Synthesis and characterization of new (E,E)-dioximes and their divalent metal complexes

Article abstract of DOI:10.1134/S1070328407120093

Two new soluble vic-dioxime ligands, 4-isopropylanilineglyoxime (L ¹H₂) and 4-benzylpiperidineglyoxime (L²H ₂) were prepared by reacting 4-isopropylaniline and 4-benzylpiperidine with anti-chloroglyoxime. Ten me

Full text of DOI:10.1134/S1070328407120093

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2007, Vol. 33, No. 12, pp. 922–926. © Pleiades Publishing, Ltd., 2007.
Synthesis and Characterization of New (E,E)-dioximes
and Their Divalent Metal Complexes1
P. Deveci, E. Özcan, and B. Taner
Department of Chemistry, Faculty of Arts and Sciences, Selcuk University, Konya, 42031, Turkey
e-mail: pervindeveci@gmail.com
Received August 25, 2006
Abstract—Two new soluble vic-dioxime ligands, 4-isopropylanilineglyoxime (L1H2) and 4-benzylpiperidineg-
lyoxime (L2H2) were prepared by reacting 4-isopropylaniline and 4-benzylpiperidine with anti-chloroglyoxime.
Ten metal complexes were obtanied by reacting both ligands with Cu(II), Ni(II), Co(II), Zn(II), and Cd(II) cations.
1
The ligands and their metal complexes were elucidated by elemental analysis, IR, UV-vis, H NMR, and 13C
NMR and also magnetic moments of the complexes were determined.
DOI: 10.1134/S1070328407120093
1
INTRODUCTION
Anti-chloroglyoxime was prepared by a reported pro-
cedure [12, 13].
vic-Dioxime complexes, which were synthesized
for the first time by Tschugaev, have been the focus of
a great deal of interest through the decades of never-
ending series of interesting reports due to their similar-
ity to vitamin B12 [1–5].The exceptional stability and
unique electronic properties of these complexes can be
attributed to their planar structure that is stabilized by
hydrogen-bonded bridges [1].
Physical measurement. Elemental analyses of the
synthesized compounds (C, H, N) were performed
using a LECO-932 CHNSO model analyzer. 1H NMR
and 13C NMR spectra were recorded on a Bruker
GmbH Dpx-400 MHz High Performance Digital
FT-NMR spectrometer (in DMSO-d6). IR spectra were
measured on a Perkin Elmer Model 1605 FT-IR spec-
trophotometer as KBr pellets. The UV-vis spectra were
recorded on a Shimadzu 160 A spectrofotometer. Mag-
netic moments of the complexes were measured using
a Sherwood Scientific Model MX1 Gouy magnetic sus-
ceptibility balance at room temperature using
Hg[Co(SCN)4] as calibrate; diamagnetic corrections
were calculated from Pascal’s constants.
The presence of slightly basic nitrogen atoms and
mildy acidic hydroxyl groups make vic-dioximes
amphoteric ligands, which form corrin-type, square-
planar, square-pyramidal or octahedral complexes with
transition metal ions such as Cu2+, Ni2+, Pd2+, Co2+, and
Co3+ as central atoms [6, 7]. The stable complexes pre-
pared with vic-dioxime ligands have been used for var-
ious purposes such as oxidation reagents, additive
materials for the improvement of pigments, mechanic
oils, epoxy resins and rubber, in industry, etc. [8].
Oxime metal complexes are utilized in medicine as
well; Tc(V) and Cu(II) containing vic-dioximes cur-
rently are used as cerebral and myocardial perfusion
imaging agents [9–11].
Synthesis of 4-isopropylanilineglyoxime (L1H2)
and 4-benzylpiperidineglyoxime (L2H2). 4-isopropy-
laniline (1.4 ml, 5 mmol) or 4-benzylpiperidine (0.9 ml,
5 mmol) was dissolved in absolute ethanol (15 ml). A
solution containing anti-chloroglyoxime (0.6 g, 5 mmol)
in ethanol (5 ml) was added slowly at room temperature
with constant stirring. The reaction mixture was stirred
continuously for 1 h at room temperature. The pH of the
mixture was about 7.0–7.5. Its volume was then dou-
bled by adding distilled water. The precipitated ligands
were filtered off, washed with cold water, dried and
crystallized from water–ethanol (1 : 2).
In the present study, we report the synthesis and
characterization of novel soluble vic-dioxime ligands
and their mononuclear complexes with Cu(II), Ni(II),
Zn(II), Co(II), and Cd(II).
The L1H2 and L2H2 ligands are soluble in common
solvents, such as CHCI3, EtOH, THF, DMSO and ace-
tonitrile. 13C NMR spectral data for L1H2 (CDCl3, TMS,
δ, ppm): C1(23.94), C2(33.48), C3(135.75), C4(127.18),
C5(122.50), C6(145.82), C7(145.08), C8(141.78). 13C NMR
spectral data for L2H2 (CDCl3, TMS, δ, ppm):
C1(124.24), C2(126.18), C3(125.94), C4(138.70),
EXPERIMENTAL
Materials. 4-Isopropylaniline, 4-benzylpiperidine,
all solvents, and all metal salts purchased from E.
Merck were reagent grade and were used as received.
1
The text was submitted by the authors in English.
922

