11-R-Dibenzo[b,e][1,4]diazepin-1-ones, the chemosensors for transition metal cations

Article abstract of DOI:10.1134/S1070363212070109

A series of 11-R-dibenzo[b,e][1,4]diazepin-1-ones was synthesized. The luminescence, complex formation, and redox properties of these compounds were investigated. The 11-(anthracen-9-yl)-3,3-dimethyl-2,3,4,5,10,11-hexahydro-1H- dibenzo[b,e][1,4]diazepin-1-one was found to be an effective and selective fluorescent chemosensor for Cd²⁺ cations. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S1070363212070109

ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 7, pp. 1243–1249. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © I.E. Tolpygin, N.V. Mikhailenko, A.A. Bumber, E.N. Shepelenko, U.V. Revinsky, A.D. Dubonosov, V.A. Bren’, V.I. Minkin, 2012,
published in Zhurnal Obshchei Khimii, 2012, Vol. 82, No. 7, pp. 1141–1147.
11-R-Dibenzo[b,e][1,4]diazepin-1-ones,
the Chemosensors for Transition Metal Cations
I. E. Tolpygina, N. V. Mikhailenkoa, A. A. Bumberb, E. N. Shepelenkob, U. V. Revinskya,
A. D. Dubonosovb, V. A. Bren’a, and V. I. Minkina,b
a Research Institute of Physical and Organic Chemistry, Southern Federal University,
ul. Stachki 194/2, Rostov-on-Don, 344090 Russia
e-mail: tolpygin@ipoc.sfedu.ru
b Southern Research Center, Russian Academy of Sciences, ul. Chekhova, 4, Rostov-on-Don, 344010 Russia
e-mail: aled@ipoc.sfedu.ru
Received May 31, 2011
Abstract—A series of 11-R-dibenzo[b,e][1,4]diazepin-1-ones was synthesized. The luminescence, complex
formation, and redox properties of these compounds were investigated. The 11-(anthracen-9-yl)-3,3-dimethyl-
2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one was found to be an effective and selective
fluorescent chemosensor for Cd2+ cations.
DOI: 10.1134/S1070363212070109
The polycyclic heteroatomic systems containing
1,4-diazepine structure exhibit a wide spectrum of
biological activity, like inhibition of hepatitis C (HCV)
and human immunodeficiency (HIV-1) viruses [1].
They have been used to create the drugs affecting the
central nervous system, including antidepressants,
stimulants, anticonvulsants, analgesics, etc. [2–4]. The
main method of synthesis of the dibenzo[b,e][1,4]-
diazepin-1-one derivatives is the reaction of substituted
3-[(2-aminophenyl)amino]cyclohex-2-en-1-ones and
their hetero-analogs with carbonyl derivatives [5–7].
methylphenyl, 2-hydroxy-4-methylphenyl, and 2-hyd-
roxy-1-naphthyl groups.
1
The H NMR spectra of obtained derivatives VII–
XI contain two typical singlet signals of the protons of
two CH3 groups in the region 1.03–1.20 ppm, and a
singlet of the CH group at 5.91–6.52 ppm, which
clearly indicates the formation of the diazepine ring.
Diazepines VII–XI were obtained also in the
TosOH or BF3·Et2O catalyzed reaction of monoimines
II–VI with dimedone.
To study the intramolecular electron transfer from
the highest occupied molecular orbital (HOMO) to the
lowest unoccupied molecular orbital (LUMO) it is
necessary to evaluate the energies of these orbitals.
They are known to be proportional to the oxidation and
reduction electrochemical potentials, respectively, of
the compound [11]. For the occurrence of fluorescent
properties the value of the LUMO–HOMO energy gap
is very significant, which in turn is associated with ΔE,
the difference of the potentials of the first stages of
oxidation and reduction [12].
We have previously shown that the presence of
ortho-phenylenediamine fragment in the structure of a
compound and the possibility of further modification
open a way to use such systems for creation of ef-
ficient and selective fluorescent chemosensors [8–10].
