Design, syntheses and photochromic properties of dithienylcyclopentene optical molecular switches

Article abstract of DOI:10.1002/poc.3584

A kind of basal diarylethene through an easy synthetic procedure was synthesized and characterized, and a Suzuki coupling reaction was frequently operated to obtain the diarylethenes derivatives with some vivid functional groups like bromo, amido and pyridine. Two methods for derivatives of these switches contain porphyrins were described. All of their spectroscopic and photochromic properties were studied and intercompared. It is indicated that the difference in electron densities of the π-conjugated system of the closed forms has effects upon the absorption maxima in visible region of UV–Vis spectra. Dithienylcyclopentenes linked to porphyrins could emit luminescence substantially that display potentials to be used in the applications of nondestructive readout upon binary data storage and smart materials.

Full text of DOI:10.1002/poc.3584

Research article
Received: 1 March 2016,
Revised: 28 March 2016,
Accepted: 22 April 2016,
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI: 10.1002/poc.3584
Design, syntheses and photochromic
properties of dithienylcyclopentene optical
molecular switches
Chuanming Yua, Bingcheng Hua*, Cheng Liua and Jiting Lia
A kind of basal diarylethene through an easy synthetic procedure was synthesized and characterized, and a Suzuki coupling
reaction was frequently operated to obtain the diarylethenes derivatives with some vivid functional groups like bromo,
amido and pyridine. Two methods for derivatives of these switches contain porphyrins were described. All of their spectro-
scopic and photochromic properties were studied and intercompared. It is indicated that the difference in electron densities
of the π-conjugated system of the closed forms has effects upon the absorption maxima in visible region of UV–Vis spectra.
Dithienylcyclopentenes linked to porphyrins could emit luminescence substantially that display potentials to be used in the
applications of nondestructive readout upon binary data storage and smart materials.
Keywords: photochromism; diarylethene; UV–Vis spectroscopy; photo-conversion
or 6 carbons) by a Suzuki–Miyaura reaction. Another useful
method to form this ring in the last procedure is the ring closure
INTRODUCTION
Organic photochromic molecules are playing an increasing vital
role in optical electronic devices,[1,2] such as molecular
switches,[3] molecular probes[4] and optical information stor-
age[5] because of their photochromic reversibility.[6] Nondestruc-
tive readout is one of the most attractive aims[7] in optical
materials for their applications in photo memory area.[8] The
fluorescent tuning with fast response times and high sensitivity
is a convenient mean of modulating the variable properties.[9]
Photochromism is defined as reversible transformation of a mol-
ecule between two isomers having different absorption spectra
under the appropriate light.[10] Several kinds of photochromic
compounds have been reported in the past decades, including
diarylethenes,[11] spiropyrans,[12] fulguides[13] stilbenes,[14]
azobenzenes,[15] nitrones,[16] naphthopyrans,[17] spirooxazines,[18]
quinines[19] and viologens[20] etc. These compounds characteristi-
cally exhibit two different chemical forms (open-ring form and
closed-ring form) which would transformed from one to the other
upon irradiation with light of corresponding wavelength. Among
many known photochromic systems, diarylethenes exhibited the
most favorable thermal and optical stability.
reaction of a diketone by a McMurry reaction which is exhibited
in Scheme 2. Thus, the generation of substituted cycloalkene can
be achieved either through a ring-closure by a McMurry reaction
or directly get from a cycloalkene by the Suzuki coupled reac-
tion. The McMurry reaction was preferred, because the previous
materials were not obtained so conveniently in the Suzuki
coupled reaction, and the McMurry reaction can be carried out
in two successful steps in a one-pot procedure.
The key intermediates of the McMurry reaction shown in
Scheme 2 are 1,5-dithienyl-1,5-diketones 3, 7 and 9. The most di-
rect method for the preparation of thienyl diketones is a Friedel–
Crafts acylation reaction of the corresponding aryl compounds
with a glutaryl chloride. The 2- and 5-positions of thiophene
should be substituted in view of that the most active positions
in the thiophene molecule are the 2- and 5-positions, but in
the synthetic route shown in Scheme 2 the acylation must occur
at the 3-position. Thus, the chlorination reaction of 1 with N-
chlorosuccinimide was operated in THF superseding traditional
benzene because of its better solubleness and hypotoxicity.
