Synthesis, properties, and redox behavior of ferrocenyl-1,1,4,4-tetracyano-1,3-butadienes connected by arylamine and azobenzene spacers

Article abstract of DOI:10.1246/bcsj.20150165

Ferrocene-substituted 1,1,4,4-tetracyano-1,3-butadienes (FcTCBDs) connected by arylamine and azobenzene spacers were prepared by the reaction of a variety of alkynes with tetracyanoethylene (TCNE) in a [2 + 2] cycloaddition, followed by retroelectrocycliz

Full text of DOI:10.1246/bcsj.20150165

Synthesis, Properties, and Redox Behavior of
Ferrocenyl-1,1,4,4-tetracyano-1,3-butadienes Connected by
Arylamine and Azobenzene Spacers
Taku Shoji,*1,2 Natsumi Kamata,1 Akifumi Maruyama,2 Shunji Ito,3 and Tetsuo Okujima4
1Department of Chemistry, Faculty of Science, Shinshu University, Matsumoto, Nagano 390-8621
2Department of Material Science, Graduate School of Science and Technology, Shinshu University,
Matsumoto, Nagano 390-8621
3Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561
4Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University,
Matsuyama, Ehime 790-8577
E-mail: tshoji@shinshu-u.ac.jp
Received: May 10, 2015; Accepted: June 10, 2015; Web Released: June 16, 2015
Ferrocene-substituted 1,1,4,4-tetracyano-1,3-butadienes (FcTCBDs) connected by arylamine and azobenzene
spacers were prepared by the reaction of a variety of alkynes with tetracyanoethylene (TCNE) in a [2 + 2] cycloaddition,
followed by retroelectrocyclization of the initially formed [2 + 2] cycloadducts (i.e., cyclobutene derivatives). The
characteristic intramolecular charge transfer (ICT) from the donors (ferrocene and arylamine) to the acceptor (TCBD)
moieties was investigated by using UV-vis spectroscopy. The redox behaviors of the FcTCBDs were examined by cyclic
voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their promising redox properties with multi-
electron transfer depending on the number of FcTCBD moieties in the molecules. Moreover, significant color changes
were observed by visible spectroscopy under the electrochemical reduction conditions.
retroelectrocyclization (CA-RE) of the corresponding alkynes
with TCNE. Especially, TCBD derivatives substituted by aryl-
Introduction
Ferrocene has attracted interest due to its facile redox
properties, with a rather low oxidation potential that allows it to
form a stabilized positively charged state (ferrocenium ion). A
large number of donor-acceptor systems possessing a ferro-
cenyl-donor group have been synthesized and their properties
represented by their characteristic amphoteric redox properties
have been extensively studied.1
In 2002, Mochida and Yamazaki reported that the reaction of
ethynylferrocene derivatives with tetracyanoethylene (TCNE)
afforded formal [2 + 2] cycloaddition products, namely, cyclo-
butene derivatives, which exhibited a ring-opening reaction
to give the corresponding ferrocenyl-1,1,4,4-tetracyano-1,3-
butadienes (FcTCBDs).2 In recent years, several groups have
reported the synthesis and properties of FcTCBD deriva-
tives connected with various π-electron systems.3 Especially,
Diederich et al. have extensively studied these types of mole-
cules as a new class of ICT chromophores.4 A variety of
FcTCBD derivatives, which exhibit promising nonlinear opti-
cal properties, have been prepared by the reaction of alkynes
and butadiynes substituted by the ferrocenyl group with TCNE.
We have also reported the synthesis and electrochemical
properties of TCBD derivatives with various aromatic sub-
stituents (e.g., azulenyl,5 arylamino,6 2-oxo-2H-cyclohepta[b]-
3-furyl,7 and ferrocenyl8 groups) by the [2 + 2] cycloaddition-
amino6 and ferrocenyl8 groups showed electrochromic prop-
erties with rather high reversibility in the redox cycles. For
this reason, the TCBD derivatives with both ferrocenyl and
arylamino groups should exhibit highly stabilized redox cycles
and improve their electrochromic properties, rather than TCBD
derivatives substituted by either ferrocenyl or arylamino group.
Moreover, systematic investigation of the effect of the aryl-
amine cores toward the FcTCBD derivatives has not yet been
explored, although the optical and electrochemical properties
of the TCBD derivatives could be strongly affected by the
substituted π-electron systems. An intensive investigation of
the effect of arylamine cores connected to the FcTCBD units
should provide useful information for the creation of electronic
devices utilizing their amphoteric redox properties.
Herein, we describe the palladium-catalyzed synthesis of
ferrocene-substituted alkyne derivatives connected by several
arylamine cores and the transformation to that with an
azobenzene core, as well as the application of the alkyne
derivatives to the [2 + 2] CA-RE reaction with TCNE to afford
novel FcTCBD derivatives. The electronic properties of the
novel FcTCBD derivatives connected by the arylamine cores
in addition to that with an azobenzene core were examined by
absorption spectroscopy, electrochemical analysis, and spec-
troelectrochemical measurements.
1338 | Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan

cursors 3 and 4 with TCNE (Schemes 2 and 3). Tris-FcTCBD
10 with a triphenylamine core was also obtained in 81% yield
by the [2 + 2] CA-RE reaction of the corresponding tri-alkyne
5 with TCNE (Scheme 4). The reaction of 6 with TCNE in
CH2Cl2 gave 11 in 59% yield in spite of the existence of an
electron-withdrawing azo group between the para positions on
the two benzene rings (Scheme 5).
Spectroscopic Properties. These new FcTCBDs were fully
characterized based on their spectral data, as summarized in
the Experimental Section. The NMR spectroscopic assignment
of the reported compounds was confirmed by COSY, HMQC,
and HMBC experiments. High-resolution mass spectra of 7-11
ionized by FAB showed the correct molecular ion peaks. The
characteristic stretching vibration band of the C¸N moiety of
the FcTCBDs 7-11 was observed at ¯max = 2222-2226 cm¹1 in
their IR spectra. These results are consistent with the structures
of the products. UV-vis spectra of FcTCBDs 7-11 are shown
in Figure 1. The absorption maxima and coefficients (log ¾) of
the FcTCBDs 7-11 in CH2Cl2 and in the mixed hexane solvent
with certain amounts of CH2Cl2 to maintain their solubility are
summarized in Table 1.
UV-vis spectra of FcTCBDs 7-11 showed characteristic
weak absorption bands arising from the presumed ICT absorp-
tion between ferrocene and TCBD units in the visible region.
