Study of bonding characteristics of some new metal complexes of salicylaldoxime (SALO) and its derivatives by far infrared and UV spectroscopy

Article abstract of DOI:10.1016/S1386-1425(97)00221-7

New metal chelates of copper, lead and zinc with salicylaldoxime (SALO) and its derivatives have been prepared. The chelates have been characterized by elemental analysis, atomic absorption, infrared and UV spectroscopy. SALO behaves as a bidentate ligand forming neutral metal chelates through the phenolic oxygen and the oxime nitrogen. The M-O stretching frequencies for the transition metals show good agreement with the Irving-William's stability order Cu > Zn > Pb. Similar trend is seen for the M-N stretching frequencies in IR and the shift in transitions from UV spectral data for the metal chelates.

Full text of DOI:10.1016/S1386-1425(97)00221-7

Spectrochimica Acta Part A 54 (1998) 285–297
Study of bonding characteristics of some new metal complexes
of salicylaldoxime (SALO) and its derivatives by far infrared
and UV spectroscopy
V. Ramesh 1, P. Umasundari, Kalyan K. Das *
Tata Research De6elopment and Design Centre, c 54B Hadapsar Industrial Estate, Pune 411 013, India
Received 28 December 1996; accepted 17 August 1997
Abstract
New metal chelates of copper, lead and zinc with salicylaldoxime (SALO) and its derivatives have been prepared.
The chelates have been characterized by elemental analysis, atomic absorption, infrared and UV spectroscopy. SALO
behaves as a bidentate ligand forming neutral metal chelates through the phenolic oxygen and the oxime nitrogen.
The M–O stretching frequencies for the transition metals show good agreement with the Irving–William’s stability
order Cu\Zn\Pb. Similar trend is seen for the M–N stretching frequencies in IR and the shift in transitions from
UV spectral data for the metal chelates. © 1998 Elsevier Science B.V. All rights reserved.
Keywords: Salicylaldoxime; Metal chelate; Chelating ligand
1. Introduction
(SALO) for copper minerals [3]. Among the vari-
ous N, O type chelating ligands, hydroxy oximes
are very efficient solvent extraction reagents for
purification and concentration of copper leach
liquors [4].
The usefulness of the oximes as a collector in
flotation has also been investigated by Dewitt et
al. [5] as early as 1939. Later hydroxy oximes have
been used in the mineral beneficiation process as a
copper specific collector [6,7]. Commercial extrac-
tants of the LIX type were developed for the
specific extraction of copper from acidic leach
liquors, as well as from alkaline solutions [8,9]. A
survey of the literature indicate that not much
work has been published concerning the stability
of the metal complexes formed by salicylaldoxime
Chelating ligands are compounds which form
multidentate complexes by ring closure with a
metal ion [1]. A majority of chelating ligands
contain the three most important donors, e.g. N,
O and S [2]. Based on the knowledge of well
known analytical reagents and their metal ion
specificity, modified chelating ligands have been
used for the extraction of metals, e.g. dimethyl
glyoxime for nickel minerals and salicylaldoxime
* Corresponding author. Tel.: +91 212 671058; fax: +91
212 610921; e-mail: kkdas@pune.tcs.co.in
1 Present address: Cadila Pharmaceuticals, 244 Ghodasar,
Maninagar, Ahmedabad 380 008.
1386-1425/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved.
PII S1386-1425(97)00221-7

