Synthesis, spectroscopic characterization, antimicrobial and antitumor studies of mono-, bi- and tri-nuclear metal complexes of a new Schiff base ligand derived from o-acetoacetylphenol

Article abstract of DOI:10.1016/j.molstruc.2017.08.009

New mono-, bi- and trinuclear metal complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and UO₂(VI) with a new Schiff base ligand H₃L; ((E)-2-hydroxy-N′-(4-(2-hydroxyphenyl)-4-oxobutan-2-ylidene)) benzohydrazide (H₃L) have been synthesized. The ligand and its metal complexes were characterized by elemental analyses, IR, ¹H NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The metal complexes exhibited octahedral and tetrahedral geometrical arrangements. Kinetic parameters (E_a, A, ΔH, ΔS and ΔG) of the thermal decomposition stages have been evaluated using Coats–Redfern equations. Structural parameters of the synthesized compounds were calculated on the basis of DFT level implemented in the Gaussian 09 program and Hyperchem 7.52 and correlated with the experimental data. The antimicrobial activity of the present compounds was screened against Gram–positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram–negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus). The antitumor activity of the ligand and its Ni(II) and Cu(II) complexes was investigated against HepG2 cell line.

Full text of DOI:10.1016/j.molstruc.2017.08.009

Accepted Manuscript
Synthesis, spectroscopic characterization antimicrobial and antitumor studies of
mono-, bi- and tri-nuclear metal complexes of a new Schiff base ligand derived from
o-acetoacetylphenol
Omima M.I. Adly, Magdy Shebl, Hoda F. El-Shafiy, Saied M.E. Khalil, A. Taha,
Mohammed A.N. Mahdi
PII:
S0022-2860(17)31073-6
10.1016/j.molstruc.2017.08.009
MOLSTR 24147
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 14 January 2017
Revised Date: 2 August 2017
Accepted Date: 3 August 2017
Please cite this article as: O.M.I. Adly, M. Shebl, H.F. El-Shafiy, S.M.E. Khalil, A. Taha, M.A.N. Mahdi,
Synthesis, spectroscopic characterization antimicrobial and antitumor studies of mono-, bi- and tri-
nuclear metal complexes of a new Schiff base ligand derived from o-acetoacetylphenol, Journal of
Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.08.009.
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ACCEPTED MANUSCRIPT
Synthesis, spectroscopic characterization antimicrobial and
antitumor studies of mono-, bi- and tri-nuclear metal
complexes of a new Schiff base ligand drived from o-
acetoacetylphenol
a
a
a
a
Omima. M.I. Adly *, Magdy Shebl , Hoda F. El-Shafiy , Saied M.E. Khalil , A.
a
a,b
Taha , Mohammed A.N. Mahdi
a
Chemistry Department, Faculty of Education, Ain Shams University, Roxy, Cairo
1341, Egypt
Department of Industrial chemistry, Faculty of Applied science, Hajjah university,
Yemen
1
b
.
The Schiff base, H L, ligand
3

ACCEPTED MANUSCRIPT
Synthesis, spectroscopic characterization antimicrobial and
antitumor studies of mono-, bi- and tri-nuclear metal
complexes of a new Schiff base ligand derived from o-
acetoacetylphenol
a
a
a
a
a
Omima. M.I. Adly *, Magdy Shebl , Hoda F. El-Shafiy , Saied M.E. Khalil , A. Taha ,
a,b
Mohammed A.N. Mahdi
a
Chemistry Department, Faculty of Education, Ain Shams University, Roxy, Cairo
1
1341, Egypt
b
Department of Industrial chemistry, Faculty of Applied science, Hajjah university,
Yemen.
Abstract
New mono- , bi- and trinuclear metal complexes of Cr(III), Mn(II), Fe(III),
Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and UO (VI) with a new Schiff base ligand H L;
2
3
3
((E)-2-hydroxy-N'-(4-(2-hydroxyphenyl)-4-oxobutan-2-ylidene) benzohydrazide (H L)
have been synthesized. The ligand and its metal complexes were characterized by
1
elemental analyses, IR, H NMR, electronic, ESR and mass spectra, conductivity and
magnetic susceptibility measurements as well as thermal analyses. The metal complexes
exhibited octahedral and tetrahedral geometrical arrangements. Kinetic parameters (Ea,
A, ∆H, ∆S and ∆G) of the thermal decomposition stages have been evaluated using
Coats–Redfern equations. Structural parameters of the synthesized compounds were
calculated on the basis of DFT level implemented in the Gaussian 09 program and
Hyperchem 7.52 and correlated with the experimental data. The antimicrobial activity of
present compounds was screened against Gram–positive bacteria (Staphylococcus aureus
and Bacillus subtilis), Gram–negative bacteria (Salmonella typhimurium and Escherichia
coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus). The antitumor
activity of the ligand and its Ni(II) and Cu(II) complexes was investigated against HepG2
cell line.
1

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Keywords: Polydentate Schiff base; o-Acetoacetylphenol; Mono-, bi- and trinuclear
complexes; Molecular modeling; Antimicrobial activity; Antitumor activity.
1
. Introduction
A large number of 1,3-diacarbonyl compounds are of the great interest in the
synthesis of metal complexes with broad spectrum of pharmaceutical activity [1,2]. 1,3-
diacarbonyl compounds are good precursors for the synthesis of a diversity of Schiff
bases and hydrazones through reactions with a variety of amines and hydrazines [3,4].
These ligands and their metal complexes have different applications in different fields
such as bioinorganic chemistry, material science, catalysis, separation and encapsulation
processes, hydrometallurgy, formation of compounds with unusual properties and metal–
metal interactions [5-8]. Metal complexes of these Schiff bases have numerous applications
including antibacterial, antifungal [9–11] antitumor [12] anticonvulsant [13] anti-HIV [14]
and antiviral activities [15,16]. They can be used as an efficient materials in the
polymerization reactions, functional dyes and pigments, medical and pharmaceutical
areas [17,18]. Several applications have been related for these complexes in chemical
analysis [19], absorption and transport of oxygen [20] and in pesticides [21]. There is
great interest about multi-dentate ligands because their binding selectively can be altered
subtly by having the ligand enforce a specific spatial arrangement of donor atoms [22].
The aim of work is to synthesize a new Schiff base ligand, ((E)-2-hydroxy-N'-(4-(2-
hydroxyphenyl)-4-oxobutan-2-ylidene) benzohydrazide, and its metal complexes with
chromium(III), manganese(II), iron(III), cobalt(II), nickel(II), copper(II), zinc(II),
cadmium(II) and dioxouranium(VI) ions. The structures of the ligand and its metal
1
complexes were characterized by using elemental and thermal analyses, IR, H NMR,
electronic, ESR and mass spectra in addition to magnetic susceptibility and conductivity
measurements. Kinetic parameters of the thermal decomposition stages have been
evaluated using Coats-Redfern equations. Molecular modeling was carried out for the
ligand and its complexes and the results were correlated with the experimental data. The
antimicrobial activity of the ligand and its complexes was screened against selected kinds
of bacteria and fungi. Finally, the antitumor activity of the ligand and its Ni(II) and Cu(II)
complexes was investigated against HepG2 cell line.
2

