Synthesis and spectroscopic studies of copper(II) and nickel(II) complexes containing hydrazonic ligands and heterocyclic coligand

Article abstract of DOI:10.1016/j.saa.2005.04.015

Two types of copper(II) and nickel(II) complexes derived from benzophenone anthranoylhydrazone (L₁), 2-acetonaftanone anthranoylhydrazone (L₂), 4-phenylacetonaftonone anthranoylhydrazone (L₃), benzophenone salicyoylhydrazo

Full text of DOI:10.1016/j.saa.2005.04.015

Spectrochimica Acta Part A 62 (2005) 1188–1195
Synthesis and spectroscopic studies of copper(II) and nickel(II)
complexes containing hydrazonic ligands and heterocyclic coligand
∗
¨
Ramazan Gup , Bulent Kırkan
Department of Chemistry, Mugla University, 48000 Kotekli-Mugla, Turkey
Received 28 March 2005; received in revised form 14 April 2005; accepted 19 April 2005
Abstract
Two types of copper(II) and nickel(II) complexes derived from benzophenone anthranoylhydrazone (L1), 2-acetonaftanone anthranoylhydra-
zone (L2), 4-phenylacetonaftonone anthranoylhydrazone (L3), benzophenone salicyoylhydrazone (L4), 2-acetonaftanon salicyoylhydrazone
(L5), 4-phenylacetonaftanon salicyoylhydrazone (L6) and bidentate heterocyclic base [1,10-phenanthroline (phen)] with general stoichiome-
try [ML2] and [ML(phen)]Cl have been synthesized and characterized by elemental analysis, infrared spectra, UV–vis electronic absorption
spectra and magnetic susceptibility measurements. The effect of varying pH and solvent on the absorption behavior of both ligands and
complexes have been investigated. According to the IR spectra, the ligands act as monobasic bidentate and coordination takes place in the
enol tautomeric form.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Schiff base; Aroyl hydrazone; Mixed ligand; IR and electronic spectra; Copper(II) and nickel(II) complexes
1. Introduction
In this paper, we report the synthesis and characteriza-
tion of benzophenone, 2-acetonaftanone, 4-phenylacetonaf-
tonone anthranoylhydrazones and salicyloylhydrazone and
their copper(II) and nickel(II) complexes [ML2] as
well as mixed-ligand complexes with 1,10-phenanthroline
[ML(phen)]Cl. The effect of varying pH and solvent upon the
absorption ability of Schiff base derivatives and their com-
plexes is also discussed in more detail.
Benzoylhydrazones of aldehydes and ketones have a set
of different bonding sites and form stable complexes with
various transition metal ions differing in the composition,
structure and properties [1–7]. Both hydrazones and their
coordination compounds present a great variety of bio-
logical activity. A number of hydrazones and their metal
complexes have been synthesized and reported to exhibit
biological activity [8–12] so far. Aromatic ketone deriva-
tives of anthranoylhydrazones and salicyoylhydrazones are
potential ligands owing to their variable bonding sites. Fur-
thermore, abilities to coordinate to metals either in keto(I)
or enol(II) tautomeric form make them attractive as ligands.
1,10-Phenanthroline (phen) is widely used as the classical
N,N’-bidentate ligand to prepare mixed-ligand complexes
in coordination chemistry. The mixed-ligand structure can
cause to be different in bonding, spectral properties and
geometry in coordination compounds.
2. Experimental
2.1. Reagents
All the chemicals used were of AR grade. Benzophe-
none, 2ꢀ-acetonaphthone, 4-acetylbiphenyl, methyl anthrani-
late, ethyl salicylate and hydrazine monohydrate were
purchased from Merck and Aldrich and used without further
purification.
2.2. Apparatus
1H NMR spectra were recorded on a Bruker 200 MHz
spectrometer in DMSO d6 with TMS as the internal standard.
