Synthesis, spectroscopic and biological activities studies of acyclic and macrocyclic mono and binuclear metal complexes containing a hard-soft Schiff base

Article abstract of DOI:10.1016/j.saa.2012.04.057

Mono- and bi-nuclear acyclic and macrocyclic complexes with hard-soft Schiff base, H₂L, ligand derived from the reaction of 4,6-diacetylresorcinol and thiocabohydrazide, in the molar ratio 1:2 have been prepared. The H₂L ligand reacts with Co(II), Ni(II), Cu(II), Zn(II), Mn(II) and UO₂(VI) nitrates, VO(IV) sulfate and Ru(III) chloride to get acyclic binuclear complexes except for VO(IV) and Ru(III) which gave acyclic mono-nuclear complexes. Reaction of the acyclic mono-nuclear VO(IV) and Ru(III) complexes with 4,6-diacetylresorcinol afforded the corresponding macrocyclic mono-nuclear VO(IV) and Ru(IIII) complexes. Template reactions of the 4,6-diacetylresorcinol and thiocarbohydrazide with either VO(IV) or Ru(III) salts afforded the macrocyclic binuclear VO(IV) and Ru(III) complexes. The Schiff base, H₂L, ligand acts as dibasic with two NSO-tridentate sites and can coordinate with two metal ions to form binuclear complexes after the deprotonation of the hydrogen atoms of the phenolic groups in all the complexes, except in the case of the acyclic mononuclear Ru(III) and VO(IV) complexes, where the Schiff base behaves as neutral tetradentate chelate with N₂S₂ donor atoms. The ligands and the metal complexes were characterized by elemental analysis, IR, UV-vis ¹H-NMR, thermal gravimetric analysis (TGA) and ESR, as well as the measurements of conductivity and magnetic moments at room temperature. Electronic spectra and magnetic moments of the complexes indicate the geometries of the metal centers are either tetrahedral, square planar or octahedral. Kinetic and thermodynamic parameters were calculated using Coats-Redfern equation, for the different thermal decomposition steps of the complexes. The ligands and the metal complexes were screened for their antimicrobial activity against Staphylococcus aureus as Gram-positive bacteria, and Pseudomonas fluorescens as Gram-negative bacteria in addition to Fusarium oxysporum fungus. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.

Full text of DOI:10.1016/j.saa.2012.04.057

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectroscopic and biological activities studies of acyclic and macrocyclic
mono and binuclear metal complexes containing a hard-soft Schiff base
b
Azza A.A. Abou-Hussein a, , Wolfgang Linert
⇑
a Faculty of Women for Arts, Science and Education, Ain Shams University, Heliopolis, Cairo, Egypt
b Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-AC, 1060 Vienna, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
Mono- and bi-nuclear acyclic and macrocyclic complexes with hard-soft Schiff base, H2L, ligand derived
from the reaction of 4,6-diacetylresorcinol and thiocabohydrazide, in the molar ratio 1:2 have been pre-
pared. The H2L ligand reacts with Co(II), Ni(II), Cu(II), Zn(II), Mn(II) and UO2(VI) nitrates, VO(IV) sulfate
and Ru(III) chloride to get acyclic binuclear complexes except for VO(IV) and Ru(III) which gave acyclic
mono-nuclear complexes. Reaction of the acyclic mono-nuclear VO(IV) and Ru(III) complexes with
4,6-diacetylresorcinol afforded the corresponding macrocyclic mono-nuclear VO(IV) and Ru(IIII) com-
plexes. Template reactions of the 4,6-diacetylresorcinol and thiocarbohydrazide with either VO(IV) or
Ru(III) salts afforded the macrocyclic binuclear VO(IV) and Ru(III) complexes. The Schiff base, H2L, ligand
acts as dibasic with two NSO-tridentate sites and can coordinate with two metal ions to form binuclear
complexes after the deprotonation of the hydrogen atoms of the phenolic groups in all the complexes,
except in the case of the acyclic mononuclear Ru(III) and VO(IV) complexes, where the Schiff base
behaves as neutral tetradentate chelate with N2S2 donor atoms. The ligands and the metal complexes
were characterized by elemental analysis, IR, UV–vis 1H-NMR, thermal gravimetric analysis (TGA) and
ESR, as well as the measurements of conductivity and magnetic moments at room temperature. Elec-
tronic spectra and magnetic moments of the complexes indicate the geometries of the metal centers
are either tetrahedral, square planar or octahedral. Kinetic and thermodynamic parameters were calcu-
lated using Coats–Redfern equation, for the different thermal decomposition steps of the complexes.
The ligands and the metal complexes were screened for their antimicrobial activity against Staphylococcus
aureus as Gram-positive bacteria, and Pseudomonas fluorescens as Gram-negative bacteria in addition to
Fusarium oxysporum fungus. Most of the complexes exhibit mild antibacterial and antifungal activities
against these organisms.
Received 14 February 2012
Received in revised form 30 March 2012
Accepted 10 April 2012
Available online 22 April 2012
Keywords:
Hard-soft Schiff base
Acyclic and macrocyclic complexes
Spectral studies
Antimicrobial activities
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
nium thiocarbohydrazone macrocyclic complexes made attention
due to their oxidation processes for possible applications as SOD-
Over the past few years, Schiff base acyclic complexes with
thiocarbohydrazones have become increasingly important, due to
their potential in medicinal inorganic chemistry and have exhibit
interesting physicochemical and chemotherapeutic properties
[1–5]. Furthermore, the increasing interest in the coordination
chemistry is focused on the potential applications of macrocylic
Schiff base complexes because of their mixed soft-hard donor char-
acter, versatile coordination behavior, pharmacological [6], anti-
cancerous [7] and antitumor properties [8,9], where, many
transition metal ions in living systems work as enzymes or carriers
in a macrocyclic ligand environment, and the metal is bound in a
macrocyclic by the conformational arrangement of the protein
[10–12]. On the other hand, recent articles on vanadium and ruthe-
like activities and for their antitumoral properties [13–15]. Also,
vanadium compounds have been reported to be reducing the need
for daily insulin injections [16]. On the other hand, more attention
is focused on the first raw of the transition metal the thiocarbohyd-
razone complexes, were some complexes behaves as fungicides for
textile fabrics [17] and others behaves as inactivators of HSV-1
ribonucleotide reductase [18]. In continuation of our laboratory re-
search on the metal complexes of the thiocarbohydrazone deriva-
tives and 4,6-diacetylresorcinol, it is highly desirable to synthesize
the first raw transition metal complexes, beside the vanadium and
ruthenium complexes with soft-hard donor Schiff base ligand
derived from 4,6-diacetylresorcinol and thiocarbohydrazide in
different molar ratios. In the present study, mononuclear and binu-
clear complexes have been prepared from the Schiff base, H2L,
ligand derived from 4,6-diacetylresorcinol (DAR) and thicarbohyd-
razide in the molar ratio 1:2. Scheme 1 is a representative structure
⇑
Corresponding author. Tel. +20 2 (0)123778705; fax: +20 (02) 26849677.
E-mail address: azza_aly2000@yahoo.com (A.A.A. Abou-Hussein).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.04.057

