Effect of the substitutional groups on the electrochemistry, kinetic of thermal decomposition and kinetic of substitution of some uranyl Schiff base complexes

Article abstract of DOI:10.1007/s13738-016-0807-0

Uranyl(VI) complexes, [UO₂(X-saloph)(solvent)], where saloph denotes N,N'-bis(salicylidene)-1,2-phenylenediamine and X = NO₂, Cl, Me, H; were synthesized and characterized by ¹H NMR, IR, UV-Vis spectroscopy, thermal gravim

Full text of DOI:10.1007/s13738-016-0807-0

J IRAN CHEM SOC
DOI 10.1007/s13738-016-0807-0
ORIGINAL PAPER
Effect of the substitutional groups on the electrochemistry, kinetic
of thermal decomposition and kinetic of substitution of some
uranyl Schiff base complexes
1
1
2
2
Zahra Asadi · Rahele Nasrollahi · Michal Dusek · Karla Fejfarova ·
1
1
Mohammad Ranjkeshshorkaei · Fahimeh Dehghani Firuzabadi
Received: 5 October 2015 / Accepted: 4 January 2016
©
Iranian Chemical Society 2016
Abstract Uranyl(VI) complexes, [UO (X-saloph)(sol-
vent)], where saloph denotes N,N’-bis(salicylidene)-
Keywords Nano uranyl schiff base complex · Kinetic
study · X-ray crystallography · Anticancer activity · TG ·
Cyclic voltammetry
2
1
,2-phenylenediamine and X = NO , Cl, Me, H; were
2
1
synthesized and characterized by H NMR, IR, UV–Vis
spectroscopy, thermal gravimetry (TG), cyclic voltamme-
try, elemental analysis (C.H.N) and X-ray crystallography.
Introduction
X-ray crystallography of [UO (4-nitro-saloph)(DMF)]
2
revealed coordination of the uranyl by the tetradentate
Schiff base ligand and one solvent molecule, resulting in
Schiff base ligands form stable complexes with most tran-
sition metal ions, which can be used as biological model
compounds [1–5]. Coordination complexes with substi-
tuted salicylaldehydes have structures with diverse stereo-
chemistry and a wide range of bonding interactions [6–9].
The linear dioxoactinoid (VI) ions, e.g., UO2 , have all
their exchangeable ligands in the plane perpendicular to the
linear axis. The “-yl” oxygens are substitution inert [10]
except in the case when the ion is excited by UV light [11–
13]. This coordination geometry indicates that the pathway
for ligand substitution reactions should be located in, or
close to, this plane, a very different situation from those
encountered in most other coordination geometries. How-
ever, studies of the mechanisms for ligand substitutions in
uranium (VI) complexes are scarce. Substitution mecha-
nisms have been discussed in [14, 15] and the experimen-
tal evidence seems to favor dissociative (D) or dissociative
seven-coordinated uranium. The complex of [UO (4-nitro-
2
saloph)(DMF)] was also synthesized in nano form. Trans-
mission electron microscopy image showed nano-particles
with sizes between 30 and 35 nm. The TG method and
analysis of Coats-Redfern plots revealed that the kinetics
of thermal decomposition of the complexes is of the first-
order in all stages. The kinetics and mechanism of the
exchange reaction of the coordinated solvent with tributyl-
phosphine was investigated by spectrophotometric method.
The second-order rate constants at four temperatures and
the activation parameters showed an associative mechanism
for all corresponding complexes with the following trend:
2
+
4
-Nitro > 4-Cl > H > 4-Me. It was concluded that the steric
and electronic properties of the complexes were important
for the reaction rate. For analysis of anticancer properties
of uranyl Schiff base complexes, cell culture and MTT
assay was carried out. These results showed a reduction of
jurkat cell line concentration across the complexes.
interchange (I ) mechanisms.
d
In this paper some tetradentate Schiff base ligands and
their uranyl complexes were synthesized and characterized
1
by H NMR, IR, UV–vis spectroscopy, thermal gravim-
etry (TG), cyclic voltammetry (CV), elemental analysis
*
Zahra Asadi
zasadi@shirazu.ac.ir
(C.H.N), and X-ray crystallography. Because of the impor-
tance of nano-structures in basic science as well as for tech-
nological applications [16–18], we also prepared one of the
complexes in nano form. X-ray crystallography and TG
revealed that one solvent molecule was coordinated weakly
to the uranium center, in comparison with the Schiff base
1
2
Chemistry Department, College of Sciences, Shiraz
University, Shiraz 71454, Islamic Republic of Iran
Institute of Physics ASCR, v.v.i, Na Slovance 2,
8
21182 Prague, Czech Republic
1
3

