Chemosensors based on N-(9-anthrylmethyl)-benzene-1,2-diamine

Article abstract of DOI:10.1134/S1070428008040155

A number of N-(9-antrylmethyl)-N′-arylmethylidenebenzene-1,2-diamines and 1-(9-anthrylmethyl)-2-aryl-1H-benzimidazoles were synthesized by condensation of N-(9-anthrylmethyl)benzene-1,2-diamine with aromatic and heterocyclic aldehydes. Study on their luminescent properties and complexing ability showed that 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-5- methylphenol, 2-{[2-(9-anthrylmethylamino)phenylimino] methyl}-4-methoxyphenol, and 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-6-methoxy-4-nitrophenol are effective and highly selective chemosensors for H⁺ and Hg ²⁺ ions.

Full text of DOI:10.1134/S1070428008040155

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 4, pp. 557–560. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © I.E. Tolpygin, V.P. Rybalkin, E.N. Shepelenko, L.L. Popova, Yu.V. Revinskii, A.V. Tsukanov, O.I. Dmitrieva, A.D. Dubonosov,
V.A. Bren’, V.I. Minkin, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 4, pp. 562–565.
Chemosensors Based on N-(9-Anthrylmethyl)-
benzene-1,2-diamine
I. E. Tolpygina, V. P. Rybalkinb, E. N. Shepelenkob, L. L. Popovaa, Yu. V. Revinskiia,
A. V. Tsukanova, O. I. Dmitrievaa, A. D. Dubonosovb, V. A. Bren’a,b, and V. I. Minkina,b
a Institute of Physical and Organic Chemistry, Rostov State University, pr. Stachki 194/2, Rostov-on-Don, 344090, Russia
e-mail: dubon@ipoc.rsu.ru
b Southern Research Center, Russian Academy of Sciences, Rostov-on-Don, Russia
Received September 10, 2006
Abstract—A number of N-(9-antrylmethyl)-N′-arylmethylidenebenzene-1,2-diamines and 1-(9-anthrylmethyl)-
2-aryl-1H-benzimidazoles were synthesized by condensation of N-(9-anthrylmethyl)benzene-1,2-diamine with
aromatic and heterocyclic aldehydes. Study on their luminescent properties and complexing ability showed that
2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-5-methylphenol, 2-{[2-(9-anthrylmethylamino)phenyl-
imino]methyl}-4-methoxyphenol, and 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-6-methoxy-4-nitro-
phenol are effective and highly selective chemosensors for H+ and Hg2+ ions.
DOI: 10.1134/S1070428008040155
Design of effective chemosensors implies the use of
molecules with a wide variety of receptor fragments.
Our previous studies in this field [1, 2] demonstrated
that N,N′-bis(9-antrylmethyl)substituted diamines can
be used as fluorescent chemosensors which can be
modified via introduction of a thiourea fragment. In
the present work we made an attempt to obtain chemo-
sensors on the basis of N-(9-anthrylmethyl)benzene-
1,2-diamine (I); the presence of a primary amino group
in the latter provides the possibility for subsequent
modifications.
While trying to improve the procedure described in
[3] for the synthesis of diamine I we found that ben-
zene-1,2-diamine reacts with an equimolar amount of
anthracene-9-carbaldehyde to give the corresponding
Schiff base only at one amino group and that the con-
Scheme 1.
CHO
(1) H+
N
NH2
NH2
H
(2) NaBH4, EtOH–DMF
NH2
+
I
R
N
N
[O]
RCHO
N
H
N
R
II–V
VI, VII
II, R = 2-HO-4-MeC6H3; III, R = 2-HO-5-MeOC6H3; IV, R = 2-HO-5-O2NC6H3; V, R = 2-HO-3-MeO-5-O2NC6H2;
VI, R = 2-HO-3,5-(O2N)2C6H2; VII, R = pyridin-2-yl.
557

