Preparation and characterization of new In(III), Re(III), and Re(V) complexes with thenoyltrifluoroacetone and some bidentate heterocyclic ligands

Article abstract of DOI:10.1081/SIM-120003791

New In(III), Re(III) and Re(V) complexes with the thenoyltrifluoroacetone ligand (HTTA) of the general formulae [In -(TTA)(H₂O)₄]SO₄, [Re(TTA)_n(H₂O)_x]Cl_3-n and [ReO(TTA_n

Full text of DOI:10.1081/SIM-120003791

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PREPARATION AND CHARACTERIZATION OF NEW
In(III), Re(III), AND Re(V) COMPLEXES WITH
THENOYLTRIFLUOROACETONE AND SOME BIDENTATE
HETEROCYCLIC LIGANDS
Refaat M. Mahfouz a , Khalid A. Al-Farhan a , Gamila Y. Hassen b , Abdulaziz I. Al-Wassil a
Saad M. Alshehri a & Aml A. Al-Wallan a
,
a Department of Chemistry , King Saud University College of Sciences , P.O. Box 2455,
Riyadh, 11451, Saudi Arabia
b Department of Chemistry , Alexandria University , Egypt
Published online: 15 Feb 2007.
To cite this article: Refaat M. Mahfouz , Khalid A. Al-Farhan , Gamila Y. Hassen , Abdulaziz I. Al-Wassil , Saad M. Alshehri
& Aml A. Al-Wallan (2002) PREPARATION AND CHARACTERIZATION OF NEW In(III), Re(III), AND Re(V) COMPLEXES WITH
THENOYLTRIFLUOROACETONE AND SOME BIDENTATE HETEROCYCLIC LIGANDS, Synthesis and Reactivity in Inorganic and Metal-
Organic Chemistry, 32:3, 489-508, DOI: 10.1081/SIM-120003791
To link to this article: http://dx.doi.org/10.1081/SIM-120003791
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SYNTH. REACT. INORG. MET.-ORG. CHEM., 32(3), 489–508 (2002)
PREPARATION AND
CHARACTERIZATION OF NEW In(III),
Re(III), AND Re(V) COMPLEXES WITH
THENOYLTRIFLUOROACETONE AND
SOME BIDENTATE HETEROCYCLIC
LIGANDS
Refaat M. Mahfouz,1,* Khalid A. Al-Farhan,1
Gamila Y. Hassen,2 Abdulaziz I. Al-Wassil,1
Saad M. Alshehri,1 and Aml A. Al-Wallan1
1Department of Chemistry, College of Sciences,
King Saud University, P.O. Box 2455, Riyadh 11451,
Saudi Arabia
2Department of Chemistry, Faculty of Science,
Alexandria University, Egypt
ABSTRACT
New In(III), Re(III) and Re(V) complexes with the thenoyl-
trifluoroacetone ligand (HTTA) of the general formulae [In-
(TTA)(H2O)4]SO4, [Re(TTA)n(H2O)x]Cl3-n and [ReO(TTA)n -
(H2O)x]Cl3-n (where n and x refer to the number of [TTA]ꢀ
moieties and H2O molecules, respectively) have been prepared
*Corresponding author. E-mail: rmhfouz@ksu.edu.sa
489
Copyright # 2002 by Marcel Dekker, Inc.
www.dekker.com

