INTRODUCTION:
The role of metal complexes
in production of pharmaceutical, agrichemical, flavors, fragrances,
semiconductors and ceramic precursors will continue to expand during the next
decade1. Many metal complexes form useful catalysts and consequently
are of significant industrial interest2. Synthetic chelating agents
are used in plant nutrition3, catalytically
active metal ions from biological systems4.
M. A. Mironov and his coworkers synthesized
the 2-dialkylamino-3-aryliminoindole derivatives with the subsequent formation
of zwitter ionic indolates. The structures of final products were confirmed by
X-ray analysis5.
Degradation patterns of
actinide metal o-hydroxy N,N'-dimethylbenzylamine complexes of the
formulae, [LMO2X2], [LMO2SO4] and
[LTh(NO3)4], where M = U, L= o-C6H4OHCH2N(CH3)2
and X = Cl2, NO3- were studied by their
differential thermal and thermogravimetric analyses. The evolved products were
identified on the basis of loss in weight on TG coupled with DTA curves. The
thermal decomposition of these complexes occurred with the loss of inorganic
and organic fragments and exhibited almost similar mode of degradation with
minor differences.
With the help of
microanalysis and IR spectroscopy composition of the intermediates were
confirmed. The residues, after heating above 545°C, corresponded to metal
oxides. Degradation mechanisms of these complexes had also been proposed6.
The o-carboxy
N-N'-dimethylbenzylamine complexes with uranium(VI) and thorium(IV) complexes,
o-C6H4COOHCH2N-(CH3)2UO2SO4
(I), o-C6H4COOHCH2N(CH3)2U02(N03)2
(II), o-C6H4COOHCH2N(CH3)2UO2Cl2
(III), and o-C6H4COOHCH2N(CH3)2Th(NO3)4
(IV) were prepared and studied by means of thermoanalytical techniques in
static air atmosphere to understand their mode of decomposition and thermal
stability. Their compositions were investigated by elemental analysis in order
to ensure their purity, and structure elucidations were based on proton NMR and
IR spectra. The loss of inorganic and organic fragments occurred during thermal
decomposition of these complexes. The composition of the intermediate formed during
degradation was confirmed by microanalysis and IR spectroscopy. The thermal
stability of the complexes increased in the following sequence: Complex II,
Complex IV < Complex III < Complex I.7
Complexes of o-hydroxy
N,N'-dimethylbenzylamine and o-carboxy N,N'-dimethylbenzylamine with
uranium(VI) and thorium(IV) were synthesized and characterized by elemental
analysis, IR and 'H-NMR techniques. The coordination of metal ions with the
ligand and their structures were established. The chemical and spectral properties
revealed that uranium (VI) complexes have square bipyramidal structure for
coordination number 6, and hexagonal bipyramidal structure for coordination
number 8, whereas thorium(IV) shows bicapped square antiprism structure for
coordination number 10.8
2-bromo-N, N-Dimethylbenzylamine and its
complexes with Mo(CO)6 and W(CO)6 were synthesized.
Characterization of ligand and its complexes was carried out on the basis of
physical properties, elemental analysis data, infrared and nuclear magnetic resonance
spectroscopy. It was found that the ligand has monodentate nature and
coordinates with metal through its nitrogen atom thus replacing one CO molecule
to maintain the charge density on metal centre9.
o-nitro-N,N-diethylbenzylamine
Complexes with Cu(II), Ag(II), Au(II), Zn(II), Cd(II) and Hg(II) have been
synthesized and their antimicrobial activities were investigated against some
pathogenic bacteria and fungi10,11.The derivative of
o-Nitro-N,N-diethylamine with Fe(II), Ni(II) and Co(II) have been synthesized
and their thermal behavior and their relative stabilities were also studied by
thermogravimetric and differential thermal analysis12.
o-Amino N-ethyl-N-phenylbenzylamine and its complexes
with zinc (II), cadmium (II) and mercury (II) were reported. Characterization
of the complexes was made on the basis of spectroscopic techniques and
analytical data. Compounds were investigated for their antibacterial activities
against Bacillus subtilis (B.s.), Escherichia coli (E.c.),
Micrococcus luteus (M.l.) and staphylococcus aureus (S.a.).
13
o-Cyano-N,N-dipropylbenzylamine and its complexes with
iron (II), nickel (II) and cobalt (II) were reported. Physical properties of
the legend i.e. boiling point, miscibility, relative density, refractive index,
λmax, viscosity and surface tension were given. Evaluation of
complexes was carried out on the basis of infrared spectra and analytical data.
