Stable Expanded Porphycene-Based Diradicaloid and Tetraradicaloid

Article abstract of DOI:10.1002/anie.201807411

The synthesis of a bithiophene-bridged 34π conjugated aromatic expanded porphycene 1 and a cyclopentabithiophene bridged 32π conjugated anti-aromatic expanded porphycene 2 by a McMurry coupling strategy is presented. Magnetic measurements and theoretical calculations reveal that both 1 and 2 exhibit an open-shell singlet ground state with significant radical character (y₀=0.63 for 1; y₀=0.68, y₁=0.18 for 2; y₀: diradical character, y₁: tetraradical character) and a small singlet–triplet energy gap (ΔE_S-T=?3.25 kcal mol^?1 for 1 and ΔE_S-T=?0.92 kcal mol^?1 for 2). Despite the open-shell radical character, both compounds display exceptional stability under ambient air and light conditions owing to effective delocalization of unpaired electrons in the extended cyclic π-conjugation pathway.

Full text of DOI:10.1002/anie.201807411

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Stable Expanded Porphycene-Based Diradicaloid and
Tetraradicaloid
Authors: Jishan Wu, Anup Rana, Yongseok Hong, Tullimilli Y.
Gopalakrishna, Hoa Phan, Tun Seng Herng, Priya Yadav, Jun
Ding, and Dongho Kim
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.201807411
Angew. Chem. 10.1002/ange.201807411
Link to VoR: http://dx.doi.org/10.1002/anie.201807411
http://dx.doi.org/10.1002/ange.201807411

10.1002/anie.201807411
Angewandte Chemie International Edition
COMMUNICATION
Stable Expanded Porphycene-Based Diradicaloid and
Tetraradicaloid
Anup Rana,[a] Yongseok Hong,[b] Tullimilli Y. Gopalakrishna,[a] Hoa Phan,[a] Tun Seng Herng,[c] Priya
Yadav,[a] Jun Ding,[c] Dongho Kim,*[b] and Jishan Wu*[a]
Abstract: We report the synthesis of a bithiophene bridged 34π
conjugated aromatic expanded porphycene and
raising the question about their possible global (anti)aromaticity.
Therefore, it will be of interest to see whether they have the
desired open-shell radical character and whether they can be
thermodynamically stabilized by cyclic π-conjugation.
1
a
cyclopentabithiophene bridged 32π conjugated anti-aromatic
expanded porphycene 2 by a McMurry coupling strategy. Magnetic
measurements and theoretical calculations reveal that both 1 and 2
exhibit open-shell singlet ground state with significant radical
character (y0 = 0.63 for 1; y0 = 0.68, y1 = 0.18 for 2; y0: diradical
character, y1: tetraradical character) and small singlet-triplet energy
gap (ΔES-T= - 3.25 kcal/mol for 1 and ΔES-T = -0.92 kcal/mol for 2).
Despite the open-shell radical character, both compounds display
exceptional stability under ambient air and light conditions due to
effective delocalization of unpaired electrons in the extended cyclic π-
conjugation pathway.
OBu
OBu
b
c
OBu
BuO
BuO
BuO
BuO
OBu
S
S
S
S
NH
N
NH
N
a
N
N
HN
HN
S
S
S
S
34 e
OBu
BuO
BuO
OBu
OBu
OBu
1
BuO
BuO
Mes
Mes
OBu
OBu
NH
OBu
OBu
NH
BuO
BuO
OBu
OBu
BuO
BuO
OBu
OBu
S
S
S
S
S
S
N
N
2
N
HN
N
HN
Open-shell singlet diradicaloids and polyradicaloids have
received substantial attention recently owing to their unique
electronic properties and promising applications for organic
electronics, nonlinear optics, spintronics and energy storage
devices.[1] Stabilization of highly reactive organic radicals could be
achieved by kinetic blocking and/or effective delocalization of
unpaired electrons through a large π-conjugated framework. In
this regard, porphyrin and expanded porphyrins with effective
cyclic π-conjugation pathway could be good platforms to obtain
stable materials with unpaired electrons.[2] Our particular interest
here is an isomeric porphyrin known as porphycene (Figure 1),
which was first reported in 1986[3] and has been extensively
studied material applications.[4] Our design is to construct
bithiophene and cyclopenta[2,1-b:3,4-b']bithiophene bridged
expanded porphycenes such as 1 and 2 (Figure 1). In 1, one
quinoidal bithiophene unit must be drawn in its closed-shell
resonance form, implying that the molecule has intrinsic tendency
to become open-shell diradical by recovery of two aromatic
thiophene rings (pentagons shaded in blue, Figure 1). On the
other hand, compound 2 has the tendency to become diradical
and tetraradical by recovery of two and four aromatic thiophene
rings, respectively (Figure 1). In addition, a 34π and 32π
conjugation pathway can be drawn for 1 and 2, respectively,
S
S
OBu
OBu
OBu
OBu
Mes
Mes
Mes
32
e

OBu
NH
N
OBu
BuO
OBu
S
S
S
S
N
N
N
H
H
N
N
HN
BuO
OBu
Porphycene
OBu
OBu
Mes
Figure 1. Representative resonance structures of the expanded porphycenes 1
and 2 (bold line indicates the cyclic conjugation pathway). Mes: 2-mesityl. The
structure of parent porphycene is also shown.
