Two new heterodinuclear Schiff base complexes: Synthesis, crystal structure and thermal studies

Article abstract of DOI:10.1016/j.saa.2014.08.091

Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl₂(DMF)₂] 1, and [Zn(L)NiCl₂(DMF)₂]₂, where H₂L= N,N'-bis(salicylidene)-1,3-diaminopropane and DMF = dimethylformamide have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [Ni^IIHg^II] unit and [Zn^IINi^II] in which the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the Ni(II) ion adopts an elongated octahedral geometry (NiN₂O₄) while the Hg(II) ion assumes a distorted tetrahedral arrangement (HgO₂Cl₂) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral geometry (ZnN₂O₄) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO₂Cl₂). There are intermolecular CAH.Cl AM interactions among the dinuclear complexes which are interconnected for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure for 1 and one dimensional zig-zag chains for 2.

Full text of DOI:10.1016/j.saa.2014.08.091

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Two new heterodinuclear Schiff base complexes: Synthesis, crystal
structure and thermal studies
b
c
d
c
e
Alper Yardan a, , Cigdem Hopa , Yasemin Yahsi , Ahmet Karahan , Hulya Kara , Raif Kurtaran
⇑
a Balikesir University, Dursunbey Vocational School, Department of Property Protection and Safety, TR-10800 Balikesir, Turkey
b Balikesir University, Faculty of Art and Science, Department of Chemistry, TR-10145 Balikesir, Turkey
c Balikesir University, Faculty of Art and Science, Department of Physics, TR-10145 Balikesir, Turkey
d Suleyman Demirel University, Sutculer Prof. Dr. Hasan Gurbuz Vocational School, Department of Property Protection and Safety, TR-32950 Isparta, Turkey
e Materials Science and Engineering, Alanya Engineering Faculty, Akdeniz University, TR-07400 Alanya, Antalya, Turkey
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
New heterodinuclear complexes 1
and 2 have been synthesized.
Crystal structures of 1 and 2 have
been determined by single crystal
XRD analysis.
ꢀ
1 and 2 were characterized by IR
spectroscopy, elemental and thermal
analysis.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 10 June 2014
Received in revised form 14 August 2014
Accepted 24 August 2014
Available online 3 September 2014
Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2, where
H2L = N,N0-bis(salicylidene)-1,3-diaminopropane and DMF = dimethylformamide have been synthesized
and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction.
Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which
the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the
Ni(II) ion adopts an elongated octahedral geometry (NiN2O4) while the Hg(II) ion assumes a distorted tet-
rahedral arrangement (HgO2Cl2) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral
geometry (ZnN2O4) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO2Cl2). There
are intermolecular CAHꢁꢁꢁClAM interactions among the dinuclear complexes which are interconnected
for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure
for 1 and one dimensional zig-zag chains for 2.
Keywords:
Schiff bases
Heterodinuclear complexes
Phenoxo bridge
Thermal analysis
Single crystal X-ray
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
owing to their importance in material science, molecular electron-
ics, photochemistry, biological activity, molecular magnetic mate-
Investigations of coordination complexes of transition metals
containing Schiff base ligands continue to attract strong interest
rials and nanostructure studies [1–12]. Especially, the field of
molecular magnetism has seen a number of Schiff base complexes
synthesized and characterized in the past decades in the search for
new systems that behave like a single-molecule magnet (SMM)
[13]. SMMs exhibit interesting phenomena, such as slow
⇑
Corresponding author. Tel.: +90 266 6624940; fax: +90 266 6624941.
E-mail address: alpyardan@hotmail.com (A. Yardan).
http://dx.doi.org/10.1016/j.saa.2014.08.091
1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

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A. Yardan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356
magnetization relaxation, magnetization hysteresis and quantum
tunneling of the magnetization (QTM) [14,15].
slowly to the mixture with constant stirring. The solution was fil-
tered and then allowed to stand at room temperature for three
days. Blue crystals of complex 2 were collected by filtration and
dried in an air atmosphere. Calcd. Found for 2 (C23H32Cl2N4NiO4Zn)
Yield: 0.39 g. (62%), C, 44.3; H, 5.13; N, 8.98. Found: C, 43.7; H,
5.02; N, 8.82%.
