Synthesis, structure and magnetic properties of Ni(II)-Co(II) heterodinuclear complexes with ONNO type Schiff bases as ligands

Article abstract of DOI:10.1016/j.poly.2013.04.047

Four new heterodinuclear Ni(II)-Co(II) complexes, NiL·CoCl ₂·(DMF)₂ (I), NiL·CoBr₂· (DMF)₂ (II), NiL′·CoCl₂·(DMF) ₂ (III) and NiLDM·CoCl₂(DMF)₂ (IV), have been prepared in non-aqueous DMF using the ONNO type Schiff bases N,N′-bis(2-hydroxyphenylidene)-1,3-propanediamine (LH₂), N,N′-bis(2-hydroxyphenylidene)-1,4-butanediamine (L′H₂) and N,N′-bis(2-hydroxyphenylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH₂), and the inorganic salts NiCl₂ and CoCl ₂. The complexes were characterized by elemental analysis, IR spectroscopy, thermogravimetry and X-ray diffraction. An XRD study revealed that the Ni(II) ion is situated at the center of a distorted octahedral coordination sphere formed by two iminic nitrogen and two phenolic oxygen atoms of the ONNO type Schiff base and two other oxygen atoms belonging to coordinated DMF molecules. On the other hand, the Co(II) ion is situated inside a distorted tetrahedral coordination sphere, members of which being the two halogen atoms and two oxygen atoms, bonded to form a μ-bridge. The magnetic susceptibility of the complexes was studied using a SQUID magnetometer between 2.0 and 300 K at B = 0.1 T, and the magnetization data were taken up to B = 7 T at T = 2.0 and 4.6 K. The exchange interaction between the metal centers is of a ferromagnetic nature (typically J_Co-Ni/hc = +2 cm^-1) and at low temperature single-ion zero-field splitting applies (D_Ni/hc = +8 cm^-1, D_Co/hc = +14 cm^-1).

Full text of DOI:10.1016/j.poly.2013.04.047

Accepted Manuscript
Synthesis, Structure And Magnetic Properties Of Ni(Ii)-Co(Ii) Heterodinuclear
Complexes With Onno Type Schiff Bases As Ligands
Sevi Öz, Ján Titiš, Hasan Nazır, Orhan Atakol, Roman Boča, Ingrid Svoboda,
Hartmut Fuess
PII:
S0277-5387(13)00334-3
DOI:
http://dx.doi.org/10.1016/j.poly.2013.04.047
POLY 10104
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
6 March 2013
24 April 2013
Please cite this article as: S. Öz, J. Titiš, H. Nazır, O. Atakol, R. Boča, I. Svoboda, H. Fuess, Synthesis, Structure
And Magnetic Properties Of Ni(Ii)-Co(Ii) Heterodinuclear Complexes With Onno Type Schiff Bases As Ligands,
Polyhedron (2013), doi: http://dx.doi.org/10.1016/j.poly.2013.04.047
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SYNTHESIS, STRUCTURE AND MAGNETIC PROPERTIES OF Ni(II)-Co(II)
HETERODINUCLEAR COMPLEXES WITH ONNO TYPE SCHIFF BASES AS
LIGANDS
1
2
3
3
2
4
Sevi Öz , Ján Titiš , Hasan Nazır , Orhan Atakol , Roman Boća , Ingrid Svoboda , Hartmut
4
Fuess
1
2
- Ahi Evran University, Faculty of Science and Arts, Department of Chemistry, 40100,
Kırİehir, Turkey
- Department of Chemistry, FPV, University of SS Cyril and Methodius, 917 01Trnava,
Slovakia
3
- Ankara University, Faculty of Science, Department of Chemistry, 06100, Ankara, Turkey
- Strukturforschung, FB Materialwissenschaft, TU- Darmstadt, Petersenstrasse 23, D-
4
6
4287 Darmstadt, Germany
Abstract
Four new heterodinuclear Ni(II)-Co(II) complexes, NiL.CoCl .(DMF) (I), NiL.CoBr .(DMF)
2
2
2
2
2 2 2
(II), NiL’.CoCl .(DMF)2 (III) and NiLDM.CoCl (DMF) (IV), have been prepared in non-
aqueous DMF using the ONNO type Schiff bases N,N’-bis(2-hydroxyphenylidene)-1,3-
propanediamine (LH ), N,N’-bis(2-hydroxyphenylidene)-1,4-butanediamine (L’H ) and N,N’-
2
2
bis(2-hydroxyphenylidene)-2,2’-dimethyl-1,3-propanediamine (LDMH
2
), and the inorganic salts
2 2
NiCl and CoCl . The complexes were characterized by elemental analysis, IR spectroscopy,
thermogravimetry and X-ray diffraction. An XRD study revealed that the Ni(II) ion is situated at
the center of a distorted octahedral coordination sphere formed by two iminic nitrogen and two
phenolic oxygen atoms of the ONNO type Schiff base and two other oxygen atoms belonging to
coordinated DMF molecules. On the other hand, the Co(II) ion is situated inside a distorted
tetrahedral coordination sphere, members of which being the two halogen atoms and two oxygen
atoms, bonded to form a µ-bridge.
The magnetic susceptibility of the complexes was studied using a SQUID magnetometer
between 2.0 and 300 K at B = 0.1 T, and the magnetization data were taken up to B = 7 T at T =
2
.0 and 4.6 K. The exchange interaction between the metal centers is of a ferromagnetic nature
-1
(
typically JCo-Ni/hc = +2 cm ) and at low temperature single-ion zero-field splitting applies
-1
-1
(D
Ni/hc = +8 cm , DCo/hc = +14 cm ).
Keywords: Heterodinuclear complex, Ni(II)-Co(II), Schiff base ligand, magnetic properties,
thermogravimetry
ꢀ

