Copper(II) complexes with condensation products of aminonaphthalene and benzoin derivatives

Article abstract of DOI:10.1134/S0036023606030120

New copper(II) complexes with the products of condensation of benzoin with monopotassium 1-amino-8-hydroxy-2,4-naphthalenedisulfonate and 1,8-diaminonaphthalene (complexes I and II, respectively) have been synthesized. The compounds are identified and characterized by elemental analysis; X-ray powder diffraction; thermogravimetry, and electric conductivity data; magnetic susceptibility measurements; and IR, EPR, diffuse reflectance; EXAFS spectroscopy. The geometry and stability of the stereo isomers of complex I are theoretically studied with the use of the molecular mechanics method and semiempirical quantum-chemical calculations. The compositions of the inner spheres of complexes I and II and their coordination polyhedra-a distorted planar square (I) and a distorted octahedron (II)-are determined using different physicochemical methods. Pleiades Publishing, Inc., 2006.

Full text of DOI:10.1134/S0036023606030120

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2006, Vol. 51, No. 3, pp. 408–414. © Pleiades Publishing, Inc., 2006.
Original Russian Text © L.S. Skorokhod, I.I. Seifullina, V.G. Vlasenko, I.V. Pirog, V.V. Minin, V.E. Kuz’min, L.N. Ognichenko, 2006, published in Zhurnal Neorganicheskoi
Khimii, 2006, Vol. 51, No. 3, pp. 456–462.
COORDINATION
COMPOUNDS
Copper(II) Complexes with Condensation Products
of Aminonaphthalene and Benzoin Derivatives
a
a
b
b
c
L. S. Skorokhod , I. I. Seifullina , V. G. Vlasenko , I. V. Pirog , V. V. Minin ,
d
d
V. E. Kuz’min , and L. N. Ognichenko
a
Mechnikov National University, Dvoryanskaya ul. 2, Odessa, 65026 Ukraine
b
Research Institute of Physics, Rostov State University, pr. Stachki 194, Rostov-on-Don, 344090 Russia
c
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
d
Bogatskii Physicochemical Institute, National Academy of Sciences of Ukraine,
Lustdorfskaya doroga 86, Odessa, 65080 Ukraine
Received June 6, 2005
Abstract—New copper(II) complexes with the products of condensation of benzoin with monopotassium
1-amino-8-hydroxy-2,4-naphthalenedisulfonate and 1,8-diaminonaphthalene (complexes I and II, respec-
tively) have been synthesized. The compounds are identified and characterized by elemental analysis; X-ray
powder diffraction; thermogravimetry, and electric conductivity data; magnetic susceptibility measurements;
and IR, EPR, diffuse reflectance; EXAFS spectroscopy. The geometry and stability of the stereo isomers of
complex I are theoretically studied with the use of the molecular mechanics method and semiempirical quan-
tum-chemical calculations. The compositions of the inner spheres of complexes I and II and their coordination
polyhedra—a distorted planar square (I) and a distorted octahedron (II)—are determined using different phys-
icochemical methods.
DOI: 10.1134/S0036023606030120
Previously [1, 2], we synthesized and studied Co(II) formed was filtered off, washed with ethanol, and dried
and Ni(II) complexes with the condensation products of at room temperature over anhydrous calcium chloride
aminonaphthalene and α-hydroxy-α-phenylacetophen- to constant weight. The target product is a dark claret
one (benzoin) derivatives. The complexes were synthe- compound, mp 164°C.
sized by three methods: either (1) the above condensa-
For C24H18KNO8S2 anal. calcd. (%): C, 52.27; H,
tion products (ligands) or (2) the complexes with
3.27; N, 2.54; S, 11.62; K, 7.08. Found (%) C, 52.81;
1-amino-8-hydroxy-2,4-naphthalenedisulfonic
were preliminarily prepared or (3) a template reaction
on the Co(II) or Ni(II) matrix was carried out.
acid
H, 3.11; N, 2.59; S, 11.31; K, 7.29.
OH
OH
Similar copper(II) complexes were prepared only by
the second method and characterized by different phys-
icochemical methods, including EPR [3].
CH
C6H5
OH
C6H5
N
In this paper, we report on the synthesis and the
results of physicochemical study of new Cu(II) com-
plexes with a Schiff base (L1) and of a complex isolated
from the CuCl2–1,8-diaminonaphthalene–benzoin
system.