In both cases, butoxy groups are attached onto the
periphery to ensure good solubility and bulky mesityl groups are
attached to the reactive sites to improve stability. The
intermediate dialdehyde 5 was first synthesized by Stille coupling
between 5-iodo-3,4-dibutoxypyrrole-2-aldehyde 3 (see Scheme
S1 in SI) and 5,5′-trimethylstannyl-2,2′-bithiophene 4.[5] McMurry
coupling of 5 by using Zn/TiCl4/CuCl at room temperature (RT)
followed by aerial oxidation gave the desired product 1 in 30%
yield (Scheme 1). Stille coupling of 3 with (4-mesityl-4H-
cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl)bis(tributylstannane)
6 (see Scheme S2 in SI) afforded the dialdehyde 7 in 28% yield.
Subsequent McMurry coupling of 7 under reflux condition
followed by aerial oxidation generated the dihydro- expanded
porphycene 8 in 8% yield. Further oxidative dehydrogenation of 8
by p-chloranil at RT provided the desired product 2 in 30% yield.
Compounds 1 and 2 could be purified by column chromatography
over neutralized silica gel. The structure of compound 1 was
confirmed by NMR and single-crystal analysis (vide infra).
Compound 8 showed similar properties to that of 1 given that they
have the same π-conjugated backbone, and oxidative
dehydrogenation gave compound 2 with correct high-resolution
exact mass with error of 0.3 ppm (Figure S48 in SI). Solutions of
1 and 2 in toluene are very stable under ambient condition as
followed by absorption spectra (Figures S1- S2 in SI).
[a]
[b]
[c]
Dr. A. Rana, Dr. T. Y. Gopalakrishna, Dr. H. Phan, P. Yadav, Prof.
J. Wu
Department of Chemistry, National University of Singapore
3 Science Drive 3, 117543, Singapore (Singapore)
E-mail: chmwuj@nus.edu.sg
Y. Hong, Prof. D. Kim
Spectroscopy Laboratory for Functional π-Electronic Systems and
Department of Chemistry
Yonsei University, Seoul 120-749 (Korea)
E-mail: dongho@yonsei.ac.kr
Dr. T. S. Herng, Prof. J. Ding
Department of Materials Science and Engineering
National University of Singapore, 119260, Singapore (Singapore)
Supporting information for this article can be found under:
http://dx.doi.org/
This article is protected by copyright. All rights reserved.

10.1002/anie.201807411
Angewandte Chemie International Edition
COMMUNICATION
Pd(PPh3)4, CuI, DMF
The radical character of the expanded porphycenes 1 and 2
was calculated by spin-unrestricted DFT method (UCAM-
B3LYP/6-31G**, see more details in SI). Compound 1 was
calculated to have a moderate diradical character (y0 = 0.63) and
nearly zero tetraradical character (y1). However, compound 2 was
calculated to have moderate diradical character (y0 = 0.68) and
tetraradical character (y1 = 0.18), and thus can be regarded as an
open-shell tetraradicaloid. For both 1 and 2, the spin densities of
the singlet ground state are evenly delocalized over the whole π-
conjugated framework (Figure 2b), which can well explain their
exceptional stability. Moreover, the anisotropy of induced current
density (ACID)[8] plots for 1 and 2 display clockwise and counter-
clockwise ring current, representing aromatic and anti-aromatic
nature of these molecules, respectively (Figure 2c). The π
electrons are mainly delocalized along the peripheries, and a 34
and 32 πe conjugation pathway can be drawn for 1 and 2,
respectively (Figure 1). Accordingly, 1 and 2 should be aromatic
and anti-aromatic, respectively, according to Hückel rule. This is
further supported by the calculated nucleus independent chemical
shift[9] (NICS(0)) value at central position of -15.35 ppm and +9.75
ppm for 1 and 2, respectively.
