Photochromism and electrical transport characteristics of a dyad and a polymer with diarylethene and quinoline units

Article abstract of DOI:10.1021/jo050710t

The synthesis of a series of photochromic compounds incorporating a phenylquinoline unit and the photophysical and electric transport properties are described. The dyad and polymer with a quinoline unit show a high quantum yield due to the enforced antipa

Full text of DOI:10.1021/jo050710t

Photochromism and Electrical Transport Characteristics of a
Dyad and a Polymer with Diarylethene and Quinoline Units
Hyunbong Choi,† Hyowon Lee,‡ Youngjin Kang,§ Eunkyoung Kim,*,| Sang Ook Kang,*,† and
Jaejung Ko*,†
Department of Chemistry, Korea University, Jochiwon, Chungnam 339-700, Korea, Advanced Material
Divisions, Korea Research Institute of Chemical Technology, P.O. Box 107, Yusung, Daejeon 305-600,
Korea, Division of Science Education, Kangwon National University, Chuncheon 200-701,
Korea, Department of Chemical Engineering, Yonsei University, 134 Sinchon-dong, Seodaemun-gu,
120-749 Seoul, Korea
jko@korea.ac.kr; eunkim@yonsei.ac.kr
Received April 9, 2005
The synthesis of a series of photochromic compounds incorporating a phenylquinoline unit and the
photophysical and electric transport properties are described. The dyad and polymer with a quinoline
unit show a high quantum yield due to the enforced antiparallel conformation of the dithienylethene
moieties. High carrier conductivity was observed in the closed form of the diarylethene with a
phenylquinoline unit.
SCHEME 1
Introduction
Photochromic compounds undergo reversible transfor-
mation between two distinct chemical isomers by differ-
ent colors of light.1 Switching between the two isomers
of 1,2-dithienylalkene derivatives can be accompanied by
changing physical properties such as luminescence,2
refractive index,3 electronic conductivity,4 optical rota-
tion,5 and viscosity.6 Some of the most promising candi-
dates for photochromic materials are 1,2-diarylethene
derivatives due to their remarkable thermal stability and
fatigue resistance7 (Scheme 1).
properties to excite the molecule at a desired wavelength8
or creating the electrical changes upon the photochromic
reactions. The Tsujioka9 and Taniguchi10 groups reported
(2) (a) Norsten, T. B.; Branda, N. R. J. Am. Chem. Soc. 2001, 123,
1784. (b) Tsivgoulis, G.; Lehn, J.-M. Angew. Chem., Int. Ed. Engl. 1995,
34, 1119. (c) Norsten, T. B.; Branda, N. R. Adv. Mater. 2001, 13, 347.
(d) Yam, V. W.-W.; Ko, C.-C.; Zhu, N. J. Am. Chem. Soc. 2004, 126,
12734.
The functionalization of the photochromic unit is a
major issue for reasons such as tuning the absorption
* To whom correspondence should be addressed. (J.K.) Fax:
82 41 867 5396. Tel: 82 41 860 1337. (E.K.) Fax: 82 2 361 6401. Tel:
82 2 2123 5752.
(3) (a) Kim, E.; Choi, Y.-K.; Lee, M.-H. Macromolecules 1999, 32,
4855. (b) Kim, M.-S.; Maruyama, H.; Kawai, T.; Irie, M. Chem. Mater.
2003, 15, 4539.
† Korea University.
(4) Kawai, T.; Kunitake, T.; Irie, M. Chem. Lett. 1999, 905.
(5) Feringa, B. L.; van Delden, R. A.; Koumura, N.; Geertsema, E.
M. Chem. Rev. 2000, 100, 1789.
‡ Korea Research Institute of Chemical Technology.
§ Kangwon National University.
| Yonsei University.
(6) Lucas, L. N.; van Esch, J.; Kellog, R. M.; Feringa, B. L. Chem.
Commun. 2001, 759.
