Red or near-infrared light operating negative photochromism of a binaphthyl-bridged imidazole dimer

Article abstract of DOI:10.1021/jacs.0c02455

The development of red or near-infrared light (NIR) switchable photochromic molecules is required for an efficient utilization of sunlight and regulation of biological activities. While the photosensitization of photochromic molecules to red or NIR light has been achieved by a two-photon absorption process, the development of a molecule itself having sensitivity to red or NIR light has been now a challenging study. Herein, we developed an efficient molecular design for realizing red or NIR-light-responsive negative photochromism based on binaphthyl-bridged imidazole dimers. The introduction of electron-donating substituents shows the red shift of the absorption band at the visible-light region because of the contribution of a charge-transfer transition. Especially, the introduction of a di(4-methoxyphenyl)amino group (TPAOMe) and a perylenyl group largely shifts the absorption edge of the stable colored form to 900 nm. In addition, because the absorption band of one of the derivatives substituted with TPAOMe covers the whole visible-light region, the colored form shows a neutral gray color. Upon red (660 nm) or NIR-light (790 nm) irradiation, we observed the negative photochromic reaction from the stable colored form to the metastable colorless form. Therefore, the substituted binaphthyl-bridged imidazole dimers constitute the attractive photoswitches within a biological window.

Full text of DOI:10.1021/jacs.0c02455

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Article
Red or NIR Light Operating Negative Photochromism
of Binaphthyl-Bridged Imidazole Dimer
Aya Kometani, Yuki Inagaki, Katsuya Mutoh, and Jiro Abe
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.0c02455 • Publication Date (Web): 08 Apr 2020
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Page 1 of 28
Journal of the American Chemical Society
Red or NIR Light Operating Negative Photochromism of Binaphthyl-
Bridged Imidazole Dimer
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Aya Kometani, Yuki Inagaki, Katsuya Mutoh, and Jiro Abe*
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Department of Chemistry, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258,
Japan
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ABSTRACT: The development of red or near infrared light (NIR) switchable photochromic molecules is required for an
efficient utilization of sunlight and regulation of biological activities. While the photosensitization of photochromic
molecules to red or NIR light has been achieved by two-photon absorption process, the development of a molecule itself
having sensitivity to red or NIR light has been now a challenging study. Herein, we developed an efficient molecular design
for realizing red or NIR light responsive negative photochromism based on binaphthyl-bridged imidazole dimers. The
introduction of electron donating substituents shows the red-shift of the absorption band at visible light region because of
the contribution of a charge transfer transition. Especially, the introduction of a di(4-methoxyphenyl)amino group
(TPAOMe) and a perylenyl group largely shifts the absorption edge of the stable colored form to 900 nm. In addition,
because the absorption bands of one of the derivatives substituted with TPAOMe cover the whole visible-light region, the
colored form shows neutral gray color. Upon red (660 nm) or NIR light (790 nm) irradiation, we observed the negative
photochromic reaction from the stable colored form to the metastable colorless form. Therefore, the substituted
binaphthyl-bridged imidazole dimers constitute the attractive photoswitches within biological window.
INTRODUCTION
activation of the reversible photoswitches have been
reported.
Photochoromic molecules have received much attention
because of their ability to change the molecular and the
electronic structures by light. Several applications of
photochromic molecules have been reported in both
chemical and biological research fields for switching
Negative
photochromic
molecules
showing
photoisomerization from the initial stable colored form to
the thermally metastable colorless form are representative
visible light responsive photoswitches.24–31 Negative
photochromism has several advantages over usual
photochromism: utilization of energetically low toxic
visible light and deep penetration of excitation light inside
of materials. In addition, the negative photochromic
molecules can be essentially switched only by single-
wavelength light irradiation because the conversion ratio
of the negative photochromic reaction at the
photostationary state (PSS) can be adjusted by controlling
the intensity of the excitation light and the thermal back
reaction rate of the colorless form. The binaphthyl-bridged
imidazole dimer (BN-ImD) is a new class of negative
macroscopic
bending,
surface
polarity,
electric
conductivity, catalytic activity and biological functions.1–4
In general, photochromic molecules are classified into two-
types, P- and T-type. P-type photochromic molecules have
two thermally stable isomers, and the isomerization
between the two isomers is reversible upon
photoirradiation. On the other hand, one of the isomer of
T-type photochromic molecules is thermally unstable. In
particular, P-type photochromic molecules are suitable to
be used to photochemical control of the two functions by
using the thermal stability of the two isomers in the above
mentioned applications. T-type photochromic molecules
with rapid thermal back reactions will be applied to
photochromic lenses,5,6 fluorescence switching,7,8 real-time
holographic materials9,10 and be expected as a photo-
trigger to induce an instantaneous stimulus (μs–ms) to
systems such as retinal in rhodopsin protein.11 In both cases,
for biological applications, the photoswitching molecule is
required to have a photosensitivity to red or NIR light
within the first biological window (λ = 650–950 nm), while
UV light is frequently used for conventional photochromic
molecules. Multi-photon absorption process has been
usually used for the sensitization to red or NIR light by
increasing two-photon absorption cross section and the
introduction of the light-antenna units.12–18 In contrast, the
development of photochromic molecule itself showing the
one-photon absorption reaction upon NIR light irradiation
has been a challenging subject for organic molecular
chemists19–23 although some advances for visible light
photochromic
molecules
showing
the
efficient
decoloration upon visible light irradiation even in polar
solvents.32–35 The most thermally-stable colored form
photochemically generates the short-lived biradical
species (lifetime = a few tens of nanosecond) by the C–N
bond breaking upon visible light irradiation. The
generated biradical species has two thermal relaxation
pathways, one is the thermal back reaction to reproduce
the initial colored form and the other is the thermal
isomerization to the metastable colorless form. The
colorless form thermally goes back to the initial colored
form (Scheme 1).32 Although the rates of the thermal back
reaction from the colorless state to the colored state of the
negative photochromic reaction have been accelerated to
the millisecond or second time scales,36,37 the strategy for
tuning of the color and the photosensitivity has not been
established yet. Therefore, in this study, we investigated
the efficient substitutions to the binaphthyl unit and the
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Journal of the American Chemical Society
Page 2 of 28
Scheme 1. (a) Negative Photochromic Reaction Scheme of BN-ImD and the Molecular Structures of the BN-ImD Derivatives Substituted on
(b) the Binaphthyl Unit and (c) the Imidazole Unit.
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imidazole unit of BN-ImD for increasing the
photosensitivity to red or NIR light.
to investigate the substituent effect, i.e., the BN-ImD
derivatives (Scheme 1b) substituted with phenyl groups
(Ph), nitrophenyl groups (PhNO2), methoxyphenyl groups
(PhOMe), triphenylamino groups (TPA) or di(4-
methoxyphenyl)amino phenyl groups (TPAOMe1). In
addition, we also developed the BN-ImD derivatives
substituted with electron-donating groups to the
imidazole unit (Scheme 1c), the derivatives substituted to
the imidazole unit with di(4-methoxyphenyl)amino
phenyl groups (TPAOMe2) or di(4-methoxyphenyl)amino
perylene group (APery).
