Synthesis, absorption and fluorescence properties of N-triazinyl derivatives of 2-aminoanthracene

Article abstract of DOI:10.1016/j.dyepig.2011.08.018

N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene was synthesized by substitution of one chlorine atom of 2,4,6-trichloro-1,3,5-triazine with 2-aminoanthracene. A new series of N-triazinyl-2-aminoanthracenes was prepared by nucleophilic substitution of one or both chlorine atoms on N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene with electron-donating methoxy or phenylamino groups. The UV/Vis absorption, fluorescence and excitation spectra as well as the fluorescence quantum yields of the prepared compounds were measured in 1,4-dioxane, ethyl acetate, dibutyl ether and acetonitrile; nanosecond kinetics of the fluorescence decay was measured in different solvents. The influence of the character of the substituent on triazinyl ring and of the solvent polarity upon the absorption and fluorescence spectra and fluorescence quantum yields are discussed.

Full text of DOI:10.1016/j.dyepig.2011.08.018

Dyes and Pigments 92 (2012) 1126e1131
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Synthesis, absorption and fluorescence properties of N-triazinyl derivatives
of 2-aminoanthracene
,
b
b
c
a
ꢀa
ꢀa
ꢀ
M. El-Sedika, N. Almonasya , M. Nepras , F. Bures , M. Dvorák , M. Michl , J. Cermák , R. Hrdina
ꢀ
*
a Institute of Organic Chemistry and Technology, Faculty of Chemical Technology, University of Pardubice, Studentská 573, CZ-532 10 Pardubice, Czech Republic
b
ꢀ
ꢀ
Department of Physical Electronics, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, v Holesovickách 2, CZ-180 00 Prague, Czech Republic
c Research Institute for Organic Syntheses, Rybitví 296, CZ-533 54 Pardubice 20, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene was synthesized by substitution of one chlorine
Received 17 May 2011
Received in revised form
25 August 2011
Accepted 27 August 2011
Available online 12 September 2011
atom of 2,4,6-trichloro-1,3,5-triazine with 2-aminoanthracene.
A new series of N-triazinyl-2-
aminoanthracenes was prepared by nucleophilic substitution of one or both chlorine atoms on N-(4,6-
dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene with electron-donating methoxy or phenylamino
groups. The UV/Vis absorption, fluorescence and excitation spectra as well as the fluorescence quantum
yields of the prepared compounds were measured in 1,4-dioxane, ethyl acetate, dibutyl ether and
acetonitrile; nanosecond kinetics of the fluorescence decay was measured in different solvents. The
influence of the character of the substituent on triazinyl ring and of the solvent polarity upon the
absorption and fluorescence spectra and fluorescence quantum yields are discussed.
Keywords:
2-aminoanthracene
Synthesis
Ó 2011 Elsevier Ltd. All rights reserved.
N-derivatives
UV/Vis spectra
Fluorescence quantum yield
Fluorescence quenching
1. Introduction
and s-triazinyl ring as the spacer [3]. A better understanding of
interesting features of EET in these systems needed study of the
The ideal bichromophoric compound consists from two chro-
mophores separated and at the same time electronically decoupled
by a molecular unit (spacer). Thus, the absorption spectrum of the
bichromophoric system should consist from the absorption spectra
of individual chromophores. In molecular systems with different
chromophores, the excitation energy localized (at least tempo-
rarily) on one chromophore may be transferred to another chro-
mophore. This process is known as the excitation (or electronic)
energy transfer (EET) and was first described by Foerster [1]. The
manifestation of EET is a more or less complete quenching of
fluorescence of the donor chromophore and the appearance of
fluorescence of the acceptor chromophore. The influence of
molecular structure of chromophores and spacers on EET has been
an area of recent great interest, inspired by biology and optoelec-
tronics, e.g. [2]. We have investigated the synthesis, UV/Vis
absorption and fluorescence spectra and photo-physical properties
of bi- and trichromophoric systems consisting from
1-aminopyrene, and 3-aminobenzanthrone as the chromophores
potential role of photo-physical characteristics of corresponding
molecular subsystems, i.e. of the N-triazinyl derivatives of the
aminochromophores.
