Ligational, analytical and biological applications on oxalyl bis(3,4-dihydroxybenzylidene) hydrazone

Article abstract of DOI:10.1016/j.saa.2010.05.026

The molecular modeling and parameters have been calculated to confirm the geometry of oxalyl bis(3,4-dihydroxybenzylidene) hydrazone, H₆L. The metal complexes of Cr³⁺, VO²⁺, ZrO²⁺, HfO ²⁺, UO₂²⁺ and MoO₂²⁺ with H₆L have been prepared and characterized by partial elemental analysis, spectral studies (electronic; IR), thermal analysis and magnetic measurements. The data suggest the formation of polymer complexes with a unit [Cr(H₄L)(H₂O)₃Cl]·H₂O, [VO(H₄L)(H₂O)₂], [Hf(H₄L)(H ₂O)]·H₂O [UO₂(H₄L)(H ₂O)₂]·2H₂O [MoO₂(H ₄L)] and [(ZrO)₂(H₂L)-(C₂H ₅OH)₂]. The ligand behaves as a dibasic bidentate in all complexes except ZrO²⁺ which acts as a tetrabasic tetradentate with the two ZrO²⁺ ions. An octahedral geometry was proposed for the Cr³⁺, HfO²⁺, MoO₂²⁺and UO ₂²⁺ complexes and square pyramid for VO²⁺. The Cr³⁺ is necessary to degrade the DNA of eukaryotic subject completely; the other complexes have little effect. H₆L was found suitable as a new reagent for the separation and preconcentration of ZrO ²⁺ ions from different water samples using flotation technique with satisfactory results.

Full text of DOI:10.1016/j.saa.2010.05.026

Spectrochimica Acta Part A 77 (2010) 297–303
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Ligational, analytical and biological applications on oxalyl
bis(3,4-dihydroxybenzylidene) hydrazone
Ahmed A. El-Asmy∗, O.A. El-Gammal, H.A. Radwan, S.E. Ghazy
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
Article history:
The molecular modeling and parameters have been calculated to confirm the geometry of oxalyl
bis(3,4-dihydroxybenzylidene) hydrazone, H6L. The metal complexes of Cr3+, VO2+, ZrO2+, HfO2+, UO2
2+
Received 23 March 2010
Received in revised form 11 May 2010
Accepted 15 May 2010
2+
and MoO2 with H6L have been prepared and characterized by partial elemental analysis, spectral
studies (electronic; IR), thermal analysis and magnetic measurements. The data suggest the forma-
tion of polymer complexes with a unit [Cr(H4L)(H2O)3Cl]·H2O, [VO(H4L)(H2O)2], [Hf(H4L)(H2O)]·H2O
[UO2(H4L)(H2O)2]·2H2O [MoO2(H4L)] and [(ZrO)2(H2L)-(C2H5OH)2]. The ligand behaves as a dibasic
bidentate in all complexes except ZrO2+ which acts as a tetrabasic tetradentate with the two ZrO2+ ions. An
octahedral geometry was proposed for the Cr3+, HfO2+, MoO22+and UO22+ complexes and square pyramid
for VO2+. The Cr3+ is necessary to degrade the DNA of eukaryotic subject completely; the other complexes
have little effect. H6L was found suitable as a new reagent for the separation and preconcentration of
ZrO2+ ions from different water samples using flotation technique with satisfactory results.
© 2010 Elsevier B.V. All rights reserved.
Keywords:
Oxalyl bis(3,4-dihydroxybenzylidene)
hydrazone
Flotation
Spectra
2+
2+
Cr3+, VO2+, ZrO2+, HfO2+, UO2 and MoO2
complexes
1. Introduction
2-aceto-1-naphthol-N-salicoyl hydrazone have been prepared and
characterized. The 1:2 (M:L) complexes of Cu(II), Ni(II), Co(II) and
Mn(II) have an octahedral structure while 1:1 of Cu(II) and Ni(II)
are square planar. The ligand was used for the microdetermination
of metal ions in solution [9].
The synthesis and structural characterization of metal com-
plexes of hydrazones have much interest to compare their
coordinative behavior with their antimicrobial activities. Cop-
per(II) complexes of certain hydrazones have antitumor activity
[1]. Diacetylmonoxime thiosemicarbazone is effective against vac-
cinia infections in mice by chelating some essential metal ions from
the virus [2]. Oximinohydrazones have antiparasitic, fungicidal
and bactericidal properties [3]. Compounds containing oxime and
amino groups are used as analytical reagents for the microdeter-
mination of some transition metal ions and as ion exchange resins
[4]. Series of pyridazinyl hydrazones were found to inhibit tyro-
sine hydroxylase and dopamine hydroxylase in vivo and in vitro [5].
