New organocobaloxime derivatives - Synthesis, characterization, catalase-like activity and DFT studies

Article abstract of DOI:10.1016/j.jorganchem.2014.01.023

New organocobaloxime derivatives of the types [Co(HL)₂(Bz)Py] and [CoL₂(Bz)PyB₂F₄] [H₂L = 4-(4-chlorophenylamino)biphenylglyoxime; Bz = Benzyl; Py = Pyridine] were synthesized and characterized by ele

Full text of DOI:10.1016/j.jorganchem.2014.01.023

Accepted Manuscript
New Organocobaloxime Derivatives – Synthesis, Characterization, Catalase-like
Activity and DFT Studies
Mukadder Erdem-Tunçmen, Fatma Karipcin, Murat Atiş, Sabriye Perçin-Özkorucuklu
PII:
S0022-328X(14)00038-2
10.1016/j.jorganchem.2014.01.023
JOM 18464
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 6 September 2013
Revised Date: 14 January 2014
Accepted Date: 18 January 2014
Please cite this article as: M. Erdem-Tunçmen, F. Karipcin, M. Atiş, S. Perçin-Özkorucuklu, New
Organocobaloxime Derivatives – Synthesis, Characterization, Catalase-like Activity and DFT Studies,
Journal of Organometallic Chemistry (2014), doi: 10.1016/j.jorganchem.2014.01.023.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Two new organocobaloxime derivatives synthesized and characterized by elemental, thermal
1
analysis, FT-IR, H NMR, magnetic susceptibility measurements, cyclic voltammetry and
DFT calculations. The experimental and theoretical chemical shift results are generally in
good agreement. Synthesized compounds were also evaluated for their catecholase-like
activity.

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
New Organocobaloxime Derivatives – Synthesis, Characterization,
Catalase-like Activity and DFT Studies
Mukadder Erdem-Tunçmena, Fatma Karipcinb*, Murat Atişc, Sabriye Perçin-
Özkorucuklua
aDepartment of Chemistry, Sciences and Arts Faculty, Süleyman Demirel University, 32260,
Isparta-TURKEY
bDepartment of Chemistry, Sciences and Arts Faculty, Nevsehir Hacı Bektaş Veli University,
50300, Nevsehir-TURKEY
cKayseri Vocational School, Erciyes University, 38039 Melikgazi, Kayseri-TURKEY
*Tel: +90 384 2153900 Fax: +90 384 2153948 E-mail: fkaripcin@nevsehir.edu.tr
Abstract
New organocobaloxime derivatives of the types [Co(HL)2(Bz)Py] and [CoL2(Bz)PyB2F4]
[H2L = 4-(4-chlorophenylamino)biphenylglyoxime; Bz = Benzyl; Py = Pyridine] were
synthesized and characterized by elemental analysis, molar conductance, FT-IR, 1H NMR and
magnetic susceptibility measurements. The structural and vibrational spectroscopic data of the
molecule in the ground state were calculated by the density functional method using the 6-
31G(d) basis set. Isotropic chemical shifts (1H and 13C NMR) were calculated using the
gauge-invariant atomic orbital (GIAO) method. In addition, the thermal decomposition of
complexes with H2L was studied in nitrogen atmosphere. The IR spectra indicated that the
complexes coordinate through the N atom of the oxime group of the ligand. The diamagnetic
susceptibilities of the complexes indicated that they are diamagnetic (low-spin d6 octahedral).
The catalase-like activities of the complexes for the disproportionation of hydrogen peroxide
were investigated in the presence of imidazole. The redox behaviors of the ligand and its
complexes were investigated by cyclic voltammetry at the platinum electrode in DMF.

ACCEPTED MANUSCRIPT
+
Keywords: Organocobaloximes, BF2 bridged, catalase-like activity, CV, DFT, B3LYP
1. Introduction
The chemistry of oxime/oximato metal complexes has been investigated actively since the
time of the first synthesis, e.g. preparation of nickel(II) dimethylglyoximate, and recognition
of the chelate five-membered character of this complex by Tschugaeff [1] and has been
reviewed in several studies [2-5]. Oximes and their metal complexes are of current interest for
their rich physicochemical properties, reactivity patterns and potential applications in many
important chemical processes in the areas of medicine, bioorganic systems, catalysis,
electrochemical and electrooptical sensors [6].
Vitamin B12 is one of the naturally occurring coordination compounds in biology. The
active component of liver extract was first separated and finally crystallized in 1948 [7, 8]. In
1965, Dorothy Hodgkin determined the structure crystallographically. The successful
determination of the molecular structure of coenzyme B12 provided an unexpected surprise in
that it contained an apparently stable carbon–cobalt bond. This is the only naturally occurring
organometallic compound. An intriguing aspect of the B12 system is the great stability of the
carbon–cobalt bond. Although the alkyl–cobalt bond in alkyl cobalamins is surprisingly
stable, it can be cleaved and transferred into a number of other chemical species. The
organometallic chemistry of cobalt in vitamin B12 and its derivatives is unusual and
interesting. The most commonly mentioned B12 model system is the
bis(dimethylglyoximato)cobalt complex. These complexes are often referred to as
cobaloximes. The common feature of the different models is that each possesses a very strong
equatorial ligand field [8].
The organocobaloximes RCo(DH)2L, where R = alkyl group, DH = monoanion of
dimethylglyoxime and L = neutral ligand, were synthesized at the beginning of the 1960s [9].
2

ACCEPTED MANUSCRIPT
The immediately became the subject of extensive studies, because they were considered as
good models of vitamin B12 [10-27].
In this paper, we report on the synthesis, characterization and thermal stabilities of a series
of
cobalt(III)
glyoximato
complexes
using
the
dioxime
ligand
[4-(4-
chlorophenylamino)biphenylglyoxime], axial base (py) and benzyl as alkyl. Additionally we
+
prepared BF2 -bridge containing complexes by replacing the bridging protons of the
cobalt(III)–dioxime complex with the BF2 group. Particularly significant in this work is the
inclusion of the BF2 bridge group, which we anticipated would generate some unique
structural diversity. We also report the results of the calculated structure, the vibrational and
NMR spectra of the title molecules, the calculations being made on the basis of the density
functional theory (DFT) approximations. In a subsequent paper, we will be reporting studies
on the use of organocobaloxime analogues as models of vitamin B12.
2. Results and discussion
2.1. Synthesis
The ligand [4-(4-chlorophenylamino)biphenylglyoxime](Fig. 1) was obtained by the
reaction of p-chloroaniline with 4-biphenylchloroglyoxime in the presence of triethylamine.
1
The product, a yellow powder material, was characterized by IR, H NMR spectroscopy and
elemental analyses. Attempts to isolate crystals of the complexes suitable for X-ray
diffraction were unsuccessful. Therefore, elemental analysis, spectroscopic techniques,
conductivity and magnetic susceptibility techniques were employed in order to determine the
structural characteristics of the complexes. The analytical and physical data for the ligand and
its complexes are in good agreement with expected values.
The molar conductance of the complexes was an aid for their proposed formulas. The
conductivity measurements of the complexes were determined using freshly prepared
3

