162
F. Hu et al. / Dyes and Pigments 136 (2017) 161e167
in Scheme 1B, the triphenylamine and terpyridyl-based dithieny-
lethene (I-5o) shows the photocyclization-dependent ratiometric
fluorescent switch behaviors, affording the ring-closed isomer (I-
5c). It is worth mentioning that other dithienylethenes (by intro-
wt) under nitrogen, then the above system was added to the second
flask quickly under nitrogen, and stirring was continued for 17 h at
50 ꢁC. The reaction mixture was then allowed to reach ambient
temperature, filtrate, and extracted with dichloromethane. The
combined organic layers were dried (Na2SO4), concentrated and the
product was purified by silica gel column chromatography using
(petroleum ether and dichloromethane, v/v ¼ 10:1) as the eluent to
give 1.65 g of the product. Yield: 45%. 1H NMR (400 MHz, CDCl3):
ducing donorꢀ
p
(Dꢀ
p
),
p
ꢀacceptor
(
p
ꢀA), donorꢀ ꢀdonor
p
(Dꢀp
ꢀD) [32] and acceptorꢀ
p
ꢀacceptor (Aꢀ ꢀA) dye moieties
p
into the two sides of the switch) undergo photocyclization reaction
with the fluorescent quenching (Scheme 1A).
d
7.35 (d, J ¼ 8.5 Hz, Ar-2H), 7.25 (t, J ¼ 7.7 Hz, Ar-4H), 7.10 (d,
J ¼ 7.8 Hz, Ar-4H), 7.06e6.99 (m, Ar-4H), 6.90 (s, 1H, thiophene-H),
6.62 (s, 1H, thiophene-H), 2.89e2.77 (m, 2H, CH2), 2.76e2.65 (m,
2H, CH2), 2.10e2.01 (m, 2H, CH2), 1.97 (s, 3H, CH3), 1.88 (s, 3H, CH3).
2. Materials and methods
2.1. Experimental
13C NMR (100 MHz, CDCl3):
d 147.49 (s), 146.76 (s), 139.61 (s),
137.33e134.95 (m), 133.60 (d, J ¼ 10.2 Hz), 133.18 (s), 129.23 (s),
128.63 (s), 126.42 (d, J ¼ 74.4 Hz), 124.58 (d, J ¼ 61.9 Hz), 123.90 (s),
122.88 (s), 77.32 (s), 77.00 (s), 76.68 (s), 38.37 (d, J ¼ 10.4 Hz), 22.86
(s), 14.28 (d, J ¼ 17.1 Hz). MS: m/z ¼ 537.1346 (Mþ), calculated exact
mass: 537.1352. Anal.calcd for C33H28ClNS2: C, 73.65; H, 5.24; N,
2.60. Found: C, 73.60; H, 5.20; N, 2.60.
General: All manipulations were carried out under a nitrogen
atmosphere by using standard Schlenk techniques unless other-
wise stated. Solvents were distilled under nitrogen from sodium-
benzophenone (diethyl ether, THF) or calcium hydride (dichloro-
methane). Methanol was freshly distilled over magnesium-iodine.
Triethylamine were freshly distilled over KOH pellets. The Start-
ing materials 1, 2 and 3 were prepared according to the previously
reported methods [33]. The photochromic dithienylethenes I-1 [34]
and I-2 [35] were prepared according to literature reports.
Elemental analyses (C, H, and N) were performed by the Microan-
alytical Services, College of Chemistry, CCNU. 1H and 13C NMR
spectra were collected on American Varian Mercury Plus 400
spectrometer (400 MHz). 1H and 13C NMR chemical shifts are
relative to TMS. UVeVis spectra were obtained on U-3310 UV
spectrophotometer. UV light was irradiated using ZF5 UV lamp
2.2.1.2. Synthesis of I-4. The synthesis procedure is similar to I-3.
The product was purified by silica gel column chromatography
using (petroleum ether and dichloromethane, v/v ¼ 10:1) as the
eluent to give the product. Yield: 40%. 1H NMR (400 MHz, CDCl3):
d
7.36 (d, J ¼ 8.6 Hz, 4H, AreH), 7.28e7.20 (m, 8H, AreH), 7.15e7.07
(m, 8H, AreH), 7.02 (dd, J ¼ 11.1, 4.4 Hz, 8H, AreH), 6.95 (s, 2H,
thiophene-H), 2.83 (t, J ¼ 7.4 Hz, 4H, CH2), 2.11e2.04 (m, 2H, CH2),
1.97 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3):
d 147.47 (s), 146.63 (s),
139.35 (s), 136.57 (s), 134.45 (s), 133.62 (s), 128.97 (d, J ¼ 43.9 Hz),
(302 nm), and visible light irradiation (l > 420 nm) was carried out
128.74e126.74 (m), 126.03 (s), 124.06 (d, 31.5 Hz),
J
¼
by using a LZG 220 V 500 W tungsten lamp with cutoff filters. The
quantum yields were determined by comparing the reaction yields
of the diarylethenes against 1, 2-bis (2-methyl-5-phenyl-3-thienyl)
cyclopentene.
