Tetrathiafulvalene Vinylogue-Fluorene Co-oligomers: Synthesis, Properties, and Supramoleclar Interactions with Carbon Nanotubes

Article abstract of DOI:10.1021/acs.joc.5b00792

A series of bis(dithiafulvenyl)-end-capped fluorene derivatives was prepared and subjected to a one-pot iodine-promoted oxidative polymerization to yield π-conjugated co-oligomers containing tetrathiafulvalene vinylogue and fluorene repeat units. The resu

Full text of DOI:10.1021/acs.joc.5b00792

Article
pubs.acs.org/joc
Tetrathiafulvalene Vinylogue−Fluorene Co-oligomers: Synthesis,
Properties, and Supramoleclar Interactions with Carbon Nanotubes
Mohammadreza Khadem and Yuming Zhao*
Department of Chemistry, Memorial University, St. Johns, NL A1B 3X7, Canada
*
S Supporting Information
ABSTRACT: A series of bis(dithiafulvenyl)-end-capped fluorene derivatives
was prepared and subjected to a one-pot iodine-promoted oxidative
polymerization to yield π-conjugated co-oligomers containing tetrathiafulva-
lene vinylogue and fluorene repeat units. The resulting π-oligomers were
characterized to take either acyclic or cyclic molecular structures, depending
on the π-conjugation length of the monomer used for the polymerization.
Electronic and electrochemical redox properties were examined by UV−vis
spectroscopic and cyclic voltammetric analyses, while the supramolecular
interactions of the π-oligomers with single-walled carbon nanotubes were
investigated by UV−vis−NIR and Raman spectroscopy.
INTRODUCTION
Scheme 1. General Mechanism for the Oxidative
Dimerization of a Phenyl-DTF
■
Redox-active π-conjugated oligomers and polymers have
offered numerous exciting prospects in the current materials
science and nanotechnology, on the basis of which active
1
research has been dedicated to the development of molecular
2
3
4,5
wires, organic photovoltaics, electrochromic devices,
6
7
molecular switches, chemical sensors, and stimuli-responsive
8
,9
materials and soft actuators in recent years. A commonly
employed strategy to impart desired redox-activity to π-
conjugated oligomers and polymers is to have electron donors
and/or acceptors either appended to the polymer side chain o1r
placed directly in the repeat unit through π-conjugation.
Tetrathiafulvalene vinylogues (TTFVs) are a class of π-
extended analogues of the well-known organic electron
10
donor, tetrathiafulvalene (TTF). TTFVs can not only serve
as excellent π-electron donors with tunable redox potentials but
also show unique redox-triggered conformational switching
1
1
properties. The interesting molecular properties of TTFVs
have sparked surging research interest in developing new
TTFV-based functional materials over the past few years,
The DTF dimerization reaction provides an efficient C−C
bond forming approach through which π-conjugated oligomers
and polymers with diverse 1D and 2D structures can be
conveniently assembled under either chemical or electro-
chemical conditions using suitably designed aryl-substituted
9
,12
5
including conjugated polymers,
macrocycles, switchable
1
3
14
15
ligands, molecular rotors, and chemosensors. TTFV
derivatives with aryl groups substituted at the vinylic positions
are versatile building blocks for various TTFV-containing π-
conjugated systems. The aryl-substituted TTFVs can be made
via an oxidative coupling reaction in which a certain
dithiafulvene (DTF) precursor is dimerized through a radical
mechanism as exemplified by the dimerization of a phenyl-DTF
9,12,19
DTFs as precursors.
Scheme 2 depicts the oxidative
polymerization of a generic bis(DTF)-π building block I, which
20
leads to the formation of a linear cationic polymer III.
Subsequent reductive workup yields the neutral polymer
product with a TTFV moiety embedded in each of its repeat
units. Typically, such a one-pot polymerization reaction as
shown in Scheme 2 should give a mixture of polymers with
varied chain lengths, whereas precise control over the degree of
polymerization is usually not an easy task to accomplish. For
1
6
in Scheme 1. The synthetic scope of this methodology
17,18
encompasses numerous aryl-substituted DTFs,
wherein the
presence of aryl groups facilitates the formation of DTF radical
cation in the first step of the mechanism and enables the
molecular structure to be further elaborated into diverse π-
conjugated motifs.
Received: April 21, 2015
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.joc.5b00792
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Scheme 2. General Polymerization Route Using DTF
Oxidative Dimerization as the Key Step for Polymer Chain
Growth
polymerization after exhaustive reaction will yield π-oligomers
with good monodispersity of chain length. One way to tune
down the reactivity of a DTF radical cation is to increase the
degree of π-delocalization. Linking the DTF group with π-
extended arene units presents a feasible means to attain this
goal. Another possible outcome for the one-pot polymerization
is the formation of cyclic products, namely macrocycles. TTFV-
based macrocycles were rarely reported in the literature. In our
recent work, we synthesized a series of trimeric TTFV
macrocycles via a one-pot Pd/Cu-catalyzed alkynyl homocou-
5
pling of acetylenic TTFV precursors. The DTF oxidative
dimerization reaction, however, has not yet been demonstrated
as a viable synthetic tool for direct construction of TTFV-
containing macrocycles.
This paper addresses the synthetic scope of bis(DTF)-
functionalized π-building blocks in terms of making various π-
conjugated oligomers and macrocyclic structures. A series of
fluorene-centered bis(DTF) derivatives was accordingly de-
signed and synthesized. They were then subjected to a one-pot
oxidative polymerization in the solution phase, and the
resulting TTFV−fluorene co-oligomers were characterized by
electrochemical and UV−vis analyses to understand their redox
and electronic properties. Moreover, the supramolecular
interactions of these electron-rich conjugated oligomers with
single-walled carbon nanotubes (SWNTs) were investigated. π-
Conjugated polymers containing TTFV units have been found
to give rise to effective and selective dispersion of SWNTs in
instance, in our previous studies, bis(DTF)-end-capped π-
conjugated butadiyne and octatetrayne derivatives were
5
polymerized in solution using iodine as oxidant. The reactions
resulted in the formation of a number of relatively short
oligomers rather than long-chain polymers. The observed low
polymerization degree can be rationalized by noting that when
the polymer chain is elongated the terminal DTF groups
gradually lose the reactivity toward oxidative dimerization as a
result of increased π-delocalization and intermolecular electro-
static repulsion.
9
organic solvents. Herein, the study of SWNT dispersion with
TTFV−fluorene co-oligomers will further expand the applica-
tion scope of TTFV-based π-oligomers in nanoscience and
supramolecular chemistry.
The poor efficiency found in DTF polymerization, on the
other hand, might suggest a useful synthetic route to prepare
relatively short, structurally defined TTFV-based π-oligomers.