ACCEPTED MANUSCRIPT
solutions of the complexes in DMF at room temperature. The values of the molar conductance
in DMF in 10-3 mol L-1 solutions are 20 and 30 Ω-1 cm2 mol-1, suggesting a non-electrolytic
nature for mononuclear complexes (respectively 1, 2) [28,29].
The magnetic susceptibility measurements of the complexes were carried out in the solid
state at room temperature and provided information regarding their structures. The magnetic
susceptibility measurements showed that the mononuclear cobalt complexes (1, 2) are
diamagnetic, which corresponds to the +3 oxidation state of cobalt (low spin octahedral d6-
system, S = 0).
2.2. IR Spectra
The observed IR spectra of the free ligand and its complexes exhibit various bands in the
400–4000 cm-1 region. The theoretical wavenumbers along with their relative intensities are
given as Supporting Information in Tables S1-S3. Because there was no imaginary frequency
for the stationary points, the optimized structures were accepted as real minimums. To bring
the theoretical values closer to the experimental values, we used two different scaling factors,
i.e. 0.983 up to 1700 cm-1 and 0.958 for greater than 1700 cm-1 [30]. The observed IR
spectrum of the dioxime ligand showed a υ(C=N) peak at 1596 and 1635 cm-1 and a υ(N-O)
peak at 1092 cm-1, as reported for similar ligands [31–33]. The appearances of two bands for
the C=N groups indicate the asymmetrical nature of the free ligands. The appropriate
calculated frequencies of υ(C=N) are positioned at 1520 and 1634 cm-1 and υ(N-O) is
positioned at 1093 cm-1, when the DFT/B3LYP/6-31G(d) method was applied.
The bands are assigned to the υ(C=N) stretching frequency shift to 1575 and 1590–1592
cm-1 in the complexes. These bands are shifted to lower wavenumbers in the complexes.
Burger et al. [34] reported, on the basis of the frequency shift of the C=N vibrations that the
lower the C=N vibration frequency, the stronger the metal → N=C donor π-bond. The results
4

ACCEPTED MANUSCRIPT
suggest that the increase in electron density on the cobalt causes the increase of back donation
from cobalt to the nitrogen atoms of the dioxime ligands, resulting in the increase in
conjugation of the five-membered chelate rings. The same vibrations appear in the theoretical
calculation at 1591-1554 and 1615-1620 cm-1. Similar trends have been reported in the
literature for cobaloxime derivatives [33, 34]. The υ(N–O) stretching frequencies shift to
1011-1091 cm-1 in the complexes and their corresponding calculated wavenumbers appeared
at 1096 and 1094 cm-1.
The coordination of the axial electron donating base to the Co atom causes an increase in
electron density in the Co atom. This facilitates the back donation from Co to the nitrogen
atoms of the dioxime ligands, resulting in an increase in electron densities in the C=N and N–
O bonds. The increase in electron density in N–O bonds causes stronger hydrogen bridges of
O–H…O and the higher frequency shifts of N–O stretching vibrations. The facilitated back
donation from cobalt to the nitrogen atoms of the dioxime ligand results in increased metal-
donor π-bond in the equatorial moiety of cobaloximes, which causes the stronger interaction
of Co with equatorial N atoms and brings about conjugation in the five-membered chelate
rings including Co atom, resulting in lower frequency shift of the υ(C=N) vibrations [33, 35,
36]. The spectra of all the complexes exhibit a new band at around 500 cm-1 (498 and 515
cm-1) which is not found in the spectrum of free ligand. In agreement with IR spectral studies
on cobaloximes this band is assigned to Co–N stretching frequency between Co and the
nitrogen atoms of the dioxime ligands. We assigned a band due to the Co–N stretching based
on the TED calculations, and obtained bands at 480 and 483 cm-1 in the complexes.
In the mononuclear complex (1), (Fig. 2) the υ(O–H) band due to the O–H…O hydrogen
bridges in the ligand is assigned at 3400 cm-1 and it appears as a very broad band. The IR
+
+
spectrum of the BF2 bridged complex (2) (Fig. 3) did not show this band. In the BF2 bridged
complex (2), bands at 1123 and 1035 cm-1 were observed for the B-O and B-F resonances,
5

ACCEPTED MANUSCRIPT
respectively [32, 37, 38]. Their corresponding calculated wavenumbers appeared at 1142 and
1036 cm-1. Details of the non-discussed modes are given as Supplementary Data in Tables
S1-S3. The majority of the theoretical FT-IR values show good agreement with experimental
values.
2.3. 1H NMR Spectra
1
The theoretical H NMR chemical shift values are given in Table 1. The atom positions
are numbered in Fig. 1-3. The NMR spectra recognized that accurate predictions of molecular
geometries are essential for reliable calculations of magnetic properties. Therefore the
molecular structures of the title compounds were optimized before NMR calculations. Then,
1
gauge-including atomic orbital (GIAO) H NMR chemical shift calculations were carried out
by using the DFT/B3LYP functional with the 6-31G(d) basis set. In the 1H NMR spectrum of
the ligand, the chemical shifts due to OH, NH and the phenyl ring hydrogens were observed at
δ = 8.10, 7.03 and 7.15-7.68 ppm respectively. Their corresponding calculated chemical shifts
appeared at 6.49 ppm for NH, at 7.30 and 5.75 ppm for OH and at 7.27-7.74 ppm for the
1
phenyl ring. However, in the Cl bonded phenyl ring the H NMR spectrum values decreased
1
to the 6.50-7.09 ppm range. The H NMR spectrum of complex (1) shows a singlet at 7.03
and 9.95 ppm assigned for hydrogen bonded NH and OH protons, respectively. These values
were calculated as 5.54, 5.55 ppm for NH and as 13.04, 13.14 ppm for OH bonds. Chemical
shifts for the hydrogen of the aromatics were assigned in the 7.05-7.59 region [15, 39, 40].
Additional signals at 7.81-8.43 ppm were caused by the coordinated pyridine molecule. They
are theoretically found in the 6.53-7.57 ppm range for phenyl rings. Only the H14 and H47
atoms in the phenyl ring have the chemical shifts at 8.50 and 8.40 ppm, respectively. In the Cl
1
1
bonded phenyl rings, H NMR spectrum values decrease to 5.58-7.04 ppm range. In the H
NMR spectrum of complex (2), the deuterium exchangeable O–H…O bridged protons
6

