Preparation, thermal analyses and biological activities of Co(II) and Cr(III) complexes with 2-acetylpyridine-6-bromo-2-naphthoyl acylhydrazone

Article abstract of DOI:10.1016/j.poly.2019.05.059

Novel six-coordinated octahedral Co(II) complex [C₃₆H₂₆Br₂CoN₇O₅, 1] and Cr(III) complex [C₃₆H₂₆Br₂CrN₆O₂, 2] were prepared by the chelation reac

Full text of DOI:10.1016/j.poly.2019.05.059

Accepted Manuscript
Preparation, Thermal Analyses and Biological Activities of Co (II) and Cr (III)
Complexes with 2-Acetylpyridine-6-Bromo-2-Naphthoyl Acylhydrazone
Xin-jie Zong, Xiang-rong Liu, Shun-sheng Zhao, Zai-wen Yang
PII:
S0277-5387(19)30397-3
https://doi.org/10.1016/j.poly.2019.05.059
POLY 13984
DOI:
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
20 January 2019
24 May 2019
29 May 2019
Please cite this article as: X-j. Zong, X-r. Liu, S-s. Zhao, Z-w. Yang, Preparation, Thermal Analyses and Biological
Activities of Co (II) and Cr (III) Complexes with 2-Acetylpyridine-6-Bromo-2-Naphthoyl Acylhydrazone,
Polyhedron (2019), doi: https://doi.org/10.1016/j.poly.2019.05.059
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Preparation, Thermal Analyses and Biological Activities of
Co (II) and Cr (III) Complexes with
2
-Acetylpyridine-6-Bromo-2-Naphthoyl Acylhydrazone
a
a,
a
a
Xin-jie Zong , Xiang-rong Liu *, Shun-sheng Zhao , Zai-wen Yang
aCollege of Chemistry and Chemical Engineering, Xi’an University of Science and Technology, Xi’an
7
10054, China
*
Corresponding author. E-mail address: liuxiangrongxk@163.com.
1

ABSTRACT
Novel six-coordinated octahedral Co(II) complex [C H Br CoN O , 1] and Cr(III)
3
6
26
2
7
5
complex [C H Br CrN O , 2] were prepared by the chelation reaction of the ligand 4-
3
6
26
2
6
2
methoxybenzaldehyde-6-bromo-2-naphthoyl acylhydrazone and 2-acetylpyridine with
Co(NO ) ·6H O or CrCl ·6H O in ethanol, and it is interesting that the coordination
3
2
2
3
2
organic group wasn't the original acylhydrazone. Based on X-ray single crystal
diffraction technique, the structures of 1 and 2 were characterized, which revealed 1
belonged to monoclinic system and P2 /n space group, whereas 2 belonged to triclinic
1
system and P-1 space group. The apparent activation energies of the thermal
decomposition of 1 and 2 showed 1 had far better thermal stability than 2. Both of 1 and
2
1
quenched the intrinsic fluorescence of BSA through static processes, which suggested
and 2 could bind to BSA effectively and the non fluorescent ground state complexes
were formed. UV-vis spectra indicated each complex bound to ct-DNA by an
intercalative mode. Microcalorimetry experiments illustrated the interactions of two
complexes with BSA and ct-DNA were both spontaneous endothermic processes and
the binding activities of 1 with BSA and ct-DNA were greater than that of 2. The
minimum inhibitory concentrations(MIC) of each complex against Escherichia coli,
Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa were all 50
-
1
μg·mL .
Keywords: Complex; Thermal stability; BSA; ct-DNA; Biological activity
1
. Introduction
Acylhydrazone was a special Schiff base and the bioactive group (-CONHN=CH-)
existed in its molecular structure, so it had wide application in fields of pesticide and
medicine [1-6]. The existence of nitrogen and oxygen atoms in the bioactive group
made it possess strong coordination abilities, and the existence of tautomer made it have
2

various coordination modes [7], especially acylhydrazone metal complexes, which can
serve as drugs for antibacterial [8], antitumor [9], antiviral [10] and anticancer [11].
According to the reports [12,13], acylhydrazone Co(II) and Cr(III) complexes had
certain better bioactivities. For example, C.Z. Zheng studied the inhibition activities of
Ni(II) and Cr(III) complexes with 2-furaldehyde benzoylhydrazone against Escherichia
coli, Staphylococcus aureus and Pseudomonas aeruginosa by oxford cup methods,
which showed these complexes had certain inhibition activities against three kinds of
bacteria [12]. R.S. Hunoor designed Co(II), Ni(II), Cu(II) and Zn(II) complexes with
isatinyl-2-aminobenzoylhydrazone, and studied the vitro anticancer activities of these
complexes against EAC cells, adenocarcinoma HT29, kidney cancer K293 and breast
cancer MDA231 by MTT assay, they found Co(II) complex exhibited impressive
activities with IC against EAC cells and HT29, was a potential anticancer drug [13].
5
0
Naphthalene was one of PAHs and compounds containing naphthalene rings also
had strong bioactivities and were widely applied in pesticide and medicine [14-15]. In
this paper, compounds containing naphthalene rings were introduced into the molecular
structure of acylhydrazone to obtain novel acylhydrazone compounds and their metal
complexes possessing biological activities of both groups.
Based on the above facts, this paper focusedonthepreparationofCo(II)
and Cr(III) complexes with 2-acetylpyridine-6-bromo-2-naphthoyl
acylhydrazone, which were characterized by elemental analyses and X-ray single
crystal diffraction. The thermal decomposition behaviors of the complexes were
analyzed by thermogravimetry. The interaction modes of the complexeswith BSA
and ct-DNA were studied by fluorescence spectrometry, UV-vis spectrometry and
microcalorimetry. The inhibition activities of the complexes against four kinds of
bacteria were studied by oxford cup method. Preparation routes of Co(II) complex(1)
3

