Synthesis, Photophysical, and Electrochemical Properties of Pyrenes Substituted with Donors or Acceptors at the 4- or 4,9-Positions

Article abstract of DOI:10.1021/acs.joc.7b03227

We report herein an efficient and direct functionalization of the 4,9-positions of pyrene by Ir-catalyzed borylation. Three pinacol boronates (-Bpin), including 4-(Bpin)-2,7-di(tert-butyl)pyrene (5), 4,9-bis(Bpin)-2,7-di(tert-butyl)pyrene (6), and 4,10-bis(Bpin)-2,7-di(tert-butyl)pyrene (7), were synthesized. The structures of 6 and 7 have been confirmed by single-crystal X-ray diffraction. To demonstrate the utility of these compounds, donor (NPh₂)-substituted compounds 4-diphenylamino-2,7-di(tert-butyl)pyrene (1) and 4,9-bis(diphenylamino)-2,7-di(tert-butyl)pyrene (2) have been synthesized on a gram scale. Acceptor (BMes₂)-substituted compounds 4,9-bis(BMes₂)pyrene (3) and 4,9-bis(BMes₂)-1,2,3,6,7,8-hexahydropyrene (4) were synthesized for comparison. The photophysical and electrochemical properties of compounds 1-4 have been studied both experimentally and theoretically. The S₀ → S₁ transitions of the 4- or 4,9-disubstituted pyrenes, 1-3, are allowed, with moderate fluorescence quantum yields and radiative decay rates. The photophysical and electrochemical properties of 1-3 were compared with the 2,6-naphthalenylene-cored compound 4 as well as the previously reported 2,7- and 1,6- pyrenylene-cored compounds.

Full text of DOI:10.1021/acs.joc.7b03227

Subscriber access provided by Stockholm University Library
Article
Synthesis, Photophysical, and Electrochemical Properties of Pyrenes
Substituted with Donors or Acceptors at the 4- or 4,9-Positions
Lei Ji, Ivo Krummenacher, Alexandra Friedrich, Andreas Lorbach, Martin
Haehnel, Katharina Edkins, Holger Braunschweig, and Todd B Marder
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b03227 • Publication Date (Web): 26 Feb 2018
Downloaded from http://pubs.acs.org on February 26, 2018
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
The Journal of Organic Chemistry is published by the American Chemical Society.
1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the
course of their duties.

Page 1 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Synthesis, Photophysical, and Electrochemical Properties of Pyrenes
Substituted with Donors or Acceptors at the 4- or 4,9-Positions
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
Lei Ji, Ivo Krummenacher, Alexandra Friedrich, Andreas Lorbach,+ Martin Haehnel,
Katharina Edkins,† Holger Braunschweig, Todd B. Marder*
Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis
with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg,
Germany
ABSTRACT: We report herein an efficient and direct functionalization of the
4,9-positions of pyrene by Ir-catalyzed borylation. Three pinacol boronates (-Bpin),
including
4-(Bpin)-2,7-di-(tert-butyl)pyrene
(6),
(5),
4,9-bis(Bpin)-2,7-di-(tert-butyl)pyrene
and
4,10-bis(Bpin)-2,7-di-(tert-butyl)pyrene (7) were synthesized. The structures of 6 and
7 have been confirmed by single-crystal X-ray diffraction. To demonstrate the utility
of
these
compounds,
donor
(NPh2)
substituted
compounds
4-diphenylamino-2,7-di-(tert-butyl)pyrene
(1)
and
4,9-bis(diphenylamino)-2,7-di-(tert-butyl)pyrene (2) have been synthesized on a gram
scale. Acceptor (BMes2) substituted compounds 4,9-bis(BMes2)pyrene (3) and
4,9-bis(BMes2)-1,2,3,6,7,8-hexahydropyrene (4) were synthesized for comparison.
The photophysical and electrochemical properties of compounds 1-4 have been
studied both experimentally and theoretically. The S0S1 transitions of the
4,9-disubstituted pyrenes, 1-3, are allowed, with moderate fluorescence quantum
yields and radiative decay rates. The photophysical and electrochemical properties of
1-3 were compared with the 2,6-naphthalenylene-cored compound 4 as well as the
previously reported 2,7- and 1,6- pyrenylene-cored compounds.
INTRODUCTION
Organic π-conjugated compounds, such as polycyclic aromatic hydrocarbons
(PAHs), are of fundamental importance in organic electronics.1 These compounds
have been used in flexible organic semiconductor devices and as luminescent
1
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 2 of 19
1
2
3
4
5
6
7
8
materials. Because the demands of material properties are diverse, electron donors or
acceptors with different strengths are introduced onto the PAH core to adjust the
HOMO and LUMO levels of PAHs, and thus their photophysical and electrochemical
properties.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. The position numbering system in pyrene and the chemically reactive
positions
Besides the donor/acceptor strength, the positions at which the PAHs are substituted
are very important. For example, the HOMO/LUMO of pyrene have their largest
co-efficients at the 1,3,6,8-positions, and thus their mixing with the π-orbitals of
substituents at these positions is very efficient.1 In comparison, the π-orbitals of
substituents at the 2,7-positions of pyrene (Scheme 1), which lie on the nodal planes
of both the HOMO and LUMO, do not interact with the HOMO and LUMO, but do
interact strongly with the HOMO-1 and LUMO+1 of pyrene.2-5 Therefore, we have
reported recently that the photophysical properties of 1- and 2- substituted pyrenes
differ.6 We also found that substitution at the 2,7-positions of pyrene with strong
donor or acceptor moieties can switch the energy ordering of its HOMO/HOMO-1
and LUMO/LUMO+1, respectively.3-4, 7 For example, the unpaired electron in
reduced 2-(BMes2)pyrene and 2,7-bis(BMes2)pyrene (i.e. their radical anions) is
delocalized between the -BMes2 groups and pyrene.7
While the 1,3,6,8-positions of pyrene can be easily substituted by direct
electrophilic reactions,1 such as halogenation, the sterically directed Ir-catalyzed C-H
borylation of pyrene reported by Marder et al. has recently facilitated the synthesis of
a wide range of 2- and 2,7- substituted pyrenes, as the pinacol boronates can be
converted to numerous other substituents.8-9 However, the functionalization of pyrene
at the K-region is still limited by either low overall yield in multi-step syntheses, or
the variety of structures that could be prepared.10-19 For example, 4,9-dibromopyrene
was synthesized in three steps, including reduction with sodium, bromination with
bromine, and dehydrogenation with Chloranil or DDQ, in low overall yield. In fact,
2,7-di-(tert-butyl)-4,9-dibromopyrene has been synthesized by direct bromination of
2,7-di-(tert-butyl)pyrene, but with a very low yield (3%).20 The synthesis of
4,10-substituted pyrenes is even less well documented.
2
ACS Paragon Plus Environment