Salen type tetradentate (ONNO) Schiff base ligands derived
from N,N0-bis(salicylidene)-1,3-diaminopropane (H2L), have been
used for complexation in recent years [16,17]. Salen-type Schiff
base complexes themselves can act as ligand-complexes and can
chelate a second metal substrate using phenolate oxygen atoms
of the Schiff base ligand to construct extended homo- or hetero-
polynuclear complexes [18–22].
X-ray structure determination
Recently, the structural characterization of homodinuclear
ZnAZnCl2 [23,24], ZnAZnBr2 [25], CoACoCl2 [26], CuACuCl2 [27]
and heterodinuclear NiAHgCl2 [28,29], NiAHgBr2 [30], NiAZnCl2
[31,32], NiAZnBr2 [33], NiACoCl2 [34], NiACoBr2 [34], ZnACdBr2
[35], ZnAHgI2 [36] ONNO type Schiff base complexes have been
reported. To the best of our knowledge, the structural characteriza-
tion of the phenoxo-bridged heterodinuclear ZnANiCl2, ONNO type
Schiff base complex, (2), is described here for the first time.
This work reports the synthesis of two new phenoxo-bridged
heterodinuclear NiIIAHgII (1) and ZnIIANiII (2) complexes along
with their characterization, single crystal X-ray structures and
thermal studies.
Intensity data for suitable single crystals of 1 and 2 were col-
lected using an Oxford Diffraction Xcalibur-3 single crystal X-ray
diffractometer equipped with
a
Mo
Ka radiation source
(k = 0.71073 Å at 296 K). Data collection and data reductions were
performed using the CRYSALIS CCD and CRYSALIS RED programs
[37]. The structures were solved by direct methods and refined
using full-matrix least-squares against F2 using SHELXTL [38]. All
non-hydrogen atoms were assigned anisotropic displacement
parameters and refined without positional constraints. Hydrogen
atoms were included in idealised positions with isotropic displace-
ment parameters constrained to 1.5 times the Uequiv of their
attached carbon atoms for methyl hydrogens, and 1.2 times the
Uequiv of their attached carbon atoms for all others. The Level B
Alerts result from the C3, C6, C8, C9, C23 atoms for complex 1
and the C20 atom for complex 2 which were refined isotropically
due to its high thermal motion. The absolute structure was deter-
mined on the basis of the Flack parameter [39] x = 0.063(9) for 1
and 0.042(16) for 2. A Flack parameter value close to 0 is indicative
of a non-centrosymmetric structure.
Details of the data collection parameters and crystallographic
information for the complexes are summarized in Table 1. Selected
bond lengths and angles are listed in Table 2 for complex 1 and
Table 3 for complex 2, respectively. Hydrogen bond geometries
of the complexes are shown in Table 4. Molecular drawings were
obtained using MERCURY [40]. The crystal structures of 1 and 2
along with the atom numbering scheme are given in Figs. 1 and
3, respectively. Packing diagrams are displayed in Fig. 2 for 1 and
in Fig. 4 for 2.
Experimental section
Materials and methods
All reagents and solvents were purchased from Merck, Aldrich
or Carlo Erba and used without further purification. Elemental
analyses for the ligand and complex were carried out using stan-
dard methods with a Eurovector 3018 CHNS analyzer. IR spectra
were recorded using a Perkin–Elmer 1600 series automatic record-
ing FT-IR spectrophotometer with the KBr disk technique over the
range 400–4000 cmꢂ1. The thermogravimetry/differential thermal
analysis (TG/DTA) measurements were undertaken using a Perkin
Elmer Diamond DTA/TG thermal analyzer. In this study, thermo-
gravimetric curves were obtained using a flow rate of the nitrogen
carrier gas (at 3 bar) of 200 mL/min and a heating rate of 20 °C/min
and with ceramic crucibles.
Synthesis
Table 1
Synthesis of complex 1
Crystal data and structure refinements for 1 and 2.
N,N0-bis(salicylidene)-1,3-propanediamine (H2L) was prepared
by reacting a basic ethanolic solution of salicylaldehyde and 1,3-
diamino propane as described previously in the literature [33]. Tri-
ethylamine (Et3N) was added dropwise to the solution of Schiff
base ligand (1 mmol, 0.282 g) in 20 mL DMF. A solution of NiCl2.6-
H2O (1 mmol, 0.237 g) in ethanol (20 mL) was added to the DMF
solution. The solution was stirred at the boiling point under an
air atmosphere. A solution of HgCl2 (1 mmol, 0.271 g) in ethanol
(20 mL) was added to the resulting solution and this too was stir-
red at the boiling point under an air atmosphere. The solution was
filtered and then allowed to stand at room temperature for five
days. Green crystals of complex 1 were collected by filtration and
dried in an air atmosphere. Calcd. Found for 1 (C23H30Cl2HgN4-
NiO4): Yield: 0.51 g. (68%), C, 36.4; H, 3.96; N, 7.40. Found: C,
35.7; H, 4.12; N, 7.58%.