A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
597
HO
OH
H2N
H
HO
OH
N
C
2 h
+
NH2
H
N
N
H
C2H5OH
N
C
N
C
N
H
S
O
O
H2N
NH2
N
H
S
N
H
S
1 mole
4,6-Diacetyl resorcinol
2 mole
Thiocarbohydrazone
H2L
Scheme 1. Schematic preparation of the Schiff base, H2L.
of the Schiff base, H2L, ligand. The H2L ligand reacts with cobalt(II),
nickel(II), copper(II), manganese(II), zinc(II) and dioxouranium(VI)
nitrates, and ruthenium(III) chloride and oxovanadium(IV) sulfate.
All reactions afforded acyclic binuclear complexes except Ru(III)
and VO(IV) which gave acyclic mono-nuclear complexes. Reaction
of the acyclic mononuclear VO(IV) and Ru(III) complexes with 4,6-
diacetylresorcinol afforded macrocyclic mononuclear VO(IV) and
Ru(III) complexes, as a result of the condensation reaction between
the two free ANH2 in the H2L ligand and the two carbonyl groups
in the 4,6-diacetylresorcinol. Template reactions of the 4,6-
diacetylresorcinol, thiocarbohydrazide and either VO(IV) or Ru(III)
salts in the molar ratio 1:1:1 afforded binuclear macrocyclic VO(IV)
and Ru(III) complexes. The complexes were characterized by ele-
mental analysis, IR, UV–vis, 1H-NMR, thermal gravimetric analysis
(TGA) and ESR, as well as the measurements of conductivity and
magnetic moments at room temperature. Kinetics and thermody-
namic parameters of the decomposition steps of the complexes
have been studied using Coats–Redfern equation. The bacterial
activity of the Schiff base, H2L, ligand and its metal complexes have
been investigated against two pathogenic bacteria: (Staphylococcus
aureus) as Gram-positive bacteria, and (Pseudomonas fluorescens) as
Gram-negative bacteria in addition to Fusarium oxysporum fungus
to assess their antimicrobial properties.
measurements were carried out on a Shimadzu-GC-Ms-QP mass
spectrometer model 1000 EX using a direct inlet system, at 220 °C
and 70 eV in the Micro Analytical Center, Cairo University, Egypt.
1H-NMR spectra of the ligand, Zn(II) and UO2(IV) complexes, as
solutions in DMSO-d6, were recorded on a Bruker WP 200 SY, spec-
trometer at room temperature using TMS as an internal standard, at
national research center, Giza, Egypt. Magnetic susceptibilities of
the complexes were measured at room temperature using a
Johnson Matthey, Alfa Products, model MKI magnetic susceptibility
balance. The effective magnetic moments were calculated from the
expression leff. = 2.828(v vM is the molar suscep-
MT)1/2 B.M., where
tibility corrected using Pascal’s constants for the diamagnetism of
all atoms in the compounds [20]. TGA curves were obtained using
NETZSCH-Gerateban Bestell-Nr,348472c. Thermal gravimetric
analysis (TGA) data were measured from room temperature to
800 °C at a heating rate 20 °C/min in dynamic N2 atmosphere,
Central laboratory, Cairo University. ESR spectra of the copper com-
plexes were recorded on a Bruker BioSpin GmbH spectrometer, at
the Research Centre for Nuclear and Radiation Safety, Naser City,
Cairo, Egypt. Molar conductivities were measured in DMF solutions
of the complexes (10ꢀ3 M) using a model LBR, WTWD-812,
Weilheim Conductivity meter fitted with a model LTA100 cell.
Synthesis of the Schiff base, H2L
Experimental
The Schiff base, H2L, ligand, Scheme 1, was prepared in two
steps [21]. The first step was acetylation of resorcinol (5.00 g,
45.5 mmol) with acetic anhydride (9.28 g, 91.0 mmol) in presence
of excess zinc chloride (10.0 g, 73.4 mmol) at 140 °C in a paraffin
oil path. The hot mixture was cooled to room temperature and
poured onto 140 mL 50% dilute hydrochloric acid. An orange pre-
cipitate was formed and increased with standing for 1 h. The or-
ange crude product was obtained by filtration with suction,
washed with distilled water till the color of the filtrate is nearly
colorless. Colorless needle crystals were obtained by crystallization
using ethanol. The yield of 4,6-diacetylresorcinol (DAR) was 6.88 g,
78%, m.p. 179 °C.
Materials
The nitrate salts of cobalt(II), nickel(II), copper(II), zinc(II) diox-
ouranium(VI) and lithium(I) hydroxide monohydrate are Merck or
DBH. Oxovanadium(IV)sulfate monohydrate is Aldrich. Ruthe-
nium(III)chloride trihydrates is purchased from Sigma. Organic
solvents (absolute ethyl alcohol, methyl alcohol, acetone, dimeth-
ylformamide (DMF) and dimethylsulfoxide (DMSO) are reagent
grade and were used without further purification.
Physical measurements
The second step was the addition of a solution of thiocarbohyd-
razide (1.36 g, 12.85 mmol) in ethanol (40 mL) to 4,6-diacetylres-
orcinol (DAR) in the molar ratio 2:1, i.e. (1.25 g, 6.44 mmol) for
DAR in ethanol (40 mL). The solutions were refluxed for 3 h. Yellow
crystals were formed on cooling the solutions slowly to room tem-
perature and the precipitates were collected by filtration, washed
with ethanol then diethylether and finally air-dried. The yield
was 1.43 g (62.71%), m.p. 243 °C for H2L.
Microanalyses of carbon, hydrogen and nitrogen were carried
out on Perkin-Elmer 2400 Series II Analyzer. Electronic spectra of
the metal complexes, in DMF solutions were carried out by using
UV–VIS Perkin–Elmer Model Lamda 900. NIR IR and Mid-range FTIR
spectra of the compounds were recorded as KBr-pellets within the
range 4000–400 cmꢀ1 using a Perkin–Elmer 16PC FTIR spectrome-
ter. Far FTIR spectra were recorded within the range 200–600 cmꢀ1
on a Perkin–Elmer System 2000 spectrometer as polyethylene pel-
lets at Institute of Applied Synthetic Chemistry, Vienna University
of Technology. Analyses of the metals in the complexes were car-
ried out by the dissolution of the solid complex in concentrated
HNO3 acid, neutralizing the diluted aqueous solutions with ammo-
nia and the metal solutions were titrated with EDTA [19]. 0.1 g of
dioxouranium(VI) complex was placed in a clean and dry weighed
crucible and ignited on Bunsen flame for 15 min. After that, the cru-
cible was ignited in a muffle at 1000 °C to constant weight for 2 h.
The residue was cooled and weighed again as U3O8. Mass spectra
Synthesis of the transition metal complexes of the Schiff base
Reaction of the Schiff base ligand with cobalt(II), nickel(II),
copper(II), manganese(II), ruthenium(III), oxovanadium(IV) and
dioxouranium(VI) ions in the molar 1:2 ratio (1 ligand:2 metal),
afforded the corresponding stoichiometry transition metal com-
plexes, with the exception of Ru(III) and VO(IV) ions which afforded
a mono-nuclear complex. Binuclear complexes for the other of the
metal complexes were obtained with the ligand in its binegative

598
A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
hexadentae form. Three different methods are used in preparing the
metal complexes. An example for the detailed preparations is given
for each method to obtain a mon- or a bi-nuclear metal complex in
acyclic or macrocylic geometry. In the preparation of VO(IV) com-
plex, 0.1 g of sodium acetate was added as a buffering agent to raise
the pH medium. Lithium hydroxide monohydrate was added to
facilitate the deprotonation of the ligand in the mole ratio 2:1
(2LiOHꢁH2O:1H2L) [22]. However, trials to prepare VO(IV) and
Ru(III) complexes of the Schiff base, to afford the stoichiometry of
the metal ion to the ligand in the mole ratio 2:1 were unsuccessful.
Both complexes are mono-nuclear even by using template method,
indicating that, the Schiff base acts as a neutral tetradentate ligand.
This behavior has been further supported by elemental analysis as
well as by conductivity measurements. The macrocyclic of mono
and bi-nuclear complexes of Ru(III) and VO(IV) have been success-
fully prepared and investigated by different spectroscopic methods.
Condensation reaction (preparation of mononuclear macrocylic
complex)
A trial to condense 4,6-diacetylresorcinol (DAR) with the VO(IV)
and Ru(III) complexes of the ligand to prepare the mononuclear
macrocyclic complex was carried out. This was performed by add-
ing a solution of 4,6-diacetylresorcinol (without adding LiOHꢁH2O)
in absolute ethanol gradually to a solution of the metal complex in
the same solvent. The solution was stirred for 30 min and refluxed
for 8 h. The precipitate formed on cooling was filtered off, washed
with ethanol, and then diethyl ether and finally air dried.
Condensation reaction of [(VO)(H2L)]ꢁSO4ꢁH2O,7 with DAR. A solution
of 4,6-diacetylresorcinol (1.00 g, 5.153 mmol) in ethanol (30 mL)
was added gradually to
a
solution of [(VO)(H2L)]ꢁSO4ꢁH2O
(2.840 g, 5.153 mmol) in ethanol (40 mL). The solution was stirred
for 30 min and heated to reflux for 3 h. A brown precipitate was
formed on hot. The precipitate was filtered off, washed with etha-
nol, and then diethyl ether and finally air dried. The yield was
2.562 g (66.71%). Scheme 2, represents the condensation reaction
of [(VO)(H2L)]ꢁSO4ꢁH2O, 7 with 4,6-diacetylresorcinol to afford
[(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O, 11.
Non-template method
Two moles of the metal anions in ethanol were added gradually
with constant stirring to an ethanolic solution of 1 mole of the
Schiff base ligand (with adding LiOHꢁH2O). The reaction is refluxed
for 3 h, where solid complexes were precipitated and filtered off,
washed with several portions of ethanol, then diethyl ether and fi-
nally dried over anhydrous CaCl2 in a desiccators. The complexes
are air stable in the solid state, soluble completely in DMF and
DMSO.
Template reaction (preparation of binuclear macrocylic complex)
A mixture of a solution of thiocarbohydrazone in ethanol and
4,6-diacetyl resorcinol (without adding LiOHꢁH2O), in ethanol
was added gradually to a solution of the metal ions in ethanol in
either the molar ratio 1:1:1 to obtain the binuclear complexes of
the macrocyclic ligand. The solutions were stirred for 30 min,
and heated to reflux for 8 h. The solid complexes were precipitated
and filtered off, washed with ethanol then diethyl ether and finally
air-dried. The complexes are air stable in the solid state, soluble in
DMF and DMSO.
Synthesis of [Ni2(L)(NO3)2]ꢁ3H2O, 2. A solution of LiOHꢁH2O (0.453 g,
10.795 mmol) in methanol (20 mL) was added gradually to a solu-
tion of the Schiff base ligand (2.00 g, 5.398 mmol) in ethanol
(40 mL). Then, a solution of Ni(NO3)2ꢁ6H2O (3.139 g, 10.794 mmol)
in ethanol (20 mL) was added gradually to the ligand. The solution
was stirred for 30 min. and heated to reflux for 5 h. A brownish red
precipitate was formed on hot. The precipitate was filtered off,
washed with ethanol, then diethyl ether and finally air-dried. The
yield was 1.89 g (77.38%).
Synthesis of [Ru2(H2L)(DAR)(Cl6)]ꢁ4H2O, 10. A solution mixture of
thiocarbohydrazone (0.445 g, 4.200 mmol) in ethanol (20 mL) and
4,6-diacetyl resorcinol (0.815 g, 4.200 mmol) in ethanol (30 mL)]
OH
HO
HN
NH
O
O
HO
OH
OH
S
N
N
H
H
N
N
SO4. H2O
O
OH
HO
V
N
SO4.2H2O
N
V
N
NH2
N
C
H2N
C
S
, 8 h
S
S
N
N
H
HO
O
H
4,6-Diacetyl resorcinol
NH
HN
[(VO)(H2L)].SO4.H2O
7
[(VO)(H2L)(DAR)]SO4.2H2O, 11
Scheme 2. Condensation reaction of [(VO)(H2L)]ꢁSO4ꢁH2O, complex 7 with 4,6-diacetylresorcinol to afford [(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O, 11.
HO
OH
HO
O
OH
O
H2N
H
Cl
Cl
N
C
C2H5OH
+
+
2 RuCl3.3H2O
N
N
NH2
, 8 h
NH
NH
HN
HN
N
H
S
4H2O
Cl
S
S
Cl
2 moles
Thiocarbohydrazone
2 moles
4,6-Diacetyl resorcinol
Ru+3
N
N
Cl
Cl
HO
OH
Scheme 3. Schematic preparation of macrocyclic complex [Ru2(H2L)(DAR)(Cl6)]ꢁ4H2O, 11.