(1) (a) Irie, M. Chem. Rev. 2000, 100, 1685. (b) Kawata, S.; Kawata,
Y. Chem. Rev. 2000, 100, 1777. (c) Morimoto, M.; Kobatake, S.; Irie,
M. J. Am. Chem. Soc. 2003, 125, 11080. (d) Kaieda, T.; Kobatake, S.;
Miyasaka, H.; Murakami, M.; Iwai, N.; Nagata, Y.; Itaya, A.; Irie, M.
J. Am. Chem. Soc. 2002, 124, 2015. (e) Higashiguchi, K.; Matsuda, K.;
Tanifuji, N.; Irie, M. J. Am. Chem. Soc. 2005, 127, 8922.
(7) Hanazawa, M.; Sumiya, R.; Horikawa, Y.; Irie, M. J. Chem. Soc.,
Chem. Commun. 1992, 206
(8) (a) Peters, A.; McDonald, R.; Branda, N. R. Chem. Commun.
2002, 2274. (b) Kawai, T.; Iseda, T.; Irie, M. Chem. Commun. 2004,
72. (c) Frigoli, M.; Mehl, G. H. Chem. Commun. 2004, 818.
10.1021/jo050710t CCC: $30.25 © 2005 American Chemical Society
Published on Web 09/14/2005
J. Org. Chem. 2005, 70, 8291-8297
8291

Choi et al.
SCHEME 2a
a Reagents and conditions: (i) acetic anhydride, SnCl4, CH2Cl2, reflux (82%); (ii) 2-aminobenzophenone, diphenyl phosphate, toluene,
120 °C (76%).
SCHEME 3a
a Reagents and conditions: (i) diphenyl phosphate, m-cresol, 135 °C (74%).
that the diarylethenes with triphenylamine groups showed
good hole-transport characteristics. One can thus envi-
sion that the incorporation of 1,2-diarylethene with
molecules and polymers containing oxadiazole,11 benzo-
bisazole,12 quinoxaline,13 and quinoline14 offer highly
efficient electron-transport material. Recently, Jenekhe
and co-workers15 reported that a new n-type conjugated
copolymer containing 3,3′-dialkylthiophene and bis-
(phenylquinoline) moieties was shown to be a good
electron-transport material for polymer LEDs. One chal-
lenge of particular focus here is the development of more
efficient and robust electron-transport photochromic
compounds which can be utilized as a nondestructive
readout method of photomode optical memory using a
photocurrent detection16 and organic semiconductor
memory device.17 Accordingly, we attempted to synthe-
size such compounds by incorporating the diarylethene
with quinoline unit because the polyquinolines are
characterized by high thermal and good film forming
properties.18 Here, we report the photoswitching of a dyad
1 and polymer 3 containing diarylethene and quinoline
units and their electron-transport property.
Results and Discussion
Molecular Design and Synthesis. Schemes 2 and 3
describe the synthetic routes of monomer 1 and polymer
3 by the Friedla¨nder condensation reaction. Compound
1 was made in two steps from the 1,2-bis(2-methyl-3-
thienyl)perfluorocyclopentene according to the previous
procedures.15 The acetylation of the dithienyl perfluoro-
cyclopentene in the presence of acetic anhydride and
SnCl4 catalysts gave the diacetyl monomer. Phenyl
quinolinylation of diacetyl monomer with 2-aminobenzo-
phenone resulted in formation of dyad 1 in 74% yield
after column chromatography. The diacetyl monomer was
copolymerized with 3,3-dibenzoylbenzidine to yield the
copolymer 3 that contained the diarylethene. The dyad
1 was obtained as a colorless powder, which was soluble
in dichloromethane and tetrahydrofuran. The closed-ring
dyad 2 was prepared by irradiating a dichloromethane
solution of 1 with UV light (λ ) 365 nm) and isolated
from the blue solution by HPLC. The dyads (1 and 2)
and polymer 3 were identified by NMR, IR, and elemental
analysis. In the 1H NMR spectrum of 1, one methyl
(9) Tsujioka, T.; Masuda, K. Appl. Phys. Lett. 2003, 83, 4978.
