Metal exchange in cadmium porphyrins with spatially shielded coordination centers

Article abstract of DOI:10.1134/S0036023613090027

Shielding of coordination centers in metalloporphyrins (MPs, M = Cd) through covering it with a covalently bonded lid or by an endocyclic N-substituent results in retardation of metal exchange reaction (Cd/Zn or Cd/Cu) by up to 10 times. A decrease in the metal exchange rate was observed in spite of the fact that the shielding gave rise to a pronounced distortion of the predominately planar structure of aromatic ligands in the MP structure in the studied objects, which was confirmed by electronic and fluorescence spectroscopy as well as by ¹H NMR spectroscopy. It was found that 2,8,12,18-tetramethyl-3,7,13,17-tetrabutyl-10,20-di-ortho-methoxyphenylporphin exists as a mixture of cis- and trans-atropisomers with a ratio of 1: 2.

Full text of DOI:10.1134/S0036023613090027

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2013, Vol. 58, No. 9, pp. 1052–1057. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © D.B. Berezin, N.V. Lazareva, O.V. Shukhto, R.S. Kumeev, A.S. Semeikin, 2013, published in Zhurnal Neorganicheskoi Khimii, 2013, Vol. 58, No. 9,
pp. 1177–1182.
COORDINATION COMPOUNDS
Metal Exchange in Cadmium Porphyrins
with Spatially Shielded Coordination Centers
D. B. Berezin , N. V. Lazareva , O. V. Shukhto , R. S. Kumeev , and A. S. Semeikin
a
a
a
b
a
a
Research Institute of Macroheterocyclic Compounds, Ivanovo State University of Chemical Technology,
pr. Engelsa 7, Ivanovo, 153000 Russia
Krestov Institute of Solution Chemistry, Russian Academy of Sciences,
b
ul. Akademicheskaya 1, Ivanovo, 153045 Russia
eꢀmail: berezin@isuct.ru
Received November 15, 2012
Abstract—Shielding of coordination centers in metalloporphyrins (MPs, M = Cd) through covering it with
a covalently bonded “lid” or by an endocyclic Nꢀsubstituent results in retardation of metal exchange reaction
(Cd/Zn or Cd/Cu) by up to 10 times. A decrease in the metal exchange rate was observed in spite of the fact
that the shielding gave rise to a pronounced distortion of the predominately planar structure of aromatic
ligands in the MP structure in the studied objects, which was confirmed by electronic and fluorescence specꢀ
1
troscopy as well as by H NMR spectroscopy. It was found that 2,8,12,18ꢀtetramethylꢀ3,7,13,17ꢀtetrabutylꢀ
10,20ꢀdiꢀorthoꢀmethoxyphenylporphin exists as a mixture of cisꢀ and transꢀatropisomers with a ratio of 1 : 2.
DOI: 10.1134/S0036023613090027
Metal exchange reactions (1)) find wide applicaꢀ
In this work there was analyzed the influence of two
tion in the synthesis of complex organometallic and types of spatial shielding of the coordination center in
coordination compounds [1, 2]. Metalꢀexchange cadmium porphyrins (CdP) through meso mesoꢀpheꢀ
reactions are used for the preparation of heterometalꢀ nyl covering thereof by a covalently bonded “lid” (in
lic binuclear metal complexes (metalloporphyrins; compounds
III) or by an endocyclic ꢀsubstitution
–
I–
N
MPs) and supramolecular structures on their basis [3, 4] of the coordination center (in compounds IV and
V)
in the chemistry of porphyrins (Н2Р), implemented on the proceeding of a metalꢀexchange reaction in
for analytical and biomedical purposes for the develꢀ CdP/Cu(OAc) /DMF and CdP/Zn(NO ) /DMSO
2
3 2
opment of fluorescent labels [5] as well as applied in systems [9, 15], respectively. The effect of the shielding
catalysis of reactions of coordination interaction [6–8]. of the coordination center of corresponding H2P
ligands (Ia
–Va ) on the change in planar structure of
ML + M'X (Solv)
n
→
M'L + MX (Solv) n. (1)
n m –
m – n
their aromatic macrocycles was demonstrated on the
A study of the influence of different factors on basis of the spectroscopic data. For this purpose,
metal exchange in solutions of MPs allows not only for 2,8,12,18ꢀtetramethylꢀ3,7,13,17ꢀtetrabutylꢀ10,20ꢀdiꢀ
better understanding the mechanism of the process [9, orthoꢀmethoxyphenylporphin
{Н2(
[16] and its 1,4ꢀphenylene
IIa) [17] and 9,10ꢀanthracenylene (IIIa) [18] derivaꢀ
several orders of magnitude more rapidly than in the tives, as well as corresponding cadmium complexes
direct reaction of an Н2Р ligand with a metal salt [6, 7]. (compounds
III) were synthesized. The results
β
ꢀМе Bu )msꢀ
4 4
1
0] but also for choosing optimal conditions for the transꢀ
(оꢀМеОPh) P} (Ia)
2
synthesis of MPs, which are formed by reaction (1)
(
I–
An investigation of steric effects on the reactivity of obtained (Tables 1, 2) were compared with spectralꢀ
complex organic molecules remains one of the most kinetics data [9, 14, 15] on the influence of spatial
important directions in chemistry. Certain types of spatial shielding of the coordination center of cadmium porꢀ
shielding of reaction centers make it possible to inhibit phyrin (compounds IV and
V) through the Nꢀsubstituꢀ
–
some reactions and, in contrast, to accelerate others and tion of its macrocyclic ligand (X = AcO ) on the
to simulate their proceeding in vivo [11–14].