ACCEPTED MANUSCRIPT
+
belonging to the H-bonded dioxime complex were BF2 bridged derivatives. The other
chemical shifts in this complex, which belong to aromatic, aliphatic and NH protons, were
1
very similar to this hydrogen-bonded Co(III) complex. In the H NMR spectrum of the
diamagnetic Co(III) complex, the singlet observed at δ=7.03 ppm can be assigned to the NH
signal and signals at 7.91-8.71 ppm were caused by the coordinated pyridine molecule. The
theoretical 1H chemical shifts due to NH were found as 6.01 and 5.31 ppm. The 1H NMR data
of the complex support the proposed structure and are in good agreement with those of known
oxime complexes [39-41].
2.4. 13C NMR Spectra
The theoretical 13C NMR chemical shift values are given in Table 2. Gauge-including
atomic orbital (GIAO) 13C NMR chemical shift calculations were carried out by using the
DFT/B3LYP functional with the 6-31G(d) basis set. The atom positions are numbered in Fig.
1-3. 13C values have been assigned for only a few organocobaloximes in the literature [17-20].
13C NMR spectra of complexes in the literature show some general trends that are described
1
below. The H and 13C resonances of pyridine in complexes on coordination to the
cobaloxime moiety shift downfield and this coordination shift (∆δ = δ complex - δ free Py)
follows the order ∆δ13C Pyγ ≥ ∆δ13C Pyβ > ∆δ13C Pyα. The same order follows based on the 1H
NMR values. This coordination shift can be taken as a measure of the trans influence of the
axial alkyl ligand.
The δ (C=N) is known to be sensitive to any change in the axial or equatorial environment
in cobaloximes. C=N and Pyα resonances occur very close to each other. Theoretical values
compared with literature values, similar trends were found to be.
2.5. Thermal Analyses
7

ACCEPTED MANUSCRIPT
The thermal data of the complexes are given in Table 3. The TG/DTG diagrams of two
complexes are given in Figs. 4 and 5. Thermochemical studies on cobalt complexes have been
the focus of recent work. Brown et al. suggested that the first step involves the loss of the
bottom axial base ligand. For the next stage, they propose the loss of the top axial ligand.
Finally the complex, now bereft of both axial ligands, undergoes decomposition to form
products, the nature of which was unreported [42]. Our results show that for the complexes,
the above three transitions are not clearly separable, and the process of losing axial ligands is
accompanied by the rupture of the equatorial dioxime ligand.
We can see from Fig. 4 that the thermal decomposition of complex (1) appears as a results
of the loss of the axial pyridine ligand, benzyl group, biphenyl, and p-chloroaniline
(temperature range 42–611 ºC, weight loss exp. 76.80 %; calc. 76.30). The complex shows
residues not conforming to the corresponding metallic residue, such as metal oxide or metallic
cobalt, even at 900ºC, indicate that the decomposition of the organic moiety remains
incomplete even at this temperature.
+
Fig. 5 illustrates the thermal decomposition of the BF2 bridged cobalt complex (2) which
shows the loss of one axial pyridine ligand, a benzyl, two BF2, two biphenyl and two p-
chloroaniline (temperature range 19–892ºC, exp. 80.80 %; calc. 79.00 %). The
decomposition of the organic moiety remains incomplete even at 900ºC.
2.6. Electrochemical Studies
The electrochemical properties of the ligand and its metal complexes were investigated in
DMF containing 0.1 M TBAP as a supporting electrode by cyclic voltammetry (CV). All the
measurements were carried out in 1x10-3 M solutions of the free ligand and its complexes at
room temperature. For all CV measurements of the compounds at different scan rates in the
range of 50-500 mVs-1, the Epa values appear to depend only slightly on the scan rate (Fig. 6).
8

ACCEPTED MANUSCRIPT
Furthermore, in all cases, a linear relationship between the cathodic peak current (ipa) and the
square root of the scan rate was observed. This implies that these electrochemical processes
are mainly diffusion-controlled.
The cyclic voltammogram of the ligand in DMF strongly shows one anodic wave in the
positive range (+1.25 V) which can be attributed to the redox behavior (Fig. 7). The anodic
peak current increases with increasing concentration of the ligand. This anodic wave, which is
seen in the CVs for all metal complexes, is presumed to be ligand based oxidation.
The voltammograms of the metal complexes, in addition to the ligand peak, also have
oxidation peaks. The representative voltammograms of complex (1) compared with the CV of
the ligand is shown in Fig. 8. The obtained oxidation peak of the complex at the positive
potential side indicated that the processes take place on the metal center of the complex.
2.6. Catalase-like Activity
Catalase enzymes are present in most aerobic forms of life and are responsible for the
decomposition of hydrogen peroxide to molecular oxygen and water. Biomimetic compounds
may help providing valuable insights into the mechanisms of these enzymes. Indeed,
comparison of the activity of structurally characterized complexes can help delineating the
functional roles of the ligands and that play a key function in H2O2 disproportionation.
Several families of iron and manganese based catalysts are described [43-45], but the present
study is focused on catalase like activity of the cobaloxime derivatives.
The catalase mimetic properties of the ligand and its complexes (1 and 2) in the
presence of the base imidazole were investigated by measuring the volume of evolved oxygen
during the course of the reaction. None of the compounds on their own exhibited catalytic
activity. The imidazole base by itself causes only a very slight disproportionation of peroxide
and that this reaction is greatly enhanced when the complexes are included in the reaction
9

ACCEPTED MANUSCRIPT
mixture. Such an enhancement in the presence of added base has also been reported by other
researchers [46-48].
The results from these reactions are summarized in Table 4 and Fig. 9. Table 4 shows
the rate of evolution of oxygen from the respective reactions for the complexes over the first
15 min. All the complexes show activity for the catalytic decomposition of H2O2 in the
presence of imidazole. Examination of Table 4 shows that, over the first minute, complex 2
appears to be the most efficient catalyst with 69 molecules of peroxide disproportionated by
one molecule of the complex. The ligand appears to be the least efficient catalyst over the first
minute with one molecule of the compound knocking down just 32 molecules of the peroxide.
A comparison of the total number of molecules of H2O2 disproportionated by one molecule of
the complex shows that complex 2 is the most effective catalyst with 173 molecules. The time
course of the O2 evolution is shown in Fig. 9. The H2O2 disproportionate efficiency of the
complexes in the presence of imidazole, according to the total number of molecules of H2O2
disproportionated by one molecule, follows the order 2 > 1 > H2L. In the absence of a
heterocyclic base, the compounds decompose hydrogen peroxide slowly but the
decomposition of H2O2 is enhanced in the presence of a heterocyclic base such as imidazole
because of its strong π-donating ability [49]. On the other hand, heterocyclic bases themselves
cause only a very slight disproportionation of the peroxide. As a result of catalase-like
activity, the present complex (2) was found to have higher disproportionation efficiency when
compared to other synthesized compounds.
2.7. Description of the Crystal Structure
Because of unsuccessful X-ray diffraction, the theoretical and recent literature data were
used to clarify the geometric properties of the title molecules. The lowest energy structures
found after an automatic conformational search were optimized with the DFT/6-31G(d) basis
10