To study the complexing properties of such
compounds, we synthesized 2,3,4,5,10,11-hexahydro-
1H-dibenzo[b,e][1,4]diazepin-1-ones VII and VIII
containing a fluorescent fragment, anthracene or
naphtho[2,3-b]furan, in 11-position (Scheme 1). The
main method of synthesis of these compounds is the
reaction of the amine I [5] with the corresponding
aldehydes under acid catalysis. To study the effect of
substituents on the chemosensory properties, we
synthesized also compounds IX–XI containing 4-
In preliminary experiments with different rates of
the variation of the polarizing voltage (0.5, 0.2, 0.1,
0.05, and 0.02 V s–1) we found that the slope of the
plot of logarithm of the maximum current vs. the
1243

1244
TOLPYGIN et al.
Scheme 1.
RCHO
N
R
NH2
NH2
NH2
II−VI
O
O
O
Me
Me
Me
Me
O
H
Me
Me
NH
O
N
RCHO
Me
Me
HN
H
NH2
R
O
VII−XI
I
II, VII R = anthracen-9-yl, III, VIII R = 2-methyl-9-(5-methylfuran-2-yl)naphtho[2,3-b]furan-4-yl, IV,IX R = p-tolyl, V, X
R = 2-hydroxy-4-methylphenyl, VI, XI R = 2-hydroxynaphthalen-1-yl.
logarithm of the rate falls for the studied compounds in
the range 0.39–0.42. These values, combined with a
directly proportional dependence between the value of
the maximum current and the diazepine concentration
allow us to consider the oxidation processes as
diffusion and irreversible [13]. Therefore we could
estimate the number of transferred electrons in each
stage of the electro-oxidation from the value of the
peak current, comparing it with the authentic processes
of one-electron oxidation of ferrocene and anthracene
under the same conditions [14]. As follows from the
form of cyclic voltammograms of compound IX
containing tolyl substituent, the diazepine fragment,
which is a cyclic diamine, is oxidized in two one-
electron steps, therewith in the first step an unstable
radical cation is formed (Scheme 2, IXa). This follows
from the existence of the reverse signal on the cathodic
branch of the curve (Fig. 1a).
Scheme 2.
Me
Me
H
N
+
+
N
HN
−e, −H+
N
−e
+e
H
H
H
O
H
Me
Me
Me
IXа
IXb
IX
In the second step of oxidation an unstable dication
is formed, which decays with the removal of a proton
to produce structure IXb, the peak of which is
observed at the potential of 0.05 V. The presence of
protons was confirmed by an increase in the signal at
0.05 V at the adding 0.002 M perchloric acid. The
oxidation proceeds by a scheme similar to that of the
oxidation of aliphatic amines [15].
Compound VII containing anthryl substituent behaves
differently. Here, in the first stage an unstable radical
cation also appears (Fig. 1b). However, judging from
the maximum current, the second stage of oxidation is
a partially reversible two-electron process. By the
magnitude of the peak of the oxidation potential this
stage is close to the second stage of the diazepine VII
oxidation and to the process of oxidation of anthracene
(Scheme 3).
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11-R-DIBENZO[b,e][1,4]DIAZEPIN-1-ONES
1245
Scheme 3.
Me
Me
H
N
−e, −H+
N
−e
+e
−e
+e
+
+
+
HN
N
N
H
O
H
H
Ant
H
Ant
H
Ant+
VIIа
VIIb
VIIc
VII
Ant = 9-anthryl.
All the compounds are reduced difficultly and
irreversibly, probably due to the presence of keto
groups, and in the case of compounds VII, VIII the
reduction process involves the anthracen-9-yl and
naphthafuryl substituents. Data on the electrochemical
properties of the diazepines are listed in the table.
their electrochemical properties, the diazepines VII
and VIII are actually anthracene and naphthofuran
with diazepine as a substituent. In both oxidation and
reduction of these compounds there is mutual influence
of the composing fragments on the correspond-ing
potentials (see the table).