SYNTHESIS AND CHARACTERIZATION
923
Table 1. Analytical and physical data for the ligands and their complexes
Content (calcd/found), %
H
Molecular formula
Compound
L1H2
Color
White
M.p., °C Yield, %
(F.W., g/mol)
C
N
C11H15N3O2
(221.25)
141
266*
295
299
172*
278
148
227
68
60
42
62
48
44
60
75
59.72/60.33)
6.82/6.25)
5.65/5.70
4.78/4.60
6.02/6.50
5.10/4.80
4.75/5.12
8.73/7.99
6.26/6.02
18.99/19.14)
12.82/13.10
12.46/12.85
15.70/16.00
11.20/11.70
12.39/13.12
16.08/1580
14.51/13.28
(L1H)2Ni
(L1H)2Cu
C22H28O4N6Ni
(499.19)
Dark red
Green
52.93/53.01
49.18/50.10
49.35/49.30
37.80/36.20
38.96/39.15
64.35/63.28
58.05/57.75
C22H28O4N6Cu
(504.04)
(L1H)2Co · 2H2O C22H32N6O6Co
(535.46)
(L1H)Cl(H2O)Cd C11H16N3O3ClCd Yellow
(388.80)
(L1H)Cl(H2O)Zn C11H16N3O3ClZn
(339.12)
Brown
White
White
Red
L2H2
C14H19N3O2
(261.31)
(L2H)2Ni
C28H36N6O4Ni
(579.31)
(L2H)2Cu
C28H36N6O4Cu
(584.35)
Dark green
Brown
178*
251
40
65
58
55
54.55/54.80
54.63/53.50
43.13/42.45
44.35/43.28
5.34/5.40
6.54/5.50
5.73/5.80
5.31/5.80
13.14/13.80
13.65/13.20
13.28/12.40
11.08/(12.12
(L2H)2Co · 2H2O C28H40N6O6Co
(615.56)
(L2H)Cl(H2O)Cd C14H20N3O3ClCd Yellow
(426.19)
(L2H)Cl(H2O)Zn C14H20N3O3ClZn
(379.18)
161*
150
White
* Decomposition point.
C5(40.70), C6(34.92), C7(30.98), C8(45.20), C9(150.18), C7(145.80), C8(136.35); 13C NMR (CDCl3, TMS, δ,
C10(130.83).
ppm): C1(127.20), C2(126.10), C3(130.24), C4(136.72),
C5(40.68), C6(36.20), C7(30.80), C8(43.20), C9(150.16),
Table 1 gives analytical and physical data for the
1
ligands. IR, H NMR, and UV-vis spectra data of the C10(128.62).
ligands are given in tables 2–4, respectively.
Synthesis of the Cd(II), Zn(II) complexes with
Synthesis of the Ni(II), Co(II), and Cu(II) com-
plexes with L1H2 and L2H2. A solution of the metal salt
(NiCl2 · 6H2O (1.189 g, 5 mmol) or CoCl2 · 6H2O
(1.190 g, 5 mmol) or CuCl2 · 2H2O (0.852 g, 5 mmol))
dissolved in H2O (15 ml) was added dropwise to a
stirred solution of the ligand (L1H2 (2.8 ml, 10 mmol)
or L2H2 (1.8 ml, 10 mmol)) dissolved in EtOH (20 ml).
The pH of the reaction mixture 3.5–4.0 was then
adjusted to 5.5–6.0 by the addition of 1% NaOH in
EtOH. The mixture was stirred on a water bath at 45–
50°C for 1 h. The precipitates were filtered off, washed
with cold water, and dried.
L1H2 and L2H2. A solution of the metal salt (CdCl2 ·
H2O (1.005 g, 5 mmol) or ZnCl2 (0.670 g, 5 mmol)) dis-
solved in H2O (15 ml) was added dropwise to a stirred
solution of the ligand (L1H2 (1.4 ml, 5 mmol) or L2H2
(0.9 ml, 5 mmol)). The pH of the reaction mixture
3.5−4.0 was then adjusted to 10.0–11.0 for Cd(II) com-
plex and 7.0–7.5 for the Zn(II) complex by the addition
of 1% NaOH in EtOH. The mixture was stirred on a
water bath at 45–50°C for 1 h. The precipitates were fil-
tered off, washed with cold water, and dried.
L1H2 and L2H2 were prepared by a one-step reaction
between anti-chloroglyoxime and corresponding
amines. The reactions of preparing of vic-dioxime
The Ni(II) complexes are soluble in DMSO, DMF,
and CHCl3. Spectral data for the Ni(II) complexes:
13C NMR (CDCl3, TMS, δ, ppm): C1(24.10), C2(39.61),
C3(132.61), C4(127.63), C5(123.82), C6(148.10), ligands are given below:
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 12 2007

