Two-dimensional scaffolds for the parallel alignment of rod-shaped conjugated molecules

Article abstract of DOI:10.1021/jo062261i

Described is a method for creating two-dimensional, ordered arrays of linear, conjugated organic molecules on polyimide scaffolds. Key to the design was the enforcement of consecutive 90° twist angles along the polyimide backbone. Rod molecules that are templated by such scaffolds are held parallel and in the same plane and have optical properties that are similar to those of monomeric analogues. As supporting evidence for the structures of the polymers, a series of model compounds were synthesized and characterized by X-ray crystallography. The polymeric materials are soluble and have been characterized by ¹H NMR, ¹³C NMR, MALDI-TOF, and UV-vis spectroscopy.

Full text of DOI:10.1021/jo062261i

Two-Dimensional Scaffolds for the Parallel Alignment of
Rod-Shaped Conjugated Molecules
Zhenzhen Dong, Xiaozhong Liu, Glenn P. A. Yap,† and Joseph M. Fox*
Brown Laboratories, Department of Chemistry and Biochemistry, UniVersity of Delaware,
Newark, Delaware 19716
jmfox@udel.edu
ReceiVed NoVember 1, 2006
Described is a method for creating two-dimensional, ordered arrays of linear, conjugated organic molecules
on polyimide scaffolds. Key to the design was the enforcement of consecutive 90° twist angles along the
polyimide backbone. Rod molecules that are templated by such scaffolds are held parallel and in the
same plane and have optical properties that are similar to those of monomeric analogues. As supporting
evidence for the structures of the polymers, a series of model compounds were synthesized and
characterized by X-ray crystallography. The polymeric materials are soluble and have been characterized
1
by H NMR, 13C NMR, MALDI-TOF, and UV-vis spectroscopy.
Introduction
In this contribution, a method for creating two-dimensional,
ordered arrays of linear, conjugated organic molecules is
described. The concept is depicted in Figure 1 and hinges upon
the ability to create scaffolds that can hold conjugated rod
molecules in parallel and in the same plane. This strategy is
complementary to traditional approaches of creating aligned
networks of conjugated molecules (e.g., self-assembly), as rod
molecules on scaffolds are held apart by ∼1.1 nm and have
electronic properties similar to those of monomeric analogues.
Potential applications for such scaffolds include the organization
of sensory polymers and nonlinear optical (NLO) chromophores
and in the creation of parallel circuits based on molecular wires.
Supramolecular organization has a direct impact on the
properties of conjugated organic molecules and on their
subsequent utility in applied technologies (e.g., sensory devices,1-3
FIGURE 1. Strategy for the creation of ordered, 2-D arrays of
conjugated molecules.
polarized electroluminescence devices,4 field-effect transistors,5,6
organic light-emitting diodes,7 and nonlinear optical materials).8,9
(3) Zhou, H. C.; Baldini, L.; Hong, J.; Wilson, A. J.; Hamilton, A. D.
J. Am. Chem. Soc. 2006, 128, 2421-2425.
(4) Grell, M.; Bradley, D. D. C. AdV. Mater. 1999, 11, 895-905.
(5) Horowitz, G. AdV. Mater. 1998, 10, 365-377.
(6) Bao, Z. N.; Rogers, J. A.; Katz, H. E. J. Mater. Chem. 1999, 9, 1895-
1904.
(7) Kraft, A.; Grimsdale, A. C.; Holmes, A. B. Angew. Chem., Int. Ed.
1998, 37, 402-428.
(8) Kajzar, F.; Lee, K. S.; Jen, A. K. Y. AdV. Polym. Sci. 2003, 161,
1-85.
† QuestionsregardingX-rayshouldbeaddressedtoDr.Yap(gpyap@chem.udel.edu).
(1) McQuade, D. T.; Pullen, A. E.; Swager, T. M. Chem. ReV. 2000,
100, 2537-2574.
(2) Wright, A. T.; Anslyn, E. V. Chem. Soc. ReV. 2006, 35, 14-28.
10.1021/jo062261i CCC: $37.00 © 2007 American Chemical Society
Published on Web 12/20/2006
J. Org. Chem. 2007, 72, 617-625
617

Dong et al.
FIGURE 2. (a) Design of two-dimensional templates for parallel alignment of conjugated rod molecules. Two views of a molecular diagram for
a segment of this polymer illustrates (b) the parallel alignment of the rods and (c) the planarity of the structure.
There are a number of highly successful strategies for creating
organized assemblies of conjugated molecules. The controlled
imposed through direct contact with a neighboring molecule
and/or by epitaxial alignment by a surface.
assembly of molecules onto surfaces (e.g., into monolayers10,11
)
While a closely packed arrangement is desirable for many
applications, there are notable exceptions. For example, second
order NLO chromophores typically require alignment within a
polymer matrix (poling) in order to be efficient, but the
aggregation of those chromophores dramatically decreases the
efficiency of the poling process.8 A closely packed arrangement
can also have a deleterious impact on the highly conjugated
polymers that are used in fluorescence-based sensors. Although
intermolecular energy migration can be most efficient in
molecularly ordered films or aggregates, the close interaction
of such polymers will quench fluorescence.1 Swager has
developed an elegant method that minimizes fluorescence
quenching by incorporating hindered iptycenes into the back-
bones of the conjugated polymers.19,20 While exciton migration
through conjugated polymers is obviously an extremely complex
phenomenon, it is clear that controlling alignment and patterning
has a profound effect. Finally, it is pointed out that the scaffolds
proposed in Figure 1 could be used to create insulated, parallel
circuits from molecular components and thereby have applica-
is a widely employed approach for controlling the relative
molecular orientation of molecules, including conjugated mol-
ecules,12 and modern lithiographic techniques can be used to
create oriented patterns with line widths on the nanoscale.13-16
Noncovalent molecular self-assembly can also result in unusual
and enhanced properties relative to those of nonaggregated
molecules.17 Furthermore, liquid crystalline media can be used
to orient conducting polymers and oligomers.18 A feature that
is common to these approaches is that the organization is
(9) Bai, Y. W.; Song, N. H.; Gao, J. P.; Sun, X.; Wang, X. M.; Yu,
G. M.; Wang, Z. Y. J. Am. Chem. Soc. 2005, 127, 2060-2061.
(10) Love, J. C.; Estroff, L. A.; Kriebel, J. K.; Nuzzo, R. G.; Whitesides,
G. M. Chem. ReV. 2005, 105, 1103-1169.
(11) Ulman, A. Chem. ReV. 1996, 96, 1533-1554.
(12) Chen, J.; Reed, M. A.; Asplund, C. L.; Cassell, A. M.; Myrick,
M. L.; Rawlett, A. M.; Tour, J. M.; Van Patten, P. G. Appl. Phys. Lett.
1999, 75, 624-626.
(13) Odom, T. W.; Thalladi, V. R.; Love, J. C.; Whitesides, G. M.
J. Am. Chem. Soc. 2002, 124, 12112-12113.
(14) Hong, S.; Mirkin, C. A. Science 2000, 288, 1808-1811.