Introduction
2
It is well known that the Schiff base N,N’-bis(2-hydroxyphenylidene)-1,3-propanediamine (LH )
readily forms polynuclear complexes. There are numerous reports on trinuclear [1-10],
tetranuclear [11-13] and polynuclear [14-15] complexes of this ligand and its derivatives. Being
an ONNO type ligand, the molecule is able to coordinate Ni(II) and Cu(II) ions between its
donor atoms and the second metal ion by the phenolic oxygen atoms, forming a bridge (Fig 1).
Such a dinuclear coordination was first observed in a dinuclear Cu(II)-Cu(II) complex [16]. This
class of dinuclear complex possesses interesting magnetic properties due to the magnetic
exchange interactions [17-23]. In the mentioned studies, Cu(II)-Cu(II) [17-19], Cu(II)-Mn(II),
Cu(II)-Ni(II) [20], Cu(II)-Cu(III) [21] and Cu(II)-In(III) [23] complexes with similar ligands
were prepared. Their magnetic properties were also reported. Also, the antimicrobial, antifungal
and luminescence properties of a heterodinuclear Mn(II)-Zn(II) complex were investigated [22].
LH
2
and its derivatives readily give NiL and CuL complexes with Ni(II) and Cu(II) ions [24],
and these complexes have the tendency to coordinate the salts of the 12-group elements, namely
2
+
2+
2+
2+
Zn , Cd and Hg [25-28]. The literature also describes similar complexes prepared from Sn
2
+
and Pb halides [29-30].
S
H
H
R
C=N
O
N=C
O
M1
M2
X
X
2
+
2+
2+
2+
2
Fig 1 Sketch of the dinuclear complexes prepared via LH : M1 = Ni or Cu ; M2 = Cu , Zn ,
2+
2+
2+
-
-
-
Cd , Hg , Sn ; X = Cl , Br , I ; S = dioxane or DMF.
The literature is silent about complexes of the above type with M2 = Co(II). This gap is filled by
the present communication where four heterodinuclear Ni(II)-Co(II) complexes were synthesized
(Fig 2). In parallel with preliminary studies, these complexes were prepared in dry DMF [28].
The complexes were characterized by elemental analysis, X-ray structure analysis and
thermogravimetry. Their magnetic properties were investigated by SQUID magnetometry.
ꢁ

S
R
C=N
O
N=C
O
Ni
Co
S
X
X
-
Fig 2 Sketch of heterodinuclear complexes: R = -(CH
2
)
3
-, X = Cl , S = DMF (I); R = -(CH
2
)
3
-, X
-
-
-
=
=
Br , S = DMF (II); R = -(CH
2
)
4
-, X = Cl , S = DMF (III); R = -CH -C(CH -CH
2
3
)
2
2
-, X = Cl , S
DMF (IV).
Experimental
Apparatus
An FTIR-spectrometer (Shimadzu) equipped with three reflection ATR units was used in taking
the IR spectra. The C, H and N analyses were performed using an Elemantal Vario Micro Cube
instrument. Metal analyses were recorded on a GBC Avanta PM Model atomic absorption
spectrometer using the FAAS mode. The mass spectra were obtained by a Shimadzu, 2010 plus
with a DI unit with an electron impact ionizer. The DI temperature was varied between 40 and
o
1
40 C and the ionization was carried out with electrons of 70 eV energy. The NMR spectra
were recorded on a Varian Mercury 400 MHz FT-NMR spectrometer using d
solvent.
6
-DMSO as the
The thermogravimetric analyses were performed by a Shimadzu DTG-60H. In the
o
thermogravimetric analyses, the emperature was varied between 30 and 600 C. These analyses
o
were performed at 10 C/min scan rate and under a N
2
atmosphere in Pt pans. Calibration of the
instrument was done with metallic In, Pb or Zn. The stoichiometry of the complexes was
estimated with the help of the mass loss data of the coordinatively bonded DMF molecules and
the thermal decomposition properties of the complexes were determined.
The magnetic data were taken with a SQUID apparatus (MPMS-XL7, Quantum Design) using
the RSO mode of detection. The temperature dependence of the magnetic susceptibility taken at
B = 0.1 T has been corrected for the underlying diamagnetism and converted to the effective
ꢂ