The Friedel–Crafts acylation of 3 and 6 with glutaryl dichloride
in CH2Cl2 using AlCl3 as a Lewis acid gave the oily reaction prod-
ucts, from which the desired 1,5-diketone 3 and 7 could be sep-
arated by column chromatography with petroleum-ether (PE) in
both about 40% yield. Ring closure of 3, 7 and 9 by a McMurry
reaction with Zn and TiCl4 in THF at 65 °C gave the desired 1,5-
dithienylcyclopentenes 4, 8 and 10 in 56%, 12% and 32% yield
after purification using column chromatography with PE.
Recently we synthesized a series of diarylethenes through a rather
easy synthetic procedure[21] wherein than perfluorocyclopentene de-
rivatives are prepared. In this paper we present the full details on the
synthesis and derivatization of these dithienylcyclopentene through
a Suzuki coupling reaction. We also report methods for derivatization
of these switches with porphyrins, and conclude with preliminary
data on the photochromic properties of these compounds.
RESULTS AND DISCUSSION
* Correspondence to: Bingcheng Hu, (Prof. Dr.), School of Chemical Engineering,
Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China.
Email: hubingcheng210094@163.com
Synthesis
The synthetic approach to functionalized dithienylcyclopentenes
is shown in Scheme 1. In this route, the central cycloalkene ring
is formed from the halogenated cycloalkene (always contain 4, 5
a C. Yu, B. Hu, C. Liu, J. Li
School of Chemical Engineering, Nanjing University of Science and
Technology, Nanjing 210094, China
J. Phys. Org. Chem. (2016)
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C. YU ET AL.
coupled reaction. So we attempted to synthesize the 1,5-bis(2-
methyl-5-bromothiophene)-cyclopentene 17 followed the
synthetic routes in Scheme 3 starting from 2-bromo-5-methy-
lthiophene 13 which is brominated from 2-methylthiophene 1
with NBS. The next Friedel–Crafts acylation of 13 with glutaryl
chloride and AlCl3 was carried out in CH2Cl2 to afford an oleosus
bar, in which the desired product 16 was unfortunately not been
detected, however the 1,5-diketone 14 and 15 were isolated by
column chromatography with PE in 28% and 21% yield. Because
of the lack of 1,5-diketone 16, another approach was performed
in accordance with Scheme 4. Before the addition of bromine,
the 1,5-diketone 4 was lithiated with n-BuLi in THF at À78 °C to
gave the product 17.
The photochromic switch 4 can easily be functionalized in
many different ways. Compound 4 can successfully achieve a
lithium exchange at a low temperature (Scheme 4) thus provid-
ing an available bridge for the introduction of functionality. The
Suzuki coupled reaction provides a productive way to obtain
many functional photochromic switches. The synthetic routes
shown in Scheme 5 exhibited the practicability of Suzuki
coupled reaction on 1,5-dithienylcyclopentenes ulteriorly. The
photochromic switches 18 and 19 were easily obtained in 68%
and 71% yield by employing Suzuki coupled reaction with the in-
termediates 11, 12 and paradibromobenzene (PDBB) in THF; the
Pd(PPh3)4 and Na2CO3 were added as the catalysts. The synthesis
of target product 18 and 19 can be severally achieved by con-
trolling the different molar ratios when feeding materials. So
we attempted to synthesize the photochromic switch 20 as the
same method, but no desired diarylethene could be achieved.
