Dipyreno- and diperyleno-anthracenes from glyoxylic Perkin reactions

Article abstract of DOI:10.1039/c3cc44044c

Twofold Perkin condensation of 2,5-dibromophenylene-1,4-diacetic acid with arylglyoxylic acids followed by cyclo-dehydrobromination leads to dipyreno- and diperyleno-anthracene tetraesters and diimides. The imides show surprisingly large absorption shifts

Full text of DOI:10.1039/c3cc44044c

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Dipyreno- and diperyleno-anthracenes from glyoxylic
Perkin reactions†
Cite this: DOI: 10.1039/c3cc44044c
Parantap Sarkar, Fabien Durola and Harald Bock*
Received 29th May 2013,
Accepted 27th June 2013
DOI: 10.1039/c3cc44044c
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Twofold Perkin condensation of 2,5-dibromophenylene-1,4-diacetic small-bandgapped arenes by fusing two or more PTCDA moieties,
acid with arylglyoxylic acids followed by cyclo-dehydrobromination directly or via the insertion of acene units.5–7
leads to dipyreno- and diperyleno-anthracene tetraesters and diimides.
A surprisingly overlooked and in our eyes particularly appealing
The imides show surprisingly large absorption shifts versus the esters, strategy for the construction of vic-dicarboxy-substituted polycyclic
illustrating that electron-withdrawing substituents at the anthracene arenes is what we have come to call the ‘‘glyoxylic’’ Perkin reaction, i.e.
unit efficiently impart long wavelength absorption in such electron- a variant of the Perkin reaction8 reported over 70 years ago by Koelsch
deficient graphene nanoribbon fragments.
and Wawzonek,9 where an arylglyoxylic acid is condensed with an
arylacetic acid. To transform the resulting diarylmaleic acid into a
Oligocarboxylic derivatives of polycyclic arenes show great potential fully condensed arene derivative, an a priori robust modern approach
as particularly stable dyes and pigments for various applications is the Pd-assisted elimination of HBr, recently optimised by Felpin
including organic electronic devices. Vicinal pairs of carboxylic and co-workers for similar mono-alkoxycarbonyl-substituted stilbene
substituents – diester, imide, free diacid – can differ greatly in their derivatives.10 This necessitates a bromine ortho to the acetic acid or
solubilising and electronic effects, and thus present a means for the glyoxylic acid site in one of the Perkin reaction precursors.
the tuning of physical properties. This feature can be further
Polycyclic arenes such as pyrene 1 and perylene 2 are often
reinforced if more than one vic-dicarboxylic moiety is incorporated regiospecifically monosubstituted by Friedel–Crafts acylation adja-
into the molecule. For example, the electronic differences between cent to ring junctions,11 leaving only one specific hydrogen-bearing
tetraester and diimide derivatives of perylene-3,4,9,10-tetracarboxylic ortho position open for post-Perkin ring closure. The reaction with
dianhydride (PTCDA) are manifest in the pronounced difference ClCOCO2Et is known to introduce a glyoxylic moiety into benzene,
between their LUMO energies that make the diimides pronounced naphthalene, acenaphthene and thiophene,12–15 and we presumed
electron acceptors,1 whereas the tetraesters can accept both holes it to be similarly feasible on larger arenes such as 1 and 2. Selective
and electrons, and thus can serve as an emitter layer in LEDs.2,3 The ortho-bromination of the products on the other hand seemed not to
bathochromic effect of carboxylic substituents on the absorption of be straightforward.
polycyclic arenes (perylene is yellow, its tetraesters are orange, its
If no bromine can be easily introduced in a convenient position
diimides are deep red) is of interest for the elaboration of long- in the arylglyoxylic acid, then its introduction into the arylacetic
wavelength absorbing charge transport materials for organic photo- acid must be considered. From the known 2-bromination of
voltaics. The reduction of the band gap of aromatic dyes towards 4-cyanophenyl-acetic acid,16 we projected that p-phenylenediacetic
values of inorganic semiconductors such as Si (1.1 eV) or GaAs acid 3 should easily undergo double bromination to yield a
(1.4 eV) is facilitated by carboxylic substituents because their batho- convenient substrate for twofold glyoxylic Perkin reactions followed
chromic effect on sufficiently sextet-stabilised (and thus large- by ring-closure. Thus, pairs of arylglyoxylic moieties would be fused
bandgapped) arenes can help avoiding the use of highly reactive via a tetrasubstituted anthracene moiety into large chromophores
systems with weak sextet stabilisation such as pentacene.4 A current with modifiable functional substituents.
research target is the construction of large oligocarboxy-substituted
Indeed, we found that 2,5-dibromophenylene-1,4-diacetic acid
4 is obtained as the major bromination product, accompanied by
2,3-dibromophenylene-1,4-diacetic acid and smaller amounts of
monobromo- and tribromo-phenylene-1,4-diacetic acid. The desired
unpolar 2,5-isomer could be separated from the polar 2,3-isomer
due to its lower solubility in the quite polar solvents THF and
acetone and its higher solubility in the less polar solvent ethyl
acetate, allowing its isolation on a 100 g scale in 44% yield.
