Synthesis and Characterization of Transition Metal Complexes with 2,2'-[(Propylene-1,3-diyldioxy)bis(nitrilomethylidyne)]diphenol

Article abstract of DOI:10.14233/ajchem.2013.15633

In anhydrous ethanol medium, a series of transition metal complexes have been synthesized by the reaction of 2,2'-[(propylene-1,3- diyldioxy) bis(nitrilomethylidyne)]diphenol (H₂L) with Cu(II), Ni(II), Co(II) and Mn(II) acetate hydrate. All the

Full text of DOI:10.14233/ajchem.2013.15633

Asian Journal of Chemistry; Vol. 25, No. 16 (2013), 9362-9364
http://dx.doi.org/10.14233/ajchem.2013.15633
Synthesis and Characterization of Transition Metal Complexes with
2,2'-[(Propylene-1,3-diyldioxy)bis(nitrilomethylidyne)]diphenol
1
2
2
2
FENG-YING CHAI , XIN-YING ZHANG , MENG-MENG ZHAO , ZHENG-KUN WANG ,
2
2
1,*
JIAO-LONG MENG , LI-SHA ZHANG and KE-TAI WANG
1School of Chemical Engineering, Lanzhou University of Arts and Sciences, Lanzhou 730000, P.R. China
2School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P.R. China
*Corresponding author: E-mail: wang_kt@126.com
(Received: 13 April 2013;
Accepted: 25 September 2013)
AJC-14179
In anhydrous ethanol medium, a series of transition metal complexes have been synthesized by the reaction of 2,2'-[(propylene-1,3-
diyldioxy)bis(nitrilomethylidyne)]diphenol (H2L) with Cu(II), Ni(II), Co(II) and Mn(II) acetate hydrate. All these metal complexes were
characterized by elemental analyses, IR spectra, UV-VIS spectra, molar conductances and TG-DTA analyses.
Key Words: Transition metal complexes, Salamo-type compound, Synthesis, Characterization.
TEX70 FT-IR spectrophotometer, with samples prepared as
KBr (4000-400 cm-1). UV-visible absorption spectra were
recorded on a Shimadzu UV-2550 spectrometer. TG-DTA
analyses were carried out at a heating rate of 5 ºC/min on a
ZRY-1P thermoanalyzer. Molar conductance value measure-
ments were carried out on a model DDS-11D type conductivity
bridge using 1.0 × 10-3 mol dm-3 solution in DMF at 21 ºC.
Melting points were obtained by use of an X4 microscopic
melting point apparatus made in Beijing Taike Instrument
Limited Company and were uncorrected.
Synthesis of 2,2'-[(propylene-1,3-diyldioxy)bis(nitrilo-
methylidyne)]diphenol (H2L): The ligand H2L was synthe-
sized with a slightly modified method reported literature1.
Synthetic route to salamo-type bisoxime ligand H2L is shown
in Fig. 1.
INTRODUCTION
Transition metal complexes with salen-type or oxime-type
ligands are extensively investigated, which have long been used
as chelating ligands in the synthesis of transition metal comp-
lexes due to their ease of preparation and structural variety.
These compounds play a seminal role in the development of
modern coordination chemistry, which can accommodate
several metal centers and form homo- and heteronuclear metal
complexes with favourable properties1, such as their enormous
variety of structural topologies, as well as their potential
applications in optoelectronics, magnetism, non-linear optical
materials2, biological activity3 and catalysis4-8. To change the
structures or improve the functions of the resulted complexes,
herein, a new salamo-type bisoxime ligand, 2,2'-[(propylene-
1,3-diyldioxy)bis(nitrilomethylidyne)]diphenol (H2L) and its
transition metal complexes have been synthesized and struc-
turally characterized.
