Magnetoactive binuclear copper(II) complexes based on β- aminovinylimines

Article abstract of DOI:10.1134/S1070328406040105

β-Aminovinylimines containing bulky substituents at the donor nitrogen atoms and copper(II) chelates based on them were synthesized. The compounds were studied by single crystal and powder X-ray diffraction, EXAFS, NMR, EPR, and UV/Vis spectroscopy, and magnetochemistry. The complexes with halide bridges exhibit a ferromagnetic type of spin-spin interaction. The metal chelate containing a phenyl substituent in the γ-position of the aminovinylimino ligand absorbs atmospheric oxygen in a methylene dichloride solution, which gives rise to a dimer with oxygen bridges exhibiting an antiferromagnetic type of spin-spin interaction. Pleiades Publishing, Inc., 2006.

Full text of DOI:10.1134/S1070328406040105

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2006, Vol. 32, No. 4, pp. 287–296. © Pleiades Publishing, Inc., 2006.
Original Russian Text © A.I. Uraev, V.N. Ikorskii, M.P. Bubnov, K.A. Lysenko, V.G. Vlasenko, I.G. Borodkina, G.S. Borodkin, D.A. Garnovskii, A.D. Garnovskii, 2006, published
in Koordinatsionnaya Khimiya, 2006, Vol. 32, No. 4, pp. 299–308.
Magnetoactive Binuclear Copper(II) Complexes Based
on b-Aminovinylimines
A. I. Uraev*, V. N. Ikorskii**, M. P. Bubnov***, K. A. Lysenko****, V. G. Vlasenko*****,
I. G. Borodkina*, G. S. Borodkin*, D. A. Garnovskii******, and A. D. Garnovskii*
* Institute of Physical and Organic Chemistry, Rostov State University, pr. Stachki 194/3, Rostov-on-Don, 344104 Russia
** International Tomography Center, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
*** Institute of Organometallic Chemistry, Russian Academy of Sciences, ul. Tropinina 49, Nizhni Novgorod, 603600 Russia
**** Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 119991 Russia
***** Research Institute of Physics, Rostov State University, pr. Stachki 194, Rostov-on-Don, 344104 Russia
****** Southern Scientific Center, Russian Academy of Sciences, Rostov-on-Don, Russia
Received June 14, 2005
Abstract—β-Aminovinylimines containing bulky substituents at the donor nitrogen atoms and copper(II) che-
lates based on them were synthesized. The compounds were studied by single crystal and powder X-ray dif-
fraction, EXAFS, NMR, EPR, and UV/Vis spectroscopy, and magnetochemistry. The complexes with halide
bridges exhibit a ferromagnetic type of spin–spin interaction. The metal chelate containing a phenyl substituent
in the γ-position of the aminovinylimino ligand absorbs atmospheric oxygen in a methylene dichloride solution,
which gives rise to a dimer with oxygen bridges exhibiting an antiferromagnetic type of spin–spin interaction.
DOI: 10.1134/S1070328406040105
In recent years considerable attention has been plexes with different structures of the coordination
devoted to magnetoactive metal complexes having a
substantial potential as multi-purpose functional mate-
rials [1–9]. Among these, coordination compounds of
Schiff’s bases and their derivatives are widely encoun-
tered [10–17].
Metal chelates of bis(nitrogen) analogs of Schiffs
bases, β-aminovinylimines, may be promising as ferro-
magnetic complexes [8–18]. By varying substituents in
polyhedron and, as a consequence, different physico-
chemical properties. In recent years, this compounds
have attracted enhanced attention of a number of world
leading schools of chemistry [19–26].
The purpose of this work is to synthesize and study
the structure and magnetic properties of β-aminovi-
nyliminate complexes using ligand systems I and II and
these ligands, one can obtain a broad range of com- copper metal chelates III–V as examples.
R
H
R
R
R
N
N
N
N
Cl
Cl
R1
O2N
Cu
N
Cu
NO2
N
R
R
I, II
III
R = 2,6-(i-Pr)2C6H4
R = 2,6-(i-Pr)2C6H4
R1 = NO2 (I), Ph (II)
287

288
URAEV et al.
R
R
R
R
N
N
N
N
Cl
Cl
=
Ph
Cu Cl
Ph
Cu
N
Cu
Ph
Ph
Cu Cl
N
R
N
N
R
R
R
n
IV‡,b
n = 1–2
IVa
n = 1
IVb
n = 2
R = 2,6-(i-Pr)2C6H4
R
H
N
Ph
H
Cl
R
O
Cu O
Cl
Cu
N
N
R
H
Ph
N
H
R
V
R = 2,6-(i-Pr)2C6H4
EXPERIMENTAL
γ = 90°, V = 2820.6(14) Å3, ρ(calcd) = 1.099 g cm–3,
space group P21/c, Z = 4. A total of 11703 reflections
were measured, and 5634 observed reflections (Rint
0.0488) were used in further calculations.