Tridentate hydrazones have been evaluated as potential oral iron-
chelating drugs for genetic disorders such as thalassemia [6]. The
X-ray crystal structure of the ferric complex of pyridoxalisonicoti-
noyl hydrazone showed that the ligand acts as a tridentate planar
chelating agent with the remaining sites around the iron occupied
by chloride ions or water molecules [7]. Salicylaldehydebenzoyl
hydrazone appeared to be unusually potent inhibitor of DNA syn-
thesis and cell growth in a variety of human and rodent cell lines [8].
The complexes of Cu(II), Co(II), Ni(II), Mn(II), Ce(III) and UO22+ with
Binuclear complexes of VO2+, Co2+, Ni2+, Cu2+ and Zn2+ with
oxalyl bis(diacetylmonoxime hydrazone) were prepared. The data
suggest a 2:2 (M:L) molar ratio. An octahedral geometry for
VO2+ complex, tetrahedral for Zn2+ and square planar for the
rest complexes were proposed [10]. Complexes of UO22+, VO2+
and ZrO2+ ions with vitamin B13 (orotic acid) were reported
and formulated as: [M(C5H3N2O4)2(H2O)2]·(H2O)n. The antibacte-
rial activity of orotic acid and its complexes were tested against
gram positive/negative bacteria [11]. 2,5-Dihydroxyacetophenone-
isonicotinoyl hydrazone (H2L) was synthesized as well as its metal
complexes with Cr3+, Mn3+, Fe3+, VO2+, Zr4+ and UO22+. The Schiff
base behaved as a flexidentate ligand and commonly coordinated
through the oxygen atom of the deprotonated phenolic group and
the azomethine nitrogen. The thermal data were analyzed for the
kinetic parameters. All the compounds were screened for their
antimicrobial activity by agar cup-plate method against various
organisms and the results compared [12]. Series of mono and bin-
uclear Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, La3+, Ru3+, Hf4+, ZrO2+
2+
and UO2 complexes of phenylamino-dibenzoyl hydrazone were
synthesized and characterized [13].
Up to date, no work on complexes containing Cr3+, VO2+
,
ZrO2+, HfO2+, UO2 and MoO2 ions with the investigated ligand,
H6L.
2+
2+
∗
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.2010.05.026

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A.A. El-Asmy et al. / Spectrochimica Acta Part A 77 (2010) 297–303
cell was shaken well for few seconds to ensure complete complex-
ation. To this solution, 3 mL of 1.0 × 10−5 mol L−1 HOL were added
and the cell was then inverted upside down many times by hand.
After complete separation, the scum containing ZrO2+–H6L com-
plex was separated, eluted with 4 mL of 4 M HCl, diluted to 10 mL
in a volumetric flask and subjected to spectral determination.
Scheme 1. Formula of H6L.
2.4. Antibacterial and genotoxicity studies
H6L and metal complexes were screened for their antimicrobial
activity using Gram positive (BT) and Gram negative bacteria (E.
coli). The media prepared for bacteria were as reported earlier [14].
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−1
DMSO. An equal volume of each compound and DNA were mixed
thoroughly and kept at room temperature 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.
2. Experimental
VOSO4·2H2O, CrCl3·3H2O, ZrCl4, HfCl4, UO2(OAc)2 and
(NH4)2MoO4, diethyl oxalate, hydrazine hydrate, 3,4-
dihydroxybenzaldehyde, ethanol, diethyl ether, DMF and DMSO
were obtained from the BDH chemicals.
2.1. Synthesis of H6L
Oxalyl bis(3,4-dihydroxybenzylidene) hydrazone, Scheme 1,
was prepared by heating a suspension (6 g, 0.05 mol) of oxalic
acid dihydrazide (NH2NHCOCONHNH2) in 20 mL EtOH with 13.8 g
(0.1 mol) of 3,4-dihydroxybenzaldehyde in 10 mL EtOH on a water
bath for 1 day. Complete reaction is tested by thin layer chromatog-
raphy (TLC) in petroleum ether-ethyl acetate (1:2) as eluent. It gives
one spot with Rf = 0.34. The precipitate was filtered off, recrys-
tallized from ethanol and dried; the yield is 79%. The ligand was
characterized by spectral studies and elemental analysis. The 1H
NMR spectrum of the ligand gives different signals at ı = 12.05, 9.48,
7.41–6.85 and 2.32 ppm corresponding to the protons of OH, NH,
aromatic CH and aliphatic CH, respectively.
