Syntheses, characterizations and structures of NO donor Schiff base ligands and nickel(II) and copper(II) complexes

Article abstract of DOI:10.1016/j.molstruc.2011.04.037

New Schiff base derivatives (L¹ and L²) were prepared by the condensation of 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with 5-methylfurfurylamine. Two new complexes [Ni(L¹

Full text of DOI:10.1016/j.molstruc.2011.04.037

Journal of Molecular Structure 997 (2011) 53–59
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Syntheses, characterizations and structures of NO donor Schiff base ligands
and nickel(II) and copper(II) complexes
b
c
Cemal Sßenol a, Zeliha Hayvali a, , Hakan Dal , Tuncer Hökelek
⇑
a Department of Chemistry, Ankara University, Faculty of Science, 06100 Ankara, Turkey
b Department of Chemistry, Anadolu University, Faculty of Science, 26470 Eskisehir, Turkey
c Department of Physics, Hacettepe University, 06800 Ankara, Turkey
a r t i c l e i n f o
a b s t r a c t
New Schiff base derivatives (L1 and L2) were prepared by the condensation of 2-hydroxy-3-methoxybenz-
aldehyde (o-vanillin) and 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with 5-methylfurfurylamine.
Two new complexes [Ni(L1)2] and [Cu(L1)2] have been synthesized with bidentate NO donor Schiff base
ligand (L1). The Ni(II) and Cu(II) atoms in each complex are four coordinated in a square planar geometry.
Schiff bases (L1 and L2) and complexes [Ni(L1)2] and [Cu(L1)2] were characterized by elemental analyses,
FT-IR, UV–vis, mass and 1H, 13C NMR spectroscopies. The crystal structures of the ligand (L2) and com-
plexes [Ni(L1)2] and [Cu(L1)2] have also been determined by using X-ray crystallographic technique.
Ó 2011 Elsevier B.V. All rights reserved.
Article history:
Received 7 March 2011
Received in revised form 21 April 2011
Accepted 21 April 2011
Available online 28 April 2011
Keywords:
Schiff bases
Nickel(II) complexes
Copper(II) complexes
Crystal structure
1. Introduction
mass, 1H and 13C NMR, UV–vis and X-ray single crystal diffraction
(Scheme 1).
Schiff base ligands have played an important role in the devel-
opment of coordination chemistry, especially their metal com-
plexes exhibit wide applications in biological and industrial
systems [1–6]. Furthermore, the Schiff bases are very important
tools for the inorganic chemists as these are widely used to design
molecular ferromagnets, in catalysis, in biological modeling appli-
cations, as liquid crystals and as heterogeneous catalysts [7–9].
Schiff base ligands containing various donor atoms (like N, O, S,
etc.) show broad biological activity and are of special interest
because of the variety of ways in which they are bonded to the
transition metal ions [10,11]. Schiff base nickel(II) complexes have
been regarded as models for enzymes such as urease [12]. Vanilline
and furfurylamine Schiff base derivatives are very useful biochem-
ical materials having biological activities [13,14]. Although the
oxygen atom of the furan ring could not coordinate to the transi-
tion metals, the special tendency of the oxygen atom will be effec-
tive on the crystal structures of the complexes [15,16].
2. Experimental
2.1. Reagents
2-Hydroxy-3-methoxybenzaldehyde (o-vanillin) and 3-hydro-
xy-4-methoxybenzaldehyde (iso-vanillin) were purchased from Al-
drich, and used without further purification. Solvents were dried
and distilled before use according to the standard procedure.
2.2. Physical measurements
Melting points were measured on a Thomas-Hoover apparatus
using a capillary tube. 1H and 13C NMR spectra were recorded on
a Varian Mercury, High Performance Digital FT-NMR (400 MHz)
spectrometer (SiMe4 as a internal standard). Chemical shifts for
proton and carbon resonances were reported in ppm (d) (1H and
13C NMR chemical shifts are given according to the numbering
scheme). IR spectra were obtained from PEL-DATA spectrum 100
series spectrometer. Carbon, nitrogen and hydrogen analyses were
performed on LECO CHNS-932 elemental analyzer. Mass spectro-
metric analyses were performed on the Waters 2695 Allonce ZQ
LC/MS spectrometer. Magnetic susceptibilities were determined
on a Sherwood Scientific Magnetic Susceptibility Balance (Model
MKI) at room temperature (300 K). UV–vis spectra were recorded
using a Unicam UV2–100 series spectrometer.
In the previous works, we reported the syntheses and crystal
structures of different Schiff base compounds and their metal com-
plexes [17–20]. In this article, we have succeeded in the syntheses
of new Schiff base compounds (L1 and L2) and complexes [Ni(L1)2],
[Cu(L1)2] and their characterizations by elemental analyses, FT-IR,
⇑
Corresponding author. Tel.: +90 312 2126720; fax: +90 312 2232395.
