Studies on mononuclear chelates derived from substituted sdchiff bases ligands (Part 3). Synthesis and characterization of a new 5-nitrosalicylidene-p- aminoacetophenoneoxime and its complexes with Co(II), Ni(II), Cu(II), and Zn(II)

Article abstract of DOI:10.1007/s11173-005-0113-3

A new ligand, 5-nitrosalicylidene-p-aminoacetophenoneoxime (HL), was synthesized from p-aminoacetophenoneoxime and 5-nitrosalicylaldehyde under reflux in absolute EtOH at 60°C for 3 h. Mononuclear complexes with a metal : ligand ratio of 1 : 2 were prepared with Co^II, Ni ^II,Cu^II, and Zn^II salts. Their structures were determined on the basis of elemental analyses, IR, ¹H and ¹³C NMR, electronic spectra, magnetic susceptibility measurements, molar conductivity, and thermogravimetric analyses. According to the results, two ligands were suggested to be coordinated to each metal atom by phenolic oxygen and imino nitrogen to form high-spin tetrahedral complexes with cobalt(II), nickel(II), and copper(II) while forming a diamagnetic complex with zinc(II).

Full text of DOI:10.1007/s11173-005-0113-3

Russian Journal of Coordination Chemistry, Vol. 31, No. 6, 2005, pp. 415–419.From Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 441–445.
Original English Text Copyright © 2005 by Canpolat, Kaya.
Studies on Mononuclear Chelates Derived from Substituted
Schiff Bases Ligands (Part 3). Synthesis and Characterization
of a New 5-Nitrosalicylidene-p-aminoacetophenoneoxime
and Its Complexes with Co(II), Ni(II), Cu(II), and Zn(II)1
E. Canpolat and M. Kaya
Department of Chemistry, Faculty of Arts and Sciences, University of Firat, 23119, Elazig, Turkey
Received September 9, 2004
Abstract—A new ligand, 5-nitrosalicylidene-p-aminoacetophenoneoxime (HL), was synthesized from p-ami-
noacetophenoneoxime and 5-nitrosalicylaldehyde under reflux in absolute EtOH at 60°C for 3 h. Mononuclear
complexes with a metal : ligand ratio of 1 : 2 were prepared with CoII, NiII, CuII, and ZnII salts. Their structures
were determined on the basis of elemental analyses, IR, 1H and 13C NMR, electronic spectra, magnetic suscep-
tibility measurements, molar conductivity, and thermogravimetric analyses. According to the results, two
ligands were suggested to be coordinated to each metal atom by phenolic oxygen and imino nitrogen to form
high-spin tetrahedral complexes with cobalt(II), nickel(II), and copper(II) while forming a diamagnetic com-
plex with zinc(II).
1
In modern coordination chemistry, many different were recorded on a Mattson 1000 FT-IR spectrometer
inorganic and organic compounds are used as ligands. with KBr pellets. H and 13C NMR spectra were
1
In spite of the tremendous variety of these ligand sys- recorded on a Bruker GmbH Dpx-400 MHz high-per-
tems, typical structures are defined as a basis for the formance digital FT-NMR spectrometer at TUBITAK.
study of their coordination chemistry [1–5].
Electronic spectra were obtained on a Shimadzu 1240 UV
spectrometer. Magnetic susceptibilities were determined
on a Sherwood Scientific Magnetic Susceptibility Bal-
ance (Model MK1) at room temperature using
Hg[Co(SCN)4] as a calibrant; diamagnetic corrections
were calculated from Pascal’s constants. Melting points
were determined on a Gallenkamp melting point appa-
ratus. Molar conductances of the Schiff base ligand and
its transition-metal complexes were determined at
room temperature using a CMD 750 WPA conductivity
meter. Thermogravimetric analyses (TGA) were car-
ried out using Shimadzu TG-50 thermobalance.
Due to recent increasing use of coordination com-
pounds in various fields of chemistry, biochemistry,
analytical, pigment, and medicinal chemistries, many
investigators have studied these topics [6]. One of the
important subjects of this topic is Schiff bases, particu-
larly, Schiff bases derived from substituted salicylalde-
hydes are well-known polydentate ligands coordinating
in deprotonated or neutral forms [7].
In order to emulate the biological activity of pro-
teins and enzymes, various model complexes were pre-
pared. A lot of investigations on the synthesis and bio-
logical activity of metal complexes have been done
recently. These investigations have shown that these
compounds are active against bacteria, viruses, and
cancers [8].