110 °C, 36 h
69%
BuO
BuO
OHC
OBu
OBu
CHO
BuO
OBu
CHO
Me3Sn
S
S
5
I
NH
HN
N
H
3
S
H
S
SnMe3
4
Zn/TiCl4/CuCl
THF, rt, 16 h
30%
Mes
Pd(PPh3
)
4
1
CuI, DMF
110 °C, 36 h
28%
Bu3Sn
Mes
S
H
SnBu3
S
S
6
OBu
NH
OBu
BuO
Zn/TiCl4/CuCl
OBu
OBu
Mes
H
S
S
OBu
N
OBu
BuO
8
OBu
THF, reflux, 2 h
8%
S
S
NH
N
HN
7
HN
OHC
S
CHO
BuO
OBu
OBu
p-chloranil
rt, 2 h, 30%
2
Mes
H
Scheme 1. Synthesis of the expanded porphycenes 1 and 2. Mes: 2-mesityl.
X-ray crystallography analysis on a single crystal of 1
reveals
a
nearly planar conformation (Figure 2a).[6] The
bithiophene units in the macrocycle adopted a trans configuration
to avoid steric repulsion. However, the macrocyclic structure of
expanded porphycene 1 exhibits a slight out-of-plane distortion of
bithiophene part (Figure S3 in SI) due to steric repulsion of
opposite thiophene units. There is also intermolecular
bithiophene-bithiophene π-π stacking with a distance of about
3.44 Å (Figure S4 in SI). The bond lengths of pyrroles and cisoid
positions show a smaller bond length alternation compared to the
structurally resembled expanded porphycene analogue, i.e.,
octamethoxy[22]-porphyrin(2.2.2.2) (9, Figure 2a),[7] indicating
more effective cyclic conjugation in 1. However, we could not
1
The H NMR spectrum of 1 recorded in THF-d8 at RT only
gave well-resolved peaks for the butyl groups, and the
resonances for the aromatic region protons were fully broadened
(Figures S5-S8 in SI). Upon cooling down to 253 K, one broad
signal appeared at 8.81 ppm (4H) corresponding to the meso
protons a (see labelling in Figure 1), which gradually sharpened
upon further lowering the temperature. Like many other open-
shell singlet diradicaloids, the NMR broadening is due to the
existence of the thermally populated paramagnetic triplet
species.[1] The appearance of the resonance of protons a at low
field also indicates a global aromatic character of 1. Two
resonances at 5.04 (8H) and 4.84 ppm (8H) can be assigned to
the two sets of -OCH2- protons (b and c in Figure 1), and they are
also de-shielded. The NMR intensity decreased again at lower
temperatures due to partial precipitation of 1. The peak
corresponding to the beta protons of thiophene ring was not
observed, presumably due to aggregation. The 1H NMR spectrum
of 2 was fully broadened even at -60 oC (Figure S9 in SI),
indicating existence of more thermally populated triplet species
which is in consistent with the calculated larger diradical and
tetraradical character for 2.
crystallize 2 despite of our numerous effort.
(a)
9
1
(c)
(b)
1
1'
ESR measurements of compounds 1 and 2 either in solid or
in dichloromethane (DCM) gave featureless broad signal with ge
= 2.0030 and 2.0035, respectively (Figures 3a and 3c), in
accordance with effective spin delocalization in the entire cyclic
π-conjugated system (Figure 2b). The singlet-triplet energy gap
(ΔES-T) was evaluated by superconducting quantum interference
device (SQUID) measurements of the solid samples. The product
of the molar magnetic susceptibility and temperature (M•T) of 1
gradually increased above 150 K and fitting of the data by using
Bleaney-Bowers equation[10] gave a ΔES-T of -3.25 kcal/mol
(Figure 3b). Similarly, the M•T value of the porphycene 2 steadily
increased above 50 K and fitting resulted in a smaller ΔES-T of -
0.92 kcal/mol (Figure 3d). The SQUID measurements clearly
reveal that both compounds have open-shell singlet ground and
can be thermally populated to the lowest energy triplet excited
state, with a smaller excitation energy for 2 which is also in
consistent with the VT NMR measurements.