During the past several years, we have investigated the
synthesis, UV/Vis absorption and fluorescence spectra and photo-
physical properties of N-triazinyl derivatives of 1- and 2-
aminopyrenes [4], and 3-aminoperylene [5]. We have found that
the number of chlorine atoms on the triazinyl ring and the solvent
polarity are the most significant factors affecting the fluorescence
quantum yield (qF) of the studied compounds. The gradual
replacement of chlorine atoms with electron-donating groups
(methoxy or phenylamino groups) leads to increasing of qF. This
effect was observed for all studied compounds. Recently, we have
explained this phenomenon by semi-empirical quantum chemical
calculations of N-triazinyl derivatives of L-aminopyrene [6]. As the
chlorine atoms increase the withdrawing character of the triazinyl
ring and by its electronegativity, new strong polar excited states (CT
states) accompanied with a transfer of
p-electrons from the ami-
nopyrene moiety to the triazinyl ring were revealed. Owing to
a solvent relaxation, the energy of these CT states could decrease
close or even below an emitting S1 state and thus open a new
nonradiative deactivation channel.
* Corresponding author. Tel.: þ420 466 038 500; fax: þ420 466 038 004.
E-mail address: numan.almonasy@upce.cz (N. Almonasy).
0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2011.08.018

M. El-Sedik et al. / Dyes and Pigments 92 (2012) 1126e1131
1127
Scheme 1.
Herein, to confirm the common validity of this model, we
present the synthesis of new 2-aminoanthracene-derived N-
triazines. The influence of the chromophore structure and the
solvent effects on the absorption and fluorescence spectra, the
fluorescence lifetime and the fluorescence quantum yield were
studied. The obtained results will be important for the study of EET
in bi- and trichromophoric systems with 2-aminoanthracene
chromophore, the synthesis of that is now in progress in our
laboratory.
substances were checked by TLC, HPLC, and by comparison of
fluorescence excitation spectra with absorption spectra of the final
products. The melting points of the synthesized compounds were
determined on a Buchi 510 melting point apparatus.
The samples for absorption spectra and fluorescence measure-
ments were prepared by preparative TLC on Silufol UV 254 plates.
All the solvents used were of spectroscopic grade and were checked
for their own fluorescence.
The absorption spectra were measured on a UV/Vis Perkine
Elmer Lambda 35 spectrophotometer at room temperature. The
steady-state fluorescence spectra were measured on a Hitachi
PerkineElmer LS 55 spectrophotometer. The instrument provides
corrected excitation spectra directly; the fluorescence spectra were
corrected for the characteristics of the emission monochromator
and for the detection photomultiplier response. For fluorescence
measurements, very weakly absorbing solutions (optical
density w 0.05 at the exciting wavelength in 1-cm cell) were used.
The fluorescence quantum yields (qF) were measured using quinine
2. Experimental
2.1. General
Cyanuric chloride, 2-aminoanthracene (AA), aniline, methanol
and other solvents were used as received without further purifi-
cation. Sodium methanolate was prepared according to the litera-
ture procedure [7]. The course of the reactions and purity of the
Table 1
Absorption (lA) and fluorescence (lF) maxima (nm) and fluorescence quantum yields (qF).
NO
Dibutylether
Dioxan
Ethylacetate
Acetonitril
a
a
a
a
lA
lF
qF
lA
lF
qF
lA
lF
qF
lA
lF
qF
1
2
3
4
5
395
396
398
398
402
e
e
396
394
394
398
402
e
e
394
398
395
396
402
e
e
398
397
395
397
401
e
e
405, 429
411, 435
412, 430
420, 441
0.25
0.39
0.35
0.41
411, 432
415, 435
415, 436
424, 442
0.25
0.45
0.42
0.62
409, 430
414, 432
413, 433
424, 440
0.12
0.26
0.23
0.30
410, 431
414, 431
418, 432
425, 441
0.03
0.37
0.18
0.43
a
lA corresponds to the maximum of the first long-wavelength vibronic band.

