Nickel(II) and cobalt(II) chelates with products of condensation of 1,8-diaminonaphthalene and salycylaldehyde

Article abstract of DOI:10.1134/S107032840705003X

Six Ni(II) and Co(II) chelates were synthesized from different reagents (Ni(II), Co(II) chlorides and 1,8-diaminonaphthalene or the products of a single or double condensation of the latter with salicylaldehyde) and identified and characterized by elemental analysis, powder X-ray diffraction, thermogravimetry, and conductivity methods. The ligand coordination mode and the spatial structure of the complexes were established from the magnetochemistry and spectroscopy (IR, diffuse reflection) data. The dimeric structure of one of the complexes formed due to the chloride bridges was confirmed by EXAFS method. Nauka/Interperiodica 2007.

Full text of DOI:10.1134/S107032840705003X

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2007, Vol. 33, No. 5, pp. 328–334. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © L.S. Skorokhod, I.I. Seifullina, V.G. Vlasenko, I.V. Pirog, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 5, pp. 338–344.
Nickel(II) and Cobalt(II) Chelates with Products of Condensation
of 1,8-Diaminonaphthalene and Salycylaldehyde
L. S. Skorokhoda, I. I. Seifullinaa, V. G. Vlasenkob, and I. V. Pirogb
aMechnikov University, ul. Petra Velikogo 2, Odessa, 270100 Ukraine
bResearch Institute of Physics, Rostov State University, pr. Stachki 194, Rostov-on-Don, 344104 Russia
Received April 20, 2006
Abstract—Six Ni(II) and Co(II) chelates were synthesized from different reagents (Ni(II), Co(II) chlorides and
1,8-diaminonaphthalene or the products of a single or double condensation of the latter with salicylaldehyde)
and identified and characterized by elemental analysis, powder X-ray diffraction, thermogravimetry, and con-
ductivity methods. The ligand coordination mode and the spatial structure of the complexes were established
from the magnetochemisty and spectroscopy (IR, diffuse reflection) data. The dimeric structure of one of the
complexes formed due to the chloride bridges was confirmed by EXAFS method.
DOI: 10.1134/S107032840705003X
The Schiff bases as ligands are always in the focus hol was added, and the reaction mixture was stirred on
of attention of researchers in coordination chemistry. A a magnetic stirrer for 1 h with heating.
large number of the metal complexes with different
The Schiff bases, i.e., L1 (monoazomethine) and L2
electronic structures have been synthesized using the
(bis(azomethine)) (Table 2), were prepared by the con-
above ligands [1–4]. Metal chelates are commonly pre-
densation reaction of solutions of 1,8-DAN (0.03 mol)
pared from the previously synthesized Schiff bases or
in 50 ml alcohol and SA (0.06 mol for L1, 0.069 mol for
by the template synthesis (via the reaction of aldehydes
L2) in 10 ml alcohol for 1.5 h with heating.
and ketones with amine complexes) [5–9].
In order to synthesize Ni(II) and Co(II) complexes
This work continues our systematic studies in the
with L1 (V, VI) and L2 (VII, VIII), a mixture of satu-
field of development of the synthesis of novel 3d metal
rated alcohol solutions of the respective ligand and
MCl2 taken at a molar ratio M : L = 1 : 1 was stirred for
complexes [10–13]. The goal of this work was to syn-
thesize the Ni(II) and Co(II) complexes with the prod-
1 h with heating. After the reaction mixtures were
ucts of the condensation reaction of 1,8-diaminonaph-
cooled, a solution of NH4OH was added to them by
thalene and salycylaldehyde. The choice of the subjects
drops until the precipitates were formed. Then, the pre-
of the study, as well as the direction of investigation
cipitates of L1, L2, III–VIII were treated in the same
way as in the syntheses of I and II.
open new prospects in the synthesis of the complexes
with different structures.
Thus, complexes III–VIII were synthesized by two
methods from different reagents that were prepared
beforehand: from Ni(II) and Co(II) chlorides and
1,8-DAN (for III and IV, respectively); from Ni(II) and
Co(II) chlorides and Schiff bases (L1, L2), i.e., the prod-
ucts of different condensation reactions of 1,8-DAN
and SA (V–VIII).
EXPERIMENTAL
1,8-Diaminonaphthalene (1,8-DAN), nickel(II) and
cobalt(II) chlorides, and salycylaldehyde (SA) of
chemically pure grade were used.
At first, compounds I and II (Table 1) were synthe-
sized as follows. A mixture of solutions of 1,8-DAN
(0.01 mol) in 50 ml alcohol and MCl2 (0.01 mol) in
15 ml alcohol was stirred on a magnetic stirrer for 0.5 h
with heating. On cooling, the precipitates formed were
filtered off, washed with alcohol, ether, and dried over
anhydrous CaCl2 to a constant weight. Compounds I, II
were used further to obtain complexes III, IV (Table 1).
For this purpose, to a hot saturated solution of com-
pound I (0.002 mol) in 60 ml alcohol or compound II
(0.0025 mol) in 50 ml alcohol, a solution of SA
The elemental analysis data and some physicochem-
ical characteristics of complexes I–VIII are given in
Table 1. The analysis for Co and Ni was performed by
spectral X-ray fluorescence method on a SPARK-1
spectrometer with Cu radiation at U = 12 kV, I = 10 mA
and at a counting rate 400 pulses per second.
X-ray diffraction pictures were recorded on a
DRON-05 diffractometer on an iron anticathode. The
interplanar spaces were determined from tables [14].
The thermogravimetric analysis was performed on
(0.004 mol and 0.005 mol, respectively) in 10 ml alco- Paulik-Paulik–Erdey Q-derivatograph in a static air
328

