Synthesis and optoelectronic properties of janus -dendrimer-type multivalent donor-acceptor systems

Article abstract of DOI:10.1021/jo502367h

A convergent, multistep protocol was employed for the synthesis of a Janus-type multivalent donor-acceptor system. The synthetic approach is based on a Sonogashira cross-coupling of two differently ferrocene-(Fc) substituted dendrons and a final sixfold [

Full text of DOI:10.1021/jo502367h

Article
pubs.acs.org/joc
Synthesis and Optoelectronic Properties of Janus-Dendrimer-Type
Multivalent Donor−Acceptor Systems
Cagatay Dengiz,† Benjamin Breiten,† Jean-Paul Gisselbrecht,‡ Corinne Boudon,‡ Nils Trapp,†
W. Bernd Schweizer,† and Francois Diederich*,†
̧
†Laboratorium fur Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, CH-8093 Zurich, Switzerland
̈
̈
̈
‡Laboratoire d’Electrochimie et de Chimie Physique du Corps Solide, Institut de Chimie-UMR 7177, C.N.R.S., Universite
́
de
Strasbourg, 4, rue Blaise Pascal, 67000 Strasbourg, France
S
* Supporting Information
ABSTRACT: A convergent, multistep protocol was employed
for the synthesis of a Janus-type multivalent donor−acceptor
system. The synthetic approach is based on a Sonogashira
cross-coupling of two differently ferrocene-(Fc) substituted
dendrons and a final sixfold [2 + 2] cycloaddition−retroelec-
trocyclization (CA−RE) reaction with tetracyanoethene, which
occurs regioselectively at only one of the rigidly linked
dendrons. The structural and optoelectronic properties of the
compounds were investigated by X-ray analysis, UV/vis
spectroscopy, and electrochemistry. The target Janus-system
displays redox-amphoteric behavior. The nonalkynylated Fc
end groups in one dendron are readily and reversibly oxidized.
The second dendron, in which the terminal Fc-activated
alkynes underwent the CA−RE reaction to give tetracyano-
buta-1,3-dienes in the final step of the synthesis, undergoes four reversible 3-e− reductions in the very narrow potential range of 1
V. A spontaneous intramolecular charge transfer from the donor into the acceptor hemisphere was not observed. Furthermore,
the oxidation potential of the Fc donors in one hemisphere is hardly perturbed by the push−pull acceptors in the other, which
suggests that electronic communication along the π-system, with several meta-connectivities, is not efficient. Therefore, the
charge-transfer bands seen in the Janus-type system originate from the interaction of the Fc donors with the directly connected
tetracyanobuta-1,3-diene acceptors in the same hemisphere.
oxidation steps in cyclic voltammetry (CV), as reported in
particular for ferrocene (Fc) end groups by Astruc and co-
workers.5 The group of Nierengarten described the synthesis
of dendrimers with multiple electron-accepting groups, in
particular fullerenes, lining the pheriphery, which feature
multiple reversible reduction steps in their CV traces.6 Our
group prepared multivalent dendrimer-type systems with up
to 12 terminal N,N-dialkylanilino-activated buta-1,3-diynes
that underwent a [2 + 2] cycloaddition−retroelectrocycliza-
tion (CA−RE) reaction with tetracyanoethene (TCNE)7 to
give donor-substituted tetracyanobuta-1,3-diene (TCBD) end
groups undergoing both reversible electron oxidation and
reduction steps in CV.8
While dendritic systems with either multiple donor,
multiple acceptor, or push−pull donor−acceptor end groups
are well studied, Janus-dendrimer-type multivalency systems
with strong electron-donor and strong electron-acceptor
hemispheres have not been reported. Our goal in this project
was to develop an efficient synthesis for such systems. Both
INTRODUCTION
■
Dendrons and dendrimers are among the most popular
multivalent systems.1 Most known dendrimers feature a single
type of end group to ensure synthetic feasibility. Those built
from dendrons with different, orthogonal functional end
groups, however, are desirable. They allow the formation of
polar systems, which have been coined Janus-dendrimers,
bearing the name of the mythological two-faced god of
beginnings and transitions in ancient Roman religion who
looks to the future and past.2 The first Janus-dendrimer was
́
reported by Frechet and co-workers and was obtained by a
convergent synthetic strategy using dendrons of different
polarities.2a The resulting spherical dendrimer was amphi-
philic, featuring one side with lipophilic benzyl end groups
and the other with polar terminal carboxylates. Janus-
dendrimers have been investigated for various molecular
functions, such as drug delivery, catalysis, and liquid crystalline
organization.2h,k,3 They also enabled self-assembly to a variety
of supramolecular systems and shapes.4
Dendrimers with redox-active end groups have attracted
much attention. Peripheral decoration with electron donor
termini yielded systems that underwent multiple reversible
Received: October 15, 2014
© XXXX American Chemical Society
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Figure 1. Targeted Janus-dendrimer-type multivalency systems 1 and 2 featuring an electron-donor hemisphere and an electron-acceptor
hemisphere.
Scheme 1. Synthesis of Precursor 10 to Dendron 3
target compounds 1 and 2 possess one hemisphere
comprising Fc donor termini, whereas the second hemisphere
features different donor-substituted TCBDs, originating from
the CA−RE reaction, as strong electron acceptors (Figure 1).
We were interested in exploring whether spontaneous
intramolecular charge transfer from the donor into the
acceptor hemisphere under formation of zwitterionic Janus-
dendrimer-type system would occur, as had previously been
observed in case of a simpler push−pull chromophore.9 Here,
we report the synthesis and optoelectronic properties of 2 and
the difficulties that ultimately prevented the preparation of 1.
RESULTS AND DISCUSSION
■
Synthesis of Dendrons 3 and 4. The core of the target
structures is reminiscent of dendrimer cores first introduced
by Moore and co-workers.10 The reaction sequence to access
dendron 3, needed for the construction of both 1 and 2, starts
with the conversion of 2,6-diiodo-4-nitroaniline (5)11 to 1,2,3-
triiodo-5-nitrobenzene (6)12 via a Sandmeyer reaction
(Scheme 1). Following SnCl2-mediated reduction, 3,4,5-
triiodoaniline 7 was obtained in 75% yield.12 Diethyltriazene
8 was prepared by trapping the diazonium salt from 7 with
diethylamine.13 The NMR spectral data at 298 K showed two
different sets of ethyl resonances due to the restricted rotation
around the N−N bond.14 The next step was the threefold
Suzuki coupling15 with 4-bromophenylboronic acid to afford
B
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Scheme 2. Synthesis of Precursor 16 to Dendron 3
compound 9,16 which was then converted into the more
reactive iodo compound 10 by halogen-metal exchange and
subsequent quenching of the lithiated intermediate with
iodine (Scheme 1). The structures of compounds 9 and 10
were confirmed by X-ray analysis (Scheme 1). Similarly, the
synthesis of precursor 16 to dendron 3 started from 4-
iodoaniline (11), from which compound 14 was prepared via
12 and 13, according to literature procedures.17 Suzuki
coupling of compound 14 with ferroceneboronic acid afforded
compound 15,18 and removal of the TIPS group with nBu4NF
in wet THF gave dendron precursor 16 (Scheme 2).
Synthesis of Dendron 29. For the preparation of Janus-
dendrimer-type system 2, two dendrons were required for
Sonogashira coupling: dendron 3 and the new dendron 29.
The synthesis of 29 started from commercially available 1,3,5-
tribromobenzene (30), which was subjected to a single
Sonogashira coupling with TMS-acetylene to give alkyne 31.
Halogen-metal exchange and subsequent treatment with
iodine afforded 32, which was doubly cross-coupled with
ethynylferrocene to yield compound 33, and by deprotection
terminal alkyne 34. The structure of 33 was confirmed by X-
ray analysis (Scheme 6). Sonogashira coupling of alkyne 34
with iodo derivative 10 provided triazene 35, which was
converted to dendron 29 upon treatment with MeI (Scheme
Sonogashira coupling19 of alkyne 16 with triiodide 10
provided triazene 17, which was converted into aryl iodide 18
upon treatment with MeI (Scheme 3). Sonogashira coupling
of 18 with TMS-acetylene afforded 19, and alkyne-
1
6). The H and 13C NMR spectra of 29 confirmed its C2v-
symmetric structure (Figures S54 and S55, Supporting
Information).
1
deprotection yielded target dendron 3 (Scheme 3). The H
Synthesis of Janus-Dendrimer-Type Donor−Acceptor
System 2. Sonogashira coupling between dendrons 3 and 29
delivered the multivalent precursor 36 to target 2 in 57%
yield (Scheme 7). Its formation, however, was accompanied
by homocoupling of terminal alkyne 3 to afford 37 as a
byproduct in 20% yield. Compounds 36 and 37 were purified
by recycling gel permeation chromatography (R-GPC,
column: JAI-gel 2H with CHCl3 as eluent). In order to
avoid the unwanted dimerization, a copper-free Sonogashira
reaction between dendrons 3 and 29 was also attempted, but
no reaction was observed.24
The precursor 36 features 12 terminal Fc groups. In one
hemisphere, they are attached directly to a phenyl ring,
whereas, in the other, they are coupled to acetylenes, which
become activated by the electron-donating metallocenes25 to
undergo the CA−RE reaction with TCNE. With compound
36 in hand, we performed the key CA−RE step with TCNE,
which gratifyingly afforded the charge-transfer Janus-system 2
as a dark green solid (Scheme 7). The structure of 2 was
confirmed by HR-MALDI-MS (m/z = 4354.5059, calc. for
C266H154Fe12N24+: 4354.5090) (Figure 2). Additionally, we
subjected the mixture of the dendritic systems 36 and 37 to
the CA−RE reaction with TCNE. When the mixture 36/37
was reacted with an excess (12 equiv) of TCNE in (CH2Cl)2,
a crude product mixture was isolated that, in the mass
spectrum (HR-MALDI-MS), showed two major ions corre-
and 13C NMR spectra of 3 reflected its C2v symmetry (Figures
S36 and S37 in the Supporting Information).