and Cr(III) complex(2) were shown in Scheme 1.
Scheme 1
2
. Experimental
2
.1. Materials and methods
Hydrazine hydrate(80%), ethanol, methanol and DMF were obtained from Fuyu
Fine Chemical Industry. 4-methoxybenzaldehyde, 2-acetylpyridine, cobalt nitrate
hexahydrate, chromium chloride hexahydrate and BSA were attained from Bailingwei
Co. Ltd.. Methyl 6-bromo-2-naphthoate and ct-DNA were bought from Bide
Pharmatech Ltd. and Sigma Aldrich, respectively. Escherichia coli, Staphylococcus
aureus, Bacillus subtilis and Pseudomonas aeruginosa were purchased from China
Center of Industrial Culture Collection (CICC). All reagents and chemicals were
purchased from commercial sources and used without purification.
Single crystal structures were recorded on Bruker Smart Apex II CCD X-ray single
crystal diffractometer. Melting points were determined by WRS-2U melting point
apparatus. Elemental compositions were performed on PE-2400-II elemental analyzer.
Thermogravimetric data were obtained by TG-DSC1 HT thermogravimetric analyzer.
UV-vis spectra were measured by TU-1950 UV spectrophotometer. Fluorescence
spectra were carried out with LS 55 fluorescence spectrometer. Thermogenic curves
were studied by C80 microcalorimeter.
2
2
.2. Preparation of 1 and 2
.2.1. Preparation of [C H BrN O ](precursor ligand)
1
9
15
2
2
6
-bromo-2-naphthoyl acylhydrazine was synthesized as described previously [16].
A mixture of 4-methoxybenzaldehyde (6.1 μL, 0.05 mmol), 6-bromo-2-naphthoyl
acylhydrazine (0.0133g, 0.05 mmol) and methanol (20 mL) was refluxed with stirring at
6
0 ℃ for 2 h. Transparent acicular crystal could be obtained after about 2 days. Yield:
4

-1
7
3%. m.p.: 230~231 ℃. Found for C H BrN O (383.24 g·mol ): C, 59.67; H, 4.03;
19 15 2 2
N,7.36. Calcd: C, 59.55, H, 3.95; N, 7.31.
.2.2. Preparation of [C H Br CoN O ](1) and [C H Br CrN O ](2)
2
3
6
26
2
7
5
36 26
2
6
2
A mixture of precursor ligand (0.0383g, 0.1 mmol), 2-acetylpyridine (6 drops) and
absolute ethanol (20 mL) was refluxed at 60 ℃ for 5 min, and then ethanol solution(5
mL) containing Co(NO ) ·6H O (0.0146 g, 0.05 mmol) was added to the mixture for
3
2
2
refluxing at 73 ℃ for 6 h with stirring. Red-brown transparent acicular crystal 1 could
be obtained about 10 days. Yield: 73%. m.p.: 267~268 ℃. Found for
-1
C H Br CoN O (855.46 g·mol ): C, 50.29; H, 3.26; N, 11.61. Calcd: C, 50.50; H,
3
6
26
2
7
5
3
.04; N, 11.46.
Complex 2 was obtained as reddish black transparent acicular crystal in a manner
similar to that used to obtain 1, except using CrCl ·6H O instead of Co(NO ) ·6H O,
3
2
3 2
2
and the reaction time was 9 h. Yield: 86%. m.p.: 227~228 ℃. Found for
-1
C H Br CrN O (788.46 g·mol ): C, 55.21; H, 3.47; N, 10.43. Calcd: C, 54.79; H,
3
6
26
2
6
2
3
.30; N, 10.65.
In order to explore the preparation mechanism of two complexes, two preparation
routes were designed in Scheme 2.
Scheme 2
As seen from Scheme 2, the new ligands in two complexes can't be prepared in the
case of single or mixed solvents by the above two methods. So we infered the
preparation mechanisms of two complexes, which were shown in Scheme 3. In Scheme
3
, precursor ligand was firstly hydrolyzed in the presence of acids (Hydrolysis of metal
ions caused the solution to be weak acidic) and ethanol (step ), and 6-bromo-2-
naphtholy acylhydrazine was formed [17]. Then, the new ligands in two complexes
were obtained in the order of nucleophilic addition reaction(step ), rearrangement
5

reaction(step ), and elimination reaction(step ). Finally, two complexes were
prepared by the chelation reaction of new ligand and metal ions (Co(II) and Cr(III))
(step ).
Scheme 3
.3. X-ray structure determination and refinement
2
The X-ray diffraction measurements of 1 and 2 were collected on Bruker Smart
Apex II CCD diffractometer with ω/2θ and Mo Kα radiation (λ=0.71073 Å) at 296(2) K.
The structures of 1 and 2 were solved by direct methods, which yielded the positions of
all non-hydrogen atoms, and then isotropical and anisotropical parameters of them were
refined using full-matrix least square method based on SHELX-97 Program [18].
2
.4. Thermal stability experiments
The thermal decomposition processes of 1 and 2 were studied at heating rates of 5,
-1
1
0 and 15 ℃·min from room temperature to 800 ℃ by thermogravimetric analyzer
under nitrogen atmosphere.
.5. BSA binding experiments
2
-7
-1
The BSA solution (1×10 mol·L ) was prepared by dissolving BSA solid in Tris-
-1
-5
HCl buffer solution (0.01 mol·L , pH 7.2, 50 mL). Each complex solution (1×10
-1
mol·L ) was obtained by a mixture of DMF and Tris-HCl buffer solution (v/v=5:95,
0 mL). The interactions of the complexes with BSA by fluorescence spectra were
5
performed keeping fixed BSA concentration while varying the complex concentration.
Each fluorescence curve was recorded every 2 min. The excitation wavelength was 280
nm.
2
.6. ct-DNA binding experiments
The Tris-HCl buffer solution was obtained in a manner similar to that used in BSA
binding experiments, except that the pH was 7.9. ct-DNA solution was prepared and its
6