(15) Piner, R. D.; Zhu, J.; Xu, F.; Hong, S.; Mirkin, C. A. Science 1999,
283, 661-663.
(16) Hong, S.; Zhu, J.; Mirkin, C. A. Science 1999, 286, 523-525.
(17) Hoeben, F. J. M.; Jonkheijm, P.; Meijer, E. W.; Schenning, A. Chem.
ReV. 2005, 105, 1491-1546.
(19) Thomas, S. W. I.; Long, T. M.; Pate, B. D.; Kline, S. R.; Thomas,
E. L.; Swager, T. M. J. Am. Chem. Soc. 2005, 127, 17976-17977.
(20) Nesterov, E. E.; Zhu, Z. G.; Swager, T. M. J. Am. Chem. Soc. 2005,
127, 10083-10088.
(18) Hulvat, J. F.; Stupp, S. I. Angew. Chem., Int. Ed. 2003, 42, 778-
781.
618 J. Org. Chem., Vol. 72, No. 2, 2007

Parallel Alignment of Rod-Shaped Conjugated Molecules
FIGURE 3. Molecular diagrams of crystallographically characterized model compounds for which alternating aromatic subunits are held in the
same plane. Steric interactions between the tert-butyl group and the imide carbonyls constrain the twist angle between neighboring aromatics
to 90°.
tion in the fabrication of devices based on molecular
electronics.21
der Waals contacts between the tert-butyl hydrogens and the
carbonyl oxygens. Thus, any significant deviation from a 90°
twist angle22 would invoke a severe steric penalty. Curran has
elegantly shown that chiral ortho-(tert-butyl)phenylmaleimides
are resolvable at room temperature.23-25 The crystal structure
of N-(2,5-di-tert-butylphenyl)maleimide was determined, and
it was shown that the maleimide and aromatic rings were
perpendicular.25 A study by Kishikawa and co-workers also
supports the design in Figure 2.26 These workers synthesized
N,N-bis(2-tert-butylphenyl)pyromellitic bisimide for the prepa-
ration of inclusion complexes. A variety of host/guest complexes
were crystallized, and in each case, the phenyl groups were held
fixed in the same plane.
We envisioned that the concept in Figure 1 could be realized
by synthesizing two-dimensional materials that can align linear,
conjugated molecules along the backbone of a linear polyimide.
As shown in Figure 2, the key to the design is that consecutive
90° twist angles along the polyimide backbone ensure that
adjacent oligomers are held in the same plane. Herein, we
describe the successful execution of this strategy. The design
is flexible and can be used as a scaffold for linear, conjugated
molecules [e.g., oligophenylenes and oligo(phenylene ethy-
nylene)s]. The polymers synthesized in this work are soluble
1
and have been characterized by H NMR, 13C NMR, mass
spectrometry (MALDI-TOF), and UV-vis spectroscopy.
For the preparations of 1 and 3, the condensations produce
approximately equal amounts of two diastereomers (designated
as anti or syn, in reference to the facial alignment of the tert-
butyl groups that are closest to the pyromellitimide). In the case
of 1, only the anti-diastereomer crystallized, whereas the syn-
diastereomer crystallized for 3. Comparison of their crystal
Results and Discussion
As supporting evidence for the structures of the polymers, a
series of model compounds have been synthesized and char-
acterized both in solution and by X-ray crystallography. The
structures of three compounds (1-3) are shown in Figure 3.
Synthesis of 1-3 involves condensation of the appropriate
anilines and phthalic or pyromellitic acid derivatives (described
in the Supporting Information). In each structure, the tert-
butylbenzene groups are nearly perpendicular to the phthalimide
or pyromellitimide groups. Their structures (after the hydrogens
were added using Chem3D) show that there are already van
(22) For a definition of twist angle, see: Jaffe´, H. H.; Orchin, M. In
Theory and Applications of UltraViolet Spectroscopy; Wiley: New York,
1962; Chapter 15, pp 384-449.
(23) Petit, M.; Lapierre, A. J. B.; Curran, D. P. J. Am. Chem. Soc. 2005,
127, 14994-14995.
(24) Curran, D. P.; Qi, H.; Geib, S. J.; DeMello, N. C. J. Am. Chem.
Soc. 1994, 116, 3131-3132.
(25) Curran, D. P.; Geib, S.; DeMello, N. Tetrahedron 1999, 55, 5681-
5704.
(26) Kishikawa, K.; Tsubokura, S.; Kohmoto, S.; Yamamoto, M.;
Yamaguchi, K. J. Org. Chem. 1999, 64, 7568-7578.
(21) Tour, J. M. Acc. Chem. Res. 2000, 33, 791-804.
J. Org. Chem, Vol. 72, No. 2, 2007 619

Dong et al.
SCHEME 1. Synthesis of Co-monomer 8
structures shows that the twist angle is not effected significantly
by the relative orientation (syn vs anti) of the tert-butyl groups
for 1 and 3, respectively. As shown in the crystal structure of
3, the distance between the tert-butyl groups is large enough
so that their syn-orientation has very little influence on the twist
angle, although it does impose minor out-of-plane bending
between the phthalimides and the central core. Importantly, it
can be inferred that the stereochemical relationship of the tert-
butyl groups will not affect the coplanar orientation of alternat-
ing subunits within polymers.
Preparation of Co-monomers. Co-monomer 8 was prepared
as shown in Scheme 1. The synthesis takes advantage of the
low reactivity of arylchlorides toward oxidative addition with
many Pd catalysts [e.g., (PPh3)nPd].27 Thus, it was possible to
selectively couple dibromide 4 with 4-chlorophenylboronic acid
to produce dichloride 5. The 4-chlorophenyl groups of 5 survive
the harsh conditions of KMnO4 oxidation and subsequent
alkylation to give 6. Recently developed methods for Pd-
catalyzed cross-coupling enable efficient reactions of arylchlo-
rides when specialized ligands are utilized. We have found
2-dicyclohexylphosphino-2′-N,N-dimethylaminobiphenyl/Pd-
(OAc)2-catalyzed Suzuki reactions of 6 to be particularly
efficient.28,29 Thus, the quinquephenyl-derived co-monomer 8
could be prepared via reaction of 6 with 4-dodecylphenylboronic
acid and subsequent saponification. Polymeric materials derived
from monomer 8 are described in this work. However, it is also
demonstrated that the cross-coupling strategy used to prepare
6 can also be employed to prepare co-monomers with extended
conjugation (Scheme 2). Thus, the extended co-monomer 10
could be prepared from 6 via a sequence of Suzuki coupling
with 4-(triisopropylsilylethynyl)phenylboronic acid, alkyne depro-
tection, and Sonogashira-Heck-Cassar coupling with 4-dode-
cylphenylboronic acid. Much longer co-monomers should be
available through this synthetic strategy, as rod-shaped oli-
gophenylene ethynylenes are readily prepared by the convergent/
divergent methods pioneered by Tour30-34 and Moore.35-37
known,41-48 it was unclear if conventional methods would be
effective for the synthesis of polyimides from sterically de-
manding 2,5-di-tert-butyl-1,4-phenylenediamine. In particular,
we considered that isoimide formation might compete with
imide formation.38,49 As a model for the polymerization reaction,
we screened a variety of conditions for the coupling of phthalic
acid with 2,5-di-tert-butyl-1,4-phenylenediamine. For the reac-
tion to be useful in polymerization, it is essential to produce
only the imide linkage in high yield (Scheme 3). After screening
a variety of conditions, the best results were obtained by simply
heating phthalic acid and the diamine in acetic acid at 100 °C.