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V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
and its derivatives [10]. Stability constants or
binding strength have long been employed as an
effective measure of the affinity of a ligand for a
metal ion in solution. There are several techniques
to estimate the binding strength. Among them,
Far IR studies, especially M–O and M–N
stretching frequencies have been used as an effec-
tive measure to predict the strength of interaction
of metal ions with a chelating ligand. Metal-lig-
and vibrations are expected in the region below
700 cm−1. The metal-oxygen vibrations in this
region provide information about the strength of
the M–O bonds and hence the stability of the
complexes. Normal coordinate analysis and metal
isotopic substitution studies in acetylacetonates
have shown that pure M-O stretch absorbs near
response of difficult-to-float carbonate minerals of
copper, zinc and lead namely malachite, smith-
sonite and cerussite. In the present study, the
focus is on elucidating the binding strength of
some divalent metal complexes with SALO and its
derivatives using various spectroscopic techniques
with a special emphasis on Far IR technique. In
the text the compounds C5M–SALO and C5S–
SALO represent SALO derivatives containing five
carbon alkyl chains on the aromatic ring and on
oxime carbon atom, respectively.
2. Experimental procedure
2.1. Preparation of the ligand
450 cm−1
.
Morley [11] carried out some investigations of
electronic and structural effects in organic transi-
tion metal complexes of o-hydroxyaryloximes.
Syal et al. [12] studied the IR spectral data of
different metal complexes of SALO. Complexes of
iron(II), cobalt(II), nickel(II), copper(II) and
zinc(II) with SALO were studied by Luo et al.
[13]. These investigators characterized both 1:1
and 1:2 complexes of SALO with some of these
metals. Agarwal and coworkers [14] carried out
magnetic and spectroscopic studies on salicylal-
doxime and o-hydroxy napthaldoxime complexes
of some divalent 3d metal ions.
Jyothi and Rao [15] characterized some metal
complexes of 3-phenyl-4-acetyl-5-isoxazolone and
determined the strength of the complexes based
on the metal-oxygen stretching vibrations. Okafor
[16] conducted similar studies with metal com-
plexes of substituted pyrazolones. Studies by
Behnke and Nakamoto [17] have indicated metal-
olefinic and metal-carbon bonded chelates in
acetylacetonates of Pt(II). Nakamoto [18] calcu-
lated force constants of the metal-oxygen bond
obtained for various acetylacetonates.
Oxime of the alkyl aryl type (Fig. 1a) (R1=H,
R2=C5H11 i.e. C5S–SALO) was prepared from
1-(2-hydroxy phenyl hexanone) [19] obtained by
the Fries rearrangement of the appropriate pheno-
lic ester, i.e. phenyl hexanoate using anhydrous
aluminium chloride at 150–155°C. Ketone was
converted to the oxime by refluxing with hydroxy-
lamine hydrochloride in the presence of pyridine
and recrystallized from petroleum ether as color-
less crystals. The spectral characteristics of C5S–
SALO are given below:-
(a)1H NMR (CDCl3): ( 1.0 (s, 3H, CH2–C3H6–
CH3), ( 1.6 (m, 6H, –CH2–C3H6–CH3), ( 2.9 (t,
2H, CH2–C3H6–CH3), ( 6.9–7.8 (m, 4H, aro-
matic), (b) Mass spectra: m/z=207 (M+).
C5M–SALO [20] was prepared from phenol by
the low temperature Friedel–Crafts synthesis in
which the phenol was treated with n-pentanoyl
chloride and anhydrous aluminium chloride in
nitrobenzene at 0°C. Subsequently p-pentanoyl
phenol was reduced to p-pentyl phenol by the zinc
amalgam method [21]. The aldehyde obtained by
the Rieman–Tiemann reaction of p-n-pentyl phe-
nol was converted to oxime by hydroxylamine
hydrochloride. The spectral characteristics of
C5M–SALO are given below:
For a systematic investigation, in this work two
series of derivatives were synthesized where sub-
stitution was either on aromatic ring (main chain
substituted salicylaldoxime, CM-SALO series) or
on oxime carbon atom (side chain substituted
salicylaldoxime, CS-SALO series). These ligands
were synthesized primarily to study the flotation
1H NMR (CDCl3): ( 0.9 (t, 3H, CH2–C3H6–
CH3), ( 1.6 (m, 6H, –CH2–C3H6–CH3), ( 2.5 (t,
2H, CH2–C3H6–CH3), ( 7–7.6 (m, 3H, aro-
matic), ( 8.38 (s, 1H, CHꢀN–), ( 9.8 (s, 1H,
–CꢀN–OH).

