Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
Research Article, Issue 2
Analytical Methods in Environmental Chemistry Journal
Journal home page: www.amecj.com/ir
AMECJ
Analysis of complexation between new bidentate bis-NHC
ligand and some metal cations at different temperature
Nur Rahimah Said a, Majid Rezayi b,c,d,*, Ninie Suhana Abdul Manan e,f, Amirhossein Sahebkar g,h,m,n, Yatimah Alias e,f,*
a School of Chemistry and Environment, Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), Cawangan Negeri
Sembilan, Kampus Kuala Pilah, 72000 Kuala Pilah, Negeri Sembilan, Malaysia
b Medical Toxicology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
c Metabolic Syndrome Research Center, Mashhad University of Medical Science, Mashhad, Iran
d Department of Medical Biotechnology and Nanotechnology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
e Department of Chemistry, Faculty of Science, University of Malaya Centre for Ionic Liquids, University of Malaya, 50603,
Kuala Lumpur, Malaysia
f Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia
g Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran
h Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
m School of Medicine, The University of Western Australia, Perth, Australia
n Department of Biotechnology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
ABSTRACT
In this research, the determination and complexation process between
3,3’-(2,2’-(4-methyl-phenylenesulfonamido)bis(ethane-2,1-diyl))
bis(1-benzyl-3H-benzo[d]imidazol-1-ium)dibromide with Ni2+,
Zn2+, Pd2+, Ag+, and Hg2+ cations in the binary mixture of methanol
(MeOH) and water (H2O) at different temperatures (15, 25, 35 and
45ºC) were studied using a conductometric method. The results
show that the stoichiometry of the complexes in all binary mixed
solvents for Ni2+, Zn2+, and Pd2+ were 1:1 (M:L), while in other cases
1:2 (M:L) and 2:1(M:L). The stability constants (log ) of complex
formation have been determined by tting molar conductivity curves
using a computer program (GENPLOT). The obtained data shows
that in the pure methanol solvent system, the stability order is Ni2+<
Pd2+<Zn2+<Hg2+<Ag+ and the complexation process seems more
stable in pure methanol in most cases. The thermodynamic parameters
),,(
οοο
CCC
SHG ∆∆∆
were determined conductometrically. The
complexes in all cases were found to be enthalpy destabilized but
entropy stabilized. The experimental data was tested by using an
articial neural network (ANN) program and was in good agreement
with the estimated data.
Keywords:
Analysis,
Complexation process,
Ligand,
Conductometric method,
Binary mixed solvent,
Thermodynamic parameters.
ARTICLE INFO:
Received 25 Jan 2022
Revised form 10 Apr 2022
Accepted 12 May 2022
Available online 28 Jun 2022
*Corresponding Author: Nur Rahimah Said and Majid Rezayi
Email: rezaeimj@mums.ac.ir, yatimah70@um.edu.my
https://doi.org/10.24200/amecj.v5.i02.169
------------------------
1. Introduction
In early 1968, Wanzlick and Schönherr pioneered
scientists that convey N-Heterocyclic carbene
(NHC) complexation to a gained general acceptance
among the researchers [1]. This effort was followed
by Ardueng who found the stable crystalline
carbene in 1991 [2]. In the meantime, numerous
studies have been reported with the various
applications so far. NHCs ligands synthesized
from benzimidazole and imidazole were founded
as attractive ligands for complexation due to their
structure variety and stability [3]. Generally, it is
more stable than other types of carbenes, such as
the Fisher and Schrock carbenes [4]. Furthermore,
these types of ligands can bond to either hard and
soft transition metal ions or atoms through strong
chelation [5-9]. Several articles have described
6Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
the interesting features of NHC ligands and their
metal complexes in detail, especially on their C-C
coupling catalysis activities [10-13]. Recently,
its application as an anticancer activity was also
reported [14-18]. Several bidentate bis-NHC
ligands derived from benzimidazole and imidazole
with a different bridging linker have been reported
[19-23]. The types of bridging linkers play the
main role in the coordination of metal complexes.
Different types of bridging linkers will be offered
for the different conformations of complexes. This
is related to the exibility, length, and size of linkers
[5]. In addition, different cavity sizes of ligand,
ionic radii of metal [24], and solvent systems are
the important factors that can inuence the stability
of complexation formation [25].
Fig. 1. 3,3’-(2,2’-(4-methyl-phenylenesulfonamido)
bis(ethane-2,1-diyl))bis(1-benzyl-3H-benzo[d]
imidazol-1-ium)dibromide, (NHCL)
To our certain knowledge, there have been few
reports of the thermodynamic study of bidentate bis-
NHC ligand complexes with different metal ions.
This encouraged us to investigate the effects of pure
and binary solvent mixtures on stability constants
and thermodynamic parameters of complexes. In
our study, bidentate bis-NHC ligand connected by
sulfonamide moiety was designated and synthesized
by a simple and efcient method [3, 19], namely
3,3’-(2,2’-(4-methyl-phenylenesulfonamido)
bis(ethane-2,1-diyl))bis(1-benzyl-3H-benzo[d]
imidazol-1-ium)dibromide (NHCL) (Fig. 1). To
determine the stability, selectivity and stoichiometry
of NHCL-Mn+ complexes with different metal
cations, the conductometric technique was chosen
[26]. This technique has several advantages
such as great sensitivity [27], low cost [28]
as well as simple experimental arrangement
[29] compared with other techniques such as
spectrophotometry, calorimetry [30], and NMR
spectroscopy [31], and potentiometry [32-35]. The
sensors based on electrochemical methods have
been used to measure the analyte concentrations
in water samples. Hence, electroanalytical
techniques such as, potentiometry, voltammetry,
and conductometry have been extensively reported.
Other techniques such as inductively coupled plasma
mass spectrometry [36], co-precipitation [37],
ame atomic absorption spectrometry (F-AAS)
[38], inductively coupled plasma optical emission
spectrometry (ICP-OES) [39], and electrothermal
atomic absorption spectrometry (ETAAS) [40]
have also been used for the determination cations
in water samples after complexation process. Thus,
this study can contribute to a better understanding
of ligand character and behavior in coordination
chemistry, and the solvent effect in its complexation
process.