X-Ray diffraction of compound II was performed
on a Smart 1000 CCD automated diffractometer at
293 K (åÓKα radiation, graphite monochromator,
ω-scan mode, 2θmax = 57°).
At 293 K, the crystals are monoclinic a = 13.029(4),
b = 11.159(3), c = 19.400(5) Å, α = 90°, β = 90.080(8)°,
=
The structure was solved by the direct method and
refined by the full-matrix least-squares method in the
anisotropic and isotropic approximations for F2. The
hydrogen atoms were located in the difference electron
density syntheses and refined by the riding model. The
final R-factors were wR2 = 0.1630, GOOF = 1.061 for
the reflections (R1 = 0.0660 was calculated based on
4053 reflections with I > 2σ(I)); the calculations were
carried out with the SHELXTL-Plus program package
[27]. The main interatomic distances and bond angles
are presented in Table 1.
Table 1. Selected bond lengths and bond angles in com-
pound II
Bond
d, Å
Bond
d, Å
N(1)–C(1)
N(1)–C(10)
N(2)–C(3)
N(2)–C(22)
1.330(3) C(1)–C(2)
1.430(3) C(2)–C(3)
1.309(3) C(2)–C(4)
1.426(3) C(4)–C(9)
1.403(4)
1.410(4)
1.479(3)
1.390(4)
X-Ray diffraction spectra were obtained on a
DRON-3M diffractometer with a GP-13 attachment for
powder diffraction and a BSV21-Cu X-ray tube (U= 35 kV,
I = 25 mA). The CuKα , α radiation (λ = 1.5406 Å) was
1
2
isolated from the total spectrum by means of a nickel
β-filter. The spectrum was recorded using a scintilla-
tion counter in the 2θ range from 5° to 60° with a step
of 0.02° and a 4 s exposure at a point.
Angle
ω, deg
Angle
ω, deg
X-Ray Cu K-edge EXAFS spectra of metal che-
lates were recorded in the absorption mode on a
EXAFS spectrometer at the Siberian Synchrotron Cen-
ter (Novosibirsk). The electron beam energy used as a
source of X-ray synchrotron radiation was 2 GeV at an
average current of 80 mA. X-radiation was monochro-
matized by a double-crystal Si(111) monochromator.
The intensities of the incident radiation and radiation
that has passed through the sample were recorded using
argon-filled ionization chambers.
C(1)N(1)C(10)
C(3)N(2)C(22)
N(1)C(1)C(2)
C(1)C(2)C(3)
C(1)C(2)C(4)
122.8(2) C(3)C(2)C(4)
120.6(2) N(2)C(3)C(2)
124.0(2) C(9)C(4)C(5)
121.3(2) C(9)C(4)C(2)
119.6(2) C(5)C(4)C(2)
119.1(2)
123.3(3)
117.2(2)
121.5(2)
121.3(2)
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

MAGNETOACTIVE BINUCLEAR COPPER(II) COMPLEXES
289
The standard procedures for the background isola- dimer–dimer exchange interactions (zJ'), the theoreti-
tion, normalization to the K-edge step, and isolation of
the atomic absorption µ0 were followed by Fourier
analysis of the resulting EXAFS (χ)-spectrum (EXAFS
or the far fine structure of the X-ray absorption spectra)
for each sample in the 2.8 to 15 Å–1 range of the photo-
electron wave vectors with the weighing function k2.
The Fourier transform modulus (FTM) obtained after
the Fourier transform of the EXAFS spectra reflects the
radial distribution function of the neighboring atoms
around the absorbing Cu atom. Exact structural param-
eters of the nearest environment of Cu were determined
by non-linear approximation of the parameters of the
corresponding coordination spheres through compari-
son of the computed EXAFS signal for the standards
compound with that isolated by the FTM. The approx-
imation quality function (Q), which was minimized
when finding the structural parameters of the nearest
environment of Cu atom, was calculated from the for-
mula
cal curves were determined by the relation
χ = χCu–Cu/[1 – (2zJ'/Ng2β2)χCu–Cu],
where χCu–Cu is the Bleany–Bauers magnetic suscepti-
bility of the dimer, g is the Cu(II) g-factor, β is the Bohr
magneton.
β-Aminovinylimines I, II and complexes III–V
based on them were synthesized by published proce-
dures [28–30].