Page 3 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
In our recent publications, we noted that Ir-catalyzed C-H borylation can be used to
borylate the K-region of pyrene when its 2,7-positions have already been substituted,
although the K-region is less active than the 2,7-positions.21-23 This approach could
provide a more efficient way to synthesize 4,9- and 4,10- disubstituted pyrenes. In this
paper, we provide examples of the synthesis of 4-, 4,9- and 4,10- substituted pyrenes.
As exemplifying examples (Scheme 2), the electron donor- (NPh2) and acceptor-
(BMes2)24-29 substituted compounds 1-3 have been synthesized, and their
electrochemical and photophysical properties have been studied. We also note that the
substituent at the 4- position does not communicate strongly with that at the 9-
position. The naphthalene-cored bis(BMes2) compound 4 has been prepared for
comparison with 3, using 1,2,3,6,7,8-hexahydropyrene instead of naphthalene to
achieve a similar BMes2/arylene twist to that in 3.
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
Scheme 2. The chemical structures of compounds 1-4
RESULTS AND DISCUSSION
Synthesis. Firstly, borylation of 2,7-di-(tert-butyl)pyrene using [Ir(COD)(OMe)]2 (5%)
as the pre-catalyst and 4,4′-di-(tert-butyl)-2,2′-dipyridyl (dtbpy, 10%) as the ligand in
THF solvent gave a mixture of 5, 6, and 7 with a ratio of 1:1.8:1.4 (Scheme 3).
Chromatography on silica gel, which had been pre-deactived by boric acid,30 allowed
the separation of the monoboronate ester 5 from the mixture of bisboronates 6 and 7.
The monoboronate 5 was converted to the monobromide 8 in a 99% yield by
refluxing with excess CuBr2.31 The bisboronates 6 and 7 could not be readily
separated by column chromatography, but we noted that the solubility of those two
compounds are quite different in hexane, methanol, and ethanol. Thus, the mixture
was suspended in methanol in a centrifuge tube, and the centrifuge tube was placed
into an ultrasonic bath for 2 h. After centrifugation, the 1H NMR spectrum shows that
the undissolved solid is pure 6, and the mother liquor contains predominantly 7
contaminated with 6.32 The purification of 7 is more difficult and only a small amount
3
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 4 of 19
1
2
3
4
5
6
7
8
9
of 7 has been isolated. The boronate esters 5-7 can be very efficient precursors for the
preparation of many K-region substituted pyrenes. Boronate ester 6 was converted to
2,7-di-(tert-butyl)-4,9-dibromopyrene 9 in 91% isolated yield, by employing the same
procedure as used for the synthesis of 8. The overall yield of
2,7-di-(tert-butyl)-4,9-dibromopyrene (9) from 2,7-di-(tert-butyl)pyrene is 21%,
which is much higher than that of previously reported methods.20
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
We also prepared 4,9-dibromopyrene, 13, via the previously reported ‘indirect
method’.33 By reduction of pyrene with 9 eq. of sodium in refluxing pentanol at 150
oC, 1,2,3,6,7,8-hexahydropyrene (10) can be isolated in only ca. 20% yield.
Bromination of 10 gave a white precipitate (43% yield), which is
4,9-dibromo-1,2,3,6,7,8-hexahydropyrene (11)34 contaminated with 10% of
1
4,10-dibromo-1,2,3,6,7,8-hexahydropyrene (12). We then checked the H NMR
spectra of the filtrate, which revealed that it contains a mixture of 11 and 12 in a ratio
1
of 1 : 1.7. In fact, a H NMR spectrum of the crude reaction mixture reveals that the
bromination of 10 gives 11 and 12 in a ratio of 1.7 : 1. Following subsequent
dehydrogenation of 11 with Chloranil or DDQ, the overall yield of 13 in the three-step
procedure from pyrene is only ca. 5%.
Scheme 3. Synthesis of compounds 1-4
4
ACS Paragon Plus Environment

Page 5 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
With bromides 8 and 9 in hand, the mono- and bis(diphenylamino)pyrenes 1 and 2
were synthesized via Buchwald-Hartwig amination,35-36 using Pd2(dba)3•CHCl3 (0.3
mol %; dba = dibenzylideneacetone) as precatalyst, SPhos (1 mol %; SPhos =
2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl) as ligand, and NaOtBu as base, in
high isolated yields (ca. 80%) and on a multi-gram scale. Compounds 3 and 4 were
synthesized in moderate yields by lithiation of 13 and 11, respectively, followed by
borylation with Mes2BF. While compound 3 was obtained as yellowish crystals,
compound 4 is a deep yellow crystalline compound, indicating the red-shifted
absorption of 4.
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
X-ray Crystal Structures. The solid-state structures 1, 3, 4, 6, and 7 were confirmed
by single-crystal X-ray diffraction. Crystal data and experimental details are listed in
Table S1 in the Supporting Information (SI). Their molecular structures are presented
in Figures S1-S5, and the key bond lengths and angles are summarized in Tables S2
and S3 in the SI. There are no strong inter-molecular interactions, such as π-π stacking,
in the crystal structures of 1, 3, 4, 6, and 7. The dihedral angles between the BC3
plane37 and the arylene-bridge in 3 (average 43.9(1) o) and 4 (43.7(1) o) are similar. It
has been noted that the C4C5 and C9C10 bonds in the K-region of pyrene can be
considered to be isolated C=C double bonds,38 which are not significantly affected by
the substituents at the 2- or 2,7- positions, even in the reduced form of
2,7-bis(BMes2)pyrene.3, 7 However, in all structures reported herein, the C4C5 and/or
C9C10 double bonds are longer than those in unsubstituted pyrene.
Photophysical Properties. The UV-Vis absorption and emission spectra of
compounds 1-4 have been measured, and those in hexane are summarized in Figure 1
and Table 1. The lowest energy absorption bands of 1-4 are broad and correspond to
intramolecular charge transfer (ICT) transitions (vide infra) between the arylene-core
and substituents. The S0S1 transitions of 1-4 are all allowed, with molar extinction
coefficients of 7200-14900 M-1cm-1 (Table 1, and Figure S6 in the SI). The two lowest
energy absorption bands between 350 and 425 nm of monoamine 1 are weaker than
those of the diamine 2, indicating that they are related to the diphenylamino group(s).
There are several intense pyrene-like transitions in the higher energy region (249, 279,
and 337 nm) in mono-substituted compound 1, which are either weaker or not
noticeable in the disubstituted pyrenes 2 and 3. The lowest energy transition of 2 in
hexane is red-shifted by only 6 nm (385 cm-1) from that of 1. This red-shift is less
than the corresponding bathochromic shift of 2,7-bis(BMes2)pyrene from
2-(BMes2)pyrene,6-7 as well as of 1,6- or 1,3- bis(BMes2)pyrene from
1-(BMes2)pyrene.6, 39 These indicate that there is less electronic coupling between
substituents at the 4- and 9- positions of pyrene than between substituents at the 2-
5
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 6 of 19
1
2
3
4
5
6
7
8
9
and 7- positions, or between substituents at the 1- and 3- or 6- positions. Both the
absorption and emission maxima of the naphthalene-bridged compound, 4, are red
shifted from those of the pyrene-bridged compounds 1-3, which indicates that the
electronic coupling between the two BMes2 groups through the 2,6-naphtalenylene
bridge is stronger than that through the 4,9-pyrenylene moiety.
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
1.0
0.8
0.6
0.4
0.2
0.0
10
8
1
2
3
4
1
2
3
4
6
4

