Electrochemical synthesis of the calix[4]resorcinol nickel complexes modified with thiophosphoryl fragments

Article abstract of DOI:10.1134/S1070363213040099

Nickel complexes of 1:1 composition with calix[4]resorcinols (L) modified with thiophosphyl fragments were synthesized. In the process of electrochemical reduction these complexes are capable of providing spherical homogeneous Ni(0)L particles with a narrow size distribution, stable both on the electrode and in the solution. The redox properties of the metal complexes were studied. The dimensions of the complexes obtained were estimated using the atomic force microscope (AFM) equipped with an electrochemical attachment.

Full text of DOI:10.1134/S1070363213040099

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 4, pp. 663–669. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.V. Khrizanforova, I.R. Knyazeva, I.R. Nizamiev, T.V. Gryaznova, V.I. Sokolova, S.A. Krasnov, M.K. Kadirov, A.R. Burilov,
Yu.G. Budnikova, O.G. Sinyashin, 2013, published in Zhurnal Obshchei Khimii, 2013, Vol. 83, No. 4, pp. 575–581.
Electrochemical Synthesis of the Calix[4]resorcinol Nickel
Complexes Modified with Thiophosphoryl Fragments
V. V. Khrizanforova, I. R. Knyazeva, I. R. Nizamiev, T. V. Gryaznova, V. I. Sokolova,
S. A. Krasnov, M. K. Kadirov, A. R. Burilov, Yu. G. Budnikova, and O. G. Sinyashin
Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of Russian Academy of Sciences,
ul. Arbuzova 8, Kazan, Tatarstan, 420088 Russia
e-mail: yulia@iopc.ru
Received March 27, 2012
Abstract―Nickel complexes of 1:1 composition with calix[4]resorcinols (L) modified with thiophosphyl
fragments were synthesized. In the process of electrochemical reduction these complexes are capable of
providing spherical homogeneous Ni(0)L particles with a narrow size distribution, stable both on the electrode
and in the solution. The redox properties of the metal complexes were studied. The dimensions of the
complexes obtained were estimated using the atomic force microscope (AFM) equipped with an electro-
chemical attachment.
DOI: 10.1134/S1070363213040099
At present the supramolecular catalysis attracts
much attention, suggesting the use of compounds with
molecular recognition function as the components of
catalytic systems: cyclodextrins and calixarenes, which,
due to the presence of the hydrophobic cavity, are
capable of forming guest-host inclusion complexes
with various organic substrates. To date, despite ex-
tensive investigation of this class of compounds, ex-
amples of their application in catalysis are scarce [1, 2].
with properties that depend on the size and shape of
the particle have a variety of interesting applications,
e. g., in catalysis, as the magnetic storage media of
information, biosensors, in the high surface energy
Raman scattering (SERS) [3–6]. In recent years, the
preparation of thin films consisting of metal
nanostructures is one of the hottest topics [7, 8].
Electrochemical synthesis of metal complexes in
low oxidation states is well known and in some cases
has significant advantages [9, 10].
One of the promising areas to search for new
catalytic systems is the creation of catalysts that
combine in a single molecule the properties of metal
complexes capable of molecular recognition. Calixa-
renes provide unique opportunity for the selective
functionalization of the upper and lower rims of the
macrocycle by the heteroatomic groups to form a
molecular system that has multiple binding sites. It is
interesting to investigate the possibility of stabilization
of the transition metals in low oxidation states, first of
all (0, +1), by the calixarenes with functional groups
containing heteroatoms (P, N, S). The latter are
effective complexing sites capable to bind a metal and
Currently, the literature presents a large number of
metal complexes based on calixarenes functionalized
with organophosphorus fragments containing tricoor-
dinated phosphorus atom [11–13]. However, these
compounds are in most cases hydrolytically unstable,
which limits their practical application. The calixa-
renes functionalized by organophosphorus fragments
containing phosphoryl and thiophosphoryl groups may
be deprived of this shortage. The presence of addi-
tional coordination sites in four organophosphorus
fragments with the tetracoordinate phosphorus atom
resistant to hydrolysis enhances the possibility of the
synthesis of organometallic complexes with calixa-
renes, and extends the area of their practical use. The
use of electrochemical methods for the synthesis of
metal(0) complexes based on calix[4]resorcinol was
form
a
supramolecular structure.