metalꢀexchange rate:
Bu
Bu
Bu
Me
Bu
Me O
Me
Me
N
Me
N
N
N
N
N
N
Cd
Cd
N
Me
Me O Bu
Me
Bu
Me
Me
O Me
Bu
O Me
Bu
I'
I''
1052

METAL EXCHANGE IN CADMIUM PORPHYRINS
H C
1053
H C
Bu
CH2
Bu
2
CH2
2
Bu
Bu
Me
O
O
O
O
Me
Me
Me
N
N
N
N
N
N
N
N
Cd
Cd
Me
Bu
Me
Bu
Me
Bu
Me
Bu
II
III
X
Ph
Cd
Ph
Cd
N
N
N
N
N
Ph
Ph
Ph
Ph
Me
N
N
N
Ph
Ph
IV
V
EXPERIMENTAL
IIIa were prepared according to
known procedures [16–18]. Complex Ia with cadꢀ
rimeter (Belarus). To record the fluorescence, samples
were irradiated at the wavelength of exciting light
Ligands Ia
–
exc
λ
= 450 nm. For this purpose, dilute solutions of
IIIa in DMF, the optical density of
cedure by mixing dimethylformamide solutions of the which in the band I of EAS did not exceed 0.1, were
mium(II) was prepared according to the routine proꢀ porphyrins Ia
–
–1
ligand and metal acetate in a molar ratio of 1 : 10 folꢀ prepared. The Stokes shift (cm ) was calculated using
lowed by heating of the mixture at 100 for 1 h. The
°C
the following formula [20]:
purity of compounds was monitored by means of analꢀ
ysis of their electronic absorption spectra (EAS) and
H NMR spectra as well as by thinꢀlayer chromatograꢀ
St
I
7
fl
1
abs
I
fl abs
Δν = 10 λ − λ
λ λ ,
(2)
1
(
)
1
I
phy (Silica F60, chloroform as an eluent).
fl
1
abs
I
N,NꢀDimethylformamide (DMF) of pure for analꢀ where
λ
and
λ
are wavelengths (nm) of boundary
ysis grade was kept over calcined MgSO and distilled bands of the fluorescence and absorption spectra,
4
in vacuum at 35–40
additionally recrystallized from acetic acid, followed
by drying in vacuum at mmHg and = 80
°
C [19]. Before use, salts were respectively.
Spectrophotometric control of metalꢀexchange
reactions (1) in complexes and II (CdP/Cd(OAc)2/
p
≈
1
T
°С.
1
I
The H NMR spectra were recorded on an Avanceꢀ
00 spectrometer (Bruker) with an operating freꢀ
Cu(OAc) /DMF) and recording of EAS of ligands Ia
–
5
2
quency of 500 MHz at 303 K, while the fluorescence IIIa were performed on a UV1800 Shimadzu apparaꢀ
spectra were obtained using an SMꢀ2203 spectrofluoꢀ tus according to the procedure described in [9, 10].