2
0
250
300
350
(nm)
400
450
400
450
500
(nm)
550
600
Figure 1. Absorption (left) and normalized emission spectra (right) of 1-4 in hexane.
Table 1. Photophysical properties of compounds 1-4 in hexane.a
λabs
nm
εc
λem Stokes shift
τ
τ0 kr
b
d
ϕ
M-1 cm-1
nm
415
426
419
456
cm-1
1400
1650
1640
1900
ns
ns 107 s-1
1 392 8 300
2 398 11 900
3 392 14 900
0.24 3.1 13 7.7
0.28 4.6 16 6.3
0.33 5.0 15 6.7
0.90 14.6 16 6.3
4 420 7200
a
Fluorescence lifetimes and quantum yields of 1-3 were measured in air, while those of 4
b
c
were measured under argon because of its long decay time; absorption maximum; molar
extinction coefficient of the S0S1 transition and d natural lifetime of the fluorescence ().
While the naphthalene-cored compound 4 shows a very high fluorescence quantum
yield and modest Stokes shift in hexane, the pyrene-cored compounds 1-3 show
moderate quantum yields, with relatively smaller Stokes shifts. The radiative decay
rates of all four compounds are similar, being in the range of 6.3-7.7 x 107 / s,
indicating that the S1S0 transitions are allowed. This is much faster than most 2- and
2,7-substituted pyrenes,3-6 but slower than 1-substituted pyrenes.6 The emission
spectra of NPh2-substituted compounds 1 and 2 are strongly dependent on solvent
polarity (Figure 2), with solvatochromic shifts of up to 3440 and 3350 cm−1 from
hexane to acetonitrile for 1 and 2, respectively, indicating that the emissions are from
6
ACS Paragon Plus Environment

Page 7 of 19
The Journal of Organic Chemistry
1
2
3
4
5
ICT states which are stabilized in more polar solvents. However, the solvatochromic
effects for the BMes2-substituted compounds, 3 and 4, are relatively smaller.
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2. Fluorescence spectra of 1-4 in hexane, THF, and acetonitrile (MeCN).
Electrochemical Properties. Cyclic voltammetry (CV) measurements (Table 2,
Figure 3) were performed to estimate the HOMO and LUMO levels of 1-4. The
NPh2-substituted pyrenes, 1 and 2, show similar reversible oxidations at ca. 0.5 V,
which is typical for triarylamines.40 They have similar reduction potentials, which are
ascribed to a pyrene-localized reduction. The HOMO-LUMO gap of 2, estimated
from the CV data, is slightly smaller than that of 1, which agrees with the ordering of
the HOMO-LUMO gaps estimated from the absorption spectra (Table 2), as well as
the DFT calculations (vide infra). We were unable to observe the oxidation of the
BMes2-substituted compounds, 3 and 4. However, the first reduction potential of 3 is
less negative than those of 1 and 2, indicating that the BMes2 substituents stabilize the
LUMO of pyrene.
A large separation of the two reduction potentials of bis(BMes2)-arylene compounds
often indicates a better conjugation with the arylene bridge, as well as stronger
electronic coupling between two BMes2 groups.7, 41-44 We found that the separation of
the two reduction potentials in the pyrene-based compound 3 of 330 mV is
significantly smaller than that in the naphthalene-based compound 4 (500 mV).
Because the distances between the two-boron centers in 3 and 4 are similar, and the
7
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 8 of 19
1
2
3
4
5
arylene/BC3 twists are identical (Table S2), we can conclude that 2,6-naphthalenylene
is a more effective conjugated bridge than 4,9-pyrenylene.
6
7
8
9
Table 2. Cyclic voltammetric data,a and experimental HOMO and LUMO
energies.
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
b
c
Eox Ered
HOMOd LUMOd Ege, f
[V] [V]
[eV]
-5.29
-5.28
[eV]
[eV]
1 0.49 -2.66
2 0.48 -2.60
-2.14
-2.20
-2.49
-2.56
3.15 (2.95)
3.08 (2.89)
-- (2.88)
-- (2.70)
3 --
4 --
-2.31, -2.64 --
-2.24, -2.74 --
a
b
Potentials are given vs. ferrocene/ferrocenium (Fc/Fc+); measured in dichloromethane;
c measured in THF; estimated by assuming that the HOMO of ferrocene lies 4.8 eV below
d
e
the vacuum level: HOMO = – (4.80 + Eox) eV; LUMO = – (4.80 + Ered) eV; the
f
HOMO-LUMO gap is calculated by Eg = LUMO-HOMO, and the values in parenthesis are
optical band gaps estimated from the onsets of the absorption spectra in hexane.
Figure 3. Cyclic voltammograms of compounds 1-4. The reduction potentials were
measured in THF and the oxidation potentials in dichloromethane. The supporting
electrolyte was 0.1 M Bu4NPF6 in all experiments.
8
ACS Paragon Plus Environment