Anibacterial activity of o-cyano-N,N-dipropylbenzylamine and its metal
complexes were investigated against some pathogenic bacteria by diffusion plate
method. 14
N,N-dimethylbenzylamine complexes
with Ag(I), Au(III), Zn(II), Cd(II) and Hg(II) were synthesized.
Characterization of complexes was made on the basis of spectroscopic techniques
and analytical data. Thermal decomposition patterns of the complexes were
determined by thermogravimetric (TG) and differential thermal analyses (DTA)
and residues were identified by atomic absorption spectroscopy (AAS) and
standard X-ray powder diffractometry pattern.15
Benzylamine, N,N-dimethylamine and their
nitro derivatives were synthesized with group IIB IVA metals. Their proposed
formulas were based upon their analytical data, chemical characterization and
spectroscopic evidence.16
N,N-dimethylbenzylamine had been synthesized
from benzylamine and methanol in the presence of hydrochloric acid catalyst
under pressure. Nitrogen pressure is helpful only to a limited extent, beyond
which it is neither helpful nor detrimental. Under optimum conditions the
conversion of benzylamine to N,N-dimethylbenzylamine was 57.09%.17
MATERIALS AND METHOD:
E. Merck grade N-Bromosuccinimide, benzoyl peroxide,
sodium bicarbonate, Carbon tetrachloride, o-toluidene, diethylamine, n-hexane,
silica gel G (type 60), nickel chloride, mercuric chloride and alcohol were
used in experimental work. All chemicals were used without further
purification.
o-Amino N, N-diethylbenzylamine was prepared by
treating o-toluidene with N-Bromosuccinimide in CCl4 using benzoyl
peroxide as catalyst under reflux for 8 hours followed by the addition of
diethylamine. The ligand was separated by passing through the column packed
with Silica gel G (type 60).
λmax of the ligand was taken on Hitachi
UV-Visible spectrophotometer model U-2800 in CCl4 .
The complexes of the ligand with Cd (II), Pb (II) and
Hg (II) metals were synthesized in ethanol: water mixture (2:1).The products
were filtered and washed with distilled water, ethanol, ether and n-hexane and
dried to get solid compounds. The melting points or decomposition points were
determined on electrothermal M. P. device model No. 1002, USA by keeping the
heating rate programmed at 30 °C per minute. The miscibility of the ligand was
noted by using common organic solvents.
FTIR absorption spectra of the ligand and metal complexes
were recorded in thin film on FTIR spectrophotometer MIDAC Corporation USA
model M-2000 series in spectral range 4000-500 cm–1.
Estimation of metals in complexes was carried out on
Hitachi Polarized Zeeman Atomic Absorption Spectrophotometer model Z-8000.X-ray
diffraction was performed on powder diffaractometer and crystalline nature of
complexes was observed.
Thermal behavior of the complexes was studied by using
SDTQ600 thermogravimetric analyzers in temperature range 1-1000ºC.
Antimicrobial activities of the metal complexes were
investigated against some bacteria such as Bacillus subtilis (B.s),
Escherichia coli (E.c), Micrococcus luteus (M.l), Staphylococcus aureus (S.a)
and Aspergillus flavus (A.f) by diffusion plate method. The antimicrobial
activities of the ligand and its complexes were compared with one another
andwith streptomycin, which was used as a positive control. An emulsion of 5%
gumacacia was used as a negative control, which shows no antimicrobial
activity.
Synthesis of the ligand o-amino N,N-diethylbenzylamine
Step No. 1
4.2.1 Bromination of o-Toluidene
o-toluidene N-Bromosuccinimide o-amino
benzylbromide
Bromination was carried out by method of H. Farooq et.
al18 as outlined below. o-toluidene (0.5mole), N-bromosuccinimide
(0.5mole) and benzoyl peroxide (1.0g) in CCl4 (250 cm3)
were charged in quickfit flask equipped with water condensor and reaction
mixture was heated under reflux for 8 hours until all the solid started
floating on the liquid surface. The mixture was allowed to cool down to room
temperature and the regenerated succinimide was filtered off.
Step No.2
Synthesis
o-amino benzylbromide Diethylamine
o-amino-N,N-diethylbenzylamine
(Compound-I)
o-Amino benzylbromide (filterate from step 1) sodium
bicarbonate (0.5 mole) and distilled water were taken in a quickfit flask (500
cm3) equipped with water condenser. Diethyl amine (0.5 mole) was
added drop wise to the reaction mixture through condenser with the help of
separating funnel. The mixture was refluxed for 4 hours. The mixture was
allowed to cool and filtered off. The filterate was then transferred to a
separating funnel where the upper organic layer was collected and passed
through a column packed with Silica gel G (type 60). Then n-hexane: ethanol (3:2)
fraction was collected which on evaporation give brownish purple oily liquid
(compound no. 1), soluble in almost all organic solvents.