O
C
O
C
O
C
Br
Br
N OH
N O O N
EXPERIMENTAL
2
rt, 75 h, DMF, Et3N
C
O
C
O
C
O
2-Hydroxy benzaldehyde (≥ 98 %) and 1,3-dibromo
propane was purchased from Alfa Aesar and used without
further purification. The other reagents and solvents were
analytical grade reagents from Tianjin Chemical Reagent
Factory and were used without further purification. Elemental
analyses for transition metals were detected by an IRIS ER/
S·WP-1 ICP atomic emission spectrometer. C, H and N analyses
were carried out with a GmbH VariuoEL V3.00 automatic
elemental analyzer. FT-IR spectra were recorded on a VER-
O
N
O
CHO
OH
N
2
NH2NH2·H2O
H2N
OH HO
H2L
O
O NH2
Ethanol
95% Ethanol, Ar
Fig. 1. Synthetic route to the salamo-type bisoxime compound

Vol. 25, No. 16 (2013)
Synthesis and Characterization of Transition Metal Complexes 9363
1,3-Bis(phthalimidooxy)propane was synthesized accor-
ding to an analogous method reported earlier1.
Synthesis of Mn(II) complex: To an ethanolic solution
(2 mL) of H2L (31.4 mg, 0.10 mmol) was added an ethanolic
solution (6 mL) of manganese(II) acetate tetrahydrate (24.5
mg, 0.10 mmol). After the mixture solution had been stirred
at 55 ºC for 6 h, the formed precipitate was separated by filtration
and washed with ethanol and ether, respectively. The product
was dried under reduced pressure to obtain 26.0 mg of Mn(II)
complex (Yield 63.0 %).
1,3-Bis(aminooxy)propane was synthesized according to
1
an analogous method reported earlier1. H NMR(400 MHz,
CDCl3) δ: 1.88 (m, 2H), 3.77 (t, 4H), 5.00(s, 4H).
Synthesis of H2L: To an ethanolic solution (10 mL) of
2-hydroxy benzaldehyde (366.4 mg, 3 mmol) was added an
ethanolic solution (5 mL) of 1,3-bis(aminooxy)propane (159.2
mg, 1.5 mmol). The solution had been stirred at 55 ºC for 4 h.
When the solution cooled to room temperature, the resulting
solid was filtered and washed with ethanol and ethanol/hexane
(1:4), respectively. The product was dried under reduced
pressure and purified with recrystallization from ethanol to
obtain 385.7 mg of white crystalline solid H2L.Yield, 81.8 %.
m.p. 80-81 ºC. 1H NMR (400 MHz, CDCl3) δ: 2.09 (t, J = 6.0
Hz, 2H), 4.25 (t, J = 6.0 Hz, 4H), 6.88 (t, J = 8.0 Hz, 4H), 7.11
(s, 2H), 7.18 (s, 2H), 8.13 (s, 2H), 9.76 (s, 2H).
Synthesis of Cu(II) complex: A solution of copper(II)
acetate monohydrate (20 mg, 0.10 mmol) in ethanol (5 mL)
was added dropwise to a solution of H2L (31.4 mg, 0.10 mmol)
in ethanol (3 mL) at room temperature. The solution became
green immediately and formed the brown flocculent precipi-
tate, then stirred for 3.5 h at room temperature. The resulting
solid was filtered off, washed with ethanol/ether (1:4) and ether,
respectively. The product was dried in vacuo and obtained
31.8 mg of Cu(II) complex (Yield 79.7 %).
RESULTS AND DISCUSSION
A new salamo-type bisoxime ligand H2L and a series of
complexes have been synthesized. The composition were
confirmed by elemental analyses and characterized by IR, UV-
visible spectra, molar conductances and TG-DTA analyses.
Composition of H2L and metal complexes: The colour,
yields and elemental analytical results of the synthesized
salamo-type bisoxime ligand and its transition metal complexes
are presented in Table-1.
