Fluorescent chemosensors based on N-aminoimidazole and N-aminobenzimidazole

Full text of DOI:10.1134/S1070428014060293

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 6, pp. 911–912. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © I.E. Tolpygin, T.A. Kuz’menko, A.Yu. Fedyanina, S.Yu. Pluzhnikova, O.S. Popova, Yu.V. Revinskii, A.D. Dubonosov, V.A. Bren’,
2014, published in Zhurnal Organicheskoi Khimii, 2014, Vol. 50, No. 6, pp. 925–926.
SHORT
COMMUNICATIONS
Fluorescent Chemosensors Based on N-Aminoimidazole
and N-Aminobenzimidazole
I. E. Tolpygina, T. A. Kuz’menkoa, A. Yu. Fedyaninaa, S. Yu. Pluzhnikovaa, O. S. Popovaa,
Yu. V. Revinskiib, A. D. Dubonosovb, and V. A. Bren’a
a Research Institute of Physical and Organic Chemistry, Southern Federal University,
pr. Stachki 194/2, Rostov-on-Don, 344090, Russia
e-mail: ietolpygin@sfedu.ru
b Southern Scientific Center, Russian Academy of Sciences,
ul. Chehova, 41, Rostov-on-Don, 344006 Russia
Received December 18, 2013
DOI: 10.1134/S1070428014060293
Nowadays chemosensors are widely used in ex-
press determination of ions and neutral compounds in
various samples [1, 2]. Ion-sensitive compounds have
found application not only in analytical and environ-
mental chemistry but also in biology. It is very impor-
tant to design efficient and selective chemosensors for
the determination and biovisualization of ions (cations
and anions) involved in biological cell processes [3, 4].
We previously demonstrated the possibility of using
anthracen-9-ylmethyl-substituted benzimidazol-2-
amines as efficient pH sensors [5, 6]. In continuation
of these studies we have synthesized N-amino deriva-
tives of imidazole and benzimidazole containing an an-
thracene fluorophore group linked to the NNH group.
By reaction of benzimidazole-1,2-diamine (I) and
1-amino-4-phenyl-1H-imidazole-2-thiol (II) with an-
thracene-9-carbaldehyde in acetic acid we synthesized
the corresponding Schiff bases which were reduced to
diamines III and IV with sodium tetrahydridoborate.
In the reaction with diamine I, only the N–NH2 amino
group was involved in the condensation. The 1H NMR
spectrum of III contained signals typical of protons in
the NH2, NH, and CH2 groups.
Amines III and IV showed anthracene-like fluores-
cence with an emission maximum at λ 414 (415) nm.
Their chemosensor properties were studied in aceto-
nitrile (c = 5×10–6 M) by comparing the fluorescence
spectra before and after addition of cations (H+, Zn2+,
Cd2+, Ni2+, Cu2+, Pb2+, Hg2+) and anions (AcO–, CN–,
NO3–, F–, Cl–, see table). The results revealed different
selectivities of III and IV toward ionic species. The
fluorescence intensity of compound III considerably
increased in the presence of H+, Zn2+, and Cd2+ ions
and decreased on addition of Cu2+ and Hg2+. Amino-
thiol IV turned out to be more sensitive in the deter-
mination of anions. It displayed selective increase in
the fluorescence intensity in the presence of acetate
ions. In all cases, addition of ions to solutions of III
and IV did not induce appreciable change in the
position of absorption and emission maxima.
R1
N
R3
R1
N
R2
N
N
(1) 9-Anthraldehyde, AcOH
(2) NaBH4, DMF–EtOH
R3
HN
R2
NH2
I, II
III, IV
I, III, R1R2 = (CH=CH)2, R3 = NH2; II, IV, R1 = Ph, R2 = H, R3 = SH.
911

TOLPYGIN et al.
912
Relative changes in the fluorescence intensities (I/I0) of compounds III and IV (c = 5×10–6 M) in acetonitrile on addition of
cations or NBu4+ An– (c = 2.5×10–5 M)
Cations
Ni2+
Anions
Compound
no.
H+
Zn2+
Cd2+
Cu2+
Pb2+
Hg2+ AcO– CN–
NO3–
F–
Cl– H2PO4–
III
IV
92.0
18.0
30.0
06.7
71.0
03.6
1.7
0.9
0.3
1.6
1.7
1.0
0.1
0.6
1.4
5.0
0.6
1.1
3.4
1.1
0.6
1.2
2.8
1.0
0.6
1.1
1
Thus, 1-(anthracen-9-ylmethylamino)-4-phenyl-
1H-imidazole-2-thiol is a selective fluorescent chemo-
sensor for acetate ions.
The H NMR spectra were recorded on a Varian
Unity 300 spectrometer (300 MHz) from solutions in
CDCl3; the chemical shifts were determined relative
to the residual proton signal of the solvent (CHCl3,
δ 7.25 ppm). The electronic absorption spectra were
measured on a Varian Cary 100 spectrophotometer.
The luminescence spectra were recorded on a Varian
Eclipse spectrofluorimeter. The IR spectra were taken
on a Varian Excalibur FTIR instrument. The mass spec-
tra were obtained on a Shimadzu GCMS-QP2010SE
spectrometer. The melting points were determined in
glass capillaries using a PTP (M) melting point appa-
ratus. The progress of reactions and the purity of prod-
ucts were monitored by TLC on Silufol UV 254 plates
using chloroform as eluent; spots were visualized by
treatment with iodine vapor in a moist chamber.
N1-(Anthracen-9-ylmethyl)-1H-benzimidazole-
1,2-diamine (III). A mixture of 0.3 g (2 mmol) of
1H-benzimidazole-1,2-diamine (I) [7] and 0.42 g
(2 mmol) of anthracene-9-carbaldehyde in 5 mL of
glacial acetic acid was heated for 2 h under reflux. The
mixture was cooled and diluted with 25 mL of water,
and the pre-cipitate was filtered off, washed with water
(4×10 mL), and dried in air. The Schiff base thus ob-
tained was dissolved in 40 mL of ethanol–DMF (2:1),
0.20 g (5 mmol) of NaBH4 was added, and the mixture
was stirred for 30 min, diluted with 100 mL of water,
and treated with dilute acetic acid to decompose excess
reducing agent. The precipitate was filtered off,
washed with water, dried in air, and recrystallized from
butan-1-ol. Yield 0.6 g (83%), mp 289–290°C (from
butan-1-ol). IR spectrum, ν, cm–1: 3334, 1665, 1450,
1370. 1H NMR spectrum, δ, ppm: 4.84 br.s (2H, NH2),
5.04 t (1H, NH, J = 5.4 Hz), 5.35 d (2H, CH2, J =
5.4 Hz), 7.12–7.64 m (8H, Harom), 8.05 d (2H, 1-H,
8-H, J = 8.6 Hz), 8.36 d (2H, 4-H, 5-H, J = 8.6 Hz),
8.54 d (2H, 10-H, J = 8.6 Hz). Fluorescence spectrum
(c = 5×10–5 M): λmax 416 nm. Found, %: C 78.03;
H 5.40; N 16.57. m/z 338 [M]+. C22H18N4. Calculated,
%: C 78.08; H 5.36; N 16.56. M 338.15.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 12-03-31375) and by the Program for Develop-
ment of Southern Federal University (project
no. 213.01-24/2013-34).
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