Polymer complexes XXXVII novel models and structural of symmetrical poly-Schiff base on heterobinuclear complexes of dioxouranium(VI)

Article abstract of DOI:10.1016/S1386-1425(01)00592-3

Some binary and ternary novel complexes of dioxouranium(VI) with 5-vinylsalicylaldehyde (VSH) have been prepared and characterized by various physico-chemical techniques. The amine exchange reactions of coordinated poly-Schiff bases in these complexes have been also carried out which give symmetrical tetradentate poly-Schiff base complexes. Metal exchange reaction of these dioxouranium(VI) complexes with copper(II) gives the corresponding Cu(II) complexes. Reaction of tetradentate poly-Schiff base complexes of Cu(II) so obtained with ZrCl₄ gives heterobinuclear polymer complexes. Magnetic, electronic and IR spectral information commensurate that configurations of square planar copper(II) polymer complexes. All the polymer complexes are coloured and appear to be nonelectrolytes in DMF. The ligands behave as bi-(O, O) and tetradentate (N₂, O₂) donors. El-Sonbati equation was used to evaluate the symmetric stretching frequency from which the f_U-O and f_{UO, UO-} were calculated.

Full text of DOI:10.1016/S1386-1425(01)00592-3

Spectrochimica Acta Part A 58 (2002) 1411–1424
www.elsevier.com/locate/saa
Polymer complexes XXXVII novel models and structural of
symmetrical poly-Schiff base on heterobinuclear complexes
of dioxouranium(VI)
a,
a
b
A.Z. El-Sonbati *, A.A. El-Bindary , I.G.A. Rashed
a
Chemistry Department, Faculty of Science (Demiatta), Mansoura Uni6ersity, Demiatta, Egypt
b
Department of Math and Physics Sciences, Faculty of Engineering, Mansoura Uni6ersity, Mansoura, Egypt
Received 2 April 2001; accepted 13 July 2001
Abstract
Some binary and ternary novel complexes of dioxouranium(VI) with 5-vinylsalicylaldehyde (VSH) have been
prepared and characterized by various physico-chemical techniques. The amine exchange reactions of coordinated
poly-Schiff bases in these complexes have been also carried out which give symmetrical tetradentate poly-Schiff base
complexes. Metal exchange reaction of these dioxouranium(VI) complexes with copper(II) gives the corresponding
Cu(II) complexes. Reaction of tetradentate poly-Schiff base complexes of Cu(II) so obtained with ZrCl4 gives
heterobinuclear polymer complexes. Magnetic, electronic and IR spectral information commensurate that configura-
tions of square planar copper(II) polymer complexes. All the polymer complexes are coloured and appear to be
nonelectrolytes in DMF. The ligands behave as bi-(O, O) and tetradentate (N , O ) donors. El-Sonbati equation was
2
2
used to evaluate the symmetric stretching frequency from which the fU–O and fUO, UO− were calculated. © 2002
Elsevier Science B.V. All rights reserved.
Keywords: Metal exchange reactions; Heterobinuclear polymer complexes; Vinylsalicylaldehyde
1
. Introduction
ligands and correlated the stabilization of the
complexes with the OꢀUꢀO stretching frequencies
by taking into consideration the overlap proper-
ties of the uranium atom with the ligand orbitals
in an equatorial plane. In our earlier communica-
tions [6] Ni(II) mixed metal polymer complexes of
2-acrylamido-1-phenyl-2-aminothiourea derived
from amidation of 2-amino-1-phenylthiourea have
been described. In the present work a series of
Study of symmetrical tetradentate poly-Schiff
base complexes has attracted considerable atten-
tion [1,2]. El-Sonbati and El-Bindary [2–6] re-
cently discusses the structures of many uranyl
complexes depend on the IR spectra and indicated
the dependence of the antisymmetric OꢀUꢀO
stretching frequency on the polarisation of the
2
+
UO2 complexes in case of homobinuclear mixed
metal and metal exchange reaction has been pre-
pared by various methods studied.
*
Corresponding author. Fax: +20-5740-3868.
E-mail address: elsonbatisch@yahoo.com (A.Z. El-Sonbati).
1
386-1425/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S1386-1425(01)00592-3

