A novel vic-dioxime ligand and its Ni(II), Cu(II) and Co(II) complexes containing calix[4]pyrrole moiety: Synthesis, characterization and redox properties

Article abstract of DOI:10.1007/s10847-012-0131-y

A new calix[4]pyrrole functionalized vic-dioxime, 3-(4-methyl-9,9,14,14,19, 19-hexaethylcalix[4]pyrrole)benzoaminoglyoxime (LH₂) was synthesized from anti-chloroglyoxime and 3-aminophenyl-calix[4]pyrrole at room temperature. The mononuclear complexes {nickel(II), copper(II) and cobalt(II)} of this vic-dioxime ligand were prepared and their structures were confirmed by elemental analysis, IR and UV-Vis spectrophotometry, magnetic susceptibility; the MS, ¹H and ¹³C NMR spectra of the LH₂ ligand and its Ni(II) complex were also recorded. The experimental results indicated that the ligand:metal ratio was 2:1 in the cases of Ni(II), Cu(II) and Co(II) complexes as is with most vic-dioximes. Electrochemical properties of the ligand, and its complexes were investigated in DMSO solution by cyclic voltammetry at 200 mV s^-1 scan rate.

Full text of DOI:10.1007/s10847-012-0131-y

J Incl Phenom Macrocycl Chem (2012) 74:391–396
DOI 10.1007/s10847-012-0131-y
ORIGINAL ARTICLE
A novel vic-dioxime ligand and its Ni(II), Cu(II) and Co(II)
complexes containing calix[4]pyrrole moiety: synthesis,
characterization and redox properties
¨
•
•
•
Bilge Taner Pervin Deveci Emine Ozcan
Ali Osman Solak
Received: 30 October 2011 / Accepted: 18 February 2012 / Published online: 4 March 2012
ꢀ Springer Science+Business Media B.V. 2012
Abstract
A
new calix[4]pyrrole functionalized vic-
Introduction
dioxime, 3-(4-methyl-9,9,14,14,19,19-hexaethylcalix[4]pyr-
role)benzoaminoglyoxime (LH2) was synthesized from
anti-chloroglyoxime and 3-aminophenyl-calix[4]pyrrole at
room temperature. The mononuclear complexes {nickel(II),
copper(II) and cobalt(II)} of this vic-dioxime ligand were
prepared and their structures were confirmed by elemental
analysis, IR and UV–Vis spectrophotometry, magnetic sus-
Theoxime ligandsare one ofthemostwidely usedligandsdue
to the ease of formation and remarkable versatility. They can
form different types of coordination compounds with transi-
tion metal ions due to several electron rich donor centers with
unique structural and chemical properties [1, 2]. The research
field dealing with vic-dioxime metal complexes is very broad
due in part to their potential interest for a number of inter-
disciplinary areas that include bioinorganic chemistry, catal-
ysis, and medicine [3, 4]. vic-Dioximes are modified by
substitution with various groups such as crown ethers,
monoaza crown ethers, ferrocene groups, tetrathiamacrocy-
cles or N2O2 macrocycles and dendritic groups [5–7].
Calix[4]pyrroles and their derivatives have long been of
interestbothascomplexationhosts for ions and molecules and
as frameworks for elaborating more complex structures [8, 9].
Although the studies of calix[4]pyrroles and their derivatives
have made great progress [10, 11], to the best of our knowl-
edge, studies on structural analyses of calix[4]pyrrole func-
tionalized vic-dioxime ligands and their transition metal
complexes in modern coordination chemistry are very rare
[12].
1
ceptibility; the MS, H and 13C NMR spectra of the LH2
ligand and its Ni(II) complex were also recorded. The
experimental results indicated that the ligand:metal ratio was
2:1 in the cases of Ni(II), Cu(II) and Co(II) complexes as is
with most vic-dioximes. Electrochemical properties of the
ligand, and its complexes were investigated in DMSO solu-
tion by cyclic voltammetry at 200 mV s-1 scan rate.