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2
. Experimental
2
.1. Materials
o-Acetoacetylphenol and 2-hydroxybezohydrazied were prepared following the
literature procedures [23, 24]. Metal acetates, metal indicators, EDTA disodium salt,
ammonium hydroxide and nitric acid were either BDH or Merck chemicals. Organic
solvents were reagent grade chemicals and were used without further purification.
2
.2. Synthesis of ((E)-2-hydroxy-N'-(4-(2-hydroxyphenyl)-4-oxobutan-2-ylidene)
benzohydrazide (H L).
3
The new Schiff base (Scheme 1) was prepared by adding o-acetoacetylphenol (2
g, 11.22 mmol) dissolved in absolute ethanol (40 mL) to 2-hydroxybezohydrazied (1.71g,
1
1.22 mmol) in absolute ethanol (40 mL). The reaction mixture was stirred for 6 h and a
yellow precipitate is formed upon cooling the solution to room temperature. The product
was filtered off and washed with few amounts of ethanol then diethylether, air-dried and
recrystallized from ethanol and the yield was 1.7 g (91%). The analytical and physical
data of the ligand (Scheme 1) and its metal complexes are listed in Table 1.
2
.3. Synthesis of the metal complexes
A hot 30 mL ethanolic solution of the metal salt was gradually added to the
solution of the ligand (40 mL) in 1:2 (L: M) molar ratio. The mixture was heated under
reflux for 7 h during which the solid complex precipitated. The precipitate was filtered
off, washed with ethanol or methanol then diethyl ether and finally air-dried and stored in
an evacuated desicator over anhydrous calcium chloride. The following representative
examples are given in details.
2
.3.1. [(H L)Ni(OAc)(H O) ].0.5C H OH, 5
3 2 2 2 5
To 0.5 g (1.60 mmol) of the ligand dissolved in 30 mL ethanol, was added 0.797g
3.20 mmol) of Ni(OAc) ·4H O dissolved in 30 mL ethanol with stirring. The reaction
(
2
2
mixture was heated under reflux for 7 h. The precipitate was filtered off, washed with
ethanol then ether and finally air-dried. Yield: 0.5 g (65%).
3

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2
2 2 2 2
.3.2 [(H L)(UO ) (OAc) ], 9
To 0.5 g (1.60 mmol) of the ligand dissolved in 30 mL methanol, was added
1
.358g (3.20 mmol) of UO (OAc) ·2H O dissolved in 30 mL methanol with stirring. The
2
2
2
reaction mixture was heated under reflux for 7 h. The precipitate was filtered off, washed
with methanol then ether and finally air-dried. Yield: 0.5 g (31%).
2
.4. Analytical and physical measurements
Elemental analyses were carried out using Vario El-Elementar at the Ministry of
Defense, Chemical War Department in Egypt. Analyses of the metals followed the same
procedure as described previously. Analyses of the metals followed decomposition of
their complexes with concentrated nitric acid. The resultant solution was diluted with
bidistilled water and filtered. The solution was then neutralized with aqueous ammonia
solution (except iron(III) complexes) and the metal ions titrated with EDTA [25-27]. IR
spectra were recorded using KBr discs on FT IR Nicolet 6700 spectrometer. Electronic
spectra were recorded as solutions in DMF or Nujol mulls on a Jasco UV–Vis
1
spectrophotometer model V-550 UV–Vis. H NMR spectra were recorded at room
temperature by using a Bruker WP 200 SY spectrometer. Dimethylsulfoxide, DMSO-d6,
was used as a solvent and tetramethylsilane (TMS) as an internal reference. The spectra
were extended from 0 to 18 ppm. The chemical shifts (δ) are given down field relative to
TMS. D O was added to every sample to test for the deutration of the samples. ESR
2
spectra of the complexes were recorded at an Elexsys, E500, Bruker company. However,
the mass spectra were recorded at 70 eV on a Gas chromatographic GCMSqp 1000 ex
Shimadzu instrument. The magnetic susceptibility measurements were carried out at
room temperature using a magnetic susceptibility balance of the type Johnson Matthey,
Alfa product, Model No. (MKI). Effective magnetic moments were calculated from the
1
/2
expression µeff. = 2.828 (χ .T) B.M., where χM is the molar susceptibility corrected
M
using Pascal’s constants for the diamagnetism of all atoms in the compounds [28]. Molar
-3
conductivities of 10 M solutions of the solid complexes in DMF were measured on the
Corning conductivity meter NY 14831 model 441. The TG–DTG measurements were
4

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carried out on a Shimadzu thermogravimetric analyzer in dry nitrogen atmosphere and a
heating rate of 20 ºC/min using the TA-50 WS1 program.
2
.5. Antimicrobial activity
The standardized disc-agar diffusion method [29,30] was followed to determine
the activity of the synthesized compounds against the sensitive organisms Staphylococcus
aureus (ATCC 25923) and Bacillus subtilis (ATCC 6635) as Gram positive bacteria,
Salmonella typhimurium (ATCC 14028) and Escherichia coli (ATCC 25922) as Gram
negative bacteria and Candida albicans (ATCC 10231) and Aspergillus fumigatus as
fungus strain. The antibiotic chloramphenicol was used as reference in the case of Gram-
positive bacteria, cephalothin in the case of Gram-negative bacteria and cycloheximide in
the case of fungi.
2
.6. Antitumor Activity
Cell toxicity was monitored on HepG2 cells by determining the effect of the test
samples on cell morphology and cell viability according to literature method [31].
3
. Results and discussion
The IR spectrum of the free ligand exhibited three characteristic bands at 3437,
-1
1
628 and 1558 cm that may be assigned to ν(O–H), ν(C=N) and ν(
) groups, respectively (Table 2) [4,31].
Electronic spectral data of the ligand in DMF (Table 3) displayed two bands at
C
O) +
ν(
C
C
-1
3
4,843 and 23,041 cm . The first band may be due to n-π* transitions of the azomethine
linkage and the aromatic benzene ring. The second band may be assigned to n-π*
transitions of the C=O group and/or charge transfer transitions within the molecule.
1
H NMR spectrum of the free ligand, dissolved in DMSO-d , presented in Figure 1,
6
showed two signals at 11.79 and 13.42 ppm, which may be assigned to phenolic OH
protons, (Scheme 1). The two signals observed at 10.88 and 10.38 ppm may be assigned
to NH protons in tautomer I (Scheme 2). Signal observed at 2.21 may be assigned to
methyl protons. The aromatic protons were observed in the range of 6.79-7.94 ppm.
5