490
MAHFOUZ ET AL.
and characterized by spectroscopy, thermogravimetry, ele-
mental analyses and X-ray diffraction. The charge densities on
the ligand atoms were calculated via CNDO-SCF calculations.
The newly prepared complexes [In(TTA)(H2O)4]SO2 and
[ReO(TTA)(H2O)2]CL2 were employed as precursors for the
synthesis of the mixed-ligand complexes [In(TTA)(HOCTA)2],
[In(TTA)(TZT)2] and [ReO(TTA)(HOTCA)]Cl using R(-)-2-
oxothiazolidine 4-carboxylicacid (H2OTCA) and 1H-1,2,4-
triazole-3-thiol (H2TZT) as ligands. The synthesized mixed-
ligand complexes were characterized by the conventional
physical and chemical methods of analysis applied earlier for
the characterization of the precursors. The investigated com-
plexes are soluble in water, ethanol and acetonitrile, insoluble
in non-polar solvents and could be of potential use for clinical
studies. The antibacterial activity of the investigated complexes
has been tested and evaluated.
INTRODUCTION
Metals offer many opportunities for designing radiopharmaceuticals
by modifying the environment around the metal and allowing specific in vivo
targeting to be incorporated into the molecule. The coordination com-
pounds of certain transition metals have wide applications as pharmaceu-
ticals and radiopharmaceuticals. Important considerations in the design and
use of the complexes in biological systems were their stability and behavior
in biological organs175. Many 111In and 186Re chelates were successfully
applied as radiodiagnostic and radiotherapeutic agents. For instance, 111In-
DTPA is used for radiographic cisternography studies (evalution of cerebral
spinal fluid pathways)6, 111In-Oxine (indium In 111 oxyquinoline solution,
Amersham International) has been approved for the labeling of leukocytes
(white blood cells) which are used for imaging sites of infections or
inflammations7.
186Re-DMSA displays selective uptake in tumors of kidney tissue
analogous to that of the Tc species and offers the possibility of therapeutic
treatment of this disease6. It has been, therefore, a great impetus for
researchers to explore the synthesis of new indium and rhenium complexes
using new classes of aliphatic or alicyclic ligands. In the present study new
complexes of indium and rhenium have been prepared using thenoyltri-
fluoroacetone and other ligands containing NS or NO donor sites.
The complexes were characterized using conventional physico-chemical

In(III), Re(III), AND Re(V) COMPLEXES
491
techniques of analysis and their antibacterial activity was tested. No previous
work concerning the preparation of these complexes has been reported.
EXPERIMENTAL
Materials and Instrumentation
All chemical used were of analytical grade and were used without
further purification. IR spectra were recorded in KBr pellets on a Perkin
Elmer FT-IR spectrometer ‘‘Spectrum 1000’’. UV-Vis spectra in ethanolic
solutions were recorded on a Cecil 599 spectrophotometer using 1 cm
1
matched silica cells. H and 13C NMR spectra were measured in DMSO-d6
as solvent on a JEOL NMR 400 MHZ spectrometer. Elemental analyses
were carried out on a Perkin Elmer 2400 CHNSO elemental analyzer.
Indium contents in the investigated indium complexes were determined by
the analytical laboratory at SABIC (R&D) (Saudi Arabia). TG measure-
ments were carried out using a Netzsch STA-429 thermal analyzer. The
weight loss was measured from ambient temperature up to 700 ꢁC at a
heating rate of 10 ꢁC=min. X-ray diffraction patterns of the complexes were
recorded using a XRD 5000 Siemens diffractometer with Cu-target.
General Method for the Preparation of [Re(TTA)(H2O)4]Cl2 (1),
[Re(TTA)2(H2O)2]Cl (2), [ReO(TTA)(H2O)2]Cl2 (3),
[ReO(TTA)2]Cl (4), and [In(TTA)(H2O)4]SO4 (5)
The amounts in mmoles of ReCl3, ReCl5, In2(SO4)3 (anhydrous) and
HTTA required for the preparation of 1:1 and 1:2 metal:ligand molar
rations complexes are listed in Table I.
Table I. Stoichiometric Amounts of the Reactants
[HTTA]
mmol (g)
[ReCl3]
mmol (g)
[ReCl5]
mmol (g)
[In2(SO4)3]
mmol (g)
Type of the Complexes
(1) [Re(TTA)(H2O)4]Cl2
(2) [Re(TTA)2(H2O)2]Cl
(3) [ReO(TTA)(H2O)2]Cl2
(4) [ReO(TTA)2]Cl
1 (0.222)
2 (0.444)
1 (0.222)
2 (0.444)
1 (0.222)
1 (0.292)
1 (0.292)
1 (0.363)
1 (0.363)
(5) [In(TTA)(H2O)4]SO4
1 (0.517)