123.74e123.67 (m), 123.74e123.67 (m), 122.94 (d, J ¼ 26.7 Hz),
77.29 (s), 77.23e77.09 (m), 76.82 (d, J ¼ 31.9 Hz), 38.46 (s), 22.94 (s),
14.43 (s). MS: m/z ¼ 746.10 (Mþ), calculated exact mass: 746.28
(Mþ). Anal.calcd for C51H42N2S2: C, 82.00; H, 5.67; N, 3.75. Found: C,
82.01; H, 5.64; N, 3.70.
2.2. Synthesis
2.2.1.3. Synthesis of I-1. The synthesis procedure is similar to I-3.
The product was purified by silica gel column chromatography
using (petroleum ether and acetone, v/v ¼ 20:1) as the eluent to
give the product. Yield: 40%. 1H NMR (400 MHz, CDCl3):
2.2.1. Synthesis of the terpyridyl-based dithienylethenes (I-1 to I-5)
2.2.1.1. Synthesis of I-3. Compound 1 (2.64 g, 8.0 mmol) was dis-
solved in 15 mL of anhydrous THF under nitrogen and cooled
to ꢀ78 ꢁC. n-BuLi (3.20 mL, 2.5 M, 8.0 mmol) was slowly added and
the mixture was stirred for 20 min. Then B(OBu)3 (3.20 mL,
8.0 mmol) was added and stirring was continued at room tem-
perature for 3 h. Then in another flask added compound 3 (2.20 g,
6.8 mmol), Pd(PPh3)4 (0.55 g, 7% mol) and Na2CO3(aq) (24 mL, 20%
d
8.75e8.66 (m, 6H, pyridine-H), 7.87 (dd, J ¼ 15.5, 7.9 Hz, 4H,
pyridine-H), 7.76 (d, J ¼ 8.4 Hz, 2H, AreH), 7.32 (t, J ¼ 19.7 Hz, 2H,
AreH), 7.09 (s, 1H, thiophene-H), 6.64 (s, 1H, thiophene-H),
2.96e2.79 (m, 2H, CH2), 2.79e2.67 (m, 2H, CH2), 2.13e1.97 (m,
5H, CH2eCH3), 1.90 (s, 3H, CH3). 13C NMR (100 MHz, CDCl3):
d
156.51 (s), 156.03 (dd, J ¼ 30.5, 12.5 Hz), 149.22 (d, J ¼ 34.5 Hz),
136.83 (s), 135.09 (s), 132.00 (s), 128.79 (s), 127.61 (s), 126.73 (s),
125.88 (d, J ¼ 58.3 Hz), 125.59 (s), 125.53 (s), 125.72e123.41 (m),
121.31 (s), 118.38 (d, J ¼ 10.9 Hz), 77.29 (s), 76.81 (d, J ¼ 32.0 Hz),
76.41e76.11 (m), 38.35 (d, J ¼ 9.6 Hz), 22.84 (s), 14.43 (s), 14.18 (s).
MS: m/z ¼ 601.02 (Mþ), calculated exact mass: 601.14 (Mþ). Anal.-
calcd for C36H28ClNS2: C, 71.80; H, 4.69; N, 6.98. Found: C, 71.77; H,
4.64; N, 6.97.
2.2.1.4. Synthesis of I-2. The synthesis procedure is similar to I-3.
The product was purified by silica gel column chromatography
using (petroleum ether and acetone, v/v ¼ 10:1) as the eluent to
give the product. Yield: 30%. 1H NMR (400 MHz, CDCl3):
d
8.79e8.69 (m, 8H, pyridine-H), 8.64 (d, J ¼ 7.9 Hz, 4H, pyridine-H),
7.92e7.81 (m, 8H, pyridine-H), 7.63 (d, J ¼ 8.3 Hz, 4H, AreH),
7.36e7.29 (m, 4H, AreH), 7.16 (s, 2H, thiophene-H), 2.89 (t,
J ¼ 7.3 Hz, 4H, CH2), 2.12 (dd, J ¼ 14.6, 7.6 Hz, 2H, CH2), 2.04 (s, 6H,
CH3). 13C NMR (100 MHz, CDCl3):
d
155.95 (d, J ¼ 31.2 Hz), 149.39
(s), 149.01 (s), 138.91 (s), 136.79 (t, J ¼ 22.1 Hz), 135.13 (s), 134.59 (s),
Scheme 1. The structure of other dithienylethenes (A) and the triphenylamine and
terpyridyl-based dithienylethene (B).
127.62 (s), 125.55 (s), 124.43 (s), 123.73 (s), 121.28 (s), 118.33 (s),