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Based on NMR spectral data, it was concluded that the ligand exists as tautomers I and II
in solution.
The mass spectrum of the free ligand showed the molecular ion peak at m/z 312
confirming its formula weight (F.W 312.32). The mass fragmentation pattern, presented
in Scheme 3, supported the suggested structure of free ligand (Scheme 1).
.
3
.2. Metal complexes
Reactions of the current ligand with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II),
Zn(II), Cd(II) and UO (VI) ions, in the molar ratio 1:2 (L: M), yielded mono-, bi- and
2
trinuclear complexes. The prepared complexes are stable at room temperature, non-
hygroscopic and insoluble in water and most common organic solvents. The elemental
analyses of the metal complexes agreed well with the proposed formulae (Table 1).
3
.2.1. IR spectra
The IR spectral data of the metal complexes are listed in Table 2. The IR spectra
of the complexes were compared with that of the free ligand in order to resolve the
coordination sites that may be involved in chelation. There are some guide peaks in the
spectrum of the ligand, which were helpful in achieving this goal. Comparison of the IR
spectra of the metal complexes with that of the free ligand revealed that the broad band
-1
around 3437 cm which was assigned to ν(OH) stretching modes in H L was observed in
3
-1
the spectra of all complexes with higher broadness in the range 3272-3470 cm . This
influence was attributed to the effect of coordination of hydroxyl oxygen and/or
coordinated or uncoordinated water molecules associated with the complexes. The
presence of coordinated or uncoordinated water molecules were confirmed by elemental
-1
and thermal analyses. The band assigned to ν(C
O
) + ν(C
C
) at 1558 cm exhibits red
-1
shift in the range 9- 37 cm for Cu(II), UO (II), Co(II) Zn(II), and Ni(II)- complexes,
2
suggesting the participation of the carbonyl oxygen in chelation [32]. However, Cr(III),
Fe(III), Mn(II) and Cd(II) complexes display a blue shift to higher frequencies in the
-1
range 5-10 cm . This might understanding in the light of HSAB (hard soft acid base)
concept, some metal ions prefer coordination with oxygen centers and other favored
6

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nitrogen coordinating centers. This interpretation supported by the negative slope of
ν
(C=O) versus
ν
(M-O);
ν
M-O = -1818.2 – 0.820
ν
C
O, r =0.96, n = 5, except (1, 2,
4
and 7) i.e., increasing the strength of M-O bond order accompanied by elongation of
C=O (decrease the bond strength according to Gutmann's bonds variation rules [33].
-1
The azomethine group ν(C=N) band which appeared as a medium peak at 1628 cm in
the spectrum of the ligand appeared at lower wavenumber for some complexes in the
-1
-1
range 22-54 cm . Nevertheless, δ(C-N) deformation mode (1480 cm ) displays a red
-1
shift in the range 7-56 cm for all the complexes, except for Mn(II)- and Ni(II)-
-1
complexes which has higher frequency 1496 and 1499 cm , respectively compared with
that of the free ligand. This approves in the participation of the azomethine group of the
enol form (see Scheme 2) in chelation [34]. This consequence confirmed by the linear
relationship of ν(C=N) with ν(M-N), νM-N = 1304.3 – 0.591 νC=N, r =0.94, n = 6,
except (3, 5 and 8). The negative slope emphasized that increasing the M-N bond strength
go along with the bond weakness of C=N. Moreover, the new bands appeared in the
-1
ranges 503-594 and 426-483 cm those assigned to ν(M-O) and ν(M-N), respectively
35-37].
Complexes 1 and 4 -7 showed new bands at (1687-1600) and (1389-1345) cm
[
-1
−
−
which may be assigned to νasym(COO ) and ν (COO ) of the acetate group. The
sym
difference between the two bands indicates the monodentate nature of the acetate group
[38-40]. On the other hand, complexes 2 and 9 showed new bands characteristic for
−
−
νasym(COO ) and ν (COO ) of the acetate group in ( 1600 and 1601) and (1496 and
sym
−
1
-1
1
497) cm , respectively. The difference between the two bands (104 cm ) indicates a
bidentate fashion of the acetate group [38-40]. Complex 3, displayed new bands at 1383
-1
–
and 1146 cm , which may be assigned to the monodentate NO
3
group [41,42]. The
-1
dioxouranium(VI) complex 9 showed a strong band at 912 cm , which may be assigned
to the ν (UO ) [35,36,43]. The value of ν is utilized to calculate the force constant (F) of
3
2
3
(O=U=O) by using McGlynn and Smith relation [44]. The calculated force constant is
6
.867mdyn/Å. The U–O distance is also calculated by using Jones relation [45]. The
value of RU–O is 1.738 Å. The calculated FU–O and RU–O values are consistent with the
reported range for the uranyl complexes [46].
7

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The molar conductivity values of the metal complexes at room temperature (Table
-1
2
-1
3
) are in the range 6.8-32.8 ꢀ cm mol indicating that all complexes have non
electrolytic nature [47]. This finding is consistent with the infrared spectral data that
showed the coordinated nature of acetate and nitrate anions.
3
.2.3. Electronic spectra and magnetic moment measurements
The electronic spectral data of the metal complexes in DMF solution and/or Nujol
mull, and magnetic moment at room temperature are and listed in Table 3.
Comparison of the UV-Vis spectra of the current metal complexes with that of the
free ligand, showed the persistence of the ligand bands in all complexes. However, the
bands were slightly shifted to blue or red regions of the spectrum in all complexes. Also,
new bands were observed in the spectra of the complexes which are listed in Table 3.
The electronic spectrum of Cr(III) complex 1 showed three absorption bands in the
-1
4
visible region at 22371, 21834 and 17301 cm those assigned to MLCT, T2g(F)
4
4
4
←
A (F) and T (F) ← A (F) of d-d transitions of the octahedral geometry [48,49].
2g 1g 2g
4
4
Whereas the third d-d transition band which is due to T1g(P) ← A2g(F) transition lies in
-1
the range of the ligand transitions that predicted at 36287cm . The ligand field
parameters of the Cr(III) complex in progress has been calculated using Tanab–Sugano
-1
-1
diagrams B (414.5 cm ), 10Dq (1730 cm ) and β (0.40). The measured magnetic
moment value found to be 3.82 B.M analogues to the spin-only of three unpaired
electrons.
The spectrum of Mn(II) complex 2 showed a series bands at 22173, 20576, 19960
-1
4
2
4
2
4
and 16807 cm , these bands assigned to A (G) ← T2g, T (E) ← T , T (G)
1
g
1g
2g
2g
2
4
2
←
T2g and
T
1g(G) ← T2g transitions, respectively, which corresponds to a tetrahedral
structure. The calculated ligand field parameters of the current Mn(II) complex are found
-1
-1
to be : B (575.5 cm ), 10Dq (10935 cm ) and β (0.60). The magnetic moment has low
of Mn(II) complex (5.11 B.M) due to metal–metal interaction [50].
The electronic spectrum of Fe(III) complex 3 showed three absorption bands at
-1
1
9608, 18450 and 17637 cm . The former band could be assigned to a charge transfer
2
2
2
2
band and the later bands can be assigned to A (I) ← T and T (F) ← T
1
g
2g
2g
2g
8