492
MAHFOUZ ET AL.
The required amounts of metal salt were dissolved separately in 10 mL
water and added dropwise to 10 mL of an ethanolic solution containing the
corresponding amount of HTTA while stirring. The reaction mixture in each
case was refluxed for about an hour while a few drops of acetate buffer
(pH ꢂ 5) were added dropwise to the reaction mixture. A solid product in each
case was precipitated. The solutions were rotary evaporated to about 1=3 of
the total volume and these allowed to stand in air over night. The resulting
solid products were collected and washed several times with diethyl ether.
General Method for the Preparation of [In(TTA)(HOTCA)2] (6),
[In(HTTA)(HTZT)2] (7), and [ReO(TTA)(HOTCA)]Cl (8)
The stoichiometric molar amounts in mmoles of the precursors
[In(TTA)(H2O)4]SO4 (5), [ReO(TTA)(H2O)2]Cl2 (3), the ligands H2OTCA
and H2TZT required for the preparation of complexes (6), (7) and (8) are
listed in Table II.
The calculated molar amounts of the precursors were dissolved sepa-
rately in 10 mL water and added dropwise to the ethanolic solutions (10 mL)
of the ligands while stirring. The reaction mixture was heated under reflux
for an hour and the volumes were reduced to about 1=3 of the total volumes
by rotatory evaporation. After standing over night solid products were
precipitated, which were collected and washed with diethyl ether.
Comparison Experiments for Preparation of the Mixed Ligand
Complexes
Comparison experiments were carried out for preparation of the
complexes (6), (7), and (8) starting from the initial reagents, HTTA,
H2OCTA, H2TZT, ReCl5 and In2(SO4)3. The stoichiometric amounts of
Table II. Stoichiometric Amounts of the Reactants
[ReO(TTA)-
H2OTCA H2TZT [In(TTA)(H2O)4]SO4 (H2O)2]Cl2
Type of the
Complexes
mmol (g) mmol (g)
mmol (g)
mmol (g)
(6) [In(TTA)(HOTCA)2] 2 (0.3)
(7) [In(TTA)(HTZT)2]
1 (0.53)
1 (0.53)
2 (0.2)
(8) [ReO(TTA)-
(HOTCA)]Cl
1 (0.15)
1 (0.53)

In(III), Re(III), AND Re(V) COMPLEXES
493
indium or rhenium salts were dissolved separately in 10 mL water. The
amounts of HTTA=H2OCTA or HTTA=H2TZT in ethanol (10 mL) were
added slowly with stirring to the aqueous metal ion solutions while stirring
with the addition of few drops of acetate of few drops of acetate buffer
solution of pH ꢂ 5. The reaction mixture was refluxed as previously to give
solid products analogous to those obtained starting with the precursors
[In(TTA)(H2O)4]SO4 (5) and [ReO(TTA)(H2O)2]Cl2 (3).
RESULTS AND DISCUSSION
The metal complexation reactions were carried out according to the
following equations:
ReCl3 þ HTTA þ 4H2O ! ½ReðTTAÞðH2OÞ4ꢃCl2 ð1Þ þ HCl
ReCl3 þ 2HTTA þ 2H2O ! ½ReðTTAÞ2ðH2OÞ2ꢃCl ð2Þ þ 2HCl
1
ReCl5 þHTTAþ2H2Oþ O2 ! ½ReOðTTAÞðH2OÞ2ꢃCl2 ð3ÞþHClþCl2
2
1
ReCl5 þ 2HTTA þ O2 ! ½ReOðTTAÞ2ꢃCl ð4Þ þ 2HCl þ Cl2
2
In2ðSO4Þ3 þ 2HTTA þ 8H2O ! 2½InðTTAÞðH2OÞ4ꢃSO4 ð5Þ þ H2SO4
The microanalytical data of the investigated complexes are tabulated in
Table III. Thenoyltrifluoroacetone molecule (HTTA) has the following
tautomeric forms (Fig. 1)
The charge densities calculations were performed via CNDO-SCF
calculations in the singlet electronic ground state configuration (Fig. 2). The
calculations indicated that the oxygen atoms of the carbonyl group (atoms
No. 10 and 14) exhibit higher values of electronic charge densities and
would, accordingly, be favorable sites for coordination of In(III), Re(III),
and Re(V) with the ligand8.
Spectroscopic Measurements
The investigated complexes were subjected to extensive spectroscopic
investigations using a combination of spectroscopic techniques.

