Spectroscopic, structure and antimicrobial activity of new Y(III) and Zr(IV) ciprofloxacin

Article abstract of DOI:10.1016/j.saa.2010.12.048

The preparation and characterization of the new solid complexes [Y(CIP)₂(H₂O)₂]Cl₃·10H ₂O and [ZrO(CIP)₂Cl]Cl·15H₂O formed in the reaction of ciprofloxacin (CIP) with YCl₃ and ZrOCl ₂·8H₂O in ethanol and methanol, respectively, at room temperature were reported. The isolated complexes have been characterized with elemental analysis, IR spectroscopy, conductance measurements, UV-vis and ¹H NMR spectroscopic methods and thermal analyses. The results support the formation of the complexes and indicate that ciprofloxacin reacts as a bidentate ligand bound to the metal ion through the pyridone oxygen and one carboxylato oxygen. The activation energies, E*; entropies, ΔS*; enthalpies, ΔH*; Gibbs free energies, ΔG*, of the thermal decomposition reactions have been derived from thermogravimetric (TGA) and differential thermogravimetric (DTG) curves, using Coats-Redfern and Horowitz-Metzeger methods. The proposed structure of the two complexes was detected by using the density functional theory (DFT) at the B3LYP/CEP-31G level of theory. The ligand as well as their metal complexes was also evaluated for their antibacterial activity against several bacterial species, such as Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) and antifungal screening was studied against two species (Penicillium (P. rotatum) and Trichoderma (T. sp.)). This study showed that the metal complexes are more antibacterial as compared to free ligand and no antifungal activity observed for ligand and their complexes.

Full text of DOI:10.1016/j.saa.2010.12.048

Spectrochimica Acta Part A 78 (2011) 854–867
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectroscopic, structure and antimicrobial activity of new Y(III) and Zr(IV)
ciprofloxacin
Sadeek A. Sadeek∗, Walaa H. El-Shwiniy, Wael A. Zordok, Akram M. El-Didamony
Department of Chemistry, Faculty of Science, Zagazig University, 9 Bab Gamma Street, Zagazig 44519, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
The preparation and characterization of the new solid complexes [Y(CIP)2(H2O)2]Cl3·10H2O and
[ZrO(CIP)2Cl]Cl·15H2O formed in the reaction of ciprofloxacin (CIP) with YCl3 and ZrOCl2·8H2O in ethanol
and methanol, respectively, at room temperature were reported. The isolated complexes have been char-
acterized with elemental analysis, IR spectroscopy, conductance measurements, UV–vis and 1H NMR
spectroscopic methods and thermal analyses. The results support the formation of the complexes and
indicate that ciprofloxacin reacts as a bidentate ligand bound to the metal ion through the pyridone
oxygen and one carboxylato oxygen. The activation energies, E*; entropies, ꢀS*; enthalpies, ꢀH*; Gibbs
free energies, ꢀG*, of the thermal decomposition reactions have been derived from thermogravimetric
(TGA) and differential thermogravimetric (DTG) curves, using Coats–Redfern and Horowitz–Metzeger
methods. The proposed structure of the two complexes was detected by using the density functional
theory (DFT) at the B3LYP/CEP-31G level of theory. The ligand as well as their metal complexes was also
evaluated for their antibacterial activity against several bacterial species, such as Staphylococcus aureus
(S. aureus), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) and antifungal screening
was studied against two species (Penicillium (P. rotatum) and Trichoderma (T. sp.)). This study showed
that the metal complexes are more antibacterial as compared to free ligand and no antifungal activity
observed for ligand and their complexes.
Received 11 April 2010
Received in revised form
11 December 2010
Accepted 14 December 2010
Keywords:
Ciprofloxacin
B3LYP/CEP-31G
Antimicrobial activity
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
by these coordination complexes. Other investigations aim to show
the effect of metal ions upon antibacterial activity [6,7]. The crystal
Ciprofloxacin (CIP) is a member of the second generation
quinolone antibiotics family. It is a broad-spectrum antibiotic that
is active against both Gram-positive and Gram-negative bacteria.
It functions by inhibiting DNA gyrase, a bacterial type II topoiso-
merase and topoisomerase IV, which is an enzyme necessary to
separate replicated DNA by inhibiting cell division [1].
Quinolones, a commonly used term for the quinolone carboxylic
acids or 4-quinolones, are a group of synthetic antibacterial agents
containing 4-oxo-1,4-dihydroquinoline skeleton [2]. They can act
as antibacterial drugs and the addition of fluorine atom to the orig-
inal quinolone antibiotic compounds, usually at position 7, yields
a new class of drugs, the fluoroquinolones, which have a broader
antimicrobial spectrum and improved pharmacokinetic properties
[3].
structures of quinolone complexes indicate that quinolone antibi-
otic can participate in the formation of complexes in a number
of ways [8–14]. The neutral ciprofloxacin in the zwitterionic state
(Scheme 1) are potentially capable to coordinate with metal ions
as a bidentate ligands forming simple complexes via one of the
oxygen atoms of the carboxylato group and ring carbonyl group
[8,9,12–14].
Infrared spectroscopic and solid state paramagnetic resonance
spectroscopy studies of metallic complexes derived from these
compounds suggest that they are formed by interaction with the
carboxylate group [15]. Density functional theory (DFT) at the
B3LYP/CEP-31G level of theory was used to compute the cation
type influence on theoretical parameters of the Y(III) and Zr(IV)
ciprofloxacin complexes and detect the exact structure of these
complexes with different coordination numbers. Such computa-
tional characterization reduces time consuming experiments for
biomedical and pharmaceutical studies of the drugs and its com-
plexes. Profiles of the optimal set and geometry of these complexes
were simulated by applying the GAUSSIAN 98W package of pro-
grams [16] at B3LYP/CEP-31G [17] level of theory.
The interactions between metal ions and various quinolones
have been reported in the literature [4,5]. These studies have been
primarily directed towards the identification of functional groups
directly linked to the metal and to establish the structure formed
To continue our investigation in the field of quinolone com-
plexes [18–24], we report in the present work, the synthesis and
∗
Corresponding author. Tel.: +20 0120057510; fax: +0553208213.
E-mail address: sadeek59@yahoo.com (S.A. Sadeek).
1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2010.12.048