1
2
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
C
23H30Cl2HgN4NiO4
C23H32Cl2N4NiO4Zn
623.51 g molꢂ1
Monoclinic
756.71 g molꢂ1
Monoclinic
Cc
Cc
a = 10.5428 (11) Å
b = 15.1258 (19) Å
c = 17.350 (3) Å
b = 97.479 (13)°
2743.3 (6) Å3
4
a = 10.4994 (5) Å
b = 15.1545 (7) Å
c = 17.1967 (6) Å
b = 98.709 (4)°
2704.7 (2) Å3
4
Volume
Z
Density (calculated)
Absorption
coefficient
h range for data
collection
1.832 g.cmꢂ3
6.51 mmꢂ1
1.531 g cmꢂ3
1.82 mmꢂ1
3.9–27.6°
3.9–28.8°
Index ranges
ꢂ10 6 h 6 13,
ꢂ19 6 k 6 19,
ꢂ22 6 l 6 22
6649
ꢂ8 6 h 6 14
ꢂ20 6 k 6 20
ꢂ23 6 l 6 23
7114
Synthesis of complex 2
Reflections collected
Independent
reflections
Complexes 1 and 2 were prepared using similar methods.
Equivalent amounts of triethylamine (Et3N) was added dropwise
to deprotonate the phenolic OH group of the solution Schiff base
ligand (1 mmol, 0.282 g) in DMF (20 mL). To a solution of ZnCl2
(1 mmol, 0.135 g) in ethanol was added to the resulting solution
and it was stirred at boiling point under an air atmosphere. A solu-
tion of NiCl2.6H2O (1 mmol, 0.237 g) in ethanol (20 mL) was added
3773 [Rint = 0.076]
4386 [Rint = 0.024]
Refinement method
Full-matrix least-squares Full-matrix least-squares
on F2
on F2
S = 0.96
R1 = 0.041, wR2 = 0.115
0.042(16)
Goodness-of-fit on F2 S = 0.71
R indices [I > 2
r
(I)]
R1 = 0.046, wR2 = 0.068
0.063(9)
Flack parameter

A. Yardan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356
353
Table 2
Some selected bond lengths [Å] and angles [°] for 1.
Bond lengths (Å)
Ni1AO1
Ni1AO2
Ni1AO3
Ni1AO4
Ni1AN1
Ni1AN2
1.980 (11)
2.008 (9)
2.136 (12)
2.159 (12)
2.043 (12)
2.032 (15)
Hg1AO1
Hg1AO2
Hg1ACl1
Hg1ACl2
2.359 (10)
2.321 (10)
2.345 (4)
2.354 (5)
Bond angles (°)
O1ANi1AO2
O1ANi1AN1
O3ANi1–O1
O3ANi1AO2
O3ANi1AN1
O3ANi1AN2
O4ANi1AO1
O4ANi1AO2
O4ANi1AO3
O4ANi1AN1
O4ANi1AN2
81.5 (4)
89.8 (6)
91.7 (5)
91.7 (4)
84.9 (4)
89.6 (5)
91.7 (5)
92.0 (4)
175.4 (5)
91.9 (4)
87.6 (5)
N1ANi1AO2
N2ANi1AO1
N2ANi1AO2
N2ANi1AN1
O2AHg1ACl1
O2AHg1ACl2
Cl1AHg1ACl2
O2AHg1–O1
Cl1AHg1AO1
Cl2AHg1AO1
Ni1AO1AHg1
Ni1AO2AHg1
170.6 (6)
171.3 (5)
89.9 (5)
98.9 (6)
107.1 (3)
103.5 (3)
139.6 (3)
67.6 (3)
104.4 (3)
111.4 (3)
104.6 (4)
105.0 (4)
Fig. 1. DTA/TG/DTG curves of complex 1.
Table 3
Some selected bond lengths [Å] and angles [°] for 2.