Keywords Oxime ꢀ vic-Dioxime ꢀ Transition metal
complex ꢀ Calix[4]pyrrole ꢀ Cyclic voltammetry
In this work, we have synthesized ligand, derived from
anti-chloroglyoxime and 3-aminophenyl-calix[4]pyrrole
and we have prepared its nickel (II), cobalt (II) and copper
(II) complexes (Scheme 1). The structure of vic-dioxime
ligand was characterized in detail for the first time to
¨
B. Taner (&) ꢀ P. Deveci ꢀ E. Ozcan
Department of Chemistry, Faculty of Science,
Selc¸uk University, Konya, Turkey
e-mail: bilgetaner@gmail.com
1
confirm the proposed structure by using H and 13C-NMR,
FTIR, UV–Vis, MS and elemental analysis. The compo-
sition of Ni(II), Cu(II) and Co(II) complexes have been
identified by elemental analysis, magnetic susceptibility
measurements, NMR, FT-IR, UV–Vis and MS. Electro-
chemical properties of the ligand, and its complexes were
investigated in DMSO solution containing 0.1 M
A. O. Solak
Department of Chemical Engineering, Faculty of Engineering,
Kyrgyz-Turk Manas University, Bishkek, Kyrgyzstan
A. O. Solak
Department of Chemistry, Faculty of Science,
Ankara University, Tandogan, Ankara, Turkey
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Scheme 1 Routes for the synthesis of vic-dioxime complexes; i NiCl2ꢀ6H2O or CuCl2ꢀ2H2O, hot ethanol, 50 ꢁC, 30 min; ii CoCl2ꢀ6H2O, hot
ethanol, 50 ꢁC, 30 min
tetrabutylamoniumtetrafluoroborate (TBATFB) as sup-
porting electrolyte by cyclic voltammetry (CV).
calix[4]pyrrole [14] were prepared according to the procedures
described in literature. All solvents were of reagent grade and
purified according to standard procedures. Elemental analyses
(C, H, N) were determined 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 with DMSO-d6 as the solvent with Me4Si
as an internal reference. The IR spectra of solid samples were
recorded in a range from 600 to 4,000 cm-1 on a Perkin Elmer
Spectrum 100 FT-IR spectrometer (Universal/ATR Sampling
Experimental section
Materials and measurements
All chemicals were of reagent grade quality and used without
purification; anti-chloroglyoxime [13] and 3-aminophenyl-
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J Incl Phenom Macrocycl Chem (2012) 74:391–396
393
Accessary). UV–Vis spectra were obtained by Shimadzu UV–
1,700 visible recording spectrophotometers. Melting points
were determined using an electrothermal apparatus and were
uncorrected. The mass analyzer was a Bruker Daltonics (Bre-
men, Germany) MicrOTOF mass spectrometer equipped with
an orthogonal electrospray ionization (ESI) source. The
instrument was operated in negative ion mode using a m/z
range of 50–1,500. Magnetic susceptibilities were determined
on a Sherwood Scientific Magnetic Susceptibility balance
(Model MK1) at room temperature using Hg[Co(SCN)4] as a
standard; diamagnetic corrections were calculated from Pas-
cal’s constants. All the electrochemical experiments were
performed using a CH Instruments electrochemical analyzer
(model 600C series) equipped with BAS C3 cell stand.
Working electrode was a bare glassy carbon (GC) disk (BAS
Model MF-2012) with a geometric area of 0.027 cm2. The
reference electrode was Ag/Ag/Ag? (0.01 M AgNO3) in
nonaqueous media, and the counter electrode was a Pt wire.
hot ethanol, was added dropwise to a stirred solution of 3
(0.1 mmol, 67.5 mg) in 5 mL of ethanol. A distinct change in
color and a decrease in the pH of the solution was observed.
Whilestirringatthesametemperature,NaOH(1%)wasadded
in order to increase the pH. The mixture was stirred on a water
bathat50 ꢁCfor30 mininordertocompletetheprecipitation.
The precipitates were then filtered and washed with water,
ethanol and ether and dried in vacuo.