2.5. Equipment and analysis
C, H and N contents of H6L and complexes were determined at
the Microanalytical Unit of Cairo University, Egypt. The metal con-
tent was determined by gravimetric or complexometric methods
[15]. The IR spectra were recorded as KBr disc on a Mattson 5000
FTIR Spectrophotometer (200–4000 cm−1). The UV–vis spectra of
the complexes were recorded on UV2 Unicam Spectrophotometer
(200–900 nm). The 1H NMR spectrum of the ligand was recorded in
deuterated dimethulsulphoxide (DMSO-d6), on a Bruker WP 200 SY
spectrometer (300 MHz) at room temperature using tetramethyl-
silane (TMS) as an external standard. The magnetic measurements
were carried out on a Johnson-Matthey magnetic balance, UK.
Thermogravimety (TGA) was measured (20–800 ◦C) on a Shimadzu
TGA-50; the nitrogen flow and heating rate were 20 mL min−1 and
10 ◦C min−1, respectively. ESR spectra were obtained on a Bruker
EMX spectrometer working in the X-band (9.78 GHz) with 100 kHz
modulation frequency. The microwave power was set at 0.004. A
powder spectrum was obtained in a 2 mm quartz capillary at room
temperature.
2.2. Preparation of complexes
The solid complexes were prepared by reacting the calculated
amounts for 2:1 ratio [M:L] of metal salt and ligand in H2O–EtOH
(v/v) solution and the mixture was heated under reflux on a water
bath for 6–8 h. In the preparation of VO2+ complex, 0.1 g of sodium
acetate was added. The precipitate thus formed was filtered off,
washed with hot water, hot ethanol and diethyl ether and finally
dried in a vacuum desiccator over anhydrous CaCl2.
2.3. Flotation method
All molecular calculations were carried out by HyperChem 7.51
software package. The molecular geometry of the ligand and its
ZrO2+ complex is first optimized at molecular mechanics (MM+)
level. Semi-empirical method PM3 is then used for optimizing the
full geometry of the system using Polak–Ribiere (conjugate gra-
A 3 mL aliquot containing 0.5 × 10−5 mol L−1 ZrO2+ was mixed
with H6L (1 × 10−4 mol L−1) and 3 mL bidistilled water. The pH was
adjusted at ∼3. The solution was then transferred quantitatively to
the flotation cell and completed to 10 mL with bidistilled water. The
Table 1
Color, melting points and partial elemental analyses of H6L and its complexes.
Compound
Color
M.P. (◦C)
% Found (calcd.)
C
H
N
M
H6L
Pale yellow
295–96
>300
53.2 (53.6)
5.5 (5.9)
14.9 (15.6)
–
C16H14N4O6, 358.32
[VO(H4L)(H2O)2]
C16H16N4O7V, 459.27
[Cr(H4L)(H2O)3Cl]H2O
Brownish green
Brown
42.2 (41.8)
36.8 (37.2)
37.0 (36.4)
33.2 (32.7)
39.3 (38.8)
26.9 (27.5)
3.7 (3.5)
3.7 (3.9)
4.0 (3.6)
3.1 (2.7)
3.8 (4.2)
3.3 (2.9)
12.6 (12.2)
10.4 (10.8)
8.1 (8.5)
11.4 (11.1)
10.5 (10.1)
31.9 (32.4
>300
C16H20N4O10CrCl, 516.73
[(ZrO)2(H2L)(C2H5OH)2]
C20H22N4O10Zr2, 660.83
[HfO(H4L)(H2O)]H2O
C16H14N4O8Hf, 586.84
[MoO2(H4L)]
C16H12N4O8, 483.91
[UO2(H4L)(H2O)2]2H2O
C16H20N4O12U, 698.45
Yellowish orange
Brownish orange
Brownish green
Brown
>300
>300
9.2 (9.5)
>300
11.8 (11.6)
>300
34.5 (34.1)

A.A. El-Asmy et al. / Spectrochimica Acta Part A 77 (2010) 297–303
299
lengths of the O–H and C–O are nearly similar, except C(16)–O(17)
and C(13)–O(15) which are smaller than the rest due to the double
bond character; (ii) the two N–N bond lengths are typical; they
surround with similar substituents; (iii) all bond angles predict sp3
and sp2 hybridization; (iv) the bond angles of C(21)–N(20)–N(18),
O(17)–C(16)–C(13) and C(16)–C(13)–O(15) are 123.39, 123.35 and
124.87 while C(23)–C(21)–N(20) is 127.39◦.