J IRAN CHEM SOC
and trans oxides. Thus it was interesting to study the kinet-
ics of exchange of this solvent molecule with tributylphos-
phine and the parameters affecting the rate constants such
as the electronic and the steric ones. From this point of view
the effect of substitutional groups on the redox potential of
these complexes was studied. The thermal stability and the
kinetics of thermal decomposition of these complexes was
also studied and revealed that only one solvent molecule is
coordinated to the central uranium. Beside them anticancer
activity of these complexes was also studied.
X
O
N
N
b
O
U
a
O
O
S
Fig. 1 Structural representation of the uranyl(VI) Schiff base com-
plex X = H, Me, NO , Cl, and S = solvent
2
Experimental
N,N’-bis(salicylidene)-1,2-phenylenediamine (saloph):
Yield: 72 %, Color: orange, m.p. = 150 °C, Anal. Found
Chemicals and apparatus
(
Calc.): C H N O (316.36): C, 75.86(75.93); H,
20 16 2 2
−1
1
4
,2-phenylenediamine,
-methyl-1,2-phenylenediamine, 4-nitro-1,2-phenylenedi-
4-chloro-1,2-phenylenediamine,
5.04(5.10); N, 8.65(8.85). IR (KBr, cm ): 3485(υO–H),
1
2900–3031(υC–H), 1611(υ
), 1481(υ ), H NMR
C=N
C=C
amine, salicylaldehyde, tri-n-butylphosphine (PBu ), meth-
anol (MeOH), acetonitrile (CH CN), potassium bromide
(250 MHz, CDCl , room temperature): δ(ppm) = 6.88–7.38
3
3
(m, 12H, ArH), 8.61(s, 2H, HC=N), 12.90 (s, 2H, OH).
3
−1
−1
(
KBr), uranylacetatedihydrate UO (OAc) , DMSO-d6,
Uv–vis. (acetonitrile): λ (nm), ε (M cm ) = 206(sh),
2
2
max
CDCl , tetrabutylammuniumperchlorate (Bu NClO ), and
226(sh), 265(~82,352), 328(~41,746).
3
4
4
diethyl ether were purchased commercially.
N,N’-bis(salicylidene)-4-Methyl-1,2-phenylenediamine
(4-Mesaloph): Yield: 95 %, Color: yellow, m.p. = 111 °C,
Anal. Found (Calc.): C H N O (330.38): C, 75.98(76.34);
All of the scanning UV–vis spectra were recorded by
using Perkin-Elmer Lambda 2 spectrophotometer equipped
with a Lauda-ecoline-RE 104 thermostat. FT-IR spec-
tra were run on a Shimadzu FTIR-8300 spectrophotom-
2
1
18
2
2
−1
H, 5.43(5.49); N, 8.55(8.48). IR (KBr, cm ): 3463(υO–H),
1
2900–3010(υC–H), 1612(υ
), 1488(υ ), H NMR
C=N
C=C
1
eter. H NMR spectra were recorded on a Bruker Avance
(250 MHz, DMSO-d , room temperature): δ(ppm) = 2.36
6
DPX-250 spectrometer in CDCl or DMSO-d solvents at
(s, 3H, CH ), 6.91–7.66 (m, 11H, ArH), 8.90(s, 2H,
3
6
3
a
b
2
50 MHz. Elemental analysis (C.H.N) was performed on
HC=N), 12.95 (s, H, OH ), 13.09 (s, H, OH ). UV–vis.
−1
−1
a C.H.N Thermo Finnigan Flash EA1112 analyzer. Cyclic
voltammetry (CV) spectra were obtained by using Auto lab
(acetonitrile): λ
(nm), ε (M cm ) = 263(~21,333),
max
326(~17,833).
3
02 N, a three-electrode system was utilized, i.e., a glassy
N,N’-bis(salicylidene)-4-chloro-1,2-phenylenediamine
(4-Clsaloph): Yield: 81 %, Color: yellow, m.p. = 138.5 °C,
Anal. Found (Calc.): C H N O Cl (350.80): C,
+
carbon working electrode, a reference electrode (Ag/Ag
in TBAP/acetonitrile solution), and a Pt auxiliary electrode.
Tetrabutylammonium perchlorate (TBAP) was used as sup-
porting electrolyte. Melting point was measured by BUCHI
2
0
15
2
2
68.39(68.48); H, 4.83(4.31); N, 7.90(7.99). IR (KBr,
−
1
cm ): 3417(υO–H), 2900–3150(υC–H), 1620(υ
),
C=N
1
5
35. Thermal gravimetric (TG) analyses were recorded on
1481(υ ), H NMR (250 MHz, DMSO-d , room tem-
6
C=C
Perkin-Elmer Pyris Diamond model. Transmission electron
microscopy (TEM) was performed on a Zeiss EM10C Acc
voltage 60 kV set. Incubator and ELISA reader (Bio-Tek’s
ELx808, USA) were used for anticancer studies. X-ray
crystallography was performed by the four-cycle diffrac-
tometer Gemini of Agilent Technologies (2012).
perature, TMS): δ(ppm) = 6.60–7.66 (m, 11H, ArH), 8.8
b a b
(s, 1H, H C=N), 8.9 (s, 1H, H C=N), 12.5 (s, 1H, OH ),
a
12.7 (s, 1H, OH ). UV–vis. (acetonitrile): λ
(nm), ε
max
−1
−1
(M cm ) = 213(~55,357), 255(sh), 327(~18,452).
N,N’-bis(salicylidene)-4-nitro-1,2-phenylenediamine(4-
Nitrosaloph): Yield: 72 %, Color: yellow, m.p. = 201 °C,
Anal. Found (Calc.):C H N O (361.36): C, 66.51(66.48);
20 15 3 4
−
H, 4.14(4.18); N, 11.69(11.63). IR (KBr, cm ): 3425(υ
O–
1
Synthesis of the ligands
1
H), 2900–3025(υC–H), 1612 (υ ), 1473(υ ), H NMR
C=N
C=C
All the tetradentate Schiff base ligands were synthesized
by the reaction of salicylaldehyde and different diamines
with the ratio of (2:1) in methanol solvent under reflux for
(250 MHz, CDCl , room temperature, TMS): δ(ppm) = 6.65–
3
b
8.33 (m, 11H, ArH), 8.95 (s, 1H, H C=N), 9.0 (s, 1H,
a
b
a
H C=N), 12.24 (s, 1H, OH ), 12.57 (s, 1H, OH ). UV–vis.
−1
−1
2
–4 h. After cooling and evaporating the solvent, products
(acetonitrile): λ
(nm), ε (M cm ) = 276(~28,035),
max
were filtered and washed with diethyl ether (Fig. 1).
342(sh).
1
3

