Novel H-shaped persistent architecture based on a dispiro building block system

Article abstract of DOI:10.1021/ol060109x

A novel dispiro building block, dispiro[fluorene-9,5′(7′ H)-diindeno[2,1-b:1′,2′-d]thiophene-7′,9″-fluorene], and its two derivatives, TBP-DSFDITF and TDOF-DSFDITF, were designed and synthesized. Because of the rigidity and orthogonality of the spiro stru

Full text of DOI:10.1021/ol060109x

ORGANIC
LETTERS
2006
Vol. 8, No. 7
1363-1366
Novel H-Shaped Persistent Architecture
Based on a Dispiro Building Block
System
Ling-Hai Xie, Xiao-Ya Hou, Chao Tang, Yu-Ran Hua, Rui-Jie Wang,
Run-Feng Chen, Qu-Li Fan, Lian-Hui Wang, Wei Wei, Bo Peng, and
Wei Huang*,†,‡
Institute of AdVanced Materials (IAM), Fudan UniVersity, Shanghai 200433, China
wei-huang@fudan.edu.cn; chehw@nus.edu.sg
Received January 14, 2006
ABSTRACT
A novel dispiro building block, dispiro[fluorene-9,5′(7′H)-diindeno[2,1-b:1′,2′-d]thiophene-7′,9′′-fluorene], and its two derivatives, TBP-DSFDITF
and TDOF-DSFDITF, were designed and synthesized. Because of the rigidity and orthogonality of the spiro structure, TBP-DSFDITF exhibits
a well-defined H-shaped architecture, which consists of two ter(biphenyls) as the arms of the H-shape and 3,4-diphenylthiophene as the rung,
connecting via completely rigid dispiro linkages with two sp3 carbon atoms.
Shape-persistent molecular architectures on the nanometer
scale,1 e.g., macromolecular disks,2 helical macromolecules,3
π-conjugated macrocycle molecules,4 and ladder macromol-
ecules,5 have currently attracted a great deal of attention
because of their many applications in the fields of supramo-
lecular chemistry and organic electronics. For example,
π-conjugated macrocycles have assembled into discotic liquid
crystals or nanotubes,4b and helicenes with a precisely ordered
stereostructure have been applied to chiral separation and
molecular recognition.6 The common feature of these mol-
ecules is a typical π-conjugated or helical conjugated
backbone. One strategy for devising new shape-persistent
molecular architectures with special self-assembly behavior
is to incorporate the stiff semiconjugated or π-interrupted
backbones into the above architectures.7 By doing this, new
supramolecular phenomena can occur, e.g., calix[4]arenes
for molecular recognition8 and bicyclic ring-bridged iptycene
for molecular motor devices,9 although strong π-π stacking
supramolecular interaction is not found.
† Institute of Advanced Materials (IAM), Nanjing University, Nanjing
210093, China.
‡ Department of Chemical and Biomolecular Engineering, National
University of Singapore, Singapore 119260, Republic of Singapore.
(1) (a) Moore, J. S. Acc. Chem. Res. 1997, 30, 402-413. (b) Moore, J.
S. Curr. Opin. Colloid Interface Sci. 1999, 4, 108-116.
(2) Fechtenko¨tter, A.; Tchebotareva, N.; Watson, M.; Mu¨llen, K.
Tetrahedron 2001, 57, 3769-3783.
(6) Martin, R. H. Angew. Chem., Int. Edit. 1974, 13, 649-660.
(7) (a) Tour, J. M.; Wu, R.; Jeffry, S. S. J. Am. Chem. Soc. 1991, 113,
7064-7066. (b) Tour, J. M.; Wu, R. L.; Jeffry, S. S. J. Am. Chem. Soc.
1990, 112, 5662-5663. (c) Ipaktschi, J.; Hosseinzadeh, R.; Schlaf, P. Angew.
Chem., Int. Edit. 1999, 38, 1658-1660. (d) Ipaktschi, J.; Hosseinzadeh,
R.; Schlaf, P.; Eckert, T. HelV. Chim. Acta 2000, 83, 1224-1238.
(8) (a) Gutsche, C. D. In Calixarenes ReVisited, Monographs in Su-
pramolecular Chemistry; Stoddart, J. F., Ed.; The Royal Society of
Chemistry: Cambridge, U.K., 1998. (b) Calixarenes: A Versatile Class of
Macrocyclic Compounds; Vicens, J., Bo¨hmer, V., Eds.; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1991.
(3) (a) Marsella, M. J.; Kim, I. T.; Tham, F. J. Am. Chem. Soc. 2000,
122, 974-975. (b) Iwasaki, T.; Kohinata, Y.; Nishide, H. Org. Lett. 2005,
7, 755-758.
(4) (a) Ho¨ger, S. Angew. Chem., Int. Edit. 2005, 44, 3806-3808. (b)
Ho¨ger, S. Chem.-Eur. J. 2004, 10, 1320-1329. (c) Li, Y.; Zhang, J.; Wang,
W.; Miao, Q.; She, X.; Pan, X. J. Org. Chem. 2005, 70, 3285-3287. (d)
Shoji, O.; Tanaka, H.; Kawai, T.; Kobuke, Y. J. Am. Chem. Soc. 2005,
127, 8598-8599. (e) Grave, C.; Schluter, A. D. Eur. J. Org. Chem. 2002,
3075-3098. (f) Grave, C.; Lentz, D.; Schafer, A.; Samori, P.; Rabe, J. P.;
Franke, P.; Schluter, A. D. J. Am. Chem. Soc. 2003, 125, 6907-6918.
(5) Yan, X. Z.; Pawlas, J.; Goodson, T., III; Hartwig, J. F. J. Am. Chem.
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10.1021/ol060109x CCC: $33.50
© 2006 American Chemical Society
Published on Web 03/08/2006