ACCEPTED MANUSCRIPT
set. The optimized structures and their atomic numbering are shown in Figs. 1-3. Because the
structures have lots of atoms, the selected bond lengths, bond angles and dihedral angles are
given as Supplementary Data in Table S4.
In the dioxime ligand, the phenyl rings are nearly planar and the angle between the two
phenyl ring planes is found as 36.94°. The Cl-phenyl bond distance is 1.76 Å and the N-O
distances are 1.37 and 1.42 Å.
In the complexes, the cobalt atom is linked to four nitrogen atoms belonging to the
equatorial plane. The Co-atom displays an approximately octahedral coordination. The
pyridine ring is practically planar and nearly perpendicular to the equatorial plane (Py-Co-N
angles varying between 89.56-90.40° and 89.22-92.92° for complex (1) and complex (2),
respectively). This is in agreement with the literature [50]. In complex (2), the angles are
varied over a wide range. This can be explained by the two hydrogen bonds between the
fluorine and pyridine hydrogen atoms. The Co-Nax distance was 2.085 Å for the mononuclear
+
complex (1) and 2.159 Å for the BF2 bridged complex (2). It is reported in the 1.966 - 2.086
Å range for cobaloxime complexes in the literature [50-56]. The distance between Co and the
axial pyridine is reported in the 1.945 - 2.066 Å range [51-56]. It was calculated as 2.022 and
2.046 Å for complexes (1) and (2), respectively. The axial angle between C-Co-N was found
as 175.95° and 177.63° for complex (1) and (2), respectively. It is reported in previous studies
at between 176.52-179.01 [51,54-56]. The Co-C-Ph angle was found as 113.63° and 119.92°
for complexes (1) and (2), respectively.
3. Conclusion
In this work, new organocobaloxime derivatives of the types [Co(HL)2(Bz)Py] and
[CoL2(Bz)PyB2F4] [H2L = 4-(4-chlorophenylamino)biphenylglyoxime; Bz = Benzyl; Py =
Pyridine] were synthesized and characterized by elemental analysis, ICP-OES, molar
11

ACCEPTED MANUSCRIPT
1
conductance, FT-IR, H NMR and magnetic susceptibility measurements. We also calculated
1
the geometric parameters, vibrational frequencies and (13C and H) NMR spectra of the title
molecules by using the DFT/B3LYP method with the standard 6-31G(d) basis set. The
experimental and theoretical chemical shift results are generally in good agreement. The
geometrical parameters are in agreement with previous experimental studies. The spectral and
magnetic susceptibility data conform to the octahedral geometry expected for the complexes
(Figs. 2, 3). There was not much variation in the magnetic properties, metal: ligand ratio and
geometry of these complexes due to the replacement of BF2 groups by the bridging protons of
the dioxime complexes. The conductance data indicate that these complexes are non-
electrolytes. The thermal analyses of the complexes show that these complexes thermally
decompose and the organic moiety remains incomplete even at 900 ºC. Moreover, the
catalytic activities of the complexes for the disproportionation of hydrogen peroxide were also
investigated in the presence of imidazole. The catalytic results indicated that complex (2) has
good catalase activity.
4. Experimental
4.1. Materials
All chemicals used in this work were of reagent grade and were used without further
purification. 4-Biphenylchloroglyoxime was prepared according to Karipcin et al. [31].
4.2. Physical Measurements
The 1H NMR spectra were obtained with a Bruker AVANCE instrument in DMSO-d6
or CDCl3, operating at 400 MHz. Proton chemical shifts δ are reported in part per million
(ppm) relative to an internal standard of TMS. Elemental analyses and metal contents were
performed by using a LECO 932 CHNS analyzer and a Perkin Elmer Optima 5300 DV ICP-
OES spectrometer. IR spectra were recorded as KBr pellets using a Shimadzu IRPrestige-21
12

ACCEPTED MANUSCRIPT
FT-IR spectrophotometer. Melting points were determined using an Electrothermal model IA
9100. The molar conductance was determined with an Optic Ivymen System conductivity
meter. The magnetic susceptibilities of the prepared solid complexes were determined at room
temperature using a Sherwood Scientific Magnetic Susceptibility Balance (Model MX1).
Thermogravimetric analyses were carried out on a Perkin Elmer Diamond TGA thermal
analyzer. The experiments were carried out in dynamic nitrogen atmosphere (20 mL min-1)
with a heating rate of 10ºC min-1 in the temperature range 20-900ºC.
4.3. Synthesis
4.3.1. Synthesis of the ligand {4-(4-Chlorophenylamino)biphenylglyoxime} (H2L,
[C20H16N3O2Cl]):
The ligand was prepared according to Karipcin et al.[31]. It was obtained by the
reaction of 4-chloroaniline, (0.281 g, 2.2 mmol) with 4-biphenylchloroglyoxime (2 mmol,
0.55 g) in the presence triethylamine (309 ꢀL, 2.2 mmol). The 4-chloroaniline and
triethylamine dissolved in 10 mL methanol were added dropwise to a suspension of 4-
biphenylchloroglyoxime in 50 mL methanol over 15 min. The mixture was stirred for a
further 5-6 h, then diluted with 100 mL water. The resulting precipitate was filtered and then
recrystallized from ethanol-water (1:4). The product was filtered, washed with water and
dried.
Yellow, mp. 105°C, was isolated in 90% yield; IR (KBr disc. ν, cm-1): 3367(N-H),
1
3212(O-H), 3030(C-H(arom)), 2830(C-H(aliph)), 1596,1635(C=N), 1493(C=C), 1092 (N-O); H-
NMR (δ, ppm): 8.10 s(2H, O-H…H), 7.15-7.68 m(13H, Ar-H), 7.03 s(1H, NH); molar
conductivity (Λm): 10 ꢁ-1cm2mol-1; elemental analyses for C20H16N3O2Cl, Anal. Calcd.(%):
C, 65.66; H, 4.38; N, 11,49, Found (%):C, 66.17; H, 4.59; N, 11.15 [30].
4.3.2. Synthesis of mononuclear complex, [Co(HL)2(Bz)Py] (1)
13

