Toward Full Zigzag-Edged Nanographenes: Peri-Tetracene and Its Corresponding Circumanthracene

Article abstract of DOI:10.1021/jacs.8b03711

Zigzag-edged nanographene with two rows of fused linear acenes, called as n-peri-acene (n-PA), is considered as a potential building unit in the arena of organic electronics. n-PAs with four (peri-tetracene, 4-PA), five (peri-pentacene, 5-PA) or more benz

Full text of DOI:10.1021/jacs.8b03711

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Communication
Toward Full Zigzag-Edged Nanographenes: peri-
Tetracene and Its Corresponding Circumanthracene
Murugan Rathamony Ajayakumar, Yubin Fu, Ji Ma, Felix Hennersdorf, Hartmut Komber, Jan J. Weigand,
Alexey Alfonsov, Alexey A. Popov, Reinhard Berger, Junzhi Liu, Klaus Müllen, and Xinliang Feng
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b03711 • Publication Date (Web): 08 May 2018
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Toward Full Zigzag-Edged Nanographenes: peri-Tetracene and Its Corre-
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sponding Circumanthracene
M. R. Ajayakumar,† Yubin Fu,† Ji Ma,† Felix Hennersdorf,‡ Hartmut Komber,⊥ Jan J. Weigand,‡ Alexey
Alfonsov,§ Alexey A. Popov,§ Reinhard Berger,† Junzhi Liu,*,† Klaus MüllenΔ and Xinliang Feng*,†
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†Center for Advancing Electronics Dresden (cfaed) & Faculty of Chemistry and Food Chemistry, Technische Univer-
sität Dresden, 01062 Dresden, Germany
‡Chair of Inorganic Molecular Chemistry, Technische Universität Dresden, 01062 Dresden, Germany
⊥Leibniz-Institut für Polymerforschung Dresden e. V., Hohe Straße 6, 01069 Dresden,
§Leibniz Institute for Solid State and Materials Research, 01069 Dresden, Germany
ΔMax Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Supporting Information Placeholder
(open-shell) in the ground state which can be explained by
the formation of additional Clar π-electron sextets for ren-
ABSTRACT: Zigzag-edged nanographene with two rows
of fused linear acenes, called as n-peri-acene (n-PA), is
dering additional aromatic stabilization energy. Among n-
considered as potential building unit in the arena of organic
PAs, perylene (2-peri-acene, 2-PA) was achieved for the first
electronics. n-PAs with four (peri-tetracene, 4-PA), five (peri-
time by Scholl et al. in 191010 and Clar reported the first syn-
pentacene, 5-PA) or more benzene rings in a row have been
thesis of bisanthene (3-peri-acene, 3-PA) in 1942.11 Both 2-PA
predicted to show open-shell character, which would be
attractive for the development of unprecedented molecular
spintronics. However, solution-based synthesis of open-shell
and 3-PA, as well as their derivatives, have since then be-
come attractive targets of materials chemistry.12-14 Higher n-
PAs (n ≥ 4) are theoretically predicted to show strong open-
n-PA has thus far not been successful because of the poor
shell properties by virtue of their narrow energy gaps, and,
chemical stability. Herein we demonstrated the synthesis
and characterization of the hitherto unknown 4-PA by a
rational strategy in which steric protection of the zigzag
hence their synthetic realization remained challenging.15
Despite the efforts from different research groups,16,17 the
next higher analogue, i.e., peri-tetracene (4-peri-acene, 4-PA,
edges playing a pivotal role. The obtained 4-PA possesses a
Scheme 1) has still remained elusive. Recently, peri-
singlet biradical character (y0 = 72%) and exhibits remarkable
pentacene (5-peri-acene, 5-PA) was accomplished under
persistent stability with a half-life time (t1/2) of ~ 3 h under
ultra-high vacuum (UHV) conditions on Au (III) surface,18
ambient conditions. UV-vis-NIR and electrochemical meas-
nevertheless, its scalable synthesis in solution remains to be
urements reveal a narrow optical/electrochemical energy gap
realized.