S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
855
O
O
F
OH
N
N
+H2N
Cl-
Scheme 1. Structure of ciprofloxacin (CIP) and its zwitterionic state.
characterization of new metal complexes formed from the inter-
action of CIP with Yttrium(III) and Zirconium(IV) in the solvent
and study the effect of oxidation state of the two ions on the bio-
logical activity of ciprofloxacin drug. The isolated solid complexes
are characterized using spectroscopic and thermal analysis tech-
niques. The thermal behavior of our complexes was studied and the
antibacterial activity was tested against several bacterial species,
such as Staphylococcus aureus (S. aureus), Escherichia coli (E. coli)
and Pseudomonas aeruginosa (P. aeruginosa) and antifungal screen-
ing was studied against two species (Penicillium (P. rotatum) and
Trichoderma (T. sp.)).
oxide, and also determined by using atomic absorption method.
Spectrometer model PYE-UNICAM SP 1900 fitted with the cor-
responding lamp was used for this purposed. IR spectra were
recorded on FTIR 460 PLUS (KBr discs) in the range from 4000
to 400 cm−1 1H NMR spectra were recorded on Varian Mercury
,
VX-300 NMR Spectrometer using DMSO-d6 as solvent. TGA-DTG
measurements were carried out under N2 atmosphere within the
temperature range from room temperature to 800 ◦C using TGA-
50H Shimadzu. Electronic spectra were obtained using UV-3101PC
Shimadzu. Molar conductivities in DMSO at 1.0 × 10−3 M were mea-
sured on CONSORT K410.
2. Materials and methods
2.4. Antimicrobial investigation
2.1. Chemicals
Antibacterial activity of the complexes/ligand was investigated
by a previously reported modified method of Beecher and Wong
[25], against different bacterial species, such as S. aureus, E. coli
and P. aeruginosa and antifungal screening was studied against two
species P. rotatum and Trichoderma sp. The tested microorganisms
isolates were isolated from Egyptian soil and identified according
to the standard mycological and bacteriological keys for identifi-
cation of fungi and bacteria as stock cultures in the microbiology
laboratory, Faculty of Science, Zagazig University. The microor-
ganisms were purchased from the laboratory of (Microbiology)
in the Faculty of Science, Zagazig University. The nutrient agar
medium for antibacterial was (0.5% peptone, 0.1% beef extract, 0.2%
yeast extract, 0.5% NaCl and 1.5% agar–agar) and for antifungal (3%
sucrose, 0.3% NaNO3, 0.1% K2HPO4, 0.05% KCl, 0.001% FeSO4, 2%
agar–agar) was prepared and then cooled to 47 ◦C and seeded with
tested microorganisms. After solidification 5 mm diameter holes
were punched by a sterile cork-borer. The investigated compounds,
ligand and their complexes, were introduced in Petri-dishes (only
0.1 ml) after dissolving in DMSO at 1.0 × 10−3 M. The plates were
then incubated for (20 h at 37 ◦C for bacteria and for 7 days at
30 ◦C for fungi). At the end of incubation period the inhibition zone
around each hole was measured.
Ciprofloxacin was purchased from Sigma, YCl3 was purchased
from Aldrich Chemical Co., ZrOCl2·8H2O, NaOH and all solvents
were purchased from Fluka Chemical Co. All the chemicals and sol-
vents were analytical reagent grade and were used as purchased
without further purification.
2.2. Synthesis
An ethanolic solution (20 ml) of ciprofloxacin hydrochlo-
ride (1 mmol, 0.3675 g) and NaOH (1 mmol, 0.04 g) was added
to an ethanolic solution of YCl3 (0.5 mmol, 0.0977 g) and
the reaction mixture was stirred at room temperature for
48 h. The solution was left for slow evaporation, after that a
yellowish-white [Y(CIP)2(H2O)2]Cl3·10H2O product was deposited.
The solid obtained was filtered under vacuum, washed with
ethanol and dried. In a similar way, the orange solid complex
[ZrO(CIP)2Cl]Cl·15H2O was prepared by using methanol as a sol-
vent instead of ethanol and using ZrOCl2·8H2O in 1:2 molar ratio.
Unfortunately we were not able to obtained appropriate monocrys-
tals to perform X-ray diffraction analysis. In order to verify that
the chloride is ionic and not coordinated, the complex solutions
were tested with an aqueous solution of AgNO3 (a precipitate was
formed). The two complexes were characterized by their elemen-
tal analysis, infrared, electronic, 1H NMR, thermal analysis as well
as density functional theory (DFT) at the B3LYP/CEP-31G level of
theory.
3. Results and discussion
The elemental analyses agree well with the proposed structure
(Scheme 2) of the two complexes (Table 1). The Y(III) complex is
yellowish-white while the Zr(IV) is orange colored complex. They
are air stable solids and the higher melting points of the two com-
plexes than ligand revealing that the complexes are much more
stable than ligand. The IR spectroscopic and thermogravimetric
data confirm the presence of water molecules in the composition
of the two complexes. Qualitative reactions revealed the presence
of chloride as counter ions in the two complexes. The conductivity
2.3. Instruments
Elemental C, H, N and halogen analysis was carried out on a
Perkin Elmer CHN 2400. The percentage of the metal ions were
determined gravimetrically by transforming the solid products into

856
S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
+
NH2
F
N
O
OH2
O
O
O
O
N
Y
N
H2O
O
N
F
+H2N
+
NH2
F
N
O
O
O
O
O
O
N
Zr
N
Cl
O
N
F
+H2N
Scheme 2. The coordination mode of Y(III) and Zr(IV) with ciprofloxacin.

