Tetradentate nitrogen-containing ligands bis-5-(2-pyridylmethylidene)-3,5- dihydro-4H-imidazol-4-ones and their coordination compounds with CuI and CuII

Article abstract of DOI:10.1007/s11172-009-0185-1

Tetradentate N₄-type organic ligands containing two 5-(2-pyridylmethylidene)-2-thio- 3,5-dihydro-4H-imidazol-4-one fragments linked by two-, four-, or six-carbon polymethylene bridges between the sulfur atoms were synthesized. Mono- and dinucle

Full text of DOI:10.1007/s11172-009-0185-1

Russian Chemical Bulletin, International Edition, Vol. 58, No. 7, pp. 1392—1399, July, 2009
1392
Tetradentate nitrogenꢀcontaining ligands
bisꢀ5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀones
and their coordination compounds with CuI and CuII
A. G. Majouga, E. K. Beloglazkina, O. V. Shilova, A. A. Moiseeva, and N. V. Zyk
Department of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Eꢀmail: bel@org.chem.msu.ru
Tetradentate N4ꢀtype organic ligands containing two 5ꢀ(2ꢀpyridylmethylidene)ꢀ2ꢀthioꢀ
3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone fragments linked by twoꢀ, fourꢀ, or sixꢀcarbon polymethylene
bridges between the sulfur atoms were synthesized. Monoꢀ and dinuclear complexes of these
ligands with copper(II) chloride, as well as with copper(I) and copper(II) perchlorates, were
prepared. The structure of the coordination compound (5Z,5´Z)ꢀ2,2´ꢀ(butaneꢀ1,2ꢀdiylꢀ
disulfanyldiyl)bisꢀ5ꢀ(2ꢀpyridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone with
copper(I) perchlorate was established by Xꢀray diffraction. The copper atom in this complex is
in a distorted tetrahedral coordination formed by four nitrogen atoms of two imidazole and two
pyridine rings. The perchlorate anion is located in the outer sphere of the complex and is not
involved in the coordination with the copper ion. The electrochemical study of the ligands and
the complexes was carried out by cyclic voltammetry and rotating disk electrode voltammetry.
The initial reduction of the complexes under study occurs at the metal atom. The length of the
polymethylene bridge in the ligand has only a slight effect on the redox properties of the ligands
and the complexes.
Key words: copper(I) complexes, copper(II) complexes, 5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdiꢀ
hydroꢀ4Hꢀimidazolꢀ4ꢀones, transition metal complexes, N4ꢀligands, electrochemical studies,
Xꢀray diffraction study.
The synthesis of lowꢀmolecularꢀweight analogs of natꢀ
taining enzymes (hemocyanin, catechol oxidase, N2O reꢀ
ductase, etc.) containing two or more copper ions are
known. The aim of the present study was to prepare new
tetradentate N4ꢀtype organic ligands by the alkylation
of thiohydantoins by α,ωꢀdibromoalkanes, synthesize
their monoꢀ and dinuclear coordination compounds
with copper(I) and copper(II) salts, and investigate the
redox properties of the resulting complexes by electroꢀ
chemical methods.
By varying the length of the alkyl chain, we planned to
obtain the environment of metal ions in the complexes
that is similar to the environment observed in natural
metalloenzymes. In our opinion, the different linker length
between the electronꢀdonating moieties will help in preꢀ
paring various dinuclear complexes with copper ions
located at different distances from each other. Thus,
it may be expected that it would be possible to syntheꢀ
size both complexes with closely spaced copper cations,
which reversibly bind an oxygen molecule as it is chaꢀ
racteristic of hemocyanin (Cu—Cu, 3.6 Å),3 and coorꢀ
dination compounds that mimic the action of dopamꢀ
ine βꢀhydroxylases containing copper atoms at a distance
of ~11 Å.1,11
ural metalloenzymes is an important field of investigation
in modern bioinorganic chemistry. Generally, enzymes
containing a metal ion in the active site catalyze various
chemical transformations, such as the oxidation, hydroxꢀ
ylation, amination, etc. Such catalyses occur under atmoꢀ
spheric pressure at room temperature and result in the
formation of products with high selectivity and in high
yield. Copperꢀcontaining enzymes are widespread both in
plants and animals. The biological role of copperꢀconꢀ
taining enzymes is associated with the following processꢀ
es: 1) the electron transfer, 2) the oxygen binding, storage,
and transport, 3) the oxidation catalysis, and 4) the reꢀ
duction of nitric oxide in the last step of the nitrogen
cycle.1—5
In recent years, we have developed synthetic approachꢀ
es to 5ꢀpyridylꢀsubstituted 3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀ
ones, which act as bidentate N2ꢀtype organic ligands and
are produced by the alkylation of available 5ꢀsubstituted
tetrahydroꢀ4Hꢀimidazolꢀ4ꢀones (2ꢀthiohydantoins), as
well as to coordination compounds with these ligands.6—10
Some of these complexes exhibit catalytic activity in oxiꢀ
dation reactions.10 It should be noted that copperꢀconꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1353—1360, July, 2009.
1066ꢀ5285/09/5807ꢀ1392 © 2009 Springer Science+Business Media, Inc.

2ꢀPyridylmethylideneꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀones
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
1393
Results and Discussion
both mononuclear and dinuclear coordination compounds
depending on the number of methylene units in the linker
between the sulfur atoms of the ligands. Thus, ligands 1
and 2 containing the twoꢀ or fourꢀcarbon bridge, respecꢀ
tively, form mononuclear complexes 12 and 13, whereas
ligands 3 and 9 containing the sixꢀcarbon bridge between
the sulfur atoms give dinuclear complexes 14 and 16, reꢀ
spectively (see Scheme 2).
The alkylation of potassium salts of thiohydantoins,
which were prepared by the treatment of the correspondꢀ
ing thiohydantoins with an ethanolic KOH solution,6 at
room temperature in DMF afforded 5ꢀ(2ꢀpyridylmethꢀ
ylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀones 1—9 (Scheme 1).