Hypothetically, if the bis(DTF)-π precursor possesses a
moderate reactivity toward DTF oxidative dimerization, it is
likely for the terminal DTF radical cations (highlighted by blue
color in Scheme 2) to become completely inert toward the
oxidation dimerization when the oligomer chain arrives at a
certain “critical length”. If such a scenario holds true, the
RESULTS AND DISCUSSION
■
Synthesis. The synthetic routes to bis(DTF)-fluorenes 5a−
c are described in Scheme 3. 2,7-Dibromofluorenes 1a−c were,
respectively, reacted with boronate 2 via the Suzuki coupling
21
to give dialdehydes 3a−c in very good yields. Compounds 3a−
c were then subjected to a phosphite-induced olefination
2
2
reaction with thione 4 to produce bis(DTF)-fluorene
derivatives 5a−c. With 5a−c in hand, iodine-promoted (ca.
Scheme 3. Synthesis of Fluorene-Cored Bis(DTF) Derivatives 5a−c and Acyclic TTFV−fluorene Oligomers 6a−c
B
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Scheme 4. Synthesis of Cyclic TTFV−fluorene Oligomers 10 Using Bis(DTF)-Oligomer 9 as Precursor
Figure 1. UV−vis spectra of TTFV−fluorene co-oligomers and related π-precursors. All spectra were measured in CHCl at room temperature.
3
2
.8 equiv) oxidative polymerization reactions were undertaken
resulting oligomers, however, were predicted to have relative
higher degrees of polymerization due to the enlarged sizes of
the monomers used for polymerization. To further explore in
this respect, the synthesis of an extended bis(DTF)-fluorene 9
was pursued as outlined in Scheme 4. Structurally, compound 9
is the dimer of 5b, but synthetically it is challenging to acquire 9
from direct oxidative dimerization of bis(DTF)-fluorene 5b due
to the presence of two equally reactive DTF groups in 5b. A
multistep synthetic route was hence devised and executed. The
synthesis began with an olefination reaction between
compound 3b and with 0.9 equiv of thione 4 in the presence
in CH Cl at room temperature. The reactions in general
2
2
completed within 5 h, as monitored by thin-layer chromato-
graphic (TLC) analysis. The major products of the polymer-
ization reactions (oligomers 6a−c) were obtained after a brief
reductive aqueous workup with Na S O . Careful flash column
chromatographic purification then afforded oligomers 6a−c as
brown semisolids in good yields. The molecular structures of
these compounds were characterized as the acyclic TTFV−
fluorene π-oligomers presented in Scheme 3 on the basis of H
NMR, gel-permeation chromatographic (GPC), and cyclic
2
2
3
1
voltammetric (CV) analyses (vide infra).
of P(OMe) under heating. The major product of this reaction
3
In addition to the bis(DTF)−fluorenes 5a−c, the one-pot
polymerization was expected to work in a similar way by using
bis(DTF)-π precursors with more extended π-skeletons. The
was mono-DTF-substituted compound 7, which could be easily
separated from other byproducts by silica column chromatog-
raphy. Compound 7 was then subjected to the iodine-induced
C
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Figure 2. Cyclic voltammograms of compounds 5a−c, 6a−c, 9, and 10 measured in multiple scans. Electrolyte: Bu NBF (0.1 M); working
4
4
−1
electrode: glassy carbon; counter electrode: Pt wire; reference electrode: Ag/AgCl; scan rate: 100 mV s .
18b
oxidative dimerization to afford TTFV-centered oligomer 8.
we recently reported,
enlargement of the dihedral bond
Repetition of the P(OMe) -promoted olefination on oligomer
angle between the two vinyl units of TTFV was found to result
in significantly increased absorptivity in the spectral range of ca.
330−350 nm. It is therefore deduced that the varied intensity of
the shoulder band at 343 nm in the UV−vis spectra of 6a−c
and 10 is tied to the different TTFV conformations in these
compounds.
3
8
with thione 4 gave bis(DTF)-oligomer 9 in a satisfactory
yield of 56%. Finally, the iodine-induced one-pot polymer-
ization of 9 was performed. To our surprise, there were no
significant amounts of acyclic π-oligomers formed out of this
reaction; instead, the major products were identified to be in
the macrocyclic structure (see 10 in Scheme 4), which was
The electrochemical redox properties of the above-
mentioned compounds were examined by cyclic voltammetric
(CV) experiments, and the detailed cyclic voltammograms are
given in Figure 2. The cyclic voltammogram of bis(DTF)-
fluorene 5a (Figure 2A) shows only one anodic peak at +0.78 V
in the first cycle of CV scan, which is assigned to the one-
1
substantiated by H NMR, GPC, and CV characterizations
(
vide infra). Such a synthetic outcome sharply contrasts with
the polymerization reactions using relatively shorter bis(DTF)-
fluorenes 5a−c as monomers, while a detailed rationalization
for this is made in the later section based on kinetic
considerations (see Figure 5).
5,16
electron oxidation of neutral DTF to its radical cation state.
Electronic and Redox Properties. The electronic
absorption properties of the bis(DTF)-fluorene derivatives
and related TTFV−fluorene co-oligomers were investigated by
UV−vis spectroscopic analysis. Figure 1A shows the UV−vis
absorption spectra of bis(DTF)-fluorenes 5a−c. All of the
spectra of the three compounds exhibit a nearly superimposable
absorption profile featuring a π → π* band at 396 nm. Clearly,
the side chains attached to the fluorene core barely have any
effect on the electronic absorption behavior of the bis(DTF)-
fluorene π-framework. The UV−vis spectra of TTFV−fluorene
co-oligomers 6a−c (Figure 1B) show the same absorption band
at 396 nm in the low energy region, indicating that the degrees
of π-delocalization of the co-oligomers are virtually unchanged
in comparison with their bis(DTF)-fluorene precursors. In
addition, each of the spectra of 6a−c exhibits a notable
absorption shoulder at 343 nm, which can be assigned to the π
In the reverse scan, a cathodic peak emerges at +0.46 V, the
origin of which is attributed to the reduction of the TTFV
dication resulting from the electrochemical dimerization taking
5
,16
place on the working electrode surface.
As the number of
scan cycles increases, another anodic peak is observed to grow
steadily at +0.52 V, which is due to the oxidation of the TTFV
product accumulated on the working electrode surface. The CV
profiles of bis(DTF)-fluorenes 5b and 5c (Figure 2B,C) exhibit
a similar pattern to that of 5a, indicating that the three
bis(DTF)-fluorene compounds have similar redox activities and
electrochemical properties.
The cyclic voltammogram of TTFV−fluorene co-oligomer
6a gives two anodic peaks at +0.63 and +0.87 V respectively,
while in the reverse scan a cathodic peak at +0.44 V is observed
(Figure 2E). The first anodic peak and the cathodic peak are
due to the reversible redox couple of the TTFV moieties in the
co-oligomer, and the second is assigned to the oxidation of the
→
π* transition of the TTFV units in the oligomer backbones.