ACCEPTED MANUSCRIPT
CoCl2.6H2O (0.95 g, 4 mmol) and H2L (2.93 g, 8 mmol) were stirred in methanol (35
mL), and dry nitrogen was passed through the mixture for 0.5 h. An aqueous solution of
sodium hydroxide (0.32 g, 8 mmol, 2 mL) was added to the mixture, followed by pyridine
(323 ꢀL, 4 mmol). The mixture was cooled to 0°C and an aqueous solution of sodium
borohydride (0.38 g, 10 mmol, 2 mL) was added. After 10 min. benzyl bromide (476 ꢀL, 4
mmol in 2 mL of diethyl ether) was added dropwise to the reaction mixture. The reaction
mixture was stirred for 5 h in nitrogen atmosphere and in the dark. Then the mixture was
poured into 100 mL of ice-cold water containing a few drops of pyridine. The precipitate was
filtered, washed with water and dried over P2O5.
Brown, mp. 289°C, was isolated in 92% yield; IR (KBr disc. ν, cm-1): 3432 (N-H),
3400(O-H), 3056(C-H(arom)), 2929(C-H(aliph)), 1575,1590 (C=N), 1490(C=C), 1091(N-O),
1
498(Co-N); H-NMR (δ, ppm): 9.95 s(2H, O-H…H), 8.43 d(αH-Py, 2H), 8.05 t(γH-Py, 1H),
7.81 t(βH-Py, 2H), 7.59-7.05 m(31H, Ar-H), 7.03 s(2H, NH), 2.85 s(2H, Bz); molar
conductivity (Λm): 20 ꢁ-1cm2mol-1; diamagnetic; elemental analyses for C52H42N7O4CoCl2,
Anal. Calcd.(%): C, 65.14; H, 4.38; N,10.23,Co, 6.16, Found (%):C, 65.35;H, 4.19; N, 10.36;
Co, 6.46 .
+
4.3.3. Synthesis of BF2 bridged complex, [Co(L)2(Bz)PyB2F4] (2)
It was prepared by modifying the reported method [57]. A large excess of C2H6OBF3
(280 ꢀL, 3 mmol) was added to [Co(HL)2(Bz)Py] (0.480 g, 0.5 mmol) that was sealed in a
flask under N2. After the suspension was stirred for 5 min, 100 mL ACN and Et3N (0.5 mL in
20 mL ACN) were added in succession. The suspension, sonicated for 10 min to break up
large particles, was stirred overnight in the dark and in N2. Then the solution was allowed to
stand at -18°C overnight. After evaporation most of ACN under a reduced pressure and was
added excess of isopropyl alcohol. The precipitate was filtered and dried over P2O5. Black,
mp. 300°C, was isolated in 35% yield; IR (KBr disc. ν, cm-1): 3446(N-H), 3057(C-H(arom)),
14

ACCEPTED MANUSCRIPT
2930(C-H(aliph)), 1592(C=N), 1490(C=C), 1011(N-O), 515(Co-N), 1084(B-O), 1035(B-F); 1H-
NMR (δ, ppm): 8.71 s(2H, O-H…H), 7.71-7.11 m(36H, Ar-H), 7.03 s(2H, NH), 2.80 s(2H,
Bz); molar conductivity (Λm): 30 ꢁ-1cm2mol-1; diamagnetic; elemental analyses for
C52H40N7O4B2F4CoCl2, Anal. Calcd.(%): C, 59.23; H, 3.82; N, 9.30, Co, 5.59, B, 2.05, Found
(%):C, 59.46; H, 3.84; N, 9.20; Co, 5.82, B, 2.17.
4.4. Electrochemical studies
All electrochemical experiments were performed using Autolab PGSTAT 302 N (Eco
Chemie, the Netherlands) Potentiostat/Galvanostat driven by the general purpose
Electrochemical System data processing software (GPES, software version 4.9). A
conventional three-electrode system was used. The working electrode was a platinum
electrode of 2 mm diameter. The reference electrode was Ag/Ag+ (0.01 M) in nonaqueous
media, and the counter electrode was a Pt wire. All solutions were purged with nitrogen steam
for 20 min before measurement and the working electrode was polished before each
experiment. Electrochemical experiments were performed in freshly distilled dry
dimethylformamide (DMF) containing tetrabutylammonium perchlorate (TBAP) as a
supporting electrolyte.
4.5. Studies on Catalase-like Function
The catalytic activity of the ligand and its complexes (1 and 2) towards the
disproportionation of hydrogen peroxide was investigated by measuring the volume of
evolved oxygen during the course of the reaction. Volumetric measurements of evolved
dioxygen during the reactions of the compounds with H2O2 were carried out as follows: A 50
mL three-necked round-bottom flask containing a solution of the complexes (0.005 mmol
solid sample) in DMF (10 mL) was placed in a water bath (25°C). One of the necks was
15

ACCEPTED MANUSCRIPT
connected to a burette and the others were stoppered by rubber septa. While the solution was
being stirred, H2O2 (2.60 mmol, 0.150 mL) was injected through the rubber septum using a
microsyringe. Volumes of evolved dioxygen were measured at 1 min time intervals. In cases
where imidazole (50 mg) was added, this was introduced into the reaction vessel before the
addition of H2O2 (in the absence of imidazole the complexes were either inactive or very
weak catalysts for this reaction).
4.6. Computational details
In the present study, Spartan 10 software [58] was used for the conformational search
by using a PM3 semi-empirical model. All other calculations were performed by using
Gaussian 09 [59] software. The calculations were carried out by solving the Kohn–Sham
equations within the DFT framework. We employed the generalized gradient approximations
(GGA) using the functionals of Becke’s three-parameter hybrid exchange functional [60] and
the Lee–Yang–Parr (LYP) nonlocal correlation functional [61]. The 6-31G(d) basis set was
employed for gas-phase geometry optimization and to compute the vibrational frequencies.
Optimized structural parameters were used for vibrational and isotropic chemical shift
calculations. Calculations for the NMR chemical shifts (1H and 13C) were carried out by using
mostly the gauge-invariant atomic orbital (GIAO) method [62, 63]. The calculations reported
were performed in chloroform solution using the IEF-PCM model, rather than in the gas
phase, in agreement with experimental chemical shifts obtained in chloroform solution. The
13
1H and C NMR chemical shifts were reported in ppm relative to tetramethylsilane (TMS).
Because there was no imaginary frequency for the stationary points, the optimized structure
was accepted as real minimum.
Acknowledgements
16