J IRAN CHEM SOC
Synthesis of uranyl complexes
[UO (4-Me-saloph)(MeOH)] yield: 87 %, color: light
2
red, m.p. > 250 °C, anal. found (Calc.): C H N O U
2
2
20
2
5
Uranyl complexes were prepared by addition of uranyl ace-
tate dihydrate (5 mmol, 20 ml methanol), into a hot metha-
nolic solution of the Schiff base (5 mmol, 10 ml) (1:1 molar
ratio). The color of the solution changed to orange-red in a
few minutes. The mixture was then refluxed for 3 h. The
precipitate was washed with ether, followed by drying at
(630.44): C, 42.03(41.91); H, 3.18(3.20); N, 4.54(4.44). IR
−1
(KBr, cm ): 3450(υO–H), 2950–3050(υC–H), 1600(υ
),
C=N
1
1440(υ ), 906(υ
), 557(υU–N), 447(υU–O). H NMR
C=C
U=O
6
(250 MHz, DMSO-d , room temperature): δ(ppm) = 2.48
(s, 3H, CH ), 3.14 (d, 3H, MeOH), 4.09 (q, 1H, MeOH),
3
a
6.67–7.80 (m, 11H, ArH), 9.48 (s, 1H, H C=N), 9.67
b
5
0 °C in vacuum.
(s, 1H, H C=N). UV–vis. (acetonitrile): λ
(nm), ε
max
−1
−1
(
M
cm ) = 243(~41,041), 278(sh), 346(~19,375),
414(sh).
UO (4-Cl-saloph)(MeOH)] yield: 75 %, color: dark
Synthesis of a nano uranyl Schiff base complex
[
2
Nano uranyl Schiff base complex was synthesized by addi-
tion of methanolic solution of uranyl acetate dihydrate
red, m.p. > 250 °C, anal. found (Calc.): C H N ClO U
(650.86): C, 38.97(38.75); H, 2.53(2.63); N, 4.20(4.30). IR
21 17 2 5
−
1
(
5 mmol in 50 ml methanol) to the hot methanolic solution
(KBr, cm ): 3350(υO–H), 2927–3068(υC–H), 1600(υ
),
C=N
1
of Schiff base (5 mmol in 60 ml methanol). Metal solution
was added dropwisely in about 6–7 h. The mixture was
then refluxed for 24 h. Transmission electron microscopy
1438(υ ), 902(υ
), 580(υU–N), 439(υU–O). H NMR
C=C
U=O
(250 MHz, DMSO-d , room temperature): δ(ppm) = 3.15
6
(d, 3H, MeOH), 4.11 (q, 1H, MeOH), 6.67–7.93 (m, 11H,
b
a
(
3
TEM) showed nano-particles with sizes between 30 and
5 nm (Fig. 2).
UO (saloph)(MeOH)] yield: 79 %, color: orange,
ArH), 9.58 (s, 1H, H C=N), 9.67 (s, 1H, H C=N). UV–vis.
−1
−1
(acetonitrile): λ
(nm), ε (M cm ) = 244.4(~44,231),
max
[
284(~28,125), 342(~18,269), 415(sh).
2
m.p. > 250 °C, anal. found (Calc.): C H N O U (616.41):
[UO (4-nitro-saloph)(MeOH)] yield: 87 %, color: red,
2
1
18
2
5
2
C, 40.88(40.92); H, 2.92(2.94); N, 4.57(4.54). IR (KBr,
m.p. > 250 °C, anal. found (Calc.): C H N O U (661.41): C,
38.31(38.14); H, 2.54(2.59); N, 6.40(6.35). IR (KBr, cm ):
21 17 3 7
−1
−1
cm ): 3456(υO–H), 2885–3038(υC–H), 1607(υ
),
C=N
1
1
445(υ ), 908(υ
), 540(υU–N), 440(υU–O). H NMR
3350(υO–H), 2927–3067(υC–H), 1604(υ ), 1438(υ ),
C=C
U=O
C=N
C=C
1
(
(
250 MHz, DMSO-d , room temperature): δ(ppm) = 3.14
902.6(υ ), 551(υU–N), 439.7(υU–O). H NMR (250 MHz,
6
U=O
d, 3H, MeOH), 4.07 (q, 1H, MeOH), 7.50–7.80 (m, 8H,
DMSO-d , room temperature): δ(ppm) = 3.16 (d, 3H,
6
ArH), 9.59 (s, 2H, HC = N). UV–vis. (acetonitrile): λ
MeOH), 4.08 (q, 1H, MeOH), 6.70–8.66 (m, 11H, ArH),
max
−1
−1
b
a
(
nm), ε (M cm ) = 240(~9769), 278(sh), 341(4611),
13(sh).
9.63 (s, 1H, H C=N), 9.74 (s, 1H, H C=N). UV–vis. (ace-
−1
−1
4
tonitrile): λ (nm), ε (M cm ) = 304(~20,416), 341(sh),
max
422(~11,041).
Crystal growth for X‑ray crystallography
Slow diffusion of diethyl ether into a solution of the metal
complex in dimethylformamide (DMF) at room tempera-
ture produced crystals of the uranyl complex [UO (4-NO -
2
2
saloph)(DMF)]. The crystals were intensely colored. The
preparation from DMF/Et O gave better single crystals
2
compared with the preparation from acetonitrile, which
was also attempted. The data were collected on Gemini dif-
fractometer with Atlas CCD detector using graphite mono-
chromated Mo-Kα radiation (λ = 0.7107 Å) and corrected
for absorption using the CrysAlisPro software. The struc-
ture was solved by the charge flipping method by program
2
Superflip [19] and refined by full matrix least squares on F
with JANA 2006 program [20].
Cell culture and MTT assay for analysis of anticancer
properties of complexes
The cancer cell lines were cultured in RPMI 1640 Medium
(HiMedia, Mumbai, India) supplemented with 10 % Fetal
Fig. 2 TEM image of [UO (4-NO -saloph)(MeOH)] nano-particles
2
2
1
3

