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Synthesis, Characterization and Antibacterial Activity of New Complexes of Some Lanthanide Ions with Benzo 18-Crown-6 and 221-Cryptand

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Abstract

Complexes of some lanthanide picrates (Ln3+ = Pr3+, Nd3+ and Dy3+) with benzo-18-crown-6 and 221-cryptand were synthesized and characterized by elemental analysis, FTIR, and UV-Visible. Spectrophotometric methods, thermal analysis (TGA & DTG), melting point, magnetic susceptibility and molar conductance. Also an in-vitro study on gram positive (Staphylococcus aureus) and gram negative bacteria (Escherichia coli, Salmonella and pseudomonas aeruginosa) was performed and the results were compared to those of the broad spectrum antibiotic Chloramphinicol. The benzo-18-crown-6 complexes have the general formula of [Ln.L.(Pic)2]Pic.nH2O , where; (Ln3+ = Pr3+, Nd3+, and Dy3+) , (L = Benzo-18-crown-6) , (Pic = Picrate anion) , (n = 1-2). In these complexes two picrate anions are coordinated to the metal ion through the phenolic oxygen and oxygen of the ortho nitro group, thus, the metal ions in these complexes have a coordination number of (10). The complexes of 221-cryptand have the general formula of [Ln.L.(Pic)]Pic2.nH2O where; (Ln3+ = Pr3+, Nd3+, and Dy3+), (L = 221-cryptand), (Pic = Picrate anion), (n = 1,2 or 7). In these complexes one picrate anion is coordinated to the metal ion, also through the phenolic oxygen and the oxygen from the ortho nitro group, thus the metal ions in the cryptand complexes have a coordination number of (9).
IOSR Journal of Applied Chemistry (IOSR-JAC) e-ISSN: 2278-5736. Volume 6, Issue 4 (Nov. Dec. 2013), PP 32-39 www.iosrjournals.org
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Synthesis, Characterization and Antibacterial Activity of New
Complexes of Some Lanthanide Ions with Benzo 18-Crown-6 and
221-Cryptand
Basim I. Alabdaly1 , Mohammed H. A. Al-Almery1, and Mustafa K. Albayaty1
1(Department of Chemistry, College of Science, Baghdad University, Iraq)
Abstract: Complexes of some lanthanide picrates (Ln3+ = Pr3+, Nd3+ and Dy3+) with benzo-18-crown-6 and
221-cryptand were synthesized and characterized by elemental analysis, FTIR, and UV-Visible.
Spectrophotometric methods, thermal analysis (TGA & DTG), melting point, magnetic susceptibility and molar
conductance. Also an in-vitro study on gram positive (Staphylococcus aureus) and gram negative bacteria
(Escherichia coli, Salmonella and pseudomonas aeruginosa) was performed and the results were compared to
those of the broad spectrum antibiotic Chloramphinicol. The benzo-18-crown-6 complexes have the general
formula of [Ln.L.(Pic)2]Pic.nH2O , where; (Ln3+ = Pr3+, Nd3+, and Dy3+) , (L = Benzo-18-crown-6) , (Pic =
Picrate anion) , (n = 1-2). In these complexes two picrate anions are coordinated to the metal ion through the
phenolic oxygen and oxygen of the ortho nitro group, thus, the metal ions in these complexes have a
coordination number of (10). The complexes of 221-cryptand have the general formula of
[Ln.L.(Pic)]Pic2.nH2O where; (Ln3+ = Pr3+, Nd3+, and Dy3+), (L = 221-cryptand), (Pic = Picrate anion), (n =
1,2 or 7). In these complexes one picrate anion is coordinated to the metal ion, also through the phenolic
oxygen and the oxygen from the ortho nitro group, thus the metal ions in the cryptand complexes have a
coordination number of (9).