Absorption bands in the visible region of these compounds
displayed slight bathochromic shifts, along with the increment
of extinction coefficients with the number of substituted
FcTCBD unit. These results suggest that multiple FcTCBD
moieties with arylamine cores expand the π-conjugation
through the nitrogen atom of central arylamine cores. When
the solvent was changed from CH2Cl2 to the mixed CH2Cl2/
Results and Discussion
Synthesis. Preparation of ethynylferrocene derivatives with
arylamine core 2-5 was accomplished by palladium-catalyzed
alkynylation of iodoarylamines with ethynylferrocene (1) under
Sonogashira-Hagihara conditions.9 Synthesis of azobenzene
derivative 6 was also established by Cu-catalyzed homo-
coupling of 2 under the conditions reported by Zhang and
Jiao.10
Cross-coupling of 1 with 4-iodoaniline in the presence of
[Pd(PPh3)4] catalyst in Et3N/THF at 50 °C afforded 4-(ferro-
cenylethynyl)aniline (2) in 58% yield (Scheme 1).11 Cross-
coupling of 1 with 4,4¤-diiododiphenylamine using [Pd(PPh3)4]
as a catalyst and subsequent chromatographic purification
on silica gel afforded the desired 4,4¤-bis(ferrocenylethynyl)-
diphenylamine (3) in 65% yield (Scheme 2). Sonogashira-
Hagihara reaction of 1 with 3,6-diiodocarbazole afforded 4
in 96% yield (Scheme 3). Tris-adduct 5 was also prepared
by the reaction of 1 with 4,4¤,4¤¤-triiodotriphenylamine in
95% yield (Scheme 4).12 Azobenzene derivative 6 was ob-
tained by oxidative coupling of compound 2 in the presence
of CuBr/pyridine catalyst in almost quantitative yield (99%,
Scheme 5).
For the synthesis of the FcTCBD derivatives connected by
arylamine core, the [2 + 2] CA-RE reaction of 2-6 with TCNE
was conducted according to the previously described proce-
dure.2-8 The reaction of 2 with TCNE in CH2Cl2 at room
temperature yielded 7 in 64% yield (Scheme 1). Bis-FcTCBD
chromophores 8 and 9, which bear diphenylamine and carba-
zole spacer, were obtained in 87% and 93% yields, respec-
tively, by the [2 + 2] CA-RE of bis(ethynylferrocene) pre-
NC
CN
I
NH2
CN
NC
[Pd(PPh3)4], CuI
NC
CH2Cl2
room temperature
CN
NH2
NH2
THF, Et3N, 50 °C
58%
Fe
Fe
1
Fe
2
CN
64%
NC
7
Scheme 1. Synthesis and [2 + 2] CA-RE reaction of compound 2.
H
N
H
N
H
N
NC
NC
CN
CN
CN
NC
NC
CN
I
I
[Pd(PPh3)4], CuI
1
Fe
THF, Et3N, 50 °C
65%
CH2Cl2, reflux
87%
Fe
CN
NC
8
NC
CN
Fe
Fe
3
Scheme 2. Synthesis and [2 + 2] CA-RE reaction of compound 3.
H
N
H
N
NC
NC
CN
CN
H
N
CN
NC
NC
Fe
CN
I
I
[Pd(PPh3)4], CuI
1
Fe
THF, Et3N, 50 °C
96%
CH2Cl2, reflux
93%
9
CN
NC
NC
CN
Fe
Fe
4
Scheme 3. Synthesis and [2 + 2] CA-RE reaction of compound 4.
Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan | 1339

I
Fe
Fe
CN
CN
NC
N
CN
NC
NC
CN
CN
I
I
[Pd(PPh3)4], CuI
1
N
N
NC
CN
Fe
THF, Et3N, 50 °C
95%
CN
CH2Cl2, reflux
81%
NC
Fe
CN
NC
CN
Fe
5
CN
10
Fe
Scheme 4. Synthesis and [2 + 2] CA-RE reaction of compound 5.
CN
NC
NC
NC
CN
CN
Fe
CN
CuBr, pyridine
NC
N
N
N
2
CN
N
Fe
toluene, 60 °C
99%
CH2Cl2, reflux
59%
NC
Fe
Fe
CN
11
6
NC
Scheme 5. Synthesis and [2 + 2] CA-RE reaction of compound 6.
Table 1. Absorption maxima [nm] and their coefficients
(log ¾) in visible region of the FcTCBDs 7-11 in CH2Cl2
and in hexanea), along with those of FcTCBDs 12-14 as
references
Sample
-
max
(log ¾) in CH2Cl2
-
max
(log ¾) in hexane
7
8
9
10
11
122
1314
148c
421 (4.29), 617 (3.41)
475 (4.71), 620 (3.76)
423 (4.32), 631 (3.62)
480 (4.64), 624 (3.82)
615 (3.65)
632 (3.32)
481 (3.85)
469 (4.45), 626 (3.45)
403 (4.28), 597 (3.35)b)
461 (4.71), 610 (3.76)c)
414 (4.32), 621 (3.55)c)
469 (4.64), 610 (3.81)c)
600 (3.62)b)
a) CH2Cl2 was added to hexane to maintain solubility of the
compounds. b) Measured in 10% CH2Cl2/hexane. c) Measured
in 30% CH2Cl2/hexane.
Wavelength/nm
Figure 1. UV-vis spectra of 7 (blue line), 8 (red line),
9 (green line), 10 (purple broken line), and 11 (light-blue
broken line) in CH2Cl2.
reported that the FcTCBD 14 with N,N¤-dimethylanilino sub-
stituent showed a broad absorption band at -max = 626 nm in
CH2Cl2.8c Thus, the longest wavelength absorption band of the
FcTCBDs 7-10 could be ascribed to the ICT absorption from
ferrocene to the TCBD units.
On the other hand, the longest wavelength absorption of
8 and 10 resembles with that of TCBD 13 (-max = 481 nm)14
and FcTCBD 14 (-max = 469 nm)8c with N,N¤-dimethylanilino
substituent in the -max value. Therefore, the strong absorption
band at around 480 nm of the FcTCBDs 8 and 10 should be
ascribed to the ICT from arylamine moiety to the TCBD units
as shown in Scheme 6. In contrast compound 9 did not show
such a strong absorption band in the region probably due to the
less effective conjugation between the TCBD moieties and the
lone pair electrons of the nitrogen atom on the carbazole. Bis-
FcTCBD 11 showed a broad absorption band centered at
hexane solvent, the FcTCBD derivatives 7-11 showed
hypsochromical solvatochromism.
A noticeable spectral feature of 7 is the presence of a distinct
absorption band at 617 nm in CH2Cl2, in which compound
7 exhibits hypsochromic shift by 20 nm (-max = 597 nm) in
the less polar 10% CH2Cl2/hexane, suggesting the ICT nature
of this band.13 Bis-FcTCBD 9, with a carbazole core, exhibits
a broad absorption band at -max = 631 nm. Whereas, bis-
FcTCBD 8 and tris-FcTCBD 10 shows a strong absorption
band (8: -max = 475 nm; 10: -max = 480 nm) along with a
broad absorption similar with that of FcTCBDs 7 and 9.
