Synthesis and characterization of coordination chain polymers of some transition metals with Schiff base

Article abstract of DOI:10.1081/SIM-120016476

The coordination chain polymers of the transition metal ions Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 1-carboxy-l′-hydroxy-2,2′-(1-isonitriloethylidyne-4- nitrilomethylidenephenyl)diphenyl (H₂SB) have been synthesized and characte

Full text of DOI:10.1081/SIM-120016476

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SYNTHESIS AND CHARACTERIZATION OF COORDINATION
CHAIN POLYMERS OF SOME TRANSITION METALS WITH
SCHIFF BASE
N. H. Patel a , K. N. Patel a & M. N. Patel b
a Department of Chemistry , Sardar Patel University , Vallabh Vidyanagar, Gujarat, 388 120,
India
b Department of Chemistry , Sardar Patel University , Vallabh Vidyanagar, Gujarat, 388 120,
India
Published online: 15 Feb 2007.
To cite this article: N. H. Patel , K. N. Patel & M. N. Patel (2002) SYNTHESIS AND CHARACTERIZATION OF COORDINATION
CHAIN POLYMERS OF SOME TRANSITION METALS WITH SCHIFF BASE, Synthesis and Reactivity in Inorganic and Metal-Organic
Chemistry, 32:10, 1879-1887, DOI: 10.1081/SIM-120016476
To link to this article: http://dx.doi.org/10.1081/SIM-120016476
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 32, No. 10, pp. 1879–1887, 2002
SYNTHESIS AND CHARACTERIZATION
OF COORDINATION CHAIN POLYMERS
OF SOME TRANSITION METALS WITH
SCHIFF BASE
N. H. Patel, K. N. Patel, and M. N. Patel*
Department of Chemistry, Sardar Patel University,
Vallabh Vidyanagar 388 120, Gujarat, India
ABSTRACT
The coordination chain polymers of the transition metal ions
Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 1-car-
boxy-10-hydroxy-2,20-(1-isonitriloethylidyne-4-nitrilomethyli-
denephenyl)diphenyl (H2SB) have been synthesized and
characterized on the basis of elemental analyses, infrared
spectra, electronic spectra, magnetic measurements and
thermogravimetric analyses.
*Corresponding author. E-mail: jeenen@rediffmail.com
1879
DOI: 10.1081=SIM-120016476
Copyright # 2002 by Marcel Dekker, Inc.
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com

1880
PATEL, PATEL, AND PATEL
INTRODUCTION
Much work has been done on the preparation of polychelates of
various aromatic aldehydes and amines with transition metals.[1] In con-
tinuation of earlier work,[2] we prepared some coordination polymers of the
type [Ni(SB)]n and [M(SB)(H2O)2]n where M ¼ Mn(II), Co(II), Cu(II),
Zn(II) and Cd(II). H2SB ¼ 1-carboxy-10-hydroxy-2,20-(1-isonitriloethyli-
dyne-4-nitrilomethylidenephenyl)diphenyl. The Schiff base acts as a dineg-
ative tetradentate ligand bonding through the oxygen and nitrogen atoms.
The structures of the polymeric chelates were established on the basis of
elemental analyses, infrared spectra, electronic spectra, magnetic measure-
ments and thermogravimetric analyses.
EXPERIMENTAL
Materials
The chemicals employed were of analytical grade and were used
without further purification.
Preparation of the Ligand H2SB
The preparation of salicylidene-4-aminoacetophenone was carried out
by refluxing an ethanolic solution (100 mL) of 4-aminoacetophenone
(0.01 mol, 0.15 g) with an ethanolic solution (100 mL) of salicylaldehyde
(0.01 mol, 0.12 g) for four hours and then cooling to room temperature
overnight. The formed yellow coloured crystals were collected and dried in
Figure 1. 1-Carboxy-10-hydroxy-2,20-(1-isonitriloethylidyne-4-nitrilomethylidene-
phenyl)diphenyl.

