Binaphthyl platform as starting materials for the preparation of electron rich benzo[g,h,i]perylenes. Application to molecular architectures based on amino benzo[g,h,i]perylenes and carborane combinations

Article abstract of DOI:10.1039/c1cc12099a

Valuable amino benzo[g,h,i]perylenes have been obtained through a one pot electrophilic aromatic substitution - Scholl reaction sequence. Novel molecular architectures combining 3D-o-carborane and planar amino benzo[g,h,i]perylene units are described. Photophysical properties of amino benzo[g,h,i]perylene and the carborane-appended derivatives are discussed.

Full text of DOI:10.1039/c1cc12099a

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COMMUNICATION
Binaphthyl platform as starting materials for the preparation of electron
rich benzo[g,h,i]perylenes. Application to molecular architectures based
on amino benzo[g,h,i]perylenes and carborane combinationsw
a
a
a
b
c
´
´
Gregory Pieters, Anne Gaucher,* Damien Prim, Thierry Besson, Jose Giner Planas,*
˜
Francesc Teixidor,c Clara Vinas,c Mark E. Lightd and Michael B. Hursthoused
Received 12th April 2011, Accepted 17th May 2011
DOI: 10.1039/c1cc12099a
Valuable amino benzo[g,h,i]perylenes have been obtained
through a one pot electrophilic aromatic substitution—Scholl
reaction sequence. Novel molecular architectures combining
3D-o-carborane and planar amino benzo[g,h,i]perylene units
are described. Photophysical properties of amino benzo[g,h,i]-
perylene and the carborane-appended derivatives are discussed.
step (Fig. 1). Oxidative Scholl-type reaction or flash vacuum
pyrolysis-induced cyclodehydrogenation has recently been
reported to promote the transformation of adequately sub-
stituted [5]helicenes.4 Our sequence started with the Suzuki
coupling between cyanomethyl bromonaphthalene 15 and
naphthalene, acenaphthene or phenanthrene boronic acids
2a, 2b or 2c respectively. It should be noted that the formation
of the binaphthyl unit does not require the use of elaborated
catalytic systems6 and can be realized under rational reaction
conditions using the commercially available [PdCl2(PPh3)2]
complex.7 Once the cyanomethylene pendant arm was installed
onto the binaphthyl unit, 3a, 3b or 3c8 was treated under acidic
conditions to promote the generation of the corresponding
electrophile and the formation of the expected [5]-amino-
helicenes 4.9 Surprisingly, the use of PPA at 110 1C did not
afford the expected helicenes. In contrast, such conditions
account for the direct access to targeted amino benzo[g,h,i]-
perylenes 5 through concomitant formation of two carbon–
carbon bonds involving the creation of the benzo-fused ring
and the perylene architecture. As shown in Fig. 1, binaphthyls
3 afforded amino benzo[g,h,i]perylenes 5a to 5c in moderate to
good yields. It is worth noting that no traces of the corresponding
[5]-aminohelicene 4 could be detected. As it can be seen from
Fig. 1, this methodology affords a convergent access to the
amino benzo[g,h,i]perylene core.
Benzo[g,h,i]perylenes also called dehydrohelicenes are valuable
intermediates in the synthesis of planar coronenes and have
applications in materials science.1 Usually such motifs are
obtained through Diels–Alder reactions involving perylene
derivatives and activated dienophiles. This strategy allowed
an access to benzo[g,h,i]perylenes substituted with electron
withdrawing groups but harsh reaction conditions are needed.2
In contrast, introduction of an electron donating group is not
trivial and at best, scarcely reported.3 In this communication, we
report that amino benzo[g,h,i]perylenes are (1) easily synthesized,
(2) valuable precursors for the preparation of carborane-
appended derivatives, and (3) fluorescent molecules.
The synthesis of amino benzo[g,h,i]perylene architectures
was envisioned through a three step sequence that would
involve the construction of a binaphthyl unit 3 through
Suzuki-type coupling reaction, followed by the polyphosphoric
acid (PPA)-promoted creation of the [5]helicene 4.
The perylene architecture 5 arises from an oxidative
cyclodehydrogenation of the parent aminohelicene in the last
a
´
Universite de Versailles-Saint-Quentin-en-Yvelines, Institut Lavoisier
de Versailles, UMR CNRS 8180, 45, Avenue des Etats-Unis,
78035 Versailles, France. E-mail: anne.gaucher@chimie.uvsq.fr,
prim@chimie.uvsq.fr; Fax: +33 1 39254452; Tel: +33 1 39254454
b
c
´
Universite de Rouen-CNRS UMR 6014 & FR3038, IRCOF
(Research Institute in Fine Organic Chemistry)rue Tesniere,
`
76130 Mont Saint Aignan, France
`
Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC),
Campus de la UAB, 08193 Bellaterra, Spain.