Keywords: crown ethers, lanthanides, picrates, cryptand
I. Introduction
The coordination chemistry of lanthanides is important. And during the last decades, an increase in the
number of publications devoted to the rare earth coordination compounds has been observed[1-6], due to their
biological, biochemical, medical and many other applications such as an excellent diagnostic and prognostic
probe in clinical diagnostics[7], an anticancer material [2,8], lanthanide complexes based X-ray contrast
imaging and lanthanide chelates based contrast enhancing agents for Magnetic Resonance Imaging (MRI)[9] are
being excessively used in radiological analysis in our body systems [8], also as shift reagents for NMR
spectrometry [9-11], as well as, their potential applications in fundamental and applied science such as organic
synthesis, bioorganic chemistry and homogeneous catalysis[9,1216]. Crown ethers are cyclic chemical
compounds that consist of a ring containing several ether groups. The most common crown ethers are oligomers
of ethylene oxide, the repeating unit is ethyleneoxy, i.e., CH2CH2O[17]. Since its discovery by Pedersen [18],
many variants of those structures have been reported, such as outin bicyclic amines and cryptands by Simmons
and Park, Lehn and coworkers, lariat ethers, aza-crown ethers, calixarenes and calixcrowns, calixtubes[19]. All
these compounds are interesting because of their remarkable selectivity on metal cations, especially from alkali
and alkaline earth metals [20-24], which is a topic of fundamental interest in both coordination and biological
chemistry [25]. Complexation reactions of crown ethers and cryptands with 4f-element salts under anhydrous
conditions promote interaction of the metal ion with the crown ether in solution; however these complexes are
often very difficult to crystallize [3,4] but we have successfully prepared, characterized and tested the
crystallized complexes against gram positive (Staphylococcus aureus) and gram negative bacteria (Escherichia
coli, Salmonella and pseudomonas aeruginosa) in-vitro. They showed good, promising results when compared
to the well-known broad spectrum antibiotic Chloramphenicol, in fact chloramphenicol had no activity at all
against the gram negative pseudomonas aeruginosa while all the tested complexes showed good inhibitions.
However further in-vivo study is required. The biological activity of these complexes against these bacteria is
believed to arise from the crown ligand (The Chelate) effect on the metal ion. The most important property of
the chelating agents, in lanthanide chelate complex, is its ability to alter the behavior of lanthanide ion with
which it binds in biological systems, and the chelation markedly modifies the bio distribution and excretion
profile of the lanthanide ions. The chelating agents increase the proportion of their complex excreted from
complexes lanthanide ion from biological systems [2].
Synthesis, Characterization and Antibacterial Activity of New Complexes of Some Lanthanide
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II. Materials And Methods
All the Starting materials were commercially available. The ligands (benzo 18-crown-6 and 221-
cryptand) were obtained from Sigma Aldrich Company, lanthanide oxides, picric acid and the solvents were
obtained from Merck Company and were used without further purification. The lanthanide content was
determined by EDTA titration using xylenol orange as an indicator. The carbon, hydrogen and nitrogen content
were determined using the Carlo Erba EA 1108 elemental analyzer. The IR spectra were recorded using KBr
pellets and an 8400 S FTIR SHIMADZU spectrometer. The UV Visible Spectra were recorded using an
1800 UV SHIMADZU spectrometer. Conductivity measurements were carried out using a HI 9811 5
Portable HANNA pH/EC/TDS/oC meters. Thermal analysis of the prepared complexes was performed using
SHIMADZU 60-H Thermo Gravimetric Analyzer. The melting points were measured using a GALLENKAMP
melting point apparatus. The magnetic properties were measured using a Johnson Matthey MSB MarkI
magnetic susceptibility balance.
Preparation of lanthanide picrate:
General procedure: (1 mmole) of lanthanide oxide was placed in a round bottomed flask, followed by the
addition of (40 ml) of (0.05 M) picric acid and refluxed at (85 0C) until all the oxide was dissolved, the process
took few hours to more than 24 hours. The clear yellow solution was filtered while still hot then the filtrate was
concentrated on a heater at (40-50 0C) to half of its volume after that the solution was left over night to be air
concentrated (if you want to accelerate the process then evaporate the solution on the heater very slowly and on
a low temperature, care must be taken since the metal salts of picric acid are highly explosive more than the acid
itself but the slower the rate of the concentration the better yield you get). After the concentration and the
evaporation of the solution yellow-dark yellow crystals were formed, all the crystals were collected and stored
in a desiccator. The colors of the salts were bright yellow-orange. The general equation for the preparation of
lanthanide picrates is shown below:
Ln2O3(s) + 6 (NO2)3C6H2OH(aq.) ∆ 2 LnPic3.xH2O
Where Ln3+ = Pr3+, Nd3+ and Dy3+
Preparation of B18-crown-6 complexes:
General procedure: a solution of (1 mmole) of B18-crown-6 in (3 ml) of absolute ethanol was added to a
solution of (0.5 mmole) of lanthanide picrate in (3 ml) of absolute ethanol and refluxed at (60 0C) for one hour,
then the solution was left overnight. The developed precipitate or crystals were collected and stored in a
desicator for 24 hours. In some cases a gummy like precipitate formed. The gummy precipitate was treated with
(40-60 0C) petroleum ether for several times till a fine powder precipitate was formed. The obtained crystals
were yellow-orange.