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electronic transition [51]. The value of the magnetic moment of complex 3 is 4.72 B.M.,
which is less than expected for octahedral Fe(III) complexes (5.92 B.M.), suggesting an
equilibrium between the high spin and low spin octahedral species in the ratio 79.73%
[52].
The electronic spectrum of Co(II) complex 4 exhibits two bands at (21413, 19268
−
1
−1
4
4
cm ). The first band at 21413cm might assigned T1g (P) ← T1g (F),(ν
3
), whereas the
−
1
4
4
second band at 19268 cm . A (F) ← T (F) (ν ) assigned to the transition, suggesting
2
g
1g
2
that there is an octahedral geometry around the Co(II) ion. This emphasized by the
magnetic moment value, µeff 5.74 B.M, the higher value may be due to orbital
contribution, that related to high spin octahedral geometry around cobalt(II) ion [42,53].
=
−
1
The ν band not observed, but it can be intended and found at 9132 cm . The calculated
1
-1
-1
ligand field parameters were B (263cm ), 10Dq (913 cm ) and β (0.27), within the range
reported for octahedral structure [52].
The UV-Vis spectrum of Ni(II)-complex 5 exhibits four bands 31250, 24450, 22831
-1
-1
and 17482 cm . The higher energy band, 31250 cm assigned to n-π* and the band at
-1
3
2
4450 cm suggested for MLCT. Whereas the other two bands assigned to T (F) ←
1g
3
3
3
A
2g(F) and T1g(P) ← A2g(F) transitions, representing octahedral structure [53]. This
finding was further emphasized by the measured magnetic moment at 3.18 B.M., which
lies in the range (2.9-3.3 B.M) of the Ni(II) octahedral complexes [54]. The spectral data
-1
-1
provide the ligand field parameters: B (501 cm ), 10Dq (8654 cm ) and β (0.46), and the
3
3
-1
first transition band, T (F) ← A (F), in the spectrum predicted at 37129 cm .
2
g
2g
-1
The electronic spectrum of the Cu(II) complex 6 showed one band at 16,313cm
2
2
that may be assigned to ( E ← T ) transition corresponding to distorted octahedral
g
2g
geometry [55]. The effective magnetic moments of the Cu(II) complex is 2.20 B.M.,
9
which is consistent with one unpaired electron (d ) [53]. This interpretation supported by
the X-band ESR spectrum of the Cu(II) complex, that recorded in the solid state at 25 °C.
The spectrum exhibits one broad band (Figure 2) with g
⊥ ǁ
= 2.05 and g = 2.30 the profile
of the spectrum is consistent with the octahedral geometry [56].
9

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The Zn(II) 7 and Cd(II) 8 complexes are diamagnetic as expected and display two
-1
absorption bands for Zn(II) 7 at 24570 and 21930 cm ; and 24691, 22371 and 21186
-1
cm for Cd(II) 8 complex. These bands might attribute to π → π * and n→ π * transitions
in the vicinity of the Schiff base ligand, in addition to MLCT transition.
The electronic spectrum of UO (VI) complex 9 showed two absorption bands at
2
-1
2
4631 and 20767 cm , just similar to that found for Zn(II) complex 7. The lower energy
band might arises from metal → ligand charge transfer (MLCT) and/or apical oxygen
o
→
F (U) [57]. However the other band in the UV region could be attributed to n→ π*
electronic transition in the vicinity of ligand The magnetic moment measurement of the
UO (VI) complex 9 refers to the diamagnetic behavior as expected.
2
3
.2.4. Thermal analysis
The simultaneous thermal gravimetric analysis (TGA) of metal complexes studied
from ambient temperature to 800 °C in nitrogen atmosphere were depicted in Figs 3-5.
TGA help to explore the associated water or solvent molecules to be in the inner or outer
coordination sphere of the central metal ion. Complexes 1, 2, 4, 5, 6 and 9 were taken as
representative examples for thermal analysis. The results of thermal analysis were
summarized in Table 4, the data given are in good agreement with the theoretical
formulae suggested from elemental analyses.
The thermogram of Cr(III) complex 1 exhibited that the compound
exhibited three decomposition stages. The first stage in the temperature range 46-101°C,
which correspond to the weight loss of half non-coordinated water molecule (weight loss;
Calc./Found%; 1.12/1.11). The second stage in the temperature range 103-180°C, which
match to the loss of two-coordinated water molecules (weight loss; Calc./Found%;
4
.87/5.18). However, the third stage which occurred between 180-434°C, which
correspond to the loss of two-coordinated water molecules and half CH COOH molecule
3
(weight loss; Calc./Found%; 8.94/8.88).
The thermogram of complex 4 showed two weigh losses in the ranges 45-190°C
o
and 190-510 °C. The first stage observed at DTG peak = 114 C that corresponding to
four coordinated water molecules (weight loss; Calc./Found%; 16.25/16.05). The second
1
0

ACCEPTED MANUSCRIPT
o
3
stage at DTG peak = 393 C which analogues to the loss of three CH COOH molecules
(weight loss; Calc./Found%; 24.44/24.30).
The thermogram of complex 5 shows three decomposition stages, 20-70°C, 84-
79 and 280-799 °C. The first stage corresponds to half non-coordinated ethanol
2
molecule (weight loss; Calc./Found%; 4.74/4.17). The second stage in the temperature
which suggest loss of two coordinated water and half CH COOH molecules (weight loss;
3
Calc./Found%; 13.72/13.83). The last stage in the temperature range 280-799°C, which
analogues to the loss of half CH
Calc./Found%; 59.20/59.04).
3 10 2 3
COOH and C14H N O molecules (weight loss;
In order to access the influence of the type of the metal on the thermal behavior of
the complexes, the order n, and the activation parameters of the various decomposition
stages were determined from the TG thermograms using the Coats-Redfern equations
[52].
The order (n) and thermo kinetic parameters: activation energy (E ), enthalpy
a
(ꢁH*), entropy (ꢁS*) and free energy changes (ꢁG*) of the thermal degradation of the
complexes are are calculated as described elsewhere and tabulated in (Table 5) [34].
Inspection of the data in Table 5 advocate, the following remarks:
The negative values of ꢁS* indicate that the activated complex is more ordered
than the reactants and/or the reactions are slow [58]. This interpretation emphasized by
the negative slope of the linear relationship of Egap versus ꢁS*, E /eV = -6.43 – 0.058
gap
ꢁS*, r = 0.97, n = 5 all TGA points included. i.e., increasing the calculated energy gap
(
vide infra) that reveal high stable complex was accompanied by more ordered complex
-ve ꢁS*). Furthermore, the negative slope of the computed ELUMO (measures the stability
(
of the complex) with the entropy changes; ELUMO/eV = -3.75 – 0.012 ꢁS*, r = 0.98, n = 4
except Cu(II)-complex, supported decreasing of entropy with the increasing of the
complex stability. Consequently, the rate of decomposition decreases with the increasing
of the stability of complexes [59]. Additionally, the positive slope of the relationship of
f f
computed ꢁH against ꢁS*, ꢁH = 1.92 e5 + 846.1 ꢁS*, r = 0.999, n = 3 except Cr(II)-
and Cu(II)-complexes, reveals again that less stable complex (high ꢁH ) is easier to
f
decompose (less –ve values of ꢁS*)
1
1