A plausible energy consideration to presume the longest
wavelength of the excitation light to induce
photochromism was suggested for T-type photochromic
molecules.22 The maximum red-shift to induce the T-type
photochromism can be considered to be related to the half-
life of the metastable state. If the energy level of the lowest
excited state is higher than the summation of the Gibbs
free energy difference (ΔG0) and the activation free energy
(ΔG‡) for the thermal back reaction, the ideal excitation
wavelength for the T-type photochromic molecule with a
half-life of seconds to minutes will be located around 1000–
1200 nm. However, because this consideration assumes
that the potential energy surface of the excited state is a
bond-dissociation type potential, it would be difficult to
presume the excitation energy for classic negative
photochromic molecules such as spiropyrans having a
predissociation type potential energy surface.38–40 In
contrast, this declares that the negative photochromic BN-
ImD is one of the ideal molecules to develop NIR
responsive photoswitches because the femtosecond
spectroscopic study and the electrochemical analysis of the
imidazole dimer derivatives have revealed the bond-
dissociation type potential energy surface of the lowest
excited singlet state.41–44
RESULTS AND DISCUSSION
Substitution Effect on the Bridging Binaphthyl Unit
Figure 1a shows the absorption spectra of BN-ImD, Ph,
PhNO2 and PhOMe in benzene at 298 K. The maximum
wavelength of the absorption band shows ca. 20-nm shift
to the longer wavelength by the introduction of the aryl
groups. The TDDFT calculation for Ph clearly shows the π-
conjugation of the diazafulvene unit extends to the
substituted phenyl ring (Figure S83). Moreover, it was
suggested that the introduction of electron-donating
groups is more efficient to induce the red-shift of the
absorption band than that of electron-withdrawing groups
because the absorption band of PhOMe is slightly red-
shifted, compared with that of PhNO2. The absorption
spectra of PhOMe, TPA and TPAOMe1 in benzene are
shown in Figure 1b. The introduction of TPA and TPAOMe
groups makes two absorption bands in the visible and NIR
light region and the absorption tail of TPAOMe1 reached
to 750 nm in benzene. It is noteworthy that TPAOMe1
absorbs the whole visible-light region, resulting in the
neutral gray color in the colored form. The changes in the
absorption spectra accompanied with the negative
photochromic reactions of the derivatives are shown in
Figures 2 and S54. The absorption bands at 545 nm and 577
nm of TPA and TPAOMe1, respectively, can be
characterized by the TDDFT calculations (MPW1PW91/6-
The characteristic absorption band at 500 nm of the
initial orange-colored form of BN-ImD can be assigned to
the ππ* transition on the diazafulvene chromophore by the
TDDFT calculation.32 This suggests that the expansion of
the π-conjugation of the diazafulvene unit is efficient to
induce the red-shift of the absorption band. In addition, a
donor-accepter interaction becomes an efficient strategy
for increasing the sensitivity to the long-wavelength light.
Therefore, we introduced different types of aryl groups
with electron-donating or -withdrawing natures to the
4,4’-positions of the binaphthyl unit which conjugate with
the diazafulvene chromophore in the colored form in order
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Page 3 of 28
Journal of the American Chemical Society
31+G(d,p)//MPW1PW91/6-31G(d) level of the theory). The of the electron-donating groups accelerated the thermal
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calculations revealed that the charge transfer (CT)
transition characters from the TPA or TPAOMe groups to
the diazafulvene unit (HOMO–2 → LUMO transition,
Figures S84 and S85) mainly contribute to the absorption
bands, indicating that the diazafulvene unit possesses an
electron-withdrawing nature. The absorption bands at 490
and 577 nm of TPAOMe1 efficiently disappeared upon 642
nm laser irradiation, and the color of the solution changes
from the gray to pale yellow by the negative photochromic
reaction at the PSS (Figure 2). To the best of our knowledge,
this is the first report of the negative photochromic
reaction from a neutral gray color to colorless only by a
single photochromic molecule although some examples of
the conventional positive photochromic molecules
showing a gray color have been reported.45–47 This negative
photochromic reaction can be repeated several times upon
visible light irradiation (Figure S57).
back reaction. The activation energies of the thermal back
reactions were estimated from the Eyring plots and
summarized in Table S2.
Since the absorption band at 577 nm of TPAOMe1 in
benzene is assigned to the CT transition, the positive
solvatochromism can be expected in polar solvents. We
carried out the TDDFT calculation of TPAOMe1 including
a solvent effect by the polarized continuum model (PCM–
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DFT,
MPW1PW91/6-31+G(d,p)//MPW1PW91/6-31G(d)
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level of the theory). The molecular structures were fully
optimized in benzene (ε = 2.247) and DMSO (ε = 46.7). The
theoretically calculated absorption spectra in benzene and
DMSO suggest that the absorption band characterized as
the CT transition shows the red shift to the NIR light region
in polar solvents (Figure S87). Figure 4 shows the
absorption spectra of TPAOMe1 in various solvents.
Although the absorption band at around 500 nm assigned
to the ππ* transition on the diazafulvene chromophore is
not affected by the solvent polarity, the CT absorption
band shifts to the longer wavelength region. In particular,
the absorption edge reaches to the wavelength at 850 nm
in DMSO due to the red-shift and broadening of the
absorption band, and the color of the solution changes to
blue. This NIR sensitivity beyond 800-nm light is
comparable to the longest wavelength sensitivity of the
molecule showing one-photon induced negative
photochromism reported to date.19–23 Upon NIR light (785
nm) irradiation, the absorption bands in visible light
region decreases by the photoisomerization to the
colorless form even in the polar solvents (Figure S55). The
thermal back reaction rates also depend on the solvent
polarity (Figure S79).
The maximum wavelengths of the stable colored forms
and the half-lives of the colorless forms in benzene at 298
K are summarized in Table 1. The time profiles of the
thermal recovery processes follow the first-order reaction
kinetics (Figure 3). The thermal back reaction of the
colorless form decelerated by the electron-withdrawing
nitro-phenyl group. On the other hand, the introduction
Table 1 The Maximum Wavelength of the Colored Form and the
Half-life of the Colorless Form at 298 K.
λmax (nm)
490
507
τ1/2 (min)
2.4
BN-ImD
Ph
1.5
PhNO2
PhOMe
TPA
513
4.5
516
1.3
Substitution Effect on the Imidazole Unit
545
1.4
The spectroscopic investigations of the BN-ImD
derivatives revealed the introduction of the electron-
TPAOMe1
TPAOMe2
APery
577
1.2
575
0.25
2.7
646
Figure 3. (a) The time profiles of the transient absorbance and (b)
the logarithm plots of the time profiles of the BN-ImD derivatives
in degassed benzene at 298 K.
Figure 1. The absorption spectra of BN-ImD, Ph, PhNO2,
PhOMe, TPA and TPAOMe1 in benzene.
Figure 4. The solvatochromic effect of the absorption spectra of
TPAOMe1 in various solvents.
ACS Paragon Plus Environment
Figure 2. Thermal absorption spectral change (time interval = 60
s) of TPAOMe1 (3.9×10
− 5
M) at 298 K in degassed benzene
recorded after irradiation with red light (642 nm, 34 mW).

Journal of the American Chemical Society
Page 4 of 28
donating group was efficient to induce the CT transition, tail of APery is slightly red-shifted to ca. 900 nm in polar
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leading to enhance the photosensitivity to red or NIR light.
Therefore, the BN-ImD derivatives having the strong
electron donor in the imidazole unit were also developed
and the photochromic properties were investigated in
detail.
solvent as shown in Figure S80.
The negative photochromic behaviors of TPAOMe2 and
APery in benzene are shown in Figure 6a. Upon red light
(660 nm) irradiation to TPAOMe2, the absorption band at
575 nm decreased and reached to the PSS, indicating the
photoisomerization from the colored form to the colorless
form. After ceasing red light irradiation, the absorption
band in the visible region gradually increases. The recovery
curve of the absorbance in the visible light region follows
the first-order kinetics and the half-life of the colorless
form is estimated to be 15 s in benzene at 298 K (Figures 7a
and 7b). This thermal back reaction of TPAOMe2 is 10
times faster than that of BN-ImD. This is the fastest
thermal back reaction in the BN-ImD system reported to
date. Therefore, the introduction of TPAOMe group to the
imidazole unit is also effective to accelerate the thermal
back reaction of the negative photochromism as similar to
the substitution to the bridging binaphthyl unit. However,
the absorption band was not completely disappeared at the
PSS in this condition because of the fast thermal back
reaction of the colorless form. Figure 6b shows the negative
photochromic reaction of APery. Upon red light
irradiation, the absorption band at around 700 nm
completely disappeared and recovered with a half-life of
2.7 min. at 298 K. In contrast, the intense absorption band
at 500 nm remained under light irradiation because this
absorption band is attributable to the localized ππ*
transition on the APery unit as discussed above. We also
demonstrated the photoswitching of APery using NIR
light as an excitation light source. As shown in Figure S55,
the absorption band at 700 nm decreases upon 790 nm
light irradiation, and therefore, this photochromism will
be applicable as a NIR light responsive photo-trigger.