(10) Taniguchi, A.; Tsujioka, T.; Hamada, Y.; Shibata, k.; Fuyuki,
T. Jpn. J. Appl. Phys. 2001, 40, 7029.
(11) Peng, Z. H.; Bao, Z. N.; Galvin, M. E. Adv. Mater. 1998, 10,
680.
(12) Alam, M. M.; Jenekhe, S. A. Chem. Mater. 2002, 14, 4775.
(13) Cui, Y.; Zhang, X.; Jenekhe, S. A. Macromolecules 1999, 32,
3824.
(14) (a) Zhang, X.; Jenekhe, S. A. Macromolecules 2000, 33, 2069.
(b) Zhang, X.; Kale, D. M.; Jenekhe, S. A. Macromolecules 2002, 35,
382.
(15) (a) Tonzola, C. J.; Alam, M. M.; Bean, B. A.; Jenekhe, S. A.
Macromolecules 2004, 37, 3554. (b) Tonzola, C. J.; Alam, M. M.;
Jenekhe, S. A. Adv. Mater. 2002, 14, 1086.
(16) Tsujioka, T.; Hamada, Y.; Shibata, A.; Taniguchi, A.; Fuyuki,
T. Appl. Phys. Lett. 2001, 78, 2282.
(18) (a) Alam, M. M.; Jenekhe, S. A. J. Phys. Chem. B 2001, 105,
2479. (b) Agrawal, A. K.; Jenekhe, S. A. Chem. Mater. 1996, 8, 579.
(17) Tsujioka, T.; Irie, M. J. Opt. Soc. Am. B 2002, 19, 297.
8292 J. Org. Chem., Vol. 70, No. 21, 2005

Photochromism of a Dyad
FIGURE 1. (A) UV-vis spectra of compound 1 (s) and a solution of 1/2 in the photostationary state (‚ ‚ ‚) in dichloromethane
after irradiation with 365 nm light for 5 min. (B) UV-vis spectra of compound 3 (‚ ‚ ‚) and a solution of 3o/3c in the photostationary
state (s) in dichloromethane after irradiation with 365 nm light for 5 min.
TABLE 1. Quantum Yields and Conversions of
nitrogen shows that the decomposition temperature of
the copolymer was in the range 420-440 °C. A glass
transition (Tg) was determined by differential scanning
calorimetry (DSC). The Tg was 221 °C. The value is
comparable to those observed for the poly(phenylquino-
line)s.20
Photochromic Reaction of 1-3 in CH2Cl2
diarylethene
Φ (%)
conversion (%)
1 f 2
64a
0.3b
68a
0.5b
7
2 f 1
100
3o f 3c
3c f 3o
100
Molecular Structure of 1 and 2. The single crystals
of 1 and 2 were obtained from the recrystallization in
the absence and presence of UV light in MeOH/THF.
Figure 2 shows ORTEP drawings of the open-ring isomer
1 and the closed-ring isomer 2. The dihedral angle
between thiophene ring and perfluorocyclopentene ring
in 1 was 40.15°, suggesting the presence of some π-con-
jugation between the thienyl ring and the ethene unit.
The distance between the two reactive carbons C6-C29
in 1 was 3.496 Å, which is short enough for the reaction
to take place.21 The two molecules 1 and 2 were identical
except for the dihedral angle between the perfluoro-
cyclopentene ring and the thiophene ring. The dihedral
angle between the thiophene ring and perfluorocyclo-
pentene ring in 2 was 6.97°, suggesting that π-electrons
were delocalized through the molecule. The bond dis-
tances of C18-C19 and C27-C28 in 2 are 1.357 and
1.54 Å, respectively. There data clearly indicate that the
C18-C19 bond is a double bond, being significantly
shorter than the other carbon-carbon single bond.22
Cyclization Quantum Yields. Table 1 summarizes
the photochemical quantum yield of cyclization and
cycloreversion reactions of the compounds. The most
interesting property we found is the cyclization quantum
yield, which was measured as 64% in 1. This is the
highest quantum yield measured in diarylethene mol-
ecules except for a few diarylethene backbone polymers.23
The opening quantum yield in 2 f 1 turns out to be 0.3%.