Scheme 1. Synthesis of dithienylethenes
The second approach of 1,5-dithienylcyclopentenes 8 and 10
shown in Scheme 2 starting from compound 4 can be more
readily functionalized by a Suzuki coupled reaction, because
the synthesis of compound 4 can be performed on a large scale
and in a satisfactory yield. The Suzuki coupled reaction was car-
ried out with n-BuLi in anhydrous THF at À78 °C under nitrogen
atmosphere, and the chlorine was substituted by lithium which
can be further replaced by –B(OBu)2 with tributyl borate at
À70 °C to afford the intermediates 11 or 12 according to the
proportion of feeding materials. The intermediates 11 and 12
can be used directly in the next Suzuki coupled reaction with
4-bromopyridinium chloride as feeding materials, and Pd(PPh3)
4, Na2CO3 were added as catalysts to gave the desire product
1,5-bis(2-methyl-5-pyridylthiophene)-cyclopentene 8 and 1-(2-
methyl-5-pyridylthiophene)-5-(2-methyl-5-chlothiophene)-
cyclopentene 10.
Halogens are very versatile functional groups, and bromine al-
ways exhibit better react activity than chlorine in the Suzuki
Scheme 2. Synthesis of dithienycyclopentenes
Scheme 3. Boron esterification for dichlorothienycyclopentene
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DITHIENYLCYCLOPENTENE OPTICAL MOLECULAR SWITCHES
Scheme 4. Tentative synthetic routes for dibromothienycyclopentene
The photochromic switches 18
and 19 were predicted to provide
a versatile handle for more func-
tional groups than diarylethene 4.
The amino is an active chemical
group, on which many reactions oc-
cur with many common chemicals
such as inorganic acids, carboxylic
acid, acyl halide, ketone, nitrite,
etc., so we attempt to join an amino
to the molecular switch. The photo-
chromic switches 21 and 22 were
obtained as the above mentioned
method (Scheme 6). This switch is
expected to react with many func-
tional groups to generate desirable
compounds.
In order to investigate the avail-
Scheme 5. Synthesis of dibromothienycyclopentenes
ability of these photochromic
switches as bridges that can link
to functional compounds. The chemicals
24 was obtained through the treatment of
10 with equal molar equivalent of 23 in
CH2Cl2 followed by precipitation with hex-
ane in Scheme 7 and detected in the mass
spectroscopy. The photoswitch 27 was syn-
thesized through the Suzuki reaction of 19
and iodicporphyrin (Scheme 8).
Photochromic behavior
The photochromic behavior of compounds
induced by photoirradiation in dichlorometh-
ane was measured at room temperature. The
diarylethene underwent photoisomerization
between ring-open isomer and ring-closed
isomer upon alternating irradia-
Scheme 6. Synthesis of dianilinothienycyclopentenes
tion with UV light and visible light
(Fig. 1). The presence of isosbestic
points in all cases indicates clean
photochemical transformations
occur. Figures 2–6 respectively
show the changes of UV–Vis ab-
sorption of 10, 19, 24 and 27 of
solution in CH2Cl2 upon the ap-
propriate UV light. Table 1 shows
the absorption maxima for the
Scheme 7. Synthesis of dithienycyclopentenes contain pyridine complexing with tetraphenylporphyrin
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C. YU ET AL.
Scheme 8. Synthesis of 1-[2-methyl-5-(4-tetraphenylporphyrinphenyl)-3-thienyl)-2-[2-methyl-3-thienyl]cyclopentene
Figure 1. Photochemical reactions of dithienylcyclopentene with irradi-
ation of UV and visible light
open and closed forms of a number of the synthesized derivatives
Figure 4. Changes in UV–Vis absorption spectra of a CH2Cl2 solution of
24 upon irradiation with 365-nm light. Irradiation periods are 0, 10, 20,
40, 60, 80, 100, 120, 150 and 180 s
Figure 2. Changes in UV–Vis absorption spectra of a CH2Cl2 solution of
10 upon irradiation with 254-nm light. Irradiation periods are 0, 30, 60,
100 and 150 s
Figure 5. Changes in UV–Vis absorption spectra of a CH2Cl2 solution of
27 upon irradiation with 282-nm light. Irradiation periods are 0, 10, 20,
40, 60, 80, 100 and 150 s
functional groups which possess π-conjugation electron arise at
~417 nm. The new absorption is the Soret band of porphyrin and al-
ways occurs nearby. Upon irradiation at wavelength of their absorp-
tion maxima, the solutions of compounds 10 and 19 turned to
purple, and new absorption bands appear in the visible region at
500–520 nm.