Figure 5 shows the UV–Vis–NIR absorption spectra of
the colored forms of BN-ImD, TPAOMe2 and APery in
benzene at 298 K. The maximum wavelength of the
absorption band of TPAOMe2 shows ca. 85-nm shift to the
red-light region, compared with that of BN-ImD. The
absorption tail of TPAOMe2 reached to 750 nm. While the
absorption band at around 500 nm of BN-ImD can be
assigned to the π-π* transition, the TDDFT calculation
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(MPW1PW91/6-31+G(d)//MPW1PW91/6-31G(d))
of
TPAOMe2 demonstrated the contribution of the CT
transitions from the TPAOMe group to the diazafulvene
unit (HOMO–3 → LUMO transition, Figure S88). The
introduction of Apery unit is more efficient to make a new
absorption band assigned to the CT transition (HOMO–1
→ LUMO transition, Figure S89) in the NIR light region.
The absorption tail of APery reaches to ca. 850 nm owing
to the electron-donating ability of the APery unit. The
intense absorption band of APery at 500 nm is attributable
to the ππ* transition localized on the APery unit. Therefore,
these substitutions are quite effective to increase the NIR
light sensitivity even in apolar solvents. This absorption
The conversion efficiency of the Negative Photochromic
Reactions
Figure 5. The absorption spectra of BN-ImD, TPAOMe2 and
APery in benzene.
The conversion efficiencies from the colored to the
colorless forms of NIR light responsive TPAOMe1,
TPAOMe2 and APery were estimated by using 1,2-bis(2-
methylbenzo[b]thiophene-3-yl)-perfluorocyclopentene
(DAE) as a standard.48 We prepared the solutions of
TPAOMe1, TPAOMe2, APery and DAE in benzene. The
absorbance of the solutions at the excitation wavelength
(517 nm for TPAOMe1 and TPAOMe2, 600 nm for APery)
was matched with that of the solution of DAE. The changes
in the absorbance upon laser irradiation (ΔODcolored and
ΔODDAE) were plotted against the laser power (see the
Supporting Information) to estimate the ΔOD values per
unit laser power (the slope of the plots). The conversion
efficiency (φcolored) of TPAOMe1 was estimated to be 0.06
from the following equation,
Figure 6. Thermal absorption spectral changes (time interval =
5.4 s) of (a) TPAOMe2 (1.1×10−5 M) and (b) APery (2.9×10−6 M) at
298 K in degassed benzene recorded after irradiation with red
light (660 nm, 270 mW)
휑푐표푙표푟푒푑 ∆푂퐷푐표푙표푟푒푑
휀퐷퐴퐸
=
×
휑퐷퐴퐸
휀푐표푙표푟푒푑
∆푂퐷퐷퐴퐸
where φDAE (0.35) is the quantum yield of the open-ring
reaction of DAE,49 εDAE (0.91×104 M−1 cm−1) and εcolroed of
TPAOMe1 (1.33×104 M−1 cm−1) are absorption coefficients of
the closed-ring form of DAE and the colored form,
ACS Paragon Plus Environment
Figure 7. (a) The time profiles of the transient absorbance and
(b) the logarithm plots of the time profiles of TPAOMe2 and
APery in degassed benzene at 298 K.

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respectively. This conversion efficiency is two times higher is also effective to increase the NIR light sensitivity even in
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than that of BN-ImD. In the similar way, the conversion
efficiencies of TPAOMe2 (εcolroed = 2.03×104 M−1 cm−1) and
APery (εDAE = 7.6×103 M−1 cm−1 and εcolroed = 1.36×103 M−1 cm−1,
at 600 nm) were estimated to be 0.005 and 0.002,
respectively. These values are sufficient to induce the
negative photochromic reactions in apolar solvent as
shown in Figure 6.
apolar solvents. These molecular designs will open up a
novel application of the negative photochromic imidazole
dimer as a NIR light operating photoswitch.
EXPERIMENTAL SECTION
Experimental Detail for Transient Absorption
Spectroscopy. The transient absorption spectra and the
time profiles of the transient absorbance were recorded on
an Ocean FX multichannel detector (Ocean Optics, Inc).
CUV-QPOD (Ocean Optics) equipped TC 125 temperature
controller (QUANTUM) was used as a cuvette holder. The
probe beam from a broadband laser driven light source,
EQ-99XFC (Tokyo Instruments, Inc) was guided with a
QP-600-1-SR optical fiber (Ocean Optics, Inc). Optical
grade solvents were used for all measurements.
The bond dissociation energy of a C–N bond has been
estimated to be 300 kJ/mol corresponding to a photon
energy of ca. 400 nm light.50 While UV light irradiation is
generally required to break a C–N bond according to the
bonding energy of a C–N bond, the BN-ImD derivatives
show the photochemical bond-breaking reaction upon
visible or NIR light irradiation. However, this bond
dissociation energy is not directly applied to the
photochromic BN-ImD because the consideration of the
change in the Gibbs energy (the summation of the ΔG0 and
ΔG‡ between the initial stable and the transient metastable
state) is required to presume the bonding energy of the C–
N bond.22 Especially, by considering the stabilization of the
radical generated after the homolytic bond-breaking
reaction of the C–N bond by the delocalization on the
diphenyl imidazole ring, the C–N bonding energy of the
BN-ImD systems will be less than 300 kJ/mol. In addition,
the potential energy surface of the excited state of BN-ImD
is expected as the bond-dissociation type as similar with
the other photochromic imidazole dimers. Therefore, the
photon energy for the S0→S1 (HOMO–LUMO) transition
(calculated to be 858 nm for TPAOMe1 and 1008 nm for
APery, respectively) will be higher than the bonding
energy of the C–N bond, leading to the NIR-light induced
negative photochromic reactions. However, the smaller
conversion efficiencies of TPAOMe2 and APery than those
of BN-ImD and TPAOMe1 are due to the large
contribution of the CT transition to the absorption band in
the red or NIR light region. Very small changes in the
absorption spectra of TPAOMe2 and APery in polar
solvent (Figures S81 and S82) would suggest the
stabilization of the excited CT state, leading to further
decrease in the conversion efficiency. It might be suggested
that the potential energy surface of the S1 state changes to
the predissociation type due to the CT state. The ultrafast
spectroscopy to reveal the excited state dynamics of the
BN-ImD derivatives would be required for the future work.
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Experimental Detail for Laser Flash Photolysis
Measurement to Estimate the Conversion Efficiency.
The laser flash photolysis experiments were carried out
with
a TSP-2000 time resolved spectrophotometer
(UNISOKU). The excitation pulse at 517 nm and 600 nm
(pulse width, 5 ns) were provided by a Continuum Surelite
II Q-Switched Nd:YAG coupled to a Continuum Panther
EX OPO. The probe beam from a halogen lamp (OSRAM
HLX64623) was used as the probe beam arranged in an
orientation perpendicular to the exciting laser beam. The
probe beam was monitored with a photomultiplier tube
(Hamamatsu R2949) through a spectrometer (UNISOKU
MD200) for time evolutions of the transient absorbance.
The excitation intensity of one pulse was estimated by an
energy detector (Gentec Electro-Optics QE12LP-S-MB)
with an energy monitor (Gentec Electro-Optics
MAESTRO). Optical grade solvents were used for all
measurements.
Materials and Reagents. All reactions were monitored
by thin-layer chromatography carried out on 0.2 mm E.
Merck silica gel plates (60F-254). Column chromatography
was performed on silica gel (Silica gel 60N, Kanto Chemical
Co., Inc.). NMR spectra were recorded at 400 MHz on a
Bruker AVANCE III 400 NanoBay. DMSO-d6, CD2Cl2 and
CDCl3 were used as deuterated solvent. ESI–TOF–MS
spectra were recorded on a Bruker micrOTOF II-AGA1.
Unless otherwise noted, all reagents and reaction solvents
were purchased-from Tokyo Chemical Industry Co., Ltd.,
Wako Pure Chemical Industries, Ltd., Sigma-Aldrich Inc.
and Kanto Chemical Co., Inc. and were used without
further purification.
CONCLUSION
We demonstrated the efficient strategy to increase the
red or NIR light sensitivity of the negative photochromic
BN-ImD. The introduction of the electron-donating
groups to the bridging binaphthyl unit or the imidazole
unit can make CT absorption bands in the red or NIR light
region because of the electron-withdrawing ability of the
Synthetic Procedure
Substitution to the bridging binaphthyl unit
Methyl-1-bromo-2-naphthoate (1) and dimethyl [1,1'-
binaphthalene]-2,2'-dicarboxylate (2) were synthesized
according to the literature procedure.51 Dimethyl 4,4'-
dibromo-[1,1'-binaphthalene]-2,2'-dicarboxylate (3) was
synthesized according to the literature procedure.52 (4,4'-
Dibromo-[1,1'-binaphthalene]-2,2'-diyl)dimethanol (4) and
diazafulvene
unit.