2. Experimental
2.1. Chemicals and Instruments
The chemicals and metal ions used, which are
nickel acetate, zinc acetate, palladium acetate,
silver acetate, and mercury nitrite were purchased
from Sigma-Aldrich (USA) and MERCK
(Germany). All chemicals were analytical grade
and used without further purication. Deionized
distilled water and methanol with HPLC grade
available from MERCK (Germany) were used
as a solvent. The conductometric measurements
were carried out using a digital Thermo Scientic
conductivity device in a JULABO F12 thermostat
water bath with a constant temperature maintained
within ±0.01ºC. A conductometric cell model
Orion 013005MD with a cell constant of 0.99cm-1
was used throughout the studies.
7
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
2.2. Synthesis of the bidentate bis-NHC ligand,
NHCL
Several steps synthesized NHCL (4) from the
diol (1) are shown in Figure 2. The synthesis of
compounds (2) and (3) has been reported previously
[19]. NHCL (4) was prepared according to the
modication method designated as follows [3].
Benzyl bromide (0.1710 g, 1.0 mmol) was stirred
in 20 ml of 1,4-dioxane, and then compound (3)
(0.2296 g, 0.5 mmol) was added to it. The reaction
mixture was reuxed at 100 ºC for 12 hours and the
pale yellow precipitated was obtained. The product
was collected by ltration, washed with fresh
1,4-dioxane (2×5 mL) and diethyl ether (2×5 mL)
and dried in vacuo to give a pale yellow powder (4).
2.3. Analysis procedure
These experimental designs were prepared
according to the altered procedure [41-43] and
were applied to all metal cations; Ni2+, Zn2+, Pd2+,
Hg2+, and Ag+. The formation constant of the
complexes will be obtained by using the procedure
designated as follow. A solution of the metal ion
with a concentration, of 5.0 × 10-5M was prepared
and xed in a titration cell. After that, the L with
concentration 2.5 × 10-3M was added to the titration
cell using a micropipette. During the reaction, the
desired temperature was xed and a magnetic stir has
been used to form a homogenized condition in the
titration cell. The conductivity values were measured
before and after each titration of ligands solution.
The procedure was repeated for all metal cations in
the MeOH-H2O binary system (mol MeOH; 0.00,
9.99, 22.66, 39.73, 63.72 and 100.00%) at different
temperatures (15, 25, 35 and 45ºC).
3. Results and discussion
The general reaction for complex formation (1:1)
can be stated by Equation 1 and the corresponding
equilibrium constant ( f
K
), is given by Equation 2.
++
↔+
nn
NHCLMNHCLM
(Eq.1)
)(
)(
)(
]][[
][
NHCL
M
n
NHCLM
n
f
ffNHCLM
fNHCLM
K
n
n
+
+
+
+
=
(Eq.2)
Fig. 2 . Synthesized scheme for NHCL (4).
8
The equation represents the equilibrium molar
concentration of the complex
][
+n
NHCLM
, the
free cation
][
+n
M
, the free ligand
][NHCL
, and the activity coefcients of the species,
f
.
Since the dilute condition was used in this work,
the activity coefcient of the uncharged ligand,
)(NHCL
f
is reasonably assumed to be unity. Dilute
condition is where the ionic strength is less than
0.001 M. Based on the Debye-Hückel limiting
law of electrolytes leads to the conclusion that
)()(
++
≅
nn
MNHCLM ff
. Thus, the above equation can
be simplied as Equation 3 [44].
]][[
][
NHCLM
NHCLM
K
n
n
f+
+
=
(Eq.3)
The specic conductivity (K) in each point of the
titration process is the value of the combination
of conductivity of both metal salts,
)(
+n
M
K
and
NHCLMn+ complex,
)(
+n
NHCLM
K
which can be seen
in the following Equation 4.
)()(
++
+=
nn
NHCLMM
KKK
(Eq.4)
Equations 5, 6 and 7 show the molar conductance
of metal salt before the addition of NHC ligand,
)(
+
Λ
n
M
, molar conductance of NHCLMn+ complex,
)(
+
Λn
NHCLM
and observed molar conductance
during titration,
Obs
Λ
.
][
)(
)( +
+
+
=Λ n
M
MM
K
n
n
(Eq.5)
][
)(
)( +
+
+=Λ n
NHCLM
ML NHCLM
Kn
n
(Eq.6)
t
n
Obs
M
K
][
+
=Λ
(Eq.7)
where the total analytical concentration of the
metal cations
t
n
M][ +
is sum of the concentration
of metal salts,
][
+n
M
and NHCLMn+ complex,
][
+n
NHCLM
as shown in Equation 8.
][][][ +++ += nn
t
nNHCLMMM
(Eq.8)
By combining and simplifying the Equations 4, 5, 6
and 7, the following Equation 9 is obtained.
][][][
)()(
+++
++
Λ+Λ=Λ
n
NHCLM
n
M
t
n
Obs
NHCLMMM
nn
][][][
)()(
+++
++
Λ+Λ=Λ
n
NHCLM
n
M
t
n
Obs
NHCLMMM
nn
(Eq.9)
Then, the observed molar conductance of the
solution can be represented as Equation 10 by
substituting of Equation 3 to Equation 9.
]][[][][ )()( NHCLMKMM n
f
NHCLM
n
M
t
n
Obs
nn
+++
++
Λ+Λ=Λ
]][[][][ )()( NHCLMKMM n
f
NHCLM
n
M
t
n
Obs
nn
+++
++
Λ+Λ=Λ
(Eq.10)
The Equation 11 can be obtained by combining
Equations 3 and 8.
(Eq.11)
Thus, the observed molar conductance of solution
can be simplied as Equation 12 by substituting
Equation 11 into Equation 10.
(Eq.12)
In contrast, the total concentration of NHC ligand,
t
NHCL][
can be described as in Equation 13.
][][][
+
+=
n
t
NHCLMNHCLNHCL
(Eq.13)
Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
9
The substitution Equation 3 into Equation 13 will
gave the following Equation 14.
(Eq.14)
Then, the combination of Equations 11 and 14 gave
Equation 15:
(Eq.15)
Rearranging Equation 15 gave Equation 16:
(Eq.16)
With obtaining of
][
+n
NHCLM
and
t
NHCL][
,
the values of other species involved by using the
appraised amount of the formation constants at the
current iteration step of the program. Renement of
the parameters is continued until the sum-of-squares
of the residuals between calculated and observed
values of the conductance for all experimental
points is minimized. The output of the program
GENPLOT comprises rened parameters, the sum-
squares and the standard deviation of the data [45].