NICKEL(II) AND COBALT(II) CHELATES
329
Table 1. Results of chemical analysis and some characteristics of complexes I–VIII
Content (found/calculated), %
Molar electrical
conductivity.
Com-
Color Molecular formula
pound
Ω
–1 cm2 mol–1
C
H
N
Cl
M
H2O
I
Bright C10H30N2O6Cl2Ni 30.02/30.30 5.38/5.56 7.31/7.07 17.80/17.93 14.90/14.90 27.00/27.28
green
11.4
II
III
Dark
C10H14N2O2Cl2Co 37.29/37.04 4.18/4.32 8.39/8.64 22.02/21.91 18.10/18.21 10.96/11.11
C48H36N4O4Cl2Ni 66.59/66.82 4.01/4.18 6.71/6.50 8.00/8.24 6.82/6.84
135.1
brown
Dark
green
11.9
IV
V
Black C48H36N4O4Cl2Co 66.99/66.82 4.00/4.18 6.13/6.50 8.03/8.24 6.11/6.84
126.3
25.1
Pale
C34H30N4O4Cl2Ni2 54.18/54.62 3.91/4.02 7.68/7.50 9.40/9.51 15.63/15.80 4.78/4.82
green
VI
Yellow- C34H30N4O4Co
brown
65.94/66.13 4.52/4.86 9.36/9.08
9.24/9.56 5.47/5.83
10.3
18.2
10.8
VII
Dark
brown
C24H22N2O4Cl2Ni 54.00/54.14 4.02/4.14 5.10/5.26 13.00/13.35 10.93/11.09 7.01/6.77
VIII Bright C24H22N2O4Cl2Co 53.93/54.14 3.98/4.14 5.35/5.26 13.61/13.35 10.90/11.09 6.56/6.77
brown
Table 2. Results of elemental analysis and some vibration frequencies of the Schiff bases (L1, L2)
Content (found/calculated), %
ν, cm–1
Schiff base
Molecular formula
Tmp, °C
C
H
N
ν(OH) ν(C=N) ν(C–O)
L1*
L2
C17H14N2O
C24H18N2O2
78.03/77.86 5.41/5.34 10.49/10.69 220
78.43/78.69 5.06/4.92 7.42/7.65 205
3480
3480
1590
1600
1190
1190
* In IR spectrum of L1, δ(NH2) 1640 cm–1.
atmosphere at 20–1000°C and heating rate 10 K/min solutions of I–VIII in DMF by an E 7–8 digital meter
within 0–10 mΩ in an Arrhenius vessel.
with α-Al2O3 as the standard.
The magnetic susceptibility was determined by the
Gouy method at 293 K with Hg[Co(NCS)4] used as the
standard for calibration.
IR spectra of L1, L2, and I–VIII were measured at
4000–400 cm–1 on a Perkin Elmer-777 spectrometer
(KBr pellets). The diffuse reflectance spectra were
recorded on a Perkin Elmer λ-300 spectrometer at
30000–3000 cm–1 with MgO as the standard.
The nickel K-edge X-ray absorption spectrum was
obtained in the transmission mode on EXAFS spec-
trometer at the Siberian Synchrotron Center (Novosi-
birsk). The energy of the electron beam used as the
The molar electrical conductivity was determined
by measuring the active resistivity of the millimolar source of X-ray synchrotron radiation was 2 GeV at an
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 5 2007