The IR spectra of complexes 10—16 show a shift of the
C=N absorption band compared to that observed in the
spectra of the starting ligands, so this confirms the inꢀ
volvement of the nitrogen atoms in the coordination of the
metal atom.
Scheme 1
The UVꢀVis spectra of coordination compounds 10—16
can be divided into three main types. The UVꢀVis specꢀ
trum of copper(II) compound 10 containing chloride anꢀ
ions has one broadened band at 380 nm (ε = 74000). Preꢀ
viously, we have shown12 that this spectral pattern is charꢀ
acteristic of the complexes of CuCl2 with 5ꢀ(2ꢀpyridylmeꢀ
thylidene)ꢀsubstituted 3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀones,
in which the copper atom is in a distorted tetrahedral
coordination environment. Based on these data, comꢀ
pound 10 was assigned the structure presented in Scheme 2
(the copper atom is in the nearly tetrahedral ligand enviꢀ
ronment and is bound to two nitrogen atoms and two
chloride anions).
DMF
The UVꢀVis spectrum of copper(II) complex 11 conꢀ
taining perchlorate anions substantially differs from the
spectrum of complex 10. Thus, the spectrum of 11 shows
peaks at 345 (ε = 10800), 361 (ε = 11000), and 405 nm
(ε = 3800). This is the evidence that the coordination
mode of the copper(II) ion in 11 differs from that observed
in the complexes containing chloride anions.
Comꢀ
pound
R
n
Yield
(%)
73
64
62
Comꢀ
pound
6
7
8
9
R
n
Yield
(%)
69
64
58
1
2
3
4
5
Ph
Ph
Ph
2
4
6
2
4
4ꢀBrC6H4
Me
6
2
4
6
Me
Me
4ꢀBrC6H4
4ꢀBrC6H4
67
71
67
The structure of compound 13 was established by Xꢀray
diffraction. The molecular structure of the [Cu(2)]+ catꢀ
ion is shown in Fig. 1, where selected bond lengths and
bond angles are also presented. Crystallographic characꢀ
teristics and the Xꢀray data collection and refinement staꢀ
tistics for compound 13 are given in Table 1. According to
the Xꢀray diffraction data, the copper atom in complex 13
is in a distorted tetrahedral coordination environment
formed by four nitrogen atoms of two imidazole rings and
two pyridine rings. The perchlorate anion is located in the
outer sphere of the complex and is not involved in the
coordination with the copper ion. In addition, the crystal
structure of complex 13 contains one ethanol molecule
and one acetonitrile molecule (these molecules are not
shown in Fig. 1).
It is possible that there are additional agostic C—H...Cu
interactions in complex 13; these interactions are indicatꢀ
ed by dashed lines (see Fig. 1); the Cu(1)...H(16B) and
Cu(1)...H(19B) distances are 2.30 and 2.36 Å, respectively.
Apparently, other complexes of this type of ligands
with copper(I) perchlorate (compounds 11 and 12) have
similar structures. This is evidenced by the virtually idenꢀ
The compositions of the compounds were confirmed
by elemental analysis, and the structures were proved by
NMR and IR spectroscopy. Ligands 1—3 and 9 were inꢀ
volved in the complexation with copper(I) and copper(II)
chlorides and perchlorates, because copper ions in copꢀ
perꢀcontaining enzymes can exist in different oxidaꢀ
tion states.
To prepare coordination compounds, we used the slow
diffusion of a solution of a metal salt into a solution of
a ligand. The structures and compositions of the resulting
complexes (Scheme 2) were determined by IR and UVꢀVis
spectroscopy and elemental analysis. The structure of comꢀ
plex 13 was established by Xꢀray diffraction.
Although an organic compound and a copper salt were
taken in a stoichiometric ratio (1 : 2) in all experiments,
the resulting complexes had different compositions and
contained the ligand and metal in a ratio of 1 : 2 or 1 : 1.
The dinuclear complexes were obtained in the reactions
with copper(II) chloride, whereas the reactions with
copper(II) perchlorate afforded mononuclear complexes.
By contrast, the reactions with copper(I) perchlorate gave

1394
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
Majouga et al.
Scheme 2
tical electronic absorption spectra of complexes 11—13.
In the UVꢀVis region of all three compounds, there
are bands at ~345 (ε = 140000), ~360 (ε = 138500), and
~400 nm (ε = 51500).
Dinuclear coordination compounds 14 and 16 were
assigned the structures containing two twoꢀcoordinate
copper(I) ions, as has been described for the deoxy form of
tyrosinase and its lowꢀmolecular analogs.13,14 The IR specꢀ
tra of complexes 14 and 16 show signals of only uncoordiꢀ
nated perchlorate ions at ~1100 cm–1, which indicates
that the ClO4– anions are not involved in the coordination
with the copper(I) ions. Alternatively, the structures of
compounds 14 and 16 can be described as complexes with
threeꢀcoordinate copper ions and the intramolecular
Cu—Cu bond by analogy with the published data15 (exꢀ
emplified by complex 16).
The molecular simulation showed that the N—Cu—N
fragment in molecules 14 and 16 may have a linear strucꢀ
ture characteristic of twoꢀcoordinate CuI complexes. Apꢀ
parently, in the crystal structure there are intraꢀ or interꢀ
molecular interactions between the copper atoms, resultꢀ
ing in that each metal atom is in a planar trigonal coordiꢀ
nation environment. However, in solution the interactions
between the copper atoms are evidently absent, as indicatꢀ

2ꢀPyridylmethylideneꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀones
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
1395
ed by the electrochemical data (see below), according to
which both copper ions in complex 14 are reduced simulꢀ
taneously at the same potential and, consequently, they
are not bound to each other. Apparently, the Cu—Cu bond
in solution is cleaved, and two CuI ions are coordinated by
the solvent (DMF) molecules.