For determination of the stability constants of
complex formation between the NHC ligand and
various metal cations, the conductometric method
has been selected as the best method in numerous
studies [25, 41, 46]. To study the complexation
reaction of L with the Ni2+, Zn2+, Pd2+, Hg2+, and
Ag+ cations, the changes in molar conductivity
(Ʌm) of the solution were supervised as a function
of molar ratio
)][][(
t
n
t
MNHCL
+
of the
proposed complex in pure MeOH, pure H2O and
in MeOH-H2O binary mixtures (mol%) at different
temperatures (15, 25, 35 and 45ºC). The resulting
Ʌm versus
)][][(
t
n
t
MNHCL
+
plots for (A) Ni2+ in
MeOH-H2O binary system (mol% MeOH=39.73)
and (B) Ag+ cations in MeOH-H2O binary system
(mol% MeOH= 9.90) are presented in Figure 3.
Fig.3. Molar conductance-mole ratio titration curves
of (A) Ni2+ cation in MeOH-H2O binary system (mol%
MeOH=39.73), (B) Ag+ cation MeOH-H2O binary
system (mol% MeOH=9.90) with NHCL at different
temperatures.
As can be seen in Figure 3 (A), the Ʌm versus
)][][(
t
n
t
MNHCL
+
plots for Ni2+ cation show
an increase in Ʌm parallel to increase of the ligand
concentration. This is corresponding to the free
solvated metal ion is less mobile compared to the
both ligand and complex. The same cases also
happened to Zn2+ and Pd2+ slope, respectively.
The slope for Ni2+, Zn2+, and Pd2+ shows that the
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
10
stoichiometric for these complexation reactions
was 1:1 [M:NHCL]. While, from the Ʌm versus
)][][(
t
n
t
MNHCL
+
plots for Ag+ cation,
Figure 3 (B) observed a slightly decreasing in
Ʌm with increasing the ligand concentration,
which indicated that ligand mobility is less than
free solvated metal cation. However, it shows the
increment after breaking points. This is indicated
that the mobility of complexes in MeOH-H2O
binary mixtures is greater than free solvated cations
[46]. The Ʌm versus
)][][(
t
n
t
MNHCL
+
plots for
Hg2+ also gave the same results as Ag+. It seems
that in both complex formations, further addition
of ligand to metal cation solution results in the
formation of 1:2 [M:NHCL] and 2:1 [M:NHCL]
complexes. Therefore, the general mechanism for
all complexation processes may suggest as follows
(Eq.17-Eq.19):
++
↔+
nn
NHCLMNHCLM
(Eq.17)
++
↔+
nn
MNHCLNHCLNHCLM
2
(Eq.18)
+
++ ↔+ n
nn NHCLMMNHCLM 2
(Eq.19)
The formation constant values (log f
K
) of
complexes for all cations were determined
using a non-linear least-squares curve tting
program, GENPLOT from the corresponding Ʌm
versus
)][][(
t
n
t
MNHCL
+
plots at different
temperatures. The obtaining data was summarized
in Table 1.
The results in Table 1 show the increase of stability
constants (log f
K
) for NHCLMn+ complexes with
an increase of temperature in most of the solvent
systems. This is an indication for an endothermic
complexation reaction between ligands and metal
cations in the solution [36]. The obtained data shows
that in the pure MeOH solvent system the stability
constant is varying as Ni2+< Pd2+<Zn2+<Hg2+<Ag +
and in the most cases complexation process seems
more stable in pure MeOH. The results proved
that the stability of the resulting complexes was
inuenced by the nature of the solvent system. In
the reaction mixture solution, the ligand should
be able to excess metal cations which are solvated
by solvent molecules to form a complex. Hence,
dissimilarities in the nature of the solvent system
may inuence in the binding properties of NHCL,
and subsequently, the stability and selectivity metal
complexes.
Fig. 4. Stability constant (log f
K
) of complexes
in MeOH-H2O binary system (mol% MeOH; 0.00,
9.99, 22.66, 39.73, 63.72 and 100.00%) at different
temperature (◊ = 15ºC, □ = 25ºC, ∆ =35ºC, X = 45ºC).
(A) for Pd2+ cation and (B) for Ag+ cation.
In the most cases, the changes in stability constant
(log f
K
) of the complexes versus the composition
of the MeOH-H2O binary systems at various
temperatures are not linear as shown in Figure 4.
This pattern is probably due to solvent-solvent
interaction that changed the structure of the
solvent mixtures and consequently changed the
solvation properties of the metal ions, ligand and
the resulting complexes [25, 41]. In other cases,
the increments of the stability constant value by the
reducing of mol% of MeOH have been observed.
Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
11
Table 1. log f
K
value of NHCLMn+ in MeOH-H2O binary mixtures at different temperatures
for the studied metals cations.