absorbance ratio A /A was considered to be up to standard for purity between 1.8
2
60
280
and 1.9. According to the conversion formula of DNA concentration : CDNA=A /6600
260
-1
-1
-4
-1
L·mol ·cm , the concentration of ct-DNA solution was 2.88×10 mol·L [19]. Each
-5
-1
complex solution(1×10 mol·L ) was obtained by a mixture of DMF and Tris-HCl
buffer solution(v/v=5:95, 50 mL). The interactions of the complexes with ct-DNA
were performed keeping fixed complex concentration while varying the DNA
concentration using UV-vis spectra. Each UV-vis spectra was recorded every 5 min.
The scanning wavelength range was 250~500 nm.
2
.7. Microcalorimetry experiments
The thermogenic curves of the interactions of each complex with BSA and ct-DNA
were investigated by C80 microcalorimetry at 28 ℃. BSA and ct-DNA solutions used
in the experiment were the same as that used in BSA and ct-DNA binding experiments.
Firstly, the Tris-HCl buffer solution (1 mL) and each complex solution (1 mL) were
added into the bottom of reference and sample cell, respectively, and then ct-DNA/BSA
solution(1 mL) was added into the upper of two cells. The solutions in upper
and bottom cells were mixedwhen the fluctuation of the heat flow was small.
2
.8. Antibacterial experiments
Four kinds of bacteria namely Escherichia coli, Staphylococcus aureus, Bacillus
subtilis and Pseudomonas aeruginosa were used to screen the antibacterial activities of
and 2, which were inoculated at least 3 times. Each complex was dissolved in DMF to
1
-1
a final concentration of 200 μg·mL . In order to determine the minimum inhibitory
concentration of 1 and 2, both of 1 and 2 were diluted by double dilution method. DMF
was considered as blank control and gentamycin sulfate was as control drug. Based on
oxford cup method, the antibacterial experiments were carried out in triplicate under
strict aseptic conditions. The diameters (mm) of inhibition zone of the complexes were
7

larger than that of blank control showed the inhibition activities of complexes, which
were expressed in terms of the average diameters of inhibition zone.
3
. Results and discussion
3
.1. Description of single crystal structures
°
Crystallographic data, selected bond length(Å) and angle( ) of 1 and 2 were shown
in Tables 1 and 2, respectively. The molecular structures of 1 and 2 were illustrated in
Figs.1 and 3, and crystal packing structures of 1 and 2 were displayed in Figs.2 and 4.
Tables 1-2
Figs.1-4
There was a Co(II) ion and two new ligands in the molecular structure of 1 in Fig.1,
a six-coordinated octahedral structure centered on Co(II) ion was obtained by the
coordination of two oxygen atoms, two imino nitrogen atoms and two pyridine nitrogen
atoms with Co(II) ion. The bond angles of [N(2)-Co(1)-O(2)], [N(5)-Co(1)-N(3)] and
°
°
°
[
O(1)-Co(1)-O(2)] were 93.3(4) , 97.9(4) and 90.5(3) , indicating the octahedral
structure was distorted. The bond lengths of Co(1)-N(2), Co(1)-N(3), Co(1)-N(5),
Co(1)-N(6), Co(1)-O(1) and Co(1)-O(2) were 1.849(9), 1.921(10), 1.865(9), 1.953(11),
1
.907(7) and 1.902(8) Å, which were comparable to the similar complexes [20]. It can
be seen that the bond lengths of Co(1)-N(2) and Co(1)-N(5) were shorter than that of
Co(1)-O(1) and Co(1)-O(2), and the bond lengths of Co(1)-O(1) and Co(1)-O(2) were
shorter than that of Co(1)-N(3) and Co(1)-N(6), indicating nitrogen atoms had better
coordination abilities than oxygen atoms in the bioactive group, oxygen atoms had
better coordination abilities than pyridine nitrogen atoms. The O(1)-C(11)(1.330(13) Å)
was a typical C-O single bond, and N(2)-C(12)(1.277 Å) was shorter than N(1)-
C(11)(1.313 Å), showing 1 existed in form of enols after coordination [21,22]. As seen
from Fig.2, there were π-π stacking interactions between naphthalene rings and pyridine
8

