Structural and models of dioxouranium(VI) with rhodanine azodyes - V

Article abstract of DOI:10.1016/S1386-1425(00)00458-3

The synthesis of several new coordination compounds of dioxouranium(VI) heterochelates with bidentate rhodanineazol compounds derived from rhodanine are described. The ligands and uranyl complexes have been characterized by various physico-chemical techniques. The bond lengths and the force constants have been calculated from asymmetric stretching frequency of O-U-O group. The infrared spectral studies showed a monobasic bidentate behaviour with the oxygen and azonitrogen donor system. The ligands contain intramolecular hydrogen bonds.

Full text of DOI:10.1016/S1386-1425(00)00458-3

Spectrochimica Acta Part A 57 (2001) 1163–1170
www.elsevier.nl/locate/saa
Structural and models of dioxouranium(VI) with rhodanine
ꢀ
azodyes – V
a
b,
b
b,1
A. El-Dissouky , A.A. El-Bindary *, A.Z. El-Sonbati , A.S. Hilali
a
Chemistry Department, Faculty of Science, Alexandria Uni6ersity, Alexandria, Egypt
b
Chemistry Department, Faculty of Science (Demiatta), Mansoura Uni6ersity, Demiatta, Egypt
Received 2 October 2000; accepted 25 October 2000
Abstract
The synthesis of several new coordination compounds of dioxouranium(VI) heterochelates with bidentate rhoda-
nineazol compounds derived from rhodanine are described. The ligands and uranyl complexes have been charcater-
ized by various physico-chemical techniques. The bond lengths and the force constants have been calculated from
asymmetric stretching frequency of O–U–O group. The infrared spectral studies showed a monobasic bidentate
behaviour with the oxygen and azonitrogen donor system. The ligands contain intramolecular hydrogen bonds.
©
2001 Elsevier Science B.V. All rights reserved.
Keywords: Rhodaninazodyes; Uranyl complexes; Bond length; Force constant
1
. Introduction
sis [10]. Chemical properties of rhodanine and its
derivatives are of interest due to coordination
capacity and their use as metal extracting agents
[5]. The coordination chemistry, novel structural
features and biological activity. A literature sur-
vey indicates, however, the absence of research on
the synthesis and properties of azodyes of Scheme
1. These molecules are capable of having keto–
enol tautomers, the enolic hydrogen substituents,
can be placed on the ligand.
In continuation of our studies on the ligating
properties of the heterocyclic nitrogen compounds
and their Schiff bases [1–8], we report herein the
preparation and characterization of the rhodanine
azodyes under investigation, together with their
uranyl complexes which were formed. Rhodanine
plays an important role in biological reactions [9],
e.g. in the inhibition of mycobacterium tuberculo-
Recently, our laboratories have initiated a se-
ries of studies of the effects of substituents at
p-position of the aromatic amine on the stoi-
chiometries of the complexes of these ligands with
uranyl acetate [7,8].
ꢀ
Part IV, see Ref. [6].
Corresponding author. Fax: +20-57403868.
Abstracted from her Ph.D.
*
1
1
386-1425/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S1386-1425(00)00458-3