ACCEPTED MANUSCRIPT
The positive values of ꢁH* mean that the decomposition stages are endothermic.
Increasing the stability of complex, leads to decreases the binding coordination sphere
with the hydrated water molecules, so they will be easier to remove from the outer
sphere. This interpretation emphasized by the –ve slope of Egap/eV versus ꢁH*; Egap
=
-1
9
.67 – 0.072 ꢁH*/kJ.mol , r =0.996, n= 4, except Cu(II)-complex. This means that
increasing the stability of complex (high Egap) accompanied by effortless dehydration of
water molecules.
The positive sign of ꢁG* values indicates autocatalytic effect of metal ions on the
thermal decomposition of the complexes and non–spontaneous processes
3
.2.5. Mass spectra
The molecular ion peaks observed in the mass spectra of free ligand and some
complexes 2- 5, 8 and 9 taken as representative examples are confirmed their proposed
formulae. Figures 6 and 7 depicts the mass spectra of complexes 2 and 5 and the mass
fragmentation pattern of complex 2 shown in Scheme 4. Complexes 2 and 4 showed the
molecular ion peaks at m/z 540 and 738 respectively which agree well with the formula
weights of the non-hydrated or non-solvated complexes; [(HL)Mn (OAc) ] and
2
2
[
(H L)Co (OAc) (H O) ]. This agrees the proposed formulae of these complexes as 2:1;
2 2 4 2 4
M:L. However, complexes 3, 5, 8 and 9 displayed the molecular ion peaks at m/z 964,
88, 827 and 986, respectively are in consistent with the proposed formulae weights
calculated for [(HL)Fe (NO (H O) ].2H O, [(H L)Ni(OAc)(H O) ]. 0.5C OH,
(H L) Cd].5H O and [(H L)(UO ) (OAc) ].H O complexes, confirming with 1:3, 1:1,
4
3
3
)
6
2
6
2
3
2
2
2 5
H
[
3
2
2
2
2 2
2
2
2
:1 and 1:2; M:L stoichiometry.
1
3
.2.6. H NMR spectra
1
2
H NMR spectral data of the metal complexes Zn(II),Cd(II) and UO (IV) dissolved
in DMSO-d , given in Figure 1 and summarized in Table 6 exhibited signals at
6
(13.88,14.12) and (13.87,15.41) ppm in Zn(II) and Cd(II) respectively, which may be
assigned to two phenolic OH protons which indicate that OH group indicating that OH
group don't participate in the coordination. In UO (IV) complex only one OH proton was
2
appeared in the spectrum at 13.68 ppm and the other one was not observed indicating its
1
2

ACCEPTED MANUSCRIPT
participation in the coordination. The two signals observed at 13.00, 12.4 and11.71 ppm
may be assigned to NH protons (tautomer II is dominant) (Scheme 2). Signals observed
at 5.28, 5.41 and 6.06 in Zn(II), Cd(II) and UO (IV) respectively attributed to CH=CN
2
(olofinic proton) and this confirm that the tautomer II is more predominant in the solution
while in the solid state the tautomer I is predominant (Scheme 2).
Based on the above interpretation of different analytical and spectral data, the
proposed structures of the metal complexes are represented in Figure 8
4
. Molecular Orbital Calculations
The molecular structures were elucidated on the basis of the spectral, molar
conductance, magnetic susceptibility and TGA data which designated that the octahedron
geometry for the current complexes. All molecular calculations were performed in the
gas phase for the elucidated structures of the free ligand and its metal complexes except
uranyl-complexes 9 (see Figures 9-12). The free ligand has been geometrically optimized
by means of Density Functional Theory (DFT) using the B3LYP and the basis set 6-31G
level, provides by the Gaussian 09 program. However, the metal complexes are
geometrically optimized, on the basis of PM3 level using semi-empirical implemented on
Hyperchem 7.52 program as a result of the complication of the presence of metal ion and
higher molecular mass, which requires unavailable workstation in our lab. The utility of
quantum chemical descriptors such as heat of formation, dipole moment and frontier
molecular orbitals (highest occupied molecular orbital and lowest unoccupied molecular
orbitals energies) are collected in Table 7 in elucidating the structure of the current
compounds.
The frontier molecular orbital (FMO) contribution is very important in
determining the charge-separated states of the studied molecules because the relative
ordering of occupied and virtual orbital provides a reasonable qualitative indication of
excitation properties and provides also the ability of electron hole transport [48]. The
energies of the frontier molecular orbitals of studied molecules are given in Table 7. A
comparison between the bond lengths of the ligand and its metal complexes was
demonstrated in Table 8. It is well known that the HOMO and LUMO energies and
energy gaps are weightily relative to optical and electronic properties.
1
3

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The detailed data of absolute energy of the frontier orbital calculated by DFT for
the free ligand. The distributions and energy levels of the HOMO-2 (-6.569 eV), HOMO-
1
(-5.930 eV.), HOMO (-5.212 eV), LUMO (-1.659 eV.), LUMO+1 (-1.074 eV) and
LUMO+2 (-0.272 eV.) orbitals were computed at the B3LYP/6-31G level for the current
ligand. Both the highest occupied molecular orbitals (HOMOs) and the lowest-lying
unoccupied molecular orbitals (LUMOs) are mainly localized on the rings of both sides
as shown in the contour plots of the frontier orbitals of the free ligand Figure 13
(HOMO& LUMO density), indicating that the HOMO are mostly the π-antibonding type
orbitals. The HOMO orbitals are mainly delocalized on the o-acetoacetyl moiety and
Schiff base linkage part, while the LUMO orbitals are mainly delocalized on phenyl rings
*
*
of both sides. Namely, electron transitions are corresponding to the n-π and π - π
electron transitions. The value of the energy separation between the HOMO and LUMO
for the free ligand (3.55 eV).and this low energy gap indicates that the current ligand is
potentially interesting for electronic transitions.
It is well established that HOMO orbitals account for the Lewis basicity [49],
whereas LUMO orbitals characterize the Lewis acidity. According to the frontier
molecular orbital approximation, high value of EHOMO infers that the molecule or ligand
can easily release electrons to the unoccupied orbital of the metal ion, indicating strong
Lewis base [49]. However, high ELUMO suggest that the metal ion can easily accept
electrons from the occupied orbital of the ligand, indicating strong binding affinity.
Furthermore, the extent of Lewis Acid-Base interaction of the current compounds
analogues to Egap values (Egap = ELUMO- EHOMO) which are linearly correlated with the
-1
stretching vibrational frequencies of νC=O, E /eV = 255.56 – 0.1617 νC=O/cm , r
gap
=
0.98, n = 4, except: Mn(II), Cu(II), Zn(II) and Cd(II)-complexes. The negative slope
emphasized that, increase the stability of the complex accompanied by the elongation of
of the carbonyl group (hypsochrmic shift of the vibrational frequency). However,
-
1
∆
H
f
/Kcal/mol = -5816 + 37 .152 ν C O/cm , r = 0.96, n = 5 except 1, 2, 6, 8 and 9
complexes. The positive slope indicates again that increasing of heat of formation, ∆Hf
relevance to weak stability of complex) lead to blue shift of the vibrational frequency of
ν C Obond (weak interaction of the carbonyl group toward the metal ion).
Furthermore, comparison between the bond lengths of the free ligand coordinating
(
1
4