Previously, Mochida et al. reported that simpler FcTCBD
derivative 12 exhibits a broad absorption centered at -max
=
632 nm in CH2Cl2 (Figure 2).2 More recently, we have also
1340 | Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan

CN
CN
CN
NC
NC
NC
H
H
R
Me2N
14: R = NMe2
15: R = H
16: R = NO2
Fe
Fe
CN
12
CN
13
CN
NC
NC
NC
Figure 2. TCBD derivatives with ferrocene and N,N-dimethylaniline substituent.
H
N
H
N
NC
CN
Fe2+
NC
Fe2+
CN
NC
CN
Fe2+
NC
Fe2+
CN
8
8"
NC
CN
8'
NC
CN
NC
CN
NC
CN
+e- -e-
H
N
NC
CN
Fe2+
NC
Fe2+
CN
8
NC
CN
NC
CN
+e- -e-
H
N
H
N
NC
CN
NC
Fe2+
CN
NC
CN
Fe2+
NC
Fe2+
CN
+2e-
-2e-
Fe2+
84
NC
Scheme 6. Plausible redox behavior of compound 8.
max = 615 nm and also strong absorption band at -max = 364
CN
NC
CN
82
NC
CN
NC
CN
-
nm that should correspond to the absorption of azobenzene
moiety.
Electrochemistry. To clarify the effect on the electrochem-
ical properties of aromatic substituents on the FcTCBD deriv-
atives 7-11, the redox behavior of the FcTCBD chromophores
7-11 was examined by CVand DPV. Cyclic voltammograms of
FcTCBDs 7 and 10 are shown in Figures 3 and 4, respectively.
Plausible redox behavior of FcTCBD 8 under the electrochem-
ical reduction conditions is illustrated in Scheme 6. The redox
potentials (in volts vs. Ag/AgNO3) of 7-11 measured under a
¹1
scan rate of 100 mV s are summarized in Table 2.
All of the FcTCBD chromophores 7-11 displayed a revers-
ible one-stage oxidation and a two- or three-stage reduction
wave on CV, due to the oxidation of the ferrocene moieties
and the reduction of the TCBD units, respectively. The first
oxidation wave of the FcTCBDs 7-11 was observed at a simi-
lar potential region (+0.54 to +0.58 V) on CV under the
electrochemical oxidation, which resembles that of simpler
FcTCBD 12 (+0.58 V).2 Thus, it should be concluded that
there is a less effective interaction between the ferrocene and
arylamine units separated by the TCBD unit, from the view
point of their oxidation potentials. In contrast to the oxidation,
the reduction of 7-11 was significantly affected by the nature
of core units, e.g., arylamine and azobenzene cores, connected
to the FcTCBD unit. FcTCBD chromophore 7 displayed a
Figure 3. Cyclic voltammogram of the reduction of 7
(1.0 mM) in benzonitrile containing Et4NClO4 (0.10 M) as
¹1
a supporting electrolyte; scan rate: 100 mV s
.
reversible two-stage reduction waves at ¹0.91 and ¹1.16 V
(Figure 3).
A reversible three-stage wave was observed by CV in bis-
FcTCBD 8 (¹0.78, ¹0.86, and ¹1.12 V), in which the third
reduction wave was a two-electron transfer in one step to form
a tetraanionic species. Electrochemical reduction of 9 showed a
reversible two-step reduction wave with half-wave potentials of
Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan | 1341

¹0.81 and ¹1.12 V, which could be attributed to the formation
of a radical dianionic and a tetraanionic species. Although the
bis-FcTCBD 8 has a symmetrical structure, two TCBD units
showed a stepwise reduction by CV, which should be attributed
to the stepwise reduction to a tetraanionic species as shown in
Scheme 6.2,8c This means the existence of redox interaction
between the intramolecular two FcTCBD moieties through
the diphenylamine spacer. On the other hand, bis-FcTCBD 9
displayed a two-step reduction wave, with respect to its
symmetrical structure. This result might be implied to the less
effective conjugation between the two FcTCBD units through
the carbazole spacer.
case, since the first reduction potential of the FcTCBDs 7-11
decreased according to the number of TCBD units in the mole-
cules, the connected TCBD units behaved as electron-with-
drawing group and increased the electron accepting property by
effective conjugation through the central arylamine cores. Bis-
FcTCBD 11 with an azobenezene core exhibited less negative
first reduction potential on CV (¹0.67 V), compared with those
of bis-FcTCBDs 7-10. Moreover, first reduction potential of
bis-FcTCBD 11 is comparable to that of FcTCBD 16 (¹0.64 V)
with an electron-withdrawing p-nitro substituent. These results
should be ascribed to the electron-withdrawing nature of the
azobenzene core.
The electrochemical reduction of tris-FcTCBD 10 also
exhibited a reversible three-step reduction wave, whose poten-
tials were identified as ¹0.73, ¹0.83, and ¹1.10 V by CV as
half-wave potentials (Figure 4). Recently, we reported the first
reduction potential of FcTCBDs 14-16 was dependant on the
nature of the para substituent on the aromatic ring.8c In this
Electrochromism is observed in reversible redox systems
that exhibit significant color changes in different oxidation
states. Stabilization of the redox cycle is very important in the
construction of electrochromic materials because the mole-
cules that are utilized for this application require high redox
stabilities.15
We have reported the synthesis of various redox-active
TCBD chromophores with the aim of creating stabilized
electrochromic materials.16 In these studies, we found the
FcTCBD units connected with the π-electron systems exhib-
ited electrochromism with rather high reversibility in which
the strong absorption bands spread into visible and/or near-
infrared regions under the electrochemical reduction condi-
tions.8 Similar to the FcTCBD derivatives reported by us pre-
viously, these FcTCBDs 7-11 should become another example
of the redox systems as the extension of the hybrid structures of
violenes and cyanines with multi-electron transfer proposed by
Hünig et al.17 Thus, the visible spectra of 7-11 were monitored
to clarify the color changes during the electrochemical reac-
tions. Constant-voltage oxidation and reduction was applied
to the solutions of 7-11 with a platinum mesh as the working
electrode and a wire counter electrode in an electrolytic cell
of 1 mm thickness. Visible spectra were measured in degassed
benzonitrile containing Et4NClO4 (0.1 M) as a supporting
Figure 4. Cyclic voltammogram of the reduction of 10
(1.0 mM) in benzonitrile containing Et4NClO4 (0.10 M) as
¹1
a supporting electrolyte; scan rate: 100 mV s
.
