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SKOROKHOD et al.
The copper, cobalt, and nickel contents were deter- sity was 2.5–3.0 times as low as the incident beam
mined by the X-ray fluorescence method on a SPARK-1 intensity. After standard procedures for background
spectrometer (Cu radiation, 12 kV, 10 mA) at a count- removal, normalization to the K-edge jump, and extrac-
ing rate of 400 counts/s. The sodium content was deter- tion of atomic absorption µ0 [7], the resulting EXAFS
mined by the flame photometry method.
(χ) spectrum was Fourier transformed in the range of
photoelectron wave vectors k from 2.6 to 13.3 Å–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 fit-
ting procedure.
Thermal analysis was carried out on a Paulik–Pau-
lik–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 a reference.
X-ray powder diffraction patterns were recorded on
a DRON-3 diffractometer (CuKα radiation, nickel fil-
ter). Interplanar spacings were determined using the
data from [5].
The diffuse reflectance spectra (5000–27000 cm–1)
were recorded on a Perkin-Elmer Lambda 9 UV VIS
NIR spectrophotometer. MgO was the reference.
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 nickel atom. The abscissas
of the FTM maxima (r) are related to the radii of coor-
dination spheres (R) by the formula r = R – α, where α
is the linear part of the phase shift. The FTM peak
amplitude is proportional to the coordination number.
The precise structural parameters of the nearest envi-
ronment of the nickel atom were determined by nonlin-
ear fitting of the parameters of the corresponding coor-
dination sphere for the calculated EXAFS signal to
those for the signal extracted from the full EXAFS
spectrum by Fourier filtration. This nonlinear fitting
was performed using the IFFEFIT-1.2.5 program pack-
age [8]. The scattering phase shifts and amplitudes of
a photoelectron wave, which were required for construct-
ing a model spectrum, were calculated with the FEFF7
program [9]. The C18H28I2N2Ni2O18S2 complex (bis(µ-7-
The IR spectra were recorded as KBr pellets on a
Perkin-Elmer spectrophotometer in the range 200–
4000 cm–1.
Magnetic suscepibility was determined at 293 K by
the Gouy method. Hg[Co(NCS)4] was used as a refer-
ence for calibration.
For the calculation of the molar conductivity, the
ohmic resistance of 1 × 10–3 M solutions of I–X in
DMF placed in an Arrhenius cell 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 a nuclear
magnetometer. Diphenylpicrylhydrazyl was used as a
reference for the determination of g values. The exper-
iments were carried out in a DMF solution with the
organic component content of 98 wt %. The concentra-
tion of I and II was 1 × 10–2 mol/L. Since the room-
temperature EPR spectra of the solutions showed a
broad band caused by the Jahn–Teller effect [6], all
measurements were taken at 77 K.
iodo-8-hydroxyquinoline-5-sulfonato-κ3-N,O:O')bis[tri-
aquanickel(II)] tetrahydrate) with a close structure of
the coordination core and known X-ray diffraction data
[10] was used as a model compound.
The goodness-of-fit function Q, which was mini-
mized when finding the structural parameters of the
nearest environment, was calculated by the formula:
[kχexp(k) – kχtheor(k)]2
∑
--------------------------------------------------------------
Q, % =
100.
[kχexp(k)]2
Nickel K-edge EXAFS spectra were recorded in the
transmission mode on an EXAFS spectrometer at the
Siberian Synchrotron Radiation Center (Novosibirsk).
The energy of the electron beam used as the source of
X-ray synchrotron radiation was 2 GeV at an average
beam current of 80 mA. The X-ray radiation was mono-
chromatized by a Si(111) double crystal monochroma-
tor. The incident and transmitted X-ray radiation inten-
sities were measured with argon ionization chambers.
∑
RESULTS AND DISCUSSION
The condensation of 2-amino-4,8-naphthalenedisul-
fonic acid with salicylaldehyde, benzoin, and 2-
hydroxy-1-naphthaldehyde yielded ligands L1, L2, and
L3. Complexes I–IV were synthesized with L1, com-
plexes V–VIII, with L2, and complexes IX and X, with
L3. The molar ratio M2+ : L = 1 : 1 in I, V, VII, VIII, and
A sample of V for recording the EXAFS spectrum
was thoroughly blended with Apiezon and placed
between thin lavsan films. The sample thickness was
selected so that the transmitted X-ray radiation inten- X and 1 : 2 in II–IV and VI.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 7 2007