Magnetism of novel Schiff-base copper(II) complexes derived from aminoacids

Article abstract of DOI:10.1016/j.poly.2013.05.045

Magnetic properties of five copper(II) complexes of the formula [CuL ³(H₂O)₂] or [CuL⁴(H₂O)] were investigated. These contain a Schiff-base L derived from salicylaldehyde and aminoacids. The ligand L is represented by four bonding isomers (1 through 4) and it is either tridentate (L³) or tetradentate (L⁴). The fifth ligand contains sulfonato group instead of the carboxyl one. Structurally, two complexes are monomers (1 and 4), one is a dimer (5), and two are polymers (2 and 3). Their magnetic behaviour is more complex: 1 behaves as an antiferromagnetic Heisenberg diad, 2 and 4 are ferromagnetic chains, 3 is a combined ferromagnetic/antiferromagnetic ladder (ribbon), and 5 exhibits a complex 3D-ordering with unusual temperature evolution of the effective magnetic moment.

Full text of DOI:10.1016/j.poly.2013.05.045

Polyhedron 61 (2013) 87–93
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Magnetism of novel Schiff-base copper(II) complexes derived from
aminoacids
⇑
ˇ
Z. Puterová-Tokárová , V. Mrázová, R. Boca
Department of Chemistry, FPV, University of SS Cyril and Methodius, Nám. J. Herdu 2, 917 01 Trnava, Slovakia
a r t i c l e i n f o
a b s t r a c t
Magnetic properties of five copper(II) complexes of the formula [CuL3(H2O)2] or [CuL4(H2O)] were inves-
tigated. These contain a Schiff-base L derived from salicylaldehyde and aminoacids. The ligand L is rep-
resented by four bonding isomers (1 through 4) and it is either tridentate (L3) or tetradentate (L4). The
fifth ligand contains sulfonato group instead of the carboxyl one. Structurally, two complexes are mono-
mers (1 and 4), one is a dimer (5), and two are polymers (2 and 3). Their magnetic behaviour is more com-
plex: 1 behaves as an antiferromagnetic Heisenberg diad, 2 and 4 are ferromagnetic chains, 3 is a
combined ferromagnetic/antiferromagnetic ladder (ribbon), and 5 exhibits a complex 3D-ordering with
unusual temperature evolution of the effective magnetic moment.
Article history:
Received 29 April 2013
Accepted 23 May 2013
Available online 1 June 2013
Keywords:
Aminoacids
Schiff base
Cu(II) complex
Magnetism
Ó 2013 Elsevier Ltd. All rights reserved.
Magnetic ordering
1. Introduction
c-aminobutyric acid which causes coordination via the unique se-
ven-membered ring [15]. Extensive investigations on modelling of
active sites of native copper oxidases by copper(II) chelates derived
from Schiff base ligands containing amino acids over past decades
provided clear insights into the relationship between the structural
features and the catalytic activity (superoxide scavenging activity,
catechol-oxidase like activity, ascorbic-oxidase like activity) of
these complexes [7–21]. Despite of this plethora publications on
the structure–activity relationship, studies concerning their mag-
netostructural correlations are rather rare [13,22]. As an extension
of such work, we have chosen five copper(II) N-salicylidene-ami-
noacidates 1–5 (Fig. 1) with different coordination modes in order
to obtain detailed information about the magnetic exchange mech-
anism and to identify factors that influence their magnetic
properties.
Copper(II) complexes with Schiff base ligands derived from
amino acids and salicylaldehyde have been reported in the litera-
ture for a long time [1]. The distorted square-pyramidal geometry
around Cu(II) ion gives Schiff base copper(II) chelates potential to
act as valuable non-enzymatic models for more complicated cop-
per metalloproteins, such as Cu,Zn-superoxide dismutase [2–4]
and catechol oxidase [5,6]. The number of reported mononuclear
copper(II) N-salicylidene aminoacidates [7–12] is superior to those
with higher nuclearities [13,14]. This is due to the fact that the
majority of ligands are produced by condensation reaction of sali-
cylaldehyde and
a-amino acid exhibiting tridentate coordination
mode around the metal centre with the most stable five-mem-
bered chelate ring. Such arrangement prefers formation of mono-
nuclear copper(II) complexes with one Schiff base ligand and two
aqua ligands adopting square-pyramidal geometry [10–12]. The
employment of b-aminoacids in the synthesis of N-salicylidene-
aminoacidato Schiff base ligand offers the possibility of construc-
tion of extended networks of higher nuclearity [13] where the
six-membered chelate ring is incorporated. Moreover, different
coordination behaviour of the carboxylato functional group in a
simple b-aminoacids (e.g. b-alanine, b-amino-iso-butyric acid)
and sulfonato functional group for example in taurine as a part
of Schiff base ligand can be observed [14]. Recently, we reported
the structure of copper(II) N-salicylidene-aminoacidate containing
2. Experimental
2.1. Materials
All chemicals were of reagent grade, obtained from commercial
sources, and used without further purification. All solvents were
dried and distilled by standard methods prior to use. Spectroscopic
grade solvents were used for spectral measurements.