Ligands 1—3 and the copperꢀcontaining complexes of
these ligands were studied by cyclic voltammetry (CV)
and rotating disk electrode (RDE) voltammetry in DMF
at glassyꢀcarbon (GC), Pt, and Au electrodes in the presꢀ
ence of a 0.1 M Bu4NClO4 solution as the supporting
electrolyte. The electrochemical oxidation and reduction
potentials measured with respect to Ag/AgCl/KCl(satur.)
are given in Table 2.
The reduction of ligands 1—3 (at a GC electrode) inꢀ
volves three steps, whereas the oxidation occurs in one
step (Fig. 2, Table 2). These ligands consist of two identiꢀ
cal fragments. Hence, each step of the redox process inꢀ
volves the twoꢀelectron reaction at two isolated parts of
the molecule. The semiempirical quantum chemical calꢀ
culations for 2ꢀmethylthioꢀ5ꢀ(pyridylmethylidene)ꢀ3,5ꢀ
dihydroꢀ4Hꢀimidazolꢀ4ꢀones performed previously16
have shown that both HOMO and LUMO of such moleꢀ
cules are located on the thiohydantoin moieties. The
orbital of the sulfur lone pair makes the major contriꢀ
bution to HOMO and, consequently, the oxidation ocꢀ
curs at the sulfur atoms, whereas LUMO is a crossꢀconjuꢀ
gated methylenehydantoin π system, which is reduced in
the first step of the electrochemical process.7 Apparently,
both the oxidation and reduction of ligands 1—3 ocꢀ
cur similarly.
C(31)
C(30)
C(14)
C(13)
C(12)
C(15)
C(18)
H(19B)
S(2)
C(17)
H(16B)
S(1)
C(32)
C(10)
C(16)
C(1)
C(19)
C(20)
N(4)
C(33)
C(34)
N(2)
C(11)
C(29)
N(5)
C(21)
O(2)
C(2)
N(3)
O(1)
C(3) N(1)
Cu(1)
C(5)
C(4)
C(22)
N(6)
C(9)
C(8)
C(28)
C(6)
C(27)
C(24)
C(26)
C(7)
C(25)
C(23)
Fig. 1. Molecular structure of the [Cu(2)]+ cation of complex 13.
The displacement ellipsoids are drawn at the 30% probabiꢀ
lity level. Selected bond lengths/Å: Cu(1)—N(1), 2.046(5);
Cu(1)—N(3), 2.032(5); Cu(1)—N(4), 2.020(5); Cu(1)—N(6),
2.077(5). Selected bond angles/deg: N(4)—Cu(1)—N(3),
111.5(2); N(1)—Cu(1)—N(4), 136.7(2); N(1)—Cu(1)—N(3),
97.0(2); N(4)—Cu(1)—N(6), 95.0(2); N(3)—Cu(1)—N(6),
109.3(2); N(1)—Cu(1)—N(6), 105.8(2).
Table 1. Crystallographic characteristics and the Xꢀray data colꢀ
lection and refinement statistics for compound 13
Parameter
[C34H28CuN6O2S2]+[ClO4]–
•CH3CN•0.5C2H5OH
•
Molecular weight
843.82
120(2)
0.71073
T/K
λ/Å
Crystal dimensions/mm
0.50×0.12×0.04,
darkꢀred plates
Monoclinic
P21/с
11.4485(16)
14.578(2)
23.61(4)
90.00
Compared to the cyclic voltammograms of the free
ligand, the cyclic voltammograms of the complexes of
ligand 1 with the CuII salts show two additional peaks in
Crystal system
Space group
a/Å
b/Å
c/Å
α/deg
I/μA
β/deg
99.389(3)
90.00
3891.1(10)
4
1.440
0.793
γ/deg
V/Å3
–20
0
Z
dcalc/g cm–3
μ/mm–1
F(000)
1740
θꢀScan range/deg
Ranges of indices
2.3—23.7
–14 ≤ h ≤ 13,
–17 ≤ k ≤ 16,
–29 ≤ l ≤ 29
7520/1938
20
40
Number of measured
/independent reflections
Number of refined parameters
Goodnessꢀofꢀfit on F2
R factors (based on
492
1.015
R1 = 0.0699, wR2 = 0.1499
1.0
0
–1.0
E/V
reflections with I > 2σ(I))
R factors
(based on all reflections)
Fig. 2. Cyclic voltammograms of ligand 1 (dashed line)
and complex 10 (solid line) (glassyꢀcarbon electrode, DMF,
5•10–4 mol L–1, Bu4NClO4).
R1 = 0.1580, wR2 = 0.2006

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
Majouga et al.
Table 2. Electrochemical reduction potentials (ERed) and oxidaꢀ
tion potentials (EOx) of ligands 1—3 and their complexes meaꢀ
sured by the CV method (Ep is the peak potential) and the
RDE method (E1/2 is the halfꢀwave potential) with respect to
Ag/AgCl/KCl(satur.) at a glassy carbon electrodeа
I/μA
–8
Red
Red
Ox
Ox
Comꢀ
pound
Ep
E1/2
Ep
E1/2
V
1
–1.19,
–1.76,
–2.06
–1.19,
–1.71,
–2.03
0.39/0.51b,
–0.85,
–1.14,
–1.71
–0.85,
0.99 sh,
–1.21,
–1.73,
–2.04
0.23/0.30b,
–0.85/0.14,
–1.22, –1.77,
–2.03
–0.82, –1.23, –0.72 (1)c
–1.72, –2.07
–0.75, –1.17, –0.69 (2),
–1.18 (2),
1.43
1.43
1.40 (2)
1.43 (2)
0
8
–1.76 (1.6),
–2.11 (1.8)
–1.17 (2),
–1.71 (2),
–2.03 (2)
0.42 (2)b,
–0.82 (2),
–1.14 (2),
–1.76
–0.78 (1),
–1.20 (2),
–1.68 (1.7),
–2.07
3
10
1.16,
1.48
1.22 (4),
1.51 (2)
16
11
12
0.38/0.27, 0.31 (1),
0
–1.0
–2.0 E/V
1.45
1.48
1.45 (2)
1.46 (2)
Fig. 3. Cyclic voltammograms of complexes 11 (solid line) and
12 (dashed line) (glassyꢀcarbon electrode, DMF, 15•10–4 mol L–1
Bu4NClO4).