Preparation of 221-cryptand complexes:
General procedure: a solution of (2 mmole) of 221-cryptand in (10 ml) of absolute ethanol was added to a
solution of (1 mmole) of lanthanide picrate in (10 ml) of absolute ethanol at room temperature. Immediate
precipitation occured along the addition, then the precipitate was filtered and washed with small proportions of
ethanol; finally the precipitate was placed in a desiccator and left for 24 hours for complete dryness. The colors
of the complexes were yellow-dark orange.
III. Results
Physical and Chemical measurements:
The carbon, hydrogen, nitrogen and metal content data alongside the melting points, colors,
conductivity values, and magnetic moments of the prepared complexes are shown in table (1).
IR spectra:
IR spectra of the lanthanide picrates: The data of the absorption frequencies of picric acid and lanthanide
picrates are listed in table (2). The most important band shift is the one that belongs to the ν (O-H) stretching
vibration which is shifted in the spectra of the salts by (367 397 cm-1) towards higher wave numbers when
compared to the spectra of picric acid, this may be due to the breaking of the intramolecular hydrogen bonding
between the phenolic hydrogen and the oxygen from the adjacent nitro group, and the formation of an ion pair
between the Ln3+ ion and Pic- [26, 36]. Some noticeable shifts in the bands of the symmetric and asymmetric
stretching vibrations of the nitro groups are observed in the spectra of the lanthanide salts when compared to the
Synthesis, Characterization and Antibacterial Activity of New Complexes of Some Lanthanide
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spectra of picric acid as it is shown in table (3), this also may indicate the breaking of the intramolecular
hydrogen bonding between the oxygen of the nitro group and the phenolic hydrogen [36-39, 41].
IR spectra of the complexes: The data of the absorption frequencies for the free ligands and their complexes
are shown in table (3). The most important band in the spectra of the complexes is that of the (C-O-C) stretching
vibration. Compared with the free ligand the ʋ (C-O-C) bands in the complexes of B18-crown-6 are shifted by
(99 cm-1) for the first band and by (35 cm-1 ) for the second band towards lower wave numbers with changes in
shape and intensity of the peaks, while the bands in the complexes of 221-crypantd are shifted by (29 - 35 cm-1)
also towards lower wave numbers and are also accompanied with changes in shapes and intensities of the peaks.
These shifts and spectral changes give an indication of the interaction between the crown compound and the
metal ion and the magnitude of the shift defines the strength of the interaction which varies from one ligand to
another due to the size matching between the cavity of the ligand and the size of the metal ion alongside other
factors [27-31]. Some new bands appear in the spectra of the complexes which are absent in the spectra of the
free ligand at around (1537 1560 and 1325 1337 cm-1 ) these bands belong to the asymmetric and symmetric
stretching vibrations of the nitro groups of the picrate anion, this confirms the formation of the complexes and
means that the picrate anions are incorporated in the skeleton of the complexes whether coordinated to the metal
ion or as a counter ion. Any shift in these bands when compared to the bands of their corresponding metal salts
indicates their coordination to the metal ion [37-39, 41]. Significant shifts are observed in the complexes when
compared to the spectra of the corresponding lanthanide salt as shown in table (3) indicating that some picrate
anions are coordinated to the metal ion which is confirmed by their conductance values. Another new band
appeared at (3092 3097 cm-1) in the spectra of 221-cryptand complexes which is absent in the spectra of the
ligand and is assigned to the aromatic ν (C-H) stretching vibration of the aromatic ring of the picrate anion, and
another band appeared at (932 943 cm-1) which belongs to the aromatic δ (C-H) bending vibration, the
appearance of these two bands mean that the picrate anions are somehow incorporated in the complex. The CH2
bending vibrations (Scissoring, wagging and rocking) experienced shifts in their bands when compared to the
free ligand, some shifts are high and obvious, some are simple and all these shifts are accompanied with changes
in shapes and intensities of the peaks. These spectral changes are may be due to the decrease in charge density
on the adjacent oxygen atom, which gives an indication of their bonding and interaction with the metal ion [30].