V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
287
Fig. 1. Formula and the chemical name of the SALO compounds.
2.2. Preparation of metal complexes
stirring to a hot solution of the metal (II) sulfate
(1 mmol) in 50 ml water. The resulting solid product
was immediately filtered under suction. After wash-
ing with aqueous ethanol (1:1 20 ml), it was dried
in air and stored in a desiccator over fused calcium
chloride. Analytical data, melting points and color
of the complexes are listed in Table 1.
General methods of preparation of i-diketo-
nates of metals were utilized for obtaining metal
chelates of SALO [15]. A typical procedure involved
dropwise addition of an ethanolic solution of the
ligand (2 mmol) in 25 ml of 95% ethanol with

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Table 1
Physical and analytical data of metal (II) chelates with SALO and its derivatives
Empirical formula
Color
Melting point (°C)
Actual %
Found %
Carbon Hydrogen Metal Carbon Hydrogen Metal
C5M–Salo
C5S–Salo
Cu (Salo)2
Cu (C5M–Salo)2
Cu (C5S–Salo)2
Zn (Salo)a
Colorless
Colorless
Green
Light green
Dark green
White
48
112
210
\300
\300
\220
200
69.56
69.56
50.06
60.50
60.50
—
8.21
8.21
3.57
6.73
6.73
—
—
—
—
—
69.76
48.78
59.86
58.45
—
7.85
3.80
7.47
7.42
—
18.93
13.36
13.36
32.47
12.73
18.33
14.30
14.50
31.77
11.78
Zn (C5M–Salo)2
White
—
—
—
—
2H2Oa
Zn (C5S–Salo)2
2H2Oa
White
193
—
—
12.73
—
—
11.90
Pb (Salo)
Pb (C5M–Salo)2
2H2O
Light yellow
Light yellow
\220
190
24.47
43.96
1.74
5.49
60.37
31.63
23.74
43.56
2.03
5.15
59.01
30.47
Pb (C5M–Salo)2
2H2O
Light yellow
190
43.96
5.49
31.63
43.38
5.30
32.65
a The elemental analysis could not be performed on the zinc chelates as zinc interferes with the analysis.
3. Results and discussion
2.3. Physical measurements
3.1. Structure of metal complexes
Infrared spectra of the various SALO ligands
were recorded on a Perkin Elmer spectrophoto-
meter employing potassium bromide disc tech-
nique while the metal chelates were recorded
using cesium bromide. Melting points were de-
termined on a melting point block apparatus.
UV spectra of the compounds were recorded on
a Shimadzu UV 240 UV-Visible spectrophoto-
meter. All the spectra were run using chloroform
as solvent against chloroform as blank.
Information regarding the structure of metal
complexes has been obtained from the following
investigations.
3.2. Elemental analyses
The elemental analyses of these compounds
reveal that the complexes have a metal:ligand
stoichiometry of 1:2 and 1:1 corresponding to
the general formula of M(HL)2, nH2O where
HL is the anion of SALO. For M=Cu, n=0
has a stoichiometry of 1:2 with all the chelating
ligands (SALO, C5M–SALO and C5S–SALO).
For M=Zn, Pb; n=2 has a stoichiometry of
1:2 for C5M–SALO and C5S–SALO complexes.
However the chelates of both zinc and lead with
SALO have a stoichiometry of 1:1 as confirmed
by both elemental analyses and metal analyses.
2.4. Elemental analyses
Microanalyses for carbon and hydrogen were
carried out using Coleman 33 carbon hydrogen
analyzer. Analysis of metal in the metal chelates
of SALO and its derivatives was performed us-
ing atomic absorption spectrophotometer by de-
composing the chelates completely with
mixture of nitric and sulfuric acids.
a