1
164
A. El-Dissouky et al. / Spectrochimica Acta Part A 57 (2001) 1163–1170
2. Experimental
ture stirred and cooled to 0°C, a solution of
sodium nitrite (740 mg, 10.73 mmol, in 20 ml of
water) was added dropwise. The so formed diazo-
nium chloride was consecutively coupled with an
alkaline solution of 3-phenyl-2-thioxo-4-thiazo-
lidinone, (31 mg, 10.73 mmol) in 20 ml of pyri-
dine. The orange precipitated, which formed
immediately was filtered, washed several
times with water. The crude product was purified
by recrystallization from hot ethanol, yield 65%.
The analytical data confirmed the expected com-
positions, Table 1. The ligands were also charac-
2
.1. Synthesis of the ligands
3-phenyl-2-thioxo-4-thiazolidinone was pre-
pared according to the previously reported
method [6].
The standard chemical aniline and 4-alkyl-anili-
nes (alkyl: CH , OCH , Cl and NO ; Aldrich
Chemical Co.) were used without any further
purification. The experimental technique has been
described previously [1–8].
3
3
2
1
terized by H NMR and IR spectroscopy, Table
2
3
.2. Preparation of 5(4-deri6ati6es phenyldiazo)-
-phenyl-2-thioxo-4-thiazolidinone (HLn)
2.
In a typical preparation, 25 ml of distilled water
2.3. Synthesis of the complexes
containing hydrochloric acid (12 M, 2.68 ml,
2.19 mmol) were added to aniline (0.979, 10.73
mmol) or a 4-alkyl-aniline. To the resulting mix-
3
A hot solution of UO (OAc) ·2H O, (0.01 mol)
in EtOH (30 cm ) was added to the appropriate
2
2
2
3
Scheme 1. General formula and proton numbering scheme of the 5-(4-derivative phenyldiazo)-4-thiazolidinone.

A. El-Dissouky et al. / Spectrochimica Acta Part A 57 (2001) 1163–1170
1165
Table 1
Analytical data of UO2 complexes of rhodanine azodyes
+
2
Compounda
Code
Experimental (Calculated) (%)
Compositionb
C
H
N
S
Metal
HL1
56.0
3.7
12.5
19.0
(
55.9)
38.6
38.8)
58.5
58.6)
40.0
40.1)
57.7
57.5)
38.7
38.7)
52.0
51.8)
35.9
36.0)
50.1
50.2)
35.3
35.3)
(3.8)
(12.2)
(18.6)
–
1
2
3
4
5
2.6
(2.6)
8.1
(8.5)
12.4
(12.9)
23.5
(24.0)
[UO (L ) (OH ) ]
2 1 2 2 2
(
HL2
HL3
HL4
HL5
3.9
(4.0)
13.0
(12.8)
20.0
(19.6)
(
–
2.4
(2.5)
8.5
(8.8)
13.0
(13.4)
24.4
(24.8)
[UO (L ) (OH ) ]
2 2 2 2 2
(
3.5
(3.5)
13.6
(13.4)
20.3
(20.4)
(
–
2.1
(2.2)
8.7
(9.0)
13.5
(13.8)
25.3
(25.6)
[UO (L ) (OH ) ]
2 3 2 2 2
(
3.0
(2.9)
12.4
(12.1)
18.1
(18.4)
(
–
1.7
(1.8)
8.2
(8.4)
12.5
(12.8)
23.3
(23.8)
[UO (L ) (OH ) ]
2 4 2 2 2
(
2.9
(2.8)
11.9
(11.7)
18.1
(17.9)
(
–
1.8
(1.8)
10.8
(11.0)
12.3
(12.5)
23.0
(23.3)
[UO (L ) (OH ) ]
2 5 2 2 2
(
a
HL –HL5 are the ligand as given in Scheme 1 and L –L are the anions.
Deprotonation is confirmed by evolution of ethanolic acid during complex formation and are assessed quantitatively by the
1
1
5
b
pH-metric technique and by a spot test technique and its characteristic colour.
Table 2
Various force constants (mdynes/A
,
), U–O bond distances (A
,
) and frequencies (cm−1) w1 and w3 of UO 22 + complexesa
t
U–O
FUO,UOb
c
FUO,UOb
Complex
w3
w1
FU–O
r
F
r
(w )
FU–O
r
1
1
2
3
4
5
910
915
920
935
940
795
800
810
830
840
6.8352
6.9105
6.9862
7.2159
7.2933
1.7391
1.7370
1.7350
1.7289
1.7269
6.0324
6.0644
6.2121
6.4648
6.5659
1.7633
1.7622
1.7575
1.7495
1.7468
−0.8180
−0.7860
−0.7917
−0.7688
−0.7401
824.6
825.2
825.9
828.9
830.1
6.2324
6.2701
6.3161
6.4471
6.5019
1.7569
1.7557
1.7543
1.7503
1.7486
−0.6180
−0.6534
−0.6877
−0.7848
−0.8041
a
FUO)t is the true value of force constant.
(
b
U–O force constant and UO,UO interaction constant with neglect the interaction of the UO bonds with the ligands,
=bond–bond interaction).
Symmetric stretching frequency evaluated by using El-Sonbati equation [16].
(F
UO,UO
c
3
ligands (0.022 mol) in EtOH (30 cm ). Polycrys-
talline solid complexes were immediately formed
in each case. The reaction mixture was then main-
tained at the reflux temperature for 1/2 h to
ensure complete reaction. The solid complexes
were filtered off while hot and washed several
times with EtOH, followed by Et O, and dried in
2
vacuo over P O .
2
5