E-mail address: zhayvali@science.ankara.edu.tr (Z. Hayvali).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.04.037

54
C. Sßenol et al. / Journal of Molecular Structure 997 (2011) 53–59
H N
O
2
CH
3
CHO
H3C
O
CHO
H C
3
O
OH
EtOH
EtOH
OH
H3C
O
O
H C
N
3
O
CH
3
N
O
CH3
HO
OH
(L2)
(L1)
Ni(CH3COO)2 . 4H2O
or
EtOH
Cu(CH3COO)2 . H2O
H C
3
O
N
CH
3
O
O
M
O
O
N
O
H C
3
CH
3
M: Ni, Cu
[Ni(L1)2] [Cu(L1)2]
Scheme 1. Preparation of Schiff bases and complexes [Ni(L1)2] [Cu(L1)2].
2.3. X-ray data collection and structure refinement
puter programs: SHELXS97 [22], SHELXL97 [22], ORTEP-3 [23].
Source of atomic scattering Factor: Int. Table for X-ray Cryst. vol.
IV, 1974 [24].
Experimental data for L2, [Ni(L1)2] and [Cu(L1)2] are listed in
Table 1, selected bond lengths and angles and hydrogen-bond
geometries are given in Tables 2 and 3, respectively. Crystallo-
graphic data were recorded on a Bruker Kappa APEXII CCD area-
2.4. Syntheses of the Schiff bases and complexes
detector diffractometer using Mo K
a radiation (k = 0.71073 Å) at
T = 100(2) K (for L2) and T = 294 K (for [Ni(L1)2] and [Cu(L1)2]).
Absorption corrections by multi-scan [21] were applied. Structures
were solved by direct methods [22] and refined by full-matrix least
squares against F2 using all data [22]. All non-H atoms were refined
anisotropically. All H atoms (for L2) and only H7 atoms for [Ni(L1)2]
and [Cu(L1)2]) were located in difference syntheses and refined iso-
tropically. The remaining H atoms were positioned geometrically
at distances of 0.93 Å (CH), 0.97 Å (CH2) and 0.96 Å (CH3) from
the parent C atoms; a riding model was used during the refinement
process and the Uiso(H) values were constrained to be 1.2Ueq(car-
rier atom) for CH and CH2 and 1.5Ueq(carrier atom) for CH3. Com-
2.4.1. 2-Methoxy-6-((E){[(5-methyl-2-
furyl)methyl]imino}methyl)phenol (L1)
5-Methylfurfurylamine (0.25 g, 2.24 mmol) was added to a stir-
red solution of 2-hydroxy-3-methoxybenzaldehyde (0.34 g,
2.24 mmol) in EtOH (50 mL). The mixture was refluxed and stirred
for 3 h and then allowed to cool to ambient temperature. The yel-
low micro crystals were filtered off and re-crystallization has been
performed in n-heptane solution. m.p.: 55 °C. Yield 83% (0.45 g,
1.85 mmol). Anal. Calcd. For C14H15NO3; C, 68.56; H, 6.16; N,
5.71. Found: C, 68.37; H, 6.33; N, 5.46%. IR (KBr, cmꢀ1):
mC@N = 1633, mCAH = 2960; 2826, mCAO = 1189.

C. Sßenol et al. / Journal of Molecular Structure 997 (2011) 53–59
55
Table 1
Crystallographic data, details of data collection and structure refinement parameters for L2, [Ni(L1)2] and [Cu(L1)2].
L2
[Ni(L1)2]
[Cu(L1)2]
Empirical formula
Colour/shape
Formula weight
Temperature (K)
C
14H15NO3
C28H28N2NiO6
Brown/block
547.21
C28H28N2CuO6
Red/block
552.06
Yellow/block
245.27
100(2)
294(2)
294(2)
Radiation used, graphite monochr.
Crystal system
Mo Ka (k = 0.71073 Å)
Monoclinic
Space group
P21/n
P21/n
P21/c
a, b, c (Å)
13.6380(3)
5.5151(1)
16.5592(3)
101.150(2)
1221.99(4)
4
9.6382(4)
7.2529(3)
18.3790(5)
102.050(5)
1256.47(8)
2
13.091(5)
10.479(4),
9.920(4)
68.595(6)
1267.0(9)
2
b (°)
V (Å3)
Z
Absorption coefficient (mmꢀ1
)
0.094
1.333
0.819
1.446
0.908
1.447
Dcalc (Mg m3)
Max. Crystal dimen. (mm)
h (max) (o)
0.19 ꢁ 0.26 ꢁ 0.28
0.20 ꢁ 0.28 ꢁ 0.30
0.12 ꢁ 0.25 ꢁ 0.46
28.29
28.40
28.60
Reflections measured
Range of h, k, l
3041
3142
3209
–18 < h < 18
–7 < k < 7
–22 < l < 20
2142
–12 < h < 12
–9 < k < 9
–24 < l < 24
2602
–17 < h < 17
–14 < k < 14
–12 < l < 13
1711
No. of refl. with I > 2r(I)
Corrections applied
Structure solution
Treatment of H atoms
Lorentz-polarization
Direct methods
Diff. Map.