A successful
implementation of macro complexes with a narrow
size distribution of particle would permit designing
catalysts for various reactions. Metal nanostructures
663

664
KHRIZANFOROVA et al.
not found in the literature. The purpose of this study is
to develop methods for the electrochemical synthesis
of nickel(0) complexes with calix[4]resorcinol func-
tionalized by the thiophosphoryl fragments, and the
evaluation of the dimension of the structures obtained
using an atomic force microscope equipped with an
electrochemical attachment, which allows monitoring
of the formation of products in time.
and, moreover, are resistant to hydrolysis and electro-
chemical oxidation. The ligands I–III have the chair
conformation with rctt- configuration of the thio-
phosphoryl substituents, namely, are characterized by
symmetrical arrangement of two pairs of binding sites
[14]. The electrochemical properties of calix[4]resor-
cinols I–III were studied by cyclic voltammetry. In the
studied range of potentials (+1.5 to –3.0 V) they are
electrochemically inactive. Further we used the CVA
method to study solutions of the calix[4]resorcinols I–
III with NiBr2 in DMF at various ratios.
As the objects of the study we selected the calix[4]
resorcinols I–III modified with thiophosphoryl
fragments, because they have high complexing ability,
CH3
CH3
HO
OH
CH
HO
OH
CH
HO
OH
CH
4
4
4
O
P
OC2H5
OC2H5
O
P
S
O
P
C2H5O
C2H5O
O
S
S
O
III
I
II
The electrochemical reduction peak of nickel
bromide contains an irreversible peak at –1225 mV, which
corresponds to the transfer of two electrons. Adding
equimolar amounts of ligands I–III to the solution of
NiBr2 in DMF results in disappearance of initial
reduction peak and appears a new peak at –1165
(NiLI), –1299 (NiLII), –1370 mV (NiLIII),
respectively. The reduction current of each of these
peaks decreases (Fig. 1). This is probably due to the
coordination of NiBr2 with the ligand and a
corresponding decrease in the diffusion coefficient.
The binding of nickel with the calixarene molecule
follows also from the decrease in the adsorption
currents. Similar examples were described in the
literature: In the study of the binding of nitroxide
ligands with Co, Ni, and Mn by the CVA method the
complexation criterion was the shift of the peaks of the
metal reduction [15, 16]. Further increase in the
concentration of nickel bromide in the investigated
solutions led only to an increase in the Ni(II)/Ni(0)
reduction current. After passing through the electrolyte
(a solution of a ligand I–III in DMF with NiBr2 at a
ratio of 1:1) 2 e– of electricity per one mol of Ni, in the
voltammograms at a potential of –1200 mV the
disappearance of the peak of Ni(II)/Ni(0) was
observed. In the studied range of potentials (+1.5 to
–3.0 V) on the polarization curves of Ni(0)LI–III the
peaks of reduction-oxidation were also absent, which
I, mA
Е, V
Fig. 1. CVA of solution of calix[4]resorcinols I-III with
NiBr2 in DMF at the component ratio 1:1. (1) Ni(II)LI, (2)
Ni(II)LII, (3) Ni(II)LIII, (4) NiBr2 (с = 5×10–3 M).
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ELECTROCHEMICAL SYNTHESIS OF THE CALIX[4]RESORCINOL NICKEL COMPLEXES
665
Table 1. Electrochemical characteristics of solutions of
calix[4]resorcinols I–III complexes with NiBr2 in DMF
may be indicative of the electrochemical stability of
the obtained complexes.
Analysis of the electrochemical characteristics
obtained at the registration of CVA of calix[4]
resorcinols I–III solutions with NiBr2 in DMF at dif-
ferent ratios showed that the shift of the peak of Ni(II)/
Ni(0) reduction with respect to the source nickel
bromide occurs at the 1:1 ratio of the reagents. The
complex Ni(II)LI is reduced easier than nickel
bromide, and the complexes Ni(II)LII,III are reduced in
a more negative region, which is probably due to
differences in the structure of the initial ligands (calix
[4]resorcinol) and the stability of the complexes
formed.
The composition of metal complexes Ni(II)LI–III
was determined by the Bent-French limited logarithm
method [17], which allows to find the coefficient n in
the equation: Ni(II) + nL = Ni(II) Ln, using a
logarithmic dependence of the optical density of the
solution on the concentration of one component. The
absorption bands of the compounds studied are shown
in Table 2. Changes in optical density with increasing
concentration of ligand were observed at 290 (280)
nm. The coefficient n for the ligands I–III was found
equal to 0.84, 0.74, and 0.79, respectively. Thus, by
calculating the slope we found that the metal: ligand
stoichiometry of the complexes formed was 1:1 (Fig. 2).
