Chelating behavior of 3-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine ligand towards some metal ions, spectral and thermal measurements as well as molecular modeling and biological studies

Article abstract of DOI:10.1016/j.molstruc.2019.127172

The 3-amino-4,6-dimethyl-1H-pyrazolo [3,4-b]pyridine ligand and its Mn(II), Pd(II), Fe(III), Cr(III), Ru(III), Hf(IV), Zr(IV) and UO₂(II) metal complexes were synthesized and characterized by means of elemental analysis, spectral studies and thermal investigation. Also, the theoretical studies that done by Spartan ‘14 V1.1.4 software supported the experimental studies. The infrared data suggest that the ligand coordinates to the metal ions as a neutral monodentate moiety through nitrogen atom of amino group. The complexes are formed with 1:2 and 1:3 (M:L) molar ratios. All complexes possesses octahedral geometry except the Pd(II) complex that presents a square planar geometry. Thermal analyses (TGA and DTG) of ligand and its metal complexes are performed in order to identify the external solvents molecules and thermal stability ranges of the complexes. The X-ray diffraction studies suggest orthorhombic structure of P type lattice for Pd(II) complex and monoclinic structure of P type lattice for Cr(III) and Zr(IV). Theoretical calculations are performed to corroborate the experimental results. Some theoretical parameters are reported in order to compare the reactivity of the compounds. The cytotoxic activity of the ligand and its Pd(II) and Ru(III) complexes is evaluated against breast MCF-7 cell line. Pd(II) complex presents a higher activity. The synthesized ligand and its Pd(II), Cr(III) and Zr(IV) metal complexes also are screened for antibacterial activity. The ligand and its tested complexes has weak activity towards a Gram-positive bacteria and no activity towards Gram-negative bacteria except Pd(II) complex.

Full text of DOI:10.1016/j.molstruc.2019.127172

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Chelating behavior of 3-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine ligand towards
some metal ions, spectral and thermal measurements as well as molecular modeling
and biological studies
Mamdouh S. Masoud, Saeyda A. AbouEl-Enein, Alaa E. Ali, Eman H. Abd Elhamed
PII:
S0022-2860(19)31281-5
DOI:
https://doi.org/10.1016/j.molstruc.2019.127172
MOLSTR 127172
Reference:
To appear in: Journal of Molecular Structure
Received Date: 18 June 2019
Revised Date: 29 September 2019
Accepted Date: 1 October 2019
Please cite this article as: M.S. Masoud, S.A. AbouEl-Enein, A.E. Ali, E.H. Abd Elhamed, Chelating
behavior of 3-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine ligand towards some metal ions, spectral
and thermal measurements as well as molecular modeling and biological studies, Journal of Molecular
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Chelating behavior of 4, 6-dimethyl-1H-pyrazolo [3, 4-b] pyridine-3-
amine ligand towards some metal ions, spectral, thermal and
molecular modeling measurements as well as biological studies
a
b
c
Mamdouh S. Masoud , Saeyda A. AbouEl-Enein *, Alaa E. Aly , Eman H. Abd
Elhamed
a
Chemistry Departmen, Faculty of Science, Alexandria University, Egypt
b
Chemistry Department, Faculty of Science, Menoufia University, Egypt
c
Chemistry DepartmenFaculty of Science, Damnhour University, Egypt
Graphical abstract

Chelating behavior of 3-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine
ligand towards some metal ions, spectral and thermal measurements as well
as molecular modeling and biological studies
a
b
c
Mamdouh S. Masoud , Saeyda A. AbouEl-Enein *, Alaa E. Ali , Eman H. Abd Elhamed
a
Chemistry Departmen, Faculty of Science, Alexandria University, Egypt
Chemistry Department, Faculty of Science, Menoufia University, Egypt
Chemistry Department, Faculty of Science, Damnhour University, Egypt
b
c
Abstract
The 3-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine ligand and its Mn(II), Pd(II),
Fe(III), Cr(III), Ru(III), Hf(IV), Zr(IV) and UO (II) metal complexes were synthesized and
2
characterized by means of elemental analysis, spectral studies and thermal investigation. Also,
the theoretical studies that done by Spartan '14 V1.1.4 software supported the experimental
studies. The infrared data suggest that the ligand coordinates to the metal ions as a neutral
monodentate moiety through nitrogen atom of amino group. The complexes are formed with 1:2
and 1:3 (M:L) molar ratios. All complexes possesses octahedral geometry except the Pd(II)
complex that presents a square planar geometry. Thermal analyses (TGA and DTG) of ligand
and its metal complexes are performed in order to identify the external solvents molecules and
thermal stability ranges of the complexes. The X- ray diffraction studies suggest orthorhombic
structure of P type lattice for Pd(II) complex and monoclinic structure of P type lattice for Cr(III)
and Zr(IV). Theoretical calculations are performed to corroborate the experimental results. Some
theoretical parameters are reported in order to compare the reactivity of the compounds. The
cytotoxic activity of the ligand and its Pd(II) and Ru(III) complexes is evaluated against breast
MCF-7 cell line. Pd(II) complex presents a higher activity. The synthesized ligand and its Pd(II),
Cr(III) and Zr(IV) metal complexes also are screened for antibacterial activity. The ligand and its
tested complexes has weak activity towards a Gram-positive bacteria and no activity towards
Gram-negative bacteria except Pd(II) complex.
Keywords: Pyrazolopyridine complexes; Thermal studies; Cytotoxic activity.
*
Correspondence author: dr.saeyda_elenein@yahoo.com
1