The calculated total energy; binding energy; electronic
energy and heat of formation are −1,041,311; −4295; −740,887
and −22 kcal mol−1
,
respectively, dipole moment = 3.144 D;
HOMO = −8.773392 eV and LUMO = −0.3302211 eV.
3.3. IR spectra of H6L and complexes
The IR spectrum of H6L showed bands at 3486, [2363(w),
2338(w)], 3374(w), 1653(vs), 1612(s), 1517(w) and 1366(s) due
to the ꢀ(OH)free, [ꢀ(OH)bonded], ꢀ(NH), ꢀ(C O), ꢀ(C N), amide II
[ı(N–H) + ꢀ(C N)] and ı(OH) vibrations, respectively. The bands at
2363 and 2338 cm−1 exist at more less wavenumbers than the free
indicating strong O–H· · ·O hydrogen bonding [16].
The absence of the OH bands (Table 2) in the spectra
of all complexes indicates the destruction of the hydrogen
bond during complexation and instead another band appears at
3396–3442 cm−1 in the spectra of all complexes, except for the
ZrO2+ complex, indicating the involvement of two OHs in chelation;
the other two are still protonated with weak hydrogen bond. In the
ZrO2+ complex, no band in this region confirming the involvement
of the four OHs in coordination. Another support for the OH coor-
dination is the appearance of the ı(OH) band at 1366 cm−1 with
low intensity as well as new one at 1338 cm−1 duo to the ı(OH)
of the coordinated water. Ethanol in the zirconyl complex is sup-
ported by the appearance of ı(OH) strong. The ꢀ(NH), ꢀ(C O) and
ꢀ(C N) bands appeared more or less at the same position as in
the spectrum of H6L indicating no chelation through these groups;
these groups exist opposite to each other (from molecular calcu-
lation). Also, the IR spectra of the complexes showed a new band
at 464–521 cm−1 due to ꢀ(M–O) vibration. The vanadyl complex
showed a strong band, at 970 cm−1, attributed to the ꢀ(V O) vibra-
tion which is an evidence for the square-pyramidal configuration
of the VO2+ complex [17].
Scheme 2. Molecular modeling of H6L.
dient) algorithm and Unrestricted Hartee-Fock (UHF) is employed
keeping RMS gradient of 0.01 kcal (Å mol−1).
3. Results and discussion
3.1. General
The color, melting points and elemental analyses of the com-
plexes are compiled in Table 1. The data are in agreement with the
formulae [Cr(H4L)(H2O)3Cl]·H2O, [M(H4L)(H2O)n]·mH2O (M = VO,
HfO, MoO2 or UO2) and [(ZrO)2(H2L)(C2H5OH)2]. The complexes
are insoluble in most common organic solvents and partially solu-
ble in dimethylformamide (DMF) and DMSO. The partial solubility
of the complexes in DMSO or DMF prevents the growing of crys-
tals for X-ray crystallography and the measurement of their molar
conductances and 1H NMR spectra. The intense color may be due
to a charge transfer or a defect of crystal during the preparation.
HfO2+ complex have more intense color than ZrO2+ complex which
may be due to high polarization; the band at 14,680 cm−1 in its
electronic spectrum is due to ligand–metal charge transfer (LMCT).
The thermal analyses indicate high stability for some complexes; a
behavior consistent with a polymeric nature of the complexes.
The IR spectrum of [UO2(H4L)(H2O)2]·2H2O displayed two
bands at 929 and 873 assigned to ꢀ3 and ꢀ1 of the dioxouranium
ion (Scheme 2). The force constant (FU–O = 7.125 mdynes Å−1) of
the U O bond is calculated by [18]: (ꢀ3)2 = (1307)2 (FU–O)/14.103.
Substituting its value in the Jones relation [19]: RU–O = 1.08
(FU–O)
−1/3 + 1.17, RU–O was 1.73 Å. These values falling within the
usual range for the uranyl complexes (Scheme 3).
MoO2 complex showed bands at 904 and 850 cm−1. Using
2+
the same above equations, FMo–O and RMo–O for O Mo O are
6.75 mdynes Å−1 and 1.74 Å, respectively. Mo–O radius is approxi-
mately similar to U–O.