223
Geom. Calc.
175
Geom. Calc. & Diff. Map.
175
No. of parameters var.
GOF
1.009
0.0394
0.0980
0.220
1.029
0.971
0.0522
0.0885
0.381
–0.519
R = ||Fo| ꢀ |Fc||/|Fo|
0.0293
0.0778
0.225
Rw
(
(
D
D
/
/
q
q
) max (eAꢀ3
) min (eAꢀ3
)
)
–0.203
–0.358
Table 2
Selected bond lenghts (Å) and angles (°) for L2, [Ni(L1)2] and [Cu(L1)2].
L2
[Ni(L1)2]
[Cu(L1)2]
N1AC7
N1AC8
O1AC2
O2AC3
O2AC14
C6AC7
C8AC9
1.2742(18)
1.4647(18)
1.3564(16)
1.3623(17)
1.4276(18)
1.462(2)
Ni1AN1
Ni1AO1
N1AC7
N1AC8
O1AC1
O2AC2
C8AC9
1.9152(12)
Cu1AN1
Cu1AO1
N1AC7
N1AC8
O1AC1
O2AC2
C8AC9
2.0088(19)
1.8758(16)
1.286(3)
1.473(3)
1.296(3)
1.362(3)
1.471(4)
1.8263(10)
1.2924(19)
1.4968(19)
1.2996(17)
1.365(2)
1.493(2)
1.483(2)
C3AO2AC14
C9AO3AC12
C7AN1AC8
C6AC7AN1
C9AC8AN1
C8AC9AC10
C8AC9AO3
O3AC9AC10
116.73(12)
106.47(10)
116.97(12)
124.54(13)
108.47(12)
133.69(13)
116.04(12)
110.26(12)
O1ANi1AN1
O1ANi1AN1’
Ni1AO1AC1
Ni1AN1AC7
Ni1AN1AC8
C7AN1AC8
N1AC7AC6
N1AC8AC9
86.92(5)
93.08(5)
O1ACu1AN1
O1ACu1AN1’
Cu1AO1AC1
Cu1AN1AC7
Cu1AN1AC8
C7AN1AC8
N1AC7AC6
N1AC8AC9
91.32(7)
88.68(7)
130.53(10)
124.70(11)
121.84(9)
113.36(13)
127.09(15)
110.43(12)
129.82(15)
123.26(16)
119.89(14)
116.80(19)
127.5(2)
111.6(2)
crystals of ligand (L2) suitable for X-ray analyses were obtained by
slow evaporation of n-hexane/CH2Cl2 solution. m.p.: 64 °C. Yield
69% (0.38 g, 1.54 mmol). Anal. Calcd. For C14H15NO3; C, 68.56; H,
6.16; N, 5.71. Found: C, 68.66; H, 6.39; N, 5.49%. IR (KBr, cmꢀ1):
Table 3
Hydrogen-bond geometries (, o) for L2, [Ni(L1)2] and [Cu(L1)2].
DAHꢂ ꢂ ꢂA
DAH
Hꢂ ꢂ ꢂA
1.82(2)
2.13
Dꢂ ꢂ ꢂA
2.7478(16)
2.671(2)
2.778(3)
DAHꢂ ꢂ ꢂA
173.2(19)
114
L2
O1AH1Aꢂ ꢂ ꢂN1i
C8AH8Bꢂ ꢂ ꢂO1
C8AH8Aꢂ ꢂ ꢂO1
0.94(2)
0.97
mC@N = 1635,
mCAH = 2964; 2835, mCAO = 1175.
[Ni(L1)2]
[Cu(L1)2]
0.97
2.28
111
Symmetry code: (i) ½ ꢀ x, ꢀ½ + y, 3/2 ꢀ z.
2.4.3. Nickel (II) complex [Ni(L1)2]
To [Ni(CH3COO)2]. 4H2O (0.24 g, 1 mmol) dissolved in 15 mL
EtOH was added Schiff base (L1) (0.49 g, 2 mmol) dissolved in
15 mL hot EtOH with stirring at reflux temperature for 3 h and then
allowed to cool to ambient temperature. The brown crystals were
filtered off and recrystallized from acetone. Single crystals of nickel
(II) complex suitable for X-ray analyses were obtained by slow
evaporation of acetone. m.p.: 183 °C. Yield 72% (0.35 g, 0.89 mmol).
