2
06
A.Z. El-Sonbati et al. / Journal of Molecular Structure 1027 (2012) 200–206
This gives effective ionic charges of the ruthenium(III) azoquin-
ability of HL
in part from the d
-bonding imparts some aromatic character to the chelate ring.
The above results show clearly the effect of substitution in the p-
position of the benzene ring on the stereochemistry of Ru(III) com-
plexes. The results also suggest that the existence of a hydroxyl
group enhances the electron density on the coordination sites
and simultaneously increases the values of Racah parameters of
Ru(III) complexes. In conclusion, the results of the present study
n
, which contain azodye group, is considered to result
oline complexes in the 0.49–0.97 range, which are considerably be-
low the formal +3 oxidation state of the metal ion. It is apparent
that the nephelauxetic ratio b depends greatly upon the electro-
negativity of the donor atoms and the ligand structure.
p-pp bonding from the metal to the ligand; this
p
As can be seen from Tables 3 and 4, the Racah parameters (B,
ꢅ
Dq, b) and Z values increase from compound 1 to 3 and from 4
to 6. This can be attributed to the fact that the effective charge
experienced by the d-electrons decrease due to the electron with-
drawing p-substituent (HL
donating character of HL
5
) while it increased by the electrons
n
indicate that the selected (HL ) ligands are suitable for building a
1
.
supramolecular structure. Moreover, since the azo compounds
experience photochemical isomerization and are, therefore, of
interest for applicative purposes [33], complexes of Ru(III) with
3.7. Thermogravimetric analysis
5
n
-(4-alkylphenylazo)-2-thioxothiazolidin-4-one(HL ) moiety may
In the mean time, the thermal analysis of ruthenium complexes
be considered as promising supramolecular, which could be useful
in molecular materials. The values of ligand field parameters orbi-
tal parameters were calculated. The thermogravimetric analyses
confirm the presence of coordinated one water molecule in the
complexes (1–3).
under study was carried out in an attempt to clarify the content
and bonding of water in the complexes. The determined tempera-
ture ranges, % loses in mass and thermal effect accompanying the
changes in the solid complexes on heating are as following:
(
i) The observed loss in mass within the temperature range
25–125 °C could be correlated with the loss of water of
hydration from all complexes. At higher temperature (125–
25 °C), the coordinated water could be eliminated from
complexes (1–3).
References
1
[
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2
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(
(
ii) Coordinated Cl could be removed within the temperature
[
range 185–280 °C.
1
(
iii) Exotherms due to oxidation, decomposition of the com-
[
[
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(
iv) The organic part of the chelate gradually burned a way and
the crucible became empty within the temperature range
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4
40–580 °C. The degradation of the organic part of the che-
[
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late was an endothermic reaction, which resulted in carbon
as residue. The decomposition of carbon dioxide was an exo-
thermic reaction [6].
1
[
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[
[
[
[
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(
The TG curve for complexes shows similar decomposition with
weight losses in two stages. In the first stage, in the temperature
range ꢁ280–320 °C is attributed to the weight loss of one molecule
of ligands. The total mass loss observed at 480–540 °C was found to
be stable metal oxides. The fragmentation patterns of the thermo-
grams agree well with theoretical calculations and support the ste-
reochemical and stoichiometrical assignments..
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[
[
[
[
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3
.8. Structural interpretation
[
[
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From all of the above observation and according to the data re-
ported in this paper based on the IR, molar conductivity, spectral
and magnetic measurements, the structure of these complexes is
given as shown in Fig. 3. The structure proposed for Ru(III)-com-
plexes is octahedral distorted. This indicates that, the ligand
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[22] J. Ladik, A. Messumer, J. Redly, Acta Chim. Acad. Sci. Hung. 38 (1963) 393–396.
(
[
1
[
23] (a) E. Sawicki, J. Org. Chem. 21 (1956) 605–609;
b) E. Sawicki, J. Org. Chem. 22 (1957) 915–919.
(
n
HL ) behaves as monobasic bidentate chelating ligand and azodye
(
nitrogen and enolic oxygen are the two sites of coordination.
[
[
[
24] L.W. Reeves, Can. J. Chem. 38 (1960) 748–751.
25] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81–84.
26] J.A. Dean, Lange‘s Hand Book of Chemistry, 14th ed., MEGRAW-Hill, New York,
4
. Conclusions
1992. p. 35.
[
[
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The present paper reports on the synthesis, characterization
1958.
and their electronic absorption spectra of ligand (azo rhodanine)
and Ru(III) complexes. The synthetic procedure in this work re-
sulted in the formation of complexes in the molar ratio (1:2)/
[
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[30] B.N. Figgis, Introduction to Ligand Field Theory, first ed., Interscience
publishers, New York, 1966.
[
(
n
1:3)(M:L ), respectively. In these complexes the azo ligand acts
31] A.B.P. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier,
Amsterdam, 1984.
as a monobasic bidentate ligand and coordinated to metal ion
through the azo-nitrogen, enolic oxygen atoms forming stable six
membered heterocyclic rings. The present study revealed octahe-
dral geometry around Ru(III)-complexes. The strong chelating
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47.
[
1