Phthalimide 11 was produced in excellent yield, and the isoimide
12 was not detected. Analogously, heating phthalic anhydride
(2 equiv) with 2,5-di-tert-butyl-1,4-phenylenediamine cleanly
gave bisphthalimide 2, as shown in Scheme 4, without isoimide
side products. A host of other conditions were also screened
for the reactions shown in Schemes 3 and 4.50 However, simple
Model Studies for Polymerization. Polyimides are a com-
mercially important class of materials that have exceptional
thermal stability, high mechanical strength, excellent electrical
properties, and chemical resistance.38-40 Accordingly, a number
of methods have been developed for their synthesis.38 While
polyimides from 3,6-diphenylpyromellitic anhydride were
(27) Grushin, V. V.; Alper, H. Chem. ReV. 1994, 94, 1047-1062.
(28) Old, D. W.; Wolfe, J. P.; Buchwald, S. L. J. Am. Chem. Soc. 1998,
120, 9722-9723.
(29) Wolfe, J. P.; Singer, R. A.; Yang, B. H.; Buchwald, S. L. J. Am.
Chem. Soc. 1999, 121, 9550-9561.
(41) Schmitz, L.; Ballauff, M. Polymer 1995, 36, 879-882.
(42) Steiner, U. B.; Caseri, W. R.; Suter, U. W.; Rehahn, M.; Schmitz,
L. Langmuir 1993, 9, 3245-3254.
(43) Schmitz, L.; Rehahn, M. Macromolecules 1993, 26, 4413-4419.
(44) Schmitz, L.; Rehahn, M.; Ballauff, M. Polymer 1993, 34, 646-
649.
(30) Tour, J. M. Chem. ReV. 1996, 96, 537-554.
(31) Pearson, D. L.; Schumm, J. S.; Tour, J. M. Macromolecules 1994,
27, 2348-2350.
(32) Huang, S.; Tour, J. M. J. Am. Chem. Soc. 1999, 121, 4908-4909.
(33) Huang, S.; Tour, J. M. J. Org. Chem. 1999, 64, 8898-8906.
(34) Wu, R.; Schumm, J. S.; Pearson, D. L.; Tour, J. M. J. Org. Chem.
1996, 61, 6906-6921.
(45) Cheng, S. Z. D.; Lee, S. K.; Barley, J. S.; Hsu, S. L. C.; Harris,
F. W. Macromolecules 1991, 24, 1883-1889.
(35) Young, J. K.; Nelson, J. C.; Moore, J. S. J. Am. Chem. Soc. 1994,
116, 10841-10842.
(36) Zhang, J.; Moore, J. S.; Xu, Z.; Aguirre, R. A. J. Am. Chem. Soc.
1992, 114, 2273-2274.
(37) Moore, J. S. Acc. Chem. Res. 1997, 30, 402-413.
(38) Ghosh, M. K.; Mittal, K. L. Polyimides: Fundamentals and
Applications; Marcel Dekker, Inc.: New York, 1996.
(39) Wilson, D.; Stenzenberger, H. D.; Hergenrother, P. M. Polyimides;
Chapman and Hall: New York, 1990.
(40) Bessonov, M. I.; Zubkov, V. A. Polyamic Acids and Polyimides:
Synthesis, Transformations, and Structure; CRC Press: Boca Raton, FL,
1993.
(46) Giesa, R.; Keller, U.; Eiselt, P.; Schmidt, H. W. J. Polym. Sci., Part
A 1993, 31, 141-151.
(47) Kim, Y.-H.; Ahn, S.-K.; Kim, H. S.; Kwon, S.-K. J. Polym. Sci.,
Part A 2002, 40, 4288-4296.
(48) Myung, B. Y.; Kim, J. J.; Yoon, T. H. J. Polym. Sci., Part A 2002,
40, 4217-4227.
(49) Cotter, R. J.; Sauers, C. K.; Whelan, J. M. J. Org. Chem. 1961, 26,
10-15.
(50) The following conditions were also explored: reflux in THF; reflux
in diglyme; reflux in xylene; heating (150 °C) in m-cresol (with and without
molecular sieves); heating (150 °C) in anisole; heating (100 °C) with NaOAc
and Ac2O; reflux in CH2Cl2 with DCC and DMAP.
620 J. Org. Chem., Vol. 72, No. 2, 2007

Parallel Alignment of Rod-Shaped Conjugated Molecules
SCHEME 2. Synthesis of Pyromellitic Acid Derivatives with
Extended Conjugation
SCHEME 3. Optimized Conditions for the Condensation of
Phthalic Acid with 2,5-Di-tert-butyl-1,4-phenylenediamine
FIGURE 4. 13C NMR spectra of (a) polymer 13 and (b) model
compound 14. Multiplicities were distinguished using an APT pulse
sequence: typical methylene and quaternary carbons appear “up”;
methine and methyl carbons appear “down”.
SCHEME 5. Preparation of Polymer 13
SCHEME 4. Optimized Conditions for the Condensation of
Phthalic Anhydride (2 equiv) with
2,5-Di-tert-butyl-1,4-phenylenediamine
heating in acetic acid was superior in terms of both yield and
selectivity for imide formation. For example, the EDC/DMAP-
mediated reaction of phthalic acid (1 equiv) with 2,5-di-tert-
butyl-1,4-phenylenediamine (1 equiv, reflux in CH2Cl2) pro-
duced 11 in only 73% yield, along with 16% of isoimide 12.
Polymerization Studies. The optimal conditions for the
synthesis of model compounds 2 and 11 were next applied to
the synthesis of polymeric materials. Heating tetraacid 8 with
2,5-di-tert-butyl-1,4-phenylenediamine for 4 days at 100 °C in
acetic acid (Scheme 5) gave a polymeric material assigned to
structure 13 (Scheme 5). The polymer is freely soluble in many
common organic solvents, including CHCl3, CH2Cl2, and THF.
Evidence for the structure assigned to polymer 13 is the
protons and aromatic protons in intensity ratios that are
appropriate. Also, the chemical shifts correlate to those of model
compound 14, with the exception that the spectrum of the
polymer is broad. (2) The phase-sensitive 13C NMR (APT)
spectrum of polymer 13 (Figure 4) shows peaks attributable to
the carbonyls of the imides (ca. 166 ppm), the aromatic carbons
(ca. 127-150 ppm), the tert-butyl groups (ca. 32 and 36 ppm),
and the side chains (ca. 14, 23, 30, and 32 ppm). The position
and phase of those peaks were analogous to those observed for
model compound 14. (3) The MALDI-TOF mass spectrum
shows peaks that correspond to two types of polymeric structures
(Figure 5). The peaks labeled a-g are assigned to polymeric
structures with up to 7 repeat units that are capped at the ends
by acetanilide functions. The peaks labeled h-l are assigned
1
following: (1) The H NMR spectrum of 13 (displayed in the
Supporting Information) shows resonances for the side-chain
J. Org. Chem, Vol. 72, No. 2, 2007 621

Dong et al.
