The synthesis of brominated-boron-doped PAHs by alkyne 1,1-bromoboration: Mechanistic and functionalisation studies

Article abstract of DOI:10.1039/c9sc05404a

The synthesis of a range of brominated-B_n-containing (n = 1, 2) polycyclic aromatic hydrocarbons (PAHs) is achieved simply by reacting BBr₃ with appropriately substituted alkynes via a bromoboration/electrophilic C-H borylation sequence. The brominated-B_n-PAHs were isolated as either the borinic acids or B-mesityl-protected derivatives, with the latter having extremely deep LUMOs for the B₂-doped PAHs (with one example having a reduction potential of E_1/2 = -0.96 V versus Fc⁺/Fc, Fc = ferrocene). Mechanistic studies revealed the reaction sequence proceeds by initial alkyne 1,1-bromoboration. 1,1-Bromoboration also was applied to access a number of unprecedented 1-bromo-2,2-diaryl substituted vinylboronate esters directly from internal alkynes. Bromoboration/C-H borylation installs useful C-Br units onto the B_n-PAHs, which were utilised in Negishi coupling reactions, including for the installation of two triarylamine donor (D) groups onto a B₂-PAH. The resultant D-A-D molecule has a low optical gap with an absorption onset at 750 nm and emission centered at 810 nm in the solid state.

Full text of DOI:10.1039/c9sc05404a

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Chemical Science
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DOI: 10.1039/C9SC05404A
ARTICLE
The Synthesis of Brominated-Boron-Doped PAHs by Alkyne 1,1-
Bromoboration: Mechanistic and Functionalisation Studies
K. Yuana, R. J. Kahanb, C. Sic, A. Williamsb, S. Kirschnera, M. Uzelaca, E. Zysman-Colman*c and M. J.
Received 00th January 20xx,
Accepted 00th January 20xx
Inglesona*
DOI: 10.1039/x0xx00000x
The synthesis of a range of brominated-Bn-containing (n = 1, 2) polycyclic aromatic hydrocarbons (PAHs) is achieved simply
by reacting BBr3 with appropriately substituted alkynes via a bromoboration/electrophilic C-H borylation sequence. The
brominated-Bn-PAHs were isolated as either the borinic acid or B-mesityl-protected derivatives, with the latter having
extremely deep LUMOs for the B2-doped PAHs (with one example having a reduction potential of E1/2 = -0.96 V versus Fc+/Fc,
Fc = ferrocene). Mechanistic studies revealed the reaction sequence proceeds by initial alkyne 1,1-bromoboration. 1,1-
bromoboration also was applied to access a number of unprecedented 1-bromo-2,2-diaryl substituted vinylboronate esters
direct from internal alkynes. Bromoboration/C-H borylation installs useful C-Br units onto the Bn-PAHs, which were utilised
in Negishi coupling reactions, including for the installation of two triarylamine donor (D) groups onto a B2-PAH. The resultant
D-A-D molecule has a low optical gap with an absorption onset at 750 nm and emission centered at 810 nm in the solid state.
with step-economy issues. Therefore, a simple route to form a
range of Bn-doped PAHs with low LUMO energies that
concomitantly installs a second useful functional group, such as
halide, would be highly attractive and facilitate access to more
complex materials with desirable properties.
Introduction
The incorporation of main group elements into conjugated
organic scaffolds is a powerful strategy to tune electronic
properties.1 Recently, this approach has been extended to the
introduction of three-coordinate boron atoms into polycyclic
aromatic hydrocarbons (PAHs).1,2 In these “B-doped”-PAHs
interaction between the empty p orbital on boron and the
extended π system often leads to molecules with low energy
LUMOs.2 B-doped PAHs now are being explored for a range of
applications including organic light-emitting diodes, thin film
transistors, solar cells, lithium batteries and electrocatalysis.2
However, two factors have limited the wider uptake of purely
B-doped PAHs (i.e. PAHs without co-doping elements e.g. N): (i)
the limited simple synthetic routes to form Bn-PAHs, particularly
for n > 1, which generally have the deeper LUMOs;2 (ii) the
challenge associated with incorporating Bn-doped-PAHs into
more complex materials, e.g. by coupling reactions to access
donor-acceptor (D-A) structures.3 Some notable progress has
been made addressing (i), with several routes to larger Bn-PAHs,
(n ≥ 2, see A – D, Figure 1) including examples with low LUMO
energies, recently reported.4,5 However, the incorporation of
Bn-PAHs into more complex materials currently requires the
post synthetic introduction of additional functionality onto the
Bn-PAH to enable subsequent steps (e.g. cross coupling).6 This
has associated challenges (e.g. selectivity in halogenation) along
OR
OR
Mes
B
Mes
B
B
Mes
Mes
Ph
B
B
B
Mes
B
B
Ph
B
Mes
Mes
OR
OR
(ref 4a)
D
(ref 4c)
C
B
(ref 4f)
(ref 4k)
A
Previous work:
R = H or alkyl
1-boraphenalene
BBr3
- HBr
Pinacol
EtNiPr2
BPin
B
BBr2
Br
Br
Br
(iii) proto-
deboronation/
E2
(i) trans-1,2-
haloboration
(ii) Boron-
Friedel Crafts
R
R
R
R
E
Compound
This work: 1,1-haloboration enabled Br2-B2-PAH synthesis and subsequent cross coupling
Br
Ar1
Ar2
BBr3
DONOR
Br
Ar2
Mes
Ar2
Ar2
B
Mes
Mes
B
B
Ar1
BBr2
Br
cross
coupling
Ar1=
Ar1=
Ar2
Perylene
Pyrene
(54% overall
yield)
B
B
Ar2
Ar2
Mes
Mes
B
Ar2
Br
Ar1
Ar2
BPin
Br
Mes
58 % yield in one
pot from the alkyne
DONOR
Br
Deep LUMO B2-PAH
E1/2Red1 (-0.96 V vs Fc+/0
a. EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK
b. School of Chemistry, University of Manchester, Manchester, M13 9PL, UK
c. Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St
Andrews, St Andrews, KY16 9ST, UK
NIR absorption
and emission
ambipolar synthon
)
Figure 1: Top, select example of some of the largest / lowest LUMO Bn-PAHs (n >
1) containing three coordinate C3B units. Middle, previous work forming
boraphenalenes by bromoboration / SEAr. Bottom, this work accessing and
utilising large, low LUMO energy dibrominated B2-PAHs.