Table 2. Redox potentialsa),b) of the FcTCBD derivatives 7-11
Sample
Method
E1ox/V
E2ox/V
E1red/V
E2red/V
E3red/V
¹
¹
7
CV
(DPV)
CV
(DPV)
CV
(DPV)
CV
+0.54
(+0.52)
+0.57
(+0.55)
+0.57
(+0.55)
+0.57
(+0.55)
+0.58
¹0.91 (1e )
(¹0.89)
¹1.16 (1e )
(¹1.14)
(+1.08)
(+1.21)
(+1.24)
(+1.26)
¹
¹
¹
8
¹0.78 (1e )
¹0.86 (1e )
¹1.12 (2e )
(¹1.10)
(¹0.76)
(¹0.84)
¹
¹
9
¹0.81 (2e )
¹1.12 (2e )
(¹0.79)
(¹1.10)
¹
¹
¹
10
¹0.73 (2e )
¹0.83 (1e )
¹1.10 (3e )
(DPV)
CV
(¹0.71)
(¹0.81)
(¹1.08)
¹
¹
11
¹0.67 (2e )
¹1.08 (2e )
(DPV)
CV
(DPV)
CV
(DPV)
CV
(+0.56)
+0.55
(+0.53)
+0.59
(+0.57)
+0.61
(¹0.65)
¹0.95
(¹0.93)
¹0.78
(¹0.76)
¹0.64
(¹1.06)
¹1.20
(¹1.18)
¹1.10
(¹1.08)
¹0.97
(¹1.73)
148c
158c
168c
(DPV)
(+0.59)
(¹0.62)
(¹0.95)
a) V versus Ag/AgNO3, 1.0 mM in benzonitrile containing Et4NClO4 (0.10 M), Pt electrode (internal
¹1
diameter: 1.6 mm), scan rate: 100 mV s and internal reference (Fc/Fc+ = +0.15 V). b) Half-wave
potentials Eox and Ered = (Epc + Epa)/2 on CV, Epc, and Epa correspond to the cathodic and anodic peak
potentials, respectively.
1342 | Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan

¹1.50 V. At the beginning in the two-stage color changes, new
absorptions in the visible region at 630 nm gradually developed
in a different way by the reduction at ¹1.00 V, and the new
absorption band was gradually decreased by further reduc-
tion at the same voltage (Figures S-19, top). Although good
reversibility was observed by CV, reverse oxidation of the
reduced solution did not regenerate the spectrum of 9
(Figures S-19, bottom). The poor reversibility for the electro-
chromisms of 8 and 9 might be attributable to the decom-
position of the anionic species produced by the electrochemical
reduction, instead of regeneration of the parents 8 and 9. When
the visible spectra of tris-FcTCBD 10 were monitored under
the electrochemical reduction conditions at ¹1.00 and ¹1.50 V,
the absorption band in the visible region that spread into the
near-infrared region gradually developed along with a color
change from brown to pale yellow (Figures S-21, top). Reverse
oxidation of the reduced species regenerated the original color
of 10 (Figure S-21, bottom). Reversible color change from red
to blue was observed in bis-FcTCBD 11 with an azobenzene
spacer. The absorption band in the visible region of 11 grad-
ually increased with the development of new absorption bands
in the near-infrared region along during the electrochemical
reduction at ¹1.00 and ¹1.50 V. Reverse oxidation of the
reduced species decreased the new absorption bands, along
with recovery of the original spectrum of 11.
Wavelength/nm
Conclusion
A series of ethynylferrocene derivatives 2-5 with an aryl-
amine core were prepared by palladium-catalyzed Sonogashira-
Hagihara reaction. The derivative with azobenzene core 6 was
also prepared by the Cu-mediated homo-coupling reaction of 2
in excellent yield. The FcTCBDs 7-11 connected by arylamine
and azobenzene cores were synthesized in a one-step procedure
consisting of formal [2 + 2] cycloaddition reaction of alkynes
2-6 with TCNE, followed by retroelectrocyclization of the
initially formed cyclobutene derivatives. Intramolecular CT
absorption bands were found in UV-vis spectra of the FcTCBD
chromophores 7-11. Analyses by CV and DPV showed that
the FcTCBDs 7-11 exhibited a reversible multi-stage reduc-
tion wave, as well as a reversible one-stage oxidation wave.
Moreover, significant color changes of the FcTCBDs were
observed during the electrochemical reduction. In particular,
FcTCBD 8 constructed by diphenylamine spacer exhibited
significant color changes, attributable to the generation of di-
and tetraanionic species during the electrochemical reaction.
To evaluate the scope of this class of molecules investigated
by this research, the preparation of novel TCBD chromophores
connected with various π-electron cores is now in progress in
our laboratory.
Wavelength/nm
Figure 5. Continuous change in the visible spectrum of 8
under constant voltage electrochemical reduction (¹1.00 V,
top) and further electrochemical reduction (¹1.50 V, bot-
tom) in benzonitrile containing Et4NClO4 (0.10 M) at 20 s
intervals.
electrolyte at room temperature under the electrochemical
reaction conditions.
The absorption band of 7 in the visible region gradually
increased and the color of the solution changed from green
to yellow during the electrochemical reduction at ¹1.08 and
¹1.40 V (Figures S-15, top). Reversible oxidation of the
yellow solution regenerated the original color and spectrum
of the compound along with the isosbestic point at 495
nm (Figure S-15, bottom). Similarly, the green color of the
solution of bis-FcTCBD 8 changed to pale-blue during the
electrochemical reduction at ¹1.00 V, and further reduction
at ¹1.50 V of the pale-blue solution turned to deep-blue
together with the development of absorption at around 750 nm
(Figure 5). Reversible oxidation of the deep-blue solution
exhibited further development of the new absorption band at
around 750 nm, instead of the regeneration of the original
spectrum of the compound. When the UV-vis spectrum of bis-
FcTCBD 9 was measured under the electrochemical reduction
conditions (¹1.00 V), a new absorption band in the visible
region at around 630 nm gradually developed. Following the
spectral change, further two-stage color changes were observed
in the visible spectra of 9 by the electrochemical reduction at
Experimental
General.
Melting points were determined with a
Yanagimoto MPS3 micromelting apparatus, and the solvent
in the parenthesis shows the solvent used for recrystallization.
The HRMS data were obtained with a JEOL JMS-700 instru-
ment using 3-nitrobenzylalcohol as a matrix for FAB-MS. The
IR and UV-vis spectra were recorded with JASCO FTIR-
1
4100 and Shimadzu UV-2550 spectrophotometers. The H and
13C NMR spectra were recorded with a JEOL ECA500 spec-
Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan | 1343

trometer at 500 and 125 MHz, respectively. The voltammetry
measurements were performed with a BAS 100B/W elec-
trochemical workstation equipped and with a standard three-
electrode configuration and all measurements were carried out
under an argon atmosphere. Tetraethylammonium perchlorate
(0.10 M) in benzonitrile was used as a supporting electrolyte,
with a platinum wire auxiliary and disk working electrodes.
