Langmuir-blodgett films of hydroxamic acid of the quinoxalinone series

Article abstract of DOI:10.1134/S0036024409040232

Amphiphilic hydroxamic acid 2-(4-decyloxyphenyl)-4-hydroxy-3-oxo-3,4- dihydroquinoxalin-1-oxide was synthesized. The conditions of the formation of hydroxamic acid and its lead, europium, cadmium, and copper salt monomolecular layers were studied. Multimo

Full text of DOI:10.1134/S0036024409040232

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2009, Vol. 83, No. 4, pp. 654–659. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © T.A. Duda, L.L. Sveshnikova, V.K. Khlestkin, K.A. Dembo, L.G. Yanusova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 4, pp. 758–764.
PHYSICAL CHEMISTRY
OF SURFACE PHENOMENA
Langmuir–Blodgett Films of Hydroxamic Acid
of the Quinoxalinone Series
T. A. Dudaa, L. L. Sveshnikovaa, V. K. Khlestkinb, K. A. Demboc, and L. G. Yanusovac
a Institute of Semiconductor Physics, Siberian Division, Russian Academy of Sciences,
pr. akademika Lavrent’eva 13, Novosibirsk, 630090 Russia
b Vorozhtsov Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
c Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 117333 Russia
e-mail: svesh@thermo.isp.nsc.ru
Received December 3, 2007
Abstract—Amphiphilic hydroxamic acid 2-(4-decyloxyphenyl)-4-hydroxy-3-oxo-3,4-dihydroquinoxalin-1-
oxide was synthesized. The conditions of the formation of hydroxamic acid and its lead, europium, cadmium,
and copper salt monomolecular layers were studied. Multimolecular systems were prepared by the Langmuir–
Blodgett method from various solvents, including chloroform, carbon tetrachloride, and toluene. The films were
characterized by small angle X-ray scattering, UV and IR spectroscopy, ellipsometry, and atomic-force micros-
copy. The UV data and monolayer compression isotherms showed changes in the state of hydroxamic acid in
various solvents in the presence of light and in the dark. The suggestion was made that changes in solutions
were related to aggregation phenomenon.
DOI: 10.1134/S0036024409040232
INTRODUCTION
Langmuir–Blodgett method, and their optical proper-
ties, structure, and surface morphology were studied.
Hydroxamic acids are organic nitrogen-containing
compounds of the general formula R–CONHOH. They
contain the N-hydroxyamine fragment –CO–N(OH)–
and exhibit weak acid properties with Ka between 8
and 11 [1]. Thanks to this fragment, hydroxamic acids,
like carboxylic acids, can form hydrogen bonds.
EXPERIMENTAL
2-(4-Decyloxyphenyl)-4-hydroxy-3-oxo-3,4-dihy-
droquinoxalin-1-oxide (1) was prepared by the conden-
sation of Ó-quinonedioxime with 4-decyloxyphenylg-
Hydroxamic acids have been extensively studied
because of their reactivity, simplicity of preparation, lyoxal following a procedure similar to that described
and several interesting properties. Some of them are in [13]. Ó-Quinonedioxime (5.54 g, 0.04 mol) was added
effective drugs (including antibiotics), plant growth
regulators, and enzyme reactivators and inhibitors [2–
4]. There are substances with pesticide activity contain-
ing a hydroxamic fragment [5]. One of the most impor-
tant properties of hydroxamic acids is the formation of
strong chelate complexes with transition metal ions
often accompanied by color changes, which finds use in
analytic chemistry [6–8].
to a solution of 4-decyloxyphenylglyoxal (12.21 g,
0.4 mol) in EtOH (100 ml). The mixture was refluxed
for 30 min, cooled, and held at –5°ë for a night. The
precipitate was filtered and washed with cold EtOH to
obtain hydroxamic acid 1 (6.58 g, 40%). The reaction
was monitored by thin-layer chromatography on a Silu-
fol UV-254 plate with hexane : EtOAc (from 5 : 2) as
an eluent. Detection was performed in UV light. The
solvents were preliminarily distilled. Commercial
reagents were used without additional purification.
There are several works on the preparation of Lang-
muir–Blodgett films of hydroxamic acids. For instance,
the preparation of Langmuir–Blodgett films was
described for iron and copper salts of octadecane
hydroxamic acid [9]. The formation of self-organized
hydroxamic acid layers on the surface of metals for pre-
venting their corrosion was also reported [10–12].