Table 1. Spectral characteristics of porphyrins Ia and IVa and their spatially hindered derivatives IIa
–IIIa and Va in DMF
EAS EES
1H NMR*
H2P
Δν , nm (cm–1)
St
I
Ar
CH
δ
NH, ppm
λ
Soret, nm
λ
I, nm
λ
1, nm
δ
,
ppm
Ia
407
626
628
647
649
654
689
2 (51)
6 (145)
8 (190)
7 (165)
13 (279)
10.21
9.87
9.48
8.75
–2.77
–1.17
–2.37
–2.76
–
IIa
415
641
IIIa
419
641
IVa [14]
Va [14]
416 (5.62)
425 (5.24)
647 (3.68)
676 (3.87)
7.46; 8.46; 8.64; 8.82
*
CDCl as a solvent.
3
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013

1054
BEREZIN et al.
Table 2. Kinetic parameters of metalꢀexchange reaction (cCdP = 2.76
10–5 mol/L)
×
3
3
–1
S#, J/(mol K)
Compound
csalt
×
10 , mol/L
T
, K
nsalt
keff
×
10 , s
Ea, kJ/mol
Δ
System CdP/Cd(OAc) /Cu(
O
Ac) /DMF
2
2
I
1.38
318
318
298
1.3
1.2
2.23 ± 0.24
4.53 ± 1.71
1.30 ± 0.31
3.25 ± 0.14
5.35 ± 0.81
0.73 ± 0.01
0.74 ± 0.01
0.67 ± 0.01
1.22 ± 0.02
1.82 ± 0.09
–
–
–
–
2
.07
.76
2
56 ± 9
–122 ± 33
3
08
18
3
II
1.38
318
318
298
–
–
–
–
2
.07
.76
2
39 ± 4
–182 ± 14
3
08
18
3
System CdP/Zn(NO ) /DMSO
3
2
IV [15]
1.12
298
0.9
0.18 ± 0.01
0.44 ± 0.01
0.85 ± 0.02
0.37 ± 0.01
0.84 ± 0.01
1.60 ± 0.08
0.98 ± 0.02
1.92 ± 0.06
3.50 ± 0.22
0.019 ± 0.002
0.21 ± 0.05
0.82 ± 0.15
1.39 ± 0.19
0.059 ± 0.007
0.17 ± 0.02
0.92 ± 0.19
1.60 ± 0.19
0.072 ± 0.007
0.41 ± 0.07
1.35 ± 0.27
1.90 ± 0.23
0.18 ± 0.04
0.39 ± 0.05
1.51 ± 0.17
2.26 ± 0.21
60 ± 5
58 ± 4
50 ± 1
91 ± 19
–124 ± 16
–125 ± 13
–142 ± 3
–136 ± 20
3
08
18
3
2
.24
.60
298
3
08
18
3
5
298
3
08
18
3
V
[9]
1.38
298
0.85
308
323
333
2.07
2.76
3.45
298
78 ± 10
73 ± 13
59 ± 7
–46 ± 17
–99 ± 20
–120 ± 20
308
323
333
298
308
323
333
298
308
323
333
RESULTS AND DISCUSSION
It follows from the analysis of the EAS and fluoresꢀ
dination center. Thus, when going from “uncovered”
macrocycle Ia to its derivatives with phenylene (IIa
and anthracenylene (IIIa) “lids”, the band I and Soret
)
cence emission electronic spectroscopy (EES) data as
band in their EASs shift bathochromically by 15 and
1
well as N NMR spectroscopy (Table 1) that the linkꢀ
8–12 nm, respectively (Fig. 1). In this case, the shifts
age of the orthoꢀpositions of transꢀphenyl rings in
compound Ia through a relatively short spacer results
in a noticeable distortion of the planar structure of pound with the bulkier, rigid lid are somewhat greater
of EAS bands for the anthraceneꢀsubstituted comꢀ
macrocycles IIa and IIIa besides shielding of the coorꢀ than that for the phenyleneꢀcovered one (Table 1).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013

METAL EXCHANGE IN CADMIUM PORPHYRINS
1055
One may also note that, as a result of a covalent meso–
St
I
Δν
mesoꢀcovering of a ligand, for example when going
from compound Ia to IIa, a noticeable decrease in the
intensity of the bands in the electronic spectra and
blurring of their structure (Fig. 1) occurs due to the
activation of outꢀofꢀplane vibrations of the molecule.
Indications of the distortion of the planar structure
of aromatic macrocycles observed in the EASs of comꢀ
pounds, such as bathochromic shifts and broadening
of bands, are only indirect ones [14]. However, using
them in combination with the data of other spectral
methods, one may say about the nonplanarity of covꢀ
ered tetrapyrrole molecules IIa and IIIa with a high
degree of ruggedness.