Page 9 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Theoretical Studies. To understand further the interaction between pyrene and
substituents at its 4- and 4,9-positions, DFT calculations at the B3LYP/6-31G(d) level
of theory in the gas phase were performed. The LUMO/LUMO+1 of 1 and 2, as well
as the HOMO of 3 and 4, are mainly localized on the arylene bridges and are similar
to those of the unsubstituted arenes. (Figure 4). The HOMOs of the NPh2-substituted
compounds, 1 and 2, are out of phase combinations of the pyrene HOMO and the lone
pair of nitrogen, destabilized by 0.44 eV and 0.47 eV, respectively from the HOMO of
pyrene. The LUMO of the BMes2-substituted compounds, 3 and 4, are in-phase
combinations of the boron empty pz orbital and the LUMO of the π-bridge. While the
LUMO of 3 is stabilized by 0.35 eV from that of pyrene, the stabilization of the
LUMO of 4 is much greater, i.e., by 1.23 eV compared to that of
1,2,3,6,7,8-hexahydropyrene (Table S4 in the SI). This agrees with the cyclic
voltammetric analysis and the bathochromic shift in the absorption spectrum of 4,
again, indicating that the mixing of the frontier orbitals in the 2,6-substituted
naphthalene derivative is much more effective than that in the 4,9-substituted pyrene.
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
Figure 4. Kohn–Sham frontier molecular orbitals of compounds 1-4 (isodensity value:
±0.015).
9
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 10 of 19
1
2
3
4
5
6
7
8
9
TD-DFT calculations at the CAM-B3LYP/6-31G(d) level in the gas phase reveal
that the S0S1 transitions of 1-4 are predominantly HOMOLUMO transitions
(Table S4), all of which are ICT transitions. The S0S1 transitions of 1-4 are all
allowed with oscillator strengths between 0.20-0.54, while the S0S1 transitions of 2-
and 2,7- substituted pyrenes are forbidden and thus very weak.45 The S0S1 transition
energy of 4 is much lower than those of 1-3, in agreement with the photophysical and
electrochemical measurements.
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
CONCLUSIONS
In conclusion, we have reported a novel, simple, and efficient way to synthesize
4,9-substituted pyrenes. The overall yields of boronate 6 and bromide 9 from pyrene,
through Ir-catalyzed C-H borylation under mild conditions, are 23% and 21%,
respectively, which are much higher than the previous synthesis of 13 which
employed highly toxic and hazardous reagents. The combination of UV-Vis
absorption spectra, time-resolved spectroscopy, as well as TD-DFT calculations
reveals that the S0S1 transitions of all our 4,9-disubstituted pyrenes, 1-3, are
allowed. Compounds 1-3 have moderate radiative decay rates and fluorescence
quantum yields. Both the absorption and emission maxima of the naphthalene-cored
compound 4 are red shifted from that of the pyrene-cored compound 3. The
HOMO-LUMO gap of 3, both estimated by absorption spectra and calculated by
TD-DFT calculations, is larger than that of 4. The less negative first reduction
potential, as well as the larger splitting of the two reduction potentials of 4, compared
to 3, indicates that 4,9-pyrenylene is a less effective conjugated π-bridge than
2,6-naphthalenylene.
EXPERIMENTAL SECTION
General Experimental Methods for Synthesis: All reagents were obtained from
commercial sources and used as received, with the exception of
[Ir(COD)(μ-OMe)]2,46
2,7-di-(tert-butyl)pyrene,47
4-bromo-2,7-di-(tert-butyl)pyrene,31
4,9-dibromopyrene,34
1,2,3,6,7,8-hexahydropyrene,33 and dimesitylboron fluoride (Mes2BF)48 which were
synthesized as reported previously. Solvents were HPLC grade, and were treated to
remove trace water using a commercial solvent purification system and deoxygenated
using the freeze−pump−thaw method. NMR spectra were recorded in CDCl3 and
CD2Cl2 solution on a 500 MHz (1H) spectrometer. 1H NMR spectra are referenced via
13
the signal of the residual protiated solvent. C NMR spectra are referenced via the
11
13C resonance of the deuterated solvent. B NMR spectra are referenced to external
BF3·Et2O. MS was performed in EI+ mode on a GC-MS and HRMS was performed
10
ACS Paragon Plus Environment

