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RSC Advances
Page 2 of 8
DOI: 10.1039/C5RA26039F
ARTICLE
Journal Name
6H, ArCHaHb-), 2.96 (s, 6H, PhCH2-), 2.77 (d, J = 15.6 Hz, 6H,
ArCHaHb-); 13C NMR (100 MHz, DMSO-d6) δ 177.2, 138.1, 134.9,
129.5, 128.0, 126.4, 60.1, 55.0, 43.0; MS (EI, relative intensity,
m/z): 602 (M+2, 3), 601 (M+1, 10), 600 (M+, 24), 554 (9), 509 (12),
463 (7), 417 (15), 347 (33), 191 (9), 91 (100).
Experimental
General
All chemicals and reagents of high purity were obtained
commercially and were used without any further purification.
DMSO (HPLC grade) was purchased from Duksan, South Korea. 1,1'-
Carbonyldiimidazole, 2-aminobenzimidazole, cyanogen bromide
and anhydrous N,N'-dimethylaceteamide (DMA) were purchased
from Aldrich Chemical Co., USA. 2,3-Diaminonaphthalene was
purchased from Alfa Aesar, USA. The solutions of anions were
prepared from their tetrabutylammonium (TBA) salts of analytical
grade procured from Aldrich Chemical Co., USA.
All the analytical measurements were conducted at room
temperature. Column chromatography was performed on
Yamagen MPLC equipped with a fluid metering pump using Merck
silica gel 60 (70-230 mesh) and CH2Cl2/MeOH mixed eluent. NMR
spectra were recorded on a Bruker AVANCE digital 400 (400 MHz)
Synthesis
benzo[d]imidazol-2-yl)carbamoyl]trindane (3)
mixture of cis,cis,cis-2,5,8-tribenzyltrindane-2,5,8-
of
cis,cis,cis-2,5,8-tribenzyl-2,5,8-tri[N-(1H-
A
tricarboxylic acid (100 mg, 0.17 mmol) and 1,1'-carbonyldiimidazole
(84 mg, 0.52 mmol) in anhydrous DMA (10 mL) was stirred under a
nitrogen atmosphere at room temperature for 12 hours. To this, a
solution of 2-aminobenzimidazole (72 mg, 0.54 mmol) in anhydrous
DMA (4 mL) was added by using a syringe. The mixture was stirred
further for 18 hours at 70 ºC. Then water (2 mL) was added to this
a
reaction mixture and stirred for
a while. The mixture was
concentrated to dryness by vacuum distillation. The residue was
purified by a column chromatography on silica gel using CH2Cl2 and
then MeOH/CH2Cl2 (2:98) to give the product as a slightly yellowish
solid powder (83.7 mg, 52%): IR (KBr, cm-1): 3380 (w), 3295 (w),
3062 (w), 3032 (w), 2924 (m), 2855 (w), 1674 (m), 1628 (m), 1566
(s), 1451 (m), 1427 (m), 1273 (m), 1196 (m), 741 (s), 702 (m), 602
(w); 1H NMR (400 MHz, DMSO-d6): δ 12.08 (br s, 3H, N-H), 11.76 (br
s, 3H, N-H), 7.51-7.39 (m, 6H, Ar-H), 7.33-7.06 (m, 21H, Ar-H), 3.32
(d, J = 15.8 Hz, 6H, ArCHaHb-), 3.28 (s, 6H, ArCH2), 3.08 (d, J = 15.8
Hz, 6H, ArCHaHb-); 13C NMR (100 MHz, DMSO-d6): δ 176.5 (br),
148.1 (br), 141.4, 138.9, 135.9, 133.4 (br), 130.4, 129.2, 127.5,
122.1, 117.8 (br), 112.6 (br), 58.0, 43.6 (br), 40 (overlapped with
1
and AVANCE III (500 MHz) spectrometer in DMSO-d6. H NMR and
13C NMR chemical shifts are given relative to TMS. UV-Vis
absorption spectra were obtained on an Optizen 2120-UV
spectrophotometer. Fluorescence spectra were measured on a
Shimadzu RF-5301 fluorescence spectrometer equipped with a
xenon discharge lamp using 1 cm quartz cells. IR spectra were
recorded on a Shimadzu IR Prestige-21 FTIR spectrometer. MALDI-
TOF data were obtained on a Voyager DE-STR mass spectrometer
and α-cyano-4-hydroxycinnamic acid (CHCA) was used as a matrix.
The stock solutions of host and anions (1 mM) were prepared in
DMSO. These solutions were appropriately diluted further for
different spectroscopic experiments to study the anion recognition
and sensing ability of the hosts 3 and 4. The spectral titrations of 3
and 4 were performed by taking 2 mL of host solution with
appropriate concentration directly into cuvette and the spectra
were recorded after each aliquot addition of TBAF (1 mM). All
fluorescence emission spectra were recorded at a fixed excitation
wavelength (λex of receptor 3: 299 nm and receptor 4: 345 nm). The
quantum yield (Ф) of the receptors before and after the addition of
DMSO-d6),
referenced
to
cis,cis,cis-2,5,8-tribenzyl-2,5,8-
tri(carbamoyl)trindane (δ 178.3, 139.3, 135.9, 130.3, 128.4, 126.6,
56.4, 44.0, 40.2); MALDI-TOF-MS, m/z (rel intensity): 946.7956
(100), 947.7957 (74), 948.7990 (23), Calcd for C60H51N9O3: m/z
946.4193 (M + H+, 100), 947.4227 (68.2), 948.4260 (22.9).