5
,16
The UV−vis spectrum of dimer 9 gives a spectral pattern
similar to those of co-oligomers 6a−c (see Figure 1C). In the
UV−vis spectrum of macrocyclic oligomer 10 (Figure 1C), the
same low energy absorption band at 396 nm can be observed.
Unlike the acyclic oligomers 6a−c and 9, the shoulder band of
macrocycle 10 at 343 nm appears to be significantly stronger in
relative intensity, which very likely results from the constraint
cyclic π-framework of the macrocycle (see Figure 4). In a
comparative study of two dinaphthyl-substituted TTFV isomers
terminal DTF groups of 6a.
After being scanned with
multiple cycles, these redox peaks do not show any significant
changes, indicating that the termianl DTF groups in 6a are
virtually unreactive toward oxidative dimerization. Similar
electrochemical redox behavior can be observed in the CV
profiles of co-oligomers 9, 6b, and 6c (Figure 2D,F,G);
however, the oxidation currents due to the TTFV and DTF
moieties show notable differences in relative intensity in the
cyclic voltammograms of 6a−c, and these results can be
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1
Figure 3. Partial H NMR spectra of 6a−c, 9, and 10 showing the aromatic and vinylic regions as well as relative integration values therein. The
singlet at 7.24 ppm in each spectrum is due to residual CHCl .
3
correlated with their different degrees of oligomerization (vide
infra). The cyclic voltammogram of macrocycle 10 (Figure 2H)
shows only a reversible redox couple at E = +0.58 V and E =
given that the unique chemical shift of the vinylic protons (Ha)
on the terminal DTF groups is distinctively separated from the
other aromatic protons on the oligomer backbone. Figure 3
shows the partial H NMR spectra of 6a−c, 9, and 10,
highlighting the aromatic and vinylic regions. In each of the
pa
pc
1
+
0.51 V in the first cycle of CV scans, which is characteristic of
the TTFV moieties in macrocycle 10. There is no anodic peak
due to DTF oxidation observed in the multicycle CV scans of
spectra, the vinylic protons of the terminal DTF groups (H
give a singlet at 6.51 ppm. In addition, a pseudo doublet
(labeled as H ) can be clearly seen at 7.31 ppm. The origin of
can be assigned to the ortho-protons on the phenyl ring
adjacent to the terminal DTF group. Other aromatic protons
)
a
10, which is congruous with the macrocyclic structure. It is also
noted that the intensities of the redox wave pair give a
significant decreasing trend with increasing number of CV
scans, while the redox potentials appear to shift anodically in a
slight degree. Such CV behavior alludes to a low degree of
electrochemical stability for TTFV−fluorene macrocycle 10.
Structural Elucidation of TTFV−Fluorene Co-
oligomers. As manifested by the CV analysis, the structures
of TTFV−fluorene co-oligomers 6a−c take an acyclic structure
with two DTF groups end-capped at the termini of each
oligomer chain. The structure of co-oligomer 10, on the other
hand, is deduced to be in a macrocyclic motif based on the
absence of DTF oxidation peaks in its cyclic voltammogram.
For these co-oligomers, determination of the degrees of
oligomerization (n, as indicated in the structures of co-
oligomers shown in Schemes 3 and 4) is of great importance
to better understanding their structural properties as well as
gaining mechanistic insight into the oxidative polymerization
b
H
b
located on the fluorene and phenyl rings (H ) collectively
Ar
contribute to the signals in the range of 7.49−7.76 ppm, which
are too significantly overlapped to attain detailed assignments.
The integral ratio of H versus the sum of H and H thus
a
b
Ar
allows the average degree of oligomerization (n) for each co-
oligomer to be calculated (see Table 1). The NMR results show
Table 1. Summary of GPC Data for TTFV−fluorene Co-
Oligomers and Their Calculated Degrees of Oligomerization
(
n)
entry
Mn
Mw
PDI M /M0 n(calcd, NMR) n(calcd, CV)
n
6
6
6
9
1
a
b
c
4392
7961
8200
6965
12303
11119
1.39
1.54
1.35
3.13
5.45
5.41
2.87
5.32
5.63
2.07
3.29
5.45
8.31
1.93
reactions.
1H NMR analysis has proven to be an indispensable tool for
0
3126
7297
2.33
1.07
determination of the n values in acyclic co-oligomers 6a−c,
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that co-oligomers 6b and 6c have similar oligomerization
degrees (i.e., at the stage of pentamer to hexamer).
Comparatively, co-oligomer 6a has a relatively lower degree
of oligomerization (n = 2.87), suggesting that the dominant
component of 6a is trimer. The relative lower oligomerization
degree of 6a can be ascribed to the long side chains on the
fluorene units, the increased steric hindrance of which may
retard the oxidative oligmerization.
contact or π-stacking. Moreover, the central cavity of the
macrocycle appears to be very small and therefore not suited to
encapsulate meaningful molecular guests.
Apart from NMR and GPC analyses, the CV data could also
serve as a meaningful way to assess the average degree of
oligomerization (n) for 6a−c. As can be seen from Figure 2, the
anodic peaks due to the oxidation of DTF and TTFV moieties
are well separated from one another in the voltammogram of
each oligomer. In principle, a DTF unit releases one electron
and a TTFV unit loses two electrons during the oxidation
processes. Assuming that the current intensity of each anodic
1
The H NMR analysis on the average degree of
oligomerization (n) was then compared with gel permeation
chromatographic (GPC) data. As listed in Table 1, TTFV−
fluorene co-oligomers 6a−c all exhibit relatively narrow
polydispersity (PDI = 1.3−1.5). The degree of oligomerization
23
peak is proportional to the number of electrons transferred,
the ratio of the current intensities for DTF and TTFV thus
offers a quantitative measure for the degree of oligomerization
(n). To evaluate the usefulness of this method, the current
intensities (ipa) of the DTF and TTFV anodic peaks for
TTFV−fluorene dimer 9 were first examined. The calculated n
value (1.93) according to the CV data is satisfactorily close to
the ideal value (n = 2) for dimer 9, corroborating the reliability
of the electrochemical method (see Table 1). Indeed, the
degrees of oligomerization (n) calculated on the basis of the
anodic peak currents are consistent with those determined by
the GPC and NMR analyses in the cases of co-oligomers 6a
and 6b. For co-oligomer 6c, however, the electrochemical
analysis yields a slightly larger n value than the other two
methods, and the exact reason for such a discrepancy awaits
more detailed investigation to clarify. It is worth mentioning
that strenuous efforts were made in our work to characterize
the TTFV−fluorene co-oligomers by MALDI-TOF MS
analysis. Unfortunately, only dimer 9 was reasonably
characterized by MS, whereas the other co-oligomers only
gave the mass peaks due to smaller fragment ions in their mass
spectra. It is therefore reasoned that these oligomers are
unstable to the laser shots under the MALDI conditions,
resulting in rapid decomposition and fragmentation which in
turn obscured the MALDI-TOF MS analysis.