2.2. Physical measurements
⇑
Corresponding author. Tel.: +421 33 5921408; fax: +421 33 5921 403.
IR spectra were measured as KBr pellets (Schimadzu, Impact
E-mail
addresses:
zita.tokarova@ucm.sk,
zita.puterova@gmail.com
(Z. Puterová-Tokárová).
400) in the 4000–400 cmꢀ1 region. Electronic spectra of DMSO
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.05.045

88
Z. Puterová-Tokárová et al. / Polyhedron 61 (2013) 87–93
OH2
Cu
O
Cu
O
N
O
S
N
H2O
Cu
N
O
O
O
O
N
N
Cu
O
O
O
O
O
Cu
O
O
O
Cu
O
O
Cu
O
O
S
Cu
N
O
O
OH2
OH2
O
OH2
OH2
OH2
OH2
H2O
4
1
2
5
3
Cu(DL-
SBAB)(H2O)2
[Cu(SAIB)(H2O)2]
[Cu(SGABA)(H2O)]
[Cu(STaurine)(H2O)]·H2O
[Cu(DL-
SBAIB)(H2O)]·H2O
Fig. 1. Sketch of complexes under study. Red (bold) atoms are from the neighbouring units. (Colour online.)
solutions of compounds (c = 4 ꢁ 10ꢀ3 mol dmꢀ3) were measured in
the 200–800 nm region (Schimadzu, UV-160). Elemental analysis
was performed by FlashEA 1112 (ThermoFinnigan). Content of cop-
per was determined by electrolysis (Pt-cathode, U = 2 V, I = 2–3 A)
after mineralization of the complexes in conc. H2SO4.
A SQUID magnetometer (MPMS-XL7, Quantum Design) has
been used for magnetic data using the RSO mode of detection.
The susceptibility taken at B = 0.1 T between T = 2–300 K has been
corrected for the underlying diamagnetism and converted to the
effective magnetic moment. The magnetization has been measured
at two temperatures: T = 2.0 and 4.6 K.
2.3.6. Compound 4 – Cu(DL-SBAB)(H2O)2
Anal. Calc. for C11H15CuNO6 (320.78 gꢂmolꢀ1): C, 41.19; H, 4.71;
N, 4.37; Cu, 19.81. Found: C, 41.52; H, 4.76; N, 4.70; Cu, 20.20%.
IR(KBr)
m = 3453 (OH, coord. water), 3050, 2974, 1638 (C@N),
1529 (COOꢀas.), 1344 (COOꢀsym), 1211, 753, 564, 454, 412 cmꢀ1
.
UV–Vis (DMSO, c = 4 ꢁ 10ꢀ3 mol dmꢀ3) kmax = 670 (log
e = 1.32),
352 (loge = 2.54) nm.
2.3.7. Compound 5 – [Cu(STaurine)(H2O)]ꢂH2O
Anal. Calc. for C18H26Cu2N2O12S2 (653.63 gꢂmolꢀ1): C, 33.10; H,
4.00; N, 4.30; S, 10.00; Cu, 20.00. Found: C, 32.99; H, 3.87; N,
4.28; S, 10.20; Cu, 20.34%. IR(KBr)
m = 3418 (OH, coord. water),
1628 (C@N), 1285 (SOOꢀas.), 1246 (phenolic Oꢀ), 1177 (SOOꢀsym),
755, 618, 415 cmꢀ1. UV–Vis (DMSO, c = 4 ꢁ 10ꢀ3 mol dmꢀ3) kmax
2.3. Synthesis
716 (loge = 1.44), 358 (loge = 2.40) nm.
2.3.1. Ligands – general procedure
The Schiff–condensation of salicylaldehyde with the corre-
sponding amino acid at a ratio 1:1 in water–alcohol solution for
3 h at room temperature resulted to the tridentate ligands: H2SAIB,
H2SGABA, H2SBAIB, H2SBAB, H2STaurine. Ligands were subse-
quently used without further purification.