∗
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.2005.04.015

R. Gup, B. Kırkan / Spectrochimica Acta Part A 62 (2005) 1188–1195
1189
IR spectra were recorded on a Perkin-Elmer 1605 FTIR spec-
2.4. Synthesis of complexes
trometer as KBr pellets. The electronic spectra of the ligands
and complexes were recorded on a UV-1601 Shimadzu spec-
trophotometer in various solvents. Magnetic susceptibility
measurements were performed at room temperature by Fara-
day method using Hg[Co(SCN)4] as a calibrent. Atomic
absorption spectrophotometer used to determine metal ion
concentration in the aqueous phase was DV 2000 Perkin
Elber ICP-AES. Melting points were determined on an Elec-
trothermal IA 9100 digital melting point apparatus and are
uncorrected.
2.4.1. Synthesis of [Cu(L)2] and [Ni(L)2]
To hot solution of the ligands (10 mmol) in 20 mL
of methanol, the metal(II) acetates (5 mmol) in 10 mL of
methanol were added. The reaction mixture was heated under
reflux for 2 h and then the volume was reduced to half of
the initial volume under reduced pressure. The separated
precipitates were filtered off, washed with water, ethanol
and finally diethyl ether and then dried in air at room
temperature.
2.4.2. Synthesis of [CuL(phen)]Cl and [NiL(phen)]Cl
The complexes [ML(phen)]Cl 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 suspension in the case of copper com-
plexes was stirred and heated for 15 min. To this, 10 mmol
ligands dissolved in hot methanol was added and refluxed
for 2 h. The colored precipitates were filtered, washed with
water, ethanol and finally with diethyl ether and then dried in
at room temperature.
2.3. Synthesis of ligands
Salicyloylhydrazine and anthranoylhydrazine were pre-
pared by refluxing ethyl salicylate (10 mmol, 1.48 mL) or
ethylanthranilate(10 mmol, 1.48 mL)withhydrazinehydrate
(2.5 mL) for 4 h, respectively [3,13,14]. The compounds sep-
arated on standing over night, filtered and washed with dis-
tilled water. The pure hydrazines were obtained by recrystal-
liztion from hot ethanol.
The ligands synthesized in this work are shown in
Scheme 1 and their syntheses are described as follows.
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 benzophenone, (10 mmol, 1.82 g),
2ꢀ-acetonaphthone (10 mmol, 1.70 g) and 4-acetylbiphenyl
(10 mmol, 1.96 g) with an equivalent amount of glacial acetic
acid in ethanol (30 mL). The reaction mixture was stirred
while refluxing for 2 h and left over night. The crystalline
compounds were filtered off and washed several times with
cold ethanol and dried in at room temperature (Scheme 1).
Some properties of the synthesized ligands and complexes
are given in Table 1.
3. Results and discussion
Hydrazones such as synthesized in this work may exit 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
[5,8,15,16]. The tautomeric keto forms of compounds were
1
also indicated by H NMR spectroscopy since 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 data for the ligands
In the 1H NMR spectra of the anthranilic acid hydrazone
derivatives L1, L2 and L3, the NH proton bonded to two
unsaturated nuclei appears as a singlet at 10.68 ppm for L1,
10.47 ppm for L2 and 10.80 ppm for L3. The singlet peak
appeared around 6.34–6.47 ppm is assigned to −NH2 pro-
tons. The other obtained values for 1H NMR chemical shifts
of these compounds are given Table 2. These data are in
agreement with previously reported for similar compounds
[2,17–19].