2.4.2. 2-Methoxy-5-((E){[(5-methyl-2-
furyl)methyl]imino}methyl)phenol (L2)
This Schiff base was prepared by a procedure similar to L1 using
3-hydroxy-4-methoxybenzaldehyde (0.34 g, 2.24 mmol). The yel-
low solid was recrystallized from n-hexane/CH2Cl2 (2:1 v/v). Single

56
C. Sßenol et al. / Journal of Molecular Structure 997 (2011) 53–59
Anal. Calcd. For C28H28N2O6Ni: C, 61.46; H, 5.12; N, 5.12. Found: C,
61.56; H, 5.49; N, 5.22%. IR (KBr, cmꢀ1):
C@N = 1609, CAH = 2918;
2833, CAO = 1167.
m
m
m
2.4.4. Copper (II) complex [Cu(L1)2]
Cu(II) complex was synthesized by similar method as described
for [Ni(L1)2], with [Ni(CH3COO)2]. 4H2O replaced by [Cu(CH3CO
O)2]. H2O (0.20 g, 1 mmol). Crude product was filtered off and
recrystallized from THF. The red single crystals of Cu(II) complex
suitable for X-ray analyses were obtained by slow evaporation of
THF. m.p.: 204 °C. Yield 63% (0.30 g, 0.88 mmol). Anal. Calcd. For
C
28H28N2O6Cu: C, 60.92; H, 5.07; N, 5.07. Found: C, 61.27; H,
4.78; N, 5.39%. IR (KBr, cmꢀ1):
C@N = 1612, CAH = 2912; 2832,.
CAO = 1165.
m
m
m
3. Results and discussion
3.1. Syntheses
The reactions between 5-methylfurfurylamine with appropriate
aldehyde in EtOH yield Schiff base ligands (L1 and L2). The ligands
(L1 and L2) were successfully synthesized with yields in the range
83% and 69%. Schiff bases (L1 and L2) are soluble in EtOH, CHCl3,
THF, acetone, DMSO, CH3CN, n-hexane and n-heptane. Schiff base
ligands (L1 and L2) were characterized by elemental analyses, IR,
1H, 13C NMR, mass and UV–vis spectra. Single crystals of ligand
(L2) suitable for X-ray analyses were obtained by slow evaporation
of n-hexane/CH2Cl2 solution.
The Schiff base L1 readily formed complexes [Ni(L1)2] and
[Cu(L1)2], treating two equivalents of ligand with one equivalent
of [Ni(CH3COO)2]. 4H2O or [Cu(CH3COO)2]. H2O in EtOH. The syn-
thesis of various mononuclear complexes of copper(II) containing
Schiff base ligands obtained in situ from appropriate amine and
aldehyde [15,25]. The stoichiometries of the complexes derived
from elemental analysis correspond to the general formula
[M(L1)2] which are confirmed by determining the X-ray crystal
structures of [Ni(L1)2] and [Cu(L1)2]. The purity of the complexes
were checked by C, H, N elemental analyses, mass and IR spectra.
1H NMR and 13C NMR spectra were detected for [Ni(L1)2], because
[Ni(L1)2] is diamagnetic and NMR active.
The magnetic susceptibility results of the complexes give indi-
cations of the geometries of the ligands around the central transi-
tion metal ions. Cu(II) complex shows room temperature magnetic
susceptibility value as expected for an isolated d9 transition metal
center. The effective magnetic susceptibility (leff) value is found to
be 1.74 B. M. at 300 K, which is very consistent with the expected
spin only magnetic moment of a S = 1/2, d9 copper(II) configura-
tion. Copper(II) complex [Cu(L1)2] was characterised by single
crystal X-ray structure determination which shows that the cop-
per(II) ion is in a square planar N2O2 environment.
The nickel(II) complex [Ni(L1)2] was diamagnetic as expected
for a d8 electronic configuration and was found to be square planar
geometry as indicated by X-ray crystallographic data.
3.2. Description of the structures of (L2), [Ni(L1)2] and [Cu(L1)2]
The X-ray structural determinations of L2, [Ni(L1)2] and
[Cu(L1)2] confirm the assignments of their structures from spectro-
scopic data. The molecular structures along with the atom-
numbering schemes are depicted in Figs. 1a–c, respectively. The
asymmetric units of [Ni(L1)2] and [Cu(L1)2] contain one-halves of
the molecules (Figs. 1b and c). The Ni1 and Cu1 atoms are located
on the inversion centers and surrounded by the two N and the two
O atoms of the symmetry related 2-methoxy-5-((E){[(5-methyl-2-
furyl)methyl]imino}methyl)phenol (L2) ligands. The four atoms in
Fig. 1. ORTEP-3 drawings with the atom-numbering schemes of L2 (a), [Ni(L1)2] (b),
and [Cu(L1)2] (c). Displacement ellipsoids are drawn at 50% probability level.
