Chemical and electrochemical synthesis, structure and magnetic properties of mono- and binuclear 3d-metal complexes of N-[2-[(hydroxyalkylimino)methyl]phenyl]-4-methylbenzenesulfonamides

Article abstract of DOI:10.1016/j.poly.2018.07.053

Complexes of Cu(II), Ni(II), Co(II) and Fe(II) ions with N-[2-[(hydroxyalkylimino)methyl]phenyl]-4-methylbenzenesulfonamides containing the (CH₂)_n-spacer of a variable length (n = 2–6) were synthesized by chemical and electrochemical methods. All the compounds were characterized by C, H and N elemental analysis, IR, EPR and X-ray absorption spectroscopy data. The dimeric structures of the copper complexes with (CH₂)_n-spacers (n = 2, 3) were determined by the magnetochemical method and by X-ray diffraction analysis for the copper complex with the (CH₂)₃-spacer.

Full text of DOI:10.1016/j.poly.2018.07.053

Accepted Manuscript
Chemical and electrochemical synthesis, structure and magnetic properties of
mono- and binuclear 3d-metal complexes of N-[2-[(hydroxyalkylimino)meth-
yl]phenyl]-4-methylbenzenesulfonamides
A.S. Burlov, V.G. Vlasenko, Yu.V. Koshchienko, S.A. Nikolaevskii, M.A.
Kiskin, V.V. Minin, E.A. Ugolkova, N.N. Efimov, A.S. Bogomyakov, A.A.
Kolodina, Ya.V. Zubavichus, S.I. Levchenkov, D.A. Garnovskii
PII:
S0277-5387(18)30452-2
https://doi.org/10.1016/j.poly.2018.07.053
POLY 13318
DOI:
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
21 June 2018
29 July 2018
Please cite this article as: A.S. Burlov, V.G. Vlasenko, Yu.V. Koshchienko, S.A. Nikolaevskii, M.A. Kiskin, V.V.
Minin, E.A. Ugolkova, N.N. Efimov, A.S. Bogomyakov, A.A. Kolodina, Ya.V. Zubavichus, S.I. Levchenkov, D.A.
Garnovskii, Chemical and electrochemical synthesis, structure and magnetic properties of mono- and binuclear 3d-
metal complexes of N-[2-[(hydroxyalkylimino)methyl]phenyl]-4-methylbenzenesulfonamides, Polyhedron (2018),
doi: https://doi.org/10.1016/j.poly.2018.07.053
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Chemical and electrochemical synthesis, structure and magnetic properties of
mono- and binuclear 3d-metal complexes of N-[2-
[(hydroxyalkylimino)methyl]phenyl]-4-methylbenzenesulfonamides
A.S. Burlova, V.G. Vlasenkob,*, Yu.V. Koshchienkoa, S.А. Nikolaevskiic, М.А.
Kiskinc, V.V. Мininc, Е.А. Ugolkovac, N.N. Efimovc, А.S. Bogomyakovd, A.A.
Kolodinaa, Ya. V. Zubavichuse, S.I. Levchenkovf, D.A. Garnovskiif
aInstitute of Physical and Organic Chemistry of Southern Federal University, Stachki ave. 194/2,
Rostov-on-Don 344090, Russian Federation;
e-mail: anatoly.burlov@yandex.ru
bInstitute of Physics of Southern Federal University, Stachki ave. 194, Rostov-on-Don 344090,
Russian Federation
cN.S. Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of
Sciences, Leninsky prosp. 31, 119991 Moscow, Russian Federation
dInternational Tomography Center, SB RAS, 3a Institutskaya Str., 630090 Novosibirsk, Russian
Federation
eNRC Kurchatov Institute, 1 Acad. Kurchatov Sq., Moscow 123182, Russian Federation
fSouthern Scientific Centre of Russian Academy of Sciences, Chekhova ave. 41, Rostov-on-Don
344006, Russian Federation
Keywords: Azomethines, complexes, EPR, X-ray absorption spectroscopy, X-ray
diffraction
ABSTRACT
Complexes of Cu(II), Ni(II), Co(II) and Fe(II) ions with N-[2-
[(hydroxyalkylimino)methyl]phenyl]-4-methylbenzenesulfonamides containing the
(CH2)n-spacer of a variable length (n =2-6) were synthesized by chemical and
electrochemical methods. All the compounds were characterized by C, H and N
elemental analysis, IR, EPR and X-ray absorption spectroscopy data. The dimeric
*Corresponding author
E-mail address: v_vlasenko@rambler.ru
1

structures of the copper complexes with (CH2)n-spacers (n = 2,3) were determined
by the magnetochemical method and by X-ray diffraction analysis for the copper
complex with the (CH2)3-spacer.
1. Introduction
Tridentate azomethine compounds derived from 2-hydroxybenzaldehyde, 2-
hydroxynaphthaldehyde, 2-N-tosylaminobenzaldehyde and alkylaminoalcohol
have attracted great scientific interest as ligands for mono-, bi- and polynuclear
metal complexes. Numerous binuclear copper complexes [1-8], nickel complexes
[9], cubane complexes of nickel and copper [3, 10] with ligands containing a
hydroxyalkylimine fragment, in which the deprotonated oxygen atoms of the
hydroxyl groups act as bridging fragments, with the realization of M2N2O4
coordination cores, were obtained and structurally characterized. Strong
antiferromagnetic or ferromagnetic exchange interactions between the
paramagnetic centers are observed in these complexes [1, 10].
In the literature there are also many examples of mononuclear intracomplex
metal compounds with such azomethine ligands, in which the alcoholic groups of
the hydroxyalkylimine fragments are involved neither in coordination with metals
[11-18] nor in the realization of M2N2O4 metallacycles.
Zinc complexes of azomethinic ligands containing hydroxyalkylamine
groups possess photo- (PL) and electroluminescent (EL) properties and biological
activities [11, 19-25]. In the literature, intracomplex metal compounds of such
ligands are represented by complexes with the coordination cores MN2O2 and
M2N2O4, and with the length n = 2 and 3 for the (CH2)n-spacer.
Here we report the synthesis, structural studies and magnetic properties of
metal chelates with azomethine compounds derived from 2-N-
tosylaminobenzaldehyde and hydroxyalkylamines with the length of the aliphatic
spacer from 2 to 6 methylene units, in which structures with coordination cores
MN4, M2N4O2 (M= Cu(II), Ni(II), Co(II) and Fe(II)) are realized.
2