2-(2,6-Diisopropylphenyl)amino-4-(2,6-diisoprop-
ylphenyl)imino-3-nitro-2-pentene (I) was prepared
by a reported method [28]. 2,6-Diisopropylaniline
hydrochloride (4.26 g, 0.02 mol) was added to a water–
ethanol solution of the sodium salt of nitromalonodial-
dehyde (1.39 g, 0.01 mol). The mixture was refluxed
for 5 h . After cooling, a solution of NaHCO3was added
to the reaction mixture up to pH 7–8. The precipitate
was filtered off, washed with water and small portions
of ethanol, and recrystallized from isopropyl alcohol.
The yield of product I formed as yellow crystals was
75–78%.
[kχexp(k) – kχth(k)]2
∑
---------------------------------------------------------
Q(%) =
.
[kχexp(k)]2
∑
1ç NMR spectra were recorded on a Varian
UNITY-300 spectrometer (300 MHz) in CDCl3 relative
to the residual proton signal of the deuterated solvent
(7.24 ppm).
For C27H37N3O2
anal. calcd. (%):
Found (%):
C, 74.45;
C, 74.22;
H, 8.56;
H, 8.23;
N, 9.65.
N, 9.44.
The EPR spectra were measured on a Bruker
ER200D-SRC instrument with a double ER 4102 reso-
nator and a ER 4111 VT temperature unit. Diphenylpi-
crylhydrazine (DPPH, g = 2.0037) was used as the ref-
erence to determine the g-factor.
1ç NMR (CDCl3, δ, ppm): 1.2 (d, 24H, 8CH3,
3JCH –CH = 6.9 Hz); 3.05 (hept, 4H, 4ëç–(ëç3)2,
3
3JCH–CH = 6.9 Hz); 7.16–7.26 (m, 6H, 2ë6ç3); 8.74 (d,
The diffuse reflection spectra (DRS) of solid sam-
ples and electronic absorption (UV/Vis) spectra of
solutions of the compounds under study in methylene
dichloride were measured on a Specord M400 instru-
ment.
3
2H, 2CH–NH, 3JCH–NH = 4 Hz); 12.79 (br.s, 1H, NH).
Synthesis of 1-(2,6-diisopropylphenyl)amino-3-
(2,6-diisopropylphenyl)imino-2-phenyl-1-propene
(II). An ethanol solution of KOH (0.336, 0.006 mol)
was added to a hot ethanol solution of the pechlorate
salt of the dimethylamine derivative of phenylmalono-
dialdehyde (1.51 g, 0.005 mol). The mixture was
refluxed for 15 min. After cooling, the solution was fil-
tered, di(isopropyl)aniline (1.77 g, 0.001 mol) in
butanol was added to the filtrate, and 12 M HCl
(1 equiv) was added dropwise. Then the reaction mix-
ture was refluxed for 10–12 h, excess butanol was evap-
orated, and the mixture was left overnight. The result-
ing mixture was neutralized with NaHCO3 and
extracted with chloroform. The chloroform extract was
dried for 12 h over MgSO4 and filtered. Chloroform
The magnetic properties of the crystalline phase
of the complexes were measured using a MPMS-5S
SQUID Quantum Design magnetometer in the temper-
ature range 2–300 K and in a 5 kOe magnetic field. No
dependence of the magnetic susceptibility on the mag-
netic field has been detected. The effective magnetic
moments were calculated from the formula
µeff(T) = 8χT,
where χ is the molar paramagnetic susceptibility cor-
rected for the diamagnetic contribution. When simulat-
ing the experimental plots with allowance for the was evaporated in a vacuum to give an oily product,
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

290
URAEV et al.
which was recrystallized from methanol. The yield was
55–60%.
X-Ray diffraction data for chelate V were reported
in [30].
For C33H42N2
RESULTS AND DISCUSSION
anal. calcd. (%):
Found (%):
C, 84.93; H, 9.07;
C, 84.75; H, 8.89;
N, 6.00.
N, 5.76.
The structures of ligands I and II in a CDCl3 solu-
1
tion were studied by NMR. The H NMR spectra of
compounds I and II exhibit broadened signals of the
NH-group protons (δ 12.79 ppm (I), 12.06 ppm (II))
and the CH protons of the β-aminovinylimine ring
(8,74 ppm (I) and 7.71 ppm (II)). In the 1H NMR spec-
tra of compound I, the CH-group protons occur as a
doublet with the vicinal constant 3JCH–NH = 4 Hz due to
the spin–spin coupling between the CH and NH pro-
tons. The vicinal spin–spin coupling constant deter-
1ç NMR (CDCl3, δ, ppm): 1.22 (d, 24H, 8CH3,
3JCH –CH = 6.9 Hz); 3.27 (hept, 4H, 4ëç–(ëç3)2,
3
3JCH–CH = 6.9 Hz); 7.0–7.4 (m, 11H, 2ë6ç3, ë6ç5);
3
7.71 (s, 2H, 2CH–NH); 12.06 (br.s, 1H, NH).