rings (J-type stacking) in 1, belonging to weak interactions, the π-π stacking interaction
extended to a three dimensional network structure. The constitutes and structures of 2
were similar to 1.
3
.2. Thermal stability analyses
Figs.5 and 6 dispalyed the TG-DTG curves of 1 and 2 at heating rates of 5, 10 and
-1
1
5 ℃·min , respectively. There were two steps for the thermal
decomposition of 1. At the first stage, the mass loss at heating rate of 5 ℃·min-1
was 2.95% at 91.72~171.74 ℃, connected with the loss of water(Calcd: 2.34%). At the
-1
second stage, the mass losses at heating rates of 10 and 15 ℃·min were great different
-1
from that of at heating rate of 5 ℃·min , the mass losses at heating rates of 5, 10 and
-1
1
5 ℃·min were 71.57%, 55.14 and 53.83% from 225 to 800 ℃, it was inferred that
the mass loss resulted from the complete fracture of naphthalene rings, pyridine rings
and C-Br single bonds(Calcd: 73.32%), which was similar to the mass loss at heating
-1
rate of 5 ℃·min , it was because the greater the heating rate was, the more serious the
temperature hysteresis was. If the heating rate was too fast, the complexes didn't
respond adequately and the weightless step would be inaccurate or unmeasured. After
-1
8
00 ℃, the remaining amount of 1 was 25.48% at heating rate of 5 ℃·min , it was
inferred that the residue was tricobalt tetraoxide(Calcd: 24.34%). The thermal
decomposition process of 2 was the same as that of 1, the first stage at heating rates of 5,
-1
1
0 and 15 ℃·min with mass losses of 5.70%, 4.89% and 5.54% from 78.13 to 160.41 ℃
were assigned to the loss of water. The second decomposition stage with the mass losses
of 54.22%, 46.27% and 45.70% at heating rates of 5, 10 and 15 ℃·min-1 was
considered as the complete fracture of naphthalene rings, pyridine rings and C-Br
single bonds(Calcd: 54.09%), which was similar to the mass loss at heating rate of
9

-1
-1
5
℃·min . At last, the remaining amount of 1 was 40.27% at heating rate of 5 ℃·min ,
it was inferred the residue was chromium oxide (Calcd: 36.21%).
Figs.5-6
The apparent activation energy(E ) of 1 and 2 at the second stage can be obtained
a
by Kissinger [23] and Ozawa equation [24], the formulas were as follows.











Tp
AR
Ea
ln   ln

Kissinger
Ozawa
(1)
(2)
2

Ea
RTp


AEa

Ea
lg  lg
 2.315 0.4567


RG(α)
RTp


Where E refers to the apparent activation energy, T is the maximum temperature
a
P
of endothermic peak, β is the heating rate, A is the pre-exponential factor, R is the gas
constant and G(α) is the integral mechanism function.
The results were shown in Table 3. As seen from Table 3, E (1) was more than
a
twice as much as E (2), showing 1 was more stable than 2, this was because the bond
a
lengths of all coordination bonds of 1 were generally shorter than those of
corresponding coordination bonds of 2, so that the bond energies of all coordination
bonds of 1 were higher than those of corresponding coordination bonds of 2, so 1
needed to absorb more energies than 2 in the thermal decomposition processes.
Table 3
3
.3. BSA binding studies
In virtue of the existences of amino acid residues in BSA, so BSA emits
fluorescence when it is excited [25]. Fluorescence quenching is divided into static
quenching and dynamic quenching, static quenching is caused by the formation of
ground state complexes between quencher and BSA, while dynamic quenching results
from colliding with each other. The abilitites of complexes to quench the fluorescence
were related to the interactions between complexes and BSA, which could be described
1
0

by Stern-Volmer and Lineweaver-Burk equations [26,27], respectively. The formulas
were as follows.
F0 / F  K
sv

Q

q
1 K 0

Q

1
 lg KA
Where F /F refers to fluorescence intensity ratio before and after the addition of
Stern-Volmer
(3)
lg

F0  F

/ F  nlg

Q

Lineweaver-Burk (4)


0
-8
the quencher, Q is the concentration of complexes, τ (10 s) is the average lifetime of
0
the biomolecule without quencher, K is the Stern-Volmer quenching constant, K is the
sv
q
bimolecular quenching constant, n is binding site and K is the binding constant.
A
The fluorescence emission spectra of the interactions of 1 and 2 with BSA were
shown in Figs.7 and 8 (Inset: Plots of F /F against Q of 1 and 2 ). BSA solution showed
0
strong fluorescence emission peak at 342 nm, and the fluorescence intensity slightly
decreased and the emission peak occurred weak-blue shift with the increase of the
concentration of 1 and 2, illustrating each complex caused the changes of
microenvironment and conformation for BSA.
Figs.7-8
Firstly, it was assumed that the interactions between two complexes and BSA were
the dynamic quenching processes. According to the Stern-Volmer equation, K and K
sv
q
for static quenching interaction were obtained from the plots of F /F and Q (as insets in
0
Figs.7 and 8) and shown in Table 4. As seen from Table 4, both of K were larger than
q
1
0
-1 -1
the maximum scatter collision quenching constant(2×10 L·mol ·s ), indicating the
non fluorescent ground state complexes were formed between each complex and BSA,
corresponding to static quenching mechanism.
On the basis of Lineweaver-Burk equation, n and K were obtained from the plots
A
of lg[(F -F)/F] against lg[Q] in Fig.9 and listed in Table 5. It can be seen from Table 5,
0
the non fluorescent ground state complexes were formed through each complex with
BSA in proportion to 1:1 [28], and K (1) was slightly larger than K (2), showing the
A
A
1
1

binding ability of 1 with BSA was greater than that of 2.
Fig.9
Tables 4-5
3
.4. DNA binding studies
Figs.10 and 11 displayed UV-vis spectra of the interaction of each complex with
ct-DNA(Inset: Plots of Cct-DNA/(ε -ε ) against C of 1 and 2). The maximum
ct-DNA
a
f
absorption peaks of 1 were relatively flat at 332 and 389 nm where the bands exhibited
hypochromism of 8.36% and 8.83% with slight red-shift [29-30] during the increase of
the concentration of ct-DNA, indicating there was an intercalative mode between 1 and
DNA [31], which was due to π→π* intercoupling between the π* empty orbit of 1 and
the π orbital of ct-DNA base pairs after 1 inserted into ct-DNA [32,33]. The behavior of
the interaction of 2 with ct-DNA was in a manner similar to 1.
Figs.10-11
In order to determine and compare the binding abilities of
1
and 2 with ct-DNA, the binding constants K were calculated using Benesi-
b
Hildebrand equation [34], the formula was as follows.
Cct-DNA Cct-DNA
1


