Synthesis, characterization and biological study on Cr3+, ZrO2+, HfO2+ and UO22+ complexes of oxalohydrazide and bis(3-hydroxyimino)butan-2-ylidene)-oxalohydrazide

Article abstract of DOI:10.1016/j.saa.2010.04.012

Cr³⁺, ZrO²⁺, HfO²⁺ and UO₂²⁺ complexes of oxalohydrazide (H₂L¹) and oxalyl bis(diacetylmonoxime hydrazone) [its IUPAC name is oxalyl bis(3-hydroxyimino)butan-2-ylidene)oxalohydrazide] (H₄L²) have been synthesized and characterized by partial elemental analysis, spectral (IR; electronic), thermal and magnetic measurements. [Cr(L¹)(H₂O)₃(Cl)]·H₂O, [ZrO(HL¹)₂]·C₂H₅OH, [UO₂(L¹)(H₂O)₂] [ZrO(H₃L²)(Cl)]₂·2H₂O, [HfO(H₃L²)(Cl)]₂·2H₂O and [UO₂(H₂L²)]·2H₂O have been suggested. H₂L¹ behaves as a monobasic or dibasic bidentate ligand while H₄L² acts as a tetrabasic octadentate with the two metal centers. The molecular modeling of the two ligands have been drawn and their molecular parameters were calculated. Examination of the DNA degradation of H₂L¹ and H₄L² as well as their complexes revealed that direct contact of [ZrO(H₃L²)(Cl)]₂·2H₂O or [HfO(H₃L²)(Cl)]₂·2H₂O degrading the DNA of Eukaryotic subject. The ligands and their metal complexes were tested against Gram's positive Bacillus thuringiensis (BT) and Gram's negative (Escherichia coli) bacteria. All compounds have small inhibitory effects.

Full text of DOI:10.1016/j.saa.2010.04.012

Spectrochimica Acta Part A 76 (2010) 496–501
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
2+
Synthesis, characterization and biological study on Cr3+, ZrO2+, HfO2+ and UO2
complexes of oxalohydrazide and
bis(3-hydroxyimino)butan-2-ylidene)-oxalohydrazide
A.A. El-Asmy∗, O.A. El-Gammal, H.A. Radwan
Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Dakhalia 35516, Egypt
a r t i c l e i n f o
a b s t r a c t
Cr3+, ZrO2+, HfO2+ and UO2 complexes of oxalohydrazide (H2L1) and oxalyl bis(diacetylmonoxime
hydrazone) [its IUPAC name is oxalyl bis(3-hydroxyimino)butan-2-ylidene)oxalohydrazide] (H4L2)
have been synthesized and characterized by partial elemental analysis, spectral (IR; electronic),
thermal and magnetic measurements. [Cr(L1)(H2O)3(Cl)]·H2O, [ZrO(HL1)2]·C2H5OH, [UO2(L1)(H2O)2]
[ZrO(H3L2)(Cl)]2·2H2O, [HfO(H3L2)(Cl)]2·2H2O and [UO2(H2L2)]·2H2O have been suggested. H2L1 behaves
as a monobasic or dibasic bidentate ligand while H4L2 acts as a tetrabasic octadentate with the two metal
centers. The molecular modeling of the two ligands have been drawn and their molecular parameters
were calculated. Examination of the DNA degradation of H2L1 and H4L2 as well as their complexes revealed
that direct contact of [ZrO(H3L2)(Cl)]2·2H2O or [HfO(H3L2)(Cl)]2·2H2O degrading the DNA of Eukaryotic
subject. The ligands and their metal complexes were tested against Gram’s positive Bacillus thuringiensis
(BT) and Gram’s negative (Escherichia coli) bacteria. All compounds have small inhibitory effects.
© 2010 Elsevier B.V. All rights reserved.
2+
Article history:
Received 6 December 2009
Received in revised form 20 March 2010
Accepted 14 April 2010
Keywords:
Oxalohydrazide
Oxalyl bis(diacetylmonoxime hydrazone)
2+
Cr3+, ZrO2+, HfO2+ and UO2 complexes
etry for the VO2+ complex, tetrahedral for the Zn(II) and square
1. Introduction
planar for Co(II), Ni(II) and Cu(II) complexes. The in vitro antimi-
The synthesis and structural characterization of hydrazone com-
plexes have recently developed to compare their coordinative
behavior with their antimicrobial activities. Hydrazones of pyri-
doxal phosphate and its analogous have been studied to understand
the mechanism of action for vitamin B6-containing enzymes [1].