A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
599
was added gradually to a solution of the RuCl3ꢁ3H2O (1.098 g,
4.199 mmol) in ethanol (40 mL) in the molar ratio 1:1:1 to obtain
the macrocyclic binuclear Ru(III) complex, Scheme 3. The solutions
were stirred for 30 min, and heated to reflux for 3 h. The solid com-
plexes were precipitated and filtered off, washed with ethanol then
diethylether and finally air-dried. Green precipitates were formed
which, in both cases of the different mole ratios, gave products of
the same formula [Ru2(H2L)(DAR)(Cl6)]ꢁ3H2O. The complex is air
stable in the solid state, soluble in DMF. The yield was 2.121 g
(87.89%).
elucidated by comparing the IR spectra of the complexes with
the spectra of the free ligand. These complexes are investigated
also by elemental analyses and different spectroscopic methods.
A variety of acyclic or macrocyclic mono- or binuclear complexes
were obtained with the ligand in tri-, tetra- or hexa-dentate forms.
3.1. Characterization of Schiff base, ligand, H2L
The Schiff base ligand was investigated by elemental analysis,
mass spectra, infrared, UV-visible, and 1H-NMR. The mass spec-
trum of the ligand revealed the molecular ion peak at m/e 371
which coincides with the formula weight after addition of one pro-
ton and supports the identity of the structure. The schematic frag-
mentation of the ligand is depicted (Supplementary material). The
ligand is obtained from the condensation of the carbonyl com-
pound (DAR) and thiocarbohydrazide in the 2:1 mole ratio. There
are two main features in the infrared spectrum of the newly
hard-soft, H2L, ligand. The first one is the disappearance of the
characteristic carbonyl group at 1710 cmꢀ1 of DAR, while the sec-
Biological studies
In vitro antibacterial activity studies were carried out by using
the standardized disc-agar diffusion method [23] to investigate
the inhibitory effect of the synthesised ligand and complexes
against Gram-positive bacteria, such as S. aureus (ATCC25923),
Gram-negative bacteria: as P. fluorescens (S97) and F. oxysporum
as a kind of fungi. The antibiotic chloramphencol was used as the
standard reference in the case of Gram-negative bacteria and
cephalothin was used as the standard reference in the case of
Gram-positive bacteria and cycloheximide was used as standard
antifungal reference. An inhibition zone diameter indicates that
the tested compounds are active against the used kinds of the bac-
teria and fungus. The studies were carried out at Faculty of Agricul-
ture, Department of plant Pathology, Al-Azhar University, Egypt.
ond feature is the appearance of the intense band at 1639 cmꢀ1
which is assigned to (C@N), the azomethine moiety, and confirm-
,
m
ing the condensation [24]. The Infrared spectra of the ligand
showed a broad band centered at 3267 cmꢀ1, due to the stretching
vibration of the AOH groups. The broadness may be due to the
intermolecular hydrogen bonding between the phenolic and the
azomethine groups, while the band observed at 1270 cmꢀ1 is as-
cribed to the phenolic CAO stretching vibrations [25]. The two ob-
served medium bands at 3273 and 3289 cmꢀ1 could be ascribed to
the asymmetrical and symmetrical stretching frequencies of (NH2)
groups, respectively. The Schiff base can undergo thione/thiol tau-
tomerism. However, the infrared spectrum of H2L, shows two
bands at 3148 and 3132 cmꢀ1 which are assigned to the stretching
Results and discussion
The physical and analytical data of the ligand and their corre-
sponding transition metal complexes are listed in Table 1. The
mode of binding of the Schiff base to the metal ions were
Table 1
Physicochemical properties of the Schiff base H2L ligand and its transition metal complexes.
Ligand/complex
M.F.
M.Wt.
Yield (%)
Color
D.P. °C
Elemental analysis, Calc.(Found)
%C %H %N
38.90 4.89 30.24
%M
-
H2L
C12H18N8O2S2
370.46
682.381
663.886
655.576
659.264
674.376
613.918
551.475
1068.536
736.044
1015.51
727.621
68.97
58.76
67.42
75.15
63.61
61.45
71.26
63.53
68.62
68.62
75.11
68.62
Yelow
Blue
193
>250
>250
>250
>250
>250
>250
>250
>250
>250
>250
>250
(38.55)
21.12
(4.85)
3.54
(29.24)
20.52
(1)I*
(2)I
[Co2(L)(NO3)2(H2O)2]ꢁ2H2O
C12H24Co2N10O12S2
C12H22Ni2N10O11S2
C12H20Cu2N10O10S2
C12H20N10O10S2Zn2
C12H24Mn2N10O12S2
C12H22Cl3N8O4S2Ru
C12H20N8O8S3V
17.27
(16.68)
17.68
(18.27)
19.38
(20.43)
19.83
(17.61)
16.29
(16.85)
16.46
(16.85)
9.23
(10.37)
45.91
(44.55)
13.73
(20.85)
21.71
(3.72)
3.34
(20.32)
21.09
[Ni2(L)(NO3)2]ꢁ3H2O
Green
(21.27)
21.98
(3.67)
3.07
(20.02)
21.36
(3) I
[Cu2(L)(H2O)2](NO3)2
[Zn2(L)(NO3)2]ꢁ2H2O
[Mn2(L)(NO3)2(H2O)4]
[Ru(H2L)(H2O)2]ꢁCl3
Blue
(21.22)
21.86
(4.56)
3.05
(20.44)
21.24
(4)I
white
(21.24)
21.37
(3.48)
3.58
(20.83)
20.76
(5)I
Orange
Pink
(21.09)
23.47
(3.13)
3.61
(20.68)
18.25
(6)II*
(7)II
(22.87)
26.13
(4.15)
3.65
(18.68)
20.31
[(VO)(H2L)]ꢁSO4ꢁH2O
[(UO2)2(L)(H2O)2]ꢁNO3)2
[Ru(H2L)(DAR)]ꢁCl3
Dark Green
Orange
Black
(25.81)
13.48
(3.31)
1.88
(19.77)
13.10
(8)I
C12H20N10O14S2U2
C22H24Cl3N8O4RuS2
C22H32Cl6N8O8Ru2S2
C22H28N8O11S3V
(13.34)
35.90
(1.96)
3.28
(12.97)
15.22
(9)III*
(10)III
(11)III
(12)III
(35.68)
26.02
(3.64)
3.18
(14.68)
11.03
(14.29)
19.91
(20.48)
7.00
[(Ru)2(H2L)(DAR)(Cl6)]ꢁ4H2O
[(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O
Black
(26.54)
36.31
(3.14)
3.87
(11.48)
15.39
Dark Green
(36.78)
(3.34)
(15.73)
(6.18)
[(VO)2(H2L)(DAR)(H2O)2]ꢁSO4)2
C22H28N8O16S4V2
890.656
58.48
Green
>250
29.66
(30.27)
3.16
(2.64)
12.58
(12.06)
11.43
(10.87)
All reactions were heated to reflux for 2 h, except in the formation of mon- and bi-nuclear macrocyclic Ru(III) and VO(IV) complexes (9,10,11,12) where the reaction was
heated to reflux for 8 h.
The oxovanadium(IV) sulfate monohydrate and dioxouranium(VI) hexa-nitrate were dissolved in a least amount of water then 30 mL methanol was added.
*
The notations of the preparative methods are: (I) Non-template reaction with LiOH (II) Non-template reaction without LiOH. (III) Condensation reaction of with 4,6-
diacetylresorcinol to afford mononuclear and binuclear macrocyclic complexes (9,10,11,12).