1
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A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
An attempt has been made to correlate these
physical properties.
form, the residue was extracted several times with
petroleum ether (40–60 °C); yield crystal needles
of 5-vinylsalicylaldehyde monomer (VSH) was
formed on cold (m.p. 19–20 °C). (Calculated: C,
73.0; H, 5.4; Found: C, 73.1; H, 5.5%).
2. Experimental
2.1. Materials
2.3. Preparation of the uranyl polymer complexes
Salicylaldehyde (Aldrich Chemical Co, Inc) was
PVSH homopolymer and uranyl polymer com-
degassed and twice distilled on a vacuum line,
dried over anhydrous sodium sulphate. Paraform-
aldehyde (Merck Chemical Co, Inc) was used
without purification, and 2,2%-azobisisobutyroni-
trile (AIBN) (Estman Kodak) was purified by
dissolving in hot ethanol and filtering [7].
plexes was prepared by the method described by
Diab, El-Sonbati and El-Bindary [6,8,9].
2.3.1. Uranyl polymer complex (1)
The polymer complex was prepared by adding
a warm solution of the required uranyl acetate
3
(
0.2 mmol) in DMF (50 cm ) to a vigorously
2.2. Preparation of 5-6inylsalicyaldehyde
3
stirred solution of VSH in 50 cm (0.2 mmol) of
DMF, with 0.1 w/v AIBN as the initiator, until
the mixture became a homogeneous solution; then
the polymer complex was reflux for 2 h to com-
plete the reaction. The polymer complex was pre-
cipitated by pouring into a large excess of distilled
monomer
Preparation of the monomer was carried out
through the following steps.
2.2.1. Preparation of 5-chloromethylsalicyalde-
H O containing dilute HCl, to remove the metal
2
hyde
salt incorporated into the polymer complex. The
polymer complex was filtered and washed with
water and finally with ether and dried in a vac-
uum oven 40 °C for several days.
A
mixture of salicylaldehyde (0.25 mol),
paraformaldehyde (0.15 mol) and 150 ml of conc.
HCl was stirred at room temperature for 48 h.
The precipitate was filtered, washed with 0.5%
NaHCO solution, then with water till neutral,
and dried in vacuum. The product was crystal-
lized from benzene and petroleum ether.
3
2
.3.2. Uranyl mixed ligand polymer complex (2)
The mixed ligand uranyl complex was prepared
as follows, the ligand (VSH) (0.2 mmol) a long
with pyridine (1 ml) in DMF (50 cm ) and 0.1
3
2.2.2. Preparation of 3-formyl-4-hydroxybenzyl-
(
w/v) AIBN as initiator and to this was added an
triphenyl phosphonium chloride
A mixture of 5-chloromethyl salicylaldehyde
solution of uranyl acetate (0.2 mmol) with stirred
and reflux for 6 h during the course of the reac-
tion. The resulting polymer complex was precipi-
tated by pouring it into a large amount of distilled
(
0.2 mol) and triphenylphosphine (0.2 mol) in 500
ml benzene was refluxed for 1 h and cooled. The
precipitated phosphonium salt was filtered off and
washed with ether. To a vigorously stirred suspen-
sion of the phosphonium salt (0.18 mol) in 600 ml
H O containing dil. HCl to remove the metal salt
2
incorporated into the polymer complex. The
product was filtered, washed with water and dried
in a vacuum oven 40 °C for several days.
40% aqueous formaldehyde, 195 ml of 12.5 M
NaOH solution was added dropwise at a rate that
the reaction temperature does not exceed 40 °C.
After stirring for additional 2 h, the reaction
mixture was worked up by extracting with ben-
zene. The aqueous layer was neutralized with dil.
HCl under cooling and then extracted with chlo-
roform. After complete evaporation of the chloro-
2.3.3. Bis(5-6inylsalicylaldeneaminato)uranyl
polymer complex (3)
Liquor ammonia (1 ml) was added to 0.2 mol
of 5-vinylsalicylaldehyde dissolved in 50 ml of
ethanol–DMF (2:1). The solution was refluxed