(
n) can be worked out using the formula n = M /M , where in
n 0
M is the number-average molecular weight determined by
n
GPC and M is the molecular weight of the monomer used for
0
the polymerization. The degrees of oligomerization calculated
for 6a−c based on GPC data show a good agreement with
those derived from NMR analysis, testifying to the reliability of
both methods in elucidating the structures of bis(DTF)-end-
capped TTFV−fluorene co-oligomers. The GPC data for
macrocycle 10 gave an M value very close the molecular
n
weight of dimer 9, indicating that the dominant reaction
pathway in the macrocyclization of 9 was a ring closure
resulting from intramolecular coupling of the two terminal
DTF groups rather than intermolecular expansion. Never-
theless, the relatively wide polydispersity (PDI = 2.33)
measured for 10 suggests that larger macrocycles were also
formed via intermolecular cycloaddition pathways to a certain
extent. The molecular structure of the macrocycle resulting
from the intramolecular cyclization of 9 was simulated by the
molecular mechanics (MM) approach using the MMFF force
field implemented in Spartan’10 (Wave function, Inc.). As
shown in Figure 4, the optimized geometry of the macrocycle
shows that the dihedral angle between the two vinyl groups in
each of the TTFV moieties is about 76−80°, which is larger
than those observed for typical phenyl-substituted TTFV
Mechanisms of Polymerization. The various character-
ization data have congruously indicated that the one-pot
oxidative polymerization of bis(DTF)-fluorenes 5a−c led to the
formation of acyclic TTFV−fluorene co-oligomers with
relatively narrow polydispersity. In contrast, treatment of
compound 9, which is the dimer in the series of co-oligomer
1
8
compounds as a result of the macrocyclic strain energy.
The two fluorene units are somehow parallelly oriented, but
they are not close enough to induce significant van der Waals
6b, under the same oxidative conditions yielded only cyclic
products. The different synthetic outcomes suggest that the
DTF oxidative polymerization does not follow a conventional
polymerization mechanism in which the monomers and/or
intermediary oligomers react with each other nonselectively.
The fact that dimer 9 predominantly underwent an intra-
molecular cyclization reaction suggests that the intermolecular
DTF coupling between dimers and/or higher oligomers is a
sluggish and disfavored pathway in the polymerization
mechanism. It is therefore reasonable to propose that the
mechanism for the polymerization of 5a−c predominantly
follows the chain-length growth pathway illustrated in Figure 5,
in which the monomer is added to each of the termini of the
intermediary oligomers in a stepwise fashion. When the
oligomer is grown to a “critical chain length” where the
terminal DTFs become completely inert to the oxidative
dimerization reaction, the polymerization reaction is termi-
nated. As such, the final products of the polymerization should
converge toward a peculiar chain length with much better
monodispersity than the outcome of a conventional polymer-
ization pathway. Experimentally, the narrow polydispersity of
Figure 4. Space-filling model of macrocycle 10 (n = 1) optimized
using the MMFF force field: (A) side view, (B) top view. Long alkyl
chains were replaced by CH to save computational costs.
3
F
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Figure 5. Illustration of different reaction pathways involved in the one-pot oxidative polymerization of bis(DTF)-fluorenes.
co-oligomers 6a−c determined by GPC analysis attests to the
proposed selective chain length growth mechanism. Another
valid argument supporting the proposed mechanism is that in
the oxidative polymerization of 5b the first intermediate formed
was actually dimer 9 in its oxidized state. If the conventional
polymerization mechanism took place in a significant degree,
the polymerization of 5b would also produce macrocyclic
oligomer 10 as one of the major products, but this scenario was
not observed experimentally.
and bis(DTF) end-capped π-oligomers were able to wrap
around or stick to the surface of single-walled carbon nanotubes
(SWNTs), resulting in effective and selective dispersion of
9
SWNTs in various organic solvents. Along this line, we further
envisioned that the unique folding features of the TTFV−
fluorene co-oligomers together with their π-rich conjugated
backbones should engender favorable supramolecular inter-
actions with SWNTs. MM simulations of the interactions
between the model oligomer and a segmental (10,0) SWNT
have revealed a wrapping mode (Figure 6C,D) dictated by
intimate π-stacking between the oligomer π-framework and the
SWNT surface.
Supramolecular Interactions of TTFV−Fluorene Co-
oligomers with Single-Walled Carbon Nanotubes. The
conformational properties of TTFV−fluorene co-oligomers
6
a−c were investigated by molecular mechanics (MM)
To validate the prediction by the molecular modeling studies,
two commercially available SWNT samples (namely, HiPCO
and CoMoCAT) were acquired and subjected to dispersion
experiments in organic solvents using co-oligomers 6a−c as
dispersing agents. In this work, SWNT dispersion was
conducted by the ultrasonication/filtration procedures we
simulations, where a model co-oligomer featuring the same π-
framework as those of 6a−c but without alkyl side chains was
examined. The chain length of the model oligomer was set at
the pentamer stage (n = 5) to be consistent with the average
oligomerization degrees of co-oligomers 6b and 6c. As can be
seen from Figure 6A,B, the optimized geometry of the model
oligomer adopts a “squarelike” folding structure with a central
cavity of ca. 1−2 nm in diameter. Our previous studies have
demonstrated that TTFV-containing π-conjugated polymers
9
reported previously. It was found that all the co-oligomers
could effectively disperse HiPCO nanotubes into two common
organic solvents, CHCl and THF, to form stable suspensions.
3
The effectiveness of dispersion in CHCl appeared to be better
3
than in THF. For the CoMoCAT nanotubes, however, there
was no significant dispersion observed in common organic
solvents.
The HiPCO SWNT suspensions dispersed with co-
oligomers 6a−c in CHCl were characterized by UV−vis−
3
NIR analysis, and the results are shown in Figure 7A. The
variously distinct absorption bands in the vis−NIR region are
characteristic of the interband transitions of debundled SWNTs
24
in the solution. The SWNTs dispersed by the three TTFV−
fluorene co-oligomers give nearly superposable spectral
patterns in Figure 7A, suggesting that the three π-oligomers
have similar selectivity for the types of SWNTs dispersed in
CHCl . In THF, the vis−NIR absorption spectra of the
3
SWNTs dispersed by 6a and 6b (see Figure 7B) bear similar
features to one another as well as to those determined in
CHCl . For the SWNTs dispersed with oligomer 6c in THF,
3
however, the vis−NIR spectrum is notably different in
comparison with the others. The relatively lower solubility of
6c than the other two co-oligomers in THF, due to the short
Figure 6. Optimized geometries of a TTFV−fluorene pentamer (A:
front view; B: side view) and the oligomer wrapping around a (10,0)
nanotube (C: front view; D: side view).