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289
Table 2
Observed infrared frequencies (cm−1) of SALO and its derivatives
SALO
C5M–SALO
C5S–SALO
Assignments
3380 br
—
3353 br
2929
1626
1594
1290
1259
1006
883
3318 br
2950
1630
1612
1290
1254
1054
860
O–H stretching vibration
C–H stretching vibration of alkyl groups
CꢀN stretching vibration of oxime group
Phenyl ring CꢀC
O–H bending vibration (in plane)
Aromatic C–O stretching vibration
OH deformation vibration (out of plane)
N–O stretching vibration
1621
1576
1290
1254
989
896
—
563
563
Chelate ring vibrations
br: Broad.
region is free of absorption indicating the absence
of coordinated water. The chelates of Zn(II), Pb(II)
with SALO have a stoichiometry of 1:1. Since these
complexes are formed with difficulty and at alkaline
pH (\11), both the phenolic OH and the oxime
OH have been ionized in formation of the com-
plexes (Fig. 1d). The absence of peak at 3300–3500
cm−1 in the metal chelates indicates that there is
no free OH or coordinated water molecule. This
was also found by Cecile et al. [22] who carried out
the infrared spectral study of species formed on
malachite surface by adsorption from aqueous
SALO solution. They isolated three types of oxime
complexes of copper which are also shown in Fig.
1. Complex III has been less studied and its
formation constant i2 is not known. It was ob-
tained by deprotonating the oxime group of the
complex II [22] at pH\11.
The complexes are formed only at highly alkaline
pH (\11) indicating that the type of the complex
is as given in Fig. 1d [22].
3.3. Infrared spectral studies of the metal (II)
complexes
The infrared spectral data of SALO, its deriva-
tives (C5M–SALO and C5S–SALO) and their
metal chelates are listed in Tables 2 and 3. In the
spectra of metal complexes of SALO and its
derivatives, tentative assignments for the observed
frequencies have been made by comparison with
the spectra of the ligands. However, since the
spectra are complex it is possible that some of the
bands may be combination bands. The given as-
signments are supported by the fact that frequen-
cies associated with SALO moiety change upon
chelation with metals, whereas those which are not
associated with the chelate ring change relatively
less. The spectra are grouped into three main
regions for convenience, 4000–1800 cm−1, 1800–
700 cm−1 and 700–200 cm−1 and are discussed
accordingly.
3.5. 1800–700 cm−1
Infrared spectra of SALO and its metal com-
plexes are quite complex in this region. This re-
gion contains bands derived from benzene,
aromatic C–O stretching, N–O stretching, CꢀN
stretching and chelate ring vibrations. On the
basis of normal coordinate analyses and isotopic
substitution studies, Nakamoto et al. [23,24]
showed that CꢀO peak occurs at a higher fre-
quency than CꢀC. The positions of these bands in
the metal complexes are dependent on the nature
of the metal ion. The strength of the complex can
be seen from the CꢀN stretching vibration fre-
quencies. Copper chelates appear at 1650 cm−1 as
3.4. 4000–1800 cm−1
The chelates of Zn(II) with C5M and C5S–
SALO and Pb(II) with C5M–SALO showed broad
peaks in the 3300–3500 cm−1 (Table 3), which can
be attributed to the –OH functionality of coordi-
nated water. However in the pure salicylaldoxime
chelates of Cu(II), Pb(II), Zn(II) and the copper
chelates of C5M–SALO and C5S–SALO; this