E-mail: jginerplanas@icmab.es; Fax: +34 93 580 57 29;
Tel: +34 93 580 18 53 (Ext. 361)
d School of Chemistry, University of Southampton, Highfield,
Southampton, SO17 1BJ, UK
w Electronic supplementary information (ESI) available: Experimental
preparations for 5a, 5b, 5c, 7 and 8. CCDC 818695 (7). For ESI and
crystallographic data in CIF or other electronic format see DOI:
10.1039/c1cc12099a
Fig. 1 Direct access to amino benzo[g,h,i]perylene architectures.
Chem. Commun., 2011, 47, 7725–7727 7725
c
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Fig. 2 DFT geometry optimisation for 5a–5c.
Scheme 2 Combination of 3D-o-carborane and planar amino benzo-
As already known, DFT geometry optimization described in
Fig. 2 confirmed a large plane deformation in 5c by comparison
with the fully planar perylene 5a, plausibly due to the additional
installation of a condensed phenyl ring in 5c. The presence of
an ethylidene fragment in 5b only poorly affects the planar
geometry of 5b by comparison with 5a.10
[g,h,i]perylene units.
The construction of benzo[g,h,i]perylenes 5 results from
the creation of two carbon–carbon bonds. The first step of
this mechanism most likely involves an SEAr reaction after
PPA-promoted generation of the electrophile. The second step
may result from the successive formation and delocalization of
an arenium cation and further Scholl-type reaction11 allowing
the creation of the second carbon–carbon bond and thus the
expected perylene core. Rearomatization under acidic conditions
accounts for the obtention of benzo[g,h,i]perylenes 5. Thus, a
plausible mechanism would involve a SEAr-Scholl reaction
sequence as described in Scheme 1.
Fig. 3 Supramolecular assembly of 7 showing the p–p stacking and
C–HÁ Á Áp interactions in A. See ESIw for metric parameters. Color
code: B—pink; C—grey; H—white; N—violet.
an unprecedented ‘‘3D-planar’’ molecular architecture but also
the first exemplification of the benzo[g,h,i]perylene nitrogen atom
nucleophilicity and the investigation of the carboranyl moiety
effect on physical and photophysical properties of benzo[g,h,i]-
perylene.
Based on previous results,18 we envisioned the alkylation of
amino benzo[g,h,i]perylene with chloro(phenylmethyl)carborane
6 using Et3N, KI in refluxing acetonitrile (Scheme 2).
If the aforementioned mechanism shows the helicene unit as
a key intermediate, the required activation allowing the SEAr
reaction seems high enough to in situ generate the Scholl-
induced carbon–carbon bond formation giving rise to the perylene
architecture. This unprecedented one pot methodology does
not require the use of further cyclodehydrogenation oxidative
process to promote the formation of perylenes from helicenes
as recently described.3,12 Because microwave-assisted heating
has been shown to reduce processing times and increase product
yields, some experiments were performed in a monomode
cavity. Unfortunately despite various trials, no enhancement
of the yields was observed.13
Benzo[g,h,i]perylene is a well known fluorescent molecule.14
In the emerging context of photophysical properties originated
from 3D-pseudoaromaticity and electron withdrawing
properties15 of carborane cages, the association of organic
molecules to 3D-carboranes has recently raised the interest
of the scientific community. Incorporation of carboranes to
p-based organic units leading to an extended conjugation has
been shown to affect both absorption and emission.16 Carborane-
appended systems in which the carborane and a p-conjugated
molecule are separated by a methylene group that interrupts
conjugation have also been shown to exhibit photophysical
properties with enhanced quantum yields.17 In the latter case,
emission may be strongly impacted depending on the ability of
the 3D-carborane unit to prevent p–p staking interactions. In
this context, combination of a carborane unit with an amino
benzo[g,h,i]perylene would allow not only the preparation of
For convenience, we selected perylenes 5a and 5c for testing
the alkylation reaction. Under these conditions, architectures
7 and 8, combining 3D-o-carborane and planar amino
benzo[g,h,i]perylene units, were obtained in reasonable yields.
Single crystals of 7 were obtained by slow evaporation of a
dichloromethane solution. Solid state analysis confirmed the
molecular structure of 7 and evidenced the formation of
supramolecular dimers by both p–p interactions between two
benzo[g,h,i]perylene units as well as edge-to-face interactions
between the amino benzo[g,h,i]perylene and the phenyl substi-
tuent of the carboranylmethyl unit (Fig. 3).