600
A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
vibrations of the two NH groups and indicating that the ligand is in
shielded by electrons due to mesomeric (+M) effect and inductive
effect (+I). These two signals showed related signals in slightly
lower frequencies which are due to the tautometric isomers of
the H2L ligand in solution [28].
the thione form. Furthermore, the thioamide [NHAC@S] group
exhibits bands observed at 1530 cmꢀ1
[
m
(CN) + d(NH)], 1263
(C@S)] respectively [26].
The appearance of these bands together with the absence of
(SH), between 2600 and 2800 cmꢀ1, confirm the presence of thion
cmꢀ1 (CN)] and 837 cmꢀ1
[m(CS) + m [m
m
Characterization of the complexes of the Schiff base ligand
form in the solid state.
The electronic spectrum of the Schiff Base ligand shows mainly
four absorption bands at 228, 297, 322 and 372 nm. The first two
Infrared spectra
The IR spectra reveled that all the metal complexes are coordi-
nated in the thione form, Table 2. This behavior is confirmed by the
appearance of two intense peak around the range 3142–3186 and
3128–3124 cmꢀ1, a characteristic feature of the NH stretching
frequency indicating the existence of the NH groups. Moreover,
the downfield shift of the thiocarbonyl group vibrations of the
thio-Schiff base suggest that the sulfur atoms take part in the
coordination to the metal atom, This observation has been further
confirmed by the appearance of new bands around the range 363–
bands at higher energy arise from
rings, while the band appearing at the lower energy side is attrib-
uted to a p–
pꢂ transition associated with the azomethine chromo-
p–
pꢂ transitions of the phenyl
spheres. The last broad band at 410–412 nm is due to the n ? pꢂ
transition which is overlapping with the intermolecular CT from
the phenyl ring to the azomethine group. On complexation the
absorption bands undergo a bathocromic shift compared to the
free ligand as a result of coordination via the nitrogen atoms of
the azomethine groups.
386 cmꢀ1 assignable to
of (NH2) assigned to the asymmetric and symmetric stretching
m(MAS). The highest stretching vibrations
Schiff bases derived from the thioamide functional group
(ANHAC@S) have previously been found to remain as the thione
tautomer. In solution, they however, can exist as an equilibrium
mixture of both the thione and thiol tautomers. 1H-NMR spectrum
of the ligand in DMSO-d6, showed that the thione form is more
dominate than thiol form, the absence of a signal at ca. 4.0 ppm
in the 1H NMR spectrum attributable to the SH proton provides a
strong evidence for the thione form of H2L. The spectrum shows
d(ppm) 2.61, ðs;6H;2CHa3Þ; 9.62 (s, 2H, 2NHb); 9.13 (s, 2H, 2NHc),
4.65 ðs; br;4H;2NHd2Þ, 6.31 (s, 1H, ArAHe); 8.02 (s, 1H, ArAHf) and
12.59 (s, br, 2H, ArAOHg) [27]. The signals at 9.62 and 9.13 were
assigned to the NHA groups, where one of them is deshielded to
a lower chemical shift than the other due to the anisotropic effect
of C@S group. It is observed that the signals due to the protons of
(2NHb), (2NHc) and ArAOHg groups completely disappeared on
adding D2O. The presence of the N(H) and (OH) signals at highly
downfield signals are probably due to intermolecular hydrogen
bond of ANH with a thione sulfur or the AOH of the ligand. On
the other hand, the two signals at 6.31 and 8.02 ppm were assigned
to the aromatic proton of the Schiff base ligand. The former signal
occurred downfield relative to the latter one and is assigned for the
protons in the meta-position for the two hydroxyl groups which is
m
terminal NH2 groups appeared nearly at the same position in the
metal complexes compared to the free ligand (ca. 3273 and
3289 cmꢀ1), as an indication of the non participation of amino
groups in coordination. The lower shift of the azomethine group
of the ligand on complexation supports that the coordination oc-
curs through the two nitrogen atoms of the azomethine This is con-
sistent with the presence of new bands at 447–468 cmꢀ1
assignable to
One of the most conceptual features of the observed infrared
spectra of the complexes is the coordination behavior of (OH) of
m(MAN) vibration [29].
m
the phenolic group, crystalline or coordinated water molecules
associated with the complex formation. IR spectra of the ligand
showed band at 1270 cmꢀ1 which is ascribed to the stretching
vibration of the phenolic aromatic oxygen. This band is shifted to
higher frequency (1287–1296 cmꢀ1) in the spectra of acyclic binu-
clear complexes of Co(II), Ni(II), Cu(II), Zn(II), Mn(II) and UO2(VI)
indicating that, the metal ions are coordinated through the pheno-
lic oxygen atoms after its deprotonation. The shifting to higher en-
ergy is expected due the increases in the double bond character
through resonance in the chelate ring of the Schiff base [30,31].
This observation has been further supported by the elemental
Table 2
Infrared frequencies of the main characteristic bands of the Schiff base ligand H2L and transition metal complexes.
Ligand/complex
m
(OH)/(H2O)
m(C@N)
m(CAO)
m(CS + CN)
m
(C@S)
m
(MAO)
m(MAN)
m(MAS) Other assignments
I
H2L
3267 br
3361 br
1639s
1592s
1270s
1287s
1263
1193m
837m
821m
–
–
–
(1)
[Co2(L)(NO3)2(H2O)2]ꢁ2H2O
510m
466m
447m
374m
1435(ms), 1257(ms), 1023(mas)
Bidentate NO3 group
1436s, 1317s, 1026
Unidentate NO3 group
1373s, ionic NO3
(2)
[Ni2(L)(NO3)2]ꢁ3H2O
3345s, br
1600s
1283s
1186m
783m
524m
364m
as
(3)
(4)
[Cu2(L)(H2O)2](NO3)2
[Zn2(L)(NO3)2]ꢁ2H2O
3356s, br
3345s, br
1589s
1606s
1292s
1285s
1224m
1168m
772m
757s
531s
517m
450m
466m
381m
366m
1350s, 1294s, 1017
as
Unidentate NO3 group
1344s, 1276s, 1021as
Unidentate NO3 group
Ionic complex
(5)
[Mn2(L)(NO3)2(H2O)4]
3426s, br
1583s
1278s
1211m
814s
527m
464m
364m
(6)
(7)
[Ru(H2L)(H2O)2]ꢁCl3
[(VO)(H2L)]ꢁSO4ꢁH2O
3354s, br
3398s, br
1570s
1531s
1270s
1270s
1183m
1197m
766s
776s
–
–
456m
448m
366m
383m
987 w,
(ionicsO4)
910m, 898 mas(UO2) and ms(UO2),
m(VO), 1136 br, 630m
m
(8)
(9)
[(UO2)2(L)(H2O)2]ꢁNO3)2
[(Ru)(H2L)(DAR)]ꢁCl3
3446s, br
3433s,br
3358s, br
3462s, br
1578s
1296s
1268s
1273s
1270s
1272s
1173m
1120m
1182m
1188m
1197m
792m
816m
826m
835m
786m
508m
463m
456m
458m
468m
458m
367m
363m
386m
–
1380s, ionic NO3 group
Ionic complex
1565s
1630s
1548s
1627m
1565s
1624s
1548s
1632m
–
–
–
–
(10) [(Ru)2(H2L)(DAR)(Cl6)]ꢁ4H2O
(11) [(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O
Neutral complex
983 w,
m
(VO) 1124 br, 634m
(VO) 1130 br, 623m
m
(ionicsO4)
(12) [(VO)2(H2L)(DAR)(H2O)2]ꢁ(SO4)2 3462s, br
376m
985 w,
m
m
(ionic SO4)
Strong, w = weak, m = medium, and br = broad, ms : A single degenerate state which is symmetrical about the principle axis.
as: Antisymmetrical state with respect to the three C2v axis, m0s: A symmetrical state with respect to the three C2v axes.
m