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V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
291
compared to Zn(II) and Pb(II) which appear at
1610 and 1600 cm−1, respectively. There is also a
shift in vibration of the CꢀN stretching frequen-
cies from the corresponding chelating ligand
(SALO, C5M–SALO and C5S–SALO). The
trend in binding of metal complexes is Cu(II)\
Zn(II)\Pb(II). More energy is required to stretch
the CꢀN bond in the case of copper chelate than
zinc and lead chelates. The aromatic C–O stretch-
ing vibration show that for the copper–SALO
chelate, the strength of the C–O is stronger than
that of the chelates of Zn(II) and Pb(II). This
means that C–O is more stretched and it requires
higher energy for vibration. The same effect is
observed for the chelates of C5M–SALO with
copper, lead and zinc. There is no significant shift
in frequencies for the C5S–SALO chelates.
loximes was carried out by Morley [11] who has
examined the crystallographic data of both SALO
and its copper chelates. An examination of crys-
Infrared spectral study of species formed on
malachite surface by adsorption from aqueous
salicylaldoxime solution have been studied by Ce-
cile et al. [22]. They have characterized the ligand
and the metal–ligand complex based on N–O
stretching vibration frequency. It has been shown
that adsorbed species have a structure different
from that of the pure complex (II), at concentra-
tions up to about 1.0×10−5 mol m−2. The band
at 960 cm−1 was attributed to the N–O stretching
frequencies. In the metal complexes of Cu(II),
Zn(II) and Pb(II) the N–O stretching shifted to
higher frequencies as compared to the corre-
sponding ligands (Table 3). This can be explained
by the formation of a bis-complex in which the
hydrogen atom of the ꢀN–OH oxime group
would participate in intermolecular hydrogen
bonding. The effect would be to shift the N–O
bond to higher frequencies because of hydrogen
bonding, as the N–O bond is stretched. The effect
is more in the case of copper than lead and zinc
chelates.
3.6. 700–200 cm−1
The metal ligand vibrations are expected in this
region. The weak M–O and M–N vibrations in
this region provide information about the strength
of M–O bonds and M–N bonds and hence the
stability of complexes. An investigation of elec-
tronic and structural effects in o-hydroxyary-
Fig. 2. Infrared spectra of SALO complexes of Cu, Zn and Pb.

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V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
Fig. 3. Infrared spectra of C5M–SALO complexes of Cu, Zn
and Pb.
Fig. 4. Infrared spectra of C5S–SALO complexes of Cu, Zn
and Pb.

V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
293
Table 4
Comparison of M–O frequencies (cm−1) and bond energies of metal chelates of SALO and its derivatives
Reagent SALO
C5S–SALO
C5M–SALO
Frequency
Metal
Frequency (cm−1)Bond energy
Frequency (cm−1)Bond energy
(eV)
Bond energy
(eV)
(eV)
(cm−1
)
Copper
Zinc
Lead
485
450
400
0.0601
0.0558
0.0496
460
440
435
0.0570
0.0545
0.0539
490
480
420
0.0607
0.0595
0.0520
Bond energy, E=hcw¯.
E (in eV)=1.24×10−4×w¯.
tallographic data for the bis (salicylaldoximato O,