A
.3
0
0
0
St
I
Δν
.2
.1
1
2 3 4
One of the simplest characteristics of the nonplaꢀ
narity of aromatic macrocycles in solutions is an
0
4
St
increase in the Stokes shift (ΔνI ) of the boundary
70
570
670
, nm
bands in fluorescence emission spectra and absorption
spectra [14, 20, 21]. In the case of the considered covꢀ
λ
ered compounds IIa
–
IIIa, the Stokes shift is someꢀ
Fig. 1. Electronic absorption (
emission ( and
respectively, in DMF (the spectra are normalized).
1
and 2) and fluorescence
–1
3
4) spectra of compounds Ia and IIa,
what increased from 2 nm (50 cm ) to 6–8 nm (150–
–1
1
90 cm ) as compared to the unsubstituted porphyrin
Table 1).
It follows from the values of Stokes shift that the
total increase in the nonplanarity of a macrocycle in
the case of its covalent meso meso linkage is relatively
(
3.78
3.73
–
small, because spectral methods take into account, as
a rule, the average deviation of atoms of the planar part
of a molecule from the initial plane [21]. In the case of
meso
maximum value for
directly bonded to a spacer lid, whereas C and C
–mesoꢀcovered compounds IIa and IIIa, it has a
10
20
С
and C atoms which are
5
15
atoms deviate slightly from the initial plane, for which
reason nonplanar structure of the macrocycle in its
most stable conformation is strongly asymmetric.
The distortion of the planar structure of an Н2Р
molecule results in a decrease in its aromaticity and, as
a consequence, in a decrease in the ꢀelectron ring
π
current in the macrocycle, which is traced in the
1
H NMR spectra of the compounds due to the fulfillꢀ
ment of the magnetic criterion of aromaticity. Thus,
when going from “uncovered” compound (Ia) to pheꢀ
nylene (IIa) and anthracenylene (IIIa) derivatives of
1.02
2.03
3.72
3.88
3.80
3.64
, ppm
1
δ
β
ꢀoctaalkylꢀmeso
nal of mesoꢀCH protons is upfield shifted by 0.34 and
.73 ppm (Table 1), respectively. In this case, analysis
ꢀtransꢀdiphenyl porphyrin, the sigꢀ
Fig. 2. Manifestation of atropisomerism in the H NMR
spectrum of compound Ia (CDCl3).
0
of the position of endocyclic NH protons of porphyrin
in its H NMR spectrum does not allow for tracing the
tendency for a downfield shift of the signal upon tying
of the molecule, which is probably due to the influence
of the ring current of the lid itself and due to different
locations of the lid near the coordination center of the
1
1
seen in the H NMR spectrum of compound Ia, where
two signals of methoxy groups with a ratio of 1 : 2 are
observed. It seems that the transꢀisomer (66%) prevails in
the mixture, which does not favor high yield in the synꢀ
thesis of covered derivatives of macrocycle Ia
.
macrocycle in compounds IIa
–
IIIa
When analyzing the H NMR spectrum of Н2(
Ме Bu )ms transꢀ(orthoꢀMeOPh) P (Ia), it was found
.
1
βꢀ
Previously [9], the influence of the endocyclic
ꢀsubstitution in a mesoꢀtetraphenylporhin molecule
ꢀ
N
4
4
2
that this compound exists as a mixture of atropisomers (H TPP, IVa) was studied on the proceeding of metalꢀ
2
I'
and , which differ from each other by the location
I''
exchange reaction (1) in its cadmium complex
of methoxy groups (Fig. 2). Atropisomerism is clearly (AcO)Cd( ꢀMe)TPP ( ). ꢀSubstitution also results
a
a
N
V N
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013

1056
BEREZIN et al.
are upfield shifted from 8.75 to an average of 8.35 ppm
–
logkeff
(
Table 1) [14].