The melting point of compound 1 was measured on
a Bofitius-type heating block (Kofler stage), it was
127°ë (from EtOH). The NMR spectrum was recorded
on a Bruker AM-400 instrument (400.13 MHz) in
CDCl3. The signal of the solvent was used as an internal
reference. 1ç NMR spectrum (CDCl3; δ, ppm; J, Hz):
0.87 (t, J = 5.7, CH3), 1.27 (m, 12H, CH2), 1.45 (m, 2H,
OCH2CH2CH2), 1.78 (d, 2H, OCH2CH2), 3.99 (t, J =
This work is concerned with the behavior of
amphiphilic hydroxamic acid 2-(4-decyloxyphenyl)-4-
hydroxy-3-oxo-3,4-dihydroquinoxalin-1-oxide (1) and
its salts in thin layers and solutions. Multilayers of 6.0, 2H, OCH2), 6.96 (d, J = 8.4, 2H, CHarom), 7.43 (t,
hydroxamic acid 1 and its salts were produced by the J = 8.3, 1H, CHarom), 7.71 (t, J = 8.3, 1H, CHarom),
654

LANGMUIR–BLODGETT FILMS OF HYDROXAMIC ACID OF THE QUINOXALINONE SERIES
655
7.81 (d, J = 8.3, 1H, CHarom), 7.91 (d, J = 8.4, 2H,
CHarom), and 8.48 (d, J = 8.3, 1H, CHarom).
The formula of the compound and signal assign-
ments are given below:
π, mN/m
60
1
2
8
3
1.78m
0.87t
40
7.91d
7
O
N
O
5
6.96d
3.99t 1.45m
8.48d
1.27m
7.71t
7.43t
6
7.91d
6.96d
20
4
N
O
7.81d
(1)
OH
The IR spectrum was recorded on a Bruker Vektor
22 spectrometer (pellets with KBr, concentration
0.25%, l = 1 mm). The IR bands of the main character-
istic vibrations were (ν, cm–1) 3440, 2482 (OHbroad),
1683 (C=O), and 1600 (C=N). The high-resolution
mass spectrum was obtained on a Finnigan MAT 8200
spectrometer. Mass spectrum (m/z): 410.2200 (found),
410.2180 (calculated for C24H30N2O3–M+).
Hydroxamic acid 1 and its cadmium, europium,
lead, and copper salt films were prepared by the Lang-
muir–Blodgett method. For the formation of monolay-
ers, substances (3 × 10–4 M) were dissolved in chloro-
form, carbon tetrachloride, or toluene and spread on the
surface of deionized water filtered through 0.2 µm
membranes. The Y-type transfer of a monolayer onto
solid substrates was performed at a constant surface
pressure π = 19 mN/m and temperature 20°ë. Silicon
and quartz plates were used as substrates. Silicon plates
were preliminarily degreased in toluene and refluxed in
a 1 : 100 HCl–H2O2 solution. To remove natural silicon
oxide, the plates were treated with concentrated hydrof-
luoric acid. Additional quartz plate surface hydrophobi-
zation was performed by holding the plates in hexame-
thylsilazane for 10–15 min.
0
0
20
40
60
σ, Å2/molecule
Fig. 1. Compression isotherms of hydroxamic acid 1 mono-
layers on (1–6) water and (7, 8) a solution of CdCl ; solu-
tions of acid 1 in (1–4, 7, 8) chloroform and (5, 6) toluene;
(1, 5, 7) freshly prepared solutions, (2, 6, 8) solutions held
in the dark, (3) solution held in the light, and (4) solution
after evaporation in the light.
2
tra were obtained over the wavelength range 200–
1200 nm.
The structure of films was studied by small-angle
X-ray scattering in reflection from the surface of films
on anAMUR-K small-angle diffractometer with a posi-
tion-sensitive detector (a BSV-22 X-ray tube with a
copper anode and a nickel filter, voltage on the tube
30 kV); the angular resolution of the detector was
0.02°. The morphology of Langmuir–Blodgett films
was studied using a SOCVER-PRO NT MDT scanning
probe microscope under semicontact conditions.
To study the behavior of hydroxamic acid 1 mono-
layers, solutions in chloroform, toluene, and CCl4 were
prepared. Each solution was divided into three parts.