(1.11 eV) for 4-PA. Moreover, the bay regions of 4-PA enable
the efficient two-fold Diels-Alder reaction, yielding a novel
full zigzag-edged circumanthracene.
Scheme 1. Structures of perylene, bisanthene, bis-
tetracene and peri-tetracene.
Atomically precise nanographenes and graphene nanorib-
bons (GNRs)1,2 can be constructed with suitable oligo-
phenylene and polyphenylene precursors3 through oxidative
intramolecular cyclodehydrogenation. Advantageously, such
a rational bottom-up protocol can tune the energy gaps
through the molecular size, edge structures or incorporation
of appropriate heteroatoms.4,5 Among the nanographenes,
acene6 and n-peri-acene7 (n-PA) with rich zigzag edges are
potential candidates for organic field effect transistors
(OFETs), organic light-emitting diodes (OLEDs), organic
spintronics, etc.8 Acenes are linearly cata-condensed polycy-
clic aromatic hydrocarbons whereas n-PAs constitute two
rows of peri-fused acenes (Scheme 1). Typically, the solution
synthesis of longer acenes (larger than hexacenes) remains
elusive due to their poor stability under ambient conditions.9
Indeed, the longer acenes possess singlet biradical character
Herein we demonstrate the first solution synthesis of 4-PA
where steric protection of the zigzag periphery with appro-
priate phenyl substituents is essential. The successful for-
mation of 4-PA is supported by high-resolution (HR) matrix-
assisted laser desorption/ionization time-of-flight (MALDI-
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°
TOF) mass spectrometry, together with electron paramag-
netic spectroscopy (EPR) and NMR analysis. Owing to its
pronounced stability under inert conditions, 4-PA is isolated
and its optoelectronic properties are revealed by the aid of
UV-vis-NIR spectroscopy and cyclic voltammetry (CV). 4-PA
displays a remarkable redox active nature and the opti-
cal/electrochemical energy gap is found to be only 1.11 eV.
The strong open-shell character (y0 = 72%) of 4-PA is further
rationalized by density functional theory (DFT) and Hartree–
Fock (HF) calculations. Moreover, a two-fold Diels-Alder
reaction is established between the bay regions of 4-PA and
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) at room
temperature (RT), yielding a novel electron deficient tetracy-
ano-circumanthracene (TC-4-PA) with full zigzag-edged
structure.19
fonic acid in dry dichloromethane (DCM) at 0 C which af-
forded 6,15-bis(4-(tert-butyl)phenyl)-5,14-
1
2
3
4
5
6
7
8
diiodotetrabenzo[a,cd,j,lm]perylene (5) in 70% yield. Despite
the large steric hindrance generated by the iodine atoms, the
Scholl reaction was successful and the formation of 5 was
unequivocally confirmed by its crystal structure (Scheme 2,
Fig. S1a). Afterwards, double nucleophilic additions were
executed between n-butyllithium treated 5 and mesitalde-
hyde. Subsequent Friedel−Crafts cyclisation reaction pro-
moted by BF3•OEt2 provided precursor 6 in 50% yield. Single
crystals of 6 were grown by slow evaporation of its 1,1,2,2-
tetrachlorethane/acetonitrile solution, and its structure was
unambiguously confirmed (Scheme 2, Fig. S1b). It is notewor-
thy that the phenyl substituents at the periphery of 6 render
a fair solubility in non-polar organic solvents.
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Scheme 2: Synthesis of peri-tetracene (4-PA).
R1
R1
R1
R1
I
I
I
I
Br
Br
(i)
(ii)
(iv)
(iii)
Br
Br
1
I
I
5
2
3
R1
R1
4
R1
R1
R1
R2
R2
R2 R1
R1
(vi)
(v)
Figure 1: HR MALDI-TOF mass spectra of 4-PA.