1
In the H NMR spectra of the ligands derived from sal-
icyloylhydrazine and ketones L4, L5 and L6, the phenolic
OH and amide NH resonances appear as a singlet at δ 12.03
and 11.55 ppm for L4, 11.98 and 12.44 ppm for L5 and
12.10 and 11.60 ppm for L6. The movements of phenolic OH
proton absorptions to lower frequency can be explained by
strong intramolecular hydrogen bonding in these compounds
Scheme 1. (i) NH2NH2·H2O reflux 4 h and (ii) 4-chloroacetophenone,
benzophenone, 2ꢀ-acetonaphthone or 4-acetylbiphenyl, EtOH, CH3COOH,
reflux 2 h. Ligands referred to here are L1 = X: −NH2, Ar: C6H5−, Arꢀ:
C6H5−; L2 = X: −NH2, Ar: CH3−, Arꢀ: C10H7−; L3 = −NH2, Ar: CH3−,
Arꢀ: C12H9−; L4 = X: −OH, Ar: C6H5−, Arꢀ: C6H5−; L5 = X: −OH, Ar:
CH3−, Arꢀ: C10H7−; L6 = X: −OH, Ar:: CH3−, Arꢀ: C12H9−.

1190
R. Gup, B. Kırkan / Spectrochimica Acta Part A 62 (2005) 1188–1195
Table 1
Elemental analytical results and some properties of the ligands and complexes
Complex
Empiric formula
mp (◦C)
Yield (%)
B.M. (µeff
)
Calculated (found)
C
H
N
M
–
L1
1
2
3
4
C20
H
17N3O
150
257
>300
234
87
79
77
78
76
–
76.20 (75.92)
69.46 (69.23)
64.86 (65.01)
69.97 (70.14)
65.40 (65.73)
5.40 (5.31)
4.63 (4.86)
4.05 (3.86)
4.66 (4.31)
4.08 (3.90)
13.30 (12.98)
12.15 (11.89)
11.82 (11.66)
12.24 (12.64)
11.92 (11.68)
C40H32N6O2Cu
C32H24N5OCuCl
C40H32N6O2Ni
1.79
1.94
2.98
3.14
9.11 (9.54)
10.64 (10.93)
8.45 (8.19)
C32
19H17N3O
C38H32N6O2Cu
C31 24N5OCuCl
H24N5ONiCl
>300
9.88 (10.11)
L2
5
6
7
8
C
196
211
233
315
278
86
89
74
83
76
–
75.25 (75.55)
68.36 (68.20)
64.13 (64.50)
68.88 (68.73)
64.69 (64.47)
5.61 (5.83)
4.79 (4.54)
4.13 (4.33)
4.83 (4.88)
4.17 (4.30)
13.86 (14.08)
12.60 (12.92)
12.06 (11.79)
12.68 (12.67)
12.17 (12.40)
–
1.68
1.78
2.96
3.12
9.44 (9.12)
10.86 (11.01)
8.76 (8.83)
10.08 (9.89)
H
C38H32N6O2Ni
C31H24N5ONiCl
L3
9
10
11
12
C
21H13N3O
248
223
324
198
310
84
81
73
77
75
–
76.59 (76.44)
70.10 (69.80)
70.39 (70.56)
65.34 (65.21)
65.89 (66.06)
5.77 (5.91)
5.00 (5.11)
5.04 (4.91)
4.30 (4.08)
4.32 (4.51)
12.76 (12.53)
11.68 (11.43)
11.76 (11.50)
11.55 (11.80)
11.65 (11.30)
–
C42H36N6O2Cu
C42H36N6O2Ni
C
C
1.76
1.80
2.69
2.76
8.76 (8.99)
8.12 (8.30)
10.40 (10.12)
9.65 (9.42)
33H26N5OCuCl
33H26N5ONiCl
L4
13
14
15
16
C
C
20H16N2O2
40H30N4O4Cu
225
232
240
268
348
76
83
86
78
71
–
75.95 (75.66)
69.26 (68.76)
64.75 (64.49)
69.76 (70.01)
65.30 (65.75)
5.06 (4.92)
4.33 (3.83)
3.87 (3.99)
4.36 (4.53)
3.91 (3.57)
8.86 (8.60)
8.08 (7.98)
9.44 (9.21)
8.15 (7.99)
9.52 (9.38)
–
1.68
1.87
2.61
2.95
9.09 (9.28)