As shown in Fig. 4, the absorption maximum of the open form
of compound 24 in dichloromethane was observed at 325 nm
and 373 nm. Within the first 10 s of irradiation with the UV light,
absorption band centered between 500 and 700 nm appears as
the photochromic compound is converted from the
light-colored ring-open form to the linearly π-conjugated
dark-colored ring-closed form. The absorption maxima of com-
pound 24 occurs at a longer wavelength and the band is
Figure 3. Changes in UV–Vis absorption spectra of a CH2Cl2 solution of
19 upon irradiation with 254-nm light. Irradiation periods are 0, 10, 20,
30, 50, 70, 100, 130 and 160 s
described in this article and their corresponding color. The absorp-
tion maxima of the open forms of 10 and 19 both appear at
wavelengths < 305 nm, but new absorption of the switches with
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DITHIENYLCYCLOPENTENE OPTICAL MOLECULAR SWITCHES
Figure 7. Emission spectra of photochrome 24 in solutions of CH2Cl2 (a)
open form and (b) closed form. λex = 490 nm, λem = 779, 841 nm
Figure 6. Cycling between the open and closed forms of the 27 by re-
petitive irradiation at λ = 282 nm and visible light at 20 °C in CH2Cl2. The
ordinate shows the formation of the closed form as monitored by the ab-
sorbance at 674 nm
In summary, a practical synthetic route to diarylethene 4 has
been described. The Suzuki coupling reaction can be repeatedly
performed to add some functional groups to the diarylethene. A
variety of dithienylcyclopentene-based compounds were ob-
tained to be used as molecure switches. The porphyrin-based
diarylethenes 24 and 27 show excellent switching behavior
and little fatigue and considerable luminescence. Furthermore,
it is foreseen that these favorable properties together with ad-
vanced electron devices will mightily accelerate the application
in photo-information storage with high-speed and high-capacity
and smart materials.
broader and arranges from 490 to 800 nm compared to com-
pound 10. Compound 27 shows a similar UV–Vis absorption
as shown in Fig. 5. Furthermore, it has a short region arranged
from 530 to 610 nm with very low absorption which could pro-
vide a potential nondestructive readout at this region in appli-
cation of data storage.
Another interesting phenomenon is that the Soret band of 24
red shifts from 417nm to 446 nm with the irradiation of the UV
light. And the similar redshift occurs on 27 and turned from
418 nm to 447 nm (Fig. 5). The reason may be that the form of
ring-closed isomer could increase the electronic density of the por-
phyrin and the transition energy reduces and results in redshift.
Irradiation of solutions of 10, 19, 24 and 27 in CH2Cl2 with vis-
ible light causes the absorption bands in the visible region to dis-
appear and the absorption band in the UV region between 250
and 340 nm was restored. Apparently, photochemical switching
between the ring-open and ring-closed form is reversible. Espe-
cially the photochromic switching of compounds 24 and 27 is
excellent, and at least five photochemical switching cycles be-
tween the open and closed form can be performed without
any obvious sign of degradation (Fig. 6). The added porphyrin
group possesses obvious luminescence which could be used to
read out the state of photoswitches.
Compound 24(open) phosphoresces at 779 nm and 841 nm
when induced with the light (λ = 490 nm) which has little effect
on the photochemical interconversion of 24 in either direction.
Accordingly, the ring-closed isomeric form luminesce quenched
while excited with this light (Fig. 7). Hence, a nondestructive
readout method would be provided refer to above. Moreover,
the emission intensity could be modulated by actinic reaction
between the open and closed isomers.
EXPERIMENTAL SECTION
Chemicals and solvents are purchased in Aladdin or Energy-
chemical. All solvents used in the reactions were distilled freshly
from appropriate drying agents before use. 1H NMR spectra
were recorded on a Bruker AVIII 300 or 500-MHz spectrometer
with CDCl3 or d6-DMSO as the solvents and TMS as the internal
standard. Chemical shifts are reported in δ (parts per million)
values. Mass spectra (MS) were recorded using
a TSQ
Quantum-HPLC/MS/MS (Thermo, USA). UV–Visible spectra were
measured by Shimadzu UV-1800 spectrophotometer. The irradi-
ation intensity of UV light is 100 μW/cm2 (365 nm) and
125 μW/cm2 (254 nm). The UV light (282 nm) comes from a Ultra-
violet High Pressure Mercury Lamps (UV LAMP, 500 μW/cm2)
with a specific filter. The Visible light comes from the sunshine
with a barrier filter, and the intensity is 320 μW/cm2.