2. Experimental
2.1. Materials required and general methods
All solvents, 2-amino-1-ethanol, 3-amino-1-propanol, 4-amino-1-butanol, 5-
amino-1-pentanol and 6-amino-1-hexanol were purchased from Alfa Aesar and
used as received. 2-(N-Tosylamino)benzaldehyde has been synthesized using the
reported procedure [26].
C, H and N elemental analyses were carried out on a Carlo Erba Instruments
TCM 480 apparatus using sulfanilamide as a reference. The metal content was
determined gravimetrically in the analytical laboratory of the Institute of Physical
and Organic Chemistry (SFU, Rostov-on-Don, Russia). Melting points were
measured on a Kofler table.
Infrared spectra were recorded using a Varian Excalibur-3100 FT-IR
spectrophotometer for powders of compounds 1-3.
ESR spectra were measured using a Bruker «ELEXSYS E-680X»
spectrometer in the X-band at T = 293 K.
2.2. General procedure for the synthesis of the complexes of copper(II), nickel(II),
cobalt(II) and iron(II) with N-[2-[(hydroxyalkylimino)methyl]phenyl]-4-
methylbenzenesulfonamides (2).
Chemical synthesis (CS). A solution of 2 mmol of the corresponding amino
alcohol (0.12 g of 2-amino-1-ethanol, 0.15 g of 3-amino-1-propanol, 0.18 g of 4-
amino-1-butanol, 0.21 g of 5-amino-1-pentanol or 0.23 g of 6-amino-1-hexanol) in
10 ml of acetonitrile was added to a solution of 0.55 g (2 mmol) of 2-N-
tosylaminobenzaldehyde in 30 ml of acetonitrile. The mixture was refluxed for 1 h.
To the resulting solution was added a solution of 1 mmol of the corresponding
metal acetate (0.20 g of copper(II) acetate monohydrate, 0.25 g of nickel(II) acetate
tetrahydrate, 0.25 g of cobalt(II) acetate tetrahydrate or 0.34 iron(II)
tetrafluoroborate hexahydrate) in 10 ml of methanol and the mixture was refluxed
3

for 1 h. After cooling, precipitates of the complexes were filtered off, washed with
acetonitrile, methanol, hexane and dried in vacuo at 150 °C.
Electrochemical synthesis (ES) of complexes was performed by a standard
method [27] using a potentiostat EG&GPAR/173 in an acetonitrile solution with a
platinum electrode as the cathode and metal plates (Cu, Co, Ni) as the anode. The
working solution (25 ml) contained 0.4 mmol of the corresponding H2L compound
(1a-e) described and characterized in [11] and 0.020 g of [Et4N]ClO4 as a
conductive additive.
Electrolysis was carried out in a U-shaped glass tube with undivided anode
and cathode spaces under a current of 15 mA and an initial voltage of 12 V for 1.5
h. The formed precipitates of the complexes were filtered off, washed with hot
isopropanol and dried in vacuo.
2.2.1.
Bis{N-[2-[(Z)-2-hydroxyethyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}copper(II) (2a). Red-brown crystals, m.p. > 250 °С.
Yield (CS): 0.64 g, 92 %, (ES): 0.66 g, 94%. Anal. Calc. for С32H34CuN4O6S2: C,
55.04; H, 4.91; N, 8.02; Cu, 9.1%. Found: (CS) C, 55.16; H, 5.02; N, 8.17; Сu,
9.18%. (ES) C, 55.18; H, 5.10; N, 8.12; Сu, 9.15%. IR spectrum, selected bands,
cm-1: 3341 ν(OH), 1626 ν(CH=N), 1288 νas(SO2), 1133 νs(SO2). µeff =1.95 µB (298
K); 1.85 µB (77 K)
2.2.2.
Bis{N-[2-[(Z)-2-hydroxyethyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}dicopper(II) (3a). Green crystals, m.p. decomposition
> 280 °С. Yield (CS): 0.60 g, 79 %. Anal. Calc. for С32H32Cu2N4O6S2: C, 50.58; H,
4.24; N, 7.37; Cu, 16.73%. Found: (CS) C, 50.64; H, 4.38; N, 7.50; Сu, 16.84%.
IR spectrum, selected bands, cm-1: 1628 ν(CH=N), 1296 νas(SO2), 1139 νs(SO2).
µэфф. =1.26 µB (294 K); 0.41 µB (77.4 K) 2J = -334 cm-1, g = 2.08, f = 0.08
2.2.3.
Bis{N-[2-[(Z)-3-hydroxypropyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}copper(II) (2b). Red-brown crystals, m.p. > 300 °С.
Yield (CS): 0.63 g, 88 %, (ES): 0.65 g, 90%. Anal. Calc. for С34H38CuN4O6S2: C,
52.22; H, 5.27; N, 7.71; Cu, 8.75%. Found: (CS) C, 52.31; H, 5.30; N, 7.81; Сu,
8.80%. (ES) C, 52.28; H, 5.32; N, 7.79; Сu, 8.77%. IR spectrum, selected bands,
4