3. Results and discussion
3.1. Synthesis of complexes
All the complexes were synthesized by two step procedure as
we had previously described elsewhere [15]. First, by condensation
of salicylaldehyde and appropriate amino acid in water–ethanol
(1:1) solution Schiff base ligands were formed in situ. In the next
step, the coordination was performed by the reaction of copper(II)
acetate dihydrate with Schiff base ligand leading to final copper(II)
complexes 1–5 (Fig. 1) in 62–67% yields.
2.3.2. Complexes – general procedure
To a water/ethanol solution (1:1, 60 cm3) of appropriate Schiff
base ligand (10 mmol), an aqueous solution of copper acetate dihy-
drate (10 mmol in 60 cm3 of water) was added and stirred for 1 h
at 50 °C accompanied by a colour change to dark green. The resul-
tant reaction mixture was filtered off and the filtrate was left to
crystallise spontaneously for several days at room temperature. Fi-
nal complexes were separated and washed with cold ethanol.
3.2. IR and electronic spectra of the complexes
The electronic spectral data recorded in DMSO (c = 4ꢂ10ꢀ3
-
2.3.3. Compound 1 – [Cu(SAIB) (H2O)2]
Anal. Calc. for C11H15CuNO5 (304.78 g molꢀ1): C, 43.35; H, 4.96;
N, 4.60; Cu, 20.85. Found: C, 45.69; H, 4.52; N, 4.88; Cu, 20.19%.
mol dmꢀ3) of compounds 1–5 exhibit a similar absorptions, dis-
playing
a
d–d transitions in the range 658–716 nm
IR(KBr)
m = 3446 (OH, coord. water), 3290, 2984, 1636 (C@N),
corresponding to the square-pyramidal arrangement of {CuNO4}
chromophore. Absorption bands at 350–360 nm are attributed to
the ligand-to-metal charge transfer (CT) transitions. IR spectra of
all complexes display strong band at 1628–1638 cmꢀ1 characteris-
tic for the stretching frequencies of (C@N) group. The asymmetric
1541 (COOꢀas.), 1340 (COOꢀsym), 1206, 755, 549, 442 cmꢀ1. UV–
Vis (DMSO, c = 4 ꢁ 10ꢀ3 mol dmꢀ3) kmax = 658 (log
e = 1.65), 353
(loge = 2.39), 264 nm.
vibration of the coordinated carboxylato group [
m
(COOꢀas.)] in
2.3.4. Compound 2 – [Cu(SGABA)(H2O)]
Anal. Calc. for C11H13CuNO4 (286.76 g molꢀ1): C, 46.07; H, 4.57;
complexes 1–4 are observed at 1529–1540 cmꢀ1 region, and a
band within the region 1340–1350 cmꢀ1 is assigned to symmetric
N, 4.88; Cu, 22.16. Found: C, 46.37; H, 4.45; N, 4.70; Cu, 22.54%.
vibration of carboxylato group [m
(COOꢀsymm)] [15]. The frequen-
IR(KBr)
m = 3442 (OH, coord. water), 3030, 2917, 1635 (C@N),
1540 (COOꢀas.), 1352 (COOꢀsym), 1210, 752, 557, 459, 415 cmꢀ1
.
cies characteristics of the (S–O) stretching modes in compound 5
are observed at 1285 and 1177 cmꢀ1, respectively [14]. The band
around 1200–1250 cmꢀ1 can be assigned to (C–O) vibrations of
the phenolic group in all complexes.
UV–Vis (DMSO, c = 4 ꢁ 10ꢀ3 mol dmꢀ3) kmax = 682 (log
e = 1.48),
352 (loge = 2.60), 282 nm.
2.3.5. Compound 3 – [Cu(DL-SBAIB)(H2O)]ꢂH2O
Anal. Calc. for C11H15CuNO6 (320.78 gꢂmolꢀ1): C, 41.19; H, 4.71;
3.3. Description of the structures 1–3 and 5
N, 4.37; Cu, 19.81. Found: C, 40.90; H, 4.50; N, 4.76; Cu, 20.11%.
IR(KBr)
m
= 3444 (OH, coord. water), 3042, 2959, 1627 (C@N),
The crystal structures of complexes [Cu(SAIB)(H2O)2] (1),
[Cu(SGABA)(H2O)] (2), [Cu(DL-SBAIB)(H2O)]ꢂH2O (3), and [Cu(STa-
urine)(H2O)]ꢂH2O (5) were already described elsewhere [14,15].