Mediuma/ Ni2+ log Kf ± SDb
15ºC 25ºC 35ºC 45ºC
Pure MeOH 2.50 ± 0.14 2.43 ± 0.10 2.47 ± 0.07 2.48 ± 0.22
36.27%H2O-63.72%MeOH 2.49 ± 0.31 2.46 ± 0.31 2.56 ± 0.27 2.40 ± 0.36
60.27%H2O-39.73%MeOH 2.42 ± 0.19 2.57 ± 0.07 2.51 ± 0.08 2.46 ± 0.08
77.34%H2O-22.66%MeOH 2.46 ± 0.08 2.55 ± 0.08 2.64 ± 0.07 2.45 ± 0.18
90.10%H2O-9.90%MeOH 2.35 ± 0.31 2.60 ± 0.10 2.45 ± 0.12 2.85 ± 0.10
Pure H2O 2.49 ± 0.08 2.56 ± 0.14 2.77 ± 0.08 2.45 ± 0.09
Mediuma/ Zn2+
Pure MeOH 2.55 ± 0.08 2.76 ± 0.08 2.76 ± 0.08 2.75 ± 0.08
36.27%H2O-63.72%MeOH 2.43 ± 0.14 2.40 ± 0.15 2.55 ± 0.08 2.56 ± 0.10
60.27%H2O-39.73%MeOH 2.41 ± 0.16 2.43 ± 0.13 2.43 ± 0.15 2.45 ± 0.12
77.34%H2O-22.66%MeOH 2.48 ± 0.11 2.42 ± 0.13 2.55 ± 0.07 2.57 ± 0.07
90.10%H2O-9.90%MeOH 2.55 ± 0.12 2.64 ± 0.06 2.27 ± 0.32 2.86 ± 0.11
Pure H2Oc c c c
Mediuma/ Pd2+
Pure MeOH 2.46 ± 0.21 2.51 ± 0.39 2.77 ± 0.17 2.58 ± 0.27
36.27%H2O-63.72%MeOH 2.29 ± 0.31 2.45 ± 0.29 2.52 ± 0.17 2.67 ± 0.19
60.27%H2O-39.73%MeOH 2.45 ± 0.21 2.83 ± 0.15 2.82 ± 0.13 2.32 ± 0.25
77.34%H2O-22.66%MeOH 2.86 ± 0.10 2.50 ± 0.10 2.51 ± 0.09 2.45 ± 0.19
90.10%H2O-9.90%MeOH 2.77 ± 0.08 2.41 ± 0.14 2.57 ± 0.08 2.76 ± 0.07
Pure H2O 2.68 ± 0.17 2.54 ± 0.18 2.57 ± 0.19 2.76 ± 0.20
Mediuma/ Hg2+
Pure MeOH 3.85 ± 0.12 3.86 ± 0.11 3.86 ± 0.12 3.85 ± 0.12
36.27%H2O-63.72%MeOH 3.27 ± 0.35 3.42 ± 0.24 3.41 ± 0.25 3.46 ± 0.22
60.27%H2O-39.73%MeOH 3.45 ± 0.21 3.82 ± 0.26 3.84 ± 0.21 3.84 ± 0.21
77.34%H2O-22.66%MeOH 3.88 ± 0.12 3.45 ± 0.22 3.44 ± 0.30 3.43 ± 0.31
90.10%H2O-9.90%MeOH c c c c
Pure H2Oc c c c
Mediuma/ Ag+
Pure MeOH 3.46 ± 0.38 3.86 ± 0.20 3.84 ± 0.20 3.47 ± 0.40
36.27%H2O-63.72%MeOH 3.71 ± 0.19 3.87 ± 0.22 3.78 ± 0.24 3.81 ± 0.23
60.27%H2O-39.73%MeOH 3.51 ± 0.27 3.79 ± 0.22 3.84 ± 0.20 3.86 ± 0.17
77.34%H2O-22.66%MeOH 3.85 ± 0.17 3.46 ± 0.32 3.44 ± 0.34 3.86 ± 0.17
90.10%H2O-9.90%MeOH 3.86 ± 0.23 3.58 ± 0.32 3.86 ± 0.22 3.86 ± 0.22
Pure H2O 3.58 ± 0.29 3.57 ± 0.29 3.57 ± 0.29 3.86 ± 0.22
aComposition of binary mixtures is expressed in mol% for solvent system,
bSD = Standard deviation,
c The data cannot be tted to the equation in GENPLOT.
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
12
These results can be explained by the Gatmann
acceptor-donor number effect. In this study binary
mixture of MeOH-H2O has been used. Pure solvent
MeOH and H2O have acceptor numbers 41.5 and
54.8 kcal mol-1, respectively [47]. Therefore, the
complexation in the solvent with lower acceptor
ability will increase the stability constant value.
This is due to the less competition of the ligand
with the solvent molecules for the metal ions,
thus increase the stability in the formation of
complexes. The effect of a Gatmann donor
number of solvents and their mixtures in this study
is negligible because of their approximately equal
value (DNWater=18 kcal/mol; DNMeOH=19 kcal/mol).
By ignoring this parameter, the dielectric constant
of solvents, ɛ, plays another important role in the
stability constants of complexes. According to
the previous studies, the interaction between the
oppositely charged ions in the solvent with low
dielectric constant (Methanol, ɜ=32.6), in compared
to water (ɜ=81.7), would be increased and cause to
form the complexes. In order to better understand
the complexation proceed discussed, it is useful to
consider the enthalpy and entropy contribution to
these reactions. The
ο
C
H∆
and
ο
C
S∆
parameters
were estimated according to the van’t Hoff plots
that shows the corresponded lnKf- temperature
data according to the van’t Hoff’s equation.
All the van’t Hoff plots of ln f
K
versus 1000/T
for all different metal cations, were constructed
individually. Several cases were shown in Figure 5.
Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
Fig. 5. Van’t Hoff plot for L-Mn+ with Ni2+ cation in MeOH-H2O binary system (mol%
MeOH; ◊ = 100, □ = 63.72, ∆ = 39.73, X = 22.66, + = 9.90, ○ = 0.00) at different
temperature.
13
The data demonstrated that these complexations
process are temperature dependent. The value of
standard enthalpy (
ο
C
H∆
) for the complexation
reaction was determined from the slope of the
van’t Hoff plots based on van’t Hoff’s equation
(Equation 20). Other thermodynamic parameters,
the free energy of complex formation (
ο
C
G∆
) and
the value of the standard entropy (
ο
C
S∆
) were obtained
from thermodynamic relation Equation 21[39]. The
calculated results are summarized in Table 2.
Table 2. Summary of thermodynamic parameters values of the NHCLMn+ complexes
in MeOH-H2O binary mixture solvent.