,
0.30 (1)b,
–0.83 (1),
–1.71 (2)
electron Cu0
CuII transition giving rise to the startꢀ
ing complex. This is confirmed by the fact that the repeatꢀ
ed cathodic scan results in the reproduction of the voltamꢀ
mogram of the starting complex.
13
14
0.18/0.06, 0.16 (1)c
1.29
0.13/0.05
0.04 (2)
It should be noted that the experiments performed on
metal electrodes (to a lesser extent on a Pt electrode and to
a greater extent on an Au electrode) led apparently to the
disproportionation of the intermediate that is formed by
the oneꢀelectron reduction to give the starting complex
and a Cu0ꢀcontaining compound (Fig. 4, Table 2). For
–1.68,
–2.00
–1.16 (2),
–1.64 (1.7)
a The number of electrons transferred in each step, which was
determined by the RDE method (2800 rpm) by comparing with
the height of the oneꢀelectron oxidation wave of ferrocene, is
given in parentheses; the peak potentials on the reverse scans of
the cyclic voltammograms are given after the slash.
b The initial potential was 0.7 V.
c In the RDE experiments, the electrochemical processes are
complicated by the adsorption of the product formed. The elecꢀ
troreduction or electrooxidation occurs on the modified surface,
resulting in a decrease in the current. Because of this, it was
impossible to determine the number of transferred electrons for
subsequent peaks.
I/μA
–8
0
8
the cathodic scans at less negative potentials (Fig. 3,
Table 2) than the potential of the first peak of the free
ligand. The first quasiꢀreversible peak at anodic potentials
corresponds to the CuII → CuI transition, whereas the
second peak is assigned to the CuI → Cu0 transition. The
intermediates containing CuI and Cu0 are stable (at a GC
electrode). This is proved by the absence of the peak of
oxidative desorption of copper metal after the potential of
the second cathodic peak corresponding to the formation
of the Cu0ꢀcontaining intermediate. On the reverse scan
of the voltammograms, the reoxidation peak is observed at
Ep,a ≈ 0.4 V. Evidently, this peak is attributed to the twoꢀ
16
0
–1.0
–2.0
E/V
Fig. 4. Cyclic voltammogram of complex 10 (Au electrode,
DMF, 5•10–4 mol L–1, Bu4NClO4).

2ꢀPyridylmethylideneꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀones
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
1397
of the working electrodes was polished with an aluminum
oxide powder with a particle size smaller than 10 microns
(SIGMA—ALDRICH). The potential scan rates were 200
(CV method) and 20 mV s–1 (RDE method). The potentials are
given with iR compensation. The numbers of electrons transꢀ
ferred in the redox processes were determined by comparing the
limiting wave current in the RDE experiments with the oneꢀ
electron oxidation current of ferrocene taken at an equal conꢀ
centration.
All measurements were carried out under dry argon. The
samples were dissolved in a preꢀdeaerated solvent. Dimethylforꢀ
mamide (highꢀpurity grade) was purified by stirring over freshly
calcined K2CO3 for 4 days followed by the successive distillation
in vacuo first over P2O5 and then over anhydrous CuSO4.
Potassium salts of 5ꢀ[(Z)ꢀ2ꢀpyridylmethylidene]ꢀ2ꢀthioxoꢀ
3ꢀphenylimidazolꢀ4ꢀone, 3ꢀ(4ꢀbromophenyl)ꢀ5ꢀ[(Z)ꢀ2ꢀpyridylꢀ
methylidene]ꢀ2ꢀthioxoimidazolꢀ4ꢀone, and 3ꢀmethylꢀ5ꢀ[(Z)ꢀ2ꢀ
pyridylmethylidene]ꢀ2ꢀthioxoimidazolꢀ4ꢀone were synthesized
according to a known procedure.6
Synthesis of ligands 1—9 (general procedure). The correꢀ
sponding α,ωꢀdibromoalkane (0.5 equiv.) was added to a soluꢀ
tion of the potassium salts of 5ꢀ[(Z)ꢀ2ꢀpyridylmethylidene]ꢀ2ꢀ
thioxoꢀ3ꢀphenylimidazolꢀ4ꢀone, 3ꢀ(4ꢀbromophenyl)ꢀ5ꢀ[(Z)ꢀ2ꢀ
pyridylmethylidene]ꢀ2ꢀthioxoimidazolꢀ4ꢀone, or 3ꢀmethylꢀ5ꢀ
[(Z)ꢀ2ꢀpyridylmethylidene]ꢀ2ꢀthioxoimidazolꢀ4ꢀone in DMF
(20 mL) at room temperature. The reaction mixture was stirred
at room temperature for 2 h. Then water (50 mL) was added.
The white precipitate that formed was filtered off, successively
washed with water, ethanol, and diethyl ether, and dried in air.
(5Z,5´Z)ꢀ2,2´ꢀ(Ethaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone] (1).
Compound 1 was prepared in a yield of 0.23 g (73%), m.p. 260 °C,
from 5ꢀ[(Z)ꢀ2ꢀpyridylmethylidene]ꢀ2ꢀthioxoꢀ3ꢀphenyltetraꢀ
hydroꢀ4Hꢀimidazolꢀ4ꢀone (0.3 g, 0.001 mol) and 1,2ꢀdibromoꢀ
ethane (0.1 g, 0.5 mmol). 1H NMR (CDCl3), δ: 8.75 (d, 1 H,
αꢀHpy, J = 8.0 Hz); 8.66 (d, 1 H, β´ꢀHpy, J = 3.9 Hz); 7.81 (td, 1 H,
βꢀHpy, J1 = 7.8 Hz, J2 = 1.8 Hz); 7.42 (m, 3 H, HPh); 7.31 (m, 2 H,
HPh); 7.20 (m, 2 H, γꢀHpy, CH=); 3.43 (t, 2 H, SCH2,
J = 6.2 Hz). IR, ν/cm–1: 1710 (C=O), 1670 (C=N), 1640 (C=C).