Synthesis of bis{µ(Cl2)-(2,6-diisopropylphen-
yl)amino-4-(2,6-diisopropylphenyl)iminatocop-
per(II)-3-nitro-2-pentene} (III). A hot solution con-
taining CuCl2 · H2O (0.17 g, 0.001 mol) in ethanol was
added to a hot solution of ligand I (R1 = NO2) (0.435 g,
0.001 mol) in 10 ml of ethanol. The mixture was
refluxed for 20–30 min. The precipitated brown crystals
were filtered off, washed with ethanol, and dried. mp >
200°C, yield 60%.
mined is twice as low as the usual value (3JCH–NH
=
8 Hz). This is indicative of fast, on the NMR time scale,
intramolecular chemical exchange with the NH proton
being located with equal probability at any of the dianil
nitrogen atoms.
In the 1H NMR spectrum of ligand II, the CH-group
protons give rise to a singlet. The broadened signal of
the NH proton and the singlet for the methine frag-
ments attest to intermolecular exchange processes. The
1H NMR data indicate that dianils I and II exist in
CDCl3 as the amino-imine tautomers containing an
intramolecular hydrogen bond [31–34].
For C54H72Cl2Cu2N6O4
anal. calcd. (%):
Found (%):
C, 60.78; H, 6.80; N, 7.87.
C, 60.47; H, 6.54; N, 7.53.
The molecular structure of ligand II is shown in
Fig. 1. Molecule II contains an intramolecular hydro-
gen bond, NH···N, the H-bonded ring being nearly pla-
nar, as found in the previous study [21–23, 34]. The
N(1)−H(1) (N(2)–H(1)) and N(1)–C(1) (N(2)–C(2))
bond lengths are 1.11 (1.74) and 1.330 (1.309) Å,
respectively. For these systems, the observed C–N bond
lengths vary in the 1.29–1.24 Å range [22, 24].
DRS (λmax, nm): 226, 270 sh, 320 sh, 344, 458,
542 sh, 622 sh, 874.
UV/Vis (ëH2Cl2, λmax, nm (ε, mol–1 cm–1)): 282 sh
(17633), 340 (51734), 474 (4332), 620 sh (1199).
Bis{µ(Cl )(2,6-diisopropylphenyl)amino-3-(2,6-
2
diisopropylphenyl)iminatocopper(II)-2-phenyl-1-
propene} ((LCuCl) ) (IV) was synthesized by the
n
The angle between the plane of the aromatic ring
located in the γ-position of the aminovinylimine ligand
and the H-bonded ring equals 37°. The aryl substituents
at the nitrogen atoms are rotated relative to the
H-bonded ring through 104.7° and 60.5°. The hydrogen
atom at the donor nitrogen protrudes from the
N(1)C(1)C(2)C(3)N(2) plane by 0.09 Å.
procedure used to prepare complex III but with ligand
II as the starting reagent. Yield 56%.
For C66H82Cl2Cu2N4
anal. calcd. (%):
Found (%):
C, 70.19;
C, 70.35;
H, 7.32;
H, 7.56;
N, 4.96.
N, 4.89.
Complexes III and IV were prepared in ethanol by
direct reaction of ligands I or II with CuCl2 · H2O in
1 : 1 molar ratio.
DRS (λmax, nm): 226 sh, 270 sh, 304, 372, 454, 570
sh, 608 sh, 628, 863 sh.
UV/Vis (ëH2Cl2, λmax, nm (ε, mol–1 cm–1)): 282
(37261), 330 (15212), 378 (32095), 488 sh (3472), 514
(4124), 618 sh (1017), 672 sh (884), 838 (450).
Complex V was prepared from compound IV by
growing crystals from benzene–heptane or acetoni-
trile–methanol–chloroform mixtures (green crystals).
Complexes III and IV behave in different ways in a
methylene dichloride solution. The UV/Vis spectrum
of metal chelate III in CH2Cl2 exhibits the following
absorption bands (nm): 340, 474, 262 sh, and 620 sh.