cm-1: 3400 ν(OH), 1627 ν(CH=N), 1281 νas(SO2), 1138 νs(SO2). µeff =2.20 µB (293
K)
2.2.4.
Bis{N-[2-[(Z)-3-hydroxypropyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}dicopper(II) (3b). Dark green crystals, m.p. > 300 °С.
Yield (CS): 0.65 g, 82 %. Anal. Calc. for С34H36Cu2N4O6S2: C, 51.83; H, 4.61; N,
7.11; Cu, 16.13%. Found: (CS) C, 51.79; H, 6.71; N, 7.18; Сu, 16.20%. IR
spectrum, selected bands, cm-1: 1628 ν(CH=N), 1282 νas(SO2), 1139 νs(SO2). µeff –
diamagnetic (293 K).
2.2.5.
Bis{N-[2-[(Z)-3-hydroxypropyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}nickel(II) (2b Ni). Light green powder, m.p. > 300 °С.
Yield (CS): 0.60 g ,83 %, (ES): 0.63 g, 87%. Anal. Calc. for С34H38NiN4O6S2: C,
56.60; H, 5.31; N, 7.77; Ni, 8.13%. Found: (CS) C, 56.64; H, 5.34; N, 7.80; Ni,
8.15%. (ES) C, 56.58; H, 5.28; N, 7.75; Ni, 8.17%. IR spectrum, selected bands,
cm-1: 3066 ν(OH), 1622 ν(CH=N), 1274 νas(SO2), 1126 νs(SO2). µeff =3.42 µB (298
K)
2.2.6.
Bis{N-[2-[(Z)-3-hydroxypropyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}cobalt(II) (2b Co). Red-brown powder, m.p.= 290-293
°С. Yield (CS): 0.56 g, 78 %, (ES): 0.60 g, 83%. Anal. Calc. for С34H38СoN4O6S2:
C, 56.58; H, 5.31; N, 7.76; Co, 8.17%. Found: (CS) C, 56.61; H, 5.37; N, 7.80; Co,
8.19%. (ES) C, 56.63; H, 5.35; N, 7.81; Co, 8.21%. IR spectrum, selected bands,
cm-1: 3343 ν(OH), 1616 ν(CH=N), 1288 νas(SO2), 1129 νs(SO2). µeff =4.66 µB (298
K)
2.2.7.
Bis{N-[2-[(Z)-3-hydroxypropyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}iron(II) (2b Fe). Orange powder, m.p. > 270 °С. Yield
(CS): 0.54 g, 75 %. Anal. Calc. for С34H3FeN4O6S2: C, 56.82; H, 5.33; N, 7.80; Fe,
7.77%. Found: (CS) C, 56.91; H, 5.40; N, 7.78; Fe, 7.82%. IR spectrum, selected
bands, cm-1: 3062 ν(OH), 1613 ν(CH=N), 1298 νas(SO2), 1124 νs(SO2). µeff =5.38
µB (298 K)
2.2.8.
Bis{N-[2-[(Z)-4-hydroxybutyliminomethyl]penyl]-4-
methylbenzenesulfonamide}copper(II) (2c). Red-brown crystals, m.p.= 267-268
5

°С. Yield (CS) 0.67 g, 90 %, (ES) 0.71 g, 95%. Anal. Calc. for С36H42CuN4O6S2:
C, 57.31; H, 5.61; N, 7.43; Cu, 8.42%. Found: (CS) C, 57.37; H, 5.72; N, 7.51; Сu,
8.52%. (ES) C, 57.18; H, 5.59; N, 7.38; Сu, 8.57%. IR spectrum, selected bands,
cm-1: 3340 ν(OH), 1630 ν(CH=N), 1287 νas(SO2), 1133 νs(SO2). µeff =1.87 µB
(296.5 K)
2.2.9.
Bis{N-[2-[(Z)-5-hydroxypentyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}copper(II) (2d). Red-brown crystals, m.p.= 269-270
°С. Yield (CS): 0.73 g, 93 %, (ES): 0.74 g, 95%. Anal. Calc. for С38H46CuN4O6S2:
C, 58.33; H, 5.93; N, 7.16; Cu, 8.12%. Found: (CS) C, 58.45; H, 6.00; N, 7.27; Сu,
8.28%. (ES) C, 58.48; H, 6.10; N, 7.14; Сu, 8.24%. IR spectrum, selected bands,
cm-1: 3350 ν(OH), 1626 ν(CH=N), 1289 νas(SO2), 1133 νs(SO2). µeff =1.89 µB
(296.5 K)
2.2.10.
Bis{N-[2-[(Z)-6-hydroxyhexyliminomethyl]phenyl]-4-
methylbenzenesulfonamide}copper(II) (2e). Red-brown crystals, m.p.= 265-266
°С. Yield (CS) 0.70 g, 87 %, (ES) 0.72 g, 89%. Anal. Calc. for С40H50CuN4O6S2:
C, 59.27; H, 6.22; N, 6.91; Cu, 7.84%. Found: (CS) C, 59.40; H, 6.35; N, 7.10; Сu,
7.95%. (ES) C, 59.35; H, 6.18; N, 7.14; Сu, 7.68%. IR spectrum, selected bands,
cm-1: 3344 ν(OH), 1626 ν(CH=N), 1288 νas(SO2), 1133 νs(SO2). µeff =1.88 µB
(296.5 K)
2.3. X-ray absorption spectroscopy
The Fe, Co, Ni and Cu K-edge EXAFS spectra for complexes 2a-e,
2b Ni, 2b Co, 2b Fe and 3a,b were recorded at the "Structural Materials Science"
beamline of the Kurchatov Synchrotron Radiation Source (Moscow, Russia) [28]
with the storage ring operating at electron energy of 2.5 GeV and with a current of
100-120 mA. A Si(111) channel-cut monochromator was used for the energy
selection. All data were measured in the transmission mode. Sample thicknesses
corresponded to an absorption jump Δμx = 0.5–1.0.
EXAFS data (χexp(k)) were analyzed using the IFEFFIT data analysis
package [29]. EXAFS data reduction used standard procedures for the pre-edge
6