Calculated (%): C, 65.31; H, 4.08; N, 14.29. C32H24N6O2S2.
Found (%): C, 65.28; H, 4.10; N, 14.11.
(5Z,5´Z)ꢀ2,2´ꢀ(Butaneꢀ1,4ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone] (2).
Compound 2 was prepared in a yield of 0.20 g (64%), m.p. 249 °C,
from 5ꢀ[(Z)ꢀ2ꢀpyridylmethylidene]ꢀ2ꢀthioxoꢀ3ꢀphenyltetraꢀ
hydroꢀ4Hꢀimidazolꢀ4ꢀone (0.3 g, 0.001 mol) and 1,2ꢀdibromoꢀ
butane (0.1 g, 0.5 mmol). 1H NMR (CDCl3), δ: 8.80 (d, 1 H,
αꢀHpy, J = 7.9 Hz); 8.67 (d, 1 H, β´ꢀHpy, J = 4.0 Hz); 7.65
(td, 1 H, βꢀHpy, J1 = 7.8 Hz, J2 = 1.7 Hz); 7.50 (m, 3 H, HPh);
7.34 (m, 2 H, HPh); 7.22 (s, 1 H, CH=); 7.19 (m, 1 H, γꢀHpy);
3.35 (t, 2 H, SCH2, J = 7.1 Hz); 1.86 (q, 2 H, CH2, J = 4.1 Hz).
IR, ν/cm–1: 1700 (C=O), 1670 (C=N), 1630 (C=C). Calculatꢀ
ed (%): C, 66.23; H, 4.55; N, 13.64. C34H28N6O2S2. Found (%):
C, 65.86; H, 4.07; N, 13.27.
example, this process for complex 10 is described by
the equation
I
II
2 Cu (1)Cl2
Cu (1)Cl2 + Cu0(1)Cl2.
The second cathodic peak corresponding to the
CuI → Cu0 transition is less intense.
The complexes of ligands 1—3 with CuI are initially
reduced at the metal atom at Ep,c ≈ –0.8 V to form the
stable intermediate containing Cu0. Their reduction curves
are similar to the corresponding curves for the CuII comꢀ
plexes, except for the absence of the CuII
CuI peak.
Actually, the voltammogram recorded during the repeated
cathodic scan is completely analogous to that observed for
the CuII complexes.
It should be noted that ligands 1—3 apparently well
stabilize the complexes with copper in the low oxidation
state, and the destruction of the complexes does not occur
up to the potential Ep,c = –2.0 V, which is evident from
the absence of the peak of oxidative desorption of copper
metal and the absence of a black metal deposit on the
electrode surface. After the peaks corresponding to the
reduction of copper ions, the cyclic voltammograms of all
the complexes under consideration show cathodic reducꢀ
tion peaks of the ligand fragments of the molecules. The
length of the polymethylene bridge in the ligand has no
substantial effect on the redox properties of both the ligands
and the complexes.
In dinuclear complexes 10 and 14, both copper ions
are reduced simultaneously at the same potential accomꢀ
panied by the twoꢀelectron transfer. This is evidence
that both copper ions in these complexes are not bound
to each other.
In conclusion, we synthesized new organic ligands of
the 5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ
4ꢀone series, which allows the preparation of both monoꢀ
and dinuclear metal complexes. Based on these ligands,
we synthesized coordination compounds with copper(I)
and copper(II) salts. The investigations of the catalytic
activity of these complexes in oxidation reactions are curꢀ
rently underway.
Experimental
The 1H NMR spectra were recorded on a BrukerꢀAvance
instrument operating at 400 MHz. The IR spectra were meaꢀ
sured on a URꢀ20 instrument (in Nujol mulls) and on a Terꢀ
moNicolet IR200 Fourierꢀtransform instrument. The UVꢀVis
spectra were recorded on a Perkin—Elmer λꢀ25 instrument.
Electrochemical studies were carried out on a PIꢀ50ꢀ1.1 poꢀ
tentiostat equipped with a PRꢀ8 programmer. Glassyꢀcarbon
(d = 2 mm), platinum (d = 3 mm), and gold (d = 2 mm) disks
were used as the working electrodes; a 0.1 M Bu4NClO4 soꢀ
lution in DMF served as the supporting electrolyte;
Ag/AgCl/KCl(satur.) was used as the reference electrode; a platꢀ
inum plate was used as the auxiliary electrode. The surface
(5Z,5´Z)ꢀ2,2´ꢀ(Hexaneꢀ1,6ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone] (3).
Compound 3 was prepared in a yield of 0.19 g (62%), m.p. 240 °C,
from 5ꢀ[(Z)ꢀ2ꢀpyridylmethylidene]ꢀ2ꢀthioxoꢀ3ꢀphenyltetraꢀ
hydroꢀ4Hꢀimidazolꢀ4ꢀone (0.3 g, 0.001 mol) and 1,6ꢀdibromoꢀ
1
hexane (0.13 g, 0.5 mmol). H NMR (CDCl3), δ: 8.77 (d, 1 H,
αꢀHpy, J = 7.5 Hz); 8.54 (d, 1 H, β´ꢀHpy, J = 3.9 Hz); 7.70

1398
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
Majouga et al.
(td, 1 H, βꢀHpy, J1 = 7.5 Hz, J2 = 1.8 Hz); 7.44 (m, 3 H, HPh);
7.30 (m, 2 H, HPh); 7.17 (s, 1 H, CH=); 7.13 (m, 1 H, γꢀHpy);
3.32 (t, 2 H, SCH2, J = 6.9 Hz); 1.90 and 1.57 (both q, 2 H each,
CH2, J = 6.9 Hz). IR, ν/cm–1: 1715 (C=O), 1665 (C=N),
1600 (C=C). Calculated (%): C, 67.06; H, 5.00; N, 13.03.
C36H32N6O2S2. Found (%): C, 66.71; H, 5.04; N, 12.65.