A series of pyridazinyl hydrazones were found to inhibit tyrosine
hydroxylase and dopamine-hydroxylase in vivo and in vitro [2].
Tridentate hydrazones have been evaluated as potential oral iron-
chelating drugs for genetic disorders such as thalassemia [3]. It
was noted that salicylaldehydebenzoyl hydrazone (H2Sb) is unusu-
ally potent inhibitor of DNA synthesis and cell growth in a variety
of human and rodent cell lines [4]. Testing of [Cu(HSb)Cl]·H2O
showed a significant increase in potency when compared with the
free ligand leading to the suggestion that the metal complexes
are more biologically active than the free ligand. Compounds con-
taining oxime and amino groups were used as analytical reagents
for the micro-determination of some transition metal ions and as
ion exchange resins [5]. Previous papers [6–11] were reported on
some oxime hydrazone complexes. Binuclear complexes of oxalyl
bis(diacetylmonoxime hydrazone) suggested an octahedral geom-
crobial activity of the investigated compounds revealed a higher
activity of the ligand than its complexes [12]. The antimicrobial
properties of polyesters containing Schiff-base metal complexes
were investigated against selected microorganisms and was found
higher than the standard drugs [13].
Up to my knowledge, no work was done on the complexes con-
taining Cr3+, ZrO2+, HfO2+ and UO22+ ions with oxalohydrazide and
oxalyl bis(diacetylmonoxime hydrazone).
2. Experimental
CrCl3·3H2O, ZrCl4, HfCl4 and UO2(OAc)2, diethyl oxalate,
hydrazine hydrate, diacetylmonoxime, ethanol, diethyl ether, DMF
and DMSO were of pure chemical grade and obtained from the BDH
chemicals.
2.1. Synthesis of the ligands
Oxalohydrazide (NH2NHCO)2 and oxalyl bis(diacetylmonoxime
hydrazone) [IUPAC name: bis(3-hydroxyimino)butan-2-ylidene)-
oxalohydrazide] were prepared as previously reported [14,12]. The
purity was checked by melting point and thin layer chromatogra-
phy (TLC).
∗
Corresponding author. Tel.: +20 101645966; fax: +20 502236787.
E-mail address: aelasmy@yahoo.com (A.A. El-Asmy).
1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2010.04.012

A.A. El-Asmy et al. / Spectrochimica Acta Part A 76 (2010) 496–501
497
2.2. Preparation of the complexes
The residue was cooled and 3–4 drops of KMnO4 were added.
The beaker was covered with a glass watch and heated gently for
15 min. Sodium azide solution was added drop wise. The solution
was cooled and transferred to 25 mL standard measuring flask, and
1 mL of diphenylcarbazide solution was added and completed to
the mark with bidistilled water. The solution was stirred thoroughly
and the absorbance was measured at 545 nm using water as a refer-
ence. 0.1 g of uranyl complex was placed in a clean and dry weighed
crucible and ignited on bunzen flame for 15 min. After that, the cru-
cible was ignited in a muffle at 1000 ◦C to constant weight for 2 h.
The residue was cooled and weighed again as U3O8.
In the preparation of zirconyl and hafnyl complexes, the calcu-
lated amounts of zirconium tetrachloride heptahydrate or hafnium
tetrachloride were dissolved in bidistilled water to give their
oxysalts. In the preparation of H2L1 complexes, the calculated
amount (1.18 g; 0.01 mol) of the ligand was dissolved in 20 mL
bidistilled water and then mixed with equimolar amount (0.01 mol)
of zirconyl chloride, chromium chloride or uranyl acetate in bidis-
tilled water. The reaction mixture was heated under reflux on a
water bath for 4–6 h. For H4L2 complexes, 0.057 g (0.005 mol) of the
ligand was dissolved in 30 mL EtOH and mixed with the amount
of zirconyl, hafnyl, chromium chlorides, or uranyl acetate salts
(0.005 mol) dissolved in 10 mL bidistilled water.