J IRAN CHEM SOC
Calf Serum (FCS) (Biochrom, Germany). 100 IU/ml of
penicillin and 100 mg/ml of streptomycin were also added
to the media as antibiotics to control the growth of contam-
inating microorganisms. The cells were cultured in 96 well
tissue culture plates (Greiner, USA), and kept at 37 °C in a
humidified atmosphere of 5 % CO in a CO incubator. All
the experiments were done using cancer cell line (Jurkat)
of 10–15 passage. The growth inhibitory effect of uranyl
complexes (D, E, F) toward the cancer cells was measured
Synthesis of the kinetic product
To refluxing solution of [UO (saloph)(solvent)]
(0.017 mmol), in acetonitrile (25 ml) tri-n-butylphos-
phine (0.017 mmol) was added. The reaction mixture was
refluxed for 24 h under nitrogen atmosphere. The resulting
oil was grinded with n-hexane to extract impurities, and
finally a powdery product was obtained.
a
2
2
2
[UO (saloph)(PBu )]: yield: 87 %, color: orange,
2
3
using
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo-
m.p. = 150–155 °C, anal. found (calc.): C H N O U
3
2
41
2
4
liumbromide (MTT) assay. D, E and F are: D = [UO (4-
(755.72): C, 50.71(50.86); H, 5.54(5.47); N, 3.60(3.71).
2
1
Cl-saloph)(DMSO)], E = [UO (saloph)(DMSO)] and
H NMR (250 MHz, DMSO-d , room temperature):
2
6
F = [UO (4-Me-saloph)(DMSO)].
δ(ppm) = 0.82 (t, 9H, CH ), 1.33 (m, 12H, CH ), 1.61
2
3
2
The cleavage and conversion of the soluble yellowish
MTT to the insoluble purple formazan by active mito-
chondrial dehydrogenises of living cells has been used
to develop an assay system alternative to other assays for
measurement of cell proliferation [21]. The drug treat-
(t, 6H, CH ), 6.80–7.68 (m, 12H, ArH), 9.34 (s, 2H,
2
−
1
HC=N). IR (KBr, cm ): 2869–3056 (υC–H), 1604(υ
),
C=N
1535(υ ), 1188 (υ ), 895(υ
), 540(υU–N), 439(υU–O).
C=C
C–O
U=O
ment performed as the harvested cells were seeded into
Results and discussion
4
9
6-well plate (2.5 × 10 cell/well) with varying concen-
trations of the sterilized uranyl complexes (0–100 μM)
and incubated for 24 and 48 h. Four hours to the end of
incubations, 25 μl of MTT solution (5 mg/ml in PBS) was
added to each well containing fresh and cultured medium.
Finally, the insoluble formazan was dissolved in solu-
tion containing 10 % SDS and 50 % DMF (left for 1 h at
Characterization of the complexes
Crystal structure determination of [UO (4‑NO ‑saloph)
2
2
(DMF)] complex
Crystal data, data collection, and structure refinement
details are listed in Table 1. The ORTEP view of this com-
plex is shown in Fig. 3, with selected bond parameters
3
7 °C in dark conditions) and optical density (OD) was
read against reagent blank with multi well scanning spec-
trophotometer (ELISA reader, Bio-Tek’s ELx808, USA)
at a wavelength of 570 nm. The absorbance is a function
of concentration of converted dye. The OD value of study
groups was divided by the OD value of untreated control
and presented as percentage of control (as 100 %). Also
the values of IC50 (the concentrations required for 50 %
growth inhibition), after 24 h of incubation with the com-
plexes were calculated.
Table 1 Crystal data, data collection and structure refinement details
for [UO (4-NO -saloph)(DMF)]
2
2
Complex
Formula
C H N O U
2
3
20
4
7
Formula weight
Crystal system
Space group
a (Å)
702.46
Monoclinic
P2 /c
1
Kinetic studies of the exchange reactions
33.0314 (7)
7.76870 (10)
27.7752 (6)
90
b (Å)
A solution of the uranyl complexes with known concen-
−
5
c (Å)
tration (2.5–5) × 10 M in acetonitrile was prepared.
.5 ml of each complex was poured in a cell, and a
α (˚)
2
β (˚)
105.444(2)
90
known excess concentration of PBu solution in acetoni-
3
γ (˚)
vol/Å3
Z,Z′
Dcalcd. (Mg m−3)
Abs. coeff. (mm−1)
F(000)
trile (runs from 10.0 to 40.0 ± 0.1 °C) was added to the
complex by using a microsyringe. After rapid stirring
by a microsyringe, the absorbance in the UV–vis region
was monitored with time. The kinetics was followed at
a wavelength of maximum absorbance, where the dif-
ference in the absorbance between the substrate and the
product was the largest (λmax). This wavelength was dif-
ferent for each complex.
6870.06
12.3
2.0375
7.141
4008.0
R1, wR2 [I > 3σ(I)]
R1, wR2 (all data)
0.0326, 0.0581
0.0550, 0.0337
1
3

J IRAN CHEM SOC
Fig. 3 Molecular structure of
[
UO (4-NO -saloph)(DMF)],
2 2
(
50 % probability ellipsoids, H
atoms omitted for clarity)
listed in Table 2. The complex contained three symmetry-
independent molecules, which are chemically identical but
they differ considerably by, e.g. angles between the aro-
matic rings. The molecules are compared in Table 2.
For each molecule, uranium had a pentagonal–bipyrami-
dal coordination geometry with an axial O=U=O [22]. The
ligand bound in a tetradentate fashion along the equatorial
axis of the uranyl ion and a solvent molecule occupied the
fifth coordination site in the equatorial plane. The geometry
around each uranium center deviates from the planar geom-
etry as can be recognized from the angles in Table 2.
One DMF molecule was coordinated to each of the
three symmetry-independent molecules. The bond length
between U and O (oxygen of DMF) was longer than U with
O (Schiff base oxygens), suggested that the coordination of
DMF was not as strong as the coordination of the Schiff
base [23]. The angle between oxygen atoms of axial oxy-
Table 2 Selected bond distances (Å) and angles (°) for [UO (4-NO -
saloph)(DMF)]
2
2
U1–O1
2.426(4)
2.421(3)
2.431(3)
1.776(3)
1.779(3)
1.775(3)
1.785(3)
1.784(3)
1.786(3)
2.225(3)
2.283(3)
175.9(2)
177.7(1)
177.3(1)
154.9(8)
63.5(1)
U2–O9
2.268(3)
2.231(3)
2.220(3)
2.241(3)
2.561(4)
2.539(4)
2.549(4)
2.613(3)
2.600(3)
2.520(4)
157.1(1)
62.6(1)
U2–O8
U2–O10
U3–O15
U3–O16
U1–O6
U3–O17
U1–O7
U1–N2
U2–O13
U1–N3
U2–O14
U2–N6
U3–O20
U2–N7
U3–O21
U3–N10
U1–O2
U3–N11
U1–O3
O2–U1–O3
N2–U1–N3
N2–C11–C16
N3–C12–C13
N7–C35–C36
N6–C34–C39
N11–C58–C59
N10–C57–C62
O2–U1–O7
O13–U2–O14
O20–U3–O21
O16–U3–O17
N10–U3–N11
O9–U2–O10
N6–U2–N7
123.0(4)
124.2(4)
123.5(4)
121.4(4)
122.2(4)
123.8(4)
gens (UO ) was 175.9°, 177.7° and 177.3° that were not
2
equal and were less than 180°.
Notable feature was the anharmonic behavior of ura-
nium, namely U1. For this atom, displacement described
157.2(1)
63.9(1)
1
3