924
DEVECI et al.
1CH3
OH
O
N
H
H
C
5
Cl
6C
C
NH
CH3
HC
CH3
NH2
4
7C
8C
C
C
N
N
–HCl
3C
+
2HC
1CH3
N
O
H
H
OH
(L1H2)
2C 3C
4C 5CH2
O
N
H
C7 8C
6C
Cl
OH
OH
C
N
1
C
N
9C
–HCl
CH2
NH +
.
C
N
10C
H
N
O
H
H
(L2H2)
RESULTS AND DISCUSSIONS
3238 cm–1, respectively, as a broad absorption. The NH,
C=N, and NO stretching vibrations are at 3400–3420,
1656–1659, and 990–970 cm–1, respectively, as
expected for the substituted aminoglyoximes [14–16].
L1H2 and L2H2 are highly soluble in common
organic solvents, such as EtOH, CHCl3, acetonitrile, or
DMSO. The results of elemental analysis of L1H2 and
L2H2 are in agreement with theoretical expectations
(Table 1). In the IR spectrum of the ligands (Table 2),
1
In the H NMR spectrum of L1H2 and L2H2 in
DMSO-d6 (Table 3) two peaks are observed for the pro-
tons, since the OH protons of the oxime groups are not
an OH stretching vibration is observed at 3314 and equivalent [17–19]. The chemical shifts of =N–OH pro-
Table 2. Characteristic IR bands (cm–1) of the ligands and complexes as KBr pellets
Compounds
ν(O–H )
ν(N–H )
ν(O···H–O )
ν(C=N)
ν(N–O )
Others
L1H2
3314
3400
3394
3393
3392
3287
3160
3420
3415
3412
3424
3340
3280
1656
1616
1615
1618
1630
1618
1659
1620
1618
1622
1620
1630
990
980
970
976
956
970
970
960
955
958
960
950
(L1H)2Ni
1770
1760
1770
(L1H)2Cu
(L1H)2Co · 2H2O
(L1H)CI(H2O)Cd
(L1H)CI(H2O)Zn
L2H2
3430 (H2O)
3305
3310
3238
(L2H)2Ni
(L2H)2Cu
(L2H)2Co · 2H2O
(L2H)CI(H2O)Cd
(L2H)CI(H2O)Zn
1765
1780
1800
3450 (H2O)
3310
3310
1
Table 3. H NMR spectra of the ligands and their Ni(II) complexes in DMSO-d6
Compound
L1H2
(L1H)2Ni
L2H2
(L2H)2Ni
O–Ha
11.80
O–Ha
10.75
HArom.
aHN–C=
=CH
O–H···O
6.40–7.20
6.20–7.15
6.90–7.20
6.80–7.20
7.62
7.60
7.20
7.18
7.25
7.25
15.20
16.10
11.01
11.10
a
Dissappears on D O exchange.
2
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 12 2007