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
1413
and the excess of ammonia was removed. To the
resulting Schiff base was added uranyl acetate (0.1
mol) in 50 ml ethanol and 0.1 (w/v) AIBN as
initiator. On digesting the resultant solution for
2.3.3.4. (4c) Preparation of heterobinuclear poly-
mer complexes starting from [Cu (VSR)] (10, 11).
To a suspension of Cu(VSR) (0.0035 mol, in 80
ml DMF), with constant stirring, a solution of
zerconyl chloride (0.002 mol, in 70 ml ethanol–
DMF, 1:1 v/v) was added. The mixture was
refluxed for 6 h with constant stirring. The result-
ing solid was filtered, washed thoroughly with a
chloroform–acetone mixture (2:1, v/v) and dried
well in vacuo.
1/2 h, a crystalline solid separated out. It was
filtered, washed with ethanol, dried well in vacuo
and analysed (Table 1).
2.3.3.1. (1c): Uranyl polymer complex symmetrical
tetradentate Schiff base deri6ed from diamine by
amine exchange reaction (4, 5). The Schiff base
complex of uranyl (0.1 mol) was suspended in 200
ml of ethanol–DMF mixture (1:1, v/v) was
refluxed with 1,2-diaminoethan or 1,2-di-
aminobenzene (0.1 mol) in 50 ml of ethanol for 2
h with intermittent stirring. Another method as
follows: the tetradentate Schiff base complex (1c)
was prepared by refluxing for 1 h a mixture
containing 5-vinylsalicylaldehyde (0.2 mmol), di-
amine (0.1 mmol), uranyl acetate (0.1 mmol) and
2.3.3.5. (5c): Preparation of mixed metals or
bimetallic polymer complexes [UO (VSR)ZrCl ]
2
4
(12, 13). The bimetallic polymer complexes were
prepared by mixing the UO (II) polymer complex
2
obtained above (1c) with ZrCl in dry DMF in the
4
molar ratio 1:1. It was left to stand out at room
temperature for several hours with occasional
shaking. The precipitated binuclear complex was
suction filtered, washed repeated with dry DMF
followed by ether, and finally dried in a vacuum
oven at 40 °C for several days.
0.1 w/v AIBN as the initiator in ethanolic
medium. The resulting solid was filtered, washed
with ethanol and dried well in vacuo.
2.3.4. Preparation of ternary polymer complexes
2.3.3.2. (2c): Preparation of homonuclear polymer
of the type [UO (VSA) ] (3)
2
2
complex starting from [UO (VSR)] (R=1, 2-di-
aminoethane=ED or 1,2-diaminobenzene=O ph.)
To the ethanolic solution of uranyl nitrate am-
monia (1:1) was added drop by drop with con-
stant stirring until the precipitate of metal
hydroxide formed redissolved forming the metal–
ammine complex (d-Scheme 1). It was heated to
85 °C and to the hot solution an ethanolic solu-
tion of 5-vinysalicylaldehyde (1:1 molar ratio) was
added with constant stirring. The reaction mixture
was refluxed for 2 h after adding 0.1 w/v AIBN as
initiator. The green solid obtained was filtered,
washed with ethanol and dried well in vacuum
oven at 40 °C for several days.
2
(
6, 7). The coordination homonuclear polymer
complex was prepared by refluxing for 2 h an
equimolar mixture of UO (VSR) (0.1 mol) and
2
uranylacetate (0.1 mol) dissolved in the minimum
quantity of DMF-ethanol mixture (4:1, v/v). The
product formed was filtered and washed a number
of times with hot DMF and then with ethanol to
remove unreacted metal. The purified sample was
then dried in a vacuum oven at 40 °C for several
days.
2
.3.3.3. (3c): Metal exchange reaction of
2.3.5. Dinitrato (1, 2-diaminoethane) uranium(VI)
(14) and dinitrato(1, 2-diaminobenzene)
uranium(VI) (15)
[UO (VSR)] (8). To a suspension of [UO (VSR)]
2
2
(
0.0035 mol in 25 ml DMF) was added, with
constant stirring, a solution of CuCI .2H O (0.003
This material was prepared by the method of
2
2
mol dissolved in 80 ml ethanol). The mixture was
refluxed for 6 h with constant stirring. The result-
ing solid was filtered, washed well with boiling
DMF followed by hot water and finally with
acetone. The purified sample was then dried in a
vacuum oven at 40 °C for several days.
Watt and Machel [10].
2.3.5.1. (1c) Dioxo[bis-(5-6inylsalicylaldehyde)-1,
2-diamino(ethane or benzene)]uranium(VI) (4,5). A
filtered solution of compound (e-Scheme 1) (0.01
mol) in DMF (20 ml) was added to a solution of