5-Nitrosalicylidene-p-aminoacetophenoneoxime
(HL). To a solution of p-aminoacetophenoneoxime
(1.502 g, 10 mmol) in absolute EtOH (10 ml), 5-nitro-
salicylaldehyde (1.671 g, 10 mmol) and p-toluene sul-
fonic acid (0.01 mg) dissolved in absolute EtOH
(40 ml) were added dropwise at 60°C with continuous
stirring and IR monitoring of the course of the reaction.
The precipitate was filtered off, washed with cold EtOH
and Et2O several times, and crystallized from an ace-
tone–water mixture and dried at 60°C to a constant
weight.
In the present paper, we report the synthesis and
characterization of a new Schiff base ligand and its
complexes with cobalt(II), nickel(II), copper(II), and
zinc(II) ions. As far as we know, this is the first report
on this ligand.
EXPERIMENTAL
Bis(p-aminoacetophenoneoxime-5-nitrosalicylaldi-
minato)cobalt(II) CoL2. A solution of Co(AcO)2 ·
4H2O (0.125 g, 0.50 mmol) in absolute EtOH (20 ml)
was added to a hot (50°C) solution of HL (0.299 g,
1.00 mmol) in absolute EtOH (25 ml) under an argon
atmosphere. The complex formed immediately upon
Elemental analyses (C, H, N) were carried out using
LECO-932 CHNSO by Technical and Scientific
Research Council of Turkey (TUBITAK). IR spectra
1
This article was submitted by the authors in English.
1070-3284/05/3106-0415 © 2005 Pleiades Publishing, Inc.

416
Table 1. Analytical and physical data of the ligand and the complexes
Compounds Empirical formula F.W., g/mol Color M. p., °C Yield, %
Yellow
CANPOLAT, KAYA
Content (calcd/found), %
C
H
N
HL
C15H13N3O4
299.28
655.48
655.24
660.09
661.94
263
249
274
295
299
79
70
64
67
66
60.20/59.86 4.38/3.99 14.04/13.75
54.97/55.28 3.69/4.01 12.82/13.19
54.99/55.30 3.69/3.57 12.83/13.11
54.59/54.23 3.66/3.60 12.73/13.04
54.43/54.39 3.65/3.51 12.70/13.07
CoL2
NiL2
CuL2
ZnL2
CoC30H24N6O8
NiC30H24N6O8
CuC30H24N6O8
ZnC30H24N6O8
Dark yellow
Green
Mustard yellow
Yellow
Table 2. Characteristic IR bands of the ligand and the complexes (cm–1)
Compounds ν(O–H) oxime ν(O–H) phenolic ν(C=N) azomethine ν(C=N) oxime
ν(C–O)
ν(N–O)
HL
3286
3290
3289
3285
3285
3260
1644
1635
1621
1617
1620
1617
1621
1615
1616
1615
1303
1315
1320
1322
1317
1007
1011
1007
1011
1007
CoL2
NiL2
CuL2
ZnL2
addition of the metal salt solution. The precipitated
Bis(p-aminoacetophenoneoxime-5-nitrosalicylal-
complex was filtered off, washed with H2O, cold EtOH, diminato)zinc(II) ZnL2. ZnL2 was prepared following
and cold Et2O several times, and dried in vacuo.
the same procedure as described for CoL2, starting from
HL (0.299 g, 1.00 mmol) and Zn(AcO)2 · 2H2O (0.110 g,
0.50 mmol).
Bis(p-aminoacetophenoneoxime-5-nitrosalicylal-
diminato)nickel(II) NiL2. NiL2 was prepared follow-
ing the same procedure as described for CoL2, starting
from HL (0.299 g, 1.00 mmol) and Ni(AcO)2 · 4H2O
(0.124 g, 0.50 mmol).
Analytical and physical data of ligand and its com-
plexes are given in Table 1.
Bis(p-aminoacetophenoneoxime-5-nitrosalicylal-
diminato)copper(II) CuL2. CuL2 was prepared fol-
lowing the same procedure as described for CoL2, start-
ing from HL (0.299 g, 1.00 mmol) and Cu(AcO)2 · H2O
(0.100 g, 0.50 mmol).