Data for (4). Elemental analysis (Found: C, 69.92; H,
7.28; N, 13.87%. Calc.: C, 69.98; H, 7.39; N, 13.94%). IR
m
max/cm-1: 3,435 (N–H), 2,875–2,964 (C–Haliph), 1,709
1
(O–HꢀꢀꢀO), 1,574 (C=N), 986 (N–O). H NMR (400 MHz,
DMSO-d6, ppm): 0.29–0.58 (m, 36 H, CH3), 1.55–1.79
(m, 24 H CH2), 2.12 (s, 6H, CH3), 5.52–5.63 (br m, 16 H,
pyr-CH), 6.30 (s, 2H, N–H), 6.47–7.06 (br m, 8 H, Ar-
CH), 8.81 (br s, 4 H, NHpyr), 9.31 (br s, 4 H, NHpyr), 9.39
(s, 2H, CH), 14.42 (s, 2H, O–HꢀꢀꢀO, D2O-exchangeable).
MS(ES) for C82H104N14O4Ni m/z: 1406.47 [M]?, leff:
diamagnetic.
Synthesis
Data for (5). Elemental analysis (Found: C, 69.77; H,
7.32; N, 13.87%. Calc.: C, 69.73; H, 7.37; N, 13.89%). IR
m
max/cm-1: 3,431 (N–H), 2,849–2,963 (C–Haliph), 1,716
Synthesis of the ligand [LH2] (3)
(O–HꢀꢀꢀO), 1,572 (C=N), 982 (N–O), leff : 1.45.
A mixture of amino-modified calixpyrrole (2) (0.1 mmol,
59 mg), anti-chloroglyoxime (0.1 mmol, 12 mg), Et2O
(15 mL) and Et3N (0.1 mL) was stirred overnight at room
temperature. Then the solution was washed three times with
saturated NaHCO3 (3 9 15 mL) solution. The organic phase
was collected, and dried with Na2SO4 and the solvent was
removed under reduced pressure. The product was purified by
columnchromatography(MeOH/CHCl3, 5/95). Thesynthesis
of the ligand repeated several times in order to gather enough
material for the complex synthesis. Elemental analysis
(Found: C, 72.78; H, 7.78; N, 14.44%. Calc.: C, 72.89; H,
7.85; N, 14.52%). IR mmax/cm-1: 3,410 (N–H), 3,335 (O–H),
2,876–2,965 (C–Haliph), 1,587 (C=N), 998 (N–O). 1H NMR
(400 MHz, DMSO-d6, ppm): 0.46–0.68 (m, 18 H, CH3),
1.73–1.90 (m, 15 H CH2?CH3), 5.66–5.77 (br m, 8 H, pyr-
CH), 6.30–7.09 (br m, 4 H, Ar-CH), 7.39 (s, 1H CH), 7.54 (br
s, 1H, NH), 8.97 (br s, 2H,NH), 9.43 (br s, 2H, NH), 10.82 (s,
1H, N–OH, D2O-exchangeable), 11.32 (s, 1H, N–OH, D2O-
exchangeable). 13C NMR (100 MHz, DMSO-d6, ppm): 8.26,
8.38, 8.74, 8.89, 8.93, 9.35, 9.42, 28.30, 28.90, 29.20, 29.70,
30.66, 31.79, 42.59, 43.20, 43.38, 44.67, 103.11, 105.05,
105.19, 105.18, 112.13, 113.71, 115.54, 127.92, 128.96,
129.10, 130.42, 135.92, 136.75, 138.23, 145.81, 148.88. MS
(ES) for C41H53N7O2 m/z: 675.43 [M]?, 674.43 [M-H]?.
Data for (6). Elemental analysis (Found: C, 68.26; H, 7.52;
N, 13.61%. Calc.: C, 68.23; H, 7.49; N, 13.59%). IR mmax
/
cm-1: 3,431 (N–H), 3,360 (O–H), 2,849–2,963 (C–Haliph),
1,704 (O–HꢀꢀꢀO), 1,578 (C=N), 982 (N–O), leff: 2.39.