Reference electrode was formed from Ag/AgNO3 (0.01 M)
in acetonitrile containing tetrabutylammonium perchlorate
(0.10 M). The half-wave potential of the ferrocene/ferrocenium
ion couple (Fc/Fc+) under these conditions using this reference
electrode was observed at +0.15 V on CV. Accuracy of the
reference electrode was confirmed by CV measurements of the
couple in each sample as an internal ferrocene standard.
4-(Ferrocenylethynyl)aniline (2).11 To a solution of 1
(466 mg, 2.22 mmol), 4-iodoaniline (725 mg, 3.31 mmol), and
CuI (45 mg, 0.24 mmol) in triethylamine (10 mL) and THF
(10 mL) was added tetrakis(triphenylphosphine)palladium(0)
(69 mg, 0.06 mmol). The resulting mixture was stirred at 50 °C
for 22 h under an Ar atmosphere. The reaction mixture was
poured into a 10% NH4Cl solution and extracted with CH2Cl2.
The organic layer was washed with brine, dried with Na2SO4,
and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with CH2Cl2
to give 2 (389 mg, 58%) as orange crystals. Mp 185.0-
189.0 °C, decomp. (CH2Cl2), lit.: 186-188 °C;11 1H NMR (500
MHz, CDCl3): ¤H 7.28 (d, 2H, J = 8.5 Hz, 3,5-H of C6H4), 6.61
(d, 2H, J = 8.5 Hz, 2,6-H of C6H4), 4.45 (dd, 2H, J = 1.5,
1.5 Hz, Fc), 4.22 (s, 5H, Cp), 4.19 (dd, 2H, J = 1.5, 1.5 Hz, Fc),
3.77 (br. s, 2H, NH2).
mixture was poured into a 10% NH4Cl solution and extracted
with CH2Cl2. The organic layer was washed with brine, dried
with Na2SO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel
with CH2Cl2 to give 4 (560 mg, 96%) as orange crystals. Mp
220.0-221.0 °C, decomp. (CHCl3/EtOH); IR (ATR): ¯max
=
3394 (s), 3114 (w), 2203 (w), 1749 (w), 1618 (w), 1600 (w),
1575 (w), 1519 (w), 1494 (s), 1453 (m), 1436 (w), 1415 (w),
1389 (w), 1320 (w), 1295 (w), 1284 (m), 1238 (s), 1203 (w),
1160 (w), 1135 (w), 1106 (m), 1059 (w), 1032 (m), 1022 (m),
1006 (m), 948 (w), 923 (m), 893 (s), 846 (s), 818 (s), 810 (s),
787 (w), 775 (w), 761 (w), 752 (w), 734 (w), 722 (w), 714 (w),
1
707 (w), 697 (w), 671 (w), 659 (w) cm¹1; H NMR (500 MHz,
CDCl3): ¤H 8.22 (s, 2H, 4,5-H of Cz), 8.20 (s, 1H, NH of
Cz), 7.56 (dd, 2H, J = 8.5, 1.5 Hz, 2,7-H of Cz), 7.38 (br. d,
2H, J = 8.5 Hz, 1,8-H of Cz), 4.54 (dd, 4H, J = 1.8, 1.8 Hz,
Fc), 4.28 (s, 10H, Cp), 4.25 (dd, 4H, J = 1.8, 1.8 Hz, Fc);
Low solubility hampered the measurement of 13C NMR;
HRMS (FAB): calcd for C36H25Fe2N+ [M]+ 583.0686; found:
583.0686.
4,4¤,4¤¤-Tris(ferrocenylethynyl)triphenylamine (5).12 To a
solution of 1 (946 mg, 4.50 mmol), tris(4-iodophenyl)amine
(632 mg, 1.00 mmol), and CuI (57 mg, 0.30 mmol) in triethyl-
amine (10 mL) and THF (10 mL) was added tetrakis(triphenyl-
phosphine)palladium(0) (90 mg, 0.08 mmol). The resulting
mixture was stirred at 50 °C for 5 h under an Ar atmosphere.
The reaction mixture was poured into a 10% NH4Cl solution
and extracted with CH2Cl2. The organic layer was washed with
brine, dried with Na2SO4, and concentrated under reduced
pressure. The residue was purified by column chromatography
on silica gel with CH2Cl2 to give 5 (828 mg, 95%) as orange
crystals. Mp 158.0-161.0 °C, decomp. (CH2Cl2); Melting point
is not shown in the literature;12 1H NMR (500 MHz, CDCl3): ¤H
7.37 (d, 6H, J = 8.5 Hz, 3,3¤,3¤¤-H of C6H4), 7.03 (d, 6H, J =
8.5 Hz, 2,2¤,2¤¤-H of C6H4), 4.48 (dd, 6H, J = 2.0, 2.0 Hz, Fc),
4.24 (s, 15H, Cp), 4.23 (dd, 6H, J = 2.0, 2.0 Hz, Fc).