Page 11 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
using a Thermo Scientific Exactive Plus Orbitrap MS system with either an
Atmospheric Sample Analysis Probe (ASAP) or by Atmospheric Pressure Chemical
Ionization (APCI).
7
8
9
Synthesis of 4-diphenylamino-2,7-di-(tert-butyl)pyrene (1): In an argon-filled
glovebox, 4-bromo-2,7-di-(tert-butyl)pyrene (1.17 g, 3.0 mmol, 1 eq), Pd2dba3•CHCl3
(30 mg, 0.03 mmol, 0.01 eq), SPhos (40 mg, 0.1 mmol, 0.03 eq), NaOtBu (500 mg,
5.2 mmol, 1.7 eq), diphenylamine (680 mg, 4.0 mmol, 1.3 eq), and toluene (20 mL)
were added to a Young’s tube. The tube was then sealed with a PTFE tap, taken out of
the glovebox, and heated in an oil bath at 120 °C for 3 h, until GC-MS monitoring
indicated that the reaction was complete. The solution was cooled to r.t., and the
solvent and volatiles were removed in vacuo. Purification was performed by flash
chromatography through a silica gel column with dichloromethane: pentane 1:9 as the
eluent. Recrystallization by layer diffusion of methanol into a dichloromethane
solution gave the title compound as a yellow crystalline solid (1.09 g, 76%).
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
Mp 168−171 °C; 1H NMR: (500 MHz, CD2Cl2): 8.26 (d, J = 2 Hz, 1 H), 8.19 (s, 1 H),
8.16 (d, J = 2 Hz, 1 H), 8.09 (s, 1 H), 8.04 (s, 2 H), 7.88 (s, 1H), 7.24-7.20 (m, 4 H),
7.18-7.16 (m, 4 H), 6.97 (t, J = 7 Hz, 2 H), 1.55 (s, 9 H), 1.31 (s, 9 H); 13C{1H} NMR:
(125 MHz, CD2Cl2): 149.5, 149.1, 149.0, 143.7, 131.61, 131.60, 131.0, 129.5, 128.9,
127.9, 127.6, 127.4, 124.8, 122.8, 122.6, 122.33, 122.28, 122.25, 121.8, 120.5, 35.52,
35.45, 32.0, 31.8; MS (EI+): m/z 481.3 [M+]; Anal. Calcd for C36H35N: C, 89.77; H,
7.32; N, 2.91. Found: C, 89.11; H, 7.57; N, 2.92; HRMS (APCI+) m/z: [M+H]+ Calcd
for C36H36N1 482.2842; Found: 482.2840.
Synthesis
of
4,9-bis(Bpin)-2,7-di-(tert-butyl)pyrene
(6)
and
4,10-bis(Bpin)-2,7-(di-tert-butyl)pyrene (7): In an argon-filled glovebox,
2,7-di-(tert-butyl)pyrene (1.26 g, 4 mmol, 1 eq), B2pin2 (3.04 g, 12 mmol, 3 eq),
4,4′-di-(tert-butyl)-2,2′-bipyridine (dtbpy) (114 mg, 0.42 mmol, 0.1 eq),
[Ir(COD)(μ-OMe)]2 (132 mg, 0.21 mmol, 0.05 eq), and THF (5 mL) were added to a
Young’s tube. The tube was sealed with a PTFE tap and heated at 88 °C in an oil bath
for 4 days. A 1H NMR spectrum reveals that the ratio of compounds
4,9-bis(Bpin)pyrene, 4,10-bis(Bpin)pyrene, and 4-(Bpin)pyrene is 1.8: 1: 1.4 (Figure
S7). After removal of the solvent in vacuo, the residue was purified by column
chromatography
(silica;
1:4
dichloromethane/pentane),
11
to
obtain
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 12 of 19
1
2
3
4
5
6
4-(Bpin)-2,7-di-(tert-butyl)pyrene (450 mg, 1.02 mmol, 26%) and a mixture of
bis(Bpin)pyrenes.
7
8
9
The bis(Bpin)pyrene mixture was washed with 50 mL of methanol using an ultrasonic
bath to obtain the pure 4,9-bis(Bpin)-2,7-di-(tert-butyl)pyrene (6) as a white solid
(520 mg, 23%).
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
1
Mp. > 350 °C decomp.; H NMR: (500 MHz, CDCl3): 9.22 (s, 2 H), 8.67 (s, 2 H),
8.24 (s, 2 H), 1.58 (s, 18 H), 1.51 (s, 24 H); 13C{1H} NMR: (125 MHz, CDCl3): 148.4,
139.2, 133.1, 130.1, 125.9, 124.6, 124.1, 122.9, 83.9, 35.5, 32.1, 25.3; MS (EI+): m/z
566 [M]+; HRMS (APCI+) m/z: [M+H]+ Calcd for C36H49B2O4 567.3811; Found:
567.3796.
The solvent was removed from the washings under vacuum to give a brown powder.
Recrystallization by layer diffusion of acetonitrile into a dichloromethane solution
gave 4,10-bis(Bpin)-2,7-di-(tert-butyl)pyrene (7) as colorless crystals. A few crystals
were selected, and NMR spectra show them to be pure 7, the structure of which was
confirmed by single-crystal X-ray diffraction.
1H NMR: (500 MHz, CDCl3): 9.16 (s, 2 H), 8.62 (s, 2 H), 8.25 (s, 2 H), 1.60 (s, 9 H),
1.54 (s, 9 H), 1.51 (s, 24 H); 13C{1H} NMR: (125 MHz, CDCl3): 148.4, 148.2, 137.9,
133.2, 130.0, 127.2 (brs), 125.4, 123.8, 123.3, 122.7, 83.9, 35.7, 35.2, 32.1, 32.2, 25.2;
MS (EI+): m/z 566 [M]+; HRMS (APCI+) m/z: [M+H]+ Calcd for C36H49B2O4
567.3811; Found: 567.3811.
Synthesis
of
4,9-dibromo-2,7-di-(tert-butyl)pyrene
(9):
4,9-bis(Bpin)-2,7-di-(tert-butyl)pyrene (980 mg, 1.73 mmol, 1 eq) was dissolved in a
mixture of THF (20 mL) and methanol (30 mL). A solution of CuBr2 (2.76 g, 12.4
mmol, 7.2 eq) in water (30 mL) was added dropwise. The reaction mixture was stirred
vigorously at 90 °C for 2 days, and more CuBr2 (2.76 g, 12.4 mmol, 7.2 eq) was
o
added and then the reaction mixture was stirred at 90 C for another 2 days. GC-MS
of the reaction mixture showed that the reaction was complete. The crude mixture was
extracted with toluene and then passed through a short silica pad with toluene as the
eluent. Removal of the solvent gave the title compound (9) as a yellowish solid (740
mg, 91%).
12
ACS Paragon Plus Environment