2'
2'
Figure 2. X-ray crystallographic structures and bond lengths (in Ă) of 1 along
with an expanded porphycene 9 for comparison. All alkoxy chains are omitted
for clarity. (b) Calculated spin distribution maps of the open-shell singlet states
of 1 and 2. (c) Calculated ACID plots of 1 and 2. The blue and red arrows
indicate diamagnetic and paratropic ring current flow, respectively. The butoxy
groups are replaced by methoxy during the calculations.
This article is protected by copyright. All rights reserved.

10.1002/anie.201807411
Angewandte Chemie International Edition
COMMUNICATION
1000
800
600
400
(a)
(a)
(b)
6
4
2
0
ES-T = -3.25 kcal/mol
1
200
0
400
800
1200
1600
Wavelength (nm)
(c)
(d)
(b)
1.2
0.8
0.4
0.0
ES-T = -0.92 kcal/mol
2
400
800
1200
1600
2000
Figure 3. ESR spectra of (a) 1 and (c) 2 measured in solid at state room
temperature. χMT-T curves in the SQUID measurement for the solid of (c) 1 and
(d) 2, the measured data were plotted as circles and the fitting curves were
drawn in red solid line.
Wavelength (nm)
Figure 4. (a) UV-vis-NIR absorption spectrum (black line) and TPA spectrum
(blue line) of 1, the TPA spectrum is plotted at λex/2. (b) UV-vis-NIR absorption
spectrum of 2. Inset are the photos for the solutions of 1 and 2 in DCM.
The UV-vis-NIR absorption spectrum of compound 1 in
DCM exhibits intense Soret-like (B-like) bands at 547/668 nm
along with distinct Q-like bands at 1006/1070/1170 nm (Figure 4a).
The Soret and Q-type bands are 87 and 311 nm bathochromically
shifted compared to those of 26π aromatic bronzaphyrin[11] due to
more extended π-conjugation. Compound 8 shows a similar
absorption spectrum to 1 due to a similar π-conjugation pathway
(Figure S10 in SI). However, the absorption spectrum of
compound 2 displays broad bands in the visible region (max = 433
nm) and a long tail band extended beyond 2000 nm (Figure 4b).
The weak long tail is typical feature of an anti-aromatic systems[12]
and/or molecules with large radical character.[13]
π-Conjugated molecules with moderate diradical character
were theoretically predicted to show enhanced third order non-
linear optical properties such as two-photon absorption (TPA).[14]
Therefore, TPA measurement of compound 1 was conducted by
using Z-scan technique in the wavelength range of 1800 to 2400
nm, where the contribution from one-photon absorption is
negligible. The highest TPA cross-section was measured to be
670 GM at 2000 nm in toluene (Figure 4a and Figure S11 in SI).
The enhanced TPA cross-section observed for 1, compared to the
previously reported TPA cross-section value for closed-shell
expanded porphycene 9 (380 GM at 1500 nm),[7] can be explained
by its relatively larger π-conjugation pathway and moderate
diradical character. Nevertheless, the TPA cross section value of
1 is not high compared with other polycyclic hydrocarbon and
porphyrinoid-based diradicaloids,1 presumably due to its
conformational flexibility.15 The excited state dynamics of 1 was
studied by femto-second transient absorption (TA) measurement
in toluene. The TA spectrum of 1 displayed ground-state
bleaching signals around 550 and 670 nm and broad excited-state
absorption signals in the range of 580-650 and 700-850 nm
(Figures S12-S13 in SI). The singlet excited state lifetime for
porphycene 1 was estimated to be 7 ps. The ultrafast decay could
be attributed to its moderate diradical character. However,
compound 2 underwent photo-degradation during the TA and
TPA measurements owing to its larger radical character, which
limited the accurate measurements.