Benesi-Hildebrand(5)
εa  εf
εb  εf K (ε  ε )
b
b
f
Where Cct-DNA refers to the concentration of ct-DNA in base-pairs, K is apparent
b
binding constant, ε is the apparent extinction coefficient of complexes, ε is the
a
b
extinction coefficient of the complexes in the bound form and ε is the extinction
f
coefficient of the complexes in the free form. K were obtained from the plots of C
b
ct-DNA
and Cct-DNA/(ε -ε ) (as insets in Figs.10 and 11) and listed in Table 6. It was clearly seen
a
f
from Table 6, the binding constant K of each complex with ct-DNA reached the order
b
7
of magnitude of 10 , and K (1)＞K (2), showing the binding ability of 1 with ct-DNA
b
b
1
2

was greater than that of 2.
Table 6
.5. DNA and BSA binding studies by microcalorimetry
Microcalorimetry was also used to study the biological activities between
3
complexes and biological specimen [35-37]. Figs.12 and 13 displayed the thermogenic
curves of each complex with ct-DNA and BSA at 28℃, respectively.
Figs.12-13
The maximum endothermic peaks of the interactions of 1 and 2 with ct-DNA
appeared at 5.3 and 5.1 min and the reactions ended at 51.4 and 49.4 min, respectively,
which were endothermic processes. The enthalpy changes(H) obtained by integrating
the peak area were listed in Table 7. As seen from Table 7, H values were both beyond
4
-1
2
.0×10 kJ·mol and H(1-ct-DNA)＞H(2-ct-DNA), showing the binding ability of 1
with ct-DNA was greater than that of 2, consistent with the results of ct-DNA binding
experiments. The maximum endothermic peaks of the interactions of 1 and 2 with BSA
occurred at 5.2 and 6.5 min, and the reactions ended at 49.0 and 50.1 min, respectively,
which were also endothermic processes, and H(1-BSA) was almost four times than

H(2-BSA), indicating the binding ability of 1 with BSA was greater than that of 2,
corresponding to the results of BSA binding experiments. In order to calculate the S
and G, the binding constants K from BSA binding experiments and K from ct-DNA
A
b
binding experiments were substituted into the thermodynamic equations [38],
respectively. The formulas were as follows.

G  RTlnK
(
6)
7)

S  (H  G) / T
(
Where G refers to Gibbs function change, S is the entropy change, H is the
enthalpy change, K is the apparent binding constant, T is the temperature in kelvin and
b
1
3

R is the gas constant. S and G were listed in Table 7. As seen from Table 7, G<0,
S>0, and H>0, illustrating the interactions of 1 and 2 with ct-DNA and BSA were

spontaneous endothermic and entropy promoting processes.
Table 7
3
.6. Antimicrobial activities
Fig.14 dispalyed the inhibition zones of 1 and 2 against Escherichia coli,
Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa. The average
diameters (mm) of inhibition zones of DMF, gentamycin sulfate, 1 and 2 solutions were
listed in Table 8. It is revealed that DMF (blank control) had a little effect on four kinds
of bacteria, while gentamycin sulfate (control drug) had strong inhibition activities to
them. Each complex exhibited obvious inhibition zones, the inhibition activity of 1
against Pseudomonas aeruginosa (16.36 mm) was strongest, followed by Bacillus
subtilis (15.72 mm), but the inhibition activities of 1 against four kinds bacteria were
not as great as that of gentamycin sulfate, while the inhibition activities of 2 against
Escherichia coli (17.49 mm) and Pseudomonas aeruginosa (22.23 mm) were
-1
comparable to that of gentamycin sulfate at the concentration of 200 μg·mL . When the
-1
concentrations of 1 and 2 were diluted to 50 μg·mL , the average diameter of inhibition
zones of 1 and 2 against four kinds of bacteria were similar to that of DMF (blank
control), indicating the minimum inhibitory concentrations(MIC) of 1 and 2 against four
-1
kinds of bacteria were all 50 μg·mL .
Fig.14
Table 8
4
. Conclusions
Co(II) and Cr(III) complexeswere prepared and X-ray single crystal diffraction
indicated coordination atoms in two complexes exhibited octahedral geometry. The
1
4

thermal stabilities of 1 and 2 were studied by TG, showing 1 was more stable than 2.
BSA binding experiments indicated both of 1 and 2 quenched the intrinsic fluorescence
of BSA through static processes. ct-DNA binding experiments displayed both of 1 and 2
bound to DNA efficiently by an intercalative mode. Microcalorimetry experiments
illustrated the interactions of 1 and 2 with BSA and ct-DNA were both spontaneous
endothermic and entropy promoting processes, and the interactions of 1 with BSA and
ct-DNA were greater than that of 2, corresponding to the results of BSA and ct-DNA
binding experiments. The minimum inhibitory concentrations of each complex against
-1
four kinds of bacteria were all 50 μg·mL and 2 exhibited strong inhibition activities
against Escherichia coli and Pseudomonas aeruginosa at the concentration of 200
-1
μg·mL , comparable to gentamycin sulfate.
Acknowledgments
The work was supported by the National Natural Science Foundation of
China(Nos.21073139 and 21373158), Science and Technology on Combusion and
Explosion Laboratory Foundation of Shaanxi (No.6142603010301), and Analytical
Instrumentation Center of XUST.
Appendix A. Supplementary data
CCDC 1812120(1) and 1832625(2) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/ retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44)1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
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Scheme Captions
Scheme 1. Preparation routes of Co(II) complex(1) and Cr(III) complex(2).
1
7