R1 R2
R1 R2
To examine the desired 4-PA formation, precursor 6 was
dehydrogenated with a slight excess of DDQ (~ 1.2 equiv.) in
dry toluene at RT. The reaction mixture was purified by silica
column chromatography with degassed DCM/acetonitrile as
eluent under inert conditions and submitted for HR MALDI-
TOF analysis (Fig. 1). At positive mode, an intense signal at
948.469 was obtained which is consistent with the calculated
value of m/z 948.470 [M+]. The isotopic distribution was in
agreement with the simulated spectra and hence supported
the formation of 4-PA. To obtain a better insight, the reac-
4-PA
6
Reagents and conditions: (i) 4-tert-butylphenylacetylene,
PdCl2(PPh3)2, CuI, Et3N, THF, RT, 24 h, 87%; (ii) Pd(PPh3)4,
°
K2CO3, p-dioxane/H2O, 110 C, 24 h, 92%; (iii) ICl, toluene, -
°
°
78 C, 3 h, 93%; (iv) DDQ, CF3SO3H, DCM, -10 C, 30 min,
°
70%; (v) 1) n-BuLi, mesitaldehyde, toluene, -10 C, 2 h; 2)
BF3·OEt2, DCM, RT, 30 min, 50% (two steps); (vi) DDQ,
toluene, RT, 1 h, quantitative yield. Crystal structures of 5
and 6 are shown where displacement ellipsoids are drawn at
20 and 50% probability level for 5 and 6, respectively, and the
hydrogen atoms and solvent molecules are omitted for clarity
(grey, C; pink, I).
1
tion of 6 with 1-5 equiv. of DDQ was monitored by H NMR
spectroscopy (Fig. 2a and S4). With the addition of 1 equiv.
DDQ in 1,1,2,2-tetrachloroethane-d2 (C2D2Cl4) solution of 6
under inert conditions and RT, the color of the solution
instantly changed from bright yellow to dark brown and the
aromatic signals of 6 had nearly vanished. The solution did
not show any new signals in the aromatic region, which
suggested the presence of open-shell 4-PA. Cooling the solu-
tion of 6 with 1 or 2 equiv. of DDQ or the chromatographical-
ly isolated product over a temperature range from RT to –60
°C did not show significant changes, but rather remained
silent in the aromatic region (Fig. S5-S8). Such a behavior
can be expected for species with strong biradical character.21
We also detected an intense EPR signal of solid 4-PA, which
we ascribed to its open-shell feature (Fig. S9). Notably, by
treating 6 with excess equivalents of DDQ (5 equiv.) for an
Recently, bis-tetracene (Scheme 1) has been synthesized by
our group.16c However, due to its poor stability, its oxidative
dehydrogenation to generate 4-PA remained an arduous
task. Therefore, we turned to a different design, where the
fairly stable precursor (8,16-bis(4-(tert-butyl)phenyl)-7,15-
dimesityl-7,15-dihydrotetrabenzo[bc,ef,kl,no]coronene,
6)
was synthesized firstly, which could afford 4-PA upon dehy-
drogenation under mild reaction conditions (Scheme 2). It is
also crucial to kinetically block the active zigzag edges of
targeted 4-PA by using phenyl substituents. Towards a de-
tailed synthesis, we firstly prepared 4,4'-((2,5-dibromo-1,4-
phenylene)bis(ethyne-2,1-diyl))bis(tert-butylbenzene)
from 1,4-dibromo-2,5-diiodobenzene (1) via Sonagashira
coupling.20
two-fold Suzuki coupling of with 2-
(2)
1
extended reaction time (~ 5 days) at RT, the H NMR spec-
trum features a new set of resonance in the aromatic region
(Fig. 2a). Based on our analysis, these peaks can be attributed
to the formation of a novel full zigzag-edged circumanthra-
cene (CA) derivative with four cyano groups (TC-4-PA, vide
infra, Fig. 2b). The TC-4-PA (yield ~ 30%) was obtained via a