Synthesis of cis,cis,cis-2,5,8-tribenzyl-2,5,8-tri[N-(1H-naphtho[2,3-
d]imidazol-2-yl)carbamoyl]trindane (4)
Synthesis of 1H-naphtho[2,3-d]imidazol-2-amine [30]: In a 100
mL round bottom flask, 2,3-diaminonaphthalene (158 mg, 1 mmol)
was dissolved in a mixture of MeOH/water (1:1, 20 mL). The
reaction mixture was treated with cyanogen bromide (165 mg, 1.55
mmol) and heated at 50 ºC for 1 hour. After cooling to room
temperature, the solvent was removed in vacuo, and the residue
was basified with 1 M KOH (to pH 10) and extracted with EtOAc (30
mL X 3). The combined organic fractions were dried with MgSO4,
filtered and concentrated in vacuo. The reaction mixture was
purified by recrystallization from n-hexane/THF to yield greenish
brown powder (180 mg, 98%): 1H NMR (400 MHz, DMSO-d6) δ
10.88 (br s, 1H, N-H), 7.81 (m, 2H, Ar-H), 7.51 (s, 2H, Ar-H), 7.25 (m,
2H, Ar-H), 6.67 (br s, 2H, -NH2).
F- was calculated by applying the relationship [29]:
2
Ф = Фref (I/Iref) (Aref/A) (η/ηref
)
where, Ф is the radiative quantum yield of the receptor, Фref is the
quantum yield of quinine sulfate in 0.1 M aqueous H2SO4 (Фref
=
0.54), I is the integrated emission, A is the absorbance at the
excitation wavelength, and η is the refractive index of the solvent.
For 1H NMR titration, the receptor solution (0.5 mL, 4.0 mM, DMSO-
d6) was taken in NMR tube and then the spectra were recorded
after each stepwise addition of fluoride anion as their TBA salt
prepared in DMSO-d6.
Synthesis of trindane receptor 4: A mixture of cis,cis,cis-2,5,8-
tribenzyltrindane-2,5,8-tricarboxylic acid (100 mg, 0.17 mmol) and
1,1'-carbonyldiimidazole (84 mg, 0.52 mmol) in anhydrous DMA (10
mL) was stirred under a nitrogen atmosphere at room temperature
for 12 hours. To this solution was added a solution of 1H-
naphtho[2,3-d]imidazole-2-amine (100 mg, 0.54 mmol) in
anhydrous DMA (5 mL) via a syringe. The mixture was stirred
further for 18 hours at 70 ºC. After cooling to room temperature, to
this reaction mixture was added water (5 mL) and stirred for a
while. The mixture was concentrated by vacuum distillation. The
residue was purified by a column chromatography on silica gel using
CH2Cl2 and then MeOH/CH2Cl2 (2:98) to give the product (97 mg,
52%): IR (KBr, cm-1): 3378 (m), 3055 (w), 2921 (w), 2847 (w), 1677
(m), 1648 (m), 1567 (s), 1504 (m), 1424 (s), 1263 (m), 1160 (m), 858
(m), 732 (m), 700 (m); 1H NMR (400 MHz, DMSO-d6): δ 12.17 (br s,
Synthesis of cis,cis,cis-2,5,8-tribenzyltrindane-2,5,8-tricarboxylic
acid (2)
The mixture of triethyl cis,cis,cis-2,5,8-tribenzyltrindane-2,5,8-
tricarboxylate (70 mg, 0.11 mmol) and KOH (33 mg, 0.50 mmol) in
THF (5 mL), water (5 mL) and ethanol (5 mL) medium was heated at
reflux condition for 12 hours. The clear solution was concentrated
under reduced pressure. The residue was acidified with conc. HCl
(6 mL) and cooled in an ice bath. The precipitate was filtered and
washed with 3N HCl (10 mL). The white mixture was dried. The
dried mixture was taken up in THF (10 mL), and filtered to remove
insoluble inorganic salt. The filtrate was concentrated and dried
under high vacuum to give white solid (65 mg, 98%): IR (KBr, cm-1):
(KBr) 3062, 3027, 2924, 1702, 1201; 1H NMR (400 MHz, DMSO-d6) δ
12.47 (s, 3H, -CO2H), 7.28 (t, J = 7.30 Hz, 6H, Ar-H), 7.21 (t, J = 7.30
Hz, 3H, Ar-H), 7.15 (d, J = 7.32 Hz, 6H, Ar-H), 3.07 (d, J = 15.6 Hz,
2 | J. Name., 2012, 00, 1-3
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