Peroxo complexes of uranium(VI) containing nitrogen and oxygen donor ligands1

Article abstract of DOI:10.1134/S003602361208013X

The uranium(VI) peroxo complexes containing Mannich base ligands having composition [UO(O₂)L-L(NO₃)₂] {where L-L = morpholinobenzyl acetamide (MBA), piperidinobenzyl acetamide (PBA), morpholinobenzyl benzamide (MBB), piper

Full text of DOI:10.1134/S003602361208013X

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 8, pp. 1079–1088. © Pleiades Publishing, Ltd., 2012.
COORDINATION COMPOUNDS
Peroxo Complexes of Uranium(VI) Containing Nitrogen
and Oxygen Donor Ligands1
Balgar Singh, Simpy Mahajan, H. N. Sheikh, Mohita Sharma, and Bansi Lal Kalsotra
Department of Chemistry, University of Jammu, Jammuꢀ1800 06 (India)
eꢀmail: hnsheikh@rediffmail com
Received December 28, 2010
Abstract—The uranium(VI) peroxo complexes containing Mannich base ligands having composition
[
UO(O2)LꢀL(NO3)2] {where LꢀL = morpholinobenzyl acetamide (MBA), piperidinobenzyl acetamide
(PBA), morpholinobenzyl benzamide (MBB), piperidinobenzyl benzamide (PBB), morpholinomethyl benꢀ
zamide (MMB), piperidinomethyl benzamide (PMB), morpholinobenzyl formamide (MBF), piperidiꢀ
nobenzyl formamide (PBF)} are reported. In a typical reaction UO2(NO3)2 6H2O (1 mmol, 0.502 g) was
⋅
dissolved in methanol. An equimolar (1 mmol) methanolic solution (30 mL) of the ligand (Mannich bases)
was added to a solution of uranyl nitrate followed by addition of potassium hydroxide (KOH) (2 mmol, 0.1122 g).
The solution was refluxed for 15 min and then 10 mL of 30% hydrogen peroxide (H2O2) was added dropwise
and was refluxed for an additional 1 h. The synthesized complexes have been characterized by various physꢀ
icoꢀchemical techniques, viz. elemental analysis, molar conductivity, magnetic susceptibility measurements,
infra red, electronic, mass spectral and TGA/DTA studies. These studies revealed that the synthesized comꢀ
plexes are nonꢀelectrolytic and diamagnetic in nature. The ligands are bound to metal in a bidentate mode
through carbonyl oxygen and the ring nitrogen. Thermal analysis result provides conclusive evidence for the
absence of water molecule in the complexes. Mass spectra confirm the molecular mass of the complexes.
Antibacterial activity of complexes revealed enhanced activity of complexes as compared to corresponding
free ligands. Molecular modeling suggests pentagonal bipyramidal structure for complexes.
DOI: 10.1134/S003602361208013X
1
Metal peroxo complexes have been the object of try [27, 28]. Studies on metal complexes of the formꢀ
intense investigation for the past several years, for a
variety of reasons including their role as oxidation catꢀ
alyst [1, 2] and biochemical relevance [3–10]. They
are widely used in stoichiometric as well as catalytic
oxidation in organic and biochemistry [11], for examꢀ
ple in the oxidation of thioanisole [12, 13], methylꢀ
benzenes [14], tertiary amines, alkenes, alcohols [15,
16], bromide [17] and also in olefin epoxidations [18–
22]. Peroxo complexes of molybdenum and tungsten
are attracting interest as oxidants in organic synthesis
[23]. As uranium somewhat resembles the group VIB
elements, it was of interest to discover whether it
would form analogous peroxo complexes which conꢀ
tain organic moieties. The preeminence of the UO2
group distinguishes uranium from molybdenum and
tungsten, however, and this factor may have hitherto
prevented the generation of peroxo complexes from
uranyl salts and organic reagents. Various peroxo comꢀ
plexes of uranium have been reported with organic
ligands [24]. The coordination number for metal
chelates of Th(IV) and UO2(VI) have been reported
[25, 26].
aldehyde and benzaldehydeꢀbased Mannich bases
have already been reported [29]. The synthesis of
Nꢀ(morpholinobenzyl) benzamide and its complexꢀ
ation with CuII, CoII, NiII and ZnII has been
reported [30]. In the present manuscript we describe
the synthesis and characterization of peroxo comꢀ
plexes of uranium(VI) with some formaldehyde and
benzaldehydeꢀbased Mannich base ligands. The strucꢀ
tures of ligands are given in scheme.