As follows from the tabulated data, the compound
IX behaves at the oxidation like aliphatic amines. The
reduction runs like that of aliphatic ketones [14]. By
While examining compounds X and XI we revealed
four oxidation steps. The first and the third steps,
judging from the closeness of their potentials to those
(a)
I, μА
(b)
I, μА
E, V
E, V
Fig. 1. Cyclic voltammograms of oxidation of compounds IX (a) and VII) (b).The dotted line shows the reversible signal indicating
the formation of ion radical.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 7 2012

1246
TOLPYGIN et al.
Characteristics of cyclic voltammograms of diazepines and model compoundsa
Reduction
Compound
Oxidation
ΔE, V
2.80
I0
Epc
Ipc
Еpa
Iпа
Еpa
Ipa
Epc
Ipc
–2.17
–2.42
–2.10
72
82
81
–2.05
–2.30
–
62
11
–
0.68
1.43
0.80
1.24
1.85
0.70
1.25
1.70
2.10
47
84
41
43
71
54
38
43
55
0.54
1.44
1.10
1.70
12
15
14
24
1.80
8.19
VII
2.90
VIII
–2.24
77
–
–
0.65
10
3.04
0.18
IX
0.00
56
–2.10
–2.15
73
74
–
–
–
–
0.80
1.65
56
60
0.70
–
10
52
2.90
3.0
4.39
2.63
X
0.05
0.65
1.20
1.65
2.00
1.13
53
40
39
55
0.55
XI
9-Furylnaphtho[2,3-b]furan
–2.00
82
–
–
3.13
3.33
2300
2000
Anthracene
–2.03
–2.30
78
81
–1.90
–2.20
71
11
1.30
0.45
50
68
1.20
0.40
Ferrocene
64
a
E
pc is cathode peak potential, V, Ipc is the catode peak current, μA, Epa is anode peak potential, V, Ipa is anode peak current, μA, ΔE is the
difference between the potentials of the first oxidation and first reduction peaks, V, I0 is relative fluorescence intensity.
in the oxidation of diazepine IX, correspond to the
oxidation of the amine moiety, while the second and
fourth correspond to hydroxy substituents.
intensity. However, except for a tricycle VII, the
protonation of the diazepines VIII–XI results in a
significant blue shift of the fluorescence maxima (λmax
at 492, 515, 540, and 504 nm of compounds VIII–XI,
respectively) by 75, 95, 37, and 122 nm, respectively .
In the case of compound X all the examined cations
cause a similar effect (shift by 25–40 nm.
Note that fluorescence of the diazepines VII and
VIII is reduced considerably compared with the
reference compounds, anthracene and 9-furylnaphtho-
[2,3-b]furan, primarily due to the presence of nitrogen
donor center and the fluorescence quenching through
the PET-effect. This allows us to investigate the
diazepines obtained for the presence of chemosensory
properties [16].
Thus, the oxidation of the diazepines proceeds, like
that of cyclic amines, in two stages, resulting in the
first step in the formation of an unstable radical cation.
The second step is completely irreversible and
proceeds with the removal of a proton. The presence of
a fluorescent substituent in the structures of the
diazepines VII and VIII allows to use these com-
pounds as fluorescent chemosensors that significantly
expands the scope of application of such systems.
Study of chemosensory ability of the compounds
VII–XI toward the cations H+, Zn2+, Cd2+, Cu2+, Co2+,
Ni2+, Pb2+, and Hg2+ in acetonitrile was carried out on
the basis of the data of corresponding fluorescence
spectra (Fig. 2).
EXPERIMENTAL
The spectral studies showed that in this series of
cyclic derivatives only the diazepine VII is fairly
selective. Only in the presence of Cd2+ ions occurs a 9-
fold flare up of its fluorescence. Adding trifluoroacetic
acid to acetonitrile solutions of the studied compounds,
despite the presence of two amine centers, does not
lead to a significant change in the fluorescence
1H NMR spectra were obtained on a Varian Unity
300 spectrometer (300 MHz) in CDCl3 or DMSO-d6.