The
introduction
of
di(methoxyphenyl)amino phenyl groups red-shifts the CT
absorption band to the NIR light region and the colored
form shows a neutral gray color. In addition, the
substitution of di(methoxyphenyl)amino perylene groups
4,4'-dibromo-[1,1'-binaphthalene]-2,2'-dicarbaldehyde
(5)
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Journal of the American Chemical Society
2,2'-(4,4'-Diphenyl-[1,1'-binaphthalene]-2,2'-diyl)bis(4,5-
Page 6 of 28
were synthesized according to the literature procedure
(Scheme 2).53
bis(4-methoxyphenyl)-imidazole) (6-Ph). Compound 5-Ph
(37 mg, 0.079 mmol), p-anisil (61 mg, 0.22 mmol), and
ammonium acetate (265 mg, 2.7 mmol) were refluxed in
acetic acid (2 mL) for 2 days. After cooling to room
temperature, the reaction mixture was neutralized with
aqueous NH3. The slurry precipitate formed by
neutralization was filtered off, washed with water, and
then dried. The residue was purified by silica gel column
chromatography (CH2Cl2/AcOEt = 5/1) to afford 6-Ph as
1
2
3
4
5
6
7
8
2,2'-(4,4'-dibromo-[1,1'-binaphthalene]-2,2'-diyl)bis(4,5-
bis(4-methoxyphenyl)-imidazole) (6). Compound 5 (10 mg,
0.021 mmol), p-anisil (18 mg, 0.060 mmol), and ammonium
acetate (143 mg, 1.7 mmol) were refluxed in acetic acid (1.5
mL) for 8 h. After cooling to room temperature, the
reaction mixture was neutralized with aqueous NH3. The
slurry precipitate formed by neutralization was filtered off,
washed with water, and then dried. The residue was
purified by silica gel column chromatography
(CH2Cl2/AcOEt = 20/1) to afford 6 as yellow solid (13 mg,
0.0134 mmol, 63 %). 1H NMR (400 MHz, DMSO-d6) δ: 12.98
(s, 2H), 8.62 (s, 2H), 8.27 (s, 2H), 8.26 (d, J = 7.52 Hz, 2H),
7.62 (t, J = 7.52 Hz, 2H), 7.36 (t, J = 7.79 Hz, 2H), 7.19 (br,
4H), 7.14 (br, 2H), 6.89 (br, 9H), 6.67 (br, 4H), 3.73 (s, 6H),
3.68 (s, 6H); HRMS (ESI-TOF) calculated for
C54H40Br2N4O4 [M−H]−: 967.1489, found: 967.1509.
9
1
yellow solid (28 mg, 0.029 mmol, 37 % over 2 steps). H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
NMR (400 MHz, DMSO-d6) δ: 13.06 (s, 2H), 8.15 (s, 2H),
7.95 (d, J = 8.36 Hz, 2H), 7.74 (d, J = 7.16 Hz, 4H), 7.66 (t, J
= 7.58 Hz, 4H), 7.61–7.54 (m, 3H), 7.46 (t, J = 7.10 Hz, 2H),
7.32 (t, J = 7.76 Hz, 2H), 7.20 (d, J = 8.56 Hz, 2H), 7.16 (d, J
= 8.76 Hz, 4H), 7.02 (d, J = 8.72 Hz, 3H), 6.86 (d, J = 8.76,
4H), 6.64 (d, J = 8.84, 4H), 3.72 (s, 6H), 3.67 (s, 6H); HRMS
(ESI-TOF) calculated for C66H50N4O4 [M+H]+: 963.3905,
found: 963.3916.
2'-(4,5-Bis(4-methoxyphenyl)imidazol-2-ylidene)-8,9-
bis(4-methoxyphenyl)-4',5-diphenyl-spiro[benzo[e]imidazo
[2,1-a]isoindole-11,1'-naphthalene] (Ph). All manipulations
were carried out with the exclusion of light. Under
nitrogen, to a solution of 6-Ph (18 mg, 0.018 mmol) in
degassed benzene in benzene (10 mL) was added a solution
of potassium ferricyanide (1.33 g, 3.7 mmol) and KOH (420
mg, 5.8 mmol) in water (10 mL), and the reaction mixture
was vigorously stirred for 2.5 h. After the reaction was
completed, the reaction product was extracted with
benzene, and washed with water. The crude mixture was
purified by silica gel column chromatography using
AcOEt/CHCl3 = 1/25 as eluent to give a red solid (1 mg, 0.001
4,4'-Diphenyl-[1,1'-binaphthalene]-2,2'-dicarbaldehyde (5-
Ph, Scheme 3). Under N2 atmosphere, compound 5 (43.0
mg, 0.092 mmol) and phenylboronic acid (55 mg, 0.40
mmol) were added to degassed THF (2 mL) and 1 M
aqueous
Na2CO3
(0.55
mL)
and
tetrakis(triphenylphosphine)palladium (0) (38 mg, 0.022
mmol) was added. The mixture was stirred at 70 °C for 16
h. After celite filtration, the filtrate was transferred to a
separation funnel and extracted with AcOEt. The organic
layer was collected and the aqueous phase was extracted
with AcOEt. The combined organic layers were washed
with water and brine, and AcOEt was evaporated in vacuo.
The crude mixture was purified by silica gel column
chromatography using CH2Cl2/hexane = 7/3 and used in
1
mmol, 5 %). H NMR (400 MHz, CDCl3) δ: 8.25 (s, 1H), 7.99
(s, 1H), 7.91–7.85 (m, 1H), 7.61–7.57 (m, 1H), 7.57–7.50 (m,
7H), 7.50–7.45 (m, 5H), 7.44 (d, J = 8.72 Hz, 2H), 7.42–7.38
(m, 1H), 7.30 (d, J = 7.72 Hz, 2H), 6.84 (d, J = 8.68 Hz, 2H),
6.77 (d, J = 8.76 Hz, 2H), 6.73 (d, J = 8.76 Hz, 2H), 4.68 (q,
J = 4.68, 4H), 3.81 (s, 6H), 3.75 (s, 3H) 3.73 (s, 3H); HRMS
(ESI-TOF) calculated for C66H48N4O4 [M+H]+: 961.3748,
found: 961.3790.
1
the next step without further purification. H NMR (400
MHz, CDCl3) δ: 9.75 (s, 2H), 8.16 (s, 2H), 8.10 (d, J = 8.52
Hz, 2H), 7.66−7.64 (m, 2H), 7.64–7.62 (m, 3H), 7.62–7.60
(m, 2H), 7.60–7.59 (m, 3H), 7.58–7.57 (m, 2H), 7.55 (t, J =
1.6 Hz, 1H), 7.53–7.52 (m, 1H), 7.44–7.43 (m, 2H), 7.43–7.41
(m, 2H); HRMS (ESI-TOF) calculated for C34H22O2
[M+Na]+: 485.1510, found: 485.1512.
4,4'-Bis(4-nitrophenyl)-[1,1'-binaphthalene]-2,2'-
dicarbaldehyde (5-PhNO2). Under N2 atmosphere,
compound 5 (308 mg, 0.64 mmol), Pd(OAc)2 (30 mg, 0.12
Scheme 2. Synthesis of lophine derivartive 6.
mmol),
dicyclohexyl(2',6'-dimethoxy-[1,1'-biphenyl]-2-
yl)phosphine (SPhos) (56 mg, 0.13 mmol) and Na2CO3 (453
Scheme 3. Synthesis of Ph, PhNO2 and PhOMe.
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Journal of the American Chemical Society
mg, 3.8 mmol) were added to degassed THF (5 mL) and (315 mg, 2.6 mmol), 2-dicyclohexylphosphino- 2',6'-
1
2
3
4
5
6
7
8
water (1 mL). The mixture was stirred at 70 °C for 15.5 h.
After celite filtration, the filtrate was transferred to a
separation funnel and extracted with AcOEt. The organic
layer was collected and the aqueous phase was extracted
with AcOEt. The combined organic layers were washed
with water and brine, and AcOEt was evaporated in vacuo.