Centre de Recherche Paul Pascal, Centre National de la Recherche Scientifique,
´
Universite de Bordeaux, 115 avenue Schweitzer, 33600 Pessac, France.
E-mail: bock@crpp-bordeaux.cnrs.fr; Fax: +33-556845600; Tel: +33-556845673
† Electronic supplementary information (ESI) available: Crystallographic struc-
ture, synthetic procedures, 1H- and 13C-NMR spectra. CCDC 941140. For ESI and
crystallographic data in CIF or other electronic format see DOI: 10.1039/
c3cc44044c
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Having in hand a convenient dibrominated bifunctional building boiling Ac2O for 12 h leading to diphenylmaleic anhydride, giving a
block for the assembly of large arenes by double glyoxylic Perkin yield of 43%.9 Fields et al.17 applied the same procedure to 3 and
reactions, we investigated the Friedel–Crafts acylation of 1 and 2 with obtained phenylene-1,4-bis(phenylmaleic anhydride) in 88% yield
ClCOCO2Et. We found that in contrast to its reaction with acetyl, within 1 h. This higher yield on a double reaction in much shorter
chloroacetyl or benzoyl chloride, 1 undergoes monoacylation pre- time seems to indicate that unnecessarily long reaction times (or, by
dominantly with excess ClCOCO2Et and AlCl3 in DCM overnight, with analogy, unnecessarily high reaction temperatures) may be detri-
only traces of diacylation products. A somewhat cleaner product is mental. The Perkin reaction of benzaldehyde with sodium 1-bromo-
obtained if ZrCl4 is used in place of AlCl3, and ethyl pyrenyl- 2-naphthylacetate is reported to give a yield of only 34% under
1-glyoxylate 5 is obtained on a 100 g scale in over 80% yield and similar conditions18 (boiling acetic anhydride, 7 h), indicating that a
saponified quantitatively to pyrenyl-1-glyoxylic acid 6 with aqueous sterically hindering ortho-bromo substituent might render the
sodium bicarbonate. The analogous reactions of perylene 2 produced Perkin condensation less efficient.
ethyl perylenyl-3-glyoxylate 7 and its acid 8 in similar yields (Fig. 1).
To avoid the need to isolate a salt of the arylglyoxylic acid or the
Koelsch and Wawzonek’s original procedure9 describes the arylacetic acid, we conducted all Perkin condensation reactions with
reaction of potassium phenylglyoxylate with phenylacetic acid in the free acids as starting materials and with triethylamine as base, as
is standard in conventional (aldehydic) Perkin reactions.8 We found
that cleaner products are obtained if the condensation is performed
in refluxing dioxane or THF for a few hours, in the presence of a
minor amount of acetic anhydride. As the purification of the poorly
soluble bis(maleic anhydride)s is cumbersome, we esterified them
directly in situ in the presence of excess DBU with 1-bromoalkane and
the corresponding alkanol, a smooth procedure we have relied upon
in the past.19–21 We thus obtained the fourfold esterified double
condensation products of 4 with either 6 or 8 in satisfactory isolated
overall yields of 74% and 73% in a one-pot procedure.
For both the pyrene and the perylene derived condensation
1
products 9 and 10, the H-NMR spectra show very broad peaks
for most of the aromatic protons and for the aliphatic protons of
one of the two distinct pairs of alkyl chains, pointing to considerably
sterically hindered rotation around the aryl–vinyl single C–C bonds.
As these 1H-NMR spectra did not allow a satisfactory identification
of the Perkin condensation products, we were fortunate to obtain
crystals suitable for X-ray crystallography from the pyrene-derived
tetraethyl ester 9a, confirming the presumed structure (see ESI†).
9 and 10 were smoothly doubly cyclised in 81% and 80%
yield in DMA at 110 1C in the presence of Pd(OAc)2, PCy3 and
K2CO3, following the procedures optimised for the cyclisation of
2-bromo-a-phenyl-trans-cinnamates.10 The resulting elongated
fourfold alkoxycarbonyl-substituted dipyrenoanthracene 11 and
diperylenoanthracene 12 (orange and red, respectively) again
showed well-resolved 1H-NMR spectra, evidencing their fully
condensed structure with no slow internal rotations remaining.