Results and discussion
In the IR spectrum of the vic-dioxime ligand, the –OH and
–NH stretching vibrations were observed as a broad band at
3,335 and 3,410 cm-1, respectively. The very strong
absorption band at 1,587 cm-1 due to v(C=N) of azome-
thine group in the structure of the ligand was observed. The
spectrum of the ligand also shows absorption bands in the
1,416–1,490 cm-1 region which are assigned to the aro-
matic ring stretching vibrations. In the IR spectrum of the
complexes, strong v(NH), v(C=N) and v(NO) characteristic
stretching vibration bands were observed at 3,435, 1,574
and 986 cm-1 for complex 4; at 3,431, 1,572 and 982 for
complex 5; 3,431, 1,578 and 982 for complex 6. In the IR
spectrum of the Co(II) complex (6), coordinated H2O
molecules were identified by a strong broad OH absorption
around 3,360 cm-1 [15]. In the IR spectra of the com-
plexes, displacements of the absorption bands to lower
frequencies compared to the free ligand were observed,
indicating the coordination of the ligand to the metal ion.
For example, the IR spectra of the complexes shows that
the v(C=N) band is shifted to lower frequencies, compared
to that of the free ligand at 1,587 cm-1 [15, 16]. The oxime
hydroxyl stretching of the free ligand is not observed, while
Synthesis of mononuclear complexes, [Ni(LH)2] (4),
[Cu(LH)2] (5), [Co(LH)2.(H2O)2] (6)
A solution of 0.05 mmol metal salt [NiCI2ꢀ6H2O (0.0118 g),
CuCl2ꢀ2H2O (0.0084 g) CoCl2ꢀ6H2O (0.0116 g)] in 5 mL of
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new vibrational bands of an intermolecular hydrogen bond
v(O–HꢀꢀꢀO) between the two oxime groups appeared near
1,704–1,716 cm-1 [4, 12, 17] in the complexes (Table 1).
1
The H and 13C NMR spectral results obtained for the
LH2 vic-dioxime ligand in DMSO-d6, together with
respective assignments, have been given above in experi-
mental section. When the 1H NMR spectra of the ligand in
DMSO was examined, peaks corresponding to N–OH
protons (11.32 and 10.82 ppm) was observed downfield.
This assignment was further substantiated by disappear-
ance of the corresponding OH peaks when ligand under-
went deuterium exchange [17]. A single chemical shift for
each OH protons showed that the LH2 ligand was in the
(E,E)-configuration [1, 4, 12]. The red colour of the Ni(II)
complex of LH2 indicated that the ligand was in the (E,E)
form, the anti-form of the ligand [17]. The N–H proton
give only one broad singlet at 7.54 ppm. Two broad
singlets were observed one at 8.97 ppm and the other at
9.43 ppm for pyrrole N–H groups. The 13C NMR spectrum
of the ligand clearly indicated the presence of hydroxyi-
mino carbon atoms (C=N–O) at 148.88 and 145.81 ppm.
The mass spectrum and the elemental analysis of (3) sup-
port the occurrence of the condensation reaction between
the starting materials (1 and 2). The mass spectrum of the
ligand shows the molecular ion [M]? peak with the
expected isotopic pattern at the m/z value of 675.43
(Fig. 1). Although the solubility of the Ni(II) complex in
Fig. 1 Mass spectrum of the ligand (3)
1
organic solvents was limited, we were able to obtain H
NMR spectra for this complex (Fig. 2).
1
The H NMR spectra of the Ni(II) complex was charac-
terized by the existence of intra-molecular D2O-exchangeable
H-bridge (O–HꢀꢀꢀO) protons which were observed by a new
signal at low field, d = 14.42 ppm. The sharp NMR peaks in
DMSO-d6 is consistent with square-planar structure of dia-
magnetic Ni(II) d8 complex [12, 15, 17].
Fig. 2 The 1H-NMR spectrum of the nickel(II) complex (4) in
DMSO-d6 at 25 ꢁC
The UV–Vis spectra of ligand and complexes were
taken in DMSO in order to assign the geometries around
the metal ions. As Fig. 3 shows, the free ligand (3)
absorption spectrum reveals bands at 260 and 286 nm
which can be assigned to p?p* transitions of the aromatic
rings and n?p* transitions of the C=N groups, respec-
tively [18]. It can be seen that the absorption peaks of
Ni(II) complex (4) are obviously different from those of the
ligand upon complexation. Two bands at 328 and 482 nm
in the Ni(HL)2 spectrum may originate from the LMCT
and d–d electron transfer, respectively [18, 19]. The weak
d–d transition of the complexes [Cu(LH)2] (5) and
[Co(LH)2ꢀ(H2O)2] (6) could not be observed. The d–d
bands should also be present in this range with low
intensities, but they are masked by the stronger CT
absorption band [19].