The synthesis of the second dendron 4 for the preparation
of target Janus-system 1 also started from 2,6-diiodo-4-
nitroaniline (5) and proceeded via a 9-step protocol (Schemes
4 and 5). Diazonium chemistry was used to transform 5 into
1,3-diiodo-5-nitrobenzene (20).20 SnCl2-mediated reduction
gave 21,21 which was transformed via the diazonium ion into
diethyltriazene 22 (Scheme 4).13 Sonogashira coupling of 22
with an excess of 4-ethynyl-N,N-dihexylaniline (23)22
provided 24. To avoid any quaternization of aniline moieties,
Me3SiCl/NaI under relatively mild conditions (CCl4/MeCN,
60 °C, 20 min.) was used instead of MeI to afford iodo
compound 25.23 Sonogashira coupling of 25 with TMS-
acetylene gave 26, which was deprotected to terminal alkyne
27 (Scheme 4).
Triazene 28 was obtained by Sonogashira coupling of 27
with 10 (Scheme 5). Unfortunately, multiple attemps
(treatment with Me3SiCl/NaI or MeI) to prepare target
dendron 4 failed due to problems with the quaternization of
the aniline moieties, which could not be avoided. We
abandoned the synthesis of 1 due to this roadblock in the
final step and turned to the multivalent Janus-dendrimer-type
system 2 featuring all-Fc donors in both dendrons, thereby
eliminating the aforementioned synthetic limitations.
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Scheme 3. Synthesis of Dendron 3
1
sponding to target compound 2 originating from the addition
of 6 TCNE moieties (m/z = 4354.4866, calc. for
C
observed the complication of the interpretation of the H and
13C NMR spectra of both dendrimer-type and acyclic
oligomeric push−pull chromophores resulting from the
CA−RE reaction, reflecting complex conformational equilibria
and the existence of rotamers in solution.8,26 We decided to
run a series of control experiments to confirm this hypothesis.
Investigation of Rotamer Equilibria on Model
Systems. We used compounds 38 and 39 (Figure 3) as
model systems for the multivalent system 2. They were
prepared by the CA−RE reaction of the acetylenic substrates
27 and 34 with TCNE. Two products were formed according
to the 1H NMR spectrum in the reaction of ferrocene-
substituted 34. In contrast, only one product was obtained in
the transformation of the anilino derivative 27. We
subsequently monitored the progress of the reaction of 34
266H154Fe12N24+: 4354.5090) and unreacted 37 (m/z =
3466.4399, calc. for C220H154Fe12+: 3466.4350) (Figure S17 in
the Supporting Information). This approach allowed for the
easy separation of 2 from byproduct 37 left from the previous
step by R-GPC (column: JAI-gel 2H with CHCl3 as eluent)
(Figure S15 in the Supporting Information). Compound 36
was fully converted to 2, whereas 37 stayed unreacted during
the reaction, confirming our hypothesis that only alkynes,
which are directly activated by an adjacent donor, will react.
1
The H and 13C NMR spectra (Figures S64 and S65 in the
Supporting Information) measured at room temperature, on
the other hand, showed a complex signal pattern, which did
not seem in agreement with the proposed C2v symmetry of 2.
This is in contrast to the NMR spectra of 36 and 37, which
reflected the symmetry of the molecules, and therefore, the
spectral complexity must be related to the formation of the
Fc-substituted TCBD moieties. We had in previous work
1
by H NMR spectroscopy in CDCl3 at 298 K (Figures S66
and S67, Supporting Information). Initially, CA and CA−RE
reactions take place to form monoadducts. After 4 h, we
observed the compound formed by a single CA−RE reaction
D
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Scheme 4. Synthesis of Precursor 27 to Dendron 4
Scheme 5. Attempted Synthesis of Dendron 4
as the predominant product. After 8 h, a second CA−RE
reaction with TCNE took place under formation of 39. We
propose that the two products seen in the NMR spectra of 39
are rotamers originating from severe steric crowding in the
compound. Calculations at the B3LYP/6-31G** + LANL2DZ
level of theory gave a series of minima structures for model
compound 39 within 3 kcal mol−1 above the global
minimum.27 1H NMR predictions and structure-chemical
shift relations further supported our rotamer proposal (for
further details on the computational investigations and
methods, see the Supporting Information).
Only one spot was detected on the TLC in all tested eluent
mixtures (CH2Cl2/hexane 99:1 to 1:99, EtOAc/hexane 99:1
to 1:99). Additionally, GPC and HPLC separation attempts
on both 2 and 39 only caused peak broadening without any
separation (Figure S14, Supporting Information).
Mass spectrometric analysis (HR-MALDI-MS) of the
mixture showed only a single peak corresponding to the
+
molecular formula of 39 (m/z = 774.0660, C44H22Fe2N8 :
774.0662), suggesting that we had obtained two, presumably
conformationally isomeric, species with the same molecular
weight (Figure S19, Supporting Information). Additional
support for their structures is provided by the 1H NMR
spectrum. Both rotamers feature aromatic doublet and triplet
signals between 7 and 8 ppm and the terminal acetylene
signal around 3 ppm. These patterns can only be obtained if
To further investigate and characterize the two species
formed in the CA−RE reaction of ferrocene-substituted 39,
we tried to separate and purify them. However, all attempts to
separate these species from each other were unsuccessful.
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Scheme 6. Synthesis of Dendron 29
the groups in the push−pull systems in the meta position to
the terminal acetylene have the same chemical environment.
We measured VT-1H NMR spectra (500 MHz, (CDCl2)2)
from 30 to 120 °C (Figure S68, Supporting Information). No
interconversion was detected between the species, and the
spectra only featured temperature-dependent shifts of the
aromatic protons. Crystals of 39 suitable for X-ray analysis
were obtained by slow evaporation from EtOAc/hexane
solution at 20 °C (Figure 4).
The structure of compound 39 confirmed the double
CA−RE addition of TCNE. According to the crystal packing,
only one of the rotamers crystallized (Figure 4; Figures S7
and S8, Supporting Information). Packing effects could be one
explanation for the crystallization of only one conformer.
Thus, we decided to investigate the mother liquor and the
rest of the crystals. The separated mother liquor was colorless,
and none of 39 was detected by 1H NMR spectroscopy
following evaporation of the solvent. Powder XRD is the most
appropriate method to compare the identity of the remaining
crystal bulk. Unfortunately, this could not be utilized due to
the ethyl acetate present in the crystal packing and the large
cell volume. Therefore, 15 random crystals were measured,
and the results for all of them were in good agreement with
the first X-ray analysis (Figure 4). A mixture of two
conformers was again observed by 1H NMR spectroscopy
after dissolving the X-ray-measured crystals.
double CA−RE reaction of 34 with TCNE to give bis-TCBD
derivative 39. It is clear that the spectral situation must be
severely complicated in the case of 2, which is formed by six
CA−RE reactions in proximity to ferrocenes, and therefore,
the control studies support our hypothesis that the NMR
spectra of 2 are complicated by the presence of a complex
mixture of noninterchanging rotamers.
UV/vis Spectroscopy. During the reaction of compound
36 with TCNE, the color of solutions in (CH2Cl)2 changed
from orange to dark green. In agreement with this visible
observation, a broad intramolecular charge-transfer (CT) band
appears at λmax = 643 nm (1.93 eV, ε = 10 100 M−1 cm−1)
with the end absorption reaching into the near-infrared region
(Figure 5).28 The spectra of compounds 36 and 37 without
push−pull TCBD moieties lack this intense bathochromically
shifted band (Figure 5).
A key question is the origin of this CT band: does it arise
from intramolecular CT between the stronger (see electro-
chemical data below) Fc donors in one hemisphere to the
TCBD acceptors in the second, or is the CT mainly a feature
of the (weaker) Fc donors interacting with the directly
attached TCBD moieties? In other words, is there electronic
communication between the two hemispheres in Janus-system
2? Unfortunately, size and conformational flexibility of 2
prevented us to address this question by precise computa-
tional study.
Taken together, these experiments suggest that two highly
Experimentally, the absence of long-distance CT inter-
stable rotamers are formed in near equal amounts in the
actions through the Janus-system was confirmed by comparing
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Scheme 7. Synthesis of Janus-Dendrimer-Type Donor−Acceptor System 2
Figure 2. HR-MALDI-MS spectrum (DCTB as matrix) of Janus-dendrimer-type donor−acceptor system 2.
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1
Figure 3. H NMR spectra (400 MHz) of compounds 38 and 39 in CDCl3 at 298 K. Set of peaks for the products are highlighted with “blue”,
“red”, and “black” circles.
Electrochemistry. Cyclic voltammetry (CV; Table 1;
Figures S10−S12, Supporting Information) and rotating disk
voltammetry (RDV; Table 1) in CH2Cl2 (+ 0.1 M nBu4NPF6,
internal standard Fc+/Fc) revealed that model compounds 38
and 39 undergo one reversible oxidation whose peak
characteristics are those of a one-electron transfer. However,
the wave amplitudes observed by RDV indicate that this
oxidation step involves two electrons. The appearance of a
two-electron process indicates that both ferrocene and DAA
(dialkylanilino) donor groups behave as independent redox
centers.7b Both compounds exhibit four TCBD-centered
reduction steps with well-resolved one-electron transfers.
Figure 4. ORTEP representation of 39 with vibrational ellipsoids
shown at the 50% probability level, T = 100 K. H atoms and solvent
The dendrimer-type systems 36 and 37 show only one
oxidation step on the available potential range. The anodic
peak of 37 has the characteristics of a reversible one-electron
transfer from the shape of the peak. Oxidation of the
ferrocenes occurs at the same potential, denoting that they
behave as independent redox centers. An observed redis-
solution peak implies that the 12-electron-oxidized species
precipitate on the electrode surface and undergo a reduction
to the soluble neutral species on the reverse scan. This
behavior may result from the poor solubility of highly charged
species in CH2Cl2. A similar behavior is observed for 36, but
the two sets of ferrocenes are oxidized at different potentials,
as shown by the presence of a shoulder on the oxidation peak.
Nevertheless, the oxidized species are insoluble and similar to
37; a redissolution peak is observed on the reverse scan.