3. Results and discussion
All the reaction mixtures were heated under reflux on a water
bath for 2–6 h. The resulting solid complexes were filtered immedi-
ately while the solution was still hot, washed with ethanol followed
by diethyl ether and dried in a vacuum desiccator over anhydrous
CaCl2.
Elemental analysis, yield and color of the complexes formed
between oxalohydrazide (H2L1) or oxalyl bis(diacetylmonoxime
hydrazone) (H4L2) and Cr3+, ZrO2+, HfO2+ or UO22+ are summarized
in Table 1. The results confirm the formulae [ZrO(HL1)2]·C2H5OH,
[Cr(L1)(Cl)(H2O)3],
[UO2(L1)(H2O)2],
[ZrO(H3L2)(Cl)]2·2H2O,
[HfO(H3L2)(Cl)]2·2H2O and [UO2(H2L2)]·2H2O. The complexes are
insoluble in most common organic solvents. The partial solubility
of the complexes in DMSO or DMF prevents the measurements
of their molar conductances. They are thermally stable and have
high melting points (>300 ◦C). All complexes are diamagnetic as
revealed from their complete or incomplete d- or f-orbitals, except
of the Cr3+ complex which measures 4.9 B.M. The electronic spectra
showed charge transfer bands which are the main reason for the
intense color of the complexes.
2.3. Antibacterial and genotoxicity studies
The organic ligands and their metal complexes were screened
for their antimicrobial activity using Gram’s positive Bacillus
thuringiensis (BT) and Gram’s negative bacteria (Escherichia coli).
The media prepared for bacteria were as reported earlier [15]. For
a genotoxicity study, a solution of 2 mg of calf thymus DNA was
dissolved in 1 mL of sterile distilled water where the investigated
ligand and its complexes were prepared by dissolving 2 mg/mL
DMSO. An equal volume of each compound and DNA were mixed
thoroughly and kept at roomtemperature for 2–3 h. The effect of the
compounds on the DNA was analyzed by agarose gel electrophore-
sis. A 2 ␮l of loading dye were added to 15 ␮l of the DNA mixture
before being loaded into the well of an agarose gel. The loaded mix-
tures were fractionated by electrophoresis, visualized by UV and
photographed.
3.1. IR and electronic spectra
3.1.1. IR spectra of H2L1 and its complexes
The IR spectrum of H2L1 showed bands at 3291, 3253, 3195,
1685, 1535, 1272 and 977 cm−1 assignable to ꢀas(NH2), ꢀs(NH2),
ꢀ(NH), ꢀ(C O) and amide (III and IV) group, respectively (Table 2).
In the IR spectrum of [ZrO(HL1)2]·C2H5OH, the ꢀ(C O) band
appeared weak indicating that one of the carbonyl groups
participates in coordination by removing the amide proton
(HNC O → N C–O−) while the other group still uncoordinated;
the weak band at 490 cm−1 is assigned to ꢀ(M–O). The shoulder
at 1633 cm−1 assigned to ꢀ(C N) is due to the enolization of NHCO
group. The broad multiple bands at 3461–3289 may include the
ꢀ(OH) of ethanol, the ꢀ(NH) and the NH2 vibrations. Evidence for
participation of NH2 comes from the shift of the 1618 cm−1 band
in the ligand to 1563 cm−1 in the complex. The new strong band
at 1020 cm−1 is due to ꢀ(Zr O). All these observations suggest the
monobasic bidentate (C–O and NH2) nature of H2L1 in this complex.
In [Cr(L1)(H2O)3(Cl)]H2O and [UO2(L1)(EtOH)2], the ligand
behaves as a dibasic bidentate coordinating via the two carbonyl
groups (enolic form). This mode of chelation is confirmed by the
complete disappearance of ꢀ(C O) and ꢀ(NH) with the appear-
ance of a new band at 1620–1633 cm−1 due to ꢀ(C N*). The new
band is found strong due to its overlap with ␦(NH2). The ꢀ(NH2)
bands appear broad centered at 3246 cm−1 more or less at the same
position as in the ligand spectrum confirming its non-coordination.