magnetic moment. The field dependence of the magnetization has been measured at two
temperatures: T = 2.0 and T = 4.6 K.
X-ray analysis
Single crystals of I, II, III and IV were mounted on an Xcalibur (TM) single crystal X-ray
diffractometer (Oxford Diffraction) with a sapphire CCD detector using MoK
.71073 Å) operating in the ꢁ/2ꢂ scan mode. The unit cell dimensions were determined and
refined by using the angular settings of 25 automatically centered reflections in the 2.79 ≤θ≤
6.36 range for complex I, 2.81 ≤θ ≤27.82 range for complex II, 2.62 ≤θ ≤27.97 range for
ꢀ
radiation (ꢀ =
0
2
complex III and 3.07 ≤θ≤27.93 range for complex IV. The data of complexes I, II and III were
collected at T = 293(2) K and the data of complex IV was collected at 105(2) K. The empirical
absorption corrections were applied by the semi-empirical method via the CrysAlis CCD
software [31]. Models were obtained from the results of the cell refinement and the data
reductions were carried out using the solution software SHELXL97 [32]. The structures of all the
complexes were solved by direct methods using the SHELXS97 software implemented in the
WinGX package [33].
Synthesis
The used reagents were from Merck or Fluka, and they were used without further purification.
Preparation of N,N’-bis(2-hydroxyphenylidene)-1,3-propanediamine (LH )
2
This Schiff base was prepared via a condensation reaction in EtOH under hydrothermal
conditions using 2-hydroxy-benzaldehyde and 1,3-diaminopropane. 2-Hydroxy-benzaldehyde
3
(
0.02 mol, 2.44 g) was dissolved in 40 cm of warm EtOH, then 0.01 mol (0.74 g) of 1,3-
diaminopropane was added to this solution and heated up to the boiling point. After cooling,
yellow crystals were filtered and air-dried. Yield: 92-95 %, mp 58 °C (determined by TG).
Elemental analysis for C17
18 2 2
H N O : theoretical C 72.3, H 6.43, N 9.92 %; found C 71.9, H 6.45,
3
-1
-1
3
-
N 10.47 %. ꢁmax = 243 nm, ꢂ = 7045 dm mol cm in DMSO, ꢁmax = 242 nm, ꢂ = 7865 dm mol
1
-1
-1
cm in MeOH. IR (cm ): ꢃ
2627, ꢃC-H(Ar) 3021-3019, ꢃC-H(aliph) 2929-2862, ꢃC=N 1629,
O-H
1
ꢃ
C=C(ring) 1608, ꢃC-O(phenol) 1274-1151, ꢄC-H(Ar) 762. H-NMR in d
6
-DMSO: 13.51 (s) (O-H), 8.60
13
(
2 2
s) (-CH=), 7.43 (d) (HAr), 7.32 (t) (HAr), 6.88 (t) (HAr), 3.68 (t) (N-CH -), 2.01 (p) (-CH -). C-
NMR in d -DMSO: 166.6, 161.1, 132.7, 132.1, 119.1, 118.9 (C ), 116.9 (-C=N), 58.5 (N-CH -),
6
Ar
2
+
+
31.9 (-CH
2
-). m/z: 282 [M] , 161 [HO-C
6
H
4
-CH=N-CH
2
-CH
2
-CH
2
] , 148 [HO-C
6
H
4
-CH=N-
+
+
+
+
CH
2
-CH
2
] (BP), 134 [HO-C
6
H
4
-CH=N-CH
2
] , 120 [HO-C
6
H
4
-CH=N] , 107 [HO-C
6
H
4
-CH
2
] ,
+
7
7 [C H ] .
6
5
Preparation of N,N’-bis(2-hydroxyphenylidene)-1,4-butanediamine (L’H ):
2
ꢃ

This Schiff base was prepared following the same procedure as for LH from 0.02 mol (2.44 g)
2
2
-hydroxy-benzaldehyde and 0.01 mol (0.88 g) 1,4-diaminobutane. Yield: 89-92 %, mp: 92 °C
determined by TG). Elemental analysis for C18 : theoretical C 72.9, H 6.80, N 9.44 %;
found C 72.5, H 6.14, N 9.33 %. ꢁmax = 242 nm, ꢂ = 8055 dm mol cm in DMSO, ꢁmax = 241
(
20 2 2
H N O
3
-1
-1
3
-1
-1
-1
nm, ꢂ = 6005 dm mol cm in MeOH. IR (cm ): ꢃO-H 2635, ꢃC-H(Ar) 3021-3019, ꢃC-H(aliph) 2929-
1
2
862, ꢃC=N 1629, ꢃC=C(ring) 1608, ꢃC-O(phenol) 1274-1151, ꢄC-H(Ar) 762. H-NMR in d
6
-DMSO: 13.51
(s) (O-H), 8.38 (s) (-CH=), 7.29 (d,t) (HAr), 7.24 (d,d) (HAr), 6.95 (d) (HAr), 6.86 (d,t) (HAr), 3.63
13
(t) (N-CH
2
-), 1.79 (t) (-CH
2
-CH
2
-). C-NMR in d
6
-DMSO: 165.16, 161.44, 132.38, 131.43,
+
118.98, 118.75 (CAr), 117.22 (-C=N), 59.48 (N-CH
2
-), 28.75 (-CH
2
-CH
2
-). m/z: 296 [M] , 175
+
+
[
HO-C
6
H
4
-CH=N-CH
2
-CH
2
-CH
2
-CH
2
] , 148 [HO-C
6
H
4
-CH=N-CH
2
-CH
2
-CH
2
] (BP), 134 [HO-
+
+
+
+
C
6
H
4
-CH=N-CH
2
] , 120 [HO-C
6
H
4
-CH=N] , 107 [HO-C
6
H
4
-CH
2
] , 77 [C
6
H
5
] .
Preparation
LDMH
This Schiff base was also prepared accordingly to the LH
hydroxy-benzaldehyde and 0.01 mol (1.02 g) 2,2’-dimethyl-1,3-diaminopropane. Yield: 87-90
, mp: 98 °C (determined by TG). Elemental analysis for C19 : theoretical C 73.5, H
.14, N 9.02 %; found C 73.4, H 6.35, N 8.72 %. ꢁmax = 243 nm, ꢂ = 7860 dm mol cm in
of
N,N’-bis(2-hydroxyphenylidene)-2,2’-dimethyl-1,3-propanediamine
(
2
)
2
procedure from 0.02 mol (2.44 g) 2-
%
22 2 2
H N O
3
-1
-1
7
3
-1
-1
-1
DMSO, ꢁmax = 243 nm, ꢂ = 7825 dm mol cm in MeOH. IR (cm ): ꢃ
2578, ꢃC-H(Ar) 3021-
O-H
1
3
019, ꢃC-H(aliph) 2929-2862, ꢃC=N 1629, ꢃC=C(ring)1608, ꢃC-O(phenol) 1274-1151, ꢄC-H(Ar) 762. H-NMR
6
in d -DMSO: 13.58 (s) (O-H), 8.36 (s) (-CH=N), 7.30 (t) (HAr), 7.25 (d,t) (HAr), 6.97 (d), 6.84
13
(
dt) (H ), 3.49 (s) (N-CH -), 1.04 (s) (-C(CH ) -). C-NMR in d -DMSO: 166.99, 161.45,
Ar
2
3 2
6
1
32.57, 131.61, 118.95, 118.87 (CAr), 117.20(-C=N), 68.36(N-CH
2
-), 34.48 (-C(CH
3
)
2
-), 24.61
+
+
(
-C(CH
3
)
2
-). m/z: 310 [M] , 176 [HO-C
6
H
4
-CH=N-CH
2
-C(CH
3
)
2
] , (BP), 134 [HO-C H -CH=N-
6 4
+
+
+
+
CH
2
] , 120 [HO-C
6
H
4
-CH=N] , 107 [HO-C
6
H
4
-CH
2
] , 77 [C
6
H
5
] .
Preparation of the Ni(II)-Co(II) complexes
All the complexes were prepared using the Schiff bases and metal salts in anhydrous DMF [28].
3
0
0
.02 mol of a Schiff base was dissolved in 40 cm of warm, anhydrous DMF, then a solution of
3
3
.002 mol (0.237 g) of NiCl
2
2 3
.6H O in 10 cm of DMF, 0.2 cm Et N and a solution of 0.085 g
-
-
3
(
0.001 mol) of CoX
2
(X= Cl or Br ) salt in 10 cm of hot anhydrous DMF was added. The
temperature was raised to 110 °C. The final solution was allowed to stand for 48 hours. The
formed blue crystals were separated by vacuum filtration and air dried.
Complex I: NiL.CoCl .DMF was prepared using 0.565 g LH, 0.475 g NiCl .6H O and 0.238 g
2
2
2
2
2 2 16 2 2 2 3 7 2
CoCl .6H O as described above. Elemental analysis for C17H N O Ni.CoCl .(C H NO) :
theoretical C 44.9, H 4.92, N 9.10, Cl 11.53, Ni 9.54, Co 9.58 %; found C 44.4, H 4.87, N 9.32,
ꢄ