ACCEPTED MANUSCRIPT
This work was supported by the Research Fund of Süleyman Demirel University, Project no:
1505-D-07 (Isparta/Turkey). We would also like to thank Prof. Dr. Emin SARIPINAR for
Spartan 10 performed at Erciyes University, Kayseri, Turkey.
References
[1] L. Tschugaeff, Ueber ein neues, empfindliches reagens auf Nickel, Ber. Dtsch. Chem.
Ges. 38 (1905) 2520-2522.
[2] A. Chakravorty, Structure chemistry of transition metal complexes of oximes, Coord.
Chem. Rev. 13 (1974) 1-46.
[3] V.Y. Kukushkin, A.J.L. Pombeiro, Oxime and oximate metal complexes: unconventional
synthesis and reactivity, Coord. Chem. Rev. 181 (1999) 147-175.
[4] P. Chaudhuri, Homo- and hetero-polymetallic exchange coupled metal-oximates, Coord.
Chem. Rev. 243 (2003) 143-190.
[5] A.G. Smith, P.A. Tasker, D.J. White, The structures of phenolic oximes and their
complexes. Coord. Chem. Rev. 241 (2003) 61-85.
[6] Z. Biyiklioglu, G. Dilber, H. Kantekin, The synthesis and characterization of a new (E,E)-
dioxime and its mono and heterotrinuclear complexes containing dioxadithiadiaza-
macrobicyclic moieties, Transit. Metal Chem. 31 (2006) 979-985.
[7] D.C. Hodgkin, J. Kamper, J. Lindsey, M. MacKay, J. Pickworth, J.H. Robertson, C.B.
Shoemaker, J.G. White, R.J. Prosen, K.N. Trueblood, The structure of vitamin B12 I. An
outline of the crystallographic investigation of vitamin B12, Proc. Roy. Soc. 242 (1957) 228-
263.
[8] K.H. Reddy, The chemistry of vitamin B12 and model compounds, Coordination
Compounds in Biology, Resonance 16 (2011) 1273-1283.
17

ACCEPTED MANUSCRIPT
[9] G.N. Schrauzer, R.J. Windgassen, Alkylcobaloximes and their relation to
alkylcobalamins, J. Am. Chem. Soc. 88 (1966), 3738-3743.
[10] F. Asaro, R. Dreos, S. Geremia, G. Nardin, G. Pellizer, L. Randaccio, G. Tauzher, S.
Vuano, Diphenylborylated derivatives of organocobaloximes and organorhodoximes:
Synthesis, spectroscopic and structural characterization, J. Organomet. Chem. 548 (1997)
211-221.
[11] R. Dreos, A. Felluga, G. Nardin, R. Randaccio, P. Siega, G. Tauzher, A new
organocobalt complex containing a Co-N-C three membered ring, Inorg. Chem. 40 (2001)
5541-5546.
[12] R. Dreos, G. Nardin, L. Randaccio, P. Siega, S. Scagliola, G. Tauzher, The effect of the
steric bulk of the ligand on the species self-assembled from Co(III) bis(dioximates) and
boronic acids, Eur. J. Inorg. Chem. (2004) 4266-4271.
[13] R. Dreos, P. Siega, S. Scagliola, L. Randaccio, G. Nardin, C. Tavagnacco, M.
Bevilacqua, Synthesis, characterization and electrochemical properties of dinuclear
complexes assembled from asymmetric CoIIIbis(dioximates) and boronic acids, Eur. J. Inorg.
Chem. (2005) 3936-3944.
[14] B.D. Gupta, V.V. Kanth, V. Singh, Organocobaloximes: Synthesis, oxygen insertion and
kinetics, J. Organomet. Chem. 570 (1998) 1-7.
[15] B.D. Gupta, K. Qanungo, Organobridged dicobaloximes: Synthesis and NMR
correlation, J. Organomet. Chem. 534 (1997) 213-220.
[16] B.D. Gupta, K. Qanungo, Pyrazine bridged organodicobaloximes: A convenient one pot
synthesis and cis influence studies, J. Organomet. Chem. 557 (1998) 243-249.
[17] B.D. Gupta, K. Qanungo, A study of cis influence in alkyl cobaloximes, J. Organomet.
Chem. 543 (1997) 125-134.
18

ACCEPTED MANUSCRIPT
[18] B.D. Gupta, K. Qanungo, R. Yamuna, A. Pandey, U. Tewari, V. Vijaikanth, V. Singh, T.
Barclay, W. Cordes, Synthesis, characterization and cis-trans influence in cobaloximes with
nioxime, J. Organomet. Chem. 608 (2000) 106-114.
[19] B.D. Gupta, V. Singh, K. Qanungo, V. Vijaikanth, R. Yamuna, T. Barclay, W. Cordes,
Organocobaloximes with mixed-dioxime equatorial ligands: a one-pot synthesis, J.
Organomet. Chem. 602 (2000) 1-4.
[20] B.D. Gupta, V. Singh, R. Yamuna, T. Barclay, W. Cordes, Organocobaloximes with
mixed dioxime equatorial ligands: A convenient one-pot synthesis. X-ray structures and cis-
trans influence studies, Organometallics 22 (2003) 2670-2678.
[21] B.D. Gupta, R. Yamuna, V. Singh, U. Tiwari, T. Barclay, W. Cordes,
Organocobaloximes with mixed dioxime equatorial ligands: a convenient one pot synthesis.
X-ray crystal structures of BnCoIII(dmgH)(dpgH)Py and BnCoIII(chgH)(dpgH)Py, J.
Organomet. Chem. 627 (2001) 80-92.
[22] K. Kumar, B.D. Gupta, Synthesis, characterization, CV, and X-ray structures of aryl
cobaloximes, J. Organomet. Chem. 695 (2010), 2233-2239.
[23] Mandal, B.D. Gupta, Cobaloximes with dimesitylglyoxime: Synthesis, characterization,
and spectral correlations with the related cobaloximes, Organometallic, 24 (2005) 1501-1510.
[24] N. Navanettha, P.A. Nagarjun, S. Satyanarayana, Study of the spectroscopic
characteristics of methyl (ligand) cobaloximes and their antibacterial activity, J. Chem. Sci.
119 (2007) 29-34.
[25] G.N. Schrauzer, R.J. Windgassen, On hydroxyalkylcobaloximes and the mechanism of a
cobamide-dependent diol dehydrase, J. Am. Chem. Soc. (1967) 143-147.
[26] Z. Xin, H. Deyan, L. Yizhi, C. Huilan, Structure and thermal decomposition studies on
alkylcobaloxime B12 model compounds with 1,2-cyclohexanedion dioxime as equatorial
ligand, Inorg. Chim. Acta. 359 (2006) 1121-1128.
19