S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
857
Table 1
Elemental analysis and physico-analytical data for the complexes.
Complexes M wt. (M.F.)
Yield (%)
Mp (◦C)
Color
Found (calcd.) (%)
C
H
N
M
Cl
[Y(CIP)2(H2O)2]Cl3·10H2O
1073.4 (C34H60N6O18F2Cl3Y)
[ZrO(CIP)2Cl]Cl·15H2O 1110.22
(C34H66N6O22F2Cl2Zr)
97.79
49.66
<360
<360
Yellowish white
Orange
(38.01) 37.98
(5.59) 5.53
(7.83) 7.83
(8.28) 8.25
(9.92) 9.90
(6.40) 6.38
(36.75)36.57
(5.95) 5.95
(7.57) 7.47
(8.22) 8.11
values of Y(III) and Zr(IV) measured in DMSO at room tempera-
ture were found at 366.08 and 511.68 S cm2 mol−1, indicating that
the complexes are higher electrolytic nature than ligand [26]. The
low conductivity values are in agreement with the low solubility
of CIP complexes in water, ethanol, chloroform, acetone and most
organic solvents. On the other hand, they are soluble in DMSO, DMF
and concentrated acids.
to be changed upon chelation. The presence of the broad bands
at 3381 and 3365 cm−1 confirms the presence of water molecules
in the prepared complexes and the presence of a group of bands
with different intensity at 2837, 2818, 2729, 2716, 2508, 2486 and
2362 cm−1 (Fig. 1), which assigned to vibration of the quaternized
nitrogen of the piperazine group, indicates the zwitterionic form of
CIP is involved in the coordination to the metal ions investigated
[27]. The two bands observed at 1706 and 1620 cm−1 in the spec-
trum of the free CIP have been assigned to the stretching vibration
of carboxylic ꢁ(COOH) and the carbonyl group ꢁ(C O), respectively,
[9,11,18–30].
3.1. IR data and bonding
The infrared spectra of the two complexes are compared with
those of the free ligand (Table 2), in order to determine the site
of coordination that may be involved in chelation. There are some
guide peaks in the spectra of the ligand, which are of good help
for achieving this goal. These peaks are expected to be involved in
chelation. The position or the intensities of these peaks are expected
The disappearance of the band at 1706 cm−1 and the shift of
the characteristic peak of the carbonyl group ꢁ(C O) to a lower
value from 1620 cm−1 to 1577 cm−1 for Y(III) and to 1583 cm−1 for
Zr(IV) indicate coordination of CIP through one of the oxygen atoms
of the carboxylato group and of the carbonyl group. The asym-
Table 2
Infrared frequencies (cm−1) and tentative assignments for (A) ciprofloxacin (CIP);
(B) [Y(CIP)2(H2O)2]Cl3·10H2O and (C) [ZrO(CIP)2Cl]Cl·15H2O.
A
B
C
Assignment
3530m
3381m
3204vw
3092m
3020w
2925m
2839m
2694ms
2617ms
2500w
2465ms
3365m, br
3381m, br
ꢁ(O–H); COOH, H2O
3044vw
3046vw
ꢁ(C–H); aromatic
ꢁ(C–H); aliphatic
2921vw
2837vw
2729vw
2932w
2818vw
2716w
+
2508m
2361ms
2358w
–
1629vs
1577ms
2486m
2362ms
2318w
–
1633s
1583vw
ꢁ(–NH2
)
1706vs
–
1620vs
ꢁ(C O); COOH
ꢁas(COO−
)
ꢁ(C O) and phenyl
breathing modes
1516vw
1486vs
1454vw
1410vw
1389vw
1346m
1310ms
1269vs
1181ms
1112vw
1035s
1000w
943vw
899vw
839vw
812m
1520vw
1481vs
1455s
1390vw
–CH; deformations of –CH2
–
1384m
1299ms
ꢁs(COO−
)
ıb(–CH2)
1318ms
1266s
1183m
1145m
1104m
1026ms
987ms
937s
1269s
ꢁ(C–O)
ꢁ(C–N)
ꢁ(C–C)
ır(–CH2)
1182ms
1145ms
1032s
949s
897s
835s
–CH bend; phenyl
835w
805w
808m
788ms
705vw
651vw
625ms
569m
539m
506ms
408m
754vw
710w
668vw
546ms
478ms
410s
781w
745vw
664w
622ms
546m
500m
ıb(COO−
)
ꢁ(M–O) + ring deformation
Fig. 1. Infrared spectra of (A) ciprofloxacin (CIP), (B) [Y(CIP)2(H2O)2]Cl·10H2O and
(C) [ZrO(CIP)2Cl]Cl·15H2O.
Keys: s = strong, w = weak, v = very, br = broad, ꢁ = stretching, ı = bending.

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S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
metric stretching vibration (ꢁas) of the ligated carboxylato group
appear at 1629 and 1633 cm−1 for Y(III) and Zr(IV) complexes. The
spectra of our two complexes also show two bands at 1389 and
1384 cm−1. These bands are absent in the spectrum of CIP and most
likely due to the symmetric vibration of the ligated COO− group.
A carboxylate ligand can coordinate to the metal ions either as a
monodentate or a bidentate ligand, giving changes in the relative
positions of the asymmetric and symmetric stretching vibrations
[20–24,30,31]. Unidentate carboxylato complexes exhibit ꢀꢁ val-
ues > 200 cm−1 [ꢀꢁ = ꢁas(COO−) − ꢁs(COO−)] [30,31]. The observed
ꢀꢁ for Y(III) and Zr(IV) CIP complexes are 240 and 249 cm−1 sug-
gesting a unidentate interaction of the carboxylato group.
New bands are found in the spectra of the isolated solid com-
plexes with different intensities at 622, 500 cm−1 for Y(III) and at
625, 569, 539, 506 cm−1 for Zr(IV) (Table 2), which are assigned
to ꢁ(M–O) stretching vibrations of coordinated carboxylato oxygen
atom and carbonyl oxygen atom. According to the above discussion
the CIP is coordinated to metal ions as a bidentate ligand through
the oxygen atom of the carboxylato group and the oxygen atom of
the carbonyl group.
3.2. UV–vis spectra
The electronic solid reflection spectra of ciprofloxacin along
with the Y(III) and Zr(IV) complexes are shown in Fig. 2. The free
ciprofloxacin reflected at 243, 298 and 338 nm which attributed to
␲–␲* and n–␲* intraligand transitions (these transitions occur in
case of unsaturated hydrocarbons which contain ketone groups)
[31]. The reflection spectra for Y(III) and Zr(IV) ciprofloxacin com-
plexes are practically identical with that of the ligand ciprofloxacin
but slightly shifted, indicative of coordination through the pyridone
oxygen and one carboxylato oxygen [32]. The two complexes have
bands at range from 523 to 576 nm which may be assigned to the
ligand to metal charge-transfer [33,34].
3.3. Thermal studies
The ciprofloxacin of Y(III) and Zr(IV) complexes are stable at
room temperature and can be stored for several months without
any changes. The Y(III) and Zr(IV) ciprofloxacin complexes were
studied by thermogravimetric analysis from ambient temperature
to 800 ◦C under a N2 atmosphere (Fig. 3). The temperature ranges
and the percentage mass losses of the decomposition reaction are
given in Table 3, together with the evolved moiety and theorti-
cal percentage mass losses. The data obtained indicate that the
ciprofloxacin is thermally stable in the temperature range 25–50 ◦C.
Decomposition of the CIP starts at 50 ◦C and finished at 750 ◦C with
two stages. The first stage of decomposition occurs at maximum
temperature of 132 ◦C and is accompanied by a weight loss of 7.81%,
Fig. 2. Electronic reflection spectra of (A) ciprofloxacin (CIP), (B)
[Y(CIP)2(H2O)2]Cl·10H2O and (C) [ZrO(CIP)2Cl]Cl·15H2O.
corresponding exactly to the loss of acetylene molecule (C2H2).
The second stage of decomposition occurs at two maxima 315 and
382 ◦C and is accompanied by a weight loss of 74.04%, correspond-
ing to the loss of 4C2H2 + C2H4 + 3NO + HF + 1.5H2. The actual weight
loss from these stages is equal to 81.85%, very closer to calculated
value 81.88%.
The thermal decomposition of [Y(CIP)2(H2O)2]Cl3·10H2O com-
plex in inert atmosphere proceeds approximately with two
Table 3
The maximum temperature Tmax (◦C)and weight loss values of the decomposition stages for Y(III) and Zr(IV) ciprofloxacins.
Compounds
Decomposition
Tmax (◦C)
Weight loss (%)
Calc.
Lost species
Found
CIP (C17H18N3O3F)
First step
132
7.86
7.81
C2H2
Second step
Total loss, residue
315, 382
74.02
81.88, 18.12
74.04
81.85, 18.15
4C2H2 + C2H4 + 3NO + HF + 1.5H2
[Y(CIP)2(H2O)2]Cl3·10H2O
First step
86
13.415
13.411
8H2O
(C34H60N6O18F2Cl3Y)
Second step
311, 373, 574
70.477
70.476
10C2H2 + 4C2H4 + 3HCl + 2HF + CO + 6NO + 1.5H2O
Total loss, residue
83.892, 16.108
83.887, 16.113
[ZrO (CIP)2Cl] Cl·15H2O
First step
55
12.970
12.973
8H2O
(C34H66N6O22F2Cl2Zr)
Second step
410, 553
67.284
67.276
10C2H4 + 3C2H2 + 2HCl + 2HF + 6NO2
Total loss, residue
80.254, 19.746
80.249, 19.751