two-fold Diels-Alder reaction between the bay regions of in-
situ generated 4-PA (dienes) and CN-C=C-CN (dienophiles)
of DDQ (Fig. S10).22
A
2
biphenylboronic acid gave 1,4-bis(2’-biphenyl)-2,5-bis(4-
(tert-butyl)phenyl)ethynylbenzene (3) in 92% yield. ICl-
mediated benzannulation was performed to convert 3 into
5,12-bis(4-(tert-butyl)phenyl)-6,13-diiodo-1,8-
diphenylbenzo[k]tetraphene (4) in 93% yield. Next, we car-
ried out the Scholl reaction of 4 with 2,3-dichloro-5,6-
dicyano-1,4-benzoquinone (DDQ) and trifluoromethanesul-
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The optoelectronic and electrochemical properties of 4-PA
play a disjoint feature. The zigzag C atoms, which are
blocked with phenyl substituents, possess the highest spin
densities (0.44) compared to the unprotected ones (0.23)
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2
3
4
5
6
7
8
were examined with UV-vis-NIR, CV and differential pulse
voltammetry (DPV) measurements (Fig. 3 and S11). As shown
in Fig. 3a, a solution of isolated 4-PA in DCM showed clear
vibronic structures with an intense absorption at 881 nm
along with two shoulders at 788 and 1021 nm in the NIR
region. The optical energy gap (Egopt) was determined to be
1.11 (±0.01) eV based on the lowest energy absorption onset.
In order to investigate the stability of 4-PA under ambient
condition, we exposed the solution to air and continued to
measure the absorption spectra at different time intervals.
Notably, the pale brownish-green colored solution gradually
changed to brown and the spectra displayed increasing ab-
sorptions in the region between 385-745 nm with concomi-
tant decrease of the peak intensities in the UV and NIR re-
gions. A plot of the absorbance change at 881 nm against
(Fig. S36). In addition, the singlet-triplet energy gap (ΔES–T
)
of 4-PA is -0.994 kcal mol-1 (UCAM-B3LYP/6-31G*), indicat-
ing the singlet biradical ground state.
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time shows a gradual intensity decrease and the half-life (t1/2
)
Figure 3: a) UV-vis-NIR spectra of isolated 4-PA and its
time-dependent absorption changes under ambient condi-
tions in DCM. Inset shows the absorbance change at 881 nm
with respect to time, and color change of the solution before
and after air exposure. b) CV and DPV of 4-PA in a 0.1 M
solution of TBAPF6 in DCM.
was found to be ~ 3 h. CV and DPV of 4-PA (Fig. 3b) were
performed in DCM solution containing 0.1 M of TBAPF6 (vs
Ag/AgCl). One reversible and one pseudo-reversible oxida-
tion occurred at 0.21 (E1ox) and 0.73 V (E2ox), respectively,
whereas one irreversible and one reversible reduction was
seen at -0.90 (E1red) and -1.31 V (E2red), respectively. Each
oxidation and reduction waves are accounted to respective
one-electron redox process. Accordingly, the frontier orbitals
are calculated as HOMO = -4.61 eV and LUMO = -3.50 eV,
The formation of TC-4-PA was unambiguously proven by X-
ray crystallography (Fig. 4 and S2). The 4-tert-butylphenyl
and mesityl groups are bent 8.37 and 4.57o, respectively, in
opposite directions and severely twisted against the cores.
Notably, the CN groups situated at the core positions show a
torsional angle of 5.41o. The bond length analysis of TC-4-PA
reveals that the C-C bonds at the peri-position, i.e., a and b
show stronger double-bond character compared to the other
C-C bonds of the CA core, which is estimated to be 1.35 Å.