3.2. Molecular modeling of H6L
The molecular numbering of H6L is shown in Scheme 2. Analysis
of the data in Tables 1S and 2S calculated for both length and angle
for each bond, one can conclude the following remarks: (i) all bond
The broad bands at ∼3360, ∼890 and ∼540 cm−1 in
the spectra of [VO(H4L)(H2O)2], [Cr(H4L)(H2O)3Cl]·H2O and
[UO2(H4L)(H2O)2]·2H2O are attributed to ꢁ(OH), ꢂr(H2O) and
Table 2
Assignments of the IR spectral bands of H6L and its complexes.
Compound
ꢀ(OH)
ꢀ(NH)
ꢀ(C O)
ꢀ(C N)
[ı(N–H) + ꢀ(C–N)]
ı(OH)
ꢀ(M–O)
H6DPOH
3486, 2363, 2338
3396, –
3343, –
–
3442, –
3344, –
3419, –
3374
3242
3247
3247
3247
3247
3180
1653
1644
1653
1656
1656
1653
1679
1612
1593
1611
1614
1614
1607
1589
1517
1517
1517
1515
1515
1516
1530
1367
1366
–
468
470
466
464
467
521
[VO(H4L)(H2O)2]
[Cr(H4L)(H2O)3Cl]H2O
[(ZrO)2(H2L)(C2H5OH)2]
[HfO(H4L)(H2O)]H2O
[UO2(H4L)(H2O)2]2H2O
[MoO2(H4L)]
1337a, 1366
1365a
1338a, 1359
1369
1372
a
ı(OH) of the coordinated water.

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A.A. El-Asmy et al. / Spectrochimica Acta Part A 77 (2010) 297–303
Scheme 3. Structure of [UO2(H4L)(H2O)2]·2H2O.
Table 3
Magnetic moments and electronic spectral bands of the compounds.
Compound
ꢃeff (BM)
State
Intraligand and charge transfer (cm−1
)
d–d transition (cm−1
)
H6L
–
–
3.69
–
–
DMF
DMF
DMF
DMSO
NujolDMF
Nujol
Nujol
35,740; 33,000; 32,050; 27,900; 26,455
36,765; 32,680; 29,410; 27,470
35,970; 32,895
35,710; 33,110; 27,860; 24,340
34,720; 31,650; 27,625; 26,040 × 33,110;28,250; 24,040; 19,840
33,110; 28,250; 23,920
–
–
[(ZrO)2(H2L)(C2H5OH)2]
[Cr(H4L)(H2O)3Cl]H2O
[UO2(H4L)(H2O)2]2H2O
[MoO2(H4L)]
[VO(H4L)(H2O)2]
[HfO(H4L)(H2O)]H2O
22,830; 21,830; 18,050; 16,450
–
–
19,840
–
1.74
–
24,330; 22,330; 21,190; 14,640
ꢂw(H2O), respectively, confirming water of coordination [20];
these bands absent in the rest complexes.
The spectrum of [UO2(H4L)(H2O)2)]·2H2O showed a band at
24,340 cm−1 similar to the O
U O symmetric stretching frequency
for the first excited state [22].
The electronic spectrum of [MoO2(H4L] in Nujol (DMF) showed
bands at 34,720 (33,110), 31,650, 27,625 (28,250) and 26,040
(24,040) cm−1 which are more or less similar to those in the lig-
and spectrum. The band at 24,040 cm−1 is similar to that in the UO2
spectrum indicating O Mo O moiety. The shoulder at 19,840 cm−1
in DMF spectrum arising from O pseudo-sigma combinations to
the singly occupied Mo 4d orbital in the xy plane suggesting a
considerable covalency in the ground-state electronic structure of
[MoO2(H4L)]n (Scheme 5). There is no evidence for any d–d tran-
sition and the data cast no doubt about the six coordination of the
complex [23,24].
3.4. Electronic and magnetic studies
The magnetic moment values of the VO2+ and Cr3+ complexes
are 1.74 and 3.57 BM, consistent with the presence of one and three
unpaired electrons. The other complexes have a diamagnetic nature
in accordance with the d0 or d10 configuration.
The spectrum of H6L showed ␲ → ␲* and n → ␲* bands at
35,740–26,455 cm−1. Changes are observed on the spectra of its
complexes (Table 3).