S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
859
occurs at maxima temperature of 311, 373 and 574 ◦C. The
weight loss at this step is 70.476%, corresponding to the
loss of 10C2H2 + 4C2H4 + 3HCl + 2HF + CO + 6NO + 1.5H2O as will be
described by the mechanism of the decomposition, the final ther-
mal product obtained at 800 ◦C is YO1.5 + 5C.
Hydrated Zr(IV) ciprofloxacin complex loss upon heating eight
water molecules in the first stage at maximum temperature 55 ◦C
(Table 3). The second step of decomposition occurs at two max-
ima temperature at 410 and 553 ◦C. This step is associated with the
loss of ciprofloxacin forming ZrO2 + 8C as a final product. The found
weight loss associated with each step of decomposition for our
complexes agree well with the calculated weight loss (Table 3). The
final products of two complexes obtained at 800 ◦C were confirmed
with infrared spectra.
The proposed structure formula on the basis of the results dis-
cussed in this paper located as shown in Scheme 2.
3.4. The kinetics data
Coats and Redfern [35] and Horowitz and Metzger [36]
are the two methods mentioned in the literature related to
decomposition kinetics studies. The thermodynamic activation
parameters of decomposition processes of two complexes namely
of [Y(CIP)2(H2O)2]Cl3·10H2O and [ZrO(CIP)2Cl]Cl·15H2O, the acti-
vation energies, E*; pre-exponential factor, A; entropies, ꢀS*;
enthalpies, ꢀH*; Gibbs free energies, ꢀG*, were calculated graph-
ically by employing the Coats Redfern relation. The entropy of
activation, ꢀS*, enthalpy of activation, ꢀH* and the free energy
change of activation, ꢀG*, were calculated using the following
equations:
ꢀ
ꢁ
ꢂꢃ
Ah
KT
ꢀS∗ = 2.303 log
R
ꢀH∗ = E∗ − RT
ꢀG∗ = ꢂH∗ − TꢀS∗
The linearization
Horowitz–Metzger methods are shown in Fig. 4 and all cal-
culations are summarized in Table 4. The entropy of activation was
found to have negative values in the two complexes which indicate
that the decomposition reactions proceed with a lower rate than
normal ones. The correlation coefficients of the Arrhenius plots (r)
of the thermal decomposition steps were found to lie in the range
curves
of
Coats
Redfern
and
Fig. 3. TGA and DTG diagrams of (A) ciprofloxacin (CIP), (B) [Y(CIP)2(H2O)2]Cl·10H2O
and (C) [ZrO(CIP)2Cl]Cl·15H2O.
main degradation steps. The first step of decomposition occurs
at maximum temperature of 86 ◦C and is accompanied by
a
weight loss of 13.411%, corresponding to the loss of
eight water molecules. The second stage of decomposition
Table 4
Thermal behavior and kinetic parameters determined using the Coats–Redfern (CR) and Horowitz–Metzger (HM) operated for ciprofloxacin and their complexes.
Compounds
Decomposition
range (K)
Ts (K)
Method
Parameter
Ra
SDb
E* × 104
A (s−1
)
ꢀS* × 102
ꢀH* × 104
ꢀG* × 105
(J mol−1
)
(J mol−1 K−1
)
(J mol−1
)
(J mol−1
)
CIP (C17H18N3O3F)
323–490
577–754
405
588
CR
HM
CR
8.202
8.112
8.545
8.257
18.08 × 108
83.09 × 108
1.03 × 106
2.97 × 106
−0.7023
−0.5755
−1.3544
−1.2663
7.866
7.776
8.057
7.769
1.0708
1.0105
1.6015
1.5209
0.9575
0.9544
0.9470
0.9349
0.16
0.08
0.21
0.11
HM
[Y(CIP)2(H2O)2]Cl3·10H2O 304–466
359
CR
3.574
3.574 × 104
−1.692
3.275
0.9350
0.9759
0.16
(C34H60N6O18F2Cl3Y)
HM
CR
HM
4.067
4.939
4.721
1.48 × 105
0.443 × 103
0.135 × 104
2.601 × 103
−1.475
−1.998
−1.907
3.768
4.454
4.236
0.9063
1.6116
1.5367
0.9682
0.9850
0.9651
0.09
0.11
0.08
568–780
584
328
[ZrO(CIP)2Cl]Cl·15H2O
280–383
513–683
CR
2.810
−1.8032
2.537
0.84513
0.9576
0.17
(C34H66N6O22F2Cl2Zr)
HM
CR
HM
3.292
3.763
6.413
3.292 × 104
−1.5922
3.040
3.195
5.845
0.8262
1.784
1.808
0.9493
0.9872
0.9975
0.09
0.08
0.02
683
0.0893 × 103 −2.145
0.0627 × 105 −1.791
a
Correlation coefficients of the Arrhenius plots.
Standard deviation.
b

860
S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
Fig. 4. The diagrams of kinetic parameters of ciprofloxacin; [Y(CIP)2(H2O)2]Cl·10H2O and [ZrO(CIP)2Cl]Cl·15H2O complexes using Coats–Redfern (CR) and Horowitz–Metzger
(HM) equations.