4,4¤-Bis(ferrocenylethynyl)azobenzene (6). To a solution
of 2 (218 mg, 0.72 mmol) in toluene (10 mL) was added CuBr
(10 mg, 0.07 mmol) and pyridine (31 mg, 0.39 mmol). The
resulting mixture was stirred at 60 °C for 22 h under air. The
reaction mixture was poured into water and extracted with
CH2Cl2. The organic layer was washed with brine, dried with
Na2SO4, and concentrated under reduced pressure. The residue
was purified by column chromatography on silica gel with
CH2Cl2 to give 6 (216 mg, 99%) as red crystals. Mp 183.0-
187.0 °C, decomp. (CH2Cl2); IR (ATR): ¯max = 3093 (w), 2201
(m), 1594 (s), 1556 (w), 1520 (w), 1503 (m), 1457 (w), 1411
(m), 1298 (w), 1286 (w), 1227 (w), 1152 (m), 1106 (m), 1038
(m), 1019 (m), 1000 (m), 927 (m), 895 (m), 877 (w), 855 (s),
823 (s), 811 (s), 780 (w), 758 (m), 748 (m), 733 (m), 718 (m),
693 (m), 683 (m), 675 (m), 664 (w), 655 (w) cm¹1; UV-vis
(CH2Cl2): -max (log ¾) = 260 (4.53), 292 sh (4.54), 334 (4.74),
465 (4.55), 626 sh (3.06), 690 sh (2.49) nm; 1H NMR (500 MHz,
CDCl3): ¤H 7.89 (d, 4H, J = 8.5 Hz, 2,6,2¤,6¤-H of C6H4), 7.61
(d, 4H, J = 8.5 Hz, 3,5,3¤,5¤-H of C6H4), 4.55 (br. s, 4H, Fc),
4.29 (br. s, 4H, Fc), 4.28 (s, 10H, Cp); 13C NMR (125 MHz,
CDCl3): ¤C 151.77 (C-1,1¤ of C6H4), 132.30 (C-3,5,3¤,5¤ of
C6H4), 127.19 (C-4,4¤ of C6H4), 123.16 (C-2,6,2¤,6¤ of C6H4),
91.90 (C¸C), 86.05 (C¸C), 71.80 (CH of Fc), 70.25 (Cp of Fc),
4,4¤-Bis(ferrocenylethynyl)diphenylamine (3). To a solu-
tion of 1 (258 mg, 1.23 mmol), bis(4-iodophenyl)amine (210
mg, 0.50 mmol), and CuI (19 mg, 0.10 mmol) in triethylamine
(10 mL) and THF (10 mL) was added tetrakis(triphenylphos-
phine)palladium(0) (58 mg, 0.05 mmol). The resulting mixture
was stirred at 50 °C for 22 h under an Ar atmosphere. The
reaction mixture was poured into a 10% NH4Cl solution and
extracted with CH2Cl2. The organic layer was washed with
brine, dried with Na2SO4, and concentrated under reduced
pressure. The residue was purified by column chromatography
on silica gel with CH2Cl2 to give 3 (189 mg, 65%) as orange
crystals. Mp 164.0-166.0 °C (CHCl3/EtOH); IR (ATR): ¯max
=
3389 (w), 3087 (w), 2203 (w), 1599 (s), 1578 (w), 1518 (s),
1483 (w), 1459 (w), 1436 (w), 1412 (w), 1397 (w), 1378 (w),
1318 (s), 1237 (w), 1204 (w), 1182 (w), 1160 (w), 1107 (m),
1058 (w), 1029 (w), 1001 (m), 925 (m), 877 (w), 814 (s), 752
(w), 723 (w), 714 (w), 691 (w), 676 (w), 669 (w), 661
1
(w) cm¹1; H NMR (500 MHz, CDCl3): ¤H 7.40 (d, 4H, J =
8.7 Hz, 3,3¤,3¤¤-H of C6H4), 7.03 (d, 4H, J = 8.7 Hz, 2,2¤,2¤¤-H
of C6H4), 4.49 (dd, 4H, J = 1.8, 1.8 Hz, Fc), 4.25 (s, 10H, Cp),
4.23 (dd, 4H, J = 1.8, 1.8 Hz, Fc); Low solubility hampered
the measurement of 13C NMR; HRMS (FAB): calcd for
C36H27Fe2N+ [M]+ 585.0842; found: 585.0843.
3,6-Bis(ferrocenylethynyl)carbazole (4). To a solution
of 1 (638 mg, 3.04 mmol), 3,6-diiodocarbazole (419 mg, 1.00
mmol), and CuI (38 mg, 0.20 mmol) in triethylamine (10 mL)
and THF (10 mL) was added tetrakis(triphenylphosphine)-
palladium(0) (68 mg, 0.06 mmol). The resulting mixture was
stirred at 50 °C for 20 h under an Ar atmosphere. The reaction
1344 | Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan

69.29 (CH of Fc), 65.17 (ipso-C of Fc); HRMS (FAB): calcd for
solution of 4 (291 mg, 0.50 mmol) in CH2Cl2 (10 mL). The
resulting mixture was refluxed for 22 h under an Ar atmos-
phere. The solvent was removed under reduced pressure. The
residue was purified by column chromatography on silica gel
with CH2Cl2 to give 9 (391 mg, 93%) as green crystals. Mp
+
C36H26Fe2N2 [M]+ 598.0795; found: 598.0783.
4-(1,1,4,4-Tetracyano-2-ferrocenyl-1,3-butadien-3-yl)-
aniline (7). TCNE (127 mg, 0.98 mmol) was added to a solu-
tion of 2 (148 mg, 0.49 mmol) in CH2Cl2 (5 mL). The resulting
mixture was stirred for 1 h at room temperature under an Ar
atmosphere. The solvent was removed under reduced pressure.
The residue was purified by column chromatography on silica
gel with CH2Cl2 to give 7 (136 mg, 64%) as green crystals. Mp
212.0-213.0 °C, decomp. (CH2Cl2/hexane); IR (ATR): ¯max
=
3403 (w), 2224 (w), 1631 (w), 1602 (w), 1525 (s), 1443 (w),
1411 (w), 1380 (w), 1332 (w), 1308 (w), 1254 (m), 1188 (w),
1146 (w), 1110 (w), 1045 (w), 1004 (w), 931 (w), 897 (w), 822
(m), 771 (w), 706 (w), 659 (w) cm¹1; UV-vis (CH2Cl2): -max
(log ¾) = 286 (4.44), 306 sh (4.43), 347 (4.44), 423 (4.32), 631
(3.62) nm; UV-vis (30% CH2Cl2/hexane): -max (log ¾) = 284
(4.45), 304 sh (4.42), 345 (4.43), 414 (4.32), 621 (3.55) nm;
1H NMR (500 MHz, CDCl3): ¤H 8.94 (s, 1H, NH), 8.38 (d, 1H,
J = 1.8 Hz, 4-H or 5-H of Cz), 8.33 (d, 1H, J = 1.8 Hz, 4-H
or 5-H of Cz), 7.80 (dd, 2H, J = 7.0, 7.0 Hz, 2,7-H of Cz),
7.55 (dd, 2H, J = 7.0, 7.0 Hz, 1,8-H of Cz), 5.33 (m, 2H, Fc),
5.02 (m, 1H, Fc), 5.00 (m, 1H, Fc), 4.87 (m, 1H, Fc), 4.85
(m, 1H, Fc), 4.69 (m, 2H, Fc), 4.48 (s, 5H, Cp), 4.45 (s, 5H,
Cp); Low solubility hampered the measurement of 13C NMR;
HRMS (FAB): calcd for C48H25Fe2N9+ [M]+ 839.0932; found:
839.0938.
4,4¤,4¤¤-Tris(1,1,4,4-tetracyano-2-ferrocenyl-1,3-butadien-
3-yl)triphenylamine (10). TCNE (116 mg, 0.91 mmol) was
added to a solution of 5 (174 mg, 0.20 mmol) in CH2Cl2 (10
mL). The resulting mixture was refluxed for 22 h under an Ar
atmosphere. The solvent was removed under reduced pressure.