The bands do not change for a long period of time. It is
of interest that binuclear copper(II) β-aminovinyliminate
complex with oxygen bridges (R = 2,4,6-(CH3)3C6H3)
contains one intense band at ~353 nm [26]. The UV/Vis
For C66H82Cl2Cu2N4O2
anal. calcd. (%):
Found (%):
C, 68.26; H, 7.12; N, 4.82. spectrum of complex IV has the bands (nm) at 282,
330, 378, 514, 488 sh, 618 sh, and 838 sh, which are
transformed with time into a broad band with shoulders
C, 68.17; H, 7.40; N, 4.71.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

MAGNETOACTIVE BINUCLEAR COPPER(II) COMPLEXES
291
C(32)
C(20)
C(12)
C(13)
C(14)
C(26)
C(25)
C(18)
C(27)
C(29)
C(31)
N(2)
C(11)
C(15)
C(24)
H(1N)
C(16)
C(19)
C(23)
C(10)
C(22)
C(21)
N(1)
C(33)
C(3)
C(28)
C(17)
C(1)
C(30)
C(2)
C(4)
C(9)
C(8)
C(5)
C(6)
C(7)
Fig. 1. Molecular structure of ligand II.
at 264, 290, 374 nm and weak bands (ε = 80–98) at
630–750 nm (Fig. 2). The UV/Vis spectrum of β-ami-
novinylimine complexes, in which the Cu coordination
sphere contains two N atoms and one Cl atom, exhibits
bands at 340, 507, 657, and 840 nm [20]. As shown pre-
viously [26] for dimeric copper complexes with dianils,
the nature of the substituent and the temperature have
an influence on the UV/Vis spectra of dimeric cop-
per(II) β-aminovinyliminate chelates with chlorine
bridges (for example, R1 = Cl, R = 2,6-(CH3)2C6H4). In
various temperature ranges and depending on the
nature of N-substituents in the β-aminovinylimine ring,
the spectra of both three-coordinate mononuclear cop-
per and the dimer are observed. In our case, the UV/Vis
spectral pattern of complex IV recorded immediately
after dissolution in CH2Cl2 (Fig. 2) is virtually identical
to the spectra of metal chelates described previously
[26]; this implies that CH2Cl2 solutions contain metal
chelates IVa and IVb.
D
282
3.5
378
3.0
2.5
2.0
1.5
1.0
0.5
0
1
330
2
3
300
400
500
600
700
800
λ, nm
The EPR spectrum of dimer III (powder) is a
broad line (more than 100 G) with two centrosymmet-
ric shoulders. The g-factor of the central component
Fig. 2. UV/Vis spectrum of complex IV in CH Cl :
(1) immediately after dissolution and (2, 3) after keeping for
(2) 3 and (3) 24 h.
2
2
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

292
URAEV et al.
and the distance between the shoulder tops varies with grounds for assigning the spectrum to a monomeric
temperature without substantial change in the line copper(II) complex (d9). The only unpaired electron is
located predominantly on the Cu2+ ion. The obtained
EPR parameters of complex IV are very similar to
those for the mononuclear β-aminovinyliminate com-
plex of three-coordinate copper containing two nitro-
gen atoms and one chlorine atom in the coordination
sphere [20]. However, the presence of a dimer also can-
not be ruled out, because it may be EPR non-detectable.
This depends on the complex geometry and symmetry
of the orbitals containing unpaired electrons.
width (Fig. 3). In addition, an EPR signal occurs in the
“half” field, g = 4.33 (T = 130 K). The spectra appar-
ently belong to a radical pair (two weakly interacting
electrons, the triplet ground state) with two unpaired
electrons being located on Cu2+ ions (d9). The zero-field
splitting parameter 2D or D'' allows one to estimate the
effective distance between the localization centers of
the unpaired electrons for various temperatures
290 K: g = 2.085, 2D (D'') = 1551 G, r = 3.3 Å;
220 K: g = 2.107, 2D (D'') = 1752 G, r = 3.17 Å;
130 K: g = 2.122, 2D (D'') = 1847 G, r = 3.11 Å,
Complex V does not produce any EPR spectrum in
solutions (CH2Cl2, 2-ëH3–C4H7O). According to X-ray
diffraction data [30], compound V is a binuclear cen-
trosymmetric metal chelate containing an oxygen
bridge. The nearest environment of the copper atom is
composed of nitrogen, oxygen, and terminal chlorine
atoms. A complex with a similar structure has been
reported in [25].
where g is the g-factor of the central line or the
“monoradical signal”; 2D(D'') is the zero-field split-
ting parameter; r is the effective distance between the
unpaired electrons. The g-factor value of the central
line is typical of Cu2+ (d9). The resulting r values are
consistent with the published data for dimers with
chlorine bridges [26]. The half-field signal refers to
the forbidden transition with ∆MS = 2 (spin quantum
number, MS = 1, 0, –1). Compound III does not
exhibit an EPR spectrum in solution. Thus, complex
III can be assigned a dimeric structure with chlorine
bridges.