TOLPYGIN et al.
558
densation product readily undergoes reduction with
sodium tetrahydridoborate in ethanol–dimethylform-
amide (3:2) to afford the target compound I in high
yield. By reactions of I with a series of substituted
salicylaldehydes we obtained N-(9-anthrylmethyl)-N′-
arylmethylidenebenzene-1,2-diamines II–V as poten-
tial chelating ligands (Scheme 1).
mained unchanged (PET effects). A necessary condi-
tion for photoinduced electron transfer is the presence
of an electron-donating group in the arylmethylidene
moiety.
Addition of a solution of zinc or copper acetate to
a solution of compound II or V in acetonitrile (to
a molar ratio of 1:10) resulted in appearance of new
fluorescence bands (λmax 471 and 474 nm, respec-
tively), which are typical of chelate compounds [4].
The fluorescence spectrum of methoxy derivative III
changed upon addition of a wider variety of metal
cations, including Zn2+, Cd2+, etc. Compound IV
showed fluorescence at λmax 342 nm but exhibited no
appreciable sensor properties (see figure). The sensi-
tivity to protons sharply increases in the series II <
III < V (see figure), while the sensitivity to Hg2+ ions
simultaneously decreases.
The reactions of diamine I with 2-hydroxy-3,5-di-
nitrobenzaldehyde and pyridine-2-carbaldehyde did
not stop at the stage of formation of the corresponding
Schiff base: Intermediate N-(9-anthrylmethyl)-N′-aryl-
methylidenebenzene-1,2-diamines underwent oxida-
tion with atmospheric oxygen to the corresponding
benzimidazole derivatives VI and VII which were iso-
lated as the major product (Scheme 1).
Amine I showed a low sensitivity and selectivity
for most cations, except for protons (see figure). Com-
pounds II–V are capable of acting as chemosensors
according to two mechanism. The first of these in-
volves formation of stable chelates with participation
of the azomethine and hydroxy groups in the ortho
position with respect to each other, which exhibit
intrinsic fluorescence [4]. The second mechanism is
photoinduced electron transfer due to the presence of
a 9-aminomethylanthracene fragment [5–9].
Benzimidazole derivatives VI and VII turned out to
be less efficient chemosensors as compared to ortho-
hydroxy-substituted Schiff bases. Compound VI hav-
ing two nitro groups displayed a weak anthracene type
fluorescence, and the fluorescence pattern almost did
not change upon addition of various cations (see
figure). The sensitivity of 1-(9-anthrylmethyl)-2-(pyr-
idin-2-yl)-1H-benzimidazole (VII) to H+ and Hg2+ ions
is related to fluorescence quenching by the action of
these cations; in the presence of excess H+ and Hg2+
ions, the fluorescence intensity decreases by a factor of
77 and 50, respectively (see figure). Presumably, the
anthryl fragment in VII acts as the strongest electron
donor in the complex formation.
The sensor properties of compounds II–VII were
estimated on the basis of the fluorescence spectra in
the region corresponding to local fluorescence of
anthracene (λ 390 nm). The fluorescence intensity of
compounds II, III, and V increased by a factor of 68,
46, and 4, respectively, upon addition of mercury ace-
tate and by a factor of 11, 160, and 300, respectively,
upon addition of trichloroacetic acid (see figure). In all
cases, the structure of the fluorescence spectra re-
Thus chemosensors based on N-(9-anthrylmethyl)-
benzene-1,2-diamine (I) are sensitive to a number of
cations, while 2-{[2-(9-anthrylmethylamino)phenyl-
imino]methyl}-5-methylphenol (II), 2-{[2-(9-anthryl-
methylamino)phenylimino]methyl}-4-methoxyphenol
(III), and 2-{[2-(9-anthrylmethylamino)phenylimino]-
methyl}-6-methoxy-4-nitrophenol (V) are highly ef-
fective chemosensors for protons and mercury(II) ions.
I/I0
I
II
III
250
IV
200
V
150
EXPERIMENTAL
VI
VII
1
100
The H NMR spectra were recorded on a Varian
Unity 300 spectrometer (300 MHz) from solutions in
CDCl3 or DMSO-d6 using the residual proton signals
of the solvent as reference (δ 7.25 and 2.50 ppm,
respectively). The IR spectra were measured on
a Specord 75IR instrument from samples dispersed in
mineral oil. The electronic absorption spectra were
obtained on a Specord M-40 spectrophotometer. The
fluorescence spectra were recorded on a Hitachi 650-
50
0
H+
Zn2+
Cd2+
Cu2+
Hg2+
Relative change in the fluorescence intensity (I/I0) of com-
pounds I–VII in acetonitrile (c = 5×10–5 mol/l) in the pres-
ence of various cations (acetate as counterion, c = 5×10–4 M,
λ 390 nm).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