Bond lengths (Å)
Zn1AN2
Zn1AN1
Zn1AO1
Zn1AO2
Zn1AO4
Zn1AO3
2.009 (4)
2.012 (5)
2.020 (4)
2.019 (4)
2.124 (4)
2.140 (4)
Ni1AO2
Ni1AO1
Ni1ACl1
Ni1ACl2
1.985 (4)
2.003 (4)
2.200 (2)
2.224 (2)
Bond angles (°)
N2AZn1AN1
N2AZn1AO1
N1AZn1AO1
N2AZn1AO2
N1AZn1AO2
O1AZn1AO2
N2AZn1AO4
N1AZn1AO4
O1AZn1AO4
O2AZn1AO4
N2AZn1AO3
N1AZn1AO3
99.7 (2)
O1AZn1AO3
O2AZn1AO3
O4AZn1AO3
O2ANi1AO1
O2ANi1ACl1
O1ANi1ACl1
O2ANi1ACl2
O1ANi1ACl2
Cl1ANi1ACl2
Ni1AO1AZn1
Ni1AO2AZn1
89.34 (16)
91.01 (16)
177.10 (18)
80.01 (15)
112.00 (13)
116.38 (13)
111.94 (12)
111.77 (13)
118.52 (8)
100.04 (17)
100.70 (17)
169.53 (18)
90.80 (18)
90.76 (18)
169.44 (18)
78.79 (14)
88.54 (17)
86.99 (19)
92.35 (16)
91.62 (16)
90.22 (17)
90.64 (18)
Fig. 2. DTA/TG/DTG curves of complex 2.
The spectrum of the free ligand (H2L) shows significant bands at
1611 cmꢂ1 for C@N stretching, 2752–2748 cmꢂ1 for phenolic
OAH stretching and 1294 cmꢂ1 for phenolic CAO. When the IR
spectra obtained from complex 1 is compared with that from the
Results and discussion
free ligand, the complex exhibits a
m
(C@N) band at 1624 cmꢂ1
showing a shift to higher wavenumbers indicating that the nitro-
IR spectra
gen atom of the azomethine group is coordinated to the nickel
(II) ion [41]. In addition, the phenolic
spectrum disappeared in the complex spectrum [42]. These results
m(OAH) band in the ligand
The interest of the IR spectrum of the title complexes lies
mainly in the bands arising from the azomethine and hydroxyl
groups of the ligands, and the carbonyl group from the DMF ligand.
prove the complexation [43]. The
m
(C@O) stretching vibration of
Table 4
Hydrogen bond geometry (Å, °) of compounds 1 and 2.
DAHꢁ ꢁ ꢁAa
DAH
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
DAHꢁ ꢁ ꢁA
Symmetry
1
2
C11AH11ꢁꢁꢁCl2
C19AH19CꢁꢁꢁCl1
C8AH8ꢁꢁꢁCl1
0.93
0.96
0.93
2.76
2.92
2.88
3.603
3.708
3.711
151
140
150
x, ꢂy, ꢂ1/2 + z
ꢂ1/2 + x, 1/2 + y, z
x, ꢂy, ꢂ1/2 + z
CAHꢁꢁꢁ
p
1
C9AH9AꢁꢁꢁR2
0.97
0.96
0.96
0.93
0.97
0.96
0.96
2.96
2.98
2.67
2.94
2.86
2.92
2.73
3.836
3.468
3.552
3.689
3.736
3.527
3.494
151
113
153
139
150
122
137
x,ꢂy, ꢂ1/2 + z
C20AH20BꢁꢁꢁR2
C23AH23BꢁꢁꢁR1
C5AH5ꢁꢁꢁR3
ꢂ1/2 + x, ꢂ1/2 + y, z
1/2 + x, 1/2 + y, z
ꢂ1/2 + x, 1/2 ꢂ y, ꢂ1/2 + z
x, ꢂy, 1/2 + z
2
C16-H16AꢁꢁꢁR2
C20AH20BꢁꢁꢁR2
C23AH23BꢁꢁꢁR3
1/2 + x, ꢂ1/2 + y, z
ꢂ1/2 + x, 1/2 + y, z
a
D: Donor, A: Acceptor, [R1: C12ꢂC13ꢂC14ꢂC15ꢂC16ꢂC17, R2: C2ꢂC3ꢂC4ꢂC5ꢂC6ꢂC7 for 1]. [R3: C9ꢂC10ꢂC11ꢂC12ꢂC13ꢂC14, R2: C2ꢂC3ꢂC4ꢂC5ꢂC6ꢂC7 for 2].