S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
861
Fig. 4. (Continued ).
0. 9349–0.9975, showing a good fit with linear function. It is clear
that the thermal decomposition process of the two complexes is
non-spontaneous, i.e., the complexes are thermally stable.
3.5. The 1H NMR spectra
The formation of the metal complexes was confirmed by
1H NMR spectra. Fig.
5
represents the 1H NMR spectra of
[Y(CIP)2(H2O)2]Cl3·10H2O and [ZrO(CIP)2Cl]Cl·15H2O complexes
which was carried out in DMSO-d6 as a solvent. Upon compari-
son with the free ligand, the absent of the characteristic signal for
H(COOH) at ı 11.00 ppm in our two complexes indicate coordi-
nation of CIP ligand to Y(III) and Zr(IV) through the deprotonated
carboxylic group [18–25,37]. The spectra also show characteris-
tic signals for quaternary nitrogen (–+NH2) at ı 2.484, 2.495 and
2.502 ppm for Y(III) complex and at ı 2.491, 2.497 and 2.502 ppm
for Zr(IV) complex. The signal characteristic for water molecules
was observed at ı 3.274, 3.340, 3.583, 3.599 and 3.270, 3.330, 3.542,
3.641 ppm for Y(III) and Zr(IV) complexes, respectively, which was
not found in the free ciprofloxacin. Also on comparing main signals
of ciprofloxacin with its complexes, it is observed that all signals
of the free ligand are present in the spectra of the two complexes
with chemical shift upon binding of the quinolones to the metal
ions [38]. The 1H NMR data for free CIP and those complexes are
summarized in Table 5 and all assignments are given.
3.6. Biological activities test
The susceptibility of certain strains of bacterium, such as S.
aureus, E. coli and P. aeruginosa and antifungal screening was stud-
ied against two species P. rotatum and Trichoderma sp. towards
Fig. 5. 1H NMR spectra of [Y(CIP)2(H2O)2]Cl·10H2O and [ZrO(CIP)2Cl]Cl·15H2O com-
plexes in DMSO, ıTMS
.

862
S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
Table 5
1H NMR values (ppm) and tentative assignments for (A) ciprofloxacin (CIP); (B) [Y(CIP)2(H2O)2]Cl3·10H2O and (C) [ZrO(CIP)2Cl]Cl·15H2O.
A
B
C
Assignments
1.33
2.00
–
–
2.78, 3.46
6.04, 8.01, 8.66
11.00
1.157, 1.222, 1.249, 1.273
–
2.484, 2.495, 2.502
3.274, 3.340, 3.583, 3.599
0.818, 1.040, 1.221, 1.260, 1.358
–
ı H, –CH3
ı H, –NH; piperazine
2.491, 2.497, 2.502
3.270, 3.330, 3.542, 3.641
3.877, 3.991, 4.069
6.763, 7.511, 7.957, 8.654
–
ı H, –+NH2
ı H, H2O
3.873
ı H, –CH2 aliphatic
ı H, –CH2 aromatic
ı H, –COOH
7.589, 7.614, 7.910,8.704
–
Table 6
The inhibition diameter zone values (mm) for CIP and their complexes.
Compounds
Microbial species
Bacteria
Fungi
Escherichia coli
Pseudomonas aeruginosa
23 0.1155
Staphylococcus aureus
Penicillium rotatum
Trichoderma sp.
CIP
27 0.3464
26 0.4041
0
0
0
0
0
0
0
0
Y(III)/CIP
Zr (IV)/CIP
Control (DMSO)
29+1
0.4450
0.3227
25+1
34+2
0.4041
0.2540
36+3
37+3
0.1472
0.3868
29.5+1
0
0
0
Statistical significance P(NS)P not significant, P > 0.05; P(+1)P significant, P < 0.05; P(+2)P highly significant, P < 0.01; P(+3)P very highly significant, P < 0.001; Student’s t-test.
ciprofloxacin and its complexes was judged by measuring size of
the inhibition diameter. As assessed by color, the complexes remain
intact during biological testing (Table 6, Fig. 6). A comparative study
of ligand and their metal complexes showed that the metal com-
plexes exhibit higher antibacterial activity for Gram-positive one
S. aureus and Zr(IV) is more effective antibacterial for P. aeruginosa
than E. coli Gram-negative but Y(III) showed moderated antibacte-
rial activity for E. coli and P. aeruginosa (Table 6), and no antifungal
activity observed for ligand and their metal complexes. The results
are promising compared with the previous studies [39–41]. Such
increased activity of metal chelate can be explained on the basis of
the oxidation state of the metal ion, overtone concept and chelation
theory. According to the overtone concept of cell permeability, the
lipid membrane that surrounds the cell favors the passage of only
lipid-soluble materialsin which liposolubility is animportant factor
that controls the antimicrobial activity. On chelation the polarity
of the metal ion will be reduced to a greater extent due to over-
lap of ligand orbital and partial sharing of the positive charge of
the metal ion with donor groups. Further it increases the delocal-
ization of ␲-electrons over the whole chelate ring and enhances
the lipophilicity of the complexes [40]. This increased lipophilicity
enhances the penetration of complexes into the lipid membranes
and blocks the metal binding sites in enzymes of microorganisms.
These complexes also disturb the respiration process of the cell and
thus block the synthesis of proteins, which restricts further growth
of the microorganisms. We also found that the increasing of oxi-
dation state of the metal ion increasing the antibacterial activity
of ciprofloxacin drug. Also, the Y(III) and Zr(IV) ions are increasing
the solubility of ciprofloxacin, this increase of hydrophilicity can
enhance the ability of drug molecules in crossing the membrane of
a cell, and hence raise the biological utilization ratio and activity
of the drug. The differences between the free ciprofloxacin ligand
and the two complexes are statistically significant, the ꢀ values
are lying down in the error-range of the method and the statistical
treatment of the results is clearly specified as shown in Table 6 and
Fig. 6.
3.7. Computational details
Computational method used: the computer used in theoret-
ical studies was a CPU: AMD A Thlon XP 2.4 GHz, Ram 512
DDR/333 MHz; Cache: 512 K. The geometrical optimization was
carried out at DFT level of theory using the Gaussian 98W package of
programs [16]. The DFT methods compute electron correlation via
general functionals of the electron density. The calculations carried
out at B3LYP/CEP-31G level of theory [17]. The basis set CEP-31G is
more accurate for the studying of the d-block elements. This high
basis set has been chosen to detect the dipole moment at a very
accurate level.
3.7.1. Computational method
The geometric parameters and energies were computed by den-
sity functional theory (DFT) at the B3LYP/CEP-31G level of theory,
using the GAUSSIAN 98W package of the programs, on geometries
that were optimized at CEP-31G basis set. The high basis set was
chosen to detect the energies at a highly accurate level. The atomic
charges were computed using the natural atomic orbital popula-
tions. The B3LYP is the key word for the hybrid functional [42],
which is a linear combination of the gradient functionals proposed
by Becke [43] and Lee et al. [44], together with the Hartree–Fock
local exchange function [45].
Fig. 6. Statistical representation for biological activity of ciprofloxacin acid and its
metal complexes.

