Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents
Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes of two types K1 and K2 in a series of isotropic solvents were studied. It was shown that the photoluminescent spectra depend both on nature of solvent (formation of associates with solvent owing to hydrogen bonds between...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2006
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irk-123456789-1215962017-06-15T03:03:53Z Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents Gorishnyi, M.P. Shevchuk, A.F. Manzhara, V.S. Koval'chuk, A.V. Koval'chuk, T.N. Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes of two types K1 and K2 in a series of isotropic solvents were studied. It was shown that the photoluminescent spectra depend both on nature of solvent (formation of associates with solvent owing to hydrogen bonds between the dye and alcohol or aggregates of dye molecules) and the dye concentration (concentration decay). The frequencies of electron transitions and frequency of intramolecular fluctuation were determined, and conclusions concerning the nature of absorption bands were made. 2006 Article Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents / M.P. Gorishnyi, A.F. Shevchuk, V.S. Manzhara, A.V. Koval'chuk, T.N. Koval'chuk // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 1. — С. 73-78. — Бібліогр.: 12 назв. — англ. 1560-8034 PACS 78.55.-m http://dspace.nbuv.gov.ua/handle/123456789/121596 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes of two types K1 and K2 in a series of isotropic solvents were studied. It was shown that the photoluminescent spectra depend both on nature of solvent (formation of associates with solvent owing to hydrogen bonds between the dye and alcohol or aggregates of dye molecules) and the dye concentration (concentration decay). The frequencies of electron transitions and frequency of intramolecular fluctuation were determined, and conclusions concerning the nature of absorption bands were made. |
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Gorishnyi, M.P. Shevchuk, A.F. Manzhara, V.S. Koval'chuk, A.V. Koval'chuk, T.N. |
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Gorishnyi, M.P. Shevchuk, A.F. Manzhara, V.S. Koval'chuk, A.V. Koval'chuk, T.N. Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents Semiconductor Physics Quantum Electronics & Optoelectronics |
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Gorishnyi, M.P. Shevchuk, A.F. Manzhara, V.S. Koval'chuk, A.V. Koval'chuk, T.N. |
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Gorishnyi, M.P. |
| title |
Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents |
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Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents |
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Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents |
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Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents |
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Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents |
| title_sort |
absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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2006 |
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http://dspace.nbuv.gov.ua/handle/123456789/121596 |
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Absorption and photoluminescent spectra of dimethylaniline ethylene ketone dyes in isotropic solvents / M.P. Gorishnyi, A.F. Shevchuk, V.S. Manzhara, A.V. Koval'chuk, T.N. Koval'chuk // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 1. — С. 73-78. — Бібліогр.: 12 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
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2025-07-08T20:11:34Z |
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 73-78.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
73
PACS 78.55.-m
Absorption and photoluminescent spectra
of dimethylaniline ethylene ketone dyes in isotropic solvents
M.P. Gorishnyi1, A.F. Shevchuk2, V.S. Manzhara1, A.V. Koval’chuk1, T.N. Koval’chuk3
1Institute of Physics, NAS of Ukraine, 46, prospect Nauky, 03028 Kyiv, Ukraine
2Vinnitsa State Agricultural University, 3, Sonyachna str., 21008 Vinnitsa, Ukraine
3V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 45, prospect Nauky, 03028 Kyiv, Ukraine
Abstract. Absorption and photoluminescent spectra of dimethylaniline ethylene ketone
dyes of two types K1 and K2 in a series of isotropic solvents were studied. It was shown
that the photoluminescent spectra depend both on nature of solvent (formation of
associates with solvent owing to hydrogen bonds between the dye and alcohol or
aggregates of dye molecules) and the dye concentration (concentration decay). The
frequencies of electron transitions and frequency of intramolecular fluctuation were
determined, and conclusions concerning the nature of absorption bands were made.
Keywords: absorption and photoluminescent spectra, dimethylaniline ethylene ketone
dye, isotropic solvent.