Their compositions agree with the formulae. The ligand
is stable in air and soluble in methanol, ethanol, acetone,
chloroform, dichloromethane, tetrahydrofuran, acetonitrile,
ether, DMF and DMSO while insoluble in n-hexane. The molar
conductance values of the complexes at 21 ºC in 1.0 × 10-3
mol dm-3 DMF solutions are 1.67, 1.58, 1.60 and 1.72 S cm2
mol-1, respectively, indicating that all of these complexes are
non-electrolytes9.
IR spectra of H2L and complexes: The IR spectral details
of the salamo-type bisoxime ligand H2L and its corresponding
transition metal complexes are given in Table-2.
Synthesis of Ni(II) complex: To an ethanolic solution
(3 mL) of H2L (31.4 mg, 0.10 mmol) was added an ethanolic
solution (6 mL) of nickel(II) acetate tetrahydrate (24.8 mg,
0.10 mmol). After the mixture solution had been stirred at
55 ºC for 4 h. The formed precipitate was separated by filtration
and washed successively with ethanol and ether. The product
was dried under reduced pressure to obtain 27.9 mg of Ni(II)
complex (Yield 66.9 %).
Synthesis of Co(II) complex: To an ethanolic solution
(2 mL) of H2L (31.4 mg, 0.10 mmol) was added an ethanolic
solution (8 mL) of cobalt(II) acetate tetrahydrate (24.9 mg,
0.10 mmol). After the mixture solution had been stirred at
55 ºC for 3 h. The resulting solid was filtered off, washed with
ethanol and ether, respectively. The product was dried in vacuo
and obtained 27.8 mg of Co(II) complex (Yield 66.6 %).
The characteristic C=N stretching band of the free ligand
H2L appears at 1609 cm-1, while the C=N bands of the
complexes are observed at 1604, 1605, 1603 and 1603 cm-1,
respectively. The Ar-O stretching band occurs at 1270 cm-1
for H2L, whereas those at 1246, 1247, 1242 and 1240 cm-1 for
the complexes, respectively. These shifts of C=N and Ar-O
stretching frequencies indicate that the M-N and M-O bonds
are formed between the transition metal ions and the oxime N
and the phenolic O atoms of deprotonated (L)2- unit1a. Mean-
while, a O-H stretching band of the free ligand H2L at 3410
cm-1 disappears in the complexes, indicating the oxygen in
phenolic alcohol of the complexes has been deprotonated and
TABLE-1
COLOUR, YIELDS AND ANALYTICAL DATA OF H2LAND ITS TRANSITION METAL COMPLEXES
Found (calcd.) (%)
Yield
(%)
Compound
m.f. (m.w.)
Colour
C
H
N
M
H2L
C17H18N2O4 (314.3)
White
Gray
81.8
79.7
66.9
66.6
63.0
64.88 (64.96)
53.97 (54.20)
54.88 (54.71)
54.74 (54.68)
55.42 (55.21)
5.80 (5.77)
5.02 (4.80)
5.11 (5.32)
5.19 (5.31)
5.22 (5.36)
8.65 (8.91)
6.94 (7.02)
6.58 (6.72)
6.53 (6.71)
6.64 (6.78)
–
C18H19N2O4.5Cu (398.9)
C19H22N2O5Ni (417.1)
C19H22N2O5Co (417.3)
C19H22N2O5Mn (413.3)
15.96 (15.93)
14.32 (14.07)
14.35 (14.12)
13.43 (13.29)
[CuL]⋅0.5CH3CH2OH
[NiL]⋅CH3CH2OH
[CoL]⋅CH3CH2OH
[MnL]⋅CH3CH2OH
Green
Yellow
White
TABLE-2
IR SPECTRAL (cm-1) DATA FOR H2L AND ITS TRANSITION METAL COMPLEXES
Compound
H2L
ν(C=N)
1609
1604
1605
1603
1603
ν(Ar-O)
1270
1246
ν(O-H)
3410
3439
3429
3429
3421
ν(C=C) benzene ring skeleton
1572, 1494, 1472
1536, 1470, 1445
[CuL]⋅0.5CH3CH2OH
[NiL]⋅CH3CH2OH
[CoL]⋅CH3CH2OH
[MnL]⋅CH3CH2OH
1247
1538, 1476, 1443
1242
1543, 1470,1441
1240
1545, 1471,1440

9364 Chai et al.
Asian J. Chem.