G
DOI: 10.1021/acs.joc.5b00792
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Figure 7. (A) UV−vis−NIR spectra of HiPCO SWNTs dispersed with co-oligomers 6a−c in CHCl . (B) UV−vis−NIR spectra of HiPCO SWNTs
3
dispersed with co-oligomers 6a−c in THF. (C) Raman spectra of SWNTs dispersed with co-oligomers 6a−c. Insets: Expanded spectra showing the
radial breathing mode (RBM) region.
−
alkyl chains attached to the fluorene moieties, could be a reason
for the different spectral features in the vis−NIR region.
To shed more light on the selectivity issue, Raman
spectroscopic analysis was conducted. Figure 7C shows the
Raman spectra of SWNTs dispersed with 6a−c. Overall, the
three Raman spectra bear close resemblance to one another, in
which the dominant features are the tangential G band of
SWNTs at 1590 cm and a sharp band at 239 cm in the
radial breathing mode (RBM) region. The two characteristic
Raman bands testify to the efficient dispersion of SWNTs by
the three co-oligomers.
oligomers do not give any significant G band. Moreover, the
RBM bands of dispersed SWNTs appear to be much narrower
than those of the raw HiPCO SWNTs. The Raman data
corroborate that the dispersed SWNTs possess a better quality
than raw SWNTs in terms of structural homogeneity; in
particular, the diameters of the dispersed SWNTs are found to
be narrowly distributed, given that RBM frequency (ω) is
25
−1
−1
inversely proportional to the diameter of SWNT (d). Using
26
the equation ωRBM = 248/d, developed by Dresselhaus et al.,
the average diameter (d) of the SWNTs selectively dispersed by
a−c in CHCl is estimated to be ca. 1.04 nm. Such a good
6
3
diameter selectivity is believed to arise from the unique
wrapping mode of the oligomers with SWNTs as disclosed by
the molecular modeling studies. The development of stimuli-
responsive oligomers and polymers as SWNT dispersants has
become a topic of research recently, and one advantage of this
approach that particularly appeals to the application in SWNT-
based devices is the ease and effectiveness in regenerating
Figure 8 compares the spectra of oligomer 6b, raw HiPCO
SWNTs, and SWNTs dispersed with 6b. The Raman spectrum
−
of raw HiPCO SWNTs clearly shows a significant G band
+
together with the G band in the tangential mode region. In
−1
addition, the D band is discernible at 1329 cm . In sharp
contrast, the SWNTs dispersed with TTFV−fluorene co-
9,27
“
additive-free” SWNTs after solution-phase processing.
Along this vein, we expect that the redox-active TTFV−
fluorene co-oligomers 6a−c will find further application in
SWNT-based nanodevices and materials.
Conclusions. Oxidative dimerization of aryl-substituted
DTFs offers a direct C−C bond-forming approach through
which various extended π-conjugated systems can be generated.
In this work, bis(DTF)-end-capped fluorenes 5a−c were used
as monomers for the iodine-induced oxidative DTF polymer-
ization, yielding acyclic TTFV−fluorene co-oligomers with
narrow polydispersity. The same oxidative reaction conditions
applied to the bis(DTF) dimer 9, however, led to a completely
different synthetic outcome, wherein only cyclic oligomer
products were formed as a result of the favored intramolecular
DTF coupling. Our synthetic work has confirmed that the
reactivity of a DTF group toward the oxidative dimerization is
highly dependent on the degree of π-conjugation of the aryl
group attached to it. Another intriguing discovery is that the
mechanism for the oxidative polymerization of bis(DTF)-
Figure 8. Comparison of the Raman spectra of co-oligomer 6, raw
HiPCO SWNTs, SWNTs dispersed with 6. Insets: Expanded spectra
showing the radial breathing mode (RBM) region.
H
DOI: 10.1021/acs.joc.5b00792
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
fluorenes 6a−c follows a selective chain length growth pathway,
in which the oligomer intermediates favor to react with the
bis(DTF)-fluorene mononers. This unique reactivity has
enabled relatively monodisperse π-oligomers to be generated
as the major products through the one-pot polymerization
approach. Finally, the TTFV−fluorene co-oligomers were
demonstrated to give rise to strong supramolecular interactions
with SWNTs, which in turn allowed for effective and selective
dispersion of SWNTs in the organic solutions of TTFV−
fluorene co-oligomers. In summary, the findings disclosed in
this work have contributed useful knowledge to the develop-
ment of new redox-active functional materials based on π-
conjugated oligomers and macrocycles.
CDCl
3
) δ 10.08 (s, 2H), 7.99 (d, J = 8.4 Hz, 4H), 7.85−7.82 (m, 6H),
7
.67−7.64 (m, 4H), 2.11−2.06 (m, 4H), 1.19−0.98 (m, 16H), 0.75 (t,
1
J = 6.8 Hz, 6H). The H NMR data is consistent with the literature
2
8
reported values.
Bis(DTF)-fluorene 5a. Dibenzaldehyde 3a (1.00 g, 1.52 mmol),
thione 4 (1.75 g, 3.66 mmol), and P(OMe) (30 mL) were added to a
3
1
00 mL round-bottom flask. The mixture was heated to 145 °C and
kept at this temperature for 5 h. Then P(OMe) was removed by
3
vacuum distillation, and the crude product was purified through silica
column chromatography (hexanes) to give 5a (1.27 g, 0.83 mmol,
55%) as a yellow oil: IR (neat) 2952, 2919, 2849, 1569, 1544, 1463,
−1 1
8
7
6
9
1
1
3
2
18 cm ; H NMR (300 MHz, CDCl ) δ 7.75 (d, J = 7.9 Hz, 2H),
3
.68 (d, J = 8.4 Hz, 4H), 7.61−7.57 (m, 4H), 7.32 (d, J = 8.4 Hz, 4H),
.52 (s, 2H), 2.86−2.81 (m, 8H), 1.73−1.59 (m, 8H), 1.48−1.00 (m,
13
6H), 0.90−0.78 (m, 18H); C NMR (75 MHz, CD Cl ) δ 151.9,
2
2
40.2, 139.5, 138.9, 135.4, 132.5, 127.7, 127.33, 127,27, 125.9, 125.0,
21.3, 120.2, 114.1, 50.4, 40.6, 36.3, 36.2, 32.05, 32.04, 32.00, 31.7,
1.1, 30.2, 30.0, 29.9, 29.71, 29.68, 29.65, 29.47, 29.46, 29.40, 29.37,
EXPERIMENTAL SECTION
■
General Information. Commercially available chemicals were
used directly without purification. All reactions were conducted in
standard, dry glassware and under an inert atmosphere of nitrogen or
9.3, 29.2, 28.73, 28.71, 22.82, 22.80, 22.78, 14.3, 14.2; HRMS [M +
+
H] calcd for C H S8 1515.8955, found 1515.8929.
