Synthesis, characterization, and electrochemical behavior of a cobalt(II) salen-like complex

Article abstract of DOI:10.1016/j.poly.2015.05.025

A new tetradentate cobalt(II)-Schiff base complex has been synthesized via the reaction of the ligand 2,2′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(4-((methyl(phenyl)amino)methyl)phenol) with a stoichiometric amount of cobalt(II) acetate tetrahydrate in absolute ethanol. This cobalt(II) complex has been characterized with the aid of several spectroscopic techniques (FT-IR, UV-Vis, and mass spectrometry) as well as by thermal (TGA and DTA) and elemental analysis. Cyclic voltammetry has been employed to examine the redox behavior of the cobalt(II) complex in dimethylformamide (DMF) containing 0.10 M tetra-n-butylammonium tetrafluoroborate (TBABF₄). In addition, the electrogenerated cobalt(I) form of the complex has been (a) employed as a catalyst for the reduction of 1-iododecane and (b) compared with the behavior of cobalt(I) salen. Finally, the cobalt(II) complex has been subjected to anodic electropolymerization onto the surface of a glassy carbon electrode in DMF containing 0.10 M tetra-n-butylammonium perchlorate (TBAP).

Full text of DOI:10.1016/j.poly.2015.05.025

Accepted Manuscript
Synthesis, characterization, and electrochemical behavior of a cobalt(II) salen-
like complex
Ali Ourari, Salima Messali, Brahim Bouzerafa, Yasmina Ouennoughi, Djouhra
Aggoun, Mohammad S. Mubarak, Lauren M. Strawsine, Dennis G. Peters
PII:
S0277-5387(15)00267-3
DOI:
http://dx.doi.org/10.1016/j.poly.2015.05.025
POLY 11324
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
14 February 2015
15 May 2015
Please cite this article as: A. Ourari, S. Messali, B. Bouzerafa, Y. Ouennoughi, D. Aggoun, M.S. Mubarak, L.M.
Strawsine, D.G. Peters, Synthesis, characterization, and electrochemical behavior of a cobalt(II) salen-like complex,
Polyhedron (2015), doi: http://dx.doi.org/10.1016/j.poly.2015.05.025
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Synthesis, characterization, and electrochemical behavior
of a cobalt(II) salen-like complex
a,*
Ali Ourari , Salima Messali , Brahim Bouzerafa , Yasmina Ouennoughi , Djouhra Aggoun ,
a
b
a
a
c
Mohammad S. Mubarak , Lauren M. Strawsine , Dennis G. Peters
d
d,*
a
Laboratoire d'Electrochimie, d'Ingénierie Moléculaire et de Catalyse Rédox (LEIMCR), Faculté de Technologie, Université
Ferhat Abbas Setif-1, Route de Béjaia 19000-Algérie.
b
Laboratoire de Préparation et Modification des Matériaux Polymériques Multiphasiques (LPMMPM), Faculté de
Technologie, Université Sétif-1, Route de Béjaia 19000-Algérie.
c
Department of Chemistry, The University of Jordan, Amman 11942, Jordan.
d
Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
ABSTRACT
A new tetradentate cobalt(II)-Schiff base complex has been synthesized via the
reaction of the ligand 2,2'-((1E,1'E)-(ethane-1,2-diylbis(azanylylidene))bis(ethan-1-
yl-1-ylidene))bis(4-((methyl(phenyl)amino)methyl)phenol) with a stoichiometric
amount of cobalt(II) acetate tetrahydrate in absolute ethanol. This cobalt(II) complex
has been characterized with the aid of several spectroscopic techniques (FT-IR, UV-
Vis, and mass spectrometry) as well as by thermal (TGA and DTA) and elemental
analysis. Cyclic voltammetry has been employed to examine the redox behavior of
the cobalt(II) complex in dimethylformamide (DMF) containing 0.10 M tetra-n-
butylammonium tetrafluoroborate (TBABF
cobalt(I) form of the complex has been (a) employed as a catalyst for the reduction of
-iododecane and (b) compared with the behavior of cobalt(I) salen. Finally, the
4
). In addition, the electrogenerated
1
cobalt(II) complex has been subjected to anodic electropolymerization onto the
surface of a glassy carbon electrode in DMF containing 0.10 M tetra-n-
butylammonium perchlorate (TBAP).
Keywords: Cobalt(II)-Schiff base complex, Cyclic voltammetry, Thermal analysis, Electrocatalytic
reduction of primary alkyl iodide, Anodic formation of a cobalt-containing polymer on glassy carbon
__________
*
Corresponding authors. Tel.: +213 776 28 15 33; fax: +213 36 61 11 54 (A. Ourari). Tel.: +1 812
855 9671; fax: +1 812 855 8300 (D.G. Peters).
E-mail addresses: alourari@yahoo.fr (A. Ourari), peters@indiana.edu (D.G. Peters).