TABLE-3
UV-VISIBLE SPECTRA DATA OF H2LAND ITS TRANSITION METAL COMPLEXES
First band
ε1 (× 104 L mol-1 cm-1)
Second band
C (× 10-4 mol L-1)
Compound
λmax1 (nm)
267
λmax2 (nm)
313
ε2 (× 104 L mol-1 cm-1)
H2L
1.00
1.00
1.00
1.00
1.00
2.29
1.04
1.12
0.89
1.09
1.19
0.59
0.40
0.68
0.70
269
300
[CuL]⋅0.5CH3CH2OH
[NiL]⋅CH3CH2OH
[CoL]⋅CH3CH2OH
[MnL]⋅CH3CH2OH
280
289
279
292
275
288
coordinated to the metals. In the 1572-1440 cm-1 region, the
observed bands were attributed to aromatic C=C vibrations.
In addition, infrared spectra of the complexes show the
expected strong absorption bands due to ν(O-H) at 3439-3421
cm-1, which are the evidence for the existence of ethanol
molecules1e.
UV-visible spectra of H2L and complexes: The UV-
visible spectra of H2L and its corresponding complexes in
diluted DMF solution are presented in Table-3. The spectra of
the complexes are similar to each other, but are different from
the spectrum of the ligand H2L. The UV-visible spectrum of
the free ligand H2L exhibits two absorption peaks at 267 and
313 nm. The former absorption peak at 267 nm can be
assigned to the π-π* transition of the benzene rings, while the
latter one at 313 nm can be attributed to the intra-ligand π-π*
transition of the C=N bonds10.
Compared with the absorption peak of the free ligand,
the former absorption peaks at 269, 280, 279 and 275 nm are
observed in Cu(II), Ni(II), Co(II) and Mn(II) complexes,
respectively, which are bathochromically shifted by 2-13 nm.
Meanwhile, the second absorption peaks at 300, 289, 292 and
288 nm are observed in Cu(II), Ni(II), Co(II) and Mn(II)
complexes, respectively, which are hypsochromically shifted
by 13-25 nm. These indicate that the oxime nitrogen atom is
involved in coordination to the metal atom11,12.In addition, the
new band observed at 362 nm for the Cu(II) complex is
assigned to the n-π* charge transfer transition from the filled
pπ orbital of the bridging phenolic oxygen to the vacant d-
orbital of the Cu(II) ion, which is characteristic of the transi-
tion metal complexes with N2O2 coordination spheres13.
Thermal properties: The thermal decomposition proce-
sses of the complexes compared with the ligand are signifi-
cantly different. The ligand has a sharp endothermic peak at
83 ºC in the DTA curve, with no weight loss in the TG curve
and has a exothermic peak at 266 ºC, weight loss occurs at
239 ºC in the corresponding TG curve. The ligand decomposed
completely by one step. However, the DTA curves of all the
complexes have endothermic peaks in the range 78-142 ºC,
with weight loss in the TG curve. The weight loss values of
Cu(II), Ni(II), Co(II) and Mn(II) complexes are 5.6, 11.5, 10.7
and 11.8 %, respectively, which are close to the theoretical
values (5.8, 11.1, 11.0 and 11.2 %) of losing corresponding
ethanol molecule. The complexes have no sharp melting point.
All of the complexes have two exothermic peaks at 300 ºC,
with apparent weight loss, which are staged oxidative decom-
position of the complexes. On further heating, the final solid
products are likely to CuO, NiO, CoO and Mn2O3 with a
residual value of 19.3, 17.2, 17.0 and 18.5 %, which was found
to be close to the calculated values (19.9, 17.9, 17.9 and 19.1 %)
when the temperature is above 800 ºC.
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