ACCEPTED MANUSCRIPT
[27] C. Rovira, K. Kunc, M. Parrinello, Protonation state of the equatorial ligands and
dynamics of the OH center dot O units in a cobaloxime biomimetic, Inorg. Chem. 41 (2002)
4810-4814.
[28] N.M. Shauib, A.Z.A. Elassar, A. El-Dissouky, Synthesis and spectroscopic
characterization of copper(II) complexes with the polydentate chelating ligand 4,4’-[1,4-
phenylenedi(nitrilo)dipente-2-one, Spectrochim. Acta A 63 (2006) 714-722.
[29] F. Karipcin, B. Dede, S. Percin-Ozkorucuklu, E. Kabalcılar, Mn(II), Co(II) and Ni(II)
complexes of 4-(2-thiazolylazo)resorcinol: Syntheses, characterization, catalase-like activity,
thermal and electrochemical behavior, Dyes Pigments,84 (2010) 14-18.
[30] N. Sundaraganesan, S. Ilakiamani, H. Saleem, P.M. Wojciechowski, D. Michalska,
Spectrochim. Acta A 61 (2005) 2995.
[31] F. Karipcin, F. Arabali, F., Karatas, Synthesis and characterization of 4-
arylaminobiphenylglyoximes and their complexes, J. Chil. Chem. Soc. 51 (2006) 982–985.
[32] F. Karipcin, M. Erdem-Tuncmen, G. Baskale-Akdogan, B. Dede, Synthesis and
characterization of some borylated (4-biphenyl)(N-arylamino)glyoxime complexes, Pol. J.
Chem. 83 (2009) 525–535.
[33] N. Yamazaki, Y. Hohokabe, Studies on cobaloximes and investigation on their infrared
and far-infrared spectra, Bull. Chem. Soc. Japan, 44 (1971) 63–69.
[34] K. Burger, I. Ruff, F. Ruff, Infrared and ultra-violet spectrophotometric study of the
dimethylglyoxime complex of transition metals, J. Inorg. Nucl. Chem. 27 (1965) 179–190.
[35] K. Nakamato, Infrared spectra of inorganic and coordination compounds, Wiley, New
York, 1963.
[36] M. Erdem-Tuncmen, F. Karipcin, Synthesis and characterization of new
organocobaloxime derivatives with asymmetric dioxime ligands, J. Incl. Phenom. Macrocycl.
Chem. 77 (2013) 95-104.
20

ACCEPTED MANUSCRIPT
[37] F. Karipcin, S. Ilican, Y. Caglar, M. Caglar, B. Dede, Y. Sahin, Synthesis, structural and
optical properties of novel borylated Cu(II) and Co(II) metal complexes of 4-
benzylaminobiphenylglyoxime, J. Organomet. Chem. 692 (2007) 2473-2481.
[38] A. Bilgin, B. Ertem, F.D. Agın, Y. Gok, S. Karslıoglu, Synthesis, characterization and
extraction studies of a new vicdioxime and its complexes containing bis(diazacrown ether)
moieties, Polyhedron 25 (2006) 3165-3172.
[39] C. Lopez, S. Alvarez, M. Aguilo, X. Solans, M. Font-Altaba, Synthesis and structure of
chloro(ligand)bis(diphenylglyoximato)cobalt(III) complexes, Inorg. Chim. Acta 127 (1987)
153-159.
[40] C. Lopez, S. Alvarez, X. Solans, M. Font-Bardia, The influence of equatorial bulky
substituents on the properties of organometallic bis(dioximato)cobalt(III) compounds—
structural
comparison
between
trans-[Co(dpgh)2(R)(L)]
complexes
[dpgh
=
diphenylglyoximato(-1)] and other B-12 models, Polyhedron 11 (1992) 1637-1646.
[41] P.J. Toscano, L. Lettko, E.J. Schermerhorn, J. Waechter, K. Shufon, S. Liu, E.V.
Dikarev, J. Zubieta, Synthesis and characterization of diphenylglyoximato cobalt(III)
complexes.
The
molecular
structures
of
trans-bis(diphenylglyoximato)-
(alkyl)(pyridine)cobalt(III), with alkyl = CH2SiMe3, CH2CMe3and CF3, Polyhedron 22 (2003)
2809-2820.
[42] T.M. Brown, A.T. Dronsfield, A.S. Wilkinson, Thermochemical studies of benzyl
cobaloximes: A decomposition pathway different from that reported for the alkyl analogues,
Inorg. Chim. Acta 262 (1997) 97-101.
[43] T. Okuno, S. Ito, S. Ohba, Y. Nishida, mu-Oxo bridged diiron(III) complexes and
hydrogen peroxide: oxygenation and catalase-like activities, Dalton Trans. (1997) 3547-3551.
21

ACCEPTED MANUSCRIPT
[44] W. Sicking, H.G. Korth, G. Jansen, H. de Groot, R. Sustmann, Hydrogen peroxide
decomposition by a non-heme iron(III) catalase mimic: A DFT study, Chem. Eur. J. 13 (2007)
4230-4245.
[45] S. Signorella, C. Hureau, Bioinspired functional mimics of the manganese catalases,
Coord. Chem. Rev. 256 (2012) 1229-1245.
[46] B. Dede, I. Ozmen, F. Karipcin, M. Cengiz, Homo- and heteropolynuclear copper(II)
complexes containing a new diimine-dioxime ligand and 1,10-phenanthroline: Synthesis,
characterization, solvent-extraction studies, catalase-like functions and DNA cleavage
abilities, Appl. Organomet. Chem. 23 (2009) 512-519.
[47] S. McCann, M. McCann, M.T. Casey, M. Jackman, M. Devereux, V. McKee, Syntheses
and X-ray crystal structures of cis-[Mn(bipy)2Cl2]ꢂ2H2OꢂEtOH and cis-[Mn(phen)2Cl2] (bipy
= 2,2'-bipyridine; phen = 1,10-phenanthroline); catalysts for the disproportionation of
hydrogen peroxide, Inorg. Chim. Acta 279 (1998), 24-29.
[48] G. Fernandez, M. Corbella, M. Alfonso, H. Stoeckli-Evans, I. Castro, A comparative
XAS and X-ray diffraction study of new binuclear Mn(III) complexes with catalase activity.
Indirect effect of the counteranion on magnetic properties, Inorg. Chem. 43 (2004), 6684-
6698.
[49] E.J. Larson, V.L. Pecoraro, Manganese Redox Enzymes, Wiley-VCH, New York, 1992.
[50] B.D. Gupta, U. Tiwari, T. Barclay, W. Cordes, Inorganic cobaloximes with mixed
dioxime equatorial ligands: a convenient one pot synthesis and cis influence studies: X-ray
crystal structures of N3CoIII(dmgH)(dpgH)Py and N3CoIII(chgH)(dpgH)Py, J. Organomet.
Chem. 629 (2001) 83-92.
[51] A.D. Follett, K.A. McNabb, A.A. Peterson, J.D. Scanlon, C.J. Cramer, K. McNeill,
Characterization of Co-C bonding in dichlorovinylcobaloxime complexes, Inorg. Chem. 46,
(2007) 1645-1654.
22