Corresponding author: michael.ingleson@ed.ac.uk
Electronic Supplementary Information (ESI) available: full experimental details, NMR
spectra, crystallographic data, optoelectronic data and Cartesian coordinates for all
calculations. See DOI: 10.1039/x0xx00000x
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Chemical Science
Page 2 of 10
ARTICLE
Journal Name
In our previous work,
1-boraphenalenes via sequential
a
one-pot synthesis of
bromoboration
B2-doped PAHs were next targeted through a two-fold
bromoboration/SEAr sequence starting from 1,6-di(pent-1-yn-
View Article Online
DOI: 10.1039/C9SC05404A
/
intramolecular boron-Friedel-Crafts of 1-alkynylnaphthalenes 1-yl)pyrene, 2. However, post borylation/protection at boron,
(Fig. 1, middle) was described.7 We envisaged that this compound 2a was the only fully fused B2-PAH isolable via
methodology could be extended by: (i) using larger (than column chromatography in our hands and it was obtained in a
naphthalene) π-scaffolds to obtain B1 and B2 doped PAHs very low yield alongside 2b. Compound 2b presumably derives
possessing deeper LUMOs; (ii) utilising the bromo substituent from protodeboronation of a vinyl C-B unit (analogous to that
to access more complex materials with desirable properties via in 1a) followed by an E2 elimination reaction as previously
coupling reactions. Herein these two objectives are realised observed for the 1-boraphenalenes (see figure 1, middle right).7
enabling access to the lowest LUMO energy ambient stable Bn- Tip installation conditions also were applied to the product
doped PAH reported to date, to the best of our knowledge, and mixture derived from BBr3 / 2, however this led to the formation
a low-optical gap D-A-D material where the acceptor unit is a of compound 2c in 10% yield as the only isolable product in our
B2-PAH. In addition, mechanistic studies on the hands. The structures of 1a, 2a and 2c were confirmed by single
bromoboration/SEAr process revealed it proceeds by alkyne 1,1- crystal X-ray diffraction analysis (see subsequent discussion). It
bromoboration, a process not previously observed. Therefore should be noted that products derived from both 1,2 and 1,1-
1,1-bromoboration also was applied to simple diarylalkynes haloboration were observed (e.g. the B-Br analogues of 2a / 2c)
demonstrating its utility for forming 1-bromo-2,2-diaryl and this may explain the complex mixtures observed starting
substituted vinylboronate esters that are otherwise challenging from 2 with lower symmetry (than 2a/2c) borylated products
to access.
also observed spectroscopically (presumably containing one 1,1
and one 1,2-bromoborated boracycle in the same molecule).
In previous work 1-(arylethynyl)naphthalenes reacted with
BBr3 to give different products to that starting from 1-(alkyl-
ethynyl)naphthalenes, with the former affording products from
a 1,1-bromoboration/SEAr cyclisation process (e.g. F, inset
scheme 2, is formed instead of an analogue of E, Figure 1
middle),7 with no 1,2-bromoboration derived products
observed. Therefore, aryl-alkynyl-pyrene derivatives (e.g. 3)
were utilised in an attempt to avoid forming mixtures derived
from competing 1,1 and 1,2-bromoboration. Starting from 3,
the desired Tip protected product 3a was isolated in 75% yield
with negligible 1,2-bromoboration products observed. In
addition, the borinic acid 3b was accessible in good yield using
simple aqueous workup conditions. 3b proved sufficiently
stable for column chromatography and even survived 1 M HCl
(aq.) for at least 0.5 h. Notably, all the aryl-substituted
derivatives studied herein proved more resistant to
protodeboronation than the alkyl congeners, with protection by
mesityl also providing sufficient stabilisation for these
derivatives. The NMR data for 3a/3b are comparable to that
previously reported for the B-OH and B-aryl 1-boraphenalenes.7
Results and Discussion
Synthesis of boron-doped PAHs and 1,1-bromoboration studies
Initially, 1-(pent-1-yn-1-yl)pyrene, 1, was combined with BBr3 in
the presence of one equivalent of 2,4,6-tri-tert-butylpyridine
(TBP), targeting an analogous trans-haloboration / SEAr process
that previously afforded 1-boraphenalenes.7 Post protection at
boron by reaction with dimesitylzinc, purification afforded two
isomeric compounds, 1a and 1b (Scheme 1) in low yield, partly
due to low stability of these compounds to the column
chromatography. To provide enhanced stability, the bulkier
2,4,6-triisopropylphenyl (Tip) protecting group was used
instead of mesityl (Mes). Using similar reaction conditions,
compounds 1c and 1d were isolated in higher yields relative to
1a and 1b.
(i) 3 BBr3 / 1 TBP
oDCB,
heptane,rt, 24 h
Mes
Br
R
+
B
B
(ii) (a) ZnMes2 (1.1
equiv.), rt, toluene/
THF, 24 h or
7 (b) 3 TipMgBr toluene
/ 2-MeTHF, rt, 24 h
C3H7
C3H7
Br
(a) R = Mes
(b) R = Tip
C3H
1a
1c
(9%)
(27%)
1b
(15%)
1
3a
3b
(a) R = Tip:
(b) R = OH:
(75%)
(70%)
1d
(23%)
C6H13
C6H13
Br
Br
C6H13
(i) BBr3 (3 eq.), TBP (1 eq.)
oDCB, heptane, rt, 24 h
B
B
(i) 3 BBr3, 1 TBP
Mes
B
Br
Mes
Mes
B
oDCB,
R
(ii) (a) TipMgBr (5 eq.),
oDCB, THF, rt, 48h;
or (b) 'H2O', rt, 30 min
heptane,rt, 24 h
Mes
Br
B
+
B
Br
(ii) ZnMes2 (1.1
HO
F
Br
equiv), rt, oDCB, 24 h
3
tBu
C6H13
C6H13
(3%)
(18%)
tBu
C6H13
SEAr
2a
2a
(3%)
(1%)
2b
2b
(silica stationary phase)
(alumina stationary phase)
2
Br
tBu
C6H13
C6H13
BBr3
BBr3
C10
B
C1
(i) 3.9 BBr3, 1.95 TBP
Tip
C-C bond
undergoing
cleavage
(previous
C-C bond
undergoing
clevage
oDCB, heptane,rt, 24 h
BBr2
Br
Tip
B
Br
B
3c
(ii) TipMgBr (8.6 equiv.), rt
oDCB, 2-MeTHF, 24 h
R
C6H13
Not observed
1,1-haloboration
proposal)
Br
tBu
tBu
C6H13
2c
2
(10%)
Scheme 2: Formation of 3a and 3b and mechanistic implications.
Scheme 1: Isolated products from the reaction of alkyl-alkynyl-pyrenes with BBr3.
2 | J. Name., 2012, 00, 1-3
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Chemical Science
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Earlier studies on the bromoboration of diphenylacetylene
ARTICLE
Similar outcomes were observed with di-p-tolylacetylene (6)
View Article Online
using BBr3 by Lappert and co-workers suggested that only the and 1,2-bis(4-fluorophenyl)ethyne withDtOhIe: 101.1,013-h9/aClo9SbCo0r5a4t0io4nA
1,2-cis-bromoboration product (4, Scheme 3 inset) forms.8 product being the major species observed in DCM in both cases.