Compound 1 displayed three reversible oxidation waves in
its cyclic voltammogram with half-wave potential E1/2ox at -0.43, -
0.36 and -0.04 V and one reversible reduction wave with half-
wave potential E1/2red at -1.04 V (vs Fc/Fc+) (Figures S14-15 in SI).
ox
Similarly, compound 2 exhibited four oxidation waves with E1/2
at -0.64, -0.54, -0.09 and +0.22 V and one reduction potential with
red
E1/2 at -1.45 V. A very small electrochemical HOMO-LUMO
energy gap of 0.61 eV and 0.81 eV was estimated for 1 and 2,
respectively. Compounds
1 and 2 can be oxidized into
corresponding dicationic form 1++ and 2++ after successive
addition of NO•SbF6 (Figures S16-S17 in SI). The dicationic state
of 1 was further proved by 1H NMR, where NH protons appeared
at 19.05 ppm (de-shielded) and the meso protons appeared at
5.95 ppm (shielded) (Figures S18-S19 in SI), indicating an anti-
aromatic character. Indeed, ACID plot of the dicationic species 1++
revealed a counter-clockwise paratropic ring current along the
periphery (Figure S24 in SI) and the NICS(0) value was calculated
to be +5.77 ppm at the center. However, no well-resolved 1H NMR
spectrum could be recorded for the dication of 2 and calculations
gave a large diradical character (y0 = 0.98).
In conclusion, we have introduced two bithiophene and
cyclopentabithiophene bridged cyclic conjugated aromatic and
anti-aromatic expanded porphycenes. Notably, the bithiophene
bridged expanded porphycene 1 is the one of the molecules in
octaphyrin family, which exhibits near planar structure, instead of
“figure eight” conformation. Our experimental and theoretical
evidences prove that these molecules possess open-shell singlet
ground state with a significant radical character and a small
singlet-triplet energy gap. Despite their open-shell character,
these expanded porphycenes are very stable under ambient air
and light conditions, which can be mainly explained by its effective
cyclic π-conjugation. The present work substantiated that cyclic
conjugation would provide additional stability of molecules with
open-shell ground state, and thus design and synthesis of stable
macrocyclic open-shell singlet diradicaloids and polyradicaloids
are feasible in the future, which is important for their practical
material applications.
This article is protected by copyright. All rights reserved.

10.1002/anie.201807411
Angewandte Chemie International Edition
COMMUNICATION
Acknowledgements
J. W. acknowledges financial support from the MOE Tier 3
program (MOE2014-T3-1-004). The work at Yonsei University
was supported by the National Research Foundation of Korea
(NRF) through a grant funded by Korean government (MEST)
(No. 2016R1E1A1A01943379).
Keywords: expanded porphyrin • porphycene • diradicaloid •
polyradicaloid • octaphyrin
[1]
[2]
(a) Z. Sun, Q. Ye, C. Chi, J. Wu, Chem. Soc. Rev. 2012, 41, 7857. (b) M.
Abe, Chem. Rev. 2013, 113, 7011. (c) Z. Sun, Z. Zeng, J. Wu, Acc. Chem.
Res. 2014, 47, 2582. (d) Z. Zeng, X. Shi, C. Chi, J. T. Lopez Navarrete,
J. Casado, J. Wu, Chem. Soc. Rev. 2015, 44, 6578. (e) T. Kubo, Chem.
Lett. 2015, 44, 111. (f) T. Y. Gopalakrishna, W. Zeng, X. Lu, J. Wu, Chem.
Commun. 2018, 54, 2186.
(a) S. Hiroto, K. Furukawa, H. Shinokubo, A. Osuka, J. Am. Chem. Soc.
2006, 128, 12380. (b) T. Koide, K. Furukawa, H. Shinokubo, J.-Y. Shin,
K. S. Kim, D. Kim, A. Osuka, J. Am. Chem. Soc. 2010, 132, 7246. (c) M.
Ishida, J.-Y. Shin, J. M. Lim, B. S. Lee, M.-C. Yoon, T. Koide, J. L. Sessler,
A. Osuka, D. Kim, J. Am. Chem. Soc. 2011, 133, 15533. (d) W. Zeng, S.
Lee, M. Son, M. Ishida, K. Furukawa, P. Hu, Z. Sun, D. Kim, J. Wu, Chem.
Sci. 2015, 6, 2427. (e) D. Shimizu, J. Oh, K. Furukawa, D. Kim, A. Osuka,
Angew. Chem. Int. Ed. 2015, 54, 6613. (f) D. Shimizu, J. Oh, K. Furukawa,
D. Kim, A. Osuka, J. Am. Chem. Soc. 2015, 137, 15584. (g) K. Naoda,
D. Shimizu, J. O. Kim, K. Furukawa, D. Kim, A. Osuka, Chem. Eur.
J. 2017, 23, 8969. (h) H. Zhang, H. Phan, T. S. Herng, T. Y.
Gopalakrishna, W. Zeng, J. Ding, J. Wu, Angew. Chem. Int. Ed. 2017,
56, 13484. (i) D. Shimizu, A. Osuka, Chem. Sci. 2018, 9, 1408.