The polymer 3 also showed high quantum yield in
cyclization (68%). The reason that compound 1 has the
high cyclization quantum yield can be interpreted as the
conformational orientation of crystal 1. It is generally
accepted that diarylethene molecules in the open form
a Measured at 365 nm. b Measured at 532 nm.
resonance was observed at δ 2.03. In the blue isomer 2
and copolymer 3, distinct new resonance peaks appeared
at δ 2.31 and 2.25, respectively. IR spectroscopy of
compound 1 and copolymer 3 showed the complete
disappearance of the carbonyl group (1712 cm-1) of the
starting materials and the appearance of strong new
bands between 1400 and 1600 cm-1, which are charac-
teristic of the quinoline uint. The structure of 1 and 2
was established by single-crystal X-ray analysis. The
dyad 1 in CH2Cl2 is colorless. Irradiation of dichloro-
methane solution 1 at 365 nm light resulted in an
immediate increase in the absorption intensity at 608 nm
(Figure 1A). In the photostationary state, 88% of 1 was
converted into the closed form 2. The photostationary
1
state was analyzed with H NMR spectroscopy by com-
paring the relative intensities of methyl proton signals.
After visible light irradiation (λ > 600 nm) for 15 min,
the colored solution of 2 was completely bleached, indi-
cating the formation of initial open form. Figure 1B shows
the absorption spectral change of 3 in CH2Cl2 by photo-
irradiation. Upon irradiation with 365 nm light, the
colorless solution of the open form of polymer 3 turned
deep green, in which a characteristic absorption maxi-
mum was observed at 672 nm. This color disappeared
upon irradiation with visible light (λ > 600 nm). A
bathochromic shift of 64 nm is observed when compared
with the maximum absorption value of dyad 2 and closed-
ring polymer 3, possibly due to increased π-delocalization.
Similar results have been observed for structurally
related dithienylethene derivatives.19 The copolymer is
also soluble in organic solvents such as dichloromethane
and tetrahydrofuran. The molecular weight Mw, based
on polystyrene standards, was 24200, and the poly-
dispersity was 2.72. Thermogravimetric analysis under
(20) Agrawal, A. K.; Jenekhe, S. A. Macromolecules 1993, 26, 895.
(21) (a) Ramamuthy, V.; Venkateson, K. Chem. Rev. 1987, 87, 433.
(b) Higashiguchi, K.; Matsuda, K.; Matsuo, M.; Yamada, T.; Irie, M.
J. Photochem. Photobiol. A: Chem. 2002, 152, 141.
(22) Pu, S.; Xu, J.; Shen, L.; Xiao, Q.; Yang, T.; Liu, G. Tetrahedron
Lett. 2005, 46, 871.
(23) Stellacci, F.; Bertarelli, C.; Toscano, F.; Gallazzi, M. C.; Zolti,
G.; Zerbi, G. Adv. Mater. 1999, 11, 292.
(19) Cho, H.; Kim, E. Macromolecules 2002, 35, 8654.
J. Org. Chem, Vol. 70, No. 21, 2005 8293

Choi et al.