10.62 (10.84)
8.44 (8.60)
9.86 (9.57)
C32H23N4O2CuCl
C40H30N4O4Ni
C32H23N4O2NiCl
L5
17
18
19
20
C
C
C
19H16N2O2
38H30N4O4Cu
31H23N4O2CuCl
244
250
198
>300
285
80
72
70
76
73
–
74.51 (74.77)
68.16 (68.40)
64.02 (63.80)
68.67 (68.55)
64.58 (64.36)
5.88 (6.00)
4.48 (4.29)
3.95 (4.12)
4.52 (4.30)
3.99 (3.76)
9.15 (9.33)
8.37 (8.56)
9.64 (9.49)
8.43 (8.70)
9.72 (9.54)
–
1.96
1.87
2.80
2.77
9.41 (9.20)
10.84 (10.67)
8.73 (9.02)
10.06 (9.89)
C38
H30N4O4Ni
C31H23N4O2NiCl
L6
21
22
23
24
C21 18N2O2
H
230
245
215
211
302
87
81
79
83
80
–
76.36 (76.60)
69.90 (69.67)
65.23 (65.66)
70.39 (70.09)
65.78 (65.61)
5.45 (5.31)
4.71 (4.59)
4.12 (4.34)
4.75 (4.59)
4.15 (3.99)
8.48 (8.71)
7.76 (7.99)
9.22 (9.50)
7.82 (7.99)
9.30 (9.56)
–
C
C
C
42H34N4O4Cu
33H25N4O2CuCl
42H34N4O4Ni
1.63
1.74
2.78
2.90
8.73 (9.00)
10.37 (10.03)
8.10 (7.89)
9.63 (9.89)
C33H25N4O2NiCl
Fig. 1. Tautomeric forms of the ligands.
Table 2
1H NMR spectra data of the ligands, δ (ppm)
Complex
OH
NH
Aromatic proton
−NH2
−CH3
L1
L2
L3
L4
L5
L6
–
–
–
10.68 (s, 1H)
10.47 (s, 1H)
10.80 (s, 1H)
11.55 (s, 1H)
11.44 (s, 1H)
11.60 (s, 1H)
6.73–7.89 (m, 14H)
6.81–8.01 (m, 11H)
6.97–8.17 (m, 13H)
6.82–7.90 (m, 14H)
6.77–8.10 (m, 14H)
6.89–7.96 (m, 13H)
6.34 (s, 2H)
6.40 (s, 2H)
6.47 (s, 2H)
–
–
–
–
2.48 (s, 3H)
2.63 (s, 3H)
–
2.40 (s, 3H)
2.59 (s, 3H)
12.03 (s, 1H)
11.98 (s, 1H)
12.10 (s, 1H)

R. Gup, B. Kırkan / Spectrochimica Acta Part A 62 (2005) 1188–1195
1191
Fig. 2. Intramolecular hydrogen bonding of L4, L5 and L6.
[14,17,20] (Fig. 2). The other proton resonances of these lig-
ands are given in Table 2.
absent in the IR spectra of the complexes, but two new bands
appear between 1615–154 and ∼1150 cm−1, probably due to
>C N N C< and C O, respectively, suggesting that the NH
proton is lost via enolazition and the resulting enolic oxygen
and the azomethine nitrogen take place in coordination [4–7]
The movement of ν(N N) stretch of the complexes to higher
energy by ∼30–35 cm−1 compared to that of free ligand can
be another evidence for the involvement of azomethine nitro-
gen in coordination. The symmetric and asymmetric stretch-
ing vibrations of amino group ν(NH2) of anthranoylhydra-
zone derivatives are observed almost at the same position
with those of free ligands indicating their non-involvement
on coordination [2,3,7]. The IR spectra of complexes derived
from L4, L5 and L6 show a broad band around 3450 cm−1
which can be attributed to the free OH stretch indicating non-
participation of phenolic OH group in coordination.