Compound
Ni(II)LI
–Ered, mV
I, mA
ΔEred, mVа
1165
0.0275
64
Ni(II)LII
Ni(II)LIII
NiBr2
1299
1370
1229
0.0146
0.0464
0.1212
70
141
ΔEred is difference of the reduction potentials of complexes
a
Ni(II)LI–III and pure NiBr2.
a shift of the absorption band of thiophosphoryl group
P=S to the low-frequency region by 20–30 cm–1
relative to free calix[4]resorcinols I–III. This shift may
indicate the formation of the P=S→Ni coordination
bond. Similar shift of the absorption bands of the P=S
bond vibration was observed by the example of
complexes of Ni(II) with N-thiophosphorylthioureas
[18]. The 31P NMR spectra of the initial ligands I–III
are characterized by a singlet signal in the range of
63.0–78.4 ppm. When the calixarene was mixed with
the nickel bromide at subsequent electrochemical
reduction of the complex Ni(II)L to Ni(0)L there was
only a slight shift of the resonance signal of the
phosphorus atom (1–0.5 ppm). In the 1H NMR spectra
of the complexes obtained the greatest shift of the
peaks, by 1.2–1.6 ppm, was observed for the
methylene protons of ethoxy groups located at the
phosphorus atom, in the Ni(0)LI,II complexes, or
endocyclic methylene protons in the complex Ni(0)
LIII. The values of molecular weights of the Ni(0)LII,III
complexes determined by the MALDI mass spec-
trometry indicate the formation of 1:1 complexes. The
composition of the complexes was confirmed by
elemental analysis with the atomic-emission spec-
trometer.
Joint electrochemical reduction of calix[4]resor-
cinols I–III with nickel bromide was carried out in a
separated electrolytic cell with platinum cathode and
anode, in DMF. 2 F of electricity per 1 mole of nickel
salt was passed through the solution. During the
synthesis the reaction mixture changed color from
orange to dark cherry. The resulting reduction products
1
were studied by 31P, H NMR spectroscopy, IR, UV
spectroscopy, and mass spectrometry. In the IR spectra
of the isolated metal complexes Ni(0)LI–III is observed
Table 2. Spectral characteristics of the products of electrochemical reduction of calix[4]resorcinols I–III complexes with
nickel bromide
IR, ν, cm–1 (P=S)
31Р NMR, δР, ppm (DMSO) Mass-spectrum (MALDI) m/z
UF, nm (DMF)
L
L
Ni(0)L
L
Ni(0)L
61.9
L
Ni(0)L 1:1
1523.1
L
Ni(0)L 1:1
290, 360
830
799
802
797
63.0
290, 350
290
I
820
832
62.1
78.4
61.8
78.0
1519.6
1400.0
1578.9
1459.9
290, 370
280, 370
II
280
III
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666
KHRIZANFOROVA et al.
by the substrate. A similar pattern was observed at the
–log A
electrolysis of a solution of the complex Ni(II)LII.
Therefore, the size of particles of the resulting
complexes Ni(0)LI–III was studied after the completion
of electrolysis, extraction of sample from the liquid
medium and drying it on a substrate for 1 h at 60ºC,
using intermittent contact atomic force microscopy.
The results obtained showed that at the electro-
chemical reduction of the complex Ni(II)LI individual
spherical particles are formed with an average size of
450 nm (Fig. 5).
–log c(L)
Fig. 2. The logarithmic dependence of the optical density
of the solution on the concentration of the ligands I–III.
Reduction of the Ni(II)LII complex resulted in the
formation of ensembles with an average size of
600 nm combined of individual particles (Fig. 6).
The size of the Ni(0)L particles was studied by
means of atomic force microscopy with an electro-
chemical attachment. When a current was passed through
a solution of Ni(II)LI in DMF spherical particles
formed with an average size of 100 nm (Fig. 3), and
this size did not vary with the time of the electrolysis.
After electrolysis of the solution of the complex
Ni(II)LIII, the entire surface of the substrate was
covered with a dense layer of particles. As in the case
of the complex based on calixarene II the ensembles
consisting of individual particles could be distin-
guished. The average size of these ensembles is
350 nm (Fig. 7).