The target Janus-system 2 gave rise by CV to two oxidation
steps, the first one being reversible, whereas the second
oxidation shows characteristics of a deposit formation on the
electrode surface during oxidation, followed by a redissolution
peak on reduction. The first reversible oxidation occurs on the
molecules are omitted for clarity.
the UV/vis spectra of 2 and model system 39. Compound 39
shows an intramolecular CT band at λmax = 640 nm (1.94 eV,
ε = 2500 M−1 cm−1) (Figure 6). Not only the maxima but
also the overall shapes of the CT bands in both 2 and 39 are
quite similar. The higher molar extinction coefficient of the
CT band in the spectrum of 2 can be readily explained by the
fact that the Janus-system contains three substructures
corresponding to 39.
On the basis of these experimental findings, we suggest that
there is no electronic communication between the two
hemispheres in Janus-dendrimer-type system 2 and that
charge-transfer transitions are due to the independent Fc-
substituted TCBD push−pull chromophores in one hemi-
sphere. The long π-bridge with two or more meta-
connectivities between the Fc donors in one hemisphere
and the TCBD acceptors in the other prevents their electronic
communication.
H
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Figure 5. UV/vis spectra of compounds 2 (green line), 36 (orange line), and 37 (blue line) in CH2Cl2 at 298 K.
Figure 6. UV/vis spectra of compounds 2 (blue line) and 39 (green line) in CH2Cl2 at 298 K.
six aryl-bound Fc moieties at the typical potential of Eo =
+0.00 V. On the other hand, the irreversible oxidation of the
CONCLUSION
■
An efficient multistep synthesis of the ferrocene-containing
Janus-dendrimer-type donor−acceptor system 2 was reported.
Two dendrons, one with Fc moieties directly attached to
benzene rings and one with Fc moieties attached to
acetylenes, are connected by Sonogashira cross-coupling.
The Fc-moieties activate the adjacent acetylenes, and TCNE
undergoes an efficient [2 + 2] cycloaddition−retroelectrocyc-
lization under formation of push−pull donor-substituted
tetracyanobuta-1,3-dienes (TCBDs). This synthetic route
should also enable the introduction of even more potent
electron acceptors, such as TCNQ and F4-TCNQ, which also
undergo the CA−RE reaction.9 We performed a series of test
experiments to explain the observation of rotamers in the
NMR spectra of 2. The UV/vis spectrum of this Janus-system
clearly shows the formation of a broad intramolecular CT
band, with the end absorption reaching into the near-infrared
region. UV/vis spectral comparisons reveal that there is no
communication between the hemispheres of the target
dendritic system and that the independent push−pull
chromophoric units in one hemisphere are responsible for
the CT transitions. Electrochemical study confirms that the
ferrocenes in the two hemispheres of 2 behave as independent
six TCBD-conjugated Fc moieties at Ep = +0.43 V is strongly
anodically shifted.25b
The reduction of 2 occurs in four well-separated steps
centered on the strongly electron-accepting TCBD moieties at
similar potentials to those observed for the model system 39.
The amplitude of limiting current for the first oxidation is
twice the amplitude of each of the four reductions. It turns
out that each reduction corresponds to an exchange of three
electrons.
The fact that the isolated ferrocenes in the one hemisphere
are undisturbed in their oxidation potential corroborates the
findings from the UV/vis study, that there is no electronic
communication with the remote TCBD acceptors. The nice
reversibility of this first oxidation is an indication that the
generated hexacation remains perfectly soluble in our
experimental conditions. According to the spectroelectro-
chemical investigations, no spectral changes are observed
during the first oxidation process. However, small changes
were observed during reduction, as shown in Figure S13
(Supporting Information). Observed spectral evolutions are
quite similar at the plateau potential of the second and fourth
reduction steps.
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(TLC) was performed on aluminum sheets coated with silica gel 60
F254. Visualization was achieved using UV light (254 or 366 nm) or
by staining with iodine adsorbed on SiO2 or with ceric ammonium
molybdate solution (120 g (NH4)6Mo7O24·4H2O, 5 g (NH4)2Ce-
(NO3)6 in 800 mL 10% H2SO4). Evaporation in vacuo was
performed at 25−60 °C and 900−10 mbar. Reported yields refer
to spectroscopically and chromatographically pure compounds that
were dried under high vacuum (0.1−0.05 mbar) before analytical
characterization. 1H and 13C nuclear magnetic resonance (NMR)
spectra were recorded at 600 or 400 MHz (1H) and 150 or 100
MHz (13C), respectively. Temperatures of measurements are
indicated in the procedures and on the spectra. Chemical shifts δ
are reported in ppm downfield from tetramethylsilane using the
residual solvent signals as an internal reference (CDCl3: δH = 7.26
ppm, δC = 77.0 ppm; CD2Cl2: δH = 5.32 ppm, δC = 53.8 ppm;
(CD3)2CO: δH = 2.05 ppm, δC = 206.3 ppm). For 1H NMR,
coupling constants J are given in Hz and the resonance multiplicity is
described as s (singlet), d (doublet), t (triplet), q (quartet), quint
(quintet), sext (sextet), sept (septet), m (multiplet), and br. (broad).
Table 1. Electrochemical Data Measured by Cyclic
Voltammetry (CV) and Rotating Disk Voltammetry (RDV)
a h
,
in CH2Cl2 + 0.1 M nBu4NPF6
CV
RDV
b
c
d
e
f
E° [V] ΔEp [mV]
Ep [V]
E1/2 [V]
slope [mV]
60
2
+0.43
+0.00
60
+0.00 (6e−)
−0.67
100
spread out
unresolved
waves
−0.95
−1.27
−1.37
120
95
75
g
36
+0.19
+0.08
+0.08
+0.17 (6e−)
+0.05 (6e−)
g
70
55
g
37
38
+0.05 (12e−)
+0.91 (2e−)
−0.82 (1e−)
−1.04 (1e−)
−1.30 (1e−)
−1.50 (1e−)
+0.49 (2e−)
−0.74 (1e−)
−0.95 (1e−)
−1.30 (1e−)
−1.41 (1e−)
+0.89
−0.77
−0.97
−1.25
−1.38
+0.48
−0.72
−0.90
−1.23
−1.33
100
110
110
90
60
Infrared (IR) spectra are reported as wavenumbers ν
̃
(cm−1) with
60
band intensities indicated as s (strong), m (medium), w (weak), br
(broad). For FT-ICR-MALDI measurements, the matrix was 2-
[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile
(DCTB) or 3-hydroxypyridine-2-carboxylic acid (3-HPA). The most
important peaks are reported in m/z units with M+ as the molecular
ion and with the corresponding intensities in %. UV/vis spectroscopy
was recorded on a UV/vis/NIR spectrophotometer. Electrochemical
measurements were carried out in CH2Cl2 containing 0.1 M
nBu4NPF6 in a classical three-electrode cell by cyclic voltammetry
(CV) and rotating-disk voltammetry (RDV). The working electrode
was a glassy C disk (3 mm in diameter), the auxiliary electrode was a
Pt wire, and the pseudo reference electrode was a Pt wire. The cell
was connected to a potentiostat driven by software running on a
personal computer. All potentials are given versus Fc+/Fc used as
internal reference and are uncorrected from Ohmic drop.
Compounds 6,12 7,12 12,17a13,17a 14,17b 20,20 21,21 22,8 23,22
31,30 and 3231 were prepared according to literature procedures.
1-(3,4,5-Triiodophenyl)-3,3-diethyltriaz-1-ene (8). A solution
of 3,4,5-triiodoaniline (7) (4.14 g, 8.79 mmol) in a mixture of Et2O/
THF/MeCN 7:6:1 (100 mL), was treated with conc. HCl (11 mL),
cooled to −5 °C, treated with a solution NaNO2 (2.06 g, 29.89
mmol) in MeCN/H2O 2:3 (25 mL), and stirred for 1.5 h at −5 °C.
The mixture was poured into a cold solution of K2CO3 (6.06 g,
43.85 mmol) and diethylamine (3.57 g, 5.03 mL, 48.81 mmol) in
MeCN/H2O 2:1 (150 mL). The mixture was stirred for 3 h at 25 °C
and extracted with CH2Cl2 (3 × 100 mL). The combined organic
layers were dried over MgSO4, filtered, and concentrated in vacuo.
FC (SiO2; hexane/CH2Cl2 2:1) gave triazene 8 (2.44 g, 50%) as a
brown oil. Rf = 0.57 (hexane/CH2Cl2 2:1); 1H NMR (400 MHz,
CDCl3, 25 °C): δ = 1.19 and 1.31 (2 br. s, 6 H), 3.70−3.80 (m, 4
H), 7.90 ppm (s, 2 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ =
60
80
130
80
100
60
39
100
100
100
100
60
60
80
100
a
All potentials are given versus the Fc+/Fc couple used as internal
standard. Working electrode: glassy carbon electrode; pseudo counter
b
electrode: Pt; reference electrode: Pt. Scan rate: 0.1 V s−1. E° = (Epc
+
Epa)/2, where Epc and Epa correspond to the cathodic and anodic peak
c
potentials, respectively. ΔEp = Eox − Ered, where the subscripts ox and
red refer to the conjugated oxidation and reduction steps, respectively.
d
e
f
Ep = Irreversible peak potential. E1/2 = Half-wave potential. Slope of
the linearized plot of E versus log[I/(Ilim − I)], where Ilim is the
g
limiting current and I the current. On the reverse scan, a redissolution
h
peak was observed at +0.05 V. All potentials are given versus
ferrocene, used as internal standard.
redox centers. The oxidation potentials of the aryl-bound
ferrocenes are undisturbed and appear at the typical potential
of ferrocenes (Eo = 0.00 V), whereas the TCBD-bound Fc
moieties feature a strong anodic shift (Ep = +0.43 V). The
strong Fc electron donors in one hemisphere are not in
electronic communication with the strong electron acceptors
in the second: the extended π-system with several meta-
connectivities behaves similar to a σ-bonded tunneling bridge.
Therefore, the described Janus-dendrimer-type donor−accept-
or system could serve as a new structural motif for molecular
rectifiers according to the concept by Aviram and Ratner.29
̃
11.2, 14.6, 41.6, 49.5, 106.5, 114.4, 131.2, 152.6 ppm; IR (ATR): ν =
2971 (w), 2930 (w), 1552 (m), 1514 (m), 1448 (s), 1397 (m), 1378
(m), 1330 (s), 1230 (m), 1184 (w), 1107 (m), 1075 (m), 993 (m),
872 cm−1 (m); HR-EI-MS (70 eV): m/z (%): 555.8157 (14, [M +
+
H]+, calc. for C10H13I3N3 : 555.8165); 454.7278 (45, [M −
+
+
EXPERIMENTAL SECTION
C4H10N3 ], calc. for C6H2I3 : 454.7291).