O
O
N CH HN C CH3
MBA
O
N CH HN C CH3
Metal complexes of Mannich bases have played a
vital role in the development of coordination chemisꢀ
PBA
Scheme 1. Structure of ligands.
1
The article is published in the original.
1079

1080
SINGH et al.
EXPERIMENTAL
dure [34]. In a typical reaction UO2(NO3)2
⋅
6H2O
(1 mmol, 0.502 g) was dissolved in methanol. An
equimolar (1 mmol) methanolic solution (30 mL) of
the ligand (Mannich bases) {MBA (0.234 g), PBA
(0.232 g), MBB (0.296 g), PBB (0.294 g), MBF
(0.220 g), PBF (0.218 g), MMB (0.220 g), PMB
(0.218 g)} was added to a solution of uranyl nitrate
solution followed by addition of potassium hydroxide
(KOH) (2 mmol, 0.1122 g). The solution was refluxed
for 15 min. Then 10 mL of 30% H2O2 was added dropꢀ
wise and was refluxed for an additional 1 h. The resultꢀ
ing yellow coloured precipitates were filtered after
cooling and washed successively with methanol, ether
and dried in vacuo.
All the reagents used were chemically pure and of
analytical reagent grade. Solvents used were purified
and dried according to standard procedures [31].
Dimethyl sulphoxide (Ranbaxy), dimethyl formamide
(Qualigens), and ethanol (commercial) were used after
distillation; morpholine (Ranbaxy), piperidine (SDS),
benzaldehyde (Ranbaxy), benzamide (Thomas Baker),
acetamide (Ranbaxy), formaldehyde (Ranbaxy), forꢀ
mamide (Loba), uranyl nitrate (SISCO) and hydrogen
peroxide (Merck) were used as supplied. The ligands
were prepared by the reported method [30, 32]. The
analysis of uranium was carried out gravimetrically as
uranyl oxinate UO2(C9H6ON)2C9H7ON after decomꢀ
posing the complex with concentrated nitric acid [31].
Carbon, hydrogen, nitrogen were analyzed micro anaꢀ
lytically using CHNS analyzer Leco Modelꢀ932. The
total peroxide content of the complexes was deterꢀ
mined by adding a weighed amount of the compound
to a cold solution of 1.5% boric acid (w/v) in 0.7 M
sulfuric acid (100 mL) and then titrating against stanꢀ
dard Cerium(IV) solution [33]. Molar conductivity of
complexes was measured at room temperature by a
Digital Conductivity Meter of model 611E having a
conductivity cell with a cell constant of 1.0 + 10%
using 10–3 molar solution of complexes in DMF. Magꢀ
netic susceptibility measurements were carried out by
Gouy’s method at room temperature using
Hg[Co(NCS)4] as standard. IR spectra of complexes
over the region 400–4000 cm–1 were recorded on Perꢀ
kin Elmer’s FTIR spectrophotometer model RX1,
using KBr discs. Melting points were determined on
Analab melting point apparatus and are corrected
should be replaced by corrected. Mass spectral data
were obtained on ESIꢀesquires 3000 Bruker Daltonics
spectrometer. Electronic spectra over the region 200–900
nm were recorded by UVꢀvisible single beam spectroꢀ
photometer systronics using 10–3 M DMF solution of
complexes. TGA/DTA studies were recorded on Linꢀ
seis STA PTꢀ1000 (Pyris Diamond) thermoanalyser at
UO2 NO ⋅ 6H2O + H2O2 + LꢀL
(
)
3
2
→ UO O LꢀL NO
+ 7H O
2
(
)
(
)
]
[
2
3
2
Antimicrobial study. The invitro biological screenꢀ
ing effects of the investigated compounds (Table 6)
were tested against two bacteria viz. Staphylococcus
aureus and Escherichia coli. The paper disc plate
method (disc diffusion method) described by Skinner
was employed to evaluate bactericidal activity using
agar nutrient as the medium. The test solutions were
prepared by dissolving the ligands in ethanol and the
complexes in DMF. In a typical procedure, discs of filꢀ
ter paper were dipped into the solution of each chemꢀ
ical separately for two hours. Seeded petri plates were
then prepared by pouring the nutrient agar medium in
each petri plate, followed by inoculation of bacterial
suspension. After the solidification of the medium, the
discs of chemicals were put on seeded plates and the
plates were incubated at 25 C for 24 h. PDA mixed
°
with test solution was poured into sterilized petriꢀ
plates.
