Preparation of triazatriphenylene cations, promising chemosensors for nitro compounds

Full text of DOI:10.1007/s10593-013-1276-3

Chemistry of Heterocyclic Compounds, Vol. 49, No. 3, June, 2013 (Russian Original Vol. 49, No. 3, March, 2013)
PREPARATION OF TRIAZATRIPHENYLENE CATIONS,
PROMISING CHEMOSENSORS FOR NITRO COMPOUNDS
D. S. Kopchuk1,2, I. N. Egorov1, T. A. Tseitler1, A. F. Khasanov1,
I. S. Kovalev1, G. V. Zyryanov1,2*, V. L. Rusinov1, 2, and O. N. Chupakhin1,2
Keywords: 2-aryl[1,2,4]triazino[1,6-f]phenanthridin-13-ium-4-olate, picrate, 2-R-5,6,7,8,9,10,11,12-
octahydro[1,2,4]triazino[1,6-f]phenanthridin-13-ium-4-olate, aromatization, fluorescence.
Triphenylene and its poly(hetero)aromatic derivatives are of significant interest as potential chemical
sensors for polynitroaromatic compounds due to their photoluminescent properties and their ability to form
stable, non-fluorescent -complexes with electron deficient substrates [1, 2]. In such an interaction the
efficiency of photoluminescence quenching depends on the rate of electron transfer from the polyaromatic
compound as donor to the nitro compound as acceptor. According to literature data, the efficiency of this
electronic interaction can be increased by the introduction of Lewis acid fragments, e.g., metals or azinium
cations into the poly(hetero)aromatic sensor molecule [3]. The structure of the polynitro compounds include
Lewis base fragments (the oxygen atoms of the nitro groups), and hence an interaction with cations and other
Lewis acids accelerates the "donor-acceptor" electronic communication, thus enhancing the photoluminescence
quenching [4].
The most frequently used method for preparing azatriphenylenes is the Skraup synthesis [5, 6], which
requires forcing conditions. Contemporary synthetic methods frequently use hard to obtain alkenes or
arylacetylenes in transition metal-catalyzed cycloaddition reactions with aromatic substrates [7, 8]. On the other
hand, a method of synthesizing aliphatic triphenylene precursors by cyclotrimerization of cyclohexanone [9] is
widely known, and we have previously reported the preparation of 2-R-5,6,7,8,9,10,11,12-octa-
hydro[1,2,4]triazino[1,6-f]phenanthridin-13-ium-4-olates by reaction of 3-R-1,2,4-triazin-5(4H)-ones with
cyclohexanone under acid catalysis conditions [10]. The 1,2,4-triazines 1a,b prepared in this way are of interest
as triazatriphenylene precursors.
We have used several methods for the aromatization of compounds 1a,b to the corresponding
triphenylenes. The most effective was refluxing of compounds 1a,b in o-xylene solution for 24 h in the presence of
2,3-dichloro-5,6-dicyanobenzoquinone (6 equivalents). The reaction products were obtained in up to 60% yield.
The structure of the compounds obtained was confirmed by 1H and 13C NMR spectroscopy, mass
_______
*To whom correspondence should be addressed, e-mail: gvzyranov@gmail.com.
1Ural Federal University named after the First President of Russia B. N. Yeltsin, 19 Mira St., Yekaterinburg
620002, Russia.
2I. Ya. Postovskii Institute of Organic Synthesis, 22 Akademicheskaya / 20 S. Kovalevskoi St., Yekaterinburg
620219, Russia; e-mail: chupakhin@ios.uran.ru.
_________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 538-540, March, 2013. Original
article submitted October 23, 2012.
0009-3122/13/4903-0503©2013 Springer Science+Business Media New York
503