J IRAN CHEM SOC
with an ellipsoid was not sufficient to explain strong
residua in the difference Fourier map. On the other hand,
description of U1 displacement with the third-order
anharmonic tenzor explained sufficiently the residua and
decreased significantly the R(obs) value (from 0.0326 to
UV–Vis spectra
In ligands, the band in the region of 300–500 nm corre-
sponded to the n–π* transition of the lone pair electrons
of nitrogen atom to the antibonding π* orbital of –CH=N,
and the band in the 200–300 nm region involved the π–π*
transition of the phenyl ring and the azomethine chromo-
phore [31].
0
.0301). The deposited CIF does not contain this anhar-
monic model because it is not important for the crystal
chemistry.
The peak around 330 and 350 nm of the complex could
be assigned to the LMCT transition. In uranyl complexes,
U(VI) has no electrons in valence shell; therefore U(VI)
had only LMCT transitions. There were two kinds of
charge transfer bands in the investigated uranyl complexes:
one corresponding to the electron transfer from the axial
oxygens to the central metal (2p of oxygen to 5f), and the
other caused by the electron transfer from the phenolate
group of the Schiff base ligand to the metal [32].
IR spectra
In the IR spectra of the ligand, bands observed in the
−
1
regions 3402–3500 cm were assigned to the OH group.
The absence of these peaks in the complexes indicated the
phenolic oxygen atoms coordinate to the metal center [24].
−
1
The bands at 2734–3055 cm in the Schiff base ligands
and complexes were related to aliphatic and aromatic C–H
modes of vibrations. Data showed also a shift of the C=N
−
1
vibration of the free ligand at 1597–1607 cm region to a
lower frequency in the complexes. This indicated the coor-
dination of the azomethine nitrogen to uranium [25, 26].
The ring skeletal vibrations (C=C) were consistent in all
Thermal analysis
Thermal properties of the metal complexes were investi-
gated up to 1000 ℃ under nitrogen atmosphere at a heat-
ing rate of 10 ℃/min. The TG spectra showed weight loss
−
1
derivatives in the region 1527–1572 cm and unaffected
by complexation.
up to 100 ℃ indicating the presence of solvent (CH OH)
3
The presence of the uranyl (VI) group can be easily
molecule coordinated to metal. The absence of weight loss
up to 80 ℃ indicated that there was no water molecule in
the crystalline solid. All the complexes were decomposed
in three steps. The first step of decomposition was related
to the release of (MeOH) and the percent of found and cal-
culated weight loss were nearly identical. Thermal decom-
position data of uranyl complexes are collected in Table 3.
−
1
proved by the strong IR band at 855–910 cm due to the
−
1
υ O=U=O [27]. The bands at 472–662 cm in the com-
3
plexes were related to (υ ) vibrations.
U–N
1H NMR spectroscopy The H NMR spectra of all the
1
Schiff bases showed a singlet or doublet signal at 12.71–
1
3.71 ppm corresponding to the hydrogen of the free OH
group of salicylaldehyde. After coordination of Schiff base
to the uranyl center, this signal was eliminated. The pres-
ence of a peak at 9.10–10.33 ppm, was due to the imine
HC=N protons [28]. The azomethine proton signal shifted
to lower fields which was also consistent with coordination
of the metal to the nitrogen. The spectra exhibited a multi-
plet at 6.50–8.18 ppm for the aromatic hydrogens [29]. Ali-
phatic hydrogens showed signals at about 2–4 ppm.
Kinetic aspects of thermal decomposition
DTG curves were used to study the kinetics of decompo-
sition of the complexes. Coats-Redfern equation (1) was
used to calculate kinetic parameters [33].
ꢀ
ꢁ
ꢀ
ꢁ
−
log(1 − a)
2
A ∗ R
βE
2RT
E
log
= log
1 −
−
T
E
2.303RT
(
1)
In uranyl Schiff base complexes, MeOH was coordi-
nated to metal center in the fifth coordination site in the
equatorial plane of the uranyl Schiff base complexes. By
(
w0−wt)
w0−wf)
In this equation; a = (
. w = initial mass of the
0
sample; w = mass of the sample at temperature T; w = the
t
f
using DMSO-d as solvent for NMR studies, DMSO could
final mass at a temperature when the mass loss is approxi-
6
expel methanol from coordination sphere. The presence of
free MeOH in the solution caused that two signals were
observed: methyl hydrogens had a doublet signal 3.14 ppm
due to coupling with hydrogen of hydroxyl group and
another peak was relevant to the hydrogen of OH group in
mately unchanged; β = the heating rate; R = the gas con-
ꢀ
ꢁ
−
log(1−a)
stant. A plot of log
against 1/T gives a straight
2
T
line with the slope of –E/2.303R (Fig. 4). A* values can be
calculated from the intercept of this plot. The entropy of
#
activation ꢀS . can be obtained using Eq. (2):
4
.07 ppm as a quartet [30].
1
3

J IRAN CHEM SOC
Table 3 Thermal decomposition data of uranyl complexes
Complex (F.W.)
TGA (Wt. loss %) calc. (found)
Temp. range in TG (°C)
Decomposition assignment
[
(
UO (saloph)(MeOH)]
616)
5.2(5.19)
140–400
400–540
Loss of MeOH
Loss of C H
2
1
2.8(12.33)
6
4
8
2(82.46)
7.6(7.47)
.4(5.3)
Loss of C H O N U
14 10 4 2
[
(
UO (4-Cl-saloph)(MeOH)]·H O
40–340
340–425
420–625
Loss of MeOH + H O
2
2
2
668.8)
5
Loss of Cl
1
7
1.3(11.2)
Loss of C6H3
5.7(75.94)
Loss of C H O N U
1
4
10
4
2
[
UO (4-NO -saloph)(MeOH)]
2.54(2.65)
4.36(4.7)
30–185
185–340
340.695
Loss of H O
2
2
2
H O
2
Loss of MeOH
Loss of C H NO
2
(
679)
1
7.6(17.82)
5.5(75.26)
5.6(5.1)
6
3
7
Loss of C H O N U
1
4
10
4
2
[
(
UO (4-Me-saloph)(MeOH)]
100–220
220–490
490–1000
Loss of MeOH
Loss of C7H6
2
630.4)
1
4.4(14.27)
3
8(37.43)
Loss of C H N O
14 10 2
2
4
2.82(42.82)
Loss of UO2
-
6
complexes the kinetic of thermal decomposition is first-
order in all stages [34].
-
-
-
-
6.2
6.4
6.6
6.8
The electrochemical study of uranyl complexes
Electrochemical studies of the uranyl saloph complexes
-
7
−
3
were carried out in acetonitrile solution (1.00 × 10 M)
and tetrabutylammoniumperchlorate (TBAP) (0.10 M) was
added as the supporting electrolyte. Electrochemical spec-
tra were measured at the potentials applied in the range
from 0 to −1.3 volt.
-
-
-
7.2
7.4
7.6
y = -2.2752x - 0.7432
R² = 0.9966
2
.4
2.5
2.6
2.7
2.8
2.9
3
3
-1
1
0 . T (°C)
The cyclic voltammograms of the synthesized uranyl
complexes all exhibit a quasi-reversible redox process
Fig. 4 Coats–redfern plots of [UO (4-Cl-saloph)(MeOH)] complex,
A = log(W /W − W)
2
2+
+
which is most likely due to the {UO } /{UO } couple.
2
2
f
f
V
The electron density on U atom is larger than that on
UVI atom because unlike U O , U O has one 4f elec-
VI
2+
V
+
2
2
tron. Upon reversal of the scan direction, the U(V) complex
is oxidized to U(VI) at overpotentials. The main influence
on the potential for the U(VI)/U(V) couple of uranyl com-
plexes is the level of π-donation from the ligand environ-
KTs
S#/T
∗
A =
e
.
(2)
h
where h = the Planck constant, K = the Boltzmann con-
stant; T = the peak temperature obtained from DTG. The
ment [35]. A typical cyclic voltammogram of [UO (4-Cl-
s
2
enthalpy and free energy of activation can be calculated
using Eqs. (3, 4):
saloph)(CH CN)] is shown in Fig. 5. The formal potentials
3
(E (VI↔V)) for the U(V/VI) redox couple were calcu-
1
/2
lated as the average of the cathodic (E ) and anodic (E )
#
pc
pa
E = H + RT
(3)
(4)
peak potentials. The redox and formal potentials for the dif-
ferent complexes are collected in Table 5.
#
#
#
G = H − TS
Biological activities of uranyl Schiff base complexes
Activation parameters obtained for all the complexes
are presented in Table 4. From these data it can be con-
cluded that the Gibbs energy grew from stage to stage.
This is probably due to the stable intermediate of the pre-
sent stages. According to Coats-Redfern plots, in these
This experiment is carried out on three complexes D, E, F
and the results are well shown in the Fig. 6 and Table 6.
By considering the results, it can be found that all the com-
plexes have a good anticancer activity.
1
3