1128
M. El-Sedik et al. / Dyes and Pigments 92 (2012) 1126e1131
Fig. 1. Absorption (A) and fluorescence (F) spectra of AA (left) and absorption spectrum of 1 (right) in 1,4-dioxane.
sulphate (qF ¼ 0.54 in 0.5 mol/L H2SO4) [8] as the standard.
Deaeration of the samples by bubbling with N2 did not change the
spectra and qF; therefore, the data presented here correspond to
aerated solutions.
recorded in mass range 50e1500 Da. The ion trap analyzer was
tuned to obtain an optimal response in the range of expected m/z
values. Other APCI ion source parameters were as follows: a drying
gas flow of 7 l minꢁ1, a nebulizer gas pressure of 60 psi and drying
gas temperature 350 ꢀC. The samples were dissolved in acetonitrile
for HPLC (SigmaeAldrich) at appropriate concentrations for MS
identification.
The fluorescence kinetics was performed on an Edinburgh
Analytical Instruments FS/FL spectrophotometer that employs
time-correlated single photon counting (TCSPC) detection. Pulse
diode IBH Nanoled-03 (370 nm ns LED) was used as the excitation
source to excite the set of studied compounds near the centre of the
absorption band. Instrument response function FWHM was <1.5 ns.
The fluorescence signal was recorded at 450 nm at the maximum of
the fluorescence band. The fluorescence lifetimes were obtained by
multiexponential reconvolution fitting process.
The synthesis of target compounds 1e5 is shown in Scheme 1.
2.1.1. N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene (1)
Cyanuric chloride (1.8 g, 9.8 mmol) and NaHCO3 (0.5 g) were dis-
solved inacetone(100mL). Thesolutionwascooled to0e5ꢀCinanice
bath. Subsequently 2-aminoanthracene (2 g, 10.03 mmol) in 10 ml of
acetone was added dropwise. The reaction mixture was stirred at
0e10 ꢀC and the reaction course was monitored by TLC until the 2-
aminoanthracene spot had completely disappeared. After 3 h, the
product was isolated by filtration, washed with water aþnd dried to
obtain 1 g of 1 in 29% yield; m.p 219e221 ꢀC. MS: (APCI ): m/z 341
[M þ H]þ (M.W. 340 g/mol). 1H NMR (DMSO-d6, 400 MHz):
The chemical structures were confirmed by MS, 1H and 13C NMR
spectra and elemental analysis.
1H and 13C NMR spectra were recorded at 400 and 100 MHz
respectively, with a Bruker AVANCE 400 instrument at 25 ꢀC.
Chemical shifts are reported in ppm relative to the signal of Me4Si.
The residual solvent signal in the 1H and 13C NMR spectra was used
as an internal reference (DMSO-d6 e 2.55 and 39.51 ppm). Apparent
resonance multiplicities are described as s (singlet), br s (broad
singlet), d (doublet) and m (multiplet).
d
¼ 7.52e7.58 (m, 2H,), 7.74 (d, 1H, J ¼ 9.2 Hz), 8.10e8.17 (m, 3H), 8.41
(s, 1H), 8.57 (d, 2H, J ¼ 10.0 Hz), 11.46 (s, 1H). 13C NMR (DMSO-d6,
100 MHz):
d
¼ 117.26, 121.77, 125.41, 125.59, 125.84, 126.03, 127.84,
Mass spectra were acquired on a LC/MS system LC-MSD TRAP
XCT Plus (Agilent Technologies, USA) using direct infusion
measurement. Negative and positive-ion APCI mass spectra were
128.08,128.84,129.00,130.89,130.99,131.75,134.05,163.96,168.Anal.
calcd. for C17H10Cl2N4: C (59.84%) H (2.95%) Cl (20.78%) N (16.42%);
found: C (59.79%) H (2.81%) Cl (20.74%) N (16.36%).