330
SKOROKHOD et al.
Table 3. X-ray patterns of complexes I, V, VI
Table 4. Assignment of basic vibration frequencies (cm–1) in
IR spectra of 1,8-DAN and complexes I–IV*
I
V
VI
Com-
pound
1,8-DAN
I
II
III
IV
d, Å
I/I0, %
d, Å
I/I0, %
d, Å
I/I0, %
ν(OH)
3480
1630
1542
3480
7.61
6.85
5.79
4.91
3.79
2.88
19
13
10.70
8.80
8.02
7.35
100
64
2.41
2.09
2.03
1.48
1.26
1.21
59
100
31
δ(H2O)
ν(C=N)
δ(NH2)
ν(C–O)
ν(M–N)
1630
1589
650
1630
1580
630
1556
18
32
1640
24
20
44
1190
590
1190
100
18
13
600
–1
–1
–1
19
* SA—ν(OH) 3480 cm ; ν(C=O) 1680 cm ; ν(C–O) 1190 cm .
IR spectra of I, II have almost identical absorption
bands corresponding to vibrations of the bond between
a central metal atom and the donor atoms of 1,8-DAN.
As compared to IR spectrum of DAN, in the spectra of
I and II, the band corresponding to δ(NH2) vibration is
shifted toward low frequencies, and a new band appears
due to ν(M–N) vibrations, which indicates that the
amino groups are coordinated by a metal. The presence
of water molecules (crystallization and /or coordinated
water molecules) is confirmed by the δ(H2O) bands
(Table 4) in IR spectra of compounds I, II.
average current of 80 mA. The X-radiation was mono-
chromatized using a two-crystal Si(111) monochroma-
tor. The intensities of the incident and transmitted
X-radiation were recorded by ionization chambers
filled with argon.
The preparation of the samples for measuring the
EXAFS spectra and the determination of precise struc-
tural parameters of the nearest environment of the Ni
atom were performed as described in [13]. The stan-
dards used in non-linear fitting of the structural param-
eters were the data obtained for the complexes bis(µ-2-
chloro)-tetrakis(ethylenediamine)-dinickel(II)-bis(tet-
On the basis of diffuse reflectance spectra and the
effective magnetic moments (Table 5) it was concluded
that compound I has an octahedral [17] and compound
II has a tetrahedral structure [18]
raphenylborate)
pyridyomethyl)amino-N,N',N",N'"-dinickel(II) [16],
calculated from the results of X-ray diffraction study.
[15],
bis(µ-2-chloro)-bis(tris(2-
Cl
H2
N
RESULTS AND DISCUSSION
OH2
OH2
The electrical conductivity measurements (Table 1)
indicate that compound I is a non-electrolyte, whereas
compound II is a three-ion electrolyte, i.e., the Cl– ions
in compound I are in the inner sphere, while in com-
pound II, they are in the outer sphere. Complex I is
characterized by an individual set of interplanar dis-
tances (Table 3), compound II is X-ray inactive.
According to thermogravimetric data, the removal
of four molecules of water of crystallization from com-
pound I occurs at 90–110°ë; then, two coordinated
water molecules are eliminated at ~150°ë and the chlo-
ride ions (at ~170°ë). The thermal decomposition of
compound II also proceeds in steps. At first, two outer-
· 4H2O (I)
Ni
Cl
N
H2
OH2
Co
H2
N
· Cl2 (II)
OH2
N
H2
Complexes III, IV obtained from compounds I, II,
sphere Cl– ions are removed (at 108°C) and then, two respectively, are X-ray inactive; complex III is a non-
coordinated water molecules (~150°ë) and inner- electrolyte; complex IV is a three-ion electrolyte. Com-
sphere Cl– ions (~170°ë) are eliminated. The final plex III is thermally more stable than complex IV: the
destruction of I, II is observed at ~280°C and ~260°C, removal of two Cl– ions occurs at 170°C (III), 108°ë
respectively.
(IV). Obviously, this can be explained by the inner- and
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 5 2007