-1
Cl 10.91±0.71, Ni 9.68±0.18, Co 9.35±0.15 %. IR (cm ): ꢃ
3033-3017, ꢃC-H(aliph) 2937-
C-H(Ar)
2864, ꢃC=O(DMF) 1644,
ꢃC=N 1624, ꢃC=C(ring) 1596, ꢃC-O(phenol) 1278-1148, ꢄC-H(Ar) 758.
Determination of DMF by TG: found 22.81±0.74, calculated 23.75 %.
Complex II: NiL.CoBr .DMF was prepared from 0.565 g LH , 0.475 g NiCl
CoBr by the procedure given above. Elemental analysis for C17 Ni.CoBr
theoretical C 39.2, H 4.30, N 7.95, Br 22.7, Ni 8.34, Co 8.37 %; found C 38.8, H 3.93, N 8.07,
2
2
2
2
.6H
2
O and 0.219 g
2
.(C NO) :
2
H
16
N
2
O
2
2
3
H
7
-1
Br 21.34±0.52, Ni 7.91±0.27, Co 7.87±0.19 %. IR (cm ): ꢃC-H(Ar) 3029-3011, ꢃC-H(aliph) 2949-
2
2
866, ꢃC=O(DMF) 1644, ꢃC=N 1625, ꢃC=C(ring) 1593, ꢃC-O(phenol) 12734-1155, ꢄC-H(Ar) 756. DMF: found
1.11±1.23, calculated 20.75 %.
Complex III: NiL’.CoCl
2
.DMF
2
was prepared from 0.592 g L’H
2
, 0.475 g NiCl
2
.6H
2
O and
for
0
.238 CoCl .6H O
g
2
2
as described above. Elemental
analysis
C H N O Ni.CoCl .(C H NO) : theoretical C 45.8, H 5.13, N 8.90, Cl 11.27, Ni 9.33, Co 9.37
18
18
2
2
2
3
7
2
-1
%
; found C 46.1, H 4.95, N 9.14, Cl 10.88±0.27, Ni 8.94±0.34, Co 8.89±0.47 %. IR (cm ): ꢃC-
H(Ar) 3034-3015, ꢃC-H(aliph) 2991-2866, ꢃC=N 1627, ꢃC=O(DMF) 1645, ꢃC=C(ring) 1601, ꢃC-O(phenol) 1271-
1
155, ꢄC-H(Ar) 758. DMF: found 23.01±1.13, calculated 23.22 %.
Complex IV: NiLDM.CoCl .DMF was prepared with 0.620 g LDMH
and 0.238 CoCl .6H as described above. Elemental
C H N O Ni.CoCl .(C H NO) : theoretical C 46.7, H 5.32, N 8.70, Cl 11.02, Ni 9.13, Co 9.16
2
2
2
2
, 0.475 g NiCl .6H
2
O
g
2
2
O
analysis
for
19
20
2
2
2
3
7
2
-1
%
; found C 46.4, H 4.97, N 8.76, Cl 10.49±0.64, Ni 8.81±0.21, Co 8.95±0.71 %. IR (cm ): ꢃC-
H(Ar) 3031-3017, ꢃC-H(aliph) 2950-2867, ꢃC=O(DMF) 1644, ꢃC=N 1627, ꢃC=C(ring) 1605, ꢃC-O(phenol) 1284-
1156, ꢄC-H(Ar) 757. DMF: found 22.49±1.33, calculated 22.70 %.
Results and discussion
X-ray structure
The molecular structures obtained by the X-ray diffraction analysis are shown in Fig. 3. The
crystal data, data collection and refinement parameters are given in Table 1. Selected bond
lengths and angles are listed in Table 2.
Fig. 3 reveals that the Ni(II) atom lies in plane formed by two phenolic oxygen atoms and two
iminic nitrogen atoms. The oxygen atoms of the coordinated DMF molecules are located in axial
4 2
positions in the NiN O coordination sphere, so this coordination sphere is distorted octahedral.
The Co(II) atom is coordinated by two phenolic oxygens and two halogen atoms, and the
CoO Cl coordination sphere is distorted tetrahedral.
2
2
The chelate rings in vicinity of the Ni(II) central atom are 6-membered in complexes I, II and
IV, whereas it is 7-membered in complex III. The expected conformation of the 6-membered
ꢅ