J IRAN CHEM SOC
Table 4 The activation parameters of kinetics of TG studies
Compound
Slope
Intercept
0.37
TS
Ea
66.1
A
∆S
∆H
62.0
∆G
23.3
[
UO (saloph)(MeOH)]
−3.45
216.9
2.5E7
−107.3
2
°
°
1
80 –230
[
3
UO (saloph)(MeOH)]
80 –420
−4.99
−2.82
−6.36
−2.57
−1.79
−0.50
−1.13
−1.80
−2.27
−3.76
0.88
2.73
6.73
2.99
2.01
5.54
4.90
4.38
0.74
0.87
400.9
537.5
189.6
443.3
48.9
95.5
53.9
121.7
49.2
34.2
9.7
1.19E8
1.9E4
1.0E14
9.5E3
5.7E4
14.4
−97.1
−171.1
19.6
89.9
47.2
117.9
43.3
31.3
5.8
39.0
92.0
−3.6
78.0
11.6
41.7
87.9
141.6
17.6
53.4
2
°
°
[
UO (saloph)(MeOH)]
2
°
°
5
30 –545
[
UO (4-Me-saloph)(MeOH)]
2
°
°
1
75 –205
[
UO (4-Me-saloph)(MeOH)]
−176.0
−155.1
−226.3
−215.4
−205.1
−130.3
−132.6
2
°
°
4
10 –450
[
UO (4-NO -saloph)(MeOH)]
2
2
°
°
2
8.5 –100
[
UO (4-NO saloph)(MeOH)]
184.5
408.0
690.3
134.9
402.5
2
2
°
°
1
00 –190
[
UO (4-NO -saloph (MeOH)]
21.7
34.5
43.6
72.0
79.3
16.0
26.5
40.2
66.4
2
2
°
°
3
60 –410
[
UO (4-NO -saloph (MeOH)]
389.1
1.3E6
1.6E6
2
2
°
°
6
80 –705
[
UO (4-Cl-saloph)(MeOH)]
2
7
3–138 °C
[
UO (4-Cl-saloph)(MeOH)]
2
°
°
3
88 –430
1
E-05
-4.5E-18
-
-
-
-
-
-
-
1E-05
2E-05
3E-05
4E-05
5E-05
6E-05
7E-05
-
1.35
-1.15
-0.95
-0.75
-0.55
E / V
Fig. 6 Growth inhibition of the compounds investigated on Jurkat
cell line for 24 h. Cell viability was evaluated by the MTT colorimet-
ric assay. The vertical bars represent standard deviation of the tripli-
cate determinations. D [UO (4-Cl-saloph)(DMSO)], E [UO (saloph)
Fig. 5 The cyclic voltammogram of [UO (4-Cl-saloph)(CH CN)]
2
3
2
2
Table 5 The cyclic voltammetry data for uranyl compounds
(
DMSO)] and F [UO (4-Me-saloph)(DMSO)]
2
Compounds
Eox
Ered
∆E
[
[
[
[
UO (4-NO -saloph)(CH CN)]
−0.792
−0.799
−0.794
−0.779
−0.93
−0.91
−0.91
−0.93
−0.085
−0.083
−0.088
−0.123
2
2
3
Table 6 The IC50 values (μm) of the ligands against Jurkat cell line
UO (4-Cl-saloph)(CH CN)]
2
3
Ligand
IC50
D
E
F
UO (saloph)(CH CN)]
2
3
UO (4-Me-saloph)(CH CN)]
7
6.15
9.6
2
3
1
3