RESULTS AND DISCUSSION
The analytical and spectroscopic results (Tables 1–3)
showed that all complexes have general formula
the heating rate of 10°C per minute in an atmosphere
[UO(O2)LꢀL(NO3)2] (where LꢀL = MBA, PBA,
of air in the temperature range 23–1000
°C.
MBB, PBB, MMB, PMB, MBF, PBF). The isolated
solid complexes are stable to air and light and are
insoluble in common organic solvents but soluble in
DMSO and DMF. All the complexes are yellowish
colored. All complexes decompose on heating and do
not have sharp melting points.
Conductance and magnetic measurements. The
molar conductivity values, λM of the complexes (Table 1)
measured in DMF solution lie in the range of 8–
13 ohm–1 cm2 mol–1 which indicates the nonꢀelectroꢀ
lytic nature of these complexes [35]. Moreover, magꢀ
netic studies show that all the complexes are diamagꢀ
netic as expected for d0 system of uranyl(VI) peroxo
complexes.
Preparation of ligands. The ligands MBA, PBA,
MBB, PBB, MMB, PMB, MBF, PBF were prepared
by the reported method [30]. In a typical reaction aceꢀ
tamide/benzamide/formamide (0.1 mol) in 20 mL of
ethanol was mixed with piperidine/morpholine
(0.1 mol) with constant stirring to get a clear solution
under ice cooled condition. To the resulting solution,
benzaldehyde/formaldehyde (0.1 mol) was added
dropwise with stirring for 15–20 min under ice cooled
condition.
The reaction mixture was then kept at room temꢀ
perature for 2 days. The colourless solid obtained was
filtered, washed with distilled water and recrystallized
from ethanol.
IR spectra. The characteristic IR absorptions and
Preparation of uranyl peroxo complexes. The perꢀ their assignments for the ligand and metal are given in
oxo complexes were synthesized by reported proceꢀ Table 2. The IR spectra of all the complexes exhibit
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 8 2012

PEROXO COMPLEXES OF URANIUM(VI)
1081
Table 1. Analytical data and some physical properties of uranium(VI) peroxo complexes
Empirical
formula
Found
H
(Calcd.) %
U
Dec.
Colour temp.
C)
λM
(Ohm–1 cm2 mol–1)
Complex
(formula wt.)