TABLE 1. Calculated and Observed Peaks in the MALDI-TOF
Spectrum of Polymer 13
structure
formula
C90H114N4O6Ag
m/z (calcd)
m/z (obsd)
13a (n ) 1)
13b (n ) 2)
13c (n ) 3)
13d (n ) 4)
13e (n ) 5)
13f (n ) 6)
13g (n ) 7)
13h (n ) 2)
13i (n ) 3)
13j (n ) 4)
13k (n ) 5)
13l (n ) 6)
1453.8a
2499.2
3542.7
4586.2
5629.6
6673.1
7716.5
3298.3
4341.8
5385.2
6428.7
7472.2
1454.2a
2499.7
3543.4
4586.8
5630.3
6673.5
7716.7
3298.8
4342.5
5386.2
6429.2
7472.3
C162H200N6O10Ag
C234H286N8O14Ag
C306H372N10O18Ag
C378H458N12O22Ag
C450H544N14O26Ag
C522H630N16O30Ag
C218H262N6O14Ag
C290H348N8O18Ag
C362H434N10O22Ag
C434H520N12O26Ag
C506H606N14O30Ag
a The calculated mass of 13a is based on monoisotopic mass. The
calculated masses of 13b-13l were based on average mass.
FIGURE 6. Comparison of the UV-vis absorption spectra of polymer
13 (blue line, 1.0 × 10-5 M) to model compound 14 (black line, 1.0 ×
10-5 M) and isoimide 12 (red line, 1.0 × 10-4 M).
FIGURE 5. MALDI-TOF mass spectrum of polymer 13. Two types
of end groups were identified. Although MALDI-TOF provides absolute
molecular weights of oligomers within the mixture, it does not provide
a measure of Mw distribution. H NMR end group analysis suggests
that the polymer contains an average of ∼7 repeat units (Mn ∼ 7400).
(from the MALDI-TOF data) that ∼80% of the polymers were
capped at both ends with acetanilide functions, and that the other
20% had one acetanilide and one phthalic anhydride.
1
The UV-vis absorption spectra for polymer 13, model
compound 14, and isoimide 12 were recorded and are displayed
in Figure 6. The spectra of the polymer and 14 are very similar
and provide evidence that there is negligible conjugation
between adjacent quinquephenyls along the backbone of poly-
mer 13. Comparison was made to the UV-vis spectrum of 12
to verify that the polymerization created imide linkages and not
isoimide linkages. In Figure 6, the spectrum of the isoimide is
displayed on twice the scale because the model (14) and the
polymer (13) have two imide functions, whereas 12 has only
one isoimide. As displayed in Figure 6, the isoimide 12 has an
absorption maximum at 405 nm (ꢀ ) 6333). In contrast, the
polymer 13 and model 14 absorb only weakly at this wavelength
(ꢀ ) 1250 and 750, respectively). It can be conservatively
estimated that >95% of the linkages in the polymer are imides,
and that isoimides account for not more than 5% of the linkages.
The crystal structures of 1 and 3 also show that the aromatic
groups directly attached to the pyromellitimide are twisted out
of plane relative to the core. For example, twist angles for each
of the biphenyl moieties of 1 are 55° in the crystal. Conjugation
through biphenyl linkages is attenuated, but not eliminated, by
to structures with up to 6 repeat units that are capped by a
phthalic anhydride on one end and an acetanilide function on
the other end. Table 1 shows that the observed data correlate
((1 Da) with the expected mass spectrum. Although the
MALDI-TOF mass spectrum provides evidence of structure, it
does not provide a measure of the molecular weight distribution.
For polydisperse samples (PDI > 1.2), MALDI is known to
underestimate the higher mass polymer distribution, and there
is often an upper mass limit above which individual oligomers
cannot be distinguished.51,52 The number-average molecular
weight (Mn) of polymer 13 could be estimated by end group
analysis of the 1H NMR spectrum. Thus, the number of repeat
units in the polymer was estimated to be 7 (Mn ∼ 7400) by
comparing the integrals of peaks assignable to the acetate end
groups (2.3 ppm) and the benzylic methylenes (2.7 ppm) of
the repeat unit. For the end group analysis, it was estimated
(51) Macha, S. F.; Limbach, P. A. Curr. Opin. Solid State Mater. Sci.
2002, 6, 213-220.
(52) Wu, K. J.; Odom, R. W. Anal. Chem. 1998, 70, 456A-461A.
622 J. Org. Chem., Vol. 72, No. 2, 2007

Parallel Alignment of Rod-Shaped Conjugated Molecules
twist angles of this magnitude.22 Future studies will involve the
preparation of scaffolds in which the quinquephenyls of polymer
13 are replaced by oligo(phenylene ethynylenes), so that
conjugation will not be affected by the steric influence of the
amide carbonyls.
compound 11 (11.2 mg, 0.032 mmol), and glacial acetic acid (1.0
mL). The test tube was flushed with N2 and capped, and the reaction
mixture was allowed to stir with heating at 100 °C for 24 h. Water
(10 mL) was added to the mixture, and a precipitate was filtered
and chromatographed (50% ethyl acetate/hexane) to give a ∼1:1
mixture of syn- and anti-3 as a light yellow solid. The yield was
16 mg (92%), mp >290 °C. The purity was measured to be g95%
by 1H NMR. Pure syn-3 could be obtained by crystallization from
DMF/hexane. Spectral properties of the syn/anti mixture: 1H NMR
(400 MHz, CDCl3, δ) 7.94-7.96 (m, 4H), 7.80-7.82 (m, 4H),
7.49-7.51 (m, 8H), 7.07-7.11 (m, 4H), 1.20-1.28 (m, 36H); The
13C NMR spectrum of the mixture of diastereomers is displayed;
IR (cm-1) 2964, 2916, 2850, 1773, 1724, 1390, 1265, 1130, 1103,
1081, 1015, 839, 821, 721, 668; HRMS (ESI+) m/z [M + Na],
calcd for C66H56O8N4Cl2, 1125.3373; found, 1125.3347; UV-vis
(1 × 10-5 M in CH2Cl2) λmax 229, 274.
Conclusion
In conclusion, a strategy for the coplanar alignment of
conjugated, rod-shaped organic oligomers on a polyimide
template has been described. The structures are supported by
1
their H NMR, 13C NMR, MALDI-TOF, UV-vis spectra and
by analogy to a number of smaller molecules that have been
characterized by X-ray crystallography. Although oligomers are
held rigidly in the same plane, their electronic spectra suggest
that conjugation is minimal. Future work will involve the
incorporation of longer rod molecules onto polyimide templates
and in the application of templated rod molecules in molecular
electronics and nonlinear optics.