The crude mixture was purified by silica gel column
chromatography using CH2Cl2/hexane = 4/1 and used in
the next step without further purification.1H NMR (400
MHz, CDCl3) δ: 9.74 (s, 2H), 8.49 (s, 2H), 8.47 (s, 2H), 8.18
(s, 2H), 7.96 (d, J = 8.32 Hz, 2H), 7.84 (d, J = 8.72, 4H), 7.68
(t, J = 6.82 Hz, 2H), 7.48 (d, J = 5.48 Hz, 2H), 7.44 (d, J =
7.72 Hz, 2H); HRMS (ESI-TOF) calculated for C34H20N2O6
[M+Na]+: 575.1214, found: 575.1190.
2,2'-(4,4'-Bis(4-nitrophenyl)-[1,1'-binaphthalene]-2,2'-
diyl)bis(4,5-bis(4-methoxyphenyl)-imidazole) (6-PhNO2).
5-PhNO2 (120 mg, 0.23 mmol), p-anisil (189 mg, 0.64
mmol), and ammonium acetate (688 mg, 7.84 mmol) were
refluxed in acetic acid (5 mL) for 12 h. After cooling to room
temperature, the reaction mixture was neutralized with
aqueous NH3. The slurry precipitate formed by
neutralization was filtered off, washed with water, and
then dried. The residue was purified by silica gel column
chromatography (CH2Cl2/AcOEt = 6/1) to afford 6-PhNO2
as yellow solid (63 mg, 0.0723 mmol, 31 % over 2 steps). 1H
NMR (400 MHz, DMSO-d6) δ: 13.01 (s, 2H), 8.52 (d, J = 8.72
Hz, 4H), 8.26 (s, 2H), 8.05 (d, J = 8.68 Hz, 4H), 7.94 (d, J =
7.80 Hz, 2H), 7.51 (t, J = 7.60 Hz, 2H), 7.36 (t, J = 7.76 Hz,
2H), 7.25 (d, J = 8.64 Hz, 2H), 7.18 (d, J = 8.52 Hz, 4H), 6.95
(d, J = 9.12 Hz, 3H), 6.87 (d, J = 8.56 Hz, 5H), 6.63 (d, J =
8.84 Hz, 4H), 3.73 (s, 6H), 3.67 (s, 6H); HRMS (ESI-TOF)
calculated for C66H48N6O8 [M+H]+: 1053.3615, found:
1053.3615.
dimethoxybiphenyl (36 mg, 0.086 mmol) and
palladium(II) acetate (24 mg, 0.077 mmol) were added to
degassed THF (5 mL), water (1 mL) and was added. The
mixture was stirred at 70 °C for 16 h. After celite filtration,
the filtrate was transferred to a separation funnel and
extracted with AcOEt. The organic layer was collected and
the aqueous phase was extracted with AcOEt. The
combined organic layers were washed with water and brine,
and AcOEt was evaporated in vacuo. The crude mixture
was purified by silica gel column chromatography using
CH2Cl2/hexane = 4/1 and used in the next step without
further purification. 1H NMR (400 MHz, CDCl3) δ: 9.73 (s,
2H), 8.14 (s, 3H), 7.57 (d, J = 8.68 Hz, 6H), 7.42–7.40 (m,
4H), 7.12 (d, J = 8.72 Hz, 6H), 3.95 (s, 6H); HRMS (ESI-TOF)
calculated for C36H26O4 [M+Na]+: 545.1723, found: 545.1746.
2,2'-(4,4'-Bis(4-methoxyphenyl)-[1,1'-binaphthalene]-2,2'-
diyl)bis(4,5-bis(4-methoxyphenyl)-imidazole) (6-PhOMe).
5-PhOMe (15 mg, 0.040 mmol), p-anisil (29 mg, 0.112
mmol), and ammonium acetate (188 mg, 1.4 mmol) were
refluxed in acetic acid (2 mL) for 8 h. After cooling to room
temperature, the reaction mixture was neutralized with
aqueous NH3. The slurry precipitate formed by
neutralization was filtered off, washed with water, and
then dried. The residue was purified by silica gel column
chromatography (CH2Cl2/AcOEt = 6/1) to afford 6-PhOMe
as yellow solid (6.3 mg, 0.0072 mmol, 18 % over 2 steps). 1H
NMR (400 MHz, DMSO-d6) δ: 13.21 (s, 2H), 8.07 (s, 2H),
7.98 (d, J = 7.96 Hz, 2H), 7.66 (d, J = 8.56 Hz, 4H), 7.58 (t, J
= 7.48 Hz, 2H), 7.31 (t, J = 7.64 Hz, 2H), 7.21 (d, J = 8.64 Hz,
4H), 7.14 (dd, J = 8.92 Hz, 6H), 7.05 (d, J = 7.72 Hz, 3H), 6.85
(d, J = 8.92 Hz, 4H), 6.66 (dd, J = 5.74 Hz, 5H), 3.90 (s, 6H),
3.72 (s, 6H), 3.67 (s, 6H); HRMS (ESI-TOF) calculated for
C68H48N4O6 [M+H]+: 1023.4116, found: 1023.4108.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2'-(4,5-Bis(4-methoxyphenyl)-imidazol-2-ylidene)-8,9-
bis(4-methoxyphenyl)-4',5-bis(4-nitrophenyl)-
2'-(4,5-Bis(4-methoxyphenyl)-imidazol-2-ylidene)-
4',5,8,9-tetrakis(4-methoxyphenyl)-
spiro[benzo[e]imidazo[2,1-a]isoindole-11,1'-naphthalene]
(PhNO2). All manipulations were carried out with the
exclusion of light. Under nitrogen, to a solution of 6-
PhNO2 (50 mg, 0.0047 mmol) in benzene (10 mL) was
added a solution of potassium ferricyanide (2.924g, 9.8
mmol) and KOH (759 mg, 15 mmol) in water (10 mL), and
the reaction mixture was vigorously stirred for 8 h. After
the reaction was completed, the reaction product was
extracted with benzene, and washed with water. The crude
mixture was purified by silica gel column chromatography
using CH2Cl2/AcOEt = 20/1 as eluent to give red solid (1 mg,
spiro[benzo[e]imidazo[2,1-a]isoindole-11,1'-naphthalene]
(PhOMe). All manipulations were carried out with the
exclusion of light. Under nitrogen, to a solution of 6-
PhOMe (17 mg, 0.0017 mmol) in benzene (5 mL) was
added a solution of potassium ferricyanide (1.37 g, 4.06
mmol) and KOH (414 mg, 6.1 mmol) in water (5 mL), and
the reaction mixture was vigorously stirred overnight.
After the reaction was completed, the reaction product was
extracted with benzene, and washed with water. The crude
mixture was purified by preparative thin-layer
chromatography (PTLC) using CH2Cl2/AcOEt = 20/1 as
eluent to give red solid (1 mg, 0.98 μmol, 57 %).1H NMR
(400 MHz, CDCl3) δ: 8.19 (d, J = 8.76 Hz,1H), 8.02 (d, J =
8.81 Hz,1H), 7.97 (s, 1H), 7.54 (s, 1H), 7.52 (s, 2H), 7.49–7.42
(m, 5H), 7.39–7.33 (m, 6H), 7.25–7.17 (m, 2H), 7.11 (t, J = 6.76
Hz, 1H), 7.04 (d, J = 8.80 Hz, 3H), 6.99 (d, J = 8.60 Hz, 2H),
6.85 (d, J = 8.85 Hz, 2H), 6.79 (d, J = 8.88 Hz, 2H), 6.73 (d,
J = 8.92 Hz, 2H), 6.58 (d, J = 8.84 Hz, 2H), 6.51 (d, J = 8.80
Hz, 2H), 3.93 (s, 3H), 3.87 (s, 3H), 3.81 (s, 6H),3.73 (s, 3H),
3.72 (s, 3H); HRMS (ESI-TOF) calculated for C68H52N4O6
[M+H]+: 1021.3960, found: 1021.3920.
1
0.072 mmol, 31 %). H NMR (400 MHz, DMSO-d6) δ: 8.43
(dd, J = 8.56 Hz, 3H), 8.15 (s, 1H), 7.88–7.83 (m, 3H), 7.78
(d, J = 8.40 Hz, 1H), 7.75–7.69 (m, 2H), 7.53–7.46 (m, 4H),
7.43 (dd, J = 9.14 Hz, 6H), 7.31 (t, J = 7.06 Hz, 1H), 7.25 (d, J
= 8.00 Hz, 1H), 6.99 (d, J = 8.08 Hz, 1H), 6.93 (t, J = 8.62 Hz,
1H), 6.78 (d, J = 8.84 Hz, 2H), 6.72 (d, J = 8.64 Hz, 2H),6.44
(d, J = 8.56 Hz, 2H), 3.79 (s, 3H), 3.77 (s, 3H), 3.71 (s, 3H),
3.66 (s, 3H); HRMS (ESI-TOF) calculated for C66H46N6O8
[M+H]+: 1051.3450, found: 1051.3426.