Further support for the enolization is the appearance of a strong
band at 1308 cm−1 due to ꢀ(C–O). In [Cr(L)(H2O)3Cl]H2O, the two
2.4. Equipment
The IR spectra were recorded as KBr disc on a Mattson 5000
FTIR Spectrophotometer. The UV–vis. spectra of the complexes
were recorded on UV2 Unicam Spectrophotometer. The magnetic
measurements were carried out on a Johnson Matthey magnetic
balance, UK. Thermogravimetric measurements were recorded on
a DTG-50 Shimadzu thermogravimetric analyzer. The nitrogen flow
and heating rate were 20 mL min−1 and 10 ◦C min−1, respectively.
The molecular geometry of the ligands is first optimized and the
Semi-empirical method PM3 is then used for optimizing the full
geometry of the system using Polak–Ribiere (conjugate gradient)
algorithm and unrestricted Hartee–Fock (UHF) is employed keep-
ing RMS gradient of 0.01 kcal/Å mol.
2.5. Analyses
Carbon, hydrogen and nitrogen contents of the ligands and their
complexes were determined at the Microanalytical Unit of Cairo
University, Egypt. Zirconium was determined according to Mar-
czenko method [16]. A solution containing 30 ␮g of ZrO2+ sample
was placed in a 25 mL standard measuring flask and diluted with
bidistilled water. One mL of this solution was added to 1 mL of
ascorbic acid solution and 1 mL of xylenol orange indicator and
diluted with 0.6 M HCl to the mark. It mixed well and allowed to
stand for 10 min. The absorbance of the solution was measured
at 535 nm using 1% aqueous solution of ascorbic acid as a stan-
dard. Chromium was determined as described in Vogel [17]: 20 ␮g
of Cr(III) complex was evaporated with little amount of H2SO4.
new bands at 601 and 551 cm−1 are due to ꢀ(M–OH2) [18]. The 1
H
NMR spectrum of [UO2(L)(EtOH)2] in DMSO-d6 showed the NH2
protons at 7.89 ppm. The signals at 2.79 and 1.75 may be due to the
CH3 and CH2 of ethanol. Scheme 1 shows the proposed geometry
of [UO2(L1)(EtOH)2].
3.1.2. Electronic spectra of H2L1 and its complexes
The UV spectrum of H2L1 showed bands at 43,860 and
42,020 due to the ␲ → ␲* and n → ␲* transitions of the C
O

498
A.A. El-Asmy et al. / Spectrochimica Acta Part A 76 (2010) 496–501
Table 1
Color, melting points, yields and partial elemental analyses of the ligands and their complexes.
Compound, formula (formula weight)
Color
Yield (%)
%Found (calcd.)
C
H
M
N
Cl
H2L1
White
84
76
81
89
67
80
71
85
19.9
(20.3)
9.0
(8.7)
19.0
5.4 (5.1)
3.9 (4.3)
3.9
–
47.1
(47.4)
19.9
(20.3)
–
–
C2H6N4O2 (118.110)
[Cr(L1)(H2O)3(Cl)]H2O
C2H12N4O6ClCr (275.59)
[ZrO(HL1)2]·C2H5OH
C6H16N8O6Zr (387.39)
[UO2(L1)(EtOH)2]
C4H12N4O6U (506.26)
H4L2
Pale green
Yellowish orange
Yellow
19.1 (18.8)
27.3
(27.6)
47.4
13.3
(12.8)
(18.6)
14.2 (14.2)
(4.2)
2.4 (2.4)
–
–
(47.0)
–
–
–
White
42.3
(42.2)
27.5
(27.1)
21.6
(21.9)
21.3
(21.0)
6.0
(5.7)
3.6
(3.9)
3.4
(3.4)
3.2
(3.2)
29.3
(29.6)
18.6
(18.9)
15.1
(15.3)
14.3
C
10H16N6O4 (284.29)
[ZrO(H3L2)(Cl)]2·2H2O
Yellow
24.0
(24.1)
–
7.9
(8.0)
6.1
(6.5)
–
C
20H34N12O12Cl2Zr2 (887.82)
[HfO(H3L2)(Cl)]2·2H2O
C20H34N12O12Cl2Hf2 (1097.86)
[UO2(H2L2)]·2H2O
Yellowish orange
Yellow
41.2
(41.6)
C10H18N6O9U (571.33)
(14.7)
Table 2
Assignments of the IR spectral bands of H2L1 and its complexes.