O22–
(
°
C
N
g mol–1
[UO(O2)MBA(NO3)2] UCl3Hl8N4O11 Yellow >320 24.19 2.73
(644)
[UO(O2)PBA(NO3)2] UC14H20N4O10 Greenish >335 26.11 3.08
8.66
4.95 36.90
8
(24.23) (2.80) (8.70) (4.97) (36.96)
8.70 4.95 37.00
(26.16) (3.12) (8.72) (4.98) (37.07)
[UO(O2)MBB(NO3)2] UC18H20N4O10 Yellow >345 30.52 2.80 7.89 4.50 33.68
(704) (30.59) (2.83) (7.93) (4.53) (33.71)
[UO(O2)PBB(NO3)2] UC19H22N4O10 Yellow >331 32.36 3.10 7.91 4.50 33.78
(704) (32.39) (3.13) (7.95) (4.55) (33.81)
[UO(O2)MMB(NO3)2 UCl2H16N4O11 Yellow >340 22.82 2.50 8.85 5.05 37.75
(630) (22.86) (2.54) (8.89) (5.08) (37.78)
[UO(O2)PMB(NO3)2 UC13H18N4O10 Yellow >337 24.80 2.82 8.90 5.06 37.86
(628) (24.84) (2.87) (8.92) (5.10) (37.90)
[UO(O2)MBF(NO3)2] UC12H16N4O9 Yellow >343 28.21 2.65 9.33 5.33 39.75
(598) (28.23) (2.68) (9.36) (5.35) (39.80)
[UO(O2)PBF(NO3)2 UC7H14N4O10 Yellow >345 15.19 2.51 10.11 5.26 43.09
(552) (15.22) (2.54) (10.14) (5.30) (43.12)
10
13
11
8
yellow
(642)
9
12
10
bands characteristic of the coordinated oxo, peroxo ing bonding of the ligands through carbonyl oxygen
groups and the ligand molecule. The metal peroxo and ring nitrogen of morpholine/piperidine (Table 2).
group gives rise to three IR active vibrational modes. Ring nitrogens of alicyclic amines in various ligands
These are due to
ν
(O–O),
ν
asym(UO2) and
ν
sym(UO2)
.
have been reported to coordinate metal ion [37].
In MBB and PBB ligands, a sharp band due to
These characteristic vibration modes appear around
861–900, 669–707 and 460–508 cm–1 respectively in
η
ν
(C=O) of amide group appeared at 1631 and
1637 cmꢀ1 respectively and band due to
(C–N–C) of
morpholine and piperidine rings appeared at 1137 and
1120 cm–1 respectively. Another band due to
(N–H)
stretching appeared at 3174 and 3180 cm–1 respecꢀ
tively. In both the complexes [UO(O2)MBB(NO3)2
and UO(O2)PBB(NO3)2], the (C=O) band
complexes. These bands confirm the
2ꢀcoordination
ν
of the peroxo group [36]. In all complexes, an addiꢀ
tional sharp band around 930–973 cm–1 has been
ν
assigned to ν(U=O) mode [3] and [24]. Thus, IR
spectra confirms the presence of [UO(O2)]2+ moiety
]
in these complexes.
[
ν
In order to study the binding mode of Mannich appeared at 1630 and 1625 cm–1, the band due to
base ligands with uranium in the peroxo complexes,
ν
(C–N–C) of morpholine and piperidine rings
the IR spectra of the free ligands were compared with appeared at 1129 and 1113 cm–1 respectively. The
those of corresponding metal complexes (Table 2).
In MBA and PBA ligands, a sharp band at 1641 and
band due to (N–H) stretching appeared at 3155 and
ν
3167 cm–1 respectively. All the bands exhibit negative
shifts relative to their corresponding positions in free
ligands, indicating the coordination through carbonyl
oxygen and ring nitrogen [38].
1631 cm–1 appeared due to
ν
(C=O) of amide group
respectively and another band assigned to (C–N–C)
ν
of morpholine and piperidine rings appeared at 1111
and 1138 cm–1 respectively (Table 2). Also, bands at
In MMB and PMB ligands,
(C–N–C) of morpholine and
ing of ligands. In the corresponding complexes piperidine rings appeared at 1150 and 1113 cm–1 and
UO(O2)MBA(NO3)2 and UO(O2)PBA(NO3)2], another band due to (N–H) stretching appeared at
these bands appear at lower frequencies at 1631, 1621, 3058 and 3056 cm–1 respectively. In both the complexes
1104, 1112, 3080 and 3156 cm–1 respectively indicatꢀ
UO(O2)MMB(NO3)2 and UO(O2)PBB(NO3)2],
ν
(C=O) appeared at
3121 and 3161 cm–1 appeared due to
ν
(NꢀH) stretchꢀ 1639 and 1640 cm–1,
ν
[
]
[
ν
[
]
[
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1082
SINGH et al.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 8 2012

PEROXO COMPLEXES OF URANIUM(VI)
1083
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1084
SINGH et al.