Furthermore, alkyne 1,1-haloboration using boron electrophiles Exact ratios of the BBr2 1,1 : 1,2-haloboration (both cis and trans
was to the best of our knowledge unprecedented prior to this isomers) products in DCM are challenging to determine in-situ
work, with 1,2-haloboration or 1,1-carboboration the general by NMR spectroscopy due to uncertainty in isomer assignment.
outcomes.9 Thus, in our previous report on the bromoboration Furthermore, ratios of BPin/vinyl C-H products post work-up
of 1-(arylalkynyl)-naphthalenes,7 a mechanism was proposed and isolation are not indicative of in-situ ratios due to
for forming F that avoided 1,1-bromoboration. According to competing pinacol protection
that previously proposed mechanism, compound 3c (inset retrohaloboration (see Supporting Information section 4 for
Scheme 2) should be obtained starting from 3 via cleavage of further discussion). For di-p-tolylacetylene mixture of
/
protodeboronation
/
a
the pyrene C1-Calkyne bond. However, X-ray diffraction analysis bromoboration products (ca. 3:10) was formed in DCM 10
of the haloboration products 3a and 3b confirmed that boron minutes after the addition of BBr3 at room temperature. To
was attached to C10 of pyrene and that the C1-Calkyne bond determine the identity of the major isomer the fact that alkyne
remains intact. These observations indicate the reaction most 1,2-bromoboration products (e.g. 4) are converted rapidly back
likely proceeds through 1,1-bromoboration followed by into the starting alkyne on adding pyridine,8 (concomitantly
electrophilic C-H borylation (Scheme 2, bottom right). forming pyridine-BBr3) was exploited. Upon addition of pyridine
Therefore, the bromoboration of other diarylalkynes, including to the 3:10 bromoboration reaction mixture, the minor
diphenylacetylene, using BBr3 was revisited to probe the bromoboration product, assigned as 6a (Scheme 4), was
apparent discrepancy with earlier work.
converted into the starting alkyne and pyridine-BBr3, while the
On combining diphenylacetylene with BBr3 in heptane, major bromoboration product, assigned as 6b, formed an
crystals precipitated over the course of 5 mins. X-ray diffraction adduct, 7, with pyridine at room temperature. Upon heating at
analysis on these revealed them to be the 1,2-cis- 60 °C, compound 7 also converted into di-p-tolylacetylene and
bromoboration product, 4 (inset scheme 3). NMR studies under pyridine-BBr3. Addition of excess BBr3 to the mixture containing
the same conditions revealed that only one product is observed 7 to sequester all pyridine as pyridine-BBr3 regenerated the
in solution, assigned as compound 4. Protodeboronation of this mixture of 1,2- and 1,1-haloboration products in an identical
reaction mixture afforded 1-bromo-1,2-diphenylethene, 4-H 3:10 ratio to that originally observed. Combined these results
with no 1,1-bromoboration isomer (5-H, Scheme 3) observed. indicate that 1,1-haloboration dominates in DCM, that this
While these observations are consistent with previous work,8 reaction reaches its equilibrium position rapidly in DCM, and
upon heating the reaction mixture in heptane at 60 °C an that both 1,2- and 1,1-bromoboration are reversible. DFT
additional product, assigned as 5, was observed (by 13C{1H} and calculations (at the M06-2X/6-311G(d,p) PCM (DCM) level)
11B NMR spectroscopy). Protodeboronation of this reaction revealed the 1,1- and 1,2-bromoboration products (e.g. 4 and 5)
mixture afforded 1-bromo-2,2-diphenylethene, 5-H, derived were effectively isoenergetic (all pairs of isomers had E < 1.3
from 1,1-haloboration as the major product along with minor and G < 0.8 kcal mol-1) consistent with the observation of
amounts of 1-bromo-1,2-diphenylethene (4-H). Notably, when mixtures on reaching equilibrium. Finally, 1,1-bromoboration is
bromoboration was performed in DCM, both 1,2- and 1,1- not limited to diarylalkynes, with 1-phenyl-1-propyne also
bromoboration products were observed after short reaction leading to 1,1-bromoboration products.
o
times at 20 C (ca. 10 minutes by NMR spectroscopy and by
Br
BBr2
analysis of products post protodeboronation). These
observations suggest that 1,1-bromoboration proceeds through
a polar transition state(s), and potentially a vinyl cation type
intermediate(s), more stabilised by the polar solvent DCM.
Identical product distributions also were observed using 3
equiv. of BBr3 in place of 1.5 equiv. of BBr3.
Br
DCM
rt
+
BBr2
(major)
+ BBr3
1.5 eq
6a
(minor)
6
6b
(
)
6a : 6b
3:10
N
rt
1.5 eq.
Br
60oC
BBr3
6a : 6b
3 : 10
6
+
py-BBr3
Br
B
Br
py
7
compound
6
+
+ py-BBr3
Scheme 4: Bromoboration in DCM, and reactivity of products towards pyridine.
The preparation of fully-substituted 1-bromo-1-alkenyl
boronate esters currently is challenging (the major route to
these types of compounds proceeds via hydroboration of
alkynyl-halides thus is limited to forming tri-substituted
Scheme 3: The observation of 1,1- and 1,2-bromoboration under different
conditions. Inset, the solid state structure of 4, hydrogens omitted for clarity.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
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ARTICLE
Journal Name
alkenes).10 Indeed diaryl-derivatives (such as 8a-f Scheme 5), multiple haloborated isomers, e.g. 8h, had formed that could
View Article Online
DOI: 10.1039/C9SC05404A
have not been previously reported to the best of our not be separated in our hands.
knowledge. While 1,1-bromoboration represents a simple
approach to these compounds to be useful protection at boron hand, the extension of 1,1-haloboration/SEAr to other
without (or with minimal) competing formation of the starting substrates was explored. Using 1,6-bis((4-(tert-
alkyne by retro-bromoboration is required. In the presence of butyl)phenyl)ethynyl)pyrene, 9 (an analogue of 2) and BBr3 this
With an understanding of the bromoboration process in
excess triethylamine, the 1,1-bromoboration products (e.g. 5)
sequential transformation worked effectively and post mesityl
installation afforded 9a in 58% yield in a one-pot reaction
staring from 9. Compound 9a proved bench stable (as 9-12 a/b
all are) and was purified via column chromatography. The
borinic acid 9b could also be prepared from 9 in 62% yield via a
simple hydrolytic work-up. Starting from 7-(tert-butyl)-1,3-
bis((4-(tert-butyl)phenyl)-ethynyl)pyrene, 10, both the Mes-
protected product 10a and the borinic acid 10b also were
accessible, albeit isolated in lower yields. 1,1-haloboration/SEAr
also was applicable to perylene substrates. For 3-(p-
tolylethynyl)perylene, 11, the Tip-protected product 11a (50%)
and the borinic acid 11b (88%) were isolated post column
chromatography. The bromoboration/SEAr cyclisation reaction
R
Ar
(i) DCM, rt
BBr
+
Ar
R
3
(ii) Pinacol, NEt3
O
Br
B
R = Aryl, Me
O
8b
Solid-state structure of
Br1
Ph
Ph
Br
B
Pin
Br
B
Pin
8a
, 26%
8b
, 33%
B1
O2
Br
F
F
O1
Br
Br
Br
B
Pin
also
worked
with
3,9-bis((4-(tert-
BPin
, 39%
8c
8d
butyl)phenyl)ethynyl)perylene, 12, to yield the Mes-protected
compound B2-PAH 12a (54% yield) and the borinic acid 12b
(82% yield) depending on the protection protocol.