Thus, EPR data attest to a dimeric structure of che-
late III and to the presence of the mononuclear com-
plex IVa. However, the data of UV/Vis spectra indicate
that both monomer IVa and dimer IVb are present in
the solution.
Compound IV in solutions (for example, in CH2Cl2)
is converted with time into dimer V. The UV/Vis spec-
trum of chelate IV changes with time both in the UV
and in the visible regions (Fig. 2). The spectrum of
complex IV having been kept for 24 h is virtually iden-
The EPR spectrum of complex IV in 2-methyltet-
rahydrofuran (2-ëH3–C4H7O) is a broad asymmetric
line with giso ≅ 2.09. An EPR spectrum with the param-
eters a||(Cu) = 131 G, g|| = 2.23, g⊥ = 2.02 was recorded
in a glassy solvent matrix at 120 K (Fig. 4). The main tical to the spectrum of crystals of V dissolved in
values of the g-tensor (g|| = 2.23, g⊥ = 2.02) provide CH2Cl2. Similar changes in the UV/Vis spectra have
DPPH
× 5
200 G
powder
‡
× 5
× 5
b
c
× 5
× 5
× 5
Fig. 3. EPR spectra of complex III at T of (a) 290, (b) 220, (c) 130 K.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

MAGNETOACTIVE BINUCLEAR COPPER(II) COMPLEXES
293
for the atoms of the nearest coordination spheres in
complexes IV and V were studied by EXAFS. The
experimental FTM EXAFS spectra of complexes IV
and V are similar and contain two well-resolved major
peaks corresponding to scattering of the photoelectron
wave on the nearest coordination sphere and weaker
peaks with great r corresponding to the long-range
coordination sphere (Fig. 6). Table 2 presents the
parameters of the nearest environment of the copper
atom in the complexes, which have been determined by
approximating the theoretically calculated χ(k) values
of the models chosen to the experimental EXAFS spec-
tra. The coordination sphere parameters obtained from
approximation for complex V are close to the corre-
sponding X-ray diffraction values [30] and describe the
model of a copper dimer with two oxygen bridges and
two terminal chlorine atoms. In the case of freshly pre-
pared complex IV, the best approximation corresponds
to the model in which the first coordination sphere con-
sists of two nitrogen atoms and two bridging chlorine
atoms.
DPPH
100 G
Fig. 4. EPR spectra of complex IV.
been noted in oxidation of copper(II) β-aminovinylim-
inates [20, 25].
Spectroscopic studies of a freshly prepared solution
of complex IV in CH2Cl2 and the crystal of V confirm
the results of powder X-ray diffraction, attesting to
their different structures (Fig. 5).
On the basis of the physicochemical studies and
published data [20, 25], we suggest that the reaction of
The composition and characteristics (radius, coordi- dianil II with CuCl2 · 2H2O yields complex IV, which
nation numbers, and Debye–Waller factors) (Table 2) is oxidized by air oxygen in a CH2Cl2 solution, being
Intensity, rel.u
3000
2000
2
1000
1
0
10
20
30
40
50
2θ
Fig. 5. X-ray diffraction patterns of complexes IV and V: (1) compound isolated immediately after the reaction, IV; (2) oxidized
compound, V. Wavelength λ = 1.5406 Å.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

294
URAEV et al.
converted into dimer V. The hypothetical mechanism of atmospheric oxygen to give intermediate compounds
this reaction that includes oxidation of chelate IV with VI and VII can be represented as follows:
O
O
R
R
N
N
Cl
Cl
O2
IV
Ph
Cu
N
Cu
Ph
N
R
R
(VI)
R
H
N
Ph
O
R
R
H
Cl
R
N O Cl
Cu
N
Cu
N
Ph
Cu
Ph
N
Cu O
R
N Cl O N
H
Cl
R
R
Ph
N
H
R
(VII)
(V)
The magnetochemical investigations demonstrated the magnetic moment and exchange parameters of
that complex III tends to exhibit a ferromagnetic type complex III are presented in Fig. 7. Study of a large
of spin–spin coupling. The temperature dependence of group of compounds in which the exchange coupling
Table 2. Structural data for the copper coordination spheres in complexes IV and V found by the multisphere approximation
of EXAFS data*
Compound
C.N.