1
. Introduction
Pyrazol and pyridine rings are fused to give different pyrazolopyridine ring systems [1].
4
,6-dimethy-l-1H-pyrazolo[3,4-b]pyridine-3-amine is the most important pyrazolopyridine
derivative that is used as versatile precursor to prepare several heterocyclic derivatives
fluorescence dyes, Schiff base, hydrazide and etc…..). A number of heterocyclic compounds
(
containing pyrazolopyridine systems have been associated with several pronounced medicinal
and biological activities as anxiolytic, antiviral and anti-inflammatory agents [2-9]. Also, in
coordination chemistry, pyrazolopyridine derivatives can be used as ligands coordinating to
metals in the different ways. The amidine moiety (-N=CH-NH ) of these molecules is a
2
favorable site of coordination found in some metallic complexes with biological applications.
Also, their transition metal complexes have different applications and are used for anticorrosion
protection of stainless steel in aggressive media [10].
Along with transition metals, inner transition metals can offer remarkable physico-chemical
properties and have applications both in the technological field (sensor devices, optical fibers,
lasers, etc.) and in the medical field (in diagnosis and therapy). The potential of inner metal complexes
for this type of applications is mainly dependent on the metal center, chromophore and on the nature
of the ligands [11,12]
The present work explores experimentally and theoretically the coordination behave of 3-
amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine towards some transition and inner metal ions.
The structure of synthesized metal complexes [(Mn(II), Pd(II), Fe(III), Cr(III), Ru(III), Hf(IV),
2
Zr(IV) and UO (II)] is elucidated using elemental analysis, spectral, magnetic, molar
conductance measurements and thermogravimetric analysis as well as XRD studies. The
cytotoxicity activity of ligand and its Pd(II) and Ru(III) complexes is evaluated against breast
MCF-7 cell line also, the antimicrobial activity is done for ligand and its Pd(II), Cr(III) and
Zr(IV) metal complexes. The geometry of ligand and its metallic complexes was obtained
through Semi-Empirical (PM3) calculations.
2

2
2
. Experimental
.1. Materials and Methods
All chemicals are of analytical grade (BDH, Sigma or Aldrich) and are used as received
without further purification. Micro analytical data of (C, H, N) are performed on a Perkin Elmer-
400 elemental analyzer at Main Defense Chemical Laboratory, Egypt. Mn(II) and Fe(III) ions
2
are assayed by complexmetric titration [13]. However Pd(II), Ru(III), Hf(IV), Zr(IV), Cr(III) and
UO (II) ions are evaluated by gravimetric analysis. The chloride ions are estimated by Mohr's
2
method [13]. Infrared spectra of solid potassium bromide samples are recorded on a Nicolet FT-
-1
1
6
IR spectrophotometer in the range 4000-400 cm . H NMR spectra are measured in DMSO-d on
a Varian Gemini 200 NMR spectrophotometer at 300 MHz. The electronic absorption spectra are
obtained in Nujol mulls using a Perkin Elmer Lambda 4B spectrophotometer. Molar conductance
-3
measurements of metal complexes are determined in DMSO solution (10 M) at room
temperature using a type CD6N Tacussel conductimeter. The thermogravimeteric investigation
ο
(
TG/DTG) are diagrammed under a heating rate of 10 C/min, nitrogen atmosphere and a flowing
rate of 20 mL/min by using a Shimadzu DAT/TG-50 thermal analyzer. A Johnson Matthey
magnetic susceptibility balance using Gouy method at room temperature is employed to measure
the magnetic susceptibility values. Diamagnetic corrections are calculated using Pascal’s
corrt
M
1/2
constants [14]. The effective magnetic moments are calculated from ꢀeff =2.84(X
T)
equation. Fast Atom Bombardment (FAB) mass spectra for the ligand and some metal complexes
are recorded on a Shimadzu Qp-2010 Plus spectrometer at Al-Azhar University, the Regional
Center for Mycology and Biotechnology. Powder X‐ray diffraction for some complexes are
registered by using an X‐ray diffractmeter equipped with a graphite monochromator in the range
of (2θ = 5‐90°) by nickel separated CuKα radiation (λ = 1.54060 A°). The theoretical quantum
chemical calculations are done by Spartan '14 V1.1.4 software. The cytotoxicity is carried out at
Medicinal Technology Center, Medicinal Research Institute, Alexandria University. However,
the antibacterial activity of samples is evaluated in the Regional Center for Mycology and
Biotechnology at Al-Azhar University, respectively. Melting points are measured by using
Stuart melting point apparatus.
2
.2. Preparation of 3-Amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine (HL) ligand
3

The ligand was prepared as reported [15,16]. The cyanoacetamide reacts with
acetylacetone in n-butanol on boiling and in presence of a few drops of pipridine to give 2-
hydroxy-2,6-dimethylpyridine-3-carbonitrile (1). The compound (1) was treated with phosphorus
3
oxychloride (POCl ) to give 2-chloro-4,6-dimethylpyriine-3-carbonitrile (2). The compound (2)
was reacted with hydrazine hydrate in boiled n-butanol to give 3-amino-4,6-dimethyl-1H-
pyrazolo[3,4-b]pyridine. The melting point of the product is 273°C. The reactions steps for
synthesis of 3-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine are shown in Scheme1
Insert Scheme 1 and its caption here
2
.3. Preparation of metal complexes
The complexes are prepared by adding an ethanolic solution of appropriate metal chloride
salts (Mn(II), Pd(II), Fe(III), Cr(III), Ru(III), Hf(IV), Zr(IV)) and UO (II) nitrate to an ethanolic
2
suspension solution of ligand with molar ratio (1M:2L). The reaction mixture is refluxed for
hours with magnetically stirring. The products are cooled, filtered off, washed several times with
ethanol and dried in vacuum desiccator over anhydrous CaCl . The melting points of all
2
complexes are higher than 360°C
2
2
.4. Biological Activity
.4.1. Antitumor Activity
The MTT (3-(4,5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide) assay is a
colorimetric method which was used to measure the viable cells without the need for counting
the viable cells [17,18]. This method is based on changing the yellow MTT salt to insoluble
purple Formazan using active cell line (MCF-7). This assay is utilized to measure the in vitro
cytotoxicity or cytostatic activity of drugs on cell lines. Evaluation of cytotoxicity of HL ligand
and some of its metal complexes (Pd(II) and Ru(III)) was tested against breast MCF-7 cell line.
2
These cell lines are cultured in (75 cm ) culture flasks using Dulbecco's modified Eagle's
3
medium (DMEM) supplemented with 10% (v/v) fetal bovine serum (FBS). Then 3x10
cells/well are maintained and incubated at 37°C for 48h in a moist atmosphere containing 5%
CO . The growth medium must be changed every other day until the use of cell lines. The test
2
compounds and a positive control compound (doxorubicin) are dissolved in dimethyl sulfoxide
(
DMSO) and then diluted with H O to prepare a series of concentrations (1.562, 3.125, 6.25,
2
1
2.50, 25.0, 50.0 and 100 ꢀg/mL). The cells were washed twice and treated with each
concentrations of the test compounds and re-incubated for 48h. Then cytotoxicity is determined
4