93 143
1
13
Bis(DTF)-fluorene 5b. Dibenzaldehyde 3b (0.40 g, 0.66 mmol),
thione 4 (0.76 g, 1.60 mmol), and P(OMe) (20 mL) were reacted
under the same conditions as described in the synthesis of 5a to give
compound 5b (0.70 g, 0.48 mmol, 72%) as a yellow oil: IR (neat)
argon unless otherwise noted. H and C NMR spectra were recorded
on a 500 MHz or a 300 MHz multinuclear spectrometer. Chemical
shifts (δ) are reported in ppm downfield relative to the signals of the
internal reference SiMe or residual solvent signals from CHCl δ =
3
4
3
−1 1
2
952, 2920, 2850, 1681, 1569, 1463, 1087, 819 cm ; H NMR (300
7
.24 ppm and δ = 77.2 ppm, CH Cl δ = 5.32 ppm and δ = 54.0 ppm,
2 2
MHz, CDCl ) δ 7.76 (d, J = 7.9 Hz, 2H), 7.68 (d, J = 8.4 Hz, 4H),
respectively. Coupling constants (J) are reported in hertz. MALDI-
TOF MS analysis was performed in the positive mode using dithranol
as the matrix. High-resolution EI-TOF MS analysis was performed in
the positive mode. Raman spectroscopic analysis was done on a
Raman microscope equipped with a laser source at the wavelength of
3
7
.61−7.57 (m, 4H), 7.32 (d, J = 8.4 Hz, 4H), 6.52 (s, 2H), 2.86−2.81
(
m, 8H), 2.06−2.97 (m, 4H) 1.73−1.56 (m, 8H), 1.49−0.97 (m,
13
8
1
1
3
1
0H), 0.92−0.75 (m, 18H); C NMR (75 MHz, CDCl ) δ 151.9,
3
40.2, 139.6, 138.9, 135.4, 132.56, 127.65, 127.33, 127.29, 125.90,
25.00, 121.31, 120.18, 114.11, 55.4, 40.6, 36.3, 36.2, 32.0, 31.9, 30.2,
0.0, 29.9, 29.71, 29.69, 29.48, 29.47, 29.4, 29.3, 28.7, 24.0, 22.8, 22.7,
8
30 nm. Gel permeation chromatographic (GPC) analysis was
performed using THF as the eluent at a flow rate of 1.0 mL/min
and monitored by a photodiode array detector and a refractive-index
detector. Polystyrene standards were used for calibration.
+
4.3, 14.2; HRMS [M + H] calcd for C H S8 1459.8329, found
89 135
1459.8292.
4
,4′-(9,9-Didecyl-9H-fluorene-2,7-diyl)dibenzaldehyde (3a).
,7-Dibromo-9,9-didecyl-9H-fluorene (1a) (1.70 g, 2.81 mmol),
benzaldehyde 2 (1.60 g, 6.89 mmol), Cs CO (14.6 g, 44.8 mmol),
Bis(DTF)-fluorene 5c. Dibenzaldehyde 3c (0.57 g, 0.99 mmol),
thione 4 (1.30 g, 2.25 mmol), and P(OMe) (20 mL) were reacted
under the same conditions as described in the synthesis of 5a to give
compound 5c (0.95 g, 0.62 mmol, 62%) as a yellow oil: IR (neat)
3023, 2952, 2920, 2850, 1569, 1544, 1463, 818 cm ; H NMR (300
MHz, CDCl ) δ 7.75 (d, J = 8.0 Hz, 2H), 7.68 (d, J = 8.4 Hz, 4H),
2
3
2
3
and Pd(PPh ) (0.33 g, 0.29 mmol) were added to a 100 mL round-
3
4
−1 1
bottom flask. THF (35 mL) and deionized water (15 mL) were added
to the flask under an atmosphere of argon. The mixture was refluxed
for 2 h under argon. After that, the mixture was cooled to room
temperature and then poured into brine. The resulting mixture was
extracted twice with CH Cl . The combined organic layers were dried
3
7.63−7.54 (m, 4H), 7.32 (d, J = 8.4 Hz, 4H), 6.52 (s, 2H), 2.86−2.81
(m, 8H), 2.09−1.96 (m, 4H), 1.72−1.59 (m, 8H), 1.50−0.99 (m,
13
72H), 0.92−0.70 (m, 18H); C NMR (75 MHz, CDCl ) δ 151.9,
3
2
2
over MgSO , and the solvent was evaporated off under vacuum. The
140.2, 139.5, 138.9, 135.4, 132.6, 127.7, 127.33, 127.27, 125.5, 125.0,
121.3, 120.2, 114.1, 55.4, 40.6, 36.3, 36.2, 32.0, 31.6, 30.0, 29.9, 29.71,
4
residue was crude product 3a, which was further purified through silica
column chromatography (Et O/EtOAc 1:4) to give pure 3a (1.50 g,
29.68, 29.47, 29.46, 29.3, 28.73, 28.70, 23.9, 22.8, 22.7, 14.3, 14.1;
HRMS [M + H] calcd for C85
TTFV−Fluorene Co-oligomer 6a. To a solution of compound 5a
(0.11 g, 0.072 mmol) in CH Cl (10 mL) were added iodine chips
(0.050 g, 0.20 mmol). The resulting dark solution was stirred at room
temperature for 5 h. After that, a saturated aqueous solution of
2
+
2
1
1
7
.30 mmol, 80%) as a pale yellow oil: IR (neat) 2921, 2850, 2728,
H
127
S
8
1403.7703, found 1403.7718.
−1 1
697, 1600, 1249, 1210, 812 cm ; H NMR (300 MHz, CDCl ) δ
3
0.09 (s, 2H), 8.00 (d, J = 8.4 Hz, 4H), 7.86−7.83 (m, 6H), 7.69−
2
2
.61(m, 4H), 2.10−2.04 (m, 4H), 1.31−1.11 (m, 32H), 0.82 (t, J = 6.9
13
Hz, 6H); C NMR (75 MHz, CDCl ) δ 191.9, 152.0, 147.5, 140.9,
3
1
2
6
38.8, 135.1, 130.3, 127.7, 126.5, 121.7, 120.54, 55.5, 40.3, 31.8, 29.9,
Na
stirred for another 3 h at room temperature. The resulting yellow
organic layer was separated, washed with water, dried over MgSO
and concentrated under reduced pressure. The resulting crude product
was subjected to silica gel column chromatography (hexanes/CH Cl
4:1), giving co-oligomer 6a (0.066 g, 59%) as a yellow oil: IR (neat)
2 2 3
S O (10 mL) was added to the dark solution, and the mixture was
+
9.6, 29.5, 29.3, 29.2, 22.6, 14.1; HRMS [M] calcd for C H O
47
58
2
54.4437, found 654.4418.