Hydrogen bonds are shown as dashed lines.
the equatorial planes around the Ni1 and Cu1 atoms form slightly
distorted square-planar arrangements (Table 2). The NiAO
[1.8263(10) Å], NiAN [1.9152(12) Å] and CuAO [1.8758(16) Å],

C. Sßenol et al. / Journal of Molecular Structure 997 (2011) 53–59
57
CuAN [2.0088(19) Å] bonds are in good agreement with the corre-
sponding values [1.833(2) and 1.902(2) Å] in (C26H24O6N2Ni) and
[1.8932(2) and 2.006(2) Å] in (C26H24O6N2Cu) [18], [1.896(1) and
2.000(2) Å] in (C24H20O4N2Cu) and [1.867(2) and 1.976(2) Å] in
(C26H24O4N2Cu) [25], [1.826(2) and 1.913(2) Å] in [Ni(C14H14NO2)2]
[26] and [1.819(2), 1.922(2) and 1.823(2), 1.914(3) Å] in
[Ni(C16H18NO2)2] [27]. The rings A (C1-C6) and B (O3/C9–C12)
are, of course, planar and they are oriented at dihedral angles of
A/B = 79.04(4)° (for L2), 75.20(5)° (for [Ni(L1)2]) and 82.07(11)°
(for [Cu(L1)2]). The ring C (Cu1/O1/N1/C1/C6/C7) (for [Cu(L1)2])
adopts envelope conformation with Cu1 atom displaced by
ꢀ0.2738(4) Å from the plane of the other ring atoms, while ring
C (Ni1/O1/N1/C1/C6/C7) (for [Ni(L1)2]) is planar. The intramolecu-
lar CAHꢂ ꢂ ꢂO hydrogen bonds (Table 3) result in the formations of
the five membered rings D ((Ni1/O1/N1/C8/H8B) (for [Ni(L1)2])
and D (Cu1/O1/N1/C8/H8A) (for [Cu(L1)2]) having envelope confor-
mations with H8B and H8A atoms displaced by 0.3097(1) and
ꢀ0.3880(4) Å, respectively, from the planes of the other ring atoms.
In the crystal structures, the intermolecular OAHꢂ ꢂ ꢂN hydrogen
bonds link the molecules into double chains through the bifurcated
hydrogen bonds (Table 3) along the b-axis for L2 (Fig. 2a), while the
Ni1 and Cu1 (for [Ni(L1)2] and [Cu(L1)2], respectively) atoms are
located at the corners of the unit cells (Figs. 2b and c). The mole-
cules are alongated along the a-axis (for [Ni(L1)2]) and c-axis (for
[Cu(L1)2]) and stacked along the b-axes.
3.3. IR spectra
The IR spectra of the Schiff base free ligands (L1 and L2) show
strong bands at 1633 and 1635 cmꢀ1 due to mC@N of imine, which
indicate that the Schiff base ligands have been obtained. The IR
spectra of the ligand (L1) and the corresponding complexes Ni(II)
and Cu(II) are very similar. In metal complexes [Ni(L1)2] and
[Cu(L1)2], azomethine band (
mC@N) was shifted to lower frequen-
cies (1609 and 1612 cmꢀ1) after complexation. This lower shift
could be attributed to a weakening of the C@N bonds on adduct
formation and this can be explained by the donation of electrons
from nitrogen to the empty d-orbitals of the transition metal ions
[28–32]. The strong bands at 1189 and 1175 cmꢀ1 in the free Schiff
base ligands (L1 and L2) are due to the phenolic CAO stretchings.
On complex formation, these bands are shifted to lower frequen-
cies (1167 and 1165 cmꢀ1) indicating coordinations through the
phenolic oxygens.
3.3.1. 1H and 13C NMR spectra
The 1H NMR spectral data of the Schiff base ligands (L1 and L2)
and complex [Ni(L1)2] are listed in Tables 4. In the 1H NMR spectra
of the Schiff bases (L1 and L2), the phenolic OH proton was detected
as a broad singlet in the offset region at 13.70 and 13.67 ppm. The
characteristic signals at 8.38 and 8.22 ppm are assigned to AHC@N
for compounds L1 and L2. The 1H NMR spectra of the Schiff bases
indicate the presence of the aliphatic protons (such as ACH3,
AOCH3 and ACH2 protons) in the range of 2.26, 3.90 and
4.72 ppm (for compound L1) and 2.27, 3.90 and 4.70 ppm (for com-
pound L2) as singlets. The aromatic protons of the free ligands (L1
and L2) were observed as multiplets in the aromatic region.