The coordination polyhedron around each copper(II) centre of all
1540 (COOꢀas.), 1350 (COOꢀsym), 1205, 769, 606, 470, 410 cmꢀ1
.
UV–Vis (DMSO, c = 4 ꢁ 10ꢀ3 mol dmꢀ3) kmax = 667 (log
e = 1.28),
352 (loge = 2.48) nm.

Z. Puterová-Tokárová et al. / Polyhedron 61 (2013) 87–93
89
complexes 1–3, 5 is best described as a slightly distorted tetragonal
pyramid as confirmed by the structural parameter [23]; 1:
= 0.0352; 5:
= 0.0402. The crystal structure of [Cu(SAIB)(H2O)2] (1) is formed
model of the [S1, S2] = [1/2, 1/2] diad. The susceptibility and mag-
netization data sets have been treated simultaneously, by minimiz-
s
s
s
1 = 0.1939,
s
2 = 0.0898; 2:
s
= 0.0740; 3:
s
ing a functional F = R(
the susceptibility and magnetization. The minor corrections ac-
count for some temperature independent magnetism TIM),
v) ꢁ R(M) that accounts for relative errors of
by single molecules with five-membered metallocycle ring coordi-
nated with cooper(II) ion. The studied crystal was non-merohed-
rally twinned with a ratio of twin components 0.52:0.48. The
ligand connectivity in the compound 3 – [Cu(DL-SBAIB)(H2O)]ꢂH2O
is very similar to that found in 1 except that the DL-H2SBAIB dian-
ion forms a six-membered ring. The {CuNO4} chromophore is in 1
and 3 coordinated by two oxygen atoms from the phenolic group
(1:Cu1–O1, and Cu21–O21; 3: Cu1–O1) and carboxylato group
(1:Cu1–O2 and Cu21–O22; 3: Cu1–O2) and one nitrogen atom
from imine group (1: Cu1–N1and Cu21–N21; 3: Cu1–N1) of L
and two oxygen atoms of water, one in equatorial position (1:
Cu1–O4 and Cu21–O24; 3:Cu1–O4) and one in axial position (1:
Cu1–O5 and Cu21–O25; 3: Cu1–O5). The crystal structure of com-
pound 2 – [Cu(SGABA)(H2O)] is formed by dimers in which car-
(v
molecular-field correction (zj), and eventually a presence of a
monomeric paramagnetic impurity (xPI). The conventional spin-
Hamiltonian
ꢀ2
^
^
^
H ¼ ꢀJðS1 ꢂ S2Þꢀh
þ
lBBzgisoðS1z þ S2zÞ
ð1Þ
gave the following set of magnetic parameters: J/hc = ꢀ18.9 cmꢀ1
,
giso = 2.148,
factor R(
v
TIM = ꢀ5.0 ꢁ 10ꢀ9 m3 molꢀ1, xPI = 0.0039; discrepancy
v
) = 0.020 and R(M) = 0.033.
The compound 2 differs from 1 in the feature that the carboxy-
lato oxygen atom bears a bridging function; this causes a formation
of dinuclear units (C22H14Cu2N2O8, Mr = 561.43) that form a zigzag
chain structure (Fig. 4). The magnetic behaviour is completely dif-
ferent: the effective magnetic moment on cooling rises progres-
sively showing that a ferromagnetic exchange interaction applies
(Fig. 5). The magnetic data were fitted by a model of a finite Hei-
senberg ring: cyclo-[S = 1/2]. Eight members have been chosen
boxyl oxygen O3 is bonded in
copper(II) ion in the equatorial plane and axially to the adjacent
molecule. Coordination via -amino-butyric acid chain of the H2-
a bidentate manner to one
c
SGABA ligand causes the formation of unusual seven-membered
ring. The coordination polyhedron is in basal plane completed with
phenolic oxygen (Cu1–O1), carboxylato oxygen (Cu1–O2), imino
nitrogen (Cu1–N1) and carboxyl oxygen (Cu1–O3) from the neigh-
bouring molecule. Water oxygen (Cu1–O5) is bonded axially. Com-
pound 5 is a centrosymmetric dimer. At each copper centre, the
basal plane of the square pyramid is occupied by three oxygen
atoms, one each from the phenolato group (Cu1–O1), sulfonato
group (Cu1–O2), aqua ligand (Cu1–O5), and nitrogen (Cu1–N1)
from imine group. The apical sites of copper(II) ion are occupied
by the oxygen atoms (Cu1–O3) of the sulfonato group from the
neighbouring molecule [14].
and the data fitting gave: J/hc = +7.1 cmꢀ1, giso = 2.156,
vTIM = -
ꢀ7.5 ꢁ 10ꢀ9 m3 molꢀ1; R(
v) = 0.016, R(M) = 0.0091.