FIGURE 2. (a) Crystal structure of open-ring isomer 1 (top) and a diagram showing intermolecular interactions between two
adjacent molecules in 1 (bottom). (b) Crystal structure of close-ring isomer 2 (top) and diagram showing intermolecular interactions
between two adjacent molecules in 2 (bottom) along with the atomic numbering scheme. Displacement ellipsoids are drawn at
the 50% probability level. Disordered C44′ and C45′ and solvent in 2 are omitted for clarity.
may exist as two conformational isomers labeled C2 and
Cs.24 To achieve high quantum yield, it is crucial to
increase the population of the antiparallel conformation
in the ground state.25 As shown in the crystal structure
of 1, the distortion angle between thiophene ring and
perfluorocyclopenten ring is relatively small. Thus, com-
pound 1 showed a high cyclization quantum yield due to
the enforced antiparallel conformation of the dithi-
8294 J. Org. Chem., Vol. 70, No. 21, 2005

Photochromism of a Dyad
FIGURE 3. B3LYP/3-21G-optimized structures of 1.
FIGURE 4. Applied voltage dependence of the current for a photocell containing polystyrene (90 wt %) and (a) 1 (10 wt %) or
(b) 3 (10 wt %) and (c) the pure polymer film of 3 upon irradiation with 365 nm light (colored, dotted line) and 532 nm (bleached,
solid line).
enylethene moieties.23 Although the crystal structure of
1 provided a partial explanation for the high cyclization
quantum yield, the photochromic reaction was carried out
in solution. Thus, further information about the confor-
mation of 1 in solution is important. Therefore, we have
carried out ab initio calculations to investigate the
relative stability of antiparallel and parallel conformers
of 1 (Figure 3). The density functional theory with
exchange correlation functionals of B3LYP was employed
with 3-21G for the geometry optimization, and B3LYP/
6-31G* calculations were carried out to obtain the rela-
tive energy at the B3LYP/3-21G-optimized geometries.
All of the calculations were carried out using a suite of
Gaussian 98 programs.26 The relative stability in solution
(solvent is dichloromethane, MC, and its dielectric con-
stant is 8.93) was compared by the self-consistent reac-
tion field (SCRF) calculations using the Onsager model,27
which places the solute in a spherical cavity within the
solvent reaction field. For Onsager model calculations,
the radii of solute molecules of parallel and antiparallel
structures were estimated to be 6.71 and 6.60 Å, respec-
tively, from the volume calculations. On the basis of the
B3LYP/6-31G* results in the gas phase, the antiparallel
conformer is lower in energy than parallel one by
1.30 kcal/mol, and in MC solution, it is lower by 1.50 kcal/
mol. The relative stability is almost the same in both the
gas and solution phase. These calculation results support
our discussion.
Electric Characteristics. We have examined the
redox potentials of 1 and 3 by CV. The CV of the solution
containing open form of compound 1 (1 × 10-3 mol/L) in
dichloromethane showed an irreversible current increase
beyond 1.5 V (vs Ag/AgCl). Upon excitation with UV light,
the colored solution showed an irreversible oxidation
peak at ∼1.6 V, indicating that the oxidation potential
of the closed form becomes lower than that of the open
isomer. In the case of polymer 3, the open form showed
an irreversible oxidation peak at 1.1 V, which was shifted
to ∼1.2 V upon excitation with a UV light (365 nm) (see
the Surporting Information). To examine the photo-
induced electric property change, current-voltage (I-V)
(24) Irie, M.; Mohri, M. J. Org. Chem. 1988, 53, 803.
(25) Lammi, R. K.; Ambroise, A.; Balasubramanian, T.; Wagner, R.
W.; Bocian, D. F.; Holten, D.; Lindsey, J. S. J. Am. Chem. Soc. 2000,
122, 7579.
(26) Frisch, M. J. et al. Gaussian 98, revision A6; Gaussian Inc.:
Pittsburgh, PA, 1999.
(27) (a) Onsager, L. J. Am. Chem. Soc. 1936, 58, 1486. (b) Wong,
M. W.; Frisch, M. J.; Wiberg, K. B. J. Am. Chem. Soc. 1991, 113, 4776.
(c) Wong, M. W.; Wiberg, K. B.; Frisch, M. J. J. Am. Chem. Soc. 1992,
114, 523. (d) Wong, M. W.; Wiberg, K. B.; Frisch, M. J. J. Am. Chem.
