Stability constants of Ni(II)- and Cu(II)-N-heterocycle complexes according to spectrophotometric data

Article abstract of DOI:10.1134/S0036024415120250

The interaction of Ni(II) and Cu(II) with ethyl 4-(4-hydroxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine- 5-carboxylate [Ligand 1], 4-(1H-benzimidazol-2-yl)phenol [Ligand 2], and 2-(3-phenylamino- 4,5-dihydro-1,2-oxazol-5-yl)phenol [Ligand 3] have been studied by spectrophotometric technique at 0.01 M ionic strength and 28°C in 70% dioxane - water mixture. The data obtained were used to estimate the stability constant of these ligands. Spectrophotometric investigation of Ni(II) and Cu(II) complexes with these ligands shows 1: 1 complex formation. The formation of complexes has been studied by Job's variation method. The values of conditional stability constants of Cu(II) complexes are greater than the corresponding Ni(II) complexes. The greater value of stability constant of Cu(II) complexes may be due to the fact of more stable nature of Cu(II). The value of stability constant of Cu(II) - Ligand 2 complex is greater than that of Cu(II)-Ligand 1 and Cu(II)-Ligand 3. The same of Ni(II)-Ligand 3 complex is greater than that of Ni(II)-Ligand 1 and Ni(II)-Ligand 2.

Full text of DOI:10.1134/S0036024415120250

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2015, Vol. 89, No. 12, pp. 2254–2258. © Pleiades Publishing, Ltd., 2015.
STRUCTURE OF MATTER
AND QUANTUM CHEMISTRY
Stability Constants of Ni(II)– and Cu(II)–N-Heterocycle
Complexes According to Spectrophotometric Data1
Samata Badhe, Pradip Tekade*, Sonal Bajaj, and Shrikant Thakare
Department of Chemistry, Jankidevi Bajaj College of Science, Jamnalal Bajaj Marg, Civil Lines, Wardha, India
*e-mail: pradiptekade@gmail.com
Received October 24, 2014
Abstract—The interaction of Ni(II) and Cu(II) with ethyl 4-(4-hydroxyphenyl)-6-methyl-2-oxo-1,2,3,4-tet-
rahydropyrimidine-5-carboxylate [Ligand 1], 4-(1H-benzimidazol-2-yl)phenol [Ligand 2], and 2-(3-phe-
nylamino-4,5-dihydro-1,2-oxazol-5-yl)phenol [Ligand 3] have been studied by spectrophotometric tech-
nique at 0.01 M ionic strength and 28°C in 70% dioxane—water mixture. The data obtained were used to esti-
mate the stability constant of these ligands. Spectrophotometric investigation of Ni(II) and Cu(II) complexes
with these ligands shows 1 : 1 complex formation. The formation of complexes has been studied by Job’s vari-
ation method. The values of conditional stability constants of Cu(II) complexes are greater than the corre-
sponding Ni(II) complexes. The greater value of stability constant of Cu(II) complexes may be due to the fact
of more stable nature of Cu(II). The value of stability constant of Cu(II)—Ligand 2 complex is greater than
that of Cu(II)–Ligand 1 and Cu(II)–Ligand 3. The same of Ni(II)–Ligand 3 complex is greater than that of
Ni(II)–Ligand 1 and Ni(II)–Ligand 2.
Keywords: nickel complexes, copper complexes, heterocyclic ligands, Job’s variation method.
DOI: 10.1134/S0036024415120250
INTRODUCTION
mixture. Bhargava and Tondon [10] determined the
metal-ligand stability constant of Pt(IV) with substi-
tuted alkyl/aryl thiourea complexes spectrophotomet-
rically. Sawalakhe et al. [11] studied the interaction of
metals with 1,3-diketone, pyrazole and pyrazolines
spectrophtometrically. Raghuwanshi et al. [12] studied
the conditional stability constant of Cu(II) complexes
with some substituted isoxazolines in 70% dioxane-
water mixture spectrophotometrically. Conditional
stability constants of transition metal ions with some
amino acid peptides have been studied by Sondawale
and Narwade [13]. Raut et al. [14] studied the condi-
tional stability constants of transition metal ion com-
plexes with the antibiotic drug captopril. Mixed ligand
Cu(II) complexes of 2-aminobenzamide and amino
acids viz., glycine, L-alanine, L-valine, and L-phenyl-
alanine have been synthesized and characterized by var-
ious physico-chemical and spectral techniques [15].
Spectrophotometric study of triethylenetetramine
dihydrochloride interaction with Cu(II) and Zn(II)
have been reported by Nurchi et al. [16]. Spectrophoto-
metric study of stability constants of Cr(III), Ni(II) and
Cu(II) complexes with a Schiff bases in different sol-
vents have been studied by Lere et al. [17].
Rowland and Meloan [1] investigated cinnamohy-
droxamic acid chelates spectrophotometrically and
reported the composition and the molar extinction
coefficients of these chelates. Khobragade et al. [2]
have investigated the metal-ligand stability constants
of UO2(II) and Cu(II) complexes with some substi-
tuted sulfonic acids. Narwade et al. [3] have studied Fe
(III) complexes with substituted chalcones spectro-
photometrically. Narwade et al. [4] investigated the
stability constants of some lanthanide ions with sul-
phonic acid spectrophotometrically. The metal che-
lates of hydrazo-dimedone dyes are studied by Atef
et al. [5]. Sunita and Gupta [6] have worked on spec-
trophotometric determaination of cyanide in biologi-
cal complex. Manimekalai et al. [7] have determined
the stability constants and composition of 3-(2-fura-
nyl)-2-propenhydroxamic acid chelates by Job’s
method at continuous variations in 30% ethanol-water
medium. Chavan and Joshi [8] have studied the spec-
trophotometric determination of micro amounts of
gold (III) using cyclopentane-spiro-2'-(l'-methyl-
2',4'-dithio)-5-triazine. Sawalakhe [9] also deter-
mined stability constant and composition of the
Fe(III)–l-(2-hydroxyphenyl-3-phenyl-l,3-propandi-
one) chelates by Job’s method in 70% dioxane-water
Substituted isoxazolines, pyrimidines, and ben-
zimidazoles are good complexing agents due to the
presence of electron donor oxygen. Dihydropyrimidi-
none are known to exhibit a wide range of biological
activities such as antiviral, antitumour, antibacterial,
1
The article is published in the original.
2254