Compound
H2L1
ꢀ(H2O) or ꢀ(OH)
ꢀ
as(NH2)ꢀs(NH2)
ꢀ(NH)
ꢀ(C O)
ı(NH2)
ꢀ(C N)a
ꢀ(M–O)
–
3291(s)
3195(m)
1685 (s)
1618(s)
1563(w)
1633(w)
1620(s)
–
–
3253(m)
3289(sh)
3250(sh)
3290(sh)
3250(sh)
3290(sh)
3250(sh)
[ZrO(HL1)2]·C2H5OH
[Cr(L1)(Cl)(H2O)3]H2O
[UO2(L1)(EtOH)2]
3461(br)
3421(br)
3417 (br)
3127(w)
1687 (w)
1633(m)
1633(m)
1620(s)
1020(s)
–
–
–
–
601a(m)
551(m)
942(s)
810(m)
S = strong; m = medium; w = weak; sh = shoulder; br = broad
a
This band may be due to ꢀ(Cr–OH2).
Table 3
Electronic spectral data of the ligands and their complexes.
Compound
State
Intraligand and charge transfer (cm−1
)
H2L1
DMF
Nujol
DMF
DMSO
DMF
DMF
DMF
43860, 42020
33110, 26178
32895, 25320, 23920, 17545
36230, 32155, 24630, 9230, 18050
48540, 45450, 43470, 39210, 36495, 4480
35460, 33785, 26455, 24270
[ZrO(HL1)2]·C2H5OH
[Cr(L1)(Cl)(H2O)3]H2O
[UO2(L1)(EtOH)2]
H4L2
[ZrO(H3L2)(Cl)]2·2H2O
[HfO(H3L2(Cl)]2·2H2O
26520, 25780, 24330, 22220, 21190
group (Table 3). [ZrO(HL1)2]·C2H5OH showed bands at 33,110
and 26,180 cm−1 which could be assigned to the intraligand
and charge transfer transitions. The electronic spectrum of
[Cr(L1)(H2O)3Cl]·H2O showed strong absorption bands at 17545
values of B and ˇ can be calculated applying the equation [19]:
Bꢀ = (2 × ꢀ12) − 3 × ꢀ1 × ꢀ2 + ꢀ22/15 ꢀ2 − 27ꢀ1, ˇ = Bꢀ/B, where B is
the electronic repulsion reported for the free metal ion. It is found
that 10 Dq = 17,544 cm−1, B = 620 cm−1 and ˇ = 0.67. In addition, the
ꢁeff value (4.9 B.M) is in the range reported for the Cr(III) octahedral
geometry.
4
4
(ꢀ1), 23920 (ꢀ2) and 25320 (ꢀ3) due to the A2g(F) → T2g (F)
4
4
(ꢀ1), 4A2g(F) → T1g(F) (ꢀ2) and 4A2g(F) → T1g(P) (ꢀ3), transitions,
In the electronic spectrum of [UO2(L1)(EtOH)2], the band at
respectively. The ꢀ1 transition is a direct measure of 10 Dq. The
24,630 cm−1 is assigned to the 1ꢂg+ → ␲4 transition similar to the
3
OUO symmetric stretching frequency for the first excited state [20]
while that at 26,040 cm−1 is assigned to a charge transfer transition,
probably O → U.
3.1.3. IR spectra of H4L2 and its complexes
The IR spectrum of H4L2 showed bands at 3395, 3305, 1695,
1602, 1508, 1430 and 1004 cm−1 attributed to ␯(OH)oxime, ␯(NH),
␯(C O), ␯(C N)hydrazone, amide II, ␯(C N)oxime and ␯(NOH), respec-
tively (Table 4).
In
the
IR
spectra
of
[ZrO(H3L2)(Cl)]2·2H2O;
[HfO(H3L2)(Cl)]2·2H2O and [UO2(H2L2)]2·2H2O, the ligand coordi-
nates to the two metal centers as a dibasic tetradentate through
the four azomethine nitrogen’s (oxime and hydrazone). This
confirmed through the shift of ␯(C N)hydrazone and ␯(C N)oxime
Scheme 1. Structure of [UO2(L1)(EtOH)2].

A.A. El-Asmy et al. / Spectrochimica Acta Part A 76 (2010) 496–501
499
Table 4
Assignments of the IR spectral bands of H4L2 and its complexes.