■
General. Reagents were purchased as reagent grade and used
without further purification. Solvents for extraction or column
chromatography were distilled from technical grade. Dry solvents
(THF, CH2Cl2, diethyl ether, MeCN, and toluene) for reactions
were purified by a solvent drying system under a nitrogen
atmosphere (H2O content < 10 ppm as determined by Karl Fischer
titration). All other solvents were purchased in p.a. quality. Reactions
in the absence of air and moisture were performed in oven-dried
glassware under an Ar or N2 atmosphere. Flash column
chromatography (FC) was performed using SiO2 (60 Å, 230−400
mesh, particle size 0.040−0.063 mm) at 25 °C with a head pressure
of 0.0−0.5 bar. The used solvent compositions are reported
individually in parentheses. Analytical thin-layer chromatography
3,3-Diethyl-1-[3,4,5-tris(4-bromophenyl)phenyl]triaz-1-ene
(9). A suspension of 8 (500 mg, 0.9 mmol), 4-bromophenylboronic
acid (1.08 g, 5.41 mmol), K2CO3 (3.73 g, 27.04 mmol), and Aliquat
336 (11 mg, 0.03 mmol) in toluene (50 mL) was deoxygenated
three times via a “freeze−pump−thaw” cycle. [Pd(PPh3)4] (121 mg,
0.1 mmol) was added, and the solution was stirred for 18 h at 80 °C.
The mixture was diluted with H2O (30 mL) and extracted with
CH2Cl2 (3 × 30 mL). The combined organic layers were dried over
MgSO4, filtered, and concentrated in vacuo. FC (Al2O3; hexane/
CH2Cl2 4:1) gave 9 (411 mg, 71%) as a yellow greasy solid. Rf =
1
0.21 (SiO2; hexane/CH2Cl2 4:1); mp 167−168 °C; H NMR (400
MHz, CDCl3, 25 °C): δ = 1.27 (br. t, J = 7.2 Hz, 6 H), 3.79 (br. q, J
= 7.2 Hz, 4 H), 6.67 (br. d, J = 8.4 Hz, 2 H), 6.95 (br. d, J = 8.5 Hz,
J
DOI: 10.1021/jo502367h
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
4 H), 7.15 (br. d, J = 8.4 Hz, 2 H), 7.30 (br. d, J = 8.5 Hz, 4 H),
7.44 ppm (s, 2 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ = 27.1,
120.5, 120.8, 121.9, 130.9, 131.0, 131.6, 133.4, 134.2, 138.2, 140.8,
(37 mg, 35%) as an orange viscous film. Rf = 0.32 (SiO2; hexane/
CH2Cl2 1:1); H NMR (400 MHz, CDCl3, 25 °C): δ = 1.32 (br. t, J
1
= 7.0 Hz, 6 H), 3.84 (br. q, J = 7.0 Hz, 4 H), 4.06 (s, 10 H), 4.09 (s,
20 H), 4.32 (t, J = 1.9 Hz, 4 H), 4.35 (t, J = 1.9 Hz, 8 H), 4.68 (t, J
= 1.9 Hz, 4 H), 4.71 (t, J = 1.9 Hz, 8 H), 6.91 (br. d, J = 8.2 Hz, 2
H), 7.19 (br. d, J = 8.3 Hz, 4 H), 7.31 (br. d, J = 8.2 Hz, 2 H),
7.43−7.56 (m, 13 H), 7.58 ppm (s, 2 H); 13C NMR (100 MHz,
CDCl3, 25 °C): δ = 66.6, 66.7, 69.25, 69.27, 69.82, 69.84, 84.5, 84.6,
89.1, 89.2, 90.1, 90.2, 120.8, 121.3, 121.9, 123.28, 123.31, 123.7,
123.8, 126.76, 126.80, 130.2, 131.0, 131.2, 132.1, 135.1, 139.7, 139.8,
139.9, 142.1, 142.2, 150.7 ppm (32 out of 34 signals expected); IR
̃
141,5, 150.6 ppm (13 out of 14 signals expected); IR (ATR): ν =
2972 (w), 2902 (w), 1590 (m), 1486 (m), 1436 (m), 1395 (m),
1332 (s), 1244 (m), 1071 (m), 1009 (s), 741 (s), 663 (m), 636
cm−1 (m); HR-MALDI-MS (DCTB): m/z (%): 639.9596 (33, [M +
+
H+], calc. for C28H25Br3N3 : 639.9593), 640.9434 (18), 641.9576
(100), 642.9610 (29), 643.9556 (96), 644.9588 (30), 645.9536 (32).
3,3-Diethyl-1-[3,4,5-tris(4-iodophenyl)phenyl]-triaz-1-ene
(10). A solution of 1.6 M nBuLi in hexane (4.1 mL, 6.56 mmol) was
added dropwise to a solution of 9 (1.00 g, 1.56 mmol) in THF (200
mL) at −78 °C. The mixture was stirred for 20 min at this
temperature, treated dropwise with a solution of I2 (4.73 g, 18.64
mmol) in THF (40 mL), stirred for 30 min, then warmed to 20 °C,
diluted with Et2O, and washed with an aq. 5% Na2S2O3 solution and
brine. The aqueous phase was extracted with Et2O (3 × 100 mL).
The combined organic layers were dried (MgSO4), filtered, and
concentrated in vacuo. FC (SiO2; hexane/CH2Cl2 4:1) and
crystallization from CH2Cl2 gave 10 (657 mg, 54%) as a white
̃
(ATR): ν = 2970 (w), 2930 (w), 2161 (w), 1587 (s), 1509 (m),
1435 (m), 1408 (m), 1332 (m), 1244 (m), 1105 (s), 1031 (m),
1000 cm−1 (s); HR-MALDI-MS (DCTB): m/z (%): 1805.3078 (4),
1806.3107 (5), 1807.3034 (29), 1808.3059 (36), 1809.2997 (85, M+,
+
calc. for C112H87Fe6N3 : 1809.2998), 1810.3016 (100), 1811.3042
(66), 1812.3070 (29), 1813.3096 (10), 1814.3115 (3).
1,2,3-Tris{4-[2-(3,5-diferrocenylphenyl)ethynyl]phenyl}-5-io-
dobenzene (18). A solution of 17 (100 mg, 0.06 mmol) in MeI (5
mL) was deoxygenated thoroughly by bubbling Ar for 30 min and
then stirred in a sealed tube at 120 °C for 16 h. Evaporation and FC
(Al2O3; hexane/CH2Cl2 3:1) gave 18 (87 mg, 86%) as a red viscous
1
solid. Rf = 0.20 (SiO2; hexane/CH2Cl2 4:1); mp 195−196 °C; H
NMR (400 MHz, CDCl3, 25 °C): δ = 1.27 (br. t, J = 7.2 Hz, 6 H),
3.78 (br. q, J = 7.2 Hz, 4 H), 6.54 (d, J = 8.3 Hz, 2 H), 6.82 (d, J =
8.4 Hz, 4 H), 7.34 (d, J = 8.3 Hz, 2 H), 7.42 (s, 2 H), 7.50 ppm (d,
J = 8.4 Hz, 4 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ = 92.2,
92.4, 121.9, 131.9, 133.7, 134.1, 136.8, 137.0, 138.8, 141.46, 141.49,
1
foam. Rf = 0.11 (SiO2; hexane/CH2Cl2 3:1); H NMR (400 MHz,
CDCl3, 25 °C): δ = 4.05 (s, 10 H), 4.08 (s, 20 H), 4.32 (t, J = 1.9
Hz, 4 H), 4.35 (t, J = 1.9 Hz, 8 H), 4.67 (t, J = 1.9 Hz, 4 H), 4.70
(t, J = 1.9 Hz, 8 H), 6.86 (br. d, J = 8.3 Hz, 2 H), 7.11 (br. d, J =
8.3 Hz, 4 H), 7.31, (br. d, J = 8.3 Hz, 2 H), 7.40−7.60 (m, 13 H),
7.86 ppm (s, 2 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ = 66.66,
66.69, 69.29, 69.30, 69.8, 69.9, 84.47, 84.52, 88.8, 88.9, 90.5, 90.7,
93.5, 121.6, 122.0, 123.1, 123.2, 123.9, 124.0, 126.76, 126.80, 130.0,
131.2, 131.4, 131.6, 138.2, 138.4, 138.6, 139.79, 139.83, 140.2, 143.4
̃
150.7 ppm (12 out of 14 signals expected); IR (ATR): ν = 2975
(w), 2932 (w), 1586 (m), 1483 (m), 1432 (s), 1398 (m), 1379 (m),
1329 (s), 1221 (m), 1161 (w), 1099 (m), 1076 (m), 1003 (s), 891
(w), 829 (m), 817 (s), 772 (w), 728 cm−1 (w); HR-MALDI-MS
+
(DCTB): m/z (%): 783.9181 (100, [M + H+], calc. for C28H25I3N3 :
783.9177), 784.9215 (31), 785.9248 (5).
̃
ppm; IR (ATR): ν = 2953 (w), 2868 (w), 2234 (w), 1587 (s), 1507
[2-(3,5-Diferrocenylphenyl)ethynyl]triisopropylsilane (15).
A solution of 14 (700 mg, 1.68 mmol) and ferroceneboronic acid
(850 mg, 3.7 mmol) in toluene (50 mL) was deoxygenated
thoroughly by bubbling Ar through for 30 min. K3PO4 (1.78 g,
8.39 mmol) and [PdCl2(dppf)2] (25 mg, 0.031 mmol) were added.
The mixture was stirred under Ar at 80 °C for 12 h and evaporated.
FC (SiO2; hexane/CH2Cl2 3:1) gave 15 (452 mg, 43%) as an orange
(m), 1437 (m), 1410 (m), 1385 (m), 1251 (m), 1106 (s), 1032 (m),
999 cm−1 (s); HR-MALDI-MS (DCTB): m/z (%): 1833.1277 (6),
1834.1205 (29), 1835.1237 (36), 1836.1172 (83, M+, calc. for
C108H77Fe6I+: 1836.1167), 1837.1188 (100), 1838.1215 (64),
1839.1245 (29), 1840.1273 (9), 1841.1300 (3).
