelectrochemical data,
spectrum of the charge-separated state in these strongly
interacting D-A systems was possible to deduce. Such procedure
aided in characterizing excited state charge separation (CS)
products from species associated spectrum (SAS) generated
from target analysis of femtosecond transient absorption (fs-TA)
spectral data. This new procedure paves a way to better handling
and analysis of transient spectral data and secure kinetic
information on the ultrafast events.
+
-
withdrawing TCBD and DCNQ in 2 and 3. The PTZ -TCBD and
+
-
PTZ -DCNQ CT origin of this transition was further acertained
by negative solvatochromism, resulting in blue-shift of the
absorption maximum to 545 nm in the case of 2 and 637 nm in
the case of 3 in toluene. These results suggest that the PTZ-
TCBD and PTZ-DCNQ entities in
the multi-modular conjugates are
highly-polarized revealing strong
CT in the ground state. Figure S16
shows color of solutions in CH
for 1, 2, and 3. Conjugate 2 revealed
dark orange while conjugate
2 2
Cl
3
revealed dark brown due to wide-
band capture of the CT transitions.
Fluorescence behavior of
these compounds was also studied
as shown in Figure 1b. Truxene 1a
revealed weak emission at 360 nm
when excited at 340 nm while
pristine PTZ revealed weak
emission at 390 nm (Figure S2).
Truxene 1, when excited at 380 nm
corresponding to PTZ, revealed
strong emission at 500 nm. In
truxenes 2 and 3, excitation of the
conjugates corresponding to either
of their absorption peak maxima revealed quantitative quenching
of PTZ fluorescence due to strong excited-state interactions.
Scanning the wavelength to higher wavelengths revealed very
weak, broad emission around 700 nm for 2 and 810 nm for 3 due
to CT emission. Lifetime of 1PTZ* in 1 was measured using
TCSPC technique yielded a lifetime of 3.64 ns, close to that of
pristine PTZ. These results indicate lack of photochemical events
Scheme 1. Synthesis of multiple PTZ (1), PTZ-TCBD (2), or PTZ-DCNQ (3)
bearing truxene scaffold.
The syntheses of PTZ substituted truxenes are shown in
Scheme 1. The truxene core was synthesized by 1-indanone in
the presence of acetic acid and HCl followed by alkylation reaction
of the truxene with bromo-hexane and further iodination reaction
1
from PTZ* to central truxene in 1, and absence of intramolecular
interactions among the PTZ entities within 1.
3 2
in the presence of HIO and I to yield hexahexylated tri-iodo
[
14]
truxene 1a in 80% yield (Scheme S1). The intermediate ethynyl
phenothiazine (1b) was synthesized by reported procedure.[15]
The Pd-catalyzed Sonogashira cross-coupling reaction of tri-iodo
truxene 1a with ethynyl phenothiazine, 1b resulted truxene 1 in
75% yield (Scheme 1). The TCBD and DCNQ linked truxenes 2
and were synthesized via [2 2] cycloaddition–
3
+
retroelectrocyclization reaction of the truxene 1 with 3 equivalents
of TCNE and TCNQ resulting in 65% and 60% yields, respectively.
Compounds 1-3, were soluble in common organic solvents, and
were fully characterized by 1H and 13C NMR and MALDI
techniques.
UV-vis studies carried out for 2 and 3 showed significant
differences compared to 1 and 1a (Figure 1a). Truxene 1a
revealed peaks at 327, 340, and 354 nm in benzonitrile, while PTZ
linked truxene 1 revealed peaks at 342 and 380 nm. The PTZ
peak were red-shifted by ~60 nm compared to that in pristine PTZ
Figure 1. (a) Absorption and (b) fluorescence spectra of indicated compounds
in benzonitrile. The samples were excited at their peak maxima.
2
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201814388
COMMUNICATION
The strong intramolecular CT interactions between the
closely spaced donor and acceptor entities in 2 and 3 were also
borne out from the frontier orbitals generated at the B3LYP/6-
peaks at 317, 411, and 577 nm (Figure 3a). For one-electron
reduced product, positive peaks at 336, 489, and 692 nm and
negative peaks at 310, 366(sh), 428, and 547 nm were observed
(Figure 3b). Both oxidation and reduction processes perturbed
entire spectra, that is, decrease of peak intensity corresponding
to neutral species and appearance of new peaks corresponding
to oxidized or reduced product were observed.