2-Chloro-5-methylthiophene (2)
2-Methylthiophene (10 ml, 0.10 mol) and N-chlorosuccinimide
(13.3 g, 0.1 mol) were added to a stirred solution of THF (30 ml)
and acetic acid (30 ml). The suspension was stirred for 30 min
Table 1. UV–Vis absorption data of the open and closed forms of several compounds
Compounds
λ
max/nm
Ring-closed form
Isobestic points
Color of the
Ring-open form
Ring-open form
Ring-closed form
10
19
24
27
282
301
325, 373, 417
272, 418
505
519
446, 617
446, 672
329
338
Colorless
Colorless
Light red
Light red
Purple
Purple
Dark magenta
Dark magenta
429, 349, 362
370–380, 530–600
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C. YU ET AL.
at room temperature, then, after 1 h of heating at reflux, the
cooled mixture was poured into a 3 M NaOH solution (30 ml).
The organic phase was washed with a 3 M NaOH solution
(3 × 300 ml), dried (Na2SO4), filtered and the solvent evaporated
in vacuo to yield a slightly yellow liquid. Purification of the prod-
uct by vacuum distillation (19 Torr, 55 °C) afforded a colorless liq-
uid(11.7 g, 88%). b.p. 55 °C(19 Torr). 1H NMR(300 M Hz, CDCl3):
δ = 2.41 (s 3H), 6.52–6.53 (d, 1H), 6.68, 6.69 (d, 1H) ppm. MS (EI):
m/z = 131 [M+].
mixture, followed by washing with water (20 ml× 2) and brine.
Flash column chromatography on silica gel (ethyl acetate/PE = 1/
5) of the concentrated residue afforded 0.29 g of 8 in a yield of
67%. 1H NMR (500 MHz, CDCl3): δ = 2.03 (s, 6H), 2.09–2.15 (m, 2H),
2.84–2.87 (t, 4H), 7.23 (s, 2H), 7.36–7.37 (d, 4H), 8.53–8.54 (d, 4H)
ppm. MS (ESI): m/z = 437.05 [M + H+].
1-[2-Methyl-5-(4-pyridyl)-3-thienyl]-2-[2-methyl-5-chloro-3-thienyl]
cyclopentene (10)
It was synthesized in the same way as described before with
halving the n-BuLi and bromopyridine hydrochloride to obtain
0.28 g of 8 as a purple solid in a yield of 75%. 1H NMR
(500 MHz, d-DMSO): δ = 1.85 (s, 3H), 1.94 (s, 3H), 1.99–2.05 (m, 2H),
2.75–2.78 (t, 2H), 2.80–2.83 (t, 2H), 6.86 (s, 1H), 7.52–7.53 (d, 2H),
7.60 (s, 1H), 8.52–8.54 (d, 2H) ppm. MS (ESI): m/z=371.96 [M+H+].
Compounds 14,15 were obtained concurrently according to
the procedure of 3.
1,5-Bis(5-chloro-2-methylthien-3-yl)pentane-1,5-dione (3)
Under fast stirring of an ice-cooled solution of dry AlCl3 powder
(4.61 g, 34.5 mmol) in dichloromethane (50 ml), glutaryl
dichloride (2.05 g, 11.5 mmol) and 2 (3.06 g, 23.4 mmol) were suc-
cessively dropwise added. After addition, the reaction mixture
was stirred for 3 h at room temperature, and the color turned
to dark red. Then ice-cold mixture solution of conc HCl (20 ml)
and ice (30 g) were carefully added to the reaction mixture,
and the water layer was extracted with dichloromethane
(3 × 20 ml). The combined organic phases were washed with sat-
urated aqueous solution of NaHCO3, water and NaCl saturated
solution, dried (MgSO4), filtered and the solvent was evaporated
in vacuo to yield a brown tar (3.37 g, 80%). This tar can be puri-
fied by flash chromatography (PE:ethyl acetate = 10:1) to provide
a white solid (2.85 g, 68%), m.p. 82–85 °C. For further reaction, it
is, however, not necessary to purify this tar. 1H NMR (500 MHz,
CDCl3): δ 2.03–2.09 (m, 2 H), 2.66 (s, 6 H), 2.85–2.88 (t, 2 H), 7.19
(s, 2 H) ppm. MS (EI): m/z = 359.99 [M+].
