Molecular Rotors as Fluorescent Viscosity Sensors
Vis spectra were taken on a HP8453 UV/Vis spectrophotometer. solid was washed with petroleum ether to give 6b (2.1 g, 80.0%).
Fluorescence spectra were recorded on JASCO FP-6500 and Sanco
970 CRT spectrofluorometers. Fluorescence quantum yields were
measured with quinine sulfate as the reference (Φ = 0.54 in 0.5 m
H2SO4). Fluorescence lifetimes were measured on a Horiba Jobin
Yvon Fluoro Max-4 (TCSPC) instrument. For the synthesis of ro-
tors 1 and 2, see the Supporting Information. The numbering of
the solvents used in the viscosity study (refer to the figures in the
main text): 1 for hexane, 2 for toluene, 3 for 1,4-dioxane, 4 for
dioxane/diethyl ether (1:1, v/v), 5 for diethyl ether, 6 for ethyl acet-
ate, 7 for tetrahydrofuran, 8 for dichloromethane, 9 for acetone, 10
for acetonitrile, 11 for ethanol, 12 for methanol, 13 for ethylene
glycol, 14 for glycerol.
1H NMR (400 MHz, CDCl3): δ = 7.13–7.18 (m, 4 H), 6.89–6.95
(m, 4 H), 4.21 (t, J = 8.0 Hz, 2 H), 4.14 (q, J = 8.0 Hz, 2 H), 2.82
(t, J = 7.6 Hz, 2 H), 1.23 (t, J = 7.6 Hz, 3 H) ppm. TOF MS EI
([C17H17O2NS + H]+) calcd. 299.0980; found 299.0985.
DMF (0.78 mL,10.7 mmol) and POCl3 (0.88 mL, 10.7 mmol) were
mixed at 0 °C. Then a solution of compound 6b (2.0 g, 7.1 mmol)
in chloroform (30 mL) was added dropwise. The temperature of the
mixture was kept below 5 °C during the addition. The mixture was
then heated at reflux for 10 h. The solvent was removed under re-
duced pressure, water was added, and the pH of the solution was
adjusted to 7–8 with NaHCO3. The mixture was extracted with
CH2Cl2 and the organic layer was dried with Na2SO4. The solvent
was removed under reduced pressure and the crude product was
purified by column chromatography to give 6c as a light yellow oil
(0.87 g, 35.0%). 1H NMR (400 MHz, CDCl3): δ = 9.72 (s, 1 H),
7.57–7.59 (m, 1 H), 7.52–7.53 (m, 1 H), 7.09–7.13 (m, 1 H), 7.04–
7.06 (m, 1 H), 6.82–6.93 (m, 3 H), 4.19 (t, J = 8.0 Hz, 2 H), 4.08
(q, J = 8.0 Hz, 2 H), 2.75 (t, J = 8.0 Hz, 2 H), 1.14 (t, J = 8.0 Hz,
3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 190.1, 171.2, 150.3,
143.5, 131.5, 130.3, 128.5, 127.8, 125.6, 124.2, 124.0, 115.8, 114.8,
61.1, 43.4, 32.5, 14.2 ppm. TOF MS EI ([C18H17O3NS + H]+)
calcd. 327.0929; found 327.0935.
{[4-(Phenylethynyl)phenyl]methylene}propanedinitrile (3): Under an
N2 atmosphere, ethynylbenzene (86.0 mg, 0.84 mmol) and 4-bro-
mobenzenealdyhed (130.0 mg, 0.70 mmol) were dissolved in NEt3/
THF (10 mL, 3:2, V/V). Then, CuI (10.0 mg), [PdCl2(PPh)2]
(10.0 mg), and PPh3 (5.0 mg) were added. The mixture was heated
at 75 °C for 9 h. After the reaction, the mixture was filtered and
the crude product was subjected to column chromatography (silica
gel; CH2Cl2/petroleum ether as the eluent, 3:1, v/v) to give 3a as a
white solid (45.0 mg, 31.0%). 1H NMR (400 MHz, CDCl3): δ =
10.02 (s, 1 H), 7.86 (d, J = 8.4 Hz, 2 H), 7.66 (d, J = 8.4 Hz, 2 H),
7.54–7.57 (m, 2 H), 7.38 (d, J = 3.2 Hz, 2 H) ppm.
Rotor 6: Compound 6 was prepared by following the general pro-
cedure used for 3. A Dean–Stark trap was used to remove the
water. The crude product was purified by column chromatography
(silica gel; dichloromethane/petroleum ether = 1:1, v/v) to give 6 as
Compound 3a (30.0 mg, 0.15 mmol) and malononitrile (15.0 mg,
0.23 mmol) were dissolved in benzene (5 mL), then a few drops of
acetic acid and small amount of sodium acetate were added as the
catalyst. The mixture was heated at reflux for 11 h. The solvent
was evaporated and the crude product was subjected to column
chromatography (silica gel, CH2Cl2 as eluent) to give 3 (13.0 mg,
46.0%); m.p. 271.2–273.4 °C. 1H NMR (400 MHz, CDCl3): δ =
7.88 (d, J = 8.0 Hz, 2 H), 7.73 (s, 1 H), 7.64 (d, J = 8.0 Hz, 2 H),
7.56 (d, J = 3.2 Hz, 2 H), 7.39–7.40 (m, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 158.7, 133.2, 132.6, 132.0, 130.8, 130.3,
130.1, 129.4, 128.7, 122.3, 113.8, 112.7, 95.2, 88.5, 82.8 ppm. TOF
MS EI ([C18H10N2 + H]+) calcd. 254.0844; found 254.0853.