Fig. 2. Absorption (A), excitation (E) and fluorescence (F) spectra of 2 in 1,4-dioxane.

M. El-Sedik et al. / Dyes and Pigments 92 (2012) 1126e1131
1129
Fig. 3. Absorption (A), excitation (E) and fluorescence (F) spectra of 3 in 1,4-dioxane.
2.1.2. N-(4-chloro-6-methoxy-1,3,5-triazin-2-yl)-2-
aminoanthrace-ne (2)
100 MHz):
d
¼ 54.64, 115.11, 122.03, 124.93, 125.03, 125.62, 125.81,
127.71, 128.09, 128.40, 128.53, 130.46, 131.64, 131.75, 136.04,
166.20, 172.14. Anal. calcd. for C19H16 N4O2: C (68.66%) H (4.85%) N
(16.86%) O (9.63%); found: C (68.63%) H (4.98%) N (16.90%) O
(9.67%).
Compound 1 (0.5 g, 1.5 mmol) was dissolved in a mixture of
methyl alcohol (5 mL) and DMF (10 mL) whereupon NaHCO3 (0.5 g)
was added. The reaction mixture was stirred at room temperature
for 1 h, was diluted with water (30 ml) and the product was fiꢁltered
off to obtain 0.2 g (59% yield) of 2, m. p 222e225 ꢀC. MS: (APCI ): m/
z 335 [M ꢁ H]ꢁ (M.W. 336 g/mol). 1H NMR (DMSO-d6, 400 MHz):
2.1.4. N-(4-chloro-6-anilino-1,3,5-triazin-2-yl)-2-aminoanthracene
(4)
d
¼ 4.09 (s, 3H), 7.49e7.55 (m, 2H), 7.75 (d,1H, J ¼ 8.8 Hz), 8.08e8.11
(m, 3H), 8.48e8.59 (m, 3H), 10.98 (br s, 1H). 13C NMR (DMSO-d6,
100 MHz):
Aniline (1.6 mL, 17.2 mmol) was added dropwise with stirring to
a mixture of 1 (0.7 g, 2.1 mmol), acetone (50 mL) and NaHCO3
(0.5 g). The reaction mixture was stirred at 60 ꢀC for 2 h, diluted
with water (50 mL) and the product was filtered off to obtain 0.5 þg
of 4 in 61% yield; m. p > 300 ꢀC. MS: (APCIþ): m/z 398 [M þ H]
d
¼ 55.56, 115.98, 121.68, 125.14, 125.34, 125.71, 125.89,
127.74, 128.07, 128.58, 128.75, 130.67, 131.33, 131.74, 135.01, 164.88,
169.47, 171.08. Anal. calcd. for C18H13Cl N4O: C (64.19%) H (3.89%) Cl
(10.53%) N (16.64%) O (4.75%); found: C (64.14%) H (3.84%) Cl
(10.48%) N (16.58%) O (4.69%).