SO3K
SO3H
(L1)
EXPERIMENTAL
Synthesis of a Schiff base (L1). Anhydrous sodium
acetate (8.2 g, 0.10 mol) was added to a mixture of
methanol solutions of 10.71 g (0.03 mol) of mono-
potassium 1-amino-8-hydroxy-2,4-naphthalenedisul-
fonate (1,8,2,4-ahKsHs'n) in 80 ml and 6.36 g
(0.03 mol) of benzoin in 40 ml. The resulting solution
Synthesis of complex I.A reaction mixture contain-
ing 1.65 g (0.003 mol) of L1 (a solvent was a mixture of
50 ml of ethanol and 70 ml of methanol) and 0.51 g
(0.003 mol) of copper(II) chloride in 15 ml of ethanol
was refluxed on a water bath for 1 h. The precipitate
formed after cooling the solution was worked up as
was refluxed on a water bath for 1 h. The precipitate described for L1. The target product is a grey-green
408

COPPER(II) COMPLEXES WITH CONDENSATION PRODUCTS OF AMINONAPHTHALENE
409
compound insoluble in water and soluble in DMF and The energy of an electron beam used as the source of
DMSO. The compound melts at 238°C and decom- X-ray synchrotron radiation was 2 GeV at an average
poses at 300°C.
beam current of 80 mA. X-ray radiation was monochro-
matized by a Si(111) double-crystal monochromator.
The incident and transmitted X-ray radiation intensities
were measured by argon-filled ionization chambers.
For C48H36Cl2K2N2O16S4Cu anal. calcd. (%): C,
46.58; H, 2.91; N, 2.26; Cl, 5.74; K, 6.31; S, 10.35; Cu,
5.14. Found (%): C, 46.02; H, 2.99; N, 2.00, Cl, 5.75;
K, 6.03; S, 10.11; Cu, 5.26.
Synthesis of complex II. Hot ethanol solutions of
1.58 g (0.01 mol) of 1,8-diaminonaphthalene (1,8-aa'n)
in 50 ml and 4.34 g (0.02 mol) of benzoin in 30 ml were
poured together and refluxed for 1 h on a water bath.
The resulting precipitate was worked up as described
for L1 and complex I. Complex II is a dark brown crys-
talline substance soluble in DMF and DMSO and insol-
uble in water. Complex II decomposes above 250°C.
Samples for EXAFS experiments were thoroughly
blended with Apiezon and placed between thin lavsan
films. The sample thickness was selected so that the
transmitted X-ray radiation intensity was 2.5–3.0 times
as low as the incident beam intensity. After standard
procedures for background removal, normalization to
the ä-edge jump, and extraction of atomic absorption
µ0 [6], the resulting EXAFS (χ) spectra were Fourier
transformed in the range of photoelectron wave vectors
k from 2.6 to 13.3 A–1 with the weighting function
n = 2. The threshold ionization energy E0 was chosen
based on the maximum of the first derivative of the K-
edge and, then, varied in the fitting procedure.
For C24H23ClN2O3Cu anal. calcd. (%): C, 59.26; H,
4.73; N, 5.76; Cl, 7.30; Cu, 13.07. Found (%): C, 59.51;
H, 4.31; N, 5.59; Cl, 7.01; Cu, 12.89.
The copper content was determined by the X-ray
fluorescence method on a SPARK-1 spectrometer (Cu
radiation, 12 kV, 10 mA) at a counting rate of
400 counts/s. The potassium content was determined
by the flame photometry method.
Thermogravimetric analysis was carried out on a
Paulik-Paulik-Erdey Q derivatograph in air. Samples
were heated at a rate of 10 K/min in the range 20–
500°C. α-Al2O3 was used as the reference.
X-ray powder diffraction patterns were recorded on
a DRON-3 diffractometer (CuKα radiation, nickel fil-
ter). Interplanar spacings were determined using the
tables [4].
The Fourier transform magnitude (FTM) obtained
by Fourier transformation of the EXAFS spectrum rep-
resents the radial distribution function of neighboring
atoms around the absorbing metal atom. The abscissas
of the maxima of the FTM peaks (r) are related to the
radii of coordination spheres (R) by the formula r = R –
α, where α is the linear part of the phase shift. The FTM
peak amplitudes are proportional to the coordination
numbers (N). The precise structural parameters of the
nearest environment of metal atoms were determined
by nonlinear fitting of the calculated EXAFS signal to
the FTM extracted from the full EXAFS spectrum by
Fourier filtration. This nonlinear fitting was performed
with the IFFEFIT-1.2.5 program package [7]. The scat-
tering phase shifts and amplitudes of a photoelectron
wave, which were required for constructing a model
spectrum, were calculated with the FEFF7 program [8].