Mediuma /Ni2+
log Kf ± SDb
ο
C
G∆
± SDb
(kJ.mol-1)
ο
C
H∆
± SDb
(kJ.mol-1)
ο
C
S∆
± SDb
(J.mol-1)
Pure MeOH -13.9 ± 0.5 4.6 ± 1.0 62.1 ± 2.8
36.27%H2O-63.72%MeOH -14.04 ± 1.8 -5.6 ± 0.1 28.2 ± 1.9
60.27%H2O-39.73%MeOH -14.6 ± 0.4 -9.9 ± 0.3 16.0 ± 1.0
77.34%H2O-22.66%MeOH -14.5 ± 0.4 14.5 ± 0.4 97.3 ± 0.7
90.10%H2O-9.90%MeOH -14.8 ± 0.6 28.7 ± 0.3 146.1 ± 4.4
Pure H2O -14.6 ± 0.8 23.2 ± 7.4 127.0 ± 2.5
Mediuma /Zn2+
Pure MeOH -15.8 ± 0.5 11.0 ± 6.3 89.9 ± 2.0
36.27%H2O-63.72%MeOH -13.7 ± 0.9 7.3 ± 2.2 70.4 ± 6.9
60.27%H2O-39.73%MeOH -13.8 ± 0.7 1.1 ± 0.9 50.0 ± 1.6
77.34%H2O-22.66%MeOH -13.8 ± 0.7 5.5 ± 0.3 64.7 ± 2.2
90.10%H2O-9.90%MeOH -15.1 ± 0.4 17.9 ± 1.7 110.7 ± 5.6
Pure H2Oc c c
Mediuma /Pd2+
Pure MeOH -14.4 ± 2.2 6.9 ± 0.7 71.4 ± 7.0
36.27%H2O-63.72%MeOH -14.0 ± 1.7 21.0 ± 1.9 117.4 ± 3.3
60.27%H2O-39.73%MeOH -16.2 ± 0.8 32.3 ± 8.0 162.7 ± 6.3
77.34%H2O-22.66%MeOH -14.3 ± 0.6 -4.5 ± 4.0 32.9 ± 1.9
90.10%H2O-9.90%MeOH -13.8 ± 0.8 31.6 ± 2.9 152.3 ± 9.4
Pure H2O -14.7± 1.0 16.5 ± 4.0 104.6 ± 6.9
Mediuma /Hg2+
Pure MeOH -22.0 ± 0.6 -1.2 ± 0.2 69.8 ± 2.0
36.27%H2O-63.72%MeOH -19.5 ± 1.4 11.1 ± 0.9 102.6 ± 3.6
60.27%H2O-39.73%MeOH -21.8 ± 1.5 24. 6 ± 7.6 155.6 ± 5.0
77.34%H2O-22.66%MeOH -19.7 ± 1.3 -2.3 ± 0.5 58.4 ± 4.0
90.10%H2O-9.90%MeOH c c c
Pure H2Oc c c
Mediuma /Ag+
Pure MeOH -21.9 ± 1.1 32.1 ± 9.2 181.1 ± 6.4
36.27%H2O-63.72%MeOH -22.1 ± 1.8 21.7 ± 8.3 146.9 ± 7.3
60.27%H2O-39.73%MeOH -21.6 ± 1.3 28.3 ± 9.8 167.4 ± 3.7
77.34%H2O-22.66%MeOH -19.3 ± 1.9 35.9 ± 3.5 185.1 ± 8.4
90.10%H2O-9.90%MeOH -20.4 ± 1.3 -0.2 ± 0.1 67.8 ± 4.2
Pure H2O -20.4 ± 1.3 -4.8 ± 4.5 52.3 ± 4.5
aComposition of binary mixtures is expressed in mol% for solvent system,
bSD = Standard deviation,
c The data cannot be tted to equation.
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
14
(Eq.21)
(Eq.21)
The results reveal, in the most cases the changes
in
ο
C
H∆
for the complexation process is negligible,
whereas the change in
ο
C
S∆
is signicant.
Therefore, the formation of complexes between
ligand (NHCL) and all cations in MeOH-H2O
binary solvent mixtures are enthalphy destabilized
but entropy stabilized. Additionally, the different
solvent-solvent interaction in all solvent system and
changes in exibility of ligand during complexation
contribute to change in entropy. The calculated
value of
ο
C
G∆
in all cases shows negative values.
This is an evidences that the ability of the ligand
to form stable complexes with metal cations and
the process were spontaneous [42]. However, The
exitance of such a compensating e-ect between
ο
C
H∆
and
ο
C
S∆
values for all studied binary
systems is shown in Figure 6. It is clear that the
observed increase or decrease in
ο
C
H∆
value
which is depending on the nature of the metal ion
will be compensated by an increase (or decrease)
in the corresponding
ο
C
S∆
value. Then the small
changes of
ο
C
G∆
values will be resulted due
to this compensating e-ect for
ο
C
H∆
and
ο
C
S∆
,
independently.
Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
Fig. 6. Plot of
ο
C
H∆
(kJmol-1) versus
ο
C
ST∆
(kJmol-1) for NHCLMn+ (M= Ni2+, Pd2+, Zn2+,
Hg2+ and Ag+) in different MeOH-H2O systems (R2=0.9537).
15
The variation of log f
K
for all complex cases in
contrast with cationic radius for studied cations in
MeOH-H2O binary mixture at 25ºC were presented
in Figure 7. As it is seen in Figure 7, the stability
constant of complexes increase as the size of a metal
cation increases from Ni2+ to Ag+. These results can
be explained due to solvent system effect. Usually
the small metals cations will be more solvated
than the bigger metals cations in a same solvent
system and decrease its mobility. Consequently,
the competition ligand with solvent molecules was
increase and resulted in the decreasing of stability
constant [44].
3.1. Computational study
With the purpose to elucidate the obtained
experimental results, a density functional theory
(DFT) study was conducted. The DFT calculations
were carried out with the GAUSSIAN 09 software
package, with the B3LYP/LANL2DZ basis set. The
binding energy ∆E in the complexation between
NHCL and Mn+ in MeOH pure solvent is dened
by the following formula, Equation 22:
)( NHCL
MNHCLM EEEE nn +−=∆ ++
(Eq.22)
Where
++
∆nn MNHCLM EEE ,,
and
NHCL
E
are binding
energy, NHCLMn+ complex energy, free metal ion
energy and NHCL energy, respectively [48]. The
optimized structure of free and complexes NHCL
with Zn2+ and Ag+ was shown in Figure 8(A, B,
C), respectively. While the calculated results of
binding energies for all complexes in MeOH pure
solvent were listed in Table 3.
It is clear from Table 3 that the binding energy
Fig. 7. Changes of stability constant (log f
K
) of NHCL-Mn+ with all metal cation in
MeOH-H2O binary system (mol% MeOH; ◊ = 100, □ = 63.72, ∆ = 39.73, X = 22.66, +
= 9.90, ○ = 0.00) at 25ºC.
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
16 Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
Fig. 8. Optimized structure of NHC ligand
17
increases monotonically with increasing the size
of studied cations. Therefore the binding energy
of Ag+ is much larger than other cations, showing
prominent afnity to NHCL in the MeOH solvent.
The obtained experimental data in MeOH pure
solvent (Table 1) shows the same trends. As
discussed before, small cations such as Ni2+ and
Pd2+ have high solvation free energy with MeOH
that causes them to be more solvalized in the
solution, and have less interaction with free NHCL
ligand.