2
1. Introduction
Schiff bases continue to play a significant role in coordination chemistry [1],
owing especially to the attractive chemical and physical properties of metal-Schiff
base complexes [2]. Symmetrical Schiff bases, particularly tetradentate species (such
as salen) with four donor heteroatoms, have been extensively studied [3], due to their
ability to coordinate with and to stabilize many different metals in a variety of
oxidation states. In addition, metal-Schiff base complexes can be employed to modify
the surfaces of electrodes for anodic and cathodic processes [4–11]. Transition-metal
complexes of tetradentate Schiff bases display a wide range of applications in the
areas of catalysis [12] and electrocatalysis [13] and for the activation of small
molecules such as carbon dioxide [14] and molecular oxygen [15].
Coordination chemistry of cobalt(II)-Schiff base complexes has been
investigated in recent years [16]. Such complexes have been vigorously explored due
to their ability to serve as homogeneous and heterogeneous catalysts for a number of
oxidation and reduction reactions [17,18]. Additionally, electropolymerization of
cobalt complexes has been explored as an effective method for the modification of
electrode surfaces; such tailoring of an electrode surface by a symmetric cobalt(II)-
Schiff base possessing an aniline moiety was first investigated by Horwitz and
Murray [4].
Electrogenerated cobalt(I) salen has been employed as a homogeneous catalyst
for the reduction of halogenated organic compounds, including iodoethane [19],
benzyl chloride [3], 1,3-dibromopropane [5], 1,4-dibromobutane [5], 1,8-diiodooctane
[
6], and 2,6-bis(chloromethyl)pyridine [7]. For each of these systems, it was
demonstrated that the electrogenerated cobalt(I) salen species attacks the substrate to

3
form an organocobalt(III) salen intermediate, which subsequently undergoes further
reduction to afford the desired products.
As a continuation of our recent work [8] on the synthesis and study of a
nickel(II) complex possessing a Schiff-base ligand, we describe herein the
preparation, characterization, and electrochemical properties of a new tetradentate
cobalt(II)-Schiff base complex bearing an aniline moiety. Scheme 1 depicts the key
reaction between the ligand (1) and cobalt(II) acetate tetrahydrate that is involved in
the synthesis of the complex (2). This complex has been characterized with the aid of
a number of spectroscopic techniques (FTIR, UV–Vis, and mass spectrometry) as
well as by means of elemental and thermal analysis. In addition, we probed the
electrochemical behavior of 2 at glassy carbon cathodes with the aid of cyclic
voltammetry, and an initial exploration of the catalytic reduction of 1-iododecane by
the electrogenerated cobalt(I) analogue of 2 was conducted. Finally, the oxidative
polymerization of 2 onto a glassy carbon electrode has been briefly investigated.
2
. Experimental
2.1. Reagents and instrumentation
All chemicals for synthesis of the ligand (1) and its cobalt(II) complex (2)
were obtained from commercial sources and were used without further purification.
For electrochemical work, dimethylformamide (DMF, 99.9%, EMD Chemicals) was
4
used as received. Tetra-n-butylammonium tetrafluoroborate (TBABF ) and tetra-n-
butylammonium perchlorate (TBAP), used as supporting electrolytes, were
recrystallized from water–methanol and stored in a vacuum oven at 70–80 °C for a
minimum of 48 h to remove traces of water.