The electronic spectrum of [Cr(H4L)(H2O)3Cl]·H2O (Fig. 1)
showed two strong absorption bands at 18,050 and 22,831 cm−1
4
4
attributed to the 4A2g (F) → T2g (P) and 4A2g (F) → T1g (F) transi-
tions, inanoctahedralgeometry. An additionalbroadbandcentered
at 24,210 cm−1 is due to a charge transfer. The ligand field param-
eters (Dq = 1805 cm−1, B = 429.8 cm−1 and ˇ = 0.46) are further
support for the proposed geometry. The lower value of ˇ indi-
cates more covalency. The two bands at 23,920 and 19,840 cm−1
in [VO(H4L)(H2O)2] are assigned to the dxz → dxy transition in a
square-pyramidal geometry [21]. The color and IR band support
square-pyramid structure (Scheme 4).
3.5. Thermal analysis
The thermogravimetric curves (25–800 ◦C) of some complexes
were recorded to give an insight into the thermal stability of the
studied complexes. In Cr3+ and HfO2+, the first decomposition step
is due to the loss of water of crystallization in the temperature
range 40–150 ◦C. In the other complexes, the first decomposition
step begins at 205, 207 and 268 ◦C.
The TG curve of [VO(H4L)(H2O)2] (Fig. 2) displayed a thermal sta-
bility till 205 ◦C, after which five degradation steps were observed
at 205–285, 286–353, 355–434, 435–515 and 516–730 ◦C. The first
Fig. 1. Electronic spectrum of [Cr(H4L)(H2O)3(Cl)]·H2O.
Fig. 2. Thermal analysis curves (TGA, DTA) of [VO(H4L)(H2O)2].

A.A. El-Asmy et al. / Spectrochimica Acta Part A 77 (2010) 297–303
301
Scheme 4. Structure of [VO(H4L)(H2O)2].
Scheme 5. Structure [MoO2(H4L].
step is due to the removal of 2H2O with 8.0 (calcd. 7.8%) weight
[Cr(C16H12N4O6)(H2O)3Cl]H2O
loss. C7H4NO2VO still exists in the last step by 40.7 (calcd. 40.9%)
→ [Cr(C16H12N4O6)(H2O)2Cl] + {2H2O}
→ [Cr(C14H10N2O4)Cl] + {C2H2N2O2 + 2H2O}
→ [Cr(C3HO2)] + {(C11H9N2O2Cl)}
revealing a high stability of the final species at 730 ◦C.
In [(ZrO)2(H2L)(C2H5OH)2], the decomposition begins at 268 ◦C
indicating a high stability of the complex. The first step at
269–362 ◦C is due to the removal of 2C2H5OH + C4H2O2. The final
step ending at 800 ◦C is corresponding to Zr2O3.
The TGA curve of [MoO2(H4L)] (Fig. 3) showed four degrada-
tion steps. At 30–376 ◦C, the C7H7N2O2 fragment is removed with
weight loss of 30.5 (calcd. 31.2%). The second step ended at 516 ◦C is
corresponding to the loss of C4H2O2N2 with 22.2 (22.7%). The third
step ending at 591 ◦C is corresponding to the removal of CH with
2.7 (calcd. 4.3%). The residue at 591–800 ◦C [43.3 (calcd. 44.4%)] is
[MoO2(C4H3O2)]. Equations representing the degradation steps for
the complexes are:
[(ZrO)2(C16H10N4O6)(C2H5OH)2]
→ [(ZrO)2(C14H8N2O4)] + {2C2H5OH + C2H2N2O2}
→ [(ZrO)2(N2O4)] + {C14H8} → Zr2O2 + {N2O4}
[HfO(C16H12N4O6)(H2O)]·H2O
→ [HfO(C16H12N4O6)(H2O)] + {H2O}
→ [HfO(C14H10N2O4)] + {H2O + C2H2N2O2}
→ [HfO(C13H9NO4)] + {CNH}
[VO(C16H14N4O6)(H2O)2] → [VO(C16H14N4O6)] + {2H2O}
→ [VO(C9H8N3O4)] + {C7H6NO2}
→ [VO(C8H7N2O3)] + {CONH}
→ [HfO(C7H6NO4)] + {C6H3} → [HfO(C7H4NO2)] + {H2O2}
→ [VO(C7H6O2)] + {CHN2O}
[MoO2(C16H13N4O6)] → [MoO2(C9H6N2O4)] + {C7H7N2O2}
→ [MoO2(C5H4O2)] + {C4H2O2N2}
→ [MoO2(C4H3O2)] + {CH}
3.6. ESR spectrum of [VO(C16H14N4O6)(H2O)2]
The ESR spectra of the vanadyl complexes provide informa-
tion about hyperfine and superhyperfine structures. Generally, the
mononuclear VO2+ ion (S = 1/2, I = 7/2) has a characteristic octet ESR
spectrum showing the hyperfine coupling to the 51V nuclear mag-
netic moment. The superexchange interaction between the two
vanadium ions lead to a configuration in which the two electron
spins have an antiferromagnetic character [25]. Therefore, the ESR
spectrum of strongly coupled pairs has the form of a single broad
line with inhomogeneous broadening. V(IV) complexes generally
have g-values less than 2.0023.