Page 13 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Mp 258−261 °C; 1H NMR: (500 MHz, CDCl3): 8.62 (d, J = 2 Hz, 2 H,), 8.42 (s, 2 H),
13
8.18 (d, J = 2 Hz, 2 H,), 1.60 (s, 18 H); C{1H} NMR: (125 MHz, CDCl3): 150.2,
131.3, 131.0, 129.4, 123.1, 123.0, 122.84, 122.76, 35.7, 32.0 ppm; MS(EI+): m/z 472;
Anal. Calcd. for C24H24Br2: C, 61.04; H, 5.12. Found: C, 61.53; H, 5.44; HRMS
(ASAP+) m/z: [M+H]+ Calcd for C24H25Br2 473.0297; Found: 473.0283.
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
Synthesis of 4,9-bis(diphenylamino)-2,7-di-(tert-butyl)pyrene (2): In an argon-filled
glovebox, 4,9-dibromo-2,7-di-(tert-butyl)pyrene (830 mg, 1.77 mmol, 1 eq),
Pd2dba3•CHCl3 (32 mg, 0.034 mmol, 0.02 eq), SPhos (40 mg, 0.1 mmol, 0.06 eq),
NaOtBu (680 mg, 7.1 mmol, 4 eq), diphenylamine (598 mg, 3.54 mmol, 2 eq), and
toluene (20 mL) were added to a Young’s tube. The tube was then sealed with a PTFE
tap, taken out of the glovebox, and heated in an oil bath at 120 °C overnight. The
solution was cooled to r.t., and the solvent and volatiles were removed in vacuo. After
passage through a short silica pad with chloroform as the eluent and removal of all the
solvent, the residue was recrystallized by layer diffusion of ethanol into a chloroform
solution to give the title compound (2) as an off-white crystalline solid (922 mg,
80%).
Mp > 350 °C decomp.; 1H NMR: (500 MHz, CDCl3): δ = 8.21 (d, J = 2 Hz, 2 H), 7.99
(d, J = 2 Hz, 2 H), 7.89 (s, 2 H), 7.24-7.19 (m, 16 H), 6.99-6.95 (m, 4 H) ppm; 13C{1H}
NMR: (125 MHz, CDCl3): 148.9, 148.8, 143.2, 131.7, 129.3, 128.5, 127.3, 123.4,
122.5, 122.03, 121.99, 120.2, 35.3, 31.7 ppm; HRMS (ASAP+) m/z: [M+H]+ Calcd
for C48H45N2 649.3577; Found: 649.3588.
Synthesis of 4,9-bis(BMes2)pyrene (3): 4,9-Dibromopyrene (210 mg, 0.58 mmol, 1 eq)
was placed in a Schlenk tube which was then evacuated and refilled with argon before
dry and degassed THF (10 mL) was added. The suspension was cooled to –78 °C and
then n-BuLi in hexane (2.5 M, 0.6 mL, 1.5 mmol, 2.6 eq) was added. The suspension
was stirred for a further 2 h at –78 °C, before Mes2BF (380 mg, 1.4 mmol, 2.4 eq) was
added. The mixture was then stirred for another 2 h at –78 °C before warming to room
temperature and being stirred overnight. Methanol (1 mL) was added to quench the
reaction. Purification was performed by chromatography on silica gel with
dichloromethane: pentane 1:10 as the eluent to give a white solid. Further
13
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 14 of 19
1
2
3
4
5
6
recrystallization by cooling a hot chloroform solution gave the title compound as a
white powder (260 mg, 64%).
7
8
9
Mp > 350 °C; 1H NMR (CDCl3, 500 MHz): δ = 8.18 (dd, J1 = 8 Hz, J2 = 1 Hz, 2 H),
8.14 (s, 2 H), 8.04 (d, J = 8 Hz, 2 H), 7.71-7.68 (m, 2 H), 6.81 (s, 8 H), 2.32 (s, 12 H),
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
13
2.03 (br s, 24 H) ppm; C{1H} NMR (CDCl3, 125 MHz): δ = 147.2, 143.6, 141.0,
11
139.2, 137.5, 133.2, 131.1, 128.6, 127.0, 126.9, 126.1, 125.9, 23.4, 21.5 ppm; B
NMR (161 MHz, CDCl3): δ = 76 ppm; HRMS (APCI+) m/z: [M-H]+ Calcd for
+
C52H53B2 699.4328; Found 699.4324.
Synthesis
of
4,9-bis(BMes2)-1,2,3,6,7,8-hexahydropyrene
(4):
4,9-Dibromo-1,2,3,6,7,8-hexahydropyrene (360 mg, 1.0 mmol, 1 eq) was placed in a
Schlenk tube which was then evacuated and refilled with argon before dry and
degassed THF (10 mL) was added. The suspension was cooled to –78 °C, and then
t-BuLi in pentane (1.7 M, 2.6 mL, 4.4 mmol, 4.4 eq) was added. The suspension was
stirred for a further 2 h at –78 °C, before Mes2BF (630 mg, 2.4 mmol, 2.4 eq) was
added. The mixture was stirred for another 4 h at –78 °C before warming to room
temperature and being stirred overnight. Methanol (1 mL) was added to quench the
reaction. Purification was performed by chromatography on silica with
dichloromethane: pentane 1:10 as the eluent. After removing the solvent,
recrystallization by layer diffusion of ethyl acetate into a toluene solution gave the
title compound as a yellow powder (177 mg, 25%).
1
Mp 324−327 °C; H NMR (CDCl3, 500 MHz): δ = 6.98 (s, 2 H), 6.77 (s, 8 H),
2.86-2.81 (m, 8 H), 2.29 (s, 12 H), 1.99 (s, 24 H), 1.82-1.77 (m, 4 H) ppm; C{1H}
13
NMR (CDCl3, 125 MHz): δ = 143.7, 143.4, 140.5, 139.3, 138.8, 134.6, 131.2, 128.4,
11
128.3, 32.2, 31.9, 23.9, 23.3, 21.4 ppm; B NMR (161 MHz, CDCl3): δ = 78 ppm;
HRMS (APCI+) m/z: [M-H]+ Calcd for C52H57B2 703.4641; Found 703.4648.
Bromination
of
1,2,3,6,7,8-hexahydropyrene:
A
solution
of
1,2,3,6,7,8-hexahydropyrene (4 g, 19.2 mmol, 1 eq) in dichloromethane (75 mL) was
placed in a 250-mL round bottom flask, and a solution of bromine (2 mL, 38.8 mmol,
2 eq) in dichloromethane (10 mL) was added dropwise in 1 h. The solution was stirred
1
for an additional 2 h during which a white precipitate formed. After filtration, a H
14
ACS Paragon Plus Environment