Soc. 1992, 114, 1645.
J. Org. Chem, Vol. 70, No. 21, 2005 8295

Choi et al.
0.71073 Å) radiation, operating at 50 kV and 30 mA and a
CCD detector; 45 frames of two-dimensional diffraction images
were collected and processed to obtain the cell parameters and
orientation matrix. All data collections were performed at
223 K. The data collection 2θ ranges are 3.24-56.88° for 1,
3.06-49.42 for 2, respectively. No significant decay was
observed during the data collection. The raw data were
processed to give structure factors using the SAINT program.
Each structure was solved by direction methods and refined
by full matrix least squares against F2 for all data using
SHELXTL software (version 5.10).30 All non-hydrogen atoms
in compounds 1 and 2 were anisotropically refined. All other
hydrogen atoms were included in the calculated positions and
were refined by using a riding model. The crystal system in
compound 1 is triclinic and has a P1h space group. The
compounds 2 cocrystallize with methanol, and crystal system
is the triclinic space groups and P1h. There are one and a half
solvent (methanol) molecules disordered in the asymmetric
unit. The disordered solvent molecules were modeled success-
fully and their contribution was also included in the structure
factor. One of oxygen atom in methanol was heavily disordered.
Therefore, the oxygen atom was divided into two parts, O50
and O50′, with an occupancy of 0.20(2) and 0.30(2), respec-
tively. However, hydrogen atoms in methanol were not in-
cluded in the calculated positions.
Determination of Quantum Yields. The quantum yield
of the photochromic ring-cyclization of 1 was determined from
the absorption changes at λmax in UV spectra upon excitation
with UV light for the ring-closure reaction and visible light
for the ring- opening reaction. The molar extinction coefficients
of 1 and 2 are 4.6 ×104 M-1 cm-1 and 4.1 × 104 M-1 cm-1 at
365 nm, respectively. The quantum yield of the photochromic
ring-cyclization of 3 was determined from the 1H NMR signal
changes of methyl resonance peak at δ 2.05. Conversion and
the number of absorbed photons were determined at a given
radiation power and absorbance of the sample. Then, quantum
yield was determined according to the method described in ref
31.
Electric Characteristics. A photocell was fabricated by
spin coating of the solution of polystyrene (90 wt %) and
compound 1 or 3 (10 wt %) and 3 (100 wt %) onto a precleaned
ITO electrode coated glass and then dried at 70 °C for 24 h.
The thickness of the polymer film was determined by an R-step
(R-step Model-500) and was about 200 nm. Au strip (purity
>99.9%, Aldrich) was vacuum deposited to a thickness of
40 nm onto the polymer film, using a mask to form devices of
Au/polymer/ITO with an active area of 0.02 cm2 per device.
During the film formation and device fabrication, the color of
the film was maintained. The current-voltage (I-V) charac-
teristics were measured on a photocell at the room tempera-
ture. Each device was analyzed at least five times. The relative
error of the analysis was about 5%. The I-V characteristics
of the device were measured in colored state by UV excitation
and then under photostationary conditions (irradiating the
device with 532 nm laser for 2 h) to convert the diarylethene
unit in an open form. The potential change from 0 to 2 V and
2 to 0 V was repeated for at least 10 cycles but there was no
detectable decomposition during the cycles.