Formation of complexes of
o-Amino-N,N-Diethylbenzylamine
a)
Reaction of
o-amino N,N-diethylbenzylamine with Cadmium(II) chloride (CdCl2):
o-amino N,N-diethylbenzylamine (6.0 mmol)
dissolved in ethanol (30 cm3 ) was added to Cadmium chloride (3.0
mmol) dissolved in distilled water (15.0 cm3). The reaction mixture
was stirred for 3 hours. A white solid settled which was filtered and washed
with distilled water, ethanol, ether and n-hexane and dried to get white
complex (II).
b)
Reaction of
o-amino N,N-diethylbenzylamine with Lead(II) acetate
Pb (CH3COO)2:
o-Amino N,N-diethylbenzylamine (6.0 mmol)
dissolved in ethanol (30 cm3) was added to Lead acetate (3.0
mmol) dissolved in distilled water (15.0 cm3). The reaction mixture
was stirred for 3 hours. A white solid settled which was filtered and washed
with distilled water, ethanol, ether and n-hexane and dried to get white
complex (III).
c)
Reaction of
o-amino N,N-diethylbenzylamine with mercuric(II) chloride (HgCl2):
o-Amino N,N-diethylbenzylamine (6.0 mmol)
dissolved in ethanol (30 cm3 ) was added to mercuric chloride (3.0
mmol) dissolved in distilled water (15.0 cm3). The reaction mixture
was stirred for 3 hours. A brown solid settled which was filtered and washed
with distilled water, ethanol, ether and n-hexane and dried to get brown
complex (IV).
DISCUSSION:
o-Amino-N,N-diethylbenzylamine was prepared starting
from o-toluidene and N-bromosuccinimide using CCl4 as solvent and
benzoyl peroxide as catalyst followed by the addition of-N,N-diethylamine. The
reaction mixture after filteration was chromatographed. n-Hexane: ether (3:2)
eluted a reddish brown band which on evaporation gave dark brown oily liquid.
The refractive index of the ligand was determined by
using Abbe’s refractometer, to measure, how much the ligand will slow down the
light wave, when it passes through it. The value of refractive index was found
to be 1.68. Surface tension of the ligand was determined by using
stalagmometer, in order to determine the resistance the ligand exhibits to
surface penetration19. The value of surface tension was 45.86
dynes/cm at 34°C. Viscosity of the ligand was obtained with the help of
viscometer, in order to determine the resistance that ligand offers to its
flow. The value of viscosity was found to be 40.32 g/cm sec at 30°C.
The complexes of o-Amino N, N-diethylbenzylamine with
Cd(II), Pb(II) and Hg(II) were synthesized in ethanol : water mixture (2:1).
The products were filtered and washed with distilled water, ethanol, ether and
n-hexane and dried to get solid compounds. The melting points or decomposition
points for complex (II), complex (III) were found to be above 300 °C. For complex
(IV) melting points was found to be 170°C. The complexes were found to be
insoluble in almost all organic solvents.
Infrared spectrum of o-Amino N, N-diethylbenzylamine
shows the absorption band due to C−H bending at 620.240979 cm–1.
Aromatic out of plane C−H bending vibration appeared at 751.774194 cm–1,
813.520527 cm1, 867.823659 cm–1, 946.174395 cm–1.
Aromatic in plane C−H bending appeared at 1038.08562 cm–1,
1116.03575 cm–1, 1148.1813 cm–1, 1198.68651 cm–1,
1389.03561 cm–1,
The absorption band due to aromatic stretching and
−CH2 symmetric bending is indicated at 1468.36914 cm–1.
The absorption bands due to out of plane N−H bending and in plane
N−H bending appeared at 684.688731 cm–1and 1622.65429 cm–1
respectively. C−H stretching bands for methyl and methylene groups
are indicated at 2730.27097 cm–1, 2872.88556 cm–1,
2930.8063 cm–1, 2958.38526 cm–1, 3027.95173 cm–1.
The absorption bands which appeared at 3382.8393 cm–1, 3431.47297 cm–1,
3465.17301 cm–1 are due to N−H stretching vibrations20.
In case of metal complexes absorption bands appeared below 600 cm–1due
to M−N bond21. The lowering in the position of absorption
bands also depict the formation of complexes. The FTIR data of the ligand and
its complexes is given in Table No. 1.