subtraction and spline background removal. The radial pair distribution functions
around the metal ions in the complexes were obtained from the Fourier
transformation (FT) of the k3-weighted absorption function χexp(k) range of
photoelectron wavenumbers k = 2.4–13.0 Å–1. Structural parameters, including
interatomic distances (Ri), coordination numbers (Ni) and distance RMS deviations
due to the thermal motion and disorder-induced static deviations of atomic
positions, also known as Debye–Waller factors (σ2), were found by non-linear
fitting of the theoretical spectra against the experimental ones.
2Ri
n

2
2i k2
Ni F (k)
2
k
(k)  S0
e
e
sin(2kR  i 
k )

i
, (1)
R 2
i
k
i1
i
The experimental data were simulated using a theoretical photoelectron
mean-free-path (λ), photoelectron backscattering amplitude Fi(k) and phase
functions (Eq. 1), calculated using the FEFF7 program [30]. The amplitude
2
reduction factor due to extrinsic losses S0 and the edge energy shift E0 were
calibrated by fitting EXAFS data for spectra of the reference compounds with
2
known crystal structures. The amplitude reduction factors S0 were found to be
equal to 0.9 in all cases.
The accuracy of the fits was estimated by the standard mean-square
deviation criterion (Eq. 2) (Q-factor),
ki exp(ki )  ki th (ki )2
m
w(k )


i
Q2 
i1
(2)
m
w(k )

ki exp(ki ) 2


i
i1
where w(ki ) is a weighting function, m is the number of experimental points.
2.4. X-ray crystallography analysis of the copper complex 3b
The X-ray data sets for complex 3b were collected using a Bruker APEX II
diffractometer equipped with a CCD camera and a graphite-monochromated MoKα
radiation source (λ = 0.71073 Å) [31]. Semi-empirical absorption corrections were
applied [32]. The structure was solved by the direct method and refined by full-
matrix least squares against F2 with anisotropic thermal parameters for all non-
7

hydrogen atoms. The hydrogen atoms of the carbon-containing ligands were set in
geometrical positions and refined using the riding model. All calculations were
carried out with SHELX97 program package [33]. The crystallographic parameters
for complex 3b at T = 296(2) K were as follows: C34H36Cu2N4O6S2, fw = 787.87,
dark green, parallelogram, crystal size 0.10 x 0.02 x 0.02 mm, monoclinic system,
space group P21/n, a = 9.270(8) Å, b = 13.434(12) Å, c = 14.331(13) Å, β =
o
101.86(2) , V = 1747(3) Å3, Z = 2, ρcalc = 1.498 g cm-3, μ = 1.387 mm-1, 10676
measured reflections, 1774 reflections with I > 2.0σ(I), Rint = 0.104, GooF = 0.929,
R1 (I > 2σ(I)) = 0.061, wR2 (I > 2σ(I)) = 0.106, R1 (all data) = 0.165, wR2 (all data) =
0.138, Tmin/max = 0.874/0.973, residual electron density Δρmax/Δρmin = –0.373 /0.390
e Å-3.
Crystallographic data for 3b have been deposited with the Cambridge
Crystallographic Data Center, CCDC 1848471. Copies of this information may be
obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk or
www.ccdc.cam.ac.uk).
3. Results and discussion
3.1. Synthesis and spectroscopic properties of the complexes
The complex compounds of copper, nickel, cobalt and iron were obtained
chemically (by the direct reaction of 2-N-tosylaminobenzaldehyde, the respective
amine and metal acetate hydrate in acetonitrile in a molar ratio of 2:2:1) and
electrochemically (during the anodic dissolution of the metals in an acetonitrile
ligand (1a-e) solution) (Scheme 1).
8

CH3
CH3
CH3
(CH2)nOH
O
S
O
N
N
O
S
Mo, CH3CN
M
O
O
S
NH2(CH2)nOH
O
N
N
N
H
NH
.
M(CH3COO)2 nH2O
O
S
O
(M=Cu, Ni, Co),
Fe(BF4) 6H2O,
HO(CH2)n
N
O
(CH2)nOH
CH3CN
2
1
H3C
NH2(CH2)nOH
n=2 (1a);
n=3 (1b);
n=4 (1c);
n=5 (1d);
n=6 (1e)
.
M=Cu, n=2 (2a);
Cu(CH3COO)2 H2O
M=Cu, n=3 (2b Cu);
M=Ni, n=3 (2b Ni);
M=Co, n=3 (2b Co);
M=Fe, n=3 (2b Fe);
M=Cu, n=4 (2c);
CH3CN
CH3
M=Cu, n=5 (2d);
M=Cu, n=6 (2e)
(CH2)n
O
S
O
O
O
N
N
Cu
Cu
(CH2)n
3
N
N
O
S
O
n=2 (3a);
n=3 (3b)
H3C
Scheme 1. The synthesis of complexes 2a-e and 3a,b.
In all cases, for ligands with a length of aliphatic spacer from 2 to 6
methylene units, intracomplex compounds 2a-e of the ML2 composition were
isolated, according to elemental analysis data. In the case when n = 2 and 3, along
with the copper complexes 2 of a red-brown color, green color complexes of the
(ML)2 composition of type 3 were obtained. In the IR spectra of complexes 2a-e,
broad νOH absorption bands in the region 3062-3350 cm-1 were preserved. The
absorption bands νCH=N in the 1613-1630 cm-1 region, as well as absorption
9