1
a red solid (0.44 g, 49.0%). H NMR (400 MHz, CDCl3): δ = 7.73
(d, J = 8.8 Hz, 1 H), 7.58 (s, 1 H), 7.49 (s, 1 H), 7.20 (t, J = 7.2 Hz,
1 H), 7.09 (d, J = 7.6 Hz, 1 H), 7.01 (t, J = 7.6 Hz, 1 H), 7.09 (d,
J = 8.4 Hz, 2 H), 4.26 (t, J = 8.0 Hz, 2 H), 4.16 (q, J = 8.0 Hz, 2
H), 2.82 (t, J = 7.2 Hz, 1 H), 1.23 (t, J = 7.6 Hz, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 171.0, 157.5, 150.5, 142.1, 131.6,
129.5, 128.1, 127.9, 125.6, 124.6, 123.4, 115.9, 115.0, 114.6, 113.5,
78.3, 61.2, 43.4, 32.3, 29.8, 14.2 ppm. TOF MS EI ([C21H17O2N3S
+ H]+) calcd. 375.1041; found 375.1048.
{[4-(4-Methoxylphenylethynyl)phenyl]methylene}propanedinitrile (4):
This compound was obtained by using the general procedure for
rotor 3 (16.0 mg, 51.0%). 1H NMR (400 MHz, CDCl3): δ = 7.87
(d, J = 8.4 Hz, 2 H), 7.71 (s, 1 H), 7.60 (d, J = 8.8 Hz, 2 H), 7.49–
7.51 (m, 2 H), 6.89–6.92 (m, 2 H), 3.84 (s, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 160.6, 158.7, 133.6, 132.3, 130.8, 130.6,
130.0, 114.4, 113.9, 112.8, 95.8, 87.7, 82.4, 55.5 ppm. TOF MS
EI([C19H12 N2O + H]+) calcd. 284.0950; found 284.0951.
10-[(Ethyloxyl-3-propanoate-10H-phenothiazine-3-yl)methylene]pro-
panedinitrile 5-Oxide (7): Compound 6 (112 mg, 0.3 mmol) was dis-
solved in glacial acetic acid (4 mL). H2O2 (0.5 mL, 30%, 4.9 mmol)
was added dropwise. The mixture was stirred overnight. The mix-
ture was poured into water and the pH of the mixture was adjusted
to 7 with a saturated solution of Na2CO3. The yellow precipitate
was collected by filtration and washed with water to give 7
(69.0 mg, 58.0%); m.p. 193.9–196.2 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.33–8.37 (m, 2 H), 7.59 (d, J = 7.6 Hz, 1 H),7.72–
7.75 (m, 2 H), 7.56 (t, J = 7.6 Hz, 2 H), 7.42 (t, J = 7.6 Hz, 1 H),
4.68 (t, J = 8.0 Hz, 2 H), 4.25 (q, J = 8.0 Hz, 2 H), 2.94–2.98 (m,
2 H), 1.31 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 170.4, 156.9, 141.8, 136.8, 136.7, 134.0, 133.8, 132.1, 125.4,
125.3, 124.6, 124.4, 116.6, 116.3, 114.0, 113.1, 80.7, 61.7, 43.9, 31.7,
14.3 ppm. APCI-MS (positive, [C21H17O3S + H]+) calcd. 391.1;
found 392.0.
2-(4-{2-[4-(Dimethylamino)phenyl]ethynyl}benzylidene)malononitrile
(5): The preparation of rotor 5 follows the general procedure used
to obtain 3. The crude product was purified by column chromatog-
raphy (silica gel; dichloromethane/petroleum ether = 5:1, v/v). A
dark-red solid was obtained (19.0 mg, 71.0%); m.p. 90.3–92.8 °C.
1H NMR (400 MHz, CDCl3): δ = 7.86 (d, J = 8.8 Hz, 2 H), 7.71
(s, 1 H), 7.59 (d, J = 8.4 Hz, 2 H), 7.46 (d, J = 8.8 Hz, 2 H), 6.84
(d, 2 H), 3.05 (s, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
158.7, 150.9, 133.4, 132.0, 131.4, 130.9, 129.4, 114.1, 113.0, 111.8,
108.6, 98.0, 87.7, 81.6, 40.2 ppm. APCI-MS (positive, [C20H15N3 +
H]+) calcd. 297.1266; found 297.1270.
2-[(9-Ethyl-9H-carbazol-3-yl)methylene]propanedinitrile (8): 9-
Ethyl-9H-carbazole-3-carbaldehyde (81.0 mg, 0.3 mmol) and mal-
ononitrile (40.0 mg, 0.6 mmol) were dissolved in THF (5 mL).
MgSO4 and a few drops of triethylamine were added. The solution
changed from colorless to golden yellow. The mixture was stirred
at room temp. for 2 h. The mixture was filtered and the solvent was
evaporated under reduced pressure. The crude product was purified
by column chromatography (silica gel. CH2Cl2/petroleum ether =
1:1, v/v) to give 8 as a yellow solid (26.0 mg, 31.0%); m.p. 160.8–
162.3 °C. 1H NMR (400 MHz, CDCl3, TMS): δ = 8.64 (s, 1 H),
10-[(Ethyloxyl-3-propanoate-10H-phenothiazine-3-yl)methylene]pro-
panedinitrile (6): Compound 6a (2.4 g, 8.9 mmol) was dissolved in
EtOH/toluene (11 mL/22 mL), then H2SO4 (1 mL) was added and
the mixture was heated at reflux for 12 h. The solvent was removed
and water (100 mL) was added and extracted with ethyl acetate.
The organic layers were combined and dried with anhydrous
Na2SO4. The solvent was removed under reduced pressure. The
Eur. J. Org. Chem. 2011, 4773–4787
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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