31G* optimized structures (Figure S3). In both cases, partial
HOMO on the acceptor entity and partial LUMO on the donor
entity was observed.
Electrochemical and spectroelectrochemical studies were
performed to establish the redox states and spectral
characteristics of oxidized and reduced species. Figure 2 shows
differential pulse voltammograms (DPVs) of 1-3 in benzonitrile;
the first oxidation of 1 corresponding to PTZ was located at 0.30
+
V vs. Fc/Fc . No reduction corresponding to either PTZ or truxene
was observed. The electron deficient TCBD in 2 revealed two
reductions at -0.80 and -1.18 V while the PTZ oxidation was
anodically shifted by 210 mV and appeared at 0.51 V. Similar
results were observed for 3 wherein the first two reductions of
DCNQ were located at -0.62 and -0.78 V and the first oxidation of
phenothiazine was at 0.39. From these results, the electron
deficient nature of TCBD and DCNQ – the latter being a better
electron acceptor – were borne out. The observed stronger CT in
3
compared to that in 2 is attributed to the superior electron
acceptor ability of DCNQ. The electrochemical HOMO-LUMO gap,
measured as the potential difference between the first oxidation
and first reduction were found to be 1.31 V for 2 and 1.01 V for 3.
That is, smaller HOMO-LUMO gap for 3 compared to 2 was
witnessed.
Figure 3. Differential absorption spectra obtained during (a) first oxidation and
(b) first reduction of 2 in benzonitrile containing 0.2 M (TBA)PF
6
. Figure c and d,
.
+
respectively, show the differential absorption spectrum generated for the PTZ -
TCBD.- and PTZ -DCNQ charge separated states by averaging the radical
cation and radical anion spectrum shown in Figures 3a and b for 2, and Figures
S2a and b for 3, and subtracting that with the initial spectrum of neutral 2 or 3.
.+
.-
Photoexcitation of the donor PTZ entity in 2 and 3 generates
.
+
.-
.+
.-
PTZ -TCBD and PTZ -DCNQ CS states with positive charge
mainly located on easily oxidizable PTZ and the negative charge
mainly on easily reducible TCBD or DCNQ entities, with some
contributions on their counter parts due to the existence of earlier
discussed intramolecular interactions. Under such a situation, the
spectrum of the electron transfer product would be close to the
average of one-electron oxidized and one-electron reduced
products. In the present study, we have made an effort to
Figure 2. DPVs of 1, 2 and 3 in benzonitrile containing 0.1 (TBA)PF
6
. The peak
shown by asterisk corresponds to oxidation of internal standard, ferrocene.
generate
such
a
spectrum
using
the
above
Spectroelectrochemistry is
a
powerful technique to
spectroelectrochemical results. For this, we averaged differential
absorption spectrum of one-electron oxidized and reduced
products and subtracted from the neutral compound (Figures 3c
and d). The differential absorption mode and subtraction from the
neutral compound was necessary since in the transient spectral
measurements differential absorption spectra are recorded. Such
analysis resulted in a spectrum for the electron transfer product
shown in Figures 3c and d. If our hypothesis were correct, then
the spectrum of SAS from target analysis of the transient data
corresponding to electron transfer product would closely match
with the spectrum shown in Figure 3c and d (vide supra).