1
166
A. El-Dissouky et al. / Spectrochimica Acta Part A 57 (2001) 1163–1170
2.4. Elemental analyses
The absence of any peak attributable to the
−
1
C–OH (3440 and 3180 cm ) moiety implies that
in solution the ligands remains predominantly in
form IA. However, in solution and in the presence
of uranyl ion these compounds exist in a tau-
tomeric equilibrium IBUIC. The main change is
observed in the carbonyl stretching vibration, thus
suggesting that the form (IC) prevails. The tau-
tomeric form (IC) reacts with uranyl ion by loss
of enolic proton as mononegative chelating agents
producing of (CO)/(OH) mode of the free ligands.
New bonds assigned to w(OH) in the free ligands
is absent, suggesting the cleavage of intramolecu-
lar hydrogen bonded wOH [6] with subsequent
deprotonation of enolic OH group and coordina-
tion of oxygen to the metal ion. The positive shift
The uranium content of each complex was de-
termined by igniting a definite mass of the com-
plex at :1000°C and weighing the residue as
U O . Carbon, hydrogen and nitrogen contents
3
8
were determined at the Microanalytical Unit at
Cairo University, Cairo, Egypt. The analytical
data are given in Table 1. Sulphur was determined
as barium sulphate after oxidative decomposition
with mixed acids.
3
. Reseults and discussion
3
.1. Stoichiometeries of the new uranyl complexes
−
1
of w(C–O) by 5–15 cm
in all the complexes
The
fact
that
HLn
complexes
with
further confirms through the oxygen [12]. A new
broad absorption in the region 3150–3500 cm
−
1
UO (CH COO) ·2H O involving 2:1 ligand to
2
2
2
3
2
2
+
UO
ratio (Table 1), have been isolated, clearly
is observed in complexes which is attributed to the
presence of coordinated water [7]. Its presence is
further confirmed by the appearance of a non-lig-
illustrates that the ligands under study does not
introduce sufficiently severe steric hindrance as to
preclude the formation of [UO (L ) ·2H O] com-
plexes, but its steric feature and arrangement in
space can also favorably influence the stabiliza-
tion of 2:1 complexes. All complexes are diamag-
netic and sparingly soluble in most common
organic solvents, and it is thus difficult to deter-
−
1
and bond at 820–840 cm
All the complexes exhibit w(C=C) in the region
.
2
n 2
2
−
1
1595–1610 cm . The phenyl ring vibration ap-
−
1
pears at 1480–1510 cm . The presence of an
p-substituted benzene ring in the ligands as well as
in the complexes is indicated by strong and sharp
1
−1
mine the molecular weights and to record the H
bands around 630–650 cm . Bands at 2940–
−
1
−1
NMR spectra. At 100–110°C these complexes
lose two molecules of water and become con-
verted into [UO (L ) ].
3040 cm
for the ligands and at :2960 cm
for the complexes are assigned to w(C–H) vibra-
tion of the aromatic system.
2
n 2
3.2. Infrared spectra and nature of coordination
3.3. Electronic spectra
−
1
The mode of bonding of the azodyes to the
HLn exhibits bands at 26 415–26 250 cm
−
1
uranyl ions was elucidated by investigating the IR
spectra of the chelates 1M:2L as compared to
those of the free ligands.
(CS) (n“p*), 30 674–30 540 cm (CO) (n“p*),
−1
33 550–33 444 cm
tion), 40 480–39 470 cm
p*) [11] and 29 410–29 250 cm
(H-bonding and associa-
−
1
(phenyl) (ph–ph*, p–
−
1
In the IR spectra of all the ligands at :1550
transition of
−
1
cm
due to the w(–N=N–) mode. In the metal
phenyl rings overlaped by composite broad p–p*
of azo structure. In the dioxouranium(VI) com-
plexes, the (CS)(n–p*) transition shifts slightly to
lower energy and remain almost constant. The
(CO) (n“p*) transition disappears with the
chelates, this frequency is lowered to :1540
−
1
cm
indicating the bonding of the azo nitrogen
to the uranyl atom. The w(C–N) vibration ap-
−
1
pearing at :1480 cm
in the ligands suffers a
−
1
downward shift of :10 cm thereby supporting
the coordination of one of the azo nitrogen atoms
to the uranyl ion.
simultaneous appearance of
a
new bands
−
1
($29 500 cm ), being attributed to p“p* (C=
C) as a sequences of enolization. The band due to