4
Purity of the synthesized Schiff base (1) was checked by means of TLC with
glass plates, precoated with silica gel (60F, Merck). High-resolution mass spectra
(
HRMS) for both 1 and the cobalt(II) complex (2) were acquired via electrospray
ionization–mass spectrometry (ESI–MS) with the aid of a Bruker APEX-2 instrument.
Perkin-Elmer 1000 and Unicam UV-300 spectrophotometers were employed,
respectively, to record FT–IR and UV-visible spectra. Using a EuroVector EA3000
elemental analyzer, we determined the C, H, and N content of 2; the results agreed
with the calculated percentages to within ±0.4%. Thermogravimetric analysis (TGA)
and differential thermal analysis (DTA) for both 1 and 2 were carried out with a
–
1
Perkin-Elmer instrument; measurements were done at a heating rate of 10 °C min
–
1
under a dry nitrogen atmosphere at a flow rate of 50 mL min over the temperature
range of 20–1000 °C.
2.2. Electrochemistry
Procedures and data acquisition methods for cyclic voltammetry have been
described in previous publications [20,21]. Cyclic voltammetry experiments were
carried out in a one-compartment (undivided) cell described in an earlier paper [20].
We fabricated a planar, circular glassy carbon working electrode, with a geometric
2
area of 0.071 cm , by press-fitting a short piece of glassy carbon rod (Grade GC-20,
3.0-mm-diameter, Tokai Electrode Manufacturing Company, Tokyo, Japan) into the
end of a machined Teflon tube; electrical contact to this working electrode was made
via a 3.0-mm-diameter stainless-steel pole that extended upward through the tube. A
coil of platinum wire served as the auxiliary (counter) electrode. Our reference
electrode consisted of a cadmium-saturated mercury amalgam in contact with DMF
saturated with both cadmium chloride and sodium chloride, which has a potential of

5
–0.76 V vs. an aqueous saturated calomel electrode (SCE) at 25 °C [22–24]; however,
all potentials in this paper have been converted to the SCE scale.
2.3. Synthesis of the cobalt(II) complex of 2,2'-((1E,1'E)-(ethane-1,2-
diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(4-
((methyl(phenyl)amino)methyl)phenol)
2
Preparation of the Schiff-base ligand (H L, 1) was carried out by means of the
method described in a previous publication [8]. Synthesis of the cobalt(II) complex of
this Schiff base was accomplished according to the following procedure: 200 mg
(
0.374 mmol) of 1 was dissolved in 10 mL of absolute ethanol, and the solution was
transferred to a 50-mL three-necked flask fitted with a reflux condenser. After an
ethanolic solution (10 mL) of 93 mg (0.374 mmol) of cobalt(II) acetate tetrahydrate
was added dropwise to the solution of the ligand, the stirred mixture was refluxed for
20 h. After being cooled to room temperature, the solution was reduced to half of its
original volume and was stored in a refrigerator overnight. Finally, the green
precipitate was collected by filtration, washed with ethanol, and dried under reduced
pressure for several hours to afford the desired complex (2) in 56% yield before being
–
1
–1
characterized: (a) UV-Vis: λmax(n) (nm), εmax(n) [M cm ]: λmax(1) (235), εmax(1)
[
(
11830]; λmax(2) (256), εmax(2) [4750]; λmax(3) (361), εmax(3) [1410]; (b) IR (KBr): ν
x
–
1
cm ): νC–H(aliph) (2900–3000), νC=N (1576), νCH –N (1302), νC–O (1370), νNi–O (525).
2
+
ν
Ni–N (478); (c) HRMS (ESI) m/z: calcd. for C34
found 614.20657; (d) anal. calculated for C38 46CoN
O): C, 61.20; H, 6.22; N, 7.51, found: C, 61.49; H, 6.08; N, 7.33. Repeated
efforts to grow a single crystal of 2, suitable for structural analysis, were unsuccessful.
H36CoN
4
NaO
2
: [M + Na] 614.20680,
H
4 8 3
O (i.e., Co(II)L + 2 CH COO +
2
H
2