bands at 1274-1290 cm-1 (νasSO2) and 1122-1135 cm-1 (νsSO2) in complexes 2a-e
shift to lower frequencies in comparison to the ligands 1a-e.
Such spectral behavior indicates the formation of chelate structures 2a-e, in
which the alcoholic groups are not involved in coordination with the metal center,
regardless of the (CH2)n-spacer length.
The complexes 2a-e are identical, according to elemental analysis and IR
spectral data, independent of the synthetic method (CS or ES). However, the ES
method is carried out under milder conditions with 10-15% higher yields of the
complexes compared to the CS method.
Similar changes are observed in the IR spectra of the green color complexes
3a,b, except for the disappearance of the νOH absorption bands in the region 3305-
3361 cm-1.
The copper complexes 2a-e are paramagnetic. The values of µeff in the range
1.87-2.20 µB (298 K) correspond to a spin value, taking into account the
contribution of the orbital component, and they do not change with decreasing
temperature. This evidences their mononuclear structure, which confirms the
analysis of the EPR spectra.
3.2. The electron paramagnetic resonance of complexes
Figure 1 shows the EPR spectrum of compound 2a in the polycrystalline
state. The spectrum is described by the spin Hamiltonian (SH) of rhombic
symmetry with the Zeeman interaction (Eq. 3):
ˆ
ˆ
ˆ
ˆ
H  gzHzSz  gxHxSx  gyHySy
(3),
where gz, gx, gy are, respectively, the z, x, y components of the monomer g-
tensor, Sz, Sx, Sy are projections of the monomer spin operator onto the coordinate
axes, S=1/2.
The parameters of the complex were found by the best approximation
method between the experimental and theoretical spectra by minimizing the error
functional (Eq. 4):
10

F  (YT Y E )2 / N

i
i
i
(4),
where YiE is the array of experimental values of the EPR signal intensities
with a constant step of the magnetic field H, YiТ are theoretical values for the same
values of the field H, and N is the number of points. The theoretical spectra were
constructed by the method described in [34]. As the line shape function, the sum of
the Lorentz and Gauss functions was used [35].
During the minimization, the g-factors, widths and shapes of the lines were
varied. The obtained SH parameters are given in the caption to Fig. 1.
1
2
200
300
400
500
H, mT
Fig. 1. The EPR spectrum of 2а, powder, Т = 293 K. 1 – experiment (solid
line), 2 - simulation (circles) with parameters of SG gz = 2.264; gx = 2.126; gy =
2.023.
The EPR spectrum of compound 3a has the form characteristic for a
complex with a total spin S = 1, when the splitting in a zero field is close to the
frequency h and this spectrum is superimposed on the spectrum of a monomeric
impurity in the region of ~300 mT (Fig. 2). The presence of a monomeric impurity
is confirmed by magnetic susceptibility data: at low temperatures the magnetic
11

moment of the compound does not decrease to zero, but remains equal to 0.41
Bohr magnetons. The SH describing the dimer spectrum has the form (Eq. 5):
1
2
2
2
ˆ
H  gx Sx Hx  gy Sy Hy  gz Hz Sz  D(Sz  (S 1)S)  E (Sx  Sy )
(5),
3
ˆ
ˆ
ˆ
S  S1  S2
where
is the total spin operator of the dimer S = 1, D and Е are
the fine structure tensor components. The spectrum of the monomeric impurity is
described by the SH (Eq. 3).
Numerical calculations of the resonant fields of the spin Hamiltonian Eq. (3)
and Eq. (5) for construction of the theoretical spectrum were carried out with the
help of the Belford method [36].
1
2
0
200
400
600
H, mT
Fig. 2. The EPR spectra of 3а, powder, Т = 293 K. 1 – experiment (solid
line), 2 - simulation (circles) with parameters of SG (1) and (2): Сdime r =75% gz =
2.310; gx = 2.041; gy = 2.031; D = 0.3560 cm-1; E = 0.0225 cm-1. Сmonomer = 25%. gz
= 2.310; gx = 2.041; gy = 2.031.
3.3 Magnetic properties of the complexes
The temperature dependences of µeff of the copper complexes are shown in
Fig. 3. Such a temperature dependence of μeff (T) for 2c, 2d and 2e is characteristic
12

for mononuclear complexes. The nickel, cobalt and iron complexes 2b are
paramagnetic. The values of µeff are 3.42 µB (298 K) (2b Ni), 4.66 µB (298 K) (2b
Co), 5.38 µB (298 K) (2b Fe) and these do not change with decreasing
temperature, which indicates their mononuclear structure.
2,4
2,4
2,2
2,2
2,0
2,0
1,8
1,8
1,6
1,6
0
50
100
150
200
250
300
0
50
100
150
200
250
30
T(K)
T(K)
b
a
2,4
2,2
2,0
1,8
1,6
50
100
150
200
250
300
T(K)
c
d
Fig. 3. Temperature dependence of µeff for the copper complexes 2c (a), 2d
(b), 2e (c) and 3a (d).
The value µeff = 1.20 µB (294 K) of the copper complex 3a (n = 2) decreases
with decreasing temperature to µeff = 0.41 µB (77.4 K) and indicates its dimeric
structure, in which an antiferromagnetic exchange interaction is observed between
the copper atoms in the dimeric molecule, with parameters 2J = -334 cm-1, g =
13

