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Abstract
Summary
The chemistry of Schiff base ligands and their metal complexes have
attracted a lot of interest due to their facile synthesis and wide range of
applications including antifungal, antibacterial, anticancer, catalytic and
electrical fields. The complexes of 2-hydroxy-1-naphteldehyde Schiff base are
considered to be among the most important stereochemical models in main
group and transition metal coordination chemistry due to their preparative
accessibility and structural variety.
The thesis entitled ”Synthesis and spectroscopic characterization of some
transition metal complexes ”comprises of four Chapters:
Chapter one contains a literature survey of the importance and structural
chemistry of 2-hydroxy-1-naphthaldehyde schiff bases compounds and their
Ru(III) complexes. Also, it includes a literature survey of biological and
electrical activity of 2-hydroxy-1-naphteldehyde schiff bases derevatives.
Chapter two concerned with the experimental work. The following ligands
(HL
n
) were prepared:
HL
= 2-Hydroxy-1-naphthylidene-4-methoxyaniline.
HL
1
= 2-Hydroxy-1-naphthylidene-4-methylaniline.
HL
2
= 2-Hydroxy-1-naphthylideneaniline.
HL
3
= 2-Hydroxy-1-naphthylidene-4-chloroaniline.
HL
4
5
= 2-Hydroxy-1-naphthylidene-4-nitroaniline.
Ru(III) complexes were prepared from the reaction of these ligands (HL
with [RuCl
3
.nH
2
O]. The formed complexes are [Ru(L
n
)
2
(H
2
O)
2
]Cl.
Elemental analysis (C, H and N), molar conductivity measurements,
magnetic measurements, spectral studies (IR, electronic,
1
n
)
H NMR spectra),
thermal studies (TGA), catalytic oxidation, antimicrobial investigation and ac
conductivities of the synthesized ligands and complexes were provided.
The results and discussion were included in two Chapters:
(HL
Chapter three includes the synthesis of bidentate Schiff base ligands
n
) by condensation of 2-hydroxy-1-naphthaldehyde with aniline and its p-
substituted derivatives in ethanol. Ruthenium(III) complexes of the type
[Ru(L
n
)
2
(H
2
O)
2
]Cl have been synthesized by the reaction of RuCl
the Schiff base ligands (in a molar ratio 1:2) in ethanol. The ligands and their
Ru(III) complexes have been characterized by elemental analysis, magnetic
susceptibility, spectroscopic (FTIR, UV–vis,
1
3
.nH
2
O with
H NMR and X-ray diffraction)
and thermal analysis techniques. All the ruthenium(III) complexes are found to
be stable, paramagnetic, low spin and octahedrally coordinated by the ligands
through the nitrogen atom of the azomethine (–C=N–) group and the oxygen
atom of the deprotonated phenolic hydroxyl group. The molecular and electronic
structures of the investigated ligands (HL
n
) were also studied using quantum
chemical calculations. The complexes (1, 3 and 5) exhibited a catalytic activity
for the oxidation of benzoin to benzil with moderate to high yield in the
presence of sodium periodate as co-oxidant. The antibacterial activities of the
ligands (HL
n
) and their Ru(III) complexes towards Gram positive and Gram
negative bacteria have been investigated.
Chapter four describes the measurement of solid state electrical
conductivity and optical properties of these Schiff base ligands. The ac
conductivity measurements showed a semiconductor behavior. The electrical
conduction mechanism was also investigated and found to be correlated barrier-
hopping (CBH) and quantum mechanical tunneling (QMT) mechanisms
depending on the function group. The spectral distribution of absorption (α)
coefficient for the ligands under investigation showed five absorption peeks and
shoulders which are assigned as π -π
*
and n-π
transitions were found to be direct forbidden transition for HL
The optical energy gap (E
g
*
transitions. The electronic
1
and HL
) near the absorption edge is found to be in the range
of 2.5 - 3.7 eV depending on the function group. The effect of adsorbed NH
on the electrical conductivity and dielectric constants of ligand HL
investigated and the results showed that the adsorbed NH
conductivity.
3
5
ligands.
4
3
gas
was
gas increases the ac