N) copper(II) complexes and the related com-
plexes of the bis (salicylaldimines) shows that the
oxygen–nitrogen distance seldom varies from the
The C5M–SALO complexes of metals show a
slightly higher M–O stretching frequency and
also higher bond energy as compared to com-
plexes with SALO. This can be explained as due
to the inductive effect experienced by the benzene
ring which makes the phenolic OH electron rich
thereby increasing the stretching frequency. Step-
niak [27] studied the stability constants of copper
complexes with different SALO derivatives and
observed that as the alkyl chain increased on the
aromatic ring, there was an increase in the stabil-
ity constant for the corresponding copper chelate.
They attributed the increase in stability to in-
crease in hydrophobicity and to the acid dissocia-
tion constant of the SALO derivatives.
˚
value of 2.790.01 A irrespective of the sub-
stituent attached to nitrogen. This represents a
substantial increase in the corresponding distance
˚
found in SALO (2.658 A) which is able to in-
crease without restriction during the formation of
the copper chelate. However IR analyses in the
low frequency region can indicate the strength of
the bond and hence the strength of the metal
complexes from the metal–oxygen and metal–ni-
trogen stretching frequencies.
Normal coordinate analyses and metal isotopic
substitution studies in acetylacetonates [18] have
shown that pure M–O stretch absorbs near 450
cm−1 region. In the complexes of SALO the
peaks at 485 cm−1 (Cu), 450 cm−1 (Zn), 400
cm−1 (Pb) are assigned to the stretching fre-
quency of M–O with the spectrum of SALO as a
reference (Figs. 2–4). From the M–O stretching
frequencies and the bond energies, the order of
complexation with metals is as follows (Table 4)
Cu\Zn\Pb and this agrees well with the Irv-
ing–William’s [25] stability order. Dahl [10] had
carried out extraction of different metals with
SALO and reported a similar order of complexa-
tion. Ramesh and Rao [26] carried out extraction
of different metals with LIX622, a substituted
SALO and found the same order of complexation
of metals. They calculated the extraction constant
for extraction of metals and found that copper
was extracted quicker and with a higher extrac-
tion constant than lead and zinc.
However the C5S–SALO forms less stable
complexes than parent SALO and main chain
substituted SALO. This can be explained due to
the steric effect exerted by the bulkier alkyl group
which restricts the rotation around the C–C bond
attached to oxime nitrogen. The computer gener-
ated CPK (Corun, Pauling and Kolton) model of
C5S–SALO also support the fact that the rota-
tion around C–C bond (the aryl attached to the
oxime nitrogen) is difficult because of steric hin-
derance (Fig. 5c). It also appears that the lone
pair of electrons on the oxime nitrogen are di-
rected away with the result that the strength of
the bond will be weakened (as seen in the physical
model). The side chain complexes are not formed
so readily as compared with SALO and C5M–
SALO.
Extensive listing of metal-nitrogen bands with
different ligands has been listed in the low fre-
quencies of infrared by Ferraro [28]. Strength of