(M.W. 397 g/mol). 1H NMR (DMSO-d6, 400 MHz):
d
¼ 7.19e7.30 (m,
1H,), 7.39e7.58 (m, 4H), 7.62e7.80 (m, 3H), 8.10 (d, 3H, J ¼ 8.4 Hz),
8.29 (br s, 1H), 8.55 (s, 2H), 10.43 (br s, 1H), 10.62 (br s, 1H). 13C NMR
2.1.3. N-(4,6-dimethoxy-1,3,5-triazin-2-yl)-2-aminoanthracene (3)
A mixture of methyl alcohol (5 mL) and sodium methanolate
(10 mL) were added to compound 1 (0.5 g, 1.5 mmol). The reaction
mixture was refluxed for 2 h, was diluted with water (50 mL) and
the product was filtered off to obtain 0.35 g of 3 in 70% yield. m. p
206e208 ꢀC. MS: (APCIꢁ): m/z 331 [M ꢁ H]ꢁ (M.W. 332 g/mol). 1H
(DMSO-d6, 100 MHz):
d
¼ 115.77, 121.97, 122.14, 124.17, 124.92,
125.09, 125.82, 125.94, 127.71, 128.15, 128.53, 128.62, 128.80, 130.54,
131.55, 131.69, 135.42, 138.30, 164.06, 164.22, 168.16. Anal. calcd. for
C23H16Cl N5: C (69.43%) H (4.05%) Cl (8.91%) N (17.60%); found: C
(69.39%) H (4.08%) Cl (8.97%) N (17.66%).
NMR (DMSO-d6, 400 MHz):
d
¼ 4.02 (s, 6H), 7.47e7.54 (m, 2H),
2.1.5. N-(4,6-dianilino-1,3,5-triazin-2-yl)-2-aminoanthracene (5)
A mixture of acetone (50 mL), compound 1 (0.7 g, 2.1 mmol),
aniline (3.2 mL, 34.4 mmol) and NaHCO3 (0.5 g) was placed in
7.79 (d, 1H, J ¼ 8.8 Hz), 8.07 (d, 3H, J ¼ 8.8 Hz), 8.50 (d, 2H,
J ¼ 13.2 Hz), 8.65 (s, 1H), 10.44 (br s, 1H). 13C NMR (DMSO-d6,
Fig. 4. Absorption (A), excitation (E) and fluorescence (F) spectra of 4 in 1,4-dioxane.

1130
M. El-Sedik et al. / Dyes and Pigments 92 (2012) 1126e1131
Fig. 5. Absorption (A), excitation (E) and fluorescence (F) spectra of 5 in 1,4-dioxane.
a 100 mL Parr autoclave under autogenous pressure. The vessel was
sealed and heated to 140 ꢀC in an oil bath for 5 h. The reaction
mixture was cooled to room temperature, diluted with water
(30 mL) and the product was filtered off to obtain 0.6 g in 65% yield;
m. p 235e237 ꢀC. MS: (APCIþ): m/z 455 [M þ H]þ (M.W. 454 g/mol).
performed only by methanol at room temperature. Since the
solubility of compound 1 in methanol is very low, we used
a mixture of methanol-dimethylformamide as the solvent system.
Beside the target product 2, a trace of compound 3 was detected by
MS analysis. This compound fluoresces very intensely and could be
detected by TLC as well. The crude product was simply precipitated
from the reaction mixture by dilution with water, filtration and
rinsing with a small amount of hot acetone.
The reaction of 1 with 2 equiv of sodium methanolate leads to
substitution of both chlorine atoms of triazinyl ring yielding
compound 3. The product was isolated almost quantitatively and
with a very high purity.
1H NMR (DMSO-d6, 400 MHz):
d
¼ 7.03e7.12 (m, 2H,), 7.39 (t, 4H,
J ¼ 7.8 Hz), 7.47e7.56 (m, 2H), 7.85e7.93 (m, 5H), 8.08 (t, 3H,
J ¼ 7.4 Hz), 8.42 (br s, 1H), 8.52 (s, 1H), 8.82 (br s, 1H), 9.42 (br s, 2H),
9.63 (br s, 1H). 13C NMR (DMSO-d6, 100 MHz):
d
¼ 114.21, 120.61,
122.25, 122.53, 124.53, 124.66, 125.62, 125.75, 127.56, 128.22,
128.24, 128.49, 128.83, 130.18, 131.64, 132.12, 137.03, 139.94, 164.21,
164.29. Anal. calcd. for C29H22 N6: C (76.63%) H (4.88%) N (18.49%);
found: C (76.59%) H (4.91%) N (18.44%).