It is fascinating that dispiro building blocks are used to
create new shape-persistent architectures via synthesis, e.g.,
orthogonal squares, tubes, and ladder structures. The or-
thogonally cross-shaped dispiro building blocks exhibit
unique geometric profiles. In terms of the geometric features,
the dispiro compounds can be categorized into five confor-
mational structures, as shown in Figure 1, including linear
Scheme 1. Synthetic Route I to 10a
reaction involving an arylbromide and a Grignard reagent).
Compound 2 was treated with 1.2 equiv of n-BuLi in THF
at -78 °C, followed by quenching with fluorenone to give
the tertiary alcohol 6a in 75% yield. Friedel-Crafts dehydra-
tion cyclization of 6a with BF3‚OEt2/CH2Cl2 gave the
monospiro product 7 in nearly 50% yield. The above steps
were replicated to obtain the tertiary alcohol 9 in 70.5% yield
and 10a in 95% yield. It was noteworthy that route I would
be effective to prepare a variety of derivatives, especially
odd substituent 10a, which were useful building blocks for
the construction of unique architectures. For example, a
useful monobromide 10a can be obtained by reacting
2-bromofluorenone with monospiro 7.
Route I is a multistep synthetic pathway. To simplify the
complicated procedures, we attempted to prepare the thiophene
diol 4a by treating 2 with 2.2 equiv of n-BuLi in THF at
-78 °C, followed by quenching with 2.5 equiv of fluorenone
via one step (as shown in Scheme 2). However, no diol 4a
was obtained, although similar diols have been reported in
the literature.11
Figure 1. Geometric profiles of dispiro building blocks.
antarafacial I, linear suprafacial II, bent suprafacials III and
V, and bent antarafacial IV. Thus, di- or polyspirans allow
construction of novel well-defined unique scaffolds with
many potential applications on the nanometer scale. More-
over, when polyspiro-type structures are end-capped with a
trialkylsilyl or/and thio group, they are likely to develop the
“stand-up” molecules anchoring on the silicon or Au surface,
as reported in the literature.10 However, as far as we know,
there are few reports on the design and synthesis of the above
conformational structures. Our objective is to construct a
novel kind of shape-persistent molecular architecture based
on rigid cross-shaped di- or/and polyspiro building blocks.
In the present work, a fundamental dispiro building block
dispiro[fluorene-9,5′(7′H)-diindeno[2,1-b:1′,2′-d]thiophene-
7′,9′′-fluorene] (10a) with conformational structure III was
successfully designed and synthesized. In addition, its two
derivatives, TBP-DSFDITF and TDOF-DSFDITF, were fully
characterized and confirmed by 1H and 13C NMR, MALDI-
TOF-MS, and elemental analysis. Their optical and thermal
properties were also investigated.
Scheme 2. Synthetic Route II (a) to 10a
First of all, synthesis of unsubstituted 10a as a model
compound mainly involved the preparation of tertiary alcohol
and Friedel-Crafts dehydration cyclization. Dispiro 10a can
be obtained from the cyclization reaction of either tertiary
alcohol 9 or thiophene diol 4a. The former is depicted in
Scheme 1, labeled as route I; the latter is depicted in Schemes
2 and 3, labeled as route II, including routes II (a) and II
(b), respectively.
In route I, the starting material 3,4-dibromothiophene,
which is commercially available, was converted into 3,4-
diphenylthiophene (2) via Kumada-type coupling reactions
(i.e., a nickel-catalyzed Grignard-Wurtz cross-coupling
Fortunately, an efficient synthetic route II (b) to 10a was
developed, as depicted in Scheme 3. Treatment of 2 with 2
equiv of NBS led to 3 in 88% yield, which was transformed
into a double Grignard reagent by reacting with 2.1 equiv
of Mg in anhydrous THF. The Grignard reagent was then
quenched with fluorenone to provide the diol 4a in 49%
yield, together with the monosubstituted 5a (36%) and 6a
(13%). Diol 4a proceeded smoothly in BF3‚OEt2/CH2Cl2 to
obtain the desirable product 10a in overall yields of more
than 40% starting from 3. The byproducts 7 and 8 were also
(10) Deng, X.; Mayeux, A.; Cai, C. J. Org. Chem. 2002, 67, 5279-
5283.
(11) Agarwal, N.; Ravikanth, M. Tetrahedron 2004, 60, 4739-4747.
Org. Lett., Vol. 8, No. 7, 2006
1364