To transform the tetraesters 11 and 12 into their more electron-
deficient diimide counterparts, we found that the isolation of the
very insoluble dianhydrides or tetraacids can be avoided by
directly reacting the tetraester with excess dialkylmethylamine
and imidazole at 180 1C. If long amines are used that are not
very miscible with imidazole, yields are improved using refluxing
o-dichlorobenzene as the additional solvent besides excess
imidazole.
Swallow-tailed amines R2CHNH2 are known to induce far better
solubilities in PTCDA-derived diimides and their higher rylene
analogues22,23 than linear alkylamines. 6-Aminoundecane upon
reaction with 11 yields a purple product which surprisingly proves
Fig. 1 Synthesis of dipyreno- and diperyleno-anthracenes via glyoxylic Perkin con-
densation and Pd-catalysed dehydrobromination. (a) NBS, H2SO4–H2O, 25 1C, 16 h,
44%; (b) ClCOCO2Et, ZrCl4, DCM, 25 1C, 16 h, 87%/79%; (c) NaHCO3, EtOH–H2O,
to be insoluble in solvents such as chloroform or DCM. Longer
reflux, 100%/95%; (d) NEt3, Ac2O, dioxane, reflux, 3 h, then addition of ROH, RBr,
12-aminotricosane24 yields a soluble diimide 12 in 93% yield. The
DBU, reflux, 16 h, 74%/73%; (e) Pd(OAc)2, PCy3, K2CO3, DMA, 110 1C, 20 h, 80%/
striking colour change from orange to purple when transforming
the tetraester 11 into diimide 13 corresponds to a 128 nm shift of
81%; (f) (H(CH2)11)2CHNH2, imidazole, C6H4Cl2, reflux, 16 h, 93%/89%. Oct = n-octyl,
Undec = n-undecyl.
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Various approaches to chromophore extension via the fusion of
perylene units onto acenes have been reported recently, including
the lateral fusion of perylenediimides via an ethylene bridge to
diperyleno-naphthalene-tetraimides 15,6 or via a benzene bridge to
diperyleno-anthracene-tetraimides 16.7 In these cases, the batho-
chromic shift of the longest-wavelength absorption peak with
respect to the corresponding PTCDIs is modest (19 nm for 15 and
36 nm for 16, compared to 117 nm for 14) (Fig. 3). Our approach is
much more efficient in inducing longer wavelength absorption and
thus a smaller band gap than the joining of electron-deficient
perylene-diimides by non-electron-depleting acene units.
In summary, our methodology based on the glyoxylic Perkin
reaction provides a short and straightforward synthetic access
to dimers of polycyclic arenes fused by a central tetracarboxy-
anthracene moiety. The diimide derivatives absorb strongly batho-
chromically compared to the homologous tetraesters and to
acene-fused PTCDI dimers, and thus represent a superior alternative
to fusion of PTCDIs onto unsubstituted acenes as a means to impart
smaller band gaps in electron deficient extended arene systems.
This research was financed partially by CNRS and ERASMUS
MUNDUS (external co-operation window with Asia) grants. We are
grateful to Pierre Dechambenoit for the collection and treatment of
Fig. 2 Absorption spectra of dipyrenoanthracenes 11 & 13 (top) and diperyleno-
anthracenes 12 & 14 (bottom), 20 mM in CHCl3 (14: in 4:1 CHCl3 :Cl2CHCHCl2). Grey:
tetraesters 11 and 12, black: diimides 13 and 14.
´
the crystallographic data and to Rodolphe Clerac for his continuous
support.
the main long-wavelength absorption peak from 447 nm to 575 nm
(in CHCl3, Fig. 2, top). This can be compared with the shift of 66 nm
from PTCDA-derived orange tetraalkylesters (470 nm (ref. 25)) to
their corresponding red bis(dialkylmethyl)imides (526 nm (ref. 26)).
Similarly, tetraester 12 and 12-aminotricosane give diimide 14 in
89% yield, and here the colour change is even more striking, as red
12 transforms into deep green 14, with a 132 nm shift of the longest-
wavelength peak from 511 nm to 643 nm (Fig. 2, bottom), approach-
ing the value of phthalocyanine (699 nm (ref. 27)).