Scheme 2. Two preparation routes of 2-acetylpyridine-6-bromo-2-naphthoyl
acylhydrazone.
Scheme 3. The preparation mechanisms of two complexes.
Scheme 1. Preparation routes of Co(II) complex(1) and Cr(III) complex(2).
N
O
O
O
N
NH2
N
N
H
N
H
×
×
MeOH or EtOH
or MeOH+EtOH
Br
Br
Br
Br
N
O
O
O
N
N
N
N
H
N
H
O
MeOH or EtOH
or MeOH+EtOH
Scheme 2. Two preparation routes of 2-acetylpyridine-6-bromo-2-naphthoyl
acylhydrazone.
O
O
Hydrolysis
N
NH2
N
O
N
H
Acid condition
H
Br
EtOH
Br
℃
Br
Br
Br
Br
N
N
O
N
N
Rearrangement
O
Elimination
Metal salt
O
M
O
HN
NH
O
Nucleophilic
addition
-
H O
2
O
HN
HN
N
N
N
NH2
N
℃
℃
℃
℃
O
HO
Br
N
N
N
Scheme 3. The preparation mechanisms of two complexes.
Table Captions
Table 1 Crystallographic data of 1 and 2.
1
8

°
Table 2 Selected bond length(Å) and bond angle( ) of 1 and 2.
Table 3 Kinetic parameters of thermal decomposition of 1 and 2.
Table 4 Dynamic fluorescence quenching parameters of the interactions of 1 and 2 with
BSA.
Table 5 Static fluorescence quenching parameters of the interactions of 1 and 2 with
BSA.
Table 6 The binding parameters of 1 and 2 with ct-DNA.
Table 7 Thermodynamic parameters of the interactions of 1 and 2 with ct-DNA and
BSA.
Table 8 The average diameters (mm) of inhibition zones of DMF, gentamycin sulfate, 1
and 2 solutions.
Table 1 Crystallographic data of 1 and 2.
Complex
1
2
Chemical formula
C H Br CoN O
C H Br CrN O
2
3
6
26
2
7
5
36 26
2
6
1
9

Formula weight
857.46
788.46
CCDC
Crystal system
Space group
1812120
Monoclinic
1832625
Triclinic
P-1
P2 /n
1
a(Å)
b(Å)
c(Å)
α(°)
β(°)
γ(°)
V(Å3)
Z
13.680(5)
11.973(4)
23.323(8)
90.000
103.775(8)
90.000
3710(2)
4
11.4942(19)
12.459(2)
15.401(3)
72.181(3)
74.300(3)
75.692(3)
1988.6(6)
2
Dcalc(g/cm3)
1.614
1.370
F(000)
1816
824
θ Range
Goodness-of-fit on F2
1.58-26.10
0.863
1.41-25.10
1.097
-
16≤h≤16
-13≤k≤14
19≤l≤28
Final R indices[I>2sigma(I)] R = 0.0701, wR = 0.1469
-11≤h≤13
-14≤k≤14
-18≤l≤18
Limiting indices
-
R = 0.1396, wR = 0.3989
1
1
2
2
R indices (all data)
R = 0.3123, wR = 0.2684
R = 0.2250, wR = 0.4746
1
2
1
2
°
Table 2 Selected bond length(Å) and bond angle( ) of 1 and 2.
Complex
Bond
Length/Å
Bond
Angle/(°)
Co(1)-N(2)
Co(1)-N(5)
Co(1)-O(2)
Co(1)-N(3)
Co(1)-N(6)
Co(1)-O(1)
N(1)-C(11)
C(11)-O(1)
C(12)-N(2)
Cr(1)-N(2)
Cr(1)-N(5)
Cr(1)-O(2)
Cr(1)-N(3)
Cr(1)-N(6)
Cr(1)-O(1)
N(1)-C(11)
C(11)-O(1)
C(12)-N(2)
1.849(9)
1.865(9)
1.902(8)
1.921(10)
1.953(11)
1.907(7)
1.313(13)
1.330(13)
1.277(13)
1.956(9)
1.935(9)
1.961(8)
2.065(10)
2.068(9)
1.954(8)
1.317(15)
1.319(12)
1.288(15)
N(2)-Co(1)-N(5)
N(3)-Co(1)-O(1)
N(6)-Co(1)-O(2)
N(2)-Co(1)-O(2)
N(2)-Co(1)-N(3)
N(3)-Co(1)-N(6)
N(5)-Co(1)-N(3)
O(1)-Co(1)-O(2)
N(4)-N(5)-Co(1)
N(2)-Cr(1)-N(5)
N(3)-Cr(1)-O(1)
N(6)-Cr(1)-O(2)
175.3(5)
164.3(4)
164.2(4)
93.3(4)
81.6(5)
91.9(4)
97.9(4)
90.5(3)
116.0(8)
172.8(4)
155.9(4)
156.6(3)
1
N(2)-Cr (1)-O(2) 107.3(4)
2
N(2)-Cr(1)-N(3)
N(3)-Cr(1)-N(6)
N(5)-Cr(1)-N(3)
O(1)-Cr(1)-O(2)
N(4)-N(5)-Cr(1)
78.1(4)
92.3(4)
97.1(4)
94.1(4)
118.8(7)
Table 3 Kinetic parameters of thermal decomposition of 1 and 2.
Kissinger
Ea/kJ·mol-1 lgA
Ozawa
Ea/kJ·mol-1
Complex
β/℃·min-1
T /℃
P
r
r
2
0