Manuscript received 23.11.05; accepted for publication 15.12.05.
1. Introduction
Interest to research liquid crystals (LCs) is substantially
caused by opportunities of their practical application in
electrooptical devices of different types. Essential
restrictions for LC application are related with the
absence of absorption bands within the visible spectral
range. One way to improve the LC device characteristics
and extend their application fields is to introduce the
dyes possessing the absorption of visible radiation into
the LC structure. In this connection, there arose the
problem to search for dyes that effectively would fit into
the LC structure. Our investigations have shown that the
dimethylaniline ethylene ketone (DMAEK) dyes possess
a good solubility in the LC series. In particular, in the
nematic [1, 2], ferroelectric [3], and liotropic LCs, the
concentration of DMAEK dyes can achieve 10 wt.%. In
this case, the solution of DMAEK dyes in nematic LCs
appeared to be perspective for recording the dynamic
holograms of two and four-beam geometry [4]. Revealed
were essential dependences of the absorption and
luminescent spectra of DMAEK dyes on both a type of
used solvents and concentration, which can be connected
with exhibiting the aggregation effects, formation of
complexes and orientation ordering.
As in the literature there are no DMAEK molecular
spectra researches, which is necessary to discuss their
properties in LC matrixes, in this paper reported are the
results of the experimental study and analysis of
molecular spectra of DMAEK dyes in isotropic solvents.
2. Materials and methods
Dye absorption spectra within the wavelength range of
250 to 600 nm were measured using the spectrophometer
“Hitachi” equipped with a personal computer. In so
doing, the standard silica cuvettes of various thicknesses
were used that allowed us to study the optical absorption
dependence on the concentration of dyes in a solution.
As solvents, we used toluene, dimethylformamide,
ethanol, hexane and glycerine.
To measure luminescent spectra of solutions, we
used the automated spectral setup based on a
monochromator SPM-2 with photoelectric signal
registration. Photoluminescence of dyes was excited by
the mercury lamp ДРШ-250 radiation transmitted
through the filters УФС-6 and УФС-8.
3. Experimental results
Structural formulae of DMAEK molecules for dyes of
orange (K1) and yellow (K2) colors are shown in Fig. 1.
The K1 molecule contains a carbonyl group OC1
2 =〉 in
its center, to which the methylfuran radical is attached in
the position 1, and dimethylaniline ethylene one – in the
position 2. In the K2 molecule, the methylfuran radical is
substituted for metoxybenzyl. These molecules belong to
unsaturated ketones. Their fragments between furan,
benzene (K1) and benzene (K2) rings are flat, therefore the
valent electrons of C and O atoms (carbonyl group)
delocalize with formation of π-systems in K1 and K2.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 73-78.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
74
O
C
C
O
H3C
C
H
H
N
CH3
CH3
1
2
K1
..
O
C
C
C
H
H
N
CH3
CH3
1
2
O
H3C K2
..
Fig. 1. Structure formulae of 1-methoxyfuran,2-dimethyl-
aniline ethylene ketone (K1) and 1-methoxybenzyl,2- dime-
thylaniline ethylene ketone (K2).
300 350 400 450 500 550
0.0
0.1
0.2
0.3
0.4
3
2
41
D
λ, nm
Fig. 2. Absorption spectra of K1 and K2 dyes in benzene (1, 3)
and DMFA (2, 4). The dye concentration C equals:
7.0⋅10−6(1); 5.6⋅10−6(2); 7.3⋅10−6(3); 8.1⋅10−6(4) mol/l.
Oxygen atoms of carbonyl groups form π-bonds using
their 2pz-electrons. Their unseparated pairs of 2pх-elect-
rons (in Fig. 1, they are marked by circles) are located in
non-coupling orbitals. According to this analysis, ππ∗- and
nπ* -states are possible in the K1 and K2 molecules.
Absorption spectra of K1 and K2 solutions within the
range of wavelengths 280 to 500 nm are shown in Fig. 2.