, 30%
Cl
Cl
HO
OH
Cl
Me
Ph
Br
Br
B
Pin
8g
, 16%
Br
Br
8f
Br
B
B
, 32%
Pin
Pin
B
, 28%
Pin
R
B
b
a
8h
, isomeric mixture
8e
Scheme 5: 1,1-haloboration and pinacol protection with yields. Inset right, solid
state structure of 8b, hydrogens omitted for clarity, ellipsoids at 50% probability.
A = from the p-MeO derivative with ether cleavage occurring concomitantly to
haloboration. B = pinacol protected without Et3N.
R
R
B
B
Br
Br
B
R
were converted into the pinacol boronate esters, 8a-g
demonstrating that ortho, meta and para substituted aryl-
alkynes are amenable to this procedure. The yields are
moderate at best due to the presence of the 1,2-isomer in the
reaction mixture and the propensity of the Br-vinyl-BBr2
isomers (e.g. 4 and 5) to undergo retrohaloboration in
competition to pinacol protection (see supporting information
for more details). Indeed, under these conditions all the 1,2-
bromoboration products (and the mass balance of the 1,1-
haloboration products) were converted into the starting alkyne
and Et3N-BBr3. Attempts at pinacol installation in the absence
of base led to competitive protodeboronation (presumably due
to the HBr by-product from pinacol installation onto the BBr2
moiety) and lower yields of 8x in most cases. The pinacol
boronate esters were fully characterised and a number
confirmed by X-ray diffraction analysis (e.g. inset scheme 5). It
should be noted that substrates containing CF3 were not
amenable to this process due to B-F/C-Br bond formation on
addition of BBr3. Furthermore, ether cleavage occurs
concomitantly to haloboration, with substrate 8f isolated from
the 4-methoxyaryl precursor. In addition, attempts to
bromoborate 2,2’-bisthienylethyne with BBr3 were successful to
some extent, but protection with pinacol under a range of
conditions was unsuccessful. This instead led to
protodeboronation under a range of conditions. Finally an
electronically biased diaryl alkyne was subjected to
haloboration in DCM, however pinacol protection revealed that
Br
9a
R = Mes =
9b
(58%)
(62%)
R = OH =
10a
10b
R = Mes =
R = OH =
(26%)
(25%)
R
B
Br
Br
Br
B
B
R
R
11a
11b
R = Tip =
R = OH =
(50%)
(88%)
12a
R = Mes =
12b
(54%)
(82%)
R = OH =
Scheme 6: The formation of extended Bn-PAHs by bromoboration/SEAr.
Solid-State Structures:
The solid-state structures of B1-PAHs 1a, 1c and 3b revealed
effectively planar six-membered boracycles with boron atoms
adopting a trigonal planar geometry (Σ(C-B-C) ≈ 360°). Notably,
the C12-C13 bond length (1.355(5) Å in 1a) is shorter than the
C11-C12, C1-C10 and C10-C11 bond lengths (1.462(5), 1.448(5)
and 1.414(4) Å, respectively in 1a) as is the case in 1c and 3b.
The bond length alternation indicates the lack of significant π
delocalisation within the boracycle as was observed with the 1-
boraphenalenes.7 The fusion of a boracycle onto the PAH core
does have some impact, for example on the C-C bond in the K-
region of pyrene. For 1a the bond length of C1-C2 (1.367(4) Å)
is longer than that of C14-C15 (1.337(5) Å). The elongation of
4 | J. Name., 2012, 00, 1-3
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C1-C2 Vs C14-C15 may indicate some delocalisation of this π-
electron density into the boron centre.11a For compound 3b, the
B-O bond length (1.369(4) Å) is close to the reported values for
other related borinic acids, indicating some multiple bond
character between boron and oxygen. The Mes/Tip and tert-
butylphenyl groups are all almost orthogonal to the boracycle,
which precludes close face to face pi stacking involving the
boracycles in the intermolecular structure.
View Article Online
DOI: 10.1039/C9SC05404A
Figure 4: Solid state structure of 12a (two views), with hydrogens omitted for
clarity. Ellipsoids are at the 50% probability level.
Cyclic voltammetry:
Figure 2: Solid-state structures of 1a (left) and 3b (right), most hydrogens omitted
for clarity. Ellipsoids at the 50% probability level.
The first reduction potentials ranged from -1.91 V (3b) to -0.96 V
(12a, table 1). Within the scan window, the B1-doped PAHs showed
one reversible reduction wave except for compound 11a, for which
two reduction waves were observed. All B2-PAHs showed two
reversible reduction waves; however, no oxidation waves were
observed within the solvent window for these compounds. The
hydroxyl group on boron reduced the electron-accepting abilities of
the boron-doped PAHs compared with the Tip/Mes group as
previously observed.4c Also as noted by Würthner and co-workers,4c
the boron doping pattern also significantly influences the redox
properties with the first reduction potential of 9a more positive than
that of 10a by 0.15 V (for 9b vs 10b ∆E1/2red1 = 0.32 V). Notably, the
reduction potential of 9a is more positive than bis-(BMes2)-pyrenes
The solid-state structures of the B2-doped PAHs 2a, 2c, 9a, 10b
and 12a also were determined (Figures 3-4 and SI). All five
compounds show planar π-conjugated cores with the peripheral
substituents effectively orthogonal to the PAH core. As a result, no
face to face π-stacking is observed in the extended structures for
these compounds (excluding 10b, see SI). For example, the face to
face intermolecular separation of the cores of two parallel molecules
is found to be 6.67 Å for 2c. The boracycle metrics are similar to the
mono-borylated compounds with C-C bond length alternation within
the boracycles also observed (for example a C11-C12 vinylic distance
in 12a of 1.359(7) Å and long endocyclic B-C bonds 1.534(6) and
1.543(6) Å indicate minimal  delocalisation consistent with previous
NICS calculations).7 Notably, for the diborylated pyrene compounds,
the length of the C-C bonds in the pyrene K-region is longer than that
in mono-borylated compound (e.g. the bond length of C7-C10 is
1.379(3) Å for compound 2c). The elongation of C7-C10 bond length
may indicate a greater delocalisation of these π-electrons into the
boron centres for the di-borylated compounds relative to the mono-
borylated compounds.