Compound
ꢃ(OH)oxime
ꢃ(N–H)
ꢃ(C O)
ꢃ(C N)hyd
ꢃ(C N)oxime
H4L2
3396(s)
3305(s)
1695(s)
1686(s)
1695(s)
1650(s)
1602(w)
1586(w)
1590(sh)
1571(s)
1430(s)
1414(s)
1425(m)
1426(m)
[ZrO(H3L2)(Cl)]2·2H2O
[HfO(H3L2)(Cl)]2·2H2O
[UO2(H2L2)]·2H2O
3410(br)
3402(m)
3416a(br)
3310(br)
3304(m)
3340(sh)
a
ꢃ(O–H) of water.
to (1586, 590); (1414, 1425) and (1426, 1571) cm−1 with low-
ering of their intensity. The disappearance of ␯(OH)oxime in
[UO2(H2L2)]2·2H2O with the appearance of a broad band due
to the hydrated water. Also, the weakness of ␯(NOH)oxime con-
firming the participation of C Noxime in coordination; the result
is supported by a new band at 488 and 492 cm−1 assigned to
␯(M–N) in the two complexes. The ␯(Hf O) band is observed at
794 cm−1. The broadness and weakness of ␯(OH)oxime confirm
the deprotonation of one hydroxyl group and the existence of
the second uncoordinated. The carbonyl band is more or less
unshifted.
The 1H NMR spectrum of [UO2(H2L2)]2·2H2O showed no sig-
nals for the OH protons. The NH signals appear at ı = 10.2 ppm. The
methyl groups appear at ı = 2.81 and 2.50 ppm.
The investigated uranyl complexes of the two ligands exhibit
bands at 926–942 and 810–869 cm−1 assigned to the ꢀ3 and ꢀ1
vibrations, respectively, of the dioxouranium ion [21]. The value of
ꢀ3 is used to calculate the force constant (F) of (O
U O) by the
method of McGlynn and Smith [22]: (␯3)2 = (1307)2 (FU–O)/14.103.
The force constants calculated for the two complexes are found to
be 6.882 and 7.079 mdyn/Å. These values were then substituted
into Jones relation [23]: RU–O = 1.08(FU–O)
−1/3 + 1.17. The values of
RU–O are found = 1.738 and 1.730 Å for the two complexes. The cal-
culated FU–O and RU–O values fall in the usual range for the uranyl
complexes [21].
Fig. 1. Biological effect of H2L1 and its complexes on the calf thymus DNA lanes
arranged as: C—control DNA; 1—ligand; 2—UO22+; 3—ZrO2+; 4—Cr3+
.
3.1.4. Electronic spectra of H4L2 and its complexes
The UV spectrum of H4L2 showed bands at 48,540, 45,450,
43,470, 39,210, 36,496 and 34,483 cm−1 assigned to the ␲ → ␲* and
n → ␲* transitions of C O, C Nhydrazone and C Noxime [19].
The spectrum of the soluble part of [ZrO(H3L2)(Cl)]2·2H2O and
[HfO(H3L2)(Cl)]2·2H2O in DMF showed bands at 35460, 33785,
26455, 24270, and 17005 cm−1 and 26520, 25779, 24330, 22220,
and 21190 cm−1. The bands at 35460 and 33784 cm−1 in the spec-
trum of [ZrO(H3L2)(Cl)]2·2H2O are assigned to the intraligand
transitions while the other bands are due to LMCT transition [24],
probably, N → Zr and O → Zr. Scheme 2 represents the proposed
structure for the dimmer form of the complex. The high melting
points and the partial solubility confirm the dimmeric form.
3.2. Biological activity
3.2.1. Eukaryotic DNA degradation test
Examining the DNA degradation assay for H4L2 and H2L1 as
well as their metal complexes revealed variability on their imme-
diate damage on the calf thymus (CT) DNA. The complexes have
a high effect on the calf thymus DNA than the ligands; HfO2+
,
Cr3+ and ZrO2+ complexes of H4L2 degraded the CT DNA com-
pletely. The results suggest that direct contact of HfO2+ and
ZrO2+ is necessary to degrade the DNA of Eukaryotic subject
(Figs. 1 and 2).