One part was irradiated by daylight, another was held in
the dark for two months, and the third one was a fresh
solution. The isotherms were recorded on the surface of
water and solutions of Pb(NO3)2, Eu(NO3)3, CuAc2,
and CdCl2 salts.
The optical characteristics of films were measured
on an LEF-3M ellipsometer with a working laser wave-
length of 632.8 nm at beam incidence angles of 60°,
65°, and 70°. The parameters of films (d, thickness, and
n, refractive index) were determined by solving the
inverse multiangle ellipsometry problem using the
model of a monolayer film on an isotropic silicon sub-
strate.
The IR spectra of Langmuir–Blodgett hydroxamic
acid and salt films were recorded on a Bruker IFS-113 v
spectrometer over the frequency range 400–5000 cm–1
with a resolution of 2 cm–1. Solutions of hydroxamic
acid (10–4 M) in ethanol, chloroform, and carbon tetra-
RESULTS AND DISCUSSION
The compression isotherms of hydroxamic acid 1
chloride were prepared to study absorption spectra over monolayers on the surface of water and a solution of
the UV and visible ranges. For each specimen, the spec- CdCl2 are shown in Fig. 1. The collapse pressure of the
tra of a fresh solution and solution irradiated with a monolayer deposited from freshly prepared solutions
60 W tungsten lamp from a distance of 20 cm during 1, was ~50–55 mN/m; the area per molecule was then
3, and 5 h after preparation were recorded. The absorp- ≈32 Å2 (curves 1, 7). After holding solutions in the
tion spectra of solutions of hydroxamic acid were dark, compression isotherms shifted toward larger
recorded on an HP Agillent 8453 spectrometer, and the areas per molecule, to about 50–55 Å2 (curves 2, 8).
absorption spectra of films of hydroxamic acid and its The compression isotherm of a monolayer deposited
salts, on a Shimatzu spectrometer. The absorption spec- from a freshly prepared solution of hydroxamic acid 1
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 83 No. 4 2009

656
DUDA et al.
An analysis of the compression isotherms of
D
Ä
hydroxamic acid 1 monolayers showed that isotherms
of monolayers deposited from freshly prepared solu-
tions corresponded to the condensed state of monolay-
ers on the interphase boundary. Solutions stored in the
dark and held in the light were characterized by an
increase in the area per molecule in a monolayer by
~2 times and a decrease in the collapse pressure.
Curves 2 and 6 correspond to monolayer transition into
the liquid-stretched state. Curve 4 does not correspond
to either the condensed or liquid-stretched state. In
addition, hydroxamic acid 1 monolayers on the surface
of solutions of Pb(NO3)2, Eu(NO3)3, CuAc2, and CdCl2
are more stable (curve 8) than on the surface of water
(curve 2). All these changes in the behavior of hydrox-
amic acid 1 monolayers after holding solutions in the
dark or in the light were accompanied by the end of
substance transfer onto solid substrates.
The UV and visible absorption spectra of a freshly
prepared solution of hydroxamic acid 1 (10–4 mol/l) in
chloroform after irradiation with the tungsten lamp for
1 and 3 h are shown in Fig. 2. The absorption spectrum
of hydroxamic acid 1 is characterized by two main
high-intensity peaks, Ä (240–245 nm) and B (390 nm).
The irradiation of solutions with the tungsten lamp
decreases the intensity of peaks A and B and causes the
appearance of a peak at 300 nm. For comparison, we
also recorded the absorption spectra of hydroxamic
acid dissolved in ethanol and ëël4. The main spectral
features coincided with those of the spectrum shown in
Fig. 2. Photochemical changes in solution occur during
3–5 h irrespective of the nature of the solvent.A scheme
of photo- and thermochemical hydroxamic acid trans-
formations is given below:
1.5
0.5
B
1
2
3
200
300
400
500
600
λ, nm
Fig. 2. Absorption spectra of solutions of hydroxamic acid
1 in chloroform: (1) freshly prepared solution and (2, 3)
solution irradiated by a tungsten lamp for (2) 1 and (3) 3 h.
D
1
2
2.0
Ä
3
B
1.0
0
4
O
N
–1.0
R
200
300
400
500
600
λ, nm
N
O
O
N
OH
hν
T
(2)
Fig. 3. Absorption spectra of Langmuir–Blodgett films of
(1–3) hydroxamic acid 1 and (4) its Cd salt prepared from
R
O
(1, 2) chloroform, (3) CCl ; (2) films after holding in the
O
N
4
light.