6
3. Results and discussion
3.1. Chemistry
Synthesis of the Schiff base (1) was accomplished as described in a previous
publication [8]. Depicted in Scheme 1 is the reaction used to prepare the desired
cobalt(II)-Schiff base complex (2), the structure of which was confirmed with the aid
of several spectroscopic techniques, including UV-Vis, FT-IR, and mass
spectrometry.
3
.2. Spectroscopy
It is possible to explain the IR spectrum of the cobalt(II)-Schiff base complex
2) by comparison with spectral data for similar structures [9] and of the Schiff base
(
–1
itself [8]. Absorption in the region from 2900 to 3000 cm is due to the νC–H(aliph)
vibration. There is a shift in the frequency of the azomethine band (νC=N) from 1616
–1
to 1576 cm , which indicates that the nitrogen atom of the azomethine group is
coordinated to cobalt(II). This bathochromic shift can be explained by the increase in
electron delocalization through the newly coordinated metal center [10,11].
Moreover, the νCH –N absorption band is shifted to higher wavenumbers (1295–1302
2
–
cm ), due to coordination of the metal ion through the nitrogen atoms of the
1
–1
azomethine groups [25]. In addition, the new bands at 470–490 cm and 530–550
–
1
cm can be assigned to Co–N [26] and Co–O [27] vibrations, respectively,
confirming the tetradentate coordination of cobalt(II) to the ligand [28]. Finally, a
–1
broad absorption band centered at 3436 cm can be assigned to water molecules
coordinated to cobalt(II) [29].
In DMSO the electronic absorption spectrum of the cobalt(II) complex
exhibits an intense band centered at 256 nm, assigned to n–π* transitions of the

7
azomethine group, whereas a second band, observed at 361 nm, corresponds to
ligand-to-metal charge transfer [30].
A FAB-mass spectrum of the cobalt(II) complex displayed the following
+
major signals: m/z = 614.2070 (observed), 614.2068 (calculated), [M + Na] (42%);
+
N] (100%); and 107.0728
485.1517 (observed), 485.1514 (calculated), [M – C
7
H
8
+
N] (28%). In addition, a peak, identical in
(
observed), 107.0735 (calculated), [C
7
H
9
magnitude to that seen at m/z 485.1517, was detected at m/z 1205.4218 (observed),
1205.4238 (calculated), suggesting the presence of a binuclear form of the complex
+
with an accompanying sodium, i.e., [2M + Na] .
3.3. Thermal analysis
In the present study, thermal analyses (both TGA and DTA) were performed
to obtain information about the stabilities of 1 and 2 as well as to establish the
presence of water molecules either inside or outside the inner coordination sphere of
cobalt(II). To perform these measurements, the temperature was increased from
–
1
ambient to 950 °C, at a rate of 10 °C min under a nitrogen atmosphere, and the
resulting TGA and DTA curves for 1 and 2 are depicted in Fig. 1 and Fig. 2,
respectively. In addition, mass losses obtained from the TGA curves are compiled in
Table 1, together with species proposed to account for these mass losses, which shows
that observed and calculated values are in good agreement. For the ligand (1), the
TGA curve revealed a mass loss of 38.46% (calculated 39.70%) over the temperature
range of 200–332 °C, which can be attributed to loss of two fragments (C
derived from N-methylaniline. In the temperature range of 332–532 °C, the ligand
loses a C O fragment, as indicated by a mass loss of 24.61% (calculated 24.91%).
7 8
H N)
9
H
9
For the cobalt(II) complex (2), two water molecules of hydration are lost in the
temperature range of 128–186 °C, but any water molecules coordinated directly to