position of fluorene. Finally, the product was confirmed
1
by H and 13C NMR, MALDI-TOF-MS, and elemental
Scheme 3. Synthetic Route II (b) to 10a
analysis.
1
The comparison of H NMR spectra of 10a, 10b, and
TDOF-DSFDITF is illustrated in Figure 2. The H NMR
1
obtained from the following cyclization of 6a and 5a,
respectively. It was found that the double Grignard reagent
is more effective than dilithium in the addition reaction with
fluorenone.
TBP-DSFDITF and TDOF-DSFDITF were prepared via
a Suzuki coupling reaction, as shown in Scheme 4. Tetra-
Scheme 4. Synthesis of TBP-DSFDITF and TDOF-DSFDITF
Figure 2. Comparison of 1H NMR spectra of 10a, 10b, and TDOF-
DSFDITF.
spectrum of 10a exhibits two kinds of peaks with an expected
4:2 integral intensity ratio, which are readily assigned to the
protons on fluorene rings and the protons on benzene rings
at the vertical plane, respectively. Using d6-acetone as
1
solvent, the H NMR spectrum of 10b is unambiguously
brominated 10b, as a key building block for H-shaped
architectures, has been smoothly synthesized via route II (b)
in overall yields of about 45%. Despite the low solubility of
10b in toluene, the Suzuki coupling reaction of 10b with
4.4 equiv of biphenyl boronic acid proceeded smoothly in a
solvent mixture of toluene and THF at 90 °C, providing the
crude product TBP-DSFDITF in 70% yield. After the
byproducts were eluted by CH2Cl2, the main product was
effectively purified by flash column chromatography using
chloroform as eluent. Unfortunately, TBP-DSFDITF did not
show high solubility as expected; thus, no 1H NMR signals
can be observed using CDCl3 as solvent. MALDI-TOF-MS
and elemental analysis were utilized to confirm the structure.
To fully characterize the novel structure and the electronic
properties, TDOF-DSFDITF was also designed and synthe-
sized. TDOF-DSFDITF possesses sufficient solubility due
to the introduction of flexible alkyl side chains at the C-9
assigned in the absence of an overlap of two peaks observed
in CDCl3. The spectrum of TBP-DSFDITF was not gathered
because of unfavorable solubility in CDCl3, whereas TDOF-
DSFDITF can be fully confirmed by 1H and 13C NMR. It is
noteworthy that the C signals of alkyl chains at the C-9
position of fluorene exhibit a double split, which was
probably ascribed to the different chemical circumstances
between the interior and exterior of the rigid H-shaped
architecture; i.e., while one alkyl stretches inside, the other
alkyl on the same carbon atom has to stretch outside. The
optimized conformations of TBP-DSFDITF with energy
minimization have been calculated by the Gaussian 03
program at the B3LYP /3-21G* level, as shown in Figure 3.
The architecture consists of two ter(biphenyls) as the arms
of the H-shape of about 2.37 nm length and one 3,4-
diphenylthiophene as the rung, connecting via completely
rigid dispiro linkages with two sp3 carbon atoms.
Org. Lett., Vol. 8, No. 7, 2006
1365