S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
863
Scheme 3. The optimized geometrical of ciprofloxacin by using B3LYP/CEP-31G.
3.7.2. Structural parameters and models
complex consists of four coordinate bonds with two ciprofloxacin
molecules and the other two coordinate bonds may be water
molecules or chloride ions. In this part we study theoretically the
3.7.2.1. Ciprofloxacin. A role of the quinolone molecule in the struc-
ture is similar to the ionic compounds reported [9,11,46], it is
protonated at a terminal nitrogen atom of piperazine ring N18. The
bond lengths for C4–O23, C14–O22 and C14–O21 are 1.28, 1.26 and
proposed two structures of [Y(CIP)2Cl2]+ and [Y(CIP)2(H2O)2]+3
.
3.7.2.2.1. Description of the structure of [Y(CIP)2Cl2]+. Scheme 4
shows the optimized geometrical of the complex with the atomic
numbering schema. The selected bond distances and angles are
given in Table 8 and the suggested complex is composed of
[Y(CIP)2Cl2]+, where the Y(III) ion is in a distorted octahedral envi-
ronment. In the axial plane the metal ion is coordinated by four
oxygen atoms (Oketo and Ocarboxylate) of two ciprofloxacin ligands
˚
1.29 A, respectively [47]. Detailed analysis of corresponding bond
lengths in various quinolone molecules was given elsewhere [29].
All these distances as well as the angles between the atoms of the
rigid quinolone ring system and those of the piperazine ring are
similar appearance described earlier [9,11,46].
The biological activity of quinolones (ciprofloxacin) is mainly
determined by its fine structure, the ciprofloxacin has many char-
acteristic structural features. The molecule is a highly sterically
hindered, the cyclopropyl ring not located in the same plane of
quinolone ring with the dihedral angles C10–N1–C11–C13 and
C10–N1–C11–C12 are −73.47 and −143.95, also the piperazine
group out of plane of the molecule. This observation is supported
by the values of calculated dihedral angles: C20–N15–C7–C8, 65.70
and C16–N15–C7–C8, −69.70, where the values are neither zero nor
180. Scheme 3 shows the optimized geometrical of ciprofloxacin
molecule, the dihedral angles O23–C4–C3–C14, O21–C14–C3–C4
and O22–C14–C3–C4 are 0.00, −38.5 and 145.45 which confirms
that the O23 and O21 located in the same direction. The plane of
C4–O23 bond located in the same plane of C14–O21 bond while
O23 and O22 are located in the opposite direction to each other so,
the plane of C4–O23 is not found in the same plane of C14–O22.
Table 7 gives the optimized geometry of ciprofloxacin as
obtained from B3LYP/CEP-31G calculations. These data are draw-
ing to give the optimized geometry of molecule. The value of bond
angle C4–C3–C14 is 123.67 which reflects a sp2 hybridization of C8,
the same result is obtained with C4 and C14. These values of bond
distances agree well with the previously reported values for similar
ciprofloxacinate complexes [47,29,48–50].
˚
˚
at the distances vary from 2.229 A to 2.237 A, these bond lengths
are similar to those observed in related compounds [48]. The dif-
ference in the bond length for the carboxylate O21a–C14a and
˚
˚
O22a–C14a (1.350 A and 1.212 A) [49], confirms the formation of
bond between the ionic carboxylate oxygen atom and Y(III) ion. The
octahedral coordination environment is completed by two chloride
ions. The bond distances between Y–O21a and Y–O23a are 2.229
Table 7
Equilibrium geometric parameters bond lengths (Å), bond angles (◦), dihedral angles
(◦) and charge density of ciprofloxacin ligand by using DFT/B3LYP/CEP-31G.
Bond length (Å)
C4–O23
C4–C3
C2–C3
C10–N1
1.28 (1.30) [47]
1.47 (1.41)
C3–C14
1.51 (1.47) [47]
1.26 (1.23)
1.29 (1.29)
C14–O22
C14–O21
C11–N1
1.38 (1.38)
1.41 (1.40)
1.46 (1.46)
Bond angle (◦)
C7–N15–C20
C7–N15–C16
N15–C7–C8
N15–C7–C6
C4–C3–C14
115.08
114.66
121.97
120.17
123.67
O23–C4–C3
O21–C14–C3
O22–C14–C3
O21–C14–O22
C2–N1–C11
124.89
114.95
114.92
129.98
120.36
Dihedral angles (◦)
O23–C4–C3–C2
C16–N15–C7–C8
C20–N15–C7–C8
C10–N1–C11–C12
177.90
−69.70
65.70
−143.95
C10–N1–C11–C13 −73.47
C11–N1–C2–C3 177.40
O23–C4–C3–C14 0.00
Charge distribution on the optimized geometry of ciprofloxacin
is given in Table 7. There is a significant built up of charge density
on the oxygen atoms which is distributed over all molecule, the
charge on O21 of carboxylate group is −0.356 and O23 of ketone
group is −0.133, so ciprofloxacin molecule behaves as bidentate
ligand (Oketo and Ocarboxylate atoms) and the molecule is a highly
dipole ꢃ = 24.5 D.
O22–C14–C3–C4 145.45
O21–C14–C3–C4 −38.5
Charges
N1
N15
N18
C14
0.178
O23
O21
O22
C2
−0.133
−0.356
−0.369
−0.305
0.187
−0.098
−0.279
−0.018
−0.386
C4
C3
3.7.2.2. The Y(III) ciprofloxacin complexes. The Y(III) chelated with
two ciprofloxacin molecules through four oxygen atoms (Oketo and
Ocarboxylate atoms) forming four coordinate bonds. The experimen-
tal data shows set that the result complex is six-coordinate so, the
Total energy/au
Total dipole moment/D 24.5
−207.81236
( ): Ref. [47].