2.08, f = 0.08. Such a temperature dependence of μeff (T) (Fig. 3d) is characteristic
for binuclear complexes with a strong antiferromagnetic exchange interaction
between the spins of the paramagnetic centers. The value of the exchange
interaction parameter J/k is -483 (± 6) K.
The copper complex 3b (n = 3) is diamagnetic already at room temperature,
which indicates a strong antiferromagnetic exchange interaction between the
copper atoms in the dimeric molecule.
3.4. The X-ray absorption spectroscopy
The local atomic structures of all the complexes 2a-e, 2b Ni, 2b Co, 2b Fe,
and Cu 3a,b were determined by X-ray absorption spectroscopy from the analysis
of the Fe, Co, Ni, and Cu K-edges XANES and EXAFS spectra.
Figures 4a,b show the Cu K-edges XANES data and the MFT EXAFS χ(k)k3
for the copper complexes 2a-e. Cu K-edges XANES spectra for the copper
complexes 2a-e, except 3a-Cu and 3b-Cu, have a shape typical for a tetrahedrally
coordinated copper ion. This is particularly evident from the pre-edge structure
form, which is represented by the intense peak A. The nature of the pre-edge peak
A is due to 4p-3d hybridization of the copper AO in the low-symmetry
coordination polyhedron. With additional coordination or with the environment
symmetry of the absorbing ion without an inversion center (octahedron or plane),
such hybridization does not occur and the intensity of peak A is determined only
by low-intensity quadrupole electronic transitions. Such an intensity decrease of
the peak A is observed in the XANES spectra for 3a-Cu and 3b-Cu. In addition, a
peak B at the absorption edge is observed, characteristic of a plane-square
environment and is associated with the manifestation of a vacant 4pz AO
perpendicular to the coordination plane.
14

10
8
N
D E
1,4
1,2
1,0
0,8
0,6
0,4
0,2
0,0
1,4
1,2
1,0
0,8
0,6
0,4
0,2
0,0
F
0,06
0,04
0,02
6
A
2e
2e
4
n=6
n=6
2
8974 8976 8978 8980 8982
E, eV
0
10
0
1
2
3
4
5
6
8960
8980
9000
9020
9040
9060
9080
9100
E, eV
r, Å
8
6
4
2
0,06
0,04
0,02
A
2d
2d
n=5
n=5
8974 8976 8978 8980 8982
E, eV
0
8960
8980
9000
9020
9040
9060
9080
9100
0
1
2
3
4
5
6
1,4
1,2
1,0
0,8
0,6
0,4
0,2
0,0
10
E, eV
r, Å
0,06
0,04
0,02
8
6
4
2
A
2c
2c
n-4
n=4
8974 8976 8978 8980 8982
E, eV
8960
8980
9000
9020
9040
9060
9080
9100
0
0
1
2
3
4
5
6
1,4
1,2
1,0
0,8
0,6
0,4
0,2
0,0
10
E, eV
r, Å
8
6
4
2
0,06
A
0,04
0,02
2a
2a
n=2
n=2
8974 8976 8978 8980 8982
E, eV
0
8960
8980
9000
9020
9040
E, eV
9060
9080
9100
0
1
2
3
4
5
6
10
r, Å
1,4
1,2
1,0
0,8
0,6
0,4
0,2
0,0
8
6
4
2
C
Cu
0,10
A
B
B
3a
0,05
3a
n=2
n=2
0,00
8973
8976
8979
8982
E, eV
0
0
1
2
3
4
5
6
8960
8980
9000
9020
9040
E, eV
9060
9080
9100
10
r, Å
C
8
6
4
2
0
1,0
0,5
0,0
0,15
0,10
0,05
A
3b
3b
n=3
n=3
8973
8976
E, eV
8979
8982
8960
8980
9000
9020
9040
E, eV
9060
9080
9100
0
1
2
3
4
5
6
r, Å
a
b
Fig. 4. (a) Cu K-edges XANES spectra (the insets show the pre-edge
structure) and (b) MFT EXAFS χ(k)k3 for the copper complexes 2а-е, 3a-Cu and
3b-Cu (experiment – solid line, best fit theory – empty circles).
MFT EXAFS χ(k)k3 for copper complexes 2а-е consist of a main peak at 1.5-
15