In order to verify our hypothesis and to secure kinetic
information on the photoprocesses, fs-TA studies were performed
in polar benzonitrile and nonpolar toluene. The samples were
excited both at PTZ locally excited and the low-energy CT band
positions, as the CT transition can directly transform into CS state,
as depicted in the energy level diagram in Figure 4 for both
conjugates 2 and 3.[16] The transient spectral data were analyzed
characterize the oxidized and reduced products and resolve site
of electron transfer in complex molecular systems. In D-A
conjugates that undergo photoinduced electron transfer (PET),
spectroelectrochemical results are a necessity to characterize the
electron transfer products. This technique works especially well
when the donor and acceptor entities of the dyad have no
intramolecular interactions and behave like independent entities
avoiding cross communication between them. However, in
conjugates where there is strong intramolecular interactions,
either oxidation of the donor or reduction of the acceptor affect
spectral features of the entire conjugate. This seems to be the
case in 2 and 3 where the strong CT caused perturbation of the
spectral features of the entire conjugate. Figure 3a and b show
the differential spectral changes associated for 2 during first
oxidation and first reduction; similar results were also observed
for 3 (Figure S4). For one-electron oxidation product, the spectra
revealed positive peaks at 356, 469, and 892 nm and negative
3
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201814388
COMMUNICATION
using Glotaran software[17] to generate SAS and population time
constants. First, control compound 1 was studied in both
benzonitrile and toluene, as shown in Figure S5. In benzonitrile,
at 370 nm exciting mainly PTZ entity, the instantaneously formed
1PTZ* revealed positive peaks at 465, 534, 575, 662, and 767 nm
from transitions originating from this state. A negative peak at 508
nm was observed whose peak minima was close to that of
fluorescence peak maxima of PTZ in 1 (Figure 1b) indicating that
it is due to stimulated emission. Similar spectral observations
were also made for 1 in toluene (Figure S3b).
instantaneously formed PTZ* revealed a peak at 500 nm. Rapid
decay of this peak was accompanied by a positive peak at 660
nm and a dip in the 578 nm region. For 3, the instantaneously
formed singlet excited state had positive peaks at 554 and 782
nm. With time, decay of this peak accompanied by blue-shift and
a dip at 650 nm was observed. Unlike for 1, the photoprocesses
both 2 and 3 were completed in less than 200 ps, that is, the
photochemical events were rather fast. Similar spectral
observations were also made in toluene (Figure S6). Next, the
spectral data were subjected to target analysis, and the SAS
generated from such analysis revealed three components. The
first component with time constants of few ps was attributed to
first excited state. The second component was attributed to the
electron transfer product. Support for this assignment came from
the earlier discussed spectroelectrochemical studies where the
spectrum generated for CS state in the case of 2 and 3 agreed
closely with the SAS. A much weaker third component with fair
amount of noise, perhpas due to populating 3PTZ*, was also
observed. No further efforts were made to characterize this weak
component. Time constants for the first component were 2.5 and
1
4.3 ps for 2, and 2.7 and 7.8 ps for 3, in benzonitrile and toluene,
respectively. These values were significantly smaller than that of
1
the earlier discussed PTZ* time constants indicating its
involvement in CS, more efficient in polar benzonitrile than
nonpolar toluene. The lifetime of the charge-separated state was
found to be 46.7 and 9.6 ps for 2, and 19.8 and 8.7 for 3 in
benzonitrile and toluene, respectively. Faster CS due to close
proximity of the D-A entities in the conjugates, more so for 3 over
2
due to facile reduction of DCNQ in 3 compared to that of TCBD
in 2, was borne out. Next, the excitation wavelength was changed
to that corresponding to the CT absorption peak (555 nm for 2 and
690 nm for 3, Figure S7). The spectral features and time
Figure 4. Energy level diagram of 2 and 3 in benzonitrile reflecting energetic
constants were close to that obtained when the samples were
excited at the main PTZ peak maxima. These results indicate
occurrence of CS irrespective of excitation wavelength (locally
excited or CT state). To summarize, the femtosecond transient
absorption measurements are in good agreement with the
absorption/emission studies that indicated deactivation of PTZ-
TCBD and PTZ-DCNQ excited states resulting in CS states.
pathways of CS and charge recombination after excitation of PTZ, and PTZ+
-
TCBD or PTZ+-DCNQ- CT state. The energy of the polarized PTZ+-TCBD-
-
or PTZ+-DCNQ- singlet excited state, and PTZ -TCBD or PTZ -DCNQ
+
-
+
-
radical ion-pairs were derived by the CT absorption maxima, and by the addition
of the respective redox potentials, that is, first oxidation and first reduction of
conjugates 2 and 3.