In the electronic spectrum of [UO2(H2L2)]·2H2O, the band at
3
22520 cm−1 is assigned to the 1ꢂg+ → ␲ transition. This band
4
is similar to the OUO symmetric stretching frequency for the first
excited state [20]. Other bands at 28900, 26040 and 22520 cm−1
are assigned to intraligand and charge transfer transitions [25].
3.2.2. Antibacterial activity
The ligands and their metal complexes were tested against
Gram’s positive Bacillus thuringiensis (BT) and Gram’s neg-
ative bacteria (E. coli). All compounds have high inhibitory
effects on Gram’s positive bacteria; [Cr(L1)(Cl)(H2O)3]H2O has
the highest value giving zone diameter of 50 mm. The low-
est one is H2L. All compounds have small inhibitory effects
on Gram’s negative bacteria which can be attributed to the
inability of the complexes to diffuse into the cell membrane
of the organism. Examining the values for Gram’s posi-
tive bacteria in Table 5, one can arrange the compounds as:
[Cr(L1)(Cl)(H2O)3]H2O > [HfO(H3L2)(Cl)]2·2H2O > [UO2(L1)(EtOH)2]
> [ZrO(HL1)2]·C2H5OH > [UO2(H2L2)]2·2H2O > [ZrO(H3L2)(Cl)]2
·2H2O ∼ H4L2 > H2L1.
Scheme 2. Structure of [ZrO(H3L2)(Cl)]2·2H2O.

500
A.A. El-Asmy et al. / Spectrochimica Acta Part A 76 (2010) 496–501
Fig. 3. Thermal analysis curves (TGA, DTA) of [Cr(L1)(Cl)(H2O)3]H2O.
Fig. 2. Biological effect of H4L2 and its complexes on the calf thymus DNA Lanes
arranged as: C—control DNA; 1—ligand; 2—VO2+; 3—Cr3+; 4—ZrO2+
.
3.3. Thermal analysis
The TGA thermogram of [ZrO(HL1)2]·C2H5OH showed the first
step at 29–160 ◦C with a weight loss of 29.8% (calcd. 31.5) cor-
responding to the removal of C2H5OH + ON4H4. The second step
ended at 355 ◦C with a weight loss of 22.5% (calcd. 20.7) corre-
sponding to the evolution of C4O2. Thirdly, the removal of N4H6
is considered the last fragment of the ligand liberating in the tem-
perature range 356–524 ◦C with a weight loss of 17.1% (calcd. 16.1).
After which a constant weight was observed while ZrO2 becomes
the residual part with 29.5% (calcd. 31.8) weight loss.
Fig. 4. Thermal analysis curves (TGA, DTA) of [HfO(H3L2)(Cl)]2·2H2O.
→ [(ZrO)2(C16H18N12O8Cl2)] + {2H2O + 4CH3}
→ (ZrO)2(C8N8O2) + {4CH3 + C4N4O4H4 + Cl2 + H2O2}
→ 2[ZrO2N4] + 4C
[ZrO(C4H10N8O4)]·C2H5OH
→ [ZrO(C4H4N4O4)] + {C2H5OH + ON4H4}
The TGA curve of [Cr(L1)(Cl)(H2O)3]H2O (Fig. 3) showed the first
stage ended at 140 ◦C representing the elimination of the hydrated
water by 7.0% (calcd. 6.5). The second at 141–274 ◦C has 7.9% (calcd.
6.5) corresponding to the loss of one of the coordinated water
molecule. The evolution of ½Cl2 + 2H2O occurred at 275–468 ◦C
with 24.9% (calcd. 25.9). The last decomposition stage by 10.2%
(calcd. 10.8) may be attributed to the loss of N2H2 at a tempera-
ture up to 658 ◦C. A steady stable region occurred at 659–800 ◦C
referring to the residual part [CrC2H2N2O2] having 41.9% (calcd.
41.9) weight loss.
→ [ZrO(C2O4)] + {C4O2} → ZrO2 + {N4H6}
In the TGA thermogram of [ZrO(H3L2)(Cl)]2·2H2O, the first step
(37–183 ◦C) representing the loss of 2H2O + 4CH3 by a weight of
10.8% (calcd. 11.9). The second step at 184–450 ◦C representing
the removal of 4CH3 + C4H4N4O4 + Cl2 + H2O2 with a loss of 37.9%
(calcd. 37.9). The third stage at 451–700 ◦C is attributed to the loss
of 4C by 9.8% (calcd. 7.2). The residual part is 2ZrO2N4 with a mass
of 38.6% (calcd. 43.6).