3
3
2
2
.5
As a rule, nonplanar structures of porphyrin ligands
2
are in a good agreement with the degrees of nonplaꢀ
narity of their metal complexes [13]. In the case of
cadmium(II) complexes with porphyrins, the distorꢀ
tion of a ligand results in a sharp decrease of their staꢀ
bility, for example, towards dissociation in solutions
.1
.7
.3
1
[
14]. For this reason, we studied metalꢀexchange proꢀ
cesses for cadmium complexes with covered porphyrin
IIa in the CdP/Cd(OAc) /Cu(OAc) /DMF system,
2
2
that is, in the presence of a background salt of the leavꢀ
ing metal which was present in twentyꢀfold excess. An
attempt to isolate cadmium complexes (compounds II
and III) in a solid state results in their decomposition
even during washing of the reaction mixture. Previꢀ
ously, an analogous situation was observed for cadꢀ
mium complexes with strongly nonplanar the dodecaꢀ
substituted ligand mesoꢀtetraphenyltetrabenzoporꢀ
1
.9
.5
1
2
.5
2.6
2.7
2.8
2.9
logc
salt
–
Fig. 3. Logarithmic plot of the effective rate constant of
metalꢀexchange reaction (1) in the
CdP/CdOAc /CuОAc /DMF system versus the concenꢀ
tration of copper(II) salt;
tan
phin (H TBTBP) [9]. Cadmium complexes with
2
2
2
N
ꢀmethyltetraphenylporphin {H(NꢀMe)TPP} Va
Т = 318 К for (1 compound I
α
(
α
= 1.3) and (
2) compound II (tan
= 1.2).
proved to be somewhat more stable [9], apparently
owing to their structural features [12], particularly due
to a positive influence of shielding of the metal center
–
logkeff
–
by
Nꢀsubstituent (СН3ꢀ) and acidoligand (ОАс ) at
4
4
3
3
.5
the opposite sides of the macrocycle.
An analysis of the kinetics data obtained for the
reaction (1) of covered (compound II) and uncovered
.0
2
(
compound
I
) cadmium complexes of ꢀoctaalkylꢀ
β
.5
.0
meso
ꢀtransꢀdiphenyl porphyrin (Table 2) shows that
1
meso–mesoꢀtying of the coordination center of the
molecule at one side of its plane with an aryl lid results
in a twoꢀ to threefold retardation of the process. Analꢀ
ogously, a 6ꢀ to 12ꢀfold decrease in reactivity in reacꢀ
tion (1), depending on the concentrations of reagents
2.5
2.0
1.5
1.0
and temperature, is also observed for
Nꢀsubstituted
compounds as compared to unsubstituted macrocyꢀ
cles [9, 15] (Table 2). One may note that the shielding
of the coordination center when going from comꢀ
pound I to II is accompanied by a decrease in the actiꢀ
vation energy of reaction (1) whereas the metalꢀ
exchange rate decreases due to worsening the solvation
2.2
2.4
2.6
2.8
3.0
logcsalt
–
conditions in the transition state of the process
Fig. 4. Logarithmic plot of the effective rate constant of
metalꢀexchange reaction (1) in the CdP/Zn(NO ) /DMSO
#
(
⎯
Δ
S
). Contrariwise, the value of Еа in reaction (1)
ꢀmethyl substitution of one of the
3
2
increases upon the
N
system on the concentration of zinc(II) salt at
Т
= 308 К
endocyclic nitrogen atoms of the macrocycle.
for (
tan
1
) compound IV (tan
α
= 0.9) and (2) compound V
(
α
= 0.85) [9, 15].
The spatial shielding of the reaction center and of
the distortion of the planar structure of the macrocyꢀ
clic molecule are factors that influence the reactivity
of metalloporphyrins in different directions. As we
have previously found [22], distortion of the planar
structure of the macrocycle leads to an increase in the
rate of metal exchange in its labile complexes. On the
contrary, the spatial shielding of the coordination cenꢀ
in distortion of the planar structure of the molecule
and in spatial shielding of metal atom in the complex
–
by the
Nꢀsubstituent and an extra ligand (X = AcO )
[
N
12]. As a result of the distortion of ligand IVa upon its
ꢀmethylation (compound Va ), the Soret band and
band I of the electronic spectrum in CHCl are shifted ter decreases the reactivity of molecules towards metal
3
by 9 and 29 nm, respectively; the Stokes shift of exchange [14]. Therefore, as a result of the combined
boundary bands in EES and EAS increases from 160 to action of two factors, the retarding effect of the spatial
–1
2
80 cm ; and some signals of exocyclic ꢀCH protons shielding of the coordination center on metalꢀ
β
of macrocycle, mesoꢀpositions of which are occupied, exchange reaction (1) prevails in the case of both
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013

METAL EXCHANGE IN CADMIUM PORPHYRINS
1057
meso
phyrin complexes.
–
mesoꢀbonded (II) and
N
ꢀsubstituted (
V
) porꢀ
6. K. B. Yatsimirskii and Ya. D. Lampeka, The Physical
Chemistry of Metal Complexes with Macrocyclic Ligands
(Naukova Dumka, Kiev, 1985) [in Russian].