8
cobalt(II) would be eliminated at higher temperatures [31]. As seen for higher
temperatures in Table 1, the complex undergoes further decomposition in several
steps with the loss of one or more fragments (acetate, N-methylaniline, C
7 5
H O, and
5 9
C H
N), which eventually leads to production of cobalt oxides.
3.4. Cyclic voltammetric behavior of the cobalt(II) complex
Displayed in Fig. 3 is a cyclic voltammogram recorded at a scan rate of 100
–
mV s for reduction of a 1.25 mM solution of the cobalt(II) complex alone in
1
oxygen-free DMF containing 0.10 M TBABF at a freshly polished glassy carbon
4
electrode. For this cyclic voltammogram, the most important feature is the reversible
cobalt(II)–cobalt(I) redox couple with a cathodic peak potential (Epc) of –1.39 V, an
p
anodic peak potential (Epa) of –1.28 V, and a peak separation (∆E = Epa – Epc) of 110
mV. These observations are comparable to those observed in an earlier study [19] of
the reversible one-electron reduction of cobalt(II) salen (Epc = –1.32 V, Epa = –1.23 V,
p
∆E = 90 mV) under similar experimental conditions. At more negative potentials,
one sees a small irreversible cathodic peak (Epc = –1.74 V) and a second much larger
cathodic peak (Epc = –2.66 V), both of which we attribute to reduction of the ligand;
indeed these two features are observed when a cyclic voltammogram is recorded for
the ligand by itself in the solvent–supporting electrolyte. Moreover, the cyclic
voltammetric characteristics of the cobalt(II) complex are remarkably similar to those
of the corresponding nickel(II) complex that were reported previously [8].
We have investigated the electrochemical behavior of the cobalt(II) complex
with emphasis on the reversible cobalt(II)–cobalt(I) redox couple in the region of
–
1
potentials around –1.30 V. As the scan rate (v) was increased from 50 to 500 mV s ,
the peak separation (∆E ) became larger, as expected, increasing from 110 to 310 mV,
which indicates that the electron-transfer process is intrinsically sluggish. A plot of
p

9
1
the cathodic peak current (Ipc) versus v was linear, revealing that reduction of the
/2
cobalt(II) complex is a diffusion-controlled process.
3
.5. Cyclic voltammetric behavior of the cobalt(II) complex in the presence of
-iododecane
1
When the cobalt(II) complex (1.25 mM) was reduced at a freshly polished
glassy carbon electrode in the presence of 2.00 mM 1-iododecane in DMF–0.10 M
TBABF , the cyclic voltammograms shown in curve B of Fig. 4 was recorded.
4
Comparison of curve A (obtained in the absence of 1-iododecane) with curve B
reveals that the cathodic peak for reduction of the cobalt(II) complex does not
increase substantially in size, but does shift from –1.39 to –1.30 V, which is
attributable to the interaction between the electrogenerated cobalt(I) complex and
1
-iododecane to afford a decylcobalt(III) species [19]; in addition, the anodic peak for
reoxidation of the cobalt(I) complex disappears. A large irreversible peak, due to
reduction of the decylcobalt(III) intermediate is seen at a more negative potential
(
–1.81 V). As illustrated in curve C of Fig. 4, raising the concentration of
-iododecane to 5.00 mM causes an increase in current for the peak at –1.81 V, but
1
does not alter the size or potential of the peak at –1.30 V; these observations mimic
closely those reported in earlier work dealing with the cobalt(I) salen-catalyzed
reduction of iodoethane [19].
3.6. Electrooxidative formation of a polymer-coated electrode
Anodic polymerization of the cobalt complex onto the surface of a freshly
polished glassy carbon electrode was explored by sequential scanning of the potential
from 0 V to +1.5 V and then to –1.8 V vs. SCE. Shown in Fig. 5 are the first 10
–
consecutive scans recorded, without interruption, at 100 mV s for such an
1

