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property relationship was studied by experimental observation
and theoretical calculations. MPP-s exhibited the least positive
solvatochromic effect and the largest emission shift in re-
sponse to acid stimuli, whereas MPP-d-CN exhibited the oppo-
site behavior. It is concluded that the inherent ICT feature of
the compound and the emission shift after protonation and
subsequent intramolecular H-bonding are inversely related.
Therefore, through facile and rational structural adjustment,
switching between two different fluorescence emission wave-
lengths can be easily achieved. In addition, XRD analysis dem-
onstrated that the prominent AIEE feature of MPP-d-CN is in-
duced by the inhibited intermolecular p–p interaction due to
the introduction of a CN group, which intensifies the deviation
of the BT moiety from the central MP ring. The present study
contributes to the basic understanding of tailoring of molecu-
lar structures to realize different emission shifts as a response
to acid stimuli for designing high-performance AIEE-active lu-
minogens.
tate (AgI) was filtered and washed with methanol. The filtrate was
treated with saturated Na S O aqueous solution to reduce the re-
2
2
3
maining I , and the solvent was removed on a rotary evaporator.
2
The remained solid was recrystallized from 95% ethanol to give
1
yellow powder in 92% yield (8.1 g). H NMR (500 MHz, CDCl ): d=
3
1
3
0.44 (s, 1H), 7.51 (s, 1H), 7.26 (s, 1H), 3.94 (s, 3H), 3.92 ppm (s,
H).
Synthesis of (E)-2-(4-iodo-2,5-dimethoxystyryl) benzo[d]thia-
zole (2)
A mixture of 2-methylbenzothiazole (563 mg, 3.77 mmol), 1 (1 g,
3
.43 mmol), acetic anhydride (3 mL), and acetic acid (1.5 mL) was
heated under reflux for 6 h, then cooled to room temperature.
After concentrated hydrochloric acid (10 mL) was added, the mix-
ture was filtered. The filtrate was neutralized with 30% aqueous
sodium hydroxide solution (20 mL) and gave a precipitate. The pre-
cipitate was purified by column chromatography on silica gel
using DCM: PE (2:1) as eluent to give bright yellow powder in 61%
1
yield (0.89 g). H NMR (500 MHz, CDCl ): d=8.04 (d, J=8.1 Hz, 1H),
3
7
1
.91 (d, J=7.8 Hz, 1H), 7.79 (d, J=16.3 Hz, 1H), 7.57 (d, J=16.3 Hz,
H), 7.52 (t, J=7.7 Hz, 1H), 7.42 (t, J=7.6 Hz, 1H), 7.39 (s, 1H), 7.09
13
(s, 1H), 3.94 ppm (s, 6H); C NMR (126 MHz, CDCl ): d=167.38,
Experimental Section
3
1
53.89, 152.76, 152.40, 134.45, 132.30, 126.35, 125.41, 125.03,
Materials
123.36, 122.99, 122.77, 121.56, 109.30, 87.53, 56.99, 56.39 ppm.
2
,5-Dimethoxybenzaldehyde, 2-methylbenzothiazole, benzothia-
Synthesis of (E)-2-(2,5-dimethoxy-4-(4,4,5,5-tetramethyl-
zole-2-acetonitrile, bis(pinacolato)diboron, 1,1’-bis(diphenylphos-
phino)ferrocene-palladium(II) dichloride [Pd(dppf)Cl ], 2-bromopyri-
1,3,2-dioxaborolan-2-yl)styryl)benzo[d]thiazole (3)
2
dine, and tetrakis(triphenylphosphine)palladium(0) [Pd(PPh ) ] were
3
4
Compound 2 (500 mg, 1.18 mmol) was dissolved in 20 mL of dry
purchased from Energy Chemical (Shanghai, China). All other mate-
rials were purchased from local commercial suppliers and were of
analytical reagent grade, unless otherwise stated. Solvents were
purified by using standard procedures. All the reactions were
monitored by thin-layer chromatography (TLC) with detection by
UV light.
1
,4-dioxane under argon atmosphere. Bis(pinacolato) diboron
(
(
625 mg, 2.46 mmol), KOAc (362.5 mg, 3.69 mmol) and Pd(dppf)Cl2
301.6 mg, 0.369 mmol) were added into the solution in turn. The
reaction mixture was degassed and heated to 1008C overnight.