The compound 4 shows analogous magnetic properties to 2
(Fig. 6); the same model has been applied for the data fitting (dinu-
clear formula unit C22H26Cu2N2O8, Mr = 573.54). To this end: J/
hc = +3.83 cmꢀ1
R(
,
giso = 2.142, vTIM ꢃ 0, zj/hc = ꢀ0.0023 cmꢀ1
;
v
) = 0.014, R(M) = 0.022.
The compound 3 is formed of mononuclear neutral complexes
(formula unit C11H15CuNO6, Mr = 320.78) for which a behaviour
like a Curie paramagnet enriched is expected. However, an ex-
change interaction of the ferromagnetic nature is evident from
the temperature dependence of the effective magnetic moment
(Fig. 7). An inspection to the crystal packing shows that there exists
a hydrogen-bond rich channel among mononuclear units (Fig. 8).
Two models of magnetic interactions can be applied. The former
considers a ferromagnetic coupling between a pair of [S1, S2] = [1/2,
1/2] centres. This could explain a drop of the effective magnetic
moment at low temperature as a consequence of the (positive)
zero-field splitting for the S = 1 ground state. However, this model
does not work properly.
3.4. Magnetic properties
The complex 1 consists of mononuclear units (C11H15CuNO5,
Mr = 304.78) for which a simple Curie–Weiss law is expected to
be obeyed. However, the magnetic susceptibility on cooling passes
through a maximum and then it turns to the zero (Fig. 2). This is a
fingerprint of an exchange coupling of the antiferromagnetic nat-
ure. The inspection to the crystal structure shows that, indeed, a
The second model mimics a dinuclear ribbon-type structure
through an octanuclear fragment (a doubled tetranuclear ring, a
ladder with four stacks) where two J-constants occur: J1 – ferro-
formation of dimers held by the p–p stacking of the benzene rings
is evident (Fig. 3). Thus the magnetic data have been fitted using a
0.05
B = 0.1 T
2
T = 4.6 K
0.2
μ
μ
μ
1
0.1
χ
T = 2.0 K
0.0
0
10
150
T/K
20
200
30
40
0.00
0
0
1
2
3
4
5 6 7
0
50
100
250
300
B/T
Fig. 2. Magnetic functions for 1: left – temperature dependence of the effective magnetic moment per formula unit, right – field dependence of the magnetization. Lines –
fitted.

90
Z. Puterová-Tokárová et al. / Polyhedron 61 (2013) 87–93
Fig. 3. Expanded short contacts in 1 evidencing formation of dimers held by p–p stacking. Hydrogen atoms are omitted for clarity.
Fig. 4. Extended dinuclear motif for 2 showing a zigzag chain-like structure. Hydrogen atoms are omitted for clarity.
B = 0.1 T
T = 2.0 K
4
3
2
1
0
2
1
0
T = 4.6 K
μ
μ
15
10
5
μ
χ
0
0
10
20
30
40
0
1
2
3
4
5 6 7
0
50
100
150
T/K
200
250
300
B/T
Fig. 5. Magnetic functions for 2: left – temperature dependence of the effective magnetic moment per dinuclear formula unit, right – field dependence of the magnetization.
Lines – fitted.
magnetic inside legs, J2 – antiferromagnetic between stacks. To this
The compound 5 was structurally characterized as a dinuclear
complex (C18H26Cu2N2O12S2, Mr = 653.63). Its magnetic behaviour
is surprisingly unusual and complex (Fig. 9); it cannot be inter-
preted like a diad. Between T = 4 and 70 K the effective magnetic
moment adopts a subnormal value and then it rises linearly until
end: J1/hc = +8.13 cmꢀ1, J2/hc = ꢀ0.98 cmꢀ1, giso = 2.264,
vTIM = -
ꢀ4.6 ꢁ 10ꢀ9 m3 molꢀ1
; R(v) = 0.021, R(M) = 0.054. Perhaps an
extension of the members of the double ring (10, 12, etc.) will im-
prove the reconstruction of the magnetization.