NICKEL(II) AND COBALT(II) CHELATES
331
Table 5. Electron transition energies and effective magnetic moments of complexes I–VII
Electron transition, cm–1
ν2
Compound
µeff, µB (T = 293 K)
ν1
ν3
3A2g
3T2g(F)
3A2g
3T1g(F)
3A2g
3T1g(P)
I
8160
7000
8900
7800
15000
12500
16000
13385
21800
21739
22400
22220
3.20
3.26
2.39
3.08
III
V
VII
A2
4T2
A2
4T1(F)
A2
4T1(P)
II
4100
7250
4T1g(F)
18120
4.61
4T1g(F)
4T2g(F)
4A2g
4T1g(F)
4T1g(P)
VI
7960
8010
16636
20100
19960
5.21
5.36
2.46
VIII
IV
16660
∆1 = 4505 cm–1; ∆2 = 16667 cm–1
outer-sphere location of Cl– in the molecules of III, IV, ν(C–O) of the aldehyde fragment remain unchanged in
which agrees with their molecular conductivities IR spectra of III, IV, which indicates that the hydroxyl
(Table 1). Further heating of compounds III, IV pro- oxygen is not involved in coordination. At the same
ceeds similarly: the obtained intermediate products are time, the absorption corresponding to ν(M–N) is
stable up to 350°C (III) and 290°ë (IV) and then, they retained.
burn with exothermal effects at 580°C (III) and 540°ë
(IV), respectively.
The molecular structures of complexes III, IV were
established from the parameters of diffuse reflectance
In IR spectra of complexes III, IV the bands corre- spectra of their polycrystalline samples and the effec-
sponding to the vibrations δ(NH2) at 1589, 1580 cm–1 tive magnetic moments (Table 5). The stereochemistry
(I, II) and ν(C=O) at 1700 cm–1 (SA) are lacking, while of compound III is well interpreted in terms of octahe-
a new band corresponding to the ν(C=N) vibrations dral symmetry [17], whereas compound IV has an
appears (Table 4). This attests to a double condensation intermediate structure formed as a result of flattening of
at the sites of coordinated amino groups. The positions a tetrahedron toward a planar square [18]. The follow-
of the bands due to the stretching vibrations ν(OH), ing structural formulas were proposed for III and IV:
HO
HO
Cl
N
N
N
N
Co/2
(III)
(IV)
Ni/
2
Cl2
HO
HO
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 5 2007