Treatment of 1 with a 1 mol equiv of aniline in boiling acetone
for 2 h afforded compound 4. The product was isolated and purified
in similar way as described above.
3. Results and discussion
The substitution of both chlorine atoms in 1 by amino phenyl
group was carried out in acetone as the solvent. Under the
described conditions, the reaction proceeded with a high reaction
selectivity by compared to compound 3.
3.1. Synthesis
As shown in the above reaction scheme, the preparation of
target compounds is based on the same principle as the previous
syntheses of N-triazinyl derivatives of the other aromatic amines
[4,5]. For instance, compound 1 was prepared by the substitution of
the cyanuric chloride with 2-aminoanthracene at 0e5 ꢀC. When the
temperature exceeds þ5 ꢀC, substitution of the second chlorine
atom also occurred. Hence, 2,4-di(2-anthracenylamino)-6-chloro-
1,3,5-triazine was identified as the by-product. The spectral and
photo-physical properties of this compound will be investigated in
connection with the study of bi- and trichromophoric compounds
with s-triazinyl spacer.
3.2. Absorption and fluorescence spectra
The absorption spectrum of anthracene has been in literature
many times well described and interpreted: the first absorption
band (La) corresponding to HOMO / LUMO transition is formed by
several vibronic bands in the region 310e380 nm. The second
absorption band (Lb) corresponding to the mixture of
HOMO / LUMO þ 1 and HOMO ꢁ 1 / LUMO configurations is
strictly forbidden and is completely overlapped by La band. By the
Because of a high reactivity, the nucleophilic substitution of the
second chlorine atom on triazinyl ring by methoxy group could be
substitution with amino group in position 2, an extension of
conjugation occurs and, in the same time, the system losses the
p-
Fig. 6. Absorption (solid line) and fluorescence anisotropy (dotted line) of 3 (left) and 5 (right) in 2-MTHF at 140 K.

M. El-Sedik et al. / Dyes and Pigments 92 (2012) 1126e1131
1131
Table 2
Similar to N-triazinyl-1-aminopyrenes [6], our unpublished
semi-empirical computations revealed strongly polar excited states
connected with electron transition from anthracenyl moiety to
triazinyl ring. Their energy decreases dramatically with the number
of chlorine atoms on triazinyl ring and with increasing the solvent
polarity. As a result, these CT states could influence the deactivation
mechanism of the emitting excited state and consequently the
fluorescence quantum yield of studied compounds.
Fluorescence lifetimes of the compounds in dioxan and ethyl acetate.
NO
Dioxan
Ethyl acetate
3
4
5
12.2 ns
10.3 ns
13.3 ns
8.2 ns
6.6 ns
9.0 ns
symmetry. Consequently, two absorption bands with practically the
same middle intensity appear: the broad band in the region
360e440 nm (lmax ¼ 400 nm), the second band with clear-cut
vibronic structure in the region 320e350 nm e.g. [9].
In the same way as the fluorescence quantum yields, the fluo-
rescence lifetimes (Table 2) decrease with increasing electron-
withdrawing nature of triazinyl ring and with increasing of the
solvent polarity.
The substitution of hydrogen atom on amino group of
2-aminoanthracene by electron-withdrawing triazinyl group cau-
ses a decrease in conjugation of the amino 2pp electrons with the
To confirm a common validity of the theoretical results pre-
sented for N-triazinyl-1-aminopyrenes [6], i.e. the dominant role of
CT states for fluorescence quenching, the detailed theoretical study
of N-triazinyl derivatives of a series of polynuclear aromatic amines
is now in progress in our laboratory.
anthracene
p-system; consequently, a hypsochromic shift of the
first absorption band was observed. Simultaneously, a well defined
vibronic structure of the spectra of N-triazinyl derivatives was
recorded. Neither solvent polarity nor a substituent on triazinyl
ring influenced the position of the absorption maxima of N-tri-
azinyl derivatives (Table 1, Figs. 1e5).