ring is the chair conformation, however complexes I, II and IV show almost a half-chair
conformation [27]. The angles between the C8C9C10 and N1C8C9N2 planes of the
NiN1C8C9C10N2 ring are calculated as 65.37° for complex I, 63.85° for complex II and 54.34°
for complex IV. These values for complexes I and II are close to those expected for an ideal
chair conformation. This angle deviates due to the steric effects of the two methyl groups. The
unexpected situation seen in the chelate rings is the small angle between the N1NiN2 and
C8N1N2C9 planes (1.5, 0.79 and 9.39° for complexes I, II and IV, respectively). Previous
studies have reported these angles to be around 10-15°. The Ni atom and the C8N1O1O2N2C9
atoms are situated in the same plane. The angle between the N1O1O2N2Ni atom plane and
O1CoO2 plane is also small: 6.26, 6.65 and 1.03° for complexes I, II and IV, respectively.
Fig 3 ORTEP drawing of complexes I through IV (in the reading direction).
The C8N1O1O2N2C9, Co(II) and Ni(II) atoms span the same planar structure. The 7-membered
chelate ring in complex III does not show analogous behavior, since the C8C11N1N2 atoms do
ꢆ

not form an exact plane. In addition, the O1N1N2O2Ni atoms exhibit a deviation from the mean
plane. The maximum deviation of the O1N1N2O2Ni atoms from the mean plane is 0.0314 Å for
the complexes I, II and IV and between 0.839-0.1229 Å for complex III. This can be related to
the torsion effect of the C9 and C10 atoms.
Thermogravimetry
TG has been utilized in studying the thermal stability and stoichiometry of the complexes. DMF
coordinated to the Ni(II) atoms can be liberated from the crystal structure in a characteristic
temperature range. Thus, measurement of the mass loss in this temperature range can help us in
determining the stoichiometry of the complexes. Fig. 4 shows comparative TG curves of the four
complexes. The thermal mass loss temperature of DMF molecules is between 168 and 195 ºC for
the complexes I and II. This interval is shifted down to 145-152 ºC and 140-155 ºC for
complexes III and IV, respectively. Since the distortion in I and II is lower (these molecules are
more symmetric), the DMF molecules tend to stay within the structure until higher temperatures.
Distortion of the structures in complexes III and IV shifts the DMF decomposition temperature
to lower values.
1
0
9
8
7
6
5
4
3
2
1
0
0
100
200
300
400
500
600
700
Temperature/°C
Fig 4 TG records for the Ni(II)-Co(II) complexes: I – dashed, II – solid, III – dotted, IV – dot
dashed.
ꢇ

2+
The electron density in the Ni-O bond decreases as the Co ions withdraw an electron from the
2+
phenolic oxygens. Consequently the Ni ions tend to accept electrons from other donors, which
are the solvent molecules. When the DMF molecules are thermally separated from the structure,
the electron of the phenolic oxygens become insufficient to stabilize both ions and the Co-O
coordination bond can disintegrate. The thermal degradation of NiL has been reported to occur at
360-380 ºC. Inspection to the TG curves confirms that a degradation of NiL proceeds at 380 ºC.
This shows that NiL degradation takes place only after liberation of DMF.
Magnetometry
One Ni(II) and one Co(II) center produce a high-temperature limit for the effective magnetic
2
2
1/ 2
moment, µeff = [g s (s +1) + g s (s +1)] µ , which amounts to 5.27 µ
B
when all g = 2.2
are applied. On cooling from the room temperature, the effective magnetic moment for complex
I slightly increases from µeff = 5.75 µ until T = 10 K and then it decreases rapidly to a value of
.15 µ at T = 2.0 K (Fig 5). This feature indicates a weak ferromagnetic coupling between the
Co Co
Co
Ni Ni
Ni
B
B
5
B
magnetic centers and some zero-field splitting that applies at low temperature. Down to 2.0 K the
molar magnetic susceptibility only increases, showing no local maximum. The molar
magnetization
per
formula
unit
possesses
the
saturation
limit
M = M / N µ = g s + g s , which yields M
1
= 5.5 for Smax = 5/2 and g = 2.2. The
= 4.8 at T = 2.0 K and B = 7 T, which
1
mol
A
B
Co Co
Ni Ni
measured magnetization adopts a value of only M
1
confirms some zero-field splitting.
The magnetic data were analyzed using the following spin Hamiltonian:
C
C
−2
(Ni)
a
(Co)
a
ˆ
ˆ
ˆ
H = −J(S ⋅S )> +[H
+ H
]
a
Ni
Co1
(1)
2
Ni,z
2
Ni
−2
2
Co,z
2
Co
−2
ˆ
ˆ
ˆ
ˆ
+
[D (S − S /3)> + D (S − S /3)> ]
Ni
Co
which accounts for the isotropic exchange (the first term), the Zeeman term (the second
contribution) and single-ion zero-field splitting (the remainder); a is the direction of the applied
magnetic field. The generated energy levels for a trial set of magnetic parameters were inserted
into the partition function, from which the magnetic susceptibility and magnetization were
reconstructed using the apparatus of statistical thermodynamics [34]. The Zeeman term was
modelled through a uniform distribution of the field orientation in 210 directions in one
hemisphere
(
kl
A)
−1
ˆ
ˆ
ˆ
ˆ
H
= µ B (g S sinϑ cosϕ + g S sinϑ sinϕ + g S cosϑ )>
(2)
B
m
A,x A,x
k
l
A, y A, y
k
l
A,z A,z
k
ꢈ