3.2. IR spectra of the ligands
IntheIRspectraofhydrazonecompounds, thecharacteris-
tic amide I band is observed at 1667–1641 cm−1. The absorp-
tion bands appearing at 1633–1604 cm−1 are assigned to the
stretching vibration of >C N group. In the case of salicyloyl-
hydrazone derivatives, a very broad medium intensity peak
is observed at 3200–2600 cm−1 region which are assigned to
the intramolecular H-bonding vibration (O H···O) [14,16]
(Fig. 2). Also the amide NH stretching bands of these com-
pounds were not observed in the IR spectra probably due
to overlapping with intramolecular hydrogen bonded OH
stretching frequencies. For derivatives of salicyloylhydra-
zone, twoisomersthathaveintramoleculerhydrogenbonding
can be possible (Fig. 2). When the IR spectra of anthranoyl-
hydrazone derivatives are compared with those of salicyloyl-
hydrazone derivatives, it is seen that the ν(C O) stretch-
ing vibrations of L4, L5 and L6 appear at lower frequency
(1641–1648 cm−1)thanthoseof(1663–1667 cm−1)ofL1, L2
and L3. This phenomena may be explained that the carbonyl
groups of salicyloylhydrazone derivatives bond to the phe-
nolic OH group by intermolecular hydrogen bonding. There-
fore, the isomer II is more suitable owing to the position of
strong intermolecular hydrogen bonding (O H···O) (Fig. 2).
In the case of IR spectra of anthranoylhydrazone deriva-
tives, the peaks observed at 3472–3463 and 3356–3346 cm−1
are attributed to symmetric and asymmetric stretching vibra-
tions of the NH2 group. The amide NH stretching vibrations
are observed around 3190 cm−1. The other characteristic IR
peaks of hydrazone compounds synthesized in this work are
given in Table 3. These values are in accord with the previ-
ously reported hydrazone derivatives [1–5,14–18].
3.4. Magnetic studies
The magnetic moment data of the solid state complexes
at room temperature are reported in Table 1. The magnetic
moment values of the copper complexes 1.63–1.96 B.M. cor-
responds to the spin value for one unpaired electron, indicat-
ing these complexes are monomeric. No definite information
can be concluded regarding the coordination geometries of
these complexes. All the nickel complexes are paramagnetic
and show magnetic moment values in the region of 2.61–312
B.M. According to magnetic values and the elemental analy-
sis results, the nickel(II) complexes have a tetrahedral geom-
etry around Ni(II) ions (Fig. 3).
3.5. Electronic absorption spectra
The electronic spectra for the hydrazone ligands recorded
in various solvents such as EtOH, DMF and CHCl3 are given
in Table 4. The effect of pH change for absorption spectra
was also performed by adding 0.1 M HCl and KOH. The
pH value of all solution used was in the range between
basic and acidic. The electronic spectral data of the ligand
exhibit 3–4 bands in the UV region. The band appearing in