(5Z,5´Z)ꢀ2,2´ꢀ(Ethaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[3ꢀ(4ꢀbroꢀ
mophenyl)ꢀ5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀ
one] (4). Compound 4 was prepared in a yield of 0.38 g (67%),
m.p. 198 °C, from 3ꢀ(4ꢀbromophenyl)ꢀ5ꢀ[(Z)ꢀ2ꢀpyridylmethylꢀ
idene]ꢀ2ꢀthioxotetrahydroꢀ4Hꢀimidazolꢀ4ꢀone (0.3 g, 0.8 mmol)
and 1,2ꢀdibromoethane (0.07 g, 0.4 mmol). 1H NMR (CDCl3),
δ: 8.87 (d, 1 H, Hpy, J = 7.6 Hz); 8.77 (d, 1 H, Hpy, J = 4.2 Hz);
ylidene]ꢀ2ꢀthioxotetrahydroꢀ4Hꢀimidazolꢀ4ꢀone (0.22 g, 0.86
mmol) and 1,4ꢀdibromobutane (0.092 g, 0.43 mmol). 1H NMR
(CDCl3), δ: 8.75 (d, 1 H, αꢀHpy, J = 8.0 Hz); 8.65 (d, 1 H,
β´ꢀHpy, J = 3.9 Hz); 7.77 (td, 1 H, βꢀHpy, J1 = 8.0 Hz, J2 = 2.0 Hz);
7.23 (s, 1 H, CH=); 7.03 (dd, 1 H, γꢀHpy, J1 = 7.6 Hz, J2 = 1.3 Hz);
3.50 (t, 2 H, SCH2, J = 11.9 Hz); 3.08 (s, 3 H, NCH3); 2.10
(q, 2 H, CH2, J = 7.5 Hz). IR, ν/cm–1: 1700 (C=O), 1670 (C=N),
1630 (C=C). Calculated (%): C, 53.53; H, 4.88; N, 17.07.
C24H24N6O2S2. Found (%): C, 58.13; H, 4.95; N, 17.51.
(5Z,5´Z)ꢀ2,2´ꢀ(Hexaneꢀ1,6ꢀdiyldisulfanyldiyl)bis[3ꢀmethylꢀ
5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone] (9).
Compound 9 was prepared in a yield of 0.18 g (71%), m.p. 205 °C,
from the potassium salt of 3ꢀmethylꢀ5ꢀ[(Z)ꢀ2ꢀpyridylmethylꢀ
idene]ꢀ2ꢀthioxotetrahydroꢀ4Hꢀimidazolꢀ4ꢀone (0.22 g, 0.86 mmol)
and 1,6ꢀdibromohexane (0.10 g, 0.43 mmol). 1H NMR (CDCl3),
7.93 (td, 1 H, H´py, J1 = 7.5 Hz, J2 = 0.9 Hz); 7.61 (d, 2 H, HAr
,
J = 7.9 Hz); 7.33 (m, 4 H, HAr, Hpy, CH=); 3.18 (t, 2 H, SCH2,
J = 8.8 Hz). IR, ν/cm–1: 1700 (C=O), 1660 (C=N), 1600 (C=C).
Calculated (%): C, 51.47; H, 2.95; N, 11.26. C32H22Br2N6O2S2.
Found (%): C, 51.191; H, 3.18; N, 11.76.
(5Z,5´Z)ꢀ2,2´ꢀ(Butaneꢀ1,4ꢀdiyldisulfanyldiyl)bis[3ꢀ(4ꢀbroꢀ
mophenyl)ꢀ5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀ
one] (5). Compound 5 was prepared in a yield of 0.21 g (71%),
m.p. 112 °C, from 3ꢀ(4ꢀbromophenyl)ꢀ5ꢀ[(Z)ꢀ2ꢀpyridylmethylꢀ
idene]ꢀ2ꢀthioxotetrahydroꢀ4Hꢀimidazolꢀ4ꢀone (0.3 g, 0.8 mmol)
and 1,4ꢀdibromobutane (0.085 g, 0.4 mmol). 1H NMR (CDCl3),
δ: 8.88 (d, 1 H, Hpy, J = 8.4 Hz); 8.70 (d, 1 H, Hpy, J = 6.0 Hz);
δ: 8.84 (d, 1 H, αꢀHpy, J = 8.0 Hz); 8.70 (d, 1 H, β´ꢀHpy
,
J = 3.9 Hz); 7.69 (td, 1 H, βꢀHpy, J1 = 7.8 Hz, J2 = 1.4 Hz); 7.20
(dd, 1 H, γꢀHpy, J1 = 7.5 Hz, J2 = 1.0 Hz); 7.18 (s, 1 H, CH=);
3.40 (t, 2 H, SCH2, J = 6.7 Hz); 3.20 (s, 3 H, NCH3); 1.95
(q, 2 H, CH2, J = 7.4 Hz); 1.60 (m, 2 H, CH2). IR, ν/cm–1: 1720
(C=O), 1645 (C=N), 1590 (C=C). Calculated (%): C, 60.00;
H, 5.38; N, 16.15. C26H28N6O2S2. Found (%): C, 61.19; H, 5.29;
N, 15.88.
Synthesis of coordination compounds (general procedure).
Ethanol (3 mL) was added to a solution of ligand 1—3 or 9
(0.085 mmol) in dichloromethane (2—3 mL) until the layers
were separated. Then a solution of the metal salt (0.17 mmol) in
ethanol (2—3 mL) was slowly added. The vessel with the reacꢀ
tion mixture was tightly closed and kept for 2—3 days until
a precipitate was obtained. The powders of the complexes were
filtered off and dried in air.
7.81 (td, 1 H, H´py, J1 = 7.7 Hz, J2 = 1.7 Hz); 7.60 (d, 2 H, HAr
,
J = 8.1 Hz); 7.17 (m, 4 H, HAr, Hpy, CH=); 3.38 (t, 2 H, SCH2,
J = 9.2 Hz); 2.21 (q, 2 H, CH2, J = 6.4 Hz). IR, ν/cm–1: 1710
(C=O), 1650 (C=N), 1615 (C=C). Calculated (%): C, 52.71;
H, 3.36; N, 10.85. C34H26Br2N6O2S2. Found (%): C, 52.23;
H, 3.49; N, 11.60.