for each centre A = Ni, Co. This procedure properly mimics the powder average.
The susceptibility data were corrected for the molecular-field correction (zj) and eventually the
temperature-independent magnetism χTIM as χcorr = χmol /[1− (zj)χmol ]+ χTIM . The latter term
accounts for the uncompensated underlying diamagnetism and the temperature-independent
paramagnetism, along with the signal of the sample holder. The susceptibility and magnetization
data sets have been fitted simultaneously by applying an error functional that multiplies the
relative error of susceptibility and magnetization: F = R( χ) ×R(M).
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
B = 0.1 T
T = 2.0 K
2
5
T = 4.6 K
µ
µ
20
15
µ
1
0
5
0
χ
0
10
20
30
40
300
0
50
100
150
200
250
0
1
2
3
4
5 6 7
T/K
B/T
Fig 5 Magnetic functions for complex I. Left - effective magnetic moment, right - magnetization
per formula unit, inset - molar magnetic susceptibility (SI units). Solid lines - fitted with J/hc =
-1
-1
-1
+
1.91 cm , DNi/hc = +8.44 cm , DCo/hc = +14.1 cm , gav = 2.362.
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
B = 0.1 T
T = 2.0 K
T = 4.6 K
2
5
µ
µ
20
15
µ
1
0
5
0
χ
0
10
20
30
40
300
0
50
100
150
200
250
0
1
2
3
4
5 6 7
T/K
B/T
Fig 6 Magnetic functions for complex II. Left - effective magnetic moment, right -
magnetization per formula unit, inset - molar magnetic susceptibility (SI units). Solid lines -
-1
-1
-1
fitted with J/hc = +2.23 cm , DNi/hc = +8.67 cm , DCo/hc = +14.1 cm , gav = 2.395; R( χ) =
.0076, R(M) = 0.051
0
ꢀ
ꢉ

7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
B = 0.1 T
T = 2.0 K
T = 4.6 K
2
5
µ
µ
20
15
µ
1
0
5
0
χ
0
10
20
30
40
300
0
50
100
150
200
250
0
1
2
3
4
5 6 7
T/K
B/T
Fig 7 Magnetic functions for complex III. Left - effective magnetic moment, right -
magnetization per formula unit, inset - molar magnetic susceptibility (SI units). Solid lines -
-1
-1
-1
fitted with J/hc = +2.08 cm , D /hc = +8.38 cm , D /hc = +11.5 cm , g = 2.322; R( χ) = 0.011,
Ni
Co
av
R(M) = 0.052.
7
6
5
4
3
2
1
0
B = 0.1 T
6
5
4
3
2
1
0
T = 2.0 K
T = 4.6 K
2
5
µ
µ
20
15
µ
1
0
5
0
χ
0
10
20
30
250
40
300
0
50
100
150
200
0
1
2
3
4 5 6 7
T/K
B/T
Fig 8 Magnetic functions for complex IV. Left - effective magnetic moment, right -
magnetization per formula unit, inset - molar magnetic susceptibility (SI units). Solid lines -
−
1
−1
−1
fitted with J/hc = +2.58 cm , DNi/hc = +8.91 cm , DCo/hc = +11.3 cm , gav = 2.286, (zj)/hc =
−
-1
0.099 cm ; R( χ) = 0.026, R(M) = 0.029.
An advanced fitting procedure using a genetic algorithm has been applied. The final set of
−
1
−1
magnetic parameters for complex I reads: J/hc = +1.91 cm , DNi/hc = +8.44 cm , DCo/hc = +14.1
−
1
cm , gav = 2.362, χTIM = 0, zj/hc = 0, discrepancy factors R( χ) = 0.0059 and R(M) = 0.047. During
the fitting procedure, the g-factors were taken as isotropic and equal each to the other. The
remaining complexes exhibit analogous magnetic behavior (Figs. 6-8). Consequently the
magnetic parameters obtained by the fitting procedure are very similar. Only in complex IV is
ꢀ
ꢀ