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A. Yardan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356
Decomposition of complex 1 starts at 53 °C and this step continues
up to 134 °C. Two DMF molecules leave in this first step (calcd./
found: 19.3/17.8%) [47,48]. In the DTA curve, there is an endother-
mic peak at 119 °C for this event. The second weight loss between
134 and 468 °C was attributed to the departure of ligand (calcd./
found: 37.3/39.9%). Over the temperature range 468–654 °C two
coordinated chlorides leave the structure with 9.9% weight loss
observed compared with the calculated theoretical value of 9.4%.
Complex 2 was thermally stable up to 120 °C and decomposi-
tion started at this temperature and finished at 1200 °C with four
stages. The TG curve (Fig. 2) indicates that DMF molecules depart
over the temperature range 119–198oC (calcd./found: 23.5/23.4%)
[28,49]. Other steps between 198 and 1200 °C involve the loss of
the ligand and two chlorides (calcd./found: 56.9/56.7%) and proba-
bly the formation of Zn-Ni as the final residue at 1200 °C (calcd./
found: 19.9/19.9%). Moreover, the thermogravimetric analyses
reveal that complex 2 is more stable than complex 1.
Fig. 3. Molecular structure of 1.
Crystal structure description of Complex 1
the DMF molecules can be assigned to the band at 1552 cmꢂ1 in
the IR spectrum, which is lower than that in free DMF molecules
(1655 cmꢂ1) because of the coordination of the DMF oxygen atoms
to the zinc ion which is consistent with the results of X-ray analy-
sis. Similarly, complex 2 exhibits a
showing a shift to lower wavenumbers indicating that the nitrogen
Complex 1 crystallizes in the monoclinic non-centrosymmetric
chiral space group Cc and the asymmetric unit contains one mole-
cule. The molecule comprises a binuclear heterometallic assembly
of nickel(II) and mercury(II) in which the Ni(II) centre is connected
to the [HgCl2] unit via two bridging phenolate oxygen atoms pro-
vided by the Schiff base anion. The molecular unit can be described
as a dinuclear species with a six-coordinated nickel atom sur-
rounded by the two phenolate oxygen and two imine nitrogen
atoms of tetradentate Schiff base ligand occupying the equatorial
positions and two oxygen atoms in the apical positions. The pheno-
late oxygen atoms bridge the mercury atom which is four-coordi-
nated by those two oxygen atoms and two chlorine atoms. The
[HgO2Cl2] unit undergoes severe distortions from ideal tetrahedral
geometry which is reflected from its wide range of bond angles,
being 67.57–139.59°. The coordination geometry around the nickel
corresponds to an elongated octahedral structure because of the
presence of the oxygen atoms in the apical positions with average
distances of 2.15 Å, while the equatorial NiAN and NiAO bond dis-
tances are 1.979–2.043 Å. The deviation of Ni(II) ions from N2O2
m
(C@N) band at 1651 cmꢂ1
atom of azomethine group is coordinated to the zinc atom [44,45].
In addition, the phenolic
m(OAH) band disappeared. The m(C@O)
stretching vibration of the DMF molecules can be assigned to the
band at 1551 cmꢂ1 in the IR spectrum [46].
Thermal analysis
To examine the thermal stabilities of the complexes, thermo-
gravimetric and differential thermal (TG/DTA) analyses were car-
ried out in a nitrogen atmosphere at a heating rate of 20 °C/min
from ambient temperature to 1200 °C. The DTA/TG/DTG diagrams
of complexes 1 and 2 are shown in Figs. 1 and 2, respectively.
Fig. 4. Molecular packing diagram of 1 in the bc plane (dashed lines denote Clꢁ ꢁ ꢁH interactions).

A. Yardan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356
355
coordination plane [O1AN1AN2AO2] is 0.026 Å. In complex 1, the
intramolecular NiꢁꢁꢁHg distance is 3.44 Å which is close to the val-
ues found in similar salen-type compounds [28]. Selected bond
lengths and angles are listed in Table 2, which lie well within the
range of reported values for corresponding bond lengths and
angles of similar hetero-dinuclear complexes [28,29,50–54].