The spectrum of orange K1 dye in benzene (curve 1)
consists of two bands: an intensive longwave band with
λ = 410 nm, ε = 5⋅104 l⋅mol−1⋅cm−1 and more weak
shortwave one with λ =315 nm, ε = 1.2⋅104 l⋅mol−1⋅cm−1.
The spectrum of the yellow K2 dye in benzene (curve 3)
is similar to the first one but has hypsochromical shift:
the longwave band is shifted by 12 nm, and the
shortwave band – by 14 nm.
In the polar solvent, in dimethylformamide (DMFA),
the longwave band of orange K1 dye is shifted
bathochromically by 12 nm (0.09 eV) relatively to the
band in the benzene solution spectrum, and the weak
shortwave band does not change its position, but in this
case its halfwidth increases and asymmetry decreases
(Fig. 2, curve 2).
When passing from benzene to DMFA, the changes
in the spectrum of yellow K2 dye (curves 3 and 4
accordingly) are precisely the same as in that of orange
K1 dye. The bathochromical shift of the longwave band
is the main change.
For K2 dye possessing the best solubility,
investigated were the absorption spectra also in other
solvents as well as for various concentrations. For the
concentration C = 2⋅10−5 mol/l in toluene, the peak of its
main, longwave, absorption band appeared to have the
same position – λ = 399 nm – as well as in the spectrum
of benzene solutions, and in alcohol it has an essential
longwave shift at λ = 452 nm. With one more order
increase in the concentration of K2 dye in alcohol, the
longwave band prevailing in the spectrum displaces
hypsochromically by 36 nm and decreases 5-fold in its
intensity. In glycerine, the peak of the longwave K2
absorption band occurs at λ = 416 nm, i.e., coincides
with the peak position in the concentrated alcohol
solution spectrum.
The photoluminescent spectrum (PLS) of the K1
dye solution of the concentration С = 2⋅10−5 mol/l is a
single band, the peak position of which essentially
depends on a solvent: λ = 466 mn in toluene and
554 nm in alcohol.
The PLS of K1 dye solution in the same solvents and
of the same concentration differ from those of K1 only in
the peak position of the band – it lies at 460 and 538 nm
when dissolving in toluene and alcohol, respectively
(Fig. 3, curves 1 and 2). With one order increase in the
concentration of K2 dye in toluene and alcohol, the
position of dye luminescent bands does not change, only
the concentration decay is observed (curves 3 and 5).
More essential changes are observed in the K2 PLS
when it dissolves in glycerine: this spectrum has two
clearly pronounced widely overlapped bands with the
peak position at 489 and 570 nm (Fig. 3, curve 5).
When measuring the PLS, the changes of spectra
occur owing to UV irradiation of solutions. These
changes vary for different solvents.
For the K1 dye solution in toluene, the changes of
spectra consists of reduction in the radiation intensity.
The analysis of some spectra of the same solution, which
have been registrated under constant conditions but after
their UV irradiation for 15 min, shows that observed is
not only increase in the peak intensity of the band, but
also the change of the spectrum shape: the radiation
intensity at the shortwave edge of the band increases. All
these spectra cross in the one – isobestic – point at
λ = 440 nm. In alcohol solution of K1 dye, the
phototransformations do not occur.
x
y
z
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 73-78.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
75
400 500 600 700
0,0
0,2
0,4
0,6
0,8
1,0
3
4
5 21
I ,
a
. u
.
λ , nm
Fig. 3. K2 luminescent spectra in toluene and alcohol before
(1, 2) and after (3, 4) irradiation as well as in glycerine before
irradiation (5). K2 concentration in toluene and alcohol equals
2⋅10–4 mol/l.