332
µ
SKOROKHOD et al.
VI is crystal hydrate and its water is removed at 90–
100°ë. After the above endotherms, all the complexes
are stable up to 320–328°ë and then, their exothermic
combustion occurs.
1.2
1.0
0.8
0.6
0.4
0.2
0
A comparison of IR spectra (cm–1) of the ligands
(Table 2) with those of the corresponding complexes
revealed the low-frequency shifts of the bands of the
latter in the regions of vibrations ν(C=N) (V–VIII),
δ(NH2) (V, VI), ν(C–O) (V, VI) due to the involvement
of these groups in coordination by a metal:
1
V
VI
VII
3480
1540
VIII
3480
1545
2
ν(OH)
ν(C=N)
δ(NH2)
ν(C–O)
1539
1560
1150
1530
1575
1145
–0.2
–0.4
1190
1190
8300
8400
8500
E, eV
This was confirmed also by the appearance of the
absorption bands in the spectra of the complexes due to
the vibrations ν(M–N) at 616 (V), 600 (VI, VIII),
590 cm–1 (VII) and ν(M–O) at 480 (V), 520 cm–1 (VI).
Fig. 1. The Ni K-edge of normalized absorption spectrum of
(1) complex V and (2) the corresponding first derivative.
–1
The absorption bands at ~1630 cm were assigned to
δ(H é) [19].
The results of the chemical analysis, thermogravi-
2
metry, and IR spectroscopy (Table 2) showed that
depending on the 1,8-DAN : SA molar ratios, different
products of their condensation reactions (single (L1) or
double (L2) condensation) were formed.
It was found that complexes V–VIII based on L1
and L2 are individual compounds stable in air and are
non-electrolytes: complexes V, VII form crystals, com-
plexes VI, VIII are X-ray inactive.
The value of µeff forV (Table 5) is lower than that for
Ni2+ in an octahedral environment, which, with a view
to the complex composition, suggests its dimeric struc-
ture and is confirmed by EXAFS data for complex V.
Figure 1 shows the fine X-ray absorption near-edge
structure (XANES) of the nickel ä-edge spectrum and
the corresponding first derivative. A special feature of
the XANES first derivative for complex V is the pres-
The thermal decomposition of V–VIII is attended ence of one major peak, which is typical of an octahe-
by endotherms and a mass loss. For VII, the mass loss dral structure of the Ni coordination unit and is related
corresponds to a removal of the inner-sphere water to degeneracy of the vacant p-orbitals of the Ni atom.
molecules (~150°C) and Cl– ions (~170°C). In the case This is confirmed by the structural parameters obtained
of V, the above processes occur simultaneously in a by the non-linear fitting of the EXAFS function per-
temperature interval 150–180°ë. Unlike them, complex formed from a model of an octahedral environment of
Table 6. Parameters of the nearest Ni environment obtained from EXAFS data fitting (R are interatomic distances, N is the coordi-
nation number, σ2 is the Debye–Waller factor, Q is the fitting quality function)
Compound
N
R, Å
σ2, Å2
Atom
Q, %
4
1
1
1
2.08
2.41
2.61
3.28
0.0025
0.0031
0.0059
0.0071
O/N
Cl
5.6
V
Cl
Ni
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 5 2007

NICKEL(II) AND COBALT(II) CHELATES
333
the Ni atoms (Table 6). Fitting of the structural param-
FTM
8
Ni−N/O
eters was carried out using the theoretical scattering
phases and amplitudes (Fig. 2) calculated for com-
plexes with similar structures of the coordination unit
[15, 16]. Like all the model compounds, complex V
also shows a considerable (0.2 Å) difference in the
lengths of the bridging Ni–Cl bonds; the Ni–Ni dis-
tance is equal to 3.28 Å. The Debye–Waller factors
obtained for all coordination sphere radii have charac-
teristic values.
7
6
5
4
3
2
1
Ni−Cl
Ni−Ni
In accordance with the above results, complex V is
a dimer:
0
1
2
3
4
5
6
7
r, Å
OH
Ni
2
H
N
2
O
N
Cl
Cl
Fig. 2. FTM of nickel K-edge EXAFS for complex V: solid
line—the experimental data and cicles—the calculation
results.
Ni
N
H
N
O
H O
2
2
With a view to the diffuse reflectance spectra and the
µ
eff values (Table 5), complexes VI–VIII have the fol-
lowing octahedral structures:
HO
H2
N
Co/2
Cl
N
N
OH2
OH2
(VII, M = Ni)
(VIII, M = Co)
N
O
M
Cl
· 2H2O
(VI)
HO
2. Che, C.-M. and Hang, J.-S., Coord. Chem. Rev., 2003,
Thus, the above study has shown that depending on
the initial reagents, different (in compositions and
structures) complexes of Ni(II) and Co(II) were formed
with the Schiff bases—the products of a single (L1) and
double (L2) condensation reaction. This is explained by
the fact that a free 1,8-DAN is condensed at both one
and two amino groups; in the composition of I, II
1,8-DAN is coordinated only at two groups.
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