Fig. 3. Thermal analysis curves (TGA, DTA) of [MoO2(H4L)].

302
A.A. El-Asmy et al. / Spectrochimica Acta Part A 77 (2010) 297–303
and; VO2+ and ZrO2+ complexes degraded the CT DNA completely.
The results suggest that direct contact of VO2+ and ZrO2+ is neces-
sary to degrade the DNA of eukaryotic subject.
The ligand and its metal complexes have been tested against
Gram positive (BT) and Gram negative bacteria (E. coli). All com-
pounds have small inhibitory effects on bacteria.
3.9. Separation and determination of ZrO2+ using H6L
Different factors affecting the flotation of ZrO2+ using H6L have
been studied to maximize its separation efficiency. The most impor-
tant are:
pH: A series of experiments were carried out to show the
effect of HCl and/or NaOH on the separation of 0.5 × 10−4 mol L−1
ZrO2+, in the presence of 1 × 10−5 mol L−1 oleic acid (HOL) and
1 × 10−4 mol L−1 H6L. The results show that the floatability of
ZrO2+–H6L increases with increasing the pH, reaching a maximum
at 2.5–3.5. Therefore, all work experiments were carried out at pH
∼3.
Fig. 4. The ESR spectrum of [VO(H4L)(H2O)2].
Ligand concentration: Trials were performed to float ZrO2+
with oleic acid individually; the efficiency does not exceed 35%.
H6DPOH was the reagent added to give good results. The floata-
The
room
temperature
(300 K)
ESR
spectrum
of
[VO(H4L)(H2O)2] gave a typical eight-line pattern (Fig. 4) similar
to those reported for mononuclear vanadium molecule [26]. The
spectra of mono vanadium complexes showed the parallel and per-
pendicular features which indicate axially symmetric anisotropy
with well resolved sixteen-lines hyperfine splitting characteristic
for the interaction between the electron and the vanadium nuclear
spin (I = 7/2) [27]. The spin Hamiltonian parameters are calculated
to be g// (1.93), g (1.97), A// (190 × 10−4 cm−1) and A (60). The
bility of a series of solutions containing 0.5 × 10−4 mol L−1 ZrO2+
,
1 × 10−5 mol L−1 HOL and various amounts of H6L at pH ∼3 was
performed. The results show a maximum efficiency (98.4%) at 1:2
(ZrO:H6L) ratio. Excess ligand has no effect, so the procedure find
application for real samples containing ZrO2+. A concentration of
H6L equals two-folds of ZrO2+ or more was used.
⊥
⊥
calculated ESR parameters indicate that the unpaired electron (d1)
is present in the dxy-orbital with square-pyramidal or octahedral
geometry [28]. The values obtained agree well with the g-tensor
parameters reported for square pyramidal geometry [29].
The molecular orbital coefficients ˛2 and ˇ2 for [VO(H4L)(H2O)2]
were calculated using the reported equations [30] and found to be
0.93 and 0.77, respectively. The lower value of ˇ2 indicates that the
in-plane ꢄ-bonding is less covalent and well consistent with other
reported data [29].
Surfactant concentration: ZrO2+ was separated using various
concentrations of HOL. The results show maximum floatability
at 1 × 10−5–3.36 × 10−2 mol L−1 of HOL, above which the flotation
decreases. Accordingly, 1 × 10−5 mol L−1 HOL was the desired con-
centration.
ZrO2+ concentration: Various amounts of ZrO2+ were floated in
the presence of 1 × 10−4 mol L−1 H6L using 1 × 10−5 mol L−1 HOL at
pH ∼3. The floatability reaches 98.2% at 0.5 × 10−4 mol L−1 of ZrO2+
corresponding to ZrO:2H6L. At higher concentration of ZrO2+, the
efficiency decreases and needs excess H6L.