The transient data was
subjected to target analysis
whose SAS revealed two
components. The rise time of
the first component was ~1 ps,
which could be due to
transitions originating from the
1
PTZ* state, while the rise time
of second component was ~5.9
ps consistent with population of
1
PTZ* state. The decay of the
1PTZ* state lasted beyond 3 ns
both in toluene and benzonitrile,
the time window of our
instrument, consistent with the
long fluorescence lifetime of
PTZ. These results suggest
1
successful formation of PTZ* in
1
.
Figure 5. Differential transient absorption spectra at the indicated delay times
of 2 (ex = 433 nm) and 3 (ex = 455 nm) in benzonitrile. The SAS and the
population kinetic profiles are shown in the panels below of each figure.
The fs-TA for 2 and 3 at the indicated delay times in
benzonitrile are shown in Figure 5a and b, respectively, while
such data in toluene are shown in Figure S6. For 2, the
4
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201814388
COMMUNICATION
In summary, the newly synthesized multi-modular
conjugates of C -symmetric truxene scaffold, having the donor
3
[4]. a) Loudet, A.; Burgess, K. Chem. Rev. 2007, 107, 4891; b) El-Khouly, M.
E.; Fukuzumi, S.; D’Souza, F. ChemPhysChem 2014, 15, 30.
[
[
5] G. Sang, Y. Zou, Y. Li, J. Phys. Chem. C, 2008, 112, 12058.
PTZ directly linked to acceptor, TCBD or DCNQ, exhibited strong,
wide-band absorptions covering the near IR region. Further, we
were able to confirm by means of optical absorption and emission,
electrochemical, computational, and spectroelectrochemical
studies the formation of strong CT interactions in the ground state,
in which PTZ interacted with the electron acceptors. The fs-TA
studies revealed that the CT state results into electron transfer
product upon photoexcitation. The spectrum of the electron
transfer product deduced from spectroelectrochemical results
was utilized in identifying the SAS corresponding to this species.
Overall, the extremely strong CT state, wide-band absorption,
HOMO-LUMO band gap as low as 1.0 eV, and PET generating
the radical ion-pairs render these D-A conjugates for applications
in molecular photovoltaic devices.
6] a) J. Huang, K. Lee, ACS Appl. Mater. Interfaces., 2014, 6, 7680. b) Z.
Wan, C. Jia, Y. Duan, L. Zhou, Y. Lin, Y. Shi, J. Mater. Chem., 2012, 22,
25140; c) G. Zhang, J. Sun, P. Xue, Z. Zhang, Peng Gong, J. Penga, R,
Lu, J. Mater. Chem. C, 2015, 3, 2925.
[7] a) M. Yamada, W. B. Schweizer, F. Schoenebeck, F. Diederich, Chem.
Commun. 2010, 46, 5334; b) M. Jordan, M. Kivala, C. Boudon, J.‐P.
Gisselbrecht, W. B. Schweizer, P. Seiler, F. Diederich, Chem.–Asian J.,
2
011, 6, 396.
8] a) T. Shoji, S. Ito, K. Toyota, M. Yasunami, N. Morita, Chem.–Eur. J., 2008,
4, 8398. b) T. Shoji, S. Ito, K. Toyota, T. Iwamoto, M. Yasunami, N.
[
[
1
Morita, Eur. J. Org. Chem., 2009, 4316.
9] a) M. Sekita, B. Ballesteros, F. Diederich, D. M. Guldi, G. Bottari, T. Torres,
Angew. Chem. Int. Ed. 2016, 55, 5560. b) K. A. Winterfeld, G. Lavarda, J.
Guilleme, M. Sekita, D. M. Guldi, T. Torres, G. Bottari, J. Am. Chem. Soc.
2017, 139, 5520.
[
[
10] a) P. Gautam, R. Sharma, R. Misra, M. L. Keshtov, S. A. Kuklin, G. D.
Sharma, Chem. Sci. 2017, 8, 2017. b) Y. Patil, R. Misra, R. Singhal, G. D.
Sharma, J. Mater. Chem. A. 2017, 5, 13625. c) P. Gautam, R. Misra, M.
B. Thomas, F. D’Souza, Chem. Eur. J. 2017, 23, 9192-9200.
11] B. Ventura, A. Barbieri, F. Barigelletti, S. E. Diring, R. Ziessel, Inorg. Chem.