1,4-Di(4-chlorophenyl)-2,3,5,6-tetramethyl Benzene (5). 1,4-
Dibromo-2,3,5,6-tetramethylbenzene54 (4) (3.71 g, 12.7 mmol),
p-chlorophenylboronic acid (7.93 g, 50.8 mmol), Pd(PPh3)4 (0.144
g, 1.23 mmol), and Na2CO3 (6.51 g, 61.4 mmol) were dissolved in
toluene (80 mL) and water (80 mL). The mixture was allowed to
reflux under N2 for 3 days. The mixture was then cooled, and the
aqueous layer was extracted with toluene. The combined extracts
were dried over MgSO4, filtered, and concentrated. Crystallization
from cold ethyl acetate gave the title compound as a white solid.
The yield was 3.83 g (85%), mp >290 °C. The purity was measured
Experimental Section
N,N′-Di(2-tert-butylphenyl)-3,6-di(4-chlorophenyl)pyromelli-
timide (1). A resealable test tube was charged with 2-tert-
butylaniline (27 mg, 0.18 mmol), 3,6-di(4-chlorophenyl)pyromellitic
acid (43 mg, 0.09 mmol), N-(3-dimethylaminopropyl)-N′-ethylcar-
bodiimide hydrochloride (0.07 g, 0.36 mmol), 4-dimethylaminopy-
ridine (0.02 g, 0.18 mmol), and dry CH2Cl2 (2 mL). The test tube
was capped, and the reaction mixture was allowed to stir with
heating at 60 °C for 16 h. The mixture was washed with water,
dried over MgSO4, concentrated, and chromatographed to give the
syn and anti products as light yellow solids. The yield of the mixture
of diastereomers was 60 mg (94%), mp >290 °C. Pure anti-1 could
be obtained by crystallization from hexane/CH2Cl2. The purity was
1
to be 94% by H NMR: 1H NMR (400 MHz, CDCl3, δ) 7.45-
7.48 (m, 4H), 7.15-7.17 (m, 4H), 1.99 (s, 12H); 13C NMR (100
MHz, CDCl3, δ) 141.4 (u), 140.7 (u), 132.8 (u), 132.4 (u), 131.3
(dn), 129.0 (dn), 18.5 (dn); IR (cm-1) 1493, 1460, 1090, 1016,
988, 864, 813; HRMS (ESI+) m/z [M+], calcd for C22H20Cl2,
354.0942; found, 354.0925.
3,6-Di(4-chlorophenyl)pyromellitic Acid. Compound 5 (3.82
g, 10.8 mmol) and KMnO4 (8.67 g, 54.9 mmol) were heated in
pyridine (125 mL) and water (16 mL) at reflux temperature under
N2 for 2 days. The mixture was filtered and concentrated. Additional
KMnO4 (8.67 g, 54.9 mmol) and NaOH (7.23 g, 181 mmol) were
added to the mixture, which was again allowed to reflux in water
(150 mL) for 16 h. EtOH (15 mL) was carefully added to the
mixture to destroy excess KMnO4. The mixture was filtered, washed
with water, and acidified (10% HCl). The white solid which
precipitated was filtered, washed with water, and dried under
vacuum. The title product was obtained as a white solid. The yield
was 3.54 g (69%), mp >290 °C. The purity was measured to be
92% by 1H NMR: 1H NMR (400 MHz, acetone-d6, δ) 7.48-7.60
(m, 4H), 7.38-7.41 (m, 4H); 13C NMR (100 MHz, acetone-d6, δ)
167.5 (u), 136.6 (u), 136,5 (u) 135.2 (u), 134.2 (u), 131.1 (dn),
128.5 (dn); IR (cm-1) 1712, 1695, 1225, 856, 728.
Tetramethyl Di(4-chlorophenyl)pyromellitate (6). A solution
of compound 3,6-di(4-chlorophenyl)pyromellitic acid (4.90 g, 10.3
mmol) in N,N-dimethylacetamide (DMA, 150 mL) was cooled by
an ice/water bath. NaH (1.86 g, 46.4 mmol) was added to this
solution, and the reaction mixture was allowed to stir at 0 °C for
15 min. Me2SO4 (10.0 mL, 103 mmol) was added to the mixture
via syringe. The ice bath was removed, and the reaction was allowed
to warm to rt while stirring under N2 for 16 h. The reaction was
then quenched by saturated NH4Cl(aq). The mixture was extracted
with CH2Cl2 (100 mL × 3) and concentrated. The DMA was
removed by distillation at 100 °C under vacuum. The mixture was
chromatographed (1:1 CH2Cl2:ethyl acetate) and dried under
vacuum to give the title product as a white solid. The yield was
4.62 g (84%), mp >290 °C. The purity was measured to be g95%
by 1H NMR: 1H NMR (400 MHz, CDCl3, δ) 7.37-7.39 (m, 4H),
7.18-7.20 (m, 4H), 3.54 (s, 12H); 13C NMR (100 MHz, CDCl3,
δ) 167.2 (u), 137.9 (u), 135.5 (u), 135.1 (u), 135.0 (u), 130.1 (dn),
129.0 (dn), 53.2 (dn); IR (cm-1) 1728, 1714, 1444, 1329, 1208,
1
measured to be g95% by H NMR. Spectral data for anti-1: 1H
NMR (400 MHz, CDCl3, δ) 7.61 (dd, J ) 8.0, 1.4 Hz, 2H), 7.48-
7.50 (m, 8H), 7.42 (app dt, J ) 7.3, 1.5 Hz, 2H), 7.29 (app dt, J )
7.3, 1.5 Hz, 2H), 6.97 (dd, J ) 8.0, 1.4 Hz, 2H), 1.36 (s, 18H); 13
C
NMR (100 MHz, CDCl3, δ) 165.8 (u), 149.3 (u), 138.1 (u), 136.3
(u), 135.2 (u), 131.5 (dn), 131.4 (dn), 130.5 (dn), 129.4 (u), 129.1
(dn), 128.8 (u), 128.5 (dn), 127.7 (dn), 36.0 (u), 32.2 (dn); IR (cm-1
)
2964, 1766, 1722, 1713, 1369, 1130, 1077, 896, 838, 770, 761,
732, 630; HRMS (ESI+) m/z [M + Na], calcd for C42H34N2O4Cl2,
723.1793; found, 723.1778; UV-vis (2 × 10-5 M in CH2Cl2) λmax
244, 332.
2,5-Di-tert-butyl-1,4-diphthalimido Benzene (2). A resealable
test tube was flushed with N2 and charged with phthalic acid (15
mg, 0.090 mmol), 2,5-di-tert-butylbenzene-1,4-diamine53 (10 mg,
0.045 mmol), and glacial acetic acid (0.5 mL). The test tube was
capped, and the reaction mixture was allowed to stir with heating
at 100 °C for 24 h. Water (10 mL) was added to the mixture. A
precipitate was filtered on a Buchner funnel and dried under vacuum
to give the title product as a white solid. The yield was 20 mg
1
(90%), mp >290 °C. The purity was measured to be 93% by H
NMR. Crystals of 2 were grown from CH2Cl2/hexane: 1H NMR
(400 MHz, CDCl3, δ) 7.97-8.00 (m, 4H), 7.81-7.83 (m, 4H), 7.16
(s, 2H), 1.27 (s, 18H); 13C NMR (100 MHz, CDCl3, δ) 168.9 (u),
148.7 (u), 134.9 (dn), 132.7 (u), 132.3 (dn), 131.4 (u), 124.3 (dn),
35.6 (u), 31.8 (dn); IR (cm-1) 2980, 1709, 1696, 1506, 1385, 1320,
1268, 1104, 1082, 868, 714, 694; HRMS (ESI+) m/z [M + Na],
calcd for C30H28N2O4, 503.1947; found, 503.1938; UV-vis (1 ×
10-4 M in CH2Cl2) λmax 235, 293.