As the internal reference the residual signals of CHCl3
(δ 7.25 ppm) and (CH3)2SO (δ 2.50 ppm) were used.
Electron absorption spectra were recorded on a Varian
Cary 100 spectrophotometer, the luminescence spectra
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 7 2012

11-R-DIBENZO[b,e][1,4]DIAZEPIN-1-ONES
1247
I/I0
VII
VIII
IX
X
XI
Cation
Fig. 2. The relative change in fluorescence intensity of diazepines VII–XI (c 5.0×10–6 M) in acetonitrile at adding various cations
(c 2.5×10–5 M).
were measured on a Hitachi 650-60 and Varian Eclipse
spectrofluorimeters. The vibrational spectra were
recorded on a Specord IR75 instrument. Melting points
were determined in glass capillaries on a PTP (M)
device. The completeness of the reactions and the
individuality of the compounds obtained were monitored
by TLC (plates Silufol U254, eluent chloroform, deve-
lopment by iodine vapor in a moist chamber).
3-[(2-Aminophenyl)amino]-5,5-dimethylcyclohex-
2-en-1-one (I) was obtained according to the pre-
viously described technique [5].
N-(Anthracen-9-yl-methylidene)-1,2-diamino-
benzene (II). In a three-neck 100 ml flask equipped
with a mechanical stirrer and a reflux condenser was
dissolved 2.4 g (22 mmol) of benzene-1,2-diamine in
40 ml of toluene and 0.2 ml of CH3COOH, and while
stirring and heating at 60–70ºC within 10 min was
added a solution of 4.1 g (20 mmol) of anthracen-9-
aldehyde in 20 ml of toluene. The reaction mixture was
refluxed for 2 h, and then the solvent was removed on
a rotary evaporator, the residue was crystallized from
1-butanol. Yield 94%, mp > 250ºC (decomp., 1-
Cyclic and differential pulse voltammograms of the
compounds were obtained by standard methods [17,
18] in acetonitrile with a water content ≤ 10–3 M using
a platinum disk electrode of 2 mm diameter, a
saturated calomel electrode as a reference electrode
and platinum wire as an auxiliary electrode against the
0.1 M tetraethylammonium perchlorate as a back-
ground solution. The concentration of the compounds
was 5×10–3 M, the concentration of added cations
5×10–2 M. The electrochemical measurements were
carried out in an argon atmosphere. Ferrocene was
used as an internal reference.
1
butanol). IR spectrum, ν, cm–1: 3200, 1500, 1465. H
NMR spectrum (CDCl3), δ, ppm: 4.25 br.s (2H, NH);
6.80–6.90 m (2H, HAr); 7.12–7.60 m (6H, HAr), 8.04 d
(2H, J 7.0 Hz, HAr); 8.53 s (1H, HAr); 8.74 d (2H, J
7.6 Hz, HAr); 9.75 s (1H, CH). The fluorescence
spectrum in acetonitrile, λmax, nm (5×10–5 M): 415.
Found, %: C 85.09, H 5.39; N 9.52. C21H16N2.
Calculated, %: C 85.11, H 5.44; N 9.45.
The voltammograms were recorded on a PA-2 polaro-
graph equipped with an XY recorder, the rate of poten-
tial sweep for the cyclic voltammetry was 0.5 V s–1, for
the differential pulse voltammetry, 0.005 V s–1 with the
pulse amplitude 12.5 mV.
General methods for preparing compounds
(VIII–XI). a. 2 mmol of 3-[(2-aminophenyl)amino]-
5,5-dimethylcyclohex-2-en-1-one (I) was dissolved in
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 7 2012

1248
TOLPYGIN et al.