The absence of the OH proton peak in the spectrum and the
upfield shift (8.56 ppm) of the azomethine proton (HC@N) peak
in complex [Ni(L1)2] with respect to the corresponding free ligand,
indicate the complexation with Ni(II). The aliphatic protons (ACH3,
AOCH3 and ACH2 for ligands L1 and L2) were detected in the ex-
pected regions.
Fig. 2. Partial packing diagrams of L2 (a), (b) [Ni(L1)2] viewed down the b-axis,
where c-axis is horizontal and a-axis is vertical, and (c) [Cu(L1)2] viewed down the
b-axis, where a-axis is horizontal and c-axis is vertical. Hydrogen bonds are shown
as dashed lines. H atoms not involved in hydrogen bonding have been omitted for
clarity.
and L2 are detected at 13.56, 56.15, 54.90 ppm and 13.62, 57.15,
56.10 ppm, respectively. The aromatic and four furyl ring carbons
are observed in the expected regions. In the 13C NMR spectra for
the Ni(II) complex, all the carbon peaks are slightly shifted upfield
and downfield. The signals of carbons are equal to the number in
the proposed structures of the Schiff bases and Ni(II) complex.
The 13C NMR spectral data of the Schiff bases and Ni(II) complex
is listed in Table 5. The free ligand Schiff bases show the azome-
thine carbon peaks at 166.06 and 162.35 ppm, respectively. The
aliphatic ACH3, AOCH3 and ACH2 carbon peaks for ligands L1

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C. Sßenol et al. / Journal of Molecular Structure 997 (2011) 53–59
Table 4
1H NMR spectral data of the Schiff bases (L1 and L2) and complex [Ni(L1)2] (in CDCl3); d in ppm; s, singlet; bs, broad singlet; d, doublet; m, multiplet; q, quartet; J = Hz.
Comp.
OH
N@CH
ACH3
AOCH3
ACH2(5)
H(2)
H(3)
H(8)
–
H(10,11,12)
L1
13.70
(bs, 1H)
–
8.38
(s, 1H)
8.56
2.26
(s, 3H)
2.29
3.90
(s, 3H)
3.87
4.72
(s, 2H)
4.71
5.94
(d, 1H) J = 2.8
6.02
6.147
(d, 1H) J = 2.9
6.18
6.82–6.99
(m, 3H)
7.03–7.17
(m, 6H)
H(11)
[Ni(L1)2]
–
(s, 2H)
(s, 6H)
(s, 6H)
(s, 4H)
(d, 2H)
(d, 2H)
H(12)
L2
13.67
8.22
2.27
3.90
4.70
5.92
6.14
7.39
6.87
7.27
(bs, 1H)
(s, 1H)
(s, 3H)
(s, 3H)
(s, 2H)
(d, 1H) J = 1.9
(d, 1H) J = 2.8
(d, 1H) J = 1.5
(d, 1H) J = 8.3
(q, 1H) J = 8.2, J = 1.5
5
5
11
12
12
12
H
C
H
C
CH2
CH2
O
O
1
2
3
1
2
7
10
O
CH3
CH3
11
11
10
6
7
6
N
N
6
4
4
7
8
4
1
9
8
3
3
8
2
CH3
CH3
10
N
H3C
H3C
5
OH
O
O
O
9
9
Ni
CH3
O
OH
O
O
O
CH3
N
(L1)
(L2)
[Ni(L1)2]
amine, only one d–d transition is observed in the visible region
at approximately 625 nm [35].
Table 5
13C NMR spectral data of the Schiff bases (L1 and L2) and complex [Ni(L1)2] (in CDCl3);
d in ppm.
Comp.
N@C(6)
H
ACH3 AOCH3 AC(5)H2 C(1ꢀ4,
7ꢀ12)
3.5. Mass spectra
L1
166.06
13.56 56.15
13.62 57.15
13.59 56.13
54.90
56.10
54.96
106.29; 108.79; 114.22;
118.00; 118.69; 123.13;
148.47; 149.07; 151.61;
152.24
106.23; 108.28; 110.31;
113.98; 121.37; 129.73;
145.89; 149.09; 150.63;
151.79
106.37; 108.93; 113.96;
117.67; 118.18; 123.17;
148.01; 148.96; 151.03;
151.79
The mass spectral data of the Schiff bases and complexes are
given in Table 7. The mass spectra fragmentation patterns of the
compounds were in good agreement with the suggested structures.