(2-{3,4,5-Tris(4-[2-(3,5-diferrocenylphenyl)ethynyl]phenyl}-
ethynyl)trimethylsilane (19). Ethynyltrimethylsilane (18 μL, 0.13
mmol), [Pd(PPh3)2Cl2] (13 mg, 0.019 mmol), and CuI (5 mg, 0.026
mmol) were added to a deoxygenated solution of 18 (110 mg, 0.06
mmol) in (iPr)2NH (25 mL) under a nitrogen atmosphere. The
mixture was stirred at 25 °C for 14 h and filtered through a silica
plug. Evaporation and FC (SiO2; hexane/CH2Cl2 2:1) gave 19 (96
mg, 89%) as a red solid. Rf = 0.12 (SiO2; hexane/CH2Cl2 2:1); mp >
1
foam. Rf = 0.54 (SiO2; hexane/CH2Cl2 3:1); mp 109−110 °C; H
NMR (400 MHz, CDCl3, 25 °C): δ = 1.18 (s, 21 H), 4.09 (s, 10
H), 4.34 (t, J = 1.9 Hz, 4 H), 4.68 (t, J = 1.9 Hz, 4 H), 7.38 (d, J =
1.7 Hz, 2 H), 7.56 ppm (t, J = 1.7 Hz, 1 H); 13C NMR (100 MHz,
CDCl3, 25 °C): δ = 11.6, 18.9, 66.8, 69.2, 69.8, 84.8, 90.2, 107.7,
̃
123.6, 124.3, 127.4, 139.6 ppm; IR (ATR): ν = 3093 (m), 2918 (m),
1
240 °C (decomp); H NMR (400 MHz, CDCl3, 25 °C): δ = 0.31 (s,
2854 (m), 2212 (s), 1581 (s), 1539 (s), 1463 (w), 1410 (m), 1109
(m), 815 (s), 675 cm−1 (w); HR-MALDI-MS (DCTB): m/z (%):
624.1795 (13), 625.1832 (5), 626.1748 (100, M+, calc. for
C37H42Fe2Si+: 626.1749), 627.1785 (37), 628.1823 (7).
9 H), 4.06 (s, 10 H), 4.09 (s, 20 H), 4.32 (t, J = 1.9 Hz, 4 H), 4.35
(t, J = 1.9 Hz, 8 H), 4.68 (t, J = 1.9 Hz, 4 H), 4.71 (t, J = 1.9 Hz, 8
H), 6.88 (br. d, J = 8.2 Hz, 2 H), 7.12 (br. d, J = 8.2 Hz, 4 H), 7.32,
(br. d, J = 8.2 Hz, 2 H), 7.44−7.50 (m, 10 H), 7.53 (t, J = 1.7 Hz, 1
H), 7.55 (t, J = 1.7 Hz, 2 H), 7.63 ppm (s, 2 H); 13C NMR (100
MHz, CDCl3, 25 °C): δ = 0.1, 66,65, 66.68, 69.28, 69.29, 69.82,
69.84, 84.47, 84.52, 88.9, 89.0, 90.4, 90.5, 95.7, 104.4, 121.5, 121.8,
122.9, 123.15, 123.20, 123.8, 123.9, 126.7, 126.8, 130.0, 131.2, 131.4,
131.7, 133.1, 138.7, 138.9, 139.76, 139.80, 140.9, 141.7 ppm; IR
1,3-(Diferrocenyl)-5-ethynylbenzene (16). A solution of 15
(500 mg, 0.8 mmol) in THF (25 mL) was treated with a 1 M
solution of nBu4NF in THF (0.94 mL, 0.94 mmol), stirred at room
temperature for 2 h, and evaporated. FC (SiO2; hexane/CH2Cl2 1:1)
gave 16 (356 mg, 95%) as a red foam. Rf = 0.65 (SiO2; hexane/
CH2Cl2 1:1); mp 190−191 °C; 1H NMR (400 MHz, CDCl3, 25
°C): δ = 3.12 (s, 1 H), 4.08 (s, 10 H), 4.36 (t, J = 1.9 Hz, 4 H),
4.68 (t, J = 1.9 Hz, 4 H), 7.44 (d, J = 1.7 Hz, 2 H), 7.56 ppm (t, J =
1.7 Hz, 1 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ = 66.7, 69.3,
̃
(ATR): ν = 2957 (w), 2160 (w), 1588 (s), 1507 (m), 1442 (m),
1411 (m), 1249 (m), 1106 (s), 1032 (m), 1000 (s), 816 cm−1 (s);
HR-MALDI-MS (DCTB): m/z (%): 1804.2647 (27), 1805.2677
(37), 1806.2613 (81, M+, calc. for C113H86Fe6Si+: 1806.2596),
1807.2628 (100), 1808.2655 (68), 1809.2681 (33), 1810.2706 (13).
1,2,3,-Tris{4-[2-(3,5-diferrocenylphenyl)ethynyl]phenyl}-5-
ethynylbenzene (3). A solution of 19 (90 mg, 0.05 mmol) in
MeOH/THF 1:1 (100 mL) was treated with K2CO3 (34 mg, 0.24
mmol), stirred at 25 °C for 2 h, diluted with CH2Cl2 (100 mL), and
̃
69.8, 76.8, 84.2, 84.4, 122.1, 124.4, 127.3, 139.9 ppm; IR (ATR): ν =
3089 (m), 2929 (m), 2203 (w), 1593 (s), 1407 (m), 1253 (m), 1102
(s), 1034 (m), 999 (s), 814 cm−1 (s); HR-MALDI-MS (DCTB): m/
z (%): 468.0461 (12), 469.0493 (4), 470.0414 (100, M+, calc. for
+
C28H22Fe2 : 470.0415), 471.0447 (29), 472.0481 (4).
3,3-Diethyl-1-[3,4,5-tris(4-{2-[3,5-di(ferrocenyl)phenyl]-
ethynyl}phenyl)phenyl]-triaz-1-ene (17). A solution of 10 (45
mg, 0.06 mmol) in iPr2NH (10 mL) was deoxygenated thoroughly
by bubbling Ar thorough for 30 min, treated with 16 (162 mg, 0.35
mmol), CuI (2 mg, 0.011 mmol), and [PdCl2(PPh3)2] (5 mg, 0.007
mmol), and stirred at 40 °C for 14 h. Evaporation, FC (SiO2;
hexane/CH2Cl2 1:1) and recycling GPC (JAI 2H; CHCl3) gave 17
washed with H2O (2
× 100 mL). Evaporation and flash
chromatography (SiO2; hexane/CH2Cl2 1:1) gave 3 (77 mg, 89%)
as an orange solid. Rf = 0.51 (SiO2; hexane/CH2Cl2 1:1); mp > 240
1
°C (decomp); H NMR (400 MHz, CDCl3, 25 °C): δ = 3.19 (s, 1
H), 4.06 (s, 10 H), 4.08 (s, 20 H), 4.32 (t, J = 1.8 Hz, 4 H), 4.35 (t,
J = 1.8 Hz, 8 H), 4.68 (t, J = 1.8 Hz, 4 H), 4.70 (t, J = 1.8 Hz, 8 H),
K
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The Journal of Organic Chemistry
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6.88 (br. d, J = 8.2 Hz, 2 H), 7.12 (br. d, J = 8.3 Hz, 4 H), 7.32, (br.
d, J = 8.2 Hz, 2 H), 7.44−7.50 (m, 10 H), 7.52 (t, J = 1.7 Hz, 1 H),
7.55 (t, J = 1.7 Hz, 2 H), 7.65 ppm (s, 2 H); 13C NMR (100 MHz,
CDCl3, 25 °C): δ = 66.66, 66.69, 69.28, 69.30, 69.8, 69.9, 78.4, 83.1,
84.48, 84.53, 88.85, 88.93, 90.5, 90.6, 121.6, 121.87, 121.94, 123.1,
123.2, 123.86, 123.94, 126.75, 126.80, 130.0, 131.2, 131.4, 131.7,
C51H73N2Si+: 741.5538), 742.5576 (55), 743.5609 (14), 744.5643
(4).
4,4′-(5-Ethynyl-1,3-phenylene)bis(ethyne-2,1-diyl)bis(N,N-
dihexylaniline) (27). A solution of 26 (670 mg, 0.9 mmol) in
MeOH/THF 1:1 (120 mL) was treated with K2CO3 (0.72 g, 5.21
mmol), stirred at 25 °C for 2 h, diluted with CH2Cl2 (100 mL), and
washed with H2O (2
× 100 mL). Evaporation and flash
133.3, 138.8, 139.1, 139.78, 139.81, 140.8, 141.8 ppm; IR (ATR): ν
̃
chromatography (SiO2; hexane/CH2Cl2 3:1) gave 27 (587 mg,
= 2924 (w), 2111 (w), 1589 (s), 1508 (w), 1442 (w), 1411 (w),
1252 (m), 1106 (s), 1032 (m), 1000 (s), 817 cm−1 (s); HR-MALDI-
MS (DCTB): m/z (%): 1732.2244 (30), 1733.2273 (36), 1734.2210
1
97%) as a colorless oil. Rf = 0.45 (SiO2; hexane/CH2Cl2 3:1); H
NMR (400 MHz, CDCl3, 25 °C): δ = 0.91 (t, J = 6.6 Hz, 12 H),
1.33 (br. s, 24 H), 1.50−1.65 (m, 8 H), 3.07 (s, 1 H), 3.28 (t, J =
7.7 Hz, 8 H), 6.57 (br. d, J = 9.0 Hz, 4 H), 7.35 (br. d, J = 9.0 Hz, 4
H), 7.49 (d, J = 1.6 Hz, 2 H), 7.58 ppm (t, J = 1.6 Hz, 1 H); 13C
NMR (100 MHz, CDCl3, 25 °C): δ = 14.2, 22.8, 27.0, 27.3, 31.9,
51.1, 77.7, 82.7, 85.9, 92.2, 108.3, 111.3, 122.6, 125.0, 133.1, 133.4,
+
(84, M+, calc. for C110H78Fe6 : 1734.2201), 1735.2225 (100),
1736.2250 (63), 1737.2280 (28).