RESULTS AND DISCUSSION
The reaction steps for the synthesis of ligand HL are
given below:
CH3
CH3
NH2OH · HCl/CH3COONa
C2H5OH/H2O
H2N
H2N
O
N
OH
(A)
O2N
O2N
12 11
13 10
14 15
CH3
9
5
7
4
8
Abs. EtOH
–H2O
CH3
H2N
+
1
6
3
2
N
N
O
OHa
OH
(B)
OH
N
OHb
(HL)
(A)
This ligand was synthesized starting from p-aminoace- magnetic susceptibility measurements, molar conduc-
tivity, and TGA were used.
tophenoneoxime (A) and 5-nitrosalicylaldehyde (B) in
absolute EtOH. For the structural characterization of
the ligand and its complexes, a combination of elemen-
Table 2 lists the characteristic IR bands of the ligand
and its complexes. The ligand contains four potential
tal analysis, IR, H and C NMR, electronic spectra, donor sites: phenolic oxygen; azomethine nitrogen;
1
13
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 6 2005

STUDIES ON MONONUCLEAR CHELATES DERIVED
Table 3. H and 13C NMR spectral data of the ligand, ppm
417
1
Compound
HL
1H NMR
13C NMR
2.20 (s., 3H, H1), 6.80 (d., 1H, H11), 6.94 (d., 1H, H13), 11.24 (C1), 121.32 (C10), 122.44 (C14), 124.09 (C5 and
7.16 (d., 1H, H14), 7.30 (d., 2H, H4 and H8), 7.61 (d., C7), 127.55 (C11), 130.19 (C4 and C8), 132.38 (C13),
2H, H5 and H7), 9.20 (s., 1H, H9), 10.99 (s., 1H, Hb), 135.64 (C3), 137.07 (C12), 147.50 (C2), 153.75 (C6),
13.68 (s., 1H, Ha)
161.54 (C9), 163.09 (C15)
Table 4. Magnetic moment, molar conductance, and electronic spectral data of the ligand and the complexes
λ
max, nm (ε, l/(mol cm))
ΛM,
Compounds
µeff, µB
cm2/(Ω mol)
d–d
C–T
n
π* azomethine
HL
2.7
3.6
5.2
5.0
6.1
390 (2.80 × 103)
381 (5.95 × 103)
386 (2.85 × 103)
385 (4.01 × 103)
380 (3.04 × 103)
CoL2
NiL2
CuL2
ZnL2
4.10
3.00
1.88
Dia
676 (185)
635 (169)
571 (177)
442 (3.00 × 103)
430 (4.00 × 103)
425 (1.30 × 103)
428 (5.00 × 103)
oxime oxygen, and oxime nitrogen. In the IR spec- ments provide information regarding the structure of
trum of HL, the most characteristic absorptions are at
the complexes. The magnetic moments of the com-
plexes were measured at room temperature and are
listed in Table 4. The cobalt(II), nickel(II), and cop-
per(II) complexes are paramagnetic, while the zinc(II)
complex is diamagnetic. The magnetic moments of the
cobalt(II), nickel(II), and copper(II) complexes of the
ligand at room temperature fall in a range of 4.10, 300,
and 1.88 µB, respectively, which is characteristic of
mononuclear tetrahedral complexes [25, 26].
3286 cm–1 ν(O–Hoxime) [9–12], 3260 cm–1 ν(O–Hphenolic),
1644 cm–1 ν(C=Nazomethine), 1617 cm–1 ν(C=Noxime
)
[13–16], 1303 cm–1 ν(C–O), and 1007 cm–1 ν(N–O).
These values are in agreement with similar com-
pounds [17, 18]. The azomethine vibration of the
ligand at 1644 cm–1 was at ~1617–1635 cm–1 for the
complexes. At the same time, the ν(C–Ophenolic) band at
1303 cm–1 in the free ligand shifted to higher frequency
by 12–19 cm–1 after complexation, which means that
the shifts are due to the coordination of the ligand to the
metal atom by the azomethine nitrogen and phenolic
oxygen [19, 20]. The practically unchanged positions
of O–H at 3296 and C=N at 1559 cm–1 of the oxime
The electronic spectra of the ligand and all the com-
plexes were recorded in DMF at room temperature. The
UV spectral data of the ligand and its complexes are
given in Table 4. The aromatic band of the ligand at
group confirm that the oxime group itself does not coor- 260 nm is attributed to the benzene π
π* transition.
dinate to metal atoms by either oxygen or nitrogen
atoms.
The band around 390 nm is due to the n
π* transition
of the nonbonding electrons present on the nitrogen of the
azomethine group in the Schiff base. The complexes of
cobalt(II), nickel(II), and copper(II) show less intense
shoulders at ~571–676 nm (ε = 169–185 l/(mol cm)),
which are assigned to the d–d transition of the metal ions.