J IRAN CHEM SOC
0.004
Kinetic studies
0.0035
When PBu was added to the solution of the complex as a
0.003
3
nucleophile, it occupied the sixth position in the equatorial
plane in a rate-determining step, and then the solvent mol-
ecule was removed in a fast step.
0.0025
.002
.0015
.001
10
20
30
40
0
0
The complete reaction was:
0
[
UO2(Schiff base)(CH3CN)] + PBu3 →
0.0005
0
[
UO2(Schiff base)(PBu3)] + CH3CN
The pseudo-first-order constants were calculated by fit-
ting data to Eq. 5:
0
.04
0.06
0.08
[
0.1
0.12
0.14
PBu ]/M
3
ln [(A − A )/(A − A )] = −k
t
t
∞
0
∞
obs
(5)
Fig. 8 Plots of kobs versus PBu3 for [UO (4-Cl-saloph)(CH CN)]
complex at different temperatures 10–40 °C
2
3
where A is the absorbance at time t; A is the absorbance at
t
0
t = 0; A is the absorbance at t = ∞. The parameter k
∞
obs
can be calculated from the slope of the linear plot of this
equation versus time (t). As an example, the variation of the
electronic spectra for [UO (4-Cl-saloph)(CH CN)], in the
where k is the first-order rate constant for a solvent path; k
1
2
is the second-order rate constant. The second-order rate con-
2
3
presence of PBu (3 M), at 25 °C in acetonitrile is shown
stants k were obtained from the slope of the linear plots of
3
2
in Fig. 7.
kobs versus [PBu ] (Fig. 8). By comparing k in different tem-
3
2
PBu with the excess concentration at least 1:10 was
peratures, it could be concluded that the values of k increased
3
2
added to the uranyl complex solution. Therefore, the kinet-
ics was followed under pseudo-first-order conditions. The
rate law thus follows Eqs. (6, 7):
in high temperatures and the reaction rates increased too.
The kobs and k values for all the complexes are collected in
2
#
#
Tables 7, 8, 9 and 10. Activation parameters ꢀH . and ꢀS
ꢀ
ꢁ
were computed using k values and Eyring equation (8);
2
R = k
complex
(6)
(7)
obs
ꢀ
ꢁ
k
ꢀH#
ꢀS#
2
k
obs
= k [PBu ] + k
2
ln
= −
+
+ 23.8.
(8)
3
1
T
RT
R
#
2
.8
.6
.4
.2
1
The plots of ln(k/T) versus 1/T provided ꢀH values
#
1
1
1
1
from the slope of this chart and ꢀS from its intercept. The
Eyring plot for the reaction of [UO (4-Cl-saloph)(CH CN)]
2
3
with PBu is shown in Fig. 9.
3
#
By using Eq. (9) ꢀG values could be obtained.
0
0
0
0
.8
.6
.4
.2
0
#
#
#
ꢀG = ꢀH − TꢀS
(9)
#
Table 11 shows the activation parameters ꢀG (at
40.0 °C), ꢀH and ꢀS for the reaction of the uranyl com-
plexes with PBu in CH CN. The large negative values
for ꢀS and small values for ꢀH indicated an associative
mechanism. The rate constants for the complexes due to
their substitutional groups were as follows:
#
#
250
300
350
400
450
500
550
3
3
wavelength
#
#
Fig. 7 The variation of electronic spectra of [UO2 (4-Cl-saloph)
CH CN)] with (PBu ) in 20 °C
(
3
3
4
− NO > 4 − Cl > H > 4 − Me
2
3
Table 7 Rate constants (k ) and 10 k for [UO (saloph)(CH CN) at different temperatures
2
obs
2
3
02 [P]/M
10.8
12
13.2
14.4
15.6
16.8
18
10 k /M s
2
−1 −1
1
2
10 °C
20 °C
30 °C
40 °C
1.18(0.11)
1.30(0.22)
1.48(0.31)
2.22(0.09)
1.22(0.10)
1.41(0.10)
1.68(0.64)
2.36(0.07)
1.28(0.44)
1.57(0.18)
1.82(0.28)
2.59(0.02)
1.43(0.28)
1.74(0.14)
1.97(0.22)
2.90(0.02)
1.53(0.32)
1.82(0.12)
2.16(0.12)
3.14(0.24)
1.62(0.34)
1.91(0.26)
2.35(0.56)
3.42(0.14)
1.73(0.34)
2.05(0.32)
2.47(0.62)
3.67(0.22)
0.80(0.05)
1.04(0.05)
1.38(0.03)
2.00(0.07)
Numbers in parentheses are standard deviations
1
3

J IRAN CHEM SOC
3
Table 8 Rate constants (k ) and 10 k for [UO (4-Me-saloph)(CH CN) at different temperatures
2
obs
2
3
02 [P]/M
12
13.2
14.4
15.6
16.8
18.0
19.2
10 k /M s
2
−1 −1
1
2
10 °C
20 °C
30 °C
40 °C
1.10(0.08)
1.33(0.09)
1.59(0.21)
1.87(0.41)
1.21(0.06)
1.43(0.03)
1.71(0.24)
2.21(0.44)
1.32(0.08)
1.55(0.02)
1.86(0.10)
2.26(0.47)
1.35(0.10)
1.67(0.02)
2.00(0.14)
2.45(0.30)
1.41(0.14)
1.75(0.03)
2.14(0.06)
2.64(0.30)
1.50(0.10)
1.81(0.05)
2.28(0.04)
2.70(0.30)
1.58(0.24)
2.02(0.14)
2.43(0.03)
3.01(0.14)
0.63(0.04)
0.90(0.05)
1.17(0.01)
1.42(0.11)
Numbers in parentheses are standard deviations
3
Table 9 Rate constants (k ) and 10 k for [UO (4-Nitro-saloph)(CH CN) at different temperatures
2
obs
2
3
02 [P]/M
1.2
2.4
3.6
4.8
6.0
7.2
8.4
10 k /M s
2
−1 −1
1
2
10 °C
20 °C
30 °C
40 °C
0.42(0.32)
0.52(0.14)
0.68(0.44)
1.22(0.40)
0.70(0.21)
0.88(0.11)
1.18(0.31)
2.04(0.33)
0.91(0.12)
1.14(0.04)
1.69(0.20)
2.80(0.34)
1.14(0.10)
1.38(0.02)
2.19(0.08)
3.57(0.23)
1.39(0.05)
1.79(0.09)
2.71(0.05)
4.05(0.12)
1.67(0.07)
2.16(0.21)
3.21(0.10)
4.90(0.08)
1.95(0.11)
2.48(0.34)
3.71(0.37)
5.71(0.38)
2.00(0.04)
2.70(0.08)
4.22(0.00)
6.00(0.14)
Numbers in parentheses are standard deviations
3
Table 10 Rate constants (k ) and 10 k for [UO (4-Cl-saloph)(CH CN) at different temperatures
2
obs
2
3
02 [P]/M
4.8
6.0
7.2
8.4
9.6
1.08
1.2
10 k /M s
2
−1 −1
1
2
10 °C
20 °C
30 °C
40 °C
0.65(0.10)
0.70(0.10)
0.80(0.04)
1.62(0.07)
0.75(0.10)
0.85(0.10)
1.04(0.03)
1.93(0.2)
0.86(0.10)
1.00(0.02)
1.30(0.03)
2.24(0.10)
0.97(0.10)
1.15(0.08)
1.50(0.20)
2.55(0.06)
1.08(0.10)
1.31(0.10)
1.70(0.20)
2.88(0.09)
1.19(0.20)
1.46(0.10)
1.90(0.06)
3.20(0.09)
1.30(0.20)
1.61(0.20)
2.04(0.20)
3.47(0.05)
9.00(0.00)
1.27(0.00)
1.74(0.06)
2.50(0.02)
Numbers in parentheses are standard deviations
-
-
-
-
9.2
9.4
9.6
9.8
reaction increased. The electron-releasing group such as
Me decreased it [36].
The effect of solvent on the kinetic of substitution
reaction
-
10
The stability and equilibrium constant between two com-
plexes with different coordination numbers are usually
related to solvent. For studying the effect of solvent on the
-
-
-
10.2
10.4
10.6
rate constant (k ) of pentavalent-uranyl Schiff base com-
2
plexes, the interaction of the complexes with tributylphos-
phine in THF and acetonitrile was carried out. The variation
of electronic spectrum of [UO (saloph)(THF)] with PBu is
310
320
330
340
350
360
1
05(1/T)
2
3
shown in Fig. 10. The kobs and k values for [UO (saloph)
2
2
Fig. 9 Plot of ln(k /T) versus (1/T) for [UO (4-Cl-saloph)(CH CN)]
complex
(THF)] complex with PBu are collected in Table 12. The
2
2
3
3
2
rate constants (10 k ) and the activation parameters for
2
reaction of [UO (saloph)] with (PBu ) were compared for
2
3
two solvents and collected in Tables 13 and 14.
Electronic factor was important. The electron-with-
These results showed that the rate constants depended
on the solvent and the trend was related to the donor num-
drawing groups such as Cl, NO made the uranium center
2
more positive; therefore, the rate of the substitution
ber of the solvent. The Gutmann donor number for CH CN
3
1
3