STABILITY CONSTANTS OF Ni(II)– AND Cu(II)–N-HETEROCYCLE
2255
and anti-inflammatory properties [18]. In addition, 4,5-dihydro-1,2-oxazol-5-yl)phenol [Ligand 3] with
these compounds have emerged [19] as potential cal- Ni(II) and Cu(II) metal ions by Job’s variation method
cium channel blockers, antihypertensive, α1-adrener- under suitable conditions spectrophotometrically.
gic antagonists and neuropeptide antagonists. Isoxaz-
oline derivatives have been reported to possess biolog-
EXPERIMENTAL
ical activity [20, 21]. Benzimidazole derivatives are
known to have numerous antimicrobial [22, 23], anti-
inflammatory [24] and anti-tumour [25] properties.
Therefore, it was thought of interest to study the che-
lating properties of N-heterocycles viz. ethyl 4-(4-
hydroxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropy-
rimidine-5-carboxylate [Ligand 1], 4-(1H-benzimid-
All the chemicals used are of laboratory grade and
used without further purification. The ligands were
prepared by known methods [26–28]. Compounds
were recrystallized before use.
The preparation of ligands is described by the
azol-2-yl)phenol [Ligand 2], and 2-(3-phenylamino- scheme:
OH
O
H
O
O
O
O
ZSM-5
50°C , Stirring
+
+
H2N
CH3
NH2
H3C
O
H3C
O
NH
OH
H3C
N
H
O
Ligand 1
HO
O
NH2
NH2
N
MW
Alumina
+
OH
N
H
OH
Ligand 2
HO
HO
NH2OH · HCl, Dry EtOH
K 10 Montmorillonite, MW
NH
NH
N
O
O
2-(3-phenylamino-4,5-dihydro-
1,2-oxazol-5-yl)phenol
Ligand 3
Distilled water used was free from carbon dioxide solving 0.255, 0.214, and 0.278 g of ligand 1, 2, and 3
respectively in 100 mL of 70% dioxane.
and pH of this water was about 6.80. Ni(II) (0.01 M)
and Cu(II) (0.01 M) ionic solutions were prepared
from nickel nitrate and copper nitrate (AR grade) and
were standardized by standard methods. The solution
of potassium nitrate was prepared (0.01 M) and used
Contech digital balance CA 224 having accuracy
0.001 g was used for weighing of samples. Systronics
108 UV–Visible spectrophotometer with 0.01 unit
accuracy was used for absorbance measurements. IR
for maintaining ionic strength constants. Ligands are spectra were recorded on Bruker Alpha IR spectrom-
eter (Germany). 1H NMR and 13CNMR spectra of the
compounds were recorded on Bruker DRX 300 NMR
insoluble in water, hence ligand solutions of 0.01 M
were prepared in 70% dioxane–water (v/v). 0.01 M
solutions of ligand were prepared separately by dis- instrument using TMS as internal standard.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 89 No. 12 2015