1
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A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
1415
5
-vinylsalicylaldehyde (VSH) (0.02 mol in 30 ml
rected for diamagnetism by using Pascal’s con-
stant. IR spectra were recorded on a Perkin-Elmer
1340 spectrophotometer, and uv-vis spectra mea-
sured (Nuzol mull) on a Pye Unicam 8800
spectrophotometer.
El-Sonbati equation has been solved by using a
computer program developed in our laboratories
using C language.
DMF) and 0.1% (w/v) AIBN as initiator. The
resulting solution was boiled under reflux for 10 h
and the resulting polymer complex was precipi-
tated by adding the mixture to a large amount of
distilled water containing a small amount of hy-
drochloric acid, the latter to remove any unreacted
metal salt. The polymer complex was filtered,
washed with water and dried in a vacuum oven at
40 °C for several days.
3
. Results and discussion
2.4. Measurements
3.1. Stoichiometries of the new uranyl complexes
The polymer complexes were analysed for their
metal and halogen contents employing standard
procedures [6,11]. The C, H, N and Cl analysis of
the resulting solid agreed with its proposed forma-
tions as a heterobinuclear complex (Table 1). Due
to the non-availability of suitable techniques, sep-
arate analysis of Cu(II) and Zr(IV) was not possi-
ble; only the mixed oxide (%) was determined and
found to agree with the expected value. Magnetic
measurements were carried out at room tempera-
ture using Gouy’s method, employing Hg[Co
The elemental analyses confirm their stoi-
chiometry. The room temperature magnetic mom-
nts of the copper(II) complexes under investigation
are characteristic of one unpaired electron.
The magnetic measurements of the dioxourani-
um(VI) complexes are independent of field
strength and temperature [12] and the ground
states of dioxouranium(VI) compounds contain no
unpaired electrons, the compounds are, therefore,
weaking diamagnetic as observed by previous
workers [13].
(
SCN) ] for calibration purposes, and were cor-
4
Fig. 1. The relation between (a) w* versus w and (b) w1 versus w3.
1
3

1
416
A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
Scheme 1.
Addition of ammonia to an ethanolic solution
of uranyl nitrate give uranylammine complex
which on treatment with 5-vinylsalicylaldehyde
shows a broad medium intensity band at 3400
-
1
cm indicating the hydrogen bonded hydroxyl
group [15] as part of a resonating ring system [16].
There are two distinguished bands at 1645 and
(
VSH) result in the formation of the imine com-
−
1
plex (c). The reaction of the above mentioned
compound (c) with 1,2-diaminoethane and/or 1,2-
diaminobenzene yield amine exchange [14] and
formation of symmetrical tetradentate Schiff base
complexes of type (1c). It is observed that this
exchange is accompained by change in geometry
of the complexes. The trans form (c) is converted
to cis form (1c).
1280 cm
due to w(CꢁO) and w(CꢀO) vibrations
of aldehydic and phenolic groups, respectively.
The IR spectra of uranyl complexes (1,2) shows a
shift of w(CꢁO) to a lower frequency by about
−
1
10–15 cm
and the w(CꢀO) of the phenolic
group is shifted to a higher frequency by about
−
1
20–25 cm
indicating that groups are involved
in the complexation. The new bands at 3440,
−
1
1
630, 890 and 570 cm
are assignable to w(OH),
3.2. Infrared spectra and nature of coordination
l(OH), r (H O) r (H O) vibrations [17]. Bands at
r
2
w
2
−
1
1
620 and 620 cm in uranyl complex (2) confirm
The IR spectrum of the homopolymer (VSH)
the presence of pyridine.