Table 4. Electronic Spectral data (nm) of uranium(VI) perꢀ
oxo complexes
ligands are coordinated to uranium in a bidentate
chelating mode.
In these complexes three additional bands which are
not present in the spectra of free ligands are observed. Of
S. No.
Complex
λ
(nm)
these a band appears around 985–980 cm–1 assigned to
1.
2.
3.
4.
5.
6.
7.
8.
[UO(O2)MBA(NO3)2]
[UO(O2)PBA(NO3)2]
[UO(O2)MBB(NO3)2]
[UO(O2)PBB(NO3)2]
[UO(O2)MMB(NO3)2]
[UO(O2)PMB(NO3)2]
[UO(O2)MBF(NO3)2]
[UO(O2)PBF(NO3)2]
307, 331, 357
314, 329, 354
308, 332, 357
310, 330, 355
313, 320, 353
311, 335, 360
306, 337, 361
305, 340, 359
–
νs(NO) (
ν
)
mode of NO3 group. Two more bands in
2
the region 1466–1458 and 1376–1384 cm–1 of the
coordinated nitrato group are assigned as νa(NO2) ν5
and νs(NO2) ν1 modes respectively. A difference in freꢀ
quencies between the higher energy bands (Δν
(ν5 –
ν1)
≈
82 cm–1), suggests unidentate coordination of
the nitrato group [39, 40]. For bidentate coordination
of nitrato group, the difference should be of the order
180 cm–1 [38].
TGA/DTA. TGA and DTA thermogram are
recorded up to 1000
°
C
for a representative complex
C/min
[
UO(O2)MBA(NO3)2] at a heating rate of 10
°
.
The TG curve (Fig. 1) for the complex corresponds to
weight loss of 14.0%. This weight loss approximates to
loss of peroxo and nitrate group (theoretical weight
these bands appeared at lower frequencies, i.e.,
(C=O) band at 1631 and 1633 cm–1,
(C–N–C) at
ν
ν
loss 14.6%). Further heating up to 1000 C shows a
°
1145 and 1109 cm–1 and
(N–H) stretching band at gradual weight loss of 2.3% (theoretical weight loss
ν
3045 and 3039 cm–1 respectively, indicating the coorꢀ
dination through carbonyl oxygen and ring nitrogen.
2.5%) attributable to loss of oxo group. A broad exoꢀ
thermic curve all along indicates oxidation of ligand
and decomposition of complex.
In MBF and PBF ligands, a sharp band due to
ESI mass spectra. The ESI mass spectra have been
recorded for complexes [UO(O2)MBA(NO3)2] (1)
and [UO(O2)MBB(NO3)2] (2). Both the complexes
show extensive fragmentation and only the most abunꢀ
dant fragment ions with relative isotopic abundance
ν
(C=O) of amide group appeared at 1631 and 1644 cm–1
,
band due to
rings appeared at 1138 and 1116 cm–1 and another
band due to (N–H) stretching appeared at 2971 and
3027 cm–1 respectively. In both the complexes
UO(O2)MBF(NO3)2 and UO(O2)PBF(NO3)2],
these bands appeared at lower frequencies, i.e.,
(C=O) band at 1626 and 1632 cm–1, the
(C–N–C)
ν
(C–N–C) of morpholine and piperidine
ν
are given in Table 3. The complex (
ular ion peak at m/e 643.34 for fragment
[UO(O2)C13H18N4O8]+ and the complex (
) at m/e
705.41 for fragment [UO(O2)C18H20N4O8]+
1) displayed molecꢀ
[
]
[
2
.