3.3. IR spectra of the complexes
The IR spectra of the complexes presented in Table 3
show significant differences from the free ligand. The bands
due to amide I ν(C O), ν(C Nimine) and amide ν(NH) are
*
the range of 238–245 nm is attributed to ␲ → ␲ transition

1192
R. Gup, B. Kırkan / Spectrochimica Acta Part A 62 (2005) 1188–1195
Table 3
IR spectral data for the ligands and complexes (KBr, cm−1
)
Complex
NH2/OH
NH
C
O
C
N
C
–
1615
1610
1609
1614
N
N
C
C
N/C
O
N N
L1
1
2
3
4
3468, 3360
3465, 3350
3455, 3340
3469, 3345
3458, 3328
3200
1663
1630
1323
1028
1023
1054
1049
1051
–
–
–
–
–
–
–
–
–
–
–
–
1318/1163
1315/1158
1320/1160
1315/1162
L2
5
6
7
8
3472, 3356
3470, 3301
3469, 3352
3465, 3358
3449, 3338
3193
1667
1628
–
1320
1027
1045
1050
1051
1055
–
–
–
–
–
–
–
–
–
–
–
–
1614
1610
1608
1612
1310/1161
1314/1162
1315/1160
1313/1155
L3
9
10
11
12
3471, 3359
3467, 3349
3460, 3334
3455, 3330
3461, 3338
3190
1659
1633
–
1325
1030
1059
1063
1058
1061
–
–
–
–
–
–
–
–
–
–
–
–
1608
1605
1609
1614
1320/1167
1317/1165
1323/1155
1315/1149
L4
13
14
15
16
2563–3222
3430
3426
3448
3456
–
–
–
–
–
1641
1604
–
1233
1026
1062
1055
1057
1051
–
–
–
–
–
–
–
–
1589
1584
1596
1590
1253, 1149
1260, 1178
1260, 1156
1263, 1143
L5
17
18
19
20
2560–3230
3439
3445
3451
3450
–
–
–
–
–
1645
1610
–
1255
1025
1049
1055
1053
1050
–
–
–
–
–
–
–
–
1592
1588
1588
1593
1253, 1149
1250, 1145
1250, 1158
1242, 1160
L6
21
22
23
24
2560–3250
3460
3443
3428
3433
–
–
–
–
–
1640
1608
–
1250
1028
1049
1056
1060
1058
–
–
–
–
–
–
–
–
1592
1587
1590
1593
1260, 1163
1254, 1158
1250, 1155
1254, 1163
of the benzenoid moiety of the ligands. The band around
266.5–278 nm can be assigned to intra ligand of ␲ → ␲* tran-
sition. The other two bands observed in the region of 303–311
changing the solvent. However, the λmax of the ligands
derived from salicylic hydrazide (L4–L6) show slightly red
shift in CHCl3 than those of in other solvents, for example
compound L4 323 nm in CHCl3, 318 nm in EtOH and 316 nm
inDMF(Figs. 4and5). Moreover, intheelectronicabsorption
spectra of L4−L6, a shoulder around 270 nm which cannot
be seen clearly in EtOH and DMF solutions of these ligands
becomes more clear in the chloroform solutions.
*
and 316–341 nm are attributed to n → ␲ electronic transi-
tions [2,21–23].
3.5.1. Solvent effect on the electronic spectra of the
ligands
The electronic absorption spectra of the compounds were
studied in various organic solvents, C2H5OH, DMF and
CHCl3. It is observed that the absorption spectra of anthra-
noylhydrazone derivatives (L1–L3) are little influenced by
3.5.2. pH effect on the electronic absorption
The effect of pH change on the electronic absorption spec-
tra of the ligands was studied in EtOH solution by adding a
Fig. 3. Proposed structure of the complexes: (a) [ML2] and (b) [ML(phen)]Cl and [M = Cu(II) or Ni(II)].