The unusual lengthening of d bond (1.44 Å) could be due to
the steric effects of the zigzag substituents. The optical prop-
erties of TC-4-PA in C2H2Cl4 (1 μM) were examined by UV-vis
and fluorescence spectroscopies (Fig. S12). The green solu-
tion of TC-4-PA shows absorption peaks at 396, 416, 594, 623,
and 644 nm. Moreover, TC-4-PA exhibits moderate fluores-
cence emissions at 650 and 707 nm (quantum yield Φf = 15%
by using rhodamine-6g as standard). TC-4-PA possesses an
optical energy gap (Egopt) of 1.89 eV, which is extracted from
the onset of λmax = 644 nm. The electrochemical behavior of
TC-4-PA (Fig. S13) was investigated by CV in dry DCM (vs
Ag/AgCl). The HOMO and LUMO levels are estimated to be
-5.48 and -3.60 eV, respectively, based on the first oxidation
and the first reduction onset potentials. Hence, the electro-
which gave an electrochemical energy gap (EgEC) of 1.11 eV
opt
that is consistent with the Eg
.
chemical energy gap (EgEC) of TC-4-PA is 1.88 eV, in good
opt
accordance with Eg
.
1
Figure 2: a) H NMR spectra (600 MHz, RT, C2D2Cl4) of 6
and DDQ-treated 6 (i, 6; ii, 6 + 1 equiv. DDQ, 20 min; iii, 6 +
2 equiv. DDQ, 20 min; iv, 6 + 5 equiv. DDQ, 20 min; v, 6 + 5
equiv. DDQ after 5 days, vi, isolated TC-4-PA). b) Reaction
pathway shows the formation of 4-PA, from 6 with 1 equiv. of
DDQ, and its two fold Diels-Alder reaction capability with
excess of DDQ that yields TC-4-PA.
For a deeper insight into the electronic nature of 4-PA, den-
sity functional theory (DFT) analysis was performed using
Gaussian 09. The occupation numbers of the natural orbitals
revealed the singlet biradical index (y0) of 72% (UHF/6-31G*),
which is significantly larger than the previously reported bis-
tetracene (y0 = 61%).16c As depicted in Fig. S36, the singly
occupied molecular orbital (SOMO) profiles of α and β dis-
Figure 4: X-ray crystal structure of TC-4-PA (top and side
views). Hydrogen atoms and solvent molecules are omitted
for clarity. Ellipsoids are drawn at 50% probability level.
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5.
(a) Bronner, C.; Stremlau, S.; Gille, M.; Brauße, F.; Haase, A.;
Hecht, S.; Tegeder, P. Angew. Chem. Int. Ed. 2013, 52, 4422-
4425. (b) Berger, R.; Giannakopoulos, A.; Ravat, P.; Wagner,
M.; Beljonne, D.; Feng, X.; Müllen, K. Angew. Chem. Int. Ed.
2014, 53, 10520-10524.
In conclusion, we have reported the efficient synthesis of 4-
PA. Our rational approach utilized suitable phenyl groups at
the spin active zigzag positions rendering sufficient steric
protection as well as adequate solubility in common organic
solvents. The achieved 4-PA possesses remarkable stability
under ambient conditions, which facilitates in-depth charac-
terizations. The singlet biradical character of 4-PA is corrob-
orated by the narrow optical/electrochemical energy gap (1.11
eV). Importantly, a novel full zigzag-edged TC-4-PA was
obtained via a two-fold Diels-Alder reaction between 4-PA
and DDQ. The synthesis developed in the current work offers
access not only to the next higher homologues of n-PAs, but
also to the corresponding circumacenes (CA) under mild
reaction conditions.
1
2
3
4
5
6
7
8
6. (a) Clar, E. Ber. Dtsch. Chem. Ges. A/B, 1939, 72, 2137-2139. (b)
Wang, C.; Dong, H.; Hu, W.; Liu, Y.; Zhu, D. Chem. Rev. 2012,
112, 2208-2267.
7.
(a) Ye, Q.; Chi, C. Chem. Mater. 2014, 26, 4046-4056. (b) Sun,
Z.; Ye, Q.; Chi, C.; Wu, J. Chem. Soc. Rev. 2012, 41, 7857-7889.