To obtain the additional data on the nature of
phototransformations of K1 dye, the researches of its
spectral changes in the course of irradiation were carried
out in the binary solvent. For this aim, before
measurement into the toluene solution of K1 dye (С =
2⋅10−4 mol/l) a small amount (less than 10−4 wt.%) of
alcohol was added. In the spectrum of unirradiated
solution, observed are two overlapped bands with the
peak position close to those in initial solvents: the more
intensive shortwave – toluene – band with the peak at
λ = 467 nm and longwave – alcohol – one with that at
λ = 544 nm (Fig. 4, curve 1). On irradiation, the intensity
of the first, toluene, band increases and that of the
second, alcohol, decreases. The isobestic point is located
at 493 nm.
400 500 600 700 800
0.0
0.2
0.4
0.6
0.8
1.0
2
1
3
I,
a.
u
.
λ, nm
Fig. 4. Luminescent spectra of K2 solution in toluene (C =
= 2.0⋅10−4 mol/l) with a small amount (10−4 wt.%) of alcohol:
1 – initial condition; 2 and 3 – sequential changes of spectra in
the course of UV irradiation.
The K2 dye is photostable in both alcohol and toluene
solutions. For the K2 dye, the most essential changes
occur under UV irradiation of its solution in glycerine
(Fig. 5). In glycerine, on irradiation the longwave
photoluminescent band with a peak λ = 570 nm first
decreases in its intensity, and on prolonged irradiation it
absolutely disappears, and instead of the band only the
widely extended longwave edge of an asymmetric
shortwave band remains. The shortwave band with λ =
= 489 nm first increases in its intensity and PLS of
irradiated glycerine solutions have an isobestic point at
510 nm. A rather photostable solution forms, the PL
band of which remains almost constant in its intensity
with a highly asymmetric longwave wing. But after
prolonged irradiation, the band also begins to decrease in
the intensity, shifts hypsochromically by 20 nm, and a
new band with λ = 435 nm arises at its shortwave edge.
4. The analysis of experimental data
In the work [5], to analyze spectra of aromatic molecules
with a pronounced oscillation structure, the harmonic
oscillation model in the Frank-Condon approximation
was used in accord with the following expression:
!
00 n
z
I
I n
nn
ν
ν
= . (1)
Here, I0 is the intensity of a band with frequency ν0, In is
the intensity of n-th peak with the frequency
νn = ν0 + nνk , (2)
where νk is the frequency of fully symmetrical oscillation
that dominates in the energy spectrum. The parameter z
is equal to the ratio of the potential energy of molecule
elastic deformation on its excitation to energy of fully
symmetrical oscillation
400 500 600 700
0.0
0.2
0.4
0.6
0.8
1.0
4
3
21I,
a.
u.
λ, nm
Fig. 5. Luminescent spectra of K2 solution in glycerine: 1 –
initial condition; 2-4 – sequential changes of spectra in the
course of UV irradiation.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 73-78.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
76
khc
Qk
z
ν2
)( 2Δ
= , (3)
where k is a force constant of bonds that form a
molecular skeleton, ΔQ is the shift of the molecule
configuration coordinate on its excitation, h is Planck’s
constant, c is the velocity of light in vacuum.
In works [6, 7], it was offered to use Eqs (1) and (2)
also for analysis of continuous wide bands without a
pronounced oscillation structure. In this method, the
number of the oscillating quantum is determined as
follows
12
1
kk
k
n
−
= , (4)
where
1
1
1
+
+=
nn
nn
I
I
k
ν
ν
, (5)
nn
nn
I
I
k
ν
ν
1
1
2
−
−= . (6)
The values k1 and k2 are determined experimentally.
For this purpose, the values νn and νk are chosen in an
arbitrary way. In the spectrum of absorption (or
luminescence), measured are the intensities In-1, In, In+1
for three frequencies νn-1, νn, νn+1 and defined are k1 and
k2. Then, from Eq. (4) the value of n is determined. By
the known values of n and νn from Eq. (2) the frequency
of 0−0 transition (ν0) is defined.