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
1417
−
1
−1
−1
wOH (3400–2960 cm ), lOH (860 cm
and
3500–3100 cm
indicating the absence of H O,
2
−
1
CꢀOH (1215 cm ) bands for the ligand were not
observed in the spectrum of the chelated polymer
complexes indicating the displacement of the OH
proton through the metal ion on complex
formation. The. w(CꢀO) (1280 cm ) (aromatic
carbon and phenolic oxygen) of the ligand is
shifted (Dw=10–15 cm ) in all complexes,
suggesting a MꢀO linkage. These changes in IR
spectra of the ligand on bonding to the metal ions
occur through a covalent linkage with the oxygen
atom of the phenolic group. w(CꢁO) (1645 cm
stretching of aldehydic group disappears and a new
NH , NH or OH groups. A strong split absorption
band at about 1620 cm supports the presence of
two different azomethine groups.
2
−
1
−
1
3.2.3. Reaction of zirconium (IV) chloride with [Cu
VSR)] (10–13)
Reaction of ZrCl with [Cu(VSR)] give heter-
obinuclear complexes (4c). [Cu(VSR)] has an ad-
ditional lone pair of electron at each of the
coordinated phenolic O and hence, it acts as a
ligand and gets coordinated with UO (CH COO)
H O. The Cu(II) band in the binuclear complex
2
shows a shift from its value in mononuclear com-
plex [Cu(VSR)]. This lowering in the ligand field
band of [Cu(VSR)] may be due to changes in the
planarity of (VSR) and also to reduction in
strength of CuꢀO bond on the formation of sec-
ond bond with metal (II) halids (19).
(
−
1
4
−
−
1
)
2
3
2
2
−
1
band appears at 1625 cm
of ꢀCꢁN bond. A sharp band appears at 3290
cm corresponding to NH stretching in bidentate
monobasic trans Schiff base complex (c).
due to the formation
−
1
3
.2.1. Reaction of[UO (VSA) ] with diamine
2 2
The performed tetradentate poly-Schiff base
complexes of the type [UO (VSR)], when treated of
2
trans polymer complex (c) with diamines give the
cis-symmetrical tetradentate Schiff base polymer
−
1
complexes (1c). w(N–H) (ꢀ3300 cm
)
(compound c) is absent in the tetradentate Schiff
base polymer complexes [18], indicating complete
exchange of NH by diamines.
3
.2.2. Reaction of [UO (VSR)] with CuCl2
2
The performed tetradentate Schiff base polymer
complex [UO (VSR)], when treated with CuCl .
2
2
2
H O, give the polymer complex [Cu(VSR)]. This
The azomethine frequency observed at 1620
2
2
+
2+
−1
indicate that UO
sequently the stability of Cu(II) tetradentate Schiff
base polymer complexes is greater than that of
UO (II) tetradentate Schiff base polymer
complexes.
is replaced by Cu
and con-
cm
1635 cm
in the parent Cu(II) complexes is shifted to
2
−
1
in the binuclear polymer c6mplexes,
suggesting a probable steric strain in ꢀOꢀNꢀNꢀOꢀ
−
1
2
sequence [20]. The phenolic w(C–O) (1275 cm ),
−
1
is shifted to 1335 cm
upon chelation with
Cu(II) complexes of symmetrical tetradentate
azomethines do not exhibit bands in the region
Cu(II) suggesting the metal-oxygen linkage [2,21],
in the bimetallic complexes it is observed at 1295