E. Vogel, M. Kocher, H. Schmickler, J. Lex, Angew. Chem. Int. Ed. Engl.
1986, 25, 257.
[3]
[4]
(a) D. Sánchez-García, J. L. Sessler, Chem. Soc. Rev. 2008, 37, 215.
(b) J. Waluk, Chem. Rev. 2017, 117, 2447. (c) G. Anguera, D. Sánchez-
García, Chem. Rev. 2017, 117, 2481.
[5]
[6]
D. Chen, Y. Zhao, C. Zhong, S. Gao, G. Yu, Y. Liu, J. Qin, J. Mater.
Chem. 2012, 22, 14639.
Crystallographic data for 1: C68H86N4O8S4. Mw: 1215.64; triclinic; space
group P-1; a = 11.6268(5)Å, b = 14.3201(5) Å, c = 20.7425(8)Å, α =
101.074(2)°, β = 106.237(2)°,  = 98.075(2)°; V = 3184.2(2)Å3; Z = 2;
ρcalcd = 1.268 Mg/m3; R1 = 0.0518, wR2 = 0.1971 (I>2σ(I)); R1 = 0.0592,
wR2 = 0.1999 (all data). CCDC 1509699 (1), contains the supplementary
crystallographic data for this paper. These data are provided free of
charge by The Cambridge Crystallographic Data Centre (CCDC).
A. Rana, S. Lee, D. Kim, P. K. Panda, Chem. Eur. J. 2015, 21, 12129.
D. Geuenich, K. Hess, F. Kohler, R. Herges, Chem. Rev. 2005, 105,
3758.
[7]
[8]
[9]
P. v. R. Schleyer, C. Maerker, A. Dransfeld, H. J. Jiao, N. J. R. V.
Hommes, J. Am. Chem. Soc. 1996, 118, 6317.
[10] B. Bleaney, K. D. Bowers, Proc. R. Soc. London Ser. A1952, 214, 451.
[11] M. R. Johnson, D. C. Miller, K. Bush, J. J. Becker, J. A. Ibers, J. Org.
Chem. 1992, 57, 4414.
[12] J.-Y. Shin, K. S. Kim, M.-C. Yoon, J. M. Lim, Z. S. Yoon, A. Osuka, D.
Kim, Chem. Soc. Rev. 2010, 39, 2751.
[13] M. Nakano, K. Yoneda, R. Kishi, H. Takahashi, T. Kubo, K. Kamada, K.
Ohta, B. Champagne, E. Botek, AIP Conf. Proc. 2012, 1504, 136.
[14] (a) M. Nakano, H. Nagao, K. Yamaguchi, Phys. Rev. A 1997, 55, 1503.
(b) M. Nakano, R. Kishi, S. Ohta, H. Takahashi, T. Kubo, K. Kamada, K.
Ohta, E. Botek, B. Champagne, Phys. Rev. Lett. 2007, 99, 033001.
[15] (a) M. Drobizhev, F. Meng, A. Rebane, Y. Stepanenko, E. Nickel, C. W.
Spangler, J. Phys. Chem. B 2006, 110, 9802. (b) T. K. Ahn, K. S. Kim, D.
Y. Kim, S. B. Noh, N. Aratani, C. Ikeda, A. Osuka, D. Kim, J. Am. Chem.
Soc. 2006, 128, 1700. (c) M. Pawlicki, H. A. Collins, R. G. Denning, H. L.
Anderson, Angew. Chem. Int. Ed. 2009, 48, 3244.
This article is protected by copyright. All rights reserved.

10.1002/anie.201807411
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Ambient stable diradicaloid and
tetraradicaloid based on expanded
porphycene! Bithiophene and
cyclopentabithiophene bridged
expanded porphycenes were
synthesized, which show moderate
open-shell diradical and tetraradical
character, respectively. They are very
stable under ambient air and light
conditions due to extended cyclic
conjugation.
A. Rana, Y. Hong, T. Y. Gopalakrishna,
H. Phan, T. S. Herng, P. Yadav, J. Ding,
D. Kim,* and J. Wu*
Page No. – Page No.
Stable Expanded Porphycene Based-
Diradicaloid and Tetraradicaloid
This article is protected by copyright. All rights reserved.