864
S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
Scheme 4. Optimized geometrical of [Y(CIP)2Cl2]+ complex by using B3LYP/CEP-31G.
˚
˚
Oketo atom and Ocarboxylate atom of ciprofloxacin ligand and two
OH atoms for water. The bond distances between Y–O21a and
and 2.234 A [50] while the distance between Y–Cl is 2.611 A [51].
˚
The bond lengths of Y–O23a and Y–O23b are 2.234 and 2.237 A
which are longer than that of Y–O21a and Y–O21b (2.229 A and
2.231 A). Both are similar to these observed in related quinolone
Y(III) compounds [50]. The bond angles around the central metal
ion Y(III) vary from 78.41 to 100.32; these values differ significantly
from these expected for a distorted octahedron.
It is important to note that, in the complex, the C14a–O21a
and C4a–O23a bond lengths become equal 1.350 and 1.289 A,
O
2
˚
˚
Y–O23a are 2.221 and 2.222 A, while the distance between Y–OH
O
2
˚
˚
is 2.44 A[50]. Also the angles around the central Y(III) metal ionwith
surrounding oxygen atoms vary from 78.84 to 122.70; these values
differ legally from these expected for a distorted octahedron. The
distances and angles in the quinolone ring system, as well as those
of piprazine rings are similar to those found in reported structure
of free ciprofloxacin [50].
˚
respectively, and slightly longer than those found in free ligand of
ciprofloxacin (1.290 and 1.280 A, respectively). The energy of this
The bond distances between Y(III) and surrounded oxygen
atoms of ciprofloxacin in water complex are shorter than that in
chloride complex as shown in Tables 8 and 9, so that the Y(III)
metal ion is bonded strongly with surrounded oxygen atoms of
ciprofloxacin in water complex more than that in chloride complex.
Also the charges accumulated on Ocarboxylate are −0.307 and −0.276
and for Oketo are −0.183 and −0.242 for water complex while for
the chloride complex the charges on Ocarboxylate are −0.304 and
−0.299 and for Oketo are 0.041 and 0.037. There is a strong inter-
˚
complex is −483.919 au and the dipole moment is weak 4.601 D, so
this complex is less stable.
3.7.2.2.2. Description of the structure of [Y(CIP)2(H2O)2]+3
.
Table 9 lists selected inter atomic distances and angles. The struc-
ture of complex with atomic numbering schema is shown in
Scheme 5. The complex consists of two units of ciprofloxacin
molecule and two water molecules with Y(III) metal ion. The
complex is six-coordinate with distorted octahedral environment
around the metal ion. The Y(III) metal ion is coordinated to one
Table 9
Equilibrium geometric parameters bond lengths (Å), bond angles (◦) and charge
density of [Y(CIP)2H2O]+3 by using DFT/B3LYP/CEP-31G.
Table 8
Equilibrium geometric parameters bond lengths (Å), bond angles (◦) and charge
density of [Y(CIP)2Cl2]+ by using DFT/B3LYP/CEP-31G.
Bond length (Å)
Y–O21a
Y–O23a
Y–O21b
Y–O23b
Y–Oa
2.221 [50]
2.222 [50]
2.333 [50]
2.181 [50]
2.400 [50]
2.440 [50]
C14b–O22b
C14b–O21b
C4a–O23a
C14a–O22a
C14a–O21a
C4b–O23b
1.264 [49]
1.322 [49]
1.296 [49]
1.261 [49]
1.323 [49]
1.298 [49]
Bond length (Å)
Y–O21a
Y–O23a
Y–O21b
Y–O23b
2.229 [50]
2.234 [50]
2.231 [50]
2.237 [50]
2.611 [51]
2.610 [51]
C4b–O23b
C14b–O21b
C14a–O21a
C4a–O23a
C14a–O22a
C14b–O22b
1.289 [49]
1.348 [49]
1.350 [49]
1.289 [49]
1.212 [49]
1.212 [49]
Y–Ob
˚
Y–Cla
Y–Clb
Y–OH
2.44 A [48]
O
2
Bond angle (◦)
O21b–Y–O23b
O21b–Y–O23a
O21b–Y–Oa
O21b–Y–Ob
O21a–Y–O23a
O23b–Y–Oa
Charges
Bond angle (◦)
O21a–Y–O23a
O21a–Y–O23b
O21a–Y–Cla
O21b–Y–Clb
O21b–Y–O23b
O23b–Y–Cla
Charges
82.86 [48]
81.64 [48]
81.65
78.84
86.93 [48]
82.96
O21a–Y–O23b
O21a–Y–Oa
O21a–Y–Ob
O23a–Y–Oa
O23a–Y–Ob
Oa–Y–Ob
122.70 [48]
101.86
81.32
80.97
81.23
81.87 [48]
79.11 [48]
99.73
100.32
79.04 [48]
91.46
O21b–Y–O23a
O21a–Y–Clb
O23a–Y–Clb
O21b–Y–Cla
Cla–Y–Clb
78.41 [48]
97.86
88.10
97.19
99.82
80.36
Y
O23a
O21a
O22a
O22b
C14b
1.173
−0.183
−0.307
−0.095
−0.112
−0.514
Oa
Ob
O23b
O21b
C14a
0.219
0.217
−0.242
−0.276
−0.529
Y
O23a
O21a
O22a
0.89
0.041
−0.304
−0.058
−0.058
Cla
Clb
O23b
O21b
−0.452
−0.449
0.037
−0.299
O22b
Total energy/au
Total dipole moment/D
−483.919
Total energy/au
Total dipole moment/D
−487.9834
4.601
36.85

S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
865
Scheme 5. Optimized geometrical of [Y(CIP)2(H2O)2]+3 complex by using B3LYP/CEP-31G.
action between central Y(III) metal ion which has become charge
equal +1.173 and more negative oxygen atoms in water complex
greater than that in chloride complex, at which Y(III) becomes has
lesspositivelycharge (+0.89)in chloridecomplex. Theenergyofthis
complex is −487.9834 au and highly dipole 36.85 D. For all these
reasons the water complex is more stable than chloride complex
and Y(III) favor coordinated with two water molecules more than
two chloride ions to complete the octahedron structure.
ciprofloxacin molecules and one coordinated bond may be with
water molecule or chloride ion beside oxygen atom of ZrO ion. In
this part we study theoretically the all possible structures can be
obtained [ZrO(CIP)2Cl]+ and [ZrO(CIP)2H2O]+2
.
3.7.2.3.1. Description of the structure [ZrO(CIP)2H2O]+2
.
Table 10 lists selected inter atomic distances and angles. The
structure of complex with atomic numbering schema is shown
in Scheme 6. The complex consists of two units of ciprofloxacin
molecule and one water molecule with Zr(IV) ion of ZrO unit. The
complex is six-coordinate with distorted octahedral environment
around the metal ion. The Zr(IV) metal ion is coordinated to one
Oketo atom and one Ocarboxylate atom of ciprofloxacin ligand and
3.7.2.3. The Zr(IV) ciprofloxacin complexes. The Zr(IV) may be
chelated with two molecules of ciprofloxacin through four oxy-
gen atoms forming four coordinate bonds (Oketo and Ocarboxylate).
The experimental data set that the result complex is six-coordinate
so, the complex consists of four coordinate bonds with two
OH
atom for water. The Zr–O21a and Zr–O21b bond lengths
O
2
˚
are 2.063 and 2.062 A, which are shorter than that of Zr–O23a
Scheme 6. Optimized geometrical of [ZrO(CIP)2H2O]+2 complex by using B3LYP/CEP-31G.

866
S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
Scheme 7. Optimized geometrical of [ZrO(CIP)2Cl]+ complex by using B3LYP/CEP-31G.
3.7.2.3.2. Description of the structure of [ZrO(CIP)2Cl]+. Table 11
lists selected inter atomic distances and angles. The structure of
complex with atomic numbering schema is shown in Scheme 7.
The complex consists of two units of ciprofloxacin molecule and one
chloride ion with Zr(IV) ion in ZrO. The complex is six-coordinate
with distorted octahedral environment around the metal ion. The
Zr(IV) metal ion of ZrO is coordinated to one Oketo atom and
˚
and Zr–O23b (2.070 and 2.067 A) and the bond distance between
˚
Zr–OH is 2.114 A [52]. Also the angles around the central Zr(IV)
O
metal 2ion with surrounding oxygen atoms vary from 82.57 to
95.41; these values not differ legally from these expected for a dis-
torted octahedron. The energy of this complex is −494.170173 au
while the dipole moment is weak 5.821 D, so this complex is less
stable.
Table 10
Table 11
Equilibrium geometric parameters bond lengths (Å), bond angles (◦) and charge
density of [ZrO(CIP)2H2O]+2 by using DFT/B3LYP/CEP-31G.
Equilibrium geometric parameters bond lengths (Å), bond angles (◦) and charge
density of [ZrO(CIP)2Cl]+ by using DFT/B3LYP/CEP-31G.
Bond length (Å)
Bond length (Å)
Zr–O21a
Zr–O23a
Zr–O21b
Zr–O23b
Zr–O
2.063 [54]
2.070 [55]
2.062 [54]
2.067 [55]
2.112
C14b–O22b
C14b–O21b
C4a–O23a
C14a–O22a
C14a–O21a
C4b–O23b
1.211
1.349
1.212
1.211
1.349
1.210
Zr–O21a
Zr–O23a
Zr–O21b
Zr–O23b
Zr–O
2.192 [54]
2.404 [55]
2.194 [54]
2.195 [55]
2.430
C14b–O22b
C14b–O21b
C4a–O23a
C14a–O22a
C14a–O21a
C4b–O23b
1.284
1.359
1.308
1.287
1.362
1.322
Zr–OH
2.114
Zr–Cl
2.299 [52,53]
O
2
Bond angle (◦)
O21b–Zr–O23b
O21b–Zr–O23a
O21b–ZrO
Bond angle (◦)
O21b–Zr–O23b
O21b–Zr–O23a
O21b–ZrO
O21b–Zr–Cl
O21a–Zr–O23a
O23b–Zr–O23a
Charges
87.53 [56]
84.34 [56]
95.41
95.15
85.09
O21a–Zr–O23b
O21a–ZrO
82.57
94.86
93.28
93.96
87.93
83.85
93.06 [56]
73.05 [56]
88.98
101.42
84.11
O21a–Zr–O23b
O21a–ZrO
O21a–Zr–Cl
O23a–ZrO
O–Zr–Cl
O23b–Zr–Cl
79.38
90.45
101.12
81.82
102.78
97.89
O21a–Zr–OH
O
2
O21b–Zr–OH
OH O–ZrO
O
2
O21a–Zr–O23a
O23b–ZrO
Charges
O223a–Zr–OH
O
2
94.27
O23b–Zr–O23a
78.23
Zr
0.829
−0.335
−0.367
−0.374
−0.376
O
0.158
−0.279
−0.376
−0.372
Zr
O23a
O21a
O22a
0.988
−0.385
−0.388
−0.421
−0.416
O
Cl
O23b
O21b
0.154
−0.297
−0.354
−0.399
O23a
O21a
O22a
O22b
OH
O
O223b
O21b
O22b
Total energy/au
Total dipole moment/D
−494.170173
Total energy/au
Total dipole moment/D
−492.57021
5.821
10.69

S.A. Sadeek et al. / Spectrochimica Acta Part A 78 (2011) 854–867
867
one Ocarboxylate atom of each ciprofloxacin ligand and Cl ion. The
I. Komaromi, R. Gomperts, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y.
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˚
Zr–O21a and Zr–O21b bond lengths are 2.192 and 2.194 A, respec-
tively, are shorter than that of Zr–O23a and Zr–O23b (2.404 and
˚
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2.195 A, respectively) and the bond distance between Zr–Cl is
˚
2.299 A [53]. Also the angles around the central Zr(IV) metal ion
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with surrounding oxygen atoms vary from 73.053 to 101.42; these
values agree with these expected for a distorted octahedron.
The charges accumulated on Ocarboxylate are −0.388 and −0.399
and for Oketo are −0.385 and −0.354 in chloride complex while for
water complex the charges on Ocarboxylate are −0.367 and −0.372
and Oketo is −0.335 and −0.376, so that the Zr(IV) metal ion is
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complex is −492.57021 au and highly dipole 10.69 D. For all these
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