1
10 ml of i-PrOH, AcOH was added as a catalyst, and
to the hot mixture a solution was added of 2 mmol of
the corresponding aldehyde in 10 ml of i-PrOH. The
reaction solution was refluxed for 1 h. The solvent was
removed on a rotary evaporator, the residue was
crystallized from a suitable solvent and dried in air.
spectrum, ν, cm–1: 3315, 1580, 1520, 1470. H NMR
spectrum (CDCl3), δ, ppm: 1.07 s (3H, CH3), 1.15 s
(3H, CH3), 2.19 s (3H, CH3), 2.23–2.72 m (4H, 2CH2);
4.44 br.s (1H, NH); 5.91 s (1H, CH); 6.31 br.s (1H,
NH); 6.40–6.50 m (1H, HAr), 6.67–6.78 m (3H, HAr),
6.86–6.99 m (4H, HAr). The fluorescence spectrum in
acetonitrile, λmax, nm (5×10–5 M): 515. Found, %: C
79.43, H 7.34; N 8.39. C22H24N2O. Calculated, %: C
79.48, H 7.28; N 8.43.
b. A solution of 2 mmol of a N-[1-R-methylidene]-
1,2-diaminobenzene (II–VI), 2 mmol of dimedone and
catalytic amount of TosOH (or BF3·Et2O) in 5–10 ml
of 1-butanol was refluxed for 4–6 h. The mixture was
evaporated under reduced pressure, the residue was
crystallized.
11-(2-Hydroxy-4-methylphenyl)-3,3-dimethyl-
2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diazepin-
1-one (X). a. Compound X was obtained from amine I
and 2-hydroxy-4-methylbenzaldehyde. Yield 78%, mp
184–185ºC (decomp., 1-butanol). IR spectrum, ν, cm–1:
11-(Anthracen-9-yl)-3,3-dimethyl-2,3,4,5,10,11-
hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one (VII).
a. From amine I and anthracene-9-aldehyde. Yield
86%, mp > 270ºC (decomp., 1-butanol). IR spectrum,
1
3350, 3200, 1570, 1500, 1467. H NMR spectrum
(CDCl3), δ, ppm: 1.14 s (3H, CH3), 1.20 s (3H, CH3),
1.93 s (3H, CH3), 2.20–2.63 m (4H, 2CH2); 5.04 br.s
(1H, NH); 6.08 s (1H, CH); 6.12–6.80 m (8H, HAr,
NH); 9.12 br.s (1H, OH). The fluorescence spectrum in
acetonitrile, λmax, nm (5×10–5 M): 540. Found, %: C
75.78, H 7.00; N 8.10. C22H24N2O2. Calculated, %: C
75.83, H 6.94; N 8.04.
1
ν, cm–1: 3320, 1586, 1520, 1467, 1370. H NMR
spectrum (DMSO-d6), δ, ppm: 1.03 s (3H, CH3), 8.1 s
(3H, CH3), q 1.81 (2H, CH2); 2.66 s (2H, CH2); br.s
4.96 (1H, NH); 6.52 s (1H, CH), 6.58–6.80 m (3H,
HAr), 7.13 d (1H, J 7.8 Hz, HAr), 7.20–7.48 m (4H,
HAr), 7.92 d (2H, J 7.6 Hz, HAr), 8.30 s (1H, HAr), 8.51 d
(2H, J 7.8 Hz, HAr), 8.84 s (1H, NH). The fluorescence
spectrum in acetonitrile, λmax, nm (5×10–5 M): 419.
Found, %: C 83.15, H 6.30; N 6.74. C29H26N2O.
Calculated, %: C 83.22, H 6.26; N 6.69.
b. From N-(2-hydroxy-4-methylbenziliden)-1,2-di-
aminobenzene (V) and dimedone. Yield 64%, mp 182–
183ºC (decomp., 1-butanol). Spectral characteristics
match the data for a substance obtained by method a.
b. From imine II and dimedone. Yield 66%, mp >
270ºC (decomp., 1-butanol). The spectral data coincide
with those described in a.
