Synthesis and spectroscopic studies of mixed-ligand and polymeric dinuclear transition metal complexes with bis-acylhydrazone tetradentate ligands and 1,10-phenanthroline

Article abstract of DOI:10.1016/j.saa.2005.08.008

Two types of dinuclear copper(II) and nickel(II) complexes with two tetradentate N₂O₂ donor ligands 1,4-bis(1-anthranoylhydrazonoethyl)benzene (L¹), 1,4-bis(1-salicyloylhydrazonoethyl)benzene (L²) and N,N′-bidentate heterocyclic base [1,10-phenonthroline (phen)] have been synthesized and characterized by elemental analysis, infrared spectra, UV-vis electronic absorption spectra and magnetic susceptibility measurements. The reaction of metal(II) acetates with the solution containing ligand and 1,10-phenonthroline in methanol gives mixed-ligand dinuclear metal(II) complexes with general formula [M₂L(phen)₂]Cl₂ (L = L¹ or L²), whereas, the ligands react with metal(II) acetates to form polymeric dinuclear complexes with general formula [(M₂L₂)_n] (L = L¹ or L²). In the complexes, the ligands act as dianionic tetradentate and coordination takes place in the enol tautomeric form with the enolic oxygen and azomethine nitrogen atoms while the phenolic hydroxyl and amino groups of aroylhydrazone moiety do not participate in coordination. The effect of varying pH and solvent on the absorption behavior of both ligands and complexes has been investigated.

Full text of DOI:10.1016/j.saa.2005.08.008

Spectrochimica Acta Part A 64 (2006) 809–815
Synthesis and spectroscopic studies of mixed-ligand and polymeric
dinuclear transition metal complexes with bis-acylhydrazone
tetradentate ligands and 1,10-phenanthroline
∗
¨
Ramazan Gup , Bulent Kırkan
Department of Chemistry, Mugla University, Kampus-Kotekli, 48000 Mugla, Turkey
Received 4 July 2005; received in revised form 8 August 2005; accepted 16 August 2005
Abstract
Two types of dinuclear copper(II) and nickel(II) complexes with two tetradentate N2O2 donor ligands 1,4-bis(1-anthranoylhydrazonoethyl)
benzene (L1), 1,4-bis(1-salicyloylhydrazonoethyl)benzene (L2) and N,Nꢀ-bidentate heterocyclic base [1,10-phenonthroline (phen)] have been syn-
thesized and characterized by elemental analysis, infrared spectra, UV–vis electronic absorption spectra and magnetic susceptibility measurements.
The reaction of metal(II) acetates with the solution containing ligand and 1,10-phenonthroline in methanol gives mixed-ligand dinuclear metal(II)
complexes with general formula [M2L(phen)2]Cl2 (L = L1 or L2), whereas, the ligands react with metal(II) acetates to form polymeric dinuclear
complexes with general formula [(M2L2)n] (L = L1 or L2). In the complexes, the ligands act as dianionic tetradentate and coordination takes place in
the enol tautomeric form with the enolic oxygen and azomethine nitrogen atoms while the phenolic hydroxyl and amino groups of aroylhydrazone
moiety do not participate in coordination. The effect of varying pH and solvent on the absorption behavior of both ligands and complexes has been
investigated.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Schiff base; bis-Acylhydrazone; Mixed-ligand; Polymeric complexes; IR and electronic spectra; Copper(II) and nickel(II) ions
is widely used as a classical N,Nꢀ-bidentate ligand to prepare
mixed-ligand complexes in coordination chemistry. The pres-
ence of mixed-ligand can infer differences in bonding, spectral
properties and geometry in coordination compounds.
Intensive investigations of the coordination chemistry of
dinuclear metal complexes with chelating ligands continue to
be stimulated by interest for metallobiomolecules [17], the
search for appropriate systems for binding and activating simple
molecules [18], catalysis [19] and magnetic interactions [20]. In
spite of the greatest effort and success in the study of dinuclear
copper(II) complexes, such complexes have still attracted much
attention due to their interesting properties and the relative sim-
plicity of their synthesis.