Z. Puterová-Tokárová et al. / Polyhedron 61 (2013) 87–93
91
B = 0.1 T
T = 2.0 K
T = 4.6 K
4
3
2
1
0
2
μ
15
μ
μ
1
0
10
5
χ
0
0
10
20
30
40
0
1
2
3
4
5 6 7
0
50
100
150
T/K
200
250
300
B/T
Fig. 6. Magnetic functions for 4: left – temperature dependence of the effective magnetic moment per dinuclear formula unit, right – field dependence of the magnetization.
Lines – fitted.
1.5
2.5
B = 0.3 T
T = 2.0 K
2.0
1.0
5
T = 4.6 K
1.5
1.0
0.5
0.0
μ
μ
4
3
2
1
0
μ
0.5
0.0
χ
0
10
150
T/K
20
30
40
0
1
2
3
4
5 6 7
0
50
100
200
250
300
B/T
Fig. 7. Magnetic functions for 3: left – temperature dependence of the effective magnetic moment per mononuclear formula unit, right – field dependence of the
magnetization. Lines – fitted.
Fig. 8. Mononuclear units and their packing in 3 evidencing a hydrogen-bond rich channel. Hydrogen atoms are omitted for clarity. Short contacts are represented by dotted
lines.
the room temperature where it becomes
magnetization shows a subnormal value. The crystal packing of 5
is complex (Fig. 10): the dinuclear units in one direction are held
l
eff = 1.32
l
B. Also the
plane they are linked by hydrogen bonds (O. . .O = 2.78 Å). These
planes are stacked thus forming a 3D-network.
Magnetic data in combination with the key structural factors
are summarized in Table 1.
together by
p–p stacking (3.56 Å); in the second direction of a

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Z. Puterová-Tokárová et al. / Polyhedron 61 (2013) 87–93
0.5
B = 0.3 T
1
μ
μ
0.4
μ
0.3
0.2
T = 2.0 K
T = 4.6 K
0.1
χ
0.0
0
10
20
30
40
0.0
0
0
1
2
3
4
5 6 7
0
50
100
150
200
250
300
B/T
T/K
Fig. 9. Magnetic functions for 5: left – temperature dependence of the effective magnetic moment per dinuclear formula unit, right – field dependence of the magnetization.
Fig. 10. Dinuclear units and their packing in 5. Hydrogen atoms are omitted for clarity.
Table 1
Key structural and magnetic characteristics of complexes 1 through 5.
Compound
Structure
Packing
1 [Cu(SAIB)(H2O)2]
monomer
2 [Cu(SGABA) (H2O)]
1D-chain
3 Cu(DL-SBAB) (H2O)2
ladder
H-bonds
ferromagnetic/antiferromagnetic ladder
+8.1 inside leg
ꢀ0.98 between stacks
4 [Cu(DL-SBAIB) (H2O)]ꢂH2O
5 [Cu(STaurine) (H2O)]ꢂH2O
n.a.
3D
p
–p
stacking
H-bonds,
complex
n.a.
p-p stacking
Magnetism
diad
ꢀ18.9
ferromagnetic 1D-chain
+7.1
ferromagnetic 1D-chain
+3.8
J/hc (cmꢀ1
)
clear complex packed into a hydrogen bond rich channel inside a
ladder; 5 – [Cu(STaurine)(H2O)]ꢂH2O is formed of dinuclear entities
containing sulfonato bridging group packed into a 3D-network via
hydrogen bonds. The common feature of all presented copper(II) N-
salicylidene-aminoacidates 1–5 is a distorted square-pyramidal
arrangement of the chromophore {CuNO4}.
4. Conclusions
The magnetic data (susceptibility and magnetization) of five
Cu(II) complexes containing Schiff base ligands of N-salicylidene-
aminoacidato type were investigated. The magnetic data for 1 were
fitted using the spin Hamiltonian and this complex behaves as an
antiferromagnetic Heisenberg diad. The magnetic susceptibility
data for 2 and 4 follow the model of a finite Heisenberg ring formed
of dinuclear entities with ferromagnetic 1D-chain behaviour. The
complex 3 is a combined ferromagnetic/antiferromagnetic ladder
with two J constants: one inside the leg and another between
stacks. The dinuclear complex 5 with sulfonato group instead of
carboxylato as it is in compounds 1–4 exhibits unusual magnetic
behaviour and cannot be interpreted like a diad. The different mag-
netic behaviour of complexes 1–5 is ascribed to a different modes
of coordination at the Cu(II) atom: 1 – [Cu(SAIB)(H2O)2] is a mono-
Acknowledgments
We gratefully acknowledge the financial support from Slovak
grant agencies (VEGA 1/0073/13, APVV-0014-11).
References
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