-
some molecular field correction essential. The zero-field splitting at the Ni(II) centre (|D| ~ 8 cm
1
)
spans the interval typical for hexacoordinate systems [35]. In tetracoordinate Co(II) complexes
-1
the D-values typically range between −1 5 and +12 cm [36]. The bond angle along the
superexchange path, Ni-O-Co, is α= 99-101°. This is a bit higher than the critical angle in
copper(II) diads (α = 97.5 °), below which the antiferromagnetic coupling switches to a
ferromagnetic one [37]. Nevertheless, the observed ferromagnetic coupling in the complexes
under study is rather weak.
Conclusion
Four Ni(II)-Co(II) heterodinuclear complexes were prepared from three Schiff bases of the
ONNO type. The stoichiometries of the complexes were determined and their molecular
structures were determined by means of X-ray diffraction. It was found that the Ni(II) ion lies
2 2
between the O N donor set of the Schiff base and the coordination is completed by two DMF
molecules. The Co(II) centre is coordinated by the phenolic oxygen atoms, that bear the function
of µ- bridges. Thermal analysis showed that the DMF molecules leave the structure with the
expected mass loss values and it was estimated that the complexes decompos at this temperature.
Magnetic susceptibility measurements were conducted between 4.6 and 300 K and the
temperature dependence of the magnetic susceptibility and field dependence of the
magnetization have been fitted simultaneously to a conventional spin Hamiltonian model. The
magnetic exchange is of a weak ferromagnetic type and the remaining magnetic parameters
-1
-1
adopt the usual values: J/hc = +1.91 to +2.58 cm , DNi/hc = +8.38 to +8.91 cm , DCo/hc = +11.5
-1
to +14.1 cm , g = 2.395 - 2.286.
av
Supplementary data
Crystallographic data for the structural analysis have been deposited with the Cambridge
Crystallographic Data Center, CCDC 924091, 924092, 924093, 924094. Copies of this
information can be obtained free of charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2, 1EZ, UK (fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.ac.uk or
www://www.ccdc.cam.ac.uk).
Acknowledgements
Slovak Grant Agencies (VEGA 1/0233/12, APVV 0014-11) are acknowledged for the financial
support. In addition, financial support of this work by the University of Ankara Scientific
ꢀ
ꢁ

Research Fund under contract no. 12B4240003 and Ahi Evran University Scientific Research
Fund under contract no. 4001.12.014 are gratefully acknowledged.
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16] R.J. Butcher, E. Sinn, Inorg. Chem. 15 (1976) 1604-1608.
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21] J.H. Wang, P.F. Yan, G.M. Li, J.W. Zhang, P. Chen, M. Suda, Y. Einaga, Inorg. Chim.
Acta 363 (2010) 3706-3713.
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(
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[
34] R. Boća, A Handbook of Magnetochemical Formulae. Elsevier, Amsterdam, 2012.
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37] O. Kahn, Molecular Magnetism. VCH, New York, 1993.
ꢀ
ꢃ

Table 1 Data collection properties and crystal data
Compound
I
II
III
IV
empirical formula
C
23
H
30
O
4
N
4
Cl
2
CoNi
C
23
H
30
O
4
N
4
Br
2
CoNi
C
24
H
32
O
4
N
4
Cl
2
CoNi
25 34 4 4 2
C H O N Cl CoNi
formula weight /g 615.05
703.97
629.08
643.10
-
1
mol
T /K
293(2)
293(2)
293(2)
105(2)
crystal size/mm
crystal system
space group
a /Å
0.36x0.35x0.12
Monoclinic
Cc
0.44x0.36x0.16
Monoclinic
Cc
0.18x0.18x0.12
Monoclinic
P21/c
0.50x0.22x0.04
Monoclinic
Cc
10.5261(3)
15.1535(5)
17.2235(5)
90.00
10.5304(4)
15.1790(5)
17.4479(6)
90.00
9.9822(5)
15.0065(7)
18.1711(9
90.00
8.5673(9)
17.611(2)
19.216(3)
90.00
b /Å
c /Å
ꢀ
/°
ꢈ /°
ꢉ /°
V /Å
Z
98.949(3)
90.00
99.066(3)
90.00
94.611(4)
90.00
101.800(10)
90.00
3
2713.83(14)
4
2754.05(17)
4
2713.2(2)
4
2838.0(6)
4
-
3
Calc. density /g cm
1.505
1.698
1.540
1.505
-
1
µ /mm
1.537
4.222
1.539
1.473
F (000)
1268
1412
1300
1332
Tmin-Tmax
0.6076-0.8370
2.79 - 26.36
0.2581- 0.5515
2.817 - 27.823
0.7691- 0.8368
2.622- 27.970
0.5262- 0.9434
3.078- 27.938

range / °
index ranges
-11<=h<=13 ,
-13<=h<=10 ,
- 17<=k<=18 ,
-14<=l<=21
5497
-12<=h<=11 ,
- 12<=k<=18 ,
-20<=l<=22
12098
-6<=h<=10 ,
- 17<=k<=22 ,
-22<=l<=24
5506
-
-
17<=k<=18 ,
21<=l<=17
reflections collected 5489
reflections unique
R1, wR2 (2ó)
3882
3852
5497
3318
0.0372 -0.0771
0.0321- 0.0728
3882/326
1.096
0.0611- 0.1634
0.0562- 0.1566
3852/327
0.0823- 0.1049
0.0468- 0.0923
5497/325
0.0634-0.1353
0.0884- 0.1523
3318/338
R1, wR2 (all)
data / parameters
2
GOOF of F
1.087
1.071
1.042
largest
difference 0.290 / -0.289
0.890/-1.237
0.417/-0.476
0.966/ -0.642
-
3
peak hole /e Å
CCDC number
924091
924092
924093
924094
ꢀ
ꢄ