(5Z,5´Z)ꢀ2,2´ꢀ(Hexaneꢀ1,6ꢀdiyldisulfanyldiyl)bis[3ꢀ(4ꢀbroꢀ
mophenyl)ꢀ5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀ
one] (6). Compound 6 was prepared in a yield of 0.21 g (69%),
m.p. 108 °C, from 3ꢀ(4ꢀbromophenyl)ꢀ5ꢀ[(Z)ꢀ2ꢀpyridylmethylꢀ
idene]ꢀ2ꢀthioxotetrahydroꢀ4Hꢀimidazolꢀ4ꢀone (0.3 g, 0.8 mmol)
and 1,6ꢀdibromohexane (0.96 g, 0.4 mmol). 1H NMR (CDCl3),
δ: 8.90 (d, 1 H, Hpy, J = 8.0 Hz); 8.75 (d, 1 H, Hpy, J = 4.8 Hz);
(5Z,5´Z)ꢀ2,2´ꢀ(Ethaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone]ꢀ
dicopper(II) (10) tetrachloride, dihydrate. Darkꢀbrown complex
10 was prepared from ligand 1 (0.05 g, 0.085 mmol) and
CuCl2•2H2O (0.03 g, 0.17 mmol). The yield was 0.045 g (63%),
m.p. 257 °C. IR, ν/cm–1: 1750 (C=O), 1635 (C=N), 1595 (C=C).
Calculated (%): C, 44.76; H, 2.80; N, 9.76. C32H24Cl4Cu2N6O2S2.
Found (%): C, 44.47; H, 3.02; N, 9.56.
(5Z,5´Z)ꢀ2,2´ꢀ(Ethaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone]ꢀ
copper(II) diperchlorate (11). Brown complex 11 was prepared
from ligand 1 (0.05 g, 0.085 mmol) and Cu(ClO4)2•6H2O (0.03 g,
0.085 mmol). The yield was 0.039 g (52%), m.p. 285 °C.
IR, ν/cm–1: 1755 (C=O), 1630 (C=N), 1590 (C=C), 1100
(ClO4). Calculated (%): C, 45.12; H, 2.82; N, 9.87; S, 7.52.
C32H24Cl4Cu2N6O8S2. Found (%): C, 45.89; H, 3.13; N, 10.61;
S, 8.29.
(5Z,5´Z)ꢀ2,2´ꢀ(Ethaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone]ꢀ
copper(I) perchlorate (12). Darkꢀbrown complex 12 was prepared
from ligand 1 (0.05 g, 0.085 mmol) and [Cu(CH3CN)4]ClO4
(0.056 g, 0.085 mmol). The yield was 0.02 g (35%), m.p. 135 °C.
IR, ν/cm–1: 1725 (C=O), 1640 (C=N), 1600 (C=C), 1100 (ClO4).
Calculated (%): C, 51.09; H, 3.19; N, 11.17. C32H24ClCuN6O6S2.
Found (%): C, 51.02; H, 3.51; N, 10.78.
(5Z,5´Z)ꢀ2,2´ꢀ(Butaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone]ꢀ
copper(I) perchlorate (13). Blackꢀred complex 13 was prepared
from ligand 2 (0.05 g, 0.081 mmol) and [Cu(CH3CN)4]ClO4
(0.027 g, 0.081 mmol). The yield was 0.034 g (46%), m.p. 232 °C.
7.76 (td, 1 H, Hpy, J1 = 8.8 Hz, J2 = 2.5 Hz); 7.66 (d, 2 H, HAr
J = 8.7 Hz); 7.26 (m, 4 H, HAr, Hpy, CH=); 3.30 (t, 2 H, SCH2,
J = 7.5 Hz); 1.86 and 1.54 (both m, 2 H each, CH2). IR, ν/cm–1
,
:
1705 (C=O), 1640 (C=N), 1600 (C=C). Calculated (%): C, 53.87;
H, 3.74; N, 10.47. C36H30Br2N6O2S2. Found (%): C, 53.90;
H, 3.80; N, 11.04.
(5Z,5´Z)ꢀ2,2´ꢀ(Ethaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[3ꢀmethylꢀ
5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone] (7).
Compound 7 was prepared in a yield of 0.16 g (64%), m.p. 215 °C,
from the potassium salt of 3ꢀmethylꢀ5ꢀ[(Z)ꢀ2ꢀpyridylmethylꢀ
idene]ꢀ2ꢀthioxotetrahydroꢀ4Hꢀimidazolꢀ4ꢀone (0.22 g, 0.86
mmol) and 1,2ꢀdibromoethane (0.08 g, 0.43 mmol). 1H NMR
(CDCl3), δ: 8.78 (d, 1 H, αꢀHpy, J = 7.9 Hz); 8.64 (d, 1 H,
β´ꢀHpy, J = 4.0 Hz); 7.59 (td, 1 H, βꢀHpy, J1 = 7.5 Hz, J2 = 1.6 Hz);
7.18 (s, 1 H, CH=); 7.15 (dd, 1 H, γꢀHpy, J1 = 7.5 Hz, J2 = 0.9 Hz);
3.40 (t, 2 H, SCH2, J = 7.9 Hz); 3.10 (s, 3 H, NCH3). IR, ν/cm–1
:
1705 (C=O), 1630 (C=N), 1590 (C=C). Calculated (%): C, 56.90;
H, 5.31; N, 18.10. C22H20N6O2S2. Found (%): C, 57.12; H, 4.45;
N, 19.06.
(5Z,5´Z)ꢀ2,2´ꢀ(Butaneꢀ1,4ꢀdiyldisulfanyldiyl)bis[3ꢀmethylꢀ
5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone] (8).
Compound 8 was prepared in a yield of 0.16 g (67%), m.p. 220 °C,
from the potassium salt of 3ꢀmethylꢀ5ꢀ[(Z)ꢀ2ꢀpyridylmethꢀ

2ꢀPyridylmethylideneꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀones
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
1399
Calculated (%): C, 52.63; H, 4.27; N, 11.31. C38H37ClCuN7O7S2.