[(ZrO)2(C20H30N12O8Cl2)]·2H2O
[Cr(C2H4N4O2)Cl(H2O)3]H2O
Table 5
→ [Cr(C2H4N4O2)Cl(H2O)2] + {H2O}
→ [Cr(C2H4N4O2)(H2O)2Cl] + H2O
→ [Cr(C2H4N4O2)] + {½Cl + 2H2O}
→ [CrO2C2N2H2] + {N2H2}.
Antibacterial activities of the ligands and their complexes.
Compound (number)
Inhibition zone (mm)a Gram’s
positive bacteria (BT)
H4L2 (5)
18
18
43
23
8
[ZrO(H3L2)(Cl)]2·2H2O (8)
[HfO(H3L2)(Cl)]2·2H2O (6)
[UO2(H2L2)]2·2H2O (9)
H2L1 (1)
The TGA curve of [HfO(H3L2)Cl]2.2H2O (Fig. 4) displayed several
decomposition stages. The first one ended at 144 ◦C is due to the
elimination of 2H2O + 4CH3 with weight loss of 8.6% (calcd. 8.7).
The second step [found 30.7% (calcd. 30.7)] ended at 434 ◦C is due
to the removal of 4CH3 + C4N4O4H4 + Cl2 + H2O2. The third stage at
434–750 ◦C with weight loss of 2.9% (calcd. 2.7) is attributed to the
[ZrO(HL1)2]·C2H5OH (10)
[Cr(L1)(Cl)(H2O)3]H2O (3)
[UO2(L1)(EtOH)2] (11)
Gentamicin
28
50
39
48
a
Value for one record.

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501
4. Conclusion
Monomer,
[ZrO(HL1)2]·C2H5OH,
[Cr(L1)(H2O)3Cl]H2O
and [UO2(L1)(H2O)2] and dimmer, [ZrO(H3L2)Cl]2·2H2O,
[HfO(H3L2)Cl]2−·2H2O and [UO2(H2L2)]·2H2O complexes were
isolated and characterized with oxalylhydrazide and oxalyl
bis(diacetylmonoxime hydrazone). All have octahedral geome-
try and stable to thermal decomposition. Some complexes are
decomposed immediately due to the presence of hydrated and
coordinated water. All complexes have high activity towards calf
thymus DNA than the ligands. They also have high inhibitory effect
on Gram’s positive than Gram’s negative bacteria.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.saa.2010.04.012.
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Scheme 3. Molecular modeling of H2L1 (a) and H4L2 (b).
loss of CN. Finally {2[HfO2C3N3]} is referred to the remaining part
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with 54.3% (calcd. 56.1) weight.
[(HfO)2(C20H30N12O8Cl2)]·2H2O
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→ [(HfO)2(C16H18N12O8Cl2)] + {2H2O + 4CH3}
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3.4. Molecular modeling of the ligands
The molecular parameters calculated for H2L1 (H4L2) are:
total energy = −36016.23 (−82347.25), binding energy = −1193.24
(−3374.40), electronic energy = −153597.20 (−539181.59), heat
of formation = −32.27 (84.37) kcal/mol, dipole moment = 1.81
(7.826) D, HOMO = −9.7720 (−9.5843) eV and LUMO = −0.1114
(−0.3313) eV. Scheme 3 represents their molecular modeling
where the bond lengths and angles are recorded in Tables 1S and 2S.
In H2L1 modeling (Scheme 3a), a hydrogen bond is formed
between the NH2 and C O groups from one side. No hydrogen
bonding for the other two groups probably due to the distance is
long. Also, the two carbonyl groups lie on different sides.
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In H4L2 modeling (Scheme 3b), no hydrogen bonds due to the
existence of each C O and the adjacent NH in opposite sides. The
distance between O(3) and H(22) is far enough to form bond. All
bond angles were found between 100.8023 and 127.4972 confirm-
ing in most cases sp2 and sp3 hybridization.
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