N
R
OH
(1)
in toluene was characterized by a collapse pressure of
~40 mN/m and an area per molecule of ~32 Å2.
N
OH
The shape of the compression isotherms of mono-
layers changes substantially after holding solutions in
the light. The collapse pressure then decreases, and the
area per molecule increases to 55 Å2 (curve 3). To
O
R = C6H4OC10H21
(3)
Attempts at the preparation of the product of the pho-
obtain isotherm 4, hydroxamic acid 1 was dissolved in tochemical transformation of compound 1 caused by
chloroform, the solvent was evaporated (evaporation tungsten lamp irradiation at a concentration of 10–2 mol/l
took 5–6 h in the light), and the acid was again dis- were unsuccessful. After irradiation for 25 h, a large
solved in chloroform. The compression isotherms of fraction of initial compound 1 (>90%) was isolated,
hydroxamic acid monolayers on the surface of solu- which was likely related to the large optical density of
tions of Pb(NO3)2, Eu(NO3)3, and CuAc2 were similar to the substance. The formation of a colored product was
the isotherm for a solution of CdCl2 (curves 7, 8).
only established by thin-layer chromatography. We
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 83 No. 4 2009

LANGMUIR–BLODGETT FILMS OF HYDROXAMIC ACID OF THE QUINOXALINONE SERIES
657
logI [arb. units]
1
0
–1
0.2
0.4
0.6
0.8
1.0
q, Å–1
Fig. 4. X-ray scattering by a Langmuir-Blodgett film of the Cd salt of hydroxamic acid 1; q = 4πsinθ/λ.
were also able to record its proton NMR spectrum. The molecular H-bond depending on the conditions. The
photochemical formation of oxaziridine 2, a product of simultaneous existence of associates of various types in
photochemical reactions typical of nitrones, should in solution is also possible; their relative concentrations
all probability be ruled out, because the product does can change depending on the temperature [1].
not cause the oxidation of KI characteristic of oxaziri-
The absorption spectra of Langmuir–Blodgett films
dine. In addition, the transformation observed was ther-
of hydroxamic acid 1 prepared from different solvents
mally irreversible. The proton NMR spectrum of the
are shown in Fig. 3. The spectra of all films are identical
product, as that of initial compound 1, contained a dou-
and contain peaks Ä at 243 nm with a poorly defined
blet signal of the quinoxaline ring proton adjacent to the
shoulder at 263 nm and split peaks B with a series of
nitrone group at 8.36 ppm, which was evidence that the
bands at 370, 390, and 410 nm. The UV spectra of
nitrone group remained intact in the reaction.
Langmuir–Blodgett films of hydroxamic acid salts also
Possibly, photochemical activation contributes to
the isomerization of the hydroxame into hydroxyni-
trone group (the transformation of 1 into 3), and com-
pound 3 is more apt to form stable dimers on the surface
of water. The end of transfer of monolayers onto solid
substrates can most likely be explained by the photo-
chemical isomerization of hydroxamic acid 1 resulting
in aggregation. The doubling of the area per structural
unit and a decrease in the collapse pressure can also be
explained by the formation of H-bonded aggregates
(supposedly, dimers), which is likely accompanied by
changes in the spatial positions of hydroxamic acid
molecules.
contain two main peaks A and B, but there is no equally
pronounced splitting of peak B (390 nm). It, however,
contains a shoulder at 410 nm.
The absorption spectra of hydroxamic acid films
obtained after daylight irradiation are indistinguishable
from the spectra shown in Fig. 3. It follows that changes
in the state of hydroxamic acid under the action of light
occur only in solutions and are not observed in films.
The thickness of a monolayer in Langmuir–
Blodgett hydroxamic acid films determined by ellip-
Layer periods of hydroxamic acid and its Cu, Cd, Eu, and Pb
salt films measured by X-ray diffraction (dX) and ellipsome-
try (de)
The IR spectra of hydroxamic acids were analyzed
in [14]. It was found that the vibrational frequencies of
the characteristic hydroxamic acid groups increased in
the passage from the solid state to solutions. These fre-
quencies, however, did not reach the values characteris-
tic of free carbonyl groups. This allowed the suggestion
to be made of the existence of an intramolecular
H-bond in hydroxamic acid molecules in solution,
because the vibrational frequencies of the carbonyl and
OH groups did not change as the concentration and
temperature were varied. It is assumed that the intramo-
lecular H-bond can be replaced with a stronger inter-
Acid salt 1 q1, Å–1
dX, Å
de, Å
r, Å
Cu
0.169
0.163
0.159
0.158
0.1555
37.2
39.0
39.6
39.8
40.5
33
0.96
1.03
1.17
1.32
–
Cd
40
Eu
40
Pb
39
Acid
39.5
Note: q is the first Bragg reflection, and r is the metal ionic radius.