The reaction was monitored by TLC. Upon completion, the mixture
was then extracted by DCM. The organic layer was separated and
dried over anhydrous Na SO , the solvent was removed under re-
2
4
Instruments
duced pressure. The crude product was purified by column chro-
1
13
matography on silica gel (DCM) to afford compound in 67% yield
H and C NMR spectra of the products were recorded on a Bruker
00 MHz NMR spectrometer in CDCl solvent using tetramethylsi-
1
as yellow oil (0.33 g). H NMR (500 MHz, CDCl ): d=8.03 (d, J=
3
5
3
8
.1 Hz, 1H), 7.90 (d, J=8.0 Hz, 1H), 7.86 (d, J=16.4 Hz, 1H), 7.60
lane (TMS) as the internal standard. Chemical shifts were given in
ppm and coupling constants (J) in Hz. HRMS spectra were recorded
on a Thermo Scientific LTQ Orbitrap XL using standard conditions
(d, J=16.3 Hz, 1H), 7.51 (t, J=7.6 Hz, 1H), 7.41 (t, J=7.5 Hz, 1H),
7
1
1
.29 (s, 1H), 7.14 (s, 1H), 3.98 (s, 3H), 3.90 (s, 3H), 1.42 ppm (s,
13
2H); C NMR (126 MHz, CDCl ): d=167.74, 158.43, 155.90, 153.67,
3
(
electrospray ionization, ESI). UV absorption spectra were obtained
51.73, 134.41, 133.12, 127.48, 126.15, 125.24, 123.59, 122.81,
on a UV/vis spectrophotometer (U-3310) in the region 200–650 nm
ꢀ1
121.51, 119.17, 109.76, 83.53, 56.71, 56.25, 24.87 ppm.
using cuvettes of 1 cm path length (scan speed: 300 nmmin ,
sampling interval: 0.5 nm). Fluorescence spectra were recorded on
a fluorospectrophotometer (F-7000), and all compounds in various
solvents were excited at their respective maximum absorption
wavelength (slit: 10 nm/10 nm). The fluorescence quantum yield
Synthesis of MPP-d
Pd(PPh ) (0.139 mmol, 45 mg) was added to a well degassed solu-
3
4
tion of 3 (0.649 mmol, 275 mg), 2-bromopyridine (0.78 mmol,
23 mg), K CO3 (1.3 mmol, 179.4 mg) in a mixture of toluene
(F ) in solution was determined by using quinine sulfate (F =0.55
f
f
1
2
in 0.1m H SO ) as a standard. F of powder was determined with a
PTIC-701 calibrated integrating sphere system. TFA/NH vapor ex-
posure was performed by keeping the doped poly(methyl metha-
crylate) (PMMA)-film-coated glass plate upside down on a centri-
fuge tube (5 mL) containing TFA or NH for 30 s.
2
4
f
(
12 mL)/ ethanol (9.0 mL)/ H O (1.0 mL). The resulting mixture was
2
3
stirred at 808C for 2 h under argon atmosphere. After cooled down
to room temperature, the mixture was subsequently diluted with
DCM, washed with water and dried over anhydrous Na SO . After
2
4
3
solvent removal under reduced pressure, the residue was purified
by silica gel column chromatography (DCM) to afford the target
product (133.7 mg, yield: 55%) as yellow solid (267.7 mg). HRMS
Synthesis and characterizations.Synthesis of 4-iodo-2,5-di-
methoxybenzaldehyde (1)
30
+
+
(ESI) m/z calcd for C H N O S [M+H] 375.1162, found 375.1167;
22 19 2 2
1
H H NMR (500 MHz, CDCl ): d=8.76 (d, J=4.7 Hz, 1H), 8.04 (d, J=
3
A mixture of 2, 5-dimethoxybenzaldehyde (5.1 g, 30 mmol), silver
nitrate (5.6 g, 33 mmol), and iodine (8.1 g, 32 mmol) was stirred in
1
8.1 Hz, 1H), 8.00 (d, J=8.0 Hz, 1H), 7.93–7.88 (m, 2H), 7.76 (d, J=
7.8 Hz, 1H), 7.63 (d, J=16.4 Hz, 1H), 7.57 (s, 1H), 7.52 (t, J=7.2 Hz,
1H), 7.42 (t, J=7.6 Hz, 1H), 7.29 (s, 1H), 7.29–7.25 (m, 1H), 4.03 (s,
25 mL of methanol under nitrogen overnight. The yellow precipi-
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Chem. Asian J. 2019, 00, 0 – 0
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