494
MAHFOUZ ET AL.

In(III), Re(III), AND Re(V) COMPLEXES
495
Figure 1. Tautomeric forms of HTTA.
The n(C¼O) IR band for the free HTTA ligand which provide evi-
dence for the mode of attachment of the ligand to the metal ion is recorded
at 1654 cmꢀ1. This band was shifted to lower wave lengths in the investi-
gated complexes. This shift can be considered as evidence for the com-
plexation through oxygen atoms. A sharp split band in the range
344373420 cmꢀ1 was observed in the IR spectra of the investigated com-
plexes (1)7(4) and is assigned to coordinated water in the structures of the
complexes. In case of the Re(V) complexes, the band due to n(Re¼O) was
recorded at 923 cmꢀ1 and 920 cmꢀ1 for [ReO(TTA)(H2O)2]Cl2 (3) and
[ReO(TTA)2]Cl (4), respectively9. 1H NMR spectral data and thermal
analyses further verify the presence of coordinated water molecules. The 1H
NMR spectrum of [In(TTA)(H2O)4]SO4 (5) shows signals at d 6.62 ppm and
Figure 2. HTTA Molecule.

496
MAHFOUZ ET AL.
at 3.45 ppm relatives to TMS which are assigned to the ¼CH (enolic) pro-
tons and coordinated water, respectively. The signal at d 3.7 ppm was
assigned to the CH2 ketonic protons. The signals due to the thiophene ring
protons were observed in the range d 7.2377.99 ppm. The 13C NMR spec-
trum of [In(TTA)(H2O)4]SO4 (5) shows a signal due to C¼O in the range
1897191 ppm. The signals due to the thiophene ring and CF3 carbon atoms
were observed in the range d 1447129 ppm. No NMR signals were recorded
for the investigated rhenium complexes, which provide an evidence for the
paramagnetic properties of the complexes. It is worthwhile to mention that
high-spin behaviour is rarely observed in the 4d and 5d series of transition
metals.
Electronic absorption spectra of the complexes were measured at
ambient temperature in ethanolic solutions. The solutions of the complexes
exhibit p–pꢄ intraligand transition bands with absorption maxima ðlmaxÞ in
the range of 2127213 nm. Another absorption band due to a n–pꢄ intrali-
gand transition with lmax in the range of 2607267 nm was observed in the
spectra of the complexes. The electronic spectra of the Re(III) complexes
show some d-d transitions with 336 nm and 335 nm absorption maxima for
[Re(TTA)(H2O)4]Cl2 and [Re(TTA)2(H2O)2]Cl, respectively. Since HTTA is
a relatively weak-field ligand, and distorted octahedral Re(III) complexes
are high-spin and the d-d transition for [Re(TTA)2(H2O)2]Cl and
[Re(TTA)(H2O)4]Cl2 (1) could be assigned to the 5Eg ! T2g transition10712
5
.
The distorted square-pyramidal structure for the [ReO(TTA)(H2O)4]Cl2 (1)
and [ReO(TTA)]Cl (4) complexes show also some d-d transition band
5
3
attributed to the T1g ! T2g transition similar to [VO(acac)2] (bisacetyla-
cetonatovanadyl) where acac is acetylaceton. A feature of square-pyramidal
structures is that there is the possibility of an additional ligand occupying
the vacant axial site to produce six-coordinate complexes. This possibility
has been tested by the small variations that have been observed in the
electronic spectra of both [ReO(TTA)(H2O)2]Cl2 (3) and [ReO(TTA)2]Cl (4)
in different solvents that are believed to be caused by a solvent molecule
being weakly binding at the sixth coordination site. There is evidence that
good donor solvents sometimes also introduce a ligating atom cis to the
rhenyl oxygen13.
A ligand to metal charge transfer band (LMCT) at lmax 336 nm was
recorded for [In(TTA)(H2O)4]SO4. This charge transfer band could be
assigned to transition from the weakly bonding p orbitals on the ligand to
the anti bonding tꢄ2g or egꢄ orbitals of the metal ion. It should be mentioned
that the change of solvent influences the position of the charge transfer
band. This influence may be attributed to some inherent polarity for the
asymmetric geometry of the complex. The UV-Vis spectrum of the inves-
tigated complex [In(TTA)(H2O)4]SO4 (5) was compared with that of the free