The residue was purified by column chromatography on silica
gel with CH2Cl2 to give 10 (204 mg, 81%) as reddish brown
crystals. Mp 203.0-205.0 °C (CH2Cl2/hexane); IR (ATR):
244.0-246.0 °C, decomp. (CH2Cl2/hexane); IR (ATR): ¯max
=
3355 (m), 2960 (w), 2226 (w), 1632 (m), 1602 (s), 1518 (s),
1445 (s), 1336 (m), 1286 (s), 1213 (s), 1180 (s), 1126 (m), 1044
(m), 872 (m), 811 (s), 775 (m), 696 (m), 666 (m) cm¹1; UV-vis
(CH2Cl2): -max (log ¾) = 236 (4.22), 270 sh (4.06), 354 (4.32),
421 (4.29), 617 (3.41) nm; UV-vis (10% CH2Cl2/hexane):
-
max (log ¾) = 234 (4.19), 262 sh (4.07), 345 (4.33), 403 (4.28),
1
597 (3.35) nm; H NMR (500 MHz, CDCl3): ¤H 7.59 (d, 2H,
J = 8.9 Hz, 3,5-H of C6H4), 6.66 (d, 2H, J = 8.9 Hz, 2,6-H of
C6H4), 5.24 (m, 1H, Fc), 4.93 (m, 1H, Fc), 4.81 (m, 1H, Fc),
4.66 (m, 1H, Fc), 4.49 (br. s, 2H, NH2), 4.44 (s, 5H, Cp);
13C NMR (125 MHz, CDCl3): ¤C 173.92 [C=C(CN)2], 164.58
[C=C(CN)2], 152.72 (C-4 of C6H4), 132.22 (C-3,5 of C6H4),
120.41 (C-1 of C6H4), 114.84 (C-2,6 of C6H4), 113.95 (CN),
113.54 (CN), 113.15 (CN), 112.98 (CN), 79.65 [C(CN)2],
78.46 [C(CN)2], 76.17 (ipso-C of Fc), 75.33 (CH of Fc), 74.75
(CH of Fc), 72.56 (Cp of Fc), 72.16 (CH of Fc), 71.95 (CH of
+
Fc); HRMS (FAB): calcd for C24H15FeN5 [M]+ 429.0677;
found: 429.0670.
4,4¤-Bis(1,1,4,4-tetracyano-2-ferrocenyl-1,3-butadien-3-yl)-
diphenylamine (8). TCNE (119 mg, 0.93 mmol) was added
to a solution of 3 (182 mg, 0.31 mmol) in CH2Cl2 (10 mL). The
resulting mixture was refluxed for 22 h under an Ar atmosphere.
The solvent was removed under reduced pressure. The residue
was purified by column chromatography on silica gel with
CH2Cl2 to give 8 (227 mg, 87%) as red crystals. Mp 150.0-
153.0 °C (CH2Cl2/hexane); IR (ATR): ¯max = 3344 (w), 2224
(m), 1590 (m), 1506 (s), 1440 (m), 1415 (w), 1383 (w), 1333
(m), 1269 (m), 1181 (s), 1110 (w), 1047 (w), 1005 (w), 937 (w),
831 (m), 774 (w), 736 (w), 700 (w), 663 (w) cm¹1; UV-vis
(CH2Cl2): -max (log ¾) = 255 (4.52), 310 sh (4.41), 353 (4.55),
475 (4.71), 620 (3.76) nm; UV-vis (30% CH2Cl2/hexane): -max
(log ¾) = 253 (4.52), 310 sh (4.40), 349 (4.54), 461 (4.71), 610
¯
max = 3116 (w), 2224 (w), 1591 (m), 1523 (s), 1500 (s),
1442 (m), 1414 (w), 1382 (w), 1333 (m), 1298 (m), 1267 (m),
1198 (m), 1184 (m), 1109 (w), 1094 (w), 1043 (w), 1004 (w),
931 (w), 895 (w), 828 (s), 773 (m), 760 (w), 742 (w), 703 (w),
692 (w), 679 (m), 669 (m) cm¹1; UV-vis (CH2Cl2): -max
(log ¾) = 256 (4.58), 308 sh (4.54), 350 (4.54), 480 (4.64),
624 (3.82) nm; UV-vis (30% CH2Cl2/hexane): -max (log ¾) =
254 (4.57), 302 (4.51), 349 (4.53), 469 (4.64), 610 (3.81) nm;
1H NMR (500 MHz, CDCl3): ¤H 7.56 (br. d, 6H, J = 9.0 Hz,
3,5,3¤,5¤,3¤¤,5¤¤-H of C6H4), 7.12 (br. d, 6H, J = 9.0 Hz,
2,6,2¤,6¤,2¤¤,6¤¤-H of C6H4), 5.48 (br. s, 3H, Fc), 5.06 (br. s,
3H, Fc), 4.90 (br. s, 3H, Fc), 4.49 (br. s, 3H, Fc), 4.47 (s, 15H,
Cp); 13C NMR (125 MHz, CDCl3): ¤C 172.61 [C=C(CN)2],
164.31 [C=C(CN)2], 149.66 (C-4,4¤,4¤¤ of C6H4), 131.12 (C-
3,5,3¤,5¤,3¤¤,5¤¤ of C6H4), 127.53 (C-1,1¤,1¤¤ of C6H4), 125.03
(C-2,6,2¤,6¤,2¤¤,6¤¤ of C6H4), 113.57 (CN), 113.00 (CN), 112.08
(CN), 111.90 (CN), 84.65 [C(CN)2], 78.90 [C(CN)2], 76.37
(CH of Fc), 75.28 (CH of Fc), 75.12 (ipso-C of Fc), 73.02 (Cp
of Fc), 72.91 (CH of Fc), 71.26 (CH of Fc); HRMS (FAB):
1
(3.76) nm; H NMR (500 MHz, CDCl3): ¤H 7.63 (d, 4H, J =
8.8 Hz, 3,5,3¤5¤-H of C6H4), 7.17 (d, 4H, J = 8.8 Hz, 2,6,2¤,6-H
of C6H4), 6.89 (s, 1H, NH), 5.39 (br. s, 2H, Fc), 5.02 (br. s, 2H,
Fc), 4.86 (br. s, 2H, Fc), 4.55 (br. s, 2H, Fc), 4.45 (s, 10H, Cp);
13C NMR (125 MHz, CDCl3): ¤C 173.23 [C=C(CN)2 © 2],
164.44 [C=C(CN)2 © 2], 146.03 (C-4,4¤ of C6H4), 131.56 (C-
3,5 or C-3¤,5¤ of C6H4), 131.48 (C-3,5 or C-3¤,5¤ of C6H4),
124.65 (C-1,1¤ of C6H4), 118.41 (C-2,6 or C-2¤,6¤ of C6H4),
118.23 (C-2,6 or C-2¤,6¤ of C6H4), 113.77 (CN © 2), 113.13
(CN © 2), 112.75 (CN © 2), 112.41 (CN © 2), 82.12 [C(CN)2],
82.09 [C(CN)2], 78.89 ([C(CN)2] © 2), 76.19 (ipso-C of Fc),
75.92 (ipso-C of Fc), 75.37 (CH of Fc © 2), 75.34 (CH of Fc),
75.09 (CH of Fc), 72.85 (Cp of Fc), 72.81 (Cp of Fc), 72.61 (CH
of Fc), 72.52 (CH of Fc), 71.61 (CH of Fc © 2); HRMS (FAB):
+
calcd for C72H39Fe3N13 [M]+ 1253.1500; found: 1253.1468.