The investigation of solution of the complex Ni(II)
LIII in DMF using atomic force microscopy showed
that in the first minutes of electrolysis the solution
began rapidly to darken, and on the HOPG substrate
appear dark formations of various shapes, poorly
connected with it. Therefore, to monitor the process we
used optical microscopy that showed the formation of
mostly spherical particles in 5 min (Fig. 4).
Thus, the data on the dimensions of the particles of
Ni(0) complexes with calix[4]resorcinols I–III, ob-
tained by atomic force microscopy, indicate the
formation of particles with narrow size distribution,
which is an important factor in the development of
catalytic systems based on them.
These particles do not differ much from each other
by size. After the break in the electrical circuit in the
cell the substrate began to clear from the deposited
particles. This process was very fast: within a few
minutes the surface became completely clean. It also
confirms the weak binding of the deposited particles
EXPERIMENTAL
Electrochemical measurements were performed in
the regime of cyclic voltammetry using a potentiostat
E2P of BAS Epsilon (USA), consisting of a measuring
unit, a Dell Optiplex 320 computer with the installed
z, nm
z, nm
x, μm
x, μm
y, μm
x, μm
y, μm
z, nm
Fig. 3. Atomic force microscopy image of particles formed at the reduction of the complex of calix[4]resorcinol I with NiBr2 (1:1
ratio) in DMF in the process of electrolysis, and their size distribution.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 4 2013

ELECTROCHEMICAL SYNTHESIS OF THE CALIX[4]RESORCINOL NICKEL COMPLEXES
667
z, nm
y, μm
y, μm
50 μm
n/N, %
x, μm
Fig. 4. The image of the electrode surface with the particles
formed at the reduction of the complex of calix[4]-
resorcinol III with NiBr2 (1:1 ratio) in DMF in the process
of electrolysis in an optical microscope at 400× magnification.
software EpsilonES-USB-V200, and the electro-
chemical cell C3. As working electrodes a stationary
glassy carbon electrode, Ag/AgCl reference electrode
for voltammetric measurements, and auxiliary elec-
trode of platinum wire of 0.5 mm diameter were used.
Measurements were carried out under argon atmosphere.
z, nm
Fig. 5. Atomic force microscopy image of particles formed
at the reduction of the complex of calix[4]resorcinol I and
NiBr2 (1:1 ratio) in DMF after drying the substrate, and
their size distribution.
an electrochemical cell of MMTMEC model (Veeco).
When scanning, we used the rectangular cantilevers
RTESP (Veeco) with silicon probes. The resonant
frequency of the cantilevers occurs in the region 250–
350 kHz, and the radius of curvature of the probe is
10–13 nm. The microscopic images were obtained with
a resolution of 256×256 pixels per frame at the scan
rate 1 Hz. We used a scanner 8279JV with the largest
field of scanning. To eliminate the distortion
associated with the vibration of the microscope under
the influence of external noise, a vibration system
SG0508 was used, able to smooth out the vibrations
with a frequency of 0.5 Hz (lower limit). The
electrochemical cell contained a silver electrode and a
platinum auxiliary electrode. The working electrode
was the HOPG substrate for atomic force microscopy
(highly oriented pyrolytic graphite).
Preparative electrolysis was performed in a three
electrode 30 ml cell using a DC source B5-49. The
value of the potential of the working electrode was
registered with a DC voltmeter B7-27. The working
surface of the cylindrical platinum cathode used as the
working electrode was equal to 20.0 cm2. In experi-
ments with separation of anodic and cathodic spaces
was used a ceramic diaphragm with the pore size
900 nm. As anode served a platinum spring, the
anolyte was a saturated solution of the background
electrolyte used in the catholyte, Bu4NBF4 in DMF.
During electrolysis, the electrolyte was stirred with a
magnetic stirrer at a constant flow of argon passed
through a drying system.
1H NMR spectra were recorded on a multinuclear
spectrometer Bruker Avance DRX 400 (400 MHz),
with respect to the signal of residual protons of
deuterated solvent as an internal reference. IR spectra
were recorded on a Bruker Vector-22 spectrometer in
the frequency range 400–3600 cm–1 in mineral oil.
Mass spectra were obtained on a MALDI mass spectro-
meter ULTRAFLEX-III. UV spectra were recorded on
a Perkin Elmer Lambda 35 spectrophotometer.
Elemental analysis data were obtained on an atomic
emission spectrometer iCAP 6300 DUO.