Metal complexes with similar structures characterized
by X-ray crystallography were used as model com-
The diffuse reflectance (DR) spectra (5000–
27000 cm–1) were recorded on a Perkin-Elmer Lambda
9 UV VIS NIR spectrophotometer. MgO was the refer-
ence. The IR absorption spectra were recorded as KBr
pellets on a Specord IR-75 spectrophotometer in the
range 400–4000 cm–1. Magnetic susceptibility was pounds.
determined at 293
K by the Gouy method.
The goodness-of-fit function Q, which was mini-
mized when finding the structural parameters of the
nearest environment, was calculated by the formula
Hg[Co(NCS)4] was used as a reference for calibration.
For calculation of molar conductivity, the ohmic
resistance of 1 × 10–3 M solutions of L1 and com-
pounds I and II in DMF placed in an Arrhenius flask
was measured using an E7-8 digital resistance meter in
the range 0–10 mΩ. The EPR spectra were recorded on
a Radiopan SE/X-2542 radiospectrometer operating at
9.4 GHz. The magnetic field sweep was calibrated with
Σ[kχexp (k) – kχtanh (k)]2
-----------------------------------------------------------
Q(%) =
× 100.
Σ[kχexp (k)]2
a
nuclear magnetometer. Diphenylpicrylhydrazyl
The geometries and relative stabilities of the stereo
isomers of complex I were calculated by both the
molecular mechanics force field (MMFF) method [9]
and the semiempirical PM3 method [10].
(DPPH) was used as a reference for the determination
of g values. Solutions in DMF with the concentration of
the complexes of 1 × 10–2 mol/l were studied. The
room-temperature EPR spectra of these solutions
showed a broad band caused by the Jahn–Teller effect
[5]; therefore, all measurements were taken at 77 K.
RESULTS AND DISCUSSION
The condensation of 1,8,2,4-ahKsHs'n with benzoin
Copper K-edge EXAFS spectra were recorded in the
transmission mode on an EXAFS spectrometer at the yielded ligand L1. Complex I was synthesized on the
Siberian Synchrotron Radiation Center (Novosibirsk). basis of this ligand. Complex II was obtained by the
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 3 2006

410
SKOROKHOD et al.
Table 1. Assignment of selected vibrational frequencies (cm–1) in the IR absorption spectra of benzoin, 1,8-aa'n, and com-
plexes I and II
Compound
ν(OH)
ν(C=N)
ν(SO2)
ν(C–O)
ν(Cu–N)
ν(Cu–O)
L1
I
3420, 3380
3530, 3200
3600–3400
1600
1570
1555
–1
1240, 1030
1240, 1030
1210
1180
1170
–1
595
587
252
490
II*
–1
–1
–1
Note: 1,8-aa'n: ν(NH) ) = 3400 cm (3300 cm in II), δ(NH ) = 1630 cm (1609 cm in II). Benzoin: ν(OH) = 3420, 3380 cm
;
2
2
–1
–1
ν(C=O) = 1680 cm ; ν(C=O) = 1210 cm
.
–1
* δ(H O) = 1620 cm
.
2
environment of Cu2+. This is consistent with the effec-
reaction of CuCl2 with 1,8-aa'n and benzoin. The
Cu2+ : ligand molar ratio is 1 : 2 in I and 1 : 1 in II. The
individuality of I and II was demonstrated by X-ray
powder diffraction data.
tive magnetic moment of I: µ = 1.860µB [12].
The EPR spectrum of I shows that hyperfine struc-
ture (HFS) lines are well resolved only in parallel ori-
entation, while only one unresolved line is observed in
perpendicular orientation. The EPR parameters deter-
mined according to [13] are g|| = 2.240 and A|| = 172.0 ×
Compounds L1 and I are X-ray amorphous. The
X-ray powder diffraction pattern of II is characterized
by an individual set of interplanar spacings and relative
intensities: d, Å (I/I0, %): 2.61 (28), 2.79 (100), 3.07
(41), 3.14 (23), 6.85 (23), 8.28 (23), 8.94 (55), and
9.81 (32).
10–4 cm–1 (g⊥ = 2.033). According to the available data,
these parameters can be assigned to a complex with the
CuO2N2 coordination core [14]; i.e., each copper ion is
coordinated to two ligand molecules through the
azomethine nitrogen atom and hydroxyl oxygen atom.