1
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A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
1419
Fig. 2. The relation between w% (cm ) and w% (cm−1).
−
1
1
3
−
1
cm
thus providing the involvement of the phe-
per(II) complexes are magnetically dilute. The
spectra showed a broad band with shoulder in the
nolic (C–O) in coordination to two metals. This
could be due to the capacity of the phenolic
oxygen to function as a tridentate site and its
linking with the tetravalent metal ion.
This also explains the unchanged stereochem-
istry around Cu(II). The w(M–O) bands in the
regions 600–525 and 335 cm
w(M–N), w(M–O) and w(MCl ) [8,9,22]. Some
new bands near 1150 and 785 cm
spectra of bimetallic complexes and these are at-
−
1
11800 and 19800 cm . These spectra are similar
to those reported for square planar copper(II)
complexes [24]. The spectra are consistent with
the data reported for analogous complexes con-
taining four-coordinate copper(II) centers in a
square-planar geometry [25].
The electronic spectra of the d–d band was
observed on going from mononuclear to binuclear
complexes, as already reported for similar adduct
−
1
are assigned to
−
−
1
appear in the
[
26,27] giving the following sequence. Mononu-
tributed to vibrational modes of the
skelton [23,24].
clear Cu(II)BCu–ZrBCu–UO2.
All the spectra show medium-weak absorptions
−
1
3
.4. Rearrangement of the ligand in the presence of
at 3040, 3010 and 2955 cm
due to aromatic
metal ions
C–H and CH stretches. Aromatic CꢁC stretches
2
−
1
give absorption at 1605–1590 and 1530 cm
.
Compound (1c) was also prepared by reaction
of 5-vinylsalicylaldehyde (VSH) with a suspension
of UO (ED)(NO ) and/or UO (o-phn.)(NO ) in
3.3. Magnetochemical and spectral studies
2
3 2
2
3 2
The magnetic moments measured at room tem-
perature (1.79–1.75 B.M.) indicate that the cop-
DMF. This reaction takes place slowly.
The principal IR bands of interest are two

1
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A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
1
strong bands at 3370 and 3180 cm attributed to
the asymmetric and symmetric NH stretching
vibrations [28]. The frequencies of these bands are
observed at a considerably lower wave number in
the complexes of the nitrogen atom of the amino
group with uranyl atom. The absence of large
systematic shifts of the w (NH ), w (NH ) and
frequencies with
a
slop corresponding to
1/2
(1+2M /M ) (Mo and Mu are the masses of
o
u
oxygen and uranium, respectively) [30,31] Fig. 1b.
It is obvious that good linearly obtains also in
case of w% and w% (Table 2 and Fig. 2).
1
3
Instead of the linear relation between w and w3
1
frequencies. El-Sonbati equation [32] has been
focus attention on their normalized differences
(Fig. 3) with a slope A (0.000192) and constant B
(1.835) do not depend on the masses of oxygen
and/or uranium atoms. The force constant for the
as
2
s
2
l(NH ) bands in the spectra of the complexes (e),
2
implies that there is no interaction between the
amino group nitrogen and the metal ion. Also,
however, the IR spectra of the complexes (e) show
no characteristic absorption assignable to NH2
function.
S
S
U–O (FU–O mdyn/A
,
), (F
) , (F
) and FUO,
U–O t
U–O o
UO, with neglect the interaction of the UꢀO
bonds with the ligands and the UꢀO bond
3
.5. Complexeation affect on uranyl ion spectra
distance (rU–O
Another observation is that a plot of (w +w ) or
A) were calculated (Table 2).
,
1
3
The results of elemental analyses (Table 1) are
generally in accordance with the composition
suggested for the various complexes.
w3 versus force constant for the U–O (FU–O
mdyn/A) and the UꢀO bond distance (rU–O
gives a straight line with increase the value of
w +w or w decrease w and increase the force
constant of the UꢀO bond (Figs. 4 and 5). This
can be explained. When oxygen donor is replaced
by N,N-donor ligands, the heterochelates exhibit
these vibrations at lower energies (Table 2). An
increase in electron density at U would lead to an
increase in repulsive force among the
non-bonding electrons of the atoms of the UO2
,
A)
,
The uranyl complexes exhibit the w (OꢁUꢁO)
as
1
3
3
UꢀO
−
1
(
865–960 cm ) and the w (OꢁUꢁO) (785–880
s
−
1
cm ) (Table 2). The force constant for the
OꢁUꢁO vibration was calculated by the method
of McGlynn [29]. The UꢁO bond distance was
calculated with the help of Jones equation [30].
The experimental results show an excellent
linear relation between w1 and w3 O–U–O
2
2
3
w +w
1
Fig. 3. The relation between
and w3.
w w
1
3