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V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
Fig. 5. (a) Corun, Pauling and Kolton (CPK) model of SALO. (b) CPK model of C5M–SALO. (c) CPK model of C5S–SALO.
the M–N bond can be decided from the metal–
nitrogen stretching frequencies which appear be-
In all the metal complexes with SALO and its
derivatives, the metal–nitrogen stretching vibra-
tion appears between 300–320 cm−1. These vi-
brations are very weak due to the nature of
metal–nitrogen bond (coordinate covalent bond).
The M–N stretching frequencies of chelates of
copper appear at higher frequencies than corre-
sponding lead and zinc chelates (Table 3 and Figs.
2–4). This means that the Cu–N bond is rela-
tively stronger than the corresponding Pb–N and
tween 250–350 cm−1
. Assignments for the
metal–nitrogen bending vibrations had received
less attention. In general, the infrared intensity of
the wmn vibration is weak to medium, and thus has
been the major cause of some confusion in the
assignments. In the case of the metal–nitrogen
bond, the bond orders may vary, as was found for
the metal–oxygen bond [18,28].

V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
295
Table 5
Observed UV spectral data of metal chelates of SALO and its derivatives
Metal chelate
Copper
Zinc
Lead
Ligand
Associated
transition
Benzene
y“y*
Non-bonding
n“y*
Benzene
y“y*
Non-bonding
n“y*
Benzene
y“y*
Non-bonding
n“y*
Benzene
y“y*
Non-bonding
n“y*
SALO
C5S–SALO
C5M–SALO
242, 269
241, 266
246, 271
346
336
355
244, 266
245, 255
234, 266
307
307
317
235, 258
245, 255
240, 260
305
307
317
224, 256
224, 256
240, 261
307
306
317
Zn–N bonds. This observation is in agreement
with the classical hard acid–base concept devel-
oped by Pearson [29].
a peak at 355 nm which is higher than the chelate
of SALO appearing at 346 nm. However, the
peak for C5S–SALO chelates of copper appear at
lower wavelength (336 nm) than SALO chelates.
This means that the copper chelate of C5M–
SALO are slightly stronger than C5S–SALO
chelate. A similar trend is seen in the IR spectral
analyses of metal chelates. Since the bonding of
the oxime nitrogen to lead and zinc may be weak
(copper prefers nitrogen donors) there is no ap-
preciable shift in wavelength of the n“y* band
in these chelates of lead and zinc as compared to
corresponding parent oximes. Dahl [10] has stud-
ied the extraction of various metals using SALO
and a similar finding was reported for the metal
complexes with SALO. UV analysis studies also
reconfirms the Far IR studies on the strength of
the bonding of the various complexes.
3.7. UV spectral studies of the metal complexes
In the present work all the substituted SALO
derivatives in chloroform medium showed well
defined peaks in the UV region, i.e. from 190 to
400 nm (Table 5) as expected of an substituted
benzene system. The peaks around 210 and 256
nm in SALO and its derivatives (pH 7-aqueous
medium) were due to y“y* transitions of ben-
zene ring and the peak around 303 nm was a
result of substituted group, i.e. (CꢀN–OH). In the
alkaline medium (pH 10) the peaks were shifted
from 210 to 224 nm and are attributed to y“y*
transitions of the benzene ring which is due to
phenolate anion (phenol is ionized at an alkaline
pH).
The UV spectral data of metal chelates in chlo-
roform show a marked variation for copper
chelate as compared to lead and zinc chelates
from the corresponding parent oximes. In the case
of copper chelate the peaks have all been shifted
to longer wavelength as compared to parent
oxime (SALO). Both the y“y* transition peak
(i) associated with phenolate anion, (ii) simple
benzene double bond, have been shifted from the
value of 224 and 256 nm in the parent oxime. As
the unpaired electrons of nitrogen forms a dative
bond with copper, more change is expected in the
n“p* transition. Due to dative bonding of oxime
nitrogen to copper, much less energy is required
for transition, resulting in shift to higher wave-
length. The C5M–SALO chelate of copper show
4. Summary
From the infrared and UV spectroscopic stud-
ies the following conclusions can be drawn: (i)
there is a shift in some of the vibrations and
transitions due to complexation compared to
chelating ligands alone; (ii) copper forms stronger
chelates than zinc and lead chelate which follows
the Irving–William’s stability order. The order of
complexation with salicylaldoxime is Cu(II)\
Zn(II)\Pb(II) as seen from the trend of metal–
oxygen and metal–nitrogen stretching vibrations;
(iii) complexes with main chain substituted SALO
are slightly stronger than side chain substituted
SALO. The reason for such a behavior is due to
two factors: (a) the bulkier alkyl group on the