The molar conductivity of I is 132.4 Ω–1 cm2 mol–1,
which corresponds to a three-ion electrolyte [11] and is
consistent with the presence of two chloride ions in the
outer sphere of the complex as found by chemical anal-
ysis. In contrast to I, compound II is a nonelectrolyte
(λ = 20.1 Ω–1 cm2 mol–1), which points to the inner-
sphere location of the chloride ion. The inner sphere
of II also involves two water molecules, since their
removal takes place at a rather high temperature
(~140°C) and is accompanied by a corresponding
weight loss.
The set of donor atoms in I determined by EPR is in
agreement with its composition and the coordination
mode of the ligands suggested above.
The IR spectrum of II shows a broad band at 3600–
3400 cm–1, and the bands due to δ(H2O), ν(NH2),
ν(C=N), and ν(NH2) (Table 1). The positions of the last
three bands indicate that the corresponding groups are
bonded to copper(II) in complex II. One more bond to
Cu(II) is through the oxygen atom of the deprotonated
hydroxy group of the benzoin moiety, which is demon-
strated by the corresponding shift of the ν(C–O) band in
the IR spectrum of II compared to its position in the
spectrum of benzoin (Table 1). Two water molecules
and a chloride ion increase the coordination number of
copper(II) to six. This is consistent with elemental anal-
ysis and thermogravimetry data, the value of the effec-
tive magnetic moment (µ = 2.00µB), and the presence of
The coordination modes of the ligands were deter-
mined from IR spectroscopy data. Comparison of the
IR spectra of L1 and complex I (Table 1) shows a low-
frequency shift of the ν(C=N) absorption band, which
is evidence that the azomethine nitrogen atom is coor-
dinated to Cu2+. The copper coordination polyhedron
in I is also formed by the oxygen atoms of the hydroxy
groups of the benzoin and naphthol moieties, which
should lead to a change in their vibrational frequencies.
Indeed, the IR spectrum of I (Table 1) shows that the
complex has nonequivalent OH groups (coordinated to
Cu2+ and free). The fact that the sulfo group vibration
frequencies in the spectrum of I remain the same as in
the spectrum of L1 allows us to conclude that these
groups do not form bonds to Cu2+ (Table 1). Thus, L1 in
complex I acts as a bidentate ligand.
one transition Eg
T2g (~14000 cm–1) in the DR
spectrum typical of the octahedral coordination of the
Cu2+ ion [15].
Additional information on the structures of the coor-
dination cores in I and II was obtained by EXAFS
studies.
Figure 1 shows the experimental copper X-ray
absorption near-edge structure (XANES) spectra and
their first derivatives.
Analysis of the XANES spectra of I and II shows
that they have very weak features in the form of pre-
edge peaks at 8982 eV and a shoulder at 8990 eV, which
The DR spectrum of a polycrystalline sample of I
shows the 2B1g
2A1g (16700 cm–1) and 2B2g
2Eg
(19500 cm–1) transitions typical of the square-planar are caused by the electronic transitions 1s
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COPPER(II) COMPLEXES WITH CONDENSATION PRODUCTS OF AMINONAPHTHALENE
411
FTM, arb. units
I, arb. units
1.4
3.0
2
1.2
1.0
0.8
0.6
0.4
0.2
2.5
2.0
1.5
1.0
0.5
0
2'
1
1'
0
2
4
6
–0.5
8950
9000
9050
9100
r, Å
E, eV
Fig. 1. Normalized copper XANES spectra of compounds
(1) I and (2) II and (1', 2') their first derivatives.
Fig. 2. FTM of CuK-edge EXAFS data for complex I.
3d(metal) and 1s
4s and 1s
4p(ligand), respec- Cu–N/O(ligand) distances, which is typical of octahe-
tively. The intensities of these features in the XANES dral copper complexes due to the Jahn–Teller effect.
spectra of 3d metals are related to the geometry of the The second and subsequent coordination spheres con-
coordination core [16]. The XANES spectrum of I has taining a large number of aromatic carbon atoms with a
two main maxima at 8990 and 8995 eV. This XANES large dispersion of distances to the absorbing copper
pattern is characteristic of a distorted planar coordina- atom were not considered.
tion of a metal atom in a complex. When symmetry is
Our findings allow us to suggest the following struc-
lowered, the degeneracy of the 4p atomic orbital of the
ture for complex II:
metal is lifted, which is manifested in the XANES spec-
trum as a near-edge absorption peak. The copper
C6H5
XANES spectrum of II differs considerably from the
H
XANES spectrum of I. First of all, the maximum at
C6H5
8995 eV has a low amplitude. This can be explained by
a lower degree of s–p mixing, i.e., by a higher symme-
try of the coordination core, which is most likely a dis-
torted octahedron.