using MTT assay. 20ꢀL of MTT solution (5mg/mL) in PBS (phosphate-buffered saline) together
with 200 ꢀL of freshly complete media are added to each well and re-incubated for four hours at
3
7°C. Following the incubation process, the medium is removed and the insoluble purple
Formazan crystals have been formed in each well. Then, 100 mL of DMSO solution containing
0 mM HCl is added to each well and re-suspended until the crystals have been dissolved. The
2
optical density is determined at 490 nm using colorimetric method. This experiment is repeated
in triplicate [19]. The quantity of the colored product is directly proportional to the number of
live cells in the culture. The results are expressed as IC (a dose of compound that inhibits cell
5
0
growth by 50%) which is calculated from cell viability percent.
ODꢀꢁOpticalꢀdensityꢂofꢀsampleꢀwell
ODꢀꢁOpticalꢀdensityꢂinꢀcontrollꢀwell
CellꢀViability% =
× 100
2
.4.2. Antimicrobial Activity
Antimicrobial activity is done on (HL) ligand and some of its metal complexes against two
positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two negative bacteria
Escherchia coli and Pseudomonas aeruginosa). The antimicrobial activity of the tested
compounds is evaluated by means of paper disk diffusion method (9 mm) on Muller Hinton agar
20]. Fresh culture of tested organisms are cleaned using sterile cotton on the surface of prepared
(
[
Muller Hinton agar. The samples are freshly dissolved in DMSO. 100 ꢀL of prepared samples
was loaded separately on paper disk and left until drying. The loaded discs are added to the
o
surface of cultured petri dishes and kept for two hours at 4 C to allow the diffusion of dissolved
compounds into agar. The antibiotic control used during assay is Tri-
Methoprim/Sulphamethoxazole (SXT) [(1.25/23.75)mcg]. Then the plates are transferred to
incubator at 37°C for 24 hrs. After incubation, the diameter of inhibition zone is measured in
millimeter (mm) [21].
3
. Results and discussion
Characterization of the ligand and its metal complexes
Table 1 represents analytical data of ligand and its metal complexes. The data shows that
the ligand coordinated with different metal ions to separate the complexes with 1:2 and 1:3
(M:L) molar ratios. The molar conductance values of investigated complexes are in the range of
−
1
2
−1
5
-24 ꢁ cm mol indicating the non-electrolytic nature of all complexes and the anions are
directly attached to central metal ion in the coordination sphere [21-25]. All the solid metal
5

complexes are stable, non-hygroscopic and partially soluble in most organic solvents such as
chloroform, methanol, ethanol, acetonitrile, DMF and completely soluble in DMSO.
Insert Table 1 and its caption here
3
.1. Mass spectra of the ligand and some of its complexes
The FAB spectrum of the ligand (Figure 1) shows accurate parent molecular ion peak at
m/z 162 amu, matched with the theoretical molecular weight. The spectrum gives other
successive degradation peaks at m/z 147, 132, 117, 104, 90, 76.08, 62 and 48 amu,
+
+
+
+
+
+
+
7 7 4 6 4 4 6 3 3 6 3 2 6 3 5 2 4
corresponding to [C H N ] , [C H N ] , [C H N ] , [C H N ] , [C H N] , [C H N] , [C HN]
+
and [C ] , respectively (Scheme S1).
4
Results of microanalyses and mass spectra of the complexes 2-8 suggest that their
molecular formula are [Pd(HL) Cl ].H O.2EtOH, [Fe(HL) Cl (OH)].4.5H O.3.75EtOH,
2
2
2
3
2
2
[
Cr(HL) Cl ].3EtOH,
[Hf(HL) Cl ].4H O.1.5EtOH,
[Zr(HL) Cl ].H O.3EtOH
and
3
3
2
4
2
2
4
2
[
UO
2
(HL)
2
(NO
3
)
2
].H
2
O.3EtOH by giving the parent molecular ions at m/z 613.21(Calc. 611.87),
8
9
87 (Calc. 885.43), 785 (Calc. 783.15), 785 (Calc. 786.36), 714 (Calc. 713.65) and 950 (Calc.
49.05), respectively. Moreover, additional peaks appear due to fragmentation of complexes that
result from rupture of different bonds inside the molecules, Figure 1.
Insert Figure 1 and its caption here
1
3
.2. HNMR spectra of the ligand and its Pd(II), Hf(IV) and UO
2
(II) complexes
1
The H NMR spectrum of ligand reveals singlet signal at 11.70 ppm assignable to (NH)
2
proton [26]. Also, it shows signal characterized to protons of (NH ) group at 5.05 ppm [27]. The
C-methyl protons signal appear as a singlet around 2.87-3.53 ppm [8]. The aromatic protons
appear at 6.56 ppm. It is easy to detect the mode of bonding of ligand with metal ions by
1
comparing the HNMR spectrum of ligand with that of its complexes containing diamagnetic
metal ions (Pd(II), Hf(IV), and UO (II)). The spectra of complexes display that all signals are
2
2
shifted to low frequency relative to free ligand. Upon complexation, the NH signal of ligand
exhibits shift in the range of 4.18-5.05 ppm relative to free ligand at (5.05 ppm), referring to its
participation in chelation. The pyrazolo (NH) group in Pd(II) complex appear as a broad nature
due to intra hydrogen bonding of nitrogen atom of pyridine ring (N…..H-N) and also cannot seen
in UO (II) and Hf(IV) complexes due to the acidic proton on the hetero atom may be interacted
2
or exchanged with the solvent molecules [28]. The methyl and aromatic protons exhibit slightly
6