4. Conclusion
Five new N-triazinyl derivatives of 2-aminoanthracene were
prepared; their structure was confirmed by elemental analysis, MS
and NMR spectra. The UV/Vis absorption and fluorescence spectra,
fluorescence quantum yields and lifetimes were measured in four
solvents. It was found that a character of a substituent on triazinyl
ring and the solvent polarity do not influence the shape and the
position of the absorption and fluorescence spectra. On the other
hand, the character of appended N-substituent and the solvent
polarity affect the qF of studied compounds significantly. In the
same way as for N-triazinyl 1-aminopyrene and 3-aminoperylene,
the dichloro derivative of N-triazinyl 2-aminoanthracene does not
fluoresce at all. The gradual substitution of chlorine atoms by
electron-donating groups causes a strong increasing of qF. We
suppose that a dramatic fluorescence quenching of dichloro
derivative is caused by a participation of CT states in deactivation
cascade, as has been recently theoretically explained for N-triazinyl
derivatives of 1-aminopyrene.
From the shape of the absorption spectra and from the character
of fluorescence anisotropy for 3 and 5 in 2-methyltetrahydrofuran
(2-MTHF) at 140 K in the spectral range 320e410 nm (Fig. 6), two
well separated bands exhibiting a very similar clear-cut vibronic
structure are evident. According to our CNDO/S calculations (Win-
MOPAC 2.0 Package, unpublished results) of presented compounds,
both bands correspond to electronic transitions to the excited states
mixed from Lb and La states localized on aminoantracenyl moiety;
the second shorter wavelength transition shows somewhat higher
character of La state (a higher CI coefficient of HOMO-LUMO
configuration). The oscillator strength of the first transitions are
0.08 (3) and 0.122 (5), of the second ones are 0.190 (3) and 0.205 (5).
A similar vibronic structure of both bands proves a significant
participation of anthracene La state in both transitions. According to
our theoretical results, the difference of transition moment direc-
tions between the first and the second transition is large (45ꢀ for 3
and 65ꢀ for 5) and is small between the second transition and the
transition corresponding to Bb, lmax ¼ 300e310 nm (15ꢀ for 3 and 4ꢀ
for 5). These results arein agreement with the decrease of anisotropy
degree in the range 320e410 nm.
Acknowledgements
The financial support provided by the Czech Ministry of
Education Youth and Sports (grant VZ MSMT No 0021627501).
The fluorescence spectra of studied compounds show a vibronic
structure and approximate mirror symmetry with the first
absorption band. With decreasing electronegativity of triazinyl ring
and with increasing the solvent polarity, the fluorescence maxima
are shifted slightly bathochromically. The Stokes shifts are small
(1e2 ꢂ 103 cmꢁ1). The excitation fluorescence and absorption
spectra are almost identical.
References
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[2] (a) El-Sayed MA, Tanaka I, Molin Y, editors. Ultrafast processes in chemistry and
photobiology (a chemistry for 21st century monograph). U.K.: IUPAC and
Blackwell Science Ltd.; 1995;
3.2.1. Fluorescence quantum yields
Similar to N-(4,6-dichloro-1,3,5-triazin-2-yl)-1-aminopyrene [4]
and N-(4,6-dichloro-1,3,5-triazin-2-yl)-3-aminoperylene [5], the
substitution of hydrogen atom of the amino group of 2-
aminoanthracene by cyanuric chloride causes almost total fluores-
cence quenching of 1 in all used solvents. The substitution of one
chlorine atom of compound 1 by electron-donating methoxy or
phenylamino group causes a significant raising of qF of the corre-
sponding derivative in non polar (1,4-dioxane, DBE) and low polar
(ethyl acetate) solvents; but a small increasing of qF was found in
highly polar acetonitrile for 2. Dimethoxy and dianilino derivatives
exhibit relatively high qF in all used solvents. These dependences may
result from an interplay of electronegativity of triazinyl ring (number
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