CHEMOSENSORS BASED ON N-(9-ANTHRYLMETHYL)BENZENE-1,2-DIAMINE
559
60 spectrofluorimeter from solutions in acetonitrile
with a concentration of 5×10–5 M. The melting points
were determined in glass capillaries on a PTP (M)
melting point apparatus. The progress of reactions and
the purity of products 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.
Fluorescence spectrum: λmax 416 nm. Found, %:
C 80.58; H 5.69; N 6.50. C29H24N2O2. Calculated, %:
C 80.53; H 5.60; N 6.48.
2-{[2-(9-Anthrylmethylamino)phenylimino]-
methyl}-4-nitrophenol (IV) was synthesized from
compound I and 2-hydroxy-5-nitrobenzaldehyde. Yield
86%, mp 254–255°C (from butan-1-ol–DMF). IR spec-
trum, ν, cm–1: 3435, 1605, 1590, 1460, 1335. 1H NMR
spectrum, δ, ppm: 5.00–5.45 m (2H, CH2), 5.80–
8.60 m (17H, Harom), 8.9–10.22 m (1H, OH, NH).
Fluorescence spectrum: λmax 342 nm. Found, %:
C 75.21; H 4.66; N 9.32. C28H21N3O3. Calculated, %:
C 75.15; H 4.73; N 9.39.
N-(9-Anthrylmethyl)benzene-1,2-diamine (I).
Acetic acid, 0.5 ml, was added to a solution of 2.38 g
(22 mmol) of benzene-1,2-diamine in 40 ml of toluene,
and a solution of 4.12 g (20 mmol) of anthracene-9-
carbaldehyde in 20 ml of toluene was added dropwise
under stirring over a period of 10 min. The mixture
was heated for 2 h under reflux, the solvent was
removed under reduced pressure, and the residue was
recrystallized from butan-1-ol. Yield of N-(9-anthryl-
methylidene)benzene-1,2-diamine quantitative. The
product was dissolved in 100 ml of a 3:2 ethanol–
dimethylformamide mixture, the solution was heated,
and 1.9 g (50 mmol) of sodium tetrahydridoborate was
added in portions under stirring. The mixture was
stirred for 2 h, diluted with 200 ml of water, and
treated with dilute acetic acid to decompose excess
NaBH4. The precipitate was filtered off, washed with
water, and dried in air. Compound I was recrystallized
from butan-1-ol with addition of charcoal (10 wt %).
Yield 5.38 g (82%), mp 183–184°C (from butan-1-ol);
published data [3]: mp 178–180°C. IR spectrum, ν,
2-{[2-(9-Anthrylmethylamino)phenylimino]-
methyl}-6-methoxy-4-nitrophenol (V) was synthe-
sized from compound I and 2-hydroxy-3-methoxy-5-
nitrobenzaldehyde. Yield 81%, mp 240–241°C (from
butan-1-ol–DMF). IR spectrum, ν, cm–1: 3380, 1600,
1
1460. H NMR spectrum, δ, ppm: 3.60–3.96 m (3H,
CH3), 4.90–5.42 m (2H, CH2), 5.80–9.00 m (16H,
Harom, N=CH). Fluorescence spectrum: λmax 425 nm.
Found, %: C 72.87; H 4.94; N 8.81. C29H23N3O4. Cal-
culated, %: C 72.94; H 4.86; N 8.86.
2-[1-(9-Anthrylmethyl)-1H-benzimidazol-2-yl]-
4,6-dinitrophenol (VI). Compound I, 0.3 g (1 mmol),
was dissolved in 5 ml of butanol, a few drops of glacial
acetic acid and 0.21 g (1 mmol) of 2-hydroxy-3,5-
dinitrobenzaldehyde were added, and the mixture was
heated for 15 min under reflux and cooled. The precip-
itate was filtered off and recrystallized from butan-