5
10
5
5
10
281.73
285.84
287.36
277.84
283.34
291.69
1
2
480.6
190.0
43.43
15.85
-0.994
-0.987
465.8
189.5
-0.994
-0.981
1
1
5
Table 4 Dynamic fluorescence quenching parameters of the interactions of 1 and 2 with
BSA.
-1
-1 -1
R2
Complex
Stern-Volmer Fitting Equations
K /L·mol
sv
K /L·mol ·s
q
5
2.45×105
3.04×105
2.45×1013
3.04×1013
1
2
F /F=2.45×10 Q +1.011
0.989
0.987
0
5
F /F=3.04×10 Q +1.023
0
Table 5 Static fluorescence quenching parameters of the interactions of 1 and 2 with
BSA.
-1
R2
Complex
Lineweaver-Burk Fitting Equations K /L·mol
n
A
1
2
lg[(F -F)/F]=0.814lg[Q]+4.25
1.79×104
1.43×104
0.814
0.779
0.988
0.997
0
lg[(F -F)/F]=0.779lg[Q]+4.16
0
Table 6 The binding parameters of 1 and 2 with ct-DNA.
-1
R2
Complex
Fitting Equations
Cct-DNA/(ε -ε )=2.69×10 C
K /L·mol
1.67×107
1.25×107
b
-
5
+1.62×10-12
+4.95×10-12
1
2
0.999
0.999
a
f
ct-DNA
ct-DNA
-5
Cct-DNA/(ε -ε )=6.19×10 C
a
f
Table 7 Thermodynamic parameters of the interactions of 1 and 2 with ct-DNA and
BSA.

G
S
H
(kJ·mol-1)
Start time
(min)
End time
(min)
Action time
(min)
System
-1
-1
-1
(kJ·mol )
(kJ·mol ·K )
1
2
1
2
+ct-DNA
+ct-DNA
+BSA
-41.62
-40.92
-24.50
-23.99
85.47
68.54
147.18
32.27
2.57×104
2.06×104
4.43×104
1.12×104
3.6
3.7
3.8
4.3
51.4
49.4
49.0
50.1
47.5
45.7
45.2
45.8
+BSA
Table 8 The average diameters (mm) of inhibition zones of DMF, gentamycin sulfate, 1
and 2 solutions.
2
1

Inhibition zone diameter (mm)
Concentration
Compound
DMF
Escherichia Staphylococcus Bacillus Pseudomonas
-1
(
μg·mL )
coli
aureus
subtilis
aeruginosa
-
9.54
9.19
16.36
13.01
11.94
10.23
10.41
9.56
9.50
16.24
15.72
13.83
12.53
11.18
9.96
9.41
22.28
16.36
22.23
12.88
11.44
10.34
10.19
Gentamycin sulfate 200
17.86
13.21
17.49
12.17
11.00
10.38
9.89
1
2
1
200
200
100
100
50
2
1
2
50
9.47
10.18
Figure Captions
Fig.1. Molecular structure of 1.
2
2

Fig.2. Crystal packing structure of 1.
Fig.3. Molecular structure of 2.
Fig.4. Crystal packing structure of 2.
Fig.5. TG-DTG curves of 1.
Fig.6. TG-DTG curves of 2.
Fig.7. Fluorescence emission spectra of the interaction of 1 with BSA(Inset: Plot of
F0/F against Q of 1).
Fig.8. Fluorescence emission spectra of the interaction of 2 with BSA(Inset: Plot of
F0/F against Q of 2).
Fig.9. Plots of lg[(F -F)/F] against lg[Q] of 1 and 2.
0
Fig.10. UV-vis spectra of the interaction of 1 with ct-DNA(Inset: Plot of Cct-DNA/(ε -ε )
a
f
against Cct-DNA of 1).
Fig.11. UV-vis spectra of the interaction of 2 with ct-DNA(Inset: Plot of Cct-DNA/(ε -ε )
a
f
against Cct-DNA of 2).
Fig.12. Thermogenic curves of the interactions between 1 and 2 with ct-DNA.
Fig.13. Thermogenic curves of the interactions between 1 and 2 with BSA.
Fig.14. (a) The inhibition zones of 1 against four kinds of bacteria. (b) The inhibition
zones of 2 against four kinds of bacteria. (A, B, C and D represent Escherichia coli,
Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa, respectively. 1,
-1
2
and 3 represent 200, 100 and 50 μg·mL , respectively.).
2
3

Fig.1. Molecular structure of 1.
Fig.2. Crystal packing structure of 1.
Fig.3. Molecular structure of 2.
2
4