R. Gup, B. Kırkan / Spectrochimica Acta Part A 62 (2005) 1188–1195
1193
Table 4
Electronic spectral data (nm) of Schiff bases and their complexes
Complex EtOH
EtOH + HCl
ETOH + KOH
DMF
CHCl3
L1
1
2
3
4
242, 296, 347
240, 295, 345
238, 296, 346
240.5, 297, 268 s, 307 s, 347
240, 264, 300, 311, 346, 361s
241, 265, 274, 301 s, 346, 366s
266, 298, 308 s 345, 373 s
241.5, 297, 343
364, 310, 341, 365 s
265, 276, 296, 309 s, 340, 360 s
Insoluble
–
–
–
–
–
–
–
–
–
–
–
–
242, 265, 295, 306 s, 345, 356 s Insoluble
L2
5
6
7
8
242, 278, 306, 341
238, 278, 306, 336 s 241, 278, 308, 345
242, 267, 280, 312, 347
241, 267, 280, 311, 343, 360 s
267, 276, 312 s, 340, 363 s
267, 310, 339, 445
243, 271, 279, 311, 336
–
–
–
–
–
–
–
–
–
–
–
–
282, 315 s, 369
243, 276 s, 295 s, 359
Insoluble
267, 278, 310 s, 344, 444
Insoluble
L3
9
10
11
12
240, 259, 306, 346
238, 301, 337 s
240, 277, 306, 346
267, 310, 343
266, 316, 374 s
244, 266, 277, 308, 361 s
242, 265, 298, 307 s, 337, 380 s Insoluble
242, 265, 276, 309 s, 338, 386 s Insoluble
241, 259, 308, 346
262, 312, 338, 371 s
262, 277, 309 s, 339, 374 s
–
–
–
–
–
–
–
–
–
–
–
–
L4
13
14
15
16
240, 266, 300, 318
241, 267, 300, 318
243, 303, 313 s, 322
239, 259, 263, 299, 317
267, 316, 365 s
266, 276, 297, 366 s
267, 301, 317, 361 s
245, 267, 274, 309 s 360 s
241, 307, 323
255, 317, 354
240, 267, 295, 303 s, 348 s
241, 325, 359
Insoluble
–
–
–
–
–
–
–
–
–
–
–
–
L5
17
18
19
20
240, 273, 282, 313
242, 270, 281, 315
242, 273 s, 282, 306, 353 242, 267, 285, 316
241, 275, 281, 322
270, 280, 312, 359
242, 276, 282, 313, 355
Insoluble
–
–
–
–
–
–
–
–
–
–
–
–
240, 266, 290, 314, 383 s
267, 276, 300 s, 313, 372 s
266, 292, 363 s
272, 315, 375
Insoluble
L6
21
22
23
24
242, 271, 304 s, 319 241, 280, 305, 317
242, 309, 352
248 267, 319
240, 291, 322
–
–
–
–
–
–
–
–
–
–
–
–
239, 266, 300, 355 s
242, 266, 304 380 s
266, 299 s, 315 s, 363 s
265, 277, 300 s, 313, 369 s
265, 295, 316, 359
240, 266, 276, 296, 317, 360
Insoluble
Insoluble
small amount of 0.1 M HCl and KOH. The λmax of the salicy-
oylhydrazone derivatives (L4, L5 and L6) in ethanolic solu-
tions are not effected by adding a small amount of 0.1 M HCl.
However, the electronic absorption spectra of these com-
pounds change considerably when adding a small amount
of 0.1 M KOH in ethanolic solution. After adding two drops
of 0.1 M KOH to ethanolic solution of these ligands, the band
appearing around 318 nm in the spectra of the neutral ethano-
lic solutions of ligands becomes shoulder and the intensity of
Fig. 4. Electronic absorption spectra of L2 in: (a) EtOH; (b) CHCl3 and (c)
DMF.
Fig. 5. Electronic absorption spectra of L4 in: (a) EtOH; (b) CHCl3 and (c)
DMF.

1194
R. Gup, B. Kırkan / Spectrochimica Acta Part A 62 (2005) 1188–1195
Fig. 7. Electronic absorption spectra of the copper(II) complexes of L2 in
different solvents: (a) [CuL2]; (b) [CuL(phen)]Cl in DMF; (c) [CuL2] and
(d) [CuL(phen)]Cl in CHCl3.
Fig. 6. Electronic absorption spectra of L4 in: (a) EtOH; (b) EtOH + HCl
and (c) EtOH + KOH.
this band slightly decreases with a slight blue shift. Further-
more, a new broad band appears around 352–362 nm indi-
cating that ligands L4−L6 exist in the anionic form in basic
solutions probably due to phenolic group. The absorption
spectra of the hydrazone compounds derived from anthranilic
acid hydrazine (L1−L3) are not changed by adding 0.1 M
KOH with respect to the absorption spectra in ethanol. Fur-
thermore, the λmax of these compounds in ethanol do not
show considerable hypsochromic effects when 0.1 M HCl
was added (Fig. 6, Table 4).