DMF was dried over potassium carbonate and then
distilled over CaH2. Benzene was distilled over
sodium, diethyl ether was refluxed over P2O5 followed
by distillation, to remove water traces. After purifica-
tion, the solvents were stored in an atmosphere of dry
argon.
Microscopic studies were performed with a Veeco
(USA) scanning probe microscope MultiMode V with
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 4 2013

668
z, nm
KHRIZANFOROVA et al.
z, nm
y, nm
y, μm
y, μm
y, μm
n/N, %
n/N, %
x, μm
z, nm
z, nm
Fig. 7. Atomic force microscopy image of particles formed
at the reduction of the complex of calix [4] resorcinol III
and NiBr2 (1:1 ratio) in DMF after drying the substrate, and
their size distribution.
Fig. 6. Atomic force microscopy image of particles formed
at the reduction of the complex of calix[4]resorcinol II and
NiBr2 (1:1 ratio) in DMF after drying the substrate, and
their size distribution.
All syntheses were carried out in an atmosphere of
two s (4H, HArh,ν); 6.61 m (16H, CH=); 8.04 and 8.25
two s (8H, OHh,ν). 31P NMR spectrum (DMF, δ, ppm):
61.97. IR spectrum (mineral oil, ν, cm–1): 799 (P=S),
3174 (–OH). MALDI mass-spectrum, m/z: 1523.1 [M]+.
Found, %: Ni 3.05. C68H76 NiO20P4S4. Calculated, %:
Ni 3.87;
dry argon.
General procedure of synthesis of Ni(0)LI–III
.
Electrochemical cell was charged with 2.5×10–4 mol
calix[4]resorcinol dissolved in 20 ml of DMF, a
solution of 2.5×10–4 mol of nickel bromide trihydrate
was added, and the mixture was stirred with a
magnetic stirrer. Through the electrolyte 2 F of elec-
tricity per one mole of nickel bromide trihydrate
(134 mA h) was passed. At the end of electrolysis the
solvent was removed on a rotary evaporator at 60ºC,
the dry residue was washed with water (3×30 ml),
insoluble precipitate was filtered off, washed with
diethyl ether, and dried in a vacuum (50ºC, 0.04 mm
Hg) to constant weight.
Nickel 4,6,10,12,16,18,22,24-octahydroxy-2,8,14,20-
tetra[3-(diethyl thiophosphoryloxy)phenyl]-5,11,17,23-
tetramethylpentacyclo[19.3.113,7.19,13.115,19]octacosa-
1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-dode-
caenylate, dark red powder, yield 0.29 g (74%), mp >
1
350ºC. H NMR spectrum (DMF-d7, δ, ppm): 0.94 t
(24H, CH3CH2, 3JHH 7.14 Hz), 3.72 m (16Р, CH3CH2);
h,ν
1.93 and 2.08 two s (12H, CH3 ); 5.73 s (4H, CH);
5.28 and 6.9 two s (4H, HArh,ν); 6.64 m (16H, CH=);
7.40 and 7.65 two s (8H, OHh,ν). 31P NMR spectrum
(DMF, δ, ppm): 61.87. IR spectrum (mineral oil, ν,
cm–1): 802 (P=S), 1057 (POC), 3539 (–OH). MALDI
mass-spectrum, m/z: 1578.9 [M]+. Found, %: Ni 2.98.
C72H84 NiO20 P4S4. Calculated, %: Ni 3.74;
Nickel 4,6,10,12,16,18,22,24-octahydroxy-2,8,14,20-
tetra[4-(diethyl thiophosphoryloxy)phenyl]penta-
cyclo[19.3.1.13,7 19,13.115,19]octacosa-1(25),3,5,7(28),9,11,-
.
13(27),15,17,19(26),21,23-dodecaenylate, brick-red
1
powder, yield 0.30 g (78.9%), mp >350ºC. H NMR
spectrum (DMF-d7, δ, ppm): 0.98 t (24H, CH3CH2,
3JHH 7.08 Hz), 3.70 m (16H, CH3CH2); 5.63 s (4H,
CH); 5.39 and 6.10, two s (4H, HArh,ν); 6.15 and 6.23
Nickel 4,6,10,12,16,18,22,24-octahydroxy-2,8,14,20-
tetra[4-(1,2,3-dioxothiophosphoryloxy)phenyl]-
5,11,17,23-tetramethylpentacyclo[19.3.113,7.19,13.115,19]-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 4 2013

ELECTROCHEMICAL SYNTHESIS OF THE CALIX[4]RESORCINOL NICKEL COMPLEXES
669
Langmuir., 2002, vol. 18, p. 10005.