11-(2-Hydroxynaphthalen-1-yl)-3,3-dimethyl-
2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diaze-
pin-1-one (XI). a. From the amine I and 2-hydroxy-
naphthalene-1-aldehyde. Yield 81%, mp 201–202ºC
(decomp., 1-butanol). IR spectrum, ν, cm–1: 3300,
11-[2-Methyl-9-(5-methyl-furan-2-yl)naphtho[2,3-
b]-furan-4-yl]-3,3-dimethyl-2,3,4,5,10,11-hexahydro-
1H-dibenzo[b,e][1,4]diazepin-1-one (VIII). a. Fom
amine I and 2-methyl-9-(5-methylfuran-2-yl)naphtho-
[2,3-b]furan-4-aldehyde. Yield 75%, mp 185–186ºC
(decomp., 1-butanol). IR spectrum, ν, cm–1: 3300,
1580, 1510, 1480. 1H NMR spectrum (CDCl3), δ, ppm:
1.14 with (3H, CH3), 1.20 s (3H, CH3), 2.22 d (2H, J
4.1 Hz, CH2), 2.30 s (3H, CH3), 2.45 s (3H, CH3), 2.64
s (2H, CH2); 4.42 br.s (1H, NH); 6.11 d (2H, J
7.2 Hz, HAr), 6.22 s ( 1H, CH), 6.38–6.93 m (6H, HAr,
CH, NH); 7.40–7.60 m (2H, HAr); 8.44 d (2H, J 8.3 Hz,
1
3250, 1580, 1515, 1475. H NMR spectrum (CDCl3),
δ, ppm: 1.16 s (6H, 2CH3), 2.22 s (2H, CH2); 2.43 s
(2H, CH2), 5.46 br.s (1H, NH); 6.14 s (1H, CH), 6.90–
8.23 m (10H, HAr, NH); 9.42 d (1H, J 14.0 Hz, HAr);
15.00 (1H, br.s, OH). The fluorescence spectrum in
acetonitrile, λmax, nm (5×10–5 M): 504. Found, %: C
78.16, H 6.23; N 7.35. C25H24N2O2. Calculated, %: C
78.10, H 6.29; N 7.29.
b. From N-(2-hydroxynaphthalen-1-ylmethylene)-
1,2-diaminobenzene (VI) and dimedone. Yield 67%,
mp 200–201ºC (decomp., 1-butanol). Spectral charac-
teristics match the data for a substance obtained by
method a.
HAr). The fluorescence spectrum in acetonitrile, λmax
,
nm (5×10–5 M): 492. Found, %: C 78.92, H 5.97; N
5.51. C33H30N2O3. Calculated, %: C 78.86, H 6.02; N
5.57.
ACKNOWLEDGMENTS
11-(4-Methylphenyl)-3,3-dimethyl-2,3,4,5,10,11-
hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one (IX).
a. From amine I and 4-methylbenzaldehyde. Yield
70%, mp 157–158ºC (decomp., 1-butanol). IR
This work was supported by the Russian
Foundation for Basic Research (project no. 09-03-
00052), Ministry of Education of Russian Federation
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11-R-DIBENZO[b,e][1,4]DIAZEPIN-1-ONES
1249
9. Tolpygin, I.E., Revinskii, Yu.V., Dubonosov, A.D.,
Bren’, V.A., and Minkin, V.I., RF Patent no. 338738,
2008, Byul. Izobret., 2008, no. 32.
10. Tolpygin, I.E., Shepelenko, E.N., Revinskii, Yu.V.,
Tsukanov, A.V., Dubonosov, A.D., Bren’, V.A., and
Minkin, V.I., Zh. Org. Khim., 2009, vol. 45, no. 2,
p. 175.
(grant RNP AVTSP HS 2.2.1.1/12630, 2.2.1.1/11794)
and the Council on Grants at the President of the
Russian Federation (grant NSh-3233.2010 .3).
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