In our previous work, we reported the synthesis and spec-
troscopic studies of mononuclear copper and nickel complexes
of Schiff base prepared by condensing aroylketones with
anthranilhydrazide and salicylohydrazide [21]. Herein, we
report the synthesis and spectroscopic studies of dinuclear
copper(II) and nickel(II) polymeric complexes containing
4-bis(1-anthranoylhydrazonoethyl)benzene (L1), 1,4-bis(1-
salicyloylhydrazonoethyl)benzene (L2) as well as mixed-ligand
complexes with 1,10-phenanthroline. The effect of varying pH
1. Introduction
The chemical properties of aroylhydrazones have been exten-
sively investigated in the past decades because of their strong
tendency to chelate transition metals and their pharmacological
applications [1–9]. A number of hydrazones and their transi-
tion metal complexes have been reported to exhibit biological
activity so far [10–15]. The copper(II) complex of salicylalde-
hyede benzoylhydrazone was found to be a potent inhibitor
of DNA synthesis and cell growth. The copper(II) complex of
salicylaldehyede acetylhydrazone has shown biological activity
[16].
Aroylhydrazones are potential ligands due to having a num-
ber of bonding sites. They can act a neutral or monoanionic
bidentate or tridentate ligand depending on the substituents
and the reaction conditions. Furthermore, abilities to coordi-
nate to metals either in keto(I) or enol(II) tautomeric form make
them attractive as ligands (Fig. 1). 1,10-Phenanthroline (phen)
∗
Corresponding author. Tel.: +90 252 2111496; fax: +90 252 2238656.
E-mail address: rgup@mu.edu.tr (R. Gup).
1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2005.08.008

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R. Gup, B. Kırkan / Spectrochimica Acta Part A 64 (2006) 809–815
Scheme 1. (i) NH2NH2·H2O reflux 4 h; (ii) 1,4-diacetylbenzene, EtOH,
CH3COOH, reflux 1 h. Ligands referred to here are L1: X = NH2, L2:
X = OH.
using Hg[Co(SCN)4] as a calibrent. Atomic absorption spec-
trophotometer used to determine metal ion concentration in the
aqueous phase was DV 2000 Perkin-Elmer ICP-AES. Melting
points were determined on an Electrothermal IA 9100 digital
melting point apparatus and are uncorrected.
Fig. 1. Tautomeric forms of the ligands.
and solvent upon the absorption ability of bis-acylhydrazones
and their complexes is also discussed in more detail.
2.3. Synthesis of ligands
2. Experimental
Salicyloylhydrazine and anthranoylhydrazine were pre-
pared by refluxing ethyl salicylate (10 mmol, 1.48 mL) or
ethyl anthranilate (10 mmol, 1.48 mL) with hydrazine hydrate
(2.5 mL) for 4 h, respectively [21–23]. The compounds precip-
itated on standing over night, filtered and washed with distilled
water. The pure hydrazines were obtained by recrystalliztion
from hot ethanol.
2.1. Reagents
All the chemicals used were of A.R. grade. 1,4-Diacetylben-
zene, ethyl anthranilate, ethyl salicylate, hydrazine monohydrate
were purchased from Merck and Aldrich and used without fur-
ther purification.
The ligands synthesized in this work are shown in Scheme 1
and their syntheses are described as follows.
2.2. Apparatus
Anthranoylhydrazine (10 mmol, 1.51 g) or salicyloylhy-
drazine (10 mmol, 1.52 g) dissolved in hot ethanol (30 mL) was
added to solution of 1,4-diacetylbenzene (5 mmol, 0.81 g) with
three drops of glacial acetic acid in ethanol (20 mL). The reac-
tion mixture was stirred while refluxing for 1 h. The compounds
which precipitated during refluxing were filtered off and washed
several times with water and hot ethanol, and dried in air at
room temperature. Some properties of the synthesized ligands
and complexes are given in Table 1.