(c) Sun, Z.; Zeng, Z.; Wu, J. Acc. Chem. Res. 2014, 47, 2582-
259.
(a) Joachim, C.; Gimzewski, J. K.; Aviram, A. Nature, 2000,
408, 541. (b) Bendikov, M.; Wudl, F.; Perepichka, D. F. Chem.
Rev. 2004, 104, 4891-4946. (c) Sirringhaus, H. Adv. Mater.
2005, 17, 2411-2425; (d) Anthony, J. E. Chem. Rev. 2006, 106,
5028-5048. (e) Allard, S.; Forster, M.; Souharce, B.; Thiem,
H.; Scherf, U. Angew. Chem. Int. Ed. 2008, 47, 4070-4098. (f)
Tao, Y.; Yang, C.; Qin, J. Chem. Soc. Rev. 2011, 40, 2943-2970.
9
8.
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
ASSOCIATED CONTENT
Supporting Information
9. (a) Krüger, J.; García, F.; Eisenhut, F.; Skidin, D.; Alonso, J.
M.; Guitián, E.; Pérez, D.; Cuniberti, G.; Moresco, F.; Peña, D.
Angew. Chem. Int. Ed. 2017, 56, 11945. (b) Einholz, R.; Fang,
T.; Berger, R.; Grüninger, P.; Früh, A.; Chassé, T.; Fink, R. F.;
Bettinger, H. F. J. Am. Chem. Soc. 2017, 139, 4435-4442. 18
10. (a) Scholl, R.; Mansfeld, J. Ber. Dtsch. Chem. Ges. 1910, 43,
1734-1746. (b) Scholl, R.; Seer, C.; Weitzenböck, R. Ber. Dtsch.
Chem. Ges. 1910, 43, 2202- 2209.
The Supporting Information is available free of charge on the
ACS Publications website. Experimental details, synthesis, X-
ray crystallography details, HR mass spectra, NMR spectra
and computational studies.
AUTHOR INFORMATION
Corresponding Author
11. (a) Clar, E. Chem. Ber. 1948, 81, 52-63. (b) Clar, E. Chem. Ber.
1949, 82, 46-60.
12. (a) Akamatu, H.; Inokuchi, H.; Matsunaga, Y. Nature 1954,
173, 168-169. (b) Würthner, F. Chem. Commun. 2004, 1564-
1579.
13. (a) Clar, E. Nature 1948, 161, 238-239. (b) Fort, E. H.; Do-
novan, P. M.; Scott, L. T. J. Am. Chem. Soc. 2009, 131, 16006-
16007. (c) Fort, E. H.; Scott, L. T. Angew. Chem. Int. Ed. 2010,
49, 6626-6628.
14. (a) Zhang, K.; Huang, K.-W.; Li, J.; Luo, J.; Chi, C.; Wu, J.
Org. Lett. 2009, 11, 4854-4857. (b) Li, J.; Zhang, K.; Zhang, X.;
Huang, K.-W.; Chi, C.; Wu, J. J. Org. Chem. 2010, 75, 856-863.
15. (a) Jiang, D.-e.; Dai, S. Chem. Chem. Phys. Lett. 2008, 466,
72-75. (b) Sancho-García, J. C.; Pérez-Jiménez, A. J. Phys.
Chem. Chem. Phys. 2009, 11, 2741-2746. (c) Plasser, F.; Pašalić,
H.; Gerzabek, M. H.; Libisch, F.; Reiter, R.; Burgdörfer, J.;
Müller, T.; Shepard, R.; Lischka, H. Angew. Chem. Int. Ed.
2013, 52, 2581-2584. (d) Malrieu, J.-P.; Trinquier, G. J. Phys.
Chem. A 2016, 120, 9564-9578.