Another new band appeared at (1610 1614 cm-1) in the spectra of 221-cryptand complexes, this band is
assigned to the ν (C=C) stretching vibration of the benzene ring of the picrate anions, this is absent in the spectra
of the free ligand [38, 39, 41].
UV Visible Spectra:
The electronic spectra of picric acid and lanthanide salts were recorded in ethanol. Picric acid shows
two main absorption bands at (λ max 359 and 220 nm). These bands are shifted to lower wave lengths in the
corresponding salts. These spectral changes may indicate the formation of ion-pair between Ln3+ ion and Pic- in
LnPic3 which is also confirmed by IR results. The electronic spectra of free ligands and their complexes were
recorded in DMSO. Table (4) shows the absorption data of picric acid, Ln salts, ligands and the complexes. All
ligands show two typical absorption bands as it is seen in table (4), one of these two bands is shifted to a higher
wave length specifically to (380 nm) in all the complexes while the other band is shifted to a lower wavelength
table (4). These spectral changes confirms that the complex is formed indicating that there is a change in the
environment and leads to the conclusion that Ln3+ is maybe incorporated in the ligand causing these spectral
changes. The picrate anion also have a pronounced effect on the formation of the complex and the nature of the
spectra and since the maximum absorption bands of the lanthanide picrate salts are shifted upon complexation to
other wave lengths that means the picrate anions one, or more are coordinated to the metal ions[32,33, 40].
Thermal analysis:
The Pr3+, Nd3+, and Dy3+ complexes of B18-crown-6 showed almost similar thermal behavior and
results. All the three complexes went through three stages in their thermal decomposition; the first stage was the
dehydration step, followed by the second stage which was the decomposition of the anhydrous complex into
unidentified intermediates due to the explosive nature of the picrate compounds, and finally the third stage, the
formation of Ln oxides [26, 34, 35]. The dehydration process took place at a temperature range of (66 120 0C).
The complex [Pr(B18-crown-6)(Pic)2]Pic.2H2O lost one water molecule when heated to (73.8 0C) and lost
another water molecule when heated to (120.52 0C), it is really hard to distinguish the coordinated water from
the uncoordinated water from the graphical data[30,31], the values of the weight loss found in the process (1.4%
and 2.03% ) are in good agreement with the calculated values (1.5% and 2.3% respectively). Both Nd3+ and
Dy3+ complexes lost one water molecule when heated to (66.35 and 76.51 0C) respectively, the weight losses
found in the process (1.58% and 1.98% respectively) were in good agreement with the calculated values (1.55%
and 2.2% respectively). All the three complexes started to decompose at a temperature range of (260 315 0C),
Synthesis, Characterization and Antibacterial Activity of New Complexes of Some Lanthanide
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an endothermic peak followed by an adjacent exothermic peak appeared at this range of temperature and
multiple explosions took place at the same temperature range due to the explosive nature of picrate compounds
forming unidentified intermediates [26]. After this temperature range other weight losses were recorded up to
(600 0C), at this temperature Ln oxides were formed [26, 27] which were stable against heating up to more than
(800 0C). The complexes of cryptand showed similar behavior, and the data are shown in table (5).
Molar conductance:
The molar conductance values of all the complexes were measured in DMSO at 25 0C. The values
obtained lie in the range (50 80 Ohm-1.cm2.mol-1), this indicates that all the complexes are electrolytes and
shows that in benzo-18-crown-6 complexes two picrate anions are coordinated to the metal ion leaving one
picrate anion uncoordinated as a counter ion, while in 221-cryptand complexes only one picrate anion is
coordinated to the metal ions [42].