The atomic absorption spectra for metal analysis
indicated the formation of metal ligand complexes in the ratio of M: L=1:1. %
age yield of metals estimated by atomic absorption spectroscopy is given in
Table No. 2.
TABLE # 2: %AGE YIELD OF METAL ESTIMATED BY ATOMIC
ABSORPTION SPECTROSCOPY
|
No. of obs.
|
COMPLEXES
|
THEORETICAL YIELD
|
EXPERIMENTAL YIELD
|
|
1.
2.
3.
|
Complex (II)
Complex (III)
Complex (IV)
|
33.51%
48.16%
43.40%
|
31.6%
46.2%
42.6%
|
Figure.1
TABLE # 3: X-RAY DIFFRACTION ANALYSIS OF COMPLEX (II)
|
Peak No.
|
2Ө (Degree)
|
d-spacing
|
|
1
2
3
4
5
6
7
8
9
10
|
16.191
23.543
29.188
30.370
36.321
39.997
43.629
50.674
53.519
57.895
|
5.46989
3.77582
3.05713
2.94083
2.47145
2.25238
2.07292
1.80000
1.71085
1.59151
|
X-ray diffraction pattern indicate the
crystalline nature of the complexes of Cd (II), Pb(II) and Hg (II).
X-ray diffraction pattern is shown in Figures
No. 1, 2, 3 and Tables No. 3, 4 and 5
respectively.
Figure.2
Thermogravimetric studies have shown that
complex of o-Amino-N,N-diethylbenzylamine
dichlorocadmium (II) is stable upto 200ºC as no weight loss was indicated
(Table No. 6, Fig No. 4). The complex started
decomposing in the temperature range of 300-380°C liberating Cl2
(theoretical 18.0%, experimental 17.0%) followed by an exotherm at 375°C. Second TG loss was noted from 610-780°C due to
loss of ligand (theoretical 46.9%, experimental 45.0%). DTA showed an exotherm
at 640°C. The residue corresponding to cadmium oxide was confirmed through
analysis by AAS and XRD.
TABLE # 4: X-RAY DIFFRACTION ANALYSIS OF COMPLEX (III)
|
Peak No.
|
2Ө (Degree)
|
d-spacing
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
|
19.930
20.838
22.336
24.288
26.603
29.100
30.280
32.051
34.184
36.046
40.359
41.176
42.401
43.763
50.4437
53.842
|
4.45150
4.25954
3.9771
3.66169
3.34803
3.06619
2.94930
2.79030
2.62087
2.48968
2.23302
2.19057
2.13004
2.06686
1.80792
1.70135
|
Figure.3
TABLE # 5: X-RAY DIFFRACTION ANALYSIS OF COMPLEX (IV)
|
Peak No.
|
2Ө (Degree)
|
d-spacing
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
|
10.369
12.032
13.344
16.625
18.376
21.263
22.226
23.976
25.813
27.170
28.220
28.788
31.588
33.338
|
8.52445
7.35000
6.62986
5.32799
4.82431
4.17523
3.99654
3.70864
3.44865
3.27950
3.15981
3.09866
2.83008
2.68541
|
o-Amino-N, N-diethylbenzylamine lead (II) acetate is
stable upto 230°C (Table No. 6, Fig No. 5). First TG loss was noted from 240-290°C due to evolution of CO2
(theoretical 9.04%, experimental 8.0%) followed by an exotherm at 370°C. Second TG loss was noted from 300-375°C due to
loss of C7H7NO (theoretical 24.0%, experimental 23.0%).
Third TG loss was noted from 240-290°C due to evolution of C4H11N
(theoretical 14.5%, experimental 12.0%) followed by an exothermic peak at
450°C. The residue corresponding to lead oxide was confirmed through analysis
by AAS and XRD.
Figure 4.
Figure.5
o-Amino-N, N-diethylbenzylamine mercuric (II) chloride
is stable upto 150°C(Table No. 6, Fig No. 6). TG
loss was noted from 225-350°C due to the evolution of C11 H18
N2HgCl2 (theoretical 9.04%, experimental 90%). No residue
was observed.
Figure.6
Antimicrobial activities of the complexes Cd(II),
Pb(II) and Hg(II) were investigated against some bacteria such as Bacillus
subtilis (B.s), Escherichia coli (E.c), Micrococcus luteus (M.l),
Staphylococcus aureus (S.a) and fungus Aspergillus flavus by
diffusion plate method. Ligand showed no antimicrobial activity. The
antimicrobial activity of complexes is in the following order Pb (II)
complex> Hg (II) complex> Cd (II) complex
The values for antimicrobial activity are shown in the
Table No.7.
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