A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
601
analysis and their electronic d–d transitions of the metal ions as
well as the magnetic moment values. The appearance of new band
significant change has been observed compared to the stretching
vibration of (C@S) group of the ligand.
at 508–527 cmꢀ1 due to
m
(MAO) supports the previous result. The
broad band at 3345–3462 cmꢀ1 corresponds to
m
(OH) the stretch-
Electronic spectra magnetic moments and molar conductance
measurements
ing vibration of the uncoordinated phenolic group, crystalline and/
or coordinated water molecules [32]. The second most important
features of the infrared spectra of some complexes are the coordi-
nation behavior of nitrate, chloride or sulfate anions. The IR spectra
of the complexes show strong absorption bands which are consis-
tent with monodentate or bidentate nitrate vibration. It is worth to
mention that, in complex 1 [Co2(L)(NO3)2(H2O)2]ꢁ2H2O, the nitrate
behaves as a bidentate ligand. In this case, nitrate possesses three
0
It is possible to draw up the electronic transitions and predict
the geometry with the aid of magnetic moments of most metal
ions (Supplementary material). Table 3 lists the characteristic elec-
tronic absorption bands, magnetic moments and molar conduc-
tance of metal complexes in DMF solutions. The main absorption
band of the ligand is also cited in the table. The bands in all metal
complexes located at 233–380 nm region and the shoulder at 396
non-degenerate modes of vibrations (ms
,
ms and
m
as), at 1435, 1294
nm were assigned to p ?
pꢂ transitions within the aromatic rings
in the ligand. The absorption band in the range 346–383 nm could
be assigned to both the C@N groups [40].
and 1023 cmꢀ1. The separation of ꢃ200 cmꢀ1 between ms and ms
0
confirmed the bidentate nature of the nitrate groups [33]. The
NOꢀ3 ions are coordinated to the metal ion in a unidentate fashion
in the complexes 2, 4 and 5 corresponding to C2v symmetry, with
0
The electronic spectrum of the Co(II) complex consists of three
4
spin allowed transitions. Since the T2g(F) 3T1g(F)(
m1) transition
three non-degenerate modes of vibrations (ms
,
ms and
mas), appeared
is essentially a two electron transition from t52geg2 to t23geg4, it is ex-
in the ranges 1436–1350, 1276–1317 and 1017–1026 cmꢀ1
respectively while the spectra of complexes [Cu2(L)(H2O)2](NO3)3,
,
pected to be weak, and the usual assignment observed are
4
4A2g(F) 4T1g(F)(
m
2) and T1g(P) 4T1g(F)(
m3) transitions corre-
3
and [(UO2)2(L)(H2O)2]ꢁ(NO3)2,
8
show one strong band at
sponding to 563 and 473 nm, respectively. These transitions are
in agreement with the formation of a high spin octahedral geome-
try. Also, the magnetic moment provides a complementary means
of octahedral geometry, the measured magnetic moment for this
complex is 5.09 B.M which lies in the range of octahedral com-
plexes. On the other hand, the electronic spectra of the Ni(II) com-
plex showed a band at 633 nm due to the 3T1(F) 3A2 transition,
which could occur in a tetrahedral d8 arrangement with another
1373 cmꢀ1 and 1380 cmꢀ1, respectively, assigned to the stretching
mode of the ionic nitrate [34].
For ruthenium acyclic and macrocyclic complexes, 6, 9 and 10,
the coordination behavior of the chloride ions was investigated by
the addition of AgNO3 solution to the Ru(III) complexes. Precipita-
tion of silver chloride occurred only in complex 6 [Ru(H2L)(H2O)2]ꢁ
Cl3 and 9 [(Ru)(H2L)(DAR)]ꢁCl3. For complex 10, no precipitation
was observed due to coordination of the chloride ions to the metal
ion. The IR-spectra of VO(IV) complexes 7, 11 and 12 display a
strong band at the range 983-987 cmꢀ1 which has no counterpart
in the spectrum of the ligand and is assigned to the stretching fre-
one at 483 nm owing to 3T1(P) 3A2(F)(
m3). The transition
m1) is out of the range. The magnetic moment of
3T2g(F) 3A2(
2.88 B.M., lies in the range reported for tetrahedral compounds
[41]. The ligand field parameters such as Racah inter-electronic
repulsion parameter (B), covalency factor b = Bcomplex/Bfree ion, were
calculated The value of 10Dq in Co(II) and Ni(II) complexes were
quency of the
m(V@O) [35]. Generally, the free sulfate ion belongs
to the high symmetry point group Td and is expected to show only
two fundamental IR active vibrations
m
d(SAO) and dd(OASAO) [36].
calculated from the transition energy ratio diagram using m3/m2 ra-
The bands in the two regions 1124–1136 cmꢀ1 and 623–634 cmꢀ1
confirm the presence of an ionic sulfate for all the previous com-
plexes 11 and 12. This observation has been further supported by
conductivity measurements. For the UO2(VI) complex, 8, the IR
spectrum displays two bands at 910 and 898 cmꢀ1, which are as-
tio [42]. The values of the parameters m3/m
2, B0, b and 10Dq are 0.84,
936, 0.963, 9403 cmꢀ1 and 0.65, 974, 0.935, 7912 cmꢀ1 for Co(II)
and Ni(II) complexes, respectively. The B0 value for the complexes
1
and 7 are lower than the free metal ion value (B for
Co(II) = 971 cmꢀ1 and for Ni(II) = 1041 cmꢀ1) [43]. This is an indica-
tion of orbital overlapping and delocalization of the d-orbital.
According to Jorgensen, the decrease in the B0 values is due to
the reduction of nuclear charge of the cation and effective charge
induced by the ligand. The b values obtained are less than unity,
suggesting a considerable overlap between the ligand and the me-
tal [44].
signed to the mas(UO2) and ms(UO2) modes, respectively. This obser-
vation suggests that the O@U@O moiety is virtually linear in these
complexes [37]. In the spectra of the macrocyclic complexes 9, 10,
11 and 12, the band corresponding to the stretching vibrations of
the carbonyl groups of 4,6-diacetylresorcinol (1710 cmꢀ1) as well
as the second terminal NH2 (3273 and 3289 cmꢀ1) of thiocarbo-
hydrazone groups disappeared as a result of the condensation
and formation of the macrocyclic structure. A conclusive evidence
is the appearance of new bands at 1630 and 1624 cmꢀ1 for the
mononuclear complexes 9 and 11 and at 1627 and 1632 cmꢀ1 for
complex 10 and 12 respectively, which could be attributed to the
formation of the second azomethine group [38]. The infrared spec-
tra of the macrocyclic complexes show similar behavior to those of
the acyclic complexes, where the metal ions are coordinated in the
thione form. This behavior has been confirmed by the appearance
of the bands corresponding to NH stretching frequency and further
supported by chelation of the soft donors to the metal [39]. From
the previous observation and discussion of the infrared spectra, it
is obvious that the bonding sites of the ligand to the metal ion
are the nitrogen atoms of the azomethine, the thion groups as well
as, the phenolic oxygen for the acyclic complexes, while the bond-
ing sites for mononuclear complexes or binuclear macrocyclic
complexes are only the azomethine and the thion groups, except
for the oxovanadium complex [(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O 11,
where the bonding sites are only the azomethine groups. No
The electronic spectrum of the green Cu(II) complex 3, exhibit
two bands at 567 and 439 nm corresponding to 2B1g ? 2Eg and
2B1g ? 2A1g transitions in a square planar geometry. The magnetic
moment value (1.89 B.M) recorded for the [Cu2(L)(H2O)2]2NO3,
complex lies within the permissible range recorded for one un-
paired electron [45]. In the Mn(II) complex, the ground state, 6A1,
corresponding to (t2g)3(eg)2 is unaffected by the crystal field and
so the d–d transition is weak. However, two absorptions have been
observed at 488 and 389 nm assigned to 6A1 ? 4T1g(G) and a
charge transfer transition, respectively, with a magnetic moment
of 5.56 B.M. suggesting an octahedral geometry. This proposal is
further supported by the elemental analysis and the electrolytic
nature of these complexes (140
X
ꢀ1 cm2 molꢀ1 for Cu(II) complex
and 145
X
ꢀ1 cm2 molꢀ1 for Mn(II) [46]. Complexes [Zn2(L)(NO3)2]ꢁ
2H2O, 4 and [(UO2)2(L)(H2O)2]ꢁ(NO3)2, 8 are of a diamagnetic nat-
ure. With the aid of the elemental analysis and Infrared-spectra,
the proposed configuration is expected to be tetrahedral for Zn(II)
and distorted octahedral for (UO2) complex. Molar conductance va-
lue in DMF is 138 and 102
the later complexes, respectively. The electronic spectrum of the
X
ꢀ1 cm2 molꢀ1 for the former and for