r, Å
σ2, Å2
Atom
Q, %
Complex IV (immediately after the reaction)
2
2
3
1
2
1
2
5
1
1.95
2.30
2.94
3.01
1.91
2.05
2.33
2.93
0.0049
0.0054
0.0060
0.0088
0.0076
0.0022
0.0052
0.0065
0.0080
N
3.5
Clbridge
C
Cu
Complex V
Cbridge
N
2.5
Clterm
C
2.97
Cu
2
* r are the radii of the coordination spheres; C.N. is the coordination number, σ is the Debye–Waller factor, Q is the approximation quality
function.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

MAGNETOACTIVE BINUCLEAR COPPER(II) COMPLEXES
295
FTM
Cu–Cl
0.020
0.018
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
Cu–N/O
Cu–Cu
2
1
0
2
4
6
r, Å
–1
Fig. 6. FTM for complexes (1) IV and (2) V in the integration range from 2.8 to 13 Å . (–) Is the experimental FTM, (ꢀ) is the
theoretical FTM obtained by approximation.
between Cu2+ ions occurs through the halide ions
showed that they mainly have the antiferromagnetic
type of spin–spin coupling [26, 35]; the cases of ferro-
magnetic exchange are very seldom [11]. In this con-
nection, note that the dimeric copper complex with a
similar structure containing ethyl rather than isopropyl
groups in the N-aryl fragments exhibits weak antiferro-
magnetism (J = –0.3 cm–1) [26].
Complex IVb obtained immediately after the reac-
tion exhibits, like III, the ferromagnetic type of spin–
spin coupling (Fig. 8). However, binuclear complex V
shows a very weak antiferromagnetic exchange (Fig. 9).
These data imply that the physicochemical proper-
ties and the reactivity of copper β-aminovinyliminate
chelates depend on the nature of substituents both at
µ , µB
eff
µ , µB
eff
3.10
3.05
3.00
2.95
2.90
2.85
2.80
2.85
2.80
2.75
2.70
2.65
2.60
2.55
0
50
100
150
200
250
300
T, K
0
50
100
150
200
250
300
T, K
Fig. 7. Temperature dependence of the magnetic suscepti-
Fig. 8. Temperature dependence of the magnetic suscepti-
–1
–1
bility of complex III (g = 2.19, J = 99 cm (142 K), J'z =
bility of complex IV (g = 2.05, J = 39 cm (56 K), J'z =
–1
–1
0.08 cm (−0.11 K)).
0.2 cm (−0.3 K)).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006

296
URAEV et al.
Meyer, T.Y., Eds., Amsterdam: Elsever-Pergamon, 2003,
p. 393.
µ , µB
eff
9. XXXVIth International Conference on Coordination
2.8
Chemistry, Merida (Yucatan, Mexico), 2004.
10. Winpenny, R.E.P., Chem. Soc. Rev., 1998, vol. 27, no. 6,
p. 447.
2.7
2.6
2.5
11. Tuna, F., Patron, L., Journaux, Y., et al., J. Chem. Soc.,
Dalton Trans., 1999, no. 4, p. 539.
12. Kahn, M.L., Rajendiran, T.M., Jeannin, Y., et al., C. R.
Acad. Sci., Paris: Serie IIc, 2000, vol. 3, p. 131.
13. Miyasaka, H., Clerac, R., Ishii, T., et al., J. Chem. Soc.,
Dalton Trans., 2002, no. 7, p. 1528.
14. Salmon, L., Thuery, P., Riviere, E., et al., J. Chem. Soc.,
Dalton Trans., 2003, no. 14, p. 2872.
15. Mukherjee, S., Weyhermuller, T., Bothe, E., and
Chaudhuri, P., Eur. J. Inorg. Chem., 2003, no. 10,
p. 1956.
0
50
100
150
200
250
300
T, K
Fig. 9. Temperature dependence of the magnetic suscepti-
bility of complex V.
16. Matsumoto, K., Sekine, N., Arimura, K., et al., Bull.
Chem. Soc. Jpn., 2004, vol. 77, no. 7, p. 1343.
17. Bian, H.-D., Xu, J.-Y., Gua, W., et al., Polyhedron, 2003,
vol. 22, no. 21, p. 2927.
nitrogen and in the β-aminovinylimine ring. In particu-
lar, it was shown that rational design of these ligand
systems opens up the way to magnetoactive binuclear
copper complexes with different types of spin–spin
coupling. Treatment of compound IV in CH2Cl2 with
atmospheric oxygen gives metal chelate V with an
unusual ligand coordination.
18. Costes, J.-P., Dahan, F., Novitchi, G., et al., Eur. J. Inorg.
Chem., 2004, no. 7, p. 1530.
19. Borget-Merle, L., Lappert, M.F., and Severn, J.R., Chem.
Rev., 2002, vol. 102, no. 9, p. 3031.