1
spectrometry, and elemental analysis. The H NMR spectra unambiguously showed an azatriphenylene type
aromatic structure, as evidenced by the presence of multiplets corresponding to the protons of phenylene
fragments and aromatic substituents in the region of 7.87-10.64 ppm.
In contrast to the aliphatic precursors, the obtained products exhibited intense photoluminescence
(max 429-430 nm). Fluorescence titration of compound 2a,b solutions with dichloromethane solutions of
2,4-dinitrotoluene and 2,4,6-trinitrophenol (picric acid) showed strong fluorescence quenching with values of
the Stern-Volmer quenching constant of Ksv ~103-104 M-1 [4]. Cocrystallization of the triazatriphenylene 2a with
2,4,6-trinitrophenol in chloroform solution led to formation of the picrate 3a, the elemental analysis of which
indicated a 1:1 stoichiometry.
O–
O2N
NO2
N
N+
O
N
HO
N
HN
N
Ar
NO2
3a
O
Ar
H+
1) CHCl3, 5 min;
2) CHCl3, 25°C, 72 h
2,4,6-Trinitrophenol
O
CN
CN
Cl
N+
N+
Cl
O
–O
N
–O
N
o-Xylene, 24 h
N
N
Ar
Ar
2a,b
1a,b
a Ar = Ph, b Ar = 4-MeC6H4
Therefore, we have prepared novel triazatriphenylene cations showing a great promise for the visual
assay of nitroaromatic compounds.
1H and 13C NMR spectra were recorded on a Bruker DRX-400 instrument (400 and 100 MHz,
respectively) using CDCl3 with TMS as internal standard. Mass spectra (electrospray ionization) were recorded
on a Bruker Daltonics micrOTOF-Q II mass spectrometer. Elemental analysis was carried out on a Perkin-Elmer
PE 2400 series II CHN analyzer. TLC analysis was performed on Merck 60F254 silica gel plates and visualized
using UV light. Column chromatography was performed on neutral aluminum oxide (Acros Organics,
Brockmann I, 50-200 m, 60 Å). UV absorption spectra were recorded on a Perkin-Elmer Lambda 45
spectrophotometer. Luminescence spectra were recorded for solutions on a Cary Eclipse (Varian)
spectrofluorimeter.
2-Aryl-5,6,7,8,9,10,11,12-octahydro[1,2,4]triazino[1,6-f]phenanthridin-13-ium-4-olates 1a,b were
prepared by a previously reported method [10].
Preparation of Compounds 2a,b (General Method). The corresponding octahydrotriazatriphenylene
1 (0.4 mmol) was dissolved in o-xylene (60 ml), the oxidant 2,3-dichloro-5,6-dicyanobenzoquinone (0.18 g,
0.8 mmol) was added, and the mixture was refluxed for 7 h. An additional portion of the oxidant (0.18 g,
0.8 mmol) was added and the mixture was refluxed for another 7 h. A further aliquot of oxidant (0.18 g,
0.8 mmol) was added, and the mixture was refluxed for 10 h. The reaction mixture was then cooled to room
temperature and filtered from the precipitate formed. The solvent was evaporated under reduced pressure, and
the residue was purified by column chromatograpy (eluent EtOAc). An analytically pure sample was prepared
by recrystallization from MeCN.
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2-Phenyl[1,2,4]triazino[1,6-f]phenanthridin-13-ium-4-olate (2a). Yield 78 mg (60%). Colorless
1
crystals; mp >250°C. H NMR spectrum, , ppm (J, Hz): 7.55 (3Н, m, H Ph); 7.87-8.05 (4H, m, H Ph, H Ar);
3
8.58 (2Н, m, H Ar); 8.66 (1Н, d, J = 8.0, H Ar); 8.71 (1Н, m, H Ar); 9.46 (1Н, m, Н-12); 10.61 (1H, d,
3J = 8.0, Н-5). 13C NMR spectrum, , ppm: 121.3; 121.5; 122.9; 123.4; 126.5; 128.4; 128.5; 129.8; 130.4;
130.7; 131.2; 131.3; 131.6; 133.3; 134.8; 135.2; 146.3; 162.6; 166.0. UV spectrum (CH2Cl2,), max, nm: 260,
384, 405. Fluorescence spectrum (CH2Cl2, at ext 405 nm), max, nm: 429. Mass spectrum, m/z (Irel, %): 324.11
[M+H]+ (100). Found, %: С 77.78; Н 3.89; N 12.85. C21H13N3O. Calculated, %: С 78.00; Н 4.05; N 12.99.
2-(p-Tolyl)[1,2,4]triazino[1,6-f]phenanthridin-13-ium-4-olate (2b). Yield 78 mg (58%). Colorless
crystals; mp >250°C. 1H NMR spectrum, , ppm (J, Hz): 2.47 (3Н, s, CH3); 7.38 (2Н, m, H Tol); 7.88-8.07 (4Н,
m, H Ar); 8.49 (2Н, m, H Tol); 8.69 (1Н, m, H Ar); 8.74 (1Н, m, H Ar); 9.51 (1Н, m, Н-12); 10.64 (1Н, d, 3J =
8.8, Н-5). Mass spectrum, m/z (Irel, %): 338.13 [M+H]+ (100). Found, %: С 78.13; Н 4.32; N 12.23. C22H15N3O.
Calculated, %: С 78.32; Н 4.48; N 12.45.
4-Hydroxy-2-phenyl[1,2,4]triazino[1,6-f]phenanthridin-13-ium Picrate (3a).
A
solution of
compound 2a (39 mg, 0.12 mmol) and 2,4,6-trinitrophenol (27 mg, 0.12 mmol) in chloroform (5 ml) was heated
under reflux for 5 min, and the mixture obtained was left at room temperature for 72 h. The light-yellow
precipitate was filtered off and dried in air. Yield 12 mg (18%). Yellow crystals; mp >250°C. Found,
%:C 58.71; H 3.12. C27H16N6O8. Calculated, %: C 58.70; H 2.92.
This work was carried out with the support of the Ministry of Education and Science of the Russian
Federation (state contracts 14.740.11.1020 and 14.A18.21.0817), the Russian Foundation for Basic Research
(grant 12-03-31726) and the Grants Council of the President of the Russian Federation (grant MK-
1511.2013.3).
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