4,4′-[5-(3,3-Diethyltriaz-1-en-1-yl)-1,3-phenylene]bis-
(ethyne-2,1-diyl)bis(N,N-dihexylaniline) (24). A solution of 22
(511 mg, 1.19 mmol) in iPr2NH (60 mL) was deoxygenated
thoroughly by bubbling Ar for 30 min, treated with 23 (852 mg, 2.98
mmol), CuI (69 mg, 0.36 mmol), and [PdCl2(PPh3)2] (168 mg, 0.24
mmol), and stirred under Ar for 12 h. Evaporation and FC (SiO2;
hexane/CH2Cl2 3:1) gave 24 (752 mg, 85%) as a yellow solid. Rf =
0.15 (SiO2; hexane/CH2Cl2 3:1); mp 90−95 °C; 1H NMR (400
MHz, CDCl3, 25 °C): δ = 0.91 (t, J = 6.4 Hz, 12 H), 1.25−1.50 (m,
30 H), 1.50−1.65 (m, 8 H), 3.28 (t, J = 7.1 Hz, 8 H), 3.78 (q, J =
7.1 Hz, 4 H), 6.58 (br. d, J = 8.8 Hz, 4 H), 7.37 (br. d, J = 8.8 Hz, 4
H), 7.40 (t, J = 1.5 Hz, 1 H), 7.47 ppm (d, J = 1.5 Hz, 2 H); 13C
NMR (100 MHz, CDCl3, 25 °C): δ = 14.2, 22.8, 27.0, 27.3, 31.9,
51.1, 87.1, 90.8, 109.0, 111.3, 122.6. 124.8, 130.6, 133.1, 148.0, 151.2
̃
134.1, 148.3 ppm; IR (ATR): ν = 3305 (w), 2953 (m), 2925 (m),
2855 (m), 2199 (w), 1606 (s), 1574 (s), 1516 (s), 1465 (m), 1399
(m), 1366 (m), 1293 (m), 1253 (m), 1190 (m), 1180 (m), 1120
(w), 960 (m), 875 (m) 810 cm−1 (s); HR-MALDI-MS (DCTB): m/
+
+
z (%): 668.5065 (100, M , calc. for C48H64N2 : 668.5064), 669.5098
(50), 670.5131 (12).
3,3-Diethyl-1-[3,4,5-tris(4-{[3,5-bis(ethyne-2,1-diyl)bis(N,N-
dihexylaniline)phenyl]-ethynyl}phenyl)phenyl]triaz-1-ene
(28). A solution of 10 (175 mg, 0.22 mmol) in iPr2NH (40 mL) and
THF (20 mL) was deoxygenated thoroughly by bubbling Ar through
for 30 min, treated with 27 (722 mg, 1.08 mmol), CuI (26 mg, 0.14
mmol), and [PdCl2(PPh3)2] (53 mg, 0.076 mmol), and stirred at 40
°C for 14 h. Evaporation and FC (SiO2; hexane/CH2Cl2 3:1) gave
28 (274 mg, 51%) as an orange amorphous film. Rf = 0.12 (SiO2;
hexane/CH2Cl2 2:1); 1H NMR (400 MHz, CD2Cl2, 25 °C): δ =
0.80−0.95 (m, 36 H), 1.24−1.42 (m, 78 H), 1.52−1.60 (m, 24 H),
3.22−3.36 (s, 24 H), 3.82 (q, J = 7.1 Hz, 4 H), 6.57−6.68 (m, 12
H), 6.91 (d, J = 8.2 Hz, 2 H), 7.16 (br. d, J = 8.3 Hz, 4 H), 7.25 (d,
J = 8.2 Hz, 2 H), 7.30−7.38 (m, 12 H), 7.40 (br. d, J = 8.3 Hz, 4
H), 7.47−7.56 ppm (m, 11 H); 13C NMR (100 MHz, CD2Cl2, 25
°C): δ = 14.4, 23.3, 27.3, 27.7, 32.3, 51.5, 86.3, 88.9, 89.0, 90.5, 90.7,
92.60, 92.64, 108.37, 108.40, 111.7, 121.1, 121.4, 122.2, 124.4,
125.51, 125.54, 130.6, 131.4, 131.6, 132.6, 133.1, 133.5, 134.1, 134.3,
135.3, 140.6, 142.5, 143.0, 148.8, 148.9, 151.2 ppm (37 out of 44
̃
ppm (16 out of 18 signals expected); IR (ATR): ν = 2953 (m),
2926 (m), 2856 (m), 2201 (m), 1606 (s), 1583 (s), 1569 (s), 1517
(s), 1465 (m), 1401 (m), 1368 (m), 1251 (m), 1190 (m), 1105 (m),
811 cm−1 (m); HR-MALDI-MS (3-HPA): m/z (%) 744.1482 (100
+
[M +H]+, calc. for C50H74N5 : 744.1481).
4,4′-(5-Iodo-1,3-phenylene)bis(ethyne-2,1-diyl)bis(N,N-
dihexylaniline) (25). NaI (247 mg, 1.65 mmol) and Me3SiCl (157
mg, 1.44 mmol) were added to a solution of triazene 24 (350 mg,
0.47 mmol) in MeCN (30 mL) and CCl4 (10 mL). The mixture was
stirred under Ar at 60 °C for 20 min. Sat. aq. NaHCO3 solution (20
mL) was added, and the mixture was extracted with CH2Cl2 (3 × 20
mL). The combined organic layers were dried (MgSO4), filtered, and
evaporated. FC (SiO2; hexane/CH2Cl2 4:1) gave 25 (156 mg, 43%)
1
as a yellow oil. Rf = 0.41 (SiO2; hexane/CH2Cl2 4:1); H NMR (400
̃
signals expected); IR (ATR): ν = 3044 (w), 2953 (m), 2929 (m),
MHz, CDCl3, 25 °C): δ = 0.92 (t, J = 6.8 Hz, 12 H), 1.33 (br. s, 24
H), 1.50−1.65 (m, 8 H), 3.28 (t, J = 7.8 Hz, 8 H), 6.57 (br. d, J =
9.0 Hz, 4 H), 7.34 (br. d, J = 9.0 Hz, 4 H), 7.55 (t, J = 1.5 Hz, 1 H),
7.72 ppm (d, J = 1.5 Hz, 2 H); 13C NMR (100 MHz, CDCl3, 25
°C): δ = 14.2, 22.8, 27.0, 27.3, 31.9, 51.1, 85.3, 92.9, 93.3, 108.1,
2855 (m), 2199 (m), 1606 (s), 1574 (s), 1516 (s), 1464 (m), 1398
(m), 1366 (m), 1293 (m), 1252 (m), 1225 (w), 1190 (m), 1118
(w), 962 (m), 872 (m) 810 cm−1 (s); HR-MALDI-MS (DCTB): m/
+
z (%): 2404.6943 (54, [M + H]+, calc. for C172H214N9 : 2404.6938),
2405.6977 (100), 2406.7011 (96), 2407.7045 (61), 2408.7085 (27),
̃
111.3, 126.3, 133.0, 133.2, 138.4, 148.3 ppm; IR (ATR): ν = 2953
2409.7117 (11).
(m), 2924 (m), 2854 (m), 2200 (m), 1605 (s), 1576 (s), 1516 (s),
1465 (m), 1399 (m), 1366 (m), 1293 (m), 1190 (m), 1121 (m),
810 cm−1 (m); HR-MALDI-MS (3-HPA) m/z (%): 771.4116 (100,
[M +H]+, calc. for C46H64N2I+: 771.4109), 772.4148 (51), 773.4179
(12), 774.5137 (2).
{5-[(Trimethylsilyl)ethynyl]-1,3-phenylene}bis(ethyne-2,1-
diyl)ferrocene (33). A solution of 32 (1.79 g, 4.20 mmol) in
iPr2NH (100 mL) was deoxygenated thoroughly by bubbling Ar for
30 min. Ethynylferrocene (1.94 g, 9.23 mmol), CuI (160 mg, 0.84
mmol), and [PdCl2(PPh3)2] (295 mg, 0.42 mmol) were added, and
the mixture was stirred under Ar for 12 h. Evaporation and FC
(SiO2; hexane/CH2Cl2 2:1) gave 33 (2.26 g, 91%) as a yellow solid.
4,4′-{5-[2-(Trimethylsilyl)ethynyl]-1,3-phenylene}bis-
(ethyne-2,1-diyl)bis(N,N-dihexylaniline) (26). A solution of 25
(700 mg, 0.91 mmol) in Et3N (60 mL) was deoxygenated
thoroughly by bubbling Ar through for 30 min. (Trimethylsilyl)-
acetylene (257 μL, 1.82 mmol), CuI (10 mg, 0.05 mmol), and
[PdCl2(PPh3)2] (23 mg, 0.03 mmol) were added, and the mixture
was stirred under Ar for 14 h. Evaporation and FC (SiO2; hexane/
CH2Cl2 4:1) gave 26 (626 mg, 93%) as a yellow oil. Rf = 0.43 (SiO2;
1
Rf = 0.52 (SiO2; hexane/CH2Cl2 2:1); mp 139−140 °C; H NMR
(400 MHz, CDCl3, 25 °C): δ = 0.26 (s, 9 H), 4.20−4.30 (m, 14 H),
4.49 (t, J = 1.9 Hz, 4 H), 7.51 (d, J = 1.6 Hz, 2 H), 7.53 ppm (t, J =
1.6 Hz, 1 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ = 0.1, 64.8,
69.2, 70.2, 71.7, 84.5, 89.8, 95.4, 103.7, 123.8, 124.6, 133.7, 133.9
̃
ppm; IR (ATR): ν = 3094 (m), 2957 (m), 2897 (m), 2218 (m),
1
hexane/CH2Cl2 4:1); H NMR (400 MHz, CDCl3, 25 °C): δ = 0.25
2163 (m), 1581 (s), 1469 (w), 1411 (m), 1105 (m), 816 (s), 681
cm−1 (m); HR-MALDI-MS (DCTB) m/z (%): 588.0856 (13),
589.0893 (5), 590.0809 (100, M+, calc. for C35H30Fe2Si+: 590.0811),
591.0846 (36), 592.0884 (6), 593.0814 (2).