characteristics were measured on a photocell containing
a 1 and 3 dispersed polymer layer. Figure 4 shows the
applied voltage dependence of the current for the
photocells containing 1 and 3 polymer layer. The cell
fabricated from closed form of 1 showed a sharp current
increase by the potential rise. The current at 2 V was
3.6 times larger than that of the cell prepared from the
open isomer 1 (bleached cell). The current increase by
the potential rise was also observed for the open isomer
1, but the slope of I against V of the cell fabricated from
the open form of 1 was much smaller than that of the
closed form. It demonstrates that the extension of
π-conjugation between the thienyl rings and the ethene
unit in the closed form leads higher current response in
the potential than in the open form where such π-con-
jugation is limited. In the photocell containing 3, the
current increases 2 times larger than that of the open
form at 2 V. It may be attributable to the geometrical
characteristics due to the enforced configuration of the
dithienylethene moieties in the polymeric form, where
dithienylethene moieties are chemically bound. The
electric-current characteristics depends on the carrier
conductivity (σ) of the layer, and the slope of I-V curve
relates to resistance (1/σ). Compounds with phenylquino-
line groups show high electrical transport characteris-
tics;15 thus, the diarylethenes with such groups are also
regarded as having electrical conductivity. Importantly,
having a photochromic diarylethenes unit, the electrical
properties can be modulated by UV and visible light,
which can increase and decrease, respectively, the elec-
trical conductivity. Indeed the electrical conductivity,
estimated typically from the slope of a linear region in
an I-V plot, is much enhanced in the closed form and
reduced in the open form, as shown in Figure 4. The
electrical modulation was possible by optically by using
UV and visible light sources. The I-V plot for the pure
film of 3 is shown in Figure 4C, indicating large increase
in conductivity when it is excited by UV light.
In summary, we have synthesized a series of photo-
chromic compounds incorporating bis(phenylquinoline)-
unit and investigated the photophysical and electric
transport properties. Compounds 1 and 3 show a high
quantum yield due to the enforced antiparallel conforma-
tion of the dithienylethene moieties. Good transport
characteristics were observed in the colored form of the
diarylethenes with phenylquinoline group.
Experimental Section
All reactions were carried out under an argon atmosphere.
1,2-Bis(2-methyl-3-thienyl)perfluorocyclopentene,2 3,3-diben-
zoylbenzidine,28 and 1,2-bis(5-acetyl-2-methyl-3-thienyl)per-
fluorocyclopentene15 were synthesized using a modified pro-
cedure from previous references. For general experimental
details and instrumentation, see our previous publication.29
X-ray Crystallography. Suitable crystals of 1 and 2 were
obtained from the recrystallization in the presence or absence
of UV light in MeOH/THF. The crystals of 1 and 2 were
attached to glass fibers and mounted on a diffractometer
equipped with a graphite-monochromated Mo KR (λ )
1,2-Bis[5-(4-phenylquinolinyl)-2-methyl-3-thienyl]per-
fluorocyclopentene (1). A mixture of 1,2-bis(5,5’-diacetyl-
2-methyl-3-thienyl)perfluorocyclopentene (1 g, 2.21 mmol),
2-aminobenzophenone (0.959 g, 4.86 mmol), and diphenyl
phosphate (11 g) in toluene (10 mL) was purged with argon
for 20 min. The mixture was refluxed at 120 °C overnight. The
mixture was precipitated into 10% triethylamine/ethanol. The
product was purified on silica gel column (eluent 1:1 CH2Cl2/
1
hexane) to give 1 in 70% yield: mp 204 °C; H NMR (CDCl3)
δ 8.12 (d, J ) 8.10 Hz, 2H), 7.85 (d, J ) 8.10 Hz, 2H), 7.73 (s,
(28) Pelter, M. W.; Stille, J. K. Macromolecules 1990, 23, 2418.
(29) (a) Kim, S.; Kim, J. S.; Kim, S. K.; Suh, I.-H.; Kang, S. O.; Ko,
J. Inorg. Chem. 2005, 44, 1846. (b) Lee, T.; Jung, I.; Song, K. H.; Lee,
H.; Choi, J.; Lee, K.; Lee, B. J.; Pak, J. Y.; Lee, C.; Kang, S. O.; Ko, J.
Organometallics 2004, 23, 5280.
(30) SHELXTL NT Crystal Structure Analysis Package, Version
5.14; Bruker AXS, Analytical X-ray System, Madison, WI, 1999.
(31) Mejiritski, A., Polykarpov, A. Y., Sarker, A. M., Neckkers, D.