4,4'-Bis(4-methoxyphenyl)-[1,1'-binaphthalene]-2,2'-
dicarbaldehyde (5-PhOMe). Under N2 atmosphere,
4,4'-(2,2'-Bis(4,5-bis(4-methoxyphenyl)-imidazol-2-yl)-
[1,1'-binaphthalene]-4,4'-diyl)bis(diphenylaniline) (6-TPA,
Scheme 4). Under N2 atmosphere, compound 6 (70 mg,
compound
5
(203
mg,
0.43
mmol),
4-
methoxyphenylboronic acid (276 mg, 1.8 mmol), Na2CO3
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Journal of the American Chemical Society
Page 8 of 28
0.073 mmol), 4-(Diphenylamino)phenylboronic acid (91
mg, 0.31 mmol) Pd(OAc)2 (8 mg, 0.013 mmol),
dicyclohexyl(2',6'-dimethoxy-[1,1'-biphenyl]-2-
(ESI-TOF) calculated for C90H66N6O4 [M+H]+: 1295.5218,
found: 1295.5166.
4,4'-(2,2'-Bis(4,5-bis(4-methoxyphenyl)-imidazol-2-yl)-
[1,1'-binaphthalene]-4,4'-diyl)bis(bis(4-
1
2
3
4
5
6
7
8
yl)phosphine (SPhos) (13 mg, 0.0015 mmol), 4-
(Diphenylamino)phenylboronic acid (92 mg, 0.31 mmol)
and Na2CO3 (52 mg, 0.44 mmol) were added to degassed
THF (5 mL) and water (1 mL). The mixture was stirred at
70 °C for 14.5 h. After celite filtration, the filtrate was
transferred to a separation funnel and extracted with
AcOEt. The organic layer was collected and the aqueous
phase was extracted with AcOEt. The combined organic
layers were washed with water and brine, and AcOEt was
evaporated in vacuo. The crude sample was purified by
silica gel column chromatography using CH2Cl2/AcOEt =
15/4 as eluent to give yellow powder (30 mg, 0.023 mmol,
32 %). 1H NMR (400 MHz, DMSO-d6) δ: 13.09 (s, 2H), 8.13
(s, 2H), 8.07 (d, J = 8.28 Hz, 2H), 7.66 (d, J = 8.32 Hz, 4H),
7.48 (t, J = 7.48 Hz, 3H), 7.39 (t, J = 7.90 Hz, 9H), 7.31 (t, J =
7.48 Hz, 3H), 7.21 (d, J = 8.48 Hz, 5H), 7.17 (d, J = 7.60 Hz,
11H), 7.12 (d, J = 7.34 Hz, 6H), 7.02 (d, J = 7.40 Hz, 3H), 6.84
(d, J = 7.04 Hz, 3H), 6.64 (d, J = 7.68 Hz, 3H), 3.71 (s, 6H),
3.63 (s, 6H) ; HRMS (ESI-TOF) calculated for C90H68N6O4
[M+Na]+: 1319.5194, found: 1319.5207.
4,4'-(2'-(4,5-Bis(4-methoxyphenyl)-imidazol-2-ylidene)-
8,9-bis(4-methoxyphenyl)-spiro[benzo[e]imidazo[2,1-
a]isoindole-11,1'-naphthalene]-4',5-diyl)bis(diphenylaniline)
(TPA). All manipulations were carried out with the
exclusion of light. Under nitrogen, to a solution of 6-TPA
(21 mg, 0.015 mmol) in benzene (5 mL) was added a
solution of potassium ferricyanide ( 1.108 g, 2.5 mmol) and
KOH (334 mg, 6.52 mmol) in water (6 mL), and the
reaction mixture was vigorously stirred overnight. After
the reaction was completed, the reaction product was
extracted with benzene, and washed with water. The crude
mixture was purified by silica gel column chromatography
using CH2Cl2/AcOEt = 10/1 as eluent to give reddish purple.
(13 mg, 0.01 mmol, 65 %). 1H NMR (400 MHz, CDCl3) δ: 8.25
(s, 1H), 7.99 (s, 2H), 7.58–7.51 (m, 4H), 7.47 (t, J = 7.32 Hz,
4H), 7.42 (t, J = 9.50 Hz, 5H), 7.35–7.29 (m, 12H), 7.20 (d, J
= 8.24 Hz, 9H), 7.17 (d, J = 7.08 Hz, 3H), 7.11 (d, J = 7.56 Hz,
2H), 7.06 (t, J = 7.54 Hz, 3H), 6.84 (d, J = 8.44 Hz, 1H), 6.77
(d, J = 8.56 Hz, 2H), 6.73 (d, J = 8.64 Hz, 2H), 6.55 (s, 3H),
3.82 (s, 3H), 3.80 (s, 3H), 3.73 (s, 3H), 3.66 (s, 3H); HRMS
methoxyphenyl)aniline) (6-TPAOMe1, Scheme 5). 4-
Methoxy-(4-methoxyphenyl)-(4-(4,4,5,5-tetramethyl-
1,3,2-dioxaborolan-2-yl)phenyl)aniline was synthesized
according to the literature procedure.54 Under N2
atmosphere, compound 6 (70mg, 0.073 mmol), 4-
methoxy-(4-methoxyphenyl)-(4-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)phenyl)aniline (138 mg, 0.31 mmol),
Pd(OAc)2 (6 mg, 0.013 mmol), SPhos (10 mg, 0.0015 mmol)
and Na2CO3 (50 mg, 0.44 mmol) were added to degassed
THF (3 mL) and water (1 mL). The mixture was stirred at
70 °C for 10.5 h. After celite filtration, the filtrate was
transferred to a separation funnel and extracted with
AcOEt. The organic layer was collected and the aqueous
phase was extracted with AcOEt. The combined organic
layers were washed with water and brine, and AcOEt was
evaporated in vacuo. This compound decomposed by using
silica gel therefore it used in the next step without further
purification. HRMS (ESI-TOF) calculated for C94H76N6O8
[M+H]+: 1417.5796, found: 1417.5765.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4,4'-(2'-(4,5-Bis(4-methoxyphenyl)-imidazol-2-ylidene)-
8,9-bis(4-methoxyphenyl)-spiro[benzo[e]imidazo[2,1-
a]isoindole-11,1'-naphthalene]-4',5-diyl)bis(diphenylaniline)
(TPAOMe1). All manipulations were carried out with the
exclusion of light. Under nitrogen, to a solution of the
crude mixture of 6-TPAOMe1 (85 mg, 0.035 mmol) in
benzene (6 mL) was added a solution of potassium
ferricyanide (2.40 g, 7.3 mmol) and KOH (617 mg, 11.0
mmol) in water (6 mL), and the reaction mixture was
vigorously stirred overnight. After the reaction was
completed, the reaction product was extracted with
benzene, and washed with water. The crude mixture was
purified by preparative thin-layer chromatography (PTLC)
using CH2Cl2/AcOEt = 10/1 as eluent to give blue solid. (9
1
mg, 0.006 mmol, 8 % over 2 steps). H NMR (400 MHz,
CDCl3) δ: 8.22 (s, 1H), 7.98 (s, 1H), 7.54–7.50 (m, 6H), 7.46
(d, J = 8.84 Hz, 4H), 7.43 (d, J = 8.76 Hz, 4H), 7.33 (d, J =
8.28 Hz, 5H), 7.17 (d, J = 2.52 Hz, 4H), 7.15 (d, J = 2.52 Hz,
5H), 7.02 (t, J = 7.82 Hz, 6H), 6.89 (t, J = 6.60 Hz, 9H),6.84
Scheme 5. Synthesis of TPAOMe1.
Scheme 4. Synthesis of TPA.