296
V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
aromatic ring in C5M–SALO exerts an inductive
effect making the phenoxide ion more electron rich
thereby increasing the binding strength; and (b) the
bulkier alkyl groups on the oxime carbon in C5S–
SALO makes the binding sterically restricted. The
same trend is seen from the UV spectral data.
9.
zinc-bis(1-(2-hydroxy
phenyl)hexanone oximato-N1O2)
(ZnHPHO)
10.
11.
lead-mono(2-hydroxy benzalde-
hyde oximato-N1O2) (PbHBO)
lead-bis(2-hydroxy-5-pentyl
benzaldehyde oximato-N1O2)
(PbHPBO)
12.
lead-bis(1-(2-hydroxy
Acknowledgements
phenyl)hexanone oximato-N1O2)
(PbHPHO)
The authors thank Dr E.C. Subbarao, Executive
Director, Tata Research Development and Design
Centre, for his encouragement and critical review
of the manuscript. Sincere thanks are also due to
Prof S. Chandrasekaran, Indian Institute of Sci-
ence, Bangalore, Dr Pradip and Mr B. Suresh
TRDDC, Pune for helpful discussions. Financial
support from the Department of Science and Tech-
nology, Government of India under SERC re-
search scheme is gratefully acknowledged.
References
[1] Y. Marcus, A.S. Kertes, Ion exchange and Solvent Ex-
traction of Metal Complexes, Wiley, New York, 1969, p.
507.
[2] Yu. A. Zolotov, Extraction of Chelate Compounds,
Humprey Science Publishing, Ann Arbor, Michigan, MI,
1970.
[3] G.N. Morrison, H. Freiser, Solvent Extraction of Metal
Chelates, Wiley, New York, 1957.
[4] J.F. Flagg, N.H. Furman, Ind. Eng. Chem. Anal. Ed. 12
(1940) 529.
[5] C.C. Dewitt, F. Von Batchelder, J. Am. Chem. Soc. 61
(1939) 1247.
[6] D.R. Nagaraj, P. Somasundaran, Trans. SME, AIME
266 (1979) 1892.
Appendix A. IUPAC name of ligands and its
metal chelates
[7] D.R. Nagaraj, Reagents in Mineral Technology, in: P.
Somasundaran, B.M. Moudgil, (Eds.), Surfactant Science
Series, vol. 27, Marcel Dekker, New York, 1987.
[8] G.M. Ritcey, Hydrometallurgy 5 (1980) 97.
[9] G.M. Ritcey, A.W. Ashbrook, Solvent Extraction: Princi-
ples and Application to Process Metallurgy, Part I, El-
sevier, Amsterdam, 1984.
[10] I. Dahl, Anal. Chim. Acta 41 (1968) 9.
[11] J.O. Morley, J. Chem. Soc. Perkin. Trans II, 1987, p.
1243.
[12] V.K. Syal, P.C. Jain, Indian J. Chem. 11 (1973) 494.
[13] Z.F. Luo, H. Wang, X. Jiang, Z. Wu, Z. You, W. Guo,
Huazhong Shiyuan Ziran Kexueban 2 (1985) 71.
[14] R.C. Agarwal, N.K. Singh, R.P. Singh, Syn. React. In-
org. Met. Org. Chem. 14 (1984) 637.
[15] A. Jyothi, G.N. Rao, Spectrochim. Acta 43A (1987) 517.
[16] E.C. Okafor, Spectrochim. Acta 37A (1981) 951.
[17] G.T. Behnke, K. Nakamoto, Inorg. Chem. 7 (1968) 330;
7 (1968) 2030.
Serial
number
IUPAC name
(abbreviation in bracket)
1.
2.
3.
4.
5.
benzaldehyde 2-hydroxy oxime
(BHO)
benzaldehyde 2-hydroxy-5-pentyl
oxime (BHPO)
1-(2-hydroxy phenyl) hexanone
oxime (HPHO)
copper-bis(2-hydroxy benzalde-
hyde oximato-N1O2) (CuHBO)
copper-bis(2-hydroxy-5-pentyl
benzaldehyde oximato-N1O2)
(CuHPBO)
copper-bis(1-(2-hydroxy
phenyl)hexanone oximato-N1O2)
(CuHPHO)
zinc-mono(2-hydroxy benzalde-
hyde oximato-N1O2) (ZnHBO)
zinc-bis(2-hydroxy-5-pentyl
benzaldehyde oximato-N1O2)
(ZnHPBO)
6.
[18] K. Nakamoto, Infrared Spectra of Inorganic and Coordi-
nation Compounds, Wiley Interscience, London, 1970,
pp. 247–256.
[19] A.H. Blatt, Org. React. 1 (1942) 342.
[20] W.J. Close, B.D. Tiffeny, M.A. Spielman, J. Am. Chem.
Soc. (1949) 1265.
7.
8.
[21] A.I. Vogel, Textbook of Practical Organic Chemistry,
Longman, Harlow, 1978.

V. Ramesh et al. / Spectrochimica Acta Part A 54 (1998) 285–297
297
[26] V. Ramesh, G.N. Rao, Proc. Indian Acad. Sci. (Chem.
Sci.) 100 (1988) 359.
[22] J. Cecile, M.I. Cruz, G. Barbery, J.J. Fripat, J. Colloid
Interface Sci. 80 (1981) 589.
[27] D. Stepniak-Biniakiewicz, Pol. J. Chem. 54 (1980) 1567.
[28] J. Ferraro, Low Frequency Vibrations of Inorganic and
Coordination Compounds, Plenum, New York, 1971, pp
89–95.
[23] K. Nakamoto, A.E. Martell, J. Chem. Phys. 32 (1960)
588.
[24] K. Nakamoto, C. Udovich, J. Takemoto, J. Am. Chem.
Soc. 92 (1970) 3973.
[25] H. Irving, R.J.P. Williams, Nature 162 (1948) 746.
[29] R.A. Pearson, J. Am. Chem. Soc. 85 (1963) 3533.
.