10
experiment with a 2.00 mM solution of the cobalt(II) complex in DMF containing
.10 M TBAP. For the first potential cycle, depicted by the dotted curve in Fig. 5,
0
one sees a pair of anodic waves at approximately +1.0 and +1.4 V that we associate,
respectively, with oxidation of cobalt(II) to cobalt(III) and with oxidative
polymerization of the salen-like ligand to produce a film on the surface of the glassy
carbon electrode; these voltammetric features appear to resemble those described in
earlier studies of the anodic polymerization of nickel(II) salen onto glassy carbon
surfaces [32–34]. For the subsequent negative-going portion of this first cycle (dotted
curve), a cathodic shoulder at –1.2 V and a Gaussian-shaped peak at –1.6 V are
observed; interestingly, however, and unlike the previously described behavior [34] of
an anodically formed poly[nickel(III) salen] film, no cathodic peaks are seen
anywhere in the potential region from +1.5 to –0.5 V in Fig. 5. Our suggested
interpretation of the cathodic response in the region of potentials from –0.5 to –1.8 V
is that there is sequential reduction of polymer-bound cobalt(III) to polymer-bound
cobalt(II), followed by reduction of the soluble cobalt(II)-Schiff base species (2) and
then by reduction of polymer-bound cobalt(II) to cobalt(I). As the potential is
scanned from –1.8 to –1.0 V, some reoxidation of cobalt(I) to cobalt(II) must occur
before the start of the second complete potential scan. From the second to the tenth
scan in Fig. 5, there is very little change in the appearance of the cyclic voltammetric
response; indeed the only notable difference is the 200-mV shift of the most cathodic
peak to a less negative potential.
4. Conclusions

11
In this work, we have synthesized a novel complex of cobalt(II) with a salen-
like ligand that bears two pendant anilinic moieties. This new compound has been
characterized with the aid of FT-IR, UV-Vis, and mass spectrometric techniques,
along with elemental and thermal analyses. At a glassy carbon electrode in DMF
4
containing 0.10 M TBABF as supporting electrolyte, the cobalt(II) complex displays
reversible one-electron reduction to the corresponding cobalt(I) species. In the
presence of 1-iododecane, the cobalt(I) form of the complex serves as an
electrogenerated catalyst for reduction of the alkyl iodide. We believe the catalytic
process involves formation of a decylcobalt(III) intermediate which is subsequently
reduced at a more negative potential to a decylcobalt(II) monoanion; the latter
decomposes to regenerate the active cobalt(I) catalyst and to give a decyl radical that
leads to three products (n-eicosane, n-decane, and 1-decene). Because the parent
cobalt(II) complex possesses anodically polymerizable anilinic substituents, we
believe that it should be possible to construct modified electrodes for use as sensors
and for heterogeneous catalysis.
Acknowledgments
Appreciation is expressed to Professor Marcel Hibert and Dr. Laurent
Désaubry (Laboratoire d’Innovation Thérapeutique, Faculté de Pharmacie, Université
de Strasbourg, France) for their valuable assistance with spectroscopic analyses.
M.S.M. acknowledges financial support from The University of Jordan during his
sabbatical year (2014–2015) at Indiana University.

12
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31] N.T. Abdel-Ghani, O.E. Sherif, Thermochim. Acta 156 (1989) 68.

14
[
32] F. Bedioui, E. Labbe, S. Gutierrez-Granados, J. Devynck, J. Electroanal. Chem.
301 (1991) 267.
[
[
33] C.E. Dahm, D.G. Peters, Anal. Chem. 66 (1994) 3117.
34] C.E. Dahm, D.G. Peters, J. Simonet, J. Electroanal. Chem. 410 (1996) 163.

15
CAPTIONS FOR SCHEME AND FIGURES
Scheme 1. Reaction of Schiff base (1) with cobalt(II) acetate tetrahydrate in ethanol
to afford the cobalt(II)-Schiff base complex (2).
Fig. 1. Thermogravimetric analysis (TGA, upper panel) and differential thermal
analysis (DTA, lower panel) curves for the ligand (1).
Fig. 2. Thermogravimetric analysis (TGA, upper panel) and differential thermal
analysis (DTA, lower panel) curves for the cobalt(II) complex (2).
–
Fig. 3. Cyclic voltammogram recorded at 100 mV s for reduction of a 1.25 mM
1
solution of the cobalt(II)-Schiff base complex (2) with a freshly polished glassy
2
carbon electrode (area = 0.071 cm ) in oxygen-free DMF containing 0.10 M TBABF
4
.
Scan goes from –0.75 to –2.80 to –0.75 V vs. SCE.
–
Fig. 4. Cyclic voltammograms recorded at 100 mV s for a 1.25 mM solution of the
1
cobalt(II)-Schiff base complex (2) with a freshly polished glassy carbon electrode
2
area = 0.071 cm ) in oxygen-free DMF containing 0.10 M TBABF
(
4
and different
concentrations of 1-iododecane: (A) no 1-iododecane; (B) 2.00 mM 1-iododecane;
C) 5.00 mM 1-iododecane. Scan A goes from –0.75 to –2.00 to –0.75 V vs. SCE;
(
scan B goes from –0.75 to –2.20 to –0.75 V vs. SCE; scan C goes from –0.75 to –1.93
to –0.75 V vs. SCE.