Page 15 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
NMR spectrum (Figure S8) of the precipitate (3.4 g, crude yield 48%) shows that it
contains 90% 4,9-diboromo-1,2,3,6,7,8-hexahydropyrene (11) and 10%
4,10-diboromo-1,2,3,6,7,8-hexahydropyrene (12). The 1H NMR spectrum (Figure S9)
of the filtrate was measured, revealing it to contain 37% 11 and 63% 12. The solvent
was removed from the filtrate to give 3.7 g of a pale solid (crude yield 52%), which
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
1
was dissolved together with the precipitate in chloroform. The H NMR spectrum
(Figure S10) of this solution shows that it contains 11 and 12 with a ratio of 1.7 : 1.
Pure 11 was isolated by recrystallization of crude 11 from chloroform.
Photophysics: All measurements were performed in standard quartz cuvettes (1 cm ×
1 cm). All solutions for photophysical measurements had a concentration of ca. 1 ×
10−5 M, except where stated. UV−vis absorption spectra were recorded using a
diode-array UV-visible spectrophotometer. All luminescence properties were
recorded using a spectrometer equipped with double monochromators for both
excitation and emission, operating in right-angle geometry mode, and all spectra were
fully corrected for the spectral response of the instrument. The fluorescence quantum
yields were measured using a calibrated integrating sphere (150 mm inner diameter).
Fluorescence lifetimes were recorded using the time-correlated single-photon
counting (TCSPC) method. Solutions were excited at 376.6 nm with a picosecond
pulsed diode laser (pulse width: 72.6 ps) at repetition rates of 1−5 MHz and lifetime
data were recorded at the emission maxima. The instrument response functions (IRF)
were ca. 950 ps fwhm. Decays were recorded to 10 000 counts in the peak channel
with a record length of at least 4000 channels. Iterative reconvolution of the IRF with
one decay function and nonlinear least-squares analysis were used to analyze the data.
The quality of all decay fits was judged to be satisfactory based on the calculated
values of the reduced χ2 and Durbin-Watson parameters and visual inspection of the
weighted and autocorrelated residuals.
Electrochemistry: A potentiostat with a standard three-electrode cell configuration
was employed using a platinum disk working electrode, a platinum wire counter
electrode, and a silver wire, separated by a Vycor tip, serving as the reference
electrode. Formal redox potentials are referenced to the ferrocene/ferrocenium
([Cp2Fe]+/0) redox couple as an internal standard. Measurements were performed
using 0.1 M tetra-n-butylammonium hexafluorophosphate ([n-Bu4N][PF6]) as the
15
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 16 of 19
1
2
3
4
supporting electrolyte with a scan rate of 250 mV/s. Compensation for resistive losses
5
6
(iR drop) was employed for all measurements.
7
8
9
Crystal structure determination Crystals suitable for single-crystal X-ray
diffraction were selected, coated in perfluoropolyether oil, and mounted on sample
holders. Diffraction data were collected on 4-circle diffractometers with CCD or
CPAD area detectors, using Mo-K radiation monochromated by graphite or
multi-layer focusing mirrors. The crystals were cooled to 100 K. The images were
processed and corrected for Lorentz-polarization effects and absorption. The
structures were solved using the intrinsic phasing method (SHELXT)49 and Fourier
expansion technique. All non-hydrogen atoms were refined in anisotropic
approximation, with hydrogen atoms ‘riding’ in idealized positions, by full-matrix
least squares against F2 of all data, using SHELXL50 software. Diamond51 software
was used for graphical representation. Full structural information has been deposited
with Cambridge Crystallographic Data Centre. CCDC-1586515 (1), 1586511 (3),
1586512 (4), 1586513 (6), and 1586514 (7).
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
Theoretical Methods All calculations (DFT and TD-DFT) were carried out with the
Gaussian 09 (rev. D.01) program package.52 The ground-state geometries were
optimized using the B3LYP functional in combination with the 6-31+G(d) basis set.
The molecular structures obtained from single-crystal X-ray diffraction of 1, 3, and 4
were used as the starting geometries. The optimized geometries were confirmed to be
local minima by performing frequency calculations and obtaining only positive
frequencies. Based on these optimized structures, the gas-phase vertical transitions
were calculated (singlets, 10 states) by TD-DFT using the CAM-B3LYP functional in
combination with the 6-31+G(d) basis set. No symmetry constraints were used in any
of the calculations.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications
website.
NMR spectra, additional data of theoretical, photophysical, and single-crystal X-ray
diffraction studies.
Crystallographic data in CIF format.
16
ACS Paragon Plus Environment