octacosa-1(25),3,-5,7(28),9,11,13(27),15,17,19(26),21,23-
dodecaenylate, dark-orange powder, yield 0.31 g
(85.1%), mp > 350ºC. H NMR spectrum (DMF-d7, δ,
9. Budnikova, Yu.G., Usp. Khim., 2002, vol. 71, no. 2,
1
p. 127.
ppm): 1.90 and 2.07 two s (12H, CH3h,ν); 3.18 m (16H,
p-CH2); 5.47 s (4H, CH); 5.76 and 6.15 two s (4H,
HArh,ν); 6.42 m (16H, CH=); 7.01 and 7.45 two s (8H,
OHh,ν). 31P NMR spectrum (DMF, δ, ppm): 78.0. IR
spectrum (mineral oil, ν, cm–1): 797 (P=S), 3407 (OH).
MALDI mass-spectrum, m/z: 1459.9 [M]+. Found, %:
Ni 3.76. C64H60Ni4O20P4S4. Calculated, %: Ni 4.04.
10. Jutand, A., Chem. Rev., 2008, vol. 108, p. 2300.
11. Steyer, S., Jeunesse, C., Harrowfield, J., and Matt, D.,
Royal Soc. Chem. Dalton Trans., 2005, p. 1301.
12. Nifantyev, E.E., Maslennikova, V.I., Goryukhina, S.E.,
Antipin, M.Yu., Lyssenko, K.A., and Vasyanina, L.K.,
J. Organomet. Chem., 2001, vol. 631, p. 1.
13. Xu, W., Rourke, J.P., Vittal, J.J., and Puddephatt, R.J.,
ACKNOWLEDGMENTS
Inorg. Chem., 1995, vol. 34, no. 1, p. 323.
This work was financially supported by the Russian
Foundation for Basic Research (grant nos. 11-03-00416-
a, 12-03-31002, 13-03-00139).
14. Knyazeva, I.R., Burilov, A.R., Fazleeva, G.M., Nuret-
dinov, I.A., Gryaznova, T.V., Budnikova, Yu.H., Khri-
zanforova, V.V., Gubaidullin, A.T., Gabidullin, B.,
Syakaev, V.V., Pudovik, M.A., and Konovalov, A.I.,
Phosphorus, Sulfur, Silicon, Rel. Elem., 2011, vol. 189,
no. 9, p. 1972.
REFERENCES
1. Homden, D.M. and Redshaw, C., Chem. Rev., 2008,
vol. 108, p. 5086.
2. Creavena, B.S., Donlona, D.F., and McGinley, J.,
Coord. Chem. Rev., 2009, vol. 253, p. 893.
15. Villamena, F.A., Horak, V., and Crist De, L.R., Inorg.
Chim. Acta., 2003, vol. 342, p. 125.
16. Lindner, E., Kehrer, U., Steimann, M., and Ströbele, M.,
3. Wei, A., Tripp, S., Liu, J., Rasama, T., and Dunin-
Borowski, R., Supramol. Chem., 2009, vol. 21, p. 189.
J. Organomet. Chem., 2001, vol. 630, p. 266.
17. Bulatov, M.I. and Kalinkin, I.P., Prakticheskoe
rukovodstvo po fotometricheskim metodam analiza (A
Practical Guide to the Photometric Analysis Methods),
Leningrad: Khimiya, 1986, p. 252.
4. Wei, A., Chem. Commun., 2006, p. 1581.
5. Sun, S., Murray, C.B., Weller, D., Folks, L., and Moser, A.,
Science, 2000, vol. 287, p. 1989.
6. Cao, Y.C., Jin, R., and Mirkin, C.A., Science, 2002,
vol. 297, p. 1536.
18. Safin, D.A., Sokolov, F.D., Szyrwiel, L., Babashki-
na, M.G., Gimadiev, T.R., Hahn, F.E., Kozlowski, H.,
Krivolapov, D.V., and Litvinov, I.A., Polyhedron.,
2008, vol. 27, p. 2271.
7. Pilent, M.P., Adv. Funct. Mater., 2001, vol. 11, p. 323.
8. He, J., Ichinose, I., Kunitake, T., and Nakao, A.,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 4 2013