The absorption and emission spectra of 5a–c, 7 and 8 in
THF are shown in Fig. 4 and Table 1. As expected, the
introduction of an electron-donating group such as –NH2 into
the benzo[g,h,i]perylene fragment to give 5a causes a shift and
broadening of the absorption and fluorescence spectra with
respect to benzo[g,h,i]perylene.19,20 The lone pair on the
nitrogen atom of these aromatic amines is probably involved
in the p bonding and thus a significant intramolecular charge
transfer character of the relevant transitions is expected. The
latter is confirmed by the fact that both the absorption and
emission spectra for all amines are broad and structureless
(Fig. 4). Amines 5a–c show close maximum absorption spectra
ranging from 311 to 308 nm with high molar extinction
coefficient values corresponding to the p–p* transition of the rigid
benzo[g,h,i]perylene fragment. Interestingly, a slight decrease
of the e value from 5a to 5c (De = 5200 MÀ1 cmÀ1) and a large
decrease of it from 5a to 5b (De = 31 000 MÀ1 cmÀ1) are
observed. All amines show photoluminescence (PL) properties
Scheme 1 Plausible mechanism.
c
7726 Chem. Commun., 2011, 47, 7725–7727
This journal is The Royal Society of Chemistry 2011

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We thank CICYT (Project CTQ2010-16237), Generalitat de
Catalunya (2009/SGR/00279), CSIC (PIE ref. 200860I097),
CNRS and MESR for financial support.
Notes and references
1 R. W. Munn and W. Siebrand, J. Chem. Phys., 1970, 52, 47;
R. W. Munn and W. Siebrand, J. Chem. Phys., 1970, 52, 6391;
D. Adam, P. Schuhmacher, J. Simmerer, L. Haeussling,
K. Siemensmeyer, K. H. Etzbach, H. Ringsdorf and D. Haarer,
Nature, 1994, 371, 141; A. M. Van de Craats, J. M. Warman,
A. Fechtenkotter, J. D. Brand, M. A. Harbison and K. Mullen,
Adv. Mater., 1999, 11, 1469; J. M. Warman, M. P. de Haas,
G. Dicker, F. C. Grozema, J. Piris and M. G. Debije, Chem.
Mater., 2004, 16, 4600; F. Wurthner and R. Schmidt,
ChemPhysChem, 2006, 7, 793.
2 S. Alibert-Fouet, I. Seguy, J. F. Bobo, P. Destruel and H. Bock,
Chem.–Eur. J., 2007, 13, 1747.
3 J.-D. Chen, H.-Y. Lu and C.-F. Chen, Chem.–Eur. J., 2010,
16, 11843. For donating group-substituted coronenes see:
A. Zinke, F. Hanus and O. Ferrares, Monatsh. Chem., 1948,
78, 343; R. Rieger, M. Kastler, V. Enkelmann and K. Muellen,
Chem.–Eur. J., 2008, 14, 6322. For dibenzo[b,pqr]perylene see:
X. Xue and L. T. Scott, Org. Lett., 2007, 9, 3937.
4 X. Xue and L. T. Scott, Org. Lett., 2007, 9, 3937; J. H. Dopper,
D. Oudman and H. Wynberg, J. Org. Chem., 1976, 40, 3398.
5 N. Aoyagi and T. Izumi, Tetrahedron Lett., 2002, 43, 5529; X. Xue
and L. T. Scott, Org. Lett., 2007, 9, 3937; J. H. Dopper,
D. Oudman and H. Wynberg, J. Org. Chem., 1975, 40, 3398.
6 V. Terrasson, J. Marrot and D. Prim, Eur. J. Inorg. Chem., 2008,
2739.
7 C. W. Whitaker and R. J. McMahon, J. Phys. Chem., 1996,
100, 1881.
8 Noteworthily nitriles 3b or 3c have been used as crude material and
do not require additional purification.
9 G. Pieters, A. Gaucher, J. Marrot and D. Prim, Chem. Commun.,
2009, 4827; G. Pieters, A. Gaucher, S. Marque, F. Maurel, P. Lesot
and D. Prim, J. Org. Chem., 2010, 75, 2096.
Fig. 4 Absorption and emission spectra of compounds in THF:
(top) amino benzo[g,h,i]perylenes: 5a (red), 5b (green), 5c (blue).
(bottom) o-Carborane-appended amino benzo[g,h,i]perylenes: 7 (black),
8 (yellow).