1H NMR spectra were recorded on a Bruker 200 MHz spec-
trometer in DMSO d6 with TMS as the internal standard. IR
spectra were recorded on a Perkin-Elmer 1605 FTIR spectrom-
eter as KBr pellets. The electronic spectra of the ligands and
complexes were recorded on a UV-1601 Shimadzu spectropho-
tometer in various solvents. Magnetic susceptibility measure-
ments were performed at room temperature by Faraday method
Table 1
Characterization of the ligands and of the complexes
Complex
Empiric formula
m.p. (◦C)
Yield (%)
B.M. µeff
Elemental analyses (%) (calcd./found)
C
H
N
M
L1
1
2
3
4
L2
5
6
7
8
C24
H
24N6O2
293–295
89
85
88
90
89
85
90
86
88
84
–
67.29/67.43
58.84/59.10
58.54/58.83
57.36/57.51
59.11/58.88
66.98/67.04
58.60/58.44
58.42/58.79
59.17/59.38
58.99/59.23
5.61/5.50
4.49/4.28
3.86/4.01
4.60/4.46
3.90/4.09
5.12/5.01
4.07/4.29
3.65/3.32
4.11/3.96
3.69/3.50
19.63/19.78
17.16/17.34
14.23/14.01
15.44/15.28
14.37/14.23
13.02/12.88
11.39/11.14
11.36/11.69
11.51/11.28
11.47/11.78
–
C
48H44N12O4Cu2
>300
>300
>300
>300
2.27
2.30
3.48
3.34
–
2.33
2.25
3.43
3.52
12.97/12.80
12.91/13.22
10.85/11.01
12.05/11.91
–
12.92/13.11
12.88/13.08
12.06/11.83
12.02/12.39
C48H38N10O2Cl2Cu2
C48H44N12O4Ni2
C
48H38N10O2Cl2Ni2
C24H22N4O4
307–308
C
C
48H40N8O8Cu2
48H36N8O4Cl2Cu2
>300
>300
>300
>300
C48H40N8O8Ni2
C48H36N8O4Cl2Ni2

R. Gup, B. Kırkan / Spectrochimica Acta Part A 64 (2006) 809–815
811
Table 2
1H NMR spectral data for the ligands (δ, ppm)
Complex
OH
NH
Aromatic proton
NH2
CH3
L1
L2
–
10.57 (s, 2H)
11.40 (s, 2H)
7.89 (s, 4H), 6.54–7.90 (m, 8H)
7.96 (s, 4H), 6.93–8.02 (m, 8H)
6.22 (s, 4H)
–
2.45 (s, 6H)
2.38 (s, 6H)
12.15 (s, 2H)
2.4. Synthesis of complexes
11.40 ppm, respectively. The shift of phenolic OH and amide
NH proton absorptions to lower frequency can be explained
by strong intramolecular hydrogen bonding in this compound
2.4.1. Synthesis of [(M2L2)n][M = Ni(II) or Cu(II), L = L1
or L2]
1
[21,23,25]. The other obtained values for H NMR chemical
The complexes [(M2L2)n] were prepared by the following
general method. To hot solution of the ligand (L1 or L2) (5 mmol)
in 20 mL of methanol, the metal(II) acetate (10 mmol) in 10 mL
of methanol were added. The reaction mixture was heated under
reflux for 4 h then the volume was reduced to half of the initial
volume under reduced pressure. The precipitate was filtered off,
washed with water and ethanol, and then dried in air at room
temperature.
shifts of these compounds are given Table 2. These data are in
agreement with that previously reported for similar compounds
[2,3,5,21,25–27].
In the IR spectra of bis-acylhydrazone compounds, the bands
appearing at 1649 and 1641 cm−1 for L1 and L2, respec-
tively, are attributed to the characteristic amide I band. The
absorption band of the C N group is observed at 1608 and
1606 cm−1 for L1 and L2, respectively. In the case of 1,4-
bis(1-salicyloylhydrazonoethyl)benzene a very broad peak is
observed in the 3285–2578 cm−1 region which is assigned to
the intramolecular H–bonding vibration (O H· · ·O) [23,21].
Also the amide NH stretching band of this compound is not
observed in the IR spectra probably because of overlapping with
intramolecular hydrogen bonded OH stretching frequency. In
the case of IR spectra of bis-anthranoylhydrazone derivative, the
peaks observed at 3467 and 3354 cm−1 are attributed to symmet-
ric and asymmetric stretching vibrations of the NH2 group. The
2.4.2. Synthesis of [M2L(phen)2]Cl2 [M = Ni(II) or Cu(II),
L = L1 or L2]
The complexes [M2L(phen)2]Cl2 were prepared by the fol-
lowing general method. To a solution of CuCl2·2H2O or
NiCl2·6H2O (10 mmol) in methanol (10 mL), a solution of 1-10-
phenanthroline (phen) (10 mmol) in 10 mL methanol was added
dropwise with constant stirring. The resulting colored solution,
which was a suspension in the case of copper complexes, was
stirred and heated for 15 min. 5 mmol of ligand dissolved in same
solvent (25 mL) was added and refluxed for 3 h. The precipitate
was filtered, washed with water and ethanol, and then dried in
at room temperature.
amide NH stretching vibration is observed around 3185 cm−1
.
The other characteristic IR peaks of hydrazone compounds syn-
thesized in this work are given in Table 3. These values are
in accord with that previously reported hydrazone derivatives
[1–6,21,23–25].