COORDINATION CHAIN POLYMERS
1881
ꢀ
air, yield 0.21 g (78%); M.p. 105 C. Anal. Calcd. for C15H13O2N (239): C,
75.31; H, 5.43; N, 5.85. Found: C, 75.28; H, 5.40; N, 5.82.
An ethanolic solution of the salicylidene-4-aminoacetophenone pre-
pared above (0.01 mol, 0.24 g) and an ethanolic solution (100 mL) of 2-
aminobenzoic acid (0.01 mol, 0.14 g) were mixed and refluxed for ten hours
on a water bath and allowed to cool overnight at room temperature. The
obtained crystals were filtered, washed successfully with water and ethanol
and were dried in air.
Preparation of the Complexes
An ethanolic solution of (100 mL) metal chloride (0.02 mol) and an
ethanolic solution (100 mL) of H2SB (0.02 mol, 0.72 g) were mixed and
refluxed on a water bath. After 25 min, 1 g sodium acetate was added and
the mixture was refluxed for four hours to ensure complete precipitation.
The mixture was then cooled to room temperature. The obtained metal
chelate was filtered and washed with water and hot alcohol. The polymeric
chelates are insoluble in all common organic solvents like acetone, ethanol,
chloroform, methanol, benzene and dimethylformamide.
Analytical Procedure
The chelates were analyzed for their metal contents by EDTA
titration.[3] The magnetic moments were obtained by Gouy’s method
using mercury tetrathiocynatocobaltate(II) as
a
calibrant (wg ¼
16.44610ꢁ6 c.g.s. units at 20 ꢀC). Diamagnetic corrections were made
using Pascal’s constants. The infrared spectra were recorded on a Nicolate
400D FT-IR spectrophotometer. The electronic spectra were measured on
a Beckman DK-2A spectrophotometer using MgO as reference. A 951
DuPont analyzer (Germany) was used for thermogravimetric analyses.
Elemental analyses were performed on a Heraeus C, H, N analyzer
(Germany). All melting points are uncorrected and were recorded in open
capillaries in a capillary melting point apparatus (Tempo Instruments Co.,
Mumbai).
RESULTS AND DISCUSSION
The analytical data of the ligand, chelates and some physical prop-
erties are litsted in Table I. The reaction to form the polychelates may be
represented as follows.

1882
PATEL, PATEL, AND PATEL

COORDINATION CHAIN POLYMERS
1883
Figure 2. [M(SB)(H2O)2]n.
NiCl2 ꢂ6H2O þ H2SB
1
2CH3COONa
!
½NiðSBÞꢃn þ 2CH3COOH þ 2NaCl þ 6H2O
n
MCl2 ꢂnH2O þ H2SB
2CH3COONa
1
½MðSBÞðH2OÞ2ꢃn þ 2CH3COOH þ 2NaCl þ nH2O
!
n
M ¼ Mn(II), Co(II), Cu(II), Zn(II) and Cd(II).
H2SB ¼ 1-carboxy-10-hydroxy-2,20-(1-isonitriloethylidyne-4-nitrilomethyl-
idenephenyl)diphenyl.
The nature of the ligand, high thermal stability metal-ligand ratio (1:1)
and insolubility of chelates in common organic solvents suggest their
polymeric nature.[4] The insolubility of the chelates in common organic
solvents limits the determination of the molecular weight but indicates a
Figure 3. [Ni(SB)(H2O)2]n.

1884
PATEL, PATEL, AND PATEL
polymeric nature.[5] Elemental analyses, physical properties and infrared
data provide good evidence that the chelates are polymeric in nature.
Magnetic Measurements
The magnetic moment value of the Cu(II) chelate (1.80 B.M.) is
slightly higher than the spin-only value (1.73 B.M.) expected for one
unpaired electron, which offers the possibility of an octahedral geometry.[6]
The magnetic moment of the Co(II) chelate (3.90 B.M.) is in good agree-
ment with a high-spin octahedral geometry.[7] The Mn(II) chelate has a
magnetic moment value (5.90 B.M.) which is very near to the spin-only
value of 5.92 B.M., but within the limits of spin-free values for five unpaired
electrons, indicating that the chelate is high-spin six-coordinated.[8] The
magnetic moment determination shows that the Ni(II), Zn(II) and Cd(II)
chelates are diamagnetic.
Electronic Spectra
The electronic spectra of the chelates were recorded in the solid
state. The electronic spectra of the nickel(II) chelate exhibit three bands at
32,300, 35,200 and 37,600 cmꢁ1 corresponding to the transitions 1A1g ? 1B1u,
1A1g ? A2u and A1g ? 1Eu, respectively, consistent with the values for
square-planer geometry.[9] The electronic spectra of the manganese(II)
chelate exhibit three weak bands at 15,000, 20,000 and 23,500 cmꢁ1 which
1
1
6
6
have been assigned to the transitions A1g ? 4T1g(4G), A1g ? 4T2g(4G) and
6A1g(F) ? 4A1g, Eg(4G), respectively, in an octahedral field of the manga-
nese(II) ion. The electronic spectra of the cobalt(II) chelate exhibit three
bands at 9050, 18,500 and 19,000 cmꢁ1 which have been assigned to the
4
transitions T1g(F) ? 4T2g, T1g(F) ? 4A2g and T1g(F) ? 4T1g(P), respec-
tively. The values of the ligand field splitting energy (10Dq), Racah inter-
electronic repulsion parameter (B), nephelauxetic ratio (b) and ratio (u2=u1)
are 10,168, 737.32, 0.759 and 2.04, respectively, and are consistent with the
values for an octahedral structure. The electronic spectra of the copper(II)
chelate[10] exhibit a band at 15,400 cmꢁ1 assigned to the 2Eg ? 2T2g transition
considering an octahedral geometry. A strong charge transfer band is
observed at 25,000 cmꢁ1.
4
4
4
Thermogravimetric Analyses
The analyses of the thermal curves of the polychelates, except for the
Ni(II) chelate, clearly show a weight loss corresponding to two water