1
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 83 No. 4 2009

658
DUDA et al.
sometry is ~20 Å, and the refractive index is n = 1.62.
(‡)
(b)
(c)
Since the length of the hydrocarbon chain in the
hydroxamic acid molecule is ~12–13 Å, and the “head”
part of the molecule has a size of ~7 Å, the conclusion
can be drawn that the hydrocarbon chain in the mono-
layer is oriented vertically with respect to the substrate.
The thickness of the monolayer in films of hydroxamic
acid salts is also ~20 Å, except the copper salt, for
which this parameter is smaller (~17 Å). The orienta-
tion of hydrocarbon chains in copper salt films can
deviate from vertical orientation with respect to the
substrate.
5
4
3
2
1
0
nm
50
40
30
20
10
0
Differences in the behavior of copper salt films are
also seen in their IR spectra. The IR spectra of Cd, Pb,
and Eu hydroxamic acid salt films contain absorption
bands at 1500–1600 cm–1 corresponding to vibrations
of acid groups bound with metals. Their frequencies are
close to those observed for carboxylic acids. In the
spectrum of the Cu salt, the hydroxamate ion absorp-
tion band is observed at 1525 cm–1. In the spectra of
carboxylic acids, the band at 1590 cm–1 corresponds to
this group. Such a shift of the absorption maximum can
likely be explained by the formation of a chelate biden-
tate five-membered complex in the interaction of
hydroxamic acid with copper. This complex is more
stable than the four-membered complex with the car-
boxylic acid [8, 12]. Like carboxylic acids, Cd, Pb, and
Eu salts of hydroxamic acid form four-membered
bidentate or monodentate complexes. The IR spectra of
hydroxamic acid and its salts contain absorption bands
at 1610–1620 and 1720–1730 cm–1. These bands corre-
spond to C=N and C=O characteristic vibrations of
hydroxamic acid molecules [15].
1
2
3
4
5
nm
30
5
4
3
2
1
20
10
14.65
10
5
X-ray scattering by the surface of Langmuir–
Blodgett films of hydroxamic acid 1 salts contains well-
defined Bragg first-order reflections, only slightly (by
1–3 Å) different from the period of hydroxamic acid
layer packing (Fig. 4). The presence of Kissig oscilla-
tions in the region of intensity decrease in front of the
first Bragg reflection shows that the surface of the film
is fairly smooth; this can be used for estimating the total
thickness of films. At the same time, intralayer packing
is poorly seen. Only the curve for the Cd salt film con-
tains four orders of Bragg reflections, which is evidence
of a good layer packing in this film and the stability of
the layer period over the whole film thickness (Fig. 4).
For the other films, Bragg reflections higher than first
order are almost indiscernible or disappear at all. Such
a picture is more characteristic of packing of liquid
crystals, when there is short-range order in the packing
of molecules, but separate layers correlate poorly.
0
1
2
3
4
5
nm
25
4
20
3
2
1
0
15
12.28
10
5
The scattering intensity curves obtained for hydrox-
amic acid films were used to calculate the periods of
layer packing of the corresponding films (table). Note
that the layer period of pure acid was found to be even
slightly larger than salt periods, although metal atom
sizes are of 2.5–3.5 Å. Possibly, metals stoichiometri-
cally occupy positions that do not increase the length of
0
1
2
3
4
5
µm
Fig. 5. Atomic-force microscopic image of Langmuir–
Blodgett hydroxamic acid 1 films; (a) hydroxamic acid,
(b) its Cd salt, and (c) its Cu salt.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 83 No. 4 2009

LANGMUIR–BLODGETT FILMS OF HYDROXAMIC ACID OF THE QUINOXALINONE SERIES
659
molecules and even slightly shorten them. However
Salt molecules in films are oriented normally to sub-
note that the layer period very insignificantly increases strates. The presence of well-defined long-range order
as the ionic radii of metals in the films grow. The data in layer packing is only characteristic of cadmium salt
on monolayer thickness of hydroxamic acid and salt films. In addition, Cd probably improves the parallel
films obtained using ellipsometry well correlate with orientation of molecules in layers.
the X-ray small-angle scattering data.