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Journal of the American Chemical Society
(d, J = 8.60 Hz, 2H), 6.76 (d, J = 8.60 Hz, 2H), 6.72 (d, J =
9.0 Hz, 4H), 3.81 (s, 12H); HRMS (ESI-TOF) calculated for
C90H66N6O4 [M+Na]+: 687.2466, found: 687.2465.
1
2
3
4
5
6
7
8
8.60 Hz, 2H), 6.55–6.52 (m, 3H), 3.84 (s, 6H), 3.82 (s, 6H),
3.81 (s, 3H), 3.79 (s, 3H), 3.73 (s, 3H), 3.66 (s, 3H); HRMS
(ESI-TOF) calculated for C94H74N6O8 [M+H]+: 1415.5640,
found: 1415.5682.
4,4',4'',4'''-([1,1'-Binaphthalene]-2,2'-diylbis(1H-imidazole-
2,4,5-triyl))tetrakis(N,N-bis(4-methoxyphenyl)aniline) (9).
[1,1'-binaphthalene]-2,2'-dicarbaldehyde (21 mg, 0.068
mmol), 8 (99 mg, 0.15 mmol), and ammonium acetate (284
mg, 3.68 mmol) were refluxed in AcOH (5 mL) for 15 h.
After cooling to room temperature, the reaction mixture
was neutralized with aqueous NH3 and extracted with
chloroform. The combined organic layer was washed with
water and brine and passed through a phase separator
paper. After the solvent was removed, the crude mixture
was purified by triethyl amine treated silica gel column
chromatography (ethyl acetate/dichloromethane/hexane
= 3/10/10), to give desired product as a pale yellow solid (31
mg, 29 %). 1H NMR (400 MHz, DMSO-d6) δ: 13.74 (s, 2H),
8.12 (d, J = 8.5 Hz, 2H), 7.99 (d, J = 8.3 Hz, 2H), 7.92 (d, J =
8.5 Hz, 2H), 7.44 (t, J = 7.7 Hz, 2H), 7.24 (t, J = 7.7 Hz, 2H),
7.08 (d, J = 8.7 Hz, 4H), 7.01–6.81 (m, 38H), 6.59–6.53 (m,
8H), 3.70 (s, 12H), 3.69 (s, 12H); HRMS (ESI-TOF)
calculated for C106H86N8O8 [M+H]+: 1599.6641, found:
1599.6597.
Substitution to the imidazole unit
[1,1'-Binaphthalene]-2,2'-dicarbaldehyde was synthesized
according to the literature procedure.32 3-Bromoperylene
(10) was synthesized according to the literature
procedure.55
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4-Methoxy-N-(4-methoxyphenyl)-N-phenylaniline
(7,
Scheme 6). A mixture of iodobenzene (612 mg, 3.00 mmol),
4,4’-dimethoxydiphenylamine (893 mg, 3.89 mmol),
Pd(dba)2 (66 mg, 0.11 mmol), Xantphos (117 mg, 0.202
mmol) and NaOtBu (450 mg, 4.68 mmol) in anhydrous
degassed toluene (30 mL) and the resulting mixture was
refluxed for 14 h. To the reaction mixture water and ethyl
acetate were added and the mixture was extracted with
ethyl acetate. The combined organic layer was washed with
brine and passed through a phase separator paper. After
the solvent was removed, the crude mixture was purified
4,4'-(2-(8,9-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-
2'H-spiro[benzo[e]imidazo[2,1-a]isoindole-11,1'-
by
silica
gel
column
chromatography
(dichloromethane/hexane = 1/1), to give desired product as
an off-white solid (771 mg, yield: 84 %). 1H NMR (400 MHz,
CDCl3) δ: 7.16 (dd, J1 = 7.4 Hz, J2 = 8.5 Hz, 2H), 7.04 (d, J =
9.0 Hz, 4H), 6.93 (d, J = 8.5 Hz, 2H), 6.86 (t, J = 7.4 Hz, 1H),
6.81 (d, J = 9.0 Hz, 4H), 3.79 (s, 6H); HRMS (ESI-TOF)
calculated for C20H19NO2 [M+H]+: 306.1489, found:
306.1487.
naphthalen]-2'-ylidene)-2H-imidazole-4,5-diyl)bis(N,N-
bis(4-methoxyphenyl)aniline) (TPAOMe2). To a solution
of 9 (27 mg, 0.017 mmol) in benzene (2 mL) was added a
solution of potassium ferricyanide (167 mg, 0.51 mmol) and
KOH (71 mg, 1.3 mmol) in water (2.5 mL), and the reaction
mixture was vigorously stirred overnight. The organic layer
was separated, exhaustively washed with water and passed
through a phase separator paper. After the solvent was
removed, the crude mixture was purified by triethyl amine
treated silica gel column chromatography (THF/benzene =
1/200 → 1/40), to give desired product as a dark blue solid
(17 mg, 63 %). 1H NMR (400 MHz, DMSO-d6) δ: 8.10 (d, J =
8.6 Hz, 1H), 8.01 (d, J = 8.6 Hz, 1H), 7.94 (d, J = 7.8 Hz, 1H),
7.86 (d, J = 9.8 Hz, 1H), 7.44 (d, J = 7.5 Hz, 1H), 7.37–7.26
(m, 10H), 7.21 (d, J = 10.0 Hz, 1H), 7.09 (t, J = 7.8 Hz, 10H),
6.99–6.87 (m, 26H), 6.70 (d, J = 7.8 Hz, 1H), 6.62–6.59 (m,
4H), 8.50 (d, J = 9.0 Hz, 1H), 6.40 (d, J = 8.6 Hz, 1H), 6.17 (d,
J = 8.6 Hz, 1H), 3.73 (m, 18H), 3.72 (s, 6H); HRMS (ESI-TOF)
calculated for C106H84N8O8 [M+H]+: 1598.6517, found:
1598.6601.
1,2-Bis(4-(bis(4-methoxyphenyl)amino)phenyl)ethane-
1,2-dione (8).
A suspension of AlCl3 (0.07 mL, 0.83
mmol) in dry dichloromethane (3 mL) was slowly added to
a solution of 7 (504 mg, 1.65 mmol) and oxalyl chloride
(0.07 mL, 0.83 mmol) in dry dichloromethane (1.5 mL) at 0
°C. The reaction mixture was stirred at ambient
temperature overnight and then quenched with ice and
concentrated HCl aq. After stirring for another 1 h, organic
layer was passed through a phase separator paper. After the
solvent was removed, the crude mixture was purified by
silica
gel
column
chromatography
(ethyl
acetate/dichloromethane/hexane
=
3/20/20), to give
1
desired product as a yellow solid (217 mg, 40 %). H NMR
(400 MHz, CDCl3) δ: 7.72 (d, J = 9.0 Hz, 2H), 7.63 (d, J = 8.8
Hz, 2H), 7.13–7.10 (m, 8H), 6.89–6.83 (m, 10H), 6.78 (d, J =
N,N-Bis(4-methoxyphenyl)perylen-3-amine (11, Scheme
7).
A mixture of 3-bromoperylene (404 mg, 1.09
mmol), 4,4’-dimethoxydiphenylamine (594 mg, 2.59
mmol), Pd2(dba)3 (72 mg, 0.079 mmol), P(tBu)3 (76 mg, 0.31
mmol) and NaOtBu (340 mg, 3.54 mmol) in dry toluene (53
mL) was stirred under a nitrogen atmosphere at 110 °C for
12 h. The reaction mixture was filtered through a Celite pad
and washed with brine. The organic layer was passed
through a phase separator paper. After the solvent was
removed, the crude mixture was purified by silica gel
column chromatography (dichloromethane/hexane = 3/2),
to give desired product as a yellow solid (359 mg, 68 %). 1H
NMR (400 MHz, CDCl3) δ: 8.18–8.11 (m, 4H), 7.83 (d, J = 8.4
Hz, 1H), 7.67 (t, J = 8.4 Hz, 2H), 7.50–7.45 (m, 2H), 7.34 (t,
J = 7.9 Hz, 1H), 7.20 (d, J = 7.9 Hz, 1H), 6.98 (d, J = 8.9 Hz,
Scheme 6. Synthesis of TPAOMe2.