A. El-Dissouky et al. / Spectrochimica Acta Part A 57 (2001) 1163–1170
1167
p“p* transition moves to lower energy at
pounds (1), (2) and (4) and (ii) w = −100+1.0w
s as
for compounds (3) and (5).
−
1
$
25 000 cm . These shifts or the disappearance
of the bands are indicative of coordination of the
Instead of the linear relation between w and w3
1
2+
ligands to UO2 . The dioxouranium complexes
frequencies, El-Sonbati equation [16] has been
focus attention on their normalized differences
(Fig. 2)
−
1
exhibits a new band at 24 390–24 210 cm
,
1
U
3
which is assigned to the S “ p transition,
typical of OUO for the symmetric stretching fre-
g
U
2
1
2
3
w +w
quency for the first excited state.
=Aw +B.
3
w w
1
3
3.4. Complexation affect on uranyl ion spectra
With
a
slope A(0.000192) and constant
B(1.835) do not depend on the masses of oxyegn
and/or uranium atoms. The force constant for the
2
+
Uranyl ion UO
is quit peculiar both in its
own structure and in its coordination compounds
12–14]. The ion reactions its identity over a wide
2
U–O (FU–O mdyn/A
interaction of the UO bonds with the ligands and
the U–O bond distance [rU–O ] were calculated
,
), FU–O,UO with neglect the
[
range of vibrations in experimental conditions
and can be considered from the geometric point
of view, as a single particle. In the present investi-
gation, the w(U=O) in all the complexes has been
assigned in 940–910 and 840–795 cm region as
w and w , respectively (Table 2).
A
,
[12–15] (Table 2). Another observation is that a
plot of (w +w )w versus force constant or w gives
1
3
3
3
a straight line with the increase in the symmetric
stretching vibration on complexation, Fig. 3.
There is also a straight line relationship between
−
1
3
1
The experimental results reveals an excellent
r
and the p. substituent, Hamelt’s constant
U–O
H
linear relation between w and w with the slope
(| ) with negative slope, i.e. the higher the value
of | , the lower r
1
3
1
/2
H
corresponding to (1+2M /M ) (MO and MU
and the higher the force
O
U
U–O
are the masses of oxygen and uranium atoms,
respectively) [12,15], Fig. 1, and the data satisfy
the equations: (i) w = −115+1.0w for com-
constant of the U–O bond, Fig. 4. The plot of
rU–O and fU–O versus w gives a straight line with
3
increase the value of w decrease r and increase
5
as
3
U–O
Fig. 1. The relation between (a) (w )* vs. w , and (b) w vs. w , number on the graph correspond to those given in Table 1.
1
3
1
3