1
shift due to change the environment. The HNMR spectral bands and their assignments are listed
in Table S1.
3
.3. Infrared spectra of (HL) ligand and its metal complexes
The main spectral bands and their assignments of ligand are given in Table S2 and
represented by Figure S1. The IR spectrum of ligand displays fundamental spectral bands located
-1
at 3397, 3290, 1623, 1312, 1074 and 491 cm characterized to υ (NH ), υ (NH ), δ(NH ),
as
2
sy
2
2
υ(C-NH ), (NH ) rocking overlapped with pyrazol ring breathing and (NH ) wagging,
2
2
2
respectively [29]. Also, the different vibration mode (υ, δ, γ) of NH; υ(C=N) and υ(N-N) of
-1
pyrazol ring are characterized by bands at 3190, 3114, 1458, (771,656); 1607 and 1127 cm ,
respectively [30, 31]. The stretching, deformation and bending vibrations modes of C-H of
-1
methyl groups are associated with the bands appear at (2971; 2890), 1407 and 826 cm ,
-1
respectively. The spectrum of ligand gives bands at (3040; 1520), 1023 and (615,579) cm refer
to stretching, breathing and bending of C-H in plane of pyridine ring, respectively [32].
The infrared spectral bands of free ligand are compared with that of its complexes to
infer the mode of bonding between ligand and metallic ion. The infrared spectral bands of all
complexes, except Ru(III), show that the υ (NH ) and δ(NH ) undergo shift towards higher
sy
2
2
-1
wavenumber by 14-59 and 19-21cm , respectively relative to that of free ligand (Table S2).
Also, the υ(C-NH ) and (NH ) of the ligand display changes in their shapes and positions
ρ
2
2
indicating the participation of nitrogen atom of amino group in chelation. The infrared spectra of
-1
complexes give new band (absent in ligand) appeared in the range of 526-558 cm assignable to
-1
υ(M-N) [33,34]. The IR spectrum of UO
2
(II) complex shows a band at 920 cm which is
-1
assigned to υ(O=U=O) [35]. Also the appearance of two bands at 1489 and 1288 cm assignable
-
-
-
to ν (NO ), ν (NO ), respectively indicating that NO group coordinates as a monodentate
as
3
sy
3
3
moiety [36].
Also, the υ(C=N), υ(N-N) of pyrazol ring and pyridine ring bending in and out of plane are
associated with very slight shift in their position. This ruled out the non-involvement of the
nitrogen atoms of imine, NH and pyridine ring in coordination to metal ion. The observed shift
of (υ, δ) of (NH) group and some bands of pyridine ring after complexation assigned to the
existence of inter \ intra molecular hydrogen bonding [37].
The above arguments prove that the ligand behaves as a neutral monodentate one and
2
coordinates with metal ions through nitrogen atom of amino group. This was due to (NH ) group
7

had higher neucleophilicity than that of (C=N) group. Also, the monodentate character of HL
behaves as similar to reported for some multidentate ligand [38].
Insert Table 2 and its caption here
3
.4. Magnetic measurements of metal complexes and electronic absorption spectra of (HL)
ligand and its metal complexes
The magnetic moment values per metal ion at room temperature and the Nujol mull
electronic absorption bands with their assignments for the ligand and its metal complexes are
collected in Table S3 and represented in Figure S2.
The spectrum of ligand gives four bands at 330, 360, 415 and 463 nm assigned to π-π*
and n-π٭ transitions, respectively [39,40]. In complexes, the band observed at 463 nm in the
spectrum of ligand assigned to n-π* transition suffered a red shift to 465-480 nm due to a
combination of LMCT with d-d transitions [41,42].
The spectrum of the Mn(II) complex displays broad strong and weak bands at 480 and 652
6
4
4
6
4
4
nm assigned to A → E ( D) (υ ) and A → T ( G) (υ ) transitions, respectively. Also, the
1
g
g
3
1g
1g
1
higher energy band overlapped with LMCT transition. These transitions are conducted to
octahedral stereochemistry around Mn(II) ion. The observed low magnetic moment value 1.83
B.M assigned to low-spin octahedral complex [43].
The Pd(II) complex gives electronic spectral bands at 465 and 668 nm in a strong and
1
1
1
1
weak feature, assigned to A → E (υ ) and A → A (υ ) transitions, respectively which are
1
g
g
3
1g
2g
1
relevant to square planar geometry around Pd(II) metal ion [44].
The Fe(III) complex reveals spectral bands at 670 and 748 nm due to A → E ( G) and
6
4
4
1
g
g
6
4
4
A
1g→ T2g( G) transitions, concerning to octahedral complex. The observed low magnetic
moment value (3.04 B.M) suggests the existence of high-low spin crossover [45]. This occurs in
octahedral complexes with between 4 and 7 electrons especially iron can be either high spin or
low spin depending on the size strength of the ligand (value of ∆), the two states have similar
energies and can coexist in measurable amounts at equilibrium [46]. The observed spectral bands
4
4
4
4
of Cr(III) complex near 480 and 678 nm due to A2g(F)→ T1g(p) and A2g(F)→ T2g(F)
transitions, respectively indicating octahedral geometry around Cr(III) ion. Also, the magnetic
moment value (4.0 B.M) is an evidence octahedral structure [47].
The spectrum of Ru(III) complex gives electronic spectral bands at 671, 755 nm in broad
2
4
2
4
and weak nature characterized to T → A and T → A transitions, respectively. The ꢀ
eff
2
g
2g
2g
1g
1
.78 B.M confirming low spin octahedral complex [48].
8

Based on elemental analysis and electronic spectra of diamagnetic Zr(IV), Hf(IV) and
UO (II) points to octahedral geometry.
2
The infrared spectra and electronic absorption spectral data as well as the magnetic moment
values for the metal complexes established the proposed structures as shown in Figure S3.
3
.5. Thermal analysis for ligand (HL) and its metal complexes
The thermogravimetric study is used to identify the type of solvents and describe the
behavior of thermal decomposition. The thermogram curves and thermoanalytical data of ligand
and its metal complexes are collected in Figure S4 and Table 3, respectively.
°
The TG curve of the ligand displays thermal stability without weight loss up to 164 C,
relevant to the absence of solvent. After that, the TG curve shows progressive weight loss
9
8.29% in 164-400°C range due to complete pyrolysis of ligand. The pyrolytic process take
°
place fastly in one step and associated with strong sharp DTG peak at Tmax = 282 C leaving
carbon residue (0.25 C). The calculated weight losses of ligand is convenient with TG weight
loss of molecule as gases at given temperature range [49]. The mechanism pathway of thermal
decomposition showed in Scheme 2.
The thermogram of [Mn(HL)
3
Cl
2
.(H
2
O)].1.5H
2
O indicates the loses of one mol of
°
hydrated water molecule in the temperature range of 25-181 C with TG weight loss 2.42 %. The
thermal decomposition of unhydrous complex achieved in three stages within 181-266, 266-345
°
and 345-542 C ranges. These stages are characterized by TG weight losses 28.07, 33.35 and
1
9.97% due to loss of one mol of pyrazolopyridine plus 0.5 mol of chlorine gas, removal of
second mol of pyrazolopyridine, 0.5 mol of chlorine gas plus three mols of carbon and evolution
of three mol of nitrogen and eight mol of hydrogen gases additional to 2.5 mol of carbon,
respectively. The first and the second decomposition stages are associated with two strong sharp
°
DTG peaks with Tmax = 248 and 302 C, while the third stage shows weak broad DTG peaks at
°
Tmax= 377 and 428 C, respectively. The DTG pattern (Figure S4) describes the thermolysis of
complex took place fastly in the first and second stages with progressive nature and with nearly
similar degradation pathway. The thermolysis process ends with formation of 0.5Mn O +2.5C as
2
3
a final thermal decomposition product [50]. The mechanism of thermal decomposition pathway
illustrated in Scheme 2.
Insert Scheme 2 and its caption here
The thermograms and thermoanalytical data of the complexes [Pd(HL) Cl ].H O.2EtOH,
2
2
2
[
Cr(HL) Cl ].3EtOH and [Ru(HL) Cl ].9.5EtOH reveals that these complexes are decomposed
3 3 3 3
9