16
CAPTIONS FOR SCHEME AND FIGURES (continued)
–1
Fig. 5. Cyclic voltammetric electropolymerization at a scan rate of 100 mV s of the
cobalt(II) complex (2.00 mM) in DMF containing 0.10 M TBAP at a freshly polished
2
glassy carbon electrode (area = 0.071 cm ). Note that the first of 10 consecutive scans
is denoted by the dotted curve, and the arrow indicates that each successive scan
begins at 0 V, goes to +1.50 V, then to –1.80 V, and back to 0 V vs. SCE.

17
Scheme 1
Ourari, Messall, Ouennoughi,
Aggoun, Bouzerafa, Mubarak,
Strawsine, and Peters
“Synthesis, characterization, and
electrochemical behavior of a
cobalt(II) salen-like complex”

18
Figure 1
Ourari, Messall, Ouennoughi,
Aggoun, Bouzerafa, Mubarak,
Strawsine, and Peters
“Synthesis, characterization, and
electrochemical behavior of a
cobalt(II) salen-like complex”

19
Figure 2
Ourari, Messall, Ouennoughi,
Aggoun, Bouzerafa, Mubarak,
Strawsine, and Peters
“Synthesis, characterization, and
electrochemical behavior of a
cobalt(II) salen-like complex”

20
Figure 3
Ourari, Messall, Ouennoughi,
Aggoun, Bouzerafa, Mubarak,
Strawsine, and Peters
“Synthesis, characterization, and
electrochemical behavior of a
cobalt(II) salen-like complex”

21
Figure 4
Ourari, Messall, Ouennoughi,
Aggoun, Bouzerafa, Mubarak,
Strawsine, and Peters
“Synthesis, characterization, and
electrochemical behavior of a
cobalt(II) salen-like complex”

22
Figure 5
Ourari, Messall, Ouennoughi,
Aggoun, Bouzerafa, Mubarak,
Strawsine, and Peters
“Synthesis, characterization, and
electrochemical behavior of a
cobalt(II) salen-like complex”

23
Table 1
Ourari, Messall, Ouennoughi,
Aggoun, Bouzerafa, Mubarak,
Strawsine, and Peters
“Synthesis, characterization, and
electrochemical behavior of a
cobalt(II) salen-like complex”
Table 1
Results of thermogravimetric analysis (TGA) of the ligand (1) and its cobalt(II)
complex (2).
–
–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
Compound Temperature Mass loss (%)
range (°C)
Proposed species lost
–
––––––––––––––––––
Observed Calculated
–
–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
1
200–332
32–532
38.46
24.61
39.70
24.91
7 8
2 C H N
3
9 9
C H O
2
128–186
5.07
4.83
2
2 H O
1
3
4
6
86–350
50–473
73–640
40–820
30.35
14.64
14.64
11.42
30.19
14.36
14.10
11.15
2 OAc + N-methylaniline
N-methylaniline
C
7
5
H
5
O
N
C
H
9
–
–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

24
Graphical abstract
A new cobalt(II)-Schiff base complex has been prepared and characterized;
its electrochemistry has been investigated, catalytic reduction of 1-iododecane
by the corresponding electrogenerated cobalt(I) species has been probed,
and the complex has been anodically polymerized onto glassy carbon.