linkages to the thiophene ring. Dispiro compounds have also
shown high thermal stability, up to about 450 °C for TBP-
DSFDITF and high glass transition temperatures, Tg (320
°C for TBP-DSFDITF).
Figure 3. Optimized conformations of TBP-DSFDITF with energy
minimization calculated by the Gaussian 03 program at the B3LYP/
3-21G* level; (top) view perpendicular to the thiophene, (bottom)
view parallel to the thiophene.
Figure 4. UV-vis and PL spectra of 10a, TBP-DSFDITF, and
TDOF-DSFDITF in chloroform solution (1 µM).
In conclusion, we have designed and synthesized dispiro
10a as a nonplanar building block to construct H-shaped
persistent architectures on the nanometer scale. The interior
and exterior parts of the rigid H-shaped architectures exhibit
different chemical circumstances identified by 13C NMR.
High thermal stability and quantum yield indicate that dispiro
10a is a potential building block for constructing organic
semiconducting materials with unique three-dimensional
structures.
The UV-vis absorption and emission spectra of dispiro
compounds 10a, TBP-DSFDITF, and TDOF-DSFDITF were
measured in dilute chloroform solutions (1 µM), as shown
in Figure 4. TBP-DSFDITF shows the π-π* absorption at
345 nm and a blue-colored emission at 386 and 405 nm,
which is very similar to the absorption (344 nm) and emission
(386 and 404 nm) of the single spiro analogue.12 The results
indicate that there exists little intramolecular interaction
between the chromophores on the parallel arms of the
H-shaped architecture, which can be an ideal model for
intermolecular interaction. Compared with TBP-DSFDITF,
the electronic absorption and emission spectra of TDOF-
DSFDITF undergo a bathochromic shift of about 7 and 3
nm, respectively. The reason is that there are longer
conjugation lengths in fluorene than in biphenyl due to the
coplanar linkage via C-9 of fluorene. Although the thiophene
ring exists in the architecture, TDOF-DSFDITF has shown
high luminescent quantum efficiency (80%) in chloroform,
which is probably attributed to the fixation of two spiro
Acknowledgment. This work was financially supported
by the National Natural Science Foundation of China under
Grants 60325412, 90406021, and 50428303, the Shanghai
Commission of Science and Technology under Grants
03DZ11016 and 04XD14002, and the Shanghai Commission
of Education under Grant 2003SG03 as well as the 4th Grad-
uate Creation Foundation of Fudan University (CQH2203003).
Supporting Information Available: The experimental
1
procedures for the new compounds and H and 13C NMR,
MS spectra, TG, and DSC thermograms. This material is
available free of charge via the Internet at http://pubs.acs.org.
(12) The single spiro analogue is 2′,7′-bis([1,1′-biphenyl]-4-yl)-spiro-
[indeno[2,1-b]thiophene-8,9′-fluorene], which shows absorption (343 nm)
and emission (385 and 403 nm).
OL060109X
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