by nearly similar pathway. The TG patterns show weight losses in the temperature range of 25-
°
2
02 C due to release of some solvent of crystallization. After that the Pd(II), Cr(III) and Ru(III)
°
°
complexes start decomposition at 202, 194 and 146 C and ended at 727, 604 and 644 C,
respectively. The thermolysis processes are accomplished mainly through two continuous stages.
The first decomposition stage characterized by estimated weight losses 29.06, 25.40 and 35.54%
°
within 202-354, 194-308 and 146-378 C, respectively. Those weight losses are equivalent to
removal of (0.5 mol of Cl ), (0.5 mol of Cl +1.5 mol of C
) and (one mol of Cl + 4 mol of
2
2
2
(EtOH)
EtOH) additional to decomposition of one mol pyrazolopyridine moiety, respectively. The
second thermal decomposition stage of Pd(II), Cr(III) and Ru(III) assigned by an estimated TG
°
weight losses 42.08, 48.74 and 44.61% up to 727, 604 and 644 C, respectively, concerning to
complete ligands pyrolysis as well as removal of rest chloride Table 3. The DTG curve of Cr(III)
°
complex gives two sharp peaks with Tmax = 243 and (380, 508 C), respectively, whereas Pd(II)
°
shows sharp peaks at Tmax =303 and (392, 456 C). However the Ru(III) displays medium;
°
shoulder and weak peaks at Tmax =190, 239, 318 and (427, 542 and 614 C) corresponding to first
and second decomposition stages, respectively. The DTG curves deduced that the decomposition
of Cr(III) complex achieved through two definite clarified processes. However, the Ru(III)
complex is decomposed through overlapped or diffused processes, while the first decomposition
stage has definite process whereas second stage has overlapped process for Pd(II) complex. All
decomposition processes leading to formation of metal oxides namely PdO, (0.5 Cr
2 3
O + 5C)
and 0.5 Ru O [51,52]. The events of the thermal decomposition pathway of Pd(II) complex is
2
3
taken as representative example and is suggested as in scheme 3.
Insert Scheme 3 and its caption here
The thermogram pattern of [Fe(HL)
3
Cl
2
(OH)].4.5H
2
O.3.75EtOH shows that the removal
°
of solvents of crystallization is in the temperature range of 25-237 C. This step subdivides into
°
two steps in the temperature ranges of 25-127 and 127-237 C and associated with TG weight
2
losses 6.59 and 20.60% assignable to removal of 1.25 mol of EtOH and 4 mol of H O plus 2.5
mol of EtOH, respectively. The low onset temperature of removal of 1.25 EtOH indicating that
the solvent is in lattice voids, whereas the rest solvents involves in lattice structure to raise the
°
thermal stability of complex up to 237 C. This step accompanied with weak and medium DTG
°
peak Tmax=102 and 186 C, respectively. Then the complex starts decomposition through two
°
°
overlapped continuous stages within temperature range of 237-419 C with T =300, 332 C and
max
°
°
4
19-651 C with T = 480, 577 C, respectively. These steps characterized by TG weight losses
max
1
0

1
3 2
2.25 and 48.25% due to dechloronation process plus removal of two mol of (CH +H ) and
complete pyrolysis of ligand, respectively. The thermal decomposition processes ends with
formation of (0.5Fe O + 2.5C) as final product [53]. (Scheme 4) shows the mechanism of
2
3
3 2 2
thermal decomposition pathway of [Fe(HL) Cl (OH)].4.5H O.3.75EtOH complex.
Insert Scheme 4 and its caption here
It is obvious from the thermogram patterns that [Hf(HL)
2 4 2
Cl ].4.H O.1.5EtOH and
[
Zr(HL) Cl ].H O.3EtOH have nearly similar behavior, indicating that they are iso-structurally
2
4
2
and isothermally. TG curves show TG weight loss in the temperature range of 25-196°C due to
removal of some solvents of crystallization. After that the TG curves register progressive weight
losses 47.92 and 55.56% in the temperature ranges of 179-354 and 196-362°C for Hf(IV) and
Zr(IV) complexes, respectively due to release of one mol of ligand and pyrolysis of the second
one to eliminate 2N gas along with dechloronation and some of lattice solvents. The process
2
associates with a sharp strong DTG peaks with Tmax=254 and 262°C, respectively and
accomplishes through a narrow temperature ranges signified that thermolysis started rapidly.
This step followed by the final decomposition step for each Hf(IV) and Zr(IV) complexes which
occurred within 354-700 and 362-700°C ranges and associated with a weak broad diffused DTG
peaks 394, 453, 500 and 390, 432, 503°C, respectively. This step is characterized by weight
2 2
losses 10.73 and 12.22% denoted to release of (5.75C +7H gas) and (7C+2H gas), respectively
leaving oxygen molecule raised from rest solvent of crystallization to form MO contaminated
2
with carbon atoms as a final thermolysis product [54,55]. The thermal decomposition pathway of
Hf(IV) complex is taken as representative example, Scheme 5.
Insert Scheme 5 and its caption here
The thermal decomposition of [UO (HL) (NO ) ].3.75H O shows TG weight loss 2.95% in
2
3
3 2
2
°
the temperature range of 23-169 C due to removal of 1.5 mol of hydrated water, however the
rest of water removed with the decomposition of complex where it was involved in lattice [56].
°
°
The weight loss 7.15% within 169-202 C with DTG sharp peak at T =185 C corresponding to
max
removal one mol of nitrate group plus 0.25 mol of water molecule. The second strong DTG peak
°
°
in the temperature range of 202-291 C with T =285 C and associated with TG weight loss
max
2
1.26% attributed to elimination of one mol of ligand as well as two mol of lattice water
molecules. The observed TG weight loss 9.22% estimated through a broad temperature range of
°
2
91-500 C equivalent to release of one mol of nitrate and two mol of methyl groups. After that
°
°
the TG curve exhibits inflection at 500 C up to 741 C with 30.88% weight loss raised from
1
1