ACCEPTED MANUSCRIPT
centers and their corresponding values in its metal complexes (Table 8) demonstrates
elongation of the coordinating centers after coordination (C=O , 1.216 (free ligand) –
a1
o
o
1
.502 A (Fe(III)-complex and C=N 1.301(free ligand – 1.519 A (Cd(II)-complex)),
1
which agree well with the Gutmann’s bonds variation rules [33]
.
The vibrational analysis of the current free ligand (H L) is performed on the basis of the
3
characteristic vibrations of functional groups modes. The vibrational frequencies
calculated given in parenthesis have been summarized in Table 2. Comparison between
the calculated and the observed vibrational spectra helps us to understand the observed
spectral features. Comparison of the frequencies calculated by B3LYP with experimental
values reveals the overestimation of the calculated vibrational modes due to neglect of
anharmonicity in real system.Inclusion of electron correlation in density functional
theory to a certain extent makes the frequency values smaller in comparison with
experimental valuesThe linear relationship between the experimental and the calculated
-1
-1
2
characteristic IR bands, νExp/cm = 1.013 νCalc/cm -18.74, R = 0.999, supports the
assignments of the characteristic IR bands
Furthermore, the linear correlation between the calculated dipole moment (µ)
-1
versus the vibrational frequency of νM-O, µ/D = -84.119 + 0.209 νM-N/cm , r= 0.973, n =
, except 1 and 9 complexes. The positive slopes put forward increase of the µ- values
was accompanied by increasing the M-N bond strength.
7
5
. Antimicrobial Activity
The Schiff base ligand and its metal complexes were screened for antimicrobial
activity against Gram positive bacteria (S. aureus, G+1 and B. subtilis, G+2), Gram
negative bacteria (S. typhimurium, G-1 and E. coli, G-2) and fungi (C. albicans, Y and A.
fumigates, F) and the results are listed in Table 10. The ligand is high active against S.
aureus, G+1 and S. typhimurium, G-1, whereas intermediate or low active against other
microorganisms under investigation. Inhibition was found to increase with increasing
concentration of metal complex as shown in Table 9.
However, the activity of the current complexes toward the screened
microorganisms could be summarized: complex 4 showed high activity towards Bacillus
subtilis (G+2) and Candida albicans (Y), while complexes 5 and 8 showed high activity
1
5

ACCEPTED MANUSCRIPT
toward Staphylococcus aureus (G+1) and complex 8 showed high activity towards
Bacillus subtilis (G+2). Whereas, complexes: 5 and 6 showed high activity against
Candida albicans (Y). Complexes 2, 6 and 9 showed moderate activity towards Bacillus
subtilis (G+2). Complexes 4, 5 and 8 showed moderate activity towards Salmonella
typhimurium (G-1). But complexes 7, 8 and 9 showed moderate activity towards Candida
albicans (Y).
Stability of the complex play again an important role on biological activity of the
current complexes as deduced from the linear relationships of the IR data versus the data
in Table 9. The negative slopes of the stretching vibrational frequencies of the carbonyl
or azomethine group (higher hypsochromic shift relevant to higher Lewis acid-base
-1
indicators) versus the biological activity against either Y1 or G+2, νC=O/cm = 1603 -
+
2
-1
1
09.5Y1, r = 0.97, n= 6 except 3, 4, 5 and G = 18.02 – 0.011
νC=N/cm , r = 996, n = 4
except 1, 2, 6, 8 and 9 complexes.
It was noticed in elucidating the microbial activity to find a correlation of Frontier
orbitals energy HOMO, LUMO and Egap, with the biological activity of the screened
organisms yield: EHOMO/eV = -5.059 – 4.417G+2, r = 0.99, n = 4 except 1, 2, 7 and 9
complexes. The negative slope reveals decreasing the biological activity toward gram
positive with the increasing of EHOMO (less stability). This interpretation emphasized by
the positive slope of the linear correlation of E , that relevance to stability of complexes
gap
against the biological activity toward the current microorganism: Egap /eV = 5.145 +
4
.772G-1, r = 0.981, n = 5; i.e., the biological activity enhanced towards gram negative
and gram positive with the increasing of complex stability. Furthermore, the extent of
electrondonating properties of ligand to the metal ion (ED) is linearly correlated with a
-1
positive slope versus the data in Table 9: ED/Kcal.mol = 5.146 + 4.77, G-1 r = 0.98
n = 5 and ED (y) = -1.642e +05 + 7.267e+05G+1, r = 0.998, n = 4 except complex 1.
The enhancement of bacterial activity of ligand after chelation can be attributed to the
positive charge of metal ion that partially or completely neutralized by the ligand anion
and/or shared with donor atoms present on ligand and possible π-electron delocalization
over the whole chelate ring. This, in turn, increases the lipophilic character of the metal
chelate and favors its permeation through the lipid layers of the bacterial membranes
resulting in interference with normal process. This interpretation supported by the
1
6

ACCEPTED MANUSCRIPT
positive slope of the linear correlations of the dipole moment against the data in Table 9:
Dipol moment (y) = -3.633 + 24.043 G+2, r = 0.986 n = 5 and Dipol moment = -16.29 +
4
0.67 F , r = 0.97, n = 5.
1
6
. Antitumor Activity
The anticancer activity of the Schiff base ligand and its Ni(II) and Cu(II)
complexes was determined in vitro against human cancer cell line liver Carcinoma
(
HEPG2). Table 10 schedules the values of IC , compared with the standard drug
50
doxorubicin The ligand and its complexes showed lower activity and the order of
.
activity is as follows: Cu(II) complex > Ni(II) complex >H L ligand. The difference in
3
activity of the complexes indicates that the type of ion may be the reason for the different
anticancer activity [60].
7
. Conclusion
A new Schiff base ligand was synthesized and characterized. Mononuclear
complexes were obtained in case of Cu(II), Ni(II), Zn(II) and Cd(II) ions. The
coordination sites of Cu(II) complex is O,N,O,O sites while Ni(II) and Zn(II) complexs
coordination sites are O,N,O sites and Cd (II) complex showed M:L ; 1:2 molar ratio.
2
binuclear complexes were obtained in case of Cr(II), Mn(II), Co(II) and UO (VI) ions.
The coordination sites is O,O,O,O sites. Trinuclure complex in case of Fe (III) complex.
The coordination sites of is O,O,N,O,O sites. The geometrical structures were proposed
for metal complexes such as octahedral structure for all complexes except Mn(II) and
Zn(II) complexes showed tetrahedral arrangement. Kinetic parameters of the thermal
decomposition stages have been evaluated using Coats–Redfern equations. The molecular
parameters of the ligand and its metal complexes have been calculated and correlated
with the experimental data. The antimicrobial activity of the ligand and its complexes
were investigated. The antimicrobial activity of the ligand and its complexes was
investigated. The antitumor activity of the ligand and its Ni(II) and Cu(II) complexes was
investigated against HepG2 cell line.
1
7