ν
ν
band at 1129 and 1108 cm–1 and the
(N–H) stretchꢀ
ν
Masses of fragment ions listed in table are calcuꢀ
lated using uranium atom mass equal to 238.05 amu.
ing band at 2961 and 3015 cm–1 respectively, indicatꢀ
ing the coordination through carbonyl oxygen and
For complex (1) base peak appears at m/e 322.33 corꢀ
ring nitrogen. Thus, IR spectra confirm that the responding to [UC5H8NO]+ and for complex (
2) it
Table 5. Selected bond lengths and bond angles for the complex [UO(O2)MBA(NO3)2]
Bond
Bond length (Å)
Angle
Bond angles (°)
N(5)–U(35)
O(16)–U(35)
O(36)–U(35)
O(37)–U(35)
O(38)–U(35)
O(39)–U(35)
O(40)–U(35)
O(37)–O(38)
O(39)–N(41)
O(40)–N(42)
2.14505
2.04156
1.98006
2.08295
2.08536
2.08533
2.09828
1.30327
1.33671
1.34338
N(5)U(35)O(16)
N(5)U(35)O(36)
O(36)U(35)O(16)
O(36)U(35)O(40)
O(36)U(35)O(39)
O(36)U(35)O(38)
O(36)U(35)O(37)
O(16)U(35)O(37)
O(38)U(35)O(37)
O(16)U(35)O(40)
83.55
120.55
52.599
63.082
110.13
70.884
54.857
92.713
36.439
58.827
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 8 2012

PEROXO COMPLEXES OF URANIUM(VI)
1085
Table 6. Antibacterial activity of the ligands and their comꢀ
plexes at 200 ppm
appears at m/e 323.38 corresponding to
[UC5H8NO]+
.
Uranium has two isotopes having atomic masses
235 and 238 amu. Their relative abundances are 0.70
and 100% respectively. Here, the most intense isotope
peak is set to 100% and percentages of other isotope
peaks are computed relative to it (Table 3). The molecꢀ
ular ion and fragments peaks containing uranium
appear in doublet at M+* and Mꢀ3* and ratios of their
relative intensities confirm the presence of Uꢀ235 and
Uꢀ238 isotopes in the fragments. In addition M+1*
and M+2* peaks also appear due to isotopic contribuꢀ
tion of C, H, N and O atoms.
Zone of inhibition in mm
S.
No.
Compound
Staphyloꢀ Escherichia
coccus aureus
coli
1. PBA(L1)
1.4
1.8
0.8
0.6
2. PBB(L2)
3. [UO(O2)PBA(NO3)2]
(UL1)
2.3
1.8
4. [UO(O2)PBB(NO3)2]
(UL2)
2.9
4.5
1.3
1.2
5. Control
Electronic spectra. The electronic spectra of the
metal complexes were recorded in 10–3 M DMF soluꢀ
tion (Table 4) in the UVꢀvisible region. The spectra
show three transitions in the range 305–314, 320–340
obtained from the energyꢀminimized structures are
given in Table 5. The probable structure thus exhibit
molecular properties in conformity with experimenꢀ
tally determined data.
and 353–361 nm ascribed to π → π
*
,
n
→ π
*
and the
uraꢀ
charge transfer transitions from uranyl oxygen
→
2−
O2
nium, i.e. LMCT,
π
→
U [35] and [41]. There was
On the basis of analytical, IR, UVꢀVis. and mass
spectral data combined with molecular modeling calcuꢀ
lations, a pentagonal bipyramidal geometry has been
proposed and the representative structure for the comꢀ
plex, [UO(O2)MBA(NO3)2], is given in Figs. 2a, 2b.
no evidence of any d–d transition. This result is conꢀ
sistent with the presence of uranium(VI) system in the
complexes.