N,N′-Di(4-phthalimido-2,5-di-tert-butylphenyl)-3,6-di(4-chlo-
rophenyl)pyromellitimide (3). A resealable test tube was charged
with 3,6-di(4-chlorophenyl)pyromellitic acid (7.6 mg, 0.016 mmol),
(54) Schmitz, L.; Rehahn, M.; Ballauff, M. Polymer 1993, 34,
646-649.
(53) Legge, D. I. J. Am. Chem. Soc. 1947, 69, 2079-2086.
J. Org. Chem, Vol. 72, No. 2, 2007 623

Dong et al.
1170, 1078, 1013, 979, 860, 730; HRMS (ESI+) m/z [M + Na],
1738, 1713, 1441, 1329, 1207, 1178, 978, 847, 826, 811, 609;
HRMS (ESI+) m/z [M + Na], calcd for C42H30O8, 685.1838; found,
685.1814.
calcd for C26H20O8Cl2, 553.0433; found, 553.0406.
Tetramethyl 3,6-Bis[4′-dodecyl-(1,1′-biphenyl)-4-yl]pyro-
mellitate (7). A mixture of compound 6 (1.35 g, 2.54 mmol), (4-
dodecylphenyl)boronic acid (7.27 g, 25.07 mmol), 2-dicyclohexy-
lphosphino-2′-N,N-dimethylaminobiphenyl (79 mg, 0.20 mmol),
Pd(OAc)2 (23 mg, 0.10 mmol), Cs2CO3 (3.27 g, 10.04 mmol), and
1,4-dioxane (70 mL) was heated at 60 °C under N2 for 5 days. The
mixture was then filtered, concentrated, chromatographed (first with
1:10 ethyl acetate:hexane, then with 1:20 ethyl acetate:CH2Cl2),
and dried under vacuum to give the title product as a white solid.
The yield was 2.20 g (91%), mp >290 °C. The purity was measured
Tetramethyl 3,6-Bis[4′-(4-dodecylphenylethynyl)-(1,1′-biphe-
nyl)-4-yl]pyromellitate. A Schlenk tube was charged with com-
pound 9 (10 mg, 0.015 mmol), 1-dodecyl-4-iodobenzene56 (56 mg,
0.15 mmol), PdCl2(PPh3)4 (0.2 mg, 0.0003 mmol), and CuI (0.1
mg, 0.0006 mmol). The tube was evacuated and refilled with N2.
Freshly distilled piperidine (1.5 mL) was added, and the mixture
was allowed to stir under N2 at rt for 3 days, and the mixture was
filtered. The filtrate was concentrated and chromatographed (10:
4:1 hexane:CH2Cl2:ethyl acetate) to give the title product as a white
solid. The yield was 12 mg (70%), mp >290 °C. The purity was
measured to be 91% by 1H NMR: 1H NMR (400 MHz, CDCl3, δ)
7.60-7.68 (m, 12H), 7.46-7.48 (m, 4H), 7.35-7.37 (m, 4H),
7.17-7.18 (m, 4H), 3.55 (s, 12H), 2.62 (t, J ) 7.6 Hz, 4H), 1.62
(m, 4H), 1.26-1.32 (m, 36H), 0.88 (t, J ) 7.1 Hz, 6H); 13C NMR
(100 MHz, CDCl3, δ) 167.6 (u), 144.0 (u), 140.5 (u), 140.1 (u),
138.5 (u), 136.5 (u), 135.0(u), 132.5 (dn), 132.0 (dn), 129.3 (dn),
129.0 (dn), 127.3 (dn), 127.1 (dn), 123.3 (u), 120.7 (u), 91.1 (u),
89.0 (u), 53.2(dn), 36.4 (u), 32.4 (u), 31.7 (u), 30.11 (u), 30.08
(2C, u), 30.02 (u), 29.9 (u), 29.8 (u), 29.7 (u), 23.1 (u), 14.6 (dn);
IR (cm-1) 2921, 2852, 1740, 1724, 1437, 1254, 1179, 985, 844,
722. Anal. Calcd for C78H86O8: C, 81.36; H, 7.53. Found: C, 81.33;
H, 7.64.
1
to be g95% by H NMR: 1H NMR (400 MHz, CDCl3, δ) 7.67-
7.70 (m, 4H), 7.60-7.62 (m, 4H), 7.35-7.38 (m, 4H), 7.31-7.33
(m, 4H), 3.57 (s, 12H), 2.70 (t, J ) 7.5 Hz, 4H), 1.70 (m, 4H),
1.31-1.38 (m, 36H), 0.93 (t, J ) 6.7 Hz, 6H); 13C NMR (100
MHz, CDCl3, δ) 167.7 (u), 143.1 (u), 141.2 (u), 138.5 (u), 137.9
(u), 135.9 (u), 135.0 (u), 129.4 (dn), 129.2 (dn), 127.3 (dn), 127.0
(dn), 53.0 (dn), 36.0 (u), 32.3 (u), 31.9 (u), 30.10 (2C, u), 30.07
(u), 30.03 (u), 29.96 (u), 29.78 (2C, u), 23.1 (u), 14.54 (dn); IR
(cm-1) 2916, 2850, 1740, 1722, 1442, 1211, 1181, 980, 806, 609;
HRMS (ESI+) m/z [M + Na], calcd for C62H78O8, 973.5594; found,
973.5574.
3,6-Bis[4′-dodecyl-(1,1′-biphenyl)-4-yl]pyromellitic acid (8).