= -1.81 V)11 and the
red1
red1
(4,9 isomer E1/2
= -2.31 V, 1,6 isomer E1/2
products from the electrophilic borylation of 1,6-(2-pyridyl)2-pyrene
(when the boron moiety = BPh2 E1/2red1 = -2.08 V)14 this is ascribed to
greater  delocalization in 9a as a result of planarization and three-
coordinate B centres. Finally, 9a has a much more positive reduction
potential than its all carbon analogue (for which E1/2red1 = -2.11 V),15
further confirming boron-doping as an effective strategy to obtain
molecules with deep LUMOs due to their electron-deficient nature
(B2-PAHs are isoelectronic to dicationic carbon analogues).
Comparing pyrene and perylene core structures the reduction
potentials of the borylated perylene compounds are positively
shifted relative to the pyrene substrates. For example, the
monoborylated compound 11a exhibited the first reduction wave at
-1.43 V more positive than 3a by 0.23 V. Indeed among all the
compounds investigated, 12a shows the least negative first
red1
reduction potential with E1/2
= -0.96 V, which is also much more
positive than the related all carbon peropyrenes.16 To the best of our
knowledge, compound 12a has the least negative reduction
potential of all ambient stable three coordinate at boron B-doped
PAHs reported to date, with compound D being the ambient stable
Bn-PAH with the next least negative reduction potential (table 1).4c
Figure 3: Solid state structures of 2c (two views) and 9a, with hydrogens omitted
for clarity. Ellipsoids are at the 50% probability level.
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DOI: 10.1039/C9SC05404A
Table 1: Optoelectronic properties of Bn-PAH compounds and a PDI for comparison
red1
red2
E1/2
(V)a
E1/2
(V)a
LUMOexp
(eV)b

abs [ / 10-3 M-1 cm-1]
PL
(nm)c
PL
(%)d
Eg
(eV)e
HOMO
(eV)f
LUMO
(eV)f
(nm)c
3a
-1.66
-
-3.49
375 [18.04], 395 [15.12], 417[13.16],
491[17.98]
553, 592
9.2
2.26
-7.04
-2.29
3b
9a
-1.91
-1.03
-
-3.24
-4.12
359[3.81], 383[3.62], 404[5.34], 449[7.86]
345[3.23], 362[4.74], 396[2.64],
536[24.13], 567[18.00]
500, 532
599, 648
8.7
2.0
2.51
2.07
-6.97
-7.26
-2.05
-2.98
-1.49
9b
-1.42
-1.30
-1.73
-2.11
-3.73
-3.85
340[2.41], 355[3.69], 390[1.56],
501[32.13],528[25.05]
332[20.75], 386[21.72], 406[35.98],
435[15.45], 508[3.64], 545[4.88],
588[3.52]
557, 598
6.8
5.9
2.23
2.00
-6.97
-7.19
-2.60
-2.67
10a
614, 668, 729
10b
11a
-1.61
-1.43
-2.25
-2.06
-3.54
-3.72
380[34.50], 417[3.93], 443[6.04],
476[8.37], 507[11.57], 543[8.22]
314[57.13], 360[8.01], 405[10.53],
431[15.93], 456[26.37], 500[16.68],
534[33.55], 573[43.71]
560, 605, 657
591, 628
46.9
0.6
2.19
2.08
-7.00
-6.76
-2.43
-2.50
11b
-1.57
-
-3.58
312[28.42], 340[5.37], 410[7.71],
433[14.85], 456[13.10],
532, 570, 618
0.4
2.31
-6.68
-2.29
487[29.85],521[31.05]
12a
12b
-0.96
-1.28
-1.28
-1.54
-1.41
-4.19
-3.87
336[5.91], 392[5.49], 528[18.02],
568[44.48], 614[68.41]
370[1.48], 494[4.90], 530[12.52],
571[19.61]
634, 686
582, 630
1.6
3.8
1.93
2.10
-7.06
-6.86
-3.08
-2.74
Dg
PDIh
-1.07
-1.02
-4.08
-4.13
611, 417
527
668
534
74
99
-
-
-7.21
-2.89
a = Measurements carried out at 298 K in THF with 0.1 M nBu4NPF6 as the supporting electrolyte. Electrochemical reduction potentials were calibrated with ferrocene as internal
standard and referenced vs Fc+/Fc. b = ELUMO = −E1/2red − 5.15 eV.12 c = Optical measurements carried out at 298 K in toluene at 1 × 10-5 M. d Under aerated conditions using [Ru(bpy)3]
(PF6)2 in CH3CN as the reference (PL: 1.8%). e = Eg were determined at the energy corresponding to 10% of the lowest energy absorption band. f = from calculations at the M06-
2X/6-311G(d,p) level. g = from ref. 4c. h = PDI refers to the perylene diimide with N-DIP substituents from ref. 13.
Photophysical properties:
Computational studies
By varying the polycyclic core and the boron substituent, a series of To provide more insight into the trends observed in the experimental
Bn-doped PAHs (n= 1, 2) are obtained forming solutions with colours data, DFT calculations were performed at the M06-2X/6-311G(d,p)
ranging from yellow to dark blue. UV-vis absorption and fluorescence level with a polarisable continuum model (PCM) of DCM, calculations
spectra were recorded and the optical energy gap estimated (Table for emulated the full compound (except for 2c, see SI). The trend in
1). All compounds showed well resolved absorption/emission the LUMO energies from the computational results were consistent
profiles with small Stokes shifts. Consistent with the observed with the trends in the cyclic voltammetry data with compound 3b,
solution colours, the obtained spectra showed the lowest energy that has the most negative reduction potential, being calculated
absorption band spanning 449 nm (3b, light yellow solution) to 614 to have the highest LUMO energy (-2.05 eV) among the
nm (12a, dark blue solution). The double borylated compound 9a compounds studied, while compound 12a with the least
showed λmax at 567 nm, which is red-shifted by 82 nm compared with negative reduction potential was predicted to have the deepest
the mono-borylated compound 3a (λmax = 491 nm). The same trend LUMO level (-3.08 eV, see Figure 5). It is noteworthy that the
was also observed for 11a/12a, due to the extended conjugation and computed LUMO energy level of 12a is lower than that of a
double boracycle annulation leading to narrower HOMO-LUMO perylene diimide (PDI, in red Figure 5) calculated at the same
gaps. In addition, all borinic acids exhibited hypsochromic shifts of level of theory. Indeed comparison of the CV data for 12a and a
their lowest absorption band by ca. 40 nm compared with the PDI compound (containing all C-H and two N-DIP groups),
Tip/Mes protected analogues. The photoluminescence quantum confirms that 12a has the deeper LUMO,13 while 9a has very
yield (PL) of the brominated compounds studied herein were similar frontier orbital energies to this PDI (Table 1). This further
relatively low, which might be attributed to the heavy atom effect of indicates that both these diborylated pyrene and perylene
bromine, as related heavy atom free analogues reported by compounds have potential as acceptor moieties in organic
Würthner and co-workers are notably more emissive (PLs up to electronics.