4,4¤-Bis(1,1,4,4-tetracyano-2-ferrocenyl-1,3-butadien-3-yl)-
azobenzene (11). TCNE (79 mg, 0.62 mmol) was added to a
solution of 6 (120 mg, 0.20 mmol) in CH2Cl2 (10 mL). The
resulting mixture was refluxed for 22 h under an Ar atmos-
phere. The solvent was removed under reduced pressure. The
residue was purified by column chromatography on silica gel
with CH2Cl2 to give 11 (101 mg, 59%) as dark green crystals.
Mp 160.0-162.0 °C, decomp. (CH2Cl2/hexane); IR (ATR):
+
calcd for C48H27Fe2N9 [M]+ 841.1088; found: 841.1109.
3,6-Bis(1,1,4,4-tetracyano-2-ferrocenyl-1,3-butadien-3-yl)-
carbazole (9). TCNE (193 mg, 1.51 mmol) was added to a
¯
max = 3109 (w), 2222 (m), 1591 (m), 1519 (s), 1444 (m), 1413
Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
© 2015 The Chemical Society of Japan | 1345

Diederich, J. Org. Chem. 2013, 78, 1760. d) C. Dengiz, B. Breiten,
J.-P. Gisselbrecht, C. Boudon, N. Trapp, W. B. Schweizer, F.
Diederich, J. Org. Chem. 2015, 80, 882.
(w), 1384 (w), 1334 (m), 1269 (m), 1181 (m), 1109 (w), 1046
(w), 1006 (w), 938 (w), 896 (w), 829 (m), 772 (m), 731 (w),
700 (w), 671 (m) cm¹1; UV-vis (CH2Cl2): -max (log ε) = 257
sh (4.32), 364 (4.73), 506 sh (3.53), 615 (3.65) nm; UV-vis
(10% CH2Cl2/hexane): -max (log ε) = 258 sh (4.28), 359
(4.71), 502 (3.54), 600 (3.62) nm; 1H NMR (500 MHz, CDCl3):
5
a) T. Shoji, S. Ito, K. Toyota, M. Yasunami, N. Morita,
Chem.®Eur. J. 2008, 14, 8398. b) T. Shoji, S. Ito, K. Toyota, T.
Iwamoto, M. Yasunami, N. Morita, Eur. J. Org. Chem. 2009, 4316.
c) T. Shoji, M. Maruyama, S. Ito, N. Morita, Bull. Chem. Soc. Jpn.
2012, 85, 761. d) T. Shoji, S. Ito, T. Okujima, N. Morita, Org.
Biomol. Chem. 2012, 10, 8308. e) T. Shoji, M. Maruyama, E.
Shimomura, A. Maruyama, S. Ito, T. Okujima, K. Toyota, N.
Morita, J. Org. Chem. 2013, 78, 12513. f) T. Shoji, M. Maruyama,
A. Maruyama, S. Ito, T. Okujima, K. Toyota, Chem.®Eur. J. 2014,
20, 11903.
¤
8.03 (d, 4H, J = 8.7 Hz, 2,6,2¤,6¤-H of C6H4), 7.78 (d,
H
4H, J = 8.7 Hz, 3,5,3¤,5¤-H of C6H4), 5.42 (br. s, 2H, Fc),
5.04 (br. s, 2H, Fc), 4.89 (br. s, 2H, Fc), 4.57 (br. s, 2H, Fc),
4.44 (s, 10H, Cp); 13C NMR (125 MHz, CDCl3): ¤C 172.07
[C=C(CN)2], 165.34 [C=C(CN)2], 154.69 (C-1 or C-4 of
C6H4), 134.11 (C-1 or C-4 of C6H4), 130.08 (C-3,5,3¤,5¤ of
C6H4), 124.49 (C-2,6,2¤,6¤ of C6H4), 113.67 (CN), 113.08
(CN), 111.54 (CN), 111.51 (CN), 87.49 [C(CN)2], 78.77
[C(CN)2], 76.35 (CH of Fc), 75.39 (CH of Fc), 74.72 (ipso-C
of Fc), 72.94 (Cp of Fc), 72.82 (CH of Fc), 71.46 (CH of Fc);
6
T. Shoji, E. Shimomura, M. Maruyama, A. Maruyama, S.
Ito, T. Okujima, K. Toyota, N. Morita, Eur. J. Org. Chem. 2013,
7785.
7
T. Shoji, J. Higashi, S. Ito, T. Okujima, M. Yasunami, N.
+
HRMS (FAB): calcd for C48H26Fe2N10 [M]+ 854.1041;
Morita, Chem.®Eur. J. 2011, 17, 5116.
found: 854.1070.
8
a) T. Shoji, S. Ito, T. Okujima, N. Morita, Eur. J. Org.
Chem. 2011, 5134. b) T. Shoji, S. Ito, T. Okujima, N. Morita,
Chem.®Eur. J. 2013, 19, 5721. c) T. Shoji, A. Maruyama, C.
Yaku, N. Kamata, S. Ito, T. Okujima, K. Toyota, Chem.®Eur. J.
2015, 21, 402.
This work was supported by the Ministry of Education,
Culture, Sports, Science and Technology, Japan through a
Grant-in-Aid for Research to T. S. (grant number 25810019).
We are grateful to Professor Dr. Hirosuke Tatsumi of Shinshu
University for valuable comments on electrochemical study.
9
a) K. Sonogashira, Coupling reactions between sp2 and sp
carbon centers in Comprehensive Organic Synthesis, ed. by B. M.
Trost, I. Fleming, Pergamon, Oxford, UK, 1991, Vol. 3, Chap. 2.4,
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Supporting Information
Figure of NMR, UV-vis spectra, cyclic and differential
pulse voltammograms of reported compounds. This material is
available electronically on J-STAGE.
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1346 | Bull. Chem. Soc. Jpn. 2015, 88, 1338–1346 | doi:10.1246/bcsj.20150165
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