J IRAN CHEM SOC
Table 11 The values of
activation parameters for uranyl
complexes
5
#
−1
#
−1
−1
#a
−1
Complex
10 ∆H /kJmol
∆S /JK mol
∆G /kJmol
[
[
[
[
[
UO (4-NO -saloph)(CH CN)]
25.3(1.7)
22.4(0.8)
19.8(1.7)
17.5(1.5)
17.8(0.3)
−189.1(5. 8)
−204.9(2.7)
−215.3(5.8)
−224.9(5.1)
−223.0(0.9)
55.4(1.8)
60.0(0.9)
63.1(1.8)
65.1(1.6)
65.3(0.3)
2
2
3
UO (4-Cl-saloph)(CH CN)]
2
3
UO (saloph)(CH CN)]
2
3
UO (4-Me-saloph)(CH CN)]
2
3
UO (saloph)(THF)]
2
Numbers in parentheses are standard deviations
a
#
∆
G was calculated at T = 20 °C
2
it. Therefore the trend of the reactivity of the studied com-
1
1
1
1
.8
.6
.4
.2
1
plexes and rate constants toward PBu according to the sol-
3
vent was as follows: CH CN > THF.
3
Conclusion
0
0
0
0
.8
.6
.4
.2
0
Several tetradentate uranyl Schiff base complexes were
synthesized and characterized by different techniques.
For one of them which was also prepared in nano form,
TEM images showed nano-particles with sizes between
30 and 35 nm. X-ray structure of [UO (4-NO -saloph)
2
90
340
390
440
490
540
wavelength
2
2
(
DMF)] confirmed that the solvent molecule occupied the
fifth position of the equatorial plane of the distorted pen-
tagonal–bipyramidal structure. The presence of one coor-
dinated solvent molecule was also confirmed by thermal
gravimetric studies. The kinetic of complex decompo-
sition was studied by using thermogravimetric method
(TG). For all the complexes, the Gibbs free energy (∆G)
grew from stage to stage. This was probably due to the
stable intermediate of the present stages. According to
coats-Redfern plots, the kinetic of thermal decomposi-
tion of studied complexes was first-order in all stages.
Fig. 10 The variation of electronic spectra of [UO (saloph)(THF)]
with PBu3
2
is 14.1 and for THF it is 20. The rate constants in THF
with higher donor number were smaller than the rate con-
stants in CH CN because the five-coordinated complex
3
was more stable in a solvent with higher donor number.
In other words, a solvent with higher donor number better
coordinated to a five-coordinated complex and stabilized
3
Table 12 Rate constants (k ) and 10 k for [UO (saloph)(THF)] at different temperatures
2
obs
2
02 [P]/M
12.0
13.2
14.4
15.6
16.8
18.0
19.2
10 k /M s
2
−1 −1
1
2
10 °C
20 °C
30 °C
40 °C
1.70(0.10)
1.86(0.20)
2.25(0.20)
2.90(0.20)
1.73(0.20)
2.00(0.20)
2.50(0.20)
3.10(0.04)
1.82(0.10)
2.13(0.20)
2.65(0.10)
3.35(0.04)
1.91(0.10)
2.25(0.20)
2.78(0.10)
3.56(0.07)
2.02(0.08)
2.37(0.10)
2.92(0.10)
3.70(0.07)
2.11(0.06)
2.45(0.10)
3.06(0.10)
3.88(0.09)
2.17(0.1)
2.55(0.03)
3.19(0.07)
4.06(0.2)
0.70(0.03)
0.95(0.03)
1.25(0.06)
1.60(0.05)
Numbers in parentheses are standard deviations
Table 13 The rate constant
2
Solvent
Donor number
10 K
2
2
(
10 k ), for [UO (saloph)] with
2
2
(
PBu3)
10 °C
20 °C
30 °C
40 °C
Acetonitril
THF
14.1
20
0.80(0.05)
0.70(0.03)
1.04(0.05)
0.95(0.03)
1.38(0.03)
1.25(0.06)
2.00(0.07)
1.60(0.05)
Numbers in parentheses are standard deviations
1
3

J IRAN CHEM SOC
Table 14 The activation parameters ∆H#, ∆S#, ∆G#, for
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UO (saloph)] with PBu
2
3
4
5, 410 (2002)
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E. Yoshida, S. Yamada, Bull. Chem. Soc. Jpn. 40, 1395 (1967)
5
#
−1
#
−1
−1
#
−1
Solvent
10 ∆H /kJmol
∆S /JK mol
∆G /kJmol
5
.
6
CH CN
19.8(1.8)
17.8(0.3)
−215.3(5.9)
−223.0(0.9)
63.1(1.8)
65.3(0.3)
3
6
.
THF
7. A. Elmali, C.T. Zeyrek, Y. Elerman, T.N. Durlu, J. Chem. Crys-
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8
9
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.
1
1
0. G. Gordon, H. Taube, J. Inorg. Nucl. Chem. 16, 272 (1961)
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1
2. Y. Kato, H. Fukutomi, J. Inorg. Nucl. Chem. 38, 1323 (1976)
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U(VI) ↔ (V)]. All the complexes had good anticancer
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#
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Nucl. React. 3, 39 (1978)
#
14. S.F. Lincoln, Pure Appl. Chem. 51, 2059 (1979)
1
5. H. Tomiyasu, H. Fukutomi, Bull. Res. Lab. Nucl. React. 7, 57
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(
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3
2
1. T. Mossman, J. Immunol. Methods 65, 55 (1983)
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2
2
22. D.J. Evans, P.C. Junk, M.K. Smith, Polyhedron 21, 2421 (2002)
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3
2
2
4. S.Y. Ebrahimipour, J.T. Mague, A. Akbari, R. Takjoo, J. Mol.
Acknowledgments We are grateful to Shiraz University Research
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2
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charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
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