1,2-Bis(2-methyl-4,5-dibromo-3-thienyl)cyclopentene (14)
Yield 28%. 1H NMR (500 MHz, CDCl3): δ = 2.15–2.21(m, 5H), 2.52
(s, 6H), 3.14–3.17(t, 4H) ppm.
1,2-Bis(2-methyl-3-thienyl)cyclopentene (15)
Yield 21%. 1H NMR (500 MHz, CDCl3): δ = 2.13–2.19(m, 2H), 2.53
(s, 6H), 2.95–2.98(t, 4H), 6.78–6.79(d, 2H), 7.55–7.56(d, 2H) ppm.
Compounds 18,19,21,22,27 were synthesized in the same
method as describe above.
1,2-Bis(2-methyl-5-chloro-3-thienyl)cyclopentene (4)
1,2-Bis[2-methyl-5-(4-bromophenyl)-3-thienyl)cyclopentene
(18)
A mixture of TiCl4 (0.8 ml, 5.2 mmol), Zn dust (0.44 g, 6.9 mmol)
and THF (25 ml) was stirred under nitrogen at reflux temperature
for 1 h. The mixture was cooled to room temperature, and 3
(1.00 g, 2.78 mmol) was added. The mixture was refluxed for
2 h, subsequently quenched with 10% aq. K2CO3 (25 ml) and ex-
tracted with dichloromethane (3× 20 ml), the combined organic
layers were washed with water (50 ml), dried with anhydrous
MgSO4 and the solvent was removed in vacuo. The compound
was purified by column chromatography (PE) to yield (0.46 g,
50%) of a white solid. m.p. 76.1–78.2. 1H NMR (500 MHz, CDCl3):
δ = 1.88 (s, 6 H),1.99–2.05 (m, 2 H), 2.70–2.73 (t, 4 H), 6.58 (s, 2 H)
ppm. MS (EI): m/z = 327.77 [M+].
Yield 44%. 1H NMR (400 MHz, CDCl3): δ = 1.99(s, 6H), 2.08(t, 2H),
2.83(t, 4H), 7.00(s, 2H), 7.34(d, 4H), 7.44(d, 4H) ppm. 13C NMR
(150 MHz, CDCl3) δ = 14.60, 23.17, 38.57, 120.84, 124.55, 126.91,
132.00, 133.57, 134.86, 135.17, 136.95, 138.55 ppm.
1-[2-Methyl-5-(4-bromophenyl)-3-thienyl)-2-[2-methyl-5-chloro-3-
thienyl]cyclopentene (19)
Yield 58%. 1H NMR (500 MHz, d-DMSO): δ = 1.84 (s,3H), 1.90
(s,3H), 1.96–2.02 (m, 2H), 2.72–2.75 (t, 2H), 2.77–2.80 (t, 2H),
6.83 (s, 1H), 7.30 (s, 1H), 7.47–7.49 (s, 2H), 7.54–7.56 (s, 2H)
ppm. 13C NMR (125.7 MHz, d-DMSO): δ = 13.89, 14.06, 37.92,
38.09, 120.20, 123.67, 124.98, 126.80, 127.38, 130.50, 130.86,
131.97, 132.94, 134.35, 134.88, 135.25, 136.67, 137.81 ppm.