,4′-(9,9-Dioctyl-9H-fluorene-2,7-diyl)dibenzaldehyde (3b).
,7-Dibromo-9,9-dioctyl-9H-fluorene (1b) (1.15 g, 2.09 mmol),
,
4
4
2
2
,
2
benzaldehyde 2 (1.13 g, 4.87 mmol), Cs CO (9.70 g, 30.0 mmol),
2
3
−1
1
and Pd(PPh ) (0.28 g, 0.24 mmol) were reacted under the same
2953, 2920, 2850, 1463, 1054, 816 cm ; H NMR (300 MHz,
3
4
conditions as described in the synthesis of 3a to yield compound 3b
CDCl
3
) δ 7.77−7.47 (m, 36H), 7.34−7.26 (m, 4H), 6.50 (s, 2H),
1
(
1.10 g, 1.83 mmol, 87%) as a pale yellow solid: H NMR (300 MHz,
2.89−2.70 (m, 26H), 2.08−1.87 (m, 10H), 1.74−1.55 (m, 26H),
3
13
CDCl ) δ 10.09 (s, 2H), 7.99 (d, J = 8.1 Hz, 4H), 7.86−7.83 (m, 6H),
7
J = 6.8 Hz, 6H). The H NMR data is consistent with the literature
reported values.
,4′-(9,9-Dihexyl-9H-fluorene-2,7-diyl)dibenzaldehyde (3c).
,7-Dibromo-9,9-dihexyl-9H-fluorene (1c) (1.00 g, 2.03 mmol),
benzaldehyde 2 (1.07 g, 4.60 mmol), Cs CO (4.40 g, 13.5 mmol),
1.49−0.95 (m, 272H), 0.92−0.75 (m, 64H); C NMR (75 MHz,
.68−7.61 (m, 4H), 2.10−2.04 (m, 4H), 1.19−1.03 (m, 24H), 0.78 (t,
CDCl ) δ 151.9, 151.8, 140.2, 139.8, 139.5, 138.9, 136.8, 136.0, 135.5,
3
1
135.4, 132.5, 129.0, 127.7, 127.32, 127.27, 127.1, 126.9, 125.9, 125.3,
125.0, 124.3, 121.3, 120.1, 114.1, 55.4, 40.7, 36.3, 36.2, 36.1, 32.08,
32.06, 32.0, 30.2, 30.0, 29.87, 29.85, 29.74, 29.72, 29.69, 29.64, 29.53,
29.48, 29.39, 29.35, 29.31, 28.75, 28.71, 24.0, 22.84, 22.79, 14.28,
14.26; GPC M = 8200, M = 11119, PDI = 1.35.
28
4
2
2
3
n
w
and Pd(PPh ) (0.22 g, 0.19 mmol) were reacted under the same
TTFV−Fluorene Co-oligomer 6b. Compound 5b (0.10 g, 0.068
3
4
conditions as described in the synthesis of 3a to yield compound 3c
mmol) and iodine (0.050 g, 0.20 mmol) were reacted in CH Cl (10
2
2
1
(
0.90 g, 1.66 mmol, 86%) a pale yellow solid: H NMR (300 MHz,
mL) under the same conditions as described in the synthesis of 6a to
I
DOI: 10.1021/acs.joc.5b00792
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
give co-oligomer 6b (0.067 g, 67%) as a yellow oil: IR (neat) 2952,
129.0, 127.6, 127.32, 127.28, 127.1, 125.9, 125.3, 125.0, 124.3, 121.31,
121.28, 120.2, 114.1, 55.4, 40.7, 36.3, 36.2, 36.1, 34.8, 34.7, 32.1, 31.9,
31.7, 30.2, 30.0, 29.8, 29.74, 29.71, 29.68, 29.52, 29.48, 29.46, 29.36,
29.34, 29.30, 29.2, 28.8, 28.73, 28.70, 27.1, 25.4, 23.9, 22.84, 22.81,
22.7, 14.3, 14.2; HRMS [M + H] calcd for C178H267S16 2916.6424,
found 2916.6499.
−1 1
2
7
4
4
1
1
1
3
2
1
920, 2850, 1463, 1434, 815 cm ; H NMR (300 MHz, CDCl ) δ
3
.74−7.45 (m, 70H), 7.32−7.28 (m, 4H), 6.50 (s, 2H), 2.88−2.73 (m,
2H), 2.06−1.92 (m, 20H), 1.70−1.54 (m, 48H), 1.44−0.96 (m,
13
+
60H), 0.89−0.72 (m, 120H); C NMR (75 MHz, CDCl ) δ 151.84,
3
51.80, 140.2, 139.8, 139.5, 138.9, 136.8, 136.1, 136.0, 135.4, 132.6,
29.0, 127.33, 127.28, 127.1, 125.9, 125.3, 125.0, 124.3, 121.3, 120.2,
14.1, 55.4, 40.7, 36.3, 36.2, 36.1, 34.8, 32.1, 31.9, 31.8, 31.1, 30.2,
0.0, 29.9, 29.8, 29.72, 29.69, 29.53, 29.49, 29.4, 29.3, 29.2, 28.8, 28.7,
5.4, 24.0, 22.85, 22.82, 22.7, 20.9, 14.3, 14.2; GPC M = 7961, M =
TTFV−Fluorene Macrocycle 10. Compound 9 (0.080 g, 0.027
mmol) and iodine (0.020 g, 0.081 mmol) were reacted in CH Cl (5
2
2
mL) under the same conditions as described in the synthesis of 6a to
yield compound 10 (0.030 g, 37%) as a yellow oil: FTIR (neat) 2953,
n
w
−1 1
2303, PDI = 1.54.
TTFV−Fluorene Co-oligomer 6c. Compound 5c (0.060 g, 0.043
mmol) and iodine (0.030 g, 0.12 mmol) were reacted in CH Cl (10
2923, 2852, 1464, 1260, 1092, 1017, 814, 803 cm ; H NMR (300
MHz, CDCl
) δ 7.71−7.46 (m, 7H), 2.96−2.64 (m, 8H), 1.92−0.92
3
(m, 40H), 0.86−0.74 (m, 9H); GPC M = 3126, M = 7297, PDI =
n w
2.33.
2
2
mL) under the same conditions as described in the synthesis of 6a to
give co-oligomer 6c (0.040 g, 66%) as a yellow oil: IR (neat) 2952,
−
1 1
2
7
4
4
1
1
1
2
2
6
920, 2850, 1463, 1433, 815 cm ; H NMR (300 MHz, CDCl ) δ
3
ASSOCIATED CONTENT
■
.76−7.48 (m, 74H), 7.34−7.27 (m, 4H), 6.51 (s, 2H), 2.91−2.73 (m,
*
S
Supporting Information
4H), 2.07−1.90 (m, 20H), 1.73−1.54 (m, 50H), 1.49−0.95 (m,
13
20H), 0.93−0.67 (m, 126H); C NMR (75 MHz, CDCl ) δ 151.9,
NMR spectra of all new compounds. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.joc.5b00792.