Molecular modeling. Since single crystals could not
be grown for these complexes, it was thought worthꢀ
while to obtain structural information through molecꢀ
Antibacterial study. The in vitro biological screenꢀ
ular modeling. The molecular modeling calculations ing effects of the ligands and the corresponding comꢀ
for the complex, [UO(O2)MBA(NO3)2], has been carꢀ plexes were tested against two bacteria viz. Staphyloꢀ
ried out using Hyperchem release 8.0 professional verꢀ coccus aureus and Escherichia coli. The paper disc
sion, which allows for rapid structural building, geometry plate method (disc diffusion method) [43] described
optimization, and molecular display [42]. Energy values by Skinner was employed to evaluate bactericidal
obtained for the complex indicate pentagonal bipyramiꢀ activity using agar nutrient as the medium. The test
dal geometry. Figures 2a and 2b show the energyꢀminiꢀ solutions were prepared by dissolving the ligands in
mized structure for complex, [UO(O2)MBA(NO3)2]. ethanol and the complexes in DMF. In a typical proꢀ
The lowest energy values obtained from this study for cedure, discs of filter paper were dipped into the soluꢀ
the complex, [UO(O2)MBA(NO3)2] is 317.599 kcal tion of each chemical separately for 2 h. Seeded petri
mol–1. Selected bond lengths (Å) and bond angles (°) plates were then prepared by pouring the nutrient agar
166Cel
76 ug/min
100
72Cel
48 ug/min
282Cel
46 ug/min
50
40
30
20
10
482Cel
26 ug/min
750Cel
21 ug/min
115
110
105
100
95
50
DТG
DТА
0
–50
–100
–150
–200
–250
–300
–350
25Cel
100%
0
99Cel
96.8%
–10
–20
–30
–40
–50
–60
200Cel
93.0%
300Cel
89.9%
400Cel
87.8%
996Cel
83.7%
90
ТG
500Cel
86.0%
600Cel
85.1%
699Cl
84.5%
800Cel
83.6%
900Cel
83.5%
85
100 200 300 400 500 600 700 800 900 1000
Temp, °C
Fig. 1. TGA/DTA thermogram of [UO(O )MBA(NO ) ].
2
3 2
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 8 2012

1086
SINGH et al.
(а)
38
37
19
36
20
45
39
1
41
35
18
21
2
40
17
43
23
16
5
46
47
4
42
6
5
25
22
33
28
24
44
7
14
29
10
26
34
8
11
32
9
13
31
27
12
30
(b)
O
O
H
O
H
O
N
O
C
U
H
O
O
O
C
H
O
C
N
C
N
C
H
H
H
H
H
O
C
O
C
C
N
H
H
H
C
C
H
C
H
Fig. 2. (a) Atomic labeling; (b) Energy minimized structure of the complex, [UO(O )MBA(NO ) ].
2
3 2
medium in each petri plate, followed by inoculation of the growth of the inoculated microorganisms was
bacterial suspension. After the solidification of the affected. The inhibition zone (clear area around the
medium, the discs of chemicals were put on seeded disc) developed on each plate was measured (Fig. 3).
plates and the plates were incubated at 25 C for 24 h. The work was carried out under aseptic conditions and
°
During this period, the test solution was diffused and a standard antibiotic Rifampicin was used as the conꢀ
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 8 2012

PEROXO COMPLEXES OF URANIUM(VI)
1087
(L1/L2)
Control
(Rifampicin)
(UL1/UL2)
Antibacterial studies of ligands and complexes against Staphylococcus aureus
(L1/L2)
Control
(Rifampicin)
Antibacterial studies of ligands and complexes against Escherichia coli
(UL1/UL2)
Fig. 3. Antibacterial activity of the ligands and their complexes at 200 ppm.
8. M. Sharma, H. N. Sheikh, M. S. Pathania, and B. L. Kalꢀ
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plexes indicates that the complexes exhibit higher
activity than the free ligands (Table 6).
Polym. 68, 876 (2008).
Therefore, the metal complexes are more potent
than the parent ligands. The chelation theory accounts
for the increased activity of the metal complexes [44].
Chelation reduces the polarity of the metal atom
mainly because of partial sharing of its positive charge
with the donor groups, thereby, increasing the liphoꢀ
philic nature of the central atom which subsequently
favours its permeation through the lipid layer of the
cell membrane. Blank tests showed that ethanol and
DMF used in the preparation of the test solutions does
not affect the test organism. Each treatment was
repeated three times to minimize error and average
data were taken as the final result.
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