1
168
A. El-Dissouky et al. / Spectrochimica Acta Part A 57 (2001) 1163–1170
2
1
2
3
Fig. 2. The relation between n n /w w and n3.
+
1 3
Fig. 3. The relation between FU–O and w +w .
1
3

A. El-Dissouky et al. / Spectrochimica Acta Part A 57 (2001) 1163–1170
1169
the force constant of the U–O bond, Fig. 5. This
can be explained. The electron withdrawing
p.substituent increase the positive charge on the
stoichiometry. The IR spectra of all complexes
show two bands attributable to the asymmetric and
−
1
symmetric cm
stretching frequency. A group
2
+
UO
leading to an increase in w and F
and
theoretical consideration [17] shows that a linear
2
3
U–O
2
2
+
subsequently a decrease in rU–O. Accordingly, rU–O
and symmetrical triatomic UO
ion possessing
values can be arranged in the order: p.OCH \
Dꢀh symmetry gives rise to three fundamental
3
p.CH \H\p.Cl\p.NO , which are consistent
modes of vibrations.
In the equatorial bonding, the more effective
overlap of O–U–O group orbital by nitrogen than
3
2
H
with the values of their | . El-Sonbati equation
16] has been used to determine the symmetric
stretching frequency (w )*. The (w )* data are in turn
[
by oxygen in the ligands leads to lower w values
3
1
1
2
+
for UO2 complexes with the former. The force
constant of U–O bond in the present investigation
has been calculated following McGlynn et al. [12],
and the U–O bond distance for the corresponding
complexes are evaluated using the Jones equation
used to evaluate the (FU–O) (force constant) and
FUO,UO’’) (bond–bond interaction) with neglect of
(
the ligand (Table 2). There is also a straight line
relationship between (w )* and w (O=U=O) (Fig.
1
3
1).
−
1/3
[13,14] RU–O=1.08 F
+1.17. The evaluated
values are given in Table 2 and such report is also
found for other uranyl complexes. The variation of
bond length in the complexes is due to presence of
electron releasing or electron withdrawing substitu-
tents in the equatorial position.
In the present investigation, it is well established
that uranyl ion possesses planar hexagonal struc-
ture with nitrogen and oxygen atoms in the
3
.5. Stereochemistry and the structure of the
complexes
5(4-derivatives
phenyldiazo)-4-thiazolidinone
(LH ) react with UO (CH COO) ·2H O (molar
n
2
3
2
2
ratio 2:1 in ethanol) giving solid, dark brown or red
complexes with expected show [UO (Ln) ·2H O]
2
2
2
Fig. 4. The variation of (a) rU–O (A) and (b) FU–O (mdyn/A
, ,
) with the p-substituent Hamett’s constant |H.

1
170
A. El-Dissouky et al. / Spectrochimica Acta Part A 57 (2001) 1163–1170
Fig. 5. The variation of (a) rU–O (A) and (b) FU–O (mdyn/A
, ,
) with the w3 cm−1.
(
2000) 621.
6] A.A. El-Bindary, A.Z. El-Sonbati, Polish J. Chem. 74
2000) 615.
axial position. Two ligands units and two water
molecules remain in the equatorial plane. It is also
suggested that the two water molecules remain in
the trans-position. In these cases, all the com-
[
[
(
7] A.F. Shoair, A.A. El-Bindary, A.Z. El-Sonbati, R.M.
Younes, Polish J. Chem. 74 (2000) 1047.
plexes are eight coordinated. HL behaves as a
chelating bidentate monobasic ligand, banding
through oxygen and azonitrogen atom.
[8] A.F. Shoair, A.A. El-Bindary, A.Z. El-Sonbati, R.M.
Younes, Spectrochim. Acta Part A (2001) in press.
n
[
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Org. Chem. 24 (1959) 1056.
[
10] S. Tadashi, O. Masaki, J. Pharm. Soc. (Jpn.) 75 (1955)
535.
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8 (1975) 885.
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