Page 17 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
AUTHOR INFORMATION
Corresponding Author
* Email: todd.marder@uni-wuerzburg.de
7
8
9
Present Addresses
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
+ Fachbereich Chemie, Universität Konstanz, 78457 Konstanz, Germany.
† School of Pharmacy, Queen’s University Belfast, 97 Lisburn Road, BT9 7BL
Belfast, UK.
Author Contributions
All authors have approved the final version of the manuscript.
ACKNOWLEDGMENT
We thank Dr. Christian Ehrenreich and Dr. Philipp Stoessel of Merck Ltd. for
suggestions and helpful discussions, the Bavarian State Ministry of Science, Research,
and the Arts through the Collaborative Research Network “Solar Technologies go
Hybrid”, the DFG (GRK 2112) and the of University of Würzburg for financial
support.
REFERENCES
1. Figueira-Duarte, T. M.; Müllen, K. Chem. Rev. 2011, 111, 7260-7314.
2. Müllen, K. Helv. Chim. Acta 1978, 61, 2307-2317.
3. Merz, J.; Fink, J.; Friedrich, A.; Krummenacher, I.; Al Mamari, H. H.; Lorenzen,
S.; Haehnel, M.; Eichhorn, A.; Moos, M.; Holzapfel, M.; Braunschweig, H.;
Lambert, C.; Steffen, A.; Ji, L.; Marder, T. B. Chem. Eur. J. 2017, 23,
13164-13180.
4. Ji, L.; Lorbach, A.; Edkins, R. M.; Marder, T. B. J. Org. Chem. 2015, 80,
5658-5665.
5. Kurata, R.; Ito, A.; Gon, M.; Tanaka, K.; Chujo, Y. J. Org. Chem. 2017, 82,
5111-5121.
6. Crawford, A. G.; Dwyer, A. D.; Liu, Z.; Steffen, A.; Beeby, A.; Pålsson, L.-O.;
Tozer, D. J.; Marder, T. B. J. Am. Chem. Soc. 2011, 133, 13349-13362.
7. Ji, L.; Edkins, R. M.; Lorbach, A.; Krummenacher, I.; Brückner, C.; Eichhorn,
A.; Braunschweig, H.; Engels, B.; Low, P. J.; Marder, T. B. J. Am. Chem. Soc.
2015, 137, 6750-6753.
8. Coventry, D. N.; Batsanov, A. S.; Goeta, A. E.; Howard, J. A. K.; Marder, T. B.;
Perutz, R. N. Chem. Commun. 2005, 41, 2172-2174.
9. Crawford, A. G.; Liu, Z.; Mkhalid, I. A. I.; Thibault, M.-H.; Schwarz, N.;
Alcaraz, G.; Steffen, A.; Collings, J. C.; Batsanov, A. S.; Howard, J. A. K.;
Marder, T. B. Chem. Eur. J. 2012, 18, 5022-5035.
10. Casas-Solvas, J. M.; Howgego, J. D.; Davis, A. P. Org. Biomol. Chem. 2014, 12,
212-232.
11. Feng, X.; Hu, J.-Y.; Redshaw, C.; Yamato, T. Chem. Eur. J. 2016, 22,
11898-11916.
12. Feng, X. Synthesis and Photophysical Properties of Pyrene-Based Blue
Light-Emitting Monomers. Ph. D. Thesis, Saga University, Saga, Japan, 2013.
17
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 18 of 19
1
2
3
4
5
6
13. Hu, J. Y.; Ni, X. L.; Feng, X.; Era, M.; Elsegood, M. R.; Teat, S. J.; Yamato, T.
Org. Biomol. Chem. 2012, 10, 2255-2262.
14. Sasaki, S.; Suzuki, S.; Igawa, K.; Morokuma, K.; Konishi, G. I. J. Org. Chem.
2017, 82, 6865-6873.
7
15. Lee, J.; Lee, H.; Jung, H.; Jo, M.; Park, J. SID Symp. Dig. Tech. Pap. 2016, 47,
1714-1716.
16. Zöphel, L.; Enkelmann, V.; Müllen, K. Org. Lett. 2013, 15, 804-807.
17. Zöphel, L.; Beckmann, D.; Enkelmann, V.; Chercka, D.; Rieger, R.; Müllen, K.
Chem. Commun. 2011, 47, 6960-6962.
18. Feng, X.; Hu, J.-Y.; Iwanaga, F.; Seto, N.; Redshaw, C.; Elsegood, M. R. J.;
Yamato, T. Org. Lett. 2013, 15, 1318-1321.
19. Mochida, K.; Kawasumi, K.; Segawa, Y.; Itami, K. J. Am. Chem. Soc. 2011, 133,
10716-10719.
20. Takaku, K.; Kitamura, T.; Watanabe, T.; Yonekuta, Y. Organic
Electroluminescence Element. US 2014/0299851 A1, Oct. 9, 2014.
21. Liu, Z.; Wang, Y.; Chen, Y.; Liu, J.; Fang, Q.; Kleeberg, C.; Marder, T. B. J.
Org. Chem. 2012, 77, 7124-7128.
22. Ji, L.; Fucke, K.; Bose, S. K.; Marder, T. B. J. Org. Chem. 2015, 80, 661-665.
23. Eliseeva, M. N.; Scott, L. T. J. Am. Chem. Soc. 2012, 134, 15169-15172.
24. Ji, L.; Griesbeck, S.; Marder, T. B. Chem. Sci. 2017, 8, 846-863.
25. Wakamiya, A.; Yamaguchi, S. Bull. Chem. Soc. Jpn. 2015, 88, 1357-1377.
26. Ren, Y.; Jäkle, F. Dalton Trans. 2016, 45, 13996-14007.
27. Jäkle, F. Chem. Rev. 2010, 110, 3985-4022.
28. Hudson, Z. M.; Wang, S. Acc. Chem. Res. 2009, 42, 1584-1596.
29. Li, S. Y.; Sun, Z. B.; Zhao, C. H. Inorg. Chem. 2017, 56, 8705-8717.
30. Hitosugi, S.; Tanimoto, D.; Nakanishi, W.; Isobe, H. Chem. Lett. 2012, 41,
972-973.
31. Bedard, A. C.; Vlassova, A.; Hernandez-Perez, A. C.; Bessette, A.; Hanan, G. S.;
Heuft, M. A.; Collins, S. K. Chem. Eur. J. 2013, 19, 16295-16302.
32. If the solid is not pure, the ultrasonication and centrifugation process can be
repeated once or twice.
33. Pratap, R.; Tominaga, Y.; Lee, M. L.; Castle, R. N. J. Heterocycl. Chem. 1981,
18, 973-975.
34. Gonzalez, A. Z.; Benitez, D.; Tkatchouk, E.; Goddard III, W. A.; Toste, F. D. J.
Am. Chem. Soc. 2011, 133, 5500-5507.
35. Surry, D. S.; Buchwald, S. L. Chem. Sci. 2011, 2, 27-50.
36. Ruiz-Castillo, P.; Buchwald, S. L. Chem. Rev. 2016, 116, 12564-12649.
37. Each boron atom is sp2 hybridized and in the same plane as the three bonded
carbon atoms, which is called the BC3 plane.
38. Clar, E.; Schoental, R., Polycyclic hydrocarbons. Academic Press: New York,
1964.
39. Yuan, N.; Wang, W.; Fang, Y.; Zuo, J.; Zhao, Y.; Tan, G.; Wang, X.
Organometallics 2017, 36, 2498-2501.
40. Zhang, Z.; Edkins, R. M.; Nitsch, J.; Fucke, K.; Steffen, A.; Longobardi, L. E.;
Stephan, D. W.; Lambert, C.; Marder, T. B. Chem. Sci. 2015, 6, 308-321.
41. Kaim, W.; Hosmane, N. S.; Záliš, S.; Maguire, J. A.; Lipscomb, W. N. Angew.
Chem. Int. Ed. 2009, 48, 5082-5091.
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
42. Fiedler, J.; Zališ, S.; Klein, A.; Hornung, F. M.; Kaim, W. Inorg. Chem. 1996, 35,
3039-3043.
18
ACS Paragon Plus Environment

Page 19 of 19
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
43. Schulz, A.; Kaim, W. Chem. Ber. 1989, 122, 1863-1868.
44. Kaim, W.; Schulz, A. Angew. Chem., Int. Ed. Engl. 1984, 23, 615-616.
45. The S0->S1 transition in 1-substituted pyrenes is also forbidden; the strong
absorption at lowest energy is the superimposition of S0->S1 and S0->S2
transitions
46. Uson, R.; Oro, L. A.; Cabeza, J. A.; Bryndza, H. E.; Stepro, M. P. Inorg. Synth.
1985, 23, 126-130.
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
47. Berg, A.; Jakobsen, J.; Johansen, S. R. Acta Chem. Scand. 1969, 23, 567-575.
48. Pelter, A.; Smith, K.; Brown, H. C., Borane Reagents. Academic Press: London,
1988; p 428-429.
49. Sheldrick, G. M. Acta Crystallogr. A 2015, A71, 3-8.
50. Sheldrick, G. M. Acta Crystallogr. A 2008, A64, 112-122.
51. Brandenburg, K. Diamond (version 3.2 i), Crystal and molecular structure
visualization, crystal impact H. Putz & K. Brandenburg GbR, Bonn (Germany).
2012.
52. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.;
Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.;
Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven,
T.; Montgomery Jr., J. A.; Peralta, J. E.; Ogliaro, F. o.; Bearpark, M. J.; Heyd, J.;
Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.;
Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi,
M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A.
J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.;
Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.;
Daniels, A. D.; Farkas, d. n.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D.
J. Gaussian 09 Revision D.01, Gaussian, Inc.: Wallingford, CT, USA, 2009.
19
ACS Paragon Plus Environment