3.6. Electronic absorption spectra of the complexes
Electronic absorption spectra of [ML2] and [ML(phen)]Cl
complexes were recorded in DMF and CHCl3 solutions
(Table 4). In the electronic spectra of all complexes, there
is a band around 350–385 nm which is usually shoulder tail-
ing into visible region in the spectra of many complexes. This
band is assigned as a CT transition (Fig. 7) [2,21]. Surpris-
ingly, the CT transition bands of the nickel(II) complexes of
2ꢀ-acetonaphthone anthranoylhydrazone (7 and 8) which are
insoluble in CHCl3 shows more red shift and appear at 445
and 436 nm, respectively (Fig. 8).
By comparison of the electronic absorption of the free
ligands and their complexes, it is observed that the bands
appearing around 310 nm for ligands L1−L3 and ∼300 nm
for ligands L4−L6 slightly decreases in intensity. In the case
of the electronic absorption spectra of the mixed-ligand com-
plexes [ML(phen)]Cl derived from salicyoylhydrazine and
aromatic ketones (L4−L6), a new shoulder appears around
275 nmwhichmaybeattributedto␲ → ␲* transitionofphen-
atranoline moiety of these compounds.
Fig. 8. Electronic absorption spectra of L2 and its nickel(II) complexes in
DMF: (a) L2; (b) [NiL(phen)]Cl and (c) [NiL2].
concluded from Table 4 that the CT transition bands in DMF
solution usually show a little more red shift than those of
in CHCl3 solutions. Unfortunately, the expected weak d–d
transition in the visible region for all complexes cannot be
detected even with concentrated solution. It may be lost in the
low energy tail of the charge transfer transition [2,22,24,25].
4. Conclusion
The present paper reports on the synthesis, characteriza-
tion and their electronic absorption spectra of Schiff bases
and their copper(II) and nickel(II) complexes. In this inves-
tigation, we also provide 12 mixed-ligand copper and nickel
complexes by using these synthesized Schiff base and biden-
tate 1,10-phenanthroline. The observation of strong ν(C O)
Although the position of CT band of all complexes do
not regular variation in DMF and CHCl3 solvents, it may be

R. Gup, B. Kırkan / Spectrochimica Acta Part A 62 (2005) 1188–1195
1195
absorption bands around 1641–1667 cm−1 in the IR spec-
tra of the ligands indicates that they are in the keto tau-
tomeric form in the solid state. The other evidence of the
keto form of the ligands is the appearance of amide NH
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1
signals around 10.47–11.01 ppm in the H NMR spectra.
However, in the IR spectra of the complexes ν(C O), ν(C N)
and ν(N H) stretching vibrations disappears but two new
bands are observed at 1615–154 and ∼1150 cm−1 due to
>C N N N< and C O stretches, respectively, suggesting
that the coordination takes place in enol tautomeric form. Fur-
thermore, the observation of phenolic ν(O H) and ν(NH2)
stretching vibration in the IR spectra of the complexes is con-
cluded as non-involements of these groups in coordination.
The results of the varying pH and solvents effect on the
absorption ability of Schiff base and their complexes are also
discussed in this paper. In the basic solutions, Schiff base
derived from salicyoylhydrazine have a considerable red shift
while the acidic medium does not effect the absorption abil-
ities of these compounds. It is also observed in this study
that the absorption spectra of anthranoylhydrazone derivative
(L1−L3) are not effected by the pH change. The λmax of the
ligands are not considerably changed by varied solvent. In the
case of the electronic spectra of the complexes, CT bands are
observed around 350–385 nm except the nickel complexes of
L2. Both types of complexes [ML2] and [ML(phen)]Cl show
very close CT pattern.
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