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7
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(
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[
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Table 1. Analytical and physical data for transition metals complexes of H L ligand.
3
No.
Reaction
Color
Yield
%)
M.P
°C
Elemental analysis, % found/(calc.)
(
Complex
M. F. [F. Wt]
C
H
N
M
H3L
[(H L)][312.32]
Yellow
Brown
91
75
188
64.40
5.05
(5.16)
9.02
(8.97)
-
3
(65.37)
C H N O
4
17
16
2
1
2
3
4
5
6
7
8
9
[(L)Cr (OAc) (H O) ].0.5H O
>300
40.94
4.10
(4.69)
3.76
(3.83)
14.85
(14.21)
H L + Cr(OAc)3
·
H O
2
2
4
2
4
2
3
(41.13)
C H N O Cr [730.06]
25
34
2
16.5
2
.
H L + Mn(OAc)2 4H O
[(HL)Mn (OAc) ]
Orange
Brown
90
75
82
65
65
85
50
75
>300
>300
>300
>300
>300
>300
>300
>300
45.97
46.86)
3.73
(3.74)
4.64
(5.20)
20.01
(20.41)
3
2
2
2
(
(
(
(
(
(
(
(
C H N O Mn [538.26]
21
20
2
8
2
H L + Fe(NO ) .·9H O [(HL)Fe (NO ) (H O) ].2H O
20.46
20.55)
2.92
(2.94)
11.33
(11.28)
16.90
(16.91)
3
3 3
2
3
3 6
2
6
2
C H N O Fe [993.447)
17
29
8
30
3
H L + Co(OAc)2·4H O [(H L)Co (OAc) (H O) ]
Yellowish
brown
39.79
40.66)
3.43
(4.91)
3.81
(3.79)
15.30
(15.96)
3
2
2
2
4
2
4
C H N O Co [738.42]
25
36
2
16
2
[(H L)Ni(OAc)(H O) ].0.5C H O
Greenish
yellow
49.62
49.21)
4.20
(5.16)
5.78
(5.73)
11.75
(12.06)
H L + Ni(OAc)2
3
·
4H O
3
2
2
2
5
2
HC H N O . Ni [488.10]
20
25
2
8 5
H L+ Cu(OAc)2·H O
[(H L)Cu(OAc) ]
Olive green
48.93
51.06)
4.27
(4.48)
6.63
(5.67)
12.71
(12.86)
3
2
3
2
C H N O Cu [493.95]
21
22
2
8
[(H L)Zn(OAc)]
Yellow
51.90
52.42)
4.10
(4.16)
6.60
(6.43)
14.30
(14.93)
H L+ Zn(OAc)2
3
·
2H O
2
2
C H N O Zn [435.35]
19
18
2
6
H L+ Cd(OAc)2.2H O
[(H L) Cd].5H O
Yellow
49.18
49.52)
4.19
(4.89)
6.85
(6.79)
13.08
(13.58)
3
2
3
2
2
C H N O Cd [824.71]
34
40
4
13
[(H L)(UO ) (OAc) ].H O
Brown
25.36
25.57)
2.23
(2.24)
3.00
(2.84)
-
H L+ UO (OAc) .2H O
2
2 2
2
2
3
2
2
2
C H N O U [986.41]
21
22
2
13
2

ACCEPTED MANUSCRIPT
Table 2. Characteristic IR spectral data of the ligand H L and its transition metals complexes chelates.
3
-1
No.
complexes
IR Spectra (cm)
ν(OH)
H O /
2
νNH
νC=N
C
O
C
N
νM-O
νM-N
Other bands
ν
+
ν
EtOH/
phenolic
3437
C
C
ν
H3L
3254
1627
1558
1480
-
-
1334 (1346), 1292 (1267), 1224
(
3286)* (1616)
(1578)
(1462),
(1208), 1162(1195),1070(1065)
‒
‒
1
[(L)Cr (OAc) (H O) ].0.5H O
2
4
2
4
2
3406
3270
1606
1563
1451
594
442
1687; ν (COO ), 1398; ν (COO );
as
s
5
43
(monodentate OAc)
‒
‒
2
3
4
5
6
7
8
9
[(HL)Mn (OAc) ]
2
2
3426
3373
3376
3410
3470
3429
3463
3272
3285
-
1591
1603
1590
1599
1599
1600
1606
1601
1567
1568
1560
1564
1521
1549
1566
1574
1450
1510
531
593
560
532
540
549
532
503
426
483
470
463
1600; ν (COO ), 1496; ν (COO );
as
s
(
bidentate OAc)
1383, 1146; ν(NO ) (monodentate)
3
‒
[(HL)Fe (NO ) (H O) ].2H O
3
3 6
2
6
2
1
468
‒
‒
[(H L)Co (OAc) (H O) ]
3260
3294
3183,
1424
1680; ν (COO ), 1345; ν (COO );
as s
2
2
4
2
4
(
monodentate OAc)
‒
‒
[(H L)Ni(OAc)(H O) ].0.5C H OH
1499
1683; ν (COO ), 1394; ν (COO );
3
2
2
2
5
as s
(
monodentate OAc)
‒
‒
[(H L)Cu(OAc) ]
1501
1447
1502
446
417
430
1620; ν (COO ), 1376; ν (COO );
3
2
as s
3
063
(monodentate OAc)
‒
‒
[(H L)Zn(OAc)]
3252
3281
3190
1600; ν (COO ), 1379; ν (COO );
3
as s
1
473
1496
470
1468
(monodentate OAc)
-
[(H L) Cd].5H O
466
429
439
3
2
2
1
‒
‒
[(H L)(UO ) (OAc) ].H O
1601; ν (COO ), 1497; ν (COO );
2
2 2
2
2
as
s
(
bidentate OAc) and 912; ν(O=U=O)
*
vibrational bands in paranthesis computed on the basis of semiemperical PM3 level by means of Hyperchem 7.52.

ACCEPTED MANUSCRIPT
Table 3. Electronic spectra, magnetic moments and molar conductivity data of the H L ligand and its complexes
3
a
d
e
b
Electronic spectral bands (nm)
µcompl
µeff.
Conductance
-1
2
-1
No.
Complex
H3L
B.M.
B.M.
(ꢀ cm mol )
b
(34,843,23,041)
-
-
12.5
c
1
[(L)Cr
[(HL)Mn
[(HL)Fe (NO
L)Co (OAc)
L)Ni(OAc)(H
L)Cu(OAc)
L)Zn(OAc)]
L) Cd].5H
L)(UO (OAc)
2
(OAc)
(OAc)
(H
(H
4
(H
2
O)
4
].0.5H
2
O
(22,371,21,834,17,301)
6.50
7.23
3.82
6.80
31.60
32.80
a
c
2
3
4
5
6
7
8
2
2
]
20,576 (22,172,20,576,19,960,16806)
5.11
a
)
O)
2
].2H
O)
O
19,608, 18,450, 17,636
8.17
8.12
3.18
2.20
-
4.72
3
3
6
6
2
a
[(H
[(H
[(H
[(H
[(H
]
21,413, 19,268
5.74
13.50
26.70
9.44
2
3
3
3
3
2
4
2
4
c
O)
2
].0.5C
2
H
2
OH
5
(31,250, 24,450, 22,831, 17,482)
-
-
-
-
b
]
2
(16,313)
c
(24,570,21,930)
20.70
22.30
c
O
2
(24,691,22,371,21,186)
-
2
c
9
[(H
2
)
2
2
2
].H
O
2
(24,630,20,746)
-
-
8.75
a
Nujol mull.
Solutions in DMF (10 M).
b
-3
c
concentrated solutions
d
µcompl. is the total magnetic moments of all cations in the complex.
µeff. is the magnetic moment of one cationic species in the complex
e