(s, 9 H), 0.91 (t, J = 6.9 Hz, 12 H), 1.33 (br. s, 24 H), 1.50−1.65
(m, 8 H), 3.27 (t, J = 7.6 Hz, 8 H), 6.56 (br. d, J = 9.0 Hz, 4 H),
7.33 (br. d, J = 9.0 Hz, 4 H), 7.47 (d, J = 1.6 Hz, 2 H), 7.53 ppm (t,
J = 1.6 Hz, 1 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ = 0.1,
14.2, 22.8, 27.0, 27.3, 31.9, 51.1, 86.0, 92.0, 94.9, 104.1, 108.4, 111.3,
(5-Ethynyl-1,3-phenylene)bis(ethyne-2,1-diyl)ferrocene
(34). A solution of 33 (500 mg, 0.85 mmol) in MeOH/THF 1:1
(100 mL) was treated with K2CO3 (235 mg, 1.7 mmol), stirred at 25
°C for 2 h, diluted with CH2Cl2 (100 mL), and washed with H2O (2
× 100 mL). Evaporation and FC (SiO2; hexane/CH2Cl2 1:1) gave
34 (417 mg, 95%) as a red solid. Rf = 0.71 (SiO2; hexane/CH2Cl2
̃
123.6, 124.9, 133.1, 133.3, 133.7, 148.2 ppm; IR (ATR): ν = 2955
(m), 2926 (m), 2856 (m), 2201 (m), 2151 (w), 1606 (s), 1574 (s),
1517 (s), 1465 (m), 1400 (m), 1367 (m), 1294 (m), 1249 (m),
1190 (m), 1119 (m), 973 (m), 842 (s) 811 cm−1 (s); HR-MALDI-
MS (3-HPA): m/z (%): 741.5542 (100, [M + H]+, calc. for
1
1:1); mp 188−189 °C; H NMR (400 MHz, CDCl3, 25 °C): δ =
L
DOI: 10.1021/jo502367h
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
3.09 (s, 1 H), 4.20−4.30 (m, 14 H), 4.50 (t, J = 1.9 Hz, 4 H), 7.52
(d, J = 1.6 Hz, 2 H), 7.57 ppm (t, J = 1.6 Hz, 1 H); 13C NMR (100
MHz, CDCl3, 25 °C): δ = 64.7, 69.2, 70.2, 71.7, 78.1, 82.4, 84.3,
NMR (150 MHz, CDCl3, 25 °C): δ = 64.8, 66.67, 66.70, 69.1, 69.2,
69.3, 69.9, 70.2, 71.7, 84.50, 84.54, 88.77, 88.84, 88.9, 89.0, 89.8,
89.86, 89.90, 90.0, 90.2, 90.4, 90.45, 90.54, 121.2, 121.5, 121.8, 122.8,
122.9, 123.15, 123.20, 123.90, 123.93, 124.7, 124.8, 126.77, 126.81,
130.0, 130.1, 131.2, 131.4, 131.69, 131.73, 132.9, 133.0, 133.28,
133.31, 133.7, 138.6, 138.8, 138.9, 139.1, 139.78, 139.81, 140.9,
̃
90.0, 122.8, 124.8, 133.8, 134.3 ppm; IR (ATR): ν = 3094 (m), 2213
(s), 1581 (m), 1468 (w), 1411 (m), 1105 (m), 814 (s), 684 cm−1
(m); HR-MALDI-MS (DCTB) m/z (%) 516.0459 (13), 517.0496
+
(5), 518.0414 (100, M+, calc. for C32H22Fe2 : 518.0416), 519.0448
̃
141.1, 141.8, 141.9 ppm; IR (ATR): ν = 3091 (m), 2926 (m), 2704
(34), 520.0485 (5).
(w), 2210 (m), 1580 (s), 1507 (m), 1410 (m), 1253 (m), 1106 (s),
1000 (s), 873 (m), 817 (s), 730 cm−1 (m); UV/vis (CH2Cl2): λmax
(ε) = 294 (sh, 262000), 310 (273600), 445 nm (7600 M−1 cm−1);
3,3-Diethyl-1-[3,4,5-tris(4-{[3,5-bis(ferrocenylethyne-2,1-
diyl)phenyl]ethynyl}phenyl)phenyl]-triaz-1-ene (35). A solution
of 10 (175 mg, 0.22 mmol) in iPr2NH (40 mL) was deoxygenated
thoroughly by bubbling Ar thorough for 30 min, 34 (496 mg, 0.96
mmol), CuI (18 mg, 0.095 mmol), and [PdCl2(PPh3)2] (34 mg,
0.048 mmol) were added, and the mixture was stirred at 40 °C for
14 h. Evaporation, FC (SiO2; hexane/CH2Cl2 1:1) and recycling
GPC (JAI 2H; CHCl3) gave 35 (245 mg, 56%) as an orange solid.
HR-MALDI-MS (DCTB): m/z (%): 3583.4360 (16), 3584.4325
+
(32), 3585.4300 (56), 3586.4276 (82, M+, calc. for C230H154Fe12
:
3586.4351), 3587.4258 (99), 3588.4268 (100), 3589.4305 (80),
3590.4339 (53), 3591.4370 (28), 3592.4404 (13).
Compound 37. Rf = 0.68 (SiO2; hexane/CH2Cl2 4:5); mp > 235
1
°C (decomp); H NMR (600 MHz, CDCl3, 25 °C): δ = 4.06 (s, 20
1
Rf = 0.25 (SiO2; hexane/CH2Cl2 1:1); mp > 147 °C (decomp); H
H), 4.08 (s, 40 H), 4.32 (t, J = 1.8 Hz, 8 H), 4.35 (t, J = 1.9 Hz, 16
H), 4.68 (t, J = 1.8 Hz, 8 H), 4.70 (t, J = 1.9 Hz, 16 H), 6.89 (br. d,
J = 8.6 Hz, 4 H), 7.14 (br. d, J = 8.6 Hz, 8 H), 7.33 (br. d, J = 8.6
Hz, 4 H), 7.45 (d, J = 1.7 Hz, 4 H), 7.46−7.50 (m, 16 H), 7.52 (t, J
= 1.7 Hz, 2 H), 7.55 (t, J = 1.7 Hz, 4 H), 7.71 ppm (s, 4 H); 13C
NMR (150 MHz, CDCl3, 25 °C): δ = 66.67, 66.70, 69.3, 69.8, 69.9,
75.1, 81.6, 84.48, 84.53, 88.8, 88.9, 90.55, 90.63, 121.5, 121.7, 122.0,
123.1, 123.2, 123.9, 124.0, 126.77, 126.81, 130.0, 131.2, 131.5, 131.6,
NMR (400 MHz, CDCl3, 25 °C): δ = 1.30 (t, J = 7.2 Hz, 6 H), 3.82
(q, J = 7.2 Hz, 4 H), 4.20−4.30 (m, 42 H), 4.45−4.55 (m, 12 H),
6.86 (br. d, J = 8.5 Hz, 2 H), 7.14 (br. d, J = 8.5 Hz, 4 H), 7.21, (br.
d, J = 8.5 Hz, 2 H), 7.38 (br. d, J = 8.5 Hz, 4 H), 7.50−7.60 ppm
(m, 11 H); 13C NMR (100 MHz, CDCl3, 25 °C): δ = 21.3, 47.6,
64.8, 69.11, 69.14, 70.2, 71.7, 84.5, 88.4, 88.5, 89.78, 89.81, 90.5,
90.7, 116.3, 120.5, 121.0, 121.9, 124.00, 124.02, 124.69, 124.72,
130.1, 131.0, 131.2, 132.0, 133.26, 133.29, 133.6, 135.0, 140.0, 142.0,
̃
133.7, 138.7, 139.7, 139.79, 139.82, 140.6, 142.0; IR (ATR): ν =
̃
142.4, 150.7 ppm (34 out of 38 signals expected); IR (ATR): ν =
3089 (m), 2953 (m), 2922 (m), 2852 (w), 2209 (m), 1582 (s), 1506
(m), 1410 (m), 1252 (m), 1105 (s), 1000 (s), 873 (m), 816 (s), 731
cm−1 (m); UV/vis (CH2Cl2): λmax (ε) = 289 (240000), 311 (sh,
188000), 446 nm (4800 M−1 cm−1); HR-MALDI-MS (DCTB): m/z
(%): 3463.4357 (16), 3464.4381 (35), 3465.4381 (56), 3466.4343
(79, M+, calc. for C220H154Fe12+: 3466.4350), 3467.4350 (100),
3468.4360 (98), 3469.4382 (80), 3470.4389 (50), 3471.4433 (25),
3472.4462 (11).
2931 (w), 2212 (m), 1579 (s), 1464 (m), 1444 (m), 1408 (m), 1331
(s), 1292 (w), 1242 (m), 1105 (s), 1042 (w), 1024 (m), 1001 (s),
821 (s), 731 cm−1 (s); HR-MALDI-MS (DCTB) m/z (%):
1951.3025 (26), 1952.30.44 (36), 1953.2987 (77), 1954.3005 (100,
+
M+, calc. for C124H87Fe6N3 : 1954.3035), 1955.3026 (69), 1956.3060
(37), 1957.3086 (13).