Antibacterial assay:
All the prepared complexes were tested in-vitro against four types of pathogenic bacteria, one gram
positive (Staphylococcus aureus) and three gram negative (Escherichia coli, Salmonella and pseudomonas
aeruginosa), and their results were compared to the results of the broad-spectrum antibiotic chloramphenicol.
They showed good promising results when compared to the commercial antibiotic, they showed clear inhibition
zones some larger than those of the antibiotic, some similar and others smaller. The notice worthy case was that
the antibiotic chloramphenicol showed no activity at all against the pathogenic bacteria pseudomonas aeruginosa
while all the prepared complexes showed very good results, another case was that the prepared complexes
showed greater activity against Staphylococcus aureus than the antibiotic. The inhibition zones measured in
millimeters are listed in table (6). Further in-vivo studies are required in order to estimate the side effects of
these complexes and to study their behavior inside the biological system.
IV. Discussion
All benzo-18-crown-6 complexes have the suggested formula [Ln.L.(Pic)2]Pic.nH2O, while all 221-
cryptand complexes have the general suggested formula [Ln.L.(Pic)]Pic2.nH2O where; (Ln3+ = Pr3+, Nd3+,
Dy3+), (L = B18-crown-6 or 221-cryptand), (Pic = picrate anion), (n = 1, 2 or 7), which is confirmed by their
elemental and thermal analysis. The molar conductance values of the complexes lie in a range which confirms
that there are two picrate anions coordinated to the Ln3+ ion in benzo-18-crown-6 complexes, and one picrate
anion coordinated to the metal ions in 221-cryptand complexes which is also confirmed by their IR spectra
through the shift in both symmetric and asymmetric (NO2) stretching vibrations, and also confirmed by their UV
Visible Spectra. The spectral changes and the shifts in the (C-O-C) stretching vibration indicates that the Ln3+
ion lies inside the cavity of B18-crown-6 and is encapsulated by 221-cryptand, these shifts also indicate the
strong interaction between the Ln3+ ions and the ligands, this is due to the size matching between the radius of
the ion and the size of the cavity of the ligand, (1.34 1.43 A) for B18-crown-6 and (1.013, 0.995, 0.912 A) for
Pr3+, Nd3+ and Dy3+ respectively. Two picrate anions are coordinated to the metal ion through their phenolic
oxygen and the oxygen of the nitro group, to give rise to the coordination number of (10) in B18-crown-6
complexes, and one picrate anion is coordinated to the metal ions in 221-cryptand to give rise to the
coordination number (9). These coordination numbers are not uncommon since lanthanides offer the possibility
of a wide range of coordination numbers (up to 12), although coordination numbers (8) and (9) are the favorable
but other coordination numbers exist too. The UV Visible Spectra of the prepared complexes confirmed their
formation through the simple shifts and changes of intensities of their peaks since it is known that the f orbitals
are deeply buried inside the atom and are well shielded from the environment so upon complexation with
ligands, only minimal changes are observed in the electronic absorption and emission spectra, such as small
displacements in the peak positions, and changes in the relative intensities of some of the emission peaks. All
the prepared complexes are of explosive nature at a temperature higher than (260 C) as it is indicated by their
thermal analysis which is the nature of all picrate compounds and a common behavior in most nitro compounds.
All the prepared complexes were tested in-vitro against four types of pathogenic bacteria, one gram positive
(Staphylococcus aureus) and three gram negative (E. Coli, Salmonella, and Pseudomonas aeruginosa), and the
results were compared to that of the broad spectrum antibiotic Chloramphenicol. The results were very good in
comparison to the antibiotic and they were the best against pseudomonas aeruginosa. Pseudomonas aeruginosa
is resistant to most of the well-known antibiotics, and chloramphenicol showed no activity at all against
Pseudomonas aeruginosa while all the prepared complexes showed very good results, their inhibition zones
measured in millimeters are listed in table (6). One of the expected mechanisms for the action of these
complexes on the tested bacteria is believed to be related to the metal-chelation or the effect of the chelate (the
ligand) on the metal ion. The most important property of the chelating agents (ligands), in lanthanide chelate
Synthesis, Characterization and Antibacterial Activity of New Complexes of Some Lanthanide
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complex, is its ability to alter the behavior of lanthanide ion with which it binds in biological systems, and the
chelation markedly modifies the bio distribution and excretion profile of the lanthanide ions.