2
complete ligand pyrolysis leading to formation of UO as a final product [57]. Scheme 6
describes the thermal decomposition processes of UO (II) complex.
2
Insert Scheme 6 and its caption here
The thermal analysis of all complexes carried out under nitrogen gas and the solvent of
crystallization were responsible for the formation of metal oxides as final products from thermal
decomposition [58].
Insert Table 3 and its caption here
3
.6. XRD Analysis
X-ray powder diffraction analysis of Pd(II), Cr(III) and Zr(IV) metal complexes is carried
out to determine the type of crystal system and lattice parameters. As shown in Figure S5. X-ray
diffractograms of these metal complexes show good intense peaks indicating high crystallinity
[59]. The results obtained from computational data reflected that Pd(II) complex had
orthorhombic structure of P type lattice while Cr(III) and Zr(IV) complexes have monoclinic
structure of P type lattice. Moreover, using the diffraction data, the mean crystallite sizes of the
complexes (D) are determined according to the Scherrer equation (D = 0.9λ/(βcosθ), where λ is
X-ray wavelength, θ is Bragg diffraction angle, and β is the full width at half maximum of the
diffraction peak [59]. The average crystallite sizes of complexes are found to be 83-113 nm.
Cr(III) and Zr(IV) metal complexes are in nano-size. The values are given in Table 4.
Insert Table 4 and its caption here
3
.7. Molecular modeling of (HL) ligand and its metal complexes
Molecular modeling is carried out to understand the “rules” that described chemical
behavior of compounds and demonstrated the better geometrical structure for HL ligand [51].
Also, numbering of the ligand skeleton is observed and shown in Figure S6.
Spartan '14 V1.1.4 software is employed to carry out the quantum chemical calculations.
Semi-Empirical (PM3) calculations are performed. Two different model structures are built for
[
3 2 2 2 2
Fe(HL) Cl (OH)] and [Pd(HL) Cl ] complexes through nitrogen atom of NH group (Figures S
7
,9) or C=N (pyrazole) (Figures S 8,10). The data in Table 5 showed the total energy of the two
proposed structures for Fe(III) and Pd(II) complexes in which, the ligand coordinates through
NH group are smaller than that the values where coordinated through C=N group. This is a
2
better agreement with the experimental data (Figures S 7,9).
1
2

Insert Table 5 and their caption here
Quantum chemical parameters such as the highest occupied molecular orbital energy
EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (∆E) and other
(
parameters that give a valuable information about the reactive behavior, such as electronegativity
χ), chemical potential (ꢀ), global hardness (η) and softness (σ) [60] are calculated quantitatively
(
to depict the reactivity of the ligand and some complexes Table 6.
Absolute hardness (η) and softness (σ) are important properties to measure the molecular
stability and reactivity. In a complex formation system, the ligand acts as a Lewis base while the
metal ion acts as a Lewis acid. Metal ions are soft acids and thus soft base ligands are most
effective for complex formation. A hard molecule has a large energy gap and a soft molecule has
a small energy gap. Soft molecules are more reactive than hard ones because they could easily
offer electrons. Ligand has higher softness (σ). It is more reactive and easily giving electrons to
metal and possess high ability for complexation.
Global hardness and softness are important properties to measure the molecular stability
and reactivity. The hardness values (Table 6) show that [Fe(HL)
less harder than ligand, so the complexes have higher potential chemical resistance to change
the number of electrons among the ligand. Also, [Fe(HL) Cl (OH)] has higher value of global
3 2 2 2
Cl (OH)] and [Pd(HL) Cl ] are
3
2
softness which indicated that the complex showed greater reactivity than its ligand. The energy
gap (ꢂE) is directly involved with hardness/softness of a chemical species. A lower value of ꢂE
made two complexes more reactive or low kinetic stability than their ligand. Computed the
electrophilicity indexes were measured the stabilization energy when the system acquires an
additional electronic charge from the environment. From the ω values (Table 6), the order of
electrophilicity as following: [Fe(HL) Cl (OH)] ˃ Ligand > [Pd(HL) Cl ]. [Fe(HL) Cl (OH)]
3
2
2
2
3
2
had the highest value of electrophilicity, which showed its high ability to accept electrons (the
most reactive compound).
Insert Table 6 and its caption here
3
3
.8. Biological Activity
.8.1. Antitumor activity
The cytotoxic activity of the ligand and its Pd(II) and Ru(III) complexes is evaluated
against breast MCF-7 cell line. The cytotoxicity of the tested compounds is expressed by (IC50),
1
3

the biological screening results of tested compounds in vitro are listed in Table 7 and compared
with the activity of doxorubicin as a reference drug.
Pd(II) complex shows high activity relative to free ligand and Ru(III) complex. Cytotoxic
activity of the complexes may be attributed to the central metal atom as explained by Tweedy's
chelation theory [51]. The cytotoxic activity of complexes resulted from the binding of metal
ions with DNA and forming cross links, these binding caused distortion of the helical structure of
DNA and by this DNA replication inhibited. It seems that the nature of the metal ion had an
effect on the biological behaviour. The Pd(II) complex shows high activity rather than other
tested compounds under the same experimental conditions. On screening, it is observed that Pd-
3
1
-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine is more toxic than Ru-3-amino-4,6-dimethyl-
H-pyrazolo[3,4-b]pyridine against the studied cell line. This occurred because of the slow
ligand-exchange of Ru(III) compounds, due to the high tendency of Ru(III) ion to form strong
bonds with ligand and it can bind with other biomolecules in the cell rather than DNA. Also, the
square planar geometry around Pd(II) ion, made Pd(II) ion more flexible for reaching to DNA
rather than the restricted octahedral Ru(III) ion [61-63].
Insert Table 7 and its caption here
3
.8.2. Antimicrobial Activity
Using the paper disk diffusion method, the ligand and some of its metal complexes are
evaluated for their antimicrobial activities. Thus, these compounds are screened against
Staphylococcus aureus; Bacillus cereus as a Gram-positive bacteria and Escherichia coli;
Pseudomonas aeruginosa as Gram-negative bacteria (Table 8). The ligand and its tested
complexes have weak activity towards a Gram-positive bacteria and no activity towards Gram-
negative bacteria except Pd(II) complex has observed activity towards Pseudomonas aeruginosa.
Insert Table 8 and its caption here
Conclusion
2
Mn(II), Pd(II), Fe(III), Cr(III), Ru(III), Hf(IV), Zr(IV) and UO (II) metal complexes of 3-
amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine ligand are prepared. Spectral (IR, UV–visible,
1
H NMR and mass spectra), magnetic and thermal studies confirm the structure of the ligand and
its metal complexes. IR spectra show that the ligand coordinates to all metal ions as a neutral
monodentate moiety through nitrogen atom of amino group. The ligand to metal (L:M)
stoichiometry is found to be 2:1 and 3:1. The electronic absorption spectra along with magnetic
1
4