A resealable Schlenk tube was charged with compound 7 (0.32 g,
0.34 mmol), 40% KOH(aq) (2 mL), and EtOH (5 mL). The tube
was sealed, and the mixture was heated at 100 °C for 20 h, during
which time the product precipitated. The solid was collected by
filtration and stirred in a mixture of ∼1:1:1 10% HCl, acetone,
and CH2Cl2 until completely dissolved. The mixture was extracted
with CH2Cl2, dried over MgSO4, filtered, and concentrated to give
the title product as a white solid. The yield was 0.24 g (80%), mp
3,6-Bis[4′-(4-dodecylphenylethynyl)-(1,1′-biphenyl)-4-yl]py-
romellitic Acid (10). The procedure was identical to that used to
prepare compound 8. Thus, 40 mg of tetramethyl 3,6-bis[4′-(4-
dodecylphenylethynyl)-(1,1′-biphenyl)-4-yl]pyromellitate gave 28
mg (74%) of 10 as a white solid, mp >290 °C. The 13C NMR
spectrum was measured by HSQC and HMBC because the solubility
was too low to directly obtain a high quality 13C NMR spectrum:
1H NMR (400 MHz, acetone-d6, δ) 7.81-7.84 (m, 8H), 7.67-
7.69 (m, 4H), 7.50-7.55 (m, 8H), 7.29-7.31 (m, 4H), 2.68 (t, J )
7.8 Hz, 4H), 1.66 (m, 4H), 1.30-1.41 (m, 36H), 0.90 (t, J ) 6.8
Hz, 6H); 13C NMR (detected by HSQC and HMBC, 100 MHz,
acetone-d6, δ) 128.8, 126.4, 124.5, 121.2, 120.7, 119.9, 117.7, 114.9,
113.1, 112.8, 111.4, 110.9, 109.8, 109.7, 93.3, 92.0, 35.9, 32.2,
31.6, 22.9, 13.9. We note that seven of the methylene carbons were
not identified because they overlap with the acetone-d6 peak. The
solubility of compound 10 in other solvents was not suitable for
13C NMR analysis. IR (cm-1): 2967, 1737, 1366, 1216, 814.
N-(4-Amino-2,5-di-tert-butyl)phthalimide (11). A resealable
test tube was flushed with N2 and charged with phthalic anhydride
(40 mg, 0.27 mmol), 2,5-di-tert-butylbenzene-1,4-diamine53 (60 mg,
0.27 mmol), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hy-
drochloride (50 mg, 0.27 mmol), 4-dimethylaminopyridine (30 mg,
0.27 mmol), and dry CH2Cl2 (2 mL). The tube was capped, and
the reaction mixture was heated in a bath at 60 °C for 16 h. The
mixture was then partitioned between CH2Cl2 and water, concen-
trated, and chromatographed (gradient of 10-40% ethyl acetate/
hexane) to give the title product as a white solid. The yield was 70
mg (73%), mp 235-237 °C. The purity was measured to be g95%
1
>290 °C. The purity was measured to be 93% by H NMR: 1H
NMR (400 MHz, acetone-d6, δ) 7.68-7.70 (m, 4H), 7.61-7.64
(m, 4H), 7.45-7.47 (m, 4H), 7.30-7.33 (m, 4H), 2.66 (t, J ) 7.7
Hz, 4H), 1.63 (m, 4H), 1.27-1.34 (m, 36H), 0.85 (t, J ) 7.0 Hz,
6H); 13C NMR (100 MHz, acetone-d6, δ) 167.7 (u), 142.7 (u), 141.0
(u), 138.0 (u), 137.0 (u), 136.7 (u), 135.2 (u), 129.9 (dn), 129.4
(dn), 127.1 (dn), 126.6 (dn), 35.7 (u), 32.2 (u), 31.8 (u), 22.8(u),
13.9(dn). We note that seven of the methylene carbons were not
identified because they overlap with the acetone-d6 peak. The
solubility of compound 8 in other solvents was not suitable for 13
C
NMR analysis. IR (cm-1): 2917, 2849, 1713, 1413, 1290, 1184,
1005, 809, 721.
Tetramethyl 3,6-Bis[4′-ethynyl-(1,1′-biphenyl)-4-yl]pyromel-
litate (9). A dry round-bottomed flask was charged with 6 (0.56 g,
1.05 mmol), 4-(triisopropylsilylethynyl)phenylboronic acid55 (2.53
g, 8.38 mmol), 2-dicyclohexylphosphino-2′-N,N-dimethylamino-
biphenyl (0.17 g, 0.04 mmol), Pd(OAc)2 (5 mg, 0.02 mmol), and
Cs2CO3 (1.36 g, 4.20 mmol). The flask was evacuated and refilled
with N2. 1,4-Dioxane (22 mL) was added, and the mixture was
heated at 60 °C under N2 for 5 days and was then filtered,
concentrated, and chromatographed (first with 1:10 ethyl acetate:
hexane, then with 1:20 ethyl acetate:CH2Cl2). The resulting white
solid was stirred in THF (25 mL) at rt. TBAF (4.2 mL, 1.0 M in
THF, 4.2 mmol) was slowly added via syringe. The mixture was
allowed to stir at rt for 14 h, and the reaction was quenched by
10% HCl. The white precipitate was filtered, washed with water,
and dried under vacuum to give the title product as a white solid.
The yield was 0.54 g (77%), mp >290 °C. The purity was measured
1
by H NMR.
An alternate method to prepare compound 11 was similar to that
used to prepare compound 2. Thus, phthalic anhydride (40 mg, 0.27
mmol), 2,5-di-tert-butylbenzene-1,4-diamine53 (60 mg, 0.27 mmol),
and glacial acetic acid (2.0 mL) gave 86 mg (90%) of 11: 1H NMR
(400 MHz, CDCl3, δ) 7.97-7.99 (m, 2H), 7.82-7.83 (m, 2H), 6.85
(s, 1H), 6.79 (s, 1H), 4.06 (br, 2H), 1.41 (s, 9H), 1.30 (s, 9H); 13
C
NMR (100 MHz, CDCl3, δ) 169.7 (u), 147.7 (u), 145.8 (u), 134.6
(dn), 132.86 (u), 132.80 (u), 130.1 (dn), 124.1 (dn), 120.2 (u), 117.9
(dn), 35.3 (u), 34.2 (u), 31.9 (dn), 29.8 (dn); IR (cm-1) 2964, 1779,
1710, 1404, 1391, 1375, 1105, 1081, 873, 729, 714; HRMS (ESI+)
m/z [M+], calcd for C22H26N2O2, 350.1994; found, 350.1996.
N-(4-Amino-2,5-di-tert-butyl)-isophthalimide (12). A resealable
test tube was flushed with N2 and charged with phthalic anhydride
1
to be g95% by H NMR: 1H NMR (400 MHz, CDCl3, δ) 7.58-
7.66 (m, 12H), 7.34-7.36 (m, 4H), 3.55 (s, 12H), 3.16 (s, 2H);
13C NMR (100 MHz, CDCl3, δ) 167.1, 140.5, 140.0, 138.0, 136.2,
134.6, 132.6, 128.9, 126.9, 126.7, 121.4, 83.4, 78.0, 52.7; IR (cm-1
)
(55) Godt, A.; Unsal, O.; Roos, M. J. Org. Chem. 2000, 65, 2837-
2842.
(56) Smith, W. B.; Ho, O. C. J. Org. Chem. 1990, 55, 2543-2545.