Acknowledgements
We are grateful for all those who helped and supported us during our work in the department. And I
present my special thanks and gratitude to my supervisors Dr. Basim I. Al-Abdaly and Dr. Mohammed H. A.
Al-Almery for their guidance, efforts, knowledge and support.
Table (1): Elemental analysis, colors, melting points, magnetic moments and the conductivity values of the
Metal salts and their corresponding complexes
Table (2): The absorption frequencies of picric acid and lanthanide picrates
Compound
ʋ (O-H) cm-1
ʋ (N-O) cm-1
δ (C-H) cm-1
ʋ (C-O) cm-1
Picric acid
3105
1527
1342
941
919
1088
Pr(Pic)3.6H2O
3502
1541
1360
921
908
1085
Nd(Pic)3.6H2O
3472
1541
1362
943
926
1083
Dy(Pic)3.3H2O
3495
1525
1340
919
1087
Table (3): The absorption frequencies of ligands and complexes
Compound
ʋ (C-
H)
aromat
ic
cm-1
ʋ(C-H)
CH2
group
cm-1
δSci.
CH2
group
cm-1
δ
wag.
CH2
group
cm-1
δroc
CH2
group
cm-1
ʋ (C-O-
C)
cm-1
δ(C-H)
aromati
c cm-1
ʋ
(C=C)
Stretch
cm-1
B18-crown-6
3053
2929
1454
1355
1255
850
1221
1117
…..
1627
[PrB18C6
(Pic)2]Pic.2H2O
3098
2877
1495
1362
1273
847
1122
1082
922
953
1634
[NdB18C6
(Pic)2]Pic.H2O
3102
2874
1425
1364
1273
847
1122
1082
926
1612
[DyB18C6
(Pic)2]Pic.H2O
3110
2872
1425
1364
1277
849
1124
1082
926
947
1630
221-cryptand
…..
2873
1471
1446
1355
1292
829
1099
1029
…..
…..
Formula
M.wt.(gm/mole)
C%
Cal.
(found)
H%
Cal.
(found)
N%
Cal.
(found)
M%
Cal.
(found)
Color
M.P. 0C
Magneti
c
moment
BM
1cm2.mol-1)
Pr(Pic)3.6H2O
933.2866
23.165
(23.055
)
1.944
(1.823)
13.507
(13.452)
15.098
(14.897)
yellow
98 100
4.4
…..
Nd(Pic)3.6H2O
936.6189
23.082
(22.938
)
1.937
(1.902)
13.459
(13.323)
15.400
(15.304)
Deep
yellow
59 62
5.9
…..
Dy(Pic)3.3H2O
900.8333
23.999
(23.713
)
1.343
(1.137)
13.994
(13.802)
18.039
(17.754)
Bright
yellow
65 68
11.1
…..