The electrochemical properties of the ligand, LH2 and
its metal complexes were investigated in DMSO solution
Table 1 Selected IR data (4,000–600 cm-1) of ligand (3) and its complexes (4, 5, 6)
Compound
vO–H
vN–H
vO–H
…
O
vN–O
vC=N
vC–H (alf.)
vC–H(arm.)
3
4
5
6
3,335
–
3,410
3,435
3,431
3,431
–
988
986
982
982
1,587
1,574
1,572
1,578
2,876–2,965
2,875–2,964
2,849–2,963
2,849–2,963
2,980–3,100
2,980–3,100
2,980–3,100
2,980–3,100
1,709
1,716
1,704
–
3,360
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J Incl Phenom Macrocycl Chem (2012) 74:391–396
395
Fig. 3 UV–Vis spectra of the ligand (3) and its complexes (4, 5, 6)
containing 0.1 M TBATFB as a supporting electrolyte by
cyclic voltammetry. All the measurements were carried out
in 1 mM solutions of free ligand and its complexes at room
temperature, in the potential range from ?1 to -2.5 V with
a scan rate of 200 mV s-1. As is seen in Fig. 4a, the cyclic
voltammogram of the ligand in DMSO shows one cathodic
wave at -1.19 V, which can be attributed to the redox
behaviors of the oxime groups present in the ligand. For
Ni(LH)2, the reduction wave (Epc:-1.32 V) corresponding
to Ni(II)/Ni(I) reaction is obtained [19, 20] in the cathodic
potential region, in addition to the ligand peak at -2.11 V.
For the Cu(II) complex, the reversible wave at E1/2
-0.52 V and an reversible peak at -0.85 V correspond to
the Cu(II)/Cu(I) and Cu(I)/Cu(0) couples, respectively, in
addition to the ligand peak at 2.02 V [21]. The reversible
character indicates that both Cu(II) and Cu(I) complexes of
LH2 are stable at the electrode surface in DMSO. Co(II)
complex displays a CV wave for Co(II)/Co(I), but cathodic
peak which belong to the vic-dioxime groups is not well-
defined, probably due to the relative stability of the Co(II)
complex as compared to the Ni(II) and Cu(II) complexes.
The CV wave for the process Co(II)/Co(I) falls at poten-
tials near -1.56 V.
Conclusions
In this work, a new vic-dioxime ligand containing
calix[4]pyrrole moiety, derived from 3-aminophenyl-
calix[4]pyrrole with anti-chloroglyoxime and, its Ni(II),
Cu(II) and Co(II) metal complexes in ethanol have been
prepared. The IR data support that the ligand is coordinated
with the metal ions through the hydroxyimino nitrogens. It
Fig. 4 Cyclic voltammograms for a ligand, b Ni(II) complex,
c Cu(II) complex, d Co(II) complex in DMSO containing 0.1 M
TBATFB at the GC electrode versus Ag/Ag/Ag? (0.01 M AgNO3).
Scan rate is 0.200 V s-1
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9. Gale, P.A., Sesler, J.L., Kral, V., Lynch, V.: Calix[4]pyrroles: old
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of the complexes are in good agreement with the proposed
formulas. Also, we have investigated redox behaviors of
Ni(II), Co(II) and Cu(II) complexes of ligand by cyclic
voltammetry at glassy carbon electrode. Electrochemical
data have shown that Co(II) complex displays a CV wave
for Co(II)/Co(I) but cathodic peak which belong to the vic-
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Acknowledgments This work was supported by TUBITAK (Sci-
entific and Technological Research Council of Turkey) with project
numbers of 108T655 and the Research Fund of Selcuk University
Project Number: 08101031 under thesis.
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ization and electrochemical investigation of a novel vic-dioxime
ligand and its some transition metal complexes. J. Incl. Phenom.
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