16. (a) Zhang, X.; Li, J.; Qu, H.; Chi, C.; Wu, J. Org. Lett. 2010, 12,
3946-3949. (b) Zöphel, L.; Berger, R.; Gao, P.; Enkelmann, V.;
Baumgarten, M.; Wagner, M.; Müllen, K. Chem. Eur. J. 2013,
19, 17821-17826. (c) Liu, J.; Ravat, P.; Wagner, M.;
Baumgarten, M.; Feng, X.; Müllen, K. Angew. Chem. Int. Ed.
2015, 54, 12442-12446.
17. Wang, X.-Y.; Narita, A.; Zhang, W.; Feng, X.; Müllen, K. J.
Am. Chem. Soc. 2016, 138, 9021-9024.
18. Rogers, C.; Chen, C.; Pedramrazi, Z.; Omrani, A. A.; Tsai, H.-
Z.; Jung, H. S.; Lin, S.; Crommie, M. F.; Fischer, F. R. Angew.
Chem. Int. Ed. 2015, 54, 15143-15146.
19. Broene, R. D.; Diederich, F. Tetrahedron Lett. 1991, 32, 5227-
5230
20. Arslan, H.; Uribe-Romo, F. J.; Smith, B. J.; Dichtel, W. R.
Chem. Sci. 2013, 4, 3973-3978.
21. Konishi, A.; Hirao, Y.; Matsumoto, K.; Kurata, H.; Kishi, R.;
Shigeta, Y.; Nakano, M.; Tokunaga, K.; Kamada, K.; Kubo, T.
J. Am. Chem. Soc. 2013, 135, 1430-1437.
22. London, G.; von Wantoch Rekowski, M.; Dumele, O.;
Schweizer, W. B.; Gisselbrecht, J.-P.; Boudonb, C.; Diederich,
F. Chem. Sci. 2014, 5, 965-972.
*xinliang.feng@tu-dresden.de
*junzhi.liu@tu-dresden.de
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
This work was financially supported by ERC grants on
2DMATER, the European Union’s Horizon 2020 research and
innovation programme under grant agreement No 696656
(Graphene Flagship Core1), Center for Advancing Electronics
Dresden (cfaed), European Social Fund and the Federal State
of Saxony (ESF-Project “GRAPHD”, TU Dresden). J. J. W.
thanks the DFG for funding a Rigaku Oxford Diffraction
SuperNova system with a dual source (INST 269/618-1). The
authors acknowledge the use of computational facilities at
the Center for information services and high performance
computing at TU Dresden.
REFERENCES
1.
(a) Wu, J.; Pisula, W.; Müllen, K. Chem. Rev. 2007, 107, 718–
747. (b) Chen, L.; Hernandez, Y.; Feng, X.; Müllen, K. Angew.
Chem. Int. Ed. 2012, 51, 7640-7654. (c) Narita, A.; Wang, X.-
Y.; Feng, X.; Müllen, K. Chem. Soc. Rev. 2015, 44, 6616-6643.
Liu, J.; Li, B.-W.; Tan, Y.-Z.; Giannakopoulos, A.; Sanchez-
Sanchez, C.; Beljonne, D.; Ruffieux, P.; Fasel, R.; Feng, X.;
2.
3.
Müllen, K. J. Am. Chem. Soc. 2015, 137, 6097-6103.
(a) Clar, E. Polycyclic Hydrocarbons; Academic Press: Lon-
don and New York, 1964; Vols. 1, 2. (b) Wang, X.-Y.; Narita,
A.; Müllen, K. Nat. Rev. Chem. 2017, 2, 00100.
4. (a) Chen, Y.-C.; de Oteyza, D. G.; Pedramrazi, Z.; Chen, C.;
Fischer, F. R.; Crommie, M. F. ACS Nano 2013, 7, 6123-6128.
(b) Cai, J.; Pignedoli, C. A.; Talirz, L.; Ruffieux, P.; Söde, H.;
Liang, L.; Meunier, V.; Berger, R.; Li, R.; Feng, X.; Müllen, K.;
Fasel, R. Nat. Nanotechnol. 2014, 9, 896-900.
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