Found (%): C, 52.86; H, 4.22; N, 11.38.
2. E. I. Solomon, R. Arangi, J. S. Woertink, A. J. Augustine,
J. Yoon, S. Ghosh, Acc. Chem. Res., 2007, 40, 581.
3. P. Gamez, P. G. Aubel, W. L. Driessen, J. Reedijk, Chem.
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4. L. M. Mirica, X. Ottenwaelder, D. Stack, Chem. Rev., 2004,
104, 1013.
5. I. S. MacPherson, M. E. Murphy, Cell. Mol. Life Sci., 2007, 1.
6. A. G. Majouga, E. K. Beloglazkina, S. Z. Vatsadze, N. A.
Frolova, N. V. Zyk, Izv. Akad. Nauk, Ser. Khim., 2004, 2734
[Russ. Chem. Bull., Int. Ed., 2004, 53, 2850].
7. E. K. Beloglazkina, S. Z. Vatsadze, A. G. Majouga, N. A.
Frolova, R. B. Romashkina, N. V. Zyk, A. A. Moiseeva,
K. P. Butin, Izv. Akad. Nauk, Ser. Khim., 2005, 2679 [Russ.
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8. E. K. Beloglazkina, A. G. Majouga, I. V. Yudin, N. V. Zyk,
A. A. Moiseeva, K. P. Butin, Izv. Akad. Nauk, Ser. Khim.,
2005, 2099 [Russ. Chem. Bull., Int. Ed., 2005, 54, 2163].
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Mironov, N. V. Zyk, Mendeleev Commun., 2007, 17, 77.
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Zyk, Tetrahedron Lett., 2006, 47, 2957.
11. D.ꢀH. Lee, L. Q. Hatcher, M. A. Vance, R. Sarangi, A. E.
Milligan, A. A. N. Sarjeant, C. D. Incarvito, A. L. Rheinꢀ
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Moiseeva, K. P. Butin, N. V. Zyk, Mendeleev Commun., 2004,
14, 115.
13. T. N. Sorrel, Tetrahedron, 1989, 45, 3.
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15. N. N. Murthy, M. MahroofꢀTahir, K. D. Karlin, Inorg.
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16. M. J. S. Dewar, E. F. Healy, J. J. P. Stewart, J. Comput.
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17. G. M. Sheldrick, SHELXSꢀ97; Acta. Crystallogr., Sect. A,
1990, 46, 467.
18. G. M. Sheldrick, SHELXLꢀ97. Program for the Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
(5Z,5´Z)ꢀ2,2´ꢀ(Hexaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[5ꢀ(2ꢀpyꢀ
ridylmethylidene)ꢀ3ꢀphenylꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone]ꢀ
dicopper(I) diperchlorate (14). Darkꢀbrown complex 14 was preꢀ
pared from ligand 3 (0.05 g, 0.08 mmol) and [Cu(CH3CN)4]ClO4
(0.052 g, 0.16 mmol). The yield was 0.025 g (48%), m.p. 212 °C.
IR, ν/cm–1: 1755 (C=O), 1630 (C=N), 1590 (C=C), 1100
(ClO4). Calculated (%): C, 46.51; H, 3.88; N, 12.33; S, 5.64.
C44H44Cl2Cu2N10O10S2. Found (%): C, 47.24; H, 4.09; N, 12.18;
S, 5.65.
(5Z,5´Z)ꢀ2,2´ꢀ(Hexaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[3ꢀmethylꢀ
5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone]diꢀ
copper(II) tetrachloride (15). Black complex 15 was prepared
from ligand 9 (0.05 g, 0.096 mmol) and CuCl2•2H2O (0.093 g,
0.19 mmol). The yield was 0.045 g (60%), m.p. 147 °C. IR,
ν/cm–1: 1740 (C=O), 1645 (C=N), 1600 (C=C). Calculated (%):
C, 39.49; H, 3.54; N, 10.63. C26H28Cl4Cu2N6O2S2. Found (%):
C, 39.76; H, 3.31; N, 10.78.
(5Z,5´Z)ꢀ2,2´ꢀ(Hexaneꢀ1,2ꢀdiyldisulfanyldiyl)bis[3ꢀmethylꢀ
5ꢀ(2ꢀpyridylmethylidene)ꢀ3,5ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀone]diꢀ
copper(I) diperchlorate (16). Darkꢀred complex 16 was prepared
from ligand 9 (0.05 g, 0.096 mmol) and [Cu(CH3CN)4]ClO4
(0.093 g, 0.19 mmol). The yield was 0.028 g (45%), m.p. 163 °C.
IR, ν/cm–1: 1745 (C=O), 1640 (C=N), 1595 (C=C), 1105
(ClO4). Calculated (%): C, 36.84; H, 3.31; N, 9.92.
C26H28Cl2Cu2N6O2S2. Found (%): C, 36.70; H, 3.70; N, 10.85.
Xꢀray diffraction study was carried out on a Bruker Smart
1000 CCD Area Detector singleꢀcrystal automatic diffractometer
(graphite monochromator, λ(MoꢀKα) = 0.71073 Å, ωꢀscanning
technique). The crystal structure was solved by direct methods17
and refined by the fullꢀmatrix leastꢀsquares method based on F2
with anisotropic displacement parameters for all nonhydrogen
atoms.18 All hydrogen atoms were located in difference electron
density maps and refined isotropically. Single crystals of comꢀ
pound 13 suitable for Xꢀray diffraction were grown from a 1 : 1
MeCN—EtOH mixture. The low quality of the experimental data
is apparently attributed to the poor quality of the single crystal.
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 07ꢀ03ꢀ00584ꢀa)
and the Russian Science Support Foundation.
References
1. I. A. Koval, P. Gamez, C. Belle, K. Semeczi, J. Reedijk,
Chem. Soc. Rev., 2006, 35, 814.
Received September 12, 2008;
in revised form April 9, 2009