Temperature: Solutions of ZrO2+, H6L and HOL were either
heated or cooled; the HOL was quickly poured into the mixture and
introduced into the flotation cell jacketed with 1 cm thick fiberglass.
The floatability does not affected by temperature (0–70 ◦C). Since
the industrial waste waters are usually hot, the introduced proce-
dure finds successful application in the direct analysis of ZrO2+ ions
wastes. The subsequent measurements were carried out at room
temperature ∼30 ◦C.
3.7. Molecular modeling of [(ZrO)2(H2DPOH)(C2H5OH)2]
The molecular parameters of [(ZrO)2(H2DPOH)(C2H5OH)2]
(Scheme 6) are calculated to be: total energy = −155,902;
binding energy = −6443; electronic energy = −1,262,984; heat
of
formation = 10.1 kcal mol−1
;
dipole
moment = 18.233 D;
HOMO = −8.1334 eV and LUMO = −0.9909 eV. The bond lengths
and the bond angles are presented in Tables 3S and 4S.
Foreign ions: Separation of 0.5 × 10−4 mol L−1 ZrO2+ using
1 × 10−4 mol L−1 H6L and oleic acid (1 × 10−5 mol L−1) was carried
out at high concentrations of various cations and anions usually
found in some water samples (Table 4). Tolerable amount (pre-
sented as ion:ZrO ratio) giving a maximum error of 2% in the
flotation efficiency. All investigated ions do not interfere except
3.8. Eukaryotic DNA degradation test
Examining the DNA degradation assay of H6DPOH and its metal
complexes revealed variability on their immediate damage on the
calf thymus (CT) DNA. The complexes have a high effect than the lig-
Scheme 6. Molecular modeling of [(ZrO)2(H2L)(C2H5OH)2].

A.A. El-Asmy et al. / Spectrochimica Acta Part A 77 (2010) 297–303
303
Table 4
seem to be polymeric in nature due to their insolubility and
high melting points. [Cr(H4L)(H2O)3Cl]·H2O, [HfO(H4L)(H2O)]·H2O,
[MoO2(H4L)] and [UO2(H4L)(H2O)2]·2H2O have been proposed
to be octahedral; [(ZrO)2(H2L)(C2H5OH)2] is four coordination
where [VO(H4L)(H2O)2] is square based pyramid. VO2+ and Cr(III)
complexes degrade the DNA of eukaryotic subject completely.
The flotation technique was found applicable for the separation
of 0.5 × 10−4 mol L−1 ZrO2+ ions using 1 × 10−4 mol L−1 H6L and
1 × 10−5 mol L−1 oleic acid at pH 3.
Effect of some foreign ions on the flotation of 5 × 10−5 mol L−1 ZrO2+ using
1 × 10−4 mol L−1 H6L and 1 × 10−3 mol L−1 HOL at pH ∼3.
Cation
Foreign/ZrO2+
F (%)
Anion
Cl−
Foreign/ZrO2+
F (%)
Na+
K+
200
200
200
20
20
20
99.2
98.4
98.5
99.5
98.5
8.5
200
20
20
20
20
99.4
92.2
80.0
86.7
99.2
2−
SO4
Citrate
Ca2+
Co2+
Ni2+
Cu2+
Zn2+
Cd2+
−
HPO4
CH3COO−
20
20
100
20
75.8
99.5
98.4
74.2
Appendix A. Supplementary data
+
NH4
Al3+
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.saa.2010.05.026.
Table 5
Recovery (R%) of ZrO2+ ions added to 10 mL of some water samples using
1 × 10−4 mol L−1 H6L and 1 × 10−3 mol L−1 HOL at pH ∼3.
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is fairly selective and can be safely employed for the separation and
determination of ZrO2+ in various materials.
−
Ionic strength: The effect of some salts resembled those in natural
water samples on the flotation efficiency of 0.5 × 0−4 mol L−1 ZrO2+
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the pH to ∼3 at 30 ◦C. After flotation, the concentration of ZrO2+
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4. Conclusion
A new chelating agent has been prepared and characterized.
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It introduced for chelation with VO2+, ZrO2+, HfO2+, MoO2 and
2+
2+
UO2
as well as Cr(III). It chelates as a mononegative biden-
tate and forms mononuclear complexes with the studied metal
ions except ZrO2+ which forms binuclear complex. The complexes