20. Holland, P.L. and Tolman, W.B., J. Am. Chem. Soc.,
1999, vol. 121, no. 31, p. 7270.
21. Holland, P.L. and Tolman, W.B., J. Am. Chem. Soc.,
2000, vol. 122, no. 26, p. 6331.
22. Yokota, S., Tachi, Y., Nishiwak, N., et al., Inorg. Chem.,
ACKNOWLEDGMENTS
2001, vol. 40, no. 21, p. 5316.
This work was supported by the integrated program
of the Presidium of the Russian Academy of Sciences
“Targeted Synthesis of Compounds with Specified
Properties and Design of Functional Materials Based
on Them” (project no. 00-04-17), the Russian Federa-
tion President grant for the State Support ofYoung Rus-
sian scientists (MK 1350.2005.3), the RF Ministry of
Education and Science (project NSh-945.2003.3), the
Russian Foundation for Basic Research (projects no.
04-03-32366, 04-03-08019ofi_a), and the foundation
BRHE NO-008-X1.
23. Dai, X. and Warren, T.H., Chem. Commun., 2001, no. 19,
p. 1998.
24. Stender, M., Wright, R.J., Eichler, B.E., et al., J. Chem.
Soc., Dalton Trans., 2001, no. 23, p. 3465.
25. Yokota, S., Tachi, Y., and Itoh, S., Inorg. Chem., 2002,
vol. 41, no. 6, p. 1342.
26. Spencer, D.J.E., Reynolds, A.M., Holland, P.L., et al.,
Inorg. Chem., 2002, vol. 41, no. 24, p. 6307.
27. Sheldrick, G.M., SHELXTL-Plus. PC Version, A. System
of Computer Programs for the Determination of Crystal
Structure from X-Ray Diffraction Data, Rev. 502, Sie-
mens Analytical X-Ray Instruments Ins., Germany, 1994.
28. Uraev, A.I., Nivorozhkin, A.L., Kurbatov, V.P., et al.,
REFERENCES
Koord. Khim., 2000, vol. 26, no. 11, p. 947.
29. Uraev, A.I., Tyl’chenko, L.S., Kurbatov, V.P., et al.,
Nauchnaya Mysl’Kavkaza. Spetsvypusk, 2001, p. 93.
30. Uraev,A.I., Kurbatov, V.P., Tyl’chenko, L.S., et al., Dokl.
Akad. Nauk, 2002, vol. 383, no. 1, p. 71 [Dokl. (Engl.
Transl.), vol. 383, no. 1, p. 57].
31. Freimanis,Ya.F., Khimiya enaminoketonov, enaminoimi-
nov, enaminotionov (Chemistry of Enaminoketones,
Enaminoimines, and Enaminotiones), Riga: Zinatne,
1974.
1. Ovcharenko, V.I and Sagdeev, R.Z., Usp. Khim., 1999,
vol. 68, no. 5, p. 381.
2. Magnetism: Molecular to Materials, Miller J.S. and
Drillon M., Eds., Verlag Chemie, 2001–2004, vols. 1–4.
3. Verdaguer, M., Polyhedron, 2001, vol. 21, nos. 11–14,
p. 1115.
4. Benelli, C. and Gatteschi, D., Chem. Rev., 2002,
vol. 102, no. 6, p. 2369.
5. Real, J.A, Gaspar, A.B., Niel, V., and Munoz, M.C.,
32. Carey, R.T., Cope-Eatough, E.K., Vilapana-Mafe, E.,
Coord. Chem. Rev., 2003, vol. 236, nos. 1–2, p. 121.
et al., J. Chem. Soc., Dalton Trans., 2003, no. 6, p. 1083.
6. Chaudhuri, P., Coord. Chem. Rev., 2003, vol. 243,
33. Ragogna, R.J., Burford, N., D’eon, M., et al., J. Chem.
nos. 1–2, p. 143.
Soc., Chem. Commun., 2003, no. 9, p. 1052.
7. Kalinnikov, V.T., Rakitin, Yu.T., and Novotortsev, V.M., 34. Garnovskii, A.D. and Vasil’chenko, I.S., Usp. Khim.,
Usp. Khim., 2003, vol. 72, no. 12, p. 1123.
2005, vol. 74, no. 3, p. 211.
35. Sain, S., Maji, T.K., Das, D., et al., J. Chem. Soc., Dalton
Trans., 2002, no. 7, p. 1302.
8. Gatteshi, D, Sessoli, R, and Cornia, A, in Comprehensive
Coordination Chemistry. II, McCleverty, J.A. and
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 4 2006