In(III), Re(III), AND Re(V) COMPLEXES
497
ligand in order to distinguish between the charge transfer band of the
complex and the intraligand band. The spectroscopic data of the prepared
complexes are summarized in Tables IV7VI.
Thermogravimetric Analysis
Thermal decomposition behaviour of the investigated complexes was
followed using thermogravimetric (TG) and differential thermogravimetric
(DTG) techniques. The decomposition occurred in one or more steps
depending on the type of the complexes investigated. Table VII summarized
the results of thermal decomposition of the investigated complexes. The
decomposition ends with the formation of the metal oxides In2O3 or Re2O3.
Determination of Reaction Order of the Decomposition
The Horowitz and Metzger equation, Cs ¼ (n)1/1ꢀn where Cs is the
weight fraction of the substance present at the DTG peak temperature, Ts, is
given as
Cs ¼ ðWs ꢀ WfÞ=ðWi ꢀ WfÞ
ð1Þ
was applied for the determination of the reaction order(n) of the decom-
position. Here Ws stands for the weight remaining at a given temperature Ts,
i.e., the DTG peak temperature Wi and Wf are the initial and final weights
Table IV. UV-Vis Spectroscopic Data of the Investigated Complexesa
UV-Vis
lmax (e, L molꢀ1 cmꢀ1 a
)
Complex
(1) [Re(TTA)(H2O)4]Cl2
(2) [Re(TTA)2(H2O)2]Cl
(3) [ReO(TTA)(H2O)2]Cl2
(4) [ReO(TTA)2]Cl
(5) [In(TTA)(H2O)4]SO4
(6) [In(TTA)(HOTCA)2]
(7) [In(TTA)(HTZT)2]
(8) [ReO(TTA)(HOTCA)]Cl
212 (250)
212 (410)
212 (410)
213 (380)
264 (710)
205 (320)
202 (470)
203 (390)
264 (510)
265 (820)
260 (810)
267 (720)
336 (950)
225 (700)
263 (350)
263 (710)
336 (510)
335 (800)
336 (950)
33 (950)
340 (300)
337 (220)
330 (900)
ae are in the range of 1027103 for six-coordinate complexes of low symmetry (spin-
allowed, Laporte-forbidden).

498
MAHFOUZ ET AL.

In(III), Re(III), AND Re(V) COMPLEXES
499

500
MAHFOUZ ET AL.

In(III), Re(III), AND Re(V) COMPLEXES
501
of substance, respectively. The calculated values of Cs are in range 0.37.04
which indicates that the decomposition follows first order kinetics for both
the dehydration and the main decomposition steps14.
For a first order process the following Coats-Redforn and Horowitz-
Metzger equations were applied for determination of activation energy Ea
and Arrhenius constant, A, of the decomposition14,15
.
ꢀ
ꢁ
ꢀlnð1 ꢀ aÞ
ꢀEa
AR
ln
¼
þ ln
ð2Þ
ð3Þ
T2
RT
jEa
EðT ꢀ TsÞ
ln½ꢀlnð1 ꢀ aÞꢃ ¼
RT2s
where a is the fraction decomposed at time t and is given by
mo ꢀ mt
a ¼
mo ꢀ mf
(mo is the mass at the beginning of the decomposition step, mt is the mass at
time t, mf is the mass at the end of the decomposition step), Ea, A, R, f and
Ts are activation energy of decomposition, Arrhenius constant gas constant,
heating rate and temperature at the DTG peak, respectively. The kinetic
parameters were calculated from the plots of the left hand side of eqs. (2)
and (3) versus 1=T and (T-Ts), respectively. The correlation coefficient r
( > 0.95) is computed using the least-square method for eqs. (2) and (3). The
activation entropy, S*, the activation enthalpy H* and the free energy of
activation G* were calculated using the following equations.
ꢂ
ꢃ
Ah
Sꢄ ¼ 2:303 log
R
ð4Þ
KT
Hꢄ ¼ Eꢄ ꢀ RT
Gꢄ ¼ Hꢄ ꢀ TsSꢄ
ð5Þ
ð6Þ
K and h are the Boltzman and Planck constants, respectively. The tem-
perature T involved in the calculations was selected as the temperature at the
end of the decomposition step. The calculated kinetic and thermodynamic
value are reported in Table VII for the various decomposition steps.