2256
SAMATA BADHE et al.
Conditional stability constants of complexes
Metal–ligand stability constants and confirmation
of complexes have been studied by McBryde [29] and
Banerjee [30]. The composition of the complexes are
confirmed by Job’s method as modified by Vosburgh
and Gold [31]. Solutions of metal salt and ligand of
equimolar concentration (1.00 × 10–2 M) are mixed
pairwise in different ratios to prepare Job’s solutions.
Final volume of each solution was made 10 ml after
adjusting the appropriate pH and maintaining the
constant ionic strength (0.1 M sodium perchlorate). In
addition to the wavelength of maximum (λmax) some
other wavelength were selected as proposed by
Vosburgh and Gold.
System
K
logK
logK' mean
Ni(II)–L1
Cu(II)–L1
Ni(II)–L2
Cu(II)–L2
Ni(II)–L3
Cu(II)–L3
0.02758
0.18674
0.01065
0.2774
0.03849
0.14559
1.4406
2.2712
1.0274
2.4431
1.5853
2.1631
1.8217
which there is maximum absorption. The absorptions
for all the compositions were recorded at constant
wavelength (λmax). Each solution is diluted up to 15 mL
and absorptions are recorded at same λmax. The data of
absorption and percentage composition of metal ion
and ligand solutions at constant pH are used and the
curves are constructed. The conditional stability con-
stants obtained by spectrophotometric techniques are
presented in the table.
It can be seen from table that for Ligands 1 and 2, the
values of conditional stability constants of Cu(II)
complexes are greater than the corresponding Ni(II)
complexes. The greater value of stability constant of
Cu(II) complexes may be due to the fact of more stable
nature of Cu(II).
RESULTS AND DISCUSSION
Spectral data for the prepared ligands are in good
agreement with literature [26–28].
The concentration of complex (x) in any metal-
ligand solution is obtained by Job’s curve. Initial con-
centrations of metal and ligand in a particular solution
are considered a and b and the equilibrium constant
was determined by the law of mass action.
x
k =
(a − x)(b − x)
or
x
x
The value of stability constant of Cu(II)–Ligand 2
complex is greater than that of Cu(II)–Ligand 1 and
Cu(II)–Ligand 3. The same of Ni(II)–Ligand 3 com-
plex is greater than that of Ni(II)–Ligand 1 and
Ni(II)–Ligand 2.
k =
.
(a1 − x)(b1 − x)(a2 − x)(b2 − x)
The composition of metal ion solution (1 × 10–2 M)
and ligand (1 × 10–2 M) were prepared in ten series.
λ
max was determined using one of the compositions at
Cu(II) + Ligand 1
Ni(II) + Ligand 1
0.24
0.23
0.22
0.21
0.20
0.19
Optical density
0.22
on dilution
0.21
Optical density
0.20
0.18
Optical density on dilution
Optical density
0.19
0.18
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
102030405060708090
Composition, %
102030405060708090
Composition, %
Fig. 2. Plot of optical density vs. composition (%) of sys-
tem Cu(II)–Ligand 1.
Fig. 1. Plot of optical density vs. composition (%) of sys-
tem Ni(II)–Ligand 1.
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STABILITY CONSTANTS OF Ni(II)– AND Cu(II)–N-HETEROCYCLE
2257
Ni(II) + Ligand 2
Cu(II) + Ligand 2
1.18
1.17
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.10
1.09
1.08
1.07
1.06
1.05
1.04
1.03
1.02
1.01
Optical density
1.16
1.15
1.14
1.13
1.12
1.11
1.10
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0.91
0.90
0.89
0.88
0.87
0.86
0.85
on dilution
Optical density
Optical density
on dilution
Optical density
102030405060708090
Composition, %
102030405060708090
Composition, %
Fig. 3. Plot of optical density vs. composition (%) of sys-
tem Cu(II)–Ligand 2.
Fig. 4. Plot of optical density vs. composition (%) of sys-
tem Ni(II)–Ligand 2.
Cu(II) + Ligand 3
Ni(II) + Ligand 3
0.23
0.22
0.21
0.22
0.21
0.20
Optical density
0.20
Optical density
on dilution
0.19
0.18
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
on dilution
0.19
0.18
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
Optical density
Optical density
102030405060708090
Composition, %
102030405060708090
Composition, %
Fig. 5. Plot of optical density vs. composition (%) of sys-
tem Ni(II)–Ligand 3.
Fig. 6. Plot of optical density vs. composition (%) of sys-
tem Cu(II)–Ligand 3.
Order of Stability Constants:
Cu(II)–Ligand 2 > Cu(II)–Ligand 1 > Cu(II)–Ligand 3,
Ni(II)–Ligand 3 > Ni(II)–Ligand 1 > Ni(II)–Ligand 2.
The curves are constructed between the values of with Ni(II) and Cu(II) metal ions was done. The for-
optical density and percentage composition of metal
ion as shown in Figs. 1–6.
mation of complexes (1 : 1) has been studied by Job’s
variation method.
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2015