Our estimations showed that the absorption band
contour of K1 and K2 dyes solutions in toluene (С =
= 2⋅10−5 mol/l) (Fig. 6) can be approximated with a
small error by formulas [5-7] with the frequency νk =
= 1110 cm−1 corresponding to the valent oscillation one
for groups ≡−≡ CC or OCC ==〉 (ketone radical)
[8]. The frequencies of peaks of these bands were
determined from Eq. (2). From Eq. (4), it was found that
n = 2. Hence, it follows that the bands are caused by
interaction of purely electron excited state with the
second oscillator excitation. Thus, with k = 750 N/m (the
force constant for carbon bonds of anthracene molecules
[6]), it yields that the derived from Eq. (3) parameter
ΔQ = 1.2⋅10−11 m.
The contour of luminescent bands well coordinates
with that following from the theory at νk =1000 cm−1.
The average value of frequency (wavenumber) of fully
symmetrical skeleton oscillation of K1 and K2 molecules
equals 1050 cm−1. Besides, one can assert that the
system of oscillator levels for the basic and first excited
electron states of the K1 and K2 molecules is the same. In
case of the harmonic approximation, these levels are
equidistant. The potential energy minimum of the first
excited state of molecules is displaced relatively to the
basic state one by 1.2⋅10−11 m.
Fig. 6 shows the spectra of absorption (ε/εmaxν = f(ν))
and photoluminescence ((I / Imaxν4 = f(ν)) of K1 and K2
dye solutions in toluene when С = 2⋅10−5 mol/l, which
were normalized to the maximal value. Here, ε and I are
the values of molar extinction and PL intensity, ε and
Imax are their maximal values, ν is the wavenumber
expressed in cm−1. Their analysis has shown that obeyed
are the Stokes-Lommel law (νexc > νLom) and mirror
symmetry rule for the absorption and luminescent
spectra. In this case, the frequencies of purely electron
transitions in K1 and K2 (ν0) were determined using the
vertical lines that pass through the crossing points of
absorption and luminescent spectra. We obtained the
following values of ν0: 22645 cm−1 (442 nm) for K1 and
22968 cm−1 (432 nm) for K2.
The nature of molecule electron bands can be
ascertained from a comparison of the spectra to the
results of quantum-mechanical calculations and
association of a band with the certain pair of molecular
orbitals. As the calculations for the K1 and K2 molecules
are unknown, their electron bands can be identified with
those of functional groups to a first approximation.
In the K1 and K2 molecules, one can find the
following conjugate chromophores: carbonyl ( OC =〉 )
and ethylene ( −=− CC ) groups, dimethylaniline
fragment, furan and benzene rings. Methoxygroup
( −CHO ) and methyl ( −3CH ) are auxochromes. They
change the intensity and characteristic band position of
chromophore, into composition of which these groups do
not enter.
Characteristic absorption bands of the
abovementioned chromophores are summerized in the
work [9]. Ethylene group, furan and benzene rings
absorb in the UV region. Carbonyl group is a constituent
of formaldehyde. It is characteristic for this group that
there are the intensive band at 155.5 nm (π→π∗-
transition polarized along the bond OC = , ε = 104) and
the weak band caused by n→π∗-transition, at 310 nm
Fig. 6. Normalized to maximal value spectra of absorption
(1, 2) and luminescence (3, 4) of K1 and K2 dyes.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 73-78.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
77
(ε = 10 l⋅mol−1⋅cm−1) in its spectrum. Conjugation of the
carbonyl and ethylene groups in α- and β-unsaturated
ketones causes significant bathochromical ππ∗-bands in
the spectral region of 220-280 nm without changing their
intensity.
The absorption spectrum of a nitrodimethylani-
line molecule consists of two bands with the peaks at
395 nm (ε = 2·104 l⋅mol−1⋅cm−1) and 229 nm (ε =
= 104 l⋅mol−1⋅cm−1). By the intensity magnitudes, these
two bands may be considered as stemming from the
π→π∗-transitions. The former band is caused by
excitation of the overall π-system of the molecule, and
the latter is localized on the benzene ring.