COORDINATION CHAIN POLYMERS
Table II. Thermogravimetric Data
1885
% Loss in Weight Found
(Calcd.)
ꢀ
Chelate
Temp C.
[Cu(SB)ꢂ(H2O)2]n
7.89(7.90)a
82.52(82.54)b
1507180
1807450
[Ni(SB)]n
7
1507180
1807450
80.28(80.27)b
[Co(SB)ꢂ(H2O)2]n
[Mn(SB)ꢂ(H2O)2]n
[Zn(SB)ꢂ(H2O)2]n
[Cd(SB)ꢂ(H2O)2]n
7.95(7.98)a
1507180
1807450
83.42(83.45)b
8.06(8.05)a
84.10(84.13)b
7.85(7.86)a
78.23(78.24)b
7.12(7.13)a
74.53(74.54)b
1507180
1807450
1507180
1807450
1507180
1807450
aLoss of two co-ordinated water molecule.
bDecomposition and formation of metal oxide.
ꢀ
molecule in the range 150 to 180 C, indicating that these water molecules
are coordinated to the metal ion.[11] The TG curves indicate that in the
temperature range between 180 to 450 ꢀC the Schiff base molecules are lost.
In all the cases the final products are metal oxides. These results are in good
accordance with the composition of the polychelates.
Infrared Spectra
The spectra of the chelates, except that of the Ni(II), compound
exhibit a band in the region of 330073400 cmꢁ1 suggesting the presence of
water molecules.[12] The two weaker bands at around 860 and 700 cmꢁ1 are
assigned to OH rocking and wagging vibrations, respectively, of the coor-
dinated water molecule in the polychelates.[13] The Schiff base exhibits a
strong band at 162071630 cmꢁ1 due to the azomethine u(C¼N) mode. This
band shifts to lower energy by 10725 cmꢁ1 in the polychelates indicating
coordination through the azomethine nitrogen.[14] The Schiff base exhibits a
medium intense band at ꢄ2700 cmꢁ1 due to intramolecularly hydrogen
bonded u(OH).[14] The absence of this band in the polychelates indicates the
deprotonation. In the free ligand a strong band at 152571540 cmꢁ1 due to
u(C7O) (phenolic) shifts to higher energy by 5710 cmꢁ1 in the polychelates

1886
PATEL, PATEL, AND PATEL
indicating the coordination of the phenolic oxygen atom to the metal ion.
This shift to higher energy is expected due to the maintenance of ring cur-
rents arising from the electron delocalization in the chelate ring. The Schiff
base shows a weak band at 264072500 cmꢁ1, which is assigned to hydrogen-
bonded O7H stretching of carboxylic groups. This band is absent in the
spectra of the polychelates, indicating the involvement of the carboxylic
group (COOH) in complexation. The strong bands at 1580 and 1350 cmꢁ1 in
the Schiff base due to C¼O and C7OH stretching disappear on com-
plexation and these bands are replaced by two equivalent C7O bonds,
intermediate in force constant between C¼O and C7OH.[15] Asymmetric
and symmetric COO stretching bands appear at about 1540 and 1380 cmꢁ1
in the polychelates. The band appearing at about 450 cmꢁ1 is attributed to
u(M7O).[16] The band appearing at about 420 cmꢁ1 is attributed to
u(M7N).[17]
ACKNOWLEDGMENT
The authors are thankful to Prof. R. M. Patel, Head, Department of
Chemistry, Sardar Patel University, Vallabh Vidyanagar, India, for pro-
viding the necessary laboratory facilities.
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1887
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Received December 1, 2001
Accepted August 21, 2002
Referee I: R. M. Richman
Referee II: J. H. MacNeil