ACCEPTED MANUSCRIPT
Table 4. Thermal gravimetric results of the H L ligand and its metal complexes
.
3
Compound
DTG
peak (ºC
Temperature
range (ºC)
Decomposition product lost
Weight loss (%)
(formula weight) found (calculated)
)
[
(L)Cr (OAc) (H O) ].0.5H O 1
80
46-103
103-180
180-434
-0.5H O
1.11 (1.21)
5.18 (4.87)
8.88 (8.94)
2
4
2
4
2
2
1
3
34
59
-2H O
2
-2H O+ 0.5CH COOH
2
3
[
[
(HL)Mn
(OAc)
] 2
270
39
221-296
297-391
-CH COOH+CO
3
16.05 (16.29)
55.38 (55.71)
2
2
3
- CH COOH+C H N O
3 14 13 2 2
(H
(H
L)Co
(OAc)
2
] 4
4
114
45-190
190-510
- 4H
O
2
9.30 (9.70)
24.44 (24.30)
2
3
93
-3 CH COOH
3
[
L)Ni(OAc)(H
3
O)
2
].0.5C H
2 2
OH 5
5
60
20-70
84-279
280-799
-0.5 C H
2
OH
5
4.17(4.71)
13.83 (13.72)
59.20 (59.04)
2
3
46
46
-2H O+ 0.5CH COOH
2
3
-0.5CH COOH +C H N O
3
14 10
2
3
[
[
(H
L)Cu(OAc)
] 6
312
292-345
345-475
-2CH
COOH
25.05(24.84)
43.92(44.65)
3
2
3
4
19
- C H O N
11 12 3 2
(H L)(UO ) (OAc) ].H O 9
85
47-153
154-605
-H O
1.85 (1.83)
8.14 (8.92)
2
2 2
2
2
2
4
7
06
36
-CH COOH+CO
3
Table 5. Temperature of

ACCEPTED MANUSCRIPT
decomposition, and the kinetic of metal complexes
Complexes
Step
First
T (K)
353
A
S )
31.09
E
∆H
(kJ mol )
∆S (kJ
mol−1K )
- 0.094221
∆G (kJ
mol )
−1
−1
−1
−1
−1
(
(kJ mol )
29.40
[
[
(L)Cr (OAc) (H O) ].0.5H O 1
26.63
58.33
87.29
33.287
93.640
102.41
2
4
2
4
2
Second
Third
407
22.46
61.71
92.53
- 0.22994
- 0.1669
631
68280.59
(HL)Mn (OAc) ] 2
First
543
613
154939.97
46.587
121.135
44.896
161.62
39.80
- 0.15885
- 0.22728
86.416
139.36
2
2
Second
[
(
(H L)Co (OAc) ] 4
First
Second
First
387
666
333
519
73.29
45.17
8.16
4.92
37.95
22.082
31.67
- 0.21972
-0.22823
- 0.22688
- 0.22766
85.04
152.04
75.573
118.19
2
2
4
43.48
H L)Ni(OAc)(H O) ].0.5C H OH
26.539
37.671
24.851
35.983
3
2
2
2
5
5
Second
1
1
Third
First
619
585
2.616×10
205.19
200.043
278.923
- 0.0407
25.408
62.453
1
9
[
[
(H L)Cu(OAc) ] 6
1.3243×10
84.95
283.787
0.107234
3
2
Second
First
692
357
679
86.466
5.088
8.871
80.715
2.120
3.226
- 0.22329
- 0.23882
- 0.24047
154.597
89.559
(H L)(UO ) (OAc) ].H O 9
6.774
2
2 2
2
2
Second
10.557
163.285

ACCEPTED MANUSCRIPT
1
Table 6: H NMR spectra of the Schiff base, H L, ligand and its Cd(II), Zn(II) and UO (VI) complexes.
2
2
CH3
CH3
OH
OH
N
OH
O
HN
N
NH
HO
O
HO
Keto form
Enol form
HO

ACCEPTED MANUSCRIPT
1
H NMR Chemical shifts
in ppm
H L ligand
2
Zn(II) complex
Cd(II)
UO (IV)
Assignment
2
7
complex 8
complex 9
2
3
5
.21
.32
.28
2.51
2.18
2.31
(s, 3H, CH3)
(s, 2H, CH)
(s, 1H, CH)
(m,2H,Ar-H)
(m,2H,Ar-H)
(m,2H,Ar-H)
(m,2H,Ar-H)
5.28
5.41
6.06
6
6
7
7
.79-6.89
.92-6.99
.31-7.55
.76-7.94
6.64-7.13
6.64 -6.73
7.08-7.16
7.56-7.58
7.75-7.84
12.4
6.75-7.08
7.21-7.58
7.70-7.81
7.94-7.99
11.71
7
7
7
.15-7.23
.58-7.60
.85-7.93
1
1
0.88
1.38
1
3.00
( bs,1H, NH ) exchangeable with D O)
2
(
(
bs,1H, NH exchangeable with D O)
2
bs,2H,2OH
exchangeable with D O)
1
3.88,14.12
13.68
2
1
1.78,13.42
13.87,15.41

ACCEPTED MANUSCRIPT
Table 7. Structural parameters of the free ligand and its metals complexes, calculated, on the basis of PM3 level using semi-empirical implemented on
Hyperchem 7.52 program, the values in the paranthesis calculated by means DFT using the B3LYP and the basis set 6-31G level provides by the Gaussian 09
program
N
o.
Total
energy
Dipol
moment
Bonding Heat of
Electronic
energy
Neuclar
energy
Energy Energy Egap
HOMO LUMO
ED
Complexes
energy
formation
H3L
[(L)Cr (OAc) (H O) ].0.5H O
-86617.27
3.617
17.27
-4227.84
-8132.06
-24.841
-719.39
-606177.00
519559.75
-9.180 -0.713
8.467
-
(
-5.21) (-1.659) (3.55)
1
-207810.37
-2133073.75 1925263.38
5.083
1.720
3.363
121193.10
2
4
2
4
2
2
3
4
5
6
7
8
[(HL)Mn (OAc) ]
-144023.59
-133959.59
-232707.66
-145508.63
-154141.36
-107004.65
-174482.77
6.121
18.130
14.200
11.140
7.898
-5678.60
-7289.73
-209.995
412.731
-1172298.75 1028296.69
-3960091.00 3646131.50
-7.830 -1.059
-4.502 -2.848
-8.191 -1.016
-8.073 -0.866
6.771
1.654
7.175
7.207
6.285
7.633
7.728
57406.32
47342.32
146090.39
58891.36
67524.09
20387.38
87865.50
2
2
[(HL)Fe (NO ) (H O) ].2H O
3
3 6
2
6
2
[(H L)Co (OAc) (H O) ]
-8436.58 -1009.110 -2298046.75 2065339.00
2
2
4
2
4
[(H L)Ni(OAc)(H O) ].0.5C H OH
-5692.53
-5784.73
-4905.51
-8583.23
-494.103
-266.628
-106.237
-46.308
-1186623.50 1041114.93
3
2
2
2
5
[(H L)Cu(OAc) ]
-1364334.63 12101193.25 -7.047 -0.762
3
2
[(H L)Zn(OAc)]
5.129
-818249.31
711244.62
-8.676 -1.043
-8.283 -0.555
3
[(H L) Cd].5H O
6.174
-1925009.25 1750526.50
3
2
2