95%).4c
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View Article Online
DOI: 10.1039/C9SC05404A
Figure 5: Calculated frontier orbitals (shown at iso-values of 0.03) for several B2-PAHs and for comparison an N-Me substituted PDI. Ar = p-tBu-phenyl.
-2.60
-2.62
-2.74
-2.89
-2.98
-3.08
Br
Br
Ar
Br
Br
Ar
Ar
OH
OH
O
N
O
Br
B
B
OH
Ar
Mes
Ar
Mes
B
B
B
B
B
HO
Ar
Br
HO
Ar
B
Br
B
HO
Ar
Mes
Ar
O
N
O
B
Br
Compound G
Compound 9b
Mes
Ar
Br
Compound 12b
CompoBurnd 12a
N-Me PDI
Compound 9a
-6.86
-6.93
-6.97
-7.06
-7.21
-7.26
As shown in Figure 5 and the SI, the LUMO and HOMO of all
molecules are delocalised over the whole π-backbone and
involve boron contributions to both. Interestingly, the frontier
molecular orbital distributions of 12a and 12b are very similar
to that of PDI. Furthermore, the frontier orbitals of all the B2-
PAHs studied herein (and indeed the related compounds
reported by Würthner et al.)4c are related closely to the
calculated HOMO and LUMO of the parent  core molecule (e.g.
the HOMO and LUMO of pyrene and perylene)17 with some
additional contributions from the appended B-C unit. For
completeness, the anthracene-based compound G (blue, Figure
5) was also calculated, which revealed that the HOMO and
LUMO of this compound also was related in character to the
HOMO and LUMO of anthracene. Note, attempts to synthesise
G failed in our hands, possibly due to the additional peri C-H
group inducing steric clash with the proximal aryl group (with
some structural distortion observed in the calculated structure
of G). It is notable that the trend in the relative HOMO/LUMO
energy and optical gap of 9b, G and 12b mirrors that of the
parent PAH core,18 with perylene (deepest LUMO / highest
HOMO) < anthracene < pyrene (highest LUMO / deepest
HOMO) for optical gap. This indicates that access to even lower
LUMO energy B2-PAHs for this series maybe possible starting
from lower energy LUMO core PAH structures.
Functionalisation of Boron Doped PAHs by Cross Coupling
One attraction of the compounds reported herein is the
potential utility of the bromide unit, derived from the
concomitant installation of B/Br in the initial step of Bn-PAH
formation. While cross coupling reactions can be performed
using the C-B units as the nucleophilic coupling partner,19 this
removes the electronic effect of B-doping, thus utilising the C-
Br unit in cross-coupling reactions offers a way to construct
complex functional electronic materials that retain the C3B units
that impart the deep LUMO character.3 Initially compound 3a
containing the sterically more demanding Tip unit, was explored
and found to be amenable to Negishi cross coupling reaction
conditions. Specifically, in the presence of Pd(PPh3)4, 3a reacted
with the in-situ generated aryl-zinc reagent affording the
desired product 13 (Scheme 7) in moderate 33% isolated yield.
We attribute the modest yield to the highly sterically
encumbered vinyl-Br position present in these B-PAHs, thus the
B-Mes derivatives were explored.
tBu
(iii) THF, Pd(PPh3)4, 80 °C
3a
B
(i) n-BuLi, THF, -78 °C
Tip
Br
13
(33%)
(ii) ZnCl2, -78 °C to rt
Scheme 7: Negishi cross coupling to form compound 13.
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The same methodology could be applied to B-Mes of the band showing a maximum at 530 nm and a shoulder at
View Article Online
DOI: 10.1039/C9SC05404A
derivatives to access a D-A-D molecule with a narrow HOMO- 600 nm are assigned to be charge transfer (CT) states from the
LUMO energy gap. Using the procedure established for 13, 9a Ph2NPh group to the B2-PAH core (S0S1, S0S2). The principal
was coupled with the organozinc compound derived in-situ distinguishable absorption features at 444 nm originate from
from 4-bromotriphenylamine to construct compound 14 (Figure mixed CT/LE (LE = locally excited) transitions, but this time the
6). The desired double cross coupled product, 14, was isolated CT contribution implicates the mesityl groups as donors to the
by column chromatography in 21% yield. Cyclic voltammetry B2-PAH core (S0S3, S0S4, see supporting information for
measurements on compound 14 showed one oxidation wave more details); the LE contribution is localized on the B2-PAH
within the solvent window (peak-current Eox = 0.49 V vs Fc/Fc+) acceptor. Higher energy bands involve increasing contributions
red1
red2
and two reduction processes (E1/2
= -1.23 V, E1/2
= -1.62 of LE transitions of the B2-PAH core. Recognizing the propensity
V). The first reduction process is shifted cathodically by 0.2 V of large acenes to aggregate in solution, even at very dilute
relative to 9a, presumably due to the replacement of inductively concentrations we next investigated the effect of concentration
electron-withdrawing bromine for the triphenylamine groups. on both the absorption and emission spectra. We note that
DFT calculations (Fig. 6, bottom) were performed on compound both the  values and the spectral features were independent
14 at a lower level due to its size (M06-2x/6-31G(d)), 9a was of concentration, precluding aggregation of the molecule in its
calculated at the same level for direct comparison (which ground state in DCM at the concentrations studied (see
confirmed effectively identical HOMO/LUMO distributions for Supporting Information). In contrast, the emission in DCM was
9a using the two basis sets). Consistent with a D-A molecule the highly concentration dependent. At 0.15 mol/mL the emission
HOMO/LUMO are spatially separated, with the HOMO is broad and unstructured and centred at 479 nm. As the
predominantly localised on the triaryl amine unit thus being concentration is increased to 63 mol/mL, there is a decrease
0.91 eV higher in energy than the HOMO of 9a. The LUMO in 14 in intensity of this band coupled with a progressive and
is localised on the B2-PAH acceptor unit and is closely related in significant red-shift of the emission. At the highest
character to the LUMO of 9a. Notably, the calculated energy for concentrations studied, the emission narrows but remains
the LUMO of 14 is 0.19 eV higher than that for 9a in excellent unstructured (Figure 7). We attribute this complex behaviour to
agreement with the CV data; again this is attributed to the the formation of mixtures of different excimers as the
exchange of inductively withdrawing Br groups for triarylamine concentration increases, presumably with higher order
units.
aggregates forming at the higher concentrations.
Figure 6: CV data, for compound 14 (1 mM solution in THF with 0.1 M [NBu4][PF6],
potential calibrated Vs Fc/Fc+). Inset bottom, HOMO and LUMO of compound 14
(isovalue 0.025) at the M06-2x/6-31G(d) level.