1H and 13C NMR spectra of ligand HL were
1
13
recorded in CDCl3/DMSO-D6. The H and C NMR
data of the ligand and their assignments are shown in
Table 3. The results confirm the proposed structure of
The former band is probably due to the 4A2
for CoL2, 3A2 3T2 (F) for NiL2, and 2T2
4T1 (P)
2E (G)
1
the ligand. The characteristic H NMR peaks are at
13.68 (Ha), 10.99 (Hb) [21–24], 9.20 (H9), 6.80–7.61 (HAr),
and 2.20 ppm (H1). The Ha and Hb signals at 13.68 ppm
disappeared upon the addition of D2O to the solution,
indicating that it is an acidic proton. More detailed
information about the structure of the ligand was pro-
vided by the 13C NMR spectral data. Carbon atoms are
observed at 11.24 (C1), 121.32 (C10), 122.44 (C14),
124.09 (C5 and C7), 127.55 (C11), 130.19 (C4 and C8),
132.38 (C13), 135.64 (C3), 137.07 (C12), 147.50 (C2),
153.75 (C6), 161.54 (C9), and 163.09 (C15) ppm, respec-
tively, for HL.
for CuL2 transition of tetrahedral geometry. All the
complexes show an intense band at ~380–386 nm
which is assigned to the n
π* transition associated
with the azomethine linkage [27]. The spectra of all the
complexes show intense band at ~425–442 nm (ε =
(1.30–5.00) × 103 l/(mol cm)), which can be assigned to
a charge-transfer transition of tetrahedral geometry
[28–31].
The observed molar conductance of the complexes
in 10–4 M solutions in DMSO lies in a range of
3.6−6.1 cm2/(Ω mol) (Table 4). This is consistent with
The metal-to-ligand ratio of all complexes was
found to be 1 : 2 according to the elemental analyses
results. As known, magnetic susceptibility measure- the nonelectrolytic nature of these complexes [32].
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 6 2005

418
CANPOLAT, KAYA
Table 5. TGA data of the ligand and the complexes
Decomposition temperature (weight loss (calcd/found), %)
Total weight loss
(calcd/found), %
Residue
(calcd/found), %
Compounds
first step
second step
HL
234–272 (25.75/26.23)
221–267 (20.15/19.64)
186–233 (20.16/19.69)
197–326 (20.00/19.05)
208–375 (25.72/26.31)
272–598 (74.25/72.97)
267–557 (68.42/67.74)
233–542 (68.44/68.82)
326–358 (67.95/68.60)
375–511 (61.99/62.17)
/99.20
88.57/87.38
88.60/88.51
87.95/87.65
87.71/88.48
/0.80
11.43/12.62
11.40/11.49
12.05/12.35
12.29/11.52
CoL2
NiL2
CuL2
ZnL2
The thermal behavior of the ligand and all the com-
plexes was investigated using thermogravimetric tech-
niques. The thermal stability data are listed in Table 5.
The decomposition temperature and weight losses of
the complexes were calculated from the TGA data. The
ligand is stable up to 234°C, and its decomposition
starts at 234°C and is completed at 598°C. As can be
seen from the TGA data in Table 5, all the complexes
and the ligand decompose in two steps in different tem-
perature ranges. All these complexes undergo complete
decomposition to the corresponding metal oxides,
CoO, NiO, CuO, and ZnO [33, 34].
ACKNOWLEDGMENTS
This work was supported by the Management Unit
of Scientific Research Projects of Firat University
(FUBAP) (project no. 835).
REFERENCES
1. Garnovskii, A.D., Sadimenko, A.P., Sadimenko, M.I.,
and Garnovskii, D.A., Coord. Chem. Rev., 1998, vol. 173,
no. 1, p. 31.
2. Comprehensive Coordination Chemistry, Wilkinson, G.,
Ed., Oxford: Pergamon, 1987, p. 1.
3. Kawaguchi, S.V., Coordination Modes of Ligands in
Metal Complexes, Berlin: Springer, 1988.
As mentioned in Introduction, our research group
has been heavily engaged in the synthesis of novel sub-
stituted oximes and their Schiff base derivatives. Many
other Schiff base derivatives containing substituted
oxime were synthesized, characterized in detail, and
used for complexation with some transition-metal salts.
Functional groups, such as oxime, have no effect on the
complexes. These functional groups are very far from
the pendants taking part in the complexation. For these
complexes, additional analytical data are given in
Tables 1–5. According to the results obtained, the
geometries of all the complexes are tetrahedral. The
suggested structures of the complexes are shown
below:
4. Garnovskii, A.D., Koord. Khim., 1988, vol. 14, no. 5,
p. 579.
5. Garnovskii, A.D., Nivorozhkin, A.L., and Minkin, V.I.,
Coord. Chem. Rev., 1993, vol. 126, no. 1–2, p. 1.