3. Results and discussion
3.2. IR spectra of the complexes
Hydrazones such as synthesized in this work may exist
in the keto(I) or in the enol(II) tautomeric form in the solid
state (Fig. 1). The observation of strong ν(C O) absorption
bands around 1641–1667 cm−1 in the infrared spectra of the
ligands suggest that the ligands are in the keto form in the
solid state [3,5,11,21,24]. The tautomeric keto forms of com-
Table 3 collects the characteristic IR frequency values of the
ligands and their complexes. The IR spectra of the complexes
show significant differences from the free ligand. The bands due
to amide I, ν(C O), ν(C Nimine) and amide ν(NH) are absent
in the IR spectra of the complexes, but two new bands appear
between 1607 and 1626 cm−1 and ∼1160 cm−1 probably due to
C N N CandC Ostretching, respectively, suggestingthatthe
NH proton is likely lost via deprotonation induced by the metal
and the resulting enolic oxygen and the azomethine nitrogen take
place in coordination [3–7,21]. The shift of ν(N N) stretch of
the complexes to higher energy by ∼20–25 cm−1 comparing to
that of free ligand can be another evidence for the involvement of
azomethine nitrogen in coordination. The symmetric and asym-
metric stretching vibrations of amino group ν(NH2) of L1 is
observed almost at the same frequencies as that of the free lig-
and indicating their non-involvement on coordination [2,7,21].
The IR spectra of complexes derived from L2 shows a broad
band around 3415 cm−1, which can be attributed to the free OH
stretching mode indicating non-participation of phenolic OH
group in coordination.
1
pounds were also indicated by H NMR spectroscopy since
the enolic OH signals of enol forms of ligands were not
observed while amide NH signal of keto forms appeared around
10.47–11.01 ppm.
3.1. 1H NMR and IR spectra of the ligands
In the 1H NMR spectra of 4-bis(1-anthranoylhydrazono-
ethyl)benzene (L1) the proton of amide group (NH) appears
as a singlet at 10.57 ppm. The ring proton resonance of the
1,4-diacetylbenzene moiety of this ligand is observed as a
singlet at 7.89 ppm while that of the anthranilic acid moiety
appears as multiplet peaks. In the 1H NMR spectra of 1,4-
bis(1-salicyloylhydrazonoethyl)benzene (L2) the phenolic OH
and amide NH resonances appear as singlets at δ 12.15 and

812
R. Gup, B. Kırkan / Spectrochimica Acta Part A 64 (2006) 809–815
Table 3
IR spectral data for the ligands and complexes (KBr, cm−1
)
Complex
NH2/OH
NH
C
O
C
N
C
–
N
N
C
C
N/C
O
N N
L1
1
2
3
4
L2
5
6
7
8
3467, 3354
3446, 3363
3466, 3378
3458, 3367
3468, 3389
2578–3285
3414
3414
3412
3422
3185
1649
–
–
–
–
1641
–
–
–
–
1630
–
–
–
–
1628
–
–
–
–
1324
1028
1044
1043
1050
1048
1021
1044
1042
1043
1039
–
–
–
–
–
–
–
–
–
1614
1614
1626
1617
1606
1617
1609
1607
1606
1314/1157
1315/1160
1310/1159
1313/1153
1233
1256/1163
1255/1161
1257/1161
1258/1162
3.3. Magnetic studies
in the region of 321–329 and 335–355 nm are most probably due
*
to n → ␲ electronic transitions of imine and carbonyl groups
The room temperature magnetic moments of the complexes
(Table 1) show both nickel(II) and copper(II) complexes are
paramagnetic. The magnetic moment values of the copper(II)
complexes are in the region of 2.27–2.33 µB while those of the
nickel(II) complexes are in the region of 3.34–3.52 µB at 303 K.
It can be observed that these magnetic moment values of both
copper and nickel complexes are slightly higher than the theo-
retical value of 1.73 µB for one d9 copper ion and 2.82 µB for
one d8 nickel ion. However, these magnetic moment values are
lower than that expected for dinuclear copper(II) and nickel(II)
complexes. These subnormal magnetic moment values of the
dinuclear complexes may be explained by weak antiferromag-
netic intramolecular interaction since this situation can occur
when two equivalent metal ions are coupled via on exchange
interaction in a polynuclear complex [28–30].
[2,21,31–33].