602
A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
Table 3
Electronic absorption bands (nm), magnetic moments (B.M.) and molar conductivities (
X
ꢀ1 cm2 molꢀ1) of the Schiff base ligand and its transition metal complexes.
Ligand/complex Electronic absorption bands their assignment, magnetic moments and molar conductivities
a
d–d Transition
d–d Transition assignment
lcomplex (B.M.)
(^ )
(I)
H2Lb
412b(0.54)c
473(0.32)
483(0.47)
439(0.56)
–
–
–
–
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
[Co2(L)(NO3)2(H2O)2]ꢁ2H2O
[Ni2(L)(NO3)2]ꢁ3H2O
[Cu2(L)(H2O)2](NO3)2
[Zn2(L)(NO3)2]ꢁ2H2O
[Mn2(L)(NO3)2(H2O)4]
[Ru(H2L)(H2O)2]ꢁCl3
563(0.21)
633(0.38)
567(0.52)
–
488(0.47)
634(0.31)
724(0.43)
525(0.53)
654(0.29)
671(0.40)
746(0.41)
782(0.35)
4T1(F) ? 4A2g(F)(m2
)
5.09
2.88
1.89
–
5.56
1.72
1.83
–
1.78
1.53
1.86
1.07
233
138
140
138
145
343
123
152
318
184
103
154
3A2g(F) ? 3T1g(F)(m2
)
2B1g
–
?
2Eg(m1
)
–
6A1
?
?
?
4T1g
(
m1
)
537(0.24)
518(0.48)
442(0.51)
556(0.34)
544(0.43)
512(0.52)
547(0.37)
2T2g
2A2g
(
m1
)
[(VO)(H2L)]SO4ꢁH2O
2B1g
2Eg(m1
)
[(UO2)2(L)(H2O)2]ꢁ(NO3)2
[(Ru)(H2L)(DAR)]ꢁCl3
[(Ru)2(H2L)(DAR)Cl6]ꢁ4H2O
[(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O
[(VO)2(H2L)(DAR)(H2O)2]ꢁ(SO4)2
Charge Transfer
2T2g
2T2g
2B1g
?
?
?
2A2g
2A2g
(
(
m1
)
)
m1
2Eg(m1
)
2B2
?
2E(m1
)
a
b
c
Molar conductance (Oꢀ1 cm2 molꢀ1) was measured in 10ꢀ3 molꢀ1 DMF solvent.
Charge transfer transition band of the ligand.
Values of emax are in parentheses and multiplied by 10ꢀ4 (L molꢀ1 cmꢀ1).
diamagnetic dioxouranium(VI) complex shows mainly two bands
where the absorption is tailing into the visible region, which pro-
duces the intense orange color. The first band is observed at
442 nm corresponding to charge transfer from equatorial donor
atoms of the ligand to the dioxouranium(VI) ion. The second band
is observed at 525 nm due to electronic transitions from apical
oxygen atom to the f-orbitals of the uranyl atom characteristic of
dioxouranium(VI) moiety [47].
previous result where the chelation of the ligand to the metal oc-
curs only through the azomethine groups. The binuclear macrocy-
clic complex of oxovandium 12 [(VO)2(H2L)(DAR)(H2O)2]ꢁ(SO4)2,
exhibits subnormal magnetic moment (leff 1.07 B.M) at room tem-
perature. The unpaired electron in the 3dxy of vanadium ion is
overlapped with the dxy orbital of the adjacent vanadium atom
which lead to direct spin-spin coupling. Such an interaction leads
to a singlet spin state and a higher triplet spin state with a lower
magnetic moment of 1.07 BM. Furthermore, the ESR spectrum of
the complex was observed as silent. This is an indication for the
formation of a strong covalency between the two vanadium cen-
ters in the complex. Absorption at 787 and 547 nm are observed
2
The ground state of Ru(III) is T2g and the first excited doublet
2
2
levels in the order of increasing energy are A2g and A1g which
arise from the t2g4eg1 configuration. In a d5 system and especially
in Ru(III) which is a relatively strong oxidizing agent, charge trans-
fer bands are prominent in the low-energy region and obscure the
weaker bands due to the d–d transitions. The electronic spectra of
Ru(III) complexes 6, 9 and 10 exhibit mainly three bands at the
ranges, 634–671 nm, 537–556 nm and 342–420 nm, respectively.
The first band is assigned to the d–d transition 2T2g ? 2A2g while
the second intense band is due to M–Lpꢂ transition. The last one
is attributed to the inter-ligand transition or to MLCT bands. The
positions of the absorption bands as well as the magnetic suscep-
tibility measurements for the mononuclear complex 6 (1.72 B.M.)
and the macrocyclic mono nuclear 9 (1.78 B.M.) respectively, indi-
cate the presence of one unpaired electron and confirm a low-spin
octahedral configuration [48]. For the macrocyclic complex
[(Ru2)(H2L)(DAR)(Cl6)]ꢁ4H2O,10 the magnetic moment is lower
than expected (1.53 B.M). This behavior can be explained by the
presence of a partial coupling interaction between the two elec-
trons of the ruthenium ions in the complex [49]. Higher molar con-
ductance values at the range 343 and 318 Oꢀ1 cm2 moleꢀ1 for
Ru(III) complex, 6 and 9 respectively, suggest a 1:3 electrolytic
behavior. This result was confirmed where chloride ions precipi-
tate by addition AgNO3 solution to these complexes. The mass
spectrum of [(Ru)(H2L)(DAR)]ꢁCl3 complex, 9, Fig. 1, was performed
to determine its molecular weight and its fragmentation pattern,
Scheme 4.
m m2) transitions
and can be assigned to 2B2 ? 2E( 1) and 2B2 ? 2B1(
attributed to a distorted octahedral geometry [51].
Molar conductivities of the complexes are recorded in DMF
(1.0 ꢄ 10ꢀ3 M). The conductivity data are in the range reported
for 1:1, 1:2 or 1:3 electrolytes. The elemental analysis agrees with
the previous results. It has been reported that DMF is a good donor
solvent has can be replaced by NOꢀ3 from the coordination sphere
of the metal complexes. This leads to the coordination nitrate ion
is exchanged with solvent and became free in the solution [52].
1H-NMR spectra
1H-NMR spectrum of [(UO2)2(L)(H2O)2]ꢁNO3)2, Table 4, showed
similar signals as for the H2L ligand, except the disappearance of
the phenolic proton (ArAOH) signals which were expected at
12.59 ppm compared with the H2L ligand This can be attributed
due to the deprotonation of the phenolic groups and subsequently
the replacement of the protons by metal. The appearance of the
signals due to 2CH3a, NHb, NHc groups and NHd2 with downfield
shielding with respect to the free H2L ligand is interpreted as a sign
of complexation of the UO2(VI) ion by the thione group as well as
the azomethine groups [53].
ESR spectra
The reflectance spectrum of each of the oxovanadium com-
plexes, 7 and 11 shows a well-defined two bands at 518 and 724
for the former and at 512 and 746 nm for the latter assigned to
1B2 ? 2E and 1B2 ? 2A1 in a square-pyramidal structure configura-
tion with effective magnetic moment of 1.83 and 1.86 B.M. for
complexes, 7 and 11 respectively [50]. For [(VO)2(H2L)(DAR)
(H2O)2]ꢁSO4ꢁ2H2O complex 11, ESR spectra, magnetic susceptibility
values as well as the thermogravimetric analysis agree well with
the proposed geometry of this complex to be square pyramidal
structure. IR spectra also provide a complementary mean for the
The powder ESR spectrum was carried out for complexes 3 and
11 (Supplementary material) at room temperature with frequency
at 9.723 Ghz and magnetic field set of 3459 G. For the Cu(II) com-
plex [Cu2(L)(H2O)2](NO3)2, 3, the spectrum reveals a broad line
with poorly resolved hyperfine structure. The g tensor values of
the Cu(II) complex can be used to derive the ground state. In
square-planar or square pyramidal complexes, the unpaired elec-
2
tron lies in the dx2
orbital giving B1g as the ground state with
ꢀy2
g|| > g\ > 2.0023, while giving 2A1g with g\ > g|| > 2.0023, if the un-
paired electron lies in the d2z orbital. From the observed values,

A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
603
Fig. 1. Mass spectra of Schiff base ligand H2L and [(Ru)(H2L)(DAR)]ꢁCl3 complex, 9.
+
HN
N
NH
HN
N
NH
HO
HO
OH
HO
OH
OH
S
S
N
N
- 3Cl-
+ H
.
- CH CN;
3
Ru
S
629.65 (629; 49% )
Ru
S
Cl3
- 40.04
- 106.36
N
N
N
OH
HO
NH
HN
NH2
HN
736.01(737, 11.2%)
589.61 (589; 589, 76% )
+
- HSCN
- C6H2O2
- NH2NH2
- C8H7O2N3
- 177.16
H2N
NH
- 59.09
530.52 (530; 57 %)
498.48 (499;39.4%)
+
- C8H8O2N
- 106.08
- 32.04
- C6H2O2
- 106.08
+
S
RuSC(NH2)2
HN
N
NH2
NCCH3
N
171.17 (170;41 %)
- 150.15
HO
Ru
S
- C(NH2)2
- HSCN
OH
427.44 (426;43.3 %)
Ru
S
- 59.09
321.32 (320;73.6 %)
- NH2NH2
- 32.04
HO
RuS+
133.14 (133; 83 %)
N
- CH3CN
- 41.04
HO
NH2
HN
+
+
+
483.53 (484; 65.5 %)
HN
N
NH2
- NH2CSNHNH2
+ 4H.
NH2
HN
N
HO
- CH3CN
- 41.04
S
OH
Ru(NCCH3)
S
Ru
- 87.10
+
HO
Ru
OH
N
308.32 (307; 56.3 %)
NCCH3
HN
NH2
HO
- HSCN
HO
HO
NH2
383.40 (382; 77%)
S
- C10H14
O
395.42 (394;58 %)
N
- 59.09
- C8H8O
- 150.20
Ru
- 120.15
+.
RuO(NCCH3)
N
RuO+
S
- CH3CN
- 41.05
HO
SC(NH2)2
NH2
- 2 CH3CN
158.12 (157; 58.1%)
RuOSC(NH2)2
HN
117.07, (118) 62.8%
190.15 (190;74.7 %)
RuO(NCCH3)2
442.49 (442; 71.1 %)
- 82.10
272.25 (272; 6.9 %)
Scheme 4. Fragmentation of the mass spectrum of [Ru(H2L)(DAR)]ꢁCl3,9ꢂCalc./[found, % intensity]. Differences between calculated and found values are due to abstraction or
addition of free H radicals.