1-[3,4,5-Tris(4-{[3,5-bis(ferrocenylethyne-2,1-diyl)phenyl]-
ethynyl}phenyl)iodophenyl (29). A solution of 35 (105 mg, 0.05
mmol) in MeI (5 mL) was deoxygenated thoroughly by bubbling Ar
for 30 min, then stirred in a sealed tube at 120 °C for 16 h, and
evaporated. FC (Al2O3; hexane/CH2Cl2 2:1) gave 29 (91 mg, 85%)
as an orange solid. Rf = 0.20 (SiO2; hexane/CH2Cl2 2:1); mp > 193
3,3′-(5-Ethynyl-1,3-phenylene)bis(2-(4-(dihexylamino)-
phenyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile) (38). TCNE
(38 mg, 0.30 mmol) was added to a solution of 27 (50 mg, 0.075
mmol) in dichloroethane (5 mL). The mixture was stirred under an
Ar atmosphere. Evaporation and FC (SiO2; CH2Cl2) gave 38 (61
1
1
°C (decomp); H NMR (600 MHz, CDCl3, 25 °C): δ = 4.20−4.30
mg, 89%) as a dark orange film. Rf = 0.60 (SiO2; CH2Cl2); H NMR
(m, 42 H), 4.46−4.52 (m, 12 H), 6.82 (br. d, J = 8.5 Hz, 2 H), 7.06
(br. d, J = 8.5 Hz, 4 H), 7.22, (br. d, J = 8.5 Hz, 2 H), 7.37 (br. d, J
= 8.5 Hz, 4 H), 7.50−7.60 (m, 9 H), 7.82 ppm (s, 2 H); 13C NMR
(150 MHz, CDCl3, 25 °C): δ = 64.8, 69.1, 69.2, 70.2, 71.7, 84.5,
88.8, 88.9, 89.8, 89.9, 90.1, 90.3, 93.5, 121.3, 121.7, 123.8, 123.9,
124.7, 124.8, 129.9, 131.2, 131.4, 131.6, 133.27, 133.30, 133.7, 133.8,
138.1, 138.5, 138.7, 140.3, 143.3 ppm (32 out of 36 signals
(400 MHz, CDCl3, 25 °C): δ = 0.92 (t, J = 6.8 Hz, 12 H), 1.29−
1.40 (m, 24 H), 1.60−1.75 (m, 8 H), 3.34 (s, 1 H), 3.41 (t, J = 7.9
Hz, 8 H), 6.70 (br. d, J = 9.4 Hz, 4 H), 7.70 (br. d, J = 9.4 Hz, 4
H), 7.76 (t, J = 1.8 Hz, 1 H), 7.97 ppm (d, J = 1.8 Hz, 2 H); 13C
NMR (100 MHz, CDCl3, 25 °C): δ = 14.1, 22.8, 26.8, 27.5, 31.7,
51.8, 72.3, 80.0, 83.1, 90.8, 110.6, 111.2, 112.9, 114.1, 114.4, 116.5,
126.3, 129.9, 132.8, 133.9, 135.9, 153.6, 160.2, 166.8 ppm; IR
̃
expected); IR (ATR): ν = 3092 (w), 2923 (m), 2853 (m), 2211
̃
(ATR): ν = 2954 (m), 2927 (m), 2856 (m), 2213 (m), 2114 (w),
(m), 1578 (s), 1410 (m), 1262 (m), 1192 (w), 1106 (m), 1024 (m),
1000 (m), 971 (m), 906 (s), 874 (s), 819 (s), 727 cm−1 (s); HR-
MALDI-MS (DCTB) m/z (%): 1978.1234 (27), 1979.1255 (35),
1980.1194 (85, M+, calc. for C120H77Fe6I+: 1980.1168), 1981.1208
(100), 1982.1230 (68), 1983.1255 (33), 1984.1281 (13).
1601 (s), 1483 (s), 1445 (s), 1414 (s), 1339 (s), 1213 (m), 1183
(s), 823 (m), 638 cm−1 (m); UV/vis (CH2Cl2): λmax (ε) = 298
(32000), 460 nm (59 700 M−1 cm−1); HR-MALDI-MS (DCTB): m/
z (%): 947.5206 (100 [M + Na]+, calc. for C60H64N10Na+:
947.5208), 948.5244 (69), 949.5274 (24), 950.5322 (5).
Sonogashira Coupling of Ethyne 3 with Iodo Compound
29. A solution of 29 (20 mg, 0.01 mmol) in iPr2NH (20 mL) and
THF (40 mL) was deoxygenated thoroughly by bubbling Ar through
for 30 min, 3 (18 mg, 0.01 mmol), CuI (1 mg, 0.005 mmol), and
[PdCl2(PPh3)2] (4 mg, 0.005 mmol) were added, and the mixture
was stirred at 25 °C for 14 h. Evaporation and purification by
recycling GPC (JAI 2H; CHCl3) gave 36 (21 mg, 57%) and 37 (7
mg) as orange solids.
3,3′-(5-Ethynyl-1,3-phenylene)bis(2-ferrocenylbuta-1,3-
diene-1,1,4,4-tetracarbonitrile) (39). TCNE (99 mg, 0.77 mmol)
was added to a solution of 34 (100 mg, 0.19 mmol) in
dichloroethane, and the mixture was stirred at 80 °C for 6 h.
Evaporation and purification by FC (SiO2; CH2Cl2) gave a rotameric
mixture of 39 (123 mg, 82%, (39a/39b: 5/3) as a dark green solid.
1
Rf = 0.52 (SiO2; CH2Cl2); mp 223−225 °C; H NMR (400 MHz,
(CD3)2CO, 25 °C): 39a: δ = 4.12 (br. s, 1 H), 4.37 (s, 10 H), 4.93−
5.00 (m, 4 H), 5.09−5.16 (m, 2 H), 5.31−5.36 (m, 2 H), 8.37 (d, J
= 1.8 Hz, 2 H), 8.44 (t, J = 1.8 Hz, 1 H); 39b: 4.12 (br. s, 1 H),
4.43 (s, 10 H), 4.88−4.92 (m, 2 H), 4.93−5.00 (m, 2 H), 5.09−5.16
(m, 2 H), 5.50−5.55 (m, 2 H), 8.16 (t, J = 1.8 Hz, 1 H), 8.37 (d, J
= 1.8 Hz, 2 H); 13C NMR (100 MHz, (CD3)2CO, 25 °C): δ = 72.1,
72.2, 73.4, 73.5, 74.5, 74.9, 75.0, 75.1, 76.6, 76.8, 77.5, 77.6, 80.1,
80.3, 80.9, 81.0, 84.6, 84.7, 91.8, 91.9, 112.39, 112.41, 112.5, 112.7,
114.78, 114.81, 115.0, 115.1, 126.8, 126.9, 129.2, 130.0, 135.0, 135.4,
Compound 36. Rf = 0.59 (SiO2; hexane/CH2Cl2 4:5); mp > 240
1
°C (decomp); H NMR (600 MHz, CDCl3, 25 °C): δ = 4.08 (s, 10
H), 4.10 (s, 20 H), 4.25−4.30 (m, 42 H), 4.34 (t, J = 1.9 Hz, 4 H),
4.37 (t, J = 1.9 Hz, 8 H), 4.51 (t, J = 1.9 Hz, 4 H), 4.52 (t, J = 1.9
Hz, 8 H), 4.70 (t, J = 1.9 Hz, 4 H), 4.72 (t, J = 1.9 Hz, 8 H), 6.90
(br. d, J = 8.5 Hz, 2 H), 6.94 (br. d, J = 8.5 Hz, 2 H), 7.15 (br. d, J
= 8.5 Hz, 4 H), 7.19 (br. d, J = 8.5 Hz, 4 H), 7.27 (br. d, J = 8.5 Hz,
2 H), 7.36 (br. d, J = 8.5 Hz, 2 H), 7.43 (br. d, J = 8.5 Hz, 4 H),
7.48 (d, J = 1.7 Hz, 2 H), 7.49−7.52 (m, 8 H), 7.53−7.58 (m, 8 H)
7.59 (d, J = 1.6 Hz, 4 H), 7.73 (s, 2 H), 7.75 ppm (s, 2 H); 13C
̃
136.7, 136.9, 163.5, 164.2, 170.9, 171.3 ppm; IR (ATR): ν = 2220
(m), 1520 (s), 1440 (m), 1413 (m), 1380 (w), 1329 (w), 1286 (w),
M
DOI: 10.1021/jo502367h
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The Journal of Organic Chemistry
Article
1171 (m), 1040 (w), 1004 (m), 835 (m), 795 cm−1 (m); UV/vis
(CH2Cl2): λmax (ε) = 308 (31000), 521 (sh, 1500), 638 nm (2900
M−1 cm−1); HR-MALDI-MS (DCTB): m/z (%) 772.0710 (12),
(2) (a) Hawker, C. J.; Wooley, K. L.; Frec
́
het, J. M. J. J. Chem. Soc.,
Perkin Trans. 1 1993, 1287−1297. (b) Pesak, D. J.; Moore, J. S.
Tetrahedron 1997, 53, 15331−15347. (c) Bo, Z.; Rabe, J. P.;
+
773.0743 (6), 774.0660 (100 [M + Na]+, calc. for C44H22Fe2N8 :
Schluter, A. D. Angew. Chem., Int. Ed. 1999, 38, 2370−2372.
̈
774.0662), 775.0697 (48), 776.0732 (12), 777.0762 (3).
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1
4361.5228 (9). For the H and 13C NMR spectra, see Figures S65
and S66 (Supporting Information).
ASSOCIATED CONTENT
* Supporting Information
■
S
1H and 13C NMR spectra and electrochemistry of all new
compounds; crystal structure data for compounds 9, 10, 33,
and 39; rotamer formation analysis by NMR, GPC, and MS;
and theoretical calculations. This material is available free of
charge via the Internet at http://pubs.acs.org.
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Chem. Soc. 2009, 131, 6283−6292. (b) Percec, V.; Wilson, D. A.;
Leowanawat, P.; Wilson, C. J.; Hughes, A. D.; Kaucher, M. S.;
Hammer, D. A.; Levine, D. H.; Kim, A. J.; Bates, F. S.; Davis, K. P.;
Lodge, T. P.; Klein, M. L.; DeVane, R. H.; Aqad, E.; Rosen, B. M.;
Argintaru, A. O.; Sienkowska, M. J.; Rissanen, K.; Nummelin, S.;
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B.-K. Soft Matter 2011, 7, 4045−4049. (d) Percec, V.; Leowanawat,
P.; Sun, H.-J.; Kulikov, O.; Nusbaum, C. D.; Tran, T. M.; Bertin, A.;
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AUTHOR INFORMATION
Corresponding Author
*E-mail: diederich@org.chem.ethz.ch (F.D.).
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the ERC Advanced grant no.
246637 (“OPTELOMAC”). Dr. Bruno Bernet (ETH Zurich),
Dr. Tristan Reekie (ETH Zurich), Geoffrey Schwertz (ETH
Zurich), and Przemyslaw Gawel (ETH Zurich) are acknowl-
edged for reviewing the manuscript. We thank Oliver Dumele
for helpful discussions regarding computations. The authors
would also like to thank Michael Solar for running X-ray
measurements.
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