C., J. Photochem. Photobiol. 1997, 108, 289.
8296 J. Org. Chem., Vol. 70, No. 21, 2005

Photochromism of a Dyad
2H), 7.68 (d, J ) 5.70 Hz, 4H), 7.52 (m, 6H), 7.48 (m, 4H),
7.42 (s, 2H), 2.03 (s, 6H); 13C{1H} NMR (CDCl3): δ 150.8, 149.5,
148.5, 145.5, 143.6, 138.0, 130.5, 129.7, 129.2, 128.7, 128.1,
127.1, 126.7, 126.0, 125.1, 117.3, 116.2, 115.2, 114.2, 15.2 Anal.
Calcd for C45H28F6N2S2: C, 69.75; H, 3.64. Found: C, 69.42; H,
3.51.
precipitated into 10% triethylamine/ethanol. The green solid
was isolated, and the polymer was extracted with 20% tri-
ethylamine/ethanol. The polymer was dissolved in CHCl3 and
precipitated into ethanol. The resulting polymer 3 was dried
1
under vacuum for 12 h: yield 0.37 g (70%); H NMR (CDCl3)
δ 8.15 (d, 2H), 8.09 (s, 2H), 8.00 (d, 2H), 7.71 (s, 2H), 7.54 (br,
10H), 7.42 (s, 2H), 2.05 (s, 6H); 13C{1H} NMR (CDCl3) δ 151.0,
149.5, 148.2, 145.6, 143.7, 138.2, 137.9, 136.2, 129.8, 129.4,
129.0, 128.7, 127.7, 126.3, 126.0, 125.5, 123.9, 117.9, 117.4,
116.3, 15.0. Anal. Calcd for C45H26F6N2S2: C, 69.94; H, 3.39.
Found: C, 69.56; H, 3.28.
Closed-Ring Isomer of 1 (2). Compound 2 was isolated
by chromatographing a photostationary solution containing 1
and 2 through HPLC (silica gel column) with hexane as the
eluent to yield a blue powder: 1H NMR (CDCl3) δ 8.14 (d, J )
9.00 Hz, 2H), 7.83 (d, J ) 8.70 Hz, 2H), 7.74 (s, 2H), 7.71 (d,
J ) 6.60 Hz, 4H), 7.55 (m, 6H), 7.45 (m, 4H), 7.08 (s, 2H),
2.31 (s, 6H); 13C{1H} NMR (CDCl3) δ 150.4, 149.2, 147.5, 144.5,
143.3, 137.8, 131.5, 129.2, 128.2, 127.3, 127.1, 126.4, 126.2,
126.0, 125.4, 118.3, 117.2, 115.2, 113.2, 15.7 Anal. Calcd for
C45H28F6N2S2: C, 69.75; H, 3.64. Found: C, 69.32; H, 3.41.
Poly(2,2’-(1,2-bis(2-methyl-3-thienyl)perfluorocyclo-
pentenylene-6,6’-bis(4-phenylquinoline))) (3). 1,2-Bis(5,
5’-diacetyl-2-methyl-3-thienyl)perfluorocyclopentene (0.30 g,
0.66 mmol), 3,3’-dibenzoylbenzidine (0.26 g, 0.66 mmol), di-
phenyl phosphate (4.83 g), and m-cresol (5 g) were placed to a
Schlenk tube. The tube was purged with argon. The reaction
temperature was raised to 130-135 °C. The polymerization
mixture was stirred at this temperature for 60 h and then
Acknowledgment. The present research was finan-
cially supported by the KOSEF (National Research
Laboratory, 2005)
Supporting Information Available: Tables listing crys-
tallographic information, atomic coordinates and U(eq) values,
and intramolecular bond distances and angle and crystal-
lographic data (CIF) for 1 and 2 and cyclic voltammogram data
for 1 and 3. This material is available free of charge via the
Internet at http://pubs.acs.org.
JO050710T
J. Org. Chem, Vol. 70, No. 21, 2005 8297