Complex 1, revealed the presence of intermolecular
CAHꢁꢁꢁClAM interactions among the dinuclear complexes which
are interconnected (Table 4). In these interactions, the metal bound
chlorine atoms Cl1 and Cl2 act as the H-bond acceptor while C11
and C19 atoms act as the H bond donor [55]. These intermolecular
interactions result in the formation of a 3D structure. This hydro-
gen bonded polymeric networks lie in the bc axis and stacks along
to the a axis. (Fig. 4). However, these dimeric units are further con-
nected by C–H. . .p interactions (H. . .R = 2.96, 2.98 and 2.67 Å) to
the other heterobimetallic dimers present in the unit cell (Table 4).
Crystal structure description of Complex 2
Complex 2 crystallizes in the monoclinic non-centrosymmetric
chiral space group Cc and the asymmetric unit contains one mole-
cule. The molecule comprises a binuclear heterometallic assembly
of zinc (II) and nickel (II) in which the Zn (II) centre is connected to
the [NiCl2] unit via two bridging phenolate oxygen atoms contrib-
uted by the Schiff base anion. The molecular unit of complex 2 can
be described as being a hetero-dinuclear species with a six-coordi-
nated zinc atom and a four-coordinated nickel atom. The Ni (II) ion
is bridged by two phenolate oxygen atoms and two chlorine atoms.
The Zn (II) ion is surrounded by N2O2 donor atoms of the Schiff
base ligand in the equatorial positions and two oxygen atoms in
the apical positions (see Fig. 5). The [NiO2Cl2] unit deviates from
ideal tetrahedral geometry with the bond angles ranging between
Fig. 5. Molecular structure of 2.
Fig. 6. (a) Molecular packing diagram of 2 along the c axis (dashed lines denote Clꢁ ꢁ ꢁH interactions), (b). Space filling representation of 2 as in Fig. 6a.

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80.00° and 118.52°. The coordination geometry around the Zn (II)
ion corresponds to an elongated octahedral structure because of
the presence of the oxygen atoms in the apical positions with aver-
age bond lengths of 2.13 Å, while the equatorial ZnAN and ZnAO
bond distances are 2.008–2.020 Å. The deviation of Zn (II) ions
from N2O2 coordination plane [O1AN1AN2AO2] is 0.011 Å and
the intramolecular ZnꢁꢁꢁNi distance is 3.44 Å. Selected bond lengths
and angles are listed in Table 3, which lie well within the range of
reported values for corresponding bond lengths and angles of sim-
ilar hetero-dinuclear complexes [28,29,50–54].
Complex 2, revealed the presence of intermolecular
CAHꢁꢁꢁClAM interactions among the dinuclear complexes which
are interconnected (Table 4). In this interaction, the metal bound
chlorine atom Cl1 acts as the H-bond acceptor while the C8 atom
acts as the H bond donor [55]. This intermolecular interaction
results in the formation of infinite one dimensional zig-zag chains
in the crystal lattice. The zig-zag chains propagate through the
crystallographic c axis (Fig. 6a and b). However, these dimeric units
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2.92 and 2.73 Å) to the other heterobimetallic dimers present in
the unit cell (Table 4).
Conclusion
Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(-
DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2 have been synthesized and
characterized using elemental analysis, IR spectroscopy, thermal
analysis and X-ray diffraction. Structural studies on 1 and 2 reveal
the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in
which the central metal ions are connected to each other by two
phenolate oxygen bridges. CAH. . .
play a major role in controlling the molecular packing for com-
sep-
p
and CAHꢁꢁꢁClAM interactions
plexes 1 and 2. In both structures the intermolecular CAHꢁꢁꢁ
p
arations are equal ꢃ2.9 Å and lie in the accepted distance range for
this type of contact [39,56–58]. These intermolecular interactions
result in the formation of a 3D structure for 1 and 1D zig-zag chains
for 2. The thermogravimetric analyses illustrate that complex 2 is
more stable than complex 1.
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The financial support of the Scientific and Technical Research
Council of Turkey (TUBITAK) Grants No: TBAG-108T431 and
Balikesir University (Project No. 2007/10) is gratefully acknowl-
edged. In addition, Yasemin Yahsi is also grateful to Dr. Lorenzo
Sorace, Dr. Andrea Caneschi (Department of Chemistry, University
of Florence) for the use of Xcalibur-3 diffractometer. We are also
very grateful to Dr. Andrew Fisher for language corrections.
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Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2014.08.091.
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