6. Eloy, F. and Lenaers, R., Chem. Rev., 1962, vol. 62,
no. 2, p. 155.
7. Hobday, M.D. and Smith, T.D., Coord. Chem. Rev.,
1973, vol. 9, no. 3–4, p. 311.
8. Huang, Y., Shen, Y., and Long, S., Synth. React. Inorg.
Met.-Org. Chem., 2002, vol. 32, no. 9, p. 1611.
9. Canpolat, E. and Kaya, M., J. Coord. Chem., 2002,
vol. 55, no. 8, p. 961.
10. Canpolat, E., Kaya, M., and Gorgulu, A.O., Polish J.
Chem., 2002, vol. 76, no. 5, p. 687.
11. Canpolat, E. and Kaya, M., Polish J. Chem., 2003, vol. 77,
no. 8, p. 961.
O2N
12. Kukushkin, V.Y., Tudela, D., Izotova, Y.A., et al., Poly-
hedron, 1998, vol. 17, no. 15, p. 2455.
13. Gungor, O., Canpolat, E., and Kaya, M., Polish J.
Chem., 2003, vol. 77, no. 4, p. 403.
CH3
N
O
N
14. Canpolat, E., Kaya, M., and Gur, S., Turk. J. Chem.,
HO
2004, vol. 28, no. 2, p. 235.
M
N
15. Canpolat, E., Kaya, M., and Yazici, A., Russ. J. Chem.,
OH
2004, vol. 30, no. 2, p. 87.
N
O
16. Canpolat, E. and Kaya, M., Transition Met. Chem. (Lon-
don), 2004, vol. 29, no. 5, p. 550.
17. Kukushkin,Y.N., Krylov, V.K., Kaplan, et al., Inorg. Chim.
Acta, 1999, vol. 285, no. 1, p. 116.
18. Patel, K.M., Patel, K.N., Patel, N.H., and Patel, M.N.,
Synth. React. Inorg. Met.-Org. Chem., 2001, vol. 31,
no. 2, p. 239.
H3C
NO2
M(L)2
M = Co2+, Ni2+, Cu2+ and Zn2+
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 6 2005

STUDIES ON MONONUCLEAR CHELATES DERIVED
419
19. Joshi, J.D., Sharma, S., Patel, G., and Uora, J.J., Synth. 26. Aboaly, M.M. and Khalil, M.M.H., Spectros. Lett., 2001,
React. Inorg. Met.-Org. Chem., 2002, vol. 32, no. 10,
vol. 34, no. 4, p. 495.
27. Celik, C., Tumer, M., and Serin, S., Synth. React. Inorg.
Met.-Org. Chem., 2002, vol. 32, no. 10, p. 1839.
28. Rasmussen, J.C., Toftlund, H., Nivorozhkin, A.N., et al.,
Inorg. Chim. Acta, 1996, vol. 251, no. 1–2, p. 291.
p. 1729.
20. Jayabakalakrishnan, C., Karvembu, R., and Natarajan, K.,
Synth. React. Inorg. Met.-Org. Chem., 2002, vol. 32,
no. 6, p. 1099.
29. Yamada, S. and Takeuchi, A., Coord. Chem. Rev., 1982,
21. Canpolat, E. and Kaya, M., J. Coord. Chem., 2002,
vol. 43, no. 5, p. 187.
vol. 55, no. 12, p. 1419.
30. Lever, A.B.P., Inorganic Electronic Spectroscopy,
22. Canpolat, E. and Kaya, M., J. Coord. Chem., 2004,
Amsterdam: Elsevier, 1997.
vol. 57, no. 14, p. 1217.
31. Wagner, M.R. and Walker, F.A., Inorg. Chem., 1983,
23. Kukushkin, Y.N., Bavina, M.V., Zinchenko, A.V., et al.,
V.Y., Polyhedron, 1997, vol. 16, no. 14, p. 2429.
vol. 22, no. 21, p. 3021.
32. Geary, W.J., Coord. Chem. Rev., 1971, vol. 7, no. 1, p. 81.
33. Yasodhai, S., Sivakumar, T., and Govindarajan, S., Ther-
mochim. Acta, 1999, vol. 338, no. 1–2, p. 57.
24. Voloshin,Y.Z., Belsky, V.K., and Trachevskii, V.V., Poly-
hedron, 1992, vol. 11, no. 15, p. 1939.
25. Cotton, F.A. and Wilkinson, G., Advanced Inorganic 34. Rakha, T.H., Transition Met. Chem. (London), 1999,
Chemistry, New York: Wiley, 1988. vol. 24, no. 6, p. 659.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 6 2005