502
MAHFOUZ ET AL.
The kinetic parameters, especially Ea and S*, are helpful in assigning
the strength of the bonding of both water molecules and ligand moieties
with the metal ion. The values of the major decomposition step of the
studied compounds i.e., the stages of the decomposition to volatile products
are in the range 2207285 kJmolꢀ1 which indicates that the ligand is strongly
bound to the metal ion. The activation energy for the dehydration step of
the complexes lies in the range 1007130 kJ=mol. These values are com-
parable of the generally accepted values of activation energy for coordinated
water16. The negative values indicate that the activated complexes have a
more ordered structure than the reactants and that the complexation reac-
tions are slower than normal17.
Two of the prepared complexes, [In(TTA)(H2O)4]SO4 (5) and
[ReO(TTA)(H2O)2]Cl2 (3), were employed as precursors for the preparation
of mixed-ligand complexes using the following ligands in Fig. 3.
Figure 3. Ligands for the mixed-ligand complexes.

In(III), Re(III), AND Re(V) COMPLEXES
503
Ligand atoms charge density calculations indicated that for the free
ligand H2OTCA the more attractive sites for coordination with In and Re
atoms are the oxygen atoms of carboxylate ion (atoms No. 11 and 12). The
favorable coordination sites of the H2TZT ligand are suggested to be
nitrogen atoms (atoms No. 2 and 9). It was found that both [In(TTA)-
(H2O)4]SO4 (5) and [ReO(TTA)(H2O)2]Cl2 (3) could undergo ligand
exchange reactions according to the following equations.
½InðTTAÞðH2OÞ4ꢃSO4 þ 2H2OCTA !½InðTTAÞðHOCTAÞ2ꢃ ð6Þ
þ 4H2O þ H2SO4
½InðTTAÞðH2OÞ4ꢃSO4 þ 2HTZT !½InðTTAÞðTZTÞ2ꢃ ð7Þ þ 4H2O
þ H2SO4
½ReOðTTAÞðH2OÞ2ꢃCl þ H2OCTA !½ReOðTTAÞðHOTCAÞꢃCl ð8Þ
þ 2H2O þ HCl
The microanalytical, spectroscopic and thermal data of the investigated
mixed ligand complexes are tabulated in Tables III–VII, respectively.
X-Ray Powder Data of [ReO(TTA)2]Cl (4)
Complex (4) was subject to a preliminary XRPD study. A Siemens
D5000 X-ray powder diffractometer, powered at 40 kV and 35 mA, was
used for data collection. Data were measured by using CuKa radiation
ðl ¼ 1:54056A). The data were collected by the continuous scanning mode
with a step width of 0.04 and a step time of 2 s. The intensity of the dif-
fraction lines was measured as peak heights and expressed in percentage of
the strongest line. The source of the initial cell parameters was the indexing
18
program DICVOL9l ½M20 ¼ 36; F20 ¼ 58:4ð0:0023; 148Þꢃ . The cell was
checked and refined by the CHECKCELL program19. a ¼ 22.8091(3),
b ¼ 10.5554 (1), c ¼ 10.9527 (1) A, b ¼ 115:786ð1Þꢁ, V=2374.40 A3. Possible
space groups are the monoclinic P21 or P21=m. The X-ray powder diffrac-
tion data are presented in Table VIII.
Based on the foregoing discussion the following structures are plau-
sible for the investigated complexes as seen in Fig. 4.