1.6 Å, corresponding to the first coordination sphere (CS), and further peaks with
small amplitudes, corresponding to more distant CS’s (Fig. 4b). However, MFT 3a
Cu and 3b Cu evidently contain peaks at 2.6-2.7 Å with significantly larger
amplitude compared to other MFT’s. These peaks may correspond to the
manifestation of a CS containing the copper ions with a higher scattering
amplitude as compared to the lighter atoms of the ligands. To prove that these CS’s
contain copper ions, EXAFS wavelet analysis was used [37-40]. Light atoms (C,
O, N) most effectively scatter photoelectrons with small wave vectors k (the
scattering maximum is at k = 4-6 Ǻ-1), while for heavier atoms the scattering
maximum shifts toward larger k. The EXAFS wavelet transform map allows the
scattering by atoms in both spatial r-coordinates as well as in the wave vector k
coordinates, to be observed, which makes it possible to isolate the contributions to
scattering from atoms of different species that are at the same distance from the
absorbing center. The WT map of copper foil (Fig. 5a) shows that the copper
atoms most effectively scatter photoelectrons with k = 8 Ǻ-1. The distances to the
first and the next CS can also be determined from the WT map (from the y-axis
without accounting for the phase shift). The EXAFS WT maps of complexes 3a
Cu and 3b Cu, shown in Fig. 5b and c, reveal the existence of a region at small r
and k coordinates corresponding to the first peak in the MFT of light scatterers
O/N. Each map at high values of k and r has a region corresponding to scattering at
the copper atoms. Thus, it can be stated that the MFT peak at r = 2.70-2.77 Å (Fig.
4b) for complexes 3a Cu and 3b Cu unambiguously corresponds to the Cu…Cu
distance, i.e., these molecules have a dimeric structure. The EXAFS WT maps of
complexes 3a Cu and 3b Cu also show additional regions with k close to the
scattering at light atoms and with r coinciding with the Cu…Cu distance, which
precludes the isolation of this scattering from the MFT’s of the respective
complexes. Based on the structure of the ligands, the appearance of these WT
regions can be explained by scattering on the sulfur and oxygen atoms of the
tosylamine moiety.
16

a
b
c
Fig. 5. (a) EXAFS WT map of copper foil in r, k- coordinates, (b) EXAFS WT map of complex 3b Cu, (c) EXAFS WT map of
complex 3a Cu.
17

The quantitative parameters of the CS’s in the 2a-e, 3a Cu and 3b Cu
complexes are obtained from the approximation of the experimental EXAFS by the
theoretically calculated curve of the optimal model of the nearest atomic
environment of the copper ions. The obtained values of the CS characteristics are
given in Table 1.
Table 1. Local structure parameters of the complexes 2а-е, 3a Cu and 3b
Cu (R is the interatomic distance, σ2 is the Debye-Waller factor, Q is the fit quality
function).
Sample
2а
CN
4
R, Å
1.97
1.93
1.96
3.03
1.95
1.95
3.03
1.97
1.96
1.97
2.02
2.00
2.05
σ2, Å2
0.0031
0.0035
0.0035
0.0042
0.0037
0.0037
0.0067
0.0030
0.0035
0.0025
0.0044
0.0033
0.0052
CS
N
Q*, %
0.7
2
O/N
O/N
Cu
O/N
O/N
Cu
N
3.2
3a Cu
2
1
2
2.6
3b Cu
2
1
4
0.8
0.8
1.0
0.4
2.9
2.8
2c
2d
4
N
4
N
2e
4
N
2b Co
2b Ni
2b Fe
4
N
4
N
Consistent data were obtained for all compounds, which made it possible to
relate the structural data to the magnetic and spectral characteristics of the copper
complexes.
Figures 6a and b show the XANES spectra of the Fe, Ni and Co K-edges and
the respective MFT EXAFS χ(k)k3 for the complexes 2b Co, 2b Ni and 2b Fe.
18

6
4
2
N
Fe K-edge
1,0
0,5
0,0
0,15
0,10
0,05
0,00
A
2b Fe n=3
7100
7105
7110
E, eV
0
8
0
1
2
3
4
5
6
7120
7200
Ni K-edge
7280
E, eV
r, Å
1,0
0,5
6
4
2
0
8
6
4
2
0
A
0,08
0,04
8330
8335
8340
2b Ni n=3
E, eV
0,0
1,2
8300
8350
8400
8450
8500
0
1
2
3
4
5
6
r, Å
E, eV
Co K-edge
0,8
0,4
0,0
0,24
0,16
0,08
A
7700
7704
7708
E, eV
2b Co n=3
0
1
2
3
4
5
6
7680
7710
7740
7770
7800
E, eV
r, Å
a
b
Fig. 6. (a)- XANES K-edges (the insets show the pre-edge structure) and (b)-
MFT EXAFS χ(k)k3 (experiment – solid line, theory – empty circles) of complexes
2b Co, 2b Ni and 2b Fe.
The XANES analysis showed that in all the 2b Ni, Co and Fe complexes, the
metal ion is in a tetrahedral ligand environment with the coordination core MN4.
The quantitative parameters of the CS for the 2b Ni, Co and Fe complexes
obtained from fitting the experimental EXAFS to the theoretically calculated curve
for the optimal model of the nearest atomic environment of metal ions are given in
Table 1. The average bond lengths of the complexes depend on the ionic radius of
the metal and varied from 2.00-2.02 Å for Ni and Co, up to 2.05 Å for Fe. Thus,
regardless of the length of the alkyl substituent, the complexes have an ML2
composition, in which the hydroxy group of the alcoholic fragment is not involved
19