[Pr(B18C6)(Pic)2]Pic.2H2
O
1173.583
34.796
(34.250
)
2.920
(2.830)
10.741
(10.410)
12.007
(11.850)
yellow
60 62
5.4
50
[Nd(B18C6)(Pic)2]Pic.H2
O
1158.9001
35.237
(35.052
)
2.783
(2.620)
10.878
(10.680)
12.446
(12.146)
orange
75 80
8.9
50
[Dy(B18C6)(Pic)2]Pic.H2
O
1177.1601
34.650
(34.450
)
2.740
(2.630)
10.709
(10.520)
13.804
(13.680)
Dark
yellow
80 84
11.2
50
[Pr(221)(Pic)]Pic2.H2O
1175.645
34.735
(34.087
)
3.429
(3.850)
13.105
(12.614)
11.986
(11.542)
Dark
orange
110 112
5.8
80
[Nd(221)(Pic)]Pic2.7H2O
1287.0685
31.728
(31.541
)
4.072
(3.821)
11.971
(11.432)
11.207
(11.013)
orange
110 114
7.1
60
[Dy(221)(Pic)]Pic2.2H2O
1215.2525
33.603
(33.090
)
3.483
(3.247)
12.678
(12.349)
13.372
(13.127)
orange
104 108
11.6
70
Synthesis, Characterization and Antibacterial Activity of New Complexes of Some Lanthanide
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[Pr (221)
(Pic)]Pic2.H2O
3097
2916
1491
1435
1364
1265
845
1070
1038
943
1612
1637
[Nd (221)
(Pic)]Pic2.7H2O
3094
2901
1489
1441
1364
1267
849
1064
1036
932
1610
1637
[Dy.(221).(Pic)]Pic2.2
H2O
3092
2878
1491
1433
1366
1269
845
1078
943
1636
Table (4): The absorption data of picric acid, lanthanide picrates, ligands and complexes
Compound
λ (nm)
A
Picric acid
359
220
1.421
1.480
Pr(Pic)3
357
213
1.260
1.385
Nd(Pic)3
344
203
1.127
2.825
Dy(Pic)3
357
204
1.622
3.476
B18-crown-6
337
278
0.018
2.893
[PrB18C6 (Pic)2]Pic.2H2O
380
254
0.833
1.077
[NdB18C6 (Pic)2]Pic.H2O
380
255
0.785
1.050
[DyB18C6 (Pic)2]Pic.H2O
380
253
0.662
0.820
221-cryptand
340
280
0.198
1.782
[Pr (221) (Pic)]Pic2.H2O
380
267
0.956
0.232
[Nd (221) (Pic)]Pic2.7H2O
380
259
0.976
0.636
[Dy (221) (Pic)]Pic2.2H2O
379
258
1.069
0.547
Table (5): The data of thermal analysis of the prepared complexes
Compound
Step
Temp. range
of the
decomposition
(0C)
Suggested formula of
the resultant
compound
m(%)
mass-loss
Temp. range of
thermal stability of
the complex (0C)
Cal.
Obs.
[PrB18C6 (Pic)2]Pic.2H2O
1
73 120
[Pr.B18C6(Pic)2]Pic
3.10
3.47
120 245
2
245 300
*
[NdB18C6 (Pic)2]Pic.H2O
1
49 66
[Nd.B18C6.(Pic)2]Pic
1.55
1.58
66 210
2
210 310
*
[DyB18C6 (Pic)2]Pic.H2O
1
45 76
[Dy.B18C6.(Pic)2]Pic
2.20
1.98
76 223
2
223 317
*
[Pr (221) (Pic)]Pic2.H2O
1
52 120
[Pr.(221).(Pic)]Pic2
2.28
2.22
120 220
2
220 287
*
[Nd (221) (Pic)]Pic2.7H2O
1
47 205
[Nd.(221).(Pic)]Pic2
9.78
10.67
205 263
2
263 322
*
[Dy (221) (Pic)]Pic2.2H2O
1
101 175
[Dy.(221).(Pic)]Pic2.
4.38
4.71
175 198
2
198 236
*
15.42
3
236 325
*
(*): explosive material (unidentified)
Table (6): Inhibition zones of the ligands, prepared complexes and the broad spectrum antibiotic measured in
millimeters (concentration of the samples 10 mg/ml=10000µg/ml)
Compound
Inhibition
zone(mm)
Escherichia coli
Inhibition
zone(mm)
Staphylococcus
aeureus
Inhibition
zone(mm)
Salmonella
Inhibition zone(mm)
Pseudomonas aeruginosa
DMSO
_
_
_
_
Chloramphinicol
22.5
13.0
25.5
_
B18-crown-6
-
-
-
-
221-cryptand
-
-
-
-
[PrB18C6 (Pic)2]Pic.2H2O
19.0
23.0
20.5
20.0
Synthesis, Characterization and Antibacterial Activity of New Complexes of Some Lanthanide
www.iosrjournals.org 38 | Page
[NdB18C6 (Pic)2]Pic.H2O
16.5
17.5
18.0
20.0
[DyB18C6 (Pic)2]Pic.H2O
12.0
19.0
17.5
18.5
[Pr (221) (Pic)]Pic2.H2O
12.0
18.0
16.0
16.5
[Nd (221) (Pic)]Pic2.7H2O
18.0
20.5
18.5
19.0
[Dy (221) (Pic)]Pic2.2H2O
13.5
17.0
15.5
16.5
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