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
1421
Fig. 4. The relation between rUO(A) and FU–O(mdyn/A
, ,
) with w +w (cm−1).
1 3
group and thus a weakening of UꢀO bond occur
12]. Also, by plotting of r , r and r3 (bond
uranyl group is almost surely linear and has the
vibrational frequencies which vary considerably
from one compound to another.
[
1
2
distance, rU–O) versus 6 give straight line with
3
increase the value of 6 decrease r
El-Sonbati equation [32] has been used to deter-
mined the symmetric stretching frequency (w*). The
(Fig. 6).
El-Sonbati and El-Bindary discusses in this pa-
per the coordination chemistry and structures of
many uranyl compounds and points out that in all
cases known the uranyl group is collinear.
Although the coordination chemistry of the
uranyl ion has received some attention [33], and
the number of known coordination compounds
probably runs into several hundred, the structure
of none of them is known in detail. It would seem,
however, that there is a definite preference for
a coordination number of eight, the axial oxygens
being considered as ligands, and that all ligands
3
U–O
l
(
w*l ) data should eventually serve as a fairly accu-
rate evaluate the (FU–O), (rU–O) and (FUO, U–O
Table 2). There is also a straight line relationship
between (w*) and w (OꢁUꢁO) (Fig. 1a).
)
(
1
3
3.6. Stereochemistry and the structure of the com-
plexes
In the above our mentioned work shows that the

1
422
A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
directly bonded to the uranium atom. The evi-
dence for these presumptions has been summa-
rized [30] elsewhere [4,5,28], however, other
problems remains. Thus even when the stoi-
chiometry is known there is some doubt as to the
way the various ligands might be attached some
could be coordinated directly to the uranium
atom, some could (in solution) be hydrogen
bonded, nitrate and acetate ions when coordi-
nated could be monodentate or bidentate. The
fact that the coordination number has been
shown to be six and eight in the complexes
studied.
The structure of uranyl complexes are known
to be reasonably close to that depicted, wherein
the nitrato/acetato groups are monodentate and
are arranged in a plane equatorial to OꢁUꢁO axis.
4. Conclusion
All physical measurements carried out in this
study commensurate that poly-Schiff bases can
adopt two types of coordination modes, giving
rise to complexes with markedly different chro-
mophores and structural arrangements. In fact
Fig. 5. The relation between rUO(A) and FU–O(mdyn/A
, ,
) with w3 (cm−1).

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 58 (2002) 1411–1424
1423
Fig. 6. The relation between (1) w3 versus r1 (2) w3 versus r2 and (3) w3 versus r3.
cis-[Cu(VSR)] and [Cu(VSR)ZrCl ] exhibit prop-
molecules remain in the trans-position. The slight
differences observed between mononuclear and
binuclear copper(II) complexes are interpreted as
arising either from greater axial from symmetrical
tetradentate (VSR) groups acting in a strongly
cis-mode could be the axial donors [19–21].
4
erties which are fully consistent with N O metal
2
2
surroundings arising from the coordination of
imine, aldehyde and hydroxy phenyl groups. Poly-
meric complexes are thus formed and the metal
environment is planar (or very nearly).
By contrast trans-polymer complexes which
have mononuclear arrangements involving two
ligand molecules coordinating through essentially
imine, aldehyde and hydroxy phenyl groups and
two water or pyridine molecules, so that the metal
coordinate is almost planar in this case also. it is
also suggested that the two water or pyridine
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