1,2-Bis[2-methyl-5-(4-pyridyl)-3-thienyl]cyclopentene (8)
To a stirred solution of compound 4 (0.33 g, 1.0 mmol) in THF
(20 ml) at À78°C under dry nitrogen in the absence of light was
added dropwise 1.6 M n-BuLi in hexane (0.13 g, 2 mmol), and the
reaction mixture was stirred at À78 °C for a further 30 min. To the
reaction mixture was quickly added tributyl borate (0.46 g, 2 mmol)
by syringe, and the reaction mixture was stirred at room tempera-
ture for 1 h. The resulting reddish solution was used directly for the
following addition. To another Schlenk flask filled with 30ml of
degassed THF were added bromopyridine hydrochloride (0.41 g,
2.1mmol) and Pd(PPh3)4 (0.08 g, 0.06 mmol). After stirring for
15 min, 2.5ml of 2 M aqueous sodium carbonate solution
(5.0mmol) and 0.30 ml of ethylene glycol were added. The solution
was stirred for another 15 min under bubbling, before the temper-
ature was raised to 40 °C. To the mixture was then added the above
prepared reddish solution in one portion. The mixture was refluxed
for 2 h. After cooling, 50 ml of ethyl acetate was added to dilute the
1,2-Bis[2-methyl-5-(4-amimophenyl)-3-thienyl)cyclopentene
(21)
Yield, 62%. 1H NMR (400 MHz, CDCl3): δ = 1.95 (s, 6H), 1.97-2.07
(m, 2H), 2.82 (t, 4H), 3.73 (s, 4H), 6.65 (d, 4H), 6.88 (s, 2H), 7.30
(d, 4H) ppm.
1-[2-Methyl-5-(4-4-amimophenyl)-3-thienyl)-2-[2-methyl-5-
chloro-3-thienyl]cyclopentene (22)
Yield 65%. 1H NMR (500 MHz, CDCl3): δ = 1.88 (s, 3H), 1.96(s, 3H),
2.0–2.05 (m, 5H), 2.72–2.75 (t, 2H), 2.78–2.81 (t, 2H), 6.59–6.60
(d, 1H), 6.62 (s, 1H), 6.74 (s, 2H), 6.83 (s, 1H), 7.23–7.25 (d, 1H),
7.31–7.32 (d, 2H) ppm.
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DITHIENYLCYCLOPENTENE OPTICAL MOLECULAR SWITCHES
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1-[2-Methyl-5-(4-tetraphenylporphyrinphenyl)-3-thienyl)-2-
[2-methyl-3-thienyl]cyclopentene (27)
Yield 55%. 1H NMR (500 MHz, CDCl3): δ = 8.84 (s, 1H), 8.56–8.60
(d, 2H), 8.22–8.23 (d, 1H), 7.99–8.00 (d, 1H), 7.75–7.76 (d, 2H),
7.47–7.50 (4H), 7.15–7.34 (13H), 6.94–7.03 (9H), 6.78–6.80 (2H),
2.72–2.76 (t, 2H), 2.65–2.68 (t, 2H), 2.03–2.09 (br, 2H), 2.00 (s,
3H), 1.92 (s, 3H), –2.76 (s, 2H) ppm. MS (ESI, m/z): 949.29 [M + H]+.
Acknowledgements
This work was supported by Nanjing University of Science and
Technology. We thank Dr. Lan Yi for the spectra on NMR and
Dr. Chong Zhang for spectra of Mass and UV–Vis.
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Figure 1. 1H NMR spectrum of 2.
Figure 2. MS spectrum of 2.
Figure 3. 1H NMR spectrum of 3.
Figure 4. MS spectrum of 3.
Figure 5. 1H NMR spectrum of 4.
Figure 6. MS spectrum of 4.
Figure 7. 1H NMR spectrum of 10.
Figure 8. MS spectrum of 10.
Figure 9. 1H NMR spectrum of 8.
Figure 10. MS spectrum of 8.
Figure 10. 1H NMR spectrum of 14.
Figure 11. 1H NMR spectrum of 15.
Figure 12. 1H NMR spectrum of 19.
Figure 13. 13C NMR spectrum of 19.
Figure 14. 1H NMR spectrum of 22.
Figure 15. MS spectrum of 24.
Figure 16. 1H NMR spectrum of 27.
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J. Phys. Org. Chem. (2016)
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