measurements suggest octahedral geometry for all synthesized metal complexes, except Pd(II)
complex. The X- ray diffraction studies suggest orthorhombic structure of P type lattice for
Pd(II) complex and monoclinic structure of P type lattice for Cr(III) and Zr(IV). Theoretical
calculations are performed to support the experimental results. Pd(II) complex presents a higher
antitumor activity against MCF-7 cell line. The synthesized ligand and its Pd(II), Cr(III) and
Zr(IV) metal complexes also are screened for antibacterial activity.
Acknowledgment
We would like to acknowledge the financial support of the Menoufia University
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58] S.M. Emam, S.A. Abou El-Enein, E.M. Emara, Spectroscopic studies and thermal
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59] M. Bal, G. Ceyhan, B. Avar, M. Kose, A. Kayraldiz, M. Kurtoglu, Synthesis and X-ray
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2
1

2
2

Elemental analyses Found/(Calcd.)%
F.W. (g/mol)
*
No.
Ʌ
Color
C
H
N
Cl
M
HL
162.26
Buff
59.31
(59.24)
6.19
(6.21)
33.95
(34.34)
-
-
-
-
-
-
C
8
H
10
N
4
[
Mn(HL)
C H N O MnCl
2
3
Cl
33 12 2.5
2
(H
2
O)].1.5H
2
O
657.54
Light brown
43.80
(43.84)
5.28
(5.37)
25.69
(25.56)
10.63
(10.80)
8.20
(8.36)
1
8
2
4
[
Pd(HL)
2
Cl
2
].H
2
O.2EtOH
2
611.87
Yellowish brown
39.19
(39.26)
5.48
(5.61)
21.19
(18.31)
11.59
(11.23)
17.39
(17.22)
2
3
13
16
C H N O PdCl
2
0
34
8
3
[
Fe(HL)
3
Cl
2
(OH)].4.5H
2
O.3.75EtOH
885.43
Dark brown
42.94
(42.78)
7.11
(7.17)
20.12
(19.54)
7.70
(8.16)
6.83
(6.31)
C31.5H63.5N O9.25FeCl2
12
[
Cr(HL) Cl ].3EtOH
783.15
Deep buff
46.41
(46.02)
6.54
(6.17)
22.12
(21.56)
14.80
(13.58)
7.10
(6.63)
3
3
4
5
6
7
11
17
C H N O CrCl
3
0
48 12
3
3
[
C
Ru(HL) Cl ].9.5EtOH
1131.87
Black
45.56
(45.59)
7.92
(7.69)
14.74
(14.84)
9.52
(9.41)
11.21
(11.11)
3
3
43
H
87
N
12
O
9.5Ru Cl
3
[
C
Hf(HL) Cl ].4H O.1.5EtOH
786.36
Deep yellow
28.80
(29.04)
5.12
(4.75)
16.54
(14.40)
18.27
(18.05)
22.90
(22.72)
2
4
2
24
17
19
H
37
N
8
O
5.5Hf Cl
4
[
Zr(HL)
2
Cl
4
].H
2
O.3EtOH
713.65
Yellowish green
37.38
(37.02)
5.37
(5.64)
16.20
(15.70)
18.97
(19.87)
12.12
(11.78)
C H N O ZrCl
2
2
40
8
4
4
[
UO
2
(HL)
37.5 14
3
(NO
3
)
2
].3.75H
2
O
949.05
Yellow
39.71
(39.83)
4.41
(4.00)
21.34
(20.75)
-
-
25.57
(25.08)
8
5
C H N O11.75U
2
4
Table 1
Analytical and Physical Data of HL Ligand and Its Metal Complexes
2
3

2
4

2
5

No.
Compound
υ NH
2
(asym)
υ(NH)
δ(NH
2
),
δ(NH)
ν(C-NH
2
),
Pyrazol ring γ(NH)
Pyring
Py ring bending ρ NH
2
ν(M-N)
+
breathing+
roking(NH ),
2
bending,in
plane
out-of- plane
υ NH
2
(sym)
υ(C=N)
ν(N-N)
Py ring
HL
3397s
3190m
3114sh
1623,
1607sp
1459m
1407s
1312m
1127w
1074s
1023m
772w
656w
615s
579w
435w
491m
-
3
290m
1
2
[Mn(HL)
3
Cl
2
(H
2
O)].1.5 H
2
O
3396w
3191w
3101w
1637s,
1603s
1455s
1419m
1308m
1122w
1054s
1024sh
779s
653m
621m
587m
442sh
442w
500w
498w
544w
542w
3
275w
[Pd(HL)
2
Cl
2
].H
2
O.2EtOH
3433w
3202w
3102vw
1637m,
1607w
1445m
1415w
1303sh
1120w
1084m
1033m
775m
643m
608sh
582m
3
304b.m
3
[Fe(HL)
3
Cl
2
OH].4.5.H
2
O.
3378sh
3324b.s
3202m
3159w
1647s,
1614w
1445m
1386m
1298sh
1127m
1082w
1035m
770m
654w
615m
576w
441w
480m
546w
3
.75 EtOH
4
5
[Cr(HL)
3
Cl
3
].3EtOH
3397s
3193m
3104m
-
1454s
1412s
1315m
1122w
1068m
1027m
769s
653m
616m
581w
438w
424w
494w
488w
547w
536w
3
296s
1606s
[Ru(HL)
3
Cl
3
].9.5EtOH
3409b.s
294b.s
-
-
1444s
1398
1300w
1121w
1079m
1038s
775sh
624m
624m
581vw
3
2986w
1598s
6
7
8
[Hf(HL)
2
Cl
4
].4H
2
O 1.5EtOH
3383w
324s
3202s
3083sh
1652s,
1609m
1437m
1400
1293w
1093s
1041m
773m
650m
615m
578w
436sh
436sh
443sh
477m
475w
481w
539w
537w
526w
3
1
132w
[Zr(HL)
2
Cl
4
].H
2
O 3EtOH.
3417m
327s
3201s
3153w
1642s,
1604w
1444s
1383m
1302sh
1123w
1076v.w
1036m
764m
651w
604m
581sh
3
[UO
2
(HL)
3
(NO
3
)
2
].3.75.H
2
O
3398s
322s
3206s
3093w
1647s,
1605m
1434s
1387s
1295m
1134w
1071vw
1036m
773m
663w
610m
573w
3
s: strong, m:medium, w:weak, b:broad, b.m: broad medium, v.w: very weak, sh: shoulder, and b.s: broad strong
Table 2.
-
1
Infrared
Bands
(cm )
and
Their
Assignments
for
ligand
(HL)and
Its
Metal
Complexes
2
6