624 J. Org. Chem., Vol. 72, No. 2, 2007

Parallel Alignment of Rod-Shaped Conjugated Molecules
(40 mg, 0.27 mmol), 2,5-di-tert-butylbenzene-1,4-diamine53 (60 mg,
0.27 mmol), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hy-
drochloride (50 mg, 0.27 mmol), 4-dimethylaminopyridine (30 mg,
0.27 mmol), and dry CH2Cl2 (2 mL). The tube was capped under
N2, and the reaction mixture was allowed to stir for 16 h at rt. The
mixture was then partitioned between CH2Cl2 and water. The
organics were dried over MgSO4, concentrated, and chromato-
graphed (10-20% ethyl acetate/hexane) to give the title product
as a yellow wax. The yield was 50 mg (52%). The purity was
measured to be 93% by 1H NMR: 1H NMR (400 MHz, CDCl3, δ)
8.01-8.03 (m, 1H), 7.96-7.98 (m, 1H), 7.81 (app dt, J ) 7.5, 0.6
Hz 1H), 7.70 (app dt, J ) 7.5, 0.6 Hz, 1H), 7.48 (s, 1H), 6.68 (s,
1H), 3.89 (br, 2H), 1.46 (s, 9H), 1.44 (s, 9H); 13C NMR (100 MHz,
CDCl3, δ) 166.3 (u), 145.1 (u), 143.5 (u), 142.3 (u), 138.4 (u),
135.6 (dn), 133.4 (u), 132.6 (dn), 131.6 (u), 127.9 (u), 125.6 (dn),
124.6 (dn), 123.4 (dn), 116.3 (dn), 35.6 (u), 34.4 (u), 31.0 (dn),
30.1 (dn); IR (cm-1) 2967, 2922, 1797, 1732, 1695, 1471, 1364,
1240, 1095, 900, 773, 732, 700; HRMS (ESI+) m/z [M + H], calcd
for C22H26N2O2, 351.2073; found, 351.2059; UV-vis (1 × 10-4
M in CH2Cl2) λmax 229, 405.
Polymer 13. A resealable test tube was flushed was N2 and
charged with compound 8 (50.0 mg, 0.056 mmol), 2,5-di-tert-
butylbenzene-1,4-diamine53 (12.3 mg, 0.056 mmol), and glacial
acetic acid (2.0 mL). The tube was capped, and the mixture was
allowed to stir for 4 days with heating in an oil bath at 100 °C.
Water (20 mL) was added to the solution. A precipitate formed
and was isolated by filtration and dried under vacuum. The resulting
solid was transferred to a resealable test tube that had been flushed
with N2. Sequentially added to the tube were triethylamine (0.02
mL, 0.12 mmol), acetic anhydride (0.02 mL, 0.12 mmol), and CH2-
Cl2 (1.5 mL). The mixture was heated at 60 °C for 16 h, washed
with water, dried over MgSO4, filtered, and concentrated. Precipita-
tion from hexane provided polymer 13 as a yellow solid. The yield
was 47 mg (75%), mp >290 °C: 1H NMR (400 MHz, CDCl3, δ)
7.60-7.72 (m, 12H), 7.26-7.28 (m, 4H), 7.04-7.09 (m, 2H), 2.68
(t, J ) 6.89 Hz, 4H), 2.25 (s, 0.8H), 1.68 (m, 4H), 1.23-1.39 (m,
54H), 0.92 (t, J ) 6.7 Hz, 6H). The 13C NMR spectrum is displayed;
IR (cm-1): 2922, 1728, 1506, 1464, 1389, 1347, 1126, 901, 835,
Anal. Calcd for C522H630N16O30 (formula of 7-mer): C, 82.40; H,
8.35. Found: C, 81.64; H, 8.25; UV-vis (1 × 10-5 M in CH2Cl2)
λmax 234, 256, 330.
to prepare compound 3. Thus, 30 mg of 8 gave 35 mg of 14 (93%)
as a light yellow solid that was a ∼1:1 mixture of syn- and anti-
isomers. Chromatography (30% ethyl acetate in hexane) separated
the diastereomers, mp >290 °C. The purity was measured to be
g95% by 1H NMR. UV-vis of the mixture of diastereomers (1 ×
10-5 M in CH2Cl2) λmax: 244, 330. Spectral data for the diastere-
omer of 14 that eluted more quickly by SiO2 chromatography: 1H
NMR (400 MHz, CDCl3, δ) 7.72-7.74 (m, 4H), 7.59-7.64 (m,
10H), 7.38-7.42 (m, 2H), 7.24-7.30 (m, 6H), 6.96-6.98 (m, 2H),
2.68 (t, J ) 7.6 Hz, 4H), 1.67-1.70 (m, 4H), 1.40 (s, 18H), 1.31-
1.37 (m, 36H), 0.92 (t, J ) 7.2 Hz, 6H); 13C NMR (100 MHz,
CDCl3, δ) 166.1(u), 149.2 (u), 142.8 (u), 142.6 (u), 139.1 (u), 138.3
(u), 135.3 (u), 131.6 (dn), 130.7 (dn), 130.3 (dn), 129.5 (u), 129.22
(dn), 129.18 (u), 129.11 (dn), 127.6 (dn), 127.5 (dn), 126.6 (dn),
36.1 (u), 32.4 (u), 32.2 (dn), 31.9 (u), 30.13 (2C, u), 30.10 (u),
30.05 (u), 29.98 (u), 29.83 (u), 29.82 (2C, u), 23.2 (u), 14.6 (dn).
Spectral data for the diastereomer of 14 that eluted more slowly
by SiO2 chromatography: 1H NMR (400 MHz, CDCl3, δ) 7.67-
7.69 (m, 4H), 7.54-7.60 (m, 10H), 7.35-7.39 (m, 2H). 7.23-
7.26 (m, 6H), 6.97-6.99 (m, 2H), 2.63 (t, J ) 7.6 Hz, 4H), 1.60-
1.68 (m, 4H), 1.33 (s, 18H), 1.23-1.33 (m, 36H), 0.89 (t, J ) 6.8
Hz, 6H); 13C NMR (100 MHz, CDCl3, δ): 165.6 (u), 148.9 (u),
142.4 (u), 142.2 (u), 138.7 (u), 137.9 (u), 134.8 (u), 131.2 (dn),
130.3 (dn), 129.9 (dn), 129.2 (u), 128.8 (dn), 128.68 (dn), 128.66
(u), 127.2 (dn), 127.1 (dn), 126.2 (dn), 35.7 (u), 31.9 (u), 31.8 (dn),
31.5 (u), 29.7 (2C, u), 29.7 (2C, u), 29.6 (u), 29.56 (u), 29.4 (2C,
u) 22.7 (u), 14.2 (dn); IR (cm-1) 2924, 2854, 1768, 1722, 1445,
1371, 1137, 895, 812, 769, 732; HRMS (ESI+) m/z [M + Na],
calcd for C78H92N2O4, 1143.6955; found, 1143.6927.
Acknowledgment. Acknowledgment is made to the donors
of The American Chemical Society Petroleum Research Fund
(ACS PRF #41187-G1) for financial support of this research.
Supporting Information Available: 1H NMR and 13C NMR
spectra are displayed for all new compounds. The UV-vis spectra
(220-600 nm) are provided for compounds 12-14. CIF files for
crystallographically characterized compounds are also provided.
This material is available free of charge via the Internet at
http://pubs.acs.org.
N,N′-Di(2-tert-butylphenyl)-3,6-di[(4′-dodecyl-1,1′-biphenyl)-
4-yl]pyromelletimide (14). The procedure was similar to that used
JO062261I
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