3.2. Mathematical Modeling
Articial neural network (ANN) as a mathematical
(or computational) model that is inspired by
the structure and function of biological neural
networks in the brain, is one of the most successful
technologies in the last two decades [49-52]. In
this research work, the ANN was applied for the
simulation of property parameters correlation, and
a good agreement in the experimental and predicted
value is obtained. A 4-11-1 (input layer-hidden
layer-output layer) network structure was used as
shown in Figure 9. The effect of four parameters
(cationic radii, temperature, molar percentage
of MeOH in the media and molar percentage of
water in the media) for the determining of complex
formation (Kf) was the input layer matrix of the
network. 59 training examples, 26 testing examples
and 20 validating examples (10 times of each node)
were prepared for training, testing and validating
the network, respectively.
Table 3. The calculated binding energies ∆E, in the formation of NHCLMn+
by DFT method, where ENHCL is -1969.8454 (Hartree).
Mn+ EM
n+ (Hartree) ENHCL-M
n+ (Hartree) ∆E (Hartree) ∆E (kJ mol-1)
Ni2+ -168.8263978 -2138.0707 0.66742646 1752.327917
Zn2+ -65.30191723 -2034.37409 0.83955559 2204.252883
Pd2+ -126.2368438 -2095.515285 0.63328753 1662.696169
Ag+-145.6275022 -2114.513658 1.02557279 2692.64097
Hg2+ -42.5030206 -2011.502124 0.91262536 2396.097536
Fig. 9. Structure of neural network adopted in this study.
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
18
The model training based on the quick prob (QP)
learning algorithm was carried out to test the data
set and determine the minimum value of RMSE
as an error function. The regression coefcient of
determination (R2) showed a fairly good correlation
between estimated and experimental data sets for both
train (0.959) and test data sets (0.943) (Figure 10 (A)
and (B)).
Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
Fig. 10. Comersion of estimated logKf with experimental data (a) training data set and (b) test data set.
19
The obtained constant formations of complex
reactions between all metal studied cations and the
proposed ligand using the various mole percentages
of water in H2O-MeOH binary media system at
different temperatures were visualized in Figure 11
by drawing surface and contour plots of the stability
constant (log Kf) for the complex formation as a
function of the mol% of H2O in the binary mixtures
and different studied cationics radius.
As seen in Figure 11, increasing of mol% of water
and cationic radius causes a decrease and an increase
in the constant stability of complexes (log Kf). The
maximum constant formation of complexes was
obtained in zero mol percentage of water (100%
of MeOH) and the highest amount of cationic radii
related to Ag+ cation (1.15Å).This result indicated
that this model is valid for the estimation of
constant stability of complexes of Ni2+, Pd2+, Zn2+,
Hg2+ and Ag+ in MeOH-Water binary mixtures at
different temperatures. The estimated results based
on the ANN program were in a good agreement
with obtaining experimental results.
4. Conclusion
According to the obtained results, the complexation
of Ni2+, Zn2+, Pd2+, Hg2+ and, Ag+ cations with NHC
ligand can be explained in terms of the size-t
concept, where the NHC ligand forms a most stable
complex with a cation having a size which ts best
with its cavity size. The obtained data shows that
in the pure MeOH solvent system the stability
constant is varying as Ni2+< Pd2+<Zn2+<Hg2+<Ag+
and the complexations process seems more
stable in pure MeOH and pure H2O.The result
also showed that in most cases, the NHCLMn+
complexes was enthalpy destabilizer but entropy
stabilizer. The stoichiometry of complexes for
Ni2+, Zn2+, and Pd2+ are 1:1[M:NHCL]. While, for
Hg2+ and Ag+, they have two stoichiometry which
is 1:2[M:NHCL] and 2:1[M:NHCL]. The changes
in the stability constant of the complex versus the
composition of the MeOH-H2O binary system at
various temperatures are not linear in most cases.
However, some results have shown that increment
in stability is constant with the decrease of mol%
MeOH in the solvent system. The effects of mole%
of water and cationic radii of studied cations on the
complexation reactions were investigated and high
correlation between experimental data and ANN
kinetic model was obtained which is a proof of the
high performance of conductometric method for
the complex formation study.
Fig. 11. Surface and contour plots of the stability constant (log Kf) as a function
of the mol% of water and ionic radius of cations (Ni2+, Pd2+, Zn2+, Hg2+ and Ag+)
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
20
5. Acknowledgement
This research was supported by AUA-UAEU
Joint Research Grant Project (IF016-2021 and
G00003485), University Malaya Centre for Ionic
Liquid (UMCiL) and Mashhad University of
Medical Sciences, Mashhad Iran. The author
gratefully acknowledge to Universiti Teknologi
MARA Cawangan Negeri Sembilan,Kampus
Kuala Pilah to pursue postgraduate studies.
6. References
[1] H.W. Wanzlick, H.J. Schönherr, Direct
synthesis of a mercury salt-carbene complex,
Angewandte Chemie International Edition
in English, 7 (1968) 141-142. https://doi.
org/10.1002/anie.196801412
[2] A.J. Arduengo, R.L. Harlow, M. Kline, A
stable crystalline carbene, J. Am. Chem.Soc.,
113 (1991) 361-363. https://doi.org/10.1021/
ja00001a054
[3] R.A. Haque, A. Washeel Salman, New
N-heterocyclic carbene mercury(II)
complexes: Close mercury–arene
interaction, J. Organometal. Chem., 696
(2011) 3507-3512. https://doi.org/10.1016/j.
jorganchem.2011.07.032
[4] C.M. Crudden, D.P. Allen, Stability and
reactivity of N-heterocyclic carbene
complexes, Coor. Chem. Rev., 248 (2004)
2247-2273. https://doi.org/10.1016/j.
ccr.2004.05.013
[5] S. Budagumpi, R.A. Haque, A.W. Salman,
Stereochemical and structural characteristics
of single- and double-site Pd(II)–N-
heterocyclic carbene complexes: Promising
catalysts in organic syntheses ranging from
CC coupling to olen polymerizations,
Coord. Chem. Rev., 256 (2012) 1787-1830.
https://doi.org/10.1016/j.ccr.2012.04.003
[6] M. Rezayi, Y.H. Lee, M.M. Abdi, N.M.D.