No. Compound
HL.
TG range
DTG peak
Mass Loss % Assignment
Found
Calcd.
T
S
ο
ο
ο
(
C)
( C)
( C)
25-164
-
282
-
34-67
248
302
-
-
Stable
164
(
d)
1
64-400
At 400
25-181
98.29 98.53 Ligand pyrolysis
(r)
1.63
2.42
1.45 0.25C
2.32 loss of one mol H
(
a)
1
2
3
4
5
6
[Mn(HL)
3
Cl
2
(H
2
O)].1.5H
2
O
2
O
181
202
237
194
146
179
(
b,d)
1
2
3
81-266
66-345
45-542
28.07 27.63 loss of (one mol of P.Py+0.5 mol of Cl
33.35 33.11 loss of (one mol of P.Py+0.5 mol of Cl +3mol of C)
2
)
2
377,428,498
-
45,148
303
392, 456
2 2
19.97 19.77 loss of (3 mol of N gas+8 mol of H gas+2.5 mol of C)
(r)
At 542
25-202
16.53 16.58 0.5 Mn O +2.5C
2 3
(
a,b)
[Pd(HL) Cl ].H O.2EtOH
8.42
8.58 loss of (one mol H O 0.75 mol of EtOH)
2 +
2
2
2
(d)
2
3
02-354
54-727
29.06 29.70 loss of (one mol of P.Py+0.5 mol of Cl2)
42.08 41.71 loss of (one mol of NH +2.75 mol of H +0.25 mol of H O+2.5 mol of
2
2
2
(
d)
C+0.5 mol of Cl
2
+ ligand pyrolysis)
(
r)
At 727
25-127
-
102
186
300,332
480, 577
-
43
243
380, 508
20.48 20.00 PdO
(
a)
2 2
[Fe(HL)Cl OH)].4.5.H O.3.75EtOH
6.59 6.44 loss of 1.25 mol of EtOH
20.60 20.90 loss of (4 mol of H O+2.5 mol of EtOH)
12.25 12.30 loss of (one mol of Cl +2 mol of (CH +H ))
1
2
4
27-237
37-419
19-651
2
(
d)
2
3
2
48.25 48.69 loss of (2 mol of L+ ligand pyrolysis)
(
r)
At 651
25-194
12.09 12.15 0.5Fe O
2 3
(
b)
[Cr(HL)
3
Cl
3
].3EtOH
8.47
8.81 loss of 1.5 mol of EtOH
(
b,d)
1
3
94-308
08-604
25.40 25.47 loss of (one mol of p.py+0.5mol of Cl +1.5mol of C)
48.74 48.27 loss of (2mol of ligand +one mol of NH +one mol of Cl +1.5 mol of
2 2
2
C+4.5mol of H )
2
(
r)
At 604
25-146
-
45
17.39 17.37 0.5Cr O +5C
2 3
(
b)
[Ru(HL)
3
Cl
3
].9.5EtOH
9.11
9.05 loss of 2.25 mol of EtOH
(
b,d)
1
3
46-378
78-644
190,239,318
427,542,614
35.54 35.42 loss of (4 mol of EtOH+one mol of P.Py+one mol of Cl2)
44.61 44.64 loss of (0.5 mol of Cl
2
+3 mol of C+1.75mol of H
2
O+4.5 mol of H
2
+2
(b,d)
mol
of
ligand+one mol of
NH2)
(
r)
At 644
25-179
-
2 3
11.21 11.11 0.5Ru O
(
b,a)
[Hf(HL)
Cl
].4H
O.1.5EtOH
46,115
`10.8 11.07 loss of (1.5 mol of EtOH+ one mol of H
O]
2
2
4
2
1
3
79-354
54-700
254
47.92 48.10 loss of (one mol of H O+2mol of Cl +2mol of N +one mol of ligand)
2
2
2
(d)
394,453, 500 10.73 10.65
(d)
At 700
-
30.54 30.22 loss of (5.75mol of C+ 7mol of H )
2
(r)
2
HfO +2.25C
(
a)
(b)
(d)
(r)
:
Dehydration, :Desolvation, :Decomposition and :final residue
Table 3. TGA Analysis of HL Ligand and Its Metal Complexes
2
7

No. Compound
TG range
DTG peak
Mass Loss %
Found Calcd.
Assignment
T
ο
S
ο
ο
(
C)
( C)
49
262
( C)
196
(
b)
7
[Zr(HL)
2
Cl
4
].H
2
O.3EtOH
25-196
9.53
55.56
12.22
9.67 Loss of 1.5 mol of EtOH
55.62 Loss of (0.5 mol of EtOH+ 2 mol of Cl +one mol of ligand +2 mol
12.33 of N
1
3
96-362
62-700
2
(
b,d)
390, 32,503
2 2
+7 mol of H )
(d)
Loss of (7mol of C+2 mol of H )
2
(r)
At 700
23-169
-
56
185
285
-
614
-
(r)
22.69
2.95
22.31 ZrO
2.06 Loss of 1.5 mol of H
2
+3C
(
a)
8
[UO
2
(HL)
3
(NO
3
)
2
].3.75.H
2
O
2
O
201
(
b)
1
69-202
02-291
91-500
00-741
7.15
7.91 Loss of (one mol of NO +0.25 mol of H O)
3
2
(
d)
2
2
5
21.26
9.22
20.9 Loss of (one mol of ligand +2 mol of H
9.71 loss of (one mol of NO +2mol of CH )
2
O)
(
d)
3
3
(
d)
30.88
28.5
31.01 complete ligand pyrolysis
28.47 UO2
(
r)
At 741
(
a)
(b)
(d)
:
Dehydration, :Desolvation, :Decomposition and :final residue
Table 3. Continued
2
8