The absorption spectrum of a benzylacetate phenone
molecule that is the K2 one without methoxy- and
dimethylamino-groups is characterized by a wide
longwave band at 370 nm (ε = 200 l⋅mol−1⋅cm−1). This
band passes into continuum (continuous absorption) for
the wavelength λ < 300 nm (ε = 104 l⋅mol−1⋅cm−1) [9]. By
its intensity value, the first band can be considered as a
π→π∗-transition, and continuum – as an excitation of π-
system of the overall molecule (λ = 300 nm) and, in
particular, benzene rings (λ < 300 nm).
Intensities of absorption bands of K1 and K2
molecules (Fig. 2, curves 1-4) in the ranges of 390-420
and 280-320 nm equal 5·104 and 1.2·104 l⋅mol−1⋅cm−1,
respectively, i.e. these are π→π∗-transitions. Taking the
above analysis into account, it is possible to assume that
the former band is caused by excitation of π-system of
K1 and K2 molecules. π-systems are formed owing to
conjugation of the carbonyl, ethylene, and dimethyl-
aniline groups. The second (shortwave) excitation is
localized at the carbonyl and ethylene groups.
Distinction in the peak positions of longwave
absorption bands of K1 and K2 solutions can be
explained by different auxochrome influence of radicals
of methylfuran (K1) and methoxybenzene (K2) on the π-
systems of dye molecules.
The longwave absorption bands of the alcohol K1
and K2 solutions are shifted bathochromically by 0.15
and 0.36 eV, respectively, relatively to their positions in
toluene solutions. It testifies to formation of associates
between the alcohol molecules and dye ones owing to
formation of hydrogen bonds between the hydroxyl and
carbonyl groups. The hypsochrome shift of the peak of
the longwave K2 absorption band and reduction of its
intensity with one order increase in the dye
concentration in alcohol solution testify to aggregation
of the dye molecules. As the changes in absorption
spectra occur simultaneously by I and II types [10], the
question of the structure of these aggregates remains
open.
PLS of K1 dyes (Fig. 4, curve 1) are caused by the
dye monomer radiation (470 nm) and its alcohol
associates (the band of 540 nm). The associate
concentration is small and aggregation of dye molecules
is absent. Decrease in the intensity of the band at 540 nm
on irradiation suggests that the associates destruct with
formation of free K1 monomers (increase in intensity of
the band at 470 nm). In so doing, the total concentration
of associated and quasi-free dye molecules is constant,
as demonstrated by the availability of the isobestic point.
Juxtaposition of the PLS structure for K2 dye solution
in glycerine to those in the other solvents, the account of
absorption spectra as well as the analysis of PLS
changes after UV irradiation of solutions allow to
suggest that, in glycerine solution, both free K2 dye
molecules and aggregated ones contribute to the PLS.
5. Conclusions
1. It was determined that, in the spectral region of 280
to 600 nm, the electron bands of the studied K1 and
K2 dyes in series of isotropic solvents are ππ∗-states.
In so doing, the longwave absorption band is caused
by excitation of the whole π-system and the
shortwave one – by the carbonyl and ethylene groups
of dye molecules. The frequencies of purely electron
transitions are equal to 22645 cm−1 (K1) and
22968 cm−1 (K2). The system of oscillation levels of
the basic and first excited states of dyes is identical,
and, in harmonic approximation, it is determined by
the frequency of intramolecular oscillation νk =
= 1055 cm−1.
2. The solutions of K1 and K2 dyes possess
photoluminescence, spectra of which depend on both
nature of solvent (formation of the associates with
solvent owing to hydrogen bonds between the dye
and alcohol or the aggregates of dye molecules), and
on the dye concentration (concentration decay).
3. It was found that photostability of dyes depends on
the solvent nature and availability of impurities, with
which the dye molecules can form associates.
Work was executed at financial support of the
budgetary theme 1.4.1 В/109 of Institute of Physics,
NAS of Ukraine.
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