The mass spectra of Schiff bases (L1 and L2) were characterized by
an intense peak m/z [M + 1]+ 246 (100%) corresponding to the
molecular ion peak (calculated value 245). The mass spectral data
of the complexes [Ni(L1)2] and [Cu(L1)2] show molecular ion peaks
L2
162.35
[Ni(L1)2] 166.18
(m/z); 547 and 552 corresponding to
C28H28N2O6Ni and
C28H28N2O6Cu, respectively. The important fragments of the
ligands and complexes at m/z 246, 152 and 95 are attributed to
the Schiff base molecular ion peak [M + H+], loss of methylfuran
ring (C8H8NO2+2H) and methylfuran ring (C6H7O+), respectively.
3.4. UV–vis spectra
The UV–vis spectra were recorded in EtOH solutions in the
range of 210–450 nm for the Schiff bases and the complexes (Table
6). The molar absorbtivities (for ligands L1 and L2) at 328 and
314 nm may be assigned to an n–pꢃ transition between lone-pair
electrons of the p orbitals of the N atoms in the azomethine
Table 7
Mass spectral data of the Schiff bases (L1 and L2) and complexes [Ni(L1)2] and
[Cu(L1)2].
Comp.
m/z
Relative intensity (%)
Fragment
(HC@N) groups and the
p bonds of the aromatic rings [32,33].
The peaks at 262 and 279 nm are assigned to the p–
pꢃ transitions
L1
246
214
100
12.3
[C14H15NO3 + H]+
C13H12NOþ2
of the Schiff bases (L1 and L2).
In the electronic spectra of the complexes [Ni(L1)2] and
[Cu(L1)2], the LMCT band in the UV region (412 nm) can be as-
signed to N ? Ni charge transfer, while the other bands at 374
and 376 nm are also due to LMCT arising out of O ? Ni charge
transfer [34]. Similar nickel(II) and copper(II) complexes with an
asymmetric bidentate Schiff base ligand derived from furfuryl-
152
149
95
86.3
38.6
21.7
23.2
C8H8NO2 + 2H
C8H8NO2 ꢀ H
C6H7O+
80
C6H5O + H
L2
246
214
152
149
95
100
[C14H15NO3 + H]+
+
15.7
85.6
33.5
20.3
23.7
C13H12NO2
C8H8NO2 + 2H
C8H8NO2 ꢀ H
C6H7O+
80
C6H5O + H
Table 6
[Ni(L1)2]
[Cu(L1)2]
547
246
152
95
20.7
100
55.9
26.3
[C28H28N2O6Ni]
UV–vis spectral data of the ligands and complexes.
C
14H14NO3 + 2H
Comp.
ak, nm (log
e)
C8H7NO2 + 3H
C6H7O+
L1
220 (3.73); 262 (3.35); 328 (2.53)
216 (3.75); 279 (3.57); 314 (3.40)
224 (3.68); 266 (3.47); 374 (2.66); 412 (2.86)
234 (3.75); 280 (3.51); 376 (2.89); 412 (2.93)
L2
552
246
152
95
22.4
100
57.1
25.3
[C28H28N2O6Cu]
[Ni(L1)2]
[Cu(L1)2]
C
14H14NO3 + 2H
C8H7NO2 + 3H
C6H7O+
a
EtOH solutions 5 ꢁ 10ꢀ4 at 300 K.

C. Sßenol et al. / Journal of Molecular Structure 997 (2011) 53–59
[2] P. Przybylski, G. Schroeder, B. Brzezinski, J. Mol. Struct. 658 (2003) 115.
59
4. Conclusion
[3] R. Dreos, G. Nardin, L. Randaccio, P. Siega, T. Tauzher, V. Vrdoljak, Inorg. Chim.
Acta 349 (2003) 239.
[4] S.M. Abu-El-Wafa, R.M. Issa, Bull. Soc. Chim. Fr. 128 (1991) 805.
[5] M.D. Cohen, S. Flavian, J. Chem. Soc. (B) 12 (1967) 317.
[6] M.T.H. Tarafder, K.B. Chew, K.A. Crouse, A.M. Ali, B.M. Yamin, H.K. Fun,
Polyhedron 21 (2002) 2683.
[7] E.J. Larson, V.L. Pecoraro, J. Am. Chem. Soc. 113 (1991) 3810.
[8] I. Ramade, O. Khan, Y. Jennin, F. Robert, Inorg. Chem. 36 (1997) 930.
[9] N. Hoshino, Coord. Chem. Rev. 174 (1998) 77.
[10] L. Shi, W.-J. Mao, H.-L. Zhu, J. Coord. Chem. 62 (2009) 3471.
[11] J. Zhao, B. Zhao, J. Liu, W. Xu, Z. Wang, Spectrochim. Acta Part A 57 (2001) 149.