in coordination with the metal.
3.5. The X-ray diffraction
The compound 3b (Fig. 7) crystallized in the P21/n space group as a
centrosymmetric binuclear moiety, the inversion center is located at the center of
the rhombic fragment Cu2O2 (Cu1…Cu1A 3.012 Å; selected bond lengths and
bond angles are summarized in the Table 2; Fig. 7). Each Schiff base ligand is
coordinated in a tridentate manner via amino- (N1) and imino-N-atoms (N2) and
also alkoxy-O-atoms (O3) and in a bridging mode (Cu1-O3-Cu1A). The geometry
of the copper atom environment (CuN2O2) corresponds to distorted square-planar
(the deviation of the Cu1 atom from the N1N2O3O3A plane is 0.036(2) Å). The
angle between planes of the aromatic rings C1–C6 and C8–C13 is 61.9°, that is
substantially reduced in comparison with the analogous angle in the free molecule
2-tosylaminobenzaldehyde (81.85(6)°) [41, 42]. Both S–O bonds have close
lengths. The Cu1…O2 distance 2.881(5) Å is non-bonding. It is worth noting that
the Cu1–O3 bond is unusually short. According to analysis of the CCDC by the
Mogul geometry check tool [43], only 15 earlier described copper complexes
contain Cu–O bonds that fall in the range 1.891-1.927 Å. Other geometrical
parameters of the organic ligands in most cases are close to common values [44].
Fig. 7. Molecular structure of the complex 3b (atoms with character A in the atom
labels are at (x-0.5, -y+0.5, z-0.5); carbon-bonded hydrogen atoms are omitted for
clarity.
20

Table 2. Selected bond lengths d (Å) and bond angles ω (deg.) for 3b.
Bond
Cu1–N1
Cu1–N2
Cu1–O3
Cu1–O3A
C1–C2
d, Ǻ
Bond
N1–S2
d, Ǻ
1.935(4)
1.953(5)
1.895(3)
1.926(4)
1.324(8)
1.384(10)
1.312(11)
1.424(6)
ω, deg.
1.599(4)
1.273(7)
1.475(8)
1.344(9)
1.372(9)
1.404(6)
1.428(4)
1.430(4)
ω, deg.
N2–C14
N2–C15
C15–C16
C16–C17
O3–C17
C2–C3
C3–C4
O1–S2
N1–C8
O2–S2
Angle
Angle
N1–Cu1–N2
O3–Cu1–N1
O3A–Cu1–N1
92.2(2)
O3–Cu1–N2
O3A–Cu1–N2
O3–Cu1–O3A
95.0(2)
163.0(2)
76.0(2)
168.8(2)
99.1(2)
It is known that molecules of complexes structurally related to 3b tend to
dimerize by the formation of axial Cu–O bonds with adjacent molecules in the
crystal [45]. However, the non-interacting O2 atom position of the SO2 group in
one fragment of the complex molecule as well as the deviation (36.6o) of the
closely located phenyl fragment C8–C13 from the plane Cu1N1N2O3O3A in
another fragment creates sterical hindrance and prevents such bond formation. As a
result, only short C–H…O contacts (С14-H…O1A 3.433 Å, H-O1A 2.55 Å, angle
С14-H…O1A 158.5°, where atom with character A in the atom label is at (x-0.5, -
y+0.5, z-0.5)) could be observed.
Conclusion
Thus, based on the set of experimental data of IR, EXAFS, XANES, EPR
spectroscopy, magnetochemistry and XRD, it was established that N-[2-
21

[(hydroxyalkylimino)methyl]phenyl]-4-methylbenzenesulfonamides
with
the
(СН2)n-spacer (n = 2-6) form mononuclear Cu(II), Ni(II), Co(II) and Fe(II)
complexes, regardless of the spacer length, in which the alcoholic group of the
hydroxyalkylamine fragment does not participate in coordination with the metal.
For copper complexes (n = 2 and3), when the length of the hydroxyalkyl moiety is
allowed to be realized by additional five- or six-membered metallacycles, dimeric
structures for the copper complexes with bridging oxygen atoms of alcoholic
groups are formed. In these copper complexes, a strong antiferromagnetic
exchange interaction is observed between the copper atoms in the dimeric
molecule.
The
dimeric
structure
of
bis{N-[2-[(2-
hydroxypropylimino)methyl]phenyl]-4-methylbenzenesulfonamide}dicopper(II)
was determined by the X-ray diffraction method.
Acknowledgements
This work was performed with financial support from the Ministry of
Education and Science of the Russian Federation (the State assignment: project
4.5388.2017/8.9). IR, NMR, UV-Vis and PL spectra were obtained using the
facilities of the “Molecular Spectroscopy” Multi-user Center of the Southern
Federal University. X-ray absorption spectra were measured at the Unique
Scientific Facility Kurchatov Synchrotron Radiation Source funded by the Ministry
of education and science of the Russian Federation (project RFMEFI61914X0002).
X-ray diffraction studies were performed at the Center of Shared Equipment of
IGIC RAS.
22

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26

1
2
200
300
400
500
H, mT
Fig. 1. The EPR spectrum of 2а, powder, Т=293 K. 1 – experiment (solid
line), 2 - simulation (circles) with parameters of SG gz = 2.264; gx=2.126; gy
=2.023.
27

1
2
0
200
400
600
H, mT
Fig. 2. The EPR spectrum of 3а, powder, Т=293 K. 1 – experiment (solid
line), 2 - simulation (circles) with parameters of SG (1) and (2): Сdimer=75% gz =
2.310; gx=2.041; gy =2.031; D = 0.3560 cm-1; E = 0.0225 cm-1. Сmonomer= 25%. gz =
2.310; gx=2.041; gy =2.031.
28

2,4
2,2
2,0
1,8
1,6
2,4
2,2
2,0
1,8
1,6
0
50
100
150
200
250
300
0
50
100
150
200
250
30
T(K)
T(K)
b
a
2,4
2,2
2,0
1,8
1,6
50
100
150
200
250
300
T(K)
d
c
Fig. 3. Temperature dependence of µeff of copper complexes 2c (a), 2d (b),
2e (c), 3a (d).
29