The photophysical properties of 14 in solution, solid-state
and dispersed in a PMMA film were investigated. Compound 14
displayed a broad absorption band stretching up to 750 nm in
dichloromethane, with the onset corresponding to a optical gap
of 1.65 eV (comparable to Eredox determined by
electrochemistry). Thus, the strong acceptor character of the
B2-PAH unit combined with the triphenylamine donor units
results in a low HOMO-LUMO energy gap. We employed time-
dependent DFT (TDDFT) calculations using the Tamm-Dancoff
approximation at the PBE0/6-31G(d,p) level of theory to assign
the spectral features observed in the absorption spectrum of
14. The lowest energy absorption features found within the tail
Figure 7: Top, photophysical data for compound 14 in DCM solution and in the
solid state (neat film and dispersed in PMMA). Bottom, variation in the emission
spectra on change of concentration of 14 in DCM solution. λexc=370 nm.
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unprecedented 1-bromo-2,2-diaryl substituted vinylboronate
View Article Online
The PL value in DCM for 14 at 0.52 μmol mL−1 is 4% and this esters direct from internal alkynes. The utility of the 1,1-
value is not sensitive to oxygen. The excited state emission bromoboration reaction is being studied further in our
decays measured at both dilute (0.52 mol mL-1) and laboratory as are the brominated-B2-PAHs, particularly to
concentrated (33 mol mL-1) solutions are multi-exponential in access useful functional materials.
nature but remain in the ns regime, consistent with a
DOI: 10.1039/C9SC05404A
fluorescence mechanism. In order to mitigate these non-
radiative pathways, we next investigated the solid-state
Conflicts of interest
photophysical properties as thin films in PMMA at 0.1, 1 and 10
wt% doping concentrations, and as neat films. Generally, the
same evolution in emission profiles is observed in the solid-
state as was observed in DCM. As a 0.1 wt% PMMA doped film
two unstructured emission bands are observed, one of higher
relative intensity at high energy at PL = 442 nm that we ascribe
to the same monomer emission observed in dilute DCM, and a
lower intensity and broader low energy band at PL = 638 nm
that we ascribe to excimeric emission. The PL of this film is 5%,
which is essentially identical to that measured in DCM. This
suggests that during the spin-coating process aggregation
remains strong even at this low doping concentration. As a 1
wt% PMMA doped film, two unstructured emission bands
remain, one at PL = 472 nm and one at PL = 726 nm; here, we
note the large red-shift and significant enhancement in
intensity of the low-energy band. The PL of this film is slightly
lower at 3%. The 10 wt% doped PMMA film also shows two
emission bands where the relative intensity of the high energy
band at PL = 434 nm is reduced further compared to the low
energy band at PL = 793 nm. The PL of this film is < 1%. The
neat film shows only a single very weak and red-shifted
emission band at PL = 824 nm with a PL < 1%. There is a
systematic shortening of the PL with increasing doping
concentrations that mirrors the decrease in PL (see Supporting
Information). Irrespective of the complexity of the emission
spectra the successful formation of the low optical gap material
14 demonstrates the utility of these dibrominated B2-PAHs in
accessing complex organic materials.
There are no conflicts to declare.
Acknowledgements
The research leading to these results has received funding from
the European Research Council under the Horizon 2020
Research and Innovation Program (Grant no. 769599), the
Leverhulme Trust (RPG-2014-340) and the EPSRC
(EP/P010482/1). C. Si thanks the China Scholarship Council
(201806890001). Dr G. Nichol is thanked for the collection of X-
ray diffraction data, Dr G. Whitehead for the structure of 2a and
Dr A. Woodward for collecting photophysical data on
compound 2c (see Supporting Information).
Notes and references
1
Main Group Strategies towards Functional Hybrid Materials,
ed. T. Baumgartner and F. Jäkle, John Wiley & Sons, Ltd.,
Chichester, 1st edn., 2018.
2
For recent reviews at least partly focused on PAHs containing
C3B units see: (a) Z. Huang, S. Wang, R. D. Dewhurst, N. V.
Ignat’ev, M. Finze and H. Braunschweig, Angew. Chem. Int.
Ed., 2019, DOI: 10.1002/anie.201911108. (b) M. Hirai, N.
Tanaka, Sakai and S. Yamaguchi, Chem. Rev., 2019, 119, 8291.
(c) X.-Y. Wang, X. Yao, K. Müllen, Sci. China Chem., 2019, 62,
1099 (d) S. K. Mellerup and S. Wang, Trends in Chemistry,
2019, 1, 77; (e) E. von Grotthuss, A. John, T. Kaese and M.
Wagner, Asian J. Org. Chem., 2018, 7, 37; (f) M. Stepien, E.
Gonka, M. Zyła and N. Sprutta, Chem. Rev., 2017, 117, 3479;
(g) L. Ji, S. Griesbeck and T. B. Marder, Chem. Sci., 2017, 8, 846;
(h) A. Escande and M. J. Ingleson, Chem. Commun., 2015, 51,
6257; (i) A. Wakamiya and S. Yamaguchi, Bull. Chem. Soc. Jpn.,
2015, 88, 1357. For their use in electrocatalysis see: (j) R. J.
Kahan, W. Hirunpinyopas, J. Cid, M. J. Ingleson, R. A. W Dryfe,
Chem. Mater. 2019, 31, 1891.
Conclusions
In conclusion, sequential bromoboration/ intramolecular
electrophilic C-H borylation enables formation of a range of
brominated Bn-doped PAHs in useful yields via an operationally
simple, one-pot route from readily available precursors (alkynes
and BBr3). Cyclic voltammetry and photophysical studies
revealed that these molecules have very low LUMO energies
thus are attractive acceptor units for use in organic electronic
applications. In particularly, compound 12a has the least
negative reduction potential among all reported ambient stable
B-boron-doped PAHs to the best of our knowledge. The C-Br
units in the Bn-PAHs can be utilised directly in Negishi cross-
coupling reactions, which enabled formation of a donor-
acceptor-donor molecule displaying solution absorption up to
750 nm. Finally, mechanistic studies on the bromoboration
reaction indicated it proceeds through the 1,1-bromoboration
of the diarylalkynes, a reaction not previously observed using
just boron electrophiles. 1,1-Bromoboration can be applied to
functionalise other diarylalkynes, enabling access to
3
4
For rare example of halogenated-Bn-PAH formation, in this
case starting from halo-aromatic precursors and their utility
in cross coupling, see: (a) C. Reus, S. Weidlich, M. Bolte, H.-W.
Lerner and M. Wagner, J. Am. Chem. Soc., 2013, 135, 12892;
(b) A. Shuto, T. Kushida, T. Fukushima, H. Kaji and S.