N
Cl
O
H2O Cu
H2O
NH2
Figures 2 and 3 show the FTMs of CuK-edge
EXAFS functions for complexes I and II. Table 2 pre-
sents the structural parameters for the nearest atomic
environment of the copper ion in complexes I and II.
In I, the first coordination sphere is composed of the
four atoms (N/O) of the ligands at a distance of 2.00 Å,
which is typical of the copper complexes with a planar
coordination. The nearest atomic environment of the
Cu ions in II was modeled assuming an octahedral
environment. The first coordination sphere in this
model contains one chlorine atom, two oxygen atoms
of the coordinated water molecules, and the nitrogen
and oxygen atoms of the ligands, their number being
varied in the course of fitting. As follows from Table 2,
the coordination of three N/O atoms with the Debye–
Waller factors typical of the given coordination sphere
leads to a very low residual factor Q, which serves as
numerical criterion for the correctness of the model
used. The distances to the oxygen atoms of the coordi-
nated water molecules are considerably longer than the
The data obtained for I give no way of unambigu-
Table 2. Structural characteristics of the nearest atomic en-
vironment of the copper atoms in I and II obtained by fitting
the EXAFS data (N is the coordination number, R is the in-
teractomic distance, σ2 is the Debye–Waller factor, Q is the
residual function)
Com-
pound
N
R, Å
σ2, Å2
Atom
Q, %
I
4
2.00
1.96
2.13
2.20
0.0053 O/N
0.0039 O/N
0.0064 O(H2O)
0.0042 Cl
1.8
0.3
II
2.8
2.0
1
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 3 2006

412
FTM, arb. units
SKOROKHOD et al.
C6H5
H
1.4
1.2
1.0
0.8
0.6
0.4
0.2
C6H5
SO3K
trans-1
H
HO3S
HO
Cu
O
N
O
N
OH
SO3K
C6H5
SO3H
H
H
C6H5
H
H
HO3S
HO3S
O
O
N
Cu
O
H
trans-2
SO3K
C6H5
N
0
2
4
6
OH
SO3K
C6H5
r, Å
H
H
C6H5
C6H5
Fig. 3. FTM of CuK-edge EXAFS data for complex II.
ously deciding which of the hydroxy groups (benzoin
or naphthol) is bonded to the copper(II) atom; there-
fore, we consider all possible structures of this com-
plex, taking into account not only different variants of
coordination of these groups but also cis and trans
isomerism.
C6H5
H
H
O
C6H5
SO3K
H
HO3S
O
trans-3
N
O
Cu
N
SO3K
C6H5
O
SO3H
H
H
H
C6H5
H
H
HO3S
HO3S
O
O1
1
Cu
cis-1
N
N
2
2
The calculated energies and geometrical character-
istics of the coordination core are summarized in
Table 3. Both approaches predict the same most stable
stereo isomers of I: cis-3, trans-2, and trans-3.
OH HO
SO3K
C6H5
SO3K
C6H5
H
H
C6H5
C6H5
In the trans isomers, the coordination core is a
somewhat pyramidally distorted planar square. In the
cis isomers, the coordination core is somewhat tetrahe-
drally distorted. The distances between the Cu2+ ion
and the donor atoms of the ligands in these isomers are
1.92 (PM3) and 2.19 Å (MMFF). These values are
close to the experimental value 1.97 Å obtained from
the EXAFS data.
C6H5
H
C6H5
SO3K
HO
H
O
HO3S
O
N
O
cis-2
Cu
N
SO3H
H
SO3K
C6H5
H
H
C6H5
Our findings show that the trans-3 isomer of com-
plex I is the most probable. Both calculation methods,
molecular mechanics and quantum-chemical calcula-
tions, predict that this isomer is the most stable. It has
five-membered chelating rings. The Cu–O bonds are
slightly out of the plane of the coordination core so that
it is somewhat pyramidally distorted. The aromatic
nuclei form a cyclic hydrophobic shell around the coor-
dination core, which is protected from above and below
by the –SO3K groups.
H
H
HO3S
SO3H
O
O
Cu
cis-3
N
N
SO3K
SO3K
C6H5
O
O
H H
C6H5
H
H
C6H5
C6H5
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COPPER(II) COMPLEXES WITH CONDENSATION PRODUCTS OF AMINONAPHTHALENE
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RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 3 2006

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SKOROKHOD et al.
8. S. I. Zabinski, J. J. Rehr, A. Ankudinov, and R. C. Alber,
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