Table2 Selected bond lengths and angles around the coordination spheres of the complexes
Complex
Bond lengths (Å)
N1 Ni1 2.019(4)
N2 Ni1 2.027(4)
O1 Co1 1.980(3)
O1 Ni1 2.023(3)
O2 Co1 1.988(3)
O2 Ni1 2.028(3)
O3 Ni1 2.135(3)
O4 Ni1 2.136(3)
Co1 Cl1 2.2277(14)
Co1 Cl2 2.2524(14)
Bond angles (°)
N1 Ni1 O1 90.10(13)
N1 Ni1 N2 100.23(16)
O1 Ni1 N2 169.55(14)
N1 Ni1 O2 168.87(13)
O1 Ni1 O2 78.77(11)
N2 Ni1 O2 90.90(14)
N1 Ni1 O3 88.76(13)
O1 Ni1 O3 92.01(12)
N2 Ni1 O3 86.64(14)
O2 Ni1 O3 91.66(12)
N1 Ni1 O4 90.44(13)
O1 Ni1 O4 90.24(12)
N2 Ni1 O4 91.29(13)
O2 Ni1 O4 89.55(12)
O3 Ni1 O4 177.62(14)
O1 Co1 O2 80.77(11)
O1 Co1 Cl1 112.65(10)
O2 Co1 Cl1 118.03(9)
O1 Co1 Cl2 112.51(9)
O2 Co1 Cl2 111.98(9)
Cl1 Co1 Cl2 115.95(6)
N1 Ni1 O1 91.2(3)
I
N1 Ni1 2.005(7)
N2 Ni1 2.023(7)
O1 Co1 1.955(6)
O1 Ni1 2.017(6)
O2 Co1 1.988(5)
O2 Ni1 2.033(6)
O3 Ni1 2.138(6)
O4 Ni1 2.127(5)
Br2 Co1 2.3230(19)
Br1 Co1 2.3439(16)
N1 Ni1 N2 100.4(3)
O1 Ni1 N2 168.2(3)
N1 Ni1 O2 169.5(3)
O1 Ni1 O2 78.4(2)
N2 Ni1 O2 90.1(3)
N1 Ni1 O4 90.2(3)
O1 Ni1 O4 90.7(2)
N2 Ni1 O4 91.2(3)
O2 Ni1 O4 88.6(2)
II
N1 Ni1 O3 89.1(3)
O1 Ni1 O3 90.8(2)
N2 Ni1 O3 87.5(3)
O2 Ni1 O3 92.3(2)
O4 Ni1 O3 178.3(3)
O1 Co1 O2 80.9(2)
O1 Co1 Br2 112.00(18)
O2 Co1 Br2 117.13(18)
O1 Co1 Br1 113.48(17)
O2 Co1 Br1 112.78(16)
Br2 Co1 Br1 115.74(7)
N1 Ni1 O1 89.11(11)
N1 Ni1 O2 164.83(11)
O1 Ni1 O2 78.55(9)
N1 Ni1 N2 101.94(12)
O1 Ni1 N2 168.59(11)
O2 Ni1 N2 90.93(11)
N1 Ni1 O3 96.91(11)
O1 Ni1 O3 82.85(10)
O2 Ni1 O3 90.33(10)
N2 Ni1 O3 92.91(11)
N1 Ni1 O4 85.21(11)
O1 Ni1 O4 94.19(10)
O2 Ni1 O4 86.91(10)
N2 Ni1 O4 89.59(11)
O3 Ni1 O4 176.31(10)
O1 Co1 O2 80.91(9)
O1 Co1 Cl1 122.16(8)
O2 Co1 Cl1 111.96(8)
O1 Co1 Cl2 107.89(8)
O2 Co1 Cl2 120.25(8)
Cl1 Co1 Cl2 111.24(5)
N1 Ni1 2.030(3)
N2 Ni1 2.054(3)
O1 Co1 1.977(2)
O1 Ni1 2.033(2)
O2 Co1 1.990(2)
O2 Ni1 2.034(2)
O3 Ni1 2.089(2)
O4 Ni1 2.139(2)
Co1 Cl1 2.2197(12)
Co1 Cl2 2.2552(12)
III
ꢀ
ꢅ

N1 Ni1 1.981(9)
N2 Ni1 2.015(8)
O1 Co1 1.948(7)
O1 Ni1 2.020(6)
O2 Co1 1.983(6)
O2 Ni1 2.041(7)
O3 Ni1 2.065(9)
O4 Ni1 2.129(9)
Co1 Cl2 2.214(4)
Co1 Cl1 2.260(5)
N1 Ni1 N2 99.0(4)
N1 Ni1 O1 91.7(3)
N2 Ni1 O1 169.3(3)
N1 Ni1 O2 169.7(3)
N2 Ni1 O2 91.2(3)
O1 Ni1 O2 78.1(2)
N1 Ni1 O3 94.2(5)
N2 Ni1 O3 89.1(4)
O1 Ni1 O3 89.9(3)
O2 Ni1 O3 87.5(3)
N1 Ni1 O4 90.8(5)
N2 Ni1 O4 88.4(4)
O1 Ni1 O4 91.7(3)
O2 Ni1 O4 87.8(3)
O3 Ni1 O4 174.7(3)
O1 Co1 O2 81.2(3)
O1 Co1 Cl2 115.2(3)
O2 Co1 Cl2 119.7(2)
O1 Co1 Cl1 111.4(3)
O2 Co1 Cl1 111.8(3)
Cl2 Co1 Cl1 113.53(17)
IV
ꢀ
ꢆ

Gaphical Abstract ()
II
II
Four heterodinuclear Ni -Co complexes were prepared using N,N’-bis(salicylidene)-1,3-
propanediamine and its derivatives. These complexes were characterized and their molecular
structures determined by the X-ray diffraction method. It was found that the Ni(II) ion lies in a
4 2
O N distorted octahedral coordination sphere, in contrast the Co(II) ion is in a distorted
tetrahedral coordination sphere. The magnetic susceptibilities of the complexes were measured
between 2 and 300 K and the µeff values were determined.
ꢀ
ꢇ

Graphical Abstract
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
B = 0.1 T
T = 2.0 K
T = 4.6 K
2
5
µ
µ
20
15
µ
10
5
0
χ
0
10
20
30
40
0
50
100 150 200 250 300
0
1
2
3
4
5 6 7
T/K
B/T
ꢀ
ꢈ