Noran, C. Esmaeili, S. B. Tavakoly Sany,
A. Salleh, L. Narimani, N. Saadati, F.
Tajalli, A thermodynamic study on the
complex formation between tris (2-Pyridyl)
methylamine (tpm) with Fe II, Fe III, Cu II
and Cr III cations in water, acetonitrile binary
solutions using the conductometric method,
Int. J. Electrochem. Sci., 8 (2013) 6922-6932.
http://www.electrochemsci.org/
[7] M. Y. Khorasani, H. Langari, S.B. Tavakoly
Sany, M. Rezayi, A. Sahebkar, The role
of curcumin and its derivatives in sensory
applications, Mater. Sci. Eng. C, 103
(2019) 109792. https://doi.org/ 10.1016/j.
msec.2019.109792
[8] S.B. Tavakoly Sany, R. Hashim, A.
Salleh, M. Rezayi, O. Safari, Ecological
quality assessment based on macrobenthic
assemblages indices along West Port,
Malaysia coast. Environ. Earth Sci., 74
(2015) 1331-1341. https://doi.org/10.1007/
s12665-015-4122-3
[9] S.B. Tavakoly Sany, R. Hashim, M. Rezayi,
M.A.Rahman, B.B.M. Razavizadeh, E.
Abouzari-lotf, D.J. Karlen, Integrated
ecological risk assessment of dioxin
compounds. Environ. Sci. Pollut. Res., 22
(2015) 11193-11208. https://doi.org/ 10.1007/
s11356-015-4511-x
[10] J. Houghton, G. Dyson, R.E. Douthwaite,
A.C. Whitwood, B. Kariuki, Structural
variation, dynamics, and catalytic application
of palladium(II) complexes of di-N-
heterocyclic carbene-amine ligands, Dalton
Trans, 28 (2007) 3065-73. https://doi.
org/10.1039/b703248j
[11] C.Y Liao, K.T. Chan, J.Y. Zeng, C.H. Hu,
C.Y. Tu, H.M. Lee., Nonchelate and chelate
complexes of Palladium (II) with N-heterocyclic
carbene ligands of amido functionality,
Organometallics, 26 (2007) 1692-1702. https://
doi.org/10.1021/om0610041
[12] Q.X. Liu, L.X. Zhao, X.J. Zhao, Z.X. Zhao,
Z.Q. Wang, A.H. Chen, X.G. Wang, Silver
(I), palladium (II) and mercury (II) NHC
complexes based on bis-benzimidazole salts
with mesitylene linker: Synthesis, structural
studies and catalytic activity, J. Organomet.
Chem., 731(2013) 35-48. https://doi.
org/10.1016/j.jorganchem.2013.01.026
Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
21
[13] S.B. Tavakoly Sany, R. Hashim, A.
Salleh, O. Safari, A. Mehdinia, M. Rezayi,
Risk assessment of polycyclic aromatic
hydrocarbons in the West Port semi-enclosed
basin (Malaysia), Environ. Earth Sci., 71
(2014) 4319-4332. https://doi.org/10.1007/
s12665-013-2826-9
[14] R.A. Haque, M.A. Iqbal, M.B Khadeer
Ahamed, A.M.S. Abdul Majid, Z.A
Abdul Hameed. Design, synthesis and
structural studies of meta-xylyl linked bis-
benzimidazolium salts: Potential anticancer
agents against’human colon cancer, Chem.
Cent. J., 6 (2012) 68. https://doi.org/
10.1186/1752-153X-6-68
[15] K.A. Abu-Saeh, A.S. Abu-Surrah, H.D.
Tabba, H.A. AlMasri, R.M. Bawadi,
F.M. Boudjelal, L.H. Tahtamouni, Novel
palladium(II) and platinum(II) complexes
with 1H-benzimidazol-2-ylmethyl-N-(4-
bromo-phenyl)-amine: structural studies and
anticancer activity, Eur. J. Med. Chem., 47
(2012) 399-411. https://doi.org/10.1016/j.
ejmech.2011.11.008
[16] R.A. Haque, M.Z. Ghdhayeb, S. Budagumpi,
A.W. Salman, M.B. Khadeer Ahamed,
A.M.S Abdul Majid, Non-symmetrically
substituted N-heterocyclic carbene–Ag(I)
complexes of benzimidazol-2-ylidenes:
Synthesis, crystal structures, anticancer
activity and transmetallation studies, Inorg.
Chim. Acta, 394 (2013) 519-525. https://doi.
org/10.1016/j.ica.2012.09.013
[17] M. Darroudi, M. Gholami, M. Rezayi, M.
Khazaei, An overview and bibliometric
analysis on the colorectal cancer therapy by
magnetic functionalized nanoparticles for
the responsive and targeted drug delivery, J.
Nanobiotechnol., 19 (2021) 1-20. https://doi.
org/10.1186/s12951-021-01150-6
[18] B. Hatamluyi, R. Sadeghian, S.B. Tavakoly
Sany, I. Alipourfard, M. Rezayi, Dual-
signaling electrochemical ratiometric strategy
for simultaneous quantication of anticancer
drugs, Talanta, 234 (2021) 122662. https://
doi.org/10.1016/j.talanta.2021.122662
[19] N. N. Al-Mohammed, Y. Alias, Z.
Abdullah, R.M. Shakir, E.M. Taha, A.
Abdul Hamid, Synthesis and antibacterial
evaluation of some novel imidazole and
benzimidazole sulfonamides, Molecules, 18
(2013) 11978-95. https://doi.org/10.3390/
molecules181011978.
[20] R.E. Douthwaite, J. Houghton, B.M. Kariuki,
The synthesis of a di-N-heterocyclic carbene-
amido complex of palladium(II), Chem.
Commun. (Camb), 10 (2004) 698-9. https://
doi.org/10.1039/b314814a
[21] D.J. Nielsen, K.J. Cavell, B. Skelton,
A. White, A pyridine bridged dicarbene
ligand and its silver (I) and palladium
(II) complexes: synthesis, structures, and
catalytic applications, Inorg. Chim. Acta,
327(2002) 116-125. https://doi.org/10.1016/
S0020-1693(01)00677-6
[22] F.J.B Dit Dominique, H. Gornitzka, A
Sournia-Saquet, C. Hemmert, Dinuclear
gold(I) and gold(III) complexes of bridging
functionalized bis(N-heterocyclic carbene)
ligands: synthesis, structural, spectroscopic
and electrochemical characterizations,
Dalton Trans, (2009) 340-52. https://doi.
org/10.1039/b809943j
[23] U.J. Scheele, S. Dechert, F. Meyer, Bridged
dinucleating N-heterocyclic carbene ligands
and their double helical mercury(II) complexes,
Inorg. Chim. Acta, 359 (2006) 4891-4900.
https://doi.org/10.1016/j.ica.2006.08.048
[24] B.A. Shah, F.A. Christy, P.S. Shrivastav, M.