Yamaguchi, Org. Lett., 2013, 15, 6234.
For seminal work in the area of forming solely Bn-doped PAHs
with three coordinate B centres see: (a) C. Dou, S. Saito, K.
Matsuo, I. Hisaki and S. Yamaguchi, Angew. Chem. Int. Ed.,
2012, 51, 12206; (b) Z. Zhou, A. Wakamiya, T. Kushida, S.
Yamaguchi, J. Am. Chem. Soc., 2012, 134, 4529. For select
recent examples on this topic see: (c) J. M. Farrell, C. Mützel,
D. Bialas, M. Rudolf, K. Menekse, A.-M. Krause, M. Stolte and
F. Würthner, J. Am. Chem. Soc., 2019, 141, 9096. (d) J. Radtke,
K. Schickedanz, M. Bamberg, L. Menduti, D. Schollmeyer, M.
Bolte, H.-W. Lerner and Matthias Wagner, Chem. Sci., 2019,
10, 9017. (e) A. John, S. Kirschner, M. K. Fengel, M. Bolte, H.-
W. Lerner and M. Wagner, Dalton Trans., 2019, 48, 1871; (f)
R. J. Kahan, D. L. Crossley, J. Cid, J. E. Radcliffe, A. W.
Woodward, V. Fasano, S. Endres, G. F. S. Whitehead and M. J.
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Ingleson Chem. Commun., 2018, 54, 9490; (g) S. Kirschner, J.- 10 In
Journal Name
1,1-bromoV-BiewpiAnr-tiacllekOennlienes
contrast
tri-substituted
M. Mewes, M. Bolte, H.-W. Lerner, A. Dreuw and M. Wagner,
Chem.–Eur. J., 2017, 23, 5104; (h) A. John, M. Bolte, H.-W.
Lerner and M. Wagner, Angew. Chem., Int. Ed., 2017, 56,
5588; (i) D. L. Crossley, R. J. Kahan, S. Endres, A. J. Warner, R.
derivatives are known, for a recent example see: Y. Pang, R.
Kojima and H. Ito, Org. Biomol. Chem.,D2O0I1: 180,.11063,96/C198S7C.0F5o4r0a4nA
early example see: H. C. Brown and T. Imai, Organometallics,
1984, 3, 1392.
A. Smith, J. Cid, J. J. Dunsford, J. E. Jones, I. Vitorica-Yrezabal 11 (a) L. Ji, I. Krummenacher, A. Friedrich, A. Lorbach, M.
and M. J. Ingleson, Chem. Sci., 2017, 8, 7969; (j) J. M. Farrell,
D. Schmidt, V. Grande and F. Würthner, Angew. Chem., Int.
Ed., 2017, 56, 11846. (k) V. M. Hertz, M. Bolte, H.-W. Lerner
and M. Wagner, Angew. Chem. Int. Ed., 2015, 54, 8800.
There are also boron containing polymers that are Bn-PAHs 12 Adapted from: C. M. Cardona, W. Li, A. E. Kaifer, D. Stockdale
with n>2, however, while chemically well-defined the value of and G. C. Bazan, Adv. Mater. 2011, 23, 2367.
n is not as they are polydisperse. For select examples see: (a) 13 A. Nowak-Krol, K. Shoyama, M. Stolete and F. Würthner,
S. Kawai, S. Saito, S. Osumi, S. Yamaguchi, A. S. Foster, P. Chem. Commun., 2018, 54, 13763.
Spijker and E. Meyer, Nat. Commun., 2015, 6, 8098; (b) R. R. 14 M. Vanga, R. A. Lalancette, F. Jäkle, Chem. Eur. J., 2019, 25,
Cloke, T. Marangoni, G. D. Nguyen, T. Joshi, D. J. Rizzo, C. 10133.
Bronner, T. Cao, S. G. Louie, M. F. Crommie and F. R. Fischer, 15 Y. Gu, X. Wu, T. Y. Gopalakrishna, H. Phan and J. Wu, Angew.
J. Am. Chem. Soc., 2015, 137, 8872. Chem. Int. Ed., 2018, 57, 6541.
For examples of post synthetic modification of Bn-PAHs and 16 W. Yang, R. R. Kazemi, N. Karunathilake, V. J. Catalano, M. A.
Haehnel, K. Edkins, H. Braunschweig, T. B. Marder, J. Org.
Chem., 2018, 83, 3599. (b) S.-B. Zhao, P. Wucher, Z. M.
Hudson, T. M. McCormick, X.-Y. Liu, S. Wang, X.-D. Feng, Z.-H.
Lu, Organometallics, 2008, 27, 6446.
5
6
subsequent functionalisation by cross coupling see: (a) T.
Kushida, C. Camacho, A. Shuto, S. Irle, M. Muramatsu, T.
Alpuche-Aviles and W. A. Chalifoux, Org. Chem. Front. 2018,
5, 2288.
Katayama, S. Ito, Y. Nagasawa, H. Miyasaka, E. Sakuda, N. 17 M. A. Filatov, S. Karuthedath, P. M. Polestshuk, S. Callaghan,
Kitamura, Z. Zhou, A. Wakamiya and S. Yamaguchi, Chem. Sci.,
2014, 5,1296; (b) C. Hoffend, K. Schickedanz, M. Bolte, H.-W.
Lerner, M. Wagner, Tetrahedron, 2013, 69, 7073.
K. J. Flanagan, T. Wiesner, F. Laquai, and Mathias O. Senge,
ChemPhotoChem., 2018, 2, 606.
18 A. P. Davis, A. J. Fry, J. Phys. Chem. A., 2010, 114, 12299.
7
8
R. J. Kahan, D. L. Crossley, J. Cid, J. E. Radcliffe, M. J. Ingleson, 19 (a) J. M. Farrell, V. Grande, D. Schmidt and F. Würthner,
Angew. Chem. Int. Ed., 2018, 57, 8084.
Angew. Chem. Int. Ed., 2019, 58, 16504. (b) E. Dimitrijevic, M.
Cusimano and M. S. Taylor, Org. Biomol. Chem. 2014, 12,
1391.
(a) M. F. Lappert, B. Prokai, J. Organomet. Chem. 1964, 1, 384.
(b) Related findings were subsequently published: J. J. Eisch,
L. J. Gonsior, J. Organomet. Chem., 1967, 8, 53.
9
For recent studies combining alkynes and R2B-X see: K. Skoch,
C. Pauly, C. G. Daniliuc, K. Bergander, G. Kehr and G. Erker,
Dalton. Trans. 2019, 48, 4837; (b) J. R. Lawson, V. Fasano, J.
Cid, I. Vitorica-Yrezabal and M. J. Ingleson, Dalton Trans.,
2016, 45, 6060. For an early example see: (c) R.-J. Binnewirtz,
H. Klingenberger, R. Welte and P. Paetzold, Chem. Ber., 1983,
116, 1271
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