2010; 49, 8333.
Acknowledgements
Support from the DST, (DST/TMD/SERI/D05 (C)), INSA
(
SP/YSP/139/ 2017/2293), Govt. of India, New Delhi, and US-
[12] a) W. B. Zhang, W. H. Jin, X. H. Zhoua, J. Pei, Tetrahedron, 2007, 63,
2907. b) J. Huang, B. Xu, J. H. Su, H. Chin, H. Tian, Tetrahedron, 2010,
National Science Foundation (1401188 to FD) is gratefully
acknowledged.
66, 7577. c) C. Yao, Y. Yu, X. Yang, H. Zhang, Z. Huang, X. Xu, G. Zhou,
L. Yue, Z. Wu, J. Mater. Chem. C, 2015, 3, 5783.
[
13] a) M. M. Boorum, Y. V. Vasil, T. Drewello, L. T. Scott, Science, 2001, 294,
Keywords: ultrafast CT• strongly coupled D-A • phenothiazine •
truxene • tetracyanobutadine
8
28. b) P. W. Rabideau, A. H. Abdourazak, Z. Marcinow, R. Sygula, A.
Sygula, J. Am. Chem. Soc. 1995, 117, 6410. c) B. Gomez-Lor, E.
Gonzalez-Cantalapiedra, O. DeFrutos, C. Ardenas, D. J. Santos, A. M.
Echavarren, Chem. Eur. J., 2004, 10, 2601. d) J. Pei, J. L. Wang, X. Y.
Cao, X. H. Zhou, W. B. Zhang, J. Am. Chem. Soc., 2003, 125, 9944.
14] a) A. L. Kanibolotsky, R. Berridge, P. J. Skabara, I. F. Perepichka, D. D.
C. Bradley, M. Koeberg, J. Am. Chem. Soc., 2004, 126, 13695. b) X. Cao,
H. Zi, W. Zhang, H. Lu, J. Pei, J. Org. Chem., 2005, 70, 3645.
References and Notes
[
[
1] a) L. Hammarstrçm, Acc. Chem. Res. 2015, 48, 840; b) A. Arrigo, A.
Santoro, F. Puntoriero, P. P. Lain¦, S. Campagna, Coord. Chem. Rev.
2
015, 304–305, 109; c) S. Fukuzumi, K. Ohkubo, T. Suenobu, Acc. Chem.
[
[
[
15] M. Poddar, P. Gautam, Y. Rout, R. Misra, Dyes and Pigments, 2017, 146,
Res. 2014, 47, 1455; d) D. Gust, T. A. Moore, A. L. Moore, Acc. Chem.
Res. 2009, 42, 1890.
368.
16] The energy levels were calculated using a procedure similar to that
[
[
2] a) R. Chitta, F. D’Souza, J. Mater. Chem. 2008, 18, 1440; b) F. D’Souza,
O. Ito, Chem. Soc. Rev. 2012, 41, 86.
reported in 10c.
17] http://glotaran.org/
3] a) The Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.;
Academic Press: San Diego, CA, 2000; Vols. 1−20. b) Claessens, C. G.;
González-Rodríguez, D.; Torres, T. Chem. Rev. 2002, 102, 835. c) Saito,
S.; Osuka, A. Angew. Chem., Int. Ed. 2011, 50, 4342.
5
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201814388
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Two, C
3
-symmetric, (phenothiazine-
-truxene and (phenothiazine-
-truxene conjugates have
R. Sharma, M. B. Thomas, R. Misra*
and F. D’Souza*
TCBD)
DCNQ)
3
3
been synthesized. Strong ground
state CT between phenothiazine and
TCBD or DCNQ, wide-band
absorption covering near-infrared
regions, HOMO-LUMO gap as low
as 1.01 eV, ultrafast excited state
electron transfer render these
compounds promising materials for
applications in molecular
Page No. – Page No.
Strong Ground and Excited State
Charge Transfer in C -Symmetric
3
Truxene Derived, Low-Band Gap,
Phenothiazine-Tetracyanobutadine
((Insert TOC Graphic here))
(
TCBD) and Expanded TCBD
Conjugates
optoelectronics.
6
This article is protected by copyright. All rights reserved.