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Page 10 of 28
4H), 6.78 (d, J = 8.9 Hz, 4H), 3.77 (s, 6H); HRMS (ESI-TOF)
separator paper. After the solvent was removed, the crude
calculated for C34H25NO2 [M+H]+: 480.1958, found:
480.1948.
mixture was purified by silica gel column chromatography
(dichloromethane/hexane = 3/2), to give desired product
1
2
3
4
5
6
7
8
1
as a dark red solid (86 mg, 71 %). H NMR (400 MHz,
10-Bromo-N,N-bis(4-methoxyphenyl)perylen-3-amine
(12). A solution of N-bromosuccinimide (NBS) (165 mg,
0.93 mmol) in dry THF (30 mL) was added to a solution of
11 (304 mg, 0.63 mmol) in dry THF (120 mL) and stirred at
0 °C under nitrogen atmosphere for 30 min. The mixture
was poured into water and extracted with
dichloromethane. The organic layer was passed through a
phase separator paper and the solvent was removed, the
residue was purified by silica gel column chromatography
(dichloromethane/hexane = 3/2), to give desired product
CDCl3) δ: 8.31 (d, J = 8.2 Hz, 1H), 8.24 (d, J = 7.6 Hz, 1H),
8.19 (d, J = 8.0 Hz, 1H), 8.14 (d, J = 8.1 Hz, 1H), 8.08 (d, J =
7.9 Hz, 1H), 7.84 (d, J = 8.0 Hz, 1H), 7.73 (d, J = 7.9 Hz, 1H),
7.61–7.58 (m, 3H), 7.43 (d, J = 8.2 Hz, 2H), 7.35 (t, J = 8.0 Hz,
1H), 7.21 (d, J = 8.1 Hz, 1H), 6.98 (d, J = 8.9 Hz, 4H), 6.78 (d,
J = 8.9 Hz, 4H), 3.78 (s, 6H), 1.36 (s, 9H); HRMS (ESI-TOF)
calculated for C46H37NO2 [M+H]+: 636.2897, found:
636.2874.
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1-(10-(Bis(4-methoxyphenyl)amino)perylen-3-yl)-2-(4-
1
as a red solid (228 mg, 64 %). H NMR (400 MHz, CDCl3)
(tert-butyl)phenyl)ethane-1,2-dione (14).
The mixture
δ: 8.23 (d, J = 8.0 Hz, 1H), 8.18 (d, J = 8.0 Hz, 1H), 8.12 (d, J
= 8.4 Hz, 1H), 8.09 (d, J = 8.0 Hz, 1H), 7.94 (d, J = 8.3 Hz,
1H), 7.86 (d, J = 8.0 Hz, 1H), 7.76 (d, J = 8.3 Hz, 1H), 7.59 (t,
J = 8.0 Hz, 1H), 7.35 (t, J = 8.0 Hz, 1H), 7.19 (d, J = 8.4 Hz,
1H), 6.97 (d, J = 9.0 Hz, 4H), 6.78 (d, J = 9.0 Hz, 4H), 3.77
(s, 6H); HRMS (ESI-TOF) calculated for C34H24NO2Br
[M+H]+: 557.0985, found: 557.1010.
of 13 (77 mg, 0.12 mmol) and PdCl2 (89 mg, 0.50 mmol) in
DMSO (9 mL) was stirred at 140 °C overnight. The reaction
mixture was diluted with water and extracted with
dichloromethane. The combined organic layer was washed
with water and passed through a phase separator paper.
After the solvent was removed, the crude mixture was
purified by silica gel column chromatography
(dichloromethane), to give desired product as a dark
10-((4-(Tert-butyl)phenyl)ethynyl)-N,N-bis(4-
1
purple solid (56 mg, 69 %). H NMR (400 MHz, CDCl3) δ:
methoxyphenyl)perylen-3-amine (13). Compound 12 (107
mg, 0.19 mmol), CuI (32 mg, 0.17 mmol) and Pd(PPh3)2Cl2
(57 mg, 0.081 mmol) were weighed into a Schlenk tube
under nitrogen atmosphere. A mixture of piperidine (3 mL,
30.3 mmol) and 1,4-dioxane (8 mL) containing 4-tert-
butylphenylacetylene (0.1 mL, 0.56 mmol) were purged
with nitrogen before syringed into the tube. The resulting
solution was stirred at 105 °C overnight. The reaction
mixture was quenched with saturated aqueous NH4Cl and
extracted with dichloromethane. The combined organic
layer was washed with water and passed through a phase
9.33 (d, J = 8.0 Hz, 1H), 8.35 (d, J = 8.0 Hz, 1H), 8.28 (d, J =
7.6 Hz, 1H), 8.19 (d, J = 8.4 Hz, 1H), 8.04 (d, J = 8.0 Hz, 1H),
7.99 (d, J = 8.4 Hz, 2H), 7.89 (d, J = 7.6 Hz, 1H), 7.87 (d, J =
8.0 Hz, 1H), 7.76 (t, J = 8.0 Hz, 1H), 7.54 (d, J = 8.4 Hz, 2H),
7.38 (t, J = 7.6 Hz, 1H), 7.19 (d, J = 8.4 Hz, 1H), 6.97 (d, J =
9.0 Hz, 4H), 6.79 (d, J = 9.0 Hz, 4H), 3.78 (s, 6H), 1.35 (s,
9H); HRMS (ESI-TOF) calculated for C46H37NO4 [M+Na]+:
690.2615, found: 590.2617.
APery. [1,1'-Binaphthalene]-2,2'-dicarbaldehyde (16 mg,
0.052 mmol), 14 (50 mg, 0.075 mmol), and ammonium
acetate (301 mg, 3.9 mmol) were refluxed in acetic acid (7
mL) for 25.5 h. After cooling to room temperature, the
reaction mixture was neutralized with aqueous NH3 and
extracted with dichloromethane. The combined organic
layer was washed with water and brine and passed through
a phase separator paper. After the solvent was removed,
the crude mixture was purified by triethyl amine treated
Scheme 7. Synthesis of APery.
silica
gel
column
chromatography
(dichloromethane/hexane = 7/3), to give a mixture of the
structural isomers of lophine presursors (15) as a dark red
solid (38 mg, 63 %) which was used for the next step
without further purification. The product was identified by
HRMS, (ESI-TOF) calcd for C114H88N6O4 [M+Na]+:
1627.6759, found: 1627.6718.
Under nitrogen, to a solution of 15 (34 mg, 0.021 mmol)
in benzene (20 mL) was added a solution of potassium
ferricyanide (3.75 g, 11.4 mmol) and KOH (858 mg, 15.3
mmol) in water (20 mL), and the reaction mixture was
vigorously stirred overnight. The organic layer was
separated, exhaustively washed with water and passed
through a phase separator paper. After the solvent was
removed, the crude mixture was purified by triethyl amine
treated
silica
gel
column
chromatography
(dichloromethane/hexane = 4/1), to give a mixture of the
structural isomers of desired product (20 mg, 59 %) as a
black solid. One of the structural isomers was isolated by
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Object with Fast Photochromic Molecules. Adv. Optical
Mater. 2016, 4 (9), 1354−1357.
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high performance liquid chromatography (MeCN/THF =
5/1). H NMR (400 MHz, DMSO-d6) δ: 8.10 (d, J = 8.6 Hz,
1
1
2
3
4
5
6
7
8
1H), 8.01 (d, J = 8.6 Hz, 1H), 7.94 (d, J = 7.8 Hz, 1H), 7.86 (d,
J = 9.8 Hz, 1H), 7.44 (d, J = 7.5 Hz, 1H), 7.37–7.26 (m, 10H),
7.21 (d, J = 10.0 Hz, 1H), 7.09 (t, J = 7.8 Hz, 10H), 6.99–6.87
(m, 26H), 6.70 (d, J = 7.8 Hz, 1H), 6.62–6.59 (m, 4H), 8.50
(d, J = 9.0 Hz, 1H), 6.40 (d, J = 8.6 Hz, 1H), 6.17 (d, J = 8.6
Hz, 1H), 3.73 (m, 18H), 3.72 (s, 6H); HRMS (ESI-TOF)
calculated for C114H86N6O4 [M+H]+: 1603.6783, found:
1603.6801.
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ASSOCIATED CONTENT
Supporting Information
NMR spectra, ESI-TOF-MS spectra, HPLC charts and the
other experimental details (PDF). This material is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*jiro_abe@chem.aoyama.ac.jp
Author Contributions
The manuscript was written through contributions of all
authors.
Notes
Any additional relevant notes should be placed here.
ACKNOWLEDGMENT
This work was supported by JSPS KAKENHI Grant Number
JP18H05263.
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