1-ol–DMF (1:1). Yield 0.2 g (41%), mp >270°C
(decomp., from butan-1-ol–DMF). IR spectrum, ν,
1
cm–1: 1595, 1500, 1460, 1435. H NMR spectrum,
δ, ppm: 3.38 m (3H, NH, NH2), 5.17 s (2H, CH2),
6.65–8.53 m (13H, Harom). Fluorescence spectrum:
λmax 416 nm. Found, %: C 84.57; H 5.98; N 9.45.
C21H18N2. Calculated, %: C 84.53; N 6.08; N 9.39.
1
cm–1: 3350, 1605, 1450. H NMR spectrum, δ, ppm:
6.65 s (2H, CH2), 6.76–8.68 m (15H, Harom). Fluores-
cence spectrum: λmax 416 nm. Found, %: C 68.67;
H 3.62; N 11.50. C28H18N4O5. Calculated, %: C 68.57;
H 3.70; N 11.42.
2-{[2-(9-Anthrylmethylamino)phenylimino]-
methyl}-5-methylphenol (II) was synthesized from
compound I and 2-hydroxy-4-methylbenzaldehyde.
Yield 78%, mp 209–210°C (from butan-1-ol). IR spec-
trum, ν, cm–1: 1600, 1467, 1380. 1H NMR spectrum, δ,
ppm: 2.20 s (3H, CH3), 4.50 s (1H, NH), 5.20 d (2H,
CH2), 6.50–8.54 m (17H, Harom), 12.23 s (1H, NH).
Fluorescence spectrum: λmax 417 nm. Found, %:
C 83.70; H 5.75; N 6.64. C29H24N2O. Calculated, %:
C 83.63; H 5.81; N 6.73.
1-(9-Anthrylmethyl)-2-(pyridin-2-yl)-1H-benz-
imidazole (VII). Compound I, 0.6 g (2 mmol), was
dissolved in 10 ml of toluene, a few drops of glacial
acetic acid and 0.21 ml (2 mmol) of pyridine-2-carb-
aldehyde were added, and the mixture was heated for
1 h under reflux. The solvent was distilled off under
reduced pressure, and the residue was recrystallized
from petroleum ether–benzene (3:1). Yield 0.49 g
(64%), mp 278–279°C (from butan-1-ol). IR spectrum,
ν, cm–1: 1600, 1465, 1380. 1H NMR spectrum, δ, ppm:
7.22 s (2H, CH2), 6.26–8.80 m (17H, Harom). Fluores-
cence spectrum: λmax 415 nm. Found, %: C 84.07;
H 5.05; N 11.94. C27H19N3. Calculated, %: C 84.13;
H 4.97; N 10.90.
2-{[2-(9-Anthrylmethylamino)phenylimino]-
methyl}-4-methoxyphenol (III) was synthesized from
compound I and 2-hydroxy-5-methoxybenzaldehyde.
Yield 72%, mp 198–199°C (from butan-1-ol). IR spec-
trum, ν, cm–1: 1615, 1465. 1H NMR spectrum, δ, ppm:
3.70 s (3H, CH3), 4.48 s (1H, NH), 5.22 s (2H, CH2),
6.60–8.54 m (17H, Harom, N=CH), 11.80 s (1H, OH).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

TOLPYGIN et al.
560
3. Plater, M.J., Greig, I., Helfrich, M.H., and Ralston, S.H.,
This study was performed under financial support
J. Chem. Soc., Perkin Trans. 1, 2001, p. 2553.
by the Russian Foundation for Basic Research (project
no. 05-03-32470), by the Ministry of Education and
Science of the Russian Federation (project nos. RNP.-
2.2.2.2.5592, RNP.2.2.2.3.9720), by the CRDF
(projects nos. REC-004/BP1M04, REC-004/BF5M04),
and by the President of the Russian Federation (project
no. NSh-4849.2006.3).
4. Knyazhanskii, M.I. and Metelitsa, A.V., Fotoinitsiiro-
vannye protsessy v molekulakh azometinov i ikh struktur-
nykh analogov (Photoinitiated Processes in Molecules of
Schiff Bases and Their Structural Analogs), Rostov-on-
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