To summarize, salt molecules in films are oriented
normally to the substrate. Distinct long-range layer
ACKNOWLEDGMENTS
The authors thank N.G. Semerikov for the atomic-
force microscopic measurements. This work was finan-
cially supported by the Siberian Division of the Russian
Academy of Sciences, integration project no. 50.
packing ordering is only observed for cadmium salt
films. The suggestion can also be made that Cd and Eu
improve parallel orientation of molecules in a layer (the
Bragg reflection is narrower for these salts than for the
initial acid), whereas only the first reflection is
observed for Cu and Pb salts, and even this reflection is
broadened compared with the initial acid film.
REFERENCES
1. G. I. Zhungietu and A. I. Artemenko, in Hydroxamic
Acids (N-Hydroxyamides) and Their Derivatives (ShTI-
INTsA, Chisinau, 1986), p. 139 [in Russian].
The photographs obtained using the atomic-force
microscope are shown in Fig. 5. The structures of the
surfaces of hydroxamic acid prepared from various sol-
vents are identical (Fig. 5a). The structures of the sur-
face of Cd and Eu salt films of hydroxamic acid 1 have
similar features and differ from the surface structures of
Cu and Pb salt films (Figs. 5b, 5c). The similarity of the
surfaces of Cd and Eu salt films is evidence in favor of
the suggestion that Cd and Eu likely improve the paral-
lel orientation of molecules in layers.
2. R. Jain, D. Chen, R. J. White, et al., Curr. Med. Chem.
12, 1607 (2005).
3. G. Kouraklis and S. Theocharis, Oncol. Rep. 15, 489
(2006).
4. Q. Li, M. F. Da Silva, and A. J. L. Pombeiro, Chemistry
10, 1456 (2004).
5. F. Mathis, Bull Soc. Chim. Fr., No. 5, 9D (1953).
6. A. T. Pilipenko and O. S. Zul’figarov, in Hydroxamic
Acids (Nauka, Moscow, 1989) [in Russian].
7. T. Surova and T. Ikanina, Abstracts of Papers, Interna-
tional Congress on Analytical Chemistry (Moscow,
1997), p. 33.
CONCLUSIONS
We found that hydroxamic acid 1 and its salts,
which possess the common property of amphiphilic
substances, form stable monolayers at the water–air
interphase boundary and can therefore be transferred
onto solid substrates by the Langmuir–Blodgett
method. This transfer can only be performed from
freshly prepared solutions of hydroxamic acid. Pro-
longed storage and the action of light cause changes in
solution that prevent the transfer of the substance onto
substrates. In all probability, these changes are related
to aggregation phenomena in solution. Aggregation
occurs as a result of the formation of intermolecular
bonds between hydroxamic acid molecules. Photo-
8. M. Birus, M. Gabricevric, O. Kronja, et al., Inorg. Chem.
38, 4064 (1999).
9. T. Keszthelyi, Z. Paszti, and T. Rigo, J. Phys. Chem. B
110, 8701 (2006).
10. A. Shaban, E. Kalman, and J. Telegdi, Electrochim. Acta
43, 159 (1998).
11. T. Rigo, A. Miko, J. Telegdi, et al., Electrochem. Solid-
State Lett. 8, 51 (2005).
12. J. P. Folkers, C. B. Gorman, P. E. Laibinus, et al., Lang-
muir 11, 813 (1995).
chemical activation can promote the isomerization of 13. V. K. Khlestkin and D. G. Mazhukin, Abstracts of
Papers, Organic Chemistry School of Young Scientists
the hydroxame into hydroxynitrone group. It is proba-
ble that the resulting compound is more apt to form sta-
ble dimers. The irreversibility of changes in solution is
evidence in favor of this suggestion. Changes in the
state of hydroxamic acid under the action of light occur
only in solution and are not observed in films.
(Yekaterinburg, 2000), p. 229.
14. D. Haczi and D. Prevorsek, Spectrochim. Acta 10, 38
(1957).
15. J. Yang, P. J. Bremer, I. L. Lamont, et al., Langmuir 22,
10109 (2006).
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 83 No. 4 2009