3.4.1. Solvent and pH effects on the electronic spectra of
the ligands
The electronic absorption spectra of the compounds were
studied in organic solvents having various polarities, MeOH,
DMF, DMSO and CHCl3. It can be seen from Table 4 that
the absorption spectra of bis-acylhydrazones are considerably
influenced by changing the solvent. In the case of the electronic
spectra of L1, the bands appearing ∼320 and ∼345 nm in MeOH
and CHCl3 are shifted to high wavelength in DMF and DMSO.
The λmax of 1,4-bis(1-salicyloylhydrazonoethyl)benzene (L2)
shows regular red shift with change in the polarity of the sol-
vents. The highest red shift is observed in DMSO; for example,
323 nminCHCl3, 329 nminMeOH, 335 nminDMFand336 nm
in DMSO. Both types of ligands have more red shift in DMF and
DMSO than other solvents. This phenomenon can be explained
by the high proton accepting character and the low ionization
potential of these solvents.
The effect of pH change on the electronic absorption spectra
of the ligands was studied in MeOH solution by adding a small
amount of 0.1 M HCl and KOH. The λmax of L1 in methano-
lic solution is not effected by adding a small amount of 0.1 M
KOH. However, the electronic absorption spectra of this com-
pound shows considerable hypsochromic effect when adding
a small amount of 0.1 M HCl in methanolic solution (Fig. 2).
After adding two drops of 0.1 M HCl to methanolic solution of
3.4. Electronic absorption spectra
The electronic absorption spectra for the hydrazone ligands
recorded in various solvents such as MeOH, DMF, DMSO
and CHCl3 are given in Table 4. The effect of pH change, by
adding two drops of 0.1 M HCl and KOH, for absorption spec-
tra was also observed. The electronic spectral data of the ligand
exhibit two to three bands in the UV region. The absorption
bands appearing in the range of 240–277 nm are attributed to
*
␲ → ␲ transition of the benzenoid moiety of the compounds
andintraligand␲ → ␲* transition. Theothertwobandsobserved
Table 4
Electronic spectral data (nm) of bis-acylhydrazones and their complexes
Complex
MeOH
MeOH + HCl
MeOH + KOH
CHCl3
DMF
DMSO
L1
1
2
3
4
L2
5
6
7
8
251, 321, 347
–
–
–
253, 311
–
–
–
251, 323, 346
–
–
–
241, 319, 344
–
–
–
267, 328 s, 353
244, 267, 318 s, 358
266, 330 s, 359
256, 265, 323 s, 363
266, 324 s, 362
260, 266, 335
266, 342
256, 267, 297, 345
266, 341
267, 300, 340
258, 328 s, 355
243, 260, 319 s, 360
260, 325 s, 357
260, 327 s, 366
259, 323 s, 364
241, 336
260, 344
277, 300, 346
259, 343
–
–
–
–
240, 329
241, 299, 323
292, 324, 364
241, 323
–
–
–
–
–
–
–
–
–
–
–
–
275, 297, 339
s: shoulder.

R. Gup, B. Kırkan / Spectrochimica Acta Part A 64 (2006) 809–815
813
Fig. 4. Electronic absorption spectra of [(M2L2)n] complexes of L1 in DMF:
(a) [(Cu2L2)n] (1); (b) [(Ni2L2)n] (3).
Fig. 2. Electronic absorption spectra of L1 in: (a) MeOH; (b) MeOH + KOH;
(c) MeOH + HCl.
3.5. Electronic absorption spectra of the complexes
this ligand, the bands appearing 321 and 347 nm in the spec-
tra of the neutral methanolic solutions of L1 disappears and a
new broad band is observed at 311 nm indicating that 1,4-bis(1-
anthranoylhydrazonoethyl)benzene exists in the cationic form in
acidic solution probably due to protonation of the amino group.
The absorption spectra of L2 are little influenced by
adding 0.1 M HCl with respect to the absorption spectra in
methanol. After adding two drops of 0.1 M HCl, the λmax
of L2 shifts slightly to lower wavelength and a shoulder at
299 nm, which cannot be seen clearly in neutral MeOH solu-
tion of this ligand becomes much clear in the acidic solu-
tion. On the other hand, the electronic absorption spectra
of 1,4-bis(1-salicyloylhydrazonoethyl)benzene shows consid-
erable bathochromic effect when adding a small amount of
0.1 M KOH in methanolic solution (Fig. 3). After adding two
drops of 0.1 M KOH to methanolic solution of this ligand,
the band appearing at 329 nm in neutral solution shows a
slight blue shift and a new shoulder at 299 nm, which can-
not be seen clearly in neutral MeOH solution of this ligand
becomes much clear in the basic solution. Furthermore, a
new broad band appears at 364 nm indicating that 1,4-bis(1-
salicyloylhydrazonoethyl)benzene exists in the anionic form in
basic solutions probably due to phenolic or enolic groups.