[12] H. Carlsson, M. Haukka, A. Bousseksou, J.-M. Latour, E. Nordlander, Inorg.
Chem. 43 (2004) 8252.
[13] Ya S. Higasio, T. Shoji, Appl. Catal. A Gen. 221 (2001) 197.
[14] L. Juhasz, Z. Dinya, S. Antus, T.E. Gunda, Tetrahedron Lett. 41 (2000) 2491.
[15] S. Mandal, A.K. Rout, A. Ghosh, G. Pilet, D. Bandyopadhyay, Polyhedron 28
(2009) 3858.
[16] W. Chen, P. Miao, Y.G. Li, H.L. Zhu, Q.F. Zeng, Russ. J. Coord. Chem. 36 (2010)
929.
In conclusion, we have prepared new Schiff bases (L1 and L2)
and transition metal complexes [Ni(L1)2] and [Cu(L1)2]. The Ni(II)
and Cu(II) ions are coordinated by two phenolic-O atoms and
two azomethine (HC@N) atoms. Spectroscopic, structural and mag-
netic data show that [Ni(L1)2] and [Cu(L1)2] are four-coordinate
metal complexes owing to the ligation of two bidentate Schiff base
moieties.
The molecular structures of the synthesized compounds were
identified by IR, 1H NMR and 13C NMR spectra, mass spectra and
elemental analyses and their results showed that all the reactions
were succesfully completed. The solid state structures of the ligand
(L2) and the complexes [Ni(L1)2] and [Cu(L1)2]) were determined
by single crystal X-ray crystallography.
[17] T. Hökelek, A. Öztürk, Z. Hayvalı, H. Dal, Z. Kılıç, Anal. Sci. 22 (2006) x143.
[18] H. Ünver, Z. Hayvalı, Spectrochim. Acta Part A 75 (2010) 782.
[19] Z. Hayvalı, H. Dal, P. Köksal, D. Sßahin, T. Hökelek, Struct. Chem. 21 (2010) 837.
[20] Z. Hayvalı, M. Hayvalı, Z. Kılıç, T. Hökelek, E. Weber, J. Inclusion Phenom.
Macrocycle Chem. 45 (2003) 285.
[21] Bruker, 2005, SADABS Bruker AXS Inc., Madison, Wisconsin, USA.
[22] G.M. Sheldrick, Acta Crystallogr. A 64 (2008) 112.
[23] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[24] International Tables for X-ray Crystallography, vol. IV, Kynoch Press,
Birmingham, Present Distributer Kluwer Academic Publisher Dordrecht, The
Netherlands, 1974.
[25] S. Mandal, A.K. Rout, G. Pilet, D. Bandyopadhyay, Transition Met. Chem. 34
(2009) 719.
[26] T. Hökelek, N. Gündüz, Z. Hayvalı, Z. Kılıç, Acta Crystallogr. C51 (1995) 880.
[27] T. Hökelek, N. Gündüz, Z. Hayvalı, Z. Kılıç, J. Chem. Crystallogr. 25 (1995) 827.
[28] E.R. Dockal, G. Castellano, G. Oliva, Polyhedron 15 (1996) 245.
[29] A.S. El-Tabl, Bull. Korean Chem. Soc. 25 (2004) 1757.
[30] Z. Rezvani, A.R. Abbasi, K. Nejati, Polyhedron 24 (2005) 1461.
[31] R. Vafazadeh, M. Kashfi, Bull. Korean Chem. Soc. 28 (2007) 1227.
[32] R. Herzfeld, P. Nagy, Curr. Org. Chem. 5 (2001) 373.
[33] H. Dal, Y. Süzen, E. Sßahin, Spectrochim. Acta Part A 67 (2007) 807.
[34] T. Akitsu, Polyhedron 26 (2007) 2527.
Supplementary material
Crystallographic data (excluding structure factors) have been
deposited with the Cambridge Crystallographic data Centre as
the supplementary publication Nos: CCDC 814578 (for compound
[Cu(L1)2]), CCDC 814579 (for compound [Ni(L1)2]) and CCDC
814580 (for ligand L2). Copies of the data can be obtained, free of
charge, on application to CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44–1223-336033 or e-mail: deposit@ccdc.cam.ac.
uk).
Acknowledgements
The authors gratefully acknowledge the financial assistance of
the Scientific and Technical Research Council of Turkey (TUBITAK),
grand Nos. TBAG 109T034 and TBAG 210T122.
[35] A.D. Khalaji, S.M. Rad, G. Grivani, D. Das, J. Therm. Anal. Calorim. 103 (2011)
747.
References
[1] W.L. Liu, Y. Zou, C.L. Ni, Y.Z. Li, Q.J. Meng, J. Mol. Struct. 751 (2005) 1.