A study of concentration dependences of the effecꢀ
tive constant of the rate of metal exchange (Figs. 3, 4;
Table 2) showed that the reaction order n with respect
to the salt practically does not change and is close to
unity when going from compounds with unshielded
reaction centers to those with spatially hindered ones.
7
. P. Hambright, The Porphyrin Handbook, Ed. by
K. M. Kadish, K. M. Smith, and R. Guilard (Academic
Press, New York, 2000), Vol. 3, p. 129).
8
. N. V. Chizhova, O. G. Khelevina, and B. D. Berezin,
Zh. Obshch. Khim. 73, 1738 (2003).
9
. D. B. Berezin, O. V. Shukhto, and M. S. Reshetyan,
Zh. Obshch. Khim. 80, 496 (2010).
The fact that n = 1 is unexpected because an associaꢀ
tive–dissociative mechanism of metal exchange [9],
which is the most characteristic for cadmium porphyꢀ
rins, has low probability to occur in the case of covered
1
0. D. B. Berezin, O. V. Shukhto, and N. V. Lazareva,
Russ. J. Inorg. Chem. 57, 744 (2012).
1
1. I. V. Berezin and K. Martinek, The Fundamentals of
Physical Chemistry of Enzymatic Catalysis (Vysshaya
Shkola, Moscow, 1977) [in Russian].
and
Nꢀsubstituted compounds due to the hindrances
produced, during the formation of the reaction transiꢀ
tion state, by substituents located at least at one of the
sides of the macrocycle plane.
12. D. K. Lavallee, The Chemistry and Biochemistry of
NꢀSubstituted Porphyrins (VCH, New York, 1987).
1
3. M. O. Senge, The Porphyrin Handbook, Ed. by
K. M. Kadish, K. M. Smith, and R. Guilard (Academic
Press, New York, 2000), Vol. 1, p. 239).
ACKNOWLEDGMENTS
1
4. D. B. Berezin, The Macrocyclic Effect and Structural
Chemistry of Porphyrins (URSS, Moscow, 2010) [in
Russian].
The work was supported by the Russian Federation
President Program for Support of Leading Scientific
Schools (project no. NShꢀ3993.2012.3) and by the
Russian Foundation for Basic Research (project
no. 12ꢀ03ꢀ97542ꢀr_center_a).
1
1
1
5. D. B. Berezin, O. V. Shukhto, M. S. Nikol’skaya, and
B. D. Berezin, Koord. Khim. 31, 104 (2005).
6. S. A. Syrbu, T. V. Lyubimova, and A. S. Semeikin,
Zh. Obshch. Khim. 71, 1747 (2001).
7. S. V. Zaitseva, S. A. Zdanovich, and A. S. Semeikin,
REFERENCES
Zh. Obshch. Khim. 73, 499 (2003).
1
. O. A. Reutov, I. P. Beletskaya, and V. I. Sokolov, Reacꢀ 18. S. V. Zaitseva, S. A. Zdanovich, A. S. Semeikin, and
tion Mechanisms of Organometal Compounds (Khimiya,
O. I. Koifman, Russ. J. Inorg. Chem. 50, 1798 (2005).
Moscow, 1972) [in Russian].
1
9. A. J. Gordon and R. A. Ford, The Chemist’s Companion:
A Handbook of Practical Data, Techniques and Referꢀ
ences (Wiley, New York, 1972; Mir, Moscow, 1976).
0. C. A. Parker, Photoluminescence of Solutions (New
York, Elsevier, 1968; Mir, Moscow, 1972).
1. I. V. Sazanovich, A. Van Hoek, A. Yu. Panarin, et al.,
2
3
4
5
. S. P. Gubin, Cluster Chemistry (Nauka, Moscow, 1987)
[in Russian].
2
2
2
. S. G. Pukhovskaya, A. V. Vakhonin, S. A. Syrbu, et al.,
Available from VINITI, No. 4492 (1994).
. G. M. Mamardashvili, N. Zh. Mamardashvili, and
J. Porph. Phthaloc.
2. S. Cromer, P. Hambright, J. Grodkowski, and P. Neta,
J. Porph. Phthaloc. , 45 (1997).
9 (1), 59 (2005).
O. I. Koifman, Usp. Khim. 77, 61 (2008).
1
. I. Spasojevic, Yu. Chen, T. J. Noel, et al., Free Radic.
Biol. Med. 42, 1193 (2007).
Translated by M. Makarov
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 9 2013