Table 1 Absorption and emission spectra were realized at 5 Â 10À6 in
THF. Excitation wavelength: 316 nm
Structure
lmax/nm
e/MÀ1 cmÀ1
lem/nm
Stokes shift
5a
5b
5c
7
311
309
308
316
314
48 300
17 300
43 100
32 800
35 700
481
475
474
453
449
170
166
166
137
135
10 DFT calculations show a slight increase of the abcd dihedral angle
8
from 0.01 (in 5a) to 0.023 (in 5b), see ESIw.
11 B. T. King, J. Kroulik, C. R. Robertson, P. Rempala, C. L. Hilton,
J. D. Korinek and J. M. Gortari, J. Org. Chem., 2007, 72, 2279;
P. Rempala, J. Kroulik and B. T. King, J. Am. Chem. Soc., 2004,
126, 15002.
12 Unsubstituted perylenes have been historically obtained through
photocyclisation of stilbenes. For example see: W. Carruthers,
J. Chem. Soc. C, 1967, 1525.
13 Performed in a reactor (MultiSYNTHt, Milestone srl.) especially
designed for organic chemistry with good control of power input,
pressure and temperature (IR pyrometer + fibre-optic probe).
14 N. Nijegorov, R. Mabbs and W. S. Downey, Spectrochim. Acta,
Part A, 2001, 57, 2673; X. Chillier, P. Boulet, H. Chermette, F. Salama
and J. Weber, J. Chem. Phys., 2001, 115, 1769; R. Waris, M. A.
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in solution at room temperature, exhibiting blue emission
under ultraviolet radiation (Table 1). Large Stokes shifts are
observed for all amines ranging from 158 to 165 nm.
As shown in Fig. 4 and Table 1, carboranyl derivatives 7
and 8 exhibited almost identical data in both absorption and
emission spectra indicating a similar effect of the carboranyl
entity. The comparison of 7 and 8 to the parent benzo[g,h,i]-
perylene amine 5a and the extended benzo[g,h,i]perylene
amine 5c deserves some comments. The presence of carboranyl
fragments in 7 and 8 induced a small red-shift of the absorption
maximum and a significant decrease of e values by comparison
with the parent amines 5a and 5c (De = 15 500 and
7400 MÀ1 cmÀ1, respectively). In addition, l emission values
for 7 and 8 are significantly blue-shifted with respect to the
parent amines with a consequent reduction of the Stokes shifts
(Table 1). Most interestingly, higher emission intensity was
observed in all carborane-appended perylenes.
15 F. Teixidor, C. Vinas, A. Demonceau and R. Nu´ nez, Pure Appl.
Chem., 2003, 75, 1305; J. Plesek, Chem. Rev., 1992, 92, 269.
16 K. Kokado, A. Nagai and Y. Chujo, Macromolecules, 2010,
43, 6463; K. Kokado, Y. Tokoro and Y. Chujo, Macromolecules,
2009, 42, 2925; K. Kokado and Y. Chujo, Macromolecules, 2009,
42, 1418; K. Kokado, Y. Tokoro and Y. Chujo, Macromolecules,
2009, 42, 9238.
In conclusion, we described the first synthesis of amino
benzo[g,h,i]perylenes through a one pot electrophilic aromatic
substitution-Scholl reaction sequence. Combination of carborane
and amino benzo[g,h,i]perylene moieties afforded novel 3D-planar
molecular architectures. Photophysical properties of these
valuable molecules showed that although absorption data
are dominated by the perylene-rigid fragment, both carborane
and organic subunits impact the emission of the new
architectures.
17 B. P. Dash, R. Satapathy, E. R. Gaillard, J. A. Maguire and
N. S. Hosmane, J. Am. Chem. Soc., 2010, 132, 6578; F. Lerouge,
C. Vinas, F. Teixidor, R. Nunez, A. Abreu, E. Xochitiotzi,
R. Santillan and N. Farfan, Dalton Trans., 2007, 1898.
18 V. Terrasson, J. Giner Planas, D. Prim, F. Teixidor, C. Vinas,
M. E. Light and M. B. Hursthouse, Chem.–Eur. J., 2009,
15, 12030.
19 For comparisons between UV spectrum for benzo[g,h,i]perylene and
amino-benzo[g,h,i]perylene in MeCN, DCM and THF see ESIw.
20 B. Valeur, Molecular Fluorescence: Principles and Applications,
Wiley-Interscience, Weinheim, 2002.
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This journal is The Royal Society of Chemistry 2011
Chem. Commun., 2011, 47, 7725–7727 7727