Electronic absorption spectra of [ML2] and [ML(phen)]Cl
complexes were recorded in DMF and DMSO solutions
(Table 4). In the electronic spectra of all complexes there is
a broad band around 339–366 nm tailing into visible region in
the spectra of many complexes. This band is assigned as a CT
transition [2,21,27,31].
Comparison of the electronic absorption of L1 and its
polymeric nickel(II) and copper(II) complexes, it is observed
that the shoulder appearing around 328 nm for L1 slightly
decreases in intensity and shows slightly blue shift. In the case
of L2 and its polymeric complexes the broad band observed
around 335 nm in free ligand becomes narrow with a slight
red shift tailing in to visible region in the electronic spectra
of polymeric complexes (Fig. 4). However, the electronic
absorption spectra of the mixed-ligand dinuclear complexes
of 1,4-bis(1-salicyloylhydrazonoethyl)benzene is considerably
different from those of the free ligand and corresponding poly-
meric complexes (Fig. 5). Two new bands which cannot be seen
in the free ligand appear around 267–277 nm and 297–300 nm.
*
The first of these bands may be attributed ␲ → ␲ transition
of phenatranoline moiety of the mixed-ligand complexes. The
*
second band can be assigned to n → ␲ electronic transition.
Fig. 5. Electronic absorption spectra of [M2L(phen)2]Cl2 complexes of L2 in
DMSO: (a) [Cu2L(phen)2]Cl2 (6); (b) [Ni2L(phen)2]Cl2 (8).
Fig. 3. Electronic absorption spectra of L2 in: (a) MeOH; (b) MeOH + HCl; (c)
MeOH + KOH.

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R. Gup, B. Kırkan / Spectrochimica Acta Part A 64 (2006) 809–815
Fig. 6. Suggested structure for the polymeric dinuclear complexes [{Cu2(L1)2}n] (1); [{Ni2(L1)2}n] (3); [{Cu2(L2)2}n] (5); [{Ni2(L2)2}n] (7).
Fig. 7. Suggested structure for the mixed-ligand dinuclear complexes [Cu2(L1)(phen)2]Cl2 (2); [Ni2(L1)(phen)2]Cl2 (4); [Cu2(L2)(phen)2]Cl2 (6);
[Ni2(L2)(phen)2]Cl2 (8).
Unfortunately the expected weak d–d transition in the visible
region for all complexes cannot be detected even with concen-
trated solution. It may be lost in the low energy tail of the charge
transfer transition [2,21,22,34,35].
vibration in the IR spectra of the complexes is concluded as non-
involvements of these groups in coordination. Considering the
elemental analysis results and spectral data, the structures pro-
posed for polynuclear and mixed-ligand complexes are given in
Figs. 6 and 7.
The results of the varying pH and solvents effect on the
absorption ability of bis-acylhydrazones and their complexes are
also discussed in this paper. The electronic absorption bands of
the presented ligands exhibit solvent dependence behavior. The
λmax of bis-salicyloylhydrazone derivative is effected by both
acidic and basic media while the basic media does not effect the
λmax of bis-anthranoylhyadrazone derivative. In the case of the
electronic spectra the complexes, CT bands are observed around
339–366 nm. The polymeric and mixed-ligand dinuclear com-
plexes exhibit slightly different CT pattern.
4. Conclusion
The present paper reports on the synthesis, characterization
and their electronic absorption spectra of bis-acylhydrazones
and their copper(II) and nickel(II) complexes. In this investiga-
tion we also provide two types of copper and nickel complexes,
mixed-ligand and polymeric, by using these synthesized Schiff
base and bidentate 1,10-phenanthroline. On the basis of IR and
1H NMR spectral data, bis-acylhydrazone ligands are in the keto
tautomeric form in the solid state. However, in the IR spec-
tra of the complexes ν(C O), ν(C N), and ν(N H) stretching
vibrations disappears but two new bands are observed due to
C N N N and C O stretching, respectively, suggesting that
the coordination takes place in enol tautomeric form. Further-
more, theobservationofphenolicν(O H)andν(NH2)stretching
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