SYNTHESIS AND CHARACTERIZATION
925
tons are observed at 11.80–10.75 ppm for L1H2 and
11.01–11.10 ppm for L2H2 as singlets. A single chemi-
cal shift for the OH proton indicates that the oxime
groups prevail in the anti form [20]. In L1H2 the NH
group appears as singlet at 7.62 ppm. These resonances
disappear upon addition of D2O to the solution. In these
ligands the CH proton adjacent to the oxime group is
observed at 7.20 and 7.25 ppm. More detailed informa-
tion about the structure of the ligands is provided by
13C NMR spectral data. In the 13C NMR spectrum, the
carbon resonances of oxime groups are observed at
145.08 and 141.78 ppm for L1H2 and 150.18 and
130.83 ppm for L2H2. Observation of dioxime carbons
in the 13C NMR spectra at two different frequencies
indicates that the vic-dioxime ligands have the anti
structure [21].
Table 4. Magnetic moments and characteristic UV-vis bands
of the ligands and complexes
Compound
µ
eff/atom, µB
λmax , nm*
L1H2
301
(L1H)2Ni
Dia**
1.69
3.81
Dia
324, 434, 476, 690
300, 660, 670
303, 635
(L1H)2Cu
(L1H)2Co · 2H2O
(L1H)Cl(H2O)Cd
(L1H)Cl(H2O)Zn
L2H2
300, 610
Dia
289, 310, 691
230, 260
(L2H)2Ni
(L2H)2Cu
(L2H)2Co · 2H2O)
(L2H)Cl(H2O)Cd
(L2H)Cl(H2O)Zn
Dia
1.89
4.04
Dia
252, 325, 440, 680
269, 328, 550, 670
270, 350, 480
280, 570
The synthesis of the mononuclear complexes was
achieved at room temperatures. The results of elemen-
tal analysis of the complexes are in agreement with the-
oretical expectations (Table 1). vic-Dioxime derivatives
L1H2 and L2H2 form probably square planar complexes
with Ni(II), Cu(II) and octahedral complexes with
Co(II) with a metal: ligand ratio of 1 : 2. The Cd(II) and
Zn(II) complexes of these ligands are with a metal:
ligand ratio of 1 : 1. In the IR spectra of the complexes
(Table 2) C=N and NO stretching vibrations are
observed at around 1615–1622 and 955–980 cm–1,
respectively. The C=N vibration is at lower frequency
than for the free ligands, attributable to N,N-chelation
[22, 23]. Weak bending vibrations of the O–H···O
bridges are observed around 1660–1800 cm–1. Disap-
pearance of the stretching vibrations of the O–H band
present in the free ligands is further evidence for
O−H···O bond formation [24]. For the Co(II) com-
plexes, coordinated H2O molecules are identified by a
broad OH absorption around 3430–3450 cm–1.
Dia
270, 300, 420
Notes: * In DMF.
** Diamagnetic.
(for Cu(II) complexes). The suggested structures of the
Cd(II) and Zn(II) complexes are shown below:
R
N
O
OH2
M
H
N
Cl
OH
(M = Cd(II), Zn(II); R = C9H12 for L1H2
R = C12H16 for L2H2).
The UV-vis spectra of the ligands and complexes in
DMF showed absorption bands between 230–690 nm.
In the complexes the low intensity bands in the range
550–690 nm are consistent with d
d transitions of
In the IR spectrum of the Zn(II) and Cd(II) com-
plexes the stretching band of ν(C=N) appeared around
1618–1630 cm–1 is shifted to 1656 cm–1 in L1H2 and
1659 cm–1 in L2H2. There is no (O···H–O) peak, as
expected for these complexes. At the same time, the
N−O band appearing around 990–960 cm–1 in the free
ligands moved to lower frequency by ~20 cm–1 after
Zn(II) and Cd(II) complex formation. These results
suggest that the ligand is coordinated to each metal ion
through nitrogen and oxygen donors. A chloride ion
and water molecule are probably coordinated to each
metal ions as reported for the Zn(II) and Cd(II) com-
plexes of vic-dioximes [25–28].
the metal ions. The 250–380 nm bands correspond to
both the π
π* and n
π* transitions of C=N and
charge-transfer transition arised from π-electron inter-
actions between the metal and ligand [29, 30].
ACKNOWLEDGMENTS
The support of the Management Unit of Scientific
Research Projects of Selcuk University (SU-BAP-
project no. 05101009) under thesis projects is grate-
fully acknowledged.
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complexes are diamagnetic. Magnetic moments are
4.04, 3.81 µB (for Co(II) complexes) and 1.69, 1.89 µB
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