Fig.4. Crystal packing structure of 2.
0
0
.014
.012
-1
-1
-1
2
81.73℃
5 ℃·min
0 ℃·min
5 ℃·min
1
00
1
1
0.010
2
85.84℃
8
6
4
2
0
0
0
0
0
0
0
0
0
.008
.006
.004
.002
.000
2
87.36℃
1
38.80℃
1
29.05℃
1
47.67℃
-0.002
0
150
300
450
600
750
Temperature(℃ )
Fig.5. TG-DTG curves of 1.
-
1
1
0.004
1
00
5 ℃·min
2
91.69℃
-
2
83.34℃
10 ℃·min
9
8
7
6
5
4
0
0
0
0
0
0
-1
2
77.84℃
1
5 ℃·min
0
.003
1
14.87℃
0.002
1
21.27℃
0
.001
.000
1
25.02℃
0
0
150
300
450
600
750
Temperature(℃ )
Fig.6. TG-DTG curves of 2.
2
5

3
38.5 nm
1.14
1.11
3
2
1
1
00
40
80
20
1
1
.08
.05
1
7
1.02
1
2
3
4 5
-1
6
-7
Q×10 (mol·L
)
1
2
3
. BSA
. BSA+1 (30μL)
. BSA+1 (60μL)
4. BSA+1 (90μL)
5
6
. BSA+1 (120μL)
. BSA+1 (150μL)
6
0
3
7. BSA+1 (180μL)
00
330
360
390
420
Wavelength(nm)
Fig.7. Fluorescence emission spectra of the interaction of 1 with BSA(Inset: Plot of F /F
0
against Q of 1).
1
.20
.16
3
40.5 nm
1
1
4
3
2
1
00
00
00
1.12
1
.08
.04
1
1
2
3-7
4
5
-1
6
7
Q×10 (mol·L
)
1
2
3
4
5
6
. BSA
. BSA+2 (30μL)
. BSA+2 (60μL)
. BSA+2 (90μL)
. BSA+2 (120μL)
. BSA+2 (150μL)
00
3
7. BSA+2 (180μL)
00
330
360
390
420
Wavelength(nm)
Fig.8. Fluorescence emission spectra of the interaction of 2 with BSA(Inset: Plot of F /F
0
against Q of 2).
-
-
-
-
-
0.6
0.8
1.0
1.2
1.4
1
2
-
7.0
-6.8
-6.6
-6.4
-6.2
lg[Q]
Fig.9. Plots of lg[(F -F)/F] against lg[Q] of 1 and 2.
0
2
6

1
0
0
0
0
0
.0
.8
.6
.4
.2
.0
8
6
4
2
0
y=2.69×10
=0.999
-5x+1.62×10-12
R
2
3
32 nm 389 nm
0
.0 0.5 1.0 1.5 2.0 2.5 3.0
ct-DNA×10-5(mol/L)
C
1
7
-
5
-1
1
.1×10 mol·L (1)
2
3
4
5
6
7
.1+ct-DNA (50μL)
.1+ct-DNA (100μL)
.1+ct-DNA (150μL)
.1+ct-DNA (200μL)
.1+ct-DNA (250μL)
.1+ct-DNA (300μL)
2
80 320 360 400 440 480 520
Wavelength(nm)
Fig.10. UV-vis spectra of the interaction of 1 with ct-DNA
(
Inset: Plot of Cct-DNA/(ε -ε ) against C
of 1).
a
f
ct-DNA
y=6.19×10-5x+4.95×10-12
2
R =0.999
4
3
2
1
0
0
0
0
0
0
0
.30
.25
.20
.15
.10
.05
2
3
30 nm
386 nm
1
7
0
1
2
3
4
5
6
7
8
Cct-DNA×10-5(mol/L)
-
5
-1
1
2
.1×10 mol·L (2)
.ct-DNA (50μL)
3.ct-DNA (100μL)
4
5
6
7
.ct-DNA (150μL)
.ct-DNA (200μL)
.ct-DNA (250μL)
.ct-DNA (300μL)
80 320 360 400 440 480 520
Wavelength(nm)
Fig.11. UV-vis spectra of the interaction of 2 with ct-DNA
(
Inset: Plot of Cct-DNA/(ε -ε ) against C
of 2).
a
f
ct-DNA
T=28℃
4
9.4 min
3
.7 min
4
-1
1
2
, ℃ H=2.57×10 kJ·mol
5
.1 min
4
-1
, ℃ H=2.06×10 kJ·mol
3
.6 min
5
1.4 min
5
.3 min
0
14
28
42
56
70
Time(min)
Fig.12. Thermogenic curves of the interactions between 1 and 2 with ct-DNA.
2
7

T=28℃
3
.8 min
49.0 min
4
-1
1
2
, ℃ H=4.43×10 kJ·mol
4
-1
, ℃ H=1.12×10 kJ·mol
5
.2 min
4
.3 min
5
0.1 min
6
.5 min
0
14
28
42
56
70
Time(min)
Fig.13. Thermogenic curves of the interactions between 1 and 2 with BSA.
a)
(b)
(
Fig.14. (a) The inhibition zones of 1 against four kinds of bacteria. (b) The inhibition
zones of 2 against four kinds of bacteria. (A, B, C and D represent Escherichia coli,
Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa, respectively. 1,
-1
2
and 3 represent 200, 100 and 50 μg·mL , respectively.).
2
8

Graphical Abstract
Two novel Co(II) and Cr(III) complexes were prepared, and the constitutes and
strctures of two complexes were characterizated by elemental analysis, melting point
test and X-ray single crystal diffraction technique. Furthermore, the thermal stabilities
of Co(II) and Cr(III) complexes were discussed and the interactions of Co(II) and Cr(III)
complexes with BSA and ct-DNA were studied by spectrometry and microcalorimetry.
The inhibition activities of Co(II) and Cr(III) complexes against four kinds of bacteria
were investigated and compared with that of gentamycin sulfate.
2
9