ACCEPTED MANUSCRIPT
[52] K. Kumar, B.D. Gupta, Synthesis, characterization and structure-property relationship
studies of cobaloximes with dithienylglyoxime as the equatorial ligand, J. Organomet. Chem.
696 (2011) 3785-3791.
[53] J. Galinkina, E. Rusanov, C. Wagner, H. Schmidt, D. Strohl, S. Tobisch, D. Steinborn,
Synthesis,
characterization,
and
reactivity
of
(fluoroalkyl)-
and
(fluorocycloalkyl)cobaloximes: Molecular structure of a (2-fluorocyclohexyl)cobaloxime
complex and hindered rotation of 2-fluorocycloalkyl ligands, Organometallics 22 (2003)
4873-4884.
[54] M. Bhuyan, M. Laskar, B. D. Gupta, Biphenyl-bridged dicobaloximes: Synthesis, NMR,
CV, and X-Ray study, Organometallics 27 (2008) 594–601.
[55] K.M. McCauley, S.R. Wilson, W.A. van der Donk, Synthesis and characterization of
chlorinated alkenylcobaloximes to probe the mechanism of vitamin B-12-catalyzed
dechlorination of priority pollutants, Inorg. Chem. 41 (2002) 393-404.
[56] P.G. Jones, L. Yang, D. Steinborn, cis-1,2-Dichlorovinyl)bis(dimethylglyoximato-
N,N')(pyridine-N)cobalt(III) chloroform solvate, [Co(dmgH)2(py)-(CCI=CHCl)]ꢂCHCl3 Acta
Crystallogr. C 52 (1996) 2399-2402.
[57] S.J. Moore, A. Kutikov, R.J. Lachicotte, L.G. Marzilli, Methyl B-12 models containing
unsubstituted imidazole as an axial ligand investigated by structural and NMR spectroscopic
methods. Evidence that mu-imidazolato-bridged dimers are formed by base addition to some
analogues with macrocyclic equatorial ligands incorporating BF2. Inorg. Chem. 38 (1999)
768–776.
[58] SPARTAN, Version 10, Wavefunction, Inc. 2006.
[59] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, G.
Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H.P.
Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M. Hada, M. Ehara, K.
23

ACCEPTED MANUSCRIPT
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T.
Vreven, J.A. Montgomery Jr, J.E. Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers,
K.N. Kudin, V.N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J.C.
Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B.
Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J.
Austin, R. Cammi, C. Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski,
G.A. Voth, P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, Ö. Farkas, J.B.
Foresman, J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian 09, Revision B.01, Gaussian Inc.,
Wallingford, CT, 2009.
[60] A.D. Becke, Density-functional thermochemistry. 3. The role of exact exchange, J.
Chem. Phys. 98 (1993) 5648-5652.
[61] C. Lee, W. Yang, R.G. Parr, Development of the Colle-Salvetti correlation-energy
formula into a functional of the electron-density, Phys. Rev. B 37 (1988) 785-789.
[62] R. Ditchfield, Molecular orbital theory of magnetic shielding and magnetic susceptibility,
J. Chem. Phys. 56 (1972) 5688-5691.
[63] K. Wolinski, J.F. Hinton, P. Pulay, Efficient implementation of the gauge-independent
atomic orbital method for NMR chemical-shift calculations, J. Am. Chem. Soc. 112 (1990)
8251-8260.
24

ACCEPTED MANUSCRIPT
FIGURE CAPTIONS
Figure 1. The 3D and 2D structure and atomic numbering of the ligand (for clarity, the
hydrogen atoms are omitted)
Figure 2. The 3D and 2D structure and atomic numbering of the complex (1) (for clarity, the
hydrogen atoms are omitted)
+
Figure 3. The 3D and 2D structure and atomic numbering of the BF2 bridged complex (2)
(for clarity, the hydrogen atoms are omitted)
Figure 4. TG/DTG diagram of complex 1 [Co(HL)2(Bz)Py]
Figure 5. TG/DTG diagram of complex 2 [Co(HL)2(Bz)PyB2F4]
Figure 6. Cyclic voltammograms of complex 1 in DMF solution (0.1 M TBAP) at different
scan rates (mV/s-1)
Figure 7. Cyclic voltammogram of 1.0x10-3 M ligand (KADO) in DMF solution (0.1 M
TBAP) at scan rate of 100 mVs-1 versus Ag/Ag+ electrode
Figure 8. Cyclic voltammograms of 1.0x10-3M complex 1 (b) in DMF (0.1 M TBAP) as
compared to the CV of ligand (a) at scan rate of 100 mVs-1 versus Ag/Ag+ electrode
Figure 9. Time courses of dioxygen evolution in the disproportionation of H2O2 by the ligand
and its complexes (1 and 2) in DMF. [compound] = 0.005 mmol, [H2O2] = 2.60 mmol, 298 K
25

ACCEPTED MANUSCRIPT
N O
23N 26O
19C 17C
21C
20C 18C
10C 7C
9C 4C
3C 5C
11C 8C
2C
N O
24N 25O
N
1N
6C
12C
15C
13C
16C
14C
Cl
22Cl
Figure 1. The 3D and 2D structure and atomic numbering of the ligand (for clarity, the
hydrogen atoms are omitted)
26

ACCEPTED MANUSCRIPT
64C
66C
65C
62C
61C
Cl
24C
23C
22C
37Cl
25C
28C
48C
63C
27C
26C
29C
30C
O
O
49C
47C
46C
20C
5O
2O
21C
50C
N
N
51C
10N
38N
45C
52C
19C
12C
N
N
6N
9N
Co
1Co
18C
N
N
17C
16C
13C
14C
C
54C
57C
7N
8N
N
11C
53C
58C
55C
56C
41C
60N
31C
43C
44C
39C
40C
15C
36C
35C
32C
33C
O
O
3O
Cl
59Cl
4O
42C
34C
Figure 2. The 3D and 2D structure and atomic numbering of the complex (1) (for clarity, the
hydrogen atoms are omitted)
27