SanyalShah, Study on complex formation
of dicyclohexyl-18-crown-6 with Mg2+, Ca2+
and Sr2+ in acetonitrile-water binary mixtures
by conductometry, J. Phys. Chem. Sci., 1
(2014) 215777300. https://doi.org/10.15297/
JPCS.V1I2.02
[25] M. Joshaghani, M.B. Gholivand, F. Ahmadi,
Spectrophotometric and conductometric
study of complexation of salophen and some
transition metal ions in nonaqueous polar
solvents, Spectrochim. Acta A, Mol. Biomol.
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
22
Spect., 70 (2008) 1073-1078. https://doi.
org/10.1016/j.saa.2007.10.015
[26] A. Nezhadali, G.Taslimi, Thermodynamic
study of complex formation between 3,5-
di iodo-hydroxy quinoline and Zn2+, Ni2+
and Co2+ cations in some binary solvents
using a conductometric method, Alexandria
Eng. J., 52 (2013) 797-800. htpps://doi.org/
10.1016/j.aej.2013.08.007
[27] M. Rezayi, S. Ahmadzadeh, A. Kassim, L.Y.
Heng, Thermodynamic studies of complex
formation between Co (Salen) ionophore
with chromate (II) ions in AN-H2O binary
solutions by the conductometric method, Int.
J. Electrochem. Sci, 6 (2011) 6350-6359.
http://www.electrochemsci.org/
[28] E. R. Enemo, T.E. Ezenwa, E.C. Nleonu,
Determination of formation constants and
thermodynamic Parameters of chromium (III)
ions with some ligands by conductometry,
IOSR J. Appl. Chem., 12 (2019) 54-58.
htpps://doi.org/ 10.9790/5736-1210015458
[29] M. Rezayi ,Y. Alias, M.M. Abdi, K.
Saeedfar, N. Saadati, Conductance
studies on complex formation between
c-methylcalix[4]resorcinarene and titanium
(III) in acetonitrile-H(2)O binary solutions,
Molecules, 18 (2013) 12041-12050. https://
doi.org/10.3390/molecules181012041
[30] L. Rao, G. Tian, Thermodynamic study
of the complexation of uranium(VI) with
nitrate at variable temperatures, J. Chem.
Thermodyn., 40 (2008) 1001-1006. https://
doi.org/10.1016/j.jct.2008.02.013
[31] S. Jaubert, G. Maurer, Quantitative
NMR spectroscopy of binary liquid
mixtures (aldehyde+alcohol) Part I:
Acetaldehyde+(methanol or ethanol or
1-propanol), J. Chem. Thermodyn., 68
(2014) 332-342. https://doi.org/10.1016/j.
jct.2013.03.022
[32] B. Ghalami-Choobar, N. Mahmoodi, P.
Mossayyebzadeh-Shalkoohi, Thermodynamic
properties determination of ternary mixture
(NaCl+Na2HPO4+water) using potentiometric
measurements, J. Chem. Thermodyn., 57
(2013) 108-113. https://doi.org/10.1016/j.
jct.2012.08.011
[33] M. Rezayi, L.Y. Heng, A. Kassim, S.
Ahmadzadeh, Y. Abdollahi, H. Jahangirian,
Immobilization of ionophore and surface
characterization studies of the titanium (III)
ion in a PVC-membrane sensor, Sensors, 12
(2012) 8806-8814. https://doi.org/10.3390/
s120708806
[34] M. Rezayi, L.Y. Heng, A. Kassim, S.
Ahmadzadeh, Y. Abdollahi, H. Jahangirian,
Immobilization of tris (2 pyridyl)
methylamine in PVC-membrane sensor and
characterization of the membrane properties,
Chem. Cent. J., 6 (2012) 40. https://doi.
org/10.1186/1752-153X-6-40
[35] M. Rezayi, M. Ghasemi, R. Karazhian,M.
Sookhakian, Y. Alias, Potentiometric chromate
anion detection based on Co (SALEN)2
ionophore in a PVC-membrane sensor, J.
Electrochem. Soc., 161 (2014) B129-B136.
https://doi.org/10.1149/2.051406jes
[36] A. Zhuravlev, A. Zacharia, M. Arabadzhi, C.
Turetta, G. Cozzi, C. Barbante, Comparison
of analytical methods: ICP-QMS, ICP-SFMS
and FF-ET-AAS for teh determination of
V, Mn, Ni, Cu, As, Sr, Mo, Cd and Pb in
ground natural waters, Int. J. Environ. Anal.
Chem., 96 (2016) 332–352. https://doi.org/1
0.1080/03067319.2016.1160380
[37] B. Feist, B. Mikula, Preconcentration
of some metal ions with lanthanum-8-
hydroxyquinoline co-precipitation system,
Food Chem., 147 (2014) 225-229. https://doi.
org/10.1016/j.foodchem.2013.09.149
[38] A. Habibiyan, M. Ezoddin, N. Lamei, K. Abdi,
M. Amini, M. Ghazi-khansari, Ultrasonic
assisted switchable solvent based on liquid
phase microextraction combined with micro
sample injection ame atomic absorption
spectrometry for determination of some
heavy metals in water, urine and tea infusion
samples, J. Mol. Liq., 242 (2017) 492–496.
https://doi.org/10.1016/j.molliq.2017.07.043
Anal. Methods Environ. Chem. J. 5 (2) (2022) 5-23
23
[39] Q. Xiong, Y. Lin, W. Wu, J. Hu, Y. Li, K. Xu,
Chemometric intraregional discrimination
of Chinese liquors based on multi-element
determination by ICP-MS and ICP-
OES, Appl. Spectrosc. Rev., 56 (2021) 115-
127. https://doi.org/10.1080/05704928.2020.
1742729.
[40] EH. Evans, J. Pisonero, C.M. Smith, R.N.
Taylor, Atomic spectrometry update: review of
advances in atomic spectrometry and related
techniques, J. Anal. At. Spectrom., 35 (2020)
830–851. https://doi.org/10.1039/d0ja90015j
Electronic Supplementary Material
(ESM: References 41-51)
Analysis of metals based on bidentate bis-NHC ligand Nur Rahimah Said and Majid Rezayi et al