3
51.8, 140.2, 139.8, 139.5, 138.9, 136.8, 136.0, 135.4, 132.6, 128.9,
27.6, 127.33, 127.27, 127.1, 125.9, 125.3, 125.0, 124.33, 121.27,
20.1, 114.1, 55.37, 55.35, 53.6, 40.7, 36.3, 36.2, 36.1, 32.1, 31.6, 30.0,
9.9, 29.8, 29.74, 29.71, 29.68, 29.52, 29.48, 29.46, 29.37, 29.35, 29.30,
8.8, 28.74, 28.70, 24.0, 22.8, 22.7, 14.3, 14.1; GPC: M = 4932, M =
AUTHOR INFORMATION
■
n
w
865, PDI = 1.39.
DTF−Fluorene 7. Compound 3b (0.32 g, 0.53 mmol), thione 4
0.23 g, 0.48 mmol), and P(OMe) (15 mL) were reacted at 125 °C
Corresponding Author
*Tel: +1 709 864 8747. Fax:+1 709 864 3702. E-mail:
yuming@mun.ca.
(
3
for 3 h under the same conditions as described in the synthesis of 5a.
The obtained crude product was purified by silica column
chromatography (hexanes/CH Cl , 4:1) to afford compound 7 (0.27
Notes
The authors declare no competing financial interest.
2
2
g, 0.26 mmol, 50%) as a yellow oil: FTIR (neat) 2952, 2921, 2851,
−
1 1
1
(
(
2
1
701, 1601, 1568, 1545, 1464, 1254, 1210, 844, 815 cm ; H NMR
ACKNOWLEDGMENTS
■
300 MHz, CDCl ) δ 10.0(s, 1H), 7.98 (d, J = 8.3 Hz, 2H), 7.89−7.75
3
We acknowledge the Natural Sciences and Engineering
Research Council of Canada (NSERC), Canada Foundation
for Innovation (CFI), and Memorial University for financial
support. Prof. A. Adronov and Mr. S. Liang of McMaster
University are acknowledged for their assistance in GPC
analysis.
m, 4H), 7.73−7.54 (m, 6H), 7.33 (d, J = 8.4 Hz, 2H), 6.53 (s, 1H),
.84 (t, J = 7.3 Hz, 4H), 2.10−1.98 (m, 4H), 1.74−1.60 (m, 4H),
13
.48−0.99 (m, 52H), 0.94−0.73 (m, 12H); C NMR (75 MHz,
CDCl ) δ 192.1, 152.1, 152.0, 147.8, 141.5, 140.05, 139.77, 138.76,
3
1
1
3
2
38.52, 135.54, 135.17, 132.7, 130.4, 127.8, 127.7, 127.34, 127.32,
26.6, 126.0, 125.0, 121.8, 121.4, 120.5, 120.4, 114.0, 55.5, 40.5, 36.3,
6.2, 32.1, 31.9, 30.1, 30.0, 29.9, 29.72, 29.69, 29.5, 29.33, 29.31, 28.74,
+
8.72, 23.9, 22.8, 22.7, 14.3, 14.2; HRMS [M + H] calcd for
REFERENCES
C H OS 1029.6109, found 1029.6112.
■
66
93
4
(
1) (a) Skotheim, T. A., Elsenbaumer, R. L., Reynolds, J. R., Eds.
TTFV−Fluorene 8. Compound 7 (0.90 g, 0.87 mmol) and iodine
0.66 g, 2.6 mmol) were added in CH Cl (15 mL), and the mixture
was stirred at room temperature for 5 h. A saturated aqueous solution
of Na S O was added, and the resulting mixture was stirred at room
temperature for another 1 h. The organic layer was separated, washed
with H O, dried over MgSO , and concentrated under vacuum. The
crude product obtained was purified through silica column
chromatography (hexanes/CH Cl , 2:3) to yield compound 8 (0.58
g, 0.28 mmol, 65%) as a yellow oil: FTIR (neat) 2953, 2924, 2853,
702, 1602, 1465, 1210, 1168, 815 cm ; H NMR (300 MHz,
(
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2
4
2
2
−1
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CDCl ) δ 10.0 (s, 2H), 7.98 (d, J = 8.4 Hz, 4H), 7.88−7.74 (m, 8H),
3
7
1
(
1
1
1
2
.68−7.65 (m, 6H), 7.60−7.56 (m, 10H), 2.90−2.76 (m, 8H), 2.09−
.97 (m, 8H), 9.83−1.58 (m, 8H), 1.49−0.98 (m, 104H), 0.92−0.72
m, 24H); 13C NMR (75 MHz, CDCl ) δ 192.1, 152.1, 151.9, 147.8,
3
41.5, 140.0, 139.8, 139.6, 138.5, 137.0, 136.2, 135.2, 130.4, 129.0,
28.9, 127.8, 127.4, 127.1, 126.6, 126.0, 125.3, 124.2, 121.8, 121.4,
20.45, 120.36, 55.5, 40.6, 36.3, 36.2, 32.1, 31.9, 30.1, 29.9, 29.8, 29.53+,
9.49, 29.3, 28.8, 28.7, 24.0, 22.8, 22.7, 14.3, 14.2.; HRMS [M + H]
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D. M. Chem. Soc. Rev. 2005, 34, 31−47;(c) Aleveque, O.; Leriche, P.;
32
183
2 8
TTFV−Fluorene 9. Compound 8 (0.35 g, 0.17 mmol), thione 4
0.24 g, 0.51 mmol), and P(OMe) (15 mL) were reacted under the
same conditions as described in the synthesis of 7 to afford compound
(0.28 g, 0.096 mmol, 56%) as a yellow oil: FTIR (neat) 2953, 2923,
̀
Cocherel, N.; Frere, P.; Cravino, A.; Roncali, J. Sol. Energy Mater. Sol.
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3
9
1
4
2
0
1
−1 1
464, 817 cm ; H NMR (300 MHz, CDCl ) δ 7.74 (d, J = 7.8 Hz,
3
H), 7.69−7.56 (m, 20H), 7.32 (d, J = 8.5 Hz, 4H), 6.52 (s, 2H),
̈
(4) (a) Sonmez, G.; Schwendeman, I.; Schottland, P.; Zong, K.;
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13
.99 (m, 160H), 0.94−0.76 (m, 36H); C NMR (75 MHz, CDCl ) δ
3
51.9, 151.8, 140.2, 139.8, 139.5, 138.9, 136.8, 136.0, 135.4, 132.5,
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