Notes and references
1 E. Kozma and M. Catellani, Dyes Pigm., 2013, 98, 160.
2 T. Hassheider, S. A. Benning, H.-S. Kitzerow, M.-F. Achard and
H. Bock, Angew. Chem., Int. Ed., 2001, 40, 2060.
3 I. Seguy, P. Jolinat, P. Destruel, R. Mamy, H. Allouchi, C. Courseille,
M. Cotrait and H. Bock, ChemPhysChem, 2001, 2, 448.
4 E. Clar, Polycyclic Hydrocarbons, Academic Press and Springer-Verlag,
London-New York, Berlin-Gottingen-Heidelberg, 1964.
¨
5 H. Qian, F. Negri, C. Wang and Z. Wang, J. Am. Chem. Soc., 2008,
130, 17970.
6 Y. Li, C. Wang, C. Li, S. Di Motta, F. Negri and Z. Wang, Org. Lett.,
2012, 14, 5278.
7 Z. Yuan, Y. Xiao and X. Qian, Chem. Commun., 2012, 46, 2772.
8 T. Rosen, Iridium Complexes Org. Synth., 1991, 2, 395.
9 C. F. Koelsch and S. Wawzonek, J. Org. Chem., 1941, 6, 684.
10 L. Nassar-Hardy, C. Deraedt, E. Fouquet and F.-X. Felpin, Eur. J. Org.
Chem., 2011, 4616.
11 Friedel–Crafts and related reactions, III: Acylation and related reactions,
ed. G. A. Olah, Interscience Publishers, New York–London–Sydney, 1964.
12 G. Lock, Monatsh. Chem., 1955, 86, 511.
13 F. F. Blicke and R. F. Feldkamp, J. Am. Chem. Soc., 1944, 66, 1087.
14 G. Lock and R. Schneider, Chem. Ber., 1955, 88, 564.
15 R. G. Micetich, Org. Prep. Proced., 1970, 2, 249.
16 D. G. Cooper, I. T. Forbes, V. Garzya, D. J. Johnson, G. I. Stevenson
and P. A. Wyman, PCT Int. Appl. WO, 2009037294, 2009.
17 E. K. Fields, S. J. Behrend, S. Meyerson, M. L. Winzenburg,
B. R. Ortega and H. K. Hall Jr., J. Org. Chem., 1990, 55, 5165.
18 C. L. Hewett, J. Chem. Soc., 1938, 1286.
With diperylenoanthracene, already the red tetraester 12 showed
only a limited solubility even though we resorted to using relatively
long octyl chains, compared to the dipyrenoanthracene analogue 11,
and the green diimide 14 is only very sparingly soluble in hot
chloroform in spite of the presence of four undecyl side chains. It is
more soluble in boiling ortho-dichlorobenzene or 1,1,2,2-tetrachloro-
ethane. The striking decrease in solubility from dipyrenoanthra-
cenes 11 and 13, with 42 carbon atoms in the polycyclic graphene
segment, to diperylenoanthracenes 12 and 14, with 50 carbons,
parallels the dramatic decrease in solubility with increasing gra-
phene segment size reported for the rylene-dialkylimide series.22,23
19 J. Kelber, H. Bock, O. Thiebaut, E. Grelet and H. Langhals, Eur. J.
Org. Chem., 2011, 707.
20 P. Sarkar, P. Dechambenoit, F. Durola and H. Bock, Asian J. Org. Chem.,
2012, 1, 366.
21 J. Kelber, M.-F. Achard, B. Garreau-de Bonneval and H. Bock, Chem.–Eur.
J., 2011, 17, 8145.
22 N. G. Pschirer, C. Kohl, F. Nolde, J. Qu and K. Mu¨llen, Angew. Chem.,
Int. Ed., 2006, 45, 1401.
23 F. Nolde, W. Pisula, S. Mu¨ller, C. Kohl and K. Mu¨llen, Chem. Mater.,
2006, 18, 3715.
24 Z. Yuan, Y. Xiao, Y. Yang and T. Xiong, Macromolecules, 2011, 44, 1788.
25 M. J. Yang, S. L. Lu and Y. Li, J. Mater. Sci. Lett., 2003, 22, 813.
26 H. Langhals, Helv. Chim. Acta, 2005, 88, 1309.
27 J. H. Sharp and M. Lardon, J. Phys. Chem., 1968, 72, 3230.
Fig. 3 Swallow-tailed perylene-tetracarboxylic diimide (PTCDI) and naphthalene-
or anthracene-fused PTCDI dimers 15 and 16, with wavelengths of their longest-
wavelength absorption maxima in chloroform or DCM;6,7 14: 643 nm; R = n-alkyl.
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun.