Synthesis, spectral characterisation and thermal studies of zirconyl complexes of biologically active molecules

Article abstract of DOI:10.1007/s10973-009-0432-6

Zirconyl complexes of hippuric acid (C₉H₉NO ₃, hipH) and monophenylbutazone (4-butyl-1-phenyl-3,5- pyrazolidinedione,MPB) were prepared using ZrOCl₂ . 8H₂O and ZrO(NO₃)₃ . xH

Full text of DOI:10.1007/s10973-009-0432-6

J Therm Anal Calorim (2010) 99:509–513
DOI 10.1007/s10973-009-0432-6
Synthesis, spectral characterisation and thermal studies
of zirconyl complexes of biologically active molecules
K. R. Jisha Æ S. Suma Æ M. R. Sudarsanakumar
Received: 27 January 2009 / Accepted: 18 August 2009 / Published online: 16 September 2009
´
´
Ó Akademiai Kiado, Budapest, Hungary 2009
Abstract Zirconyl complexes of hippuric acid (C9H9NO3,
hipH) and monophenylbutazone (4-butyl-1-phenyl-3,5-
pyrazolidinedione, MPB) were prepared using ZrOCl2 Á 8H2O
and ZrO(NO3)3 Á xH2O and characterized by elemental
analysis, molar conductance measurement and IR, UV–Vis
and NMR spectral methods. Thermal decomposition
behaviour was studied by thermogravimetry. The second
harmonic generation (SHG) conversion efficiency of hip-
puric acid complexes was also studied.
The present investigation was undertaken to study zir-
conyl complexes of hippuric acid (Fig. 1) and monophe-
nylbutazone (Fig. 2).
Experimental methods
All chemicals used were of AR or GR grade and used as
such. Monophenylbutazone was purchased from Sigma
Company (USA). Hippuric acid and metal salts were pro-
cured from CDH.
1
Keywords Hippuric acid Á H NMR Á IR Á
Monophenylbutazone Á SHG Á Thermal studies Á
Carbon, nitrogen and hydrogen were determined using
Vario EL 111 CHNS analyzer. The metal contents were found
gravimetrically by converting the compounds into ZrO2.
The IR spectra were recorded on Thermo Nicolet Avtar
310 DTGS spectrometer (4000–400 cm-1) in KBr pellets.
UV–Vis spectra were recorded in methanol for ligands and
DMF for complexes using Varian Cary 5000 spectrometer
with 1 cm quartz cell, in the range 200–800 nm. Molar
conductivity of complexes in methanol and DMF (*1 9
10-3 mol dm-3) were measured using Systronics Conduc-
tivity Meter 304.
Zirconyl complexes
Introduction
Hippuric acid, N-benzoylglycine, is one of the amino acid
found in herbivorous animals and humans. Hippuric acid is
potentially capable of forming coordinate bonds with many
metal ions through carboxylic oxygen atoms as a bidentate
ligand [1–12].
Monophenylbutazone belongs to the family of non-ste-
roidal anti-inflammatory drugs [13, 14] (NSAID). The
ligand exhibits keto-enol tautomerism which may be
expected to show various bonding and stereo chemical
behaviour [15].
1H NMR of MPB and its complexes were carried out in
methanolsolventusingJoelGSX400FT-NMRSpectrometer.
The SHG efficiency of hippuric acid and complexes were
measured with respect to KDP by powder technique devel-
oped by Kurtz and Perry [16] using a Quanta Ray Spectra
Physics Model: Prolab 170 Nd: YAG 10 ns laser with first
harmonic output of 1064 nm at the pulse repetition rate
10 Hz. The homogenous powder was tightly packed in a
microcapillary tube and mounted in the path of laser beam of
pulse energy 2.4 mJ obtained by split beam technique.
Thermo gravimetric analysis (TG, DTG) was carried out
in air with a heating rate of 10 °C/min using Perkin Elmer
Diamond TG/DTG analyser.
K. R. Jisha Á S. Suma (&)
Department of Chemistry, S.N. College, Kollam, Kerala, India
e-mail: sumasncw@gmail.com
M. R. Sudarsanakumar
Department of Chemistry, M.G College, Thiruvananthapuram,
Kerala, India
123

510
K. R. Jisha et al.
nitrate reagent (0.9 mL, 0.4 mmol) pH * 3–4, was added
drop wise with stirring. The precipitate formed was filtered,
washed with distilled water and dried.
O
NH
OH
O
Hippuric acid
Synthesis of [ZrOCl2(MPB)4]
Fig. 1 Hippuric acid
A similar procedure was followed. Here monophenylbu-
tazone (0.3 g, 1.3 mmol) and zirconyl chloride regent
[3.6 mL, 0.7 mmol] was taken.
OH
O
H
O
H
H3C
H3C
N
H
N
O
Results and discussion
The complexes are air stable. Hippuric acid complexes are
insoluble in water and most of the organic solvents, and
soluble in DMF. The elemental analysis data and proposed
composition are given in Table 1.
Monophenylbutazone
Fig. 2 Monophenylbutazone
Molar conductance measurements
Synthesis of metal complexes
The molar conductivity value of hippuric acid complexes
in DMF (*1 9 10-3 mol dm-3) and MPB complexes in
methanol (*1 9 10-3 mol dm-3) are shown in Table 1.
The conductance values are in the range expected for non-
electrolytes.
Synthesis of [ZrO(hip)(OH)H2O]
Sodium salt of hippuric acid (0.3 g, 1.67 mmol) was pre-
pared in 0.1 M NaOH (pH * 7). A slight excess of the
ligand was taken to exclude the excess alkali. The resulting
suspension was filtered. To the clear solution, zirconyl
nitrate (3.9 mL, 1.67 mmol) at pH * 3–4 was added drop
wise with stirring. The white precipitate formed was fil-
tered, washed several times with distilled water and dried.
Infrared spectra
The main IR spectral bands of hippuric acid (hipH) and its
complexes and their tentative assignments are summarized
in Table 2.
Synthesis of [ZrO(hipH)4Cl2]
In the case of [ZrO(hip)(OH)H2O] complex, v(O–H) of
the coordinated hydroxyl group, v(O–H) of water molecule
and v(N–H) merge together and shown as a broad band in the
region 3300–3400 cm-1. The strong band at 1744 cm-1 due
to v(C=O) of carboxylic acid group is absent in [ZrO(hi-
p)(OH)H2O] indicates that hippuric acid coordinates to the
metal ion through carboxylate group [17, 18]. The asym-
metric stretching of carboxylate group at 1576 cm-1 and
symmetric stretching at 1403 cm-1 support this. The above
observations support the bidentate coordination of hippu-
rate. There is no apparent shift for the band at 1744 cm-1
A similar procedure was used. Here hippuric acid (0.3 g,
1.67 mmol) and zirconyl chloride (9.6 mL, 0.4175 mmol)
were used.
Synthesis of [ZrO(MPB)3(OH)2]
Sodium salt of monophenylbutazone, (0.3 g, 1.3 mmol]
was prepared in 0.1 M NaOH (pH * 7). Here also slight
excess of the ligand was taken to exclude the excess alkali.
The suspension was filtered. To this solution zirconyl
Table 1 Analytical data of complexes
Sl. No
Complexes
Colour
C
H
N
Molar conductance/
X-1 cm-1 mol-1
1
2
3
4
[ZrO(hip) (OH)H2O]
[ZrO(hipH)4Cl2]
White
White
Yellow
Yellow
33.70 (34.35)
48.31 (47.33)
55.87 (55.10)
56.38 (55.92)
3.4 (3.95)
4.36 (4.48)
10.5
21
4
3.69 (4.58)
5.97 (4.05)
5.42 (6.29)
6.25 (6.14)
10.02 (9.33)
10.11 (9.94)
[ZrO(MPB)3(OH)2]
[ZrO(MPB)4Cl2]
5
123

Zirconyl complexes of biologically active molecules
511
Table 2 IR spectral data of hippuric acid and its complexes
Hippuric acid
[ZrO(hip)(OH)]H2O
3300–3400(b)
[ZrO(hipH)4Cl2]
Assignments
v(O–H),H2O ? v(O–H) ? v(N–H)
v(N–H)
3342(s)
3342(s)
3073
3073
3073
Aromatic v(C–H)
v(O–H) in COOH
v(C=O); COOH
v(C=O); benzoyl
vas (COO-)
2750–2478 (several bands)
2750–2478
1745(s)
1600(s)
1744(s)
1600(s)
1603(s)
1576(s)
1403(s)
481
vs (COO-)
485
v(Zr–O)
assigned to v(C=O) of COOH group in [ZrO(hipH)4Cl2].
Several bands due to carboxylic OH (2750–2478 cm-1) also
remain in the complex. These observations confirm the
neutral coordination of hippuric acid in the complex formed.
The bands at 481 cm and 485 cm-1 in the complexes are
assigned to v(Zr–O) of [ZrO(hip)(OH)H2O] and [ZrO
(hipH)4Cl2], respectively [19].
to the v(Zr–O) of the complexes[ZrO(MPB)3(OH)2] and
[ZrO(MPB)4Cl2], respectively. Thus MPB act as a mono-
dentate ligand coordinating through tautomeric carbonyl
group in the complexes.
1H NMR spectra
The important IR spectral bands of monophenylbutaz-
one and its complexes and their tentative assignments are
summarized in Table 3.
The NMR spectrums of the ligands are well reproduced in
the spectrum of the complexes with only minor changes.
The N–H of MPB is not observed in the range of mea-
surement used.
The bands at 1729 and 1685 cm-1 in the free ligand are
assigned to the stretching of the tautomeric and non-tauto-
meric carbonyl groups, respectively [15]. The IR spectrum
Electronic spectra
of the ligand also shows a medium band around 3308 cm-1
.
This is assigned to the N–H stretching of amide band. In the
complexes there is no shift for the peaks at 1685 cm-1. But
the band at 1729 cm-1 is shifted to 1737 and 1745 cm-1 in
[ZrO(MPB)3(OH)2] and [ZrOCl2(MPB)4], respectively. The
upward shift arises from the release of carbonyl group from
hydrogen bonding. The band at 3381 cm-1 is assigned to the
v(O–H) of the coordinated hydroxyl group in [ZrO
(MPB)3(OH)2]. The bands at 600 and 581 cm-1 are assigned
The electronic spectra for hippuric acid in methanol and its
complexes in DMF and monophenylbutazone and its
complexes in MeOH show ligand transitions only and did
not show any d–d transitions as expected.
Second harmonic generation efficiency
The SHG measurement was carried out for the complexes
of hippuric acid. The SHG outputs are given in Table 4.
The data show that the chloro complexes have six times
efficiency than that of hydroxo complexes.
Table 3 The IR spectral data of monophenylbutazone and its
complexes
Thermal behaviour of complexes
MPB
[ZrO(MPB)3
(OH)2]
[ZrOCl2
(MPB)4]
Assignments
The thermal analysis curves (TG and DTG) of the hippuric
acid complexes are given in Figs. 3 and 4.
3381(b)
3306(s)
3060(s)
2958
v(O–H)
3308(s)
3069(s)
2956
3307
v(N–H)
3066
aryl v(C–H)
Table 4 Measured SHG values of metal complexes of hippuric acid
2958
Saturated v(C–H)
vas (C=O); tautomeric
vas (C=O); non-tautomeric
d (N–H) bending
v(Zr–O)
Sample
SHG signal/mV
Efficiency
1729(s)
1685(s)
1597
1737(s)
1686(s)
1596
1745(s)
1688(s)
1596
[ZrO(hip)(OH)H2O]
[ZrO(hipH)4Cl2]
KDP
18
98
0.04
0.24
1
600
581
410
123

512
K. R. Jisha et al.
The thermal decomposition of all the complexes was
Table 5 Kinetic parameters of the complex [ZrO(hip)(OH)H2O] in
air
taken in air at a heating rate of 10 °C/min. For the complex
[ZrO(hip)(OH)H2O], the decomposition occurs in five
stages, as shown by five DTG peaks. The final mass of the
residue corresponds to ZrO2 [20]. The kinetic parameters
were calculated for three clear cut stages using Coats-
Redfern [21] (I), MacCallum-Tanner [22] (II) and Mad-
usudhanan Krishnan Ninan’s (III) equations and are sum-
marized in Table 5.
Stages Methods n E/
DS/
logA/
r
kJ mol-1 J K-1 mol-1 s-1
1
3
5
I
1.5 25.08
-221.98
-215.91
-217.60
-2.41
1.67
0.986466
0.980324
0.979999
II
III
I
1.5 29.19
1.5 28.98
0.9 135.31
0.9 138.42
0.9 135.35
1.8 140.26
1.8 139.41
1.8 139.19
1.98
1.89
13.13 0.990424
13.58 0.988390
13.19 0.989431
12.02 0.997766
12.00 0.997547
11.96 0.997501
II
III
I
-6.20
For the complex [ZrO(hipH)4Cl2], in air the decompo-
sition occurs in two stages, kinetic parameters calculated
for these two stages are given in Table 6.
-1.36
-23.62
-24.03
-24.92
II
III
The thermal analysis curves of MPB and its complexes
are given in Figs. 5 and 6.
The thermal decomposition of the complexes
[ZrO(MPB)3(OH)2] and [ZrO(MPB)4Cl2] take place in two
stages as shown by two DTG peaks. The kinetic parame-
ters are also calculated for the distinct stages and are
r Correlation coefficient
Table 6 Kinetic parameters of the complex [ZrO(hipH)4Cl2] in air
Stages Methods n E/
DS/
logA/
r
kJ mol-1 J K-1 mol-1 s-1
-0.002
4.0
1
2
I
1
1
1
110.30
110.23
110.02
-81.88
-80.84
8.98
9.04
8.99
2.17
1.93
1.85
0.998723
0.998588
0.998581
0.960078
0.946836
0.946156
3.5
0.002
II
III
I
3.0
-81.82
2.5
0.9 60.55
0.9 58.40
0.9 58.04
-212.33
-216.87
-218.49
0.006
II
III
2.0
0.010
1.5
1.0
0.014
0.5
200
400
600
800
1000
3.0
[ZrO(hip)(OH) H O]
2
Temperature/°C
0.000
2.5
2.0
1.5
Fig. 3 TG and DTG curves of [ZrO(hip)(OH)H2O] in air
0.005
0.010
0.015
0.020
0.025
1.0
0.5
0.0
0.00
8
7
6
5
0.02
200
[ZrO(MPB) (OH)
400
600
800
1000
]
2
3
Temperature/°C
0.04
0.06
0.08
0.10
4
3
2
1
Fig. 5 TG and DTG curve of [ZrO(MPB)3(OH)2] in air
summarized in Tables 7 and 8. The negative DS value of
the decomposition stages show that the complexes are
more ordered in the activated state than the reactant and
the reactions are slower than normal [23, 24]. Entropy of
activation follows no definite trend.
0
200
[ZrO(hipH) Cl ]
400
600
800
1000
Temperature/°C
4
2
Fig. 4 TG and DTG curves of [ZrO(hipH)4Cl2] in air
123

Zirconyl complexes of biologically active molecules
513
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air
Stages Methods n E/
DS/
logA/
r
kJ mol-1 J K-1 mol-1 s-1
1
2
I
0.9 18.92
0.9 20.54
0.9 20.28
0.9 97.02
0.9 94.51
0.9 94.18
-264.79
-269.00
-271.09
-154.78
-158.47
-159.76
-0.57 0.973304
-0.79 0.959331
-0.90 0.958479
5.17 0.985213
4.98 0.982118
4.91 0.981961
II
III
I
II
III
Table 8 Kinetic parameters of the complex [ZrO (MPB)4Cl2] in air
Stages Method n E/
DS/
logA/
s-1
r
kJ mol-1 J k-1mol-1
1
2
I
0.9 50.39
-197.07
-196.12
-197.58
-247.33
-253.35
-255.32
2.97 0.993648
3.02 0.992107
2.94 0.992021
0.34 0.962449
0.03 0.940292
-0.08 0.939027
II
III
I
0.9 51.40
0.9 51.15
0.9 35.46
0.9 34.13
0.9 33.76
II
III
Acknowledgements The authors are grateful to the authorities of
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Institute of Science, Bangalore, for NLO studies. S.S is grateful to
UGC for financial assistance and J.K.R is thankful to University of
Kerala for the award of a fellowship.
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