604
A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
Table 4
1H-NMR chemical shifts (d, ppm) of the Schiff base, H2L, ligand and its UO2(VI) complex (5) in DMSO-d6 and after addition of D2O.
(a)
(b)
(a)
(b)
H
(e)
H
N
H2O
H
(c)
H2N
HN
(e)
(f)
(c)
N
H
N
H2N
HN
N
N
H
H
N
(NO3)2
N
N
H2O
O
N
N
O
(d)
NH2
(d)
NH2
U
U
S
S
S
HO
OH
(g)
S
O
O
O
(f)
O
H2L
Complex, 5 [(UO2)2(L)(H2O)2].2NO3
H2L
(A)
[(UO2)2(L)(H2O)2]ꢁ(NO3)2 (5)
(B)
(A)
(B)
Assignment
Chemical shift, dH (ppm)
2.61
9.62
9.13
4.65
6.31
8.02
12.56
2.63
–
–
4.55
6.31
7.99
–
2.21
10.11
8.81
4.62
6.27
7.96
–
2.23
–
–
4.49
6.28
7.93
–
Ha [s, 6H, 2CH3]
Hb [s, br, 2H, 2NH]
Hc [s, br, 2H, 2NH]
Hd [s, 2H, 2NH2]
He [s, 1H, ArAH]
Hf [s, 1H, ArAH]
Hg[s,br, 2H, (ArAOH)]
(A) 1H-NMR signals in DMSO-d6 without addition of D2O. (B) 1H NMR signals in DMSO-d6 with the addition of D2O. s = singlet; br = broad.
g||(2.10) > g\(2.07) > ge(2.0023) indicate that the copper site has a
dx2 ground state characteristic of a square planar, or octahedral
The X-band ESR spectrum of a five-coordinated square pyrami-
dal [(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O, 11, gave a broad single with poorly
resolved eight hyperfine lines corresponding to the usual parallel
and perpendicular components of g- and hyperfine (hf) A-tensor
eight line pattern, and shows that a single vanadium is present
in the molecule, i.e. it is a monomer. The observed order in the
parameters g\(2.11) > g||(2.08) indicates that the unpaired elec-
tron is present in the dxy orbital with square-pyramidal geometry
around the oxovanadium(II),d1 chelates [57].
ꢀy2
geometry [54]. The g|| value is an important function for indicating
the covalent character of MAL bond for ionic character. Kivelson
and Neiman have reported that g|| > 2.3 and for the covalent char-
acter g|| < 2.3. In the present complex, the g|| is less than 2.3 reveal-
ing an appreciable covalent character for the CuAL bond [55]. In
addition, the exchange coupling interaction between two copper
centers is explained by Hathaway expression, G = (g|| ꢀ 2.0023)/
(g\ ꢀ 2.0023), if the value of G is greater than 4 the exchange inter-
action in the solid state is negligible, whereas when it is less than 4
a considerable exchange interaction is noticed in the solid com-
plex. The calculated G value, of the square planar complex [Cu2(L)
(H2O)2](NO3)2, suggests a strong interaction between Cu(II) centers
[56].
Thermogravimetric, kinetic and thermodynamic data analysis
TGA studies were carried out to illustrate the thermal stability
of the complexes and to investigate whether the water molecules
are crystalline or coordinated to the central metal ion, Fig. 2. The
complexes 10 and 11 are thermally investigated by TGA analysis
Fig. 2a. TGA/DrTGA curve of complex [(Ru)2(H2L)(DAR)(Cl6)]ꢁ4H2O, 10.

A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
605
Fig. 2b. TGA/DrTGA curve of complex [(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O, 11.
-2 SC(NH2)2
- 4H2O
*7.09(6.63)%
-CH4
*9.06(9.34)%
137-260 o
Stage 2
[(Ru)2(C22H24N8O4S2Cl6)]
M. wt = 943.472
[(Ru)2(C22H24N8O4S2Cl6)].4H2O
M. wt. = 1015. 52
[(Ru)2(C20H16N6O4SCl6)]
M.wt = 851.307
49-136 o
C
C
-3 Cl2
*42.64(43.32)%
261-628 o
Stage 3
Stage 1
- C8H8N6S
C
Residue
12H8O4Ru2
C
*41.18 (40.32)%
M. wt = 418.333
Scheme 5. Thermal degradation pattern of complex [(Ru)2(H2L)(DAR)(Cl6)]ꢁ4H2O, 10. ⁄[% of the loss of weight, Calc./(Found)].
- 2H2O
-SO3
-C2H4
-C2H4
[(VO)(C20
H20N8O4S2)]SO4
[(VO)(C22
H
24N8O4S2)].SO4.2H2O
[(VO)(C18H16N8O5S2)]
M.wt = 555.449
*14.86(14.46)%
127-246 o
Stage 2
*(8.80(8.57)%
M. wt. = 727.62
M. wt = 663.567
56-126 o
Stage 1
C
C
*54.48(54.07)%
247-525 o
C
- C17H12N6O4S
Stage 3
Residue
VO(CH4N2OS)
*21.86 (22.90)%
M. wt =159.063
Scheme 6. Thermal degradation pattern of complex [(VO)(H2L)(DAR)]SO4ꢁ2H2O, 11. ⁄[% of the loss of weight, Calc./(Found)].
"
ꢀ
#
ꢀ
ꢁ
1ꢀn
and their degradation schemes are presented in Schemes 5 and
6. The thermograms show complete decomposition around
800 °C.
The kinetic and thermodynamic parameters of the various
decomposition stages were determined from TGA thermogram
using the Coats–Redfern equation [58,59] in the following
forms:
1 ꢀ ð1 ꢀ
a
Þ
AR
BE
2RT
E
E
log
log
¼ log
1 ꢀ
ꢀ
for n–1 ð1Þ
for n ¼ 1 ð2Þ
Tð1 ꢀ nÞ
2:303RT
ꢁ
ꢀ
ꢁ
ꢀlogð1 ꢀ
T2
a
Þ
AR
BE
2RT
E
E
¼ log
1 ꢀ
ꢀ
2:303RT

606
A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
Fig. 3a. Coats–Redfern plots for complex [(Ru)2(H2L)(DAR)(Cl6)]ꢁ4H2O, 10, where Y = log[ꢀlog(1 ꢀ
a
)/T2].
Fig. 3b. Coats–Redfern plots for complex [(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O, 11, where Y = log[ꢀlog(1 ꢀ
a
)/T2].
where E, R, A, b are the heat of activation, the universal gas constant,
pre-exponential factor and heating rate, respectively. These two
equations differ only in the order of reaction, in the present work,
all complexes decomposition stages show a best fit for (n = 1) indi-
cating a first order reaction in all stages. Other n values did not give
better correlations. The correlation coefficient, R2, was computed
using the least square method for different values of the order of
the reaction, n, by plotting the left-hand side of Eq. (1), (2) versus
1000/T, Figs. 3a and 3b. The n value which gave the best fit
(R2 ꢃ 1) was chosen as the order parameter for the decomposition
stage of interest. From the intercept and linear slope of each stage,
the A and E values were determined. The thermodynamic parame-
D
D
S# ¼ R½2:303 logðAh=ktÞ ꢀ 1ꢅ
ð4Þ
ð5Þ
G#
¼
D
H# ꢀ T
D
S#
where k is the Boltzmann’s constant and h is the Planck’s constant.
The kinetic are listed in table 5. From the results, the
D
E
# values re-
veal low stability of the complexes. However, [(VO)(H2L)(DAR)]ꢁ
SO4ꢁ2H2O complex, 11 possess high stability than complex, 10
[(Ru)2(H2L)(DAR)Cl6]ꢁ4H2O. The positive sign of
D
H# indicates that
the decomposition stages are endothermic processes for both of
them. On the other hand, the positive sign of
G# reveals that all
the decomposition steps are non-spontaneous and the positive val-
ues of
S# suggest the residue after decomposition is less ordered
D
D
ters,
D
H#,
D
S# and
D
G# were calculated using the relationships;
than the starting ones.
From interpretation of the elemental analysis and infrared, elec-
D
H# ¼ E ꢀ RT;
ð3Þ
tronic spectra, magnetic susceptibility, ESR, mass spectra, 1H-NMR
Table 5
The kinetic and thermodynamic parameters of the thermal decomposition steps of the macrocyclic complexes 10 and 11.
Complex
Steps
Coats–Redfern equation
A (sꢀ1
)
D
S# (J kꢀ1 molꢀ1
)
D
H# (kJ molꢀ1
)
D )
G# (kJ molꢀ1
E
R2
n
[(Ru)2(H2L)(DAR)Cl6] 4H2O, 10
First step
Second step
Third step
71.39
38.57
36.15
0.970
0.992
0.999
0.66
1.00
2.00
4.44 ꢄ 107
10.05 ꢄ 106
5.45 ꢄ 105
14.10 ꢄ 109
3.44 ꢄ 109
4.32 ꢄ 109
21.70
19.61
27.41
68.01
36.49
33.11
140.15
80.10
100.69
[(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O, 11
First step
Second step
Third step
48.58
58.62
71.93
0.960
0.994
0.982
0.00
0.33
1.00
31.70
27.05
21.70
46.76
55.90
68.01
79.06
102.98
140.15
E – the heat of activation.
R2 – the correlation coefficient.
n – the order of the reaction.
A – the pre-exponential factor.
D
H#, S# and G# are the thermodynamic parameters.
D D