504
MAHFOUZ ET AL.
Table VIII. X-Ray Powder Diffraction Data of [ReO(TTA)2]Cl (4)
No.
2yobs
dobs
I=I0
h
K
l
2yobsꢀ2ycal
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
8.075
8.959
10.9400
9.8624
7.5962
6.8411
5.3510
5.1756
4.9995
4.8563
4.6079
3.9104
3.8407
3.6802
3.5225
3.4469
3.3489
3.2979
3.1701
2.9862
2.8068
2.7289
2.6933
2.6474
2.5213
2.4387
2.4068
2.3439
2.1908
2.1579
2.1149
2.0900
2.0229
20.8333
100.0000
32.5000
10.0000
6.6667
20.0000
27.5000
30.8333
26.6667
23.3333
28.3333
6.6667
ꢀ1
0
ꢀ1
ꢀ3
ꢀ1
2
ꢀ4
ꢀ2
ꢀ2
4
0
0
1
0
0
1
1
1
2
0
0
2
2
1
3
3
3
2
2
0
0
1
2
3
1
0
0
2
0
4
3
1
1
1
0
2
1
1
2
1
1
2
0
2
3
1
1
1
3
1
4
4
4
1
3
1
3
4
4
5
0
1
ꢀ0.0008
ꢀ0.0003
ꢀ0.0006
0.0093
0.0042
0.0001
11.640
12.930
16.553
17.118
17.726
18.253
19.246
22.721
23.139
24.163
25.262
25.826
26.595
27.014
28.125
29.897
31.856
32.791
33.237
33.831
35.577
36.825
37.331
38.371
41.171
41.826
42.718
43.254
44.763
0.0002
ꢀ0.0002
0.0045
0.0002
2
0.0001
0.0001
ꢀ0.0009
ꢀ0.0032
0.0044
ꢀ0.0014
ꢀ0.0007
ꢀ0.0004
0.0002
ꢀ0.0020
ꢀ0.0014
ꢀ0.0006
0.0001
ꢀ4
ꢀ4
ꢀ3
ꢀ1
ꢀ2
ꢀ3
ꢀ2
5
ꢀ3
ꢀ5
ꢀ4
6
10.0000
3.3333
42.5000
10.0000
29.1667
46.6667
10.8333
11.6667
9.1667
14.1667
60.0000
15.8333
10.0000
9.1667
ꢀ5
ꢀ9
4
ꢀ0.0007
0.0002
0.0006
6.6667
2
0.0007
0.0060
ꢀ0.0004
ꢀ0.0009
ꢀ0.0068
11.6667
4.1667
5.8333
ꢀ8
ꢀ2
ꢀ6
ꢀ9
11.6667
Antibacterial Activity
The antibacterial activity of the free HTTA ligand and its complexes
were tested against various gram-positive and gram-negative bacterial cul-
tures by using the agar diffusion method20. The antibacterial activities of the
investigated complexes and the free ligand were tested against various kinds
of bacteria listed in Table VIII. The bacterial strains were grown in Mueller-

In(III), Re(III), AND Re(V) COMPLEXES
505
Figure 4. Suggested structures of the investigated complexes.
TTAꢀ, HOTCAꢀ and HTZTꢀ, respectively.
,
and
refer to

506
MAHFOUZ ET AL.

In(III), Re(III), AND Re(V) COMPLEXES
507
ꢁ
Hinton agar (Merck) plates at 37 C for 18 h, and then were diluted to a
final concentration of approximately 106 CFU=mL. 0.1 mL of each bacterial
suspension was spread over the surface of the Mueller-Hinton agar plates.
10 mL of 10 mg=mL of each compound, HTTA and the investigated com-
plexes, was absorbed onto a sterilized filter paper disk of 6 mm diameter.
The sterilized filter paper disks were dried under sterile condition and then
immediately placed on the surface of Mueller-Hinton agar plates afteꢁr their
inoculation with the test bacterium. The plates were incubated at 37 C for
24 h and the diameter (mm) of the inhibition zone was recorded. The results
presented in Table IX show that the free ligand showed higher toxicity
towards the growth of gram-negative bacteria, more than gram-positive
bacteria. Upon complexation with In(III), Re(III) and Re(V) metal ions a
reduction in inhibitory power towards Y. Pseudetuberculosis and Y. enter-
ocolitica was observed. This reduction in inhibitory power also appeared
towards S. aureus upon complexation with In(III). Salmonella typhi (gram
negative) is the most resistant bacteria towards complexation with Re(III) as
[Re(TTA)(H2O)4]Cl2. The effect of the ligand and its complexes on S. aureus,
S. epidermidis and streptococcus faceless is equal and nearly negligible.
ACKNOWLEDGMENTS
This research was supported by King Abdulaziz City for Science and
Technology (KACST), project No. (At-19-43). The authors would like to
thank Mr. Mohsen H. Mukhalalati and Mr. Nasser M. Abd El-Salam for
technical help and assistance throughout the whole work.
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Received May 23, 2001
Accepted December 5, 2001
Referee I: D. P. Rillema
Referee II: D. T. Haworth