A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
607
(a)
H
N
H
N
H
N
N
N
H2O
2H2O
HN
H2N
H2O
NH2
Co
Co
S
S
O
O
O
N
O
O
O
N
O
O
[Co2(L)(NO3)2(H2O)2].2H2O,1
X
X
O
O
S
S
NH2
NH
H2N
M
M
n. Y
N
H
N
N
N
N
H
H
For M=Ni(II), X=NO3, Y= H2O and n=3
For M=Cu(II), X=H2O, Y= NO3 and n=2
For M=Zn(II), X= NO3,Y= H2O and n=2
Ni(II) 2, Cu(II) 3 and Zn(II) 4 thio-Schiff base complexes.
H
N
H
N
NO3
N
N
NO3.
H2O
H2O
NH
HN
NH2
Mn
Mn
H2O
H2N
S
S
O
O
H2O
[Mn2(L)(NO3)2(H2O)4], 5
HO
OH
HO
OH
H2O
Ru
SO4. H2O
Cl3
H
N
N
H
H
N
N
H
N
N
C
N
C
N
C
V
H2N
C
NH2
H2N
NH2
N
H
S
N
H
N
H
S
N
H
S
S
O
H2O
[(VO)(H2L)]SO4. H2O, 7
[Ru(H2L)(H2O)2].Cl3, 6
H
N
H
N
H2O
H2N
HN
H
N
N
N
H2O
2NO3
O
O
O
O
NH2
U
U
S
S
O
O
[(UO2)2(L)(H2O)2].(NO3)2, 8
Fig. 4a. Representative structures of acyclic complexes (1–8).
and molar conductivity, it is possible to draw up the tentative
structures of the transition metal complexes, Fig. 4.
of the metal atom because of partial sharing of its positive charge
with a donor group and the possible -electron delocalization over
p
the whole chelate ring [61]. Such a chelation could enhance the
lipophilic character of the central metal atom, which subsequently
favors its permeation through the lipid layers of the cell membrane
and blocking the metal binding sites on enzymes of microorganism
[62,63]. There are other factors which also increase the activity,
such as solubility, conductivity and bond length between the metal
and the ligand.
It is worth to mention that the ligand showed moderate biolog-
ical activity against the tested strains and the complexes show
higher bacterial activity as compared to the fungus. The result re-
vealed also that complexes of ruthenium and copper displayed the
maximum (significant) inhibition against the growth of the se-
lected Gram-positive, Gram-negative bacteria and fungi followed
by zinc complex and finally cobalt (II) and Ni(II). In contrast,
Biological studies
The Schiff base ligand H2L and its metal complexes were evalu-
ated for their antimicrobial activity against one strain Gram-posi-
tive bacteria S. aureus and P. fluorescens as Gram-negative
bacteria as well as one pathogenic fungus, as F. oxysporum The re-
sults of the biological studies of the ligand and the complexes are
shown in Fig. 5, Table 6. The data are compared with standard anti-
biotics, chloramphencol as Gram-negative and cephalothin as stan-
dard reference for Gram–positive bacteria. Cycloheximide was
used as antifungal standard reference. The in vitro antibacterial
and antifungal activities demonstrated that the complexes have
higher antimicrobial activity in comparison with that of the ligand.
According to Tweedy’s theory [60], chelation reduces the polarity

608
A.A.A. Abou-Hussein, W. Linert / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 596–609
Table 6
(b)
HO
OH
Antimicrobial activity of H2L, Schiff base ligand and its metal complexes.
Mean of zone diameter (mm mg mLꢀ1
Gram-positive Gram-
Fungib
a
Compound
)
Cl
Cl
HN
N
NH
N
N
bacteriab
negative
S
NH
NH
HN
HN
HO
HO
OH
OH
bacteriab
Cl
N
.4H2
O
S
Ru
S
Staphylococcus Pseudomonas Fusarium
Cl
Cl3
aureus
phaseolicol
oxysporium
Ru
N
N
S
14 0.4c
22 0.2
26 0.2
21 0.2
30 0.3
27 0.3
23 0.1
30 0.3
27 0.1
25 0.1
32 0.1
31 0.1
26 0.3
27 0.3
10 0.1
18 0.2
21 0.2
19 0.2
20 0.3
13 0.2
26 0.2
16 0.3
17 0.3
25 0.3
28 0.2
17 0.2
18 0.2
N
N
I H2L
Cl
Cl
(1) [Co2(L)(NO3)2(H2O)2]ꢁ2H2O 20 0.1
NH
HN
(2) [Ni2(L)(NO3)2]ꢁ3H2O
(3) [Cu2(L)(H2O)2](NO3)2
(4) [Zn2(L)(NO3)2]ꢁ2H2O
(5) [Mn2(L)(NO3)2(H2O)4]
(6) [Ru(H2L)(H2O)2]ꢁCl3
(7) [(VO)(H2L)]SO4ꢁH2O
(8) [(UO2)2(L)(H2O)2]ꢁNO3)2
(9) [(Ru)(H2L)(DAR)]ꢁCl3
18 0.2
27 0.1
23 0.1
16 0.2
32 0.2
19 0.2
23 0.1
30 0.2
HO
OH
[Ru(H2L)(DAR)].Cl3,9
[(Ru)2(H2L)(DAR)(Cl6)].4H2O,10
HO
OH
HN
N
NH
O
HO
OH
OH
(10) [(Ru)2(H2L)(DAR)Cl6]ꢁ4H2O 39 0.2
N
N
S
(11)[(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O 20 0.2
NH
NH
N
HN
.(SO4)2
(12) [(VO)2(H2L)(DAR)
(H2O)2]ꢁ(SO4)2
17 0.2
42
V
S
S
SO4.2H2O
H2
O
H2
O
N
Antibioticd
36
40
N
HN
S
V
HO
N
N
O
a
NH
HN
Calculated from three average values.
Chloramphenicol in the case of Gram-positive bacteria, cephalothin in the case
b
of Gram-negative bacteria and cycloheximide in the case of fungi
HO
OH
c
Error limits,
Control.
.
[(VO)(H2L)(DAR)].SO4.2H2O, 11
[(VO)2(H2L)(DAR)(H2O)2].(SO4)2, 12
d
Fig. 4b. Representative structures of macrocyclic complexes (9–12).
radentate chelate for acyclic complexes and behaves as a neutral
hexadentate or tetradentate for macrocyclic complexes. From the
infrared spectra, the chelation of the binuclear acyclic complexes
occurs through the phenolic atoms of the resorcinol moiety, the
sulfur and the nitrogen atoms of the azomethine groups of the
cheated ligand. On the other hand, for mono-nuclear acyclic com-
plexes Ru(III) and VO(IV) the donor sites are the azomethine
groups in addition to the sulfur atoms. It is worth to mention that,
whether the macrocyclic complexes are mono- or bi-nuclear, the
bonding sites are both the azomethine groups and thione sulfur ex-
cept for oxovanadium complex [(VO)(H2L)(DAR)]ꢁSO4ꢁ2H2O 11,
where the chelation occurs only through the four nitrogen atoms
of the azomethin groups. The nitrate, sulfate, chloride ions, crystal-
line or coordinated water molecules satisfy the other coordination
sites to complete the geometry around the central metal ion. The
spectral, magnetic studies and molar conductivity measurements
of the metal complexes were used to determine the type of coordi-
nation and the geometry around the central metal ion. Acyclic and
macrocyclic complexes exhibit either tetrahedral, square planner,
square pyramidal or octahedral geometries. The synthesised Schiff
base and its corresponding metal complexes were tested for the
growth inhibitory activity against phytopathogenic bacteria and
fungi. Some of them can act as practical use as antimicrobial
agents.
Fig. 5. Biological screening of the ligand and its complexes against Gram-positive
bacteria, Gram-negative bacteria and fungi.
oxouoranium and oxovanadyl complexes show moderate activity
while the manganese complex exhibit an inhibition activity similar
nearly to the ligand. From the data, conclusive evidence of struc-
ture activity relationships showed that the binuclear macrocyclic
enhances the antimicrobial activity rather than the acyclic com-
plexes. It is of interest to note that the binuclear macrocyclic ruthe-
nium complexes exhibit approximately equal inhibition to the
standard antibiotic which reveals the biological efficiency of these
complexes and showed the possibility to be useful as new drug
[64,65].
Acknowledgment
Thanks for financial support are due to the Austrian Science
foundation (Project 19335-N17).
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.04.057.
Conclusions
The Schiff base derived from the condensation between 4,6-Dia-
cetyl resorcinol and thiocarbohydrazone